This paper presents in-situ seismic performance tests of a bridge before its demolition due to accumulated scouring problem. The tests were conducted on three single columns and one caisson-type foundation. The three ...This paper presents in-situ seismic performance tests of a bridge before its demolition due to accumulated scouring problem. The tests were conducted on three single columns and one caisson-type foundation. The three single columns were 1.8 m in diameter,reinforced by 30-D32 longitudinal reinforcements and laterally hooped by D16 reinforcements with spacing of 20 cm. The column height is 9.54 m,10.59 m and 10.37 m for Column P2,P3,and P4,respectively. Column P2 had no exposed foundation and was subjected to pseudo-dynamic tests with peak ground acceleration of 0.32 g first,followed by one cyclic loading test. Column P3 was the benchmark specimen with exposed length of 1.2 m on its foundation. The exposed length for Column P4 was excavated to 4 m,approximately 1/3 of the foundation length,to study the effect of the scouring problem to the column performance. Both Column P3 and Column P4 were subjected to cyclic loading tests. Based on the test results,due to the large dimension of the caisson foundation and the well graded gravel soil type that provided large lateral resistance,the seismic performance among the three columns had only minor differences. Lateral push tests were also conducted on the caisson foundation at Column P5. The caisson was 12 m long and had circular cross-sections whose diameters were 5 m in the upper portion and 4 m in the lower portion. An analytical model to simulate the test results was developed in the OpenSees platform. The analytical model comprised nonlinear flexural elements as well as nonlinear soil springs. The analytical results closely followed the experimental test results. A parametric study to predict the behavior of the bridge column with different ground motions and different levels of scouring on the foundation are also discussed.展开更多
In maritime safety research,risk is assessed usually within the framework of formal safety assessment(FSA),which provides a formal and systematic methodology to improve the safety of lives,assets,and the environment.A...In maritime safety research,risk is assessed usually within the framework of formal safety assessment(FSA),which provides a formal and systematic methodology to improve the safety of lives,assets,and the environment.A bespoke application of FSA to mitigate accidents in marine seismic surveying is put forward in this paper,with the aim of improving the safety of seismic vessel operations,within the context of developing an economically viable strategy.The work herein takes a close look at the hazards in North Sea offshore seismic surveying,in order to identify critical risk factors,leading to marine seismic survey accidents.The risk factors leading to undesirable events are analysed both qualitatively and quantitatively.A risk matrix is introduced to screen the identified undesirable events.Further to the screening,Fault Tree Analysis(FTA)is presented to investigate and analyse the most critical risks of seismic survey operation,taking into account the lack of historical data.The obtained results show that man overboard(MOB)event is a major risk factor in marine seismic survey operation;lack of training on safe work practice,slippery deck as a result of rain,snow or water splash,sea state affecting human judgement,and poor communication are identified as the critical risk contributors to the MOB event.Consequently,the risk control options are focused on the critical risk contributors for decision-making.Lastly,suggestions for the introduction and development of the FSA methodology are highlighted for safer marine and offshore operations in general.展开更多
为评估卧式压力容器在地震作用下能否安全运行,文中推导了其地震功能失效概率的计算方法。首先,针对各典型地震失效模式,基于Zick L P提出的容器应力分析与强度设计理论,建立了考虑地震作用及容器参数的随机性的卧式压力容器可靠度分析...为评估卧式压力容器在地震作用下能否安全运行,文中推导了其地震功能失效概率的计算方法。首先,针对各典型地震失效模式,基于Zick L P提出的容器应力分析与强度设计理论,建立了考虑地震作用及容器参数的随机性的卧式压力容器可靠度分析模型;由于模型中存在非正态分布的随机变量,引入JC法计算了各失效模式下的可靠度指标和失效概率。以一部卧式压力容器为例,采用文中方法评估了其在地震作用下的安全性,研究表明:在设防地震下,地脚螺栓受剪破坏的可靠指标为2.155,失效概率达到1.56%,容器可靠度不满足要求,因此地脚螺栓是其抗震薄弱环节;在罕遇地震下,地脚螺栓受剪破坏可靠指标持续降低,失效概率达到13.47%,而垫板边缘处圆筒受压破坏与地脚螺栓受拉破坏的概率也大为增加,分别达到4.6%和2.5%,因此垫板边缘处圆筒是该容器潜在的功能失效风险点。展开更多
