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In view of the poor performance of the original mathematical model of assembly construction project precost budget, a mathematical model of assembly construction project precost budget based on improved neural network algorithm is proposed. This paper investigates the cost content of assembly construction project and analyzes its early cost. It finds that the early cost of assembly construction project includes component production cost, transportation component cost, and installation component cost. Based on the improved neural network algorithm to build an improved neural network model, the improved neural network model to mine the cost data in the early stage of assembly construction project is used. In this paper, the earned value variable is introduced to transform the project duration and project cost in the early stage of the prefabricated construction project into quantifiable cost data, and the earned value analysis method is used to estimate the implementation cost of the prefabricated construction project. According to the result of cost estimation, the mathematical model of precost budget of prefabricated construction project is built based on the project parameters. In order to prove that the cost budget performance of the mathematical model based on the improved neural network algorithm in the early stage of assembly construction project is better, the original mathematical model is compared with the mathematical model, the experimental results show that the cost budget performance of the model is better than the original model, and the cost budget performance is improved.

In traditional construction projects, the pouring of concrete mainly adopts manual scaffolding, formwork supporting, and binding of steel bars at site. However, such kind of cast-in-place can cause a variety of problems, including making construction site in a mess, generating lots of construction waste, and polluting the surrounding environment [

Under the trend of urbanization, people have put forward higher requirements for environmental protection and energy-saving performance of buildings. Therefore, prefabricated buildings are getting popular, have achieved rapid development in China, and promoted the improvement of the installation quality and component precision of prefabricated components [

As found in the cost analysis in early stage of the prefabricated construction project, the preliminary cost of prefabricated construction project includes component production cost, component transportation cost, and component installation cost. Among them, statistics found that component production cost contains labor cost, material cost, mold cost, amortization expense, cost of setting the embedded parts and pipelines, management and storage cost, and water and electricity charges. The specific contents are shown in Table

Component production cost.

No. | Name of cost | Content of cost |
---|---|---|

1 | Labor cost of component production | Higher salaries shall be paid to professional workers |

2 | Material cost of component production | Basically the same materials as required by the traditional construction method |

3 | Mold cost of component production | Cost of table molding, binding steel bar mold, concrete pouring mold, maintenance mold, and finished component mold |

4 | Amortization expense | Amortization fee based on specific types of components and specific quantities of molds |

5 | Cost of setting the embedded parts and pipelines | Costs incurred in arranging the embedded parts and pipelines in the installation components, mainly the pipeline costs |

6 | Management and storage cost | Additional management and storage costs after maintenance of component productions |

7 | Water and electricity charges | Electricity and water charges incurred by factory component production |

Component transportation cost covers the cost of transporting components from the factory to the construction site, which is directly related to the size and weight of the components, as well as the distance between the factory and the construction site [

Component installation costs involves the cost of vertical component transportation, labor cost of component installation, machinery cost of component installation, material cost of component installation, cast-in-place cost, and amortization cost, as shown in Table

Component installation cost.

No. | Name of cost | Content of cost |
---|---|---|

1 | Cost of vertical component transportation | Cost of vertically hoisting components |

2 | Labor cost of component installation | Higher labor salaries shall be paid because the vertical hoisting of components requires higher professionalism and proficiency. |

3 | Machinery cost of component installation | The cost generated by using machinery equipment during component installation |

4 | Material cost of component installation | Costs incurred by filling materials and connectors |

5 | Cast-in-place cost | Cast-in-place cost for assembly |

6 | Amortization cost | Amortization cost of tools |

As shown in the analysis of cost budget in early stage of prefabricated construction project, an improved neural network model is built based on the improved neural network algorithm so as to conduct data mining on the cost budget in early stage of prefabricated construction project [

First, the improved neural network is initialized:

The specific output of the hidden layer is computed: the specific output of the hidden layer is obtained based on the specific input variable

In formula

The specific output of the input layer is computed: the specific output of the input layer is obtained according to the specific output

In forrmula

Error calculation: the specific error of the improved neural network is predicted based on the specific output of the input layer and the specific expected output

The neuron connection weight

Threshold updating: the thresholds

The construction of improved neural network model is realized and the data mining on the cost in early stage of prefabricated construction project is performed on this basis [

