1. Management
The market mechanism is fragmented. Construction, construction, supervision, and design units are accustomed to the cast-in-place model. For subsequent work, they only solve problems when they arise, and their ability to control quality is insufficient. The in-depth design of prefabricated components is not well integrated with the cast-in-place parts; the construction unit lacks corresponding guidance capabilities on the comprehensive performance of components and lacks coordination; while the component factory lacks comprehensive design capabilities for products and does not have in-depth basic research on the node connections of prefabricated components; Inadequate consideration of node connections, earthquake resistance, etc. has resulted in products passively adapting to the market and posing serious obstacles to the development of assembly. Component splitting needs to be carried out in advance. Unreasonable splitting will hurt the economy, smoothness, and final engineering quality of the project. The negative impact and the current market is difficult to adapt to it quickly.
The quality responsibility interface needs to be further clarified. There is a lack of comprehensive management standards for the quality and production of prefabricated building construction, and the relevant management responsibilities, systems, management work standards, and processes of all parties involved in the construction are not clear enough. Prefabricated buildings require close cooperation among all units. Precisely because of the market operation mechanism, design, construction, and component companies, and in-depth design units are in a state of fragmentation, resulting in unclear quality responsibility interfaces. If water seepage occurs, the responsibility lies with the design, construction, or component factory. There is currently no mature confirmation method.
It is difficult for management systems to adapt quickly. Assembly of integrated projects requires high project integrity and management coordination, which places higher demands on the management capabilities and management methods of related enterprises. The current management system is still in the "cast-in-place" management stage and lacks overall thinking and management methods between design, component production, and before and after construction. The management system needs to be further improved by combining BIM technology, intelligent management, and other means.
2. Technical aspects
Technology lacks systematicity and integrity. It is difficult to ensure the quality of assembled integrated housing. It is not only the assembly of prefabricated components but also involves many factors such as water and electricity installation supporting technology, transportation tools, hoisting technology, fixed connection technology, etc. Although these technologies are now mature, what is more needed is the integration and support of these technologies. Due to the low degree of standardization, it affects the standardization of accessories and accessories and the integration of supporting technologies, hindering the improvement of quality.
The supporting normative and standard system is still missing. In terms of actual on-site operations, the current safety professional technical standards are still insufficiently integrated with the integrated construction of the assembly, and safety protection, formwork support, scaffolding, mechanical equipment management, etc. are still incomplete. Many of the prefabricated quality inspections, acceptance, and management are based on cast-in-place structures. For example, there is still a lack of perfect inspection methods for sleeve connections, and there is a lack of necessary guarantee measures and inspection methods for the tightness of grouting.
3. Design
Technology lacks systematicity and integrity. It is difficult to ensure the quality of assembled integrated housing. It is not only the assembly of prefabricated components but also involves many factors such as water and electricity installation supporting technology, transportation tools, hoisting technology, fixed connection technology, etc. Although these technologies are now mature, what is more needed is the integration and support of these technologies. Due to the low degree of standardization, it affects the standardization of accessories and accessories and the integration of supporting technologies, hindering the improvement of quality.
The supporting normative and standard system is still missing. In terms of actual on-site operations, the current safety professional technical standards are still insufficiently integrated with the integrated construction of the assembly, and safety protection, formwork support, scaffolding, mechanical equipment management, etc. are still incomplete. Many of the prefabricated quality inspections, acceptance, and management are based on cast-in-place structures. For example, there is still a lack of perfect inspection methods for sleeve connections, and there is a lack of necessary guarantee measures and inspection methods for the tightness of grouting.
4. Prefabricated components and transportation
The quality and supply capacity of prefabricated components still need to be further improved. Compared with cast-in-place concrete, there are fewer manufacturers to choose from for prefabricated components. Prefabricated components have the characteristics of complex structural form, high requirements for appearance quality and dimensional accuracy, and a large number of embedded parts and reserved holes. Nowadays, with the large-scale promotion of prefabricated housing in Shanghai, it is difficult to guarantee the quality of molds of many companies that have switched production. At this stage, it is not possible to achieve a leap from "centimeter-level" to "millimeter-level" errors. At the same time, prefabricated components at some construction sites still have problems such as unclear component identification, inadequate rough surface settings, and irregular placement of steel bars.
