Cost optimization in the construction of prefabricated buildings by using BIM and finite element simulation

This paper uses patterned structure to study the efficiency improvement of the practical application of BIM technology, and innovates the patterned structure method based on this. The research focus of this paper is to build a new assembly component library based on BIM model and algorithm optimization, improve its use and management efficiency, and use the core technology to design the simulation analysis model of BIM in construction, and give timely feedback of experimental information. Analyze the existing assembly structure design process, design standards and design methods, propose a BIM-based assembly structure design method, change the design idea from the whole to the component elements, and use the design method for prefabricated components. Taking the W prefabricated component library as a starting point, select the prefabricated components of the component library for assembly design to form a BIM model with a complete structure. Adjust and optimize the BIM model, and finally form a reasonable design plan. This BIM type of product includes production, transportation and assembly construction. Prefabricated buildings have obvious advantages, its comprehensive benefits are higher than other buildings, and the technical content is relatively high, through innovative prefabricated buildings, the modernization level of the building can be improved. Therefore, on the basis of in-depth investigation and study of the development status of China's construction industry, this paper studies the impact of different factors on engineering costs, including engineering schemes, engineering construction modes, etc., based on a large number of actual engineering operations and application cases, so as to achieve the purpose of reducing cost costs, improving project income, and improving project quality.


Introduction
In recent years, China's economic development has entered a new stage of development, the quality of economic development continues to improve, at the same time, due to the deepening of China's urbanization construction has led to the expansion of China's engineering construction facilities, so improving the project cost information management of construction is of great significance to the current China (Lappe and Spang 2014). At present, under the guidance of the government, there are a large number of large-scale, complex structure and significant projects, and the existing engineering technology management methods are too inefficient to achieve the set goals. In modern engineering construction projects, the main goal is to improve construction progress, improve quality and reduce costs. Therefore, when using modern management methods to control the construction process and improve the quality of the project, we must do our best to improve the economic efficiency of construction and the application of technology and technology (Makarova et al. 2012). In this context, this paper uses engineering construction information technology combined with computer technology to deeply study BIM technology (Wong et al. 2014;Li et al. 2017). The wide application of BIM technology in the construction industry can improve the efficiency of project management and construction and promote the development of construction projects in China. On the other hand, the Chinese government has promulgated a large number of relevant project management policies, which have effectively promoted the development of construction projects (Forcada et al. 2013). With the leapfrog improvement of the level of science and technology, a large number of applications of science and technology in construction have promoted the development of the building information industry. This paper uses BIM technology to test the application effect in project engineering, which effectively promotes the development of engineering informatization (Khudhair et al. 2021). In addition, by 2020, China's BIM technology will be applicable to all major projects in China.

Related work
As the American BIM technology is widely used in the management of construction equipment projects, information management has improved the speed of project construction, the degree of savings, and greatly improved the efficiency of the project. In recent years, more than half of American construction projects have applied BIM technology (Zima et al. 2020). Literature proposed the national ''3D-4D-BIM'' project, ''BIM Handbook'' and so on. At present, more than half of the construction projects in the United States have adopted BIM technology. China's development of BIM technology is similar to that of the United States, and has formulated a development plan for building information models. With strong support from the government, the China Commune has guaranteed the smooth implementation of BIM technology (Tsai et al. 2014). In 2010, the newly developed BIM technology provided guidance for the application in project construction. Around 2016, BIM technology was promoted in construction projects in South Korea, achieving the goal of reducing project costs and improving management efficiency. The British BIM technology started late, but it has developed rapidly (Guo and Wei 2016). It requires the joint management of 3D-BIM construction projects. With the support and promotion of the government, BIM technology in Singapore has also been rapidly developed and applied. The Singapore government has also issued special economic incentive measures, established a BIM construction fund and issued relevant policies for the promotion of BIM technology, and vigorously promoted the application of BIM technology in terms of engineering technology (Song et al. 2019). In 2015, the application of BIM technology to engineering entities in Singapore has reached more than 80%. In recent years, construction projects in various countries have made great progress in cost management. At the same time, the theoretical results and practical experience of construction price control have been rapidly developed (He and Lin 2017). Relevant theories for comprehensive control of project cost have been widely popularized, and