Research On Seismic Performance Of A Precast Composite Frame Based On A Novel Steel Shear Panel Damper

Nowadays,precast reinforced(RC)concrete and steel structures are widely applied in China.The precast composite structure achieves several advantages of the precast RC structures(i.e.,good integrity and low cost)and steel structures(i.e.,easy installation and good mechanical performance).Such kind of structure is gradually popularized as well.With respect to the engineering application,it was found that the composite structure can achieve the effective utilization of the cross-section.As a consequence,it can meet the requirements of the vertical loads with a relatively small cross-section.This also leads to a lack of horizontal stiffness,which causes a more obvious earthquake response.Although a larger size of the cross-section can be adopted to improve the stiffness,it will result in material waste.Besides,there is a complicated beam-column joint in the precast structure,while such a problem can hardly be solved in the traditional composite structure.This configuration can lead to great difficulty in the installation on site.In this paper,a precast composite frame based on a novel steel panel damper is proposed to avoid the unacceptable damage or global collapse of the frame.The earthquake-resistant system consists of a concrete-filled steel tubular column with the fireproof concrete wrapping up,a precast pretensioned prestressing RC beam with a steel joint inserted at both ends,and a duplex assembled I-shaped steel panel damper(DAISPD).Therefore,the members of the composite frame can be fabricated as the precast RC members,and connected as the steel structure,which achieves high efficiency in both fabrication and construction.Methods,including the experimental study,numerical study,and theoretical analysis,are adopted to investigate the working performance of the damper,the composite frame,and the energy dissipation system.The main research contents are drawn as follows:1)A duplex assembled I-shaped steel panel damper with one stiffener is developed.Five specimens were tested through the quasi-static test to investigate the effect of different configurations on the hysteretic performance,e.g.,the weakening holes and the connecting plate.Then,the numerical study was conducted for other parameters,e.g.,the layouts of the weakening holes and the stiffening configuration.The results indicated that the damper without the connecting plate achieves a better deformation capacity and energy dissipation capacity.The ductility coefficient,the over-strength factor,and the equivalent viscous damping coefficient can reach 7.40,1.70,and 0.51,respectively.Besides,the configurations,including a narrow and high weakening hole,an equal layout,and a small gap between the webs and the stiffeners,are recommended to improve the working performance of the damper.2)A duplex assembled I-shaped steel panel damper with two stiffeners is developed.The experimental and numerical studies were conducted on a basis of three specimens to investigate the effect of the weakening method and the layouts of additional carbon fiber reinforced polymer(CFRP)sheets.The results indicated that the improved configuration and the CFRP sheets benefit the deformation capacity of the web,with the ductility coefficient increasing to 12.21.The energy dissipation capacity of the web strengthened by the CFRP sheet can be improved with the increase in the width of the web.Besides,with respect to the weld connection with the structure,the boundary condition with three and a half edges welded is recommended to lengthen the effective connection and relieve the stress concentration.When the connection is valid,the DAISPD can achieve a larger relative energy dissipation capacity and similar efficiency to that with one stiffener.3)A simplified strip hysteretic model is improved for the indirect buckling restrained shear panel damper.The simplified model takes the effects of both the partial tension field action and the work-hardening performance of a thick plate into account.Then,the proposed model was validated by predicting the yield strength,the ultimate strength,and the load-displacement relationship under both the monotonic and the cyclic loading.The contribution of the different strips was discussed on the dissipated energy.The results indicated that the damper fabricated from the section steel with a small web height benefits the energy absorption with respect to the need for the same yield strength.4)A precast composite frame is proposed based on the DAISPD with two stiffeners.Quasi-static tests were conducted on two 2-floor 2-bay scaled frame specimens.One is the composite frame with a dogbone-like reduced steel joint,the other is the system consisting of the frame and the damper.The results indicated that the newly proposed system achieves good hysteretic performance,with an equivalent viscous damping ratio more than 0.33.Prior to the appearance of the plastic hinge at the ends of the beam,the additional damper can fail to work,which meets the requirement of the design concept with two lines in the earthquake-resistant defense.A proper design in the cross-section of the joint can transport the plastic hinge to the place with a distance to the beam-column joint.Besides,the local failure of the beam can be avoided by placing the bent-up reinforcement near the cross-section with abrupt changes.5)A simulation method is proposed to predict the performance of the precast composite frame installed with the DAISPD.The models of the previous joint specimens and the frame specimens were established and demonstrated to be valid.Then,a precast composite frame model and an RC frame were established to supplement the experimental results.The results indicated that the development of the plastic hinge can be reflected in the model,and a stiff joint zone can be adopted to improve the calculation efficiency.The composite frame behaves better in the bearing capacity and energy dissipation capacity than the RC frame.In the energy dissipation system,the additional horizontal stiffness and the plastic shear deformation of the damper can greatly benefit the seismic performance of the composite frame.6)A design method for the developed system is improved on a basis of the energy conversation theory.Firstly,the main structure and the additional energy dissipation system are designed individually.Then,the additional effect of the damper and the chevron brace is checked.A 12-floor office building model was established and the non-linear time history analysis was conducted.The results indicated that the energy dissipation structure example designed by the method is safe.Therefore,the proposed design method is feasible and can meet the code requirements.Besides,the additional damper system can significantly reduce the structural earthquake response.The fireproof concrete benefits the aseismic performance,however,with a limited improving effect.The fire-resistant component also decreases the expected contribution of the damper.