Reliability.- this is the property of a machine, its component or part to perform specified functions, maintaining its performance indicators (productivity, power, energy consumption, accuracy, etc.) within specified limits for the required period of time or required operating time (in kilometers, hectares, cubic meters, cycles or others)

Reliability terminology in engineering applies to any technical objects - products, structures and systems, as well as their subsystems, considered from the point of view of reliability at the stages of design, production, testing, operation and repair. Assembly units, parts, components or elements can be considered as subsystems. If necessary, the concept of “object” can include information and its media, as well as the human factor (for example, when considering the reliability of the machine-operator system).

At the development stage, the term “object” is applied to a randomly selected representative from the general population of objects.

Reliability is a complex property, generally consisting of reliability, durability, maintainability and storability. For example, for non-repairable objects, the main property may be failure-free operation. For objects being repaired, one of the most important properties that make up the concept of reliability may be maintainability.

Reliability- the property of an object to continuously maintain an operational state for some time or operating time.

Durability- the property of an object to maintain an operational state until the limit state occurs when installed system maintenance and repair.

Maintainability- property of an object, which consists in its adaptability to maintaining and restoring an operational state through maintenance and repair.

Storability- the property of an object to maintain, within specified limits, the values ​​of parameters characterizing the ability of the object to perform the required functions during and after storage and (or) transportation.

An object- a technical product for a specific purpose, considered during the periods of design, production, testing and operation.

Element- the simplest component of a product; in reliability problems, it can consist of many parts.

System- a set of jointly acting elements designed to independently perform specified functions.

12 .Reliability indicators: probability of failure-free operation, mean time to failure, failure rate, failure flow parameter, time between failures. Weibull's law to characterize the distribution of failures, a typical curve of changes in the probability density of failures during the operation of objects.

Probability of failure-free operation is the probability that, within a given operating time, an object failure does not occur. In practice, this indicator is determined by a statistical assessment

where N0 is the initial number of operational objects, n(t) is the number of failed objects during time t.

Mean time to failure Mathematical expectation of the operating time of an object until the first failure.

Run-to-failure- equivalent parameter for a non-repairable device. Since the device is not repairable, this is simply the average time that the device will work before it breaks.

Operating time- duration or volume of operation of an object, measured in hours, engine hours, hectares, kilometers, switching cycles, etc.

It is measured statistically, by testing many instruments, or calculated by methods of reliability theory.

T = 1/m * Σti where ti is the operating time of the i-th object between failures; m is the number of failures.

Failure rate. Conditional probability density of the occurrence of an object failure, determined under the condition that the failure did not occur before the considered point in time . The failure rate is the ratio of the number of failed equipment samples per unit of time to the average number of samples that work properly in a given period of time, provided that the failed samples are not restored or replaced with serviceable ones.

Failure flow parameter. The ratio of the mathematical expectation of the number of failures of a restored object over a sufficiently short operating time to the value of this operating time.

Rice. 4.1.1. Basic properties of technical systems

In accordance with GOST 27.002-89, reliability is understood as the ability of an object to maintain over time, within established limits, the values ​​of all parameters that characterize the ability to perform the required functions in given modes and conditions of use, maintenance, repairs, storage and transportation.

Thus:
1. Reliability- the property of an object to maintain over time the ability to perform required functions. For example: for an electric motor - to provide the required torque on the shaft and speed; for the power supply system - to provide power receivers with energy of the required quality.

2. The required functions must be performed with parameter values ​​within the established limits. For example: for an electric motor - to provide the required torque and speed when the engine temperature does not exceed a certain limit, the absence of a source of explosion, fire, etc.

3. The ability to perform the required functions must be maintained in specified modes (for example, in intermittent operation); under specified conditions (for example, dust, vibration, etc.).

4. The object must have the ability to maintain the ability to perform the required functions in various phases of its life: during operational operation, maintenance, repair, storage and transportation.

Reliability- an important indicator of the quality of an object. It cannot be contrasted or confused with other quality indicators. For example, information about the quality of a purification plant will be clearly insufficient if it is only known that it has a certain productivity and a certain purification coefficient, but it is unknown how consistently these characteristics are maintained during its operation. It is also useless to know that the installation stably retains its inherent characteristics, but the values ​​of these characteristics are unknown. That is why the definition of reliability includes the performance of specified functions and the preservation of this property when the object is used for its intended purpose.

Depending on the purpose of the object, it may include reliability, durability, maintainability, and storage in various combinations. For example, for a non-recoverable object not intended for storage, reliability is determined by its failure-free operation when used for its intended purpose. Information about the failure-free operation of a restored product that has been in storage and transportation for a long time does not fully determine its reliability (it is necessary to know about both maintainability and storability). In a number of cases, the ability of a product to maintain operability until the onset of a limiting state (decommissioning, transfer for medium or major repairs) becomes very important, i.e. information is needed not only about the reliability of the object, but also about its durability.

A technical characteristic that quantifies one or more properties that make up the reliability of an object is called a reliability indicator. It quantitatively characterizes the extent to which a given object or a given group of objects has certain properties that determine reliability. The reliability indicator may have a dimension (for example, mean time to recovery) or not have it (for example, the probability of failure-free operation).

Reliability in the general case is a complex property that includes such concepts as reliability, durability, maintainability, and storability. For specific objects and their operating conditions, these properties may have different relative importance.

Reliability is the property of an object to continuously remain operational for some operating time or for some time.

Maintainability is the property of an object to be adapted to prevent and detect failures and damage, to restore operability and serviceability during the process of maintenance and repair.

Durability is the property of an object to remain operational until a limit state occurs with the necessary interruption for maintenance and repairs.

Storability is the property of an object to continuously maintain a serviceable and operational state during (and after) storage and (or) transportation.

For reliability indicators, two forms of representation are used: probabilistic and statistical. The probabilistic form is usually more convenient for a priori analytical calculations of reliability, while the statistical form is more convenient for experimental studies of the reliability of technical systems. In addition, it turns out that some indicators are better interpreted in probabilistic terms, while others are better interpreted in statistical terms.

Reliability and maintainability indicators
Run-to-failure- the probability that, within a given operating time, an object failure will not occur (provided it is operational at the initial point in time).
For storage and transportation modes, the similarly defined term “probability of failure occurrence” can be used.

Mean time to failure is the mathematical expectation of the random operating time of an object before the first failure.
Average time between failures is the mathematical expectation of the random operating time of an object between failures.

Typically this indicator refers to a steady-state operating process. In principle, the average time between failures of objects consisting of elements that age over time depends on the number of the previous failure. However, as the failure number increases (i.e., with an increase in the duration of operation), this value tends to some constant, or, as they say, to its stationary value.
Mean time between failures is the ratio of the operating time of a restored object over a certain period of time to the mathematical expectation of the number of failures during this operating time.

This term can be briefly called the average time to failure and the average time between failures when both indicators coincide. For the latter to coincide, it is necessary that after each failure the object is restored to its original state.

Specified operating time- operating time during which an object must operate without failure to perform its functions.

