Current Issue : April - June Volume : 2019 Issue Number : 2 Articles : 5 Articles
External bonding of FRP laminates to the tension soffit of concrete members has become a popular method for flexural\nstrengthening. However, the long-term field performance of FRP-strengthened RC members under service conditions is still\na concern, and more work needs to be done. Based on concrete smeared-crack approach, this paper presents a finite-element (FE)\nmodel for predicting long-term behavior of FRP-strengthened RC beam, which considers the time-dependent properties of all\ncomponents including the aging effect of concrete. According to the comparison between theoretical predictions and test results,\nthe validity of the FE model is verified. The interfacial edge stresses in adhesive layer were determined through appropriate mesh\nrefinement near the plate end, and their time-dependent characteristics were investigated. The results show that creep of concrete\nand epoxy resin cause significant variations of the edge stresses with time. According to the research in this paper, the FE approach\nis found to be able to properly simulate the long-term behavior of the FRP-strengthened beam and help us better understand the\ncomplex changes in the stress state occurring over time....
A new prestressed reinforcement device (PRD) consisting of two lateral pressure plates (LPPs) and a reinforcement bar is\ndeveloped to strengthen soil embankments by improving the soil confining pressure and providing lateral constraint on embankment\nslopes. The reinforcement effects of PRDs were demonstrated by investigating the beneficial effects of increasing\nconfining pressure on the soil behavior via the performance of a series of large-scale static and cyclic triaxial tests on a coarsegrained\nembankment soil. The results show that PRDs can effectively improve the soil shear strength, bearing capacity, ability to\nresist elastic and plastic deformation, critical dynamic stress, and dynamic shear modulus, and empirical methods were also\ndeveloped to determine the critical dynamic stress and initial dynamic shear modulus of the embankment soil. Moreover, 3D finite\nelement analyses (FEAs) with an LPP width of 1.2m were performed to analyze the additional stress field in a prestressed heavyhaul\nrailway embankment. The FEAs showed that the additional stress at a given external distance from the border of an LPP first\nincreased to a maximum value and then gradually decreased with increasing depth; the additional stress was transferred to the\nzones where the subgrade tends to have higher stresses with peak stress diffusion angles of 34° (slope direction) and 27°\n(longitudinal direction); and a continuous effective reinforcement zone with a minimum additional stress coefficient of approximately\n0.2 was likely to form at the diffusion surface of the train loads, provided that the net spacing of the LPPs was 0.7 m.\nThe reinforcement zone above the diffusion surface of the train loads can act as a protective layer for the zones that tend to have\nhigher stresses. Finally, the advantages and application prospects of PRDs are discussed in detail. The newly developed PRDs may\nprovide a cost-effective alternative for strengthening soil embankments....
A non-destructive testing (NDT) method was used in a concrete face rockfill dam (CFRD)\nto identify the condition of the concrete face slab and detect any existing cavities between the concrete\nface slab and the underlying support layer. The NDT for the concrete face slab was conducted\nusing the impulse response (IR) method and the electrical resistivity tomography (ERT) method\nwith the application of non-destructive electrodes. Information regarding the dynamic stiffness and\naverage mobility of the concrete was obtained based on the mobility-frequency of the IR method, and\ncavity detection under the plate structures was analyzed using the two-dimensional (2D) electrical\nresistivity section of the ERT method. The results of the IR method showed that zones with low\ndynamic stiffness and high average mobility were expected to be found in concrete of poor quality\nand in cavities beneath the concrete face slab. The results of the ERT method showed that zones\nwith high resistivity were expected to be cavities between the concrete face slab and the underlying\nsupport layer. As a result, the tendency toward low dynamic stiffness, high average mobility, and\nhigh resistivity in both methods implies unstable concrete conditions and the possible occurrence of\na cavity. The results of the two methods also showed a good correlation, and it was confirmed that\nthe NDT method was reliable in terms of cavity estimation....
Fibre-reinforced concrete (FRC) has been used in numerous types of precast elements around the world, as has been shown that\nreductions in production costs and time can be obtained; however, there is little experience of this material in Uruguay. Therefore,\nour study analysed the feasibility of its utilisation in this country. This paper reports on the development of a simple analysis model\nthat is useful for the design of FRC precast elements. The model efficiency was evaluated through its application to a practical case\nstudyâ??vertical precast concrete sandwich panel systems tested by bending. Three different types of reinforcement were analysed:\nsynthetic fibres, metal fibres, and steel mesh. With the developed model, the cost-efficiency of different panel geometries and amounts\nof reinforcement were evaluated.Themodel allowed consideration of the contribution of the fibres to withstand internal tensile forces\nof the panels and therefore be able to substitute for the steel mesh in the panel wythes. It was found that it was possible to optimise\npanel reinforcement and geometry, thereby reducing wythe thickness. Besides the reduction in production time, it was possible to\nachieve cost savings of up to 10% by replacing steel mesh with fibres and of more than 20% if the geometry was also modified....
The present practice in Bangladesh for erection of girders is placing the girder\ndirectly on the bearing pad and joining the adjacent two spans in deck slab\nlevel by adopting expansion joints, as the bridges are presently designed as\nsimply-supported beam bridge. The main disadvantage of this type of bridges\nis that, the seismic resistance is weak, and under the external force beyond the\ndesign range, the bridges are more likely to fall in danger because of failure in\ngirders. Also they have expansion joints for each span, which affects the\ncomfort of driving and the overall integrity of the bridge deck is poor [1].\nTherefore, design and construction of the bridges have been revised to establish\ncontinuity between girders of two adjacent spans and transform the\nbridge as simply supported continuous beam bridge [2]. Temporary bearing\n(sandbox) method is proposed in this paper to solve the system transformation\nof continuous beam bridges. Design of the temporary bearing is very\nsimple and can be manufactured at site. This method has been proved in\nconstruction of Arial Kha Bridge and can be applied for other similar bridges\nin Bangladesh....
Loading....