Current Issue : January - March Volume : 2018 Issue Number : 1 Articles : 6 Articles
Retaining walls are critical geotechnical assets and their performance needs to be monitored\nin accordance to transportation asset management principles. Current practices for retaining wall\nmonitoring consist mostly of qualitative approaches that provide limited engineering information or\nthe methods include traditional geodetic surveying, which may provide high accuracy and reliability,\nbut is costly and time-consuming. This study focuses on evaluating failure modes of a 2.43 m Ã?â?? 2.43 m\nretaining wall model using three-dimensional (3D) photogrammetry as a cost-effective quantitative\nalternative for retaining wall monitoring. As a remote sensing technique, photogrammetry integrates\nimages collected from a camera and creates a 3D model from the measured data points commonly\nreferred to as a point cloud. The results from this photogrammetric approach were compared to ground\ncontrol points surveyed with a total station. The analysis indicates that the accuracy of the displacement\nmeasurements between the traditional total station survey and photogrammetry were within 1ââ?¬â??3 cm.\nThe results are encouraging for the adoption of photogrammetry as a cost-effective monitoring tool\nfor the observation of spatial changes and failure modes for retaining wall condition assessment....
Based on an example of a project in Tangshan, the high-rise buildings are\nbuilt in karst area and mined out affected area which is treated by high pressure\ngrouting, and foundation is adopted the form of pile raft foundation. By\nlong-term measured settlement of high-rise buildings, It is found that foundation\nsettlement is linear increase with the increase of load before the building\nis roof-sealed, and the settlement increases slowly after the building is\nroof-sealed, and the curve tends to converge, and the foundation consolidation\nis completed. The settlement of the foundation is about 80% - 84% of the\ntotal settlement before the building is roof-sealed. Three layer BP neural network\nmodel is used to predict the settlement in the karst area and mined affected\narea. Compared with the measured data, the relative difference of the\nprediction is 0.91% - 2.08% in the karst area, and is 0.95% - 2.11% in mined\naffected area. The prediction results of high precision can meet the engineering\nrequirements....
In combination of the actual project in Dalian Baiyun Mountain Tunnel, this paper introduces the principle of fiber optic sensor\nmonitoring system based on optical time domain reflectometer.Then, based on the orthogonal design and even design scheme, this\npaper carries out a numerical experiment on the tunnel surrounding rock and establishes a regressionmodel of themapping relation\nbetween surrounding rock parameters of operation tunnel and the monitored displacement in order to set the difference between\nthe monitored displacement and the calculated displacement as the fitness function. In the end, this paper carries out parameter\nidentification based on the differential evolution algorithm. Achievements of the study proved that real-time safety warning could\nbe realized inside the tunnel by monitoring the deformation parameters of tunnel vault at real time relying on the optical-fiber\nsensing system of the optical time domain reflectometer (OTDR). Parameters identification was carried out on the structure\nwith differential evolution according to measured data and selected parameters, and great coincidence was obtained between the\nmeasured displacement and the identified parameters displacement, which proved the strong adaptability of the method....
The use of materials of vegetal origin is increasingly being promoted in many industries due to their cost effectiveness and the\nrising sensitivity to environmental protection and sustainability. Arabic Gum Biopolymer (AGB) is a wild plant byproduct that is\nabundantly found in Sudan and is also produced in other African countries. It has long been used in various industries. However,\nits utilization is very limited in the construction sector although there appears to be a significant potential for use of AGB in the\nbuilding industry.As an example, there is evidence thatAGBmay be an effective additive to concrete mixes thatwould improve fresh\nand hardened concrete properties. The aim of the present work is to provide further experimental evidence on the improvement\nthat can be achieved in the physical and mechanical properties of hardened concrete when AGB is added to the mixture. The\nexperimental results show a significant reduction in permeability for an optimum percentage of AGB and an increase in flexural\nand tensile strength and in the elastic modulus....
Concrete fatigue strain and fatigue modulus evolution play a vital role in the evaluation of the material properties. In this paper, by\nanalyzing the advantages and disadvantages of existing concrete strain analysis methods, the level-S nonlinear fatigue strain model\nwas proposed.The parameters� physical meaning, the ranges, and the impact on the shape of the curve were all discussed.Then,\nthe evolution model of fatigue modulus was established based on the fatigue strain evolution model and the hypothesis of fatigue\nmodulus inversely related fatigue strain amplitude. The results indicate that the level-S model covered all types of fatigue strain\nevolution. It is very suitable for the description of strain evolution of concrete for its strong adaptability and high accuracy. It was\nfound that the fitting curves coincided with the experimental curves very well, and the correlation coefficients were all above 0.98.\nTheevolution curves of fatigue strain modulus both have three stages, namely, variation phase, linear change stage, and convergence\nstage. The difference is that the fatigue strain evolution curve is from the lower left corner to the upper right corner, but the fatigue\nmodulus evolution curve is from the upper left corner to the right lower corner....
The elastic modulus and deadweight of carbon fiber-reinforced polymer (CFRP) cables are different from those of steel cables.\nThus, the static and dynamic behaviors of cable-stayed bridges using CFRP cables are different from those of cable-stayed bridges\nusing steel cables. The static and dynamic performances of the two kinds of bridges with a span of 1000m were studied using the\nnumerical method. The effects of geometric nonlinear factors on static performance of the two kinds of cable-stayed bridges were\nanalyzed.The live load effects and temperature effects of the two cable-stayed bridges were also analyzed.The influences of design\nparameters, including different structural systems, the numbers of auxiliary piers, and the space arrangement types of cable, on the\ndynamic performance of the cable-stayed bridge using CFRP cables were also studied. Results demonstrate that sag effect of the\nCFRP cable ismuch smaller than that of steel cable. The temperature effects of CFRP cable-stayed bridge are less than those of steel\ncable-stayed bridge. The vertical bending natural vibration frequency of the CFRP cable-stayed bridge is generally lower than that\nof steel cable-stayed bridge, whereas the torsional natural vibration frequency of the former is higher than that of the latter....
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