The control of project cost is to reduce unnecessary capital investment and control the total investment of the project within a reasonable cost limit under the premise of ensuring the quality of the project, so as to obtain the best investment income. The control of project cost runs through the whole process of project construction. Design is the forerunner of the project, the stage of planning the implementation of the proposed project economically and technically, and the key to controlling the scale of capital construction investment and improving investment efficiency. 1 The design stage plays a decisive role in the project cost and investment income. According to relevant statistics, in the preliminary design stage, the possibility of affecting the project cost is 75% ~ 95%. In the technical design stage, the possibility of affecting the project investment is 35% ~ 75%; In the construction drawing design stage, the possibility of affecting the project investment is 5% ~ 35%. Obviously, the key to project investment control lies in the design stage before construction. Construction according to drawings is the premise of the construction unit. Once the construction drawing is confirmed, the construction unit cannot change it at will during the construction stage. Therefore, the quality of design, the modeling of equipment, the choice of materials and design standards have a direct impact on the project cost. Different structures have a more obvious impact on the cost. The researchers analyzed various structural design schemes of the same project, and the results showed that compared with the optimal design scheme, the influence of different spans on the project cost was-21%~15%; The influence of different building heights on the project cost is 8.3% ~ 33.3%; The influence of different floors on the project cost is10% ~ 20%; The influence of different plane forms on the project cost is-1% ~ 13%. Therefore, in the whole process of engineering construction, although the most investment stage is the construction stage, it is the design stage that determines the investment. 2. Related problems in the current design stage (1) The safety factor in structural design exceeds the standard: the beams and columns are oversized, the steel bars are too dense, the foundation is too deep, and the roof is too heavy. This is the most common phenomenon that design affects the project cost. For example, a cigarette factory designed a reinforced concrete column with a cross section of only 240mm-240mm, but 20 steel bars were installed. The cross-sectional area of steel bars accounts for more than 25% of the cross-sectional area of members, and the average clear distance of steel bars around the section is less than 15mm, so it is difficult to pour concrete or mortar. (2) Some specialties were omitted in the renovation design and installation project, and the equipment model was wrong. Some designers update their knowledge slowly, and the equipment they choose is even obsolete and scrapped; Some designers are so obsessed with their own design projects that they are eager to get things done in a tight time, leaving out some projects and equipment in the preliminary design. For example, in the technical renovation project design of a beverage factory in the Economic Development Zone, only the specialty of process instrumentation was set in the preliminary design stage, but two specialties of process piping and equipment were newly set in the construction drawing stage, with an additional investment of 3 million yuan, accounting for about 29% of the approved preliminary estimate. In addition, some design mistakes were exposed in the construction process, and the design must be supplemented, changed and modified, and some even had accidents and needed to be reworked and reinforced. (3) Design pursues style and luxury, lacking practical concepts: some European countries pay special attention to the application of value engineering in design, so long as production can be guaranteed, the factory buildings and ancillary facilities are very simple. But the overall design of some domestic factories is very luxurious. For example, Zhongyuan Pharmaceutical Factory chose cutting-edge process equipment without technical strength, which led to idle equipment, the factory could not be put into production immediately, and the investment could not produce benefits. 3. Factors affecting the project investment in the design stage 3. 1 Designers lack prudent working attitude in the design process, especially in the case of many design tasks and tight time, a large number of similar engineering designs are applied without detailed calculation; Only talk about insurance, not optimization, blindly increase the safety factor, increase the steel bar, increase the cross section and increase the strength. 3.2 Do not pay attention to the application of value engineering. Some designers have a weak economic concept and value technology over economy. Too ambitious in design, not making multiple choices. When it comes to the influence of design on the cost, it is naturally considered as a matter for the cost maker, not for himself. 3.3 backward tools. Designers in some design units can't skillfully use design software, and basically calculate and draw by hand. Long design cycle and poor quality. 3.4 The charges are unscientific. The current design fee is still calculated according to the scale and rate. Therefore, the designer didn't ask for reducing the project cost, even in order to overcharge the design fee, expecting the project to be large in scale and high in cost. The risk of design quality is only to make a modification and remedy plan after the accident. 3.5 After the design scheme lacking supervision mechanism comes out, the review organized by the competent department pays more attention to technology than economy. The approval of design scale, grade standard and investment amount is often a mere formality. Some designs did not exceed the standard when submitted for review, and the designs changed and modified during construction seriously exceeded the standard, lacking monitoring mechanism. 4 The idea of controlling the project cost in the design stage mainly includes four aspects: (1) perfecting the management means; (2) apply the principles and methods of value engineering to coordinate the design objectives; (3) Through technical and economic analysis, determine the influencing factors of the project cost and the measures that may reduce the cost range; (4) Adopt technical means and methods to optimize the design, so as to reduce the engineering cost. Investment control management can be divided into macro management and micro management. Macro management refers to the management of engineering design industry by government departments, including government management, management laws and regulations, and management basic work; Micro-management refers to the management work related to the design and investment control of specific projects, including contracting methods (scheme bidding; Design bidding; General contracting, special contracting), quota design, scheme evaluation, technical and economic analysis, budget review, etc. 4. 