文摘This paper presents in-situ seismic performance tests of a bridge before its demolition due to accumulated scouring problem. The tests were conducted on three single columns and one caisson-type foundation. The three single columns were 1.8 m in diameter,reinforced by 30-D32 longitudinal reinforcements and laterally hooped by D16 reinforcements with spacing of 20 cm. The column height is 9.54 m,10.59 m and 10.37 m for Column P2,P3,and P4,respectively. Column P2 had no exposed foundation and was subjected to pseudo-dynamic tests with peak ground acceleration of 0.32 g first,followed by one cyclic loading test. Column P3 was the benchmark specimen with exposed length of 1.2 m on its foundation. The exposed length for Column P4 was excavated to 4 m,approximately 1/3 of the foundation length,to study the effect of the scouring problem to the column performance. Both Column P3 and Column P4 were subjected to cyclic loading tests. Based on the test results,due to the large dimension of the caisson foundation and the well graded gravel soil type that provided large lateral resistance,the seismic performance among the three columns had only minor differences. Lateral push tests were also conducted on the caisson foundation at Column P5. The caisson was 12 m long and had circular cross-sections whose diameters were 5 m in the upper portion and 4 m in the lower portion. An analytical model to simulate the test results was developed in the OpenSees platform. The analytical model comprised nonlinear flexural elements as well as nonlinear soil springs. The analytical results closely followed the experimental test results. A parametric study to predict the behavior of the bridge column with different ground motions and different levels of scouring on the foundation are also discussed.
基金This project"Formal Safety Assessment of a Marine Seismic Survey Vessel Operation,Incorporating Risk Matrix and Fault Tree Analysis"has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 730888.
文摘In maritime safety research,risk is assessed usually within the framework of formal safety assessment(FSA),which provides a formal and systematic methodology to improve the safety of lives,assets,and the environment.A bespoke application of FSA to mitigate accidents in marine seismic surveying is put forward in this paper,with the aim of improving the safety of seismic vessel operations,within the context of developing an economically viable strategy.The work herein takes a close look at the hazards in North Sea offshore seismic surveying,in order to identify critical risk factors,leading to marine seismic survey accidents.The risk factors leading to undesirable events are analysed both qualitatively and quantitatively.A risk matrix is introduced to screen the identified undesirable events.Further to the screening,Fault Tree Analysis(FTA)is presented to investigate and analyse the most critical risks of seismic survey operation,taking into account the lack of historical data.The obtained results show that man overboard(MOB)event is a major risk factor in marine seismic survey operation;lack of training on safe work practice,slippery deck as a result of rain,snow or water splash,sea state affecting human judgement,and poor communication are identified as the critical risk contributors to the MOB event.Consequently,the risk control options are focused on the critical risk contributors for decision-making.Lastly,suggestions for the introduction and development of the FSA methodology are highlighted for safer marine and offshore operations in general.
文摘为评估卧式压力容器在地震作用下能否安全运行,文中推导了其地震功能失效概率的计算方法。首先,针对各典型地震失效模式,基于Zick L P提出的容器应力分析与强度设计理论,建立了考虑地震作用及容器参数的随机性的卧式压力容器可靠度分析模型;由于模型中存在非正态分布的随机变量,引入JC法计算了各失效模式下的可靠度指标和失效概率。以一部卧式压力容器为例,采用文中方法评估了其在地震作用下的安全性,研究表明:在设防地震下,地脚螺栓受剪破坏的可靠指标为2.155,失效概率达到1.56%,容器可靠度不满足要求,因此地脚螺栓是其抗震薄弱环节;在罕遇地震下,地脚螺栓受剪破坏可靠指标持续降低,失效概率达到13.47%,而垫板边缘处圆筒受压破坏与地脚螺栓受拉破坏的概率也大为增加,分别达到4.6%和2.5%,因此垫板边缘处圆筒是该容器潜在的功能失效风险点。