project cost control has gradually developed to an all-round development stage. For complex project fee management problems, it is necessary to find out the factors that affect the project cost and propose a solution using the Delphi Act (Landeta and Barrutia 2011;Sangaiah et al. 2018;Anni and Sangaiah 2018). The successful research and development of BIM series software realized the integration of construction project 3D model and cost management. BIM technology is mainly composed of BIM series software, and the model construction and data exchange of different software's should conform to IFC standards. For example, 3D building models, Office Project, and cost management software built by Autodesk are based on IFC standards and integrate model information and management information under the conditions of mutual integration (Zhang et al. 2015). At the same time, for different majors, such as electrical, HVAC, and construction, the model information conversion is realized through the platform. BIM technology realizes the monitoring of project execution process and the synchronous management of 3D mode, and successfully completes the project progress management of BIM technology (Zhang et al. 2018). Scholar Alvarado and others analyzed BIM technology and its function, analyzed the method of BIM technology for project management, established AEC ? FM structure, and provided model structure and implementation method for BIM project management (Xiao and Bhola 2022). It is based on the IFC standard and provides a specific process for project cost management in the basic construction stage of a physical project, and according to the corresponding objectives of project cost management, a detailed project cost and schedule joint management method is developed (García-Sánchez et al. 2019). Through the 3D model in the project design, the simulation of the construction site was realized.
3 Analysis and optimization of assembly structure BIM model The standardized universal modular components in the modular component library can quickly complete the predesign of the modular structure. The pre-designed BIM model needs to be analyzed and studied to meet the structural safety requirements. The pre-assembled collision detection can optimize the BIM model.

BIM self-optimization and sensor application
After the pre-made component library is completed, the BIM-based component structure feedback method will directly select components from the component library for structural design. Whether the model designed in advance by BIM can be used in subsequent production and construction should be discussed through analysis. Since the estimated component library is not complete enough to contain all the conditions, the stored components are selected through statistical analysis. Therefore, W cannot avoid the existence of estimated components that do not meet the specific engineering requirements. Analysis and inspection are to perform this work. Reviewing Northern Exposure is an important method to ensure structural safety. The analysis and deliberation are carried out in the state of the production elements before the design is completed, and the overall performance of the structure and the safety of the prefabricated components are ensured through inspection. Analysis and review will go through a process of structural design and an opposition. Calculate the internal force conditions based on the load action, such as torque, voltage, animal force, and review and compare them according to the specifications. The phrases used appear in the previous section. When studying the analysis, the pre-made components have been designed, so the relevant situation should be considered in the force interpretation, and the finite factor analysis method of fine adjustment should be considered, but in fact, the simplified finite factor calculation method can be considered. In this paper, a finite element analysis model is constructed, followed by a large number of data tests according to the model and finite element analysis of the experimental results. Finally, the analysis results of experimental data are compared with normative analysis to provide reference. The observation diagram clearly shows that the core technology for the conversion of BIM mode performs a large number of finite analyses of load combinations. Next, the analysis results are compared with the finite factors. In addition, excellent and satisfactory breeding should be selected. Analysis and review process as show in Fig. 1. This stage mainly includes the connection mode of BIM mode, that is, the method of converting BIM mode to FEA mode.

Analysis and review of the BIM model link method
Analysis and review must ensure that the BIM model can be used in structural analysis software for force analysis, and that the BIM model can be easily adjusted according to the analysis results. The existing modular structure design method is to use limited modular software for structural modeling, then carry out force analysis calculations, and then use TU to draw 2D construction drawings. The BIMbased modular structure design method is to call the components in the free-kick component library from the nuclear modeling software to form the BIM model for analysis and research. The BIM model refers to an H-dimensional entity model containing various design information, including various design information. Analysis models are mainly point, line, and surface models. The link calculation between the BIM model and the analysis model is the key point, because the data structure of each software has not been opened. The link method of a good model needs to have the openness and transparency of the link process, the availability of link results and the stability of the link interface. The main methods are: Adopt IFC common standards to realize data exchange between BIM core necessary model software and structural analysis software. At present, most software does not support IFC mode reading, and the IFC mode output by the software does not include structure information mode. Therefore, in order to realize data exchange between different software's, it is necessary to develop professional IFC structure transformation software.
