Research On Seismic Pounding Between Adjacent Buildings

Pounding between adjacent buildings can be referred as a lateral collision for thedistance between adjacent buildings failing to satisfy the demand of relative displacementunder earthquake. Building structures are often built close to each other as in the case ofresidential building complexes or in downtown of metropolitan cities where the cost of landis high. Due to the close proximity of these structures, they have often been found to impacteach other while responding to earthquake induced strong ground motion and brings greatcasualties and economic losses. So, the study of pounding between adjacent buildings, and todevelop seismic capacity assessment for adjacent buildings contribute a lot in the fields ofboth theoretical significance and engineering value.With the aim of studying pounding between adjacent buildings, the thesis mainlyfocuses on the following two aspects. Firstly, the thesis derives the constitutive equations ofsteel considering buckling and establishes a beam element based on fiber model. The loadingprocess of quasi-static test made by Tsinghua University is simulated. The results show thatthe beam element is available for calculation of seismic response. The paper selectsHertz-damp model, which can account for non-linearity associated with impact as well as theenergy dissipated during collision. Dynamic equations of adjacent RC frame structuresconsidering pounding get derived with Hertz-damp model. The method of variableintegration step, guaranteeing both efficiency and accuracy, is proposed. The collisionprogress of adjacent frame structures is simulated and varying process of constructiondamage index is provided by a post processor program. Then the thesis analyzes the cause ofcollision damage and the relation between structural damage index and gap between adjacentbuildings. Secondly, the thesis offers the conception of pounding spectrum of adjacentbuildings, at the same time, analyzes its characteristics and influencing factors, which canoffer good references for seismic capacity assessment and the study of pounding resistanceand reinforcement. The main contents and conclusions are as follows:(1) Simulation of pounding between adjacent RC frame buildingsThe analyses of pounding between buildings show that:1.in most cases, with wideningthe seismic joint, the structure becomes less damaged, and the collision force and the numberof pounding decrease;2.when PGA increases, the impact force and the number of poundingwill also increase;3.peak force and PGA appear to have linear relation, which indicates thatthe PGA has a significant influence on pounding;4.when the peak force is high, the mainmode shape of the lateral vibration will change;5.the pounding of structure will magnifyhorizontal acceleration, increase high frequency components, and generate directionaldifferences;6.impact of pounding on horizontal displacement is significantly less thanacceleration, and one of the main characteristics of the displacement reaction is being limited in a single direction;7.the analyses of unit damage index show that smaller seismic joint willaggravate partial or total damage of adjacent structures;8.throughout the analysis of therelation between structural damage index and interval between adjacent structures, thestructural damage index, in nearer than a certain distance of without-pounding, decreases orincreases for just a little, and basically remains unchanged. This thesis considers the degreeof structural damage within this interval unchanged, and I personally recommend the intervalvalue of adjacent structures the minimum of the interval. Examples show that the proposedcollision-interval should narrow about10%, aiming at saving the cost of land, and beingconvenient for the design and construction.(2) Study on the pounding spectrum between adjacent buildingsPounding spectrum not only is able to show the characteristics of earthquake motion,but also consider the impact between adjacent buildings to structural response. The thesismainly study the impact of different parameters to the pounding spectrum curved surfaces inits elastic range,76most unfavorable design ground motions are selected to calculate thesurfaces, the analyses indicate that:1.the impact of PGA and the width of seismic joint fit theresults of time-history analysis.2.without considering the phase difference of the inputearthquake motion, adjacent buildings with the same mass, damping ratio and ductility factorwill never collide.3. with a larger damping ratio and ductility factor, or a smaller mass andtouching stiffness, the adjacent buildings suffer a smaller collision force.4. poundinginfluence is more obvious to structure with small damping ratio on PGA than that with largeone, and in PGD aspect, the conclusion is opposite.5. for a larger mass and smaller ductilityfactor, the structure withstands a smaller impact.6. decreasing the touching stiffness is aneffective way to avoid damage.7. the type of site has some certain impact, but with a largerPGA, the impact becomes smaller.