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A modern survey method for determining live loads based on multi-source and open-access data on the Internet

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Frontiers of Structural and civil eng.neering 2024年第8期18卷 1135-1147页

作者： Chi XU Jun CHEN Jie LI School of civil eng.neering Tongji UniversityShanghai 200092China The state key laboratory on disaster reduction in civil eng.neering Tongji UniversityShanghai 200092China

Sufficient survey data are required to describe the stochastic behaviors of live ***,due to manual and on-site operation required by traditional survey methods,traditional surveys face challeng.s like occupant resistance,high costs,and long implementation *** study proposes a new survey method to access live load data online and *** samples are acquired from multi-source,open-access and dynamically updated data on the *** change intervals,geometrical dimensions and object quantities are obtained from transaction information,building attributes and virtual reality models on real estate websites,*** object weights are collected from commodity information on e-commerce *** integration of the aforementioned data allows for the extraction of necessary statistics to describe a live load *** proposed method is applied to a live load survey in China,covering 20040 m^(2),with around 90000 samples acquired for object weights and load *** survey results reveal that about 70%−80%of the amplitude statistics are attributable to 1/6 of the total object types.

关键词： live load online survey method data acquisition data integration

Multi-harmonic forced vibration and resonance of simple beams to moving vehicles

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Frontiers of Structural and civil eng.neering 2023年第7期17卷 981-993页

作者： Zhi SUN Limin SUN Ye XIA state key laboratory for disaster reduction in civil eng.neering Shanghai 200092China Department of Bridge eng.neering Tongji UniversityShanghai 200092China

This study modeled the moving-vehicle-induced forcing excitation on a single-span prismatic bridge as a multiple frequency-multiplication harmonic load on the modal coordinates of a linear elastic simple Euler–Bernoulli beam,and investigated the forced modal oscillation and resonance behavior of this type of dynamic *** forced modal responses consist of multiple frequency-multiplication steady-state harmonics and one damped mono-frequency complementary *** analysis revealed that a moving load induces high-harmonic forced resonance amplification when the moving speed is *** verify the occurrence of high-harmonic forced resonance,numerical tests were conducted on single-span simple beams based on structural modeling using the finite element method(FEM)and a moving sprung-mass oscillator vehicle *** forced resonance amplification characteristics of the fundamental mode for beam response estimation are presented with consideration to different end restraint *** results reveal that the high-harmonic forced resonance may be significant for the investigated beams subjected to vehicle loads moving at specific low *** the investigated single-span simple beams,the moving vehicle carriage heaving oscillation modulates the beam modal frequency,but does not induce notable variation of the modal oscillation harmonic structure for the cases that vehicle of small mass moves in low speed.

关键词： forced vibration linear Euler beam moving load harmonic structure frequency modulation end restraints

Simulation of steel beam under ceiling jet based on a wind–fire–structure coupling model

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Frontiers of Structural and civil eng.neering 2023年第1期17卷 78-98页

作者： Jinggang ZHOU Xuanyi ZHOU Beihua CONG Wei WANG Ming GU state key laboratory of disaster reduction in civil eng.neering Tongji UniversityShanghai 200092China Shanghai Institute of disaster Prevention and Relief Tongji UniversityShanghai 200092China

For localized fires, it is necessary to consider the thermal and mechanical responses of building elements subject to uneven heating under the influence of wind. In this paper, the thermomechanical phenomena experienced by a ceiling jet and I-beam in a structural fire were simulated. Instead of applying the concept of adiabatic surface temperature (AST) to achieve fluid–structure coupling, this paper proposes a new computational fluid dynamics–finite element method numerical simulation that combines wind, fire, thermal, and structural analyses. First, to analyze the velocity and temperature distributions, the results of the numerical model and experiment were compared in windless conditions, showing good agreement. Vortices were found in the local area formed by the upper and lower flanges of the I-beam and the web, generating a local high-temperature zone and enhancing the heat transfer of convection. In an incoming-flow scenario, the flame was blown askew significantly;the wall temperature was bimodally distributed in the axial direction. The first temperature peak was mainly caused by radiative heat transfer, while the second resulted from convective heat transfer. In terms of mechanical response, the yield streng.h degradation in the highest-temperature region in windless conditions was found to be significant, thus explaining the stress distribution of steel beams in the fire field. The mechanical response of the overall elements considering the incoming flows was essentially elastic.

