International Concrete Abstracts Portal

The influence of lap splices on the seismic behavior of low-rise reinforced concrete (RC) walls was studied through tests of four 1:2 length-scale bridge pier wall specimens subjected to constant axial load and a quasi-static cyclic loading sequence. The study parameters were horizontal reinforcement ratio (0.25 to 0.34%), splice length to shear span ratio (≈ 0.2 to 0.3), and wall-end confinement. Specimens lost 20% of maximum lateral strength at drifts between approximately 1.2 and 1.8%, increasing with horizontal reinforcement ratio, wall-end confinement, and splice length to shear span ratio. Splice failure, bar fracture, or their combination, caused abrupt strength loss and transition from flexure- to rocking-controlled behavior. Flexure-compression failure in the specimen with a splice length to shear span ratio of approximately 0.3 resulted in gradual strength degradation without transition to rocking. All specimens sustained drift demands of almost 2% without loss of axial load-carrying capacity.

To investigate the seismic behavior and resilience of reinforced concrete (RC) slit shear walls with either low-bond or debonded high-strength reinforcements, eight shear walls with different cross-sectional forms and types of longitudinal reinforcing bars were fabricated and subjected to both compressive loading and cyclic lateral loading. The experimental results indicate that the test shear walls with anchored infilled steel columns (ISCs) failed in flexure of the subshear walls due to the form of a vertical slit. The use of both low-bond high-strength reinforcing bar (SBPDN reinforcing bar) and an anchored ISC significantly increased the ductility of the shear wall without reducing the stiffness at the early deformation stage or the seismic resistance. Interestingly, the debonding of the longitudinal reinforcing bar reduced the strain of the transverse reinforcement. The debonding and low bonding of the longitudinal reinforcing bar increased the contribution ratio of deformation due to steel-bond slip but decreased the contribution ratio of shear deformation. Moreover, the anchorage of an ISC plays an important role in the contributions of shear and flexural deformation. The models proposed in the current provisions can be used to accurately predict the seismic resistance of shear walls with debonded and low-bond high-strength reinforcing bars.

Filling reinforced concrete (RC) frame spans with RC shear walls constitutes a strategic intervention to existing sub-standard buildings. The efficiency of this intervention depends, among others, on the behavior of interfaces between the shear wall and the frame elements. The failure of critical interfaces that may lead to undesirable shear sliding of the wall at its base can only be prevented if the interfaces are adequately designed. To investigate the cyclic behavior of interfaces within the composite frame-to-wall members, four frames filled with RC walls, as well as two reference specimens (that is, a bare frame and a monolithic frame/wall specimen), were subjected to cyclic horizontal displacements. The crucial effect of the interface reinforcement ratio, the detailing, the dowel distribution along the interface, and the embedment length on the behavior of the specimens, in terms of maximum capacity, drift, and failure mode, was confirmed.

Inverse analysis methods proposed by current standards for extracting the tensile properties of tension-hardening cementitious materials from indirect tension tests (for example, flexural prism tests) are considered either cumbersome and can only be performed by skilled professionals or apply to certain configuration and specimen geometries. Significant discrepancies are reported between the results of direct tension (DT) tests and inverse analysis methods. This has eroded confidence on flexural tests as a method of characterization of tension-hardening ultra-high-performance concrete (UHPC) and has motivated its abandonment in favor of DT testing. Additional concerns are size sensitivity, variability, and lack of robustness in the results of some methods. However, DT tests are even more difficult to conduct and results are marked by notable scatter. This is why some codes allow for bending tests at least for quality control of UHPC. To address the limitations of the bending tests in providing an easy and quick method for reliable estimation of the tensile characteristic properties of UHPC, a new practical method is developed in this paper based on a forward analysis (FA) of third-point bending tests. A unique aspect of the approach is that it considers the nonlinear unloading that occurs in the shear spans of the prism after strain localization in the critical region. The method was used to derive charts for direct estimation of the tensile properties from quality control bending tests, for the commonly used flexural specimen forms and material types. The goal of the study is to provide a practical alternative in characterization of tension-hardening UHPC materials. Results obtained using the proposed FA method are in good agreement with the tensile response from DT tests. However, it is noted that due to the presence of a strain gradient in bending tests and the larger strain gauge lengths employed in some DT tests, the strain values at localization from DT tests tend to be more conservative.

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.