Study On Seismic Performance Of A New Type Fabricated-isolated Frame Structure

The fabricated structure was difficultly spread in the high and medium intensity regions because the seismic performance of the structure is insufficient with weakening of the joints.This problem can be solved by isolation structures with the advantages of good damping effect,small damage and easy repair after the earthquake.Therefore,a new type of assembled frame isolation structure system named PPEFF isolation system is studied in this paper.The isolation design method and finite element modeling method,as well as research of seismic performance based on static pushover analysis,dynamic elasto-plastic analysis and earthquake vulnerabilities are included.the results reflect the superiority of the PPEFF isolation system are reflected in the results.The main contents and conclusions of this paper are as follows:(1)The seven-story frame structure of PPEFF system is designed by using the method of anti-gauge division design and the direct design method of the new code of isolation respectively,and the flow chart of the two methods and the internal force,displacement and reinforcement of the design result are compared.Combined with the advantages and disadvantages of the two design methods and the actual design requirements of the PPEFF system,the design scheme of the superstructure and the isolated story of the calculation model is determined.(2)The finite element model simulation methods of concrete,steel and other materials used in the PPEFF structural model,as well as fiber-column fiber,beam-column contact surface fiber joints,prestressed tendons and seismic isolation bearings are studied.The elasto-plastic model of seven-stories fabricated frame isolation structure is established byusing Perform-3D finite element software.The modal analysis results of the Perform-3D elasto-plastic model are compared with the ETABS and YJK models to verify the accuracy of the model.(3)Based on the capability spectrum method,the PPEFF isolated structure and the non-isolated structure were analyzed by static Pushover with two different lateral force modes under fortification and rare earthquakes.The seismic performance and damping effect of the PPEFF isolated structure was evaluated by Pushover results.The results of the Pushover curve,the performance point and the performance point of the PPEFF isolated structure and the non-isolated structure are less in the two different lateral force modes;The damping effect of the PPEFF isolated structure is obvious,but the ground motion is The strength increases and decreases,and the maximum story drift satisfies the limit requirement of the isolation standard.(4)The dynamic elasto-plastic analysis of assembled isolated structures and non-isolated structures under rare and very rare earthquakes is carried out by selecting far-field,near-field pulses and long-period ground motions respectively.By comparing and studying the ground acceleration,shear force,story drift and displacement of the isolated story of the two models,the seismic reduction effect,seismic performance and weak link of the three types of ground motion are determined.According to the rotation angle of the fiber hinge,the damage of the assembled beam-column joint is defined.The maximum superstructure story drift,displacement of isolated story and joint damage of structures with different intensities of far-field earthquake meet the requirements of the limit value of specifications,and the damping effect is over 50%.Above,the thin story of the structure is the second story.Under the action of near-field pulse and long-period ground motion,the displacement of bearing of isolated structure is more obvious than other indexes.For the long-period ground motion,the time history results show that the isolation effect only occurs in the early stage of the earthquake,and the response of the isolated structure is almost the same as that of the non-isolated structure in the later period of the earthquake,and the response of the isolated structure is almost the same as that of the non-isolated structure.This phenomenon is also increases the intensity of earthquake everywhere and becomes obvious.According to the damage results,the isolation effect of far-field ground motion is obvious.The damage caused by near-field pulse and long-period ground motion to the isolated structure is large and the isolation effect is poor.The isolation effect will be decreased with the increase of ground motion strength.(5)According to FEMA-P695,30 groups of far-field,near-field no pulse and near-fieldpulse ground motions are selected for incremental dynamic analysis and collapse vulnerability of the structure.The maximum superstructure story drift and the shear strain of isolated bearing are taken as the damage indexes of the structure.Reliability probability method is used to study the anti-collapse performance of fabricated isolated structures.The superiority of the PPEFF isolation system is showed in the results that the superstructure can greatly improve the anti-collapse reserve coefficient,reduce the collapse probability of the structure in the earthquake and enhance the safety reserve of the structure after decreasing the degree of the superstructure.The collapse failure mode of the structure under strong earthquake is the shear strain overrun of the isolation bearing.The requirements of anti-collapse performance be reached by Fabricated isolated structure under far-field rare and very rare earthquakes.The influence of near-field pulse earthquake on the fabricated isolated structure is greater than that of the non-isolated structure,and the near-field influence coefficient which is larger than the standard value should be taken into account in the design.