Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 7 Articles
Knowledge of the tensile Youngââ?¬â?¢s modulus of concrete at early ages is important for estimating the risk of cracking due to restrained\r\nshrinkage and thermal contraction. However, most often, the tensile modulus is considered equal to the compressive modulus and\r\nis estimated empirically based on the measurements of compressive strength. To evaluate the validity of this approach, the tensile\r\nYoungââ?¬â?¢s moduli of 6 concrete and mortar mixtures are measured using a direct tension test. The results show that the tensile\r\nmoduli are approximately 1.0ââ?¬â??1.3-times larger than the compressive moduli within the materialââ?¬â?¢s first week of age. To enable\r\na direct estimation of the tensile modulus of concrete, a simple three-phase composite model is developed based on random\r\ndistributions of coarse aggregate, mortar, and air void phases. The model predictions show good agreement with experimental\r\nmeasurements of tensile modulus at early age....
A web-based Geotechnical Geographic Information System (GeoGIS) was developed and tested for the Alabama Department\nof Transportation. This web-based system stores geotechnical information about transportation projects, such as subsurface data,\nconstruction drawings, and design information. Typically, this information is in a report or plan sheet format, but raw geotechnical\ndata can also be accommodated in the GeoGIS. The goal of this system is to provide easy access and storage for all geotechnical\nand subsurface structural information from across a state. Access through a secure web interface allows for keyword searches and\ninteractive map selection. The web-based GeoGIS has four geotechnical layers (project, bridge, foundation, and soil boring) that\ncan be displayed on a road map, aerial photos, or USGS 7.5 minute quadrangles. For testing purposes the GeoGIS was populated\nwith multiple document types, formats, and sizes. In all cases, the system performed above expectations....
Bridges are under various loads and environmental impacts that cause them to lose their structural integrity. A significant number\r\nof bridges in US are either structurally deficient or functionally obsolete, requiring immediate attention. Nondestructive load\r\ntesting is an effective approach to measure the structural response of a bridge under various loading conditions and to determine\r\nits structural integrity. This paper presents a load-test study that evaluated the response of a prefabricated bridge with full-depth\r\nprecast deck panels inMichigan. This load-test programintegrates optical surveying systems, a sensor network embedded in bridge\r\ndecks, and surface deflection analysis. Its major contribution lies in the exploration of an embedded sensor network that was\r\ninstalled initially for long-term bridge monitoring in bridge load testing. Among a number of lessons learned, it is concluded that\r\nembedded sensor network has a great potential of providing an efficient and accurate approach for obtaining real-time equivalent\r\nstatic stresses under varying loading scenarios....
The exploration of a series of shaking tests on circular model footing with and without cellular confinement constructed around the footing with variable depths and diameters under the effect of variable net bearing stress is studied. The effect of the confinement on the liquefaction time, final settlement, excess pore water pressure, and induced building acceleration were studied. The consequences showed that installing the cell with minimum diameter closer to footing and sufficient penetration depth significantly delayed the liquefaction time. It can be considered as an alternative technique to decrease both the lateral spreading and the final settlement below the foundation during the shaking. The results demonstrated that the cell reduced the excess pore water pressure within the confined zone and the pore water pressure migration outside the confined block where the liquefaction is induced. Moreover, the peak foundation acceleration of the confined footing soil system is reduced compared with the case of without cell confinement....
When a buoyant inflow of higher density enters a reservoir, it sinks below the ambient water and forms an underflow. Downstream\r\nof the plunge point, the flow becomes progressively diluted due to the fluid entrainment. This study seeks to explore the ability of\r\n2D width-averaged unsteady Reynolds-averaged Navier-Stokes (RANS) simulation approach for resolving density currents in an\r\ninclined diverging channel. 2D width-averaged unsteady RANS equations closed by a buoyancy-modified k - e turbulence model\r\nare integrated in time with a second-order fractional step approach coupled with a direct implicit method and discretized in\r\nspace on a staggered mesh using a second-order accurate finite volume approach incorporating a high-resolution semi-Lagrangian\r\ntechnique for the convective terms. A series of 2D width-averaged unsteady simulations is carried out for density currents.\r\nComparisons with the experimental measurements and the other numerical simulations show that the predictions of velocity\r\nand density field are with reasonable accuracy....
The authors model the emergence processes of road obstacles, such as fallen objects on roads, the deformation and destruction of\r\npavements, and the damage and destruction of road facilities, as counting processes. Especially, in order to take into account the\r\nheterogeneity of the emergence risk of a variety of road obstacles, the authors model a mixture Poisson process in which the arrival\r\nrate of road obstacles is subject to a probability distribution. In detail, the authors formulate a Poisson-Gamma model expressing\r\nthe heterogeneity of the arrival rate as a Gamma distribution and formulate the management indicator of the emergence risk of\r\nroad obstacles. Then, a methodology is developed in order to design a road patrol policy that can minimize the road obstacle risk\r\nwith a limited amount of budget. Furthermore, the authors empirically verify that it is possible to design road patrol policy based\r\non the emergence risk of actual road obstacles with the proposed methodology, by studying the cases of the application of the\r\nmethodology to general national roads....
The study of parameters selection of model sizing appropriate for use in an Eiffel type subsonic\nboundary layer wind tunnel was investigated. Using a prototype-model dimension scale of 1:300 on a 72\nm, 20 storey prototype building with ratio 1:2:6; a width of 43.33, 83.33 mm breadth and 240 mm height\nwas produced as physical model. The result of the application of methods of global modular ratio and\narea moment for parameters selection shows that the moments of inertia obtained from the two\nmethods only differ by 2.33%. The proposed hollow rectangular configuration recommended as walls\nfor the physical model are 10.5 and 20.2 mm thick along the width and breadth, respectively. The\nassemblage of the models was rigidly bounded together by using a set of G-clamping devices and\nspecial adhesives such as epoxy resin and liquid glue. The base of the physical model was mounted on\nflat steel plate which serves as an infinitely rigid foundation resting on the polystyrene that represents\nthe soil conditions which was assumed to behave as elastic base. At the end, the model was rigidly\nfastened to the wind tunnel using solenoid wires. The original data generated for the dimensions were\nintrinsically linear and they were linearized using a natural logarithm model. Ordinary least square\nregression analysis conducted on the result show that y = 1.94 + 0.433x. The analysis of variance\n(ANOVA) is significant at P = 0.001 but the corresponding standard deviation, correlation coefficients\nand student�s T are S = 0.1561, R - Sq = 93.9% and T = 9.23, respectively. All these statistically confirm\nthat there are no serious trends to show that the proposed models are inappropriate....
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