Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 5 Articles
This paper presents analyses of the seismic responses of two reinforced concrete buildings monitored for a period of more than\r\ntwo years. One of the structures was a three-storey reinforced concrete (RC) frame building with a shear core, while the other was a\r\nthree-storey RC frame building without a core. Both buildings are part of the same large complex but are seismically separated from\r\nthe rest of it. Statistical analysis of the relationships between maximum free field accelerations and responses at different points\r\non the buildings was conducted and demonstrated strong correlation between those. System identification studies using recorded\r\naccelerations were undertaken and revealed that natural frequencies and damping ratios of the building structures vary during\r\ndifferent earthquake excitations. This variation was statistically examined and relationships between identified natural frequencies\r\nand damping ratios, and the peak response acceleration at the roof level were developed. A general trend of decreasing modal\r\nfrequencies and increasing damping ratios was observed with increased level of shaking and response. Moreover, the influence\r\nof soil structure interaction (SSI) on the modal characteristics was evaluated. SSI effects decreased the modal frequencies and\r\nincreased some of the damping ratios....
New experimental data on plan dimensions for riprap mattresses used in pile group protection against edge failure are analyzed.\r\nThe influence of flow conditions and the distance between piles in plan dimensions of riprap mattresses are addressed. An\r\nalternative methodology for the experimental study of edge failure in pile groups is proposed and verified, significantly reducing\r\nthe duration of tests (from several days to a few hours) and yielding similar results. For the pile group configuration tested, a\r\ndesign expression for minimum riprap width is obtained. The influence of the distance between the piles on the width of riprap\r\ndimensions is shown to be small, and the proposed expression compares well with some of the expressions for single piers found\r\nin the literature....
The thermal conductivity measurement by a simplified transient hot-wire technique is applied to geomaterials in order to show\r\nthe relationships which can exist between effective thermal conductivity, texture, and moisture of the materials. After a validation\r\nof the used ââ?¬Å?one hot-wireââ?¬Â technique in water, toluene, and glass-bead assemblages, the investigations were performed (1) in glassbead\r\nassemblages of different diameters in dried, water, and acetone-saturated states in order to observe the role of grain sizes and\r\nsaturation on the effective thermal conductivity, (2) in a compacted earth brick at different moisture states, and (3) in a limehemp\r\nconcrete during 110 days following its manufacture. The lime-hemp concrete allows the measurements during the setting,\r\ndesiccation and carbonation steps. The recorded ?T/ ln(t) diagrams allow the calculation of one effective thermal conductivity\r\nin the continuous and homogeneous fluids and two effective thermal conductivities in the heterogeneous solids. The first one\r\nmeasured in the short time acquisitions (<1 s) mainly depends on the contact between the wire and grains and thus microtexture\r\nand hydrated state of the material. The second one, measured for longer time acquisitions, characterizes the mean effective thermal\r\nconductivity of the material....
Guided wave technique is an efficient method for monitoring structural integrity by detecting and forecasting possible damages in\r\ndistributed pipe networks. Efficient detection depends on appropriate selection of guided wave modes as well as signal processing\r\ntechniques. Fourier analysis and wavelet analysis are two popular signal processing techniques that provide a flexible set of tools\r\nfor solving various fundamental problems in science and engineering. In this paper, effective ways of using Fourier and Wavelet\r\nanalyses on guided wave signals for detecting defects in steel pipes are discussed for different boundary conditions. This research\r\ninvestigates the effectiveness of Fourier transforms and Wavelet analysis in detecting defects in steel pipes. Cylindrical Guided\r\nwaves are generated by piezo-electric transducers and propagated through the pipe wall boundaries in a pitch-catch system. Fourier\r\ntransforms of received signals give information regarding the propagating guided wave modes which helps in detecting defects by\r\nselecting appropriate modes that are affected by the presence of defects. Continuous wavelet coefficients are found to be sensitive\r\nto defects. Several types of mother wavelet functions such as Daubechies, Symlet, and Meyer have been used for the continuous\r\nwavelet transform to investigate the most suitable wavelet function for defect detection. This research also investigates the effect of\r\ndifferent boundary conditions on wavelet transforms for different mother wavelet functions....
This paper presents the results of a series of triaxial tests with dry sand at confining pressures varying from 1.5 kPa to 100 kPa at\r\nrelative densities of 0.20, 0.59, and 0.84. The results, which are in reasonable accordance with an equation given by Bolton, show\r\nthat the friction angle is strongly dependent on the stress level and on the basis of the test results, a nonlinearMohr failure criterion\r\nhas been proposed. This yield criterion has been implemented in a finite element program and an analysis of the bearing capacity\r\nof a circular shaped model foundation, diameter 100 mm, has been conducted. Comparisons have been made with results from\r\n1g model scale tests with a foundation of similar size and a good agreement between numerical results and test results has been\r\nfound....
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