The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this p...The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.展开更多
Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious m...Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious materials was first fabricated using the three-dimensional(3D)printing technique and then loaded to simulate its failure mode in the laboratory.Lead zirconate titanate piezoelectric(PZT)transducers were embedded in the surrounding rock around the tunnel in the process of 3D printing.A 3D monitoring network was formed to locate damage areas and evaluate damage extent during loading.Results show that as the load increased,main cracks firstly appeared above the tunnel roof and below the floor,and then they coalesced into the tunnel boundary.Finally,the tunnel model was broken into several parts.The resonant frequency and the peak of the conductance signature firstly shifted rightwards with loading due to the sealing of microcracks,and then shifted backwards after new cracks appeared.An overall increase in the root-mean-square deviation(RMSD)calculated from conductance signatures of all the PZT transducers was observed as the load(damage)increased.Damage-dependent equivalent stiffness parameters(ESPs)were calculated from the real and imaginary signatures of each PZT at different damage states.Satisfactory agreement between equivalent and experimental ESP values was achieved.Also,the relationship between the change of the ESP and the residual strength was obtained.The method paves the way for damage identification and residual strength estimation of other 3D printed structures in civil engineering.展开更多
山区交通工程建设会产生大量由于开挖形成的路堑边坡,此类卸荷作用强烈的人工边坡的防护工程设计不能等同于一般自然斜坡。为了弄清路堑边坡设计安全下的失稳力学机制并提出考虑补偿效应的路堑边坡加固设计方法,在调研和追踪多个失稳路...山区交通工程建设会产生大量由于开挖形成的路堑边坡,此类卸荷作用强烈的人工边坡的防护工程设计不能等同于一般自然斜坡。为了弄清路堑边坡设计安全下的失稳力学机制并提出考虑补偿效应的路堑边坡加固设计方法,在调研和追踪多个失稳路堑边坡的基础上,复核路堑边坡设计措施的安全性,检查当前计算方法存在的问题,分析设计安全下路堑边坡加固失效的原因。结果表明:路堑边坡的失稳在于开挖卸荷造成的侧向约束解除使得边坡的变形发展超出了岩土体的变形允许值,且应力损失值没有得到及时充足的补偿。设计措施提供的水平加固力4277 k N/m,小于理正计算得到的剩余水平下滑力5278 k N/m,小于考虑力的补偿效应的水平加固力5878 k N/m,加固力不足和空间布局不合理是造成路堑边坡失稳的根本原因。利用考虑力的补偿效应的极限平衡法估算路堑边坡水平加固力,所得结果大于剩余推力法,方法简单易操作,既达到安全标准也小于静止土压力且不浪费。展开更多
文摘The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.
基金The study is financially supported by the National Major Research Instrument Development Project of the National Natural Science Foundation of China(Grant No.51627812)the National Natural Science Foundation of China(Grant No.52078181)the Natural Science Foundation of Hebei Province,China(Grant No.E2019202484)。
文摘Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious materials was first fabricated using the three-dimensional(3D)printing technique and then loaded to simulate its failure mode in the laboratory.Lead zirconate titanate piezoelectric(PZT)transducers were embedded in the surrounding rock around the tunnel in the process of 3D printing.A 3D monitoring network was formed to locate damage areas and evaluate damage extent during loading.Results show that as the load increased,main cracks firstly appeared above the tunnel roof and below the floor,and then they coalesced into the tunnel boundary.Finally,the tunnel model was broken into several parts.The resonant frequency and the peak of the conductance signature firstly shifted rightwards with loading due to the sealing of microcracks,and then shifted backwards after new cracks appeared.An overall increase in the root-mean-square deviation(RMSD)calculated from conductance signatures of all the PZT transducers was observed as the load(damage)increased.Damage-dependent equivalent stiffness parameters(ESPs)were calculated from the real and imaginary signatures of each PZT at different damage states.Satisfactory agreement between equivalent and experimental ESP values was achieved.Also,the relationship between the change of the ESP and the residual strength was obtained.The method paves the way for damage identification and residual strength estimation of other 3D printed structures in civil engineering.
文摘山区交通工程建设会产生大量由于开挖形成的路堑边坡,此类卸荷作用强烈的人工边坡的防护工程设计不能等同于一般自然斜坡。为了弄清路堑边坡设计安全下的失稳力学机制并提出考虑补偿效应的路堑边坡加固设计方法,在调研和追踪多个失稳路堑边坡的基础上,复核路堑边坡设计措施的安全性,检查当前计算方法存在的问题,分析设计安全下路堑边坡加固失效的原因。结果表明:路堑边坡的失稳在于开挖卸荷造成的侧向约束解除使得边坡的变形发展超出了岩土体的变形允许值,且应力损失值没有得到及时充足的补偿。设计措施提供的水平加固力4277 k N/m,小于理正计算得到的剩余水平下滑力5278 k N/m,小于考虑力的补偿效应的水平加固力5878 k N/m,加固力不足和空间布局不合理是造成路堑边坡失稳的根本原因。利用考虑力的补偿效应的极限平衡法估算路堑边坡水平加固力,所得结果大于剩余推力法,方法简单易操作,既达到安全标准也小于静止土压力且不浪费。
