A new remedy is proposed in this study to increase the ductility of cross-braced frames to a level comparable with ductile moment frames.The suggested system consists of one or two concentric steel rings installed in ...A new remedy is proposed in this study to increase the ductility of cross-braced frames to a level comparable with ductile moment frames.The suggested system consists of one or two concentric steel rings installed in the cross-braced bay vertically.The steel rings are designed such that they fail in bending sooner than failure of the braces in compression.Then the rings act as seismic fuses with multiple bending plastic hinges.Using nonlinear static analysis,it is shown that the proposed system can be designed to behave like cross-braced frames with regard to stiffness and strength,and like special moment frames with regard to ductility.Seismic design factors for the proposed system are recommended based on nonlinear pushover and cyclic analysis studies.展开更多
Improving freight axle load is the most effective method to improve railway freight capability; based on the imported technologies of railway freight bogie, the 27 t axle load side-frame cross-bracing bogie and sub-fr...Improving freight axle load is the most effective method to improve railway freight capability; based on the imported technologies of railway freight bogie, the 27 t axle load side-frame cross-bracing bogie and sub-frame radial bogie are developed in China. In order to analyze and compare dynamic interactions of the two newly developed heavy-haul freight bogies, we establish a vehi- cle-track coupling dynamic model and use numerical calculation methods for computer simulation. The dynamic performances of the two bogies are simulated separately at various conditions. The results show that at the dipped joint and straight line running conditions, the wheel-rail dynamic interactions of both bogies are basically the same, but at the curve negotiation condition, the wear and the lateral force of the side-frame cross-bracing bogie are much higher than that of the sub-frame radial bogie, and the advantages become more obvious when the curve radius is smaller. The results also indicate that the sub- frame radial bogie has better low-wheel-rail interaction characteristics.展开更多
目的采用三维有限元数值模拟方法分析比较骨水泥棒外固定支架与交叉克氏针在力学稳定性方面的差异,为手术治疗第五掌骨颈骨折(特别是第五掌骨颈开放性骨折)提供理论依据。方法选取1名健康志愿者,采集其手腕关节的三维CT图像数据,首先利...目的采用三维有限元数值模拟方法分析比较骨水泥棒外固定支架与交叉克氏针在力学稳定性方面的差异,为手术治疗第五掌骨颈骨折(特别是第五掌骨颈开放性骨折)提供理论依据。方法选取1名健康志愿者,采集其手腕关节的三维CT图像数据,首先利用Mimics Research 21.0、Geomagic Studio 2021软件进行三维图形数据处理,在此基础上应用Solidworks 2020软件构建第五掌骨颈骨折骨水泥棒外固定支架模型(A模型)和第五掌骨颈骨折交叉克氏针固定模型(B模型)。在ANSYS Workbench 17.0中对各模型的材料属性进行赋值、划分网格,建立三维有限元模型。最后通过在第五掌骨头远端关节面进行轴向施加和第五掌骨三点弯曲实验,计算得出两种施压方式的远端骨折块的最大位移,以此评价骨水泥棒外固定支架治疗第五掌骨颈骨折的稳定性。结果(1)轴向施压时,A模型远端骨折块的最大位移、最小位移和平均位移的值大于B模型,A模型近端骨折块的最大位移、最小位移和平均位移的值小于B模型,A模型最大相对位移、最小相对位移和平均相对位移大于B模型。(2)在三点折弯给力时,A模型远端骨折块最大位移小于B模型,远端骨折块最小位移等于B模型,近端骨折块的最大位移和最小位移的均值大于B模型,A模型最大相对位移、最小相对位移和平均相对位移大于B模型。(3)与B模型相比较,A模型的总体应力、固定物应力均明显较小。结论骨水泥棒外固定支架及克氏针交叉固定在治疗第五掌骨颈骨折方面,在轴向和纵向上的位移及总位移均未超过1 mm,差异较小;但骨水泥棒外固定支架在两种施力方式中与交叉克氏针相比应力更小,提示骨水泥棒外固定支架能提供可靠的力学稳定性。展开更多
文摘A new remedy is proposed in this study to increase the ductility of cross-braced frames to a level comparable with ductile moment frames.The suggested system consists of one or two concentric steel rings installed in the cross-braced bay vertically.The steel rings are designed such that they fail in bending sooner than failure of the braces in compression.Then the rings act as seismic fuses with multiple bending plastic hinges.Using nonlinear static analysis,it is shown that the proposed system can be designed to behave like cross-braced frames with regard to stiffness and strength,and like special moment frames with regard to ductility.Seismic design factors for the proposed system are recommended based on nonlinear pushover and cyclic analysis studies.
基金supported by the National Natural Science Foundation of China (No. 50975238)
文摘Improving freight axle load is the most effective method to improve railway freight capability; based on the imported technologies of railway freight bogie, the 27 t axle load side-frame cross-bracing bogie and sub-frame radial bogie are developed in China. In order to analyze and compare dynamic interactions of the two newly developed heavy-haul freight bogies, we establish a vehi- cle-track coupling dynamic model and use numerical calculation methods for computer simulation. The dynamic performances of the two bogies are simulated separately at various conditions. The results show that at the dipped joint and straight line running conditions, the wheel-rail dynamic interactions of both bogies are basically the same, but at the curve negotiation condition, the wear and the lateral force of the side-frame cross-bracing bogie are much higher than that of the sub-frame radial bogie, and the advantages become more obvious when the curve radius is smaller. The results also indicate that the sub- frame radial bogie has better low-wheel-rail interaction characteristics.
文摘目的采用三维有限元数值模拟方法分析比较骨水泥棒外固定支架与交叉克氏针在力学稳定性方面的差异,为手术治疗第五掌骨颈骨折(特别是第五掌骨颈开放性骨折)提供理论依据。方法选取1名健康志愿者,采集其手腕关节的三维CT图像数据,首先利用Mimics Research 21.0、Geomagic Studio 2021软件进行三维图形数据处理,在此基础上应用Solidworks 2020软件构建第五掌骨颈骨折骨水泥棒外固定支架模型(A模型)和第五掌骨颈骨折交叉克氏针固定模型(B模型)。在ANSYS Workbench 17.0中对各模型的材料属性进行赋值、划分网格,建立三维有限元模型。最后通过在第五掌骨头远端关节面进行轴向施加和第五掌骨三点弯曲实验,计算得出两种施压方式的远端骨折块的最大位移,以此评价骨水泥棒外固定支架治疗第五掌骨颈骨折的稳定性。结果(1)轴向施压时,A模型远端骨折块的最大位移、最小位移和平均位移的值大于B模型,A模型近端骨折块的最大位移、最小位移和平均位移的值小于B模型,A模型最大相对位移、最小相对位移和平均相对位移大于B模型。(2)在三点折弯给力时,A模型远端骨折块最大位移小于B模型,远端骨折块最小位移等于B模型,近端骨折块的最大位移和最小位移的均值大于B模型,A模型最大相对位移、最小相对位移和平均相对位移大于B模型。(3)与B模型相比较,A模型的总体应力、固定物应力均明显较小。结论骨水泥棒外固定支架及克氏针交叉固定在治疗第五掌骨颈骨折方面,在轴向和纵向上的位移及总位移均未超过1 mm,差异较小;但骨水泥棒外固定支架在两种施力方式中与交叉克氏针相比应力更小,提示骨水泥棒外固定支架能提供可靠的力学稳定性。
