Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
In some situations, it is necessary to strengthen or rehabilitate a structure in the short\nterm, but before doing so, a critical analysis of the underlying causes is required to find the best\ntechnique to solve the problem. The structural strengthening is used to increase an elementâ??s ability\nto resist a stress when it no longer meets the original conditions or new necessities of use due to\nfaults, deterioration, thermal variations, and lack of maintenance. The present article aims to evaluate\nthe strengthening of reinforced concrete beams with 0.75 mm thick SAE 1020 steel plates bonded\nwith epoxy-based structural adhesive. The steel plates were attached to the sheared area before and\nafter the beams were taken to the breaking point load. According to the results, it was possible to\nconclude the effectiveness of the strengthening applied to healthy beams that had its bearing capacity\nincreased up to 50%. The beam that was strengthened after the shear, with a fissure that was restored\nwith epoxy-based structural adhesive, had its load bearing capacity increased by 49.2%. The beams\nwith fissures that were filled with mortar had their bearing capacity decreased by 58.70% if compared\nwith the reference beams, and thus they presented an unsatisfactory performance....
A lot of crystallizations exist on the inner wall of tunnel drainage pipes in Chongqing. Tunnel support structure often bears larger\nload than usual because the tunnel drainage pipes are blocked easily by the crystals and the groundwater level would rise. In order\nto investigate what the crystals are, site investigations and laboratory tests of crystals and groundwater were completed. Some\nvaluable results have been obtained. Firstly, the crystallizations are usually discovered in drainage pipe exits of tunnels which are\nunder construction in Chongqing. Furthermore, the results of XRD have confirmed that the crystals are calcite. And calcite\nmorphology could be found in most SEM images. But there are other morphologies in these images other than calcite because\ncalcite is often influenced by some factors, such as important ions in groundwater, pH of groundwater, kinetics effect, and so on.\nFinally, some steps and solutions to solve blocking of tunnel drainage pipes caused by crystallization are suggested. One of the best\nsolutions is that some special materials which could prevent crystals from being attached to pipes are coated on the inner surface of\ndrainage pipes. The results could contribute to understand the crystallization phenomenon profoundly and help solve the similar\nsituations of tunnel drainage pipe blocking....
This paper focuses on the seismic performance of mountainous railway\nbridges having different pier type i.e. rectangular hollow piers and solid piers.\nThe piers used were of same materials and inertial properties. For this, 3-D\nFEM models of these bridges were created by ANSYS 15.0. For seismic assessment,\nResponse Spectrum and Dynamic Time-History Analysis methods\nwere adopted. Different types of earthquake waves used were Elcentro, Wenchuan\nand Nepal earthquakes, all normalized to 0.3 g Peak Ground Acceleration\n(PGA). The study concluded that even though the hollow pier bridges\nare susceptible to large displacements, its dealing with internal forces is remarkable\ncompared to solid pier bridges....
Achieving a comprehensive and accurate understanding of the anchor reinforcement mechanism and a quantitative evaluation of\nthe surrounding rockâ??s stability for an anchored underground cavern can provide an important theoretical basis for supporting\nand excavating the cavern. First, the composite bearing structure composed of the anchor and surrounding rock was defined as the\nsurrounding rock reinforcement body by using the homogenization method, and a new method for evaluating the stability of\nsurrounding rock by the surrounding rock reinforcement body deformation and damage degree was proposed. Second, based on\nthe anchor reinforcement effect, the expression of the physical-mechanical parameters of the surrounding rock reinforcement\nbody was deduced, and the analytical solution of stress and displacement of the surrounding rock reinforcement body was\nobtained. Finally, the stability coefficient of surrounding rock indicating the degree of the surrounding rock reinforcement body\ndamage was defined. The research showed that the theoretical solution agreed well with the results of the numerical simulation,\nand the difference between the theoretical solution and the monitoring value was less than 10%, which verified the reliability of the\nmethod and the results of this paper. The design of the length and spacing of the anchor followed the principle of long but sparse\nand short but dense, and the pretightening force of the anchor and the stability coefficient of surrounding rock varied linearly. The\nanalytical solution of this paper provides a theoretical reference for understanding the mechanism of anchor support and provides\na quantitative evaluation method for the stability of surrounding rock. Compared with the traditional support design, the theory of\nthis paper gives full play to the self-stability of the surrounding rock and the strength of the anchor, which is conducive to saving\nsupport costs and avoiding the construction limitations in some projects....
The deformation characteristics of a weak foundation with high back siltation in an immersed tunnel lack empirical data; however,\nthe calculation method and control of foundation settlements are highly important to tunnel design and construction. This paper\ntakes a cross section of the natural foundation of an immersed tunnel in the Hong Kong-Zhuhai-Macao Bridge (HZMB) as the\nresearch object and conducts a centrifuge model test.Thesoil layer is divided, and the soil parameters are determined by the CPTU\nand the indoor dynamic three triaxial test. In consideration of the actual engineering scale and the ability of the centrifuge model\ntest system, the similarity ratio of the model to the prototype is studied and determined. As for the immersed tube structure, the\ndeformation characteristics are mainly studied. Therefore, the organic glass is selected as the model material by the similarity of\nthe elastic modulus and the density. The characteristics of the resilience and recompression of the natural foundation of the\nimmersed tunnel and the strain characteristics of the immersed tube structure are obtained by the analysis of the multiworking\ncondition test data. Moreover, based on the actual engineering geological conditions of the subsea tunnel, a numerical calculation\nmethod is carried out to check the reliability of the centrifuge model test results. The results of the numerical calculation are\nconsistent with the model test results....
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