Based on the data mining of cost in early stage of prefabricated construction project, a variable called earned value is introduced to convert the project duration and project cost in early stage of prefabricated construction into quantifiable cost data. Meanwhile, the cost in early stage of prefabricated construction project is estimated through the earned value analysis so as to carry out the cost budget of prefabricated construction project [

In formula

For the analysis by using the earned value, the difference variables of two analyzes must be obtained at first, including schedule deviation and cost deviation. Their calculation formulas are separately as follows:

In formula

In formula

Along with two variable indexes, including performance progress index and performance cost index, the calculation formulas are as follows:

In formula

In formula

The data of the cost budget of completed project volume, the specific cost of completed project volume, and the cost budget of planned project volume are added separately [

According to the estimated cost in the early stage of prefabricated construction project, the mathematical model of cost budget in early stage of prefabricated construction project is constructed based on project parameters. The items of material budget in early stage of prefabricated construction project are shown in Table

Items of material budget in early stage of prefabricated construction project.

No. | Items of material budget | Unit |
---|---|---|

1 | Prefabricated PC wall components | Cubic meter |

2 | Prefabricated PC floor (laminated) components | Cubic meter |

3 | Prefabricated PC stair components | Cubic meter |

4 | Prefabricated PC balcony components | Cubic meter |

5 | Prefabricated PC air conditioning panel components | Cubic meter |

6 | Prefabricated PC beam components | Cubic meter |

7 | Rebar B300HR(D < 25) | Ton |

8 | Screw-thread steel B225HR(D < 12) | Ton |

9 | Concrete C30 (premixed) | Cubic meter |

10 | Concrete C35 (premixed) | Cubic meter |

11 | Fine stone concrete C20 (premixed) | Cubic meter |

12 | Aerated light sand autoclaved block concrete | Cubic meter |

13 | Specialized component grouting | Ton |

14 | Remaining self-purchased materials (estimated value) | — |

The items of labor cost budget in early stage of prefabricated construction project are shown in Table

Items of labor cost budget in early stage of prefabricated construction project.

No. | Items of labor cost | Unit |
---|---|---|

1 | Manual cleaning of foundation pit | Cubic meter |

2 | Manual lashing of cast-in-place and steel bar making | Ton |

3 | Manual assembly and wooden template making | Cubic meter |

4 | Manual maintenance of cast-in-place and concrete pouring | Cubic meter |

5 | Manual installation of prefabricated PC components | Cubic meter |

6 | Tower crane driver, surveyor, and bell man | Cubic meter |

7 | Manual masonry | Cubic meter |

8 | Manual water resistance | Cubic meter |

9 | Manual fitment | Cubic meter |

The items of machinery budget in early stage of prefabricated construction project are shown in Table

Items of machinery budget in early stage of prefabricated construction project.

No. | Name | Unit | Type |
---|---|---|---|

1 | (Tower) crane | Set | ST50/20 |

2 | Car crane | Set | 26T |

3 | Material hoist | Set | SES160 |

The project parameters are described according to the type of project, in which the parameter of production progress in the early stage of prefabricated construction project is set to

The production process in early stage of prefabricated construction project can be summarized as follows: the first if component production, followed by component assembly and transportation. In this way, the cost in early stage of prefabricated construction project includes construction production cost, component assembly, and transportation fee [

In formula

The experiment of cost budget in early stage of prefabricated construction project is carried out by using the mathematical model of cost budget in early stage of prefabricated construction project designed based on improved neural network algorithm. With a total area of 920 square meters, the prefabricated construction project in this experiment contains 14 floors in prefabricated structures of assembled shear wall. The prefabricated component nodes are manufactured by secondary cast-in-place. The outer wall of the building is made of prefabricated thermal insulation Sandwich panel; the floor is made of concrete prestressed composite slab; the load-bearing wall is made of shear prefabricated wall panel; the staircase is prefabricated; the inner partition wall is made of lightweight wall panel. The prefabricated parts involved in this prefabricated construction project are listed as follows: prefabricated parts for stair, prefabricated parts for laminated panel, prefabricated parts for partition wall, shear wall, etc. Considering that it is a prefabricated construction project, all the prefabricated parts are produced at the prefabricated production base and then transported to the construction site after maintenance. Meanwhile, the transportation and production of prefabricated parts for different places and floors are arranged separately according to the specific project progress.

The specific building parameters of this prefabricated building project are shown in Table

Specific building parameters of this prefabricated building project.

