International Concrete Abstracts Portal

This study presents the design, construction, and shaking table testing of a two-column bridge bent developed for accelerated bridge construction with low-seismic damage objectives. The system incorporates precast post-tensioned columns connected to precast foundation and bent caps, with each column consisting of reinforced concrete cast inside a cylindrical steel shell that serves as formwork, confinement, and shear reinforcement. The steel shell is detailed to promote a rocking interface that concentrates seismic deformation demands at the column ends. Precast foundation and cap elements contain corrugated-metal-duct lined sockets, allowing on-site grouting to form the joints. A 35%-scale bent was constructed and subjected to combined horizontal and vertical ground motion inputs on a shaking table. Testing confirmed that seismic rotations concentrated at the column ends as intended, the bent exhibited excellent recentering capability, and observed damage was minimal, thus, validating the design objectives.

This study investigates the structural performance improvement when bond beams are included in stack bond walls. Nine 4.0 x 2.4 x 0.20 m masonry walls were tested under out-of-plane and axial loads. The walls were constructed in three configurations: running bond, stack bond without bond beams, and stack bond with bond beams following TMS 402/602 standard. Results show similar failure patterns and crack formation between running bond and stack bond walls, but stack bond walls with bond beams exhibited distinct behavior. Stack bond walls with bond beams showed slightly higher out-of-plane flexural capacity compared to running bond walls, with a difference ranging from 4 to 5%. These findings provide valuable insights for evaluating the structural performance of concrete masonry walls with different bonding patterns. This study suggests a potential revision to the Canadian (CSA S304) masonry design standard, potentially lifting restrictions on stack bond masonry wall construction.

Accelerated carbonation treatment is recognized as an effective method for enhancing recycled aggregates (RA), but its potential in structural concrete, particularly with respect to seismic performance, remains underexplored. To address this gap, this study is the first to integrate mesoscale modeling with structural finite element analysis (FEA) to systematically investigate the seismic behavior of carbonated recycled aggregate concrete (CRAC) shear walls under dynamic loading. At the material scale, uniaxial compression tests on CRAC cylindrical specimens with varying replacement ratios were conducted to evaluate their stress-strain behavior and mechanical properties. A mesoscale model of CRAC was developed using a random aggregate placement method, and FEA was employed to extend the analysis of replacement ratios. At the structural scale, a CRAC shear wall FEA model was established, incorporating the material-level stress-strain relationships into cyclic lateral loading simulations. Parametric analysis revealed that increasing both the axial load ratio and the replacement ratio significantly reduced the seismic performance of CRAC shear walls, with a maximum reduction of 21.7%. Based on these findings, recommended ranges for RA replacement ratios and axial load ratios are proposed, providing practical guidance for the structural application of CRAC.

In this study, the behavior of diaphragm-to-wall connections with collector reinforcement and construction joints was investigated. Four slab-to-wall connection specimens were tested under cyclic loading. Diaphragm connection details, such as shear friction reinforcement (that is, slab dowel bars anchored by 90-degree hooks within the wall) and the use of spandrel beams as collectors, were considered as test variables. When fabricating the specimens, concrete was consecutively cast for the wall and slab, and construction joints were placed on the sides of the wall and spandrel beams. The tests showed that the diaphragm connections exhibited the typical ductile behavior characterized by the robust initial stiffness and subsequent post-yield plastic behavior. Before concrete failure on the front of the wall, the load transfer from the diaphragm to the wall was governed by a nodal zone action; then, the subsequent connection behavior was dominated by shear friction as sliding failure occurred on the side of the wall along the slab construction joints. The diaphragm-to-wall connection strengths were evaluated using the strut-and-tie model and shear friction theory. The calculated strengths were in good agreement with the test strengths. Based on the investigation results, design considerations of the diaphragm-to-wall connection were proposed.

This paper presents a design model for the one-way shear of ultra-high-performance concrete (UHPC) beams without transverse reinforcement. The model unifies the shear design of UHPC with the ACI 318 shear design approach for conventional concrete. Hence, the proposed model accounts for the longitudinal reinforcement ratio and the axial load effects, while the tensile strength of UHPC replaces the concrete compressive strength term. The effects of fiber type, fiber alignment, beam shape, and beam size are incorporated through dimensionless parameters, with their values calibrated using UHPC beam and panel shear data sets. The proposed shear model was evaluated using a database of 137 UHPC nonprestressed and prestressed rectangular and I-shaped beam shear tests performed in the United States and elsewhere.