International Concrete Abstracts Portal

In this study, a detailed innovative procedure is devised to recover the full response of reinforced concrete deep beams using an improved strut-and-tie method based on ACI 318 rules. The load-deflection curve is described by two critical response levels represented by the yielding and ultimate points. The strut and tie method (STM) is used to determine the nodal displacements under a unit load and compute the yielding and ultimate load in the strut-and-tie model as the minimum force needed to realize each loading stage from all truss elements. Once the critical load at the two stages is determined, the elongation, strain, and stress of each element in the truss are extracted, thus avoiding the need to approximate the nonlinear strain profile across the depth. Also, two solution strategies using the secant and tangent stiffness are formulated, and their results are successfully compared to the experimental response of seven deep beams with a wide range of shear span-to-depth ratios. The failure modes reported experimentally perfectly match the failure member indicated by this improved analysis.

This study evaluates the seismic performance of circular columns reinforced with fiber-reinforced polymer (FRP) bars, focusing on the efficacy of existing code provisions (ACI CODE-318-19, CSA A23.3-24, CSA S806-12, CSA S6-25) in predicting drift and moment capacities. A database of 38 full-scale columns tested under lateral cyclic loading with varying axial load levels, spiral pitches, and reinforcement types (GFRP/steel longitudinal bars) was analyzed to assess code provisions, confinement effectiveness, and strength enhancements. Results demonstrate that CSA S6-25, which incorporates updated FRP compressive strain limits (0.008E_f for spirals), outperformed other codes, aligning with about 85% of experimental data in ideal performance quadrants. Close spiral pitch (≤ 75 mm [2.95 in.]) and low axial loads were critical to achieving drift ratios ≥3% and moment capacity ratios (M_max/M_o) exceeding 2.0. Replacing steel spirals with GFRP spirals did not result in substantial variation in the seismic performance of columns. Columns with GFRP longitudinal bars exhibited comparable ductility and observed a substantial increase in moment capacity (M_max) compared to unconfined nominal moment capacity (M_o) due to delayed bar buckling under effective confinement. However, columns with GFRP longitudinal bars observed a softer response, and the determination of probable moment to calculate the shear demand still remains questionable and requires more analytical investigations.

Carbon dioxide emissions from cement production pose major environmental concerns. This study investigates the combined incorporation of glass powder (GP) as a partial cement replacement and dog hair (DH) as a natural fiber reinforcement in cement paste. GP was incorporated with replacement levels of 5%, 10%, and 15%, whereas DH was incorporated with dosages of 0.25% and 0.5% by weight of cement. Both fresh and hardened properties were evaluated for a duration of up to 90 days. GP enhanced workability, increasing mini-slump by approximately 21% at 15% GP, whereas DH with 0.25% reduced workability by up to 6%. At 90 days, compressive strength improved by 26.6%, 17.6%, and 16.5% for GP5, GP10, and GP15, respectively. Flexural strength was improved by a maximum of 8.9% with the addition of DH. The porosity of all the modified mixes was reduced to a minimum of 20.4% in the GP15-0.25DH mix compared to the control mix of 28.0%. Sustainability analysis showed CO₂ emission reductions ranging from 4.06% to 16.07%, and material cost decreased to a maximum of 15.95% for GP15. These results clearly show the potential of GP and DH to enhance performance while improving economic and environmental sustainability.

This presentation discusses the behavior of a truss bridge under wind loading. To examine the wind-related responses of the bridge, state-of-the-art and traditional modeling methodologies are employed: a machine learning approach called random forest and three-dimensional finite element analysis. Upon training and validating these modeling methods using experimental data collected from the field, member-level forces and stresses are predicted in tandem with wind speeds inferred by Weibull distributions. The intensities of the in-situ wind are dominated by the location of sampling, and the degree of partial fixities at the supports of the truss system is found to be insignificant.

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.