بررسي پاسخ لرزه اي قاب هاي خمشي پيش ساخته بتني با اتصالات هيبريد

چكيده انگليسي :

Abstract The Precast Seismic Structural Systems PRESSS research proposed a total of fivedifferent seismic structural systems comprising precast concrete elements These systemswere used in various parts of the structural framing in the PRESSS Phase III experimentalbuilding that was tested at the University of California at San Diego The system identifiedas the unbonded post tensioned concrete frame with damping also called the hybridframe performed very well according to the PRESSS evaluation The hybrid frame systemoffers an important feature it allows the elimination of the residual drift of a structure afteran earthquake Hybrid frames contain precast concrete elements beams and columns thatare connected by unbonded post tensioning steel and partially debonded mild steelreinforcing bars where both types of steel contribute to the overall moment resistance ofthe connection An important feature of this type of connection is the combination of mildsteel and post tensioning steel In this hybrid connection the mild steel reinforcementdissipates energy by yielding in tension and compression and the post tensioning steelclamps the beam against the column The post tensioning force acts as a restoring force tobring the frame back to its original configuration after an earthquake and also provides forshear resistance through friction developed at the beam column interface The hybrid frame studies during the past decade include experimental verification usingcomponent Stone et al 1995 Stanton et al 1997 and structure level testing Cheok et al 1998 Priestley et al 1999 Pampanin et al 2001 Rahman 2007 More recently the hybridframe has been implemented in a few buildings including a 39 story apartment complex inSan Francisco Englekirk 2002 In these researches effect of contribution of post tensioning tendons on the nonlinear response of structures was not considered and thisparameter was constant in the height of structures In this thesis effect of contribution of post tensioning tendons on the nonlinear responseof hybrid frame has been studied and a new distribution of post tensioning in the height ofstructures has been proposed With this distribution of post tensioning hybrid frames hadless interstory drifts and so design of precast prestressed frames would be better based onearthquake demands 16 moment frames with four eight twelve sixteen stories each withthree bays were analyzed by the approximate MPA procedure Four of these frames weremonolithic and used for comparison between results of precast and monolithic frames Oneof the most important results of this study was that interstory drifts in the hybrid frames inthe upper stories were lesser than monolithic frames and in the lower stories were largerthan it For evaluating of new design method base on variable distribution of post tensioning six hybrid frames were considered Hybrid frame buildings were evaluated underearthquake input motions corresponding to three intensity levels At each intensity level the damage state in the buildings was quantified using the maximum transient interstorydrift Interstory drift is defined as the relative floor displacement divided by story height These three intensities correspond to 22 50 and 100 of a design level earthquake that isexpected in a high seismic zone for soil type C without the influence of near source effects The seismic performance of hybrid frames satisfied the performance limits underearthquake input motions with intensities similar to or below that of the design levelearthquake

حاجي احمدي، مهدي

بررسي پاسخ لرزه اي قاب هاي خمشي پيش ساخته بتني با اتصالات هيبريد