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Vulnerability of ordinary moment resistant concrete frames

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Earthquake eng.neering and eng.neering Vibration 2011年第4期10卷 519-533页

作者： Mohammad Barkhordary Saeed Tariverdilo Department of Civil eng. Faculty of Eng.Urmia University

The effects of structural modeling （bar slip in lap splice）, ground motion selection process （epsilon effect） and size of a structure （number of bays and stories） on the fragility of reinforced concrete ordinary moment resisting frames are investigated. An analytical model is developed to account for bar slip in lap splice, which exhibits good correlation with existing experimental data. Then, incremental dynamic analysis is used to derive the fragility curves for four model structures. The model structures simulate frames with a different number of bays and stories. Finally, the fragility curves are corrected for the epsilon effect. The results show that slip in the lap splice can significantly increase the failure probability, especially for the collapse prevention limit state. At the same time, it is found that spectral shape has a significant impact on the fragility curves. It is also found that accounting for or ignoring bar slip or epsilon effects increases the probability of failure for larger structures. This indicates an unconservative bias in the safety of larger structures.

关键词： lap-splice slip incremental dynamic analysis fragility curve epsilon effect

Output only modal identification and structural damage detection using time frequency & wavelet techniques

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Earthquake eng.neering and eng.neering Vibration 2009年第4期8卷 583-605页

作者： S.Nagarajaiah B.Basu Dept.of Civil & Environmental eng.and Dept.of Mechanical eng.& Material Sc. Rice University Dept.of Civil Structural& Environmental Eng.Trinity College Dublin

The primary objective of this paper is to develop output only modal identification and structural damage detection. Identification of multi-degree of freedom （MDOF） linear time invariant （LTI） and linear time variant （LTV--due to damage） systems based on Time-frequency （TF） techniques--such as short-time Fourier transform （STFT）, empirical mode decomposition （EMD）, and wavelets--is proposed. STFT, EMD, and wavelet methods developed to date are reviewed in detail. In addition a Hilbert transform （HT） approach to determine frequency and damping is also presented. In this paper, STFT, EMD, HT and wavelet techniques are developed for decomposition of free vibration response of MDOF systems into their modal components. Once the modal components are obtained, each one is processed using Hilbert transform to obtain the modal frequency and damping ratios. In addition, the ratio of modal components at different degrees of freedom facilitate determination of mode shape. In cases with output only modal identification using ambient/random response, the random decrement technique is used to obtain free vibration response. The advantage of TF techniques is that they arc signal based; hence, can be used for output only modal identification. A three degree of freedom 1：10 scale model test structure is used to validate the proposed output only modal identification techniques based on STFT, EMD, HT, wavelets. Both measured free vibration and forced vibration （white noise） response are considered. The secondary objective of this paper is to show the relative ease with which the TF techniques can be used for modal identification and their potential for real world applications where output only identification is essential. Recorded ambient vibration data processed using techniques such as the random decrement technique can be used to obtain the free vibration response, so that further processing using TF based modal identification can be performed.

关键词： Time-frequency methods short time Fourier transform Hilbert transform wavelets modal identification:output only structural health monitoring damage detection

Hydrodynamic Performance of Vertical Porous Structures Under Regular Waves

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China Ocean eng.neering 2013年第4期27卷 451-468页

作者： A.S.Koraim O.S.Rageh Water and Water Structure eng. Dept. Faculty of Eng. Zagazig University Irrigation and Hydraulics Dept. Faculty of Eng. El-Mansoura University

