International Concrete Abstracts Portal

This study presents the design, construction, and shaking table testing of a two-column bridge bent developed for accelerated bridge construction with low-seismic damage objectives. The system incorporates precast post-tensioned columns connected to precast foundation and bent caps, with each column consisting of reinforced concrete cast inside a cylindrical steel shell that serves as formwork, confinement, and shear reinforcement. The steel shell is detailed to promote a rocking interface that concentrates seismic deformation demands at the column ends. Precast foundation and cap elements contain corrugated-metal-duct lined sockets, allowing on-site grouting to form the joints. A 35%-scale bent was constructed and subjected to combined horizontal and vertical ground motion inputs on a shaking table. Testing confirmed that seismic rotations concentrated at the column ends as intended, the bent exhibited excellent recentering capability, and observed damage was minimal, thus, validating the design objectives.

The aging reserve of bridges in the United States needs load rating assessment to ensure sufficient load-carrying capacity and safety. Bridges without sufficient capacity to carry the legal loads are load posted. These load limits reroute traffic that may result in traffic congestion and longer routes and, thus, impose inconvenience to travelers and significant cost to society. This paper investigates the potential for improvement in the load rating process for simple-span concrete slab bridges. Such bridges are load rated by the Texas Department of Transportation using simplified load rating procedures, which are intended to be conservative and can have varying degrees of accuracy compared to the actual behavior of bridges. Finite element modeling was conducted to simulate the expected behavior of a representative concrete slab bridge, and the model was calibrated using experimental test data. The equivalent width results were compared with estimates from established design specifications and empirical guidelines. The methods developed for concrete slab bridges with integral curbs provided accurate estimates of moment demand for curb sections. In addition, an established analytical approach in the literature accurately predicted the moment demand for interior slab sections under one-lane loading, while the equations in current design specifications performed well for the two-lane loading case.

The two-way shear equation in ACI 440.11 was originally developed nearly two decades ago using experimental data from early FRP materials, most of which are no longer representative of modern GFRP reinforcement. With current GFRP bars exhibiting significantly improved mechanical and surface properties, the validity of the existing equation requires reassessment to ensure practical and economical design. This study evaluates the ACI 440.11 two-way shear provisions using a comprehensive database of 49 GFRP-RC interior slabs and 14 edge column connections. The current code equation was found to be highly conservative, yielding an average test-to-predicted ratio of 2.13. Updated equations are proposed for both interior and edge conditions, reducing the ratio to 1.02 and 1.04, respectively, while maintaining acceptable statistical variation. Additionally, symbolic regression (SR) is used to develop machine-learning-based expressions, which show high predictive accuracy. The proposed models provide reliable, physically grounded, and less conservative predictions of punching shear capacity, supporting broader implementation of GFRP reinforcement in structural concrete applications.

Repeated vehicle loading causes a decrease in transverse joint stiffness in concrete pavements due to damage accumulation around dowel bars. The relationship between key design parameters and damage accumulation is not well established due to limited faulting performance data and a lack of experimental data from expensive full-slab testing. A novel laboratory test setup was developed to characterize damage development caused by repeated vehicle loads. This setup was used to characterize damage for a range of key parameters at a lower cost and level of effort compared to full-scale slab testing. The concept of beam deflection energy, DE_Beam, is also introduced. Experimental results were used to develop a DE_Beam prediction model. The novel test setup developed in this study enables the rapid evaluation of a variety of dowel materials and geometries, and experimental results can be used to improve current faulting prediction performance.

Slender reinforced concrete columns have been employed as components of telecommunication and internet infrastructure since the deployment of the system more than 30 years ago. The assessment of these structures must consider the time dependent behavior of concrete. In this context, a numerical investigation is conducted to determine the critical buckling load and the stress distribution in sections subject to creep and shrinkage of concrete. The guidelines used are those from the American Concrete Institute. It is concluded that the maximum stress induced in the reinforcement is 1.14% of the steel yield stress. Therefore, no yielding of the reinforcement is registered to the examined case which ensures safety against permanent deformation. During the elapsed time of 7500 days, the modulus of elasticity of concrete decreased by 53% and the critical buckling load 40%. The results obtained can be applied to similar cases through the slenderness index and the reinforcement ratio.