A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to...A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation(u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled(u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fi xed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively infl uence the lateral pile displacements.展开更多
The distributed optical fiber sensing technology was used to investigate the fracture behavior of the Epoxy Asphalt Mixture. The spatial distribution and variation of the strain development with crack propagation were...The distributed optical fiber sensing technology was used to investigate the fracture behavior of the Epoxy Asphalt Mixture. The spatial distribution and variation of the strain development with crack propagation were acquired using the brillouin optical time-domain reflectometer through the loading experiments of the composite beam structure. In addition, a finite element model of the composite beam structure was developed to analyze the mechanical responses of the epoxy asphalt mixture using the extended finite element method. The experimental results show that the development of crack propagation becomes instable with the increase of the load, and larger loads will generate deeper cracks. Moreover, the numerical results show that the mechanical response of the crack tip changes with the crack propagation, and the worst areas that subjected to crack damage are located on both sides of the composite beam structure.展开更多
本文采用有限元法对颅骨骨折的致伤方式进行生物力学分析,为判断颅骨骨折的致伤方式提供可视化、可量化的辅助分析技术。根据实际案例信息,利用有限元法模拟比较:1)高坠时,THUMS4.02(Total Human Model for Safety4.02)人体模型以8.04 ...本文采用有限元法对颅骨骨折的致伤方式进行生物力学分析,为判断颅骨骨折的致伤方式提供可视化、可量化的辅助分析技术。根据实际案例信息,利用有限元法模拟比较:1)高坠时,THUMS4.02(Total Human Model for Safety4.02)人体模型以8.04 m/s速度左头顶部着地时的应力分布;2)钢管击打时,钢管模型以5.8 m/s速度击打左头顶部时的应力分布。模拟结果结合案例信息从生物力学角度分析颅骨骨折的致伤方式。应力云图显示,高坠时应力最先从接触部位开始,随着颅骨塌陷,应力向四周传导,最后形成类圆形应力区,而钢管击打时应力最早分布在钢管与头部的接触区,中心区应力分布不明显,结合案例左顶骨凹陷骨折形态呈锥形,提示受力由圆心向内推挤,分析认为左顶骨凹陷骨折符合高坠形成。利用有限元法可实现颅骨凹陷骨折致伤方式可视化、量化的分析。展开更多
本研究利用有限元法对拳击、胸外按压致肋骨骨折进行模拟,以期为肋骨骨折致伤方式分析提供一种可视化、可量化的辅助技术。通过采用有限元法分别模拟:1)设置拳头模型以6 m/s击打THUMS4.02(Total Human Model for Safety 4.02)人体模型...本研究利用有限元法对拳击、胸外按压致肋骨骨折进行模拟,以期为肋骨骨折致伤方式分析提供一种可视化、可量化的辅助技术。通过采用有限元法分别模拟:1)设置拳头模型以6 m/s击打THUMS4.02(Total Human Model for Safety 4.02)人体模型的左胸;2)设置按压锤模型以400 N竖直向下的力按压THUMS4.02人体模型的心前区。比较二者模拟结果的肋骨骨折分布、形态特点,从生物力学角度分析二者的损伤机制,并将模拟结果与文献报道进行比较。模拟结果显示:1)肋骨骨折形态、分布:拳击致肋骨骨折的断端形态为向内弯曲,分布于直接击打处;按压胸部致肋骨骨折的断端形态为向外翻折,分布在肋骨非直接受力处。2)生物力学响应:拳击胸部时,应变集中分布在拳击肋骨处,击打处肋骨外侧面产生压应力,内侧面产生拉应力。按压胸部时,除按压处存在应变分布外,按压侧的肋骨腋前线处出现明显应变分布,腋前线处肋骨外侧面产生拉应力,内侧面产生压应力。本研究模拟结果均得到文献支持,提示利用有限元法可实现对肋骨骨折致伤方式可视化、可量化的辅助性分析与解释。展开更多
基金Major Research Plan of National Natural Science Foundation of China under Grant No.90815009the National Natural Science Foundation of China under Grant Nos.51108134,50378031 and 50178027
文摘A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation(u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled(u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fi xed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively infl uence the lateral pile displacements.
基金Funded by the National Natural Science Foundation of China(No.51178114)the Fundamental Research Funds for the Central Universities(No.CXLX12_0117)the Scientifi c Research Foundation of Graduate School of Southeast University(No.YBJJ1318)
文摘The distributed optical fiber sensing technology was used to investigate the fracture behavior of the Epoxy Asphalt Mixture. The spatial distribution and variation of the strain development with crack propagation were acquired using the brillouin optical time-domain reflectometer through the loading experiments of the composite beam structure. In addition, a finite element model of the composite beam structure was developed to analyze the mechanical responses of the epoxy asphalt mixture using the extended finite element method. The experimental results show that the development of crack propagation becomes instable with the increase of the load, and larger loads will generate deeper cracks. Moreover, the numerical results show that the mechanical response of the crack tip changes with the crack propagation, and the worst areas that subjected to crack damage are located on both sides of the composite beam structure.
文摘本文采用有限元法对颅骨骨折的致伤方式进行生物力学分析,为判断颅骨骨折的致伤方式提供可视化、可量化的辅助分析技术。根据实际案例信息,利用有限元法模拟比较:1)高坠时,THUMS4.02(Total Human Model for Safety4.02)人体模型以8.04 m/s速度左头顶部着地时的应力分布;2)钢管击打时,钢管模型以5.8 m/s速度击打左头顶部时的应力分布。模拟结果结合案例信息从生物力学角度分析颅骨骨折的致伤方式。应力云图显示,高坠时应力最先从接触部位开始,随着颅骨塌陷,应力向四周传导,最后形成类圆形应力区,而钢管击打时应力最早分布在钢管与头部的接触区,中心区应力分布不明显,结合案例左顶骨凹陷骨折形态呈锥形,提示受力由圆心向内推挤,分析认为左顶骨凹陷骨折符合高坠形成。利用有限元法可实现颅骨凹陷骨折致伤方式可视化、量化的分析。
文摘本研究利用有限元法对拳击、胸外按压致肋骨骨折进行模拟,以期为肋骨骨折致伤方式分析提供一种可视化、可量化的辅助技术。通过采用有限元法分别模拟:1)设置拳头模型以6 m/s击打THUMS4.02(Total Human Model for Safety 4.02)人体模型的左胸;2)设置按压锤模型以400 N竖直向下的力按压THUMS4.02人体模型的心前区。比较二者模拟结果的肋骨骨折分布、形态特点,从生物力学角度分析二者的损伤机制,并将模拟结果与文献报道进行比较。模拟结果显示:1)肋骨骨折形态、分布:拳击致肋骨骨折的断端形态为向内弯曲,分布于直接击打处;按压胸部致肋骨骨折的断端形态为向外翻折,分布在肋骨非直接受力处。2)生物力学响应:拳击胸部时,应变集中分布在拳击肋骨处,击打处肋骨外侧面产生压应力,内侧面产生拉应力。按压胸部时,除按压处存在应变分布外,按压侧的肋骨腋前线处出现明显应变分布,腋前线处肋骨外侧面产生拉应力,内侧面产生压应力。本研究模拟结果均得到文献支持,提示利用有限元法可实现对肋骨骨折致伤方式可视化、可量化的辅助性分析与解释。