Based on the second development of the Revit API, a plug-in was formed, and the plug-in conversion was used to convert the model. At present, Revit can exchange models with Minobot, PKPM, Etabsw, and Staad. Revit and Robot have also achieved better model links.
Use Excel based on intermediate data files for data exchange. The Excel file type of the output BIM model includes element node coordinates, single-sided type, material information, etc. Use the Excel model generator to read the file and generate the model. The analysis process of the finite factor analysis is the prerequisite for the analysis and review. Unlike the analysis during the design, the reinforcement of the prefabricated components has been determined, and the finite element analysis is carried out according to the actual constituent factors.
Considering the refined finite element analysis of the steel bar, the complicated situation of the steel bar and the node interface in the precast component can be considered. The finite element models of reinforced concrete containment are mainly divided into three types: separated type, combined type and integral type. The separated model treats the steel bar and the concrete stop as separate units, which can take into account the adhesion between the steel bar and the concrete stop. If the reinforcement is complex, it is difficult to calculate, but the result is in line with the actual situation. The combined model has multiple concrete stop layers and reinforcing steel layers on the same section. According to the stress-strain relationship of the element, a more troublesome element stiffness expression is obtained. Therefore, the hierarchical combination model is generally used. The overall model distributes steel bars continuously and evenly throughout the unit, combining the contributions of steel and concrete to stiffness. This method is simple in model and easy to converge in calculation, but the result is relatively rough. The actual fabricated structure is generally more complicated. Rechecking with refined finite element analysis is unlikely under the current economic and technical conditions.
The combined structure that really considers the fineness of the steel bar is usually complicated. Wires can be used to replace the combined elements to complete the limited component analysis. At the same time, the role of the steel bar is taken into account through the mixed elastic coefficient. The coefficient of elasticity determines the analysis results of the structure's interpretation of strength and deformation. When the coefficient of force is high, if the effect of the coefficient of elasticity is ignored, the results will have large errors. In the analysis of finite factors, the influence of steel bars on the mixed elastic coefficient needs to be considered. The mixed elastic coefficient can be determined by experiment or theoretical formula. For each prefabricated component, under conditions, its mixed elastic coefficient can be determined through experiments. According to experimental research, there is a quantitative correlation between the elastic coefficient and the reinforcement ratio of the main constituent elements of steel solidification. According to theoretical induction, the following formula can be used when calculating the mixed elastic coefficient.
Today's structural design generally does not consider the role of steel bars to perform finite element analysis. In the process of analysis and deliberation, the same analysis method as the introduction of structural design can currently be used. When analyzing internal strength, the effect of steel bars on internal strength is not considered, but the internal strength result is used to check the review color of the constituent elements. Although there is a certain degree of error, the error is within the engineering error range.
The combined constituent elements of the combined structure generally include combined plates, fabricated beams, fabricated columns and each combined component is multiple types of components. For example, the combiner of the world structure system includes pre-stressed cushions, rehearsal boards, rehearsal columns, etc. The rehearsal dictionary stress boards have two forms: YB-42-0507-1 and YB-42-0507-2. The characteristic of BIM model analysis and review of prefabricated structures is that the number of prefabricated components of the structure is within a limited range, and the types of similar prefabricated components are also within a limited range. Although each type of rehearsal component contains more rehearsal components, as long as the largest component of each type of rehearsal component is checked, the safety of each rehearsal component can be ensured. Types and models of prefabricated components as show in Fig. 2.
The process will continue until all estimated components of this type have been checked. Move to the following types of preview component inspection modules and repeat the above requirements. When all types of rehearsal components are checked, the BIM mode will replace all rehearsal components that do not meet the requirements, and repeat this step. In the case, the BIM infrastructure design method is immature, this solution may be troublesome, but if the design method is mature, it will reduce the number of review and comparison of replacement components. Because the audit work is usually repetitive and the workload is large, it is necessary to design a calculation module. It can be seen from the above discussion that the algorithm design module should include a finite element analysis module and a review module for different types of components. In the prefabricated structure design, the prefabricated staircase review module should also be considered, and the design of a few current wave components should be considered. Figure 3 shows model design for BIM model analysis and review of fabricated frame structure.

