Advanced Materials Research Vols. 243-249

Abstract: The responses of high-speed railway bridge subjected to seismic load were investigated by numerical simulation, the whole finite element model of the multi-span bridge simply supported bridge was set up, and natural vibration properties of structure were analyzed. According to theory of elasticity and elastic-plasticity, parametric study was conducted to assess the influences of different speeds, strong motion record, pier height and earthquake acceleration on the seismic capability of high-speed bridge subjected to different strength of the earthquake, the finite element soft ware and moment-curvature program were employed to calculate the earthquake responses of bridge. The calculation results show that, with the increase of train speed, pier height and earthquake intensity, the earthquake responses of bridge are increase in general, and the bottom of piers step into states of elastic-plasticity under high-level earthquake, elastic-plastic deformation is larger, the stirrup encryption measures should be carried out.

Abstract: Characteristics of the permanent deformation and surface rupture caused by fault dislocation in 512 Wenchuan earthquake are analyzed in this paper. On the basis of the data from surveying reports and engineering geological reports of some observation station, three kinds of overlying soil model are established and analyzed, the physical parameters coming from clay and sand: thickness 30m and 50m model of the clay, thickness 30m model of the sand and thickness 50m model of the clay containing sand interlayer. Results show: The thickness of the overlying soil is same, but fault dislocation changed, the permanent deformation scale of overlying soil with velocity of shear wave from 250m/s to 500m/s is almost same, but the surface rupture zone is different: shear wave velocity of the soil is low, surface rupture zone becme wide. With thickness of the soil increassing, the rupture zone become wide too. Influence of sand interlayer is small. Considering the setback distance determination, the geometric and kinetic characteristics of faults, regional seismic activity, material properties and thickness of the overlying soil are key factors.

Abstract: The paper proposes a new method, which is used for providing ground motion input for seismic design under rare earthquake action. The crucial step of this method is to use power spectrum envelop, obtained from natural earthquake records but not deriving from response spectrum, as target curve to synthesis ground motion. The result shows that power spectrum obtained from this method fits well with the target curve, and the produced ground motion can properly predict the response spectrum of acceleration. By importing the concept of energy envelope, this method reduces the randomness of the ground motion sampling and the variability of the result in dynamic finite element analysis.

Abstract: The seismic behavior study of Fengdu Bridge will be conducted on a parameter of damping coefficient C of linear viscous dampers through linear dynamic time-history analysis. Simultaneously, the results are compared with the seismic response without viscous dampers. The parameter sensitivity study indicates that setting damper in longitudinal direction of bridge can reduce the relative displacement of key positions and the response of the bridge, the beneficial effect of the isolation in the longitudinal direction, but important amplification occurs in the vertical direction for relatively high frequency components. Moreover, the reference of application of linear viscous dampers will be provided for similar projects.

Abstract: In order to improve the seismic capacity of short-limb shear wall, two kinds of unbonded post-tensioned short-limb shear wall based on unbonded post-tensioned connections were put forward: (1) direct assembly short-limb wall; (2) hybrid assembly short-limb wall. The quasi-static cycle tests of two reduced scale specimens were conducted to simulate the seismic performance of 8-story symmetric double short-limb shear walls. The test results verified the basic design concept of unbonded post-tensioned short-limb shear wall, which requires that under strong earthquake action, the main part of coupling beam remains elastic and plastic deformation focus on the connection region of limbs and coupling beams. Therefore, the new short-limb shear wall is easier to fix. The test results also show the energy dissipation capacity of hybrid assembly short-limb wall is higher than that of direct assembly short-limb wall due to deformed bar crossing the interface between limbs and coupling beams.

Abstract: For the study of soft subgrade pavement cracking process, it establishes the pavement structure tension crack model by elastic layered theory. Based on the finite element method, it studies the tension crack evolution process. It establishes the tension crack stress criterion to the roadbed. Analysis shows that the distresses of asphalt pavement of the real highway results from the damage by asymmetric sedimentation which is under excessively axle loading on pavement structure, rather than the fatigue damage by axle loading repetitions in the condition of asymmetric intensity in the same layer. The results show that the soft degree of the subgrade is proportional to the tensile stress, the more localized soft, the easier to crack the road. The soft roadbed does not have a homogeneous structure of the road surface, the tension stress rupture occurred in the discontinuous surface. The road structure has a set of tensile stress under the circulation wheel load, it formats a new fracture surface, and the structure form corresponding evolves, and causes stress state change. At last most of the road sub-base crack, and surface cracking occurres, so the pavement failure.

Abstract: To study the stability of rock slope under dynamic load,the digital speckle correlation measurement (DSCM) is used for dynamic failure of rock slope containing two weak layers.It observes the displacement field, deformation field, and stress field during the process of crack formation, crack through the slope and slope collapse. Experimental results show that the initial deformation cracking on the surface around the structure of the weak layer, and then extended to top and the foot of the slope, and finally through the loose structure.The slope stability is controlled by the weak layer’s angle, the space form of the weak layer and the slope Mechanical Properties.It gives the failue model of the different positon in the slope.

Abstract: In this paper，the basic situation of Guangxi luocheng Kama reservoir and the potential dangers are introduced firstly, and then，different models often used to estimate the loss of life in dam failure at home and abroad are introduced and analysed.Based on the above, a suitable model for national actual situation is chosen to predict the loss due to this reservoir dam breach，and the severity according to the calculation result of assuming Kama reservoir dam-break is assessed. Finally, the relevant departments’s measures of rescuing and evacuating downstream masses etc. at danger in 2009 are proved to be correct，necessary and timely.

Abstract: Influence of earthquake directions on wind turbine tower under seismic action are numerically investigated in this paper. First, equations of motion and an integrated finite element model of a wind turbine system consisting of a rotor, a nacelle and a tower shaft are established. Second, the finite element modal analysis is discussed. Third, relationships between upper displacements in x, y directions and bottom bending stress when the angle is 0, 30, 45, 60, 90 degree respectively between earthquake directions and concentrated eccentric mass direction (x direction) are analyzed by adjusted Taft seismic wave .The results show that: seismic responses of a wind turbine tower are remarkable and seismic action may be the dominant factor in the design of wind turbine towers that located at a seismically active zone. Under different earthquake directions structure’s dynamic responses are different, 90 degree with regard to x direction is the most unfavorable direction. Both maximum upper displacements in x, y directions and bottom bending stress appear at 90 degree direction with regard to x direction.

Abstract: In order to analyze seismic response of the curved ramp bridge, this paper selected a single curved ramp bridge in a multilevel junction system as its research object. Considering the piers, beams, bearings and expansion joints simulation, it respectively built the calculating models for a curved ramp bridge and a corresponding linear one. Using nonlinear time history analysis, the paper contrasts seismic response of the curved ramp bridge with that of the linear one in several different seismic inputs. Finally the seismic response characteristic of a curved ramp bridge is put forward.