At present, the assembly building is in the pilot exploration stage, there are still some uncertainties, need a summarize and improve the process. For assembly building bidding, there are some problems and difficulties, such as: the lack of assembly building of the national operational technical regulations and provincial and municipal supporting the bill of quantities specification, bidding and tendering operational procedures in the exploration of the development of the bidding process, there is no mature bid evaluation methods, mastery of the construction technology of the enterprise is insufficient, the state, provinces and municipalities have not formulated assembly building bidding and tendering methods, and so on. Therefore, the problems about assembly building bidding need to be studied and solved gradually in the actual work.
Analysis of the current situation of assembly building bidding
First of all, all places have formulated policies to strongly support the development of assembly building.
The most common are six types of policy support methods: First, land security. Priority is given to supporting the development of the assembly building industry in the arrangement of construction land. Second, area incentives or volume rate incentives. Generally given not more than 3% of the volume rate incentives, prefabricated facades are not counted as floor area. Third, financial incentives (subsidies). For example, Shanghai Municipality provides a subsidy of 100 yuan per square meter for assembly buildings, with a maximum subsidy of 10 million yuan for a single project. Chongqing Municipality provides a subsidy of 350 yuan per cubic meter of concrete components. Fourth, tax incentives. To be reduced or exempted from enterprise income tax or enjoy the value-added tax that is 50% refund policy. Fifth, the provision of assembly-built commercial housing can be pre-sold in advance. When the construction part reaches ± 0.000, it can apply for the "commercial property pre-sale license". Sixth, the fund is given back. Exemption of new wall materials special fund, completion and acceptance of new wall materials special fund can be implemented after the preferential return.
Secondly, in order to promote the development of assembled buildings, many regions across the country have issued assembly building quotas.The regions that have been issued before 2016 include Shanghai, Liaoning, Shandong, Anhui, Fujian, Hunan, Sichuan. Tianjin, Henan, Hebei, Zhejiang, and Shenzhen, on the other hand, released them in 2016. Inner Mongolia, Qinghai, Jiangsu, Hubei and Guangdong will also be released soon.
Finally, the regulatory mechanism for assembled buildings around the world has also continued to innovate, promoting the general contracting model in all aspects of assembled building contracting. Jinan City, with component production qualifications, total investment of a certain size of the general contracting enterprises, in the bidding to give bonus points. Engineering construction in accordance with the design, component production, construction, installation of integrated general contracting enterprises, project bidding, under the same conditions, priority to win the bid. Design, construction, installation, supervision and other enterprises involved in assembly building project construction to a certain scale, in the bidding to give bonus points. Hefei City, the provisions of the initial pilot period, in some pilot projects to take a single source to determine the assembly of building construction companies, the determination of the cost of the use of traditional methods and industrialized methods of comparison, to the industrialization of a certain amount of profitability of enterprises, and gradually aligned with the market. In the future, all assembly projects are open bidding, design and construction general contracting, industrialized enterprises from the design, production of parts and components to the construction of assembly, the whole process of general contracting, the winning price is significantly lower, the construction period is greatly reduced.
It is foreseeable that with the gradual maturation of the market system and the gradual standardization of the bidding process, the construction cost of assembled buildings will be gradually reduced.
Introduction of assembly building bidding process
In accordance with the requirements of the relevant regulations, assembly building should in principle be used in the form of general engineering contracting. Therefore, I will first introduce the EPC (design-procurement-construction) engineering general contracting mode. Under the EPC engineering general contracting mode, the commissioning scope of the assembly building tender mainly includes: design, procurement, construction and commissioning. The principle of organization and implementation is unified planning, unified organization, unified command and unified coordination. Bidding requirements should be formulated in terms of construction scale, construction standards and division of responsibilities.
In addition, the assembly building bidding requirements for bidders mainly include:
One is an enterprise with the ability to manage the general contracting of the project, which can be a design, construction, developer or other project management unit. Secondly, the design, construction or project management units with corresponding qualification level bid independently or form a consortium. Third, due to the current construction market with less units with general contracting performance, it is not appropriate to take the general contracting performance as a bidding condition in the bidding, in order to promote the development of the general contracting industry.
