Advanced Materials Research Vols. 639-640

Abstract: Firstly, the motion equation for parallel composite isolation system was formulated. Then, taking system with seven degree of freedoms for an illustrative example, the nonlinear dynamic responses of ordinary aseismic system, isolation system with friction sliding bearings, isolation system with laminated rubber bearings and parallel composite isolation system with the above combined bearings were calculated. Finally, the seismic responses of the above four structures were compared and discussed comprehensively and systematically, and the hysteretic performance of isolated floor was investigated. The results show that the isolation effect of isolated systems compared with the ordinary aseismic system is very notable and the hysteretic energy dissipation performance of isolated structures is excellent.

Abstract: Different friction bearing ratios have effects on the base isolation property of parallel composite isolation system subjected to the seismic excitation. In order to deeply investigate how the friction bearing ratio affect the isolation property, the numerical simulation was carried out by the time-history analysis method, in which the seismic response of parallel composite isolation system with different friction bearing ratios under different acceleration peak values were calculated. Then, the effects of different friction bearing ratios on the base maximum shear coefficients and base maximum displacements; the hysteretic characteristics and nonlinear properties were analyzed and discussed. The results show that, for the parallel composite isolation system, friction bearing ratio is a key factor affecting the isolation property and the nonlinear properties are tightly related to the friction bearing ratio and acceleration peak values.

Abstract: The natural vibration frequency, characteristics of vibration mode and deformation of large span integral ceiling structure in a hotel under earthquake were studied using the ANSYS Software, then some useful suggestions on hoisting position, pull rod and other factors were put forward for seismic constructional design of large span integral suspended ceiling structures.

Abstract: The multi-dimensional seismic response of a single-span hangar was studied by response spectrum analysis method. The lateral displacements of the structure, forces of its supporting columns and its roof structure were calculated and compared with each other for cases of one-, two- and three-dimensional (1D, 2D and 3D) seismic inputs. The results show that, compared with the case of 1D earthquake input, the effects of horizontally 2D earthquake inputs on the internal forces and displacements of its supporting columns in the primary direction of input are obvious when it is along the symmetrical axis of the hangar and their effects in the secondary direction of input are even more important which results in great increases of the internal forces and displacements in that direction. The vertical seismic input has almost no effect on the internal forces and displacements of columns. The internal forces in different parts of the roof structure are controlled by horizontal or vertical inputs, respectively, and, compared with those from horizontally or vertically 1D inputs, the responses from 3D inputs are increased and the effects should be considered in seismic design.

Abstract: This paper is concerned with the dynamical behavior of a chaotic system which is a model for seismic response of structures. The local bifurcation of the non-hyperbolic equilibrium point of the chaotic system is investigated by using center manifold method. The transcritical bifurcation is analyzed in detail. Based on numerical simulations, spectrums of maximal Lyapunov exponent and the bifurcation diagrams are presented for the dynamic analysis. The method proposed can be used as a reference of nonlinear seismic response analysis.

Abstract: A simple method for seismic response analysis on multi-degree-of-freedom (MDOF) system with non-proportional damping is proposed. Based on the real modal theory, transforming the system from physical coordinates to modal coordinates, the damping matrix is a relatively small amount compared with the mass matrix and the stiffness matrix, so the damping matrix may be denoted as a small amount. The approximate analytical solution of the non-proportional damped system can be obtained by using the perturbation technique which can be used as a reference of seismic response analysis of complicated structures.

Abstract: In order to deeply comprehend the static properties of silty soil subjected to repeated freezing and thawing in deep seasonal frozen area, the static properties were studied on silty soil under different freeze-thaw cycles, coefficient of consolidation, water content and confining pressure. The results showed that stress-strain relationship of silty soil was work-hardening, and mainly in a ductile failure state. Correlation analysis results showed that there were good relationships between static properties, such as static modulus and static strength, and freeze-thaw cycles, coefficient of consolidation, water content and confining pressure. The cohesion decreased with in creasing of the number of freeze-thaw cycles, but there was no changing law for the internal friction angle.

Abstract: On the basis of testing the environmental vibration of the different regions of the elevated station, this paper analyzed the experimental data by the time domain, the vibration acceleration level and spectrum, and some meaningful conclusions are obtained. The vertical Z weighted vibration acceleration level of the office and waiting room achieve 80.7dB, 78.8dB, indicating a serious vibration problem about elevated station, and that some more attention should be paid. Office has an equivalent transverse and longitudinal vibration level; the vertical vibration of the office is slightly larger than the waiting room, but the lateral vibration of the office is obviously lower than the waiting room. The exposure time of the vertical vibration is longer than the horizontal vibration in the same location, and a phase difference exists between them. Lateral vibration of the first floor of the station holds a longer exposure time than the box girder, and has lagged far behind in the box girder. The vertical vibration attenuated slower than the horizontal vibration. The high-frequency vibration is attenuated in the propagation from the box girder to the station floor, while the proportion of low-frequency vibration is improved.

Abstract: Vacuum method, combined with well dewatering method, has been proved to be an effective way to solve perched water, weak aquifers water and interface residual water problems in underground construction. However, there were not enough researches on soil settlement in vacuum dewatering from soil particle loss perspective which is one of the most critical factors in vacuum dewatering. In order to research the effect of vacuum on soil settlement, two experiments were conducted. The first experiment was designed to simulate well dewatering method without vacuum. As a contrast, the other one was conducted under vacuum pressure. Then the particle size distribution curves of the soil which were obtained from the water respectively drained from the two experiments were analyzed. At the same time, the settlements of soil column were compared. The experiment result shows that the vacuum dewatering method discharges more small particles than well dewatering method, which contributes to the settlement of the soil.

Abstract: In order to ensure accuracy of positioning rescue drilling, studied over technical basis required for precise drilling location and confirmation method for locating of finished underground drill-hole and surface drilling hole. Put forward the technical basis for formulating drilling-positioning scheme, Discussed underground finishing drilling of hole positioned by synthesis method and surface drilling center determined by total station with GPS RTK and give demonstrates with cases. Related studies indicated that mutual verification with two or more methods above are key measures to ensure positioning accuracy.