PROPERTIES OF CROSS-LAMINATED TIMBER PANEL WITH LOW-VALUE LUMBER AND PERFORMANCE OF CROSS-LAMINATED TIMBER WALL SYSTEM SUBJECTED TO SEISMIC AND SEQUENTIAL SEISMIC-WIND LOADINGS PDF Download

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Abstract : The Cross laminated timber (CLT) panels extended the market of timber material in structural construction, while its laminated structure allows layup design for utilizing low-value lumber. Through mechanical tests and numerical simulation, the mechanical properties of CLT made with low-value sugar maple (Acer saccharum) was first examined. The CLT panels made with white spruce (Picea glauca) salvaged from dead standing trees were examined. The mixed-species panels were prepared with the low-value sugar maple and salvaged spruce. The CLT panels were tested with the third-point and mid-point bending tests following ASTM D198 for major-axis flexural and shear properties. The CLT panels provided adequate flexural performance per current standard PRG 320-2019. The mechanical properties of the hybrid CLT panels with sugar maple surface layers were improved. In the meanwhile, the finite element model built with orthogonal constitutive law and progressive damage criteria simulated the mechanical behaviors of the tested CLT panels. Overall, the simulation results compared favorably with test data and provided reasonable estimates. A decomposed model with equivalent springs and shell elements based on the connection properties was developed to estimate the nonlinear dynamic performance of the conventional CLT shear wall. Full-size building simulation results indicated that the developed model could accurately estimate the wall dynamic performance. The dynamic performance of PT CLT rocking wall was also evaluated with numerical simulation. The similar equivalent decomposed wall model was developed and calibrated. A full-scale platform structure was simulated and compared with test results subjected to different seismic excitations. Because of the concentrated connection damage, the impact of sequential seismic-wind hazards on CLT shear wall systems is severer than that on traditional steel or reinforced concrete structures. With the developed conventional and PT wall models, the structural dynamic responses of different CLT wall systems were evaluated in wind-only and sequential seismic-wind scenarios. The wind-excited peak story displacement and acceleration for both CLT structures were magnified in the sequential seismic-wind scenarios compared with wind-only scenarios. The simulation results indicated that the sequential seismic-wind scenarios caused large acceleration with damaged connections for the conventional CLT shear wall structure. The PT CLT wall structure had minor displacement and acceleration, which was linear to the wind loading factors. The study of mechanical properties of the CLT panels made with low-value sugar maple and salvaged spruce can promote the utilization of the low-value lumber and promote forest management. The developed panel model provided an approach to estimate the CLT mechanical properties based on the nondestructive lamination test result, which can be a tool for future layup design. The developed decomposed equivalent wall models can capture the wall behavior effectively and efficiently, which potentially be an aid for the performance assessment of CLT structures. The results demonstrated the necessity of considering sequential hazard cases for conventional CLT wall structures, which is a reference for future development of performance-based design for conventional CLT wall structures.