Study On The Design Method Of A Combined Shear-and-flexural Panel Damper And Its Seismic Mitigation Behavior

Stairs are a primary means of egress in most buildings and therefore are critical to building accessibility and survivability in the event of an emergency.However,postearthquake reconnaissance showed that stairs were vulnerable to seismic damage and exhibited more serious damage than the primary structure.Therefore,it is urgent to propose a way to protect the stair from seismic damage.To solve this problem,the paper designed a combined shear-and-flexural panel damper(SAFPD)installed in staircase by using low yield point steel.And the paper proposed a new structural measure about the installation position of damper.Sliding support was added as supplemental device,cooperating with SAFPD to play a role.On the one hand,the presence of SAFPD can weaken the connection between the landing beam and the flight,mitigate the diagonal strut effect of flight effectively,furtherly reduce the interaction between the staircase and the whole structure.On the other hand,the presence of SAFPD can dissipate the seismic energy through the hysteretic deformation of damper,and provide additional damping ratio for the whole structure,to improve the seismic performance of primary structure.In the design of a combined shear-and-flexural panel damper and study of its seismic mitigation behavior,the following three aspects were mainly conducted:(1)The section shape of flexural plate under the out-of-plane loading was determined through theoretical derivation,and its initial stiffness,yield strength and yield displacement were analyzed theoretically.The part of shear plate was provided four structural forms according to relevant studies.What’s more,theoretical analysis was conducted to study one of the structural forms which adopted pure shear core plate.Its initial stiffness,yield strength and yield displacement were obtained.Through assembly of the flexural plate and shear plate,four preliminary design schemes of SAFPD were provided.(2)The mechanical behavior of four preliminary designing SAFPD was investigated using finite element software ABAQUS.The hysteretic loop,skeleton curve,bearing capacity,stiffness parameter and equivalent viscous damping coefficient were studied.By comparing the above mechanical performance,the final design scheme of SAFPD was determined,which has the best mechanical property among four preliminary design schemes and meets the requirements of bearing installed in staircase.By changing the longitudinal clear distance between two adjacent flexural plates,the paper investigated the effect of different clear distance on the mechanical properties of SAFPD.The results show that the longitudinal clear distance between two adjacent flexural plates has little effect on the mechanical properties of SAFPD.(3)The finite element models of two types of the reinforced concrete frames(cast-in-place reinforced concrete stair and SAFPD stair)were established using software ETABS,and the nonlinear time-history analysis under frequent earthquake and rare earthquakes were conducted respectively.The dynamic characteristics of whole structure including story shear,story drift angle and story acceleration were compared.In addition,the mechanical performance of staircase components was also investigated.The results indicate that the presence of SAFPD can improve dynamic response of the whole structure and significantly reduce the inner force of partial stair components.