Papers by Keyword: Seismic Response

Abstract: The selected high-span continuous rigid frame bridge for studying is Mangjiedu Bridge in this paper. Based on the principle of structure dynamics and the method of seismic response analysis, the finite element model of the main bridge in Mangjiedu Bridge under Midas-civil was built according to the structural features, site conditions and seismic fortification intensity of the bridge. Then the characteristics of main bridge structure were studied using Lanzcos modal analysis method, and the seismic responses of main bridge are studied by earthquake response spectrum analysis and time history analysis respectively. The results show that the fundamental frequency of the main bridge is 0.1943Hz, and the transverse vibration mode shapes are most remarkable in the former 10 ordered types of vibration of main bridge. The main bridge is in the conditions of elastic range and does not failure under E1 earthquake. Both response spectrum analysis and time history analysis show that the largest displacement along the main bridge appears at the top of pier and the largest transverse displacement appears in the central position of main span. It also shows that the maximum shear and maximum moment occur at the bottom of main pier.

Abstract: Due to the uncertainties and randomness of earthquake loads, it is more logical that reliability method should be employed in dynamic geotechnical engineering analysis. A methodology of 2-D effective stress FEM analysis based on dynamic reliability of seismic response of soft ground including silt is proposed in this paper, Duncan-Chang and Hardin-Drnevich hyperbolic models are used for static and dynamic constitutive relations of soils, respectively. Furthermore, three stochastic dynamic reliability analysis approaches based on the cumulative damage, cyclic shear stress and pore water pressure ratio are respectively suggested. The proposed methodology was applied to the stochastic dynamic reliability analysis of ground seismic response of two typical soft soil profiles in Shanghai in terms of seismic wave input depths of 50m and 280m. Basically consistent conclusions can be drawn in the three aforementioned perspectives. In addition, the filtering effect of frequency components by deeper soil layers plays perhaps an important role in dynamic reliability analysis in view of the fact that remarkable differences of dynamic reliability analysis results exist between 50m and 280m seismic wave input depths.

Abstract: This paper presents nonlinear amplification of seismic ground motion by twin cavities in layered sites. The equivalent linear method is used in the dynamic analysis and Lysmer-Kuhlemeyer transmitting boundary is used at the left and right boundaries of the computation region. It is shown that, cavities have significant effect on seismic ground motion, and soil nonlinearity has significant effect on seismic ground motion around cavities. The PGAs in linear and nonlinear analysis may be increased by 24.4% and 19.2%, compared with those in the free-field response. The PGA in nonlinear analysis may be decreased by 44.6%, compared with that in the linear analysis.

Abstract: This paper studies nonlinear amplification of seismic ground motion by alluvial valley in layered sites. The equivalent linear method is used in dynamic analysis and transmitting boundaries are added at boundaries of the computation region. It is shown that, soil nonlinearity has significant effect on seismic ground motion around alluvial valley. The amplitudes in the case of linear alluvium and soil layers are the largest, those in the case of nonlinear alluvium and soil layers are the smallest, and those in the case of nonlinear alluvium and linear soil layers fall in between. The periods in the case of nonlinear alluvium and soil layers are the longest, those in the case of nonlinear alluvium and soil layers and those in the case of linear alluvium and linear soil layers are almost the same.

Abstract: The paper is combined by the 2^nd phase engineering of Dahuofang water-conveyance tunnel. The 3D finite element models of the circular tunnel were built to analyze the seismic responses of the concrete lining under homogeneous rocks and nonhomogeneous rocks. The stress distribution of the concrete lining was studied under different buried depths. The results show that the seismic responses of the concrete lining magnify first and then reduce with the increase of the buried depth. The maximum stresses appear when the buried depth is up to 25m. It affords an important engineering reference for tunnel site selection, design and construction.

Abstract: This paper presents nonlinear seismic response analysis of canyons in layered sites. The equivalent linear method is used in the dynamic analysis and Lysmer-Kuhlemeyer transmitting boundary is added at the left and right boundaries of the computation region. It is shown through numerical examples that, soil nonlinearity has significant effect on seismic ground motion around canyons. There are differences between seismic response amplitudes in nonlinear analysis and those in linear analysis, but the differences are smaller for observation points inside canyons. There are shifts between response spectra in nonlinear analysis and those in linear analysis, but the differences are much larger for observation points inside canyons.

Abstract: With the continuous development of the marine oil industry, risers have become necessary equipment in offshore drilling engineering. On the basis of mode-superposition response spectrum method which is used commonly in anti-seismic design, the seismic responses of the marine drilling riser is analyzed on the theoretical and the related anti-seismic calculation formulas of the discrete system are promoted to the continuous system. The earthquake force and the resultant internal forces when the earthquake happening are analyzed and calculated. The calculation formulas of shear force and bending moment for each cross section of a riser under the earthquake action are deduced, which can offers some theoretical reference for riser engineering design when considering earthquake action.

Abstract: The main girder and the piers of bridges are generally linked with sliding bearings. Under seismic excitation, pounding effects between the main girder and the abutment, the adjacent girder and the blocking device caused by excessive relative displacements between piers, abutments and the girder are highly probable. The effects can not only damage the structure but also lead to collapsing. Based on a continuous viaduct, the paper studied the disciplines of the pounding response under uniform seismic excitation and the spatial seismic excitation, then put forward that the composite metal damper may reduce the effect of pounding. The research shows that under same seismic intensity, the results, including pounding force, the shear force of the fixed bearings and the plastic hinge on the piers, are amplified under multi-point excitation than under uniform excitation. And composite metal dampers can reduce the seismic responds under frequent earthquakes and prevent or largely reduce the pounding effect under severe earthquakes. Therefore the effect of pounding on the dynamic performance can be lessened. The seismic reduction is widely and well-adapted under both uniform excitation and multi-point excitation.

Abstract: At present, the reinforced masonry structure has been widely concerned. The development of the reinforced masonry structure with a good seismic performance and simple construction is very important. This paper mainly studies on the bearing capacity of the ten storey reinforced masonry structure under the action of earthquakes with three different methods, and given the corresponding data.

Abstract: The reinforced masonry structure system is turned up as a new group of high-rise building structure type. This paper mainly researched the shear of reinforced masonry structure under earthquake. The maximum shears of the structure are calculated in X and Y direction by numerical analysis method. The changing of the shear bearing capacity is presented under three kinds of seismic waves.