International Concrete Abstracts Portal

The geometry of arched (vertically curved) reinforced concrete (RC) members contributes to the development of additional stresses, affecting their flexural and shear strengths. This aspect of curvilinear RC members reinforced with glass fiber-reinforced polymer (GFRP) bars has not been reported in the literature. In addition, no specific design recommendations consider the effect of curvilinearity on the flexural and shear strengths of curved GFRP-RC members. This study has performed pioneering work in developing models to predict the flexural and shear strengths of curvilinear GFRP-RC members, with a focus on precast concrete tunnel lining segments. Eleven full-scale curvilinear GFRPreinforced tunnel segment specimens were tested under bending load as the experimental database. Then, a model was developed for predicting the flexural strength of curvilinear GFRP-RC members. This was followed by the development of two shear-strength prediction models based on the Modified Compression Field Theory (MCFT) and critical shear crack theory (CSCT). After comparing the experimental and analytical results, a parametric study was performed to evaluate the effect of different parameters on the flexural and shear strengths of curvilinear GFRP-reinforced members. The results indicate that neglecting the curvilinearity effect led to a 17% overestimation of the flexural strength, while the proposed models could predict the flexural strength of the specimens accurately. The proposed models based on the MCFT—referred to as the semi-simplified Modified Compression Field Theory (SSMCFT) and the improved simplified Modified Compression Field Theory (ISMCFT)—predicted the shear strength of the specimens with 28% conservativeness. In addition, the modified critical shear crack theory (MCSCT) model was 10% conservative in predicting the shear strength of curvilinear GFRP-RC members.

Slag-based zero-cement concrete (ZC) of high strength (60 MPa [8.70 ksi]) was developed as an eco-friendly construction material. In the present study, to investigate the structural behavior of precast columns using ZC, cyclic loading tests were performed for five column specimens with reinforcement details of ordinary moment frames. Longitudinal reinforcement was connected by sleeve splices at the precast column–footing joint. The test parameters included the concrete type (Portland cement-based normal concrete [NC] vs. ZC), construction method (monolithic vs. precast), longitudinal reinforcement ratio, and sleeve size. The test results showed that the structural performance (failure mode, strength, stiffness, energy dissipation, and deformation capacity) of the precast ZC columns was comparable to that of the monolithic NC and precast NC columns, and the tested strengths agreed with the nominal strengths calculated by ACI 318-19. These results indicate that current design codes for cementitious materials and sleeve splice of longitudinal reinforcement are applicable to the design of precast ZC columns.

This paper discusses the seismic performance of precast coupled structural walls with the influence of connections and their location. Full-scale quasi-static tests were conducted on the coupled structural walls by varying the number of connections. The test results show that the number of connections and their position along the height of the coupled wall significantly influence the lateral strength, stiffness, energy dissipation, and failure modes. Walls with two connections seem to improve the strength and hysteretic response, exhibiting superior cyclic performance. Increasing the number of connections improves the initial stiffness to a certain extent, but the designs are expensive. Walls with connections closer to lateral loading lines exhibit vulnerability, requiring design to optimize energy dissipation and crack control. Connections with over-strength may need to be avoided as they may not increase the energy dissipation under earthquake loading. The outcomes of the study help in designing precast systems with better seismic resilience, good ductility, and ease of replacement after an earthquake hits the system.

This study employs advanced nonlinear finite element modeling to investigate Interface Shear Transfer (IST) behavior in RC connections, a crucial factor for bridge durability and safety. The research examines shear transfer mechanisms at the interface between precast girders and cast-in-place deck segments through three experimental methods: beam, push-off, and Iosipescu four-point bending tests. FE simulations evaluated stress distributions, IST capacity, and failure mechanisms. Validation against experimental data shows that the Iosipescu test provides the most accurate representation of IST behavior, exhibiting a stress distribution error margin of only 1%, closely aligning with observed failure patterns. In contrast, the push-off test showed a 30% deviation from empirical data, indicating reduced accuracy in predicting real-world IST behavior. These findings highlight the importance of incorporating the Iosipescu test into IST evaluation protocols, as its greater precision enhances design methodologies for concrete bridges, reduces structural failure risks, and informs future updates to IST-related codes.

To secure emulative seismic performances of precast concrete (PC) special moment frame buildings, two capacity-based connection design options (that is, strong and ductile precast connections) are provided in the current version of ACI 318. However, the evolving performance-based seismic design and response evaluation requires a reasonable estimation of the energy dissipation and corresponding hysteresis damping characteristics so that their potential performance level can be properly predicted. Therefore, this study focuses on the seismic performances, especially the energy dissipation and damping performances of the Code- compliant PC wide beam-column connections. Three PC wide beam-column connection specimens under the ductile connection design principle with different joint details and a reinforced concrete (RC) control specimen were fabricated and tested under reversed cyclic loadings. In addition, an energy-based macro-modeling method was developed to characterize the cyclic responses, including the damping response of PC wide beam-column connections. The test results revealed that the Code-required overstrength of shear-friction strength between PC beam members and cast-in-place (CIP) concrete is crucial to achieving the ductile performance of precast connections. It also appeared that the energy-based macro-modeling method could capture the hysteresis features through the relationship between the equivalent viscous damping (EVD) ratio and the ductility capacity of PC wide beam-column connections.