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Bridge networks are essential components of civil infrastructure, supporting communities by delivering vital services and facilitating economic activities. However, bridges are vulnerable to natural disasters, particularly earthquakes. To develop an effective disaster management strategy, it is critical to identify reliable, robust, and efficient indicators. In this regard, Life-Cycle Cost (LCC) and Resilience (R) serve as key indicators to assist decision-makers in selecting the most effective disaster risk reduction plans. This study proposes an innovative LCC–R optimization framework to identify the most optimal retrofit strategies for bridge networks facing hazardous events during their lifespan. The proposed framework employs both single- and multi-objective optimization techniques to identify retrofit strategies that maximize the R index while minimizing the LCC for the under-study bridge networks. The considered retrofit strategies include various options such as different materials (steel, CFRP, and GFRP), thicknesses, arrangements, and timing of retrofitting actions. The first step in the proposed framework involves constructing fragility curves by performing a series of nonlinear time-history incremental dynamic analyses for each case. In the subsequent step, the seismic resilience surfaces are calculated using the obtained fragility curves and assuming a recovery function. Next, the LCC is evaluated according to the proposed formulation for multiple seismic occurrences, which incorporates the effects of complete and incomplete repair actions resulting from previous multiple seismic events. For optimization purposes, the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) evolutionary algorithm efficiently identifies the Pareto front to represent the optimal set of solutions. The study presents the most effective retrofit strategies for an illustrative bridge network, providing a comprehensive discussion and insights into the resulting tactical approaches. The findings underscore that the methodologies employed lead to logical and actionable retrofit strategies, paving the way for enhanced resilience and cost-effectiveness in bridge network management against seismic hazards.

Bridges play an important role in providing essential services to communities as one of the most critical components of transportation infrastructure. In this regard, selecting reliable, robust, and efficient indicators is necessary to prepare a disaster management strategy. This study presents a multi-objective optimization framework for decision-makers to find the most optimal retrofit strategies that satisfy a given threshold of functionality/Resilience (R) while minimizing a structure's Life-Cycle Cost (LCC). Accordingly, various retrofit strategies include different materials (steel, Carbon Fiber Reinforced Polymer (CFRP), and Glass Fiber Reinforced Polymer (GFRP)), thicknesses, arrangements, and timing of retrofitting actions. In each scenario, the fragility curves are derived through nonlinear time-history Incremental Dynamic Analysis (IDA) to evaluate the LCC and resilience. In the subsequent step, the LCC analysis is conducted, considering the proposed formulation of multiple occurrences of seismic events, which incorporates the effects of complete/incomplete repair actions of damage conditions induced by previous seismic events. This study employs an elitist Non-dominated Sorting Genetic Algorithm II (NSGA-II) to identify the optimal set of solutions. The various aspects of the optimal retrofit strategies are thoroughly investigated and discussed for a bridge as a case study infrastructure. Results show that the considered objectives lead to reasonable and sense-making retrofit strategies.

The design and construction of irregular buildings has always been the focus of attention due to the demand for a beautiful and unique structure. Furthermore, the use of Shape Memory Alloys (SMAs) has expanded due to the improvement of the behavior of RC structures in the last decade. The main advantages of using this alloy are its super-elasticity and the reversibility of inelastic displacements of the structure. In this paper, the behavior of reinforced concrete structures with SMA alloy in regular, torsional irregularity and extreme torsional irregularity are investigated. The effect of using this alloy has been shown using fragility curves in different degrees of irregularities than conventional concrete structures. In this regard, the effects of memory-shaped alloys as longitudinal reinforcement in short-order, intermediate, and high-order structures with three different arrangements of longitudinal reinforcements have been investigated. Different types of reinforcement arrangements are the case of full Steel, the case of SMA at the plastic region of the beams and steel reinforcement in other regions and finally the case of SMA reinforcement over the entire length of the beams.Then, several increasing nonlinear dynamic analysis (IDA) were performed under the influence of the 10 selected accelerometers, and maximum drift of each analysis was obtained and the fragility curves were calculated in accordance with the HAZUS instruction for each structural case. The results indicate that the presence of memory alloy in irregular buildings will reduce the damaging effects of irregularities, including maximum drift and residual drift of the structure. This result suggests that the use of SMA alloy in torsional irregular and extreme torsional irregular buildings can reduce the structural damage caused by a possible severe earthquake.

