Seismic Response Analysis Of Long-span Super-high Gantry Structure

Large-span super-high gantry structure(LSGS) is a special kind of structure form,referring to a whole structure consisting of two or more tower body separated at thebottom and connected at a certain height through conjoined twins. It is different fromthe common tall structures, also different from ordinary large-span structure.It is thecombination of high-rise structure and large-span structure. The mechanical behavior ofthe structure is complex, its dynamic characteristics and damage forms are morecomplex than ordinary tall structures and large span structures. Based on practicalengineering background, the dynamic characteristics of LSGS, the influence of seismicdesign method, seismic response and traveling wave effect on the structure system isstudied. The main investigations are as follows:1. This paper studies the dynamic characteristic and vibration modes of LSGS. Thetheory of LSGS is analysed with simplified model, basic vibration modes of LSGS arededuced by solving the structure free vibration equation. Basis on the analysis of theLSGS vibration type participation coefficient, the difference of vibration typeparticipation coefficient between the structure and General single tower structure systemis summarized. The selected principles of the LSGS vibration type is summarized. Theresults of the modal analysis and the vibration mode analysis of actual project iscompared with that of the theory analysis.2. This paper analyses the seismic response of LSGS. The seismic responseanalysis of the three-dimensional finite-element model of the LSGS usingmode-superposition response spectrum method and elastic time history analysis iscarried out. The mechanics characteristic and the deformation behavior of this structure subjected to three dimensional seismic action are analysed deeply.3. This paper studies the traveling wave effect on the seismic response of the theLSGS. Because the LSGS length is close to150m, in order to study the influence of thetraveling wave effect, multi-dimensional and multi-support excitation analysis under thefrequent earthquake was came out. A conclusion is drawn that the seismic response ofthe long-span structures under multi-support excitation is greatly different from thatunder uniform excitation. When carrying out reasonable seismic analysis in the designprocess of LSGS structures that in the earthquake area, the influence of wave passageeffect on structure should be take into account.