Finite element conversion module
This module focuses on the conversion process and methods of BIM models. Through a large number of studies, it is necessary to make full use of the structural analysis model and improve its data accuracy. Not only that, but it is also necessary to extract the results of the transformation of the BIM model. In order to improve the convenience of extraction, the component analysis method is mainly used. Finally, the process of analyzing the results and converting them is carefully examined. Reconstruct the output by checking the input function. Based on a large number of implementation cases, this paper studies the data structure and composition of input samples. The core of the study checks the information combing results of the motherboard, and at the same time, the information processing results of the motherboard under different audit templates are compared. The comparison results are systematically recorded. Finally, a functional analysis of the comparison results is performed. Determine whether the information of the motherboard meets the standards required by the industry, and improve the motherboard that does not meet the requirements.

Motherboard review and improvement module
Reconstruct the output by checking the input function. Based on a large number of implementation cases, this paper studies the data structure and composition of input samples. The core of the study checks the information combing results of the motherboard, and at the same time, the information processing results of the motherboard under different audit templates are compared. The comparison results are systematically recorded. Finally, a functional analysis of the comparison results is performed. Determine whether the information of the motherboard meets the standards required by the industry, and improve the motherboard that does not meet the requirements. The output part is mainly used for BIM model component replacement. If it is a hemispherical main board (main board pre-stressed thin plate), and then the design of the inspection module is as follows: Internal force data under load: The combined bending moment, shear force f, standard load combined lower bending moment MK, quasi-permanent combined lower bending moment MQ, etc. under basic load are generally obtained through finite element analysis. Information on the prefabricated slab itself: the code of the slab, the calculation span of the slab, the thickness of the prefabricated part and the thickness of the rear part of the slab, the type, diameter, cross-sectional area of the prestressed tendons, and the type, diameter, cross-sectional area and concrete strength grade of the ordinary stressed steel bar Wait. Verification of required mechanical performance data: equivalent rectangular stress diagram coefficient, prestressed tendon strength design value, prestressed tendon tension control force, support negative tendon strength design value, concrete stop strength standard value, allowable board crack width, maximum allowable board lift, etc.
Checking calculation of bearing capacity of normal section: x ! 2a 0 ð5Þ r ck À r pc f tk ð6Þ x max x min The burn degree check calculation can be carried out according to the method of structural mechanics, and the stiffness and calculation under the long-term effect of the load are adopted.
Cracks are not allowed in the prestressed laminate 3.1.5 Checking calculation of superimposed surface under shear After the preemptive decision of one mode is over, the preemptive decision of the next mode must be cyclically judged. The cyclic function should automatically end the cycle for the preemptive decision of all modes. The condition for the end of the W cycle is that all preemptive decisions. The board is checked.
If the requirements are not met, a dictionary version of the label needs to be specified. The tag is essentially the code that saves the dictionary version and waits for output.
Output the marked prefabricated board number and save the result, which is used to query the prefabricated board in the BIM model and replace it with other types of prefabricated boards. For the combined overall frame of the world architectural system sample transfer, it is necessary to design the existing columns separately, and design the basement and foundation parts of the existing columns. Some design modules are not included in the review part, but are included in the design. The BIM-based assembly structure design method is to first establish a BIM model, and then conduct review and inspection. The design of the existing sight components is carried out after reviewing the prefabricated components, while also ensuring the safety of the structure, so this point is also mentioned in the assembly analysis and review section. Each analysis and review module are independent of each other, and sometimes only one or a few modules are needed for analysis and review. Analysis review is a cycle of calling these modules, one of which is, calling the finite element analysis module for analysis, and calling the Analysis Review module. The judgment condition of the loop is whether there is a component marked by each module. If there are, all marked members are replaced in the next cycle until there are no marked members.