Average downtime- mathematical expectation of the random time of forced unregulated stay of an object in a state of inoperability.

Average recovery time- mathematical expectation of the random duration of restoration of operability (repair itself).

Recovery probability is the probability that the actual duration of restoration of the object’s operability will not exceed the specified one.

Indicator of technical efficiency of operation- a measure of the quality of the actual functioning of an object or the feasibility of using an object to perform specified functions.
This indicator is quantified as the mathematical expectation of the output effect of an object, i.e. depending on the purpose of the system, it takes on a specific expression. Often the performance indicator is defined as the total probability of an object completing a task, taking into account a possible decrease in the quality of its work due to the occurrence of partial failures.

Efficiency retention rate- an indicator characterizing the influence of the degree of reliability on the maximum possible value of this indicator (i.e., the corresponding state of full operability of all elements of the object).

Non-stationary availability factor- the probability that an object will be operational at a given point in time, counted from the start of work (or from another strictly defined point in time), for which the initial state of this object is known.

Average availability factor- the value of the non-stationary availability factor averaged over a given time interval.

Stationary availability factor(availability factor) - the probability that the restored object will be operational at an arbitrarily selected point in time in the steady process of operation. (The availability factor can also be defined as the ratio of the time during which the object is in working condition to the total duration of the period under consideration. It is assumed that a steady-state operation process is being considered, the mathematical model of which is a stationary random process. The availability factor is the limiting value to which Both non-stationary and average availability factors tend to increase as the time interval under consideration increases.

Indicators that characterize a simple object are often used - the so-called downtime coefficients of the corresponding type. Each availability factor can be associated with a certain downtime factor, numerically equal to the addition of the corresponding availability factor to one. In the relevant definitions, performance should be replaced by inoperability.

Non-stationary operational readiness coefficient is the probability that an object, being in standby mode, will be operational at a given point in time, counted from the start of work (or from another strictly defined time), and from this point in time will work without failure for a given time.

Average operational readiness ratio- the value of the non-stationary operational readiness coefficient averaged over a given interval.

Stationary operational readiness ratio(operational readiness coefficient) - the probability that a restored element will be operational at an arbitrary point in time, and from this point in time will work without failure for a given time interval.
It is assumed that a steady-state operation process is being considered, to which a stationary random process corresponds as a mathematical model.

Technical utilization rate- the ratio of the average operating time of an object in units of time for a certain period of operation to the sum of the average values ​​of operating time, downtime due to maintenance, and repair time for the same period of operation.

Failure Rate- conditional probability density of failure of a non-repairable object, determined for the considered moment in time, provided that the failure did not occur before this moment.
The failure flow parameter is the probability density of the occurrence of a failure of a restored object, determined for the considered point in time.

The failure flow parameter can be defined as the ratio of the number of failures of an object over a certain time interval to the duration of this interval with an ordinary failure flow.

Recovery intensity- conditional probability density of restoration of the object’s operability, determined for the considered moment in time, provided that the restoration was not completed until this moment.

Indicators of durability and storage

When assessing the quality of building materials, their properties must be fully taken into account. According to there is a system of quality indicators, which includes: indicators of purpose, reliability and durability, ergonomic indicators, etc.

Destination indicators. These indicators characterize the beneficial effect of using the product for its intended purpose and determine the scope of its application. IN general view target indicators include strength(compressive and tensile strength, rigidity, crack resistance, impact strength, seismic resistance), as well as thermophysical indicators And resistance to external influences(frost resistance, moisture resistance, resistance to solar radiation, heat resistance, fire resistance, thermal conductivity, water resistance, sound insulation, light transmittance, etc.).

The range of designation indicators required for quality assessment is regulated by a system of standards and provides the following designation indicators for stone wall materials: compressive and bending strength limits, water absorption, release humidity, frost resistance, linear shrinkage. Considering that the materials are intended to work in the enclosing wall structure and must have high thermal resistance, the standard includes one of the most important indicators - the thermal conductivity of the wall material

When assessing the level of product quality, purpose indicators are often used in conjunction with other types of indicators. The indicators of reliability and durability are most closely related to the purpose indicators.

Also included in this group are constructiveness indicators characterize the degree of technical perfection and progressiveness of a material, product or design. For building products, the indicators of constructability are the geometric shape and dimensions, and standardized tolerances. In relation to materials, composition and structure characteristics are used as indicators of constructability. For example, for cement, a characteristic is used based on the content of the main minerals of clinker; concrete mixtures are characterized by the type and ratio of raw materials, etc.

Indicators of reliability and durability. These indicators characterize the reliability and durability properties of materials, products or construction projects. In relation to the process of manufacturing products, the reliability of the technological equipment used in the production of products and technology in general also deserves attention.

Reliability indicators characterize the degree to which a product performs its functions during a given service life under certain environmental conditions while maintaining its properties, subject to compliance with operating rules. The property of reliability is laid down at the stage of product development, ensured at the stage of its production and maintained at the stage of operation.

The problem of reliability of building structures and systems is becoming increasingly important due to the increase in the number of floors of buildings, the increase in the number of prefabricated elements and the number of joints, and the desire to make structures as light and thin as possible.

Reliability- a complex property of a product, which in general consists of particular properties: durability, reliability, maintainability and storability.

Reliability call the property of an object to continuously maintain an operational state for some time or some operating time. Basically, reliability is considered in relation to the operating mode of an object, but sometimes it is necessary to evaluate the reliability during its storage and transportation) Reliability indicators include the probability of failure-free operation, mean time to failure, time to failure, failure rate, etc.

Time to failure is the duration or volume of operation of an object from the beginning of its operation until the occurrence of the first failure. It is measured in units of time (when the product operates continuously) or in cycles when the product operates at intervals. Time to failure is used to characterize the reliability of a single product. To assess the reliability of a group (batch) of products, indicators should be used that reflect changes in product properties, taking into account their statistical variability. Such indicators are mean time to failure, gamma-percentage time to failure and failure rate, etc.

Average time to failure reflects the mathematical expectation of time to first failure. Gamma-percentage time to failure characterizes the operating time during which an object’s failure does not occur with probability y, expressed as a percentage. To quantify the reliability of non-repairable products, the failure rate indicator is used. Failure rate is the probability of failure of a non-repairable product per unit time. In the simplest case, the failure rate is inversely proportional to the mean time between failures.

The probability of failure-free operation characterizes the probability that, within a given operating time, an object failure will not occur. By the time i, counting from the start of operation of the object, the probability of its trouble-free operation is determined by the formula P(t)= 1-F(t), Where F(t) - time-to-failure distribution function, and is expressed as a certain number from zero to one or as a percentage

Under d eternity implies the property of an object to maintain operability to its limit state with the necessary breaks for repairs. The limit state is determined by the destruction of the object, safety requirements or economic considerations.

To assess the durability of building products, indicators are used that make it possible to predict the service life of products. First of all, this is a period that characterizes the calendar duration of operation of the product before transition to the limit state. There is also a distinction between the assigned service life, which reflects the calendar duration of operation of the product, upon reaching which its intended use must be discontinued, and the average service life, i.e. the mathematical expectation of the service life.

