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Life-cycle failure probability analysis of deteriorated RC bridges under multiple hazards of earthquakes and strong winds

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Earthquake engineering and engineering Vibration 2022年第3期21卷 811-823页

作者： Zheng Xiaowei Li Hongnan Jiangsu Key laboratory of Environmental Impact and Structural Safety in engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou 221116China State Lab.of Coastal and Offshore Engineering Faculty of Infrastructure EngineeringDalian University of TechnologyDalian 116024China

engineering structures may be exposed to one or more extreme hazards during their life-cycles.Current structural design specifications usually treat multiple hazards separately in designing structures and there is a limited probabilistic basis on extreme load combinations.Additionally,the performance of engineering structures will be deteriorated by the aggressive environments during their service periods,such as chloride attack,concrete carbonation,and wind-induced fatigue.This study presents a probabilistic methodology to assess the time-dependent failure probability of RC bridges with chloride-induced corrosion under the multiple hazards of earthquakes and strong winds.The loss of cross-section area of reinforcements and the reduction in strength of reinforcing steel and concrete cover induced by the chloride attack are considered.Moreover,the Poisson model is employed to obtain the occurrence probabilities of the individual and concurrent earthquake and strong wind events.The convolution integral is used to determine the joint probability distribution of combined load effects under simultaneous earthquakes and strong winds.Numerical results indicate that the structural failure probability under multiple hazards increases significantly during the bridge′s life-cycle due to the chloride corrosion effect.The contribution of each hazard event on the total structural failure probability varies with time.Thus,neglecting the combined influences of multiple hazards and chloride-induced corrosion may bring erroneous predictions in failure probability estimates of RC bridges.

关键词： life-cycle multihazard chloride occurrence model failure probability

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Numerical simulation on influence of jet angle on jet's characteristics in flowing ambient fluid

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Journal of Harbin Institute of Technology(New Series) 2008年第4期15卷 528-534页

作者：周丰孙昭晨梁书秀 state Key lab.of coastal and offshore engineering Dalian University of Technology

Based on the stress-algebraic model,the turbulent buoyant jet with variable density was studied by the relation between density and concentration.A simple expression for buoyancy coefficient was proposed.The governing equations of turbulent buoyant jet with variable density were closed by introducing the expression of β and the relation between density and concentration.Numerical results for the jet axis with density difference agree well with experimental ones.By finite volume method,the 2-D vertical jet's flow field with different jet angles was studied.The analysis of the relation among the vortex center,the position of separation point and jet angles shows that the circumfluence field is the largest when the jet angle is 90°.The area turbulent kinetic energy kA is proposed and the relationship between mixing intensity and jet angles is analyzed based on it.Results show that the jet angle of is the optimum condition for jet water mixing with environment water;and the reduced rate of difference between the centerline density of jet and the density of ambient water is the largest at the jet angle of 90°.

关键词：环境污染压力代数模型动力学技术性能

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Experimental study on retarding mortar and its application in prestressed concrete

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Journal of Harbin Institute of Technology(New Series) 2008年第1期15卷 135-140页

作者：张建玲宋玉普洪雷 state Key lab.of coastal and offshore engineering Dalian University of Technology

Based on a large number of orthogonal tests and theoretical analyses, the retarding mortar which meets the requirements of retard-bonded prestressed concrete was prepared. Initial setting time of the retarding mortar may vary from several hours to 15 d at 5 ℃-35 ℃ due to quantities and average curing temperature. And its 28 d compressive strength is above 35 MPa. Thus the influence of quantities on setting time and 28 d compressive strength, and the relationship between setting time and average curing temperature were investigated. The optimum quantities were obtained by studying the interaction of admixtures, and the retarding mechanism was discussed. Based on 52 retard-bonded prestressed strands by manual work from 24 retard-bonded prestressed concrete T-beams, static friction drag, change factor κ and friction factor μ were obtained from the test when retard-bonded prestressed strands were tensioned. Application of the retarding mortar will be vast in practical concrete projects.

