| Prestressed fabricated multi ribbed slab column structure system(referred to as IMS system)is a semi-dry-assembled structure system which can realize the efficient construction of factory prefabrication and has the characteristics of high disaster resistance,low construction cost,energy conservation and environmental protection.The system was first established in Yugoslavia.There are the following problems in the application of IMS structure in China: the built IMS structure is prone to serious damage or even collapse under the action of earthquake due to the low seismic fortification level,structural durability degradation and reaching the design service life.Due to the complexity of its construction technology and the lack of general calculation software supporting its design theory,the popularization of the system is also greatly hindered.Based on the scientific research and development project of CSCEC "Pre-research on integral prestressed prefabricated slab column structure system"(CSCEC-2017z14),this thesis provides theoretical support for structural detection and reinforcement based on the research on the connection mechanism of prefabricated components,and improves the seismic performance of IMS structural system joints,A new type of posttensioned prestressed fabricated slab column joint with hybrid connection is proposed,which can be extended to multi-story and high-rise buildings with large column network.In this thesis,the seismic performance and influencing factors of the new joint,the construction technology and the design method of the new joint are deeply studied from the aspects of theoretical analysis,joint test and numerical simulation.The main research contents and conclusions of this thesis are as follows:(1)Based on the comparative analysis of the advantages and disadvantages of IMS structural system and other mainstream fabricated systems,and the summary of the connection technology of prestressed fabricated joints and the key technology of efficient construction,it is pointed out that the friction torque at the end of composite beam in IMS structural system is an important factor affecting the structural energy consumption.Through the monotonic loading test of 8 full-scale model specimens of IMS prestressed friction joints,The factors affecting the friction performance of IMS joint joint joint surface are preliminarily explored,and the crack propagation process and the variation law of bearing capacity under different joint surface types,different joint grouting materials and different shear span ratio are discussed;It is determined that the plate angle and column angle of the extra-large column grid IMS structure are the most suitable form of cogging to improve the shear capacity of the structure,and it is determined that the joint using high-strength non shrinkage steel fiber grouting material instead of traditional fine aggregate concrete can play a very important role in improving the strength and ductility of the joint;Thus,a new structure of integral prestressed fabricated plate column joint is proposed,and the joint surface friction coefficients of IMS joints with different joint structures are determined through experiments,which determines the analysis parameters for the numerical simulation of the joint.(2)The full-scale model tests of three IMS prestressed friction joint specimens under low cyclic loading are carried out to explore the influencing factors and laws of the new joint on the seismic performance.It is found that using steel fiber high-strength non-shrinkage grouting material for joint joints can effectively delay the damage of grouting material under repeated load and reduce the loss of prestress of joints;At the same time,the prestressed reinforcement in the precast column and the open channel near the column area will be changed to the unbonded form,the strain distribution of the prestressed reinforcement in this section will be more uniform,the plastic deformation will be reduced,the structural damage and later stiffness degradation will be reduced,and the deformation capacity of the structure will be brought into full play.At the same time,in order to enhance the energy consumption of the joint,the structural form of hybrid connection of prestressed reinforcement and ordinary reinforcement is proposed in the open slot.Through ABAQUS numerical modeling and analysis,the joint structure is further optimized,and the influence laws of the position of prestressed reinforcement,the local weakening proportion of ordinary reinforcement and the bonding mode on the energy consumption capacity of the hybrid joint are obtained.The numerical results show that the seismic performance index of the hybrid joint is comparable to or even better than that of the cast-in-situ joint,and has the characteristics of self-centering and low damage.(3)Based on the optimized joint structure,the quasi-static tests of two two-way IMS spatial frame joints with laminated layers are carried out,and the experimental research is combined with finite element simulation to explore the influence of the friction torque at the end of the laminated beam caused by the lateral prestress and the friction coefficient of the joint joint surface on the seismic performance of the joint.In addition,the residual shear capacity of joints is tested on the specimens after hysteretic test to evaluate the friction and shear performance of this type of joints after large earthquake.The results show that the friction torque at the end of the composite beam has a great influence on the initial stiffness,bearing capacity,energy consumption and crack resistance of the joint,which should be considered in the design.The effect of the friction coefficient of the joint surface on the structural performance takes 0.7 as the threshold value.When it is less than the threshold value,the forward ultimate bearing capacity of the joint,the bearing capacity of the end of the composite beam,the friction torque and the initial stiffness increase with the increase of the friction coefficient;After reaching the threshold,the increase of the positive ultimate bearing capacity of the joint is no longer obvious,but the stiffness degradation rate is gradually accelerated.This type of joint can still ensure good shear performance after a large earthquake and has sufficient reserve of post-earthquake shear bearing capacity.(4)Based on the joint test and finite element analysis,the calculation formula of the bearing capacity of the end section of the new joint composite beam under the coupling action of moment shear friction torque is deduced and verified;Based on the development of the model of the slab and the calculation method of the dense rib,the YJK method is used in the calculation of the stiffness of the slab system,which is related to the calculation of the dense rib model,and is introduced in the test of the dense rib system;Finally,the construction measures related to the new joints design are given. |
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