Maintainability - a property of a product that characterizes its adaptability to restore an operational state as a result of preventing, identifying and eliminating failures. Indicators of maintainability are the average time to restore a working condition, which expresses the mathematical expectation of the restoration time, as well as the probability of restoration, i.e. the probability that the time to restore the operational state of the object will not exceed the specified one. Repairability applies only to repairable products, systems and elements.

Storability characterizes the properties of an object to maintain specified values ​​of reliability, durability and maintainability during and after the storage and transportation period established by the technical documentation. Storability is quantified by the time of storage and transportation before failure occurs. Storability can also be expressed by a decrease in the reliability indicator during subsequent operation of the product.

Construction practice shows that products can lose reliability not only during operation, but also during storage or transportation. Therefore, persistence is often presented in the form of two components: one of them manifests itself during the storage period, and the other during the use of the object after storage.

Manufacturability indicators. This group includes indicators characterizing the effectiveness of design and technological solutions, which should be aimed at achieving high labor productivity with minimal costs of materials, fuel and energy for the manufacture and repair of products

Manufacturability of products is characterized by the degree of use of standard technological processes, the most rational starting materials and products of centralized production, the best provision of consumers with spare parts and materials, which leads to an increase in labor productivity in the manufacture of products and to a reduction in the costs of production and operation of products. The main indicators of the manufacturability of industrial products include the coefficient of prefabricated (blocked) products and the coefficient of use of rational materials, as well as specific indicators of the labor intensity of production, material and energy intensity of products.

Assembly factor(block character) of a product characterizes the ease of installation of the product and represents the proportion of structural elements included in the specified blocks in the total number of elements of the entire product) In relation to building products (systems), the prefabrication coefficient expresses the proportion of prefabricated elements in the total number of components of the product (system):

Where N Sat - number of prefabricated elements in the product; N- total number of elements.

The higher the value of the prefabrication coefficient, the higher the manufacturability of the product.

Sustainable materials utilization rate determined in cases where it is advisable for technical and economic reasons to use certain effective materials in the design of a product ( aluminum alloys, polymer building materials, etc.). Material utilization rate:

(2.2)

Where M and- total weight of the product; M um - the total mass of effective material in the product.

For light, effective materials, due to their low density, the utilization coefficient will have an underestimated value, therefore, for such materials, it is necessary to enter volumes rather than masses into the expression. As the rate of use of sustainable materials increases, the level of product quality increases.

It is convenient to characterize the manufacturability of products by indicators of labor and material intensity. Labor intensity of production is determined by the amount of time spent on manufacturing a unit of product, and is expressed for industrial products in standard hours. Specific labor intensity is defined as the ratio of the total labor intensity of production T to the main product parameter IN:

q t =T/B,(2.3)

Specific material consumption - ratio of mass or volume of finished product M to its main parameter IN:

q m =M/B(2.4.)

When determining specific labor intensity and specific material intensity, indicators of the product’s purpose (strength, density, etc.) are taken as the main parameter. The technical policy at the enterprise should be aimed at reducing the specific labor intensity, material intensity and energy intensity of products; the quality level increases.

Ergonomic indicators. Ergonomic quality indicators are used to determine whether a product meets ergonomic requirements. Ergonomics studies the interaction in the “person - environment - product” system. These indicators cover the entire area of ​​factors affecting the working person and the product in use. For example, when studying a workplace, one should take into account not only the working posture of a Person and his movements, breathing, thinking, but also the dimensions of the seat, parameters of tools, means of transmitting information, etc.

Ergonomic indicators are divided into hygienic, anthropometric, physiological and psychological.

The level of ergonomic indicators is determined by ergonomist experts using a developed special rating scale in points.

Hygienic indicators characterize the product’s compliance with sanitary and hygienic standards and recommendations. These indicators are used to assess the compliance of a product with the hygienic conditions of human life and performance when interacting with the product. The group of hygienic indicators includes illumination, temperature, humidity and pressure, magnetic and electric field, levels of dust, radiation, toxicity, noise and vibration, overload (acceleration).

The influence of hygienic indicators is determined by measuring and assessing the intensity of individual factors and comparing the obtained data with standard ones. For example, when assessing the level of vibration, it is necessary to compare the existing level of vibration of process equipment (vibrating platforms, deep, surface and mounted vibrators) with the maximum permissible according to the standards. The degree of harmfulness of vibration is assessed by the limiting values ​​of vibration velocity and vibration amplitude depending on frequency.

Anthropometric indicators characterize products that are in direct contact with humans, control elements, industrial furniture, clothing and footwear. The group of anthropometric indicators includes indicators of compliance of the product design with the size and shape of the human body and its individual parts that come into contact with the product; an indicator of compliance of the product design with the distribution of human mass.

Physiological and psychophysiological indicators characterize the compliance of the product with the physiological properties of a person and the functioning of his sense organs. This includes the following indicators: compliance of the product design with the speed and strength capabilities of a person; compliance of the size, shape, brightness, contrast, color of the product and spatial position of the object of observation with the visual psychophysiological capabilities of a person; compliance of the design of the product containing the source of information with the auditory psychophysiological capabilities of a person; compliance of the product and its elements with the relative capabilities of a person.

Psychological indicators characterize the product’s compliance with the psychological characteristics of a person”, which are reflected in engineering and psychological requirements, the requirements of labor psychology and general psychology. The psychological group includes indicators of the product’s compliance with the capabilities of perceiving and processing information and the product’s compliance with fixed and newly formed human skills (taking into account the ease and speed of their formation) when using the product.

When assessing product quality using ergonomic indicators, it is necessary to identify elements in industrial products that affect human performance, productivity and fatigue.

Indicators of standardization and unification. These include indicators characterizing the degree of saturation of the product with standardized and unified parts. When developing new products, it is necessary to strive not only to reduce the number of original components, but also to reduce the number of standardized and unified parts, since, other things being equal, the higher the quality of the product, the less it contains component parts.. For uniformity in calculating indicators of standardization and unification, the component parts of a product are usually divided into standardized, unified and original. Parts of a product manufactured according to state, republican or industry standards are considered standardized. Unified parts include parts of the product that are produced according to the standards of the enterprise, as well as those received by it in finished form as component parts (from those in mass production). Original components are components designed specifically for this product.

The most important indicators of standardization and unification are applicability coefficients and repeatability coefficients.

Applicability factor characterizes the degree of saturation of the product with standardized and unified components. There is a distinction between the applicability coefficient based on standard sizes and the applicability coefficient based on the component parts of the product. For example, the applicability factor by standard size:

(2.5)

Where N rev- total number of standard sizes of product components, N rev =N st +N y +N o;

N st, N y And N about- number of standard sizes of standardized, unified and original components.

In addition, it is possible to determine applicability coefficients only by standardized or only by unified components. The higher the values ​​of the applicability coefficients, the higher, other things being equal, the level of product quality.