关键词：建筑结构凝结时间灰浆建筑材料

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New artificial boundary condition for saturated soil foundations

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Earthquake engineering and engineering Vibration 2012年第1期11卷 139-147页

作者： Xu Qiang Chen Jianyun Li Jing Fan Shuli state Key lab.of coastal and offshore Eng. Dalian University of Technology Dalian 116023 China School of Civil and Hydraulic Eng. Dalian University of Technology Dalian 116023 China

Anew artificial boundary model based on multi-directional transmitting and viscous-spring artificial boundary theories is proposed to absorb stress waves in a saturated soil foundation in dynamic analysis. Since shear waves （S-waves） are the same in a saturated soil foundation and a single-phase medium foundation, a tangential visco-elastic boundary condition for a single-phase medium foundation can also be used for saturated soil foundations. Thus, the purpose of the artificial boundary proposed in this paper is primarily to absorb two types of P-waves in a saturated soil foundation. The main idea is that the stress of the P-waves in the saturated soil foundation is decomposed into two types. The first type of stress, δra＇ is absorbed by the first artificial boundary. The second type of stress, δrb, is balanced by the stress generated by the second artificial boundary. Ultimately, both types of P-waves （fast-P-waves and slow-P-waves） are absorbed by the artificial boundary model proposed in this paper. In particular, note that the fast-P-waves and slow-P-waves are absorbed at the position of the first boundary. Thus, the artificial boundary model proposed herein can simultaneously absorb P-fast waves, P-slow waves and shear waves. Finally, a numerical example is given to examine the proposed artificial boundary model, and the results show that it is very accurate.

关键词： multi-directional transmitting artificial boundary viscous-spring artificial boundary saturated soil foundation Biot＇s equations

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Hydroelastic Investigation on A Pile Breakwater Integrated with A Flexible Tail for Long-Wave Attenuation

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China Ocean engineering 2022年第5期36卷 667-681页

作者： ZHANG Chong-wei ZHUANG Qian-ze LI Jin-xuan HUANG Luo-feng NING De-zhi state Key laboratory of coastal and offshore engineering Dalian University of TechnologyDalian 116024China School of Water Energy and EnvironmentCranfield UniversityCranfield MK430ALUnited Kingdom

A novel concept of wave attenuator is proposed for the defense of long waves,through integrating a flexible tail to the lee-side surface of a pile breakwater.The flexible tail works as a floating blanket made up of hinged blocks,whose scale and stiffness can be easily adjusted.A two-phase-flow numerical model is established based on the open-source computational fluid dynamics(CFD)code OpenFOAM to investigate its wave attenuation performance.Incompressible Navier−Stokes equations are solved in the fluid domain,where an additional computational solid mechanics(CSM)solver is embedded to describe the elastic deformation of the floating tail.The coupling of fluid dynamics and structural mechanics is solved in a full manner to allow assess of wave variation along the deforming body.The accuracy of the numerical model is validated through comparison with experimental data.Effects of the flexible tail on performance of the pile breakwater are investigated systematically.Dynamic behaviours of the tail are examined,and characteristics of its natural frequency are identified.For safety reasons,the wave loads impacting on the main body of the pile breakwater and the stress distribution over the tail are specially examined.It is found that both the length and stiffness of the tail can affect the wave-attenuation performance of the breakwater.A proper choice of the length and stiffness of the tail can greatly improve the long-wave defending capability of the pile breakwater.The maximum stress over the flexible tail can be restrained through optimising the deformation and stiffness of the tail.

关键词： wave attenuator pile breakwater OpenFOAM fluid-structure interaction wave transmission coastal protection

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Studies on structural vibration control with MR dampers using μGA

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Earthquake engineering and engineering Vibration 2005年第2期4卷 301-304页

作者：李宏男常治国宋钢兵 State Lab.of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Professor State Lab.of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Ph.D.student

A new approach to reducing the seismic response of spatial structures with magneto-theological （MR） dampers is presented in this paper. The Genetic Algorithm with small populations （μGA） is used to optimize the control for the MR dampers to reduce structural vibration, which is difficult to achieve using classical optimal control. The advantages of μGA are the use of global properties and that fewer conditions are required to obtain the optimal function. Numerical results demonstrate the effectiveness of the proposed method in reducing the seismic response of structures.

