Applied Mechanics and Materials Vols. 368-370

Abstract: Subgrade compactness is the assurance of road strength and stability requirements, is an important indicator of the quality control of road works. Summarize the subgrade compaction detection methods. Expound the inspection and assessment of the compactness methods and precautions combined with the new specification can provide technical reference.

Abstract: Fourteen concrete beams reinforced with 500MPa longitudinal steel bars, of which 6 with skin reinforcement and 8 without skin reinforcement, were tested under two-point symmetrical concentrated static loading to investigate their flexural behavior. The results indicate that the flexural behavior and deflection mode of test beams with skin reinforcement are basically consistent with those of test beams without skin reinforcement. The use of skin reinforcement can significantly reduce average crack spacing and short-time maximum crack width. And the use of skin reinforcement can also slightly increase the short-time stiffness. Under the serviceability limit state, mid-span deflections are in good agreement with the calculated values according to formula in GB50010-2010. However most of calculated average crack spacing and short-time maximum crack width are larger than measured values. According to the test results, the normal formula of crack width should be revised.

Abstract: In urban environment, the soil disturbance induced by shield tunneling can be sensitive because it can cause deformation of the ground and damage the near structure. To study this disturbance in the construction process of Tianjin metro line No.3, in-situ monitoring of pore water pressure, soil pressure and ground settlement were conducted. The pore water pressure was monitored for the soil around the tunnel. The soil pressure was monitored for the soil around the tunnel and on the tunnel face. It was revealed that the pore water pressure and soil pressure changed twice in the tunneling process and these changes were induced by cutting face and grouting at the shield tail. The soil pressure on the tunnel face reached its maximal value when the distance between the cutting face and the sensor elements was around the diameter of the tunnel. Ground settlement developed in the tunneling process. The shape of ultimate settlement trough is closed to the one obtained by Pecks method.

Abstract: Low cycle fatigue (LCF) experiments on anti-seismic steel HRB400E reinforcing steel bars under constant total strain (0.6%) control were conducted on a MTS 809 servo-hydraulic material testing machine. The specimens were then subjected to quasi-static tension until they ruptures on the machine. The mechanical properties such as cyclic stress-strain behaviour, quasi-static strength, and quasi-static ductility of the material at various levels of fatigue damage were investigated .The test results indicate that when compared to its virgin state, in a certain cycles (about 80% fatigue life) the cycle-dependent behaviors of the material can cause a slight change in the strength and ductility, and the ductility of the steel has an opposite trend to the strength. However, a significant decrease occurs to both the strength and the ductility as the cyclic cycles exceeds about 80% fatigue life.

Abstract: The paper is focused on problems of the design resistance of thin-walled cold-formed steel beams with holes, respecting the lateral flexural-torsion buckling effects. The attention is mainly paid to the design resistance determination using the results of experimental verification of the objective resistance and their statistic elaboration and probabilistic evaluation. The lateral buckling of thin-walled beams with holes is a specific problem, because of the holes influence on the torsion stiffness, and usual calculating procedures according to the rules given by the European Standards are not always generally usable. The methods based on the approaches of the design assisted by testing are used for the design resistance evaluation, here. The determination of the design resistance using test results respects the statistic characteristics and probabilistic distribution of all input variables, on which the resistance is depended. This method also takes into account the form of the probabilistic model of the resistance, from the viewpoint of the form of mathematical function and its influence on the resistance variability. The design resistance derivation applying the design assisted by testing can be used as an alternative procedure instead of the design resistance determination according to the normative documents, especially in the cases, when the usual procedures are not sufficiently usable.

Abstract: In this page, combination of finite element numerical simulation and discrete element numerical simulation is used to study the stress - deformation characteristics of rock mass of power transmission project site,whichclarifies the rock mass stress is mainly controlled by thegravitational field,the form of the potential deformationis dominated by compression deformation,andthere is no possibility of occurrence of the horizontal shear deformation.

Abstract: Ground vibration caused by pile driving is a kind of mechanical vibration, and the research of its characteristics is the premise of the effect evaluation on surrounding environment. With the engineering example by the analysis of vibration monitoring, the results show that the vibration frequency is low, and there is a power function relationship between the vibration velocity and the distance from monitoring point to the pile. It can be used for impact evaluation of vibration according to the fitting equation.

Abstract: Based on the characteristics of frequent land subsidence events caused by groundwater level fluctuation in coastal cities in China and studying on the quaternary sedimentary soft clay in Shanghai, the effects of groundwater level fluctuation on the deformation of soft clay is simulated by Geo-Studio finite element software. It has summarized the law of deformation, effective stress with the change of groundwater level fluctuation, especially the process of dissipation of pore water pressure with the groundwater level fluctuation. The low can be sued as a reference for similar engineering and land subsidence prevention.

Abstract: Base on the studies of soil-underground structure interaction of topography variation, large shaking table model tests are conducted, and test results are analyzed contrastively. By considering the influences of earthquake type, vibration amplitude ,unidirectional or bidirectional inputs etc., natural dynamic characteristics, acceleration response, spectrum characteristics and vibration amplification effect of site soil and underground structure are studied, and soil-underground structure interaction is explored, according to methods of time and frequency domain combined, and comparison of tests no topography variation. Significant conclusions have been got, which can be served as a certain basis and reference for underground structure seismic design with local site of topography variation.

Abstract: Under the action of axial compression, it is difficult to deduce the capacity of concrete-filled rectangular steel tube (CFRST) short column in theory because of the complex constraining force between the steel tube and concrete. This paper uses two methods to study the axial bearing capacity of CFRST short column, the first method is to consider the main factors influencing the axial bearing capacity of CFRST column based on a great deal of experiments and use multiple linear regression method of mathematical statistics to obtain the formula of the axial bearing capacity of CFRST short column; the second method is to simulate the axial compression test of CFRST short column by using the powerful structure finite element analysis software ANSYS, and determine the axial bearing capacity of CFRST short column through 3D solid modeling, rational meshing and correct loading method. Those two methods provide new thoughts for forecasting the axial bearing capacity of CFRST short column.