Gary R. Consolazio

Nonlinear analysis of barge crush behavior and its relationship to impact resistant bridge design

Abstract Bridge structures crossing navigable waterways must not only be designed to resist gravity, wind, and earthquake loads, but must also be capable of resisting ship and barge collision loads. Design specifications used both in the US and internationally employ empirical models of vessel crush behavior to produce codified procedures for computing equivalent static design loads due to vessel impact. In this paper, the ADINA finite element code is used to compute force-deformation relationships for several hopper barge crushing scenarios. Results obtained from the nonlinear finite element crush analyses are then compared to empirical crush models found in bridge design specifications.

MEASUREMENT AND PREDICTION OF PORE PRESSURES IN SATURATED CEMENT MORTAR SUBJECTED TO RADIANT HEATING

Evaluation of airfield pavement degradation and fire safety evaluation of concrete structures are examples of situations that involve moist porous media (concrete) subjected to severe thermal loadings. When a saturated (or partially saturated) porous medium is subjected to a high temperature heating source, pore pressures large enough to initiate explosive spalling can be developed within the pore spaces of the material. The level to which these pore pressures ultimately rise depends on the saturation and permeability of the medium as well as the rate at which heat flows into the material. In this paper, experimental and numerical studies involving the measurement and prediction of pore pressures in porous media are presented. Pore pressure data are presented for experimental tests in which saturated cement mortar specimens were subjected to high temperature radiant heating conditions. A numerical modeling technique is then presented and is used to numerically simulate the experimental work. Close agreement is shown between the pore pressures and temperatures recorded experimentally and those predicted through simulation.

Barge Bow Force-Deformation Relationships for Barge-Bridge Collision Analysis

The AASHTO specifications pertaining to bridge design for barge collision loads use a static impact force determination procedure. Incorporated within that static procedure is a force–deformation relationship that represents barge bow stiffness. Recently developed dynamic vessel collision analysis techniques, which include mass-related components of bridge response, also require the use of a force–deformation relationship (or crush curve) to model barge bow stiffness. Whether static or dynamic analysis techniques are used, the vessel crush curve largely governs impact forces and, therefore, plays a critical role in quantifying structural response to impact loads. The basis for the AASHTO crush curve is reviewed, and new crush curves are proposed on the basis of finite element crush simulations of multiple high-resolution barge bow models. The barge models developed for this study are based strictly on structural vessel plans obtained from U.S. barge manufacturers and consist of the two most common types of barges traversing U.S. inland waterways (hopper and tanker). Recommended crush curves are then proposed for use in barge–bridge collision analysis and design.

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.

ITERATIVE EQUATION SOLVER FOR BRIDGE ANALYSIS USING NEURAL NETWORKS

In this paper, a technique for enhancing finite-element analysis equation solvers for particular problem domains (particular classes of structures such as highway bridges) is presented. The technique involves merging artificial neural networks, used as a domain knowledge-encoding mechanism, together with a preconditioned conjugate gradient iterative equation-solving algorithm. In the algorithm, neural networks are used to seed the initial solution vector and to precondition the matrix system using customizable and trainable neural networks. A case study is presented in which the technique is applied to the particular domain of flat-slab highway bridge analysis. Analytical load-displacement data is generated using finite-element analyses and subsequently used to train neural networks. Acting collectively, the neural networks approximately predict displacement patterns for flat-slab bridges under arbitrary loading conditions.

Simplified Dynamic Analysis of Barge Collision for Bridge Design

The AASHTO design provisions for barge impact on bridges spanning navigable waterways use a static force approach to determine structural demand on bridge piers. Recently, however, full-scale experimental dynamic tests of barge impact have indicated that consideration should also be given to additional forces generated from dynamic effects. Specifically, mass-related inertial forces generated by the superstructure of a bridge can restrain underlying pier columns and lead to dynamic amplification of column design forces. This paper presents an algorithm for performing simplified, coupled dynamic barge impact analysis for bridge structures. This type of analysis yields structural design forces, with dynamic amplifications included, on the basis of characteristics of the design impact condition (barge mass and speed). Results from the proposed simplified analysis method are validated using full-scale experimental test data and are compared with results obtained from full-resolution analyses for a variety of barge impact energies and bridge types.

Equivalent Static Analysis Method for Barge Impact-Resistant Bridge Design

In the United States, barge impact-resistant bridge design typically involves static application of code-prescribed impact loads. However, the existing static analysis procedure neglects crucial dynamic effects in the impacted bridge. Recent experimental and analytical studies have uncovered important impact-related dynamic amplification of pier member demands, primarily stemming from superstructure inertial effects. These studies have focused on the use of dynamic structural analysis as a means of accounting for dynamic amplification. Although time-domain dynamic analysis techniques are capable of accurately predicting amplified member design forces, such techniques may not be warranted during preliminary design iterations when detailed structural parameters have not yet been established. In this paper, a static analysis procedure is developed that emulates pier response modes that arise during dynamic barge impact events. The proposed method provides a simplified means of approximating dynamic amplification effects and is shown to produce conservative predictions (in relation to dynamic analysis) of both pier and foundation design forces.

Dynamic Amplification of Pier Column Internal Forces Due to Barge–Bridge Collision

In the United States, bridge design provisions for waterway vessel collision typically involve static application of code-prescribed impact loads. However, results from full-scale experimental impact tests have revealed that significant mass-related inertial forces can develop in affected piers because of the overlying superstructure. In part on the basis of these findings, a dynamic (time history) analysis technique was previously developed; it predicts both impact load and structural response. In the current research, the dynamic analysis technique is combined with recently developed barge force–deformation relationships and a simplified bridge modeling technique to conduct a detailed investigation of collision-induced dynamic amplification phenomena. Design forces are quantified for a wide range of bridge types by using dynamic and static analyses. For each bridge considered, dynamic amplifications are numerically quantified by comparing dynamic to static predictions of pier column demand. Significant amplification effects are consistently found among the barge–bridge collision simulations conducted, indicating that dynamic phenomena should be accounted for in bridge design.

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.

Probability of Collapse Expression for Bridges Subject to Barge Collision

Accounting for waterway vessel collision is required in the structural design of bridges spanning navigable waterways. During collision events, massive waterway vessel groups such as barge flotillas are capable of dynamically transmitting horizontal forces to impacted bridge components. Furthermore, collision-induced forces can be sufficient to collapse piers or roadway spans in the vicinity of the impact location. If collapse takes place, economic loss is suffered because of subsequent traffic rerouting and bridge replacement costs. Additionally, fatalities may occur if the roadway is occupied during or shortly after collapse. This paper focuses on the development of a probability of collapse expression for bridge piers subject to barge impact loading, where the relationship can be readily integrated into existing bridge design methodologies. The expression is developed by employing probabilistic descriptions for a multitude of random variables related to barge traffic characteristics and bridge structures in conjunction with nonlinear dynamic finite-element analyses of barge-bridge collisions. Highly efficient, advanced probabilistic simulation techniques are necessarily incorporated into the barge-bridge collision analysis framework to allow feasible estimation of structural reliability parameters. These parameters facilitate the formation of an expression that, in turn, bridge designers can use to estimate probabilities of structural collapse attributable to barge collision, without performing probabilistic analyses.