Journal of Bridge Engineering

The current design guidelines for concrete barriers have not been updated much since the 1990s despite (1) several experimental, analytical, and computational studies that addressed both the demand and capacity sides of the design problem and (2) substantial increases in the velocity and weight of certain types of trucks specified in the crash testing guidelines that led to significantly higher impact demands than in the previous times. This state-of-the-art paper critically reviews the findings of previous studies and critiques their proposed design models. It highlights the lack of consensus regarding the failure mechanisms that should be considered in the design of concrete barriers and contrasts the results of a variety of proposed models with current design guidelines. Based on the review, recommended models for barrier design are proposed to aid in future revisions of the design specifications. Future research directions are also identified and discussed.

In this study, three reinforced concrete (RC) columns with and without corrosion and different reinforcement details are tested under lateral cyclic loading. One of these columns is well-confined to represent modern RC bridge piers that are designed according to the current seismic design codes, and the second column has the same detail with corrosion damage. The third column is a lightly confined corroded column to represent aging RC bridge piers that are not designed to the current seismic design codes. The experimental results showed that corrosion significantly impacts the ductility loss more than the strength loss of the tested corroded columns. In addition, although the uncorroded column was designed according to the current seismic design code, severe inelastic buckling in the vertical bars was observed during the cyclic tests.

Many of the current fatigue design specifications for cross frames, especially those in composite steel bridge systems, have primarily been based on computational studies and component-level laboratory experiments. To fully understand the behavior of cross frames when subjected to in-service truck traffic and to critically evaluate legacy design provisions, in-service field monitoring of cross frames in various composite systems is important. Therefore, select cross frames in three bridges in the greater Houston area were instrumented with strain gage sensors—one straight bridge with normal supports, one straight bridge with skewed supports, and one horizontally curved bridge with radial supports. For each bridge, rainflow counting techniques and other postprocessing procedures were implemented for a monitoring period of one month to compare the measured cross-frame response. Among other key observations, the measured data demonstrated that load-induced force effects in the cross frames of the skewed bridge system exceeded those in the bridges with normal or radial supports and that cross-frame response was highly sensitive to the longitudinal and transverse truck positions. In all cases, though, the measured damage accumulated on all instrumented cross-frame members during their respective monitoring periods, if extrapolated to the entire service life, would likely not cause significant load-induced cracking in the critical welded gusset-to-member connections.

The fatigue provisions for bridge design in North America and Europe are highly simplified for the sake of practical implementation, in comparison with the state of the art in understanding of the true fatigue behavior. Historically, one significant simplification in the calibration of damage equivalence factors has been to assume that trucks cross the bridge one at a time, when in reality trucks are known to platoon, and multiple truck presence is not uncommon on longer span structures with higher traffic volumes. While code writers have taken steps more recently to consider multiple presence effects, these efforts have been limited, and a clear understanding of the influence of key design parameters on multiple presence effects has not yet been fully established. Against this background, the present work considers real-time multilane weigh-in-motion (WIM) data and compares fatigue damage from recorded loading events over years to the damage resulting from the same vehicles crossing the bridge individually, to better understand the significance of multiple vehicle presence effects on fatigue damage. For both finite and infinite life fatigue design, the results show that multiple vehicle presence effects can be significant, depending on traffic volume, road configuration, and influence line characteristics. Multiple presence factors are therefore defined, allowing practitioners to consider multiple presence effects appropriately when designing bridges where they may be relevant.

The ability of structural health monitoring (SHM) systems to detect defects and damage in existing structures is currently a key issue in the life-cycle management of civil infrastructure. In this respect, the use of dynamic identification to detect the loss of prestress load, grouting defects, cracking, and corrosion in post-tensioned concrete (PC) bridges is receiving special interest as an attractive tool that may drive predictive maintenance for disaster risk mitigation, motivating widespread implementation of SHM systems in engineering practice. In this study, an experimental program on reduced-scale PC beams representative of typical girder bridge decks, at the Department of Structures for Engineering and Architecture, University of Naples Federico II, is presented. The specimens were characterized by different prestressing load levels, grout injection conditions of post-tensioning ducts, and strand rupture during testing. Operational modal analysis (OMA) was carried out at multiple steps of each test, which were associated with different damage states of the specimens. OMA results show that both natural frequencies and mode shapes of PC girders are not significantly influenced by slight cracking corresponding to service load levels, while indicating some frequency variations in the case of local strand failure.

Flooding occurrences have become increasingly severe, posing a serious danger to end-user safety and bridge resilience. As flood fragility assessment is a valuable tool for promoting the resilience of bridges to climate change, it is of great importance to push the development of such methods. However, flood fragility has not received as much attention as seismic fragility despite the significant amount of damage and costs resulting from flood hazards. There has been little effort to estimate the flood fragility of bridges considering various flood-related factors and the corresponding failure modes. To this end, a fragility-based approach that can explicitly address the scour-hole geometry and flood-induced lateral load is presented. First, a three-dimensional finite-element model with pile foundations and surrounding soil was established to estimate the failure mode under various flood scenarios. The loadings on pile foundations were characterized by vertical loading from the superstructure, horizontal loading from the flood-induced lateral load, and the scour effect simulated through a time-history analysis. Then, all potential failure modes of bridge pile foundations in various flood scenarios were summarized. Based on extensive parameter investigations using the deterministic method, the dominant failure mode of penetration failure was determined, and a failure envelope was fitted to guide the design of the pile foundation. Upon establishing the failure mode, a probabilistic fragility analysis considering uncertainties in hydraulic, structural, and geological parameters was finally conducted using the Latin hypercube sampling (LHS) method. The results showed the effects of variation on the fragility of the pile foundation, highlighting that the deterministic analysis without considering the uncertainties in model parameters leads to underestimating the risk due to the penetration failure and the significant influence region.

This paper presents experimental testing evaluating the ability of a bridge deck deicing system to mitigate concrete deterioration from thermal stresses, frost action, and early-age cracking. Two experimental bridge deck models were constructed with embedded heat exchanger tubing and instrumented with thermocouples and strain gauges. Model 1 evaluated the efficiency of a deicing system in deicing and mitigating concrete deterioration from thermal stresses and frost action in concrete bridge decks, while Model 2 tested the effect of a deicing system on early-age cracking in bridge decks. The models were tested in a cold chamber laboratory under conditions representative of Montana's winter weather, with the system circulating warm fluid through the decks. Results showed the system succeeded in increasing concrete temperatures at all depths. While the system did not always raise temperatures above freezing, the consistent increases suggested that the system could enable deicing and mitigate frost action given certain conditions and higher inlet fluid temperatures. The system also successfully decreased thermal movement strain by up to 40% and reduced thermal shrinkage by decreasing the difference between peak cured and stabilized temperatures. Although the system did not eliminate thermal gradients, the maximum gradient induced was insignificant. Further testing is needed on strength impacts. Overall, the deicing system showed promise to reduce thermally induced deterioration in concrete bridge decks by regulating temperatures.