| It is necessary to improve construction site safety management capability and construction management theory. The healthy development of the construction industry has become an important and indispensable force in invigorating and promoting the national economy.Nowadays, the studies on safety managent focused on safety risk management, safety environment and safety behavior, system safety evaluation and so on, which need a lot of objective and historical data support, such as risk analysis in risk management and dangerous influence in system analysis. Moreover, safety environment and safety behavior was influenced by the human being’s subjective evaluation. One hand, there are less historical construction accidents data recorded in paper. In the other hand, expert evaluation influenced by personal experience and professional standard. The two aspects restrict the development on safety studies.Recently, the researches abroad studies safety from planning stage before construction. According to document index, study on this aspect has hardly been found in china. Construction organization plan is a guide to organize the construction operation for construction firm. The plan clarified relationship among construction units in different construction stages and relationship between construction resources and construction work. Construction site is an important resource like labor, equipment, material and time and resources allocation was also important part in the construction organization plan. Construction site layout plan is optimization of construction site to put temporary facilities into free locations in construction site. A good site layout can shorten transportation time, reduce material transportation frequency, avoid material rehandling, reduced labor cost and thus to reduce construction cost. Through reasonable assignment of construction operation area, auxiliary operational area, material lay down area in construction site layout plan can avoid conflict between human and facilities, facilities and facilities, human and environment, facilities and environment thus to improve construction site safety level. The study aims to optimize construction site layout to avoid conflict in construction site, reduced safety risk and improve construction safety level. In order to guarantee the implement of construction site layout plan, the cost related to the site plan should be reduced. In the construction practice, construction safety was sacrificed when construction cost was improved, which is also the reason why construction safety level in construction firm is hard to improved. So, a good site layout should satisfy the requirement of safety improvement and cost reduction.Construction site layout planning can be regarded as a method of optimizing the usage of construction space by assigning site facilities to the available construction space, with the fulfillment of a number of conflicting and/or congruent objective functions, under a set of layout constraints. Construction site layout plan always be modeled as Quadratic Assignment Problem (QAP) and can be solve by optimization model established. In the study, a construction site layout plan safety model was proposed and the conflicting objective functions are improve safety level in construction site and reduced safety cost deduced by construction site layout plan. In order to find the optimization solution for the model, Pareto-based ant colony optimization and genetic algorithm was developed. A construction project was used to verify the proposed model. The proposed model was applicable for residential and commercial building construction but not applicable for infrastructure construction and industrial construction. It is because construction technology between residential and commercial building construction are similar while there are big differences between them to infrastructure construction and industrial construction. Construction duration for infrastructure is very long and constructon site are varied. It is hard to define construction site boundary and the facilities involved in construction operation are limited. Thus, safety influenced by construction site layout plan is limited. For industrial construction, most of structure member was precast outside construction site. The structure members are need to assembled in construction site. Thus, the temporary facilities in construction site have little influenced to the construction operation. For residential and commercial building construction, the types and amount of facilities are similar for similar construction technology. The construction site boundary can easily and clearly defined and at the same time, the temporary facilities involved in the construction site play an important part to construction operations.The research methodologies involved in proposed model are systematic layout planning, entropy theory, Pareto-based ACO-GA and technique for order preference by similarity to an ideal solution (TOPSIS). Construction site layout planning problem is facility layout problem. The problem existed not only in the planning and programming of project construction, but also in production logistic system design of the manufacturing industry. The thesis applied systematic layout planning in the manufacturing industry to analyze the interaction flows between the facilities in the construction site; The weights between qualitative and quantitative factors in interaction flows and the weights between the attributes describe the construction site layout candidates are deduced by entropy theory, the theory focus on removal of uncertainty; ACO and GA are commonly used in solving construction site layout planning problem, in order to improve the optimization capability of GA, the proposed algorithm make use of ACO to improve quality of initial population of GA. At the same time, the proposed algorithm combine Pareto optimization theory to ACO and GA to solve multi-objective construction site layout planning problem, the algorithm called Pareto-based ACO-GA; TOPSIS is a method to solve multiple attributes decision-making problem, the method based on the principle of choosing an alternative which has the shortest distance from the positive ideal solution and the longest distance from the negative-ideal solution.The proposed model consists of four parts, which are parts of input, optimization, evaluation and output. In the part of input, temporary facilities and free location in the construction site are recognized and the interaction flows between the facilities are determined via theory of logistics analysis in system layout planning. The most important part in the model is optimization part. There are two objective functions in the part, one is minimizing the safety cost in the construction site, and the other is maximizing the safety level in the construction site. The two objective functions are conflicting. In order to solve the mullet-objective function optimization problem, the research proposed Pareto optimization based ant colony optimization and genetic optimization algorithm. The algorithm helps the decision maker find "trade-off" solutions to balance all the objectives, which are conflicting or orthogonally involved. Therefore, there is hardly a global optimal solution to the objective function with the consideration of all constraints existed. Nevertheless, there is a set of optimal trade-off solutions called the Pareto set in any MOO problem. In the evaluation part, Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) was applied to select the best construction site layout among site layout candidates in terms of some pre-determined attributes, such as efficient movement of materials, tie in with external transportation, which are not considered in the objective functions. The output part is the last part in the model, the best construction site layout selected in the evaluation part was the final decision making for the site planner. In order to prove the feasibility and effectiveness of proposed model, a project in the city of Dalian was used to validate the model. The results showed that with the application of the model, the safety cost should be reduced by7.7%～11.4%and safety level should be improve by11.9%～16.3%with the comparison with the original site layout designed in the project planning.The research innovation points are transfer semi-structured problem into structured problem make use of quantitative method of logistic analysis; apply mathematic model solve construction site layout safety problem from the aspect of objective; develop pareto-based ACO-GA to solve multi-objective optimization problem.The proposed model should help the site planning to design a good site layout to improve the construction site safety level and reduced the safety cost at the same time. The research is applicable and by optimizing the construction site layout planning from the objective aspect. The development of theory of construction site layout planning optimization is benefit to domain construction management in line with internationalization. |
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