International Concrete Abstracts Portal

Concrete design standards address the reduction in shear wall lateral stiffness due to cracking by offering two primary paths: prescriptive stiffness modifiers or detailed analysis. While prescriptive modifiers may provide a practical approach for standard ordinary structures, they are inherently approximate, generally conservative, and may not be suitable for capturing the representative behavior of tall buildings or buildings with high sensitivity to lateral stiffness. Those classes of buildings often require more detailed evaluation. A new practical method is presented here that combines the simplicity of the prescriptive approach with the rigor and accuracy of detailed analysis. The procedure predicts effective shear wall stiffness by comprehensively evaluating the state of stress, tension stiffening of the cracked concrete, specific geometry, and reinforcement. Utilizing the strain energy method, it derives stiffness modifiers applicable for global, floor-by-floor, or zone-by-zone factors. The procedure can be easily implemented by post-processing the results of linear analysis, which is well-suited for practical design applications.

This study investigates corrosion-induced cracking in reinforced concrete subjected to accelerated chloride exposure, with emphasis on the applicability of Faraday’s law for predicting steel mass loss (ML). Voltage drop variation proved to be a reliable indicator of crack initiation, showing close agreement with observed surface cracking. Reduced porosity and higher electrical resistivity in low water-cement ratio (w/c) concretes restricted ionic transport, resulting in an actual corrosion level (CL) of nearly 40% of that predicted by Faraday’s law. Faraday’s law accurately estimated ML for specimens preconditioned for 28 days and cast with medium-to-high w/c, whereas shorter preconditioning durations and low w/c resulted in systematic overestimation. Concrete compressive strength, rebar diameter, w/c, concrete cover, and exposure conditions exhibited strong coupled effects on crack initiation and propagation, with crack growth rates ranging from 0.142 to 0.586 mm (0.006 to 0.023 in.) per 3% CL, highlighting the need for integrated consideration of material and geometric parameters in durability-based design and corrosion assessment. An analytical model for estimating CL at crack initiation is proposed that shows strong agreement with experimental observations.

Slender columns are highly susceptible to buckling, which induces additional bending moments and reduces their axial load capacity compared to short columns, potentially leading to stability failure. This study presents the results of 10 full-scale glass fiber-reinforced polymer-reinforced concrete columns with a slenderness ratio of 45, exploring the influence of longitudinal reinforcement ratio (1.21 or 3.44%) and eccentricity-to-diameter ratio (e/D = 0, 8.5, 17, or 34%). Reference specimens with slenderness ratios of 20 and 28 were included for comparison. Results revealed that the e/D ratio had the most significant influence, markedly reducing axial capacity and magnifying secondary moments. A threshold ofe/D = 17% was identified beyond which stability failure occurred. The contribution of reinforcement ratio became more apparent as the e/D ratio increased. Increasing the slenderness ratio from 20 to 28 reduced the axial capacity, while a further increase to 45 primarily increased secondary moments without a noticeable additional reduction in axial capacity.

A detailed nonlinear finite element (FE) model of the ribbed profile of reinforcement is used to investigate the effects of bar size, bonded length, confinement, and cover-to-bar ratio on the characteristics of local bond strength-slip laws and the type of anticipated bond failure. The ribbed bar model is verified first against experimental results from direct tension pullout tests, and then it is used to investigate and corroborate the parametric behavior of the model with the evidence provided by the experimental database compiled by ACI Committee 408, Bond and Development of Steel Reinforcement. The objective of the study is to extend the bond-slip laws used in FE simulations of concrete structures by accounting for important design variables that affect bond behavior, with particular emphasis on the effects of large bar diameters and confinement. The detailed ribbed bar model is further used to investigate the upper limit of the confinement index, (K_tr+C)/Db, which is set at 2.5 in ACI CODE-318-25, and marks the transition from bond splitting failure to pullout failure.

This study investigates the seismic performance of precast concrete column-foundation connections incorporating dry mechanical splices, so-called column shoes, designed as strong connections per ACI CODE-318-25 and ACI PCI-319-25. Two precast concrete connection specimens—designated PF (full-dry connections, bolted-column shoe only) and PS (semi-dry connections, bolted column shoe combined with grouted splice sleeves)—were tested alongside a reinforced concrete (RC) control specimen with a monolithic connection detail under quasi-static reversed cyclic loading. The precast specimens were designed to satisfy the strong-connection details of the precast concrete special moment frame system to promote the plastic hinge formation outside the mechanical splices. Their seismic response was compared with that of the RC control specimen to justify the emulative seismic performance. The precast specimens exhibited comparable cyclic responses, including the lateral strength, hysteretic behavior, and deformation capacity to that of the monolithic specimen. Strain responses in longitudinal reinforcements in the precast concrete columns across the joint showed that inelastic deformation was relocated to the intended plastic hinge region rather than the location of the mechanical splices. Although the precast specimens exhibited slightly lower post-peak strength, primarily due to localized grout damage for dry connections, the overall seismic performance fully satisfied the acceptance criteria of ACI 374.1. The results indicate that bolted-type dry mechanical splices, when designed using the strong-connection concept, can provide code-compliant seismic performance under severe cyclic inelastic demands while preventing premature damage concentration in the splice region.