Applied Mechanics and Materials Vols. 166-169

Abstract: Because of possessing the advantage of steel structures and concrete structures, the steel-concrete mixed structure has been developed rapidly and used widely. And at present, it has been a popular structural type in high-rise buildings. Although mixed structures have been used in earthquake region more and more, seismic fragility studies for this type of construction is scarce. Based on analyzing and summarizing the available studies on structural seismic fragility, present research situation on seismic fragility of mixed structures at home and abroad is described; the key problems to solving urgently in the analysis of seismic fragility for mixed structures are put forward; and the trend of development is forecasted. Study on the issues above will give some help to aseismic design, strengthening, repairing and disaster reduction of mixed structures.

Abstract: In order to understand the seismic performance of the large complex structure with multi-storey basement, the structure-pile-soil finite element model of a typical cross sections of one transfer station in a transportation junction were established by using the ANSYS software. The time history analysis was adopted, and the seismic responds of the whole system under the seismic load was analyzed, and some rules were attained. Comparing the result of the seismic responds with the rigid foundation model which the soil around the underground structure simulated by spring element, and some salutary conclusions are attained.

Abstract: Finite element models of frames with steel-bracings and with concrete filled steel tube struts are built in ETABS. Seismic performance of these models is analyzed with base-shear method, superposition of modal responses method and time history method respectively. The results show that the steel-bracings or concrete filled steel tube struts are efficient to increase the story-stiffness, and the top displacement of the frame structure decreases significantly.

Abstract: We propose a method to compute the restoring force characteristics and dissipated energy to detect damage level of viaducts for railways and highways, using only acceleration. The acceleration data were measured by accelerometers which were installed on the top and the bottom of the structures. Wireless sensor network is used to compute and collect the data. Using this system, the information of restoring force characteristic and dissipated energy can be created.

Abstract: In order to make sure reliability of ceiling system according to the current code, response acceleration of ceiling suspension points are obtained by seismic model developed by ANSYS/LS-DYNA. Then the FE model of ceiling system according to the current code is also developed in ANSYS/LS-DYNA. The input acceleration is added on ceiling suspension point. The following features are obtained from ceiling system with light steel furring and gypsum board under severe earthquake. These are: 1 Many gypsum boards which are designed according to the current code are failed and drop down，that may result in casualties. 2 The furrings are failed and did not drop down, then may drop for higher peak acceleration. 3 The ceiling system according to the current code is not safe under severe earthquake.

Abstract: The paper presents an experimental study on a new type viscoelastic damper, which is expected to have better energy dissipation capability. Tests on the dampers’ mechanical properties, including shear storage modulus, shear loss modulus, and loss factor, were conducted using reduced scale specimens, and took strain amplitude, loading frequency and ambient temperature as test parameters. Aging tests, low cycle and high cycle fatigue tests were also conducted. Particularly, the low cycle fatigue behavior under a strain of 300% and the basic mechanical behavior under strains of 300%-420% were investigated. Test results suggest that the dependency of the mechanical properties on frequency and temperature is small, the energy dissipation capacity is stable for both large and small displacement, and the damper reaches a strain of 420% without failure.

Abstract: In order to investigate the collapse mode of double-layer space trusses, the whole collapse process is simulated by the explicit finite element methods. The calculation results indicate that horizontal earthquake and vertical earthquake waves will lead to two typical collapse modes of the structure. The collapse mode of the structure under horizontal earthquake are mainly strength failure, which is characterized by the failure of members connected to the columns; the collapse mode of the structure under vertical earthquake are mainly dynamic instability, which is characterized by the V shape deformation. The analytical results agree with the experimental results.

Abstract: The forms of storey-adding structure include direct, separating, unitary, cooperating with vibration reduction and so on. The characteristic and anti-seismic capability are different for each form, and the homologous application are distinct. The paper summarises the research process of anti-seismic capability of the above four forms, and makes suggestions in some ways, such as strenghening experimental study, combining with advanced new technics on seismic isolation and absorption.

Abstract: This paper presents seismic dynamic response rules of Wuhan Changjiang River tunnel. Bilateral seismic dynamic responses of tunnel typical geology section are studied based on software of ANSYS. Conditions of gravity and water pressure are considered compared with that of no gravity. Some conclusions have been obtained:(1)The node displacement of lining arch crown is the biggest ,which of soffit lining is the least under two-way earthquake. The maximal node displacement not considering initial condition of gravity decreases 34 percent, and the relative displacement reduces 22 percent between the top and the bottom of lining compared with thinking of gravity influence; (2) The maximal equivalent node stress of the former distributes on lining side wall, which decreases 29.4 percent in comparison with the latter under two-direction earthquake;(3) The gravity factor can not be ignored in seismic analysis of underground tunnel.

Abstract: Deterministic safety factor are introduced by Z. CAO et al (2008) according to seismic Chinese code. The approach was deterministic method used the standard penetration test (SPT) to evaluate the liquefaction of soil. With this method, liquefaction of soil is predicted to occur if the factor of safety(FS), which in the ratio of critical SPT-N value(Resistance) over the actual measurement SPT-N(Load), is less than or equal to one. If the factor of safety greater than one, no soil liquefaction is predicted. Because the significant uncertainties in variable involved in the deterministic factor of safety, the probability method need to use. Probabilistic safety factor calculations provide a means of evaluating the combined effeces of uncertainties and provide a logical framework for choosing a factor of safety that is appropriate for the degree of uncertainty and consequences of failure. Then, a probabilistic assessment of soil liquefaction may be performed in which probability of failure and reliability index. By using the most widely reliability analysis as the First Order Second Moment (FOSM) method, the results of a probabilistic assessment of soil liquefaction can be used for engineering decision.