Abstract During the course of their design life, base isolators may be subjected to elevated temperatures for a variety of reasons, including fire hazards. In such scenarios of elevated temperatures, the vertical load-carrying capacity of base isolators could deteriorate. Therefore, assessment of the stability of fiber-reinforced elastomeric isolators (FREIs) under the vertical loads from the superstructure while under elevated temperatures is important. In this study, the buckling behavior of FREIs is investigated under ambient and elevated temperatures. Available closed-form expressions to predict the buckling load of FREIs at ambient temperatures are extended for applications under elevated temperatures. Under elevated temperatures, the buckling load is derived by considering the thermal expansion of the FREIs and the material degradation of the elastomers with the rise in temperature. Further, nonlinear finite-element analyses are conducted to numerically evaluate the buckling behavior of a wide range of FREIs with various inherent properties. Modified Riks analysis is utilized to estimate the nonlinear buckling behavior of the FREIs. Transient heat transfer analysis within the FREIs is conducted to observe the buckling loads of the FREIs after various time instances, and the steady-state uniform elevated temperature in the FREI is found to be the worst-case condition under the considered thermal boundary conditions. Herein, only the thermal scenarios of uniform elevated temperatures at all the faces of a single FREI are explored. It is observed that the closed-form expressions for buckling load under elevated temperatures could effectively predict the buckling loads of the FREIs, providing slightly conservative values for most cases. Interestingly, the results show that the FREIs with low aspect ratios (such as 1.20) demonstrate the maximum reduction in their vertical load-carrying capacity with the rise in temperature.
Abstract In September 2021, the European Union launched the New European Bauhaus (NEB) initiative to promote a green, inclusive, and aesthetically oriented transition across Europe. Although the NEB emphasizes sustainability, inclusiveness, and aesthetics, existing assessment frameworks rarely integrate these dimensions in a cohesive or adaptable manner. The objective of this research is to establish a flexible component-based framework capable of quantitatively capturing the core concepts of the NEB. The framework is developed through an extensive literature review and organized into a hierarchical structure that aggregates fine-grained performance metrics into dimension indices and a final composite performance index. A fuzzy Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)–based weighting mechanism is incorporated to enhance adaptability and to better reflect the inclusive and participatory ethos of the NEB. The framework’s applicability is demonstrated through its use on the Mjøstårnet timber tower in Norway. Following an initial performance evaluation, the tower is redesigned using adaptive control principles and reassessed to demonstrate the framework’s responsiveness to design modifications and its capacity to capture multidimensional performance. The results indicate that the proposed framework can function as a robust and versatile tool to support policymaking, design innovation, and performance evaluation aligned with the evolving priorities of European construction.
Abstract Focusing on typical highway structures, this study introduces a novel approach to developing structure-specific parametric seismic fragility curves. Combining the capacity spectrum method (CSM) with a structural reliability framework, the proposed method differs significantly from existing methods for fragility analysis by relying solely on cyclic or backbone pushover performance. In particular, a fragility model is shown to be generally governed by seismic capacity and spectral modification factors. These two high-level parameters are then related to geometry, material, and spectral characteristics following common seismic design and evaluation procedures. As a result, the new approach aligns naturally with deterministic or semiprobabilistic seismic analyses of structures. Additionally, it can reduce to the HAZUS fragility curves (a popular class fragility model) based on assumptions clearly laid out in this study. When the HAZUS assumptions are refined or loosened, the proposed method yields structure-specific fragility models comparable to those obtained from more sophisticated techniques for fragility curve development. The new method also enables rapid development of fragility curves for retrofitted or deteriorated structures. Finally, the approach is used to demonstrate that (1) the widely used HAZUS fragility curves may introduce considerable model uncertainty for a specific in-class structure, and (2) due to this high in-class variation, it can be challenging to use class-level baseline models to incorporate deterioration or retrofitting effects. In contrast, the proposed method is capable of capturing these effects and distinguishing between structures of the same class, supporting more targeted and effective retrofit decision-making.
Abstract Aerodynamic admittance functions (AAFs) are a key parameter determining the accuracy of buffeting analysis in long-span bridges. However, the presence of barriers and central gap complicates the aerodynamic response of in-service twin-box decks, thereby increasing uncertainties in AAF identifications when relying solely on traditional wind tunnel tests (WTTs). To improve the identification accuracy and reliability, the AAFs of a twin-box deck with barriers are investigated here by combining active wind tunnel tests, large eddy simulations (LESs), and field validations. Firstly, the AAFs in narrow-banded sinusoidal gusts are identified by combining the WTTs using the active gust generator and LESs. Then, the strongest wind event at the bridge site recorded over the service life of the bridge is simulated using LESs using a synthetic inflow to identify the AAFs under the action of broad-banded turbulent wind. The effects of barriers on AAFs are isolated by comparing the results obtained on the bare deck with those on the in-service geometry. Finally, time-domain buffeting analysis using four 1-h strong wind events is performed to validate the identified AAFs. Results show that the AAFs identified from active WTTs match well with LESs under both sinusoidal gusts and turbulent inflows, with values notably exceeding the Sears function and quasi-steady value of 1. The increase in AAFs caused by barriers is primarily attributed to reduced lift coefficient derivatives. Buffeting analysis using identified AAFs shows good agreement with field measurements, providing practical guidance for AAF identifications and buffeting estimations of in-service long-span bridges.
Abstract Transmission line towers experience frequent fluctuations in wind loads, which can cause fatigue damage in bolted connections, thereby risking their long-term reliability. Direct probabilistic fatigue assessment of transmission towers using nonlinear time-domain simulations under stochastic wind loading is computationally infeasible for long-term reliability and inspection planning, motivating the use of surrogate models to enable efficient uncertainty propagation and decision analysis. This study introduces a surrogate-based probabilistic framework to evaluate fatigue damage and inform inspection scheduling. High-fidelity finite-element models simulate joint responses under both preloaded and loosened bolt conditions, with fatigue assessed through rainflow cycle counting and Miner’s rule. The resulting simulation database is used to train neural network surrogates, enabling rapid prediction of fatigue accumulation across wind speeds and directions. These surrogates are integrated with joint wind probability distributions and a Poisson-based extreme-event model to estimate annual damage and account for uncertainty through sampling. Results identify critical fatigue-prone connections and examine how stress factors and bolt preloading influence vulnerability. Using these findings, inspection strategies are optimized by considering detection probabilities and cost-risk trade-offs. Overall, this approach offers a fast and reliability-based tool for evaluating fatigue risk and planning inspections of transmission systems.
