Basic Model of Construction Project Organization and Management Parallel contracting model (1) Characteristics of Parallel Contracting Model The so-called parallel contracting refers to the owner's subcontracting of the design, construction and material and equipment procurement tasks of construction projects to several design units, construction units and material and equipment suppliers respectively after decomposition, and signing contracts with each party.The relationship between the design units is parallel, the relationship between the construction units is parallel, and the relationship between the supply units of materials and equipment is parallel. In order to select suitable contractors, this model should first decompose the construction tasks reasonably, then classify and synthesize them, and determine the content of each contract. The following factors should be taken into account in task decomposition and contract quantity and content determination: (1) Engineering situation.The nature, scale and structure of the construction project are the important factors that determine the quantity and content of the contract.The duration of implementation of construction projects and the arrangement of plans also have an impact on the number of contracts. (2) Market conditions.Firstly, due to the different professional nature and size of various contractors in different markets, the decomposition and contracting of construction projects should be adapted to the market structure; secondly, the tasks and contents of contracts are attractive to the market, and the small and medium-sized contracts are attractive to the small and medium- sized contractors, without hindering the large- scale contractors from participating in the competition; moreover, they should also be in accordance with market habits.The content and size of the contract are determined by routine practices, market scope and relevant provisions. (3) Requirements of loan agreement.In the case of more than two lenders, the lender may have different requirements on the scope of use of the loan and the qualifications of the contractor. Therefore, it needs to be considered in determining the contract structure. (2) Advantages and disadvantages of parallel contracting mode 1. advantages (1) It is beneficial to shorten the construction period.It is possible to form overlapping relationship between design stage and construction stage, thus shortening the whole construction period. (2) It is good for quality control.The whole project is subcontracted to each contractor separately after decomposition. Contract constraints and mutual constraints enable each part to better meet the quality requirements. (3) It is advantageous for owners to choose construction units.In the construction market of most countries, the contractors with strong specialty and small scale generally account for a large proportion.The contract content of this model is relatively single, the contract value is small and the risk is small, which makes it possible for them to participate in competition.Therefore, both large-scale contractors and small and medium-sized contractors have the opportunity to compete.Owners can choose contractors in a wide range to improve the selectivity. 2. disadvantages (1) The large number of contracts will cause difficulties in contract management.The complex contract relationship increases the number of joint parts in the construction engineering system and the workload of organization and coordination.Strengthen contract management and strengthen horizontal coordination among contractors. (2) It is difficult to control investment.This is mainly manifested in the following aspects: first, the total contract price is not easy to determine, which affects the implementation of investment control; second, the large amount of project bidding tasks, which need to control a number of contract prices, increase the difficulty of investment control; third, in the construction process, more design changes and modifications lead to increased investment.