Based on the hardware design, this chapter has carried out software design for these hardware, including: Cummins system kernel and Rime protocol stack transplantation, multi-task embedded software design based on Kangzhiqi system, SX1278 radio frequency chip, various sensor chips and OLED The driver design of the display module. The transplantation of Kang Zhiqi kernel is mainly to complete the transplantation of the system clock. Just as daily life requires time reference, the operation of Kang Zhiqi's operating system also requires time reference. In the Contiki system, the execution flow of the system clock interrupt is shown in the figure, which mainly completes two things: (1) Record the running time (seconds or ticks) from the start of the operating system to the present. (2) According to whether the timer list linked list is empty and whether the E timer expires, the need spoll of the E timerprocess system process needs to be set to 1. This design uses the STM32F4 series single-chip microcomputer, which contains a special function timer Sys Tick, which is specially used to generate the clock beat of the operating system. The Sys Tick timer is a 24-bit minus one counter. When it is reduced to 0 by the count clock, it will generate a timing interrupt and automatically load the value in the RELOAD register as the initial value of the timer, start counting again, and not stop. Different from the general timer, the Sys Tick timer is bound in the NVIC, and the exception generated is the CPU core-level exception. During migration, CLOCK-CONF-SECOND is defined as 64 in the platform-conf.h file, which means that the operating system should generate 64 clock beats per second. In STM32, you can configure and start the system tick clock through the library function SysTick-Confi, where ticks is the number of count pulses in each timing cycle, which can be calculated by the following formula.
In the format, period T is the talk period of the system, ticks is the countdown number of each talk period, and cntclkf is the countdown frequency.
This design adopts HTU21D temperature and humidity sensor, and uses I2C bus to communicate with the microcontroller. HTU21D as a slave device, its write address is 0 9 80, read address is 0 9 81, and serial clock frequency is 100 kHz. For HTU21D, MCU has only a single measurement method. MCU sends corresponding measurement commands to HTU21D through I2C bus to trigger the measurement of relative humidity or temperature. After the measurement is completed, the microcontroller can read the corresponding measured value through the I2C bus. To perform the next measurement, repeat the above process. The specific operation process of the MCU on HTU21D is as follows: First, the MCU sends a start signal to the device, and then transmits the write address 0 9 80 of the slave device (including 7 slave device addresses plus 1 read and write control bit). After the MCU receives the ACK response signal from the slave, it sends a corresponding measurement command to the slave, where 0xE3 means triggering the measurement of temperature, and 0xE5 means triggering the measurement of relative humidity. When the MCU receives the ACK response signal from the slave again, it needs to enter the read mode and wait for the measured value to be read. In order to change the transmission direction, the MCU needs to send a bit start signal to the slave again. When the SCL is released from the device, it means that the internal processing of the sensor has been completed. The one-chip computer can read the measurement result through the serial data line SDA at this moment. There are two bytes of data, read the high byte first, then the low byte. After reading all the bytes, the MCU needs to send a NACK no response signal to the slave, and then send a 1-bit stop signal to end this communication. The running sequence of HTU21D is shown in Fig. 4.
The HTU21D collection output needs to convert the unsigned 16-bit number into the floating-point value of the corresponding physical quantity. The last two digits in HTU21D are status bits, please reset to 0 before calculating. The temperature measurement can be calculated like this: where T is the temperature measurement value and ST is the digital output of the temperature measurement. The measured value of relative humidity can be calculated by the formula.
Measure RH is the measurement of relative humidity, and SRH is the digital quantity output by relative humidity measurement. Temperature is the main factor that affects the relative humidity measurement. The relative humidity value calculated from the plant type must be temperature corrected to achieve the measurement accuracy required by the device. The correction method is shown in the following formula.
RH compensated is the relative humidity value of the corrected temperature, RH measure is the calculated relative humidity value, and f(T) is the corrected temperature coefficient. F(T) is the temperature correction coefficient, and T is the calculated temperature value. HTU21D can not only measure the surrounding temperature and relative humidity, but also calculate the value of the dew point temperature. The dew point temperature refers to the temperature value indicated when the water vapor reaches the saturated water vapor pressure at the current temperature.
