Applied Mechanics and Materials Vols. 94-96

Abstract: The equation to determine the neutral axis of concrete filled steel tube(CFST) component with round section is presented in this paper. The geometric equation, physical equation and static equilibrium equation of CFST are analyzed to determine its section neutral axis. The compressed mechanical properties of CFST component are analyzed with the concrete material properties divided into tension and compression parts.Comparing the numerical results with the experimental results it can be verified that the equation to determine the neutral axis of CFST component with round section is useful to solve the problems that the tension and compression material properties of concrete are different.

Abstract: Intensive research efforts have been spent on vibration-based structural condition monitoring since structural vibration parameters are closely related to structural stiffness which can be used to identify, locate and quantify structural damage. This makes the vibration-based methods quite attractive for structural condition monitoring. This paper proposes to use strain mode for structural damage identification. A new index named Breach Threshold Value of Damage Levels (BTVDL) is proposed to quantify damage. To demonstrate the proposed method, responses of a circular arch with single and multiple damages are simulated using commercial software ANSYS. The simulated dynamic responses are used to identify the location and degree of the damage of the arch. The results demonstrate that strain mode is more sensitive to damages than others indexes such as frequencies and curvature modes. To further verify the method, a scaled arch model was fabricated and tested in the laboratory. Experimental results also confirm the high sensitivity and accuracy of using strain mode in structural damage identification. It is found that the simulated damages can be reliably identified by using the first two strain modes. The proposed method is more sensitive to damages and can be applied to monitoring structural conditions.

Abstract: By taking account of the functions of shear stress couples acting on the dodecahedron element, a triple-shear unified yield criterion for materials is proposed to interpret a series of criteria, especially the commonly used criteria such as the Tresca’s yield criterion, the Von Mises’s yield criterion and the Mohr-Coulomb’s failure criterion through changing its contributive coefficient of the intermediate principal shear stress couples b and the tensile to compressive yield limit ratio α . In spite of that, problems of the limit inner pressures for thin and thick-wall cylinders are analyzed and the new unified solutions are deduced under the hypothesis of the perfectly elasto-plastic materials. The classical solutions based on the Tresca’s yied criterion, the Von Mises’s yield criterion and the Mohr-Coulomb’s failure yield criterion are only the special cases of the new unified solutions. Detailed analyses show that both the contributive coefficient of the intermediate principal shear stress couples b and the tensile to compressive yield limit ratio α have influences on the limit inner pressures for thin and thick-wall cylinders

Abstract: constructional column- core column ; Combination of reinforcement concrete block wall; Hysteresis curve; Ductility; Height-width ratio Abstract: The two groups of constructional column- core column composite of reinforced concrete block masonry wall under low cyclic test is made, considering the different height-width ratio, open hole and don't open hole, the setting of the horizontal reinforcing steel bar and reinforced such as the effect not set level parameters on the wall the failure process and failure pattern, hysteresis characteristics, bearing capacity, ductility, skeleton curves, the viscous damping coefficient, stiffness and steel strain change the properties including the influence law. Test results show that this wall system has better seismic performance.

Abstract: Permeability test for complete stress-strain process of coarse sandstone were carried out in triaxial test instrument. On the basis of test results, the influence of confining pressure and strain on the hydraulic conductivity was discussed. It is shown that in the complete stress-strain process, hydraulic conductivity changes in the law that presents the same character with the curve of stress-strain. The hydraulic conductivity reduces slightly with the increase of deviatoric stress in the stage of micro fracture compressing and elastic; In the elastoplastic stage, along with the expansion of new fractures, the hydraulic conductivity increases slowly at first and then reaches sharply to the maximum value after peak point; In the post-peak stage, the fracture which controls the hydraulic conductivity of coarse sandstone is compressed because of the confining pressure and the hydraulic conductivity decreases. During the process of deformation and failure, the hydraulic conductivity is more sensitive to the change of circumferential strain. With the increase of confining pressure, the increased value from initial to peak value and the decreased value from peak to residual value decreases.

Abstract: This article analyzes the aeroconcrete wall of vertical ultimate load capacity.We make discussions about different spacing of the concrete structure colum, the different floor height, the different wall’s thick.Then combining the result, we discuss the wall’s ductility under the horizontal cyclic loads, the hysteresis loop and so on. Finally,we study the hole wall earthquake resistance performance under the central load and the non-central load function.Comprehensive all results, the improving methods are presented for your consideration.

Abstract: Increasing numbers of tunnels adopt super large sections due to the advance of design and construction technology, but the calculation method for the loose loads of such tunnels still follows the traditional method for tunnels constructed by the method of whole face excavation. The calculated loads using such method are always lager than their actual values of super large sections tunnels, and as a result the supports for such tunnels are too conservative which lead to unnecessary construction cost. As said, a new calculation method for the loose loads of multi-arch and extra large cross section tunnels (MELCST) is proposed in this paper considering the characteristics of construction for such tunnels. The method accounts for the influences caused by the multi-step construction procedure and temporary support on tunnels. Compared with old methods, this method is more practical and close to field situation, which provides a new idea for calculating surrounding rock loose loads in MELCST. This new method is demonstrated using Luohanshan tunnel of airport-highway in Fuzhou city, China.

Abstract: It was difficult to analyze the stability of the rock slope for its complex geological structure. Rock mass was the geological body that subjected to intense deformation and suffered damage, which was composed by rock and jointed rock mass. When the rock mass was in the high steep rock, its loading state was further complicated. First we analyzed the failure mechanism of jointed rock mass in theory, and we used Flac3d with the Mohr-Coulomb yield criterion to simulate the displacements and stresses. We built three models that included angles with level line were 25°, 45° and 65°. The results showed that, all around the joints stresses concentration occurred, the maximum compressive stress occurred at the crack tip; the final crack direction always tended to the direction of maximum compressive stress; and when the angle was bigger, before the crack expended further, the strength of rock decreased first, and destroyed first.

Abstract: This paper relies on Chongqing City Transit Line 6 which is from Wulidian Station to Shanyanggou Reservoir Station nodal project, focusing on the monitoring and comparative analysis of ground sedimentation of the nearby housing estate, bridge abutment as well as the flat surface of the test section (mileage K17+300~K17+600), otherwise, monitoring and comparatively analyzing the deformation of the supporting structure inside the tunnel. This is the first application of TBM in the urban mass transit and the research achievement will accumulate valuable experience and data for the application of TBM in the urban mass transit.

Abstract: A pseudo-dynamic test has been finished to a CFST tube structure model. The model with 13 floors and a scale of 1:10 consists of an outer-tube and an inner-tube, the former is a framed-tube supported on CFST frames and the latter is an RC tube. A series of pseudo-dynamic tests on acceleration earthquake waves in four cases (peak acceleration equal to 0.22g, 0.4g, 0.62g and 1.0g) have been fulfilled by taking to the model. Some behavior of model is researched under earthquake, such as displacement time-history cure, force time-history cure and so on. The experiment has illustrated that the CFST tube structure is an outstanding structural style with excellent anti-seismic behavior.