International Concrete Abstracts Portal

While many studies have evaluated the corrosion performance of hot-dip galvanized reinforcement (ASTM A767), few have evaluated that of the newer continuously galvanized reinforcement (ASTM A1094). This study compared the corrosion resistance of A767 and A1094 reinforcement, along with uncoated reinforcement, using the Southern Exposure (SE) and cracked beam (CB) tests. The galvanized reinforcement was tested both with and without damage to the coating, as well as after bending the bars. Both A767 and A1094 reinforcement exhibited better corrosion resistance than uncoated reinforcement, but corrosion rates on both types of galvanized reinforcement increased when the bars were bent. ASTM A767 and A1094 reinforcement exhibited similar corrosion resistance and can be used interchangeably.

Engineered cementitious composites (ECC) represent a significant innovation in construction materials due to their exceptional flexibility, tensile strength, and durability, surpassing traditional concrete. This review systematically examines the composition, mechanical behaviour, and real-world applications of ECC, with a focus on how fiber reinforcement, mineral additives, and micromechanical design improve its structural performance. The present study reports on the effects of various factors, including different types of mineral admixtures, aggregate sizes, fiber hybridization, and specimen dimensions. Key topics include ECC’s strain-hardening properties, its sustainability, and its capacity to resist crack development, making it ideal for high-performance infrastructure projects. Additionally, the review discusses recent advancements in ECC technology, such as hybrid fibre reinforcement and the material’s growing use in seismic structures. The paper also addresses the primary obstacles, including high initial costs and the absence of standardized specifications, while proposing future research paths aimed at optimizing ECC’s efficiency and economic viability.

This paper investigates the seismic performance of exterior beamcolumn joints in special moment frames (SMFs) with varying axial load ratios. Cyclic testing of four additional specimens with an axial load ratio of 0.45 is compared with four companion specimens at 0.10. Each specimen was designed and constructed with Grades 60, 80, or 100 (No. 420, 550, or 690) reinforcement in accordance with ACI 318-19 provisions for special moment frame joints, except for the provisions of joint shear and confinement. While ACI 318-19 tightens confinement requirements for SMF columns and joints, especially under high axial loads, this study reveals that increasing the axial load ratio benefits joint behavior. The study also demonstrates the feasibility of using high-strength reinforcement in exterior beam-column joints of SMFs, provided that appropriate modifications are made. The findings in this study have influenced modifications from ACI 318-19 to the Building Code Requirements for Concrete Structures in Taiwan.

This research proposes a standardized arrangement of longitudinal reinforcement using Grade 690 MPa (100 ksi) high-strength steel and D32 (No. 10) or D36 (No. 11) large-diameter threaded bars to alleviate reinforcement congestion and construction difficulties. Four full-scale column specimens with the proposed standardized arrangement were tested using double-curvature lateral cyclic loading to examine their seismic performance. Test results showed that all the columns exhibited a combined axial and flexural failure mode, with ultimate drift ratios ranging from 4.07 to 5.98%, ratios of measured to nominal moment strength based on actual material strengths ranging from 1.18 to 1.51, and relative energy dissipation ratios satisfying the requirement of ACI 374.1-05. No shear or bond-splitting failures were observed. Based on the test data from this research and the literature, two modifications were proposed in the calculation of ℓd to relax the requirement of 1.25ℓd ≤ ℓu/2 as required by ACI 318-19.

Performance-based seismic standards establish acceptance criteria to determine whether structural members can adequately withstand seismic deformation demands. These criteria primarily consist of member deformation limits, such as plastic rotation. There is, however, a shift towards strain-based limits, as strains can provide more reliable estimates of material damage, strength degradation, and can better account for variations in member boundary conditions such as axial load. The process of estimating local material strains in concrete members remains challenging, mainly due to paucity of physical models and test data at the strain level. To address this challenge, a framework based on fiber-section elements and mechanics-based behavioral models is proposed. This framework allows for strain demand estimates based on member-level deformations. Particularly, the framework provides strain demands on longitudinal bars and concrete within the plastic hinge regions of frame members while accounting for differences in steel properties as grade increases.