by Abstract: from the perspective of general construction contracting, this paper selects 20 influencing factors of precast construction cost from the three aspects of component procurement, component transportation and construction and installation through literature induction, analyzes the influencing factors by entropy weight matter-element extension evaluation method, and determines the component supply relationship, component procurement mode, transportation distance Component transportation protection, vehicle type, secondary handling, coordination level between types of work, project management level and construction quality are the factors that affect the cost of precast construction, and put forward relevant countermeasures and suggestions for the above influencing factors.
Since the general office of the State Council issued the guidance on vigorously developing precast buildings in 2016, the industrialization of new buildings represented by precast buildings has been promoted rapidly, and the construction level and quality of industrialized buildings have been significantly improved.
From 2016 to 2019, the newly started area of precast buildings showed a rapid growth momentum.
In 2019, the new construction of precast buildings in China will reach 420 million m2, driving social investment of nearly 3 trillion yuan.
However, there are still many problems in the development of precast buildings in China, such as high cost, immature precast technology, lack of standards and specifications and so on.
Among them, the direct impact on the development of precast buildings is the high cost.
In the past, most scholars analyzed and studied the influencing factors of precast building cost from the whole process or construction process of precast building.
From the perspective of general construction contracting, this paper uses entropy matter-element extension to evaluate the influencing factors of precast construction cost from three aspects: component procurement, component transportation and construction and installation.
1 Analysis of influencing factors of general contracting cost of precast building construction in order to identify the influencing factors of general contracting cost of precast building construction, learn from previous research results, identify the cost influencing factors through literature induction, and establish influencing factor indicators in component procurement, component transportation and construction installation.
1.1 influencing factors of component procurement cost in the procurement process of precast components, the change of component price, the change of component market supply and demand, the selection of suppliers, as well as the component procurement mode and component supply time will lead to the change of component procurement cost.
1.2 factors affecting the transportation cost of components in the transportation process of precast components, the transportation distance between the component factory and the construction site, the vehicle type selected in the transportation process and the selection of transportation route.
In addition, the transportation protection and transportation loading efficiency of components will cause changes in the transportation cost of components.
1.3 influencing factors of component construction and installation cost during component construction and installation, secondary handling cost of components and loss of components caused by handling, component storage and maintenance, suitability of hoisting machinery and equipment, hoisting efficiency, cooperation level between types of work, technical level of installation workers, project management level, construction sequence and process, construction progress Construction quality and engineering safety will cause changes in component construction and installation costs.
1.4 list of factors affecting the cost of precast buildings according to the above analysis, the list of factors affecting the general contracting cost of precast buildings is shown in Table 1.
The establishment of entropy weight matter-element extension model, using analytic hierarchy process, interpretation structure model and other evaluation methods, inevitably has subjective problems.
This paper uses entropy weight matter-element extension model to evaluate the cost influencing factors, which is objective and reasonable.
In the evaluation process of multi-objective factors, the weight of evaluation indicators occupies an important part.
In the constructed evaluation index system, it is generally an objective level index.
The influence of subjective factors on the weight of each index should be avoided as far as possible to make the evaluation results more reliable.
The entropy weight matter-element extension is used to determine the index weight.
2.1 entropy weight method entropy represents the disorder degree of the system, and entropy weight represents the amount of useful information carried by each index.
The greater the entropy weight, the more useful information it carries, the greater the role of the index in the comprehensive evaluation, and the higher the index weight, and vice versa.
In recent years, information entropy theory has been preliminarily applied to the fields of engineering structure reliability analysis, financial risk analysis, surrounding rock stability analysis and engineering project management.
In this paper, the entropy weight method is used to determine the index weight.
The specific formula is as follows: (1) normalize the evaluation index matrix: where Xij is the scoring of J indexes by the ith individual participating in the evaluation, I = 1,2,3…, m, M is the number of people evaluated, J is the influencing factor index, and xmax and xmin are the highest and lowest scores of the index score.
(2) The entropy Di of the influencing factors of precast construction cost is: 2.2 matter-element extension model.
Matter-element extension model is a direct problem-oriented mathematical method.
In matter-element analysis, let matter-element m, the characteristic of matter-element m is C, and the corresponding eigenvalue is x, which is called the three elements of matter-element R.
That is, r = (m, C, x).
According to the setting of matter-element, in the matter-element system, matter-element combines things, features and quantitative values.
Both quantity and features should be considered when dealing with problems.
In this paper, the influencing factors of precast construction cost are the matter-element we discuss..
