Climate Change Considerations for Seismic Vulnerability Assessment of Aging Highway Bridges

Abstract

Aging affected structural components negatively impact the lateral load-resisting capacity and fragility of highway bridges during seismic shaking. Until now, a majority of existing literature on corrosion deterioration of highway bridges assumed a constant or time-varying degradation rate that is independent of initial climate conditions or their variations along service life. Recent research on climate change indicates a time-dependent shift in atmospheric temperature and relative humidity due to global warming. These effects, compounded along the service life with heightened chloride ingress, require careful consideration for bridges located in regions near marine sources and characterized by moderate to high seismicity. The present study proposes a multihazard framework to evaluate seismic fragility of highway bridges considering earthquake hazard, aging effects, and global warming due to climate change. The framework, when demonstrated on case-study multispan continuous steel girder bridges in the central and southeastern United States, reveals that potential climate change effects are likely to further exacerbate the seismic performance of aging bridge structures.

Probabilistic analysis of climate change impact on chloride-induced deterioration of reinforced concrete considering Nordic climate

“…Exposure to chlorides (from, e.g., sea salt spray, seawater wetting, and/or deicing salts), however, can lead to the breakdown of this protective layer and subsequently corrosion of reinforcement steel. The corrosion process is described by two phases [6,25,29,45]: 1) the corrosion initiation phase and 2) the corrosion propagation phase. The time it takes for chlorides to penetrate to the level of the reinforcement and accumulate in sufficient quantities to break down the protective film and initiate the corrosion process (i.e., reach a critical chloride concentration) is known as the corrosion initiation time.…”

“…Several models can be found in literature for estimating the corrosion initiation time [47][48][49]. One of the most widely used models is the model proposed in [48] based on Fick's second law of diffusion [6,25,29,50,51]. Based on this model the corrosion initiation time (t i ) [ years ] is calculated as follows:…”

“…Similar to the corrosion initiation time, several models for predicting the corrosion rate can be found in literature, see [24] for a comparison between a number of different models. For the purpose of the current article, the model proposed by [52] is used along with the temperature, relative humidity, and chloride concentration modification factors proposed by [53], see also [25,29]:…”

“…, δ i corr is a model uncertainty factor (represented by a Weibull distribution with a mean of 1.355 and a coefficient of variation (COV) of ~ 0.57 [24]), w c is the water to cement ratio, t is the concrete age [ years ], f T is a modification factor accounting for a temperature deviation from the 20 °C reference temperature considered in [52], f RH is a modification factor accounting for a relative humidity deviation from the 75% reference relative humidity considered in [52], and f Cl is a modification factor accounting for the increase in chloride concentration during the propagation phase. The different modification factors are evaluated as follows [25,29]:…”

“…Although other deterioration mechanisms of reinforced concrete elements are possible (e.g., carbonation-induced corrosion [6,25] and biodeterioration [26,27]), chloride-induced corrosion is generally more damaging and more costly to repair [28]. Several recent studies have focused on probabilistically assessing the impact of climate change on chlorideinduced corrosion [6,7,11,25,[29][30][31]. However, none of these studies considered Nordic climate conditions with very different climate zones depending on the location.…”