Comprehensive Assessment of Quality of Technological Processes in Construction

A technique is proposed for determining a comprehensive indicator of the quality of technological processes in construction. The implementation of the methodology is considered on the example of the process of excavation at the site, using statistical methods of product quality control and data analysis of acceptance control of work.


Introduction
Official statistics of the Russian Federation indicate a large increase in the number of construction accidents. According to the analysis, about 70% of accidents in construction are associated with various kinds of defects, materials used, errors of participants in the investment construction project.
The direction of scientific and methodological research in the field of improving technology and the organization of construction work in order to increase their efficiency and quality was determined by the works of domestic scientists: Afanasyev A.A., Afanasyev V.A., Bulgakov S.N., Golovnev S.G., Gusakov A.A., and others.
Foreign researchers also made a significant contribution to the development of the theory of reliability of building structures. A review of contemporary literature and a critical analysis of publications [1][2][3][4][5][6][7][8].
In the scientific literature on the problem of the effectiveness of quality management systems in construction, the proposed methods and indicators were reduced, as a rule, to the definition of savings by reducing the overhead of eliminating waste [9][10][11][12].
Studies have shown that construction control is carried out without the use of quantitative indicators, justification of the scope of control. [13 -15] In this regard, insufficiently informative control results are not a complete basis for assessing the compliance of construction and installation works (CIW) and the construction site as a whole with the established requirements.
The problem arises of the imperfection of the methods of monitoring and assessing the quality of construction of civil buildings, taking into account the level of the system for ensuring the quality of construction, accuracy of technological processes and safety indicators.
This study was aimed at the economic feasibility and development of a method for determining a comprehensive quality indicator (CQI) of technological processes in construction, affecting the economic efficiency and competitiveness of the construction industry as a whole.

Materials and methods
The goal of the work is achieved by applying statistical methods for controlling the quality of construction products based on data from the analysis of acceptance control of works, legislative and regulatory acts [16,17].
The study examines the excavation work on the site during the development of excavations and the construction of natural foundations. The control method of this process is a measuring one. Deviations of indicators during the normal course of the technological process should be within the technical limits determined by the norms. The list of indicators of operational control of various construction works can be found in SNiP and GOST [18][19][20][21].
We will consider xquantitative indicators (measured CIW) and T ithe value of the permissible deviation of the indicator from the norm.
We take the following dependence of the production of CIW (К) on the controlled indicator (х) in the form: If the control volume is specified for the indicator and is equal to n, then the indicator itself takes on values x 1 ,x 2 ,…x n . Then the quality of production of CIW (К) from the controlled indicator (х) is presented in the form: K СНИП =min{K 1 ,K 2 ,K 3 ...K n } (3) where K i -a value determined by the same dependence of the quality of production of CIW (К) on the controlled indicator (х). In this case, the value of К will be found by the following formula: where x max -a value as far as possible from the origin. Thus, if one measurement is made for each particular quality indicator, then calculation (4) is used, where K i is the value of the particular quality value. If the indicator х k is determined at which the minimum is realized, this means that the К-th condition of SNiP is poorly fulfilled.
Using the method of analysis of hierarchies, it is possible to present a complex quality indicator with a value equal to (5): K=α 1 K 1 + α 2 K 2 +...+ α n K n (5) α 1 + α 2 + ...+ α n Where (α 1 + α 2 +...+ α n )a priority vector of quality properties of construction products (a i ≥ 0). The method of pair wise comparisons known in the literature is used to find it [20]. So, it is possible to assess individual quality indicators of CIW by the required number of groups of criteria. We take the number of criteria equal to 3, the lowest level of the hierarchy are the components of the priority vector a i=1,2,3 . The matrix itself will have the property of inverse symmetry, where a ij = 1/a ij , where а ij = V i /V j . K 1 , K 2 …K n -the set of n elements (alternatives) and V 1 , V 2 ,...,V n -their weights, respectively. Let us compare the weight in pairs, of each element with the weight, or of any other element of the set with respect to their common property or purpose (in relation to the element -the parent).
To get each matrix, the expert makes n-(n -1)/2-judgments (here n -Thus, the matrix of pair wise comparisons [К] has the form: Matrix filling rule: If the element K 1 dominates the element K 2 , then the cell of the matrix corresponding to row K 1 and column K 2 , is filled with an integer, and the cell corresponding to row K 2 and column K 1 is filled with the inverse number to it. If the element K 2 dominates K 1 , then the integer is put in the cell corresponding to row K 2 and column K 1 and the fraction is put in the cell corresponding to row K 1 and column K 2 . If the elements K 1 and K 2 are equally preferable, then units are put in both positions of the matrix.