PPT amb is the partial pressure of the gas at the current temperature, and T amb is the calculated temperature value. Td is the dew point temperature value, PPT amb is the calculated gas partial pressure at the current temperature, and RH amb is the calculated relative humidity value. A, B, In this design, the lighting sensor uses the BH1750FVI chip to communicate with the microcontroller through the I2C bus. BH1750FVI acts as a slave, and its 7-bit slave address is determined by the level state of the chip pin address. In this design, it is grounded. At this time its address is b0100011, its write address is 0 9 46, its read address is 0 9 47, and its serial clock frequency is 100 kHz. BH1750FVI has two measurement modes: single measurement mode and continuous measurement mode. In this design, all sensors are collected regularly, so BH1750FVI can use a single measurement mode. The working process of the sensor is as follows: After the sensor is powered on, it automatically enters the power-off state; after the MCU sends the power-on command 0 9 01 to it through the I2C bus, it enters the power-on state, and then sends a single measurement command to make the 0 9 20 sensor start measuring.
The output of BH1750FVI is a 16-bit unsigned digital quantity, and the illuminance value is calculated as follows: In the format, E represents the luminosity value, Sout represents the digital output of the sensor, R represents the sensor resolution, 1 lx/LSB represents the measurement accuracy coefficient of the sensor, and F represents the measurement accuracy coefficient of the sensor, with a size of 1.2.
It uses ZPH01 speaker and USART interface, and the serial communication parameters of the sensor are displayed on the table. The detection frequency of the sensor is 1 Hz, and the format of the output data frame is shown in the table. The check value of the last byte is added together with the remaining 7 bytes except the start byte and then reversed. The measured low pulse rate of the output power is proportional to the dust concentration.
where R is the low pulse rate (%), N is the particle density (pieces/283 ml). In this document, the nodes that collect data include three types of sensors: temperature and humidity sensors, lighting sensors, and dust sensors. You must test whether these sensors work properly. During the test, the data collection node was wired to the PC via USB. At this point, the USB interface will provide you with a node. At the same time, the data collected from the sensor will be transmitted to the computer through the USB part through the serial port of the circuit board, and the result will be displayed in the serial debugging service software. The underlined part in the figure is the entire data frame. As shown in the table, the measurement of each sensor is the value of 4 bytes with different decimal points. Each part analyzes sentences according to the content in the table. This experiment was carried out under night lighting. According to the chart analysis, it can be seen that the measured values of each physical quantity are within the predetermined range. And each sensor must continuously collect within a period of time, and draw the transformation of each physical quantity with a curve. The following formula can calculate the standard deviation of each formula.
S is the standard deviation of the sample, Xi is the measured value of the sample, and N is the size of the sample. The calculated standard deviation of temperature is 0.05°C, standard deviation of brightness is 1.59 lx, standard deviation of relative humidity is 0.36%, standard deviation of dew point temperature is 0.14°C, and standard deviation of dust concentration is 1.86/ml. When the test environment is almost unchanged, the measurement results of each physical quantity are stable, and it can be seen that the sensors are working normally. The communication distance of wireless transmission is one of the most important parameters to determine the performance of the system, which can directly limit the applicable monitoring range of the system. To this end, through the communication between locations, test the distance of LoRa radio transmission, and maintain a certain node position in the experiment, move the node, and record the information of the receiving node. Use RSSI and packet loss rate to measure communication quality within a certain transmission distance. The DBM unit is calculated as: The above formula Precv is the power of the received signal. The RSSI value can be obtained by reading the Reg Rssi Value register inside the SX1278. The packet loss rate is calculated as follows. The node sends the byte 0xA5 every 0.5 s, a total of 100 times, totaling the 0xA5 received by the recipient. The difference in data is the packet loss rate.

The content of BIM cost optimization
After the application of the prefabricated building design and construction management platform in the No. 1 building of this project, certain results have been achieved, and the application benefits have been calculated. The detailed statistics are shown in Table 1.
Quantitative statistics on the benefits generated after application from the aspects of design optimization, shortened construction period, management efficiency, quality issues, and model value. The total benefits generated are about 521,000 yuan.
The biggest influencing factor for the promotion and application of new technologies is cost constraints. To realize the collaborative management of BIM and the Internet of Things, RFID technology, BIM technology, GPS technology, mobile Internet and other technologies must be integrated. In order to achieve the goal of collaborative management, it is necessary not only to invest in hardware equipment and software systems, but also to educate employees to learn new management methods.
