Applied Mechanics and Materials Vols. 90-93

Abstract: Liquefaction of sand soil such as silty sand was quite popular in earthquake. Gravel liquefaction, by contrast, was seldom. Soil liquefaction was popular in Chengdu Plain in Wenchuan Earthquake and there was ejeched gravel in several sites. Through drilling and tests for typical liquefied sites, the study on distribution of layers, compactedness , shear wave velocity, particle size distribution had been performed. The results shows: (a) Soil distribution is similar in 2 typical liquefied sites which are located in different location and different seismic intensity regions. Gravelly sand was the only cohesiveless soil which is possible to be liquefied,so gravel liquefaction was true; (b)The liquefied gravel was the characteristics of shallow, loose , low shear wave velosity and. the Holocene sediment. (c) Particle graduation of liquefied gravelly sand was poor and there was a short of soil fraction.

Abstract: In this paper, a modified random process model of earthquake ground motion based on the model proposed by JinPing Ou is presented. The parameters in the model except the factor S₀ are determined by using the least square method and the power spectral densities of 361 earthquake records. Then the method for determining the parameter S₀ is proposed. The good performance of the proposed model in this paper in modeling the earthquake ground motion on firm ground is demonstrated by comparing it with other random process models.

Abstract: In order to obtain runoff particle flushing and migration regularity in different functional districts, surface runoff and dust of the campus, sidewalk, business street and viaduct in Beijing city were selected as research objects. Through the particle size distribution detection of surface dust and instantaneous rainwater runoff samples, the runoff particle flushing and migration regularity in different functional districts were analyzed. The relationship between runoff particulate and COD, SS, TN, TP and other pollutants, the particle size variation regularity in the flushing and migration process were analyzed, and the reasons were construed too. The results of the runoff pollutants impact of different size particles will provide a theoretical basis for the filter design and urban runoff pollution control planning.

Abstract: Based on the mechanical properties of metal yield damper, high-rise residential building is implemented elastic-plastic response analysis for structure by using the nonlinear dynamic time-history analysis method under the effect of M8-class strong earthquake ,and judge performance level of structure and component. According to the elastic-plastic analysis results, put forward the improvement proposal for design to make the structure have the better resistance performance against the earthquake.

Abstract: The current problems on damping in seismic response analysis of bridges is presented. The Rayleigh damping theory is simply introduced in this paper. Taking the Longtan River Bridge for instance, the finite element model of Longtan River Bridge (left line) is established. Then, the dynamic properties of the bridge is analyzed. Based on this, the Rayleigh damping constants and in an ANSYS dynamic analysis are obtained.

Abstract: In this paper, both 一-shaped and L-shaped reinforced concrete frame structures are established in ANSYS, and then，the one-way seismic waves, bi-directional seismic waves and two-way plus torsion seismic wave are respectively input to the both of frame structural model, and carried out the torsion angle displacement analysis. Simulations show that: in both frame structures, the torsion angle of column under multidimensional seismic waves is around 20 % greater than it under the one-way seismic wave and corner column is particularly obvious, so we should considered multi-dimensional effects of the earthquake and pay attention to strengthening corner column in seismic design. And the torsion angle of asymmetric structure and increasing rate of it are about 2% larger than the corresponding symmetry structure. So we should pay attention to the torsion effect of irregular structure.

Abstract: The natural frequency characteristics of field has the remarkable influence to the field acceleration response. This paper realized the free field liquefaction numerical simulation experiment based on the Finn model, simultaneously performed the elastic field acceleration response comparative experiment, and has studied the acceleration response frequency features question of liquefiable field. The results indicated that, the acceleration response essential feature of liquefaction field is low-frequency amplification, high frequency reduction. The low-frequency amplification effect is higher than the high frequency reduction effect obviously. The acceleration is amplified in early time and is weakened in later period during the liquefaction process. The acceleration amplification in liquefiable field is remarkable for inputting low frequency waves, the acceleration response is 13 times to input value. Elastic fields also have “low-frequency amplification, high-frequency deflation features”, However, this feature of elastic field is not significant as liquefiable field. At the lower position of liquefiable field acceleration amplification is the largest, at the surface of elastic field acceleration amplification is maximum. The underground structure seismic design in liquefiable field was carried on as in the conventional elastic field, then caused the underground structure to be at the dangerous condition. Researching results will provide a theoretical and experimental basis for the dynamic analysis of underground structures passing through liquefaction soil layer.

Abstract: In return for the collision response of bridge girder with shearkey subjected to seismic loads, a simplified dynamic model has been built by using the finite element analysis program Ansys/Ls-dyna. Based on the analysis of calculation results, the motion feature of this model is unfolded. Also, the stress response and characteristic at the bottom of shearkeys are analyzed, which are the most important parameters reflecting the cracking of shearkeys. Furthermore, the deformation of rubber bearing is elaborated to illustrate the collision of bridge girder with shearkeys. Finally, other key properties about the bridge girder of this collision system are addressed.

Abstract: Cone Penetration Test (CPT) has been conducted at 39 liquefied and non-liquefied sites following the Xinjiang Bachu Ms6.8 earthquake. The current CPT-based liquefaction evaluation method, including Chinese code method, the Robertson method and the Olsen method, was verified by those 39 field test data. The results show that the success verification ratio of Chinese code method, the Robertson method and the Olsen method are relative low by using Bachu earthquake data. Many observed liquefied sites were predicted as non-liquefaction sites, which indicate it is progressive to apply those three methods at Bachu area. The characteristic of soils retrieved from Bachu area is quite differ from that of other areas. An appropriate local method of liquefaction evaluation in Xinjiang region should be developed.

Abstract: The analyses on the statistical response spectra have an important role in determining the earthquake demand. Elastic and inelastic spectra on acceleration of the 205 records on medium-stiff soil site for SDOF systems are presented in statistical analyses. The empirical probability distributions of the spectral values are derived according to the Kolmogorov-Smirnov (KS) goodness-of-fit test. The formula for statistical average spectra of the ground motion ensemble are recommended, which are valuable for current research and code revisal. The results show that the statistical averaged elastic α spectra fits well to the design spectra prescribed in Chinese code when the period is smaller than 2s. The inelastic responses decrease with the increase of ductility demand μ when μ<4. The coefficients of variance of the elastic and inelastic spectra are still large and the dispersion cannot be ignored. The probabilistic distribution of the spectra value on acceleration is validated as the lognormal distributions. The proposed formulas give a good fit to the statistical average values.