This paper details the development of alternative strength reduction factors that capture the behavior and variability of precast concrete insulated wall panels failing in interwythe shear at the peak flexural resistance limit state. Previous research has shown that this milestone generally manifests when most wythe connectors in a panel are past their proportional limit, which introduces a greater level of uncertainty for the panel compared with the uncertainty during its elastic response. The methodology addressed three types of uncertainties: the reliability of assessments of the variability of wythe connector data against average values, the accuracy of simplified design backbone curves, and the effectiveness of beam-spring models to capture the behavior of panels. The results facilitated recommendations for new strength reduction factors as a function of plausible safety indexes. These factors were as high as 0.881 and 0.818 for discrete and continuous wythe connectors, respectively, when assuming a very lenient probability of failure of 0.1 and a corresponding safety index of 1.28.

Adjacent box-girder bridges are a cost-effective solution for short-span bridges that require a shallow profile. These bridges use precast concrete hollow boxes erected side by side to create a bridge profile with load transfer between the adjacent girders facilitated by shear keys placed near the top of the section. Transverse post-tensioning is also provided along the span to help with load transfer. However, the traditional partial-depth shear keys are susceptible to thermal cracking. Shear-key cracking can cause leakage and loss of load transfer, leading to corrosion and deterioration of the girders. An analytical study with different shear key configurations was performed to investigate joint performance when subjected to thermal and live loads. The effectiveness of post-tensioning and shear key reinforcement in mitigating shear key cracking was assessed. It was concluded that using full-depth or middepth shear keys can potentially improve the performance of adjacent box-girder bridges, whereas post-tensioning or joint reinforcement is ineffective in leakage prevention.

The Crow Museum of Asian Art is the inaugural build¬ing of the Edith and Peter O’Donnell Jr. Athenaeum, a 12-acre arts and performance complex on the campus of the University of Texas at Dallas. The 68,000 ft2 (6300 m2) structure, which is the Crow Museum’s second location, was a design-assist project bringing together design architect Morphosis, based in Los Angeles, Calif.; general contractor The Beck Group, of Dallas, Tex.; and PCI producer member GATE Precast, based in Hillsboro, Tex.

Reentrant corner cracks have been observed in pre¬tensioned concrete slabs, but the phenomenon has not been explained in relation to the introduction of prestressing. In this study, a strand pullout experiment was conducted to confirm the occurrence of reentrant corner cracks and investigate the effect of reinforce¬ment on these cracks. The specimens were made in the shape of a unit rib of an inverted ribbed precast concrete slab, and three types of reinforcing elements were placed across the predicted surfaces of the cracks. The results showed that the maximum applied tensile load increased by up to 10.2% with reinforcement. In the specimen with mesh reinforcement, when the slip increased to 2 mm (0.079 in.), the load reduction ratio was limited to 52.2% of that of the unreinforced speci¬men. These findings provide practical insights into the behavior of reentrant corner cracks, enhancing under¬standing of how reinforcement can effectively maintain structural integrity.

This paper presents the development and implementation of a fly-ash-based alkali-activated concrete mixture for use in precast, prestressed concrete beams. Alkali-activated concrete, which contains no portland cement and often incorporates recycled materials, offers an environmentally friendly alternative to conventional concrete. The study evaluated over 40 mortar mixtures to identify a design suitable for precasting plant production. Full-scale beams and mechanical property specimens were fabricated and tested, alongside comparable portland cement concrete specimens. Results showed that the structural performance of alkali-activated concrete beams varied from code-based predictions, highlighting the need for further refinement in design and fabrication methods. The research provides practical insights into adapting alkali-activated concrete for precast applications, including lessons learned on production constraints and material behavior.

The structure at 2500 League Island Boulevard, a 130,000 ft2 (1200 m2), state-of-the-art flex production building constructed with 172 precast concrete panels, is a recent addition to the Philadelphia Navy Yard in Pennsylvania. Bill Hydock, preconstruction manager with Universal Concrete Products, says that a high degree of collaboration and open communication lines among all parties involved led to an innovative panelization approach on the project.

In this paper, a trilinear moment-curvature response is assumed to govern the behavior of prestressed concrete beams with straight strands. The trilinear moment-curvature response is integrated to yield closed-form deflection expressions that are useful for analytically assessing the deflections of prestressed concrete flexural members. To evaluate the key controlling points of the moment-curvature relationship, the derived procedure used closed-form and iterative equations to determine neutral axis locations, moments, and curvatures at the cracking, yielding, and ultimate levels to define the trilinear moment-curvature response. To derive the equations, internal stress analysis was used for the linear-elastic region upon cracking and strain compatibility and force equilibrium were used for the postcracked regions of the response, along with nonlinear material behaviors. Both strand ultimate strain and concrete crushing failure modes were analyzed for each cross section. Previously published experimental data for six prestressed concrete beams were used to check the derived short term deflection analysis procedure. Of the six specimens, some had moment-curvature graphs and others had load-deflection graphs that could be used for comparison to the equations in the proposed method. The proposed method produced accurate predictions for moment curvature and short-term load-deflection responses, and it determined deflections within the postyielding region of the load-deflection response that are not accurately predicted by methods in the American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) or the eighth edition of the PCI Design Handbook.

This paper discusses selected changes from ACI 318- 14 to ACI 318-19 that are likely to have the largest impact on precast concrete design and construction. Some of these changes have proved to be somewhat problematic. These concerns are described, and in a few cases, suggestions are offered that might mitigate some of the negative impact.

The new Governor Harry W. Nice/Senator Thomas “Mac” Middleton Bridge over the Potomac River uses precast concrete to replace the steel bridge that opened across the river in 1940. Coastal Precast Systems of Chesapeake, Va., was brought on to design and build all precast concrete elements on the new bridge.