Long-span suspension bridges are typically designed against wind and earthquake loadings without considering blast loads because existing blast-resistant design guidelines for bridges are limited and in fact not detailed enough to fully explicate the consequences of a blast event. This study performed detailed dynamic analysis of a long-span suspension bridge to parametrically evaluate its structural redundancy under small to large blasts detonated at different locations. To accomplish this, the blast-structure interaction problem was solved by a simplified approach whereby the blast aspect was modeled as nodal loads by simulating the pressure contour area on the deck surface caused by the explosion; the structural aspect was modeled as a three-dimensional fishbone skeleton finite-element model. In particular, major attention was paid to the blast load effects on the main cable and hangers designed at safety factors of 2.2 and 2.5, respectively. This study concluded that the main cable and hangers show sufficient and insufficient structural redundancies, respectively under small to medium blasts, whereas a large blast was proven to be detrimental to both the main cable and hangers, which may further trigger progressive collapse of the entire suspension bridge.

Reinforced concrete (RC) frames are an integral part of modern construction as they resist both gravity and lateral loads in beams and columns. However, the construction methodologies of RC frames are vulnerable to non-engineering defects, particularly in developing countries. The most common non-engineering defect occurs due to improper lap splice, which can compromise the structural integrity. This research demonstrates an easy, low-cost, and verifiable experimental technique incorporating micro-concrete to evaluate the seismic performance of a completely engineered RC frame with the defect of improper lap splice. The micro-concrete was prepared by using the locally available material for a target compressive strength and then two scaled-down RC frames (1/16 scale) were prepared, including one proper frame and another with improper lap splice. Finally, these frames were tested on a shake table to study their behavior under various seismic loading conditions. This study quantifies the severity of high-risk structural systems due to non-engineering defects. The experimental results demonstrate that improper lap splice can alter the frame’s damage points, triggering the failure of the whole structure.

This paper presents the numerical evaluation of structural response and fatigue life of a Reinforced Concrete Dapped-End Girder (RCDEB) and associated fatigue life under fixed pulsating and moving loads. For that, a finite element (FE) model of RCDEB is developed using a three-dimensional FE analysis code, Concrete Model of 3-Dimensions (COM3D), and analyzes the FE model under high-fatigue loads by adopting a certain percentage of verified maximum static capacity of the girder. The COM3D system is activated with a multidirectional active crack approach which considers the space averaging of stress–strain in an element. The experimental validation of the numerical analysis is also performed in the laboratory using a small-scale model of the RCDEB under the fixed pulsating load. The experimental validation demonstrates good agreement with the FE analysis. However, the moving load is not considered in the experimental scheme because of the limitation in the testing facility. Finally, it is found from the FE analysis that the moving load, as compared with the fixed pulsating load, has the greatest effect on fatigue performance of the girder, causing about a three-order reduction in fatigue life at the same percentage static capacity of the girder. An increase in the fatigue life of approximately one order is also recorded in the analysis under the static midpoint load of 350 kN as compared with the moving load. Moreover, it is also observed that the reentrant corner of the RCDEB is more vulnerable to fatigue, implying that the hanger bars close to this corner resisted the stresses after the concrete cracked. As a result, strengthening the reentrant zone is recommended.

This paper presents a novel mathematical formulation of unsteady wind loads on bridge decks by using the neural network technique while incorporating the concurrent effects of nonstationary winds and aerodynamic nonlinearity. For that, a time-delay neural network (TDNN) is developed by recognizing the inputs and target outputs, wherein the inputs entail the wind speed fluctuating components and self-excited motion components, whereas the target outputs entail the buffeting load components. A typical sigmoidal function provided by the hyperbolic function is utilized to simulate the nonlinear features of the wind–bridge interaction (WBI) system. Finally, an elegant formulation for the nonlinear unsteady aerodynamic wind loads considering the nonstationary wind effects is developed in terms of synaptic weights of neurons and biases. The proposed formulation of winds loads has also been applied to a full-scale long-span suspension bridge under real typhoon winds. The buffeting analysis results are also compared with the measured displacement data, which shows the efficacy of the proposed wind load model for real-life bridge structures.

Cable-stayed and extradosed bridges are thought to be identical structures because both bridges use stay cables for reinforcement. However, the safety factors of their stay cables are stipulated differently in many international standards, i.e., Japanese specifications suggest the safety factors of 2.5 and 1.67 for the design of cable-stayed and extradosed bridges, respectively. In this chapter, a parametric study is carried out for the evaluation of safety factors of stay cables by employing the deterministic and nondeterministic methods at limit states. As a result, it is found that the safety factors in the range of 2.3–2.5 and 1.67 are indispensable for the safe design of cable-stayed and extradosed bridges, respectively, to satisfy the conditions of limit states and target reliability index.