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Introduction Structures must be robust, so that after accidentaldamage, they will not suffer consequences dispropor-tionate to the original causes. In structural engineer-ing, the modern research on structural robustness maydate back to the progressive collapse of the RonanPoint in England in 1968, where a relatively weakexplosion led to a disproportionate failure ( seeFig.1). Following this accident, considerable at-tempts have been made on this subject though debatecontinues about the true… 相似文献
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William G.McDougal 《水道港口》2010,31(5):319-319
A-Jacks are concrete armor units that are used in both open channel and coastal applications.In open channel applications,they are used for bank and toe protection,flow and grade control,bridge pier scour protection,energy dissipation,and habitat.These small units may be fabricated in standard block machines.In coastal applications,A-Jacks are used in breakwaters,jetties,revetments,and habitat development.Coastal units are generally much larger and more robust than the small open channel units.This paper focuses on coastal applications and in particular,combines results on three topics:(1)recent hydraulic model studies,(2)alternative fabrication methods,and(3)bundle placement construction methods.Hydraulic models studies were conducted that examined the standard random and uniform placement methods,and also the bundle placement method.In bundle placement,3~20 A-Jacks are banded together,lifted with a spreader bar,and placed as a single crane pick.This significantly decreases installation time during construction.It also provides a more hydraulically stable placement technique.The hydraulic model tests examined the bundle stability in random waves for cases where the binding remains in tack and is removed.The geometry of A-Jacks enables a variety of fabrication techniques.One option is to fabricate the A-Jacks as two pieces using flat forms and then grout the two pieces together.Flat forms may be used in conventional block machines for A-Jacks sizes up to 1.3 m.Larger sizes may be wet cast in flat forms or gang forms.The A-Jacks geometry has been recently modified to increase grouting efficient and strength.Large A- Jacks may also be cast in a single piece using "clam shell" type forms. 相似文献
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As driving error is a main contributory factor of road accidents, its causes and consequences are of great interest in the road safety decision making process. This paper investigates several factors (including driver distraction, driver characteristics and road environment) that affect overall driving error behaviour and estimates a new unobserved variable which underlines driving errors. This estimation is performed with data obtained from a driving simulation experiment in which 95 participants covering all ages were asked to drive under different types of distraction (no distraction, conversation with passenger, cell phone use) in rural and urban road environment, as well as in both low and high traffic conditions. Driving error was then modeled as a latent variable based on several individual driving simulator parameters. Subsequently, the impact of several risk factors such as distraction, driver characteristics as well as road environment on driving error were estimated directly. The results of this complex model reveal that the impact of driver characteristics and area type are the only statistically significant factors affecting the probability of driving errors. Interestingly, neither conversing with a passenger nor talking on the cell phone have a statistically significant impact on driving error behaviour which highlights the importance of the present analysis and more specifically the development of a measure that represents overall driving error behaviour instead of individual driving errors variables. 相似文献
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自升式钻井平台安全系统(Safety Instrument System,SIS)是一种保护系统,用于平台事故预警、人员和设备保护,并在安全的前提下实现生产效益最大化。介绍自升式钻井平台上SIS的组成及其关键指标,开展系统功能设计和常用安全度的计算,采用可靠性框图法完成典型安全控制流程的安全度计算。 相似文献
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撞击参数对双层舷侧结构碰撞响应的影响 总被引:8,自引:1,他引:7
深入了解船体结构碰撞损伤特性和能量吸收机制是开展船舶耐撞性优化设计的前提。文章利用显式非线性有限元数值仿真技术对不同撞击条件下的双层舷侧结构碰撞响应进行了系列研究。研究结果表明:撞击位置、撞击角度和撞击速度的改变可能导致不同的碰撞损伤过程或结构损伤变形。 相似文献
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