Highway Bridge under Collision and Explosion

In this chapter, the background of highway bridges under collision is given. The literature review about vehicle and vessel collisions are further presented. Finally, the limitations in the previous work are stated.

This chapter experimentally and numerically examines the dynamic responses of double-column RC piers subjected to horizontal impacts. Firstly, a series of scaled-down horizontal impact tests were performed on five specimens of double-column RC piers, encompassing the impacted pier, its adjacent pier, and the bent cap. These tests varied in terms of the impactor’s velocity and mass, allowing for a comprehensive analysis of the collision process, impact forces, lateral displacements, and failure modes. Then, using validated material models and FE analysis approach, numerical simulations of the five impact test cases as well as an additional twelve collision scenarios are conducted to reveal the whole impact process. Furthermore, based on the pier shear resistance and the energy conversion, the ESF is deduced, and a novel ESF-based performance design or evaluation method for double-column RC pier resisting horizontal impact is further proposed. Finally, the effectiveness of CFRP shear-strengthening of double-column RC bridge piers to resist the lateral consecutive impact is studied. The present work can provide the benchmark test data for validating the FE models, and the determination approach for the ESF-based performance design of bridge piers under vehicular collisions.

Bridge piers designed according to the seismic specifications are likely to be subjected to the accidental vehicular collisions during its service life cycle, while the correlations between the seismic capacity and impact resistance of bridge pier are rarely studied, as well as the practical damage evaluation approach. Aiming to fill this gap, firstly, four double-pier RC bridges, adhering to Chinese seismic design standards and accounting for varying seismic hazard levels, are designed. The corresponding FE models of those designed bridges are established. Utilizing validated material models and numerical algorithms, a total of 108 vehicle-pier collision scenarios are systematically simulated. These scenarios encompassed a range of vehicles, including lightweight pickup trucks, medium-sized Ford 800 trucks, and heavy tractor-trailers, with varying payloads from 3 to 30 tons and collision velocities of 40–120 km/h. Through the analysis of pier deformation and vehicular impact forces, it observed that bridge piers designed with enhanced seismic capacity exhibited lower damage levels, sustaining higher impact speeds from heavy trucks and enduring consecutive cargo impacts. Furthermore, it identified five typical failure modes for seismic-designed bridge piers under vehicular collisions, such as localized pier damage and overall bridge structure collapse. To provide a more comprehensive damage evaluation, a novel explicit damage index that considers factors of pier diameter and shear-span ratio is introduced. This index can be used to assess the damage levels of vehicle-impacted piers and the entire bridge structure, and the corresponding damage evaluation diagrams are given.

In recent years, vehicle-bridge pier collisions have become increasingly prevalent. However, as one of the most importance methods, vehicle collision testing on RC bridge piers remains scarce. Full-scale studies into the impact responses and damage patterns of RC piers have been notably lacking in actual truck collision tests, impeding the advancement of this research domain. To address this gap, a full-scale crash test using a medium-duty truck and an RC single-column pier with a diameter of 1 m was conducted. The truck has a mass of 7.76 t and collided at a speed of 81 km/h. The study extensively examined the damage and failure levels of both the vehicle and the RC pier, capturing critical data such as the displacement, velocity, and acceleration time histories of the truck, as well as the deflection, acceleration, and reinforcement strain time histories of the pier. Furthermore, by analyzing the accelerations of the cargo box and engine, approximate vehicular impact forces were derived and discussed. This work offers invaluable experimental data for vehicular collisions with RC bridge piers, particularly in the calibration and validation of FE models simulating truck collisions, as well as in evaluating the impact resistance of RC bridge piers. To further investigate the dynamic responses of such collisions, a refined FE model of a typical simply supported two-span double-pier RC bridge was developed and validated using the prototype truck-pier collision test and a full-scale drop-weight test on an RC beam. Through numerical simulations of 35 truck-bridge collision scenarios, the dynamic responses and collapse processes were thoroughly analyzed.

This chapter intends to provide an assessment of the dynamic responses and damage/failure of bridge substructure during the vehicle-pier collisions, by utilizing the refined FE models of a heavy-duty truck and a standard simply-supported highway bridge. Firstly, the numerical algorithms and material model parameters that capture both flexural and shear failure modes were validated by simulating two lateral crash tests with flexible impactors. Then, a comprehensive FE model of a representative four-span RC bridge with two-pier bents was established. Furthermore, an existing high-fidelity FE model of a heavy truck was improved and verified by comparing it with experimental data from eccentric and aligned full-scale crash tests. A series of numerical simulations were conducted to study the collision dynamics of the heavy truck and analyze the failure patterns exhibited by the bridge structure. The parametric influences, including truck mass, impact speed, and angle of impact were also investigated. Finally, linear relationships between key parameters such as initial engine momentum, maximum vehicular impact force, 25-ms moving average force, sectional force, and lateral displacement were proposed.

