International Concrete Abstracts Portal

In reinforced concrete standards, equations for the development length of deformed, straight steel bars in tension have been established using statistical analyses of test data. Existing bond databases are limited in the information they offer. To address this problem, a database was assembled by the authors with significantly more test data and details than in previous databases. The additional data provide detailed information from monotonic tests of normal-weight reinforced concrete beams with deformed, uncoated, and bottom-cast steel bars. The resulting database contains 1,101 specimens, which nearly doubles the number of comparable specimens in the 2021 database by ACI Committee 408. The new database is used to evaluate the design provisions for the tension development length of straight bars in ACI 318-25, ACI 408R-03, fib MC2020, and AASHTO BDS-10. Of the four equations considered, the one from ACI 318-25 provided the poorest fit with the test data and overestimated bond strength in approximately 20% of the bars without transverse reinforcement (along the embedment or splice length) and nearly 10% of the bars with transverse reinforcement.

Coupled walls are widely used as the lateral force-resisting system in tall buildings in seismic regions. Nonlinear response history analyses of such systems rely on first-generation shear- or moment-spring models for the diagonally reinforced coupling beams; these have significant limitations and are inconsistent with the uncracked stiffness assigned to the framing walls. This paper presents a nonlinear hysteretic truss model for diagonally reinforced concrete coupling beams that resolves this inconsistency and validates it against experimental data reported in the literature. The model explicitly couples flexural, shear, and axial deformations through truss action within a unified nonlinear hysteretic framework, a clear improvement over purely phenomenological shear- or moment-spring models. Unlike these, the proposed model develops axial compression when restrained against lengthening and accounts for its effects, allowing shear redistribution between the framing walls. Its applicability is demonstrated through the nonlinear response history analysis of a 15-story coupled-wall building.

This study investigated the effects of sodium polyacrylate (PAAS) particle size and dosage on the workability, strength, and hydration of cementitious materials. The backscattered electron banding (BSE) was used to quantitatively analyze the degree of hydration of cement around PAAS voids under varying humidity levels. The results indicated that mortar fluidity, compressive strength, and flexural strength gradually decreased with increasing PAAS particle size and dosage. The incorporation of fine PAAS particles (45–50 μm) enhanced mechanical strength. While PAAS does not alter hydration product types, it promotes calcium carbonate formation, with calcium hydroxide, calcite, and C3S remaining dominant. Furthermore, it was found that higher humidity conditions and larger particle size PAAS particles can reduce the amount of unhydrated cement in the area around PAAS voids.

This presentation explores the research of Luke Snell on the oldest concrete street in the United States, located in Bellefontaine, Ohio. Built in 1891 by George Bartholomew, this pioneering project marked a significant milestone in the use of concrete for road construction. The presentation will discuss the historical context, the materials and methods used, and the impact of this early concrete pavement on modern infrastructure. Additionally, it will highlight Snell’s contributions to documenting and preserving this history, emphasizing the evolution of concrete technology, concurrent with the span of his career in the concrete industry.

As key protective structures in mountainous areas, flexible shed tunnels are susceptible to corrosion due to long-term environmental exposure, which significantly compromises their impact resistance. Most existing studies focus on uncorroded conditions, neglecting the effects of actual corrosion. This paper investigates the mechanical degradation of key components under different corrosion rates and distribution patterns using finite element simulations. The results show that with increasing corrosion, the bearing capacity, stiffness, and ductility of key components decrease significantly. At 30% corrosion, performance degradation exceeds 50%, with minimal difference between uniform and random corrosion models. Structural analysis reveals that beyond 20% corrosion, energy dissipation shifts from dissipators to rigid components, and total energy absorption drops below 40% at 30% corrosion, accompanied by brittle failure of components. The 20 to 30% corrosion range is identified as the critical stage for structural failure, providing a basis for the safety evaluation and maintenance of corrosion-affected flexible shed tunnels.