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
Using a center etched single mode optical fiber, a simple vibration senor is designed to monitor the vibrations of a simply supported beam. The sensor has high linear response to the axial displacement of about 0.8mm ...Using a center etched single mode optical fiber, a simple vibration senor is designed to monitor the vibrations of a simply supported beam. The sensor has high linear response to the axial displacement of about 0.8mm with a sensitivity of 32mV/10p, m strain. The sensor is tested for periodic and suddenly released forces, and the results are found to coincide with the theoretical values. This simple design, small in size and low cost sensor may find applications in industry and civil engineering to monitor the vibrations of the beam structures and bridges.展开更多
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.
文摘Using a center etched single mode optical fiber, a simple vibration senor is designed to monitor the vibrations of a simply supported beam. The sensor has high linear response to the axial displacement of about 0.8mm with a sensitivity of 32mV/10p, m strain. The sensor is tested for periodic and suddenly released forces, and the results are found to coincide with the theoretical values. This simple design, small in size and low cost sensor may find applications in industry and civil engineering to monitor the vibrations of the beam structures and bridges.