This chapter delves into a numerical analysis of the resilience of highway bridges supported by UHPC piers, designed specifically for seismic resistance, against heavy truck impacts. Firstly, six distinct bridge pier configurations were designed, factoring in two concrete variants, i.e., NSC and UHPC, and three seismic hazard ratings, ranging from earthquake intensities (EI) 7, 8, to 9, in accordance with Chinese seismic design guidelines. The corresponding refined FE models were then established and validated through simulations of drop hammer tests on reinforced NSC and UHPC members. Then, 54 collision scenarios were designed, referencing actual accidents, leveraging the well-validated FE models of a simply-supported double-pier curved highway bridge and a heavy truck. These scenarios were analyzed numerically using the LS-DYNA nonlinear FE analysis software. The study examined the effect of seismic fortification levels and concrete type on vehicular impact forces, the dynamic responses of the entire bridge structure, and the damage and failure patterns of the impacted pier and the bridge in its entirety. This analysis underscores the benefits of employing UHPC piers with seismic design considerations for enhancing bridge structures’ resistance to vehicular impacts. Notably, particular attention was directed towards the safety of NSC-EI7 and UHPC-EI7 piers, as well as the brittle shear failure mode observed in NSC-EI8 piers. To quantitatively compare the collision resistance of bridges supported by NSC and UHPC piers under identical seismic fortification intensities, a performance evaluation method for the entire bridge structure was introduced, grounded on the residual lateral displacement of the impacted pier. This work offers valuable insights for the practical application of UHPC in bridge piers and the practical assessment of the post-collision performance of bridge structures.

The impact force model plays a pivotal role in the design of impact-resistant bridge piers and the rapid evaluation of bridge dynamic behavior under barge collisions. In this chapter, the focus is on this critical model. Firstly, the refined FE models and corresponding material model parameters for barges and piers are validated through impact tests on scaled replicas of Jumbo Hopper barge bows and flexible impactor lateral collision tests on RC columns. Then, the validated numerical algorithm and material models are employed to reproduce a prototype barge-bridge collision test, evaluating the barge bow crushing process, depth, as well as the temporal profiles of barge impact force and pier displacement. Subsequently, to capture the intricate dynamics of barge-bridge interactions, numerical simulations of a total of 54 prototype barge impact scenarios are conducted, accounting for factors such as barge's strain rate, surrounding water, soil-pile interaction, inertial effects of the superstructure, and nonlinear deformations of both the barge and bridge. These simulations vary the impact velocity and mass of barges traversing inland waterways to assess their dynamic behaviors. Finally, based on the FE analysis results, two analytical impact force models are formulated: a triangular distribution and a multiple linear distribution. These models are further validated through an additional nine randomly generated impact cases. The proposed impact force models offer a direct means for rapidly assessing the barge impact resistance of bridge piers, without the need for complex barge modeling.

This chapter focuses on investigating the dynamic responses and damage patterns of a prototype inland double-column RC bridge when impacted by a barge. Firstly, using a horizontal collision testing facility, repeated impacts at varying velocities were performed using a scaled-down Jumbo Hopper (JH) barge bow model on three specimens of double-column RC bridge piers. This test provided valuable insights into the impact force–time histories, the deformation of the barge bow during collision, and the dynamic behaviors of the impacted as well as adjacent piers. Then, to numerically replicate this experimental setup, refined FE models were established for the barge bow-double-column RC bridge pier collision scenario using the LS-DYNA software. The FE analysis approach, including the material models and parameters, was validated by comparing the simulated results with the test data, such as impact forces, barge bow crush depths, lateral displacement histories, and damage patterns observed in the double-column RC bridge pier specimens. Finally, the analysis was extended to a prototype barge-bridge collision scenario, incorporating the material nonlinearity of the bridge pier and superstructure, soil-pile interactions, and the strain-rate effect. This allowed for a deeper discussion of the impact process and damage patterns exhibited by the bridge during collisions. Additionally, the influence of various factors, including impact velocity, barge mass, and oblique angle, on the dynamic behaviors of the prototype bridge were thoroughly examined.