关键词： CFD–FEM coupling steel beam wind ceiling jet numerical heat transfer

Physical random function model of ground motions for eng.neering purposes

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Science China(Technological Sciences) 2011年第1期54卷 175-182页

作者： WANG Ding LI Jie School of civil eng.neering Tongji University Shanghai 200092 China state key laboratory of disaster reduction in civil eng.neering Shanghai 200092 China

A physical random function model of ground motions for eng.neering purposes is presented with verification of sample level. Firstly,we derive the Fourier spectral transfer form of the solution to the definition problem,which describes the one-dimensional seismic wave field. Then based on the special models of the source,path and local site,the physical random function model of ground motions is obtained whose physical parameters are random variables. The superposition method of narrow-band harmonic wave groups is improved to synthesize ground motion samples. Finally,an application of this model to simulate ground motion records in 1995 Kobe earthquake is described. The resulting accelerograms have the frequencydomain and non-stationary characteristics that are in full agreement with the realistic ground motion records.

关键词： ground motion physical model random function narrow-band harmonic waves group non-stationarity

Calculation method of ship collision force on bridge using artificial neural network

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Journal of Zhejiang University-Science A(Applied Physics & eng.neering) 2008年第5期9卷 614-623页

作者： Wei FAN Wan-cheng.YUAN Qi-wu FAN state key laboratory for disaster reduction in civil eng.neering Tongji University Shanghai 200092 China Department of civil eng.neering Southwest Jiaotong University Chengdu 610031 China

Ship collision on bridge is a dynamic process featured by high nonlinearity and instantaneity. Calculating ship-bridge collision force typically involves either the use of design-specification-stipulated equivalent static load, or the use of finite element method (FEM) which is more time-consuming and requires supercomputing resources. In this paper, we proposed an alternative approach that combines FEM with artificial neural network (ANN). The radial basis function neural network (RBFNN) employed for calculating the impact force in consideration of ship-bridge collision mechanics. With ship velocity and mass as the input vectors and ship collision force as the output vector, the neural networks for different network parameters are trained by the learning samples obtained from finite element simulation results. The error analyses of the learning and testing samples show that the proposed RBFNN is accurate enough to calculate ship-bridge collision force. The input-output relationship obtained by the RBFNN is essentially consistent with the typical empirical formulae. Finally, a special toolbox is developed for calculation efficiency in application using MATLAB software.

关键词： Ship-bridge collision force Finite element method (FEM) Artificial neural network (ANN) Radial basis function neural network (RBFNN)

Dynamic response characteristics of super high-rise buildings subjected to long-period ground motions

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Journal of Central South University 2013年第5期20卷 1341-1353页

作者：陈清军袁伟泽李英成曹丽雅 state key laboratory of disaster reduction in civil eng.neering(Tongji University) Biology and Environment Branch of Jiaxing Vocational and Technical College

Spectrum characteristics of different types of seismic waves and dynamic response characteristics of super high-rise building structures under long-period ground motions were comparatively analyzed. First, the ground response wave （named LS-R wave） of a soft soil site with deep deposit, taking long-period bedrock seismic record as input, was calculated by wave propagation method. After that, a TOMAKOMAI station long-period seismic record from the Tokachi-Oki earthquake and conventional E1-Centro wave were also chosen. Spectrum characteristics of these waves were analyzed and compared. Then, a series of shaking table tests were performed on a 1：50 scale super high-rise structural model under these seismic waves. Furthermore, numerical simulation of the prototype structure under these excitations was conducted, and structure damages under different intensive ground motions were discussed. The results show that： 1） Spectrum characteristics of ground response wave are significantly influenced by soft soil site with deep deposit, and the predominant period has an increasing trend. 2） The maximum acceleration amplification factor of the structure under the TOM wave is two times that under the E1-Centro wave; while the maximum displacement response of the structure under the TOM wave is 4.4 times that under the E1-Centro wave. Long-period ground motions show greater influences on displacement responses than acceleration responses for super high-rise building structures. 3） Most inelastic damage occurs at the upper 1/3 part of the super high-rise building when subjected to long-period ground motions.