关键词： eccentric structure semi-active control magneto-rheological （MR） damper genetic algorithm linearization

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A Numerical Study on the Water Impact of the Rigid/Elastic Box-Like Structure

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China Ocean engineering 2023年第2期37卷 333-342页

作者： YANG Jian SUN Zhao-chen LIANG Shu-xiu state Key laboratory of coastal and offshore engineering Dalian University of TechnologyDalian 116024China

Recent damages to the box-like structures caused by wave slamming have made it necessary to study the impact problems of this kind of structure. This paper showed findings from numerical simulations of the rigid/elastic structures, aiming to gain insights into the characteristics of the problem. The results of the rigid cases showed the significance of air compressibility during the impact process, while the slamming phenomena became quite different without the effect. In the elastic cases, the trapped air made the structure vibrate at frequencies much smaller than its eigenfrequencies. Besides, the structural deformation made it easy for the trapped air to escape outwards, which weakened the air cushioning effect, especially at high impact velocities. The above analysis gives the results when the structural symmetry axis was vertical to the water(vertical impacts). In addition, the results were given when the axis was oblique to the water(oblique impacts). Compared with the vertical cases, the impact phenomena and structural response showed asymmetry. This work used the computational fluid dynamics(CFD) method to describe fluid motion and the finite element method(FEM) for the deformable structure. A two-way coupling approach was used to deal with the fluid-structure interaction in the elastic cases.

关键词： water impact fluid-structure interaction air compressibility box-like structures two-way coupling

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Experimental Study of Mooring Type Effect on the Hydrodynamic Characteristics of VLFS

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China Ocean engineering 2022年第1期36卷 155-166页

作者： FENG Ming-wei SUN Zhao-chen LIANG Shu-xiu LI Zhi LV Xuan JIA Song-lin HUXin-yue state Key laboratory of coastal and offshore engineering Dalian University of TechnologyDalian 116024China

Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation coefficient.Eight mooring cables are symmetrically arranged on both sides of the model.The floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and gravity.The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response.Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model.The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs.The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types.These results may provide a reference to facilitate the mooring design of VLFS.

关键词： VLFS hydroelastic response mooring system 3D experimental test mooring force wave reflection coefficient wave transmission coefficient wave dissipation coefficient

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Numerical Studies on the Generation and Propagation of Tsunami Waves Based on the High-Order Spectral Method

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China Ocean engineering 2022年第2期36卷 268-278页

作者： HAO Jian LI Jin-xuan LIU Shu-xue WANG Lei state Key laboratory of coastal and offshore engineering Dalian University of TechnologyDalian 116024China

An effective numerical model for wave propagation over three-dimensional(3D)bathymetry was developed based on the High-Order Spectral(HOS)method and combined with a moving bottom boundary.Based on this model,tsunami waves caused by various mechanisms were simulated and analyzed.Two-dimensional bed upthrust and the effect of the uplift velocity of the bathymetry on the wave profiles of tsunami waves were studied.Next,tsunami waves caused by 3D submarine slides were generated and the effects of the slide velocity,slide dimension and water depth on the tsunami waves were analyzed.Based on wavelet analysis,the properties of the tsunami wave propagation were investigated.The results show that the bottom movement can significantly affect the generation and propagation of tsunami waves and the studies could help understand the mechanisms of tsunamis caused by a moving bottom boundary.

关键词： tsunami waves High-Order Spectral(HOS)method moving bottom boundary wavelet analysis

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Probabilistic method for the size design of energy piles considering the uncertainty in soil parameters

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Underground Space 2023年第3期10卷 37-54页

作者： Huaibo Song Huafu Pei Peilong Zhang state Key laboratory of coastal and offshore engineering Dalian University of TechnologyDalian 116024China

Energy piles have attracted increasing attention as profitable solutions for the utilization of shallow geothermal energy.Although various complex geotechnical design models of energy piles have been proposed,a simplified sizing method that considers the uncertainty propagation in the soil is required.In this study,a Monte Carlo Simulation-based method was proposed for the size design of energy piles considering the uncertainty of parameters in the soil,such as thermal conductivity and friction angle.The small-sample analysis method of Markov chain Monte Carlo simulation combined with the Bayesian theoretical framework was developed to generate equiv-alent samples.Subsequently,the thermal response function and thermomechanical load transfer methods were employed to address the failure probability of the energy pile in the serviceability limit state and ultimate limit state.In addition,a case study was presented to illustrate the implementation of the proposed probabilistic sizing method.The analysis results of the case study confirm the necessity of modeling the soil uncertainty in the energy pile size design.

关键词： Energy pile Probability sizing method Reliability-based design Analytical model

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