This chapter endeavors to establish a reliable and efficient FE modeling technique for barge-bridge collision simulations, leveraging the explicit dynamic FE analysis software LS-DYNA. Firstly, a coupled high-resolution FE model (HRM) is formulated for the Taiyangbu Bridge, simulating its response to barge side impacts. The bridge's collapse mechanisms are numerically replicated, aligning the predicted failure patterns and collapse sequences with actual accident footage. To enhance computational efficiency, a suite of simplified bridge FE models is developed, including two superstructure models (a simplified shell model and an equivalent mass model) and two substructure models employing fiber-based beam elements. These models undergo comparative numerical simulations, leading to the identification of the optimal simplified FE modeling approach for bridges through comparisons with the HRM's predictions. Then, a decoupled dynamic impact force modeling technique is introduced, replacing the intricate barge model. This approach captures the distribution of dynamic impact forces along the pier's height and perimeter. A simplified simulation strategy for barge-bridge collision analyses is proposed, integrating the optimized simplified FE modeling for bridges and the decoupled dynamic impact force modeling. Finally, the applicability of this simplified strategy is validated for head-on collision scenarios. This work offers an efficient numerical simulation method for evaluating and designing bridges’ resistance to barge impacts, thereby contributing to the safety and durability of inland waterway bridges.

In this chapter, the background of highway bridges under explosions is given. The literature review about blast-resistant analysis and design methods for highway bridges are further presented. Finally, the limitations in the previous work are stated.

The terrorist attacks on bridges have been increasing dramatically in recent years. Under explosions, piers will lose partial axial bearing capacity, resulting in the partial or complete collapse of the whole bridge. The dynamic behaviors and axial capacity of the RC bridge piers with seismic design subjected to near-field explosion of vehicle bombs were numerically concerned in this chapter. Firstly, the erosion algorithm, Fluid–Structure Interaction method and the multi-material Arbitrary-Lagrangian–Eulerian algorithm in LS-DYNA, was adopted and a reliable finite element analysis (FEA) approach was established. The FEA approach was validated by comparing with the blast overpressure, column deflection, spalling range of concrete cover, and residual axial bearing capacity of three groups of tests. Secondly, explosion scenarios for vehicle bombs on bridge piers were designed to meet three different earthquake intensity levels (EI7–EI9) in accordance with Chinese specifications JTG/T 2231-01-2020 for prototype bridge piers and FEMA-428 for sedan bombs. Based on residual axial bearing capacity, the blast resistance of the above three seismically designed bridge piers was evaluated under two typical vehicle bombs, and the effects of seismic detailing were quantitatively assessed. On the basis of seismic design and detailing provisions, a low-complexity design approach was recommended. This study provides useful references on RC bridge piers under close-in explosions of vehicular bombs, such as damage assessment, blast-resistant design, and further strengthening.

The bridge pier, when destroyed by accidental or planned explosions, will experience a reduction in its ability to bear weight along its axis. This can lead to the partial or full collapse of the whole bridge structure. This chapter focuses on developing blast-damage evaluation and blast-resistant design methods for bridge piers. It investigates the dynamic behaviors and residual axial load-bearing capacities of RC piers that are exposed to contact explosions. Initially, a total of five RC piers with a circular cross-section and a 1/2-scale model are constructed. Each pier has a height of 3 m and a diameter of 450 mm. The field contact explosion test is performed on three pier specimens using TNT charges of 0.5 kg, 1.0 kg, and 2.0 kg, respectively. Subsequently, the three piers that have been damaged by an explosion, together with two undamaged piers, are transferred to the laboratory for the purpose of conducting experimental tests on their ability to withstand axial loads. These tests are carried out using a hydraulic testing equipment. The test data acquired includes the incident overpressure-time histories, quantitative post-blast damage profiles of piers, and the complete curves of axial force–displacement. Furthermore, accurate finite element models are established for both the contact explosion and subsequent axial compression testing. The numerical simulations are conducted using the multi-material Arbitrary-Lagrangian–Eulerian method, Fluid–Structure Interaction, and erosion methods implemented in the LS-DYNA FE program. The accuracy of the material model and finite element analysis technique is thoroughly confirmed by comparing the numerical simulated results with the test data. In addition, a set of numerical simulations is performed on the prototype bridge piers that are designed to withstand seismic activity. The purpose of these simulations is to investigate the effects of different parameters on the damage mode, residual ALC, and the associated damage index of the piers. After conducting parametric studies, a number of blast-resistant design recommendations are put forward for the prototype RC bridge piers to protect against contact explosions.

