Study On Mechanical Behavior Of Steel-CLT Composite Beam-Steel Column Composite Joints

In recent years,with the rapid transformation and upgrading of the domestic construction industry,engineered wood,as a new type of building material,is attracting increasing attention in engineering community.A combination of cross-laminated timber(CLT)as and steel frame not only exhibit maximum advantages of the two materials,but also helps to alleviate the engineered wood resources shortage in China.Meanwhile,it also provides a prefabricated building structure with many excellent properties such as easy to be disassembled,recyclable,environmental-friendly,light and earthquake-resisting.The steel-CLT composite beam-steel column(SCLTC)composite joint plays a key role in the steel frame-CLT floor composite structure.Foreign researchers have mainly investigated the flexural performance of SCLTC composite joints with flexible beam-column connections and these studies are almost laboratory experiments,few researchers have carries out systematic parametric studies.In addition,there has been scarce reports on the seismic performance of SCLTC composite joints.Therefore,the present study conducts simulation and parametric analysis on the flexural and seismic performance of the SCLTC composite joints based on the flush end plates of ABAQUS.The main work of this study are as follows:(1)The FE model of the test joints reported in previous literature were developed with ABAQUS.By comparison of the test results,the feasibility and correctness of the composite joints modeling under the effect of negative bending moment were examined.In addition,the existing beam-to-column steel joints with flush end plates in previous experiments were adopted for finite element simulation,and the model verification was conducted on the loading regime and boundary conditions under the horizontal loading mode of the column end.(2)The rotational performance of the SCLTC composite joint under the effect of negative bending moment was simulated and the parameters included the presence or absence of slabs,the thickness and width of the CLT slabs,the number and diameter of bolts between the plates,and the connection between the plates.The results showed that the strength and stiffness of the composite joint with CLT floor have been significantly improved.The relevant parameters(i.e.,the number and diameter of bolts between the slabs)at the lap joints of the slabs were sensitive to the flexural performance of the composite joint.Increase in the CLT slab size(i.e.,thickness and width)improved the flexural performance of the composite joint,but the improvement was limited.(3)The hysteretic performance of the SCLTC composite joint under low-cycle reciprocating loading was modelled,and in-depth discussion about the hysteresis curve,skeleton curve,energy dissipation and stiffness degradation were conducted.As shown by the results,the mechanical properties of composite joints under the effect of positive bending moment were improved by the combined effect of floor slabs than that of the negative bending moment.The axial pressure applied to the top of the column increased to a certain extent the ultimate bearing capacity of the beam end of the composite joint.(4)A three-parameter mathematical model for the moment-rotation angle relationship of the SCLTC composite joint under the effect of negative moment was proposed.The calculation model for the initial rotational stiffness of the composite joints was established according to the component method theory.Generally speaking,the calculated results corroborated the simulation results and the validation of the proposed model can provide theoretical basis for the design and application of the steel frame-CLT floor composite structure.