Repeatability factor characterizes the degree of unification of the components in the product and can be expressed in two forms - as a dimensionless number or as a percentage:

, (2.6)

where is the number of components in the product.

The degree of applicability of standard components can also be expressed using a cost coefficient equal to the ratio of the cost of standardized components to the cost of the product as a whole. The cost coefficient can also be classified as a group of economic indicators.

Economic indicators reflect the costs of development, manufacturing and operation of products, as well as the economic efficiency of operation. Using economic indicators, the maintainability of products, their manufacturability, the level of standardization and unification, and patent purity are assessed. Economic indicators are also taken into account when compiling integral indicators of product quality.

Aesthetic indicators of product quality. Aesthetic indicators characterize informational expressiveness, rationality of form, integrity of composition, perfection of production execution and stability of the presentation of the product.

Indicators of information expressiveness characterize the degree of reflection in the form of the product of the aesthetic ideas and cultural norms that have developed in society, which are manifested:

In the originality of the form elements that distinguish this product from other similar products (originality of form);

In the continuity of the signs of form, characterizing the stability of the means and techniques of artistic expression characteristic of the defined period of time (style correspondence);

In signs of the appearance of a product, revealing temporarily established aesthetic tastes and preferences (conformity with fashion).

Indicators of rationality of form characterize the compliance of the form with the objective conditions of manufacture and operation of the product, as well as the adequacy of the reflection in it of the functional and constructive essence of the product. The rationality of the form is:

Compliance of the shape of the product with its purpose, design solution, features of manufacturing technology and materials used (an indicator of functional and structural conditionality);

Taking into account in the form of the product the methods and characteristics of human actions with the product (an indicator of ergonomic conditionality).

Composition integrity indicators characterize the harmonious unity of parts and the whole product, the organic relationship of the elements of the product’s form and its consistency with other products. The integrity of the composition determines the effectiveness of the use of technical and artistic means when creating a single compositional solution.

Indicators of perfection of manufacturing of form elements and surfaces are characterized by:

Cleanliness of contour surfaces (indicator of contour cleanliness);

The thoroughness of coating and surface finishing (an indicator of the thoroughness of coatings and finishing);

Clarity of the image of brand names, signs, inscriptions, drawings, symbols, information materials and so on. (an indicator of the clarity of execution of signs and accompanying documentation).

Indicators of stability of presentation are as follows: resistance to damage to elements of the product’s appearance; color retention, etc.

The values ​​of aesthetic quality indicators of products are assessed using the expert method by a commission consisting of qualified specialists in the field of artistic construction and design. The expert commission evaluates the selected aesthetic indicators in points and determines the weight coefficient of each indicator. Based on the obtained values ​​of individual indicators and their weight coefficients, a generalized aesthetic indicator is calculated using the formula:

Where K i - assessment of a single i-ro aesthetic indicator in points;

m i- weight coefficient i-th indicator

P- the number of individual aesthetic indicators taken into account.

Example

Let the experts, based on the completed aesthetic and design analysis, determine the ratings and weighting coefficients of individual aesthetic indicators. It is required to find a general indicator of the aesthetics of a product. The initial data and calculation results are given in table. 2.1.

Table 2.1

Initial data for calculation

No.	Single indicator	Grade	Weight factor m i	m i× K i
	Originality	1,0	0,05	0,05
	Style matching	0,8	0,02	0,016
	Fashionable	0,5	0,03	0,015
	Functional-constructive conditioning	1,0	0,25	0,25
	Ergonomic conditionality	0,5	0,18	0,09
	Color and decorativeness	1,0	0,04	0,04
	Cleanliness of contours	0,9	0,10	0,09
	Careful coating and finishing	1,0	0,12	0,12
	Clarity of branding and accompanying documentation	0,7	0,08	0,056
	Resistance to damage	0,8	0,13	0,104

Let's find the aesthetics indicator using formula (2.7)

The obtained result indicates that the aesthetic level of quality of the evaluated product does not meet modern requirements.

Patent and legal indicators. Patent legal indicators are primarily indicators of patent protection and patent purity. To calculate the values ​​of patent-legal indicators, depending on the complexity of the product, all its components are divided into groups taking into account their weight.

Two indicators of product patent protection are used: patent protection in the country and abroad.

Product patent protection indicator within the country it is calculated as follows:

(2.8)

where is the number of significance groups;

The weight coefficient of the component parts of the product protected by patents or copyright certificates of the country;

The number of components of the product protected by patents or copyright certificates of the country;

The total number of components of the product.

Patent protection indicator domestic product patents abroad is determined by the formula:

(2.9)

where is a coefficient depending on the number of countries in which patents were obtained for the export of products;

Weight factor of product components protected by foreign patents;

Number of product components protected by patents abroad.

Overall indicator of product patent protection, represents the sum

(2.10)

Index patent purity expresses the legal possibility of selling a product both domestically and abroad. The indicator is simplified to calculate using the formula:

(2.11)

where is the number of component parts of the product (by significance groups) that are covered by patents in a given country.

Taking into account the division of the component parts of the product into particularly important, main and auxiliary patent protection indicator determined by the formula:

(2.12)

where is the individual weight coefficient of particularly important components;

The number of particularly important components in the product;

The weighting coefficient of parts protected by patents in Russia or in the countries of intended export; -th group;

The number of components of a product in a group that are covered by patents issued in the country of intended sale;

Number of significance groups.

Environmental indicators. An urgent problem today has become the dangerous impact on nature for people in the process of their life. Various objects used in labor processes become material carriers of dangerous and harmful factors for nature and humans. Such objects include: means of labor (machines, equipment and other technical products); objects and products of labor; technologies, natural and climatic conditions, etc.

Environmental indicators characterize the level of harmful effects on the environment during product operation. When justifying the need to take into account environmental indicators to assess the quality of a product, an analysis of its operation is carried out in order to identify possible harmful chemical, mechanical, light, sound, biological, radiation and other effects on the natural environment. When such impacts on nature are identified, the corresponding environmental indicators are included in the list of indicators accepted for assessing the quality level of the product.

The environmental performance of technology can be divided into three main groups:

indicators related to the use of natural resources,

indicators related to the use of natural energy resources;

indicators related to environmental pollution.

TO first The group of indicators includes: resource intensity of product manufacturing, indicators of consumption of irreplaceable material resources during operation, during repairs and disposal of products after their physical wear and tear.

Co. second group includes indicators of consumption of natural energy resources at all stages and phases life cycle products.

Third group of indicators includes parameters various types environmental pollution and damage from this pollution at various stages of the product life cycle - from production and operation to the disposal of used products.

When determining the environmental quality indicators of new technology, the relative values ​​of the actual values, for example, the concentration of harmful substances or the levels of harmful (mechanical, physical and other) effects on the natural environment, are found to their maximum permissible values. In this case, the following conditions must be met:

(2.14)

where C 1, WITH 2 , WITH 3 - concentrations of relevant harmful substances;

MPC 1 , maximum permissible concentration 2 , MPC n - maximum permissible concentrations of relevant harmful substances.

