Michael T. Davidson

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.

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.

Multi-Barge Flotilla Impact Forces on Bridges

Bridge piers located in navigable inland waterways are designed to resist impact forces from barges and flotillas in addition to other design considerations (e.g., scour, dead and live loads, etc.). The primary design tool for estimating these forces is the AASHTO Guide Specification which provides a simple hand calculation method for determining an “equivalent impact force”. The simplicity comes at a cost of excluding the effect of the pier shape, impact duration, and interaction between barges in a flotilla. The objective of this report is to present a hand calculation method for determining barge or flotilla equivalent static impact forces on bridge piers. The primary advantage of this approach lies in its incorporation of pier geometry, interaction between barges, and impact duration. The proposed method is derived from the conduct of hundreds of finite element dynamic simulations of barges and various flotilla configurations impacting rigid and flexible rectangular and circular (or rounded end) bridge piers at different velocities. Results are presented and compared with ones derived from the AASHTO method and detailed finite element modeling. The results generated by the proposed method compare very well with ones derived from the FE modeling, while the AASHTO results are up to twice as large as one from the proposed method for the examples presented in this report.

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.

Response-Spectrum Analysis for Barge Impacts on Bridge Structures

AbstractBridge structures that span navigable waterways are inherently at risk for barge collision incidents and therefore must be designed for impact loading. Current U.S. barge impact analysis procedures consist primarily of static load analysis methods that do not explicitly account for dynamic effects in barge–bridge collisions, and thus are not ideally suited to designing bridge structures to resist barge impacts. Therefore, the development of dynamic-analysis methods for estimating the responses of bridge structures to barge collisions is warranted. Dynamic-analysis procedures that use numerical time-integration techniques are capable of capturing pertinent dynamic effects but often yield voluminous amounts of time-varying results that must be post processed for use in design. In contrast, response-spectrum analysis (RSA) procedures are capable of directly producing maximum response parameters that are most pertinent to structural design. In this paper, an RSA procedure is proposed for use in barge ...

Fire Impact and Passive Fire Protection of Infrastructure: State of the Art

AbstractBuilt infrastructure in the United States is generally susceptible to damage or collapse if subjected to severe fire conditions, such as those associated with the burning of a fully loaded gasoline tanker truck. Because of the importance and heavy use of transportation systems within the United States, it is critical that susceptibilities to fire damage are investigated and mitigated to reduce the potential for substantial life-safety and economic losses. The need for infrastructure fire protection is heightened by the frequency of collapse of infrastructure components (e.g., bridge superstructures) as part of severe fire incidents. However, fire protection of infrastructure remains a developing area. Presented in this paper is the state of the art in passive fire protection of transportation structures. More specifically, the impacts of high-intensity fires on existing infrastructure and commonly used structural materials are reviewed. Additionally, design standards that provide means of assessin...

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.

Development of an Improved Probability of Collapse Expression for Bridge Piers Subject to Barge Impact

Structural design for waterway vessel collision is required for bridges crossing navigable waterways. When collision events occur, vessel impact forces can be sufficient to cause collapse of the pier or roadway in the vicinity of the impact location. Impact-induced collapse events generally result in numerous fatalities, traffic rerouting, and substantial bridge repair costs. The research presented here focuses on the means by which a probability of collapse expression can be developed for bridge piers in the event of barge-bridge collisions. The expression development is facilitated by employing probabilistic descriptions for a multitude of random variables related to barge and bridge structures. Through joint use of statistical simulation (e.g., Monte Carlo methods) and vessel collision analysis techniques, the probability of collapse—and furthermore, the proximity to applicable limit states— can be quantified for a wide array of bridge types. The structural reliability parameters can then, in turn, be used to form a revised probability of collapse expression for bridges subject to barge collision.