Infrared thermography (IRT) is a promising nondestructive evaluation technique that has been widely used for bridge deck inspection. It is a quick and fairly simple method for providing preliminary information about defected areas in bridge decks. However, detection capabilities and sensitivity to environmental conditions and material properties impose certain challenges for the application of IRT. In this paper, the effect of various concrete mixtures on passive IRT was investigated. Four concrete mixtures (i.e., conventional, high-strength, self-consolidated, and lightweight concrete) were considered in the evaluation. Various defects with relatively small sizes placed at different depths were simulated and planted in cast-in-place slabs. The casting and testing took place in the United Arab Emirates (UAE), which is considered a hot-weather region. The defected slabs were imaged, and the existence of defects was judged visually. A minimum of 0.8°C was used for successful detection to make a mor...

A fixed base is generally assumed in various dynamic response analyses and the design of bridges. However, soil–foundation flexibility and energy absorption and radiation by the soil system can alter the response of bridges to dynamic loads. This interaction between the structure, foundation, and soil, which in some cases may even change the dynamic load transmitted through the ground, is, in general, referred to as dynamic soil–structure interaction (DSSI). DSSI can either have detrimental or beneficial effects on a bridge response, particularly forces and displacements. These effects depend on several factors such as the rigidity ratio (ratio of the stiffness of the structure to the same of the soil–foundation system), slenderness ratio (height of the structure to the base width ratio), the foundation type, and the mass of the structure relative to the mass of the engaged soil–foundation system. In this paper, the dynamic characteristics of an actual bridge are inferred via an experimental study and numerical simulations. The research concentrated on the evaluation of the significance of DSSI effects under operational live load levels. The bridge was shaken using T-Rex, a large-amplitude mobile shaker from the National Hazards Engineering Research Infrastructure (NHERI) facilities. Two finite-element models were created to assess the DSSI effects on the dynamic response of the bridge. One model included elements that incorporate the DSSI effects, while the other had fixed-base boundary conditions. The response from the DSSI FEM model matched the field results better than that from the fixed-base model, in terms of the peak response amplitudes and identified natural frequencies and modes. In addition, the model incorporating the DSSI effects led to a reduction in stress levels in various bridge components, compared with that of the fixed-base model. The results of this study are applicable to bridges with similar features and site conditions.

In this paper, properties of a self-compacting lightweight concrete that has been exposed to cycles of wetting in saltwater and drying in air are investigated. Such exposure conditions are common in marine structures with pronounced sea level variation. The experimental program consisted of two phases; Phase I included monitoring of the strength development for 28 days, while in Phase II samples were exposed to wet/dry cycles for 12 months. In addition, control samples were kept in room temperature without exposure for comparison. Compressive and flexural strength, modulus of elasticity and Rapid Chloride Penetration (RCP) were included in the investigation. In addition, Scanning Electron Microscopy (SEM) was conducted to examine the microstructure of the samples in phase II. Results from the experimental program indicate that there was a negligible effect on the mechanical properties or RCP due to the exposure conditions. However, a close inspection of the SEM images showed salt deposits and micro cracking in the cement paste. This may affect the long-term durability and can lead to deterioration of the concrete structure, hence reducing the structure’s service life.