Study On Refined Investigations Of Seismic Damages Of Reticulated Domes

During the last 30 years,numerous reticulated domes have been constructed in China as the premier option for grand public buildings like stadiums and exhibition halls.These large span structures are often deemed the magnificent landmarks of cities.Seismic hazards are among the frequent and devastating natural hazards in China.Many reticulated domes were constructed in earthquake-prone areas,which could perform a significant role in accommodating those earthquake victims as sanctuaries.Therefore,it is critical to understand seismic performances of the reticulated domes and establish instructive codes for seismic designs of large-span space structures.Previous researches had made many assumptions and simplicities to seismic investigations of reticulated domes,considering some intrinsic characteristics of the dome like complicated internal force status and abundant tube components.However,with the development of research methods and computation tools,it becomes viable to apply some complex structural effects in engineering practices of reticulated domes to assessments on seismic performances of reticulated domes.This will encourage us to better disclose the actual seismic performances of the reticulated domes in practices and help design and construct more reliable and securer reticulated domes with more economic costs to resist earthquake hazards.This thesis established effective finite element methods to simulate complex damping for structural dynamic analyses and realize typical complex structural effects like effect of considering damage accumulation behavior of steel material,and effect of considering masonry infilled walls.By using these models,their influences on seismic dynamic responses and capacities of single-layer reticulated domes were extensively evaluated.Detailed contents included the following four parts:1.Influences on seismic performances of single-layer reticulated domes by introducing complex damping modelIn order to solve the problems of frequency-dependent energy dissipation and large variation on modal damping ratio of Rayleigh damping(RD)model,five-parameter integer-order derivative model was adopted to estimate ideal complex damping model in time-domain constitutive law for implicit dynamic time-history analyses of reticulated domes.The simulation method for complex damping(CD)model was verified by structural responses of simple-degree-of-freedom systems and shaking table test of scaled single-layer reticulated dome.After considering complex damping model,the damping forces of the structural tubes become smaller and therefore the internal seismic forces become larger,which induces plastic members in earlier phase and deeper plasticity.The seismic capacities of the domes in most cases decease 10% or more.The influences on the seismic responses of the single-layer reticulated domes were summarized by comparing results using CD model and RD model.2.Influences on seismic performances of single-layer reticulated domes by applying damage accumulation behavior of structural steelThe damage accumulation behavior of structural steel for beam elements was described by ductile fracture damage model considering Chaboche nonlinear kinematic hardening law to better simulate the behaviors of weakening on material stiffness and strength under cyclic loadings.The developed UMAT was proved more accurate and applicable in approximating the hysteretic curves of cyclic tests on circular tube members,and structural responses of shaking table test on a scaled single-layer reticulated dome,compared to some other previous steel constitutive model.Parametric dynamic incremental analyses(IDAs)on reticulated domes with different spans,roof masses,and rise-span ratios were conducted to extensively study the influences of effect of considering damage accumulation behavior and its mechanism was explained.The type of dome,needed to consider damage behavior of structural steel in order to obtain more accurate seismic responses and capacities,are pointed out.3.Influences on seismic performances of single-layer reticulated domes by including masonry infilled walls in the substructureBecause masonry infilled walls(MIWs)greatly contributed to the overall stiffness of substructure and they were vulnerable and easily cracked during earthquakes,the equivalent macro model with two diagonal single-struts assigned with modified Dolsek's skeleton curve was used to simulate the MIW,in order to study the interaction mechanism between substructure with MIWs and reticulated dome.This equivalent macro model was verified by hysteretic tests on masonry infilled reinforced concrete structures in two literatures.The reasons for deceased seismic capacities of single-layer reticulated domes and severe plasticity development of outer members around dome supports by including MIWs were well discussed.The influences of MIWs on seismic responses of reticulated domes were summarized through parametric IDAs of reticulated domes and the collapse mechanisms of reticulated domes considering MIWs under severe earthquakes were thoroughly investigated.4.Numeric simulation of seismic damages of Lushan County arena by considering aforementioned simulation method and structural complex effectsLushan County arena sustained severe seismic damages to the roofing reticulated dome after Lushan earthquake.In the present study,refined simulation reproductions of seismic damages of Lushan County arena were conducted.Lushan County arena was modeled with refined finite element models by including and excluding complex damping model,damage accumulation behavior of structural steel,and masonry infilled walls.Ground motion records from both station YAM and station LSF were employed in all finite element models.The developed simulation methods were verified by the actual observed damages of Lushan County arena and their influences on the seismic responses of the arena were also thoroughly studied.