When assessing the level of quality of technical products taking into account environmental indicators, they proceed from the requirements and specific standards for environmental protection.

An industrial product, the operation of which leads to a violation of established environmental requirements and environmental protection standards, cannot be classified as a product that exceeds the world level or corresponds to it, regardless of whether other quality indicators correspond to such an assessment.

Safety indicators. This group of product quality indicators characterizes the safety of service personnel, passengers - for vehicles, as well as surrounding people during operation, storage and disposal of technical products.

Safety - This is a state of working conditions in which danger is excluded with a certain probability, i.e. the possibility of damage (injury, injury) or deterioration (occupational diseases) of human health.

The following can be taken as safety indicators:

The likelihood of a person working safely for a certain period of time;

Safety factor;

A qualitative indicator of safety may be the availability of personal protective equipment, seat belts, etc.

The quality level of the product is assessed taking into account safety indicators and their standards.

When assessing safety, it is initially determined X st - degree of harmfulness (danger) of an unfavorable factor and (or) severity of work with a technical product. Degree of harm X st are assessed in points in accordance with standards.

However, many harmful and dangerous factors do not always affect a person during his work. In this case, the established indicators of the degree of harmfulness of factors are adjusted according to the formula:

Where X st- degree of harmfulness (danger) of the factor,

T - the ratio of the time of action of this factor to the duration of the work shift.

If the duration of any negative factor is more than 90% of the duration of the work shift, then it T= 1.

In a number of cases, the degree of safety of technical products is assessed by safety factors K b.

Safety factor K b is determined by the ratio of the number of safety indicators (requirements) N b corresponding regulatory and technical documentation on occupational safety with the product being evaluated, to the total number of the nomenclature of safety indicators N about related to this product:

If the safety factor is less than one, then it is necessary to carry out management and technical measures to bring the product to a regulatory safe state.

What is the security level U b The product is quantified as the ratio of the safety factors of the evaluated and base samples:

However, a more accurate assessment of the product safety level can be carried out using a differential or complex method, taking into account all individual safety indicators and their significance.

Reliability – this is the property of an object to perform specified functions, maintaining over time the values ​​of established operational indicators within specified limits, corresponding to specified modes and conditions of use, maintenance, repair, storage and transportation. This is a quality that extends over time. Therefore, the concept of reliability is close to the concept of quality, and therefore the problems of quality management are directly reflected in the concept of reliability.

Reliability is an objective property of a product; reliability can be measured. To measure reliability, the concepts of “failure”, “probability of failure-free operation”, “failure rate”, etc. were introduced. The concepts of failure and reliability are among the basic ones in reliability theory. Usually under reliability understand the ability of products to remain operational for a long time. Refusal– this is a complete or partial loss of the product’s functionality.

American authors D. Lloyd and M. Lipov in the book “Reliability” write: “Reliability affects cost, time costs, psychologically - in the form of inconvenience, and certain cases also threatens the security of people and the nation. Typically, losses due to unreliability represent not only the cost of the unit that fails, but also the cost of associated equipment that deteriorates or is destroyed as a result of the failure... A classic example of the psychological effect of unreliability is the sadly remembered Avangard satellites. The United States, acutely worried about the successes of Russia in launching Sputnik 1, tried to enter the competition using an almost untested rocket for this purpose, which had to work almost to the limit of its capabilities. The failures and the ensuing despondency and loss of prestige were very serious."

American writer, poet and scientist of the 19th century. There is a poem by Oliver Holmes called "The Priest's Masterpiece, or the Wonderful One-Horse Carriage." It talks about a priest who built a carriage, remarkable in that all its parts had exactly the same strength. This stroller lasted exactly 100 years and fell apart right along the road. All parts broke at the same time.

A product that would be destroyed in this way is the dream of any engineer and quality management specialist. But real mechanisms are destroyed randomly and at random times. Therefore, statistical methods and the probabilistic apparatus of mathematics are used to assess reliability. The probability of failure-free operation is the probability that a product failure will not occur in a given time interval or within a given operating time.

There are many numerical characteristics to assess reliability. For example, availability factor is the probability that the product will be operational at specified or random moments, – the time during which the product is operational, referred to the time of its operation.

by the consumer means the time during which a product with a manufacturer's guarantee maintains its quality parameters expected by the consumer, and therefore this time is usually called the guaranteed service life of the product.

Product service life guaranteed by the manufacturer called the durability of the product. Durability depends on the possibility of repair, after which its quality parameters can be restored, i.e. on the maintainability of the product.

Based on the actual service life, the consumer judges mainly the quality of the product he purchased, which subsequently affects his attitude towards the corresponding manufacturer and, ultimately, the image of this manufacturer in the eyes of the consumer.

The most widely used indicator in reliability studies is failure rate (λ ):

Where n– number of failed products; N- total number

products; – average test time.

The average test time is determined by the formula

where is the number of products in the test group; – duration of the test for this group.

If the number of failed products exceeds 5-10%, then adjustments are made to the calculation:

(2.3)

where is the number of failed products in this group;

– number of failures during the same test time;

Duration of tests to disable the product.

To calculate the average failure rate, it is important to select the correct time interval, since failure density usually varies over time.

EXAMPLE 2.1

When testing a certain piece of electronic equipment, λ can be determined after 1000–2000 hours. Testing is carried out in 4 groups of 250 products for 2000 hours.

The test results are as follows:

Let's calculate:

In total, 20 products failed during the tests (7 + 5 + + 4 + 4).

Parts and assemblies may fail due to manufacturing defects and other reasons.

At a constant level of failure rate per unit time, the probability distribution of failure-free operation intervals is expressed by the exponential distribution law of operational durability.

The main quality parameters for products are:

• – functional characteristics – compliance of the product with its intended purpose;
• – reliability – the number of repairable failures over the service life;
• – durability (service life) – an indicator related to reliability;
• – defect-free – the number of defects detected by the consumer.

Reliability is a concept associated primarily with technology. It can be interpreted as failure-free-

agility, ability to perform a specific task or howprobability of performing a certain function or functions within a certain time and under certain conditions .

How technical concept"reliability" is the probability (in a mathematical sense) of performing a specified function satisfactorily. Since reliability is a probability, statistical characteristics are used to evaluate it. The results of reliability measurements should include data on sample sizes, confidence limits, sampling procedures, etc.

In technology, the concept of “satisfactory performance” is also used. Precise definition This concept is associated with the definition of its opposite - “unsatisfactory performance” or “refusal”.

The general concept of “reliability” is opposed to the concept of “reliability itself” of a sample of equipment, which is the probability of failure-free operation in accordance with specified technical conditions under specified verification tests for the required period of time. In reliability testing, reliability itself is measured. It essentially represents the “operational reliability” of the equipment and is a consequence of two factors: actual reliability and operational reliability. Operational reliability, in turn, is determined by the compliance of the equipment with its use, the procedure and method of operational use and maintenance, the qualifications of personnel, the ability to repair various parts, environmental factors, etc.