An efficient logistics system has not yet been established. The logistics system is very important to the promotion of prefabricated products. An efficient logistics system can ensure the timely supply of components, reduce secondary handling, reduce damage to prefabricated components, reduce transportation and installation costs, improve installation efficiency, and play a significant role in improving the final quality of prefabricated products. important role. At present, the material transportation system is not developed enough. Improper placement leads to a lot of damage during transportation. The connection between the component factory, the transportation process, and the construction site is not enough. The transportation cost is still relatively high. In many projects, components have nowhere to go. The position and order of component placement during placement and installation affect the installation and construction progress, and the construction efficiency is not high. In practice, many projects in Pudong adopt the method of "using one layer to prepare one layer" for prefabricated components by formulating a component supply plan and closely integrating it with the construction plan, that is, preparing a sufficient layer of prefabricated components on site in case of component supply shortage. use. As the connection between transportation and the site becomes smoother, some projects can allow prefabricated components to be hoisted and installed directly on site, effectively reducing on-site stacking and secondary handling of components, reducing costs, improving transportation and installation efficiency, and ensuring component safety. installation quality.
5. Construction
The joints and grouting construction are not in place. First, there are a large number of steel bars interspersed at the structural nodes, which are easy to fight. The design requirements for the position of the steel bars cannot be accurately achieved during construction, resulting in problems such as reduced effective height, uneven thickness of the protective layer, insufficient steel bar spacing, and insufficient steel bar anchorage length. , affecting the function of the structure. Second, after the formwork commonly used in reinforced concrete molding is used many times, the plate seams are larger and grout leakage is easy to occur. In particular, it is more difficult to connect the formwork at the nodes, making it difficult to ensure the size of the nodes, and the grout leakage is more prominent. The result is honeycombs, pitted surfaces, exposed tendons, and even large cavities on the concrete surface. Third, due to the dense steel bars at the nodes, it is particularly difficult to vibrate, which can easily reduce the stiffness and strength of the nodes; fourth, the grouting is not dense enough. There are many cases where the on-site grouting does not set the silo joints according to the specifications, and the density of the grouting is difficult to guarantee.
Inadequate measures to resist cracking and seepage. For example, vertical cracks occur in prefabricated panels along the direction of the steel bars, and cracks occur during the concrete pouring process after installation; common quality problems such as water seepage from waterproof weak points in prefabricated exterior wall panels still exist; holes formed during the construction process are not effectively blocked, providing a lot of space for future water leakage.
6. On-site supervision
Supervision and supervisory measures are lacking. The use of prefabricated components requires supervision units to adopt factory-based supervision and patrol monitoring. However, the reality is that due to the tight supply of components, it is difficult for actual supervision to go to the prefabricated component production units to control the production quality of components. Because prefabricated buildings are not cast-in-place, supervisors can go to the site before the concrete is poured and can "clearly see at a glance" whether they meet the requirements of the drawings and specifications. However, prefabricated buildings lack such quality control points and are relatively scattered and hidden. Overall supervision and inspection It is difficult for supervisors to adapt in a short period.
7. Human resources
At present, many developers lack project leaders who are familiar with the prefabricated management process, design units lack "chief designers" with overall system integration suitable for prefabricated buildings, and construction units lack projects with rich practical experience that are suitable for on-site management. Managers and on-site technical managers are not familiar with the construction process, and there is a shortage of skilled workers. Supervisors who are familiar with assembly issues and processes are still very limited.
Corresponding countermeasures
1. Comprehensively build a systematic policy and regulatory system
In conjunction with the advancement of prefabricated projects, the "Outline for the Development of Prefabricated Integrated Housing" has been formulated to clarify the development path, development model, planning, goals, and specific implementation methods of housing industrialization for a long period from now to the future.
2. Improve the technical regulations and standards specification system
Develop relevant standards and specifications. In terms of standards and specifications, we not only focus on macro guidance, but also emphasize micro-specific implementation and operability, and improve the engineering construction technical standards and quality standard systems.
