Abstract
The utilization of intermediate diaphragms (IDs) in precast concrete (PC) I-girder bridges has been a topic of debate among researchers for decades, with its effectiveness remaining a subject of controversy. The consideration of intermediate diaphragms is an essential aspect of engineering practice, making it crucial to explore their role in live load moment distribution. In “Live load moment distribution effect of intermediate diaphragms in precast concrete I-girder bridges,” Shahawy et al. examine the impact of various finite element modeling practices and key parameters on the effectiveness of intermediate diaphragms. The authors chose the live load moment envelope of girders as the response indicator to evaluate the role of intermediate diaphragms. The parametric study reveals that the removal of intermediate diaphragms leads to an increase in the midspan moment of the interior girders, while the midspan moment of the exterior girders decreases. Further, the authors conclude that the rigidity of connections between intermediate diaphragms and girders, girder spacing, and span length significantly influence the role of intermediate diaphragms in PC I-girder bridges.
Horizontally curved steel I-girder bridges are commonly designed and constructed as economical options in congested areas despite their complex behavior. Girder responses during erection and deck placement are challenging to evaluate due to warping of the girder and cross-frame system, which induces fit-up concerns and causes locked-in forces. Determination of girder major-axis bending under live load is complicated by curvature, which often makes the standard line girder analysis that uses live load distribution factors invalid; quantification of lateral responses for horizontally curved steel I-girder bridges also generally relies on refined analysis. Additionally, global temperature variations and local thermal gradients on these bridges result in more complicated radial and lateral movements and stress distribution compared to straight bridges. Standard design and analysis simplifications generally do not apply to horizontally curved steel I-girder bridges. In “Research and guideline synthesis for horizontally curved steel I-girder bridges,” Zhou et al. review existing experimental and numerical research on the behavior of horizontally curved steel I-girder bridges in the past two decades and synthesize current U.S. practices for their design and analysis, which lead to observations and insights of research and application gaps.
The behavior of skew-curved bridges cannot be approximated by mere superposition of the individual effects of skewness and curvature. In “Response of skew-curved RC box-girder bridge decks using finite element method,” Agarwal et al. study bending moment, shear force, torsional moment, and vertical deflection. These values are compared with those of straight bridges. The paper examines the behavior of skew-curved bridges using parametric variations, and the equations for a skew-curved bridge with different parameters are derived. The authors indicate that incorporating skewness improves the performance of bridges with greater curvature by reducing forces and deflections. In particular, the paper concludes that double-cell curved bridges with high skewness outperform single-cell counterparts with the same curvature and the same volume of material.
The use of an instrumented vehicle for measuring bridge vibrations is practical and mobile, compared to direct measuring methods, which require the installation of sensory system on each bridge. Despite the various advantages, there are two major challenges for the indirect method. The first challenge is the effects of road roughness on the response of the moving scanning vehicle. The second challenge is the vehicle’s own vibration influence on the recorded signal by the scanning vehicle. In “Transmissibility performance of highly damped stationary vehicle and its contact-point response for indirect bridge health monitoring: Theory and experiment,” Hashlamon et al. develop a simplified equation for contact-point response that incorporates vehicle damping, allowing more realistic modeling of stationary scanning vehicles. The authors introduce a frequency-free laboratory vehicle using polyurethane wheels, whose response is shown to closely match the bridge response without the need for contact-point response post-processing.