Research On Seismic Behavior And Analysis Method Of Long Span Space Structures Under Multiple Support Excitations

The influence of spatial variation of seismic ground motion can't be neglected for long span space structures. It is a task resolved necessarily how to evaluate the seismic response under multiple support excitation. It mainly focuses on the research into seismic behavior and analysis method of long span space structures in this paper, including the application of the pseudo-excitation method in the random seismic response analysis , the setting-up of the fast multi-support response spectrum method , its application to engineering examples and the aseismatic reliability analysis of long-span space lattice structures under multiple excitation .From the beginning , the calculation quantity is a key and difficult issue in the random vibration analysis under multiple excitations , especially to long span space structure with a large number of freedom degree. By means of the pseudo-excitation method, the seismic response is analyzed by frequency analysis method for long span space structures. It shows that the structural response is divided into two parts.They are the pseudo static response due to inconsistent ground displacement and the structural dynamic response due to ground motion acceleration. The differences of the structural response are studied generally under multiple support excitation and simple support excitation from two aspects, i.e. the displacement response variance and the acceleration power spectrum of four case examples of space lattice structures and cable structures. Furthermore, the effects of the pseudo static response on these two kinds of structures are discussed.At present,because of the calculation intricacy of the multi-support response spectrum method, the new idea train of the multi-support response spectrum method based on the pseudo-excitation method and its development are put forward and the fast calculation approach is systematically studied in the paper. Firstly ,to transform the frequency response function mathematically, then to reduce the integral number in coupling coefficient from i*j*k*l to (i,j are the number of mode,k,l are the number of support) 5*j*k*l according to the characteristic of the integral, and the calculating results are precise. Moreover, to decrease the integral number to 4*j*k*l according to the main selectivity of frequency response functions to seismic wave, and the precision is good if it satisfies some conditions. The seismic response of AMECO hangar and shed of palaestra in Harbin Institute of Technology is analyzed by the fast multi-support response spectrum method including 4 apparent velocity vapp=50m/s, 100m/s, 200m/s, 500m/s, and is compared to the calculating results given by the classical response spectrum method, besides, the effects of the pseudo static response are also analyzed. The calculation results are consistent with the random vibration analysis.The statistic variation characteristic of the same series of seismic wave can be considered based on the fast multi-support response spectrum method. Meanwhile, the aseismatic reliability analysis of long-span space lattice structures under multiple excitation is carried out. The aseismatic reliability obtained by the multiple support excitation is compared to that analyzed by the simple support excitation, such as the change of the reliability indexβof each element, the difference in the distribution and the amount of dangerous elements. The relationship between the dangerous elements and the span, as well as the apparent velocity is investigated , and the effects of the pseudo static response on dangerous elements are discussed as also. These dangerous elements (positions) always are pivotal and weak, so we should attached enough importance to them. It shows that the procedure suggested in the paper is applicable to the aseismatic property analysis of the complicatestructures under multiple support excitation, such as long-span space truss and long-span space lattice shells, through the project practice, by which the connection is built up from theoretical study to practical application.The seismic behavior of long span space structures is opened out under multiple excitation based on the pseudo-excitation method and the fast response spectrum method, and the rules are consistent under this two approaches, the rules are also applicable to the aseismatic reliability analysis.