关键词： long-period ground motion super high-rise building shaking table model test numerical simulation spectrumcharacteristic analysis

Mode-based equivalent multi-degree-of-freedom system for one-dimensional viscoelastic response analysis of layered soil deposit

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Earthquake eng.neering and eng.neering Vibration 2018年第1期17卷 103-124页

作者： Li Chong Yuan Juyun Yu Haitao Yuan Yong Department of Geotechnical eng.neering Tongji University key laboratory of Geotechnical and Underground eng.neering of Ministry of Education Tongji University state key laboratory for disaster reduction in civil eng.neering Tongji University

Discrete models such as the lumped parameter model and the finite element model are widely used in the solution of soil amplification of earthquakes. However, neither of the models will accurately estimate the natural frequencies of soil deposit, nor simulate a damping of frequency independence. This research develops a new discrete model for onedimensional viscoelastic response analysis of layered soil deposit based on the mode equivalence method. The new discrete model is a one-dimensional equivalent multi-degree-of-freedom（MDOF） system characterized by a series of concentrated masses, springs and dashpots with a special configuration. The dynamic response of the equivalent MDOF system is analytically derived and the physical parameters are formulated in terms of modal properties. The equivalent MDOF system is verified through a comparison of amplification functions with the available theoretical solutions. The appropriate number of degrees of freedom（DOFs） in the equivalent MDOF system is estimated. A comparative study of the equivalent MDOF system with the existing discrete models is performed. It is shown that the proposed equivalent MDOF system can exactly present the natural frequencies and the hysteretic damping of soil deposits and provide more accurate results with fewer DOFs.

关键词： ground response analysis MDOF system mode equivalence modal properties layered soil viscoelastic amplification

Full-scale measurements of dynamic response of suspension bridge subjected to environmental loads using GPS technology

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Science China(Technological Sciences) 2010年第2期53卷 469-479页

作者： YI TingHua1,2, LI HongNan1 & GU Ming2 1state key laboratory of Coastal and Offshore eng.neering, Dalian University of Technology, Dalian 116024, China 2state key laboratory for disaster reduction in civil eng.neering, Tongji University, Shanghai 200092, China state key laboratory of Coastal and Offshore eng.neering Dalian University of Technology Dalian China state key laboratory for disaster reduction in civil eng.neering Tongji University Shanghai China

Nowadays, there are many larger and taller eng.neering structures than in the past. These structures are commonly designed to be more flexible. Thus, they are sensitive to severe wind gust and earthquake tremor. For the dynamic response prediction, finite element (FE) modal updating and structural health monitoring, the dynamic characteristics of a structure are becoming increasingly important. The aim of this paper is to show an emerging tool-the real time kinematic (RTK) global positioning system (GPS), which is used to measure and monitor the low-frequency vibration of Dalian BeiDa Bridge, a medium span suspension bridge. The modal analysis is firstly performed on the developed three-dimensional FE model according to the original blue prints of the bridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests using the accelerometers on the bridge deck are conducted just prior to the use of the GPS system in order to validate the FE model. And then, the calibration test is done to assess the dynamic displacement measurement accuracy of the GPS in three orthogonal directions. The GPS signal properties, such as the amplitude, standard deviations (STD), power spectral density (PSD), and probability density functions (PDF), are studied in details. After that, a structural health monitoring system based on the GPS is devised and installed on the bridge to provide real-time measurement of deck movement. The output-only modal parameter identification is carried out by using the Periodogram method to investigate the responses of the bridge. The result shows that the spectral densities of the displacements measured by the GPS correspond well with the results by the FEM analysis and the accelerometer vibration test. It is concluded that the GPS method is reliable and useful to clarify the ambient vibration response behaviors of the flexible structures. The integration of the GPS and accelerometer methods results in a hybrid arrangement tha

关键词： health monitoring global positioning system real-time kinematic suspension bridge modal analysis

A new fracture criterion for peridynamic and dual-horizon peridynamics

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Frontiers of Structural and civil eng.neering 2018年第4期12卷 629-641页

作者： Jinhai ZHAO Hesheng.TANG Songtao XUE Research Institute of Structural eng.neering and disaster reduction Tongji UniversityShanghai 200092China state key laboratory of disaster Prevention in civil eng.neering Tongii UniversityShanghai 200092China

A new fracture criterion based on the crack opening displacement for peridynamic (PD) and dual-horizon peridynamics (DH-PD) is proposed. When the relative deformation of the PD bond between the particles reaches the critical crack tip opening displacement of the fracture mechanics, we assume that the bond force vanishes. A new damage rule similar to the local damage rule in conventional PD is introduced to simulate fracture. The new formulation is developed for a linear elastic solid though the extension to nonlinear materials is straightforward. The performance of the new fracture criterion is demonstrated by four examples, i.e. a bilateral crack problem, double parallel crack, monoclinic crack and the double inclined crack. The results are compared to experimental data and the results obtained by other computational methods.

关键词： Castigliano’s theorem breaking energy critical extension XFEM COD PD-COD