Deliberate and unintentional explosions are likely to cause damage to as-built bridge piers. Therefore, it is necessary to take suitable steps to rehabilitate or repair piers that have been damaged to varying degrees. The objective of this chapter is to assess the efficacy of the fiber-reinforced polymer rehabilitation approach on post-blast piers through experimental and numerical analysis. Initially, the researchers performed contact explosion, CFRP rehabilitation, and axial compression testing on 1/2-scale RC pier specimens. The blast test recorded the overpressure-time histories and damage profiles of the specimens, whereas the axial compression test recorded the axial force–displacement curves, strain–time histories of FRP, and the specimens’ damage modes. Additionally, a finite element analysis method is suggested and empirically verified to replicate the interactions between blast waves and piers, as well as the dynamic responses of RC piers under explosions. This method also evaluates the axial compressive behavior of undamaged piers, piers after being subjected to blasts, and piers rehabilitated with FRP materials after blasts. This chapter further investigates the damage patterns caused by explosions and the ability of a prototype bridge pier constructed to withstand seismic activity to withstand axial forces after an explosion. It is advised to use the FRP rehabilitation plan, which includes different kinds, heights, and layers, to restore the axial capabilities of post-blast prototype piers. This is specifically recommended for three typical explosion risks stated by the Federal Emergency Management Agency. This chapter can serve as a valuable resource for the repair of RC bridge piers using FRP following explosions.

UHPC-FST pier columns are highly suitable for use in bridge engineering due to their exceptional structural and constructional capabilities. However, they are vulnerable to car bomb assaults when located in close proximity. This chapter intends to analyze the dynamic behavior of UHPC-FST specimens under close-in explosion with a significant charge weight, using both field explosion tests and numerical modelling. The initial step was conducting a field explosion test on five UHPC-FST specimens that were scaled down to 1/4 of their original size. The specimens were subjected to a TNT charge weighing 25 kg, and the test was carried out at scaled distances ranging from 0.10 to 0.17 m/kg^1/3. The objective of the test was to evaluate the effects of standoff distance and burst height. The UHPC-FST demonstrates exceptional blast resistance as the specimens were able to preserve their structural integrity despite intense blast loads. Furthermore, a comparison was made between the distinct dynamic characteristics of UHPC-FST samples acquired from current and past explosion experiments using both high and low charge weights. Additionally, in order to carry out the necessary numerical simulation, the parameters of the K&C model were thoroughly calibrated for UHPC. Furthermore, the FE models of the field explosion test on UHPC-FST specimens were established using the commercial software LS-DYNA. Ultimately, the calibrated K&C model parameters and the established FE model were thoroughly validated by comparing the predicted damage mechanism and global deflection of UHPC-FST specimens with the test findings. This chapter can offer valuable resources for the design and assessment of the blast resistance of UHPC-FST.

The deliberate and unintentional explosions pose a significant risk to vital political and economic infrastructures. The current study focuses on analyzing the model and design method for reinforced concrete beams and columns subjected to blast loads, taking into account both the local and global reactions of the members. In this chapter, the damage levels of blast loaded RC beams/columns are classified from a local response perspective. This classification is based on a total of 119 field explosion tests, which categorize the damage levels as no damage, spalling, and breach. Through these tests, the critical scaled distance that distinguishes between local and global responses of RC members is experimentally determined to be 0.78 m/kg^1/3. A logarithmic scaled thickness against logarithmic scaled distance design chart is displayed to analyze local reactions in the field explosion test. Furthermore, in terms of global reactions, a refined SDOF model is developed that takes into account the direct shear, flexural-shear, and flexural responses of RC elements. This model comprehensively considers the nonuniform distribution of blast load, the effect of strain rate, the P-Delta effect, the compressive arching effect, and the rigid body rotation of supports. In addition, the validity of the proposed SDOF model is confirmed by seven sets of explosion tests conducted on RC beams and columns. These tests involve both simply-supported and fixed-end limits and evaluate the direct shear, flexural-shear, and flexural responses. Ultimately, a comprehensive performance-based blast-resistant design technique is put forward, serving as the basis for an autonomously created code called Tongji-RC-Blast. This code functions as a dependable and efficient tool for assessing and designing blast-resistant structures, catering to the needs of protective engineers and designers.

