Jae H. Chung

Impact simulation and full scale crash testing of a low profile concrete work zone barrier

The development of a new low profile portable concrete barrier system for use in roadside work zone environments is presented. By making extensive use of non-linear dynamic finite element impact simulation, several cycles of concept refinement were carried out using simulation rather than expensive full scale crash testing. Issues such as ensuring stable vehicle redirection during impact, properly accounting for frictional effects (and associated energy dissipation), and monitoring system energy parameters are discussed together with corresponding example simulations. Results obtained from full scale crash testing of the barrier validate the simulation methodology and demonstrate successful barrier performance.

Finite-Element Analysis of Fluid-Structure Interaction in a Blast-Resistant Window System

This paper describes the development of a finite-element model capable of representing a blast-resistant flexible window (flex window) system developed by the Air Force Research Laboratory/Airbase Technologies Division. Computational fluid-structure interaction finite-element simulations are used to develop an improved understanding of the manner in which fluid phenomena, such as air compression and flow, affect the behavior of the flex-window system under blast loading. Compressible airflow interacting with a flexible thin-shell structure of the flex window (transient air-window panel interaction phenomena) is found to significantly influence system performance. The influences of shock wave propagation and fluid venting inside the damping chamber of the flex-window system are quantified and the influences of such phenomena on panel deflections, deformations, and internal forces are presented.

Computing the responses of bridges subject to vessel collision loading using dynamic analysis

Accounting for the effects of waterway vessel collision is a necessary consideration in the analysis of bridge pier structures that span navigable waterways. During collision events, impact forces are transferred along the interface between the impacting vessel and the impacted pier component. Vessel collision forces are dynamic in nature, and in turn, are coupled with dynamic bridge response. Further, the maximum magnitude of the impact forces is sensitive to the geometry of the impacted pier component. This coupling effect in vessel-bridge collisions is highlighted in this paper. Robust finite element analysis models are developed and used for a selected bridge case to illustrate the advantages of incorporating dynamic and shape-specific phenomena. Using ordinary computational resources, the bridge analysis software FB-MultiPier is showcased as a means of rapidly assessing dynamic bridge response to vessel collision loading.

Discussion of “Development of a Substructure Instrumentation System at the New I-10 Twin Span Bridge and Its Use to Investigate the Lateral Behavior of Batter Piles”

The interpretation of the load test results presented in the paper may mislead design engineers to an unconservative estimation of design loads for bridge subfoundations. Lack of error checking in the authors’ finite element analysis (FEA) model might have resulted in invalid assessment of the validity of the FB-MultiPier FEA software program.

Design of a low-profile barrier for curved alignments using finite element impact simulation

Publisher Summary This chapter presents a new low-profile portable concrete barrier intended for use in roadside work zone environments through the use of nonlinear-finite-element-impact simulation. Design decisions are based on virtual testing of the barrier system done through impact simulation rather than costly iterative crash testing. A single set of crash tests can validate compliance with pertinent crash worthiness standards. The primary innovation in the barrier design is the ability to accommodate both horizontal and vertical roadway curvatures while still maintaining a low profile and preserving the ability to redirect errant vehicles. Work zones represent a type of roadside environment, in which special attention must be given to barrier height if adequate safety is to be provided both to the traveling people and to work zone personnel. While tall profile barriers provide excellent redirection and traffic separation capabilities, they can also obscure a drivers field of view and lead to accidents.

Moisture movement and heat flow in reinforced concrete columns exposed to fire

Publisher Summary This chapter describes a finite difference model that is used for numerical prediction of hygro-thermal behavior in reinforced concrete columns exposed to fire. Multidimensional simulations can be performed under two different fire conditions—ASTM E119 and ASTM E1529. The spalling of intensively heated concrete elements is associated with the build-up of large pore pressures combined with the development of steep temperature gradients in concrete structural elements. Steel reinforcement can substantially influence both the moisture movement and temperature distribution in reinforced concrete (R/C) elements. In modeling simultaneous flow of heat and fluids through concrete—the effects of moisture movement on key flow parameters, such as permeability and conductivity, are included. Thermal conductivity within concrete can be modeled as a function of degree of saturation during the transient hygrothermal process. T0UGH2 is an excellent tool for the numerical analysis of continuum phenomena of mass and heat transfer in concrete.