How Hurricane Katrina influenced the design of hurricane protection and risk reduction systems and national approaches to risk and resilience. Part 2: Designing the Hurricane and Storm Damage Risk Reduction System and resulting long-term engineering guidance and practice changes

Following Hurricane Katrina, the US Army Corps of Engineers, supported in part by the risk and reliability analysis conducted by the Interagency Performance Evaluation Task Force (IPET), made a major shift from ‘protection’ to ‘risk reduction’ as the principal goal in flood mitigation. The mitigation of the flood risk in Southeast Louisiana was embodied in the design and construction of the ‘Hurricane and Storm Damage Risk Reduction System’, the post-Katrina initiative for New Orleans flood mitigation. It also spawned a major overhaul of many of the Corps of Engineers’ technical guidance and engineering practice documents, incorporating risk as a key measure in the planning and design processes. The criteria applied for the design of the HSDRRS are discussed, with summaries of the associated major changes in Corps engineering guidance and practice relevant to flood mitigation.

Dynamic modeling and analysis of vertical vibration reduction system for passenger train

Based on wheel-rail impact vibration and considering the body stiffness and natural damping, this paper builds a four-degree-of-freedom vibro-impact system model for passenger train’s vertical vibration reduction system. The Poincaré map of the system is determined by the analytic solution of the system derived from the motion differential equation of the multi-degree-of-freedom vibro-impact system combined with Newton's second law. It is found that the fork bifurcation, Hopf bifurcation and other dynamical behavior leading to Chaos when the system parameters are changed. On this basis, the dynamic parameters of the train are optimized to avoid chaos in the train operation, reduce the vertical vibration of the train, improve the stability and comfort of the train operation, and provide the theoretical basis for the active vibration reduction design of the train.