The first is to formulate an overall preparation plan for relevant technical standards, form a technical standard system for residential construction from planning, survey, design, production, construction, inspection, testing, etc., and prepare a series of technical standards, product standards, atlas manuals, etc.;
The second is to improve the residential building standardization system that combines mandatory and recommended standards;
The third is for enterprises to establish a construction method system suitable for prefabricated projects.
Improve relevant construction methods and processes. Pay attention to the construction methods and processes for assembling monolithic components. At present, we must focus on the research and accumulation of construction methods and processes that are suitable for assembling monolithic components, and form a corresponding system.
Strengthen supervision and management of the implementation of standards. With specifications and standards in place, the key lies in implementation. It is necessary to strengthen the supervision and management of the implementation of standards and form a strict and effective supervision and management system.
3. Clarify the lifelong quality responsibility system of all parties involved in the construction
Divide and define the quality responsibilities of different participants in the prefabricated monolithic construction project. Residential development enterprises and construction units are the first persons responsible for the quality of residential products. Strictly implement the lifelong responsibility for the quality of the project leader.
4. Study government incentive mechanisms and policy measures
It is necessary to formulate detailed rules based on the original policy to ensure the proportion of assembled integrated housing and prefabricated components, increase the proportion of other types of projects, and formulate relevant incentives.
Strengthen support for enterprises. Although the "Several Opinions on Further Promoting the Development of Prefabricated Residential Buildings in this City" (Shanghai Fuban [2013] No. 52) provides preferential policies for area "rewards" for prefabricated residential buildings, it is unable to benefit component companies, and corresponding measures should be considered. Policies (such as tax cuts, one-time subsidies for technical transformation, R&D subsidies, etc.) provide industrial support policies to component companies based on output, encourage companies to improve production processes, increase production capacity, enrich product types, improve quality, and promote the development of the prefabricated component industry. Steady development. For example, trial tax exemption or tax rebate policies for prefabricated components can reduce the cost pressure on components.
Adjust relevant fee standards. The charging base of construction, supervision, and design units shall be adjusted accordingly, and operable standards shall be formulated to provide policy inclination and support to stimulate the enthusiasm of relevant enterprises.
Policy implementation and adjustment mechanism. Ensure that housing industry policies are implemented in place. The government strengthens the interpretation and training of newly introduced policies; policies and implementation.
5. Improve publicity, mobilization, education, and training mechanisms
Improve publicity and launch. Make full use of various media, through typical case analysis, experience exchange, etc., to build a "four-in-one" housing industrialization publicity and training system of the government, associations, enterprises, and the public, conduct objective publicity, and gain the whole society's recognition of this work. Gradually agree to lay a more solid foundation for promoting the development of the housing industry.
Improve education and training mechanisms. Implement the training of technical and managerial personnel, train a large number of excellent project management talents, especially corporate leaders and project managers, and cultivate a group of management talents who are familiar with the assembly of integrated housing. "Borrow wisdom" from experts, establish an expert database, and "invite" experts to provide intellectual support for various technical problems in assembling monolithic houses and supervision of major hazard sources. For complex problems, experts go to the site to "check the pulse" of the project promptly and eliminate potential quality and safety hazards.
6. Explore specialization and integrated construction models
Promote the general contracting model integrating design, construction, and component production of prefabricated construction projects. Prefabricated construction projects invested by the government give priority to the general contracting model integrating construction and component production, encourage the formation of a "consortium" of owners, design, construction, and component production enterprises for prefabricated projects, and actively cultivate a group of people who can provide integrated design, production Enterprises that provide one-stop services integrating construction and construction, actively promote the integration of construction and decoration, and encourage integrated companies with system integration.
Promote the construction of supporting industrial chains. Further improve equipment manufacturing production capacity, supporting product production capacity and corporate integrated general contracting capabilities, enhance the production capacity and engineering construction level of key products of prefabricated housing, and improve the maturity of the prefabricated housing industry.
7. Strengthen the detailed implementation of quality management measures
Strictly control the construction application, drawing review, construction permit, completion acceptance, and other links to ensure that the prefabricated project is constructed by the prescribed standards. Supervisory agencies carry out regular special inspections of prefabricated buildings, promptly summarize and report problems discovered during inspections, seriously deal with illegal activities of all parties involved in the construction, speed up the formulation and implementation of management measures, and continue to promote the construction level of prefabricated buildings.