For each characteristic to be measured, a tolerance is specified in the technical specifications, the violation of which is considered a “failure.” The tolerance defining a failure must be optimal with the necessary allowance for wear of parts, i.e. it must be wider than the normal factory tolerance. Therefore, factory tolerances are set taking into account the fact that parts wear out over time.

Let us characterize the basic concepts related to reliability.

• 1. Serviceability – the state of the product in which it currently meets all the requirements established both in relation to the main parameters characterizing the normal performance of specified functions, and in relation to secondary parameters characterizing ease of use, appearance, etc.
• 2. Malfunction – the state of a product in which it does not currently meet at least one of the requirements characterizing the normal performance of specified functions.
• 3. Performance – the state of the product in which it currently meets all the requirements established in relation to the basic parameters characterizing the normal performance of specified functions.
• 4. Refusal – an event consisting in the complete or partial loss of a product’s functionality.
• 5. Complete refusal – a failure, until the elimination of which the use of the product for its intended purpose becomes impossible.
• 6. Partial failure – failure, until elimination of which partial use of the product remains possible.
• 7. Reliability – the property of a product to continuously maintain performance over a certain period of time.
• 8. Durability – the property of a product to maintain operability (with possible interruptions for maintenance and repair) until destruction or another limiting state. The limit state can be set based on changes in parameters, safety conditions, etc.
• 9. Maintainability – property of a product, expressed in its suitability for carrying out maintenance and repair operations, i.e. to the prevention, detection and elimination of malfunctions and failures.
• 10. Reliability (in a broad sense) – property of a product due to the reliability, durability and maintainability of the product itself and its parts and ensuring

ensuring the preservation of the performance characteristics of the product under specified conditions.

• 11. Recoverability – the ability of a product to restore the initial values ​​of parameters as a result of eliminating failures and malfunctions, as well as restore the technical life as a result of repairs.
• 12. Storability – the property of a product to maintain serviceability and reliability under certain conditions and transportation.

For some products that are relatively simple in design, the concept of “failure” can be introduced quite clearly. For example, a light bulb either lights up or doesn’t light up.

In practice, sometimes special attention is paid to improving the main components of the product, losing sight of the fact that the cause of unreliability and subsequent accidents may be structural components that are of an auxiliary nature.

To measure (estimate) reliability, it is necessary to test an apparatus that would describe random events or random processes. We are talking about probability theory and mathematical disciplines. The main quantitative indicator of reliability is the probability of failure-free operation of a product for a given period of time.

Probability of failure-free operation is the probability that a product failure will not occur within a given time interval or within a given operating time. With the introduction of this concept, it becomes possible to measure reliability and compare the reliability of a product according to this indicator. The probability of failure-free operation of the same product is not the same at different moments of its operation.

To assess reliability, there are many characteristics, in particular: probability of failure-free operation; availability factor(the probability that the product will be operational at a given or random moment); time utilization ratio(the time during which the product is operational, referred to the time of its operation).

Time of trouble-free operation of the product consumer refers to the time during which a product with a manufacturer's guarantee maintains its quality parameters expected by the consumer, and therefore this time is usually called guaranteed product service life.

Guaranteed product service life, as a rule, less than its actual service life, which is characterized by the durability of the product.

Durability depends on the possibilities of repair, after which the quality parameters of the product are restored, i.e. depends on maintainability. Durability characterizes the actual service life of a product. Based on the actual service life, the consumer judges the quality of the purchased product, which subsequently affects his attitude towards the manufacturer and, ultimately, the image of this manufacturer in the eyes of the consumer.

At the same time, the guaranteed service life of a product is of significant importance at the time of its purchase in comparison with a similar product from competitors, and the strictness of the subsequent fulfillment of all pre-agreed conditions and guarantees when purchasing a product determines the consumer’s attitude towards the reliability of not only the supplier (seller), but also the manufacturer .

If during the guaranteed service life the value of the quality parameters does not meet the consumer’s expectations, which are guaranteed by the manufacturer, then the responsibility for this lies with the manufacturer of the product (supplier), who must carry out repairs at his own expense, and if repairs are impossible, replace the low-quality product with a high-quality one.

The manufacturer must guarantee the quality of the product both during its storage and during its operation.

To predict failures in the future, actual data on the frequency of failures during the period of use of the equipment for its intended purpose is necessary.

When processing information, the inverse of the failure rate is used "mean time between failures".

Quite complex analytical techniques are used to study reliability. For example, when studying electronic systems, an engineer selects a number of key characteristics, selects the most important one, selects options for action and one of these options, examines the operating conditions and evaluates them.

Due to the high pace of modern scientific and technological progress, it is important to choose the optimal moment for the transition from scientific research and preparatory work to production. In a competitive environment, the timing of production launch is an important factor, acting in two directions: launching production “too early” can lead to the same negative consequences as launching “too late”.

The reasons for manufacturing unreliable products may be:

• – lack of regular verification of compliance with standards;
• – errors in the use of materials and improper control of materials during production;
• – incorrect accounting and reporting of control, including information on technology improvements;
• – sampling schemes that do not meet the standards;
• – lack of testing of materials for their compliance;
• – failure to comply with acceptance testing standards;
• – lack of instructional materials and instructions for conducting control;
• – irregular use of control reports to improve the technological process.

The mathematical models used to quantify reliability depend on the “type” of reliability. Modern theory distinguishes three types.

• 1. Instant Reliability(eg fuses).
• 2. Reliability with normal service life(For example, computer technology). In normal serviceability studies, the unit of measurement is "mean time between failures". The range recommended in practice is from 100 to 2000 hours.
• 3. Extremely long-term operational reliability(for example, spaceships). If service life requirements exceed 10 years, they are classified as extremely long service reliability.

Under normal operational reliability, technical prediction of reliability can be theoretical, empirical and experimental.

At theoretical Testing tools develop a scheme for this operation and check the compliance of the scheme using a mathematical model. If the diagram does not correspond to the operation, clarifications are made until compliance is achieved. This is the so-called scientific research.

Empirical approach consists in performing the necessary measurements in relation to the actual products produced and drawing conclusions about reliability.

Experimental approach occupies an intermediate position between theoretical and empirical. The experimental approach uses both theory and measurements. At the same time, methods of mathematical modeling of processes are widely used, creating experimental data on this basis. After this, the information is subjected to statistical analysis using modern computer technology, which ensures the reliability and validity of the conclusions.

Any type of test is preceded by an experimental plan.

Because reliability is a probabilistic characteristic, quantitative ratings are used to estimate the “average reliability” calculated from samples of the entire population, as well as to predict future reliability. Reliability is examined using statistical methods and can be refined with their help.

It should be noted that service life is not the only indicator of performance properties.

In some cases, other indicators are used (mileage, duration of active use, etc.); The service life of products depends on both manufacturing conditions and operating conditions.

The reliability of many products can be revealed in the conditions of their consumption. A scientifically based system for monitoring the operation of products makes it possible to identify defects caused by violations of the manufacturer’s technological process.