1 Macro management of project cost control in the design stage First of all, the competent government departments have the responsibility to formulate the basis for control in the design stage. China's infrastructure work procedures stipulate that the design must have a feasibility study report approved by the competent department. When reviewing the initial design, the competent department shall review whether the budgetary estimate meets the requirements, strictly examine and approve the initial design, and then enter the construction drawing design after approval. According to the construction drawing budget, it generally cannot exceed the approved budget estimate. In view of the phenomenon that some projects deliberately depress budget estimates or are unrealistic, the competent government departments should strictly and effectively supervise and manage the preparation and approval of budget estimates. Secondly, we should constantly improve relevant laws and regulations. Clarify the rights and responsibilities of decision-making institutions, management institutions, construction units and design units, and strictly implement the established management system. In order to reflect the design effect, the standard of design fee must pay attention to the relationship between design fee and investment control. To a certain extent, increasing the necessary design fee can increase the possibility of saving investment and reducing the use fee. For example, carrying out research projects and collecting data will increase the design cost, but more practical scientific data can be obtained, which may greatly reduce the construction cost and recurrent expenditure in the process of use; Appropriately increasing the remuneration of designers and encouraging designers to optimize their designs can not only arouse the enthusiasm of designers, but also help control costs. In addition, it is necessary to compile a general standard design atlas, which not only meets the design function requirements, but also meets the technical and economic assessment indicators, and at the same time can save time, reduce design costs and help control investment; Do a good job in the compilation and management of quota indicators to provide a basis for formulating feasible investment control targets; Make a dynamic analysis of the decision of price, interest rate, exchange rate and other changing factors, and attach importance to the dynamic factors of investment control. 4.2 Suggestions on specific management of project cost control in design stage 4.2. 1 The main purpose of adopting design scheme bidding is to select excellent design scheme through competition, and its purpose is to promote design units to improve management, adopt advanced technology to reduce project cost, shorten construction period and improve investment benefit. Therefore, there are clear requirements for reducing the project cost in the design bidding documents, and there are corresponding specific measures to reduce the cost. 4.2.2 Sign a design contract with the winning design unit, compare the economic and reasonable design and design cost according to the limited cost, and reward the saved part to the design unit and relevant designers in proportion; If design defects are found in the construction process, resulting in an increase in engineering changes, the design unit and relevant designers shall compensate the construction party accordingly. 4.2.3 Designers should make a reasonable design scheme, make a design quota at each design stage, compare and select the schemes at each stage, and make the final scheme meet the control objectives and the requirements of the construction unit. For example, the scheme of a high-rise residential building developed by a real estate company in Zhengdong New District is selected, and there are two schemes: one scheme is frame-shear structure, the outer wall is built with 240mm clay brick, and the inner wall is built with slag hollow brick; Another scheme is that the inner wall of shear wall structure is built with slag hollow brick. After comparing the usable area, the cost per unit area and the total selling price converted into usable area, the result is that the second scheme needs about 5% more income, and finally the second scheme is chosen. The goal of the quota should be reasonable, otherwise the quota will lose its due significance. For example, the high-rise commercial and residential building developed by Greentown Genting Real Estate Co., Ltd. adopts shear wall structure, external wall insulation layer and floor heating. The owner's price limit of 1.500 yuan /m2 is obviously unreasonable, because the reference price of such houses provided by the benchmark price information of Zhengzhou construction project is 1.830 yuan /m2. 4.2.4 Use the theory of value engineering to compare and select schemes, and put forward opinions on unreasonable design, so as to achieve the purpose of cost control, such as the reinforcement amount of general brick-concrete structure ≤ 25kg/m2 and the reinforcement amount of frame structure ≤55kg/m2. Choosing a reasonable design scheme can greatly reduce the project cost. 4.2.5 Implement CM(construction in Management) contract management mode, and hire CM contractors with engineering experience to participate in the project implementation process from the design stage, so as to provide construction suggestions for designers and give full play to the collective wisdom of experts. On the one hand, it can provide scientific suggestions for the owners on major issues such as construction site selection, project scale, adopted design standards, functional requirements and corresponding investment scale, as well as the selection of design units and design schemes to ensure the correctness of the owners' decisions; On the other hand, various organizational measures, economic measures and contract measures can be used to effectively control the quality, progress and investment of design, help design units avoid possible mistakes and waste in design work, optimize engineering design, and finally achieve the purpose of ensuring the safety and reliability of engineering projects and improving their applicability and economy. 4.2.6 Before organizing the construction with the blue prints.the design, relevant units shall organize design units, construction units, construction units and relevant units to carefully review the construction drawings, find design defects and errors in time, and control the engineering changes before construction. 4.2.7 Pay attention to engineering design changes. Design changes often occur in the construction stage, especially some complex projects and projects with low design quality. Design changes are generally carried out by the construction unit, construction unit, design unit and site.
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