Experimental Study And Design Method Of Novel Precast Concrete Frame Structure With Adjustable Performance

Research and development of precast buildings to meet the needs of environment-friendly construction and earthquake safety of urban is one of the key issues in promoting building industrialization.In order to improve the generalization and standardization of precast structural components while ensuring and optimizing the seismic performance of precast concrete frame structures,the research team proposed the concept of precast frame structures with adjustable performance.Introducing performance-adjustable joints and separation of the lateral and vertical load-bearing systems are two feasible ideas to realize such concept.Based on the above two ideas,two novel performance-adjustable precast frame structural systems are proposed in this study,namely(1)precast concrete adjustable joint frame(PCAJF),and(2)precast concrete buckling restrained braced hinged frame(PCBRBHF).In this study,for these two novel structural systems,details of the critical joints are proposed;multi-level theoretical,experimental and numerical studies covering critical components,joints and overall structures are carried out;the structural performance controlling mechanism is revealed;and the structural design method is proposed and verified.Based on these,the seismic performance of precast concrete frame is ensured and enhanced,and the extent of generalization and standardization of precast structural components is improved.This study can provide a reference for the industrialization of precast buildings.The main research work and results are as follows.For the PCAJF structural system:(1)A novel performance-adjustable precast beam-to-column joint is proposed,which is introduced into the precast monolithic frame structure to form the PCAJF structural system.Two forms are proposed for the novel joint,including single-stage yield type and double-stage yield type.Such joint is featured with desirable deformation and energy dissipation capacity,as well as controllable damage mode.The key mechanical parameters of the joint can be adjusted after the prefabrication process is completed,which is conducive to realizing the generalize and standardize.The optimization solution of details and assembly sequence of the joint is proposed,which is conducive to the improvement and adjustment of joint performance.(2)Experimental studies on the mechanical properties optimization of the key components of the novel joint with adjustable performance,rotational friction hinge,are carried out.The theoretical calculation method of the performance parameters of the friction hinge are derived,which provides a basis for the performance adjustment of the joint.Based on a total of 62 load cases of mechanical property tests,friction plate material optimization tests and lug plate detail optimization tests,the feasibility of the rotating friction hinge as a key component of the node is verified,and the friction plate material and form of lug plate are selected,which laid the foundation for the stable and adjustable mechanical performance of the friction hinge and the novel joint.(3)Experimental and numerical studies on the seismic performance of the performanceadjustable precast beam-to-column joint are carried out.The theoretical calculation methods of the mechanical performance parameters of the novel joint are derived,which provided the basis for the joint performance adjustment.Based on the full-scale tests and refined finite element simulations,the adjustability of single-and double-stage mechanical properties of the joint is verified,and the multi-stage behavior and energy dissipation capacity of the joint are revealed.A refined numerical simulation method of the joint considering the assembly process is proposed and verified,and the feasibility and effectiveness of the details and assembly sequence are verified.An accurate and efficient macro numerical simulation method is proposed and validated,which provides a basis for the numerical investigation on seismic performance of PCAJF.(4)Research on the seismic response control mechanism and design method of PCAJF are carried out.Based on large number of nonlinear analyses,the feasibility and multi-stage adjustable performance of PCAJF are validated,the effect of the critical parameters of the joint on the seismic performance of structure is identified and investigated,and the method optimal value selection method of joint parameters is developed.Design method of PCAJF is proposed and validated.Based on the adjustment of joint parameters,controlling of the drift concentration and maximum inter-story drift ratio under very rare earthquake is achived in addition to meeting the performance objective required by the codes.(1)Based on the concept of separation of the lateral and vertical load-bearing systems,the precast concrete buckling restrained braced hinged frame is proposed.Such structural system is featured with adjustable performance,controllable damage mode,etc.The buckling restrained braces and precast concrete beams of the structure is facilitating to realize generalization and standardization of structural components.The bracing layout,joint form and critical details of precast components are proposed,which is beneficial to improve the feasibility of the structural system.(2)Shaking table tests of the PCBRHF structural system are carried out.Under the action of multi-level earthquake actions,the structural integrity is desirable,and the seismic performance meets the requirements of the codes.The plastic damage is concentrated in the buckling restrained braces,and the precast beams and columns basically remain undamaged,achieving the expected structural features.The rationality and feasibility of the proposed forms and details of critical joints and components are verified.(3)Theoretical analysis and numerical simulation research on the behavior of PCBRBHF structural system are carried out.The feature of separation of vertical and lateral load-bearing systems are verified.The effect of precast column on optimization the deformation mode of structure(i.e.,alleviating of drift concentration)is revealed.The effect of stiffness factor and bottom boundary condition of the precast column are analyzed.(4)The analytical expressions of the deformation and force distribution of PCBRBHF are derived,which provides a theoretical basis for the detailing design of precast components.Based on large number of nonlinear time-history analyses,a method for determining the demand of stiffness factor is established,which can be used in the stiffness design of precast columns.The design method of the PCBRBHF structure is proposed and verified.Based on this,controlling of drift concentration is achieved in addition to meeting the performance objective required by the codes.