Influence of Cast-in-situ Connection and Sleeve Assembly Connection on the Seismic Performance of Wall Plate Joints
Objective Developing prefabricated buildings effectively addresses the challenges associated with green buildings.A key issue in prefabricated buildings is the connection,as the quality of node connection performance directly affects the overall quality of these structures.Three cast-in-place components and one prefabricated sleeve connection member are designed to understand the influence of cast-in-place connections and pre-fabricated sleeve connections on the seismic performance of ceramsite concrete composite wallboard joints.All the components are L-shaped and primarily consist of a core area,a wall panel composed of ceramsite concrete slabs on both sides and a sandwich core insulation board.This com-ponent provides good thermal insulation performance,mitigating the issue of detaching external wall insulation boards.Methods For the proposed member,a low-cycle repeated load test is conducted,consisting of two parts:Vertical loading and transverse loading.The seismic properties of the components,including failure mode,hysteresis and skeleton curves,bearing capacity,stiffness degradation,energy dissipation capacity,and residual deformation,are investigated through these tests.Results and Discussions The test results indicated that the failure areas of both types of components occur on the flange plate and web.The con-crete at the foot of the web tends to tear or crush,and the steel bars elongate or bend.Among the cast-in-place components,failure primarily res-ults from crushing the concrete at the web's base and the elongation and bending of the steel bars,ultimately leading to the specimen's destruc-tion.In contrast,the webfoot of the sleeve connection member shows less significant damage,with failure occurring due to the vertical reinforce-ment of the outer edge of the specimen's web being pulled out.The core areas of the nodes in both types of components remain intact,meeting the design principle of"strong nodes and weak components".The failure modes of both types of components are classified as bending and shear fail-ure.The hysteretic curves of cast-in-place components and sleeve-connected components are similar.However,the hysteresis curves of sleeve-connected components exhibit greater"pinching"compared to those of cast-in-place components,primarily because the sleeve connection further limits the slip deformation of the components.A comparison of the skeleton curves of the two specimen types shows that the positive and negat-ive yield loads of prefabricated sleeve connection members increase by 12.71%and 6.77%,respectively,while the positive and negative peak loads increase by 12.71%and 4.95%,respectively,compared to cast-in-place components.This indicates better bearing capacity performance for prefabricated sleeve connection members.Analyzing the displacement and load changes of the two specimen types during the"cracking to yield stage"(stage 1)and the"yield to peak stage"(stage 2)exhibits that the load value in stage 2 decreases compared to stage 1,while the displace-ment value increases significantly.This indicates that the relative deformation capacity of both component types is stronger in the later stages,en-hancing their seismic resistance.Due to the brittle nature of the grouting aggregate,the ultimate deformation capacity of the sleeve connection member is affected to a certain extent,resulting in a slight decrease in the displacement ductility coefficient.However,based on the test results,the deformation capacity of the sleeve connection member is close to that of the cast-in-place component,which meets the deformation capacity requirements.The strong yield ratios of the cast-in-place specimens are comparable to those of the sleeve connection members,with the strong yield ratios of the two types of components being 1.39 and 1.36 in the positive direction and 1.95 and 1.92 in the negative direction,respectively.This demonstrates that the safety reserve capacity of the two types of components is the same.The stiffness degradation of the two types of com-ponents is also similar,with significant stiffness degradation occurring before yield and slower degradation after yield.The initial stiffness of the sleeve connection member is 7.53%higher than that of the cast-in-place component,and the overall stiffness curve is located above that of the cast-in-place member,indicating that the stiffness of the sleeve connection member is significantly higher than that of the cast-in-place compon-ent.The analysis results showed that the grouting sleeve plays a role in strengthening the lateral stiffness of the component,which is more condu-cive to the overall stress deformation of the specimen.The calculated cumulative energy dissipation and the equivalent viscous coefficient of both types of components increase with loading,representing the increasing cumulative damage of the components.The equivalent viscous coefficient of the grouting sleeve connecting member at each stage is smaller than that of the cast-in-place connecting member,indicating that the overall en-ergy dissipation capacity of the sleeve connecting member is slightly inferior.The later failure of the cast-in-place component is primarily due to the crushing of the concrete at the foot,whereas the sleeve connecting member is constrained by the grouting sleeve,leading to reduced reinforce-ment slippage and smaller residual deformation after the peak load compared to the cast-in-place component.The strength degradation coefficient of the two types of components aligns closely with the strength degradation curve,and the strength change is relatively stable,indicating that the strength degradation capacity of the two types of components is essentially the same.Conclusions Therefore,the sleeve connection mode is effective,and the overall working performance of the components is satisfactory.Based on the advantages of low cost,ease of quality control,and effective shortening of the construction period,the prefabricated sleeve connection com-ponents can be a reference for applying such components in practical engineering.
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