Results
This section presents the testing of the proposed methodology. Table 1 presents the data of indicators of acceptance control of drainage channels. The presented quantitative indicators x i can be attributed to the CIW, property, namely, to the accuracy of the CIW.
According to the calculations, the matrix of pair wise comparisons of CIW during the construction of drainage systems will take the form:

K=
As a result of the calculations, the values of the components of the priority vector were obtained: A i=1 = α 1 = 0,6. A i=2 = α 2 = 0,3. A i=3 = α 3 = 0,1. Thus, knowing the values of the criteria K 1 , K 2 and K 3 , a comprehensive indicator of the quality of excavation works (К СМР ) can be expressed through unit quality indicators for individual properties (6).
The value of a single indicator of quality K 2 = min {0,34, 0,90} = 0,34. Similarly, we obtain the value of K 3the property of environmental friendliness of production. We take two quantitative indicators: П1 and П2 -respectively, the maximum permissible content in the soil of harmful impurities of the 1st and 2nd substance.
The value of a single indicator of quality K 3 = min{0,81, 0,95} = 0,81. Thus, a comprehensive quality indicator (CQI) of CIW in this area is: K CIW = α 1 K 1 + α 2 K 2 +...+ α n K n =0,6×0,50+0,3×0,34+0,1×0,81=0,3+0,102+0,081=0,483. If for some characteristic х the boundaries 0≤x≤T 1 , are set, then a particular quality criterion can be set in the form K=1-x/T i . The given dependence shows that the maximum quality value will be equal to 1, which is achieved when the construction and installation work is ideally performed; the minimum quality value is 0 if the measured indicator assumes an unacceptable value. If on one building object the measured value of the quality characteristic is x=x 1 , and on another building object the measured K 1 K 2 K 3 K 1 1/1 2/1 6/1 K 2 1/2 1/1 3/1 K 3 1/6 1/3 1/1 IOP Publishing doi:10.1088/1757-899X/1079/3/032095 5 value of this characteristic is x 1 <x 2 <T 1 , then follows from the functions K 1 =1-x 1 /T 1 and K 2 =1-x 2 /T 2 and K 1 >K 2 , i.e. quality indicators are ordered and this is a very important circumstance, since it is not necessary to know the exact quantitative value of the quality parameter and can be determined by pair wise comparing the quality of construction and installation works at the facilities under construction.
The obtained indicator has a value below the average, which corresponds to a rejection level of quality; measures are needed to improve the accuracy of technological processes, in order to achieve the calculated values of the indicators and guaranteed product strength.
Improving accuracy can be achieved by replacing design and survey work, changing and improving the methods of work, tooling, replacing suppliers of products, improving the skills of performers, strengthening control, etc.

Discussion
Building norms and rules contain their own criteria for the admissibility of certain quality attributes, which are set in the form of certain tolerance limits for the measured quality attributes. The paper proposes particular quality criteria for individual features.
The above calculations determine the function of the resulting quality, depending on all measurements made in the form of certain algorithms.
The diverse groups of properties of CIW can be described by different quantitative indicators. For example, indicators of the strength of materials, loads, and possible deviations from design schemes can be used to describe the reliability properties of CIW. This property is especially important in the process of performing CIW, as these values can vary within wide limits. There are indicators for the environmental friendliness of CIW -these may be the so-called MPC norms (maximum permissible concentrations of harmful substances in building materials).
As for the further development of the problem under study, the work done and the results obtained will allow us to determine the main directions of further research in the field under consideration, namely, further improvement of the theory and practice of multicriteria analysis of organizational and technical solutions of construction production, further development of expert assessment methods for the level of quality of construction production.

Conclusion
The considered example focused on the universality of the approach, the possibility of conducting a qualitative analysis of technological processes in the face of uncertainty, determining the level of quality in construction and as a consequence of its competitiveness.
The research results can be applied by industrial enterprises in solving problems in the field of improving the theory and practice of certification of products, production processes, operation, storage, transportation, sale, disposal, work, services, quality management systems and other processes of construction production.