The manufacturer must:

apply statistical quality control;

• – check the controllability state of processes at certain intervals;
• – strive to improve the quality and reliability of manufactured equipment;
• – ensure a correct understanding of customer requirements and their satisfaction.

An analysis of various definitions of reliability available in the literature leads to a generalized conclusion that reliability is understood as the failure-free operation of products under regulated operating conditions over a certain period of time.

Selective control. Characteristic feature control when studying reliability is that the possibilities of compiling samples are limited by the small number of pieces of equipment in the early stages of its development. As a rule, the number of units for testing is chosen by the customer. Moreover, the level of reliability of the test results varies depending on the number of units tested. The duration of the expected operating time and the degree of wear of the samples during testing have the same effect.

In practice, sampling for reliability testing is carried out in accordance with a plan that initially (and then each time a sampled product is characterized by a reduced mean time between failures) provides for a 10% consumer risk at an acceptable quality level corresponding to 10% of the units. with reliability below normal. Let us note some differences between statistical quality control and random checks in connection with technical reliability assurance. In the latter case, in addition to questions of sample representativeness, the question of the required test time arises.

Naturally, 100% testing of batches until the samples are completely worn out is impossible. Therefore, sampling schemes used in reliability studies provide for ongoing random testing of manufactured products with a weakened control regime until products with characteristics below the standard are detected. In other words, the weakened control procedure continues until a defective specimen appears in the sample. If a unit of manufactured products is detected with a characteristic lower than the norm, the normal control mode is restored, which can switch to an enhanced control mode depending on the number of defects identified in the sample. Typically, such sampling plans are developed taking into account a given mean time between failures and monthly production volumes.

When studying reliability, the method of sequential analysis is often used to decide whether to accept or reject a batch. First of all, it is determined that the mean time between failures under given conditions is at or above the established minimum. Such tests are planned after the specimens and test apparatus to be tested have been properly verified. Testing stops as soon as a decision on acceptance is made. But they do not stop if the decision is made to reject the batch. In the latter case, they continue in accordance with a precisely defined statistical control plan.

Failure is understood as the appearance of the first signs of malfunction or malfunction in the operation of the equipment. Each failure is characterized by a certain time of its occurrence.

The results of reliability research are important for the certification of products and quality systems Mazur I. I., Shapiro V. D. Quality management: textbook. allowance. M.: Omega-L, 2011.

Safety assessment of buildings and structures.

Technical inspection of structures makes it possible to establish their reliability at the time of inspection. However, to make a conclusion about further operation, establish the service life and repair of a structure, it is necessary to know the change in these properties over time. For example, if over time concrete structures retain their strength characteristics, then many new synthetic materials often lose their construction properties over a period of 10-20 years, which cannot be acceptable for permanent buildings and structures.

When operating structures, visual inspections are widely used to assess the technical condition of structures. For this purpose, there are methodological recommendations and tabular data for assessing the results of observations, which establish the reliability of the structures being examined based on external signs of their condition and damage assessment. More accurate data is obtained through instrumental measurements using various devices based on physical, radiological, electromagnetic and other influences.

As observations have shown, during the operation of structures there is a cyclic change in their reliability, which is associated with variability of loads and load-bearing capacity due to various damages.

Damage to a structure can be of two types depending on the reasons for its occurrence: from force effects and from environmental influences (temperature changes, corrosion processes, microbiological effects, etc.). The latter type of damage not only reduces the strength of the structure, but also reduces its durability.

Particular attention should be paid to the danger of terrorist influences, which have become relevant recently. The degree of protection from terrorist and other emergency impacts and the economic justification for protection measures should be determined depending on the significance of these objects for the life of the city (management facilities, etc.).

Forecasting emergency situations

An analysis of extreme situations in construction practice has shown that accidents are directly or indirectly related to violation of the requirements of the rules and regulations for the design and construction technology of buildings and structures.

Compliance with current norms and rules guarantees the reliability of construction projects under various natural influences and ensures human safety during their qualified operation. The probability of damage to these objects usually does not exceed 2.4 · 10-6, which is acceptable from the conditions of economic feasibility.

Risk assessment under emergency forecast conditions

The study of the causes of accidents served as the basis for assessing the possibility of the occurrence of conditions affecting the reliability of the structure. These conditions include the reliability of design solutions, quality of construction and operation.

Insufficient design reliability may arise due to:

• 1) inconsistency of the adopted calculation model with the actual operation of structures due to the absence or incomplete use of the requirements of design codes and standards, ambiguity of design schemes, incorrect definition of loads and operating conditions of the facility, as well as incorrect consideration of the resistance of load-bearing and enclosing structures to temporary and accidental influences;
• 2) insufficient verification and incorrect engineering assessment of the adopted design solution in real conditions (lack of experience in operating the designed buildings and structures, significant differences in the dimensions of the designed object and loads in comparison with previously constructed similar structures, etc.);
• 3) violations building codes and rules when performing design in terms of: completeness and reliability of engineering-geological studies, taking into account the aggressiveness of the external environment, errors in determining loads and impacts, incorrect tolerances for the manufacture of structures and products, low quality of materials, violations of construction methods and operating rules, etc.;
• 4) mistakes made due to the lack of sufficient experience and qualifications of designers, lack of time or funds for detailed design.

Poor quality construction of facilities can arise due to:

• - use of materials and structures that do not comply with the design;
• - low quality of construction and installation works;
• - use of unusual or untested construction methods;
• - poor control over the quality of construction, unsatisfactory interaction between designers and builders;
• - low qualification of production personnel or their frequent change;
• - unsatisfactory conditions at the construction site: lack of time, funds, poor staff relationships;
• - deviations from building codes and rules of construction practice during the construction of a structure, deviations from the original project;

Poor operation may occur due to:

• - loads exceeding the calculated design values;
• - lack of control over the condition of the structure and operation of the structure with unrepaired defects;
• - deviations from the rules of operation, use of the structure for other purposes.

The accident analysis showed that if any of the specified conditions are not met, an accident at the construction site is possible.

The probability of an accident is determined based on an analysis of space-planning and design solutions that affect the reliability of structures, the use of expert assessments, as well as calculated data or materials from field surveys.

The survey questionnaire, to which experts answer anonymously, contains a number of evaluation conditions, each of which has its own specific weight, with the total sum of all conditions equal to 1 (see Appendix 3). This appendix provides typical conditions for analyzing the reliability of a structure, taking into account design features and operating conditions.

In specific conditions, if necessary, a design reliability analysis can be carried out taking into account additional requirements, and the number of conditions can be increased or changed.

Each condition is assessed on a point scale and has five answer options: 1 (unacceptable), 2 (unsatisfactory), 3 (satisfactory), 4 (good), 5 (excellent).

The conditional reliability of a building or structure β is determined by the formula

Where R i - specific reliability assessment, obtained by multiplying the specific weight of the condition by the score.

The obtained values ​​for the structure are compared with the reliability rating scale (Table 6.1).

