International Concrete Abstracts Portal

This study investigates the seismic performance of precast concrete column-foundation connections incorporating dry mechanical splices, so-called column shoes, designed as strong connections per ACI CODE-318-25 and ACI PCI-319-25. Two precast concrete connection specimens—designated PF (full-dry connections, bolted-column shoe only) and PS (semi-dry connections, bolted column shoe combined with grouted splice sleeves)—were tested alongside a reinforced concrete (RC) control specimen with a monolithic connection detail under quasi-static reversed cyclic loading. The precast specimens were designed to satisfy the strong-connection details of the precast concrete special moment frame system to promote the plastic hinge formation outside the mechanical splices. Their seismic response was compared with that of the RC control specimen to justify the emulative seismic performance. The precast specimens exhibited comparable cyclic responses, including the lateral strength, hysteretic behavior, and deformation capacity to that of the monolithic specimen. Strain responses in longitudinal reinforcements in the precast concrete columns across the joint showed that inelastic deformation was relocated to the intended plastic hinge region rather than the location of the mechanical splices. Although the precast specimens exhibited slightly lower post-peak strength, primarily due to localized grout damage for dry connections, the overall seismic performance fully satisfied the acceptance criteria of ACI 374.1. The results indicate that bolted-type dry mechanical splices, when designed using the strong-connection concept, can provide code-compliant seismic performance under severe cyclic inelastic demands while preventing premature damage concentration in the splice region.

The interference between steel fiber and coarse aggregate reduces the homogeneity of fiber distribution and orientation, which may compromise the expected reinforcement effectiveness of steel fibers in concrete. Traditional destructive testing techniques constrain the quality control of steel-fiber distribution in prefabricated concrete segments; developing an induction-based technique contributes to nondestructive characterization of steel-fiber distribution. This work uses a Helmholtz coil to solve the magnetic field nonuniform distribution, thereby designing an inductor device to improve the accuracy of steel-fiber distribution monitoring within concrete. On this basis, a multi-parameter experiment was designed to study the coupling effect of coarse aggregate and steel fiber, with key variables including water-binder ratio (w/b), coarse aggregate gradation, steel-fiber mixing sequence, vibration duration, and casting flow distance. The C50 concrete mixture incorporates fly ash (75 kg/m3) as a supplementary cementitious material to improve workability and particle packing density. The primary findings are as follows: the induction-based method enables nondestructive evaluation of steel-fiber content and orientation in steel fiber-reinforced concrete containing coarse aggregate (SFRC‑CA), demonstrating high detection efficiency. The larger the aggregate size and w/b, the worse the steel-fiber distribution uniformity. The improper vibration will lead to steel-fiber-thickness-related settlement, while the longer the flow distances, the more uneven the orientation of the fiber. These results offer an important reference for material design and quality control of precast SFRC-CA components.

Prestressed concrete (PC) enables slender, economical, and durable structures, with post-tensioned (PT) precast girders widely used in bridge construction. Accurate design requires precise prediction of prestress losses, among which friction losses arising from duct curvature, wobble, and anchorage slip are most significant. Existing codes employ simplified exponential models, yet notable discrepancies persist between predicted and actual field values. This study presents full-scale experimental testing on PT precast girders used in Egypt’s Light Railway Transit (LRT) project. Prestress forces were measured using strain gauges to evaluate friction losses along tendon profiles. Results revealed that measured losses consistently exceeded code-based predictions, highlighting the influence of stress level and nonlinear variation along the tendon, factors often ignored by current provisions. Regression analysis yielded refined exponential models with improved accuracy and strong agreement with observations. The proposed refinements enhance predictive reliability and provide a foundation for updating design codes toward safer, more realistic PT concrete structures.

This study investigated the flexural behavior of innovative precast self-consolidating concrete stadium bleacher units with an L-shaped cross section and reinforced with glass fiber-reinforced polymer (GFRP) bars. Six full-size reinforced concrete stadium bleacher specimens with a width, height, and thickness of 950, 390, and 150 mm (37.4, 15.35, and 5.9 in.), respectively, and with a total length of 4200 mm (165.4 in.) were tested under four-point bending load up to failure. Six specimens were fabricated: three with normal concrete and sand-coated GFRP reinforcement with three different reinforcement ratios, and three with fiber-reinforced concrete (FRC) and sand-coated GFRP reinforcement. The test parameters included GFRP reinforcement ratio and concrete type. The test results were analyzed based on the cracking and ultimate moment specified in the existing FRP design codes. The comparison shows that the experimental moment capacities of the bleachers were generally conservative in the design standards. Moreover, the reinforcement ratio had a substantial impact on the serviceability performance of the bleacher specimens. Increasing the ratio of flexural reinforcement led to reduced crack widths and decreased deflections. Changing the concrete type from normal to fiber with the same bar size showed improved serviceability and moment capacity results. This research enhances the understanding of precast self-consolidating concrete stadium bleacher units with an L-shaped cross section reinforced with GFRP bars subjected to flexural load and supports their use in infrastructure.

This study evaluates the seismic performance of precast concrete shear walls (PCSW) with grouted-duct connections for low-rise buildings located in moderate seismic hazard zones, using the FEMA P-695 methodology. An experimental program was conducted with three full-scale specimens to investigate the system’s behavior and calibrate a nonlinear numerical model for collapse assessment. Nonlinear static pushover and incremental dynamic analyses were performed on six archetype buildings with PCSW as the lateral-force-resisting system. The results show that the PCSW systems provide reliable collapse safety in line with FEMA P-695 acceptance criteria. The adjusted fragility curves revealed similar seismic behavior between PCSW and special concrete shear walls (SSW), suggesting that grouted-duct connections provide emulative performance comparable to cast-in-place wall systems. These findings underscore the potential of PCSW systems as a cost-effective alternative to traditional cast-in-place systems, particularly in regions where construction speed and material efficiency are key considerations.