No. | Name of building parameters | Specific parameters |
---|---|---|

1 | Height | 40 m |

2 | Floors | 14 |

3 | Structure type | Prefabricated structure of assembled shear wall |

4 | Specific floor height | 3.6 M at 1^{st} floor^{nd} to 14^{th} floor |

5 | Covered area | 920 m^{2} |

6 | Seismic grade | 4.0 magnitude |

7 | Seismic intensity | Scale 6 |

8 | Specific flame resistance | Level 2 |

9 | Specific waterproof rating | Level 2 |

11 | Specific type of prefabricated part | Shear wall |

12 | Building nature | Residence |

13 | Plan view size | 15 × 40 |

14 | Waterproof condition (roofing) | Composite SBS waterproof |

15 | Production materials such as windows and doors | High quality aluminum alloy |

The specific contracting situation of this prefabricated construction project is shown in Table

Specific contracting situation of this prefabricated construction project.

No. | Items | Specific situation |
---|---|---|

1 | Specific project name | Project of Fuligang building #2 |

2 | Construction company | Haoqiang Real Estate co., ltd |

3 | Design contractor | Yicai Architectural Design co., ltd |

4 | Supervision company | Keli Supervision Construction co., ltd |

5 | Construction organization | Risheng Engineering Cconstruction co., ltd |

6 | Quality supervision organization | Yihe Engineering Quality Supervision co., ltd |

7 | Total project cost | RMB 12.6 million |

8 | Contracted form | Contract for labor and material |

9 | Contract scope | Decoration, main body, foundation |

10 | Planned schedule | One year |

11 | Overall quality goal | Good in quality |

In this prefabricated construction project, all the floors are standard, and the early stage is set to a six-day construction period per floor. According to the building structure and engineering quantity, the construction sequence is arranged reasonably and the whole project is divided into three phases. The specific arrangements for the construction of each floor are as follows: hoisting 60 pieces of wall in the first construction phase, hoisting 60 pieces of wall in the second construction phase, grouting sleeve in the first construction phase, grouting sleeve in the second construction phase, hoisting 30 pieces of wall in the third construction phase, grouting sleeves in the third construction phase, binging steel bars with postcasting belts, reinforcing formwork with postcasting belts, erecting supportive frames, hoisting composite beams, hoisting stairs, hoisting of 60 pieces of composite slabs, hoisting 57 pieces of composite slabs, preburying hydropower and other pipelines, binding the upper stair reinforcement, supporting formwork joints, and pouring concrete. The cost budget in early stage of this prefabricated building construction is estimated through the mathematical model. In order to ensure the effectiveness and contrast of this experiment, the original mathematical model of cost budget in the early stage of prefabricated construction project is compared to the mathematical model of cost budget in the early stage of prefabricated construction project designed based on the improved neural network algorithm in this paper. Among them, the original mathematical model of cost budget in early stage of prefabricated construction project includes the mathematical model of cost budget in early stage of prefabricated construction project based on cost control, random function, and system dynamics. As learned from comparing the performance of different mathematical models of cost budget in early stage of prefabricated construction project, that is, from analyzing the cost budget accuracy of the experimental model, the higher the cost budget accuracy, the more reasonable the cost budget result of the prefabricated construction project and the better cost budget performance [

The result of comparative experiment on cost budget performance between the original mathematical model of cost budget in early stage of prefabricated construction project and the mathematical model of cost budget in early stage of prefabricated construction project designed based on the improved neural network algorithm is shown in Figure

Result of comparative experiment on cost budget performance.

According to the result of comparative experiment on cost budget performance between two different mathematical models, the mathematical model of cost budget in early stage of prefabricated construction project designed based on the improved neural network algorithm is better in cost budget accuracy. That means the cost budget performance of the mathematical model of cost budget in early stage of prefabricated construction project based on the improved neural network algorithm is superior to that of the original mathematical model of cost budget in early stage of prefabricated construction project.

The cost budget performance of the mathematical model of cost budget in the early stage of prefabricated construction project based on the improved neural network algorithm can realize the improvement of cost budget performance in the early stage of prefabricated construction project, which is of great reference significance to accurate cost budget of the overall prefabricated construction project.

Simulation data and our model and related hyperparameters used are provided within the article.

The authors declare that they have no conflicts of interest.

This work was supported by the Chongqing Municipal Education Commission Science and Technology Research Project (KJQN201904003) and research project of Chongqing Technology and Business Institute (ZD2016-04).