Applied Mechanics and Materials Vols. 71-78

Abstract: Intermediate crack-induced debonding is one of the most dominant failure modes in FRP-strengthened RC beams. Different code models and provisions have been proposed to predict intermediate crack-induced debonding failure. Out of all the existing code provisions and models, four typical ones are investigated in the current study. A comprehensive comparison among these code provisions and models is carried out in order to evaluate their performance and accuracy. Test results of flexural specimens with intermediate crack-induced debonding failure collected from the existing literature are used in the current comparison. The effectiveness and accuracy of each model have been evaluated based on these experimental results. It is shown that the current recommendations are inadequite to effectively mitigate intermediate crack-induced debonding in flexurally strengthened members.

Abstract: Intermediate crack-induced debonding is one of the most dominant failure modes in FRP-strengthened RC beams. Different code models and provisions have been proposed to mitigate intermediate crack-induced debonding failure. Out of all the existing code provisions and models, six typical ones are investigated in the current study. These available guidance for mitigating debonding failure of externally bonded fiber reinforced polymer composites applied to concrete is evaluated based on data obtained from experimental programs. It is shown that the current recommendations are inadequate to effectively mitigate intermediate crack-induced debonding in flexural members.

Abstract: This paper aims at progressive failure within surrounding rock under continuous excavation, such as mining, underground powerhouse building, etc. A meso-damage model is proposed, which include the damage law under complex stress state for brittle materials, and the damage evolution based on stiffness degradation. The damage model is embedded into the FEM program. To test and very the damage model, a example of continuous excavation of underground mining is simulated. The result shows that the crack field growth is in accordance with that the similar material experiment.

Abstract: Flexible vegetations supply great effect on river bank protection. It is important to study the critical flow conditions, including bed shear stress, scour duration and frictional velocity etc, causing damage of grass-covered revetment. Laboratory experiments prove that, destruction of turf can be estimated by observing the variation of water head. The experimental shear stress above vegetation zone has nonlinear relation with velocity square, which agrees with theoretic derivation. Before the turf destruction occurring, shear stress above vegetation zone increases with the scour duration and then goes to stabilization. This mentioned Shear stress will change suddenly when local scour damage happens, or keep stabilization while affine damage is on-going. Under the same flow conditions, the critical bed shear stress of reinforced turf is larger than that of natural turf. As far as the same-form revetments are concerned, the bed shear stress at breaking point increases with the flow velocity.

Abstract: The basalt fiber composition reinforced material (BF) is a kind of new fiber composite material, comparison to carbon fiber, glass fiber and other composites , it has some advantages such as high temperature resistance, corrosion resistance and low cost. This paper introduces the research status of basalt fiber at home and abroad, and it pointes out its application prospect and problems which needs to be solve in bridge engineering.

Abstract: The bridge is a half-through steel-pipe concrete arch bridge with uniform catenary. Based on sufficiently considering the principle of symmetrically loading rib concrete, the pouring process of the whole concrete is calculated with emulation with the aiding of commercial package MIDAS/Civil. By analyzing the structural deformation, stress and stability, the structural responses such as the structural distortion deformation, bearing-force characteristics and stability coefficients at different construction stages are computed in this study. The motivation of this investigation is to ensure the structural safety, and the structural security can also be discussed. The made observations indicate that the whole bridge has a high safety in either construction or operation and the achievement of research may provide reference for the similar arch bridge.

Abstract: For studying seismic behavior of concrete filled steel tube (CFST) column to RBS beam connections with crossing diaphragm under cyclic loading, Base on 3-D nonlinear finite element models which were used to analyze the mechanical properties using ANSYS, compared with CFST column to H-beam connections with exterior concentric annular, the finite element analyses were conducted to investigate the influences of hysteresis loops, the stress distribution rules, stiffness degradation and failure mechanism. It found that this connection not only transfers a plastic hinge from the root of beam end to the reduce section, but it little affects stiffness degradation. In addition, due to the crossing diaphragm that is beneficial to transfer shear to core concrete and provides the tensile force to beam, it improves the deformation of column. Consequently, this joint has a better seismic capability.

Abstract: The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. In a simplified approach active persons can be modeled as external loads. While this approach may be sufficient for an activity like jumping, it has been shown already that for a bobbing person some interaction effects may occur. The question arises if also pedestrians are able to influence the dynamic characteristics of the structure they are actually crossing. Observations during a mass event with several thousand persons crossing a 66 m long bridge indicate that the damping capacity of the coupled structure may have increased. In this paper a single beam experiment was operated. The basic idea is to use a known background excitation induced by a shaker. It can be seen that both natural frequency and damping ratio have been changed comparing with empty structure. The change with passive person is stronger that an active person. Meanwhile, the linear sweep method which was used in measurement provides a good result for the analysis of dynamic properties of a structure.

Abstract: The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. Therefore, the coupled system of a structure and the occupants can hardly be described with its basic dynamic characteristics considering only the mass of the occupants. Depending on the natural frequency of the empty structure, the human body dominantly acts like a mass, a mass and a damper or a damper. If the natural frequency of the empty stand increases 3 Hz, the human body induces considerable damping into the coupled system. In the limit, the dynamic characteristics can be described based on the average values of the characteristics of the human body.

Abstract: Take Longtan river super large bridge as example,establishing finite element model with Bridge Doctor to analysis the influence shrinkage and creep.The deformation prediction of the bridge in the construction process and after completion was made based onseveral.Each prediction results were analyzed and compared.