International Concrete Abstracts Portal

Engineered cementitious composite (ECC), a prominent innovation in the realm of concrete materials in recent years, contains a substantial amount of cement in its composition, thereby resulting in a significant environmental impact. To enhance the environmental sustainability of ECC, it is plausible to substitute a large portion of cement in the composition with fly ash, a by-product of coal-fired power plants. Recent years have seen increased research in ECC containing high-volume fly ash (HVFA) binder and its wider application in construction practices. In this particular context, it becomes imperative to review the role of HVFA binder in ECC. This review first examines the effects of incorporating HVFA binder in ECC on the fiber dispersion and fiber-matrix interface behavior. Additionally, mechanical properties, including compressive strength, tensile behavior, and cracking behavior under loading, as well as durability performances of HVFA-based ECC under various exposure conditions, are explored. Last, this review summarizes the research needs pertaining to HVFA-based ECC, proving valuable guidance for future endeavors in this field.

To evaluate the calculation accuracy of traditional yield displacement models and to describe the probabilistic characteristics of yield displacement, a probabilistic model for yield displacement of reinforced concrete (RC) columns with flexural failure was developed based on the Bayesian theory and the Markov Chain Monte Carlo (MCMC) method. The analytical expression for the yield displacement of RC columns was established by applying the plane-section assumption and cross-section analysis first. Then, the probabilistic model for yield displacement of RC columns with flexural failure was developed by replacing the empirical coefficients in the analytical expression with probabilistic coefficients. Moreover, the posterior information of the probabilistic coefficients was determined based on the prior information from experimental data and the MCMC method. Finally, the calculation accuracy of deterministic models for yield displacement was evaluated based on the experimental data, probability density functions, and confidence intervals. Analysis results demonstrate that the proposed probabilistic model provides an alternative approach to evaluate the calculation accuracy of deterministic models for yield displacement of RC columns with flexural failure. Priestley's model, JTD's model, and Cui's model tend to underestimate the yield displacement of RC columns, while Fardis's model and Billah's model often overestimate the yield displacement of RC columns.

The bond property between deformed bars and concrete plays a significant role in the safety of construction. Numerous database-dependent empirical models are proposed to evaluate the bond behavior without considering the effect of additional confinement, whose application range is quite limited as a result of unstable accuracy. In this paper, a new model was established based on the thick-walled cylinder model and fictitious crack theory, which can predict bond strength and bond-slip response with fiber-reinforced polymer (FRP)-steel confinement. The effects of various factors on the bond behavior, such as concrete strength, concrete cover, rebar diameter, bar surface geometry, and FRP/steel confinement, were comprehensively discussed. According to the radial crack radius, the radial stress and displacement induced on the bond interface can be calculated, and thus the analytical formulae of bond strength and slip were respectively developed in conjunction with deformed bar surface geometry. Finally, a new analytical model was proposed, which can simulate the bond-slip curves of the specimens with different confinement levels, covering unstrengthened, FRP-strengthened, stirrup-strengthened, and FRP-stirrup dually strengthened specimens. Compared with existing models, the proposed model can provide better agreement with existing test results.

During past earthquakes, failures of beam–column joints have commonly been observed on the exteriors of buildings. However, only one side of these joints can be retrofitted because of the presence of beams on the other three sides. Therefore, this study aims to test four exterior beam–column joints with transverse beams, leaving the rear side as the only viable location for placing fiber-reinforced polymer (FRP) laminate. All four test specimens are designed with insufficient joint shear strength, as determined by ACI 318 equations, while satisfying the criteria for a strong-column–weak-beam mechanism and sufficient development length for bar anchorage. A total of two un-retrofitted specimens, with and without joint hoops, are constructed as controls. Subsequently, two similar specimens are retrofitted by applying an FRP laminate on the rear side. The results show that sufficient FRP laminate can enhance the seismic performance of joints in terms of deformability, energy dissipation, and failure delay.

Current design assumptions for precast prestressed concrete piles embedded in cast-in-place (CIP) pile caps or footings vary across states, leading to inconsistencies in engineering practices. Previous studies suggest that short embedment lengths (0.5 to 1.0 times the pile diameter) can develop approximately 60% of the bending capacity of the pile, with full fixity potentially achieved at shorter embedment lengths than current design specifications due to confinement stresses1. This study experimentally evaluates 10 full-scale pile-to-cap connection specimens with varying embedment lengths, aiming to investigate the required development length for full bending capacity. The findings demonstrate that full bending capacity can be achieved at the of pile-to-pile cap connection with shallower embedment than code provisions, challenging existing design standards and highlighting the need for more accurate guidelines for bridge foundation design.