In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structur...In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structure surrounding the spiral case was simulated with a three-dimensional finite element model. Then, the distribution and evolution of the structural damage were studied. Based on investigation of the change of gap openings between the steel liner and concrete structure, the impact of the non-uniform variation of gaps on the load-beating ratio between the steel liner and concrete structure was analyzed. The comparison of calculated results of the simplified and simulation algorithms shows that the simulation algorithm is a feasible option for the calculation of spiral case structures. In addition, the shell-spring model was introduced for optimization analysis, and the results were reasonable.展开更多
The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter,...The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in thickness, was post-prestressed with the unbonded tendons, each of which consists of 8 pieces of double-looped strands and the axial spacing of the tendons is 500 mm. Concrete strain meters, rebar meters, load cell and zero-stress meters were installed for the strain monitoring. The tensioning loads were applied incrementally in three cycles (50%, 77% and 100%) at the concrete age of 28 d and the tensioning work lasted for 187.1 h. Strain readings were taken before and after each cycle during tensioning period and at the specified time interval after tensioning period. It is found that concrete creep developed over tensioning period is 30% of total strain and 41.5% of elastic strain respectively. Prestress force in the unbonded tendon and concrete stress in the liner were evaluated according to the observed strain variations. Both of them are time-dependent, and about 5.3%, 8.3% and 9.0% of the prestress losses are observed at the age of 1 d, 30 d and 60 d respectively after stressing. The distribution of prestress in the liner is relatively uniform and meets the design requirement.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51079020)the He'nan Provincial Research Foundation for Basic and Advanced Technology (Grant No. 122300410001)the Foundation of He'nan Educational Committee (Grant No. 13A570715)
文摘In this study, the damage-plasticity model for concrete that was verified by the model experiment was used to calculate the damage to a spiral case structure based on the damage mechanics theory. The concrete structure surrounding the spiral case was simulated with a three-dimensional finite element model. Then, the distribution and evolution of the structural damage were studied. Based on investigation of the change of gap openings between the steel liner and concrete structure, the impact of the non-uniform variation of gaps on the load-beating ratio between the steel liner and concrete structure was analyzed. The comparison of calculated results of the simplified and simulation algorithms shows that the simulation algorithm is a feasible option for the calculation of spiral case structures. In addition, the shell-spring model was introduced for optimization analysis, and the results were reasonable.
基金Supported by National Natural Science Foundation of China (No. 50578110) .
文摘The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in thickness, was post-prestressed with the unbonded tendons, each of which consists of 8 pieces of double-looped strands and the axial spacing of the tendons is 500 mm. Concrete strain meters, rebar meters, load cell and zero-stress meters were installed for the strain monitoring. The tensioning loads were applied incrementally in three cycles (50%, 77% and 100%) at the concrete age of 28 d and the tensioning work lasted for 187.1 h. Strain readings were taken before and after each cycle during tensioning period and at the specified time interval after tensioning period. It is found that concrete creep developed over tensioning period is 30% of total strain and 41.5% of elastic strain respectively. Prestress force in the unbonded tendon and concrete stress in the liner were evaluated according to the observed strain variations. Both of them are time-dependent, and about 5.3%, 8.3% and 9.0% of the prestress losses are observed at the age of 1 d, 30 d and 60 d respectively after stressing. The distribution of prestress in the liner is relatively uniform and meets the design requirement.
