International Concrete Abstracts Portal

Corrosion—one of the major threats to the integrity of concrete structures—can consequently affect structure serviceability and ultimate limit state, possibly resulting in failure. Glass fiber-reinforced polymer (GFRP) can be used as an innovative alternative for conventional steel reinforcement in concrete structures, effectively addressing corrosion issues. In addition to its corrosion resistance and high strength-to-weight ratio, GFRP is commonly selected for non-prestressed bars and stirrups due to its cost advantage over other FRP materials. The study endeavored to provide a comprehensive overview of the shear resistance in GFRP-RC beams with short shear spans. The manuscript aims to synthesize and analyze shear test data based on published studies on GFRP-RC beams with a short shear span (a/d = 1.5 to 2.5). A comprehensive literature review was conducted to compile a database comprising 64 short GFRP-RC beams to evaluate the efficiency of using the strut-and-tie model (STM) for predicting the shear resistance of GFRP-RC beams. The findings reveal that the ACI 318 (2019) STM yielded the most accurate predictions of the shear resistance of GFRP-RC beams with shear span-to-depth ratios of 1.5 to 2.5, since the current ACI 440.11 and ACI 440.1R design codes and guidelines do not include shear equations using the strut-and-tie model for predicting the shear resistance of GFRP-RC beams. Based on the findings of this study, the results could contribute to establishing shear equations in the upcoming revision of the ACI 440.11 and ACI 440.1R design codes and guidelines, specifically tailored for designing short GFRP-RC beams using the strut-and-tie model. The study also provides sufficient data to apply the strut-and-tie model in the design of GFRP-RC beams.

This paper presents the effectiveness of various reinforcing schemes in the end zones of prestressed concrete bulb-tee girders. The default girder, provided by a local transportation agency, includes C-bars and spirals intended to control cracking, and is analyzed using three-dimensional finite element analysis. The formulated models are used to evaluate the breadth of end zones, strain responses, cracking patterns, damage amounts, and splitting forces, depending upon the configuration of the end-zone reinforcement. The number of C-bars is not influential in developing strand stress along the girder. The maximum principal stresses exceed the conventional limit within h/4 of the girder end, where h is the girder depth; however, the 3h/4 limit adequately encompasses the stress profiles, particularly in the web of the girder. The maximum tensile strain in the concrete varies with the elevation of the girder, and the inclined strands cause local compression in the C-bars, while spiral strains are independent of the number of bars. By positioning the C-bars, the vertical strain of the concrete decreases by more than 15.9%, which can minimize crack formation. Whereas the short-term crack width of the girder may not be an immediate concern, its long-term width is found to surpass the established limit of 0.18 mm (0.007 in.). In this regard, multiple C-bars should be placed to address concerns about undesirable cracking. The splitting cracks in the girder, resulting from the strand angles and eccentricities, can be properly predicted by published specifications within the range of 0.2h to 0.7h, beyond which remarkable discrepancies are observed in comparison with a refined approach. From a practical perspective, two to three No. 6 or No. 7 C-bars spaced 150 mm (6 in.) apart are recommended in the end zones alongside welded wire fabric.

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.

This study used finite element analysis to examine how tendon configuration affects the temperature behavior of post-tensioned concrete structures during fire exposure. The thermal behavior of various tendon configurations was modeled, showing good agreement with experimental data. Parametric studies found that unbonded single-strand tendons (S) and prestressing (pretensioned) strands (R) had lower thermal resistance than bonded post-tensioned tendons (B), unbonded post-tensioned tendons (U), and grouted extruded-strand tendons (G). The S and R specimens stayed at or below the critical temperature for one-way slabs, validating current safety codes. The B, U, and G specimens remained well below critical temperatures, indicating that a thinner concrete cover might suffice. These findings highlight the need to consider tendon configuration in structural fire-resistance evaluation and incorporate heat resistance assessment to ensure the safety and efficiency of prestressed concrete structures during fires.

No practically viable method exists yet to provide minimum shear reinforcements into pretensioned precast hollow-core slab (PHCS) units produced through the automated extrusion method. Subsequently, web-shear strength of PHCS units with untopped depth greater than 315 mm (12.5 in) should be reduced by half according to the current ACI 318 shear design provision. Meanwhile, continuous precast floor construction has been commonly adopted in current practices by utilizing cast-in-place (CIP) topping and/or core-filling concrete. However, shear test results on continuous composite PHCS members subjected to combined shear and negative bending moment are very limited in the literature. To this end, this study conducts shear tests of thick composite PHCS members with untopped depths greater than 315 mm (12.5 in) and various span-depth ratios, subjected to negative bending moments, where noncomposite and composite PHCS units subjected to shear combined with positive bending were also tested for comparison purposes. Test results showed that the flexure-shear strength can dominate the failure mode of continuous PHCS members rather than the web-shear failure, depending on the presence of CIP topping concrete and shear span-depth ratio. In addition, it was also confirmed that the shear strength of composite PHCS members is marginally improved by using the core-filling method under negative bending moment at continuous support, and thus its shear contribution seems not fully code-compliant and satisfactory to that estimated by using ACI 318 shear design equations.