Multi-objective Earthquake-resistant Optimization And Joint-damper Based Energy Dissipation Optimization Of Precast Concrete Frame Structures With Hybrid Connections

The precast concrete structure has many advantages and occupies an important position in urban construction today.But it is particularly important to ensure its seismic performance while exerting its advantages.The key factor of affecting its seismic performance is the performance of its joints or connections.At present,researches on improving the seismic performance of precast concrete structures mainly focus on the development of connections and energy dissipaters.In fact,the arrangement of developed connections and the reasonable parameter values of energy dissipaters based on their mechanical properties are also problems worthy of studying.Connections or energy dissipation devices that match the local performance requirements of the structure can effectively guarantee the rigidity,strength and ductility of the precast concrete structures.To this end,this dissertation makes use of optimization methods to search for a reasonable design form of the precast concrete structure.On the one hand,the precast concrete structure has many designable variables including the mechanical properties of the connections.Using the powerful search ability of the algorithm to replace manual design can make the design process rapider and more reliable.On the other hand,using the idea of multi-objective optimization,designers can obtain a series of solutions under specific goals and constraints for selection so as to avoid complicated repetitive design processes.In order to obtain a reasonable structural design form that considers the action of earthquakes,the main research contents of this paper are as follows:(1)An optimization method for connection distribution of precast concrete frames considering seismic action is proposed.The optimization process aims to find a reasonable arrangement of different types of connections in existing projects to save connection costs while ensuring the seismic resistance of the structure.In this process,an improved genetic algorithm is used as the optimization algorithm.Sap2000 OAPI is used to establish,modify the model and perform the finite element analysis of the structure.The rigidity of the structure under frequent earthquakes is calculated.The stiffness-related parameters include inter-story stiffness ratio and inter-story drift are set as constraints.Multi-stage connection manufacturing costs are set as the objective.The results show that,compared with the traditional connection layout,the optimized structure reduces the connection cost to a great extent and presents a more reasonable deformation form under frequent earthquakes.(2)A multi-objective optimization method for hybrid connected precast concrete frame structures is proposed to maximize the structural strength reserves while obtaining the minimum structural cost.Taking the advantage of the designability of precast concrete structural connections,the connection parameters and member cross sections are set as variables.The structural strength reserve parameters are defined to characterize the structure strength demand under the action of frequent earthquakes relative to the structural yield redundancy.Constraints are divided into structural levels and component and connection levels to control the overall and local performance.In this process,the multi-objective optimization problem is solved based on NSGA-Ⅱ.Pushover analysis is used for the nonlinear analysis of the structure and the calculation of strength reserve parameters.The method is illustrated by a plane frame design case.Results show that the system can effectively control the deformation of connections and components under earthquake action and the yield degree of the structure through the strength reserve parameters.The design process also gives the minimum cost structure forms under different strength reserves for the designer to choose.(3)In areas with high seismic fortification requirements,a method for optimal design of hybrid connected precast concrete structure with joint energy dissipation devices is proposed.The optimization design process is divided into two stages.In the first stage,the member size and connection stiffness are used as variables to control the rigidity of the structure under frequent earthquakes and the cost is minimized.In the second stage,the damper parameters are used as variables to improve the damper energy dissipation ability and minimize the cost of the damper.The two phases correspond to the constraints of the elastic and elastoplastic phases respectively.The optimization problem is handled based on improved single-object and multi-object genetic algorithms.The process is illustrated by a plane frame optimization design case.The optimized structure ensures the rigidity of the structure under frequent earthquakes and at the same time controls the damage development of the joints under strong earthquakes.