Study On Seismic Performance Of Mega Frame-Glued Laminated Timber Super High-Rise Structure

Modern wood structure systems not only have the characteristics of green,livable,and fast construction,but also have smaller seismic requirements due to their lower weight and higher strength to weight ratio.Extending wood structures to the field of high-rise buildings can meet the concept of green building development advocated by our country and alleviate the population density and land tension in our country.Currently,to develop wood structures to ultra high-rise buildings is in a bottleneck period,studying how to apply modern wood structures to higher heights has become a major challenge.Based on the benchmark model from Tongji University,this paper combines the green low-carbon glued wood structure as a sub structure with the mega column frame-core tube as a high lateral stiffness main structure,to grow up a mega frame-core tube-glued laminated timber super high-rise structure,then uses a nonlinear analysis software to establish this structure,and carries out elastic-plastic dynamic time history analysis for this structure to study the feasibility and seismic resistance of the structural Performance and strong earthquake damage.According to the strong earthquake damage situation of the structure,strengthening and damping schemes are proposed to control the strong earthquake damage of the main sub connection and the wood sub structure.Finally,the seismic vulnerability analysis of the super high-rise timber structure is adopted to evaluate the reasonable performance level of sub structure components.The conclusions of this paper are as follows:(1)The elastic-plastic dynamic time history analysis of the structure under the 7-degree earthquake were carried out.The results shows that all overall performances of the super high-rise timber structure meet the specification requirements under rare earthquake actions equivalent to 7-degree aseismic fortification.Co MPared to the benchmark model,the maximum story drift of the main structure decreases by 10.69% on average.The average severely damage ratio of the shear wall decreases by 1.1% co MPared to the original model from 2.1%,and the non damage ratio increases from 55.1% to 67.2%.It indicates that in the mega frame-core tube-glued laminated timber super high-rise structure,the damage to the main structure caused by seismic force is smaller,and the structural seismic demand is smaller.It means that the super high-rise wood structure is feasible.The results shows that the wooden frame columns of the sub structure are in the state of various working conditions that1.6% of them are severely damaged on average and 1.9% of them are seriously damaged on average.And the average value of the failure rate of the connections between mian-structure and sub-structures in the axial direction is close to 50%,while in the out-of-plane shear direction is as high as 80%,indicating that the connection are easy to damage,especially in the out-of-plane shear direction.Therefore,it is necessary to conduct strong earthquake damage control research on main sub connections and wood sub structures.(2)1.The friction damping connection independently developed in this paper is used for damage control of the main-sub connection.The research results show that under the action of a 7 degree earthquake,after the friction damping connections were equipped,the connections do not exceed the predetermined maximum sliding limit,Friction damping connection plays a role in protecting the connection in strong earthquakes.2.To strengthen timber frame sub-structure,K-braces were equipped.The research results show that under the action of a 7degree earthquake,after the K-braces were equipped,the maximum story drift of the sub structure decreases from 7% to 35% on average under the maximum earthquake,and the decrease in damage to wooden columns in each section of the structure can reach 11.6%,while the average moderate to severe damage ratio of wooden supports in the substructure is39.7%,and the severe to severe damage ratio of structural supports can reach 13.1%.3.In response to higher structural performance requirements,considering vibration reduction measures,the friction damping brace independently developed by the research team is used for damage control of the support structure.The research results show that after adopting the friction damping braces,the average proportion of the severely damaged support under each working condition decreases from 4.9% to 0.5%,it shows the damage of the support is significantly reduced.4.As the structure is a long-periodic structure,it is necessary to study the seismic performance of the structure under more than one degree of large earthquake and long-periodic earthquake.The research results show that both the wooden K-braces and the friction damping braces can play a good damage control effect and improve the seismic performance of the substructure under the action of more than one degree large earthquake and the long-periodic earthquake.5.Due to the limited additional stiffness and energy dissipation capacity of wooden K-braces,it is necessary to adopt BRB damping braces with better energy dissipation capacity to conduct damage control research on the substructure under the action of a larger than one degree earthquake.The research results show that after adopting the BRB damping braces,the average severe damage ratio of the wooden columns of the substructure under various working conditions decreases from 4.0% to 1.5%,and the average severe damage ratio decreases from 5.5% to 1.0%.This scheme has a good control effect on the damage of the substructure under the action of more than one degree of strong earthquake.(3)Co MParing the seismic vulnerability curves of initial structures and wooden K-brace schemes,it can be seen that the wooden K-braces reduces the exceeding probability of the severe damage of the wood lateral members by 27%,and reduces the exceeding probability of the severe damage by 30% under the action of a strong earthquake of 8 degrees.The support reinforcement scheme can effectively reduce the strong earthquake damage of the key lateral force resistant members in the wood substructure,and improve the seismic performance of the wooden substructure.Co MParing the seismic vulnerability curves of the wooden K-brace schemes and the friction damping brace schemes,it is found that the friction damping brace scheme reduces the exceeding probability of severe damage of the wood support by 28%under a 7 degree earthquake,and reduces the exceeding probability of severe damage of the wooden K-braces by 30% under an 8 degree earthquake.The friction damping brace scheme can effectively reduce the strong earthquake damage of the wooden K-braces and improve the seismic performance of the wooden substructure.Co MParing the seismic vulnerability curves of structures under long and short period ground motions,it can be seen that co MPared to short period ground motions,the exceeding probability of each seismic vulnerability curve of structures under long period earthquake action is greater,and the response of structures under long period earthquake action is greater.Therefore,more attention should be paid to the seismic damage response of the super high-rise wooden structure under long-periodic earthquake.