To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance asses...To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.展开更多
The permeability and sorptivity properties of the two prestressed concrete containment buildings （PCCBs） of a nuclear power plant in South China, which had been under operation for 5 years, were measured by using th...The permeability and sorptivity properties of the two prestressed concrete containment buildings （PCCBs） of a nuclear power plant in South China, which had been under operation for 5 years, were measured by using the autoclam permeability system. The air permeability, sorptivity and water permeability indexes of No.1 PCCB are smaller than or equal to 0.11 ln（102 Pa）/min, 0.98×10 ^7 m3/minl/2 and 1.93×10 ^7 m3/min1/2, respectively, and the air permeability, sorptivity and water permeability indexes of No.2 PCCB are smaller than or equal to 0.17 In（102 Pa）/min, 1.6×10 ^7 m3/min1/2 and 4.43 ×10 ^7 m3/min1/2, respectively. Based on the criteria for evaluating the protective quality of concrete structures in terms of their permeability and sorptivity properties, proposed by the research organization of the autoclam permeability system, the protective quality of No. 1 PCCB is still in very good grade and that of No.2 PCCB is not in very good grade but in good grade, and the in-service inspection of the protective quality of No.2 PCCB should be strengthened in the future.展开更多
The comparative research on the seismic performance of grouted sleeve connected pier(GS)and prestressed precast segmental concrete pier(PC)is mostly carried out by numerical simulation.In this study,the GS pier and th...The comparative research on the seismic performance of grouted sleeve connected pier(GS)and prestressed precast segmental concrete pier(PC)is mostly carried out by numerical simulation.In this study,the GS pier and the PC pier of the new railway project from Hetian to Ruoqiang are taken into consideration.Two kinds of 1/5-scale assembled double-column specimens are made,and the quasi-static tests are carried out.The overall seismic performance of the two spliced piers is studied,and compared in terms of failure mechanism,bearing capacity,ductility,stiffness and energy dissipation capacity.The results show that the failure modes of both GS pier and PC pier are characterized by bending.However,the specific failure location and form are different.The GS pier presents a complete hysteretic curve,large equivalent stiffness and strong energy dissipation capacity.The hysteretic area of the PC pier is small.However,it has good self-reset ability and quasi-static residual displacement.Finite element models are set up using DispBeamColumn fiber elements and ZeroLength elements.The models that are calibrated with the test data can effectively simulate the damage development under monotonic loading.The load−displacement curves are in good agreement with the backbone curves of the test results.展开更多
基金Project(2006.318.223.02-01) supported by the Ministry of Transportation and Communications through the Scientific and Technological Funds of ChinaProject(2007AA11Z104) supported by the High Technology Research and Development of ChinaProject(20090072110045) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.
基金Project(20050487017) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject (2009567) supported by China National Nuclear Corporation
文摘The permeability and sorptivity properties of the two prestressed concrete containment buildings （PCCBs） of a nuclear power plant in South China, which had been under operation for 5 years, were measured by using the autoclam permeability system. The air permeability, sorptivity and water permeability indexes of No.1 PCCB are smaller than or equal to 0.11 ln（102 Pa）/min, 0.98×10 ^7 m3/minl/2 and 1.93×10 ^7 m3/min1/2, respectively, and the air permeability, sorptivity and water permeability indexes of No.2 PCCB are smaller than or equal to 0.17 In（102 Pa）/min, 1.6×10 ^7 m3/min1/2 and 4.43 ×10 ^7 m3/min1/2, respectively. Based on the criteria for evaluating the protective quality of concrete structures in terms of their permeability and sorptivity properties, proposed by the research organization of the autoclam permeability system, the protective quality of No. 1 PCCB is still in very good grade and that of No.2 PCCB is not in very good grade but in good grade, and the in-service inspection of the protective quality of No.2 PCCB should be strengthened in the future.
基金Project(N2018G034)supported by China Railway Corporation。
文摘The comparative research on the seismic performance of grouted sleeve connected pier(GS)and prestressed precast segmental concrete pier(PC)is mostly carried out by numerical simulation.In this study,the GS pier and the PC pier of the new railway project from Hetian to Ruoqiang are taken into consideration.Two kinds of 1/5-scale assembled double-column specimens are made,and the quasi-static tests are carried out.The overall seismic performance of the two spliced piers is studied,and compared in terms of failure mechanism,bearing capacity,ductility,stiffness and energy dissipation capacity.The results show that the failure modes of both GS pier and PC pier are characterized by bending.However,the specific failure location and form are different.The GS pier presents a complete hysteretic curve,large equivalent stiffness and strong energy dissipation capacity.The hysteretic area of the PC pier is small.However,it has good self-reset ability and quasi-static residual displacement.Finite element models are set up using DispBeamColumn fiber elements and ZeroLength elements.The models that are calibrated with the test data can effectively simulate the damage development under monotonic loading.The load−displacement curves are in good agreement with the backbone curves of the test results.