Among them, C h is the one-time purchase cost of wireless network equipment, PC equipment, mobile terminal equipment and other related hardware equipment. C s is the research and development cost of purchasing or building a public management platform. C t is the training fee for administrators using the public platform. C m is the management fee for the daily use and after-sales maintenance and management of the common management platform. The reader/writer purchased in this project is a UHF RFID data collector for about 4000 yuan, and the purchase quantity is 5. The price of computer equipment is about 10,000, and 4 sets are purchased. The wireless network setting is a wireless network shielding system setting contract signed with an information technology company. The equipment purchase cost is 22,000 yuan and the construction cost is 3000 yuan. The development cost of the prefabricated building design and construction management platform is 500,000 yuan. The annual use and maintenance cost of the management platform are about 50,000 yuan, and the duration of this project is about 2 years. In the application process of this project, the general statistics about fixed costs are shown on Table 2.
The total cost of the fixed cost is 695,000 yuan. The socalled variable cost refers to changing the cost according to the number of various types of components. Its variable cost can be expressed as: N represents the number of labels used, and C i is the label price. Statistics on the number of components in Building No. 1 of this project are shown in Table 3.
The electronic tag is Xinyue UHF RFID metal-resistant electronic tag. The purchase price of each tag is RMB 20, and the change fee is as follows: Through comprehensive statistics and application of fixed costs and variable costs, the total application cost is about 720,000 yuan. The effect and cost comparison calculation of the combined architectural design and construction management platform for Building 1 of this project.
In other words, when the cost efficiency is greater than 1, the profit generated by the input is more. If the expense ratio is less than 1, it means that the profits generated after the application are more than the expenses invested. The cost ratio derived from the applicable benefit cost statistics of Building 1 of this project is 1.38. Building 1 of this project stated that the investment in the modular building design and construction management platform will not produce more economic effects.
The development of assembly buildings and the modernization of buildings is an industrial revolution centered on the industrialization of new buildings. Make full use of Internet technology, BIM technology, VR technology and other green technologies and concepts, replace manual labor-intensive production methods with comprehensive technology large-scale chemical factory production, and replace on-site process models with industrialized product on-site assembly to achieve factory production and construction assembly Oriented green construction.
Prefabricated buildings will change the backward production methods of the traditional construction industry. Prefabricated buildings can well control the entire process of construction, thereby reducing the risk of production safety. In terms of construction quality, it can solve the bottling problems that are common in traditional (1) The collision between reserved embedded parts and pipelines and prefabricated components is found through collision inspection, and the design is optimized in advance to reduce later construction problems and avoid material waste 2.9 (2) Calculate the cost of pipe materials at the collision point to reduce the design optimization of pipe elbow 150 mm about 240, the unit price of 150 mm pipe elbow is 55 yuan/piece, the unit price of 100 mm elbow is 350, 100 mm elbow is 45 yuan/ A total of about 240*55 ? 350''45 = 28,950 yuan 2 Shortened construction period (1) After applying the Internet of Things technology and management platform, managers can grasp the progress information of fabricated components in real time, thereby improving construction efficiency, and the actual construction period has been shortened by 20 days compared with the planned construction period 20 (2) According to the contract stipulated in the contract, the award will be 10,000 yuan per day, and the total is about 200,000 yuan 3 Management efficiency (1) The number of times that each member of the construction party has logged on to the platform is about 1,600 times. Based on the 40 times of logging on to the platform to check data, it is about 1 working day, which saves a total of 40 working days 1.6 (2) Calculated based on the daily salary of management personnel of 400 yuan, the benefit of improving management efficiency is about 40*400 = 16,000 4 Quality issues (1) All participating parties use the platform to mark and update a total of 75 quality and safety issues, thereby reducing the occurrence of quality and safety issues 7.5 (2) Calculate the cost of each quality and safety issue as 1,000 yuan, and the resulting benefit is about 75*1000 = 75,000 yuan  construction methods such as leakage and poor accuracy, and ensure the quality of the project. In terms of progress, prefabricated buildings greatly shorten the construction period and facilitate construction. In the construction process, compared with the original