Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the...Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation , is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations , a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. The final conclusions based on the numerical results will provide some guidance in engineering practice.展开更多
Purpose: The purpose of this study was to compare 4 techniques for arrival at a base after sprinting maximally to reach it: sliding head-first, sliding feet-first, running through the base without slowing, and stoppin...Purpose: The purpose of this study was to compare 4 techniques for arrival at a base after sprinting maximally to reach it: sliding head-first, sliding feet-first, running through the base without slowing, and stopping on the base. A secondary purpose of the study was to determine any advantage there may be to diving into first base to arrive sooner than running through the base.Methods: Two high-definition video cameras were used to capture 3-dimensional kinematics of sliding techniques of 9 intercollegiate baseball players. Another video camera was used to time runs from first base to second in 4 counterbalanced conditions: running through the base, sliding head-first, sliding feet-first, and running to a stop. Mathematical modeling was used to simulate diving to first base such that the slide would begin when the hand touches the base.Results: Based upon overall results, the quickest way to the base is by running through it, followed by head-first, feet-first, and running to a stop.Conclusion: There was a non-significant trend toward an advantage for diving into first base over running through it, but more research is needed,and even if the advantage is real, the risks of executing this technique probably outweigh the miniscule gain.展开更多
基金Supported by National Science Fund for Distinguished Young Scholars of China (No. 50425824)National Natural Science Foundation of China (No. 50528808)
文摘Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation , is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations , a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. The final conclusions based on the numerical results will provide some guidance in engineering practice.
文摘Purpose: The purpose of this study was to compare 4 techniques for arrival at a base after sprinting maximally to reach it: sliding head-first, sliding feet-first, running through the base without slowing, and stopping on the base. A secondary purpose of the study was to determine any advantage there may be to diving into first base to arrive sooner than running through the base.Methods: Two high-definition video cameras were used to capture 3-dimensional kinematics of sliding techniques of 9 intercollegiate baseball players. Another video camera was used to time runs from first base to second in 4 counterbalanced conditions: running through the base, sliding head-first, sliding feet-first, and running to a stop. Mathematical modeling was used to simulate diving to first base such that the slide would begin when the hand touches the base.Results: Based upon overall results, the quickest way to the base is by running through it, followed by head-first, feet-first, and running to a stop.Conclusion: There was a non-significant trend toward an advantage for diving into first base over running through it, but more research is needed,and even if the advantage is real, the risks of executing this technique probably outweigh the miniscule gain.