EPC general contracting bidding on the premise of uniformity and clarity of demand, by the bidders according to the given conceptual program (or design program), construction scale and construction standards, to prepare their own estimated bill of quantities and offer. It is recommended that a lump-sum pricing model should be adopted, but underground works should not be included in the lump-sum scope; instead, a unit-price contract simulating the quantity of works should be adopted and measured on a real basis. If you need to agree on the adjustment of material and labor costs, it is recommended that the bidding first fixed transfer materials, labor in the total price of the project as a percentage of the settlement of the winning bid multiplied by the cost of construction and safety of the project as a percentage of the base, and then adjusted in accordance with the method of the pre-agreed transfer.
The assembly building bidding also has requirements for bid evaluation and finalization. It is prudent to determine the bidder's general contracting management capability and performance ability, whether the bidder's deepened design meets the provisions of the bidding requirements, and to assess whether the bidding price is reasonable.
Electronic bid evaluation for assembly building bidding
In reality, the difficulties in evaluating the bidding documents for assembly building are concentrated in the design plan, construction plan and bidding offer. The author believes that electronic bid evaluation based on bim (building information modeling) will be more scientific and efficient for assembly building bidding.
A BIM-based electronic bid evaluation system should be established.
In the bidding and tendering stage, it includes the following aspects: modeling or model import, construction programming and optimization (simulation), construction schedule programming and optimization, resource and capital programming and optimization, construction special programming and optimization, bid document preparation tools (bidding and tendering), online bidding system, construction schedule programming software, site layout programming software, pricing software, etc.
In the bid evaluation stage, it is necessary to carry out construction program selection evaluation, construction 5D evaluation, resource plan evaluation, construction special program evaluation, design program evaluation, it should have electronic (remote) bid evaluation system, BIM technology bid evaluation subsystem.
BIM-based bid evaluation specifically includes the following aspects:
One is model checking. That is, intuitively review the component information, time information, and optimization reasonableness, select the floor and professional component types that need to be viewed, and through the attribute window, review the component parameter information, construction plan, and construction optimization reasonableness. The traditional chart text is transformed into a three-dimensional information model that can be observed in three dimensions, enhancing the relevance and depth of the bid evaluation process.
The second is progress simulation. Progress simulation is a visual evaluation of the progress plan of the technical bid, review the progress plan of the technical bid in the form of 4D animation, view the construction plan through multiple windows of the construction of different professional models in the order of construction and reasonableness, change the progress of the text and charts to show the way, so as to facilitate the evaluation of the experts to deepen the understanding of the construction organization and make accurate judgments.
Third is the check of financial resources. This step is a multi-dimensional display of the bidder's funds and resources utilization plan. From the current value or cumulative value point of view, with different time units of month, week, day, according to the smoothness of the funds presented to judge the reasonableness of the funding plan. This step facilitates the bid evaluation experts to carry out a comprehensive and in-depth assessment of the funds and resources plan.
Fourth, the site layout program evaluation. This is a three-dimensional display of the construction site and temporary facilities layout, through the three-dimensional site and entity models, measures to program models combined with roaming way, from different viewing perspectives, the site layout program evaluation. It can change the situation that two-dimensional plan drawings cannot visually present the site layout and technical programs, and enhance the accuracy of the evaluation results.
Fifth, the key node program evaluation. This is mainly in the form of animation to present the key points of the construction program, direct animation and play video two ways to check the construction process of the key points of the construction process, change the traditional long text description way, enhance the intuitive experience, easy to assess the bidding experts on the understanding of the key points of the program, and at the same time reduces the threshold of the animation program delivery.
Sixth is the evaluation of tender offer. The use of BIM technology provides the overall view of the bill of quantities function, from the project as a whole, a comprehensive and detailed display of the content of the bidder's business bid, can intuitively display the overall list of constituent content, combined with big data applications, to facilitate the experts to find the problems in the engineering quotations.
Seven is the direct fee detailed check. The BIM model area selected by the experts to visualize the business bid review. Through ticking, box selection, component query, etc., the component items to be reviewed are quickly filtered out, and the business bid data is presented from component level by combining three-dimensional information modeling and data, which facilitates the bid evaluation experts to find out the existing problems intuitively and in-depth.
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