International Concrete Abstracts Portal

Reinforced concrete (RC) bridge columns often encounter complex combinations of loads, including flexural, axial, shear, and torsional forces, during seismic events, especially in the presence of geometric irregularities such as skewed or curved bridges, unequal spans, or varying column heights. Corrosion-related deterioration in RC structures spurred the adoption of glass fiber-reinforced polymer (GFRP) as a promising alternative to steel reinforcement. This study experimentally investigates the performance of GFRP-RC circular columns under cyclic loading, including torsion with different torsion-to-bending moment ratios (tm) and longitudinal reinforcement ratios. The results showed that, with the same reinforcement ratios, the addition of torsion to cyclic bending and shear significantly altered the behavior of the GFRP-RC column in terms of mode of failure, load resistance, drift capacity, and energy dissipation. The inelastic deformability hinge shifted upward with increased tm. Higher tm accelerated stiffness degradation, while increasing the longitudinal reinforcement ratio enhanced lateral load, drift, and twist capacities.

This paper investigates the structural performance of lightweight self-consolidating concrete (LWSCC) and lightweight vibrated concrete (LWVC) beam-column joints (BCJs) reinforced with monofilament polyvinyl alcohol (PVA) fibers under quasistatic reversed cyclic loading. A total of eight exterior BCJs with different lightweight aggregate types (coarse and fine expanded slate aggregates), different PVA fiber lengths (8 and 12 mm [0.315 and 0.472 in.]), and different percentages of fiber (0.3 and 1%) were cast and tested. The structural performance of the tested joints was assessed in terms of failure mode, hysteretic response, stiffness degradation, ductility, brittleness index, and energy dissipation capacity. The results revealed that LWSCC specimens made with expanded slate lightweight fine aggregates (LF) appeared to have better structural performance under reversed cyclic loading than specimens containing expanded slate lightweight coarse aggregates (LC). Shortening the length of PVA fibers enhanced the structural performance of LWSCC BCJs in terms of initial stiffness, load-carrying capacity, ductility, cracking activity, and energy dissipation capacity compared to longer fibers. The results also indicated that using an optimized LWVC mixture with 1% PVA8 fibers and a high LC/LF aggregate ratio helped to develop joints with significantly enhanced load-carrying capacity, ductility, and energy dissipation while maintaining reduced self-weight of 28% lower than normalweight concrete (NWC).

The prestressed hollow-core slab (PHCS) system is one of the most commonly adopted precast concrete flooring systems, which can optimize productivity and structural efficiency. Because PHCS members are typically produced by the extrusion method in longline precast plants, it is extremely difficult to provide shear reinforcements due to the automated fabrication method for forming multiple hollow-cores in a cross section. However, the current ACI 318 building code stipulates that the web-shear capacity of hollowcore members over 315 mm (12.5 in.) thickness without minimum shear reinforcement should be reduced by half, which increases the demands of shear strengthening for a thick PHCS member at its end regions. In this study, the shear tests of thick PHCS members strengthened in shear, using various core-filling methods frequently used in the current precast industry, were conducted and a new analytical method was addressed to estimate the shear strengths of the PHCS members composite with core-filling concretes.

Prestressed, precast concrete hollow-core slabs (HCS) are plant-fabricated members with prestressing strands serving as the primary reinforcement. Shear resistance of such slabs is provided by concrete only because HCS units have no shear reinforcement. Recent studies indicated unconservative predictions for the web shear strength of deep HCS (thickness > 315 mm [12.4 in.]) using the ACI 318-05 equation. This paper investigates web shear capacity of a total of 24 HCS having depths ranging from 200 to 500 mm (7.87 to 19.68 in.). All slabs were manufactured using the dry-cast (extrusion) method and were provided by three different suppliers. The comparison of ACI 318-05 predictions with the obtained web shear strength of the tested slabs showed conservative predictions for shallower slabs, with the level of conservatism decreasing with the increase of slab depth. Moreover, the predictions were unconservative for deeper slabs with thicknesses of 470 and 500 mm (18.5 and 19.68 in.). On the other hand, ACI 318-14 web shear design provisions for HCS yielded very conservative predictions for the test deep slabs. Analysis of web shear strength of the tested slabs was carried out against possible causes of the unconservative ACI 318-05 predictions associated to deeper HCS. Based on that analysis, a modification to the ACI 318-05 web shear design equation was proposed and verified using the test data.

The lack of durability in concrete structures worldwide demands fast and durable repairs. To address this need, high-early-strength engineered cementitious composites (HES-ECC) were recently developed for concrete repair applications in which minimum operations disruption is desired. A detailed characterization of HES-ECC’s compressive, tensile, flexural, and shrinkage properties at different ages is reported in this paper. HES-ECC achieves a compressive strength of 23.59 ± 1.40 MPa (3422.16 ± 203.33 psi) in 4 hours and 55.59 ± 2.17 MPa (8062.90 ± 315.03 psi) in 28 days. Under uniaxial tension, HES-ECC exhibits tensile strain-hardening behavior with a strain capacity greater than 2.5%. Its flexural strength exceeds twice that of concrete with similar compressive strength. Under restrained shrinkage conditions, HES-ECC forms microcracks with a self-controlled crack width below 50 μm (0.002 in.). The combination of these properties suggests that HES-ECC material is highly suitable for fast and durable concrete repairs with shortened downtime and improved longterm durability.