One of the common methods for estimation of structural failures and earthquake damages is using fragility curves with probabilistic methods. In these methods, a structure such as a bridge can be classified into several structural types in terms of number of spans, type of connections, material used for members, even type of soil, and so on. Also, the seismic load on the bridge can be considered with indicators such as peak ground acceleration (PGA) or spectral acceleration (SA). In this research, the number of span and soil type of concrete bridges with continuous deck have been investigated on the fragility curves. For this purpose, the two, three, and four span bridges were modeled in the finite element software. Then, the fragility curves of each condition were determined by probabilistic method and by performing nonlinear incremental dynamic analysis (IDA) for far field accelerograms and for four soil types of seismic design code of Iran. The results show that the soil type of the bridge site has a significant impact on the fragility curve, and the probability that the bridges will collapse will vary with the type of soil from type I to IV and damage increases as the number of bridge spans increases.

One of the basic problems in seismic design of buildings is appropriate configuration of their plans to prevent an increase in torsional moments due to irregularity. Nowadays, usage of irregular plans because of having a specific plan and beautiful appearance is increasing. The existence of irregularities in the structure during an earthquake causes torsion of structure, which leads to the intensification of seismic displacements and forces on structure. In this study, the seismic behavior of regular and irregular reinforced concrete structure with the number 3, 6 and 9 stories under ten records for incremental dynamic analysis have been evaluated. To this purpose, indexes such as maximum drift, residual drift, base shear and response modification factor have been compared. Fragility curves, using the threshold of damage state of RC structure according to HAZUS in both regular and irregular structures have been investigated. The results indicated that by increasing irregularity, maximum drift, residual drift base shear and probability of damage are increased. The response modification factor is also reduced as irregularity increases. Furthermore, by increasing the number of stories and rate of irregularity, the damage percentage of structure is increased. Therefore, design of irregular structures in plan is not recommended as much as possible

Bridges are key elements in urban transportation system and should be designed to sustain earthquake induced damages to be utilized after earthquake. Extensive damages during last earthquakes highlighted the importance of seismic assessment and damage estimation of bridges. Skewness is one of the primary parameters effects on seismic behavior of bridges. Skew bridges are defined as bridges with skew angle piers and abutments. In these bridges, the piers have some degrees of skewness due to construction restrictions, such as those caused by crossing a waterway, railway line or road. This paper aims to investigate seismic behavior of skew concrete bridges using damage criteria and estimate probability of piers damage with fragility curves. To this end, three types of concrete bridges with two, three and four spans and varying skew angles of 00 ,100, 200 and 300 are modeled with finite element software. Seismic responses of bridge piers under 10 earthquake ground motion records are calculated using incremental dynamic analysis. Following, damage criteria proposed by Mackie and Stojadinovic are used to define damage limits of bridge piers in four damage states of slight, moderate, extensive and complete and bridge fragility curves are developed. The results show that increasing skew angles increases the probability of damage occurrence, particularly in extensive and complete damage states.

There is an increasing interest in non-destructive and real-time high-resolution approaches for corrosion studies in metals. In this paper, we propose the dynamic speckle pattern method as a low-cost, easy-to-implement, and quasi in-situ optical technique for the quantitative evaluation of pitting corrosion. This type of corrosion occurs in a specific area of a metallic structure and causes holes formation leading to structural failure. A Custom 450 stainless steel sample, placed in 3.5 wt% NaCl solution and applied to a [Formula: see text] potential to initiate the corrosion, is used as the sample. The speckle patterns formed by the scattering of a He-Ne laser light is changed over time due to any corrosion in the sample. The analysis of the time-integrate speckle pattern suggests that the growth rate of pitting decreases with time., (© 2023. The Author(s).)