Advanced Materials Research Vols. 1065-1069

Abstract: The "8.03" Ms6.5 Ludian earthquake in Yunnan province is the largest earthquake of the area in recorded history. The PGA of epicenter (Longtoushan town) reaches 948gal and the intensity of meizoseismal area arrives to IX degree. The earthquake has caused severe casualties and huge property losses. Based on the earthquake damage investigation, it is found that structure types of affected towns mainly include mud-wood, brick-wood, masonry, frame, bottom frame and composite structures. In the IX degree area, most of the mud-wood, brick-wood, unfortified masonry and composite structures turn into severely damaged or destroyed. Most bottom frame structures obtain inclined shear cracks on bottom walls. Part of the masonry structures built after 2008, which are set with ring beams, construction columns, cast-in-place floors and roofs, show well earthquake performances and suffer slight damage. What’s more, most filler walls and other non-structural components of frame structures in the meizoseismal area are severely damaged, part of their column ends or beam-column joints fall into failure, which doesn’t achieve "strong column-weak beam" yielding mechanism of the seismic design code expectation. The ending of this paper summarizes a number of recommendations for post-earthquake recovery and reconstruction work according to local conditions.

Abstract: At high frequencies, there is an obvious descending of Fourier spectrum amplitude of ground motion acceleration. This fact could be described by a low0pass filter that is controlled by parameter Kappa (κ). In most regions of the world, there are not sufficient strong ground motion records to evaluate this regional parameter. We try to acquire κ value from small-earthquake records of the broadband digital seismograph network in North China (36°-43°N, 113°-120°E). Total 1995 records from 28 small earthquakes (M_w=3.5-4.5) recorded at 155 stations of China Earthquake Network during February of 2002 to September of 2012, are analyzed. The κ value is acquired from the slope rate of the decay segment of the calculated Fourier spectrum of each record, and the mean value is obtained. The result is analyzed if κ is magnitude, focal depth or distance dependent. For the magnitude-dependence, κ values of 40 strong ground motion records are also obtained and compared. The result of the paper shows that κ is not magnitude-dependent neither focal depth-dependent. The distance-dependent is not obvious, especially for small earthquake.

Abstract: The Wenchuan earthquake in 2008 caused serious damage to electrical equipments in substations. In recent years after Wenchuan earthquake, domestic scholars and research institutions have carried out a lot of research on seismic performance of electrical equipments in substations. These research yielded good results as a whole and enhanced the seismic safety of power system in China. In this paper, seismic research progress of this filed in recent years were summarized systematically, covering the topics such as fortification targets, seismic analysis method, seismic performance testing methods, isolation technique. Future research directions on this filed are also prospected.

Abstract: As a key component of power transmission and distribution systems, HV reactor bushing made of porcelain have suffered serious damage in previous earthquakes. In order to enhance seismic ability, the new type bushing made of composite material have been used in high seismic fortify-cation intensity projects. The test requirement in this analysis included: the selection of dynamic magnification factor、the selection of excited wave、the control of tolerance between input peak acceleration and output peak acceleration. During the shaking test, the dynamic characteristics, including frequency and damping ratio, and the seismic response of the composite bushing was obtained. Based on the analysis results of the bushing, the judgment of the seismic capacity was achieved.

Abstract: Single-channel and multi-channel seismic exploration have become two important geophysical methods in offshore engineering geological investigation. Both of the two methods can present high sensitivity and high resolution information about the strata under the seafloor. However, the single-channel seismic prospecting method has some limitations in high resolution engineering surveys. For example, (1) When the depth of water is relatively shallow, the system cannot get zero offset profile; (2) The reflective events will be distorted if the terrain of the seafloor is complex, and thus make the interpretation much more difficult; (3) We cannot remove the influence of the complex multiples in single-channel seismic data processing; (4) We cannot get the lithological and physical properties directly using single-channel seismic method; and, (5) The spatial resolution of single-channel is also lower than that of multi-channel seismic method. In this paper, we presented some examples, and the above problems have been discussed to compare the two methods. All those can give a good guide for selecting appropriate exploration methods.

Abstract: The applicability of seismic waves for the seismic performance estimation of 750 kV post insulator has been investigated in full-scale shaking table test. the input seismic waves comprise El Centro seismic wave, Landers seismic wave, sine beat wave and artificial standard wave. The testing results indicate that, high dynamic responses of the equipment can be obtained under artificial standard wave condition. In addition, due to comprehensive enveloping ability and gentle spectral curve, artificial standard wave is ideal for the seismic performance evaluation of 750 kV post insulator in the test. An finite element model has been developed and numerical seismic analysis has been performed. Satisfactory match between the simulated and measured results reveals the reliability of the test. The achievements obtained in this paper are helpful in choosing reasonable input wave for shaking table test, and also provide technical support on determining seismic capacity of high voltage electrical equipment.

Abstract: Considering the important role of the electrical equipments in the power grid, electrical equipment seismic fortification level should be further improved. Through comparison of electrical equipment related seismic codes in China and abroad,it is recommended that the seismic fortification level of electrical equipment is taken as strong shock, whose exceeding probability is 2% in 50 years.Combined with the results of typical groundby seismic hazardanalysis in different fortification intensity zones, the peak acceleration values corresponding to suggest seismic fortification level was proposed, that is 2 times of the value of medium shock.

Abstract: The new-style isolation bearings that can isolate the seismic effect in horizontal and vertical direction is presented in this paper. In order to study isolation of bearings, structure seismic isolating model is established based on new-style isolation bearings. Through the input of seismic excitation, acceleration peak and storey drift are regarded as basic discrimination factor for studying seismic response, and structure seismic isolating model is contrasted with structure seismic non-isolating model. The example shows that the new-style of isolation bearings not only can isolate in the horizontal direction, but also isolation ability is better in the vertical direction.

Abstract: Slope dynamic factor of safety (FOS) under earthquake was calculated based on time history analysis method and compared with acceleration time history to analyze correspondence between them. In view of the fact that earthquake is a dynamic process, this paper proposed that three respects can be considered to analyze the slope stability rather than adopting a single FOS value. Firstly, the variation trend of the FOS time history can be combined with the forces on key points to analyze slope stability. Secondly, the displacement and stress vector fields can be adopted to evaluate the final slope stability. Thirdly, the variation trend of the displacement and velocity time history can be used as well. The above methods are applied to Beihoushan landslide in Hanyuan in Wenchuan earthquake to evaluate slope stability under earthquake and the analysis shows that the slope is stable as a whole.

Abstract: The performance-based design of structure can reach the performance objectives under different earthquakes. Mild steel shear dampers (MSSDs) have a good and stable energy dissipation capacity, and are widely used in seismic reduction structure. This paper presents a performance-based aseismic design method for RC frame with mild steel shear dampers, the numerical model of frame was established by SAP2000, then seismic performance of the frame was studied by time history analysis. Compared with pure frame, the inter-story drift ratio of MSSD frame is significantly decreased under frequent, moderate and rare earthquake respectively, and the performance objectives are satisfied, demonstrating the effectiveness of the performance-based aseismic design method.