Seismic Isolation Performance Of Strengthened Anchoring Shape Memory Alloy-Friction Pendulum Systems In Benchmark Steel Frame Structures

Friction pendulum bearings(FPBs)are an advanced isolation device that can isolate seismic inputs by a combination of pendulum and sliding friction.In addition,it has excellent load carrying and corrosion-resistance capacities,During the past decades,FPBs have been successfully applied to engineering structures.However,the traditional FPBs lack sufficient displacement restraining and re-centering capabilities under strong earthquakes.Shape memory alloys(SMAs)are newly developed smart metal materials.It is anticipated to update the seismic resilience of FPB-isolated structures by introducing superelastic SMAs to the FPB system.This is because that the adaptability and robustness of this type of novel isolation system can be improved using SMA devices.A strengthened anchoring SMA-FPB(SAS-FPB)was designed and investigated in this thesis.The hysteretic behavior of this novel isolator was examined through quasi-static experiments,and the seismic control of benchmark steel frames using SAS-FPB systems was analyzed.The main contents of this thesis are as follows:(1)A series of cyclic loading test was performed on a SAS-FPB specimen.The hysteretic behaviors of this specimen before and after using SMA wires were compared to demonstrate the control mechanism of this type of isolation bearing.The Open Sees-based numerical model of the SAS-FPB was implemented and the related accuracy was validated by comparing numerical hysteretic responses of the tested isolator specimen and experimental results obtained from the cyclic loading tests.(2)Three-story and nine-story benchmark steel frame were used as research objects.Seismic response analyses were conducted on these buildings isolated with SAS-FPB systems.Corresponding structural models were established in Open Sees,and they are used to simulate time histories of dynamic response under various seismic input intensities.The upgrade mechanisms of the example structures using SAS-FPBs were revealed by comparing seismic behaviors of the isolated and non-isolated structures.(3)Design parameter system of the SAS-FPB was proposed,and effects of the curvature radius,the friction coefficient and the number of SMA settings on the hysteretic performance of the bearing were analyzed.Moreover,SAS-FPB systems with various parameters were applied to a benchmark steel frame building with nine stories.The seismic responses of the structure isolated with different SAS-FPB-based isolation system were examined through numerical simulations,and the influence law of the parameters of isolators on their superstructures were explored.(4)Based on OpenSees,a numerical model of the SAS-FPB considering SMA failure was established.At the structure-level,the model of a base-isolated benchmark building incorporating failure elements was developed using this numerical modelling method.The effects of the SMA failure on the seismic behaviors of the isolated structure were estimated using the response time history calculation considering increased seismic excitations.