Dome structures have been used extensively for industrial,residential,and military infrastructure.Therefore,it is necessary to understand the damage risk potential for such structures for blast-resistant design consid...Dome structures have been used extensively for industrial,residential,and military infrastructure.Therefore,it is necessary to understand the damage risk potential for such structures for blast-resistant design considerations.This paper investigates the effect of blast load variability on the design value and the structural dynamic response.Therefore,the sources of uncertainty in the external blast load on dome structures were discussed firstly.Then based on the probabilistic blast load model for the dome,the rationality of a deterministic mass-increase safety method was assessed.It was found that previous deterministic design method cannot provide a consistent and sound assurance factor or reliability index on the entire dome roof.In addition,it was also proved that the assurance-based load method fails to ensure compliance with structural safety design standards on the dome roof when compared with the reliability-based blast method.A sensitivity analysis on the probabilistic blast load was conducted,and the results indicate that stand-off distance and explosive mass both act as dominant sources to influence the mean and variability of blast load.Therefore,based on the Latin hypercube sampling method,a reliability-based external blast load factor technique was proposed.This technique was further used to estimate structural damage levels of a single-layer reticulated dome under different reliability requirements,associated with a low,medium,and high level of protection grades for a specific explosion scenario,and it indicated that this technique can be useful in the building design to achieve a higher structural anti-explosion capacity.This study herein can serve as a reference for the calculation method of designed blast load.展开更多
为了量化不同驾驶次任务下驾驶人视觉负荷特征,基于驾驶模拟平台搭建各类型次任务加载下的高速公路跟车场景,招募46名被试开展试验。采集驾驶人注视、扫视及瞳孔直径等眼动指标,对比不同驾驶次任务下视觉特征变化规律。基于因子分析方...为了量化不同驾驶次任务下驾驶人视觉负荷特征,基于驾驶模拟平台搭建各类型次任务加载下的高速公路跟车场景,招募46名被试开展试验。采集驾驶人注视、扫视及瞳孔直径等眼动指标,对比不同驾驶次任务下视觉特征变化规律。基于因子分析方法构建驾驶人视觉负荷评价模型,量化不同次任务下的视觉负荷。在视觉负荷量化的基础上,引入变异系数,采用K均值聚类算法将驾驶人视觉负荷分为低、中、高稳定型类别。并通过相关性分析,探究次任务下驾驶人视觉负荷与行车安全的关系。结果表明,执行快速串行视觉呈现(Rapid Serial Visual Presentation, RSVP)任务使驾驶人扫视速度和扫视幅度显著增加,单次注视持续时间显著下降。但驾驶人通过增加注视频次,弥补了总注视持续时长的下降,即采取小幅快速搜索方式补偿了视觉信息的获取。执行延迟数字召回任务(1-Back)占用驾驶人认知资源,导致视觉搜索出现弱化。驾驶人不仅减少了对非前方道路区域的关注,且扫视频率和注视持续时长占比均显著下降。视觉负荷量化模型结果显示,RSVP手机操作次任务下相比正常驾驶视觉负荷平均上升了22.29%,执行1-Back数字记忆次任务时视觉负荷平均下降了8.93%。不同驾驶人视觉负荷存在明显个体差异,64.2%的被试视觉负荷可以保持高稳定性。驾驶人视觉负荷与车速指标虽不相关,但与车头间距、车头时距和时间裕度等安全替代指标具有显著负相关,表明次任务加载下视觉负荷过高会导致驾驶绩效下降,影响行车安全。展开更多
Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthqu...Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.展开更多
基金supports from and Na-tional key research and development program of China(project No.2018YFC0705703)the National Natural Science Foundation of China(project No.51708521,51778183).
文摘Dome structures have been used extensively for industrial,residential,and military infrastructure.Therefore,it is necessary to understand the damage risk potential for such structures for blast-resistant design considerations.This paper investigates the effect of blast load variability on the design value and the structural dynamic response.Therefore,the sources of uncertainty in the external blast load on dome structures were discussed firstly.Then based on the probabilistic blast load model for the dome,the rationality of a deterministic mass-increase safety method was assessed.It was found that previous deterministic design method cannot provide a consistent and sound assurance factor or reliability index on the entire dome roof.In addition,it was also proved that the assurance-based load method fails to ensure compliance with structural safety design standards on the dome roof when compared with the reliability-based blast method.A sensitivity analysis on the probabilistic blast load was conducted,and the results indicate that stand-off distance and explosive mass both act as dominant sources to influence the mean and variability of blast load.Therefore,based on the Latin hypercube sampling method,a reliability-based external blast load factor technique was proposed.This technique was further used to estimate structural damage levels of a single-layer reticulated dome under different reliability requirements,associated with a low,medium,and high level of protection grades for a specific explosion scenario,and it indicated that this technique can be useful in the building design to achieve a higher structural anti-explosion capacity.This study herein can serve as a reference for the calculation method of designed blast load.
文摘为了量化不同驾驶次任务下驾驶人视觉负荷特征,基于驾驶模拟平台搭建各类型次任务加载下的高速公路跟车场景,招募46名被试开展试验。采集驾驶人注视、扫视及瞳孔直径等眼动指标,对比不同驾驶次任务下视觉特征变化规律。基于因子分析方法构建驾驶人视觉负荷评价模型,量化不同次任务下的视觉负荷。在视觉负荷量化的基础上,引入变异系数,采用K均值聚类算法将驾驶人视觉负荷分为低、中、高稳定型类别。并通过相关性分析,探究次任务下驾驶人视觉负荷与行车安全的关系。结果表明,执行快速串行视觉呈现(Rapid Serial Visual Presentation, RSVP)任务使驾驶人扫视速度和扫视幅度显著增加,单次注视持续时间显著下降。但驾驶人通过增加注视频次,弥补了总注视持续时长的下降,即采取小幅快速搜索方式补偿了视觉信息的获取。执行延迟数字召回任务(1-Back)占用驾驶人认知资源,导致视觉搜索出现弱化。驾驶人不仅减少了对非前方道路区域的关注,且扫视频率和注视持续时长占比均显著下降。视觉负荷量化模型结果显示,RSVP手机操作次任务下相比正常驾驶视觉负荷平均上升了22.29%,执行1-Back数字记忆次任务时视觉负荷平均下降了8.93%。不同驾驶人视觉负荷存在明显个体差异,64.2%的被试视觉负荷可以保持高稳定性。驾驶人视觉负荷与车速指标虽不相关,但与车头间距、车头时距和时间裕度等安全替代指标具有显著负相关,表明次任务加载下视觉负荷过高会导致驾驶绩效下降,影响行车安全。
文摘Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.
