Elasto-plastic Seismic Response Analysis Of Flexibly Connected Structures With Anti-collapse Cables

The source of this paper’s thesis is one of the NSFC in2010——《The CollisionReaction Control of High-rise Flexibly Connected Structure and Anti-collapseAnalysis of Corridor under Earthquake Action》(51068008).Flexibly Connected Structure refers to the structure form that the corridor andthe towers are connected by isolate bearings with certain stiffness and damping.Flexible connection is able to reduce the torsional coupling response of the connectedstructure effectively under seismic action, but may also lead to pounding between thecorridor and the towers and even the collapse of the corridor under strong earthquakeexcitations. Nowadays, anti-collapse cables are often used as a safety structuralmeasure to keep the high altitude corridor from collapsing. In this paper, flexiblyconnected structures with corridors supported by isolate bearings and anti-collapsecables are analyzed and the contents of the research are as follows:1. The inelastic material behavior and the geometric nonlinearity will increasethe computation complexity and may lead to no convergence when the elasto-plastictime history analysis of the whole connected structure is analyzed. Given that thegeometric nonlinearity is caused by the corridor, the research strips it from theconnected structure and analyzes it with elasto-plastic time history method in the caseof considering geometric nonlinearity. The results indicate that the initial relaxedlength of the cables mainly affects the distribution of corridor’s weight betweencables and bearings. The cables are always in tension and the isolate bearings are incompression, and they are able to work together by selecting suitable initial relaxationlength of the cables. The geometric nonlinearity mainly affects the axial forces ofcables, the vertical supporting forces of bearings and the pounding forces, the impactdegree of which are25%,25%and15%.Based on these analysis results, the paper approximately considers geometricnonlinearity’s impact on the structure response by replacing the P effect withthe additional bending moment and magnifying the input load.2. The horizontal displacement of flexible bearings will lead to P effect ofcorridors’ gravity on the towers. The research replaces the P effect by inputtingan additional bending moment, which comes from the frequent earthquake and therare earthquake. The reinforcement design and the dynamic elasto-plastic time historyanalysis of connected structures are conducted. The results indicate that the yieldproperty level of the the connection section of the corridor and the towers will be too low under the rare earthquake if the additional bending moment is inputted accordingto the frequent earthquake, and if the additional bending moment is inputtedaccording to the rare earthquake, the yield property level of the the connection sectionof the corridor and the towers will increase obviously, which leads to structures’ goodanti-collapse performance. Therefore, when the elastic design is conducted, theadditional bending moment should be inputted according to the rare earthquake inorder to increase the anti-collapse performance of the connection section of thecorridor and the towers.3. Magnifying the peak ground acceleration to1.2times of the rarely occurredearthquake of intensity7, elasto-plastic seismic response of connected structures withno or one or two flexible bearings being destroyed (anti-collapse cables begin to loadand support the corridor with other flexible bearings) are analyzed. The resultsindicate that the displacements of other flexible bearings which are not destroyed aremagnified obviously after the anti-collapse cables begin to load. Besides, compared tothe connected structures supported with flexible bearings only, the pounding chancesand pounding forces of connected structures with anti-collapse cables are magnified.4. By comparing the structural dynamic responses after the anti-collapse cablesbegin to load under different seismic waves, it is shown that when the seismic designof the flexibly connected structures is conducted, if the additional bending moment isinputted according to the strong earthquake, the structures will possess goodanti-collapse performance and the connection section of the corridor and the towerswill not be destroyed easily. According to destroyed degree from large to small, theyield performance level of structure members are listed as follows: coupling beams ofshear-wall, coupling beams between shear-wall and frame columns, frame beams,columns near the corridor or at the bottom of the tower. The yield performance offrame is over the life safety level, and the shear wall yield only occurred instrengthened region at bottom, and connected structures with corridor supported byisolate bearings and anti-collapse cables possess enough performance for preventingstructural progressive collapse.