Seismic Performance And Design Methodology Of Glulam Portal And Cross-Laminated Timber Shear Wall Structures

Wood is a renewable and environmentally friendly construction material.Building multi-story or high-rising timber structures is an effective way to reduce carbon emissions of construction industry in China.Glulam portal and Cross-Laminated Timber(CLT)shear wall structure is one form of multi-story timber structures.It is composed of glulam portal frame systems and CLT shear wall systems,with beam-towall connections connecting them.The glulam frame system possesses the superiorities of aesthetic advantages,reasonable structural efficiency and flexibility of plane layout,and the CLT shear wall system can provide a sufficient lateral stiffness if properly designed.Glulam portal and CLT shear wall structures are expected to achieve all the above advantages due to hybridization.This thesis focuses on the seismic performance and design methodology of glulam portal and CLT shear wall structures.Experimental research,theoretical analyses,and numerical simulations were conducted,in order to understand the seismic mechanism,as well as build the seismic design methodology,of such structures.The main research contents and conclusions are listed as follows.A series of experimental studies were firstly conducted to obtain the mechanical performance of joints.Two energy dissipaters used as connectors between parallelly adjacent CLT wall panels,named O-shaped flexural plate(OFP)dissipater and plate with openings(PO)dissipater,were proposed.Monotonic and cyclic loading tests were conducted on such two energy dissipaters,hold-downs,angle brackets and half-lapped joints,with the failure modes and hysteretic performance being obtained and analyzed.The test results showed that low-cycle fatigue failure occurred in the cyclic loading test of PO dissipaters,which indicated limited energy dissipation of this dissipater,while the OFP dissipater was quite efficient in dissipating energy.In the cyclic loading test,the maximum equivalent viscous damping of OFP dissipaters was 60% larger than the half-lapped joints.Eight CLT shear wall specimens,considering different construction methods,were then tested under cyclic lateral loading.The failure modes,hysteretic performance,stiffness degradation,energy dissipations and contribution of deformability components of the specimens were obtained and compared.The experimental results showed that the main deformation mode of CLT shear walls was rocking,which contributed to 72.5% ～ 92.1% of the total lateral displacement,while bending and shear deformation were quite limited,respectively leading to less than 2.2% and 6.0% of the total lateral displacement.In platform-type multi-panel CLT shear walls,the deformation of parallel wall-to-wall connections positioned in the second story was larger than those in the first story.The stiffness of platform-type CLT shear walls was smaller than that of balloon-type CLT shear walls,and the stiffness of multi-panel CLT shear walls was smaller than that of single-panel CLT shear walls.Besides,there was little difference of maximum lateral resistance between platform-type single-panel CLT shear walls and balloon-type single-panel CLT shear walls.Compared to platform-type CLT shear walls,the connection in balloon-type CLT shear walls suffered more damage,which led to more obvious stiffness degradation of balloon-type CLT shear walls.The equivalent viscous damping of CLT shear walls was between 0.0379～0.2018.The balloon construction method could help OFP dissipators dissipate more energy,and the equivalent viscous damping of balloon-type CLT shear walls with OFP dissipators was1.47 times that of platform-type CLT shear walls with OFP dissipators.Based on the experimental results,Finite Element(FE)models were proposed.The research work began with the development and optimization of a uniaxial hysteretic model for dowel-type timber joints in Open Sees,named Dowel Type.Based on Dowel Type model,nonlinear FE models were developed within the Open Sees framework for hold-downs,angle brackets,half-lapped joints and OFP dissipators,and were validated by test results.The modeling technique for CLT shear walls was also proposed.The proposed FE model could provide good predictions and distinguish different deformation modes of CLT shear walls,while maintaining considerable computational efficiency.Based on the above modeling techniques and results from previous research,the FE model for glulam portal and CLT shear wall structures was developed.After that,the modeling technique was used to investigate the dynamic response of glulam portal and CLT shear wall structures.12 glulam portal and CLT shear wall structures were designed,and were subjected to seismic excitations with the hazard level of major earthquakes in Open Sees.The influence of vertical construction methods,horizontal construction methods,and parallel wall-to-wall connections on connection damage,inter-story drift,floor acceleration,structural drift,inter-story CLT shear wall damage was investigated.The applicability of the above-mentioned seismic performance indicators on the seismic performance evaluation of glulam portal and CLT shear wall structures was compared.Incremental dynamic analyses were also conducted,in order to obtain the seismic performance indicator limits for immediate occupancy(IO),life safety(LS),and collapse prevention(CP)performance levels.The results showed that,the connection damage of glulam portal frame systems was quite limited under major earthquake,indicating IO performance of glulam portal frame systems.However,some connection in CLT shear wall systems suffered serious damage,and the connection damage was greatly influenced by the vertical construction method.The inter-story drift has a close correlation with connection damage of glulam portal frame systems,while it could not describe the connection damage of CLT shear wall systems.It is recommended that the inter-story CLT shear wall damage be adopted for quantifying connection damage in CLT shear wall systems.For inter-story CLT shear wall damage,the connection damage related limits were respectively 0.18,0.48 and0.72 for IO,LS and CP performance levels.For inter-story drift,the connection damage related limits were respectively 1.5%,3.9% and 5.4% for IO,LS and CP performance levels,and the global stability related limit was 2.7% for CP performance level.Finally,the seismic design methodology was proposed for glulam portal and CLT shear wall structures.The seismic performance indicator limits for IO,LS and CP performance level were summarized,and a method was theoretically developed for estimating the deformation modes of glulam portal and CLT shear wall structures under seismic excitations.Based on the seismic performance indicator limits and deformation modes,the direct displacement-based design(DDD)procedure was improved and developed for glulam portal and CLT shear wall structures.The proposed design methodology was then utilized to design a four-story glulam portal and CLT shear wall structure as an example,and the feasibility of the design methodology was verified.