building of the same volume, the combined building has a lighter weight, a lighter foundation burden, and a smaller basic investment. The cost-effectiveness of the investment will also be improved. Compared with the existing building area, the general use area can be increased by 8-12%. Use PKPM to model the four main building structures, including beams, columns, slabs, and walls, model the site and assembly models separately, and design an appropriate construction plan in advance for analyzing cost differences. The four main architectural structure models of thin slabs, columns, slabs and walls are mainly expressed as: 6.6 9 6.9 m large-span floor slab (thickness 110 mm, 170 mm), 4.8 9 3.6 m small-span formwork (thickness 110 mm, 170 mm), 200mm 9 550mm 9 6 0.6 m large span beam, 200mm 9 400mmx6.6 m small span beam, 400m-mx400mm column, 3.0m 9 3.8m 9 200mm concrete shear wall. The structure drawing can be automatically calculated according to the PKPM software, which meets the performance standards required by China's current construction. Theoretically speaking, prefabricated construction projects require a standardized process, so the construction cost should be lower than traditional on-site prefabricated buildings. However, from the current development status of China's construction industry, the construction cost of some prefabricated construction projects is still relatively high. The main reason is that the price of part of the combined elements exceeds the standard, which requires in-depth analysis.
If the construction of prefabricated components is carried out on other parts of the building, the increase in cost will be very different. The largest increment is the prefabricated wall, and the smallest increment is the doubleleaf laminated wall. Analysis of building prefabricated structure: When a building uses a prefabricated structure, the cost increase in prefabricated walls is about 400% of the double-leaf laminated wall, while the cost increase in columns and beams is relatively small. When we judge the impact of modular buildings on construction costs through the investment analysis of construction projects, we should not only judge the increase in costs, but should consider various factors, such as construction time before judging the impact of modular buildings. Based on the above content, it can be seen that if prefabricated buildings use laminated and overlapped panels, the cost of prefabricated construction projects will be higher than the cost of on-site construction projects, and the laminated panels will increase by about 200%, and then the prefabricated walls will increase the construction cost about 150%. Second, the prefabricated price of the double-leaf composite wall in the wall prefabricated components is more cost-effective, so according to the actual situation, the cost can be saved by adding the double-wing composite type appropriately. Third, the columns and beams are made in advance, with small increments and relatively low cost performance. Therefore, the construction period and quality requirements can be comprehensively considered. Enclosure structure (20) Non-load-bearing enclosure walls, non-masonry walls 0-80% 5 10 Decorative integrated wall structure 50-80% 2-5 Inner partition 0-50% 5 Decorative layer 0% 6 Decoration equipment Floor, ground 0-70% 6 6 Decoration equipment pipeline (30) Integrated kitchen 70-90% 3-6 Pipeline separation structure 50-70% 3-6

Conclusion
In order to achieve industrialized construction methods, the development of fabricated structures has become increasingly prominent, and traditional fabricated structural design methods are no longer suitable for industrialized development and construction methods. The BIM-based modular structure design method applies BIM technology to the design and construction of modular structures, and the BIM technology fully absorbs the characteristics of fabricated structures in the actual application process. Through reading the literature and understanding of BIM technology, it is found that the application of BIM technology in the design and construction of composite structures is conducive to the realization of industrialization and automated production of composite structures, fully solving the problems of information transmission and sharing, and also solving the actual construction stage unexpected problems that arise. In summary, prefabricated buildings will have a certain impact on the project cost, construction time, quality, etc. will affect the project effect, at the same time, the project indicators will also change. Construction projects must fully consider the impact of different constituent elements and different combinations on costs. In the case of striving to ensure a high prefabrication rate, the lowest cost assembly method must be selected to achieve the goal of simultaneously controlling engineering time and cost. The construction of prefabricated buildings in various places is still in the ''immature'' stage of development, and many practitioners should fully learn from some successful experiences to improve the level of cost control and engineering construction.
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Declarations
Conflict of interest The authors declare that they have no conflict of interests.
Ethics approval This article does not contain any studies with human participants performed by any of the authors.