An Introduction to Investigative Efforts Related to Impact Events Involving Concrete Structures
Presented By: Mark Weaver
Affiliation: Karagozian & Case, Inc.
Description: In light of the barge impact disaster involving Baltimore’s Key Bridge in early 2024, this session highlights recent advances in the analysis and design of concrete structures for impact loads. Engineers with an interest in impact and penetration response phenomenology should attend. The learning objectives attached with this session are: (1) to learn common scenarios where impact involving concrete structures is a design concern and (2) to understand what analytical methodologies are available and presently being used to address these scenarios. This segment of the session will introduce the session and provide context for the speakers that follow.
Dynamic Compression Experiments for Simulation of Contact Forces Transmitted through Damaged Concrete During Extreme Impact Loading Events
Presented By: Brad Durant
Affiliation: NAVFAC Engineering and Expeditionary Warfare Cente
Description: Accurate prediction of impact forces generated between contacting bodies during extreme impact loading events is required to develop new designs and measures to mitigate the damaging effects. This presentation discusses dynamic compression experiments, and the corresponding finite element analysis simulations, conducted on confined concrete samples as part of an effort to quantify the force transmitted through damageable materials. The purpose of the experiments was to develop a database for improving and validating numerical models for problems involving dynamic indentation and penetration, where the contact forces developed between a relatively rigid indenter and a broad range of damageable materials is an important phenomenon. The resulting database and numerical studies demonstrate that these dynamic compression experiments can provide data that numerical methods developers, engineers, and designers can use to benchmark high-fidelity simulations for impact events resulting in penetration and indentation for concrete materials.
Impact Resistance Performance of Post-Tensioned and Reinforced Concrete Walls
Presented By: Thomas Kang
Affiliation: Seoul National University
Description: Structures are subjected to various impact conditions, each capable of causing distinct and often unpredictable responses. Simulating these conditions experimentally is expensive and technically complex due to intricate setups and the need for precise instrumentation. This emphasizes the importance of well-structured, high-quality datasets to ensure reliable experimental outcomes. In this study, a comprehensive dataset of 1,719 experimental data points was compiled to evaluate the accuracy, practical relevance, and safety margins of 19 penetration prediction formulas. To further enhance the dataset and better understand concrete wall behavior—particularly in nuclear power plant contexts—six high-velocity impact tests were conducted on post-tensioned and reinforced concrete walls. These tests used both deformable and non-deformable projectiles, offering a broad view of impact responses. The study identified distinct failure modes in post-tensioned walls. Finite element analysis (FEA) was also used to investigate the mechanisms behind local damage, showing that boundary conditions significantly affect damage extent, with post-tensioned walls providing superior resistance to penetration and perforation.
Investigation of Inertial Effect in Full-Scale Bridge Prestressed Concrete Girders Under Lateral Impact Loads
Presented By: Mohamed ElGawady
Affiliation: Missouri S&T
Description: Understanding the dynamic response of prestressed concrete (PC) girders under lateral impact is crucial for assessing their resilience against extreme loading events, such as overheight vehicle collisions with bridge structures. This study investigates the inertial forces and vibrational behavior of four full-scale 46-foot-long Missouri Department of Transportation (MoDOT) Type II PC girders subjected to controlled lateral impacts using a custom-designed 60-foot elevated track and a 7000-lb impact bogie, with velocities up to 23 ft/sec. The experimental setup varied impact energies by adjusting the bogie mass (4300–7000 lb) and boundary conditions, including unrestrained, top-flange-restrained, and intermediate-diaphragm configurations. Accelerometers along the girder span captured high-frequency acceleration time histories, revealing peak accelerations from 712 g to 1441 g and oscillations resembling seismic motion. Analysis using the FIP-CEB framework yielded high inertia force ratios a ranging from 0.92 to 0.99, indicating that inertial effects dominate resistance, with minimal support contribution. The study establishes a linear relationship between peak impact force which ranges from 504 kips to 656 kips and acceleration, influenced by stiffness and effective mass, and highlights the limitations of current AASHTO LRFD guidelines. These findings underscore the need for updated design criteria to enhance the impact resistance of PC girders.
Debris Impact on Pile-Supported Waterfront Concrete Structures
Presented By: Ming Liu
Affiliation: NAVFAC - EXWC
Description: Waterfront structures such as piers and wharves are often supported by piles. Since coastal flooding has become more frequent and severe due to extreme weather events, these pile-supported waterfront structures are more vulnerable to increased flooding flow velocities and associated debris impact. Historically, several approaches, including constant stiffness approach, impulse-momentum approach, and work-energy approach, have been used to estimate the impact force and duration that are a function of flow velocity and debris properties such as mass, shape, and material type (e.g. driftwood, concrete, and steel). This presentation provides a general description and discussion of the design of concrete structures under debris impact loading, and focuses on three features related to pile-supported waterfront structures:
1) Estimating the probability that a piece of debris can hit a small-diameter pile or a group of piles in terms debris size, shape, and orientation, which could improve the development of fragility curve of pile-supported concrete structures subject to debris impact.
2) Assessing the uncertainties associated with current impact load predictions through fluid-debris-structure interaction tests.
3) Performing the site hazard assessment for shipping containers, ships, and barges.
Experimental Investigation of Ultra-High Performance Concrete Panels Under Tornado Impact Loads
Presented By: Hannah Tzabari
Affiliation: National Cement
Description: Tornado events pose a threat to millions of people living in the tornadic-prone areas of the United States. Although many tornado shelters and safe rooms are commercially available that satisfy the extreme loading conditions required by the International Code Council and National Storm Shelter Association, there is a need for a simple yet safe design which can be easily assembled and used for multiple purposes.
New engineering materials, such as ultra-high performance concrete (UHPC), have the potential to improve tornado shelter options and save lives. This study experimentally investigates the performance of thin UHPC panels subjected to impact of standard wood 2x4 projectiles, following the requirements of ICC/NSSA 500, the leading standard on storm shelter design. 1.25-inch-thick and 1.625-inch-thick UHPC panels were cast and impacted with 15-lb wood projectiles at speeds ranging from 50 mph to 100 mph to maintain a similar impact-energy-to-panel-mass ratio. The failure response of each panel was characterized by excessive flexural deflection or punching shear. In the case of excessive deflection, a single-degree-of-freedom dynamic displacement model describes the motion of the panel during impact and the profile of the maximum deflection. In the case of punching shear, a modified equation from ACI 318 predicts the capacity of the panel.
The results of the impact testing show UHPC is a promising material for future tornado shelters: UHPC panels with half the thickness of a traditional concrete shelter can be built for a similar or lower price, creatively integrated into homes, and increase accessibility of the tornado shelter for residents.