The hydrodynamic efficiency of the vertical porous structures is investigated under regular waves by use of physical models. The hydrodynamic efficiency of the breakwater is presented in terms of the wave transmission （kt）, reflection （kr） and energy dissipation （ka） coefficients. Different wave and structural parameters affecting the breakwater efficiency are tested. It is found that, the transmission coefficient （kt） decreases with the increase of the relative water depth （h/L）, the wave steepness （Hi^L）, the relative breakwater widths （B/L, B/h）, the relative breakwater height （D/h）, and the breakwater porosity （n）. The reflection coefficient （kr） takes the opposite trend of kt when D/h=l.25 and it decreases with the increasing h/L, HJL and B/L when D/h〈1.0. The dissipation coefficient （kd） increases with the increasing h/L, HilL and B/L when D/h〈_l.O and it decreases when D/h=l.25. In which, it is possible to achieve values ofkt smaller than 0.3, k~ larger than 0.5, and kd larger than 0.6 when D/h=1.25, B/h=0.6, h/L〉0.22, B/L〉O. 13, and H/L 〉0.04. Empirical equations are developed for the estimation of the transmission and reflection coefficients. The results of these equations are compared with other experimental and theoretical results and a reasonable agreement is obtained.

关键词： water waves porous breakwaters wave attenuation wave transmission wave reflection wave dissipation

A neural network based methodology to predict site-specific spectral acceleration values

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Earthquake eng.neering and eng.neering Vibration 2010年第4期9卷 459-472页

作者： Kamatchi P Rajasankar J Ramana GV Nagpal AK CSIR-structural eng.neering Research Centre CSIR Campus Dept. Civil. eng. IIT Delhi New Delhi 110 016 India

A general neural network based methodology that has the potential to replace the computationally-intensive site-specific seismic analysis of structures is proposed in this paper. The basic framework of the methodology consists of a feed forward back propagation neural network algorithm with one hidden layer to represent the seismic potential of a region and soil amplification effects. The methodology is implemented and verified with parameters corresponding to Delhi city in India. For this purpose, strong ground motions are generated at bedrock level for a chosen site in Delhi due to earthquakes considered to originate from the central seismic gap of the Himalayan belt using necessary geological as well as geotechnical data. Surface level ground motions and corresponding site-specific response spectra are obtained by using a one-dimensional equivalent linear wave propagation model. Spectral acceleration values are considered as a target parameter to verify the performance of the methodology. Numerical studies carried out to validate the proposed methodology show that the errors in predicted spectral acceleration values are within acceptable limits for design purposes. The methodology is general in the sense that it can be applied to other seismically vulnerable regions and also can be updated by including more parameters depending on the state-of-the-art in the subject.

关键词： neural network response spectra local soil conditions amplification factor

Ultrasonic Approach of Rayleigh Pitch-Catch Contact Ultrasound Waves on CFRP Laminated Composites

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Journal of Materials Science & Technology 2008年第3期24卷 407-409页

作者： In-Young Yang Kwang-Hee Im Uk Heo David K Hsu Je-Woong Park Hak-Joon Kim Sung-Jin Song School of Mechanical eng. Chosun Univ Department of Automotive eng. Woosuk Univers-ity Center for Nondestructive Evaluation Iowa State University Dept.of Naval Arch.and Ocean eng. Chosun Univ School of Mechanical eng. Sungkyunkwan University

CFRP （carbon fiber reinforced plastics） composite materials have wide applicability because of their inherent design flexibility and improved material properties. However, impacted composite structures have 50%-75% less streng.h than undamaged structures. In this work, a CFRP composite material was nondestructively characterized in order to ensure product quality and structural integrity of CFRP and one-sided pitch-catch technique was developed to measure impacted-damaged area by using an automated-data acquisition system in an immersion tank. A pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave under defect conditions in the composite.

关键词： Impact damages C-scanner Carbon fiber reinforced plastics (CFRP) Pitchcatch mode

The structural eng.neering Challeng.s Following the Wenchuan Earthquake

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四川大学学报（工程科学版） 2009年第3期41卷 223-230页

作者： GRUNDY Paul Dept.of Civil eng. Monash Univ.

The "5·12" Wenchuan Earthquake presents two challeng.s-reconstruction of the devastated areas and building adequate seismic resistance into the rest of *** stages in recovery include structural condition assessment,identification of seismic weaknesses,appreciation of the variable seismicity of PR China,the development of a seismic performance index to aid the decision to relocate,rebuild or retrofit,development and application of the principles of retrofitting which recycles rubble and waste from Wenchuan "5·12",with an emphasis on integrating masonry construction into seismic *** recovery and resilience achieved through structural eng.neering must be integrated into a broader community involvement in disaster risk reduction.

