Current Issue : October - December Volume : 2013 Issue Number : 4 Articles : 5 Articles
Portland cement concrete exposed to high temperatures during mixing, transporting, casting, finishing, and curing can\r\ndevelop undesirable characteristics. Applicable requirements for such the hot weather concrete differ from country to country and\r\ngovernment agencies. The current study is an attempt at evaluating the hardened properties of the concrete exposed to hot weather\r\nin fresh state. First of all, this study reviews the current state of understanding and practice for hot weather concrete placement in\r\nUS and then roadway sites with suspected hot weather concrete problems were investigated. Core samples were obtained from the\r\nfield locations and were analyzed by standard resonance frequency analysis and the boil test. Based on the results, there does not\r\nappear to be systematic evidence of frequent cracking problems related to high temperature placement. Thus, the suspicious\r\ndeteriorations which are referable to hot weather concreting would be due to other factors....
Recently, soil-steel bridges have become more commonly used as railway-highway crossings because of their\r\neconomical advantages and short construction period compared with traditional bridges. The currently developed\r\nformula for determining the minimum depth of covers by existing codes is typically based on vehicle loads and\r\nnon-stiffened panels and takes into consideration the geometrical shape of the metal structure to avoid the failure\r\nof soil cover above a soil-steel bridge. The effects of spans larger than 8 m or more stiffened panels due to railway\r\nloads that maintain a safe railway track have not been accounted for in the minimum cover formulas and are the\r\nsubject of this paper. For this study, two-dimensional finite element (FE) analyses of four low-profile arches and four\r\nbox culverts with spans larger than 8 m were performed to develop new patterns for the minimum depth of soil\r\ncover by considering the serviceability criterion of the railway track. Using the least-squares method, new formulas\r\nwere then developed for low-profile arches and box culverts and were compared with Canadian Highway Bridge\r\nDesign Code formulas. Finally, a series of three-dimensional (3D) finite element FE analyses were carried out to\r\ncontrol the out-of-plane buckling in the steel plates due to the 3D pattern of train loads. The results show that the\r\nout-of-plane bending does not control the buckling behavior of the steel plates, so the proposed equations for\r\nminimum depth of cover can be appropriately used for practical purposes....
Measuring structural damage during earthquakes has always been a challenging problem for earthquake engineers.\r\nVarious damage indices are proposed with the objective of quantifying the structural damage in prototype and\r\nmodel structures subjected to seismic excitation. In this study, seismic vulnerability of irregular steel buildings is\r\nassessed in three dimensions considering effects of the panel zone, which has not been considered in recent\r\nstudies of the field of seismic vulnerability. The buildings are modeled with different storeys and irregular plans.\r\nSeismic performance of buildings was assessed in life-safety and collapse-prevention levels. Cumulative functions of\r\ndamage indices are applied in the nonlinear dynamic analysis of buildings in the near-field ground motions. It is\r\nconcluded that participation rates of deformation and energy in the damage of irregular buildings are 74.5% and\r\n25.5%, respectively. Severe damage and collapse due to seismic dissipated energy occurred in the initial storeys of\r\nlow-rise buildings and in the middle storeys of high-rise buildings....
In this paper, we present the analysis of a numerical and an experimental study of the Scotch Road integral\r\nabutment bridge located in Trenton, NJ, USA. Three-dimensional, nonlinear finite element (FE) model of the full\r\nbridge has been developed to study the effect of thermal loading on the bridge substructure. The bridge\r\nsubstructure was fully instrumented. Data analysis was performed to study the effect of several design parameters\r\non axial stress in piles. An analysis of the pile-soil system was performed using the finite difference software LPILE.\r\nThe maximum displacement of the bridge superstructure obtained from the FE model due to a maximum\r\nexpected temperature change of �±42�°C during the lifetime of the bridge was applied to the substructure model.\r\nThe effect of bridge skew on the build-up of soil pressure behind the abutment was studied. A significant increase\r\nin the soil pressures and axial stresses behind the abutment at the obtuse side versus the acute was observed. The\r\neffect of the size of the galvanized steel sleeve on the induced axial stresses in piles was studied. We found that\r\nincreasing the size of the steel sleeve increases their capacity to resist bending....
This article is devoted to shape optimization design of pure bending beams under single loading condition.\r\nCompliance minimization with material volume constraint, the maximum stress minimization problem, and the\r\nmaximum displacement are considered. In the case of trusses, it has been shown that the former two problems\r\nhave the same optimal topology. The possibility of extending this result for pure bending beam problems is\r\nexamined in the present work. First, the comparison of the optimum design results between the maximum\r\ndisplacement, the conventional mean compliance, and the maximum stress is carried out by an example of optimal\r\ncross-sectional design of a continuous beam. Then, geometric average displacement (GAD) is introduced in\r\noptimization models of linearly elastic structures. The elevated accuracy in results achieved with GAD is shown in\r\nthis article....
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