Piers are vital structural elements that provide support to the superstructure of a bridge. However, they are vulnerable to both deliberate and accidental explosions due to their easy accessibility. The explosion's impact on the pier might potentially lead to the complete collapse of the bridge, resulting in significant loss of life and economic damage. Therefore, it is imperative to include blast-resistant design measures for the bridge pier. The current study focused on analyzing the model and design technique for blast-loaded RC piers. The study specifically included both the direct shear and flexural responses. Initially, a series of six field ground explosion tests were conducted on 1/5-scale circular and square RC columns. These tests involved the use of TNT charges with scaled lengths ranging from 0.86 to 1.22 m/kg^1/3. Subsequently, numerical simulations were performed using the newly developed Structured Arbitrary-Lagrangian-Eulerian (SALE) solver. The accuracy of the FE analysis method was confirmed by comparing the experimental incident and reflected overpressure-time histories acting on the periphery of the pier. The deviations for most measuring points were found to be less than 20%. Subsequently, a total of 176 explosion scenarios were simulated using numerical methods. A model was developed to determine the distribution of blast loading on the pier caused by ground explosions. This model takes into account the shapes of the pier cross-sections (circular and square), the diameter or edge length of the pier (ranging from 0.2 to 1.6 m), the scaled distances of the explosive charge (ranging from 0.3 to 2.3 m/kg^1/3), as well as the effects of blast wave reflection and diffraction by the pier. In addition, an analytical model based on Timoshenko beams was developed to represent a system with multiple degrees of freedom (MDOF). This model was verified by comparing it to both existing explosion tests on RC columns and more accurate numerical simulations of bridge piers subjected to blast loads. The differences between the model and the tests or simulations were found to be less than 5%. In conclusion, a design technique that is resistant to blasts was shown. This procedure includes the blast loading distribution and MDOF models mentioned before. It offers a dependable and effective tool for evaluating and designing bridge piers to withstand blasts.

Throughout its entire lifespan, bridge constructions are susceptible to possible risks posed by military conflicts, terrorist assaults, and accidental explosions. The available research on the damage mechanisms and dynamic responses of whole reinforced concrete girder bridges under explosion loads is quite restricted. This issue is addressed by conducting high-reliability numerical simulations. The material models and corresponding parameters, as well as the numerical simulation algorithms, are sufficiently verified by comparing them with the experimental overpressure- and acceleration-time histories, as well as the damage modes from the explosion tests on 1/5 scaled two-span girder bridges. The Federal Emergency Management Agency has identified three levels of potential explosive threats: suitcase, sedan, and small moving van. These threats correspond to different cubic TNT explosive masses: 23 kg, 454 kg, and 4536 kg, respectively. The purpose of this analysis is to examine the damage modes and dynamic responses of a typical four-span prototype RC girder bridge under both below-deck and above-deck explosion scenarios. In addition, we analyzed the ability of both simply-supported and continuous girder bridges to withstand blasts, and we determined the minimum distances required for safety.

The safety of bridges is being jeopardized by a growing incidence of deliberate and inadvertent explosions. Numerical simulations were used to conduct a blast-resistant evaluation for a simply-supported RC girder bridge under below-deck explosions in this chapter. Firstly, the proposed FE analytical technique was confirmed by comparing it with three sets of field explosion tests conducted on reduced-scale RC piers/columns and bridges. Next, a precise FE model of a standard two-span prototype bridge was created, and 24 explosive scenarios were simulated using numerical methods. These scenarios were based on three specific explosion sources identified by the Federal Emergency Management Agency. Further investigation was conducted to analyze the impact of different pier designs on both the localized damage of the pier and the overall reaction of the bridge. Ultimately, a direct correlation was established between the reduction in mass of the pier and the vertical displacement of the bridge deck. As a result, it is now possible to assess the traffic capacity of a post-blast bridge by analyzing a single pier instead of the entire bridge.

Bridge piers are crucial elements that provide support for the superstructures of bridges. The blast resistance of piers has received significant attention due to the increasing number of intentional and unintentional explosive assaults on bridge structures. However, the majority of the current research is on analyzing the dynamic response of a single pier to blast-induced forces, without taking into account the redundancy of the bridge or the actual traffic performance of the entire structure. The objective of this chapter is to present a design strategy for RC bridge piers that focuses on performance and resistance to explosions caused by vehicle explosives. The distribution model of blast impulse on bridge piers is provided, taking into account both the ground reflections and diffractions of piers. This model is based on a verified FEA technique. Subsequently, the accuracy of the fiber beam element-based model and the blast impulse distribution model mentioned above was confirmed by the dynamic monotonic loading test and the explosion test conducted on an RC frame column. Moreover, a simpler prototype of an RC bridge, based on fiber element beams, was created and used for conducting parametric tests. The response surface methodology was utilized to develop a performance-based blast-resistant design procedure for three specific design basis threats outlined in FEMA: cargo van bomb, small moving van bomb, and moving van bomb. The relative vertical displacement of the mid-bent was used as the performance index in this proposed design procedure.