关键词：建筑工程抗振结构建筑结构建筑物

structural Characteristics and Mechanical Properties of Rock Mass in the Field of Tianwan Nuclear Power Plant, China

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Journal of Shanghai Jiaotong university(Science) 2006年第4期11卷 512-517,524页

作者：周念清唐益群邓永华赵在立 Dept. of Geotechnical eng. Tongji Univ. The General Company of East China Survey Foundation eng. of Metallurgical Industry Ministry Hebei Zhonghe Geotechnical eng. Co. Ltd.

The structural characteristics and mechanical properties of the rock mass are important parts of the feasibility study on the nuclear power eng.neering field. In this study, by means of in situ investigation and statistics, the structural plane and joint fissure features of the rock mass were analyzed and discussed at different plots and different depth scopes in the Tianwan Nuclear Power eng.neering field, the rock mass integrality and its weathered degree were evaluated respectively, and especially, the unfavorable geological phenomena of strongly-weathered cystid existing in the field were studied. According to the results of indoor rock mechanical tests, in combination with drilling, the shallow seismic prospecting, sonic logging and point load tests, the statistical results of physical and mechanical indices of rocks at key plots of the field were analyzed, and the design parameters of the field were calculated. It provided scientific basis for the foundation design of the nuclear power plant.

关键词： Tianwan Nuclear Power Plant structural plane joint fissure weathered degree rock mass integrality mechanical property

WiSeREmulator: An Emulation Framework for Wireless structural Health Monitoring

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Tsinghua Science and Technology 2015年第4期20卷 317-326页

作者： Rajat Khanda Rong Zheng.Gangbing Song Department of Electrical eng. University of Houston Department of Computing and Software Mc Master University

Many competing approaches exist in evaluating sensor network solutions differing by levels of ease of use, cost, control, and realism. Existing work concentrates on simulating network protocols or emulating processing units at the machine cycle level. However, little has been done to emulate the sensors and the physical environments that they monitor. The main contribution of this work is the design of WiserEmulator, an emulation framework for structural health monitoring, which gracefully balances the trade-offs between realism, controllability, and cost. WiserEmulator consists of two main components -- a testbed of wireless sensor nodes and a software emulation environment. To emulate the excitation and response of piezo-electric transducers, as well as the wave propagation inside concrete structures, the COMSOL Multi-Physics software was utilized. Digitized sensing output from COMSOL was played back via a multi-channel Digital-to-Analog Converter （DAC） connected to the wireless sensor testbed. In addition to the emulation of concrete structures, WiSeREmulator also allows users to choose pre- stored data collected from field experiments and synthesized data. A user-friendly Graphical User Interface （GUI） was developed that facilitates intuitive configurations of experimental settings, control of the on-set and progression of the experiments, and real-time visualization of experimental results. We have implemented WiSeREmulator in MATLAB. This work advances the state of the art in providing low cost solutions to evaluating Cyber Physical Systems such as wireless structural health monitoring networks.

关键词： structure health monitoring cyber physical systems emulater

Wave Uplift Forces on the Bottom of a Circular Cylinder

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China Ocean eng.neering 1996年第2期11卷 169-180页

作者： Li Yanbao and Song Reng.Associate Professor, Dept. of Hydralulic eng., Tianjin University, Tainjin 300072 . Professor, Dept. of Hydralulic eng., Tianjin University, Tainjin 300072 Dept. of Hydralulic eng. Tianjin University Tainjin 300072

The analysis of the data of model tests of two large deep wharves and monographic experimental studies show that two aspects are to be improved so as to predict the wave uplift forces on the bottom of a circular cylinder. The first aspect is the uplift pressure distribution on the bottom, and the second is the correct determination of the phase for maximum horizontal wave forces. The second problem has been solved. Synthesizing the results of theoretical analysis and experiments, we suggest a diagram for the determination of the phase when the maximum horizontal wave force appears. On the basis-ef the diagram the simultaneous wave uplift forces can be obtained for the structural stability analysis.

关键词： diffraction theory stability of circular cylinders wave uplift forces