3.1. Extraction of influencing factors based on literature review method
Keywords such as influencing factors of construction period, construction period and delay factors are searched in web of science, Google academic, CNKI and other databases. We selected the relevant literature in recent ten years and made statistics from the five dimensions of design, management, technology, policy and environment, so as to remove the factors that appear too few times. The influencing factors of construction period are preliminarily sorted out. However, there are still some subordinate and inclusive relationships among these factors, which need to be further sorted and classified. In order to ensure the scientific rationality of factor induction, the authors organized a research group, whose members are graduate students in engineering management in universities. The research group studied and discussed the influencing factors of induction. At the same time, some factors with strong inclusion and subordination were reorganized are combined into a capital chain, the lack of skilled workers is included in the shortage of human resources. Finally, 24 independent influencing factors were determined.
3.2. Determination of influencing factors based on questionnaire method
Since the premise of the study in this paper is a resource sufficiency condition, the factors affecting the schedule due to the constraint of resource limitation must be excluded. Therefore, the influencing factors must be further screened and identified. In this paper, a questionnaire is drafted by means of a questionnaire survey. The content of the questionnaire is divided into three parts. The first part is the basic information background of the respondents. Because the respondents' working years, education level and work unit directly affect their understanding of the factors affecting the construction period, it is necessary to clarify the basic information of the respondents. The second part is the questionnaire of influencing factors of construction period, which requires it to confirm and identify the influencing factors under the condition of resource sufficiency, in the form of the Likert level five scale. The respondents are required to score according to the importance of 1 ~ 5. The third part is the subjective question, which is used to collect the respondents' other opinions on the influencing factors.
A total of 160 questionnaires were distributed and 123 were recovered, of which 98 were valid, and the effective recovery rate was 61.25%. SPSS 25.0 was used to calculate the reliability coefficient of the data to ensure the reliability of the questionnaire. The test results are shown in Table 1. The reliability coefficient α = 0.763 > 0.7, which indicates that it meets the requirements of reliability test and the reliability of the questionnaire is high. After that, the whole sample is statistically analyzed to calculate the sample mean and standard deviation of each factor. The mean value represents the overall evaluation of the importance of factors by respondents in the questionnaire. And the standard deviation indicates the consistency of different respondents' views on factors. The smaller the standard deviation, the better the consistency. The 25 factors are sorted according to the mean value of the factors, and Table 2 is obtained. It can be seen from the table that some factors have little impact on the construction period under the condition of sufficient resource and should be screened out. Therefore, the average value of 3 is considered as the benchmark for factor screening, and the factors lower than 3 points are eliminated, and finally 17 influencing factors are obtained. In order to comprehensively analyze the different properties of factors, 17 factors are divided into five categories: project itself, management, logic, environment and organization. The specific factors and their classification are shown in Table 3.
Table 1
The reliability test results.
Reliability Statistics
|
Cronbach's Alpha
|
Cronbach's Alpha based on standardization term
|
Number of items
|
0.763
|
0.796
|
25
|
Table 2
The average value of the factors.
influencing factors
|
Average
|
Construction safety organization
|
3.867
|
Contractor management level
|
3.714
|
Maximum construction work surface
|
3.622
|
The management level of the owner
|
3.612
|
Natural environment
|
3.592
|
Competence level of consultants
|
3.551
|
Designer's capability level
|
3.520
|
Construction technology
|
3.500
|
Social environment
|
3.469
|
Articulation of materials or devices
|
3.408
|
The connection of construction process steps
|
3.408
|
Management level of the supplier
|
3.378
|
Political environment
|
3.286
|
Total number of floors
|
3.082
|
Function
|
3.051
|
Structure type
|
3.010
|
Total floor area
|
3.008
|
Engineering construction standards
|
2.969
|
Labor disputes and strikes
|
2.082
|
Estimated construction cost
|
1.582
|
Equipment
|
0.541
|
Material
|
0.531
|
Financial chain
|
0.520
|
Labor
|
0.520
|
Table 3
Influencing factors of the minimum construction period under sufficient resources.
Constraint Type
|
influencing factors
|
Previous literature
|
project itself
|
Total floor area(S1)
|
30,31
|
Total number of floors(S2)
|
30,31
|
Function(S3)
|
23
|
Structure type(S4)
|
23
|
management
|
The management level of the owner(S5)
|
32–34
|
Contractor management level(S6)
|
8,13,15,33,35−38
|
Designer's capability level(S7)
|
13,15,32,35−37
|
Competence level of consultants(S8)
|
15,23,33,37
|
Management level of the supplier(S9)
|
33,37,39
|
logic
|
Construction technology(S10)
|
15,32,40
|
Maximum construction work surface(S11)
|
41,42
|
environment
|
Political environment(S12)
|
15,32,33,43
|
Natural environment(S13)
|
23,35,43
|
Social environment(S14)
|
13,15,33
|
organization
|
Articulation of materials or devices(S15)
|
13,15,32,33,35,37
|
The connection of construction process steps(S16)
|
13,15,33,35,37,44
|
Construction safety organization(S17)
|
32,34,45
|
3.3. Explanation of influencing factors
1. Total floor area: It is the sum of the floor area of single or multiple buildings above and below the ground level within the construction site.
2. Total number of floors: It is the sum of the number of strata and the number of strata above the ground.
3. Function: To meet the specific purpose and use requirements, it includes space composition, functional partitioning, human flow organization, evacuation, etc.
4. Structure type: It refers to both the load-bearing structure and the enclosure structure of its building. The durability, seismic resistance, safety, and space use performance of houses of various structures are different.
5. The management level of the owner: In the process of project construction, the embodiment of the owner's management ability depends mainly on the size, quality, and structure of the owner's team.
6. Contractor management level: In the project construction process, the contractor's management capability is reflected mainly in the size, quality, and structure of the contractor's management team.
7. Designer's capability level: The degree of mastery and experience of the designer's expertise in the field of architectural design.
8. Competence level of consultants: In the process of project construction, the manifestation of the consultant's management ability depends mainly on the size, quality and structure of the consultant's management team.
9. Management level of the supplier: In the process of project construction, the embodiment of the supplier's management ability mainly depends on the scale, quality and structure of the supplier's management team.
10. Construction technology: Construction techniques for each major type of work in the construction of building projects.
11. Maximum construction work surface: It refers to a certain floor, part, or location on the construction object where workers may be arranged and machinery arranged and is used to reflect the maximum possibility of the construction process to arrange production elements in space.
12. Political environment: It refers to the external political situation of the engineering construction project, the national policy, and its changes.
13. Natural environment: It refers to the environment formed by natural things such as water, soil, region, and climate.
14. Social environment: It refers to the network of relationships between the organization and various publics, including collaborative relationships between parties, coordination of relationships with governmental publics.
15. Articulation of materials or devices: When a process starts during construction, the corresponding materials or equipment can be in place, i.e., the coordination of equipment or materials.
16. The connection of construction process steps: After the end of a certain process in the construction process, the latter process can follow in time, i.e., the coordination of the various steps and processes of construction.
17. Construction safety organization: It covers all security aspects of the operation and involves management, finance, and logistics.