Table 6.1. Scale for assessing the reliability and probability of accidents of structures based on expert assessments

Although determining the susceptibility of structures to an accident using the above method can be done quite approximately, the advantage of this method is that it is less dependent on subjective assessments.

For a more reliable assessment of the reliability of the structure and identification of possible emergency situations, an inspection is carried out by several independent experts.

In case of an unfavorable forecast, additional measures are prescribed to check the reliability of the initial materials for design, the quality of design solutions, construction and operation processes in order to identify and eliminate the causes of a possible decrease in the degree of reliability of the facility.

In addition to expert assessments, the reliability of a structure design can be established from an analysis of the structure as a structural system consisting of individual structures connected to each other in a certain sequence and interacting with various events.

Construction experience has shown that different structural systems of structures with the same purpose may have different reliability, and accidents occur when one or more joint failures within the system lead to a dangerous situation.

The solution to the complex problem of identifying the failure of the entire system is carried out by simplifying it by constructing a so-called logical fault tree.

The fault tree is a graphical representation of the relationships between the initial failures of individual system elements and events leading to the occurrence of various emergency situations, connected by the logical signs “and”, “or”.

Initial failures are events for which there is data on the probability of their occurrence. Usually these are failures of system elements: destruction of structures and structural joints, various initiating events (personnel errors during operation, accidental damage, etc.).

Establishing the reliability of a structure begins with a preliminary analysis of hazards, which is then used when constructing a fault tree.

The analysis is carried out on the basis of studying the process of operation and operation of the structural system, a detailed consideration of environmental impacts, and existing data on failures of similar structures.

First, they determine what constitutes a system failure and impose the necessary constraints on the analysis. For example, they establish the need to take into account the intensity and frequency of earthquakes, equipment failures, consider only the initial failure of a structure (failure in start date operation) or failure during the entire service life, etc.

Then, system elements that can cause hazardous conditions are identified, for example, structures, joints, foundation soils and foundations of a structure, external triggering events, etc. At the same time, they raise the question of what will happen to the system if any of the elements fails.

In order to obtain a quantitative assessment of reliability using a fault tree, you need to have data on the original failures. This data can be obtained on the basis of operating experience of individual construction projects, experiments and expert assessments of specialists.

The construction of a fault tree is carried out in compliance with certain rules. The top of the tree represents the final event. Abstract events are replaced with less abstract ones. For example, the event “oil tank failure” is replaced by the less abstract event “tank destruction”.

Complex events are divided into more elementary ones. For example, “tank failure” (Fig. 6.1), which can occur during its service life, is divided into failure during the test stage and failures in the first and subsequent 10 years of operation. This separation is caused by various causes of failure: the initial reliability of the structure and the accumulation of damage as a result of long-term operation.

Rice. 6.1. Failure tree of a steel oil tank during operation

When constructing a fault tree, for the purpose of simplification, events with very low probability are usually not included.

A quantitative indicator of system failure is the probability (Q) of one failure occurring during the accepted service life. System reliability ( R ) is determined by the expression

If a system consists of i elements connected using the "or" sign, its failure will be defined as

Where q, - probability of failure of the i-th system element.

At small value q i formula (6.3) can be approximately expressed as

For a system or subsystem of i elements connected by the sign “and”, the failure will be

Thus, the study of the reliability of structural systems allows us to solve several problems that are important for practice: qualitatively assess the reliability of a designed construction project and, in case of increased danger, implement measures to increase it, determine the relative reliability of a structure during design for various variants of structural schemes, quantitatively assess the reliability of structures and safety environment.

Determination of expected damage and destabilizing factors

Expected damage from natural and man-made impacts depends on two main destabilizing factors:

• - intensity and frequency of natural and man-made impacts on buildings and structures;
• - engineering (quantitative) knowledge about the resistance or protection of construction sites and residential areas from the destructive effects of man-made and natural phenomena.

The algorithm for calculating and assessing the economic consequences of the expected impacts is as follows.

For natural influences:

• - determine the scientifically substantiated possibility of the occurrence of destructive natural phenomena in the territory under consideration that can cause damage to engineering structures (transport communications, hydraulic engineering and energy facilities), industrial and civil facilities;
• - assess the probability of occurrence of each type of natural impact, their intensity and frequency of recurrence;
• - determine the state of the soil environment and establish the strength characteristics of load-bearing and enclosing structures;
• - perform a complex of analytical work and engineering calculations to determine the reliability of foundations and the resistance of building structures to loads arising from natural and man-made impacts during the design period of operation;
• - carry out work to strengthen the structures of buildings and structures, if necessary, to change transport communications schemes (for example, in avalanche-prone areas or mudflow areas) and other necessary solutions.

For technogenic impacts:

• - determine the possibility of man-made accidents and the likelihood of their occurrence;
• - assess the impact of man-made accidents on the environment and the safety of the population;
• - consider the possibility of preventing or preventing man-made impacts;
• - carry out work on the reconstruction and modernization of the facility to increase the level of safety and reliability of potentially dangerous facilities;
• - develop measures to localize the impact of the accident on the environment and to protect the population and production personnel.

Based on the expected impacts and determination of possible damage and destruction of construction sites and the harm caused environment the estimated values ​​of damage and losses are calculated, both in the area of ​​economic losses and in matters of health and livelihoods of the population. In this case, recommendations and conclusions can be of a restorative nature or reconstruction and modernization, as well as a fundamental change in the structure of the region’s economy and even relocation of the population from areas with serious dangers and damages that are not economically feasible to develop (for example, in areas of strong earthquakes, constant floods and avalanches ). Qualified analysis and serious public debate must be carried out on a case-by-case basis.

Development of measures to improve the reliability of construction projects and the life of the population

To ensure the reliability of construction projects, the strength characteristics of buildings and structures must be determined and compared with all types of loads and impacts that may arise during the design period of operation.

If insufficient stability and load-bearing capacity of construction objects is detected in relation to existing loads and impacts, the following types of work must be performed:

• - examine, using instruments and tools, all objects whose reliability raises doubts or concerns;
• - determine the strength characteristics of load-bearing structures and assess the condition of foundation soils, taking into account their behavior under vibration and other loads that can reduce the stability of the soil environment or cause damage to foundations;
• - develop a strengthening or reconstruction project that excludes damage or destruction of the object or loss of its overall stability under possible and expected loads and impacts in emergency situations;
• - in accordance with the developed project, they carry out the necessary complex of strengthening or reconstruction of the construction site;
• - carry out strict quality control of construction and installation works, taking into account the increased requirements provided for by the norms and standards for areas with high loads and impacts;
• - when performing construction and installation work, it is necessary to require a quality certificate for the materials and structures used with guaranteed durability during the estimated period of operation of the facilities;
• - acceptance into operation of a strengthened or reconstructed facility is carried out in accordance with norms and standards in accordance with project materials and actual performance data;
• - develop recommendations for the operation of buildings and structures, taking into account ensuring their reliability and durability under maximum design loads and impacts during the standard period.