Advanced Materials Research Vols. 724-725

Abstract: When ballast materials are subjected to cyclic loading, as a result, the change of particles micromechanical properties will lead to ballast degradation, permanent deformations on the railways step by step. In this paper, it presented a coupling discrete particle-flow simulation model of the railway ballast for cyclic tamping loading. Tamping frequency changes from 25HZ to 60HZ in numerical simulation process. Simulation results that the ballast compaction rate increases linearly with frequency up to a characteristic frequency 35HZ and then it declines in inverse proportion to tamping frequency. The aim of this paper is to study on the effects on the railway ballast under cyclic loading. The study shows that the discrete element method is a valid method for investigation of the microscopic properties of railway ballast now, while we have no other better research method.

Abstract: Threaded connection is the weak link in the system of bolting, but it has significant impact on bolting effect. By the method of laboratory tests study the Threaded connection force and deformation characteristics, including different threaded teeth, different nut thickness and shape, different nut intensity level that impact on the threaded connection, drawn thread teeth high should not be less than 0.7H ; nut thickness is 20mm, with or without flange threaded coupling strength has little effect; the nut strength should be higher than the anchor strength a level.

Abstract: “strong beam and weak column”is the main failure states of reinforced concrete frame structure in the earthquake．This paper studies the influence on the virtual cross-section bearing capacity on extremity of frame beam in reinforced concrete in experiment through the project example and analysis of finite element method,such as slab’s reinforcement，the rigidity of frame beam, the rigidity of orthogonal beam and so on．Exploring the mechanism of slab and frame work together to determine the width of effective flange，which provides references for structural design and engineering application．

Abstract: In this paper, we carried out low cyclic loading test over CFRP strengthened seismic-damaged RC frame named KJ-2 with the quasi-static test method, and compared the seismic performance with the same sections and materials RC frame named KJ-1 which was unstrengthened. We study the seismic performance such as hysteresis curve, skeleton curve, stiffness degradation, bearing capacity degeneration, displacement ductility, and energy dissipation capacity of the reinforced RC frame. On this basis, we analyzed the results of this test in order to obtain some guiding opinions for asymmetric span RC frames that strengthened by CFRP, and provide main preference basis or future national or industry standards.

Abstract: In order to confirm the calculation model of multi-ribbed slab structure and transmission of earthquake action, this paper improved the existing multi-ribbed slab structure. The calculation model of improved multi-ribbed slab structure confirmed the stress relationship among three seismic fortification lines, and the transmission of earthquake action became clear, this calculation model could be applied in structural analysis. For studying the effect of characteristic parameters of restoring force changing in the second seismic fortification line on seismic performance, and correcting the parameters of grid beam, this paper analyzed push-over model of the second seismic fortification line to get the static pushover curve. According to the study, the amount of steel bar in grid beam and sectional dimension of grid beam made the major effect on characteristic parameters of restoring force in the second seismic fortification line, concrete grade of grid beam is a unconsidered factor. Nominal elastic modulus of filling materials didnt much affect the yield strength and yield displacement of the second seismic fortification line, but made significant effect on post-yield strength.