Short-span bridge superstructures are commonly made of conventional precast concrete components. The emergence of ultra-high-performance concrete (UHPC) and the publication of the American Association of State Highway and Transportation Officials Guide Specification for Structural Design with Ultra-High Performance Concrete create new possibilities for the redesign of short-span bridge superstructures. Several section shapes optimized for use with UHPC are introduced based on existing short-span section shape types along with practical span ranges shown for each section type. Sample design aids for modified UHPC box beams are presented to show possible span lengths and their necessary strand areas. Hypothetical case studies are discussed, showcasing many of the advantages of UHPC primary structural components over conventional concrete alternatives.
The award-winning Schuylkill River pedestrian bridge in down¬town Philadelphia, Pa. is believed to be the first cable-stayed pedestrian bridge to incorporate precast concrete curved U beams. PCI-certified precast concrete producer Fort Miller Co. Inc. of Schuylerville, N.Y., fabricated eight of these beams for the project. They are 7 ft (2.1 m) tall and 73 ft 9 in. to 80 ft (22 to 24 m) long and weigh 117 to 148 tons (106 to 134 tonnes). They conform to “PCI Guide Document for Curved U Beams,” U84-4, guidelines, except for the bottom flange, which was widened from 10 ft 9 in. to 13 ft (3 to 4 m) to accommodate the 25 ft (7.6 m) wide deck.
This study presents an innovative mechanical splice system to facilitate dry connections for code-compliant precast concrete beam-column joints. To evaluate its emulative seismic performance, two precast concrete beam-column subassembly specimens were designed and fabricated in accordance with seismic design pro-visions for special and intermediate moment frames. They were tested under cyclic loading, with two con-ventional cast-in-place control specimens. The precast concrete specimens with dry mechanical splices exhib-ited strength, ductility, failure modes, strain responses, energy dissipation, and strength degradation character-istics comparable with those of the control specimens under the test conditions. This demonstrates that the proposed seismic details can achieve emulative seismic performance. Researchers developed a lumped-plastic-hinge analysis model with an explicit joint element to simulate, using nonlinear conditions, the performance of precast concrete moment frame systems with dry connections. The model's analytical hysteretic respons-es agreed with the measured cyclic behavior of the physical specimens, confirming the applicability of the model proposed for precast concrete beam-column connections.
Building the Pine Rest Pediatric Center of Behavioral Health in Grand Rapids, Mich., with 365 insulated precast concrete wall panels that alternate embedded brick with acid wash and formliner finish saved project stakeholders time and money. Fabcon Precast was the PCI-certified precast concrete producer and erector
This study investigates the in-plane tensile perfor- mance of end-bearing bar connections between hol- low-core slabs , concrete masonry walls, a critical component in precast concrete diaphragm systems for mid- and high-rise construction. Six full-scale wall- slab assemblies were tested under displacement-con- trolled pull-away loading to simulate diaphragm tension with variations in reinforcement geometry (L-shaped and U-shaped bars), parapet presence , axial compression to reflect different floor levels. The results highlight that the primary load-resisting mechanism was shear friction at the grout-to-masonry interface, with embedded reinforcement and axial load serving to delay grout cracking and maintain struc- tural integrity postpeak. U-bar configurations showed improved strain distribution and reduced displace- ment, while vertical wall reinforcement, common in western Canada practice, proved critical in confining the grout , maintaining a continuous load path. Axial compression significantly enhanced connection strength and ductility, with peak capacities reaching up to 90 kN (20 kip), well above code-prescribed minimums in the Canadian Standards Association's CSA A23.3:24, Design of Concrete Structures,, the American Concrete Institute's Building Code for Structural Concrete-Code Requirements and Commentary (ACI 318-25). . Despite severe interface cracking, all connections sustained residual tensile capacity, demonstrating the resilience of end-bearing bar connections when combined with appropriate reinforcement detailing. The findings support current design practices and offer insight into enhancing the safety and robustness of diaphragm-to-wall connec- tions in precast concrete systems.
Boccella Precast’s patented Cella-Core 8 in. (203 mm) hollow-core floor slabs provide Type IIA two-hour fire rating without any topping and STC 51 noise rating to ensure a quiet living space for the new Rowhaus apartments in Wilmington, Del.
Concrete Technology Corp., based in Tacoma, Wash., helped the Washington State Department of Transportation accelerate con¬struction of three bridges at the intersection of State Route 520 and Montlake Boulevard in Seattle, Wash., by fabricating almost 600 precast, prestressed concrete girders, voided slabs, columns, and pile caps
The project team for the National Medal of Honor Museum in Arlington, Tex., initially considered supporting the monolithic building with full-height precast concrete columns. Through engineering analysis, the precast concrete specialty engineer determined that only hollow columns could meet all load requirements while accommodating utilities. The columns’ taper angle required PCI-certified precast concrete producer Gate Precast (now Wells–Hillsboro, Tex.) to design and fabricate unique formwork for each ring, which was cast inverted and flipped postcure.
Marist University’s new Dyson Center in Poughkeepsie, N.Y., has precast concrete wall assemblies with fieldstone-inset outer panels to seamlessly clad the old and new structures in an exterior that blends in with much older campus buildings. BPDL of Alma, QC, Canada, a PCI-certified precast concrete producer, pre¬cast concrete specialty engineer, and erector, BPDL, provided a precast concrete wall system with a facade that’s more versatile, durable, and cost-effective than traditional stone masonry walls.
This paper presents five worked-out examples on the design of precast concrete shear walls using new nonproprietary short-grouted ductile reinforcing bar connections. The examples are based on precast concrete shear wall details with conventional energy-dissipation (yielding flexural) reinforcing bar connections provided by precast concrete industry partners. The focus of the design examples is to demonstrate the calculations for the connection length and the vertical, transverse, and longitudinal tie reinforcement areas around the connection ducts.
This paper presents design, detailing, and analysis recommendations for nonproprietary short-grouted ductile energy-dissipation bar connections in special seismic precast concrete shear walls. The performance of the connections was experimentally validated based on previous testing of six shear wall specimens in accordance with ACI 550.6-19. Vertical, transverse, and longitudinal tie reinforcing bars were designed for the connections to transfer the energy-dissipation bar forces into the precast concrete components. A strut-and-tie model was developed and validated to design the tie reinforcement and connection length of the energy-dissipation bars to meet the specified performance objectives. Simplified equations are presented in this paper for practicing engineers to design precast concrete components that use these connections without going into the details of the strut-and-tie model. Conventional closed-form section analysis procedures to predict the nominal and probable axial-flexural strengths of walls using short-grouted energy-dissipation bar connections are presented and validated against the measured behaviors of the tested specimens. In addition, results from nonlinear fiber-el ement analyses are compared with the experimental data to demonstrate that precast concrete walls with short-grouted connections can be simulated numerically using techniques commonly adopted for reinforced concrete shear walls. The connection design procedure is demonstrated on numerical examples of realistic wall cross sections covering a wide range of properties in an accompanying article.
Prestressed concrete composite beams enable sup-port-free construction, accelerating the construction process. However, when structures use large-span beams that bear heavy loads, reducing the cross-sec-tional dimensions of composite beams while working with limited prestressing strands in precast concrete beams is difficult. This study suggests the use of pre-embedded ducts in precast, prestressed concrete beams. After postcast (cast-in-place) concrete is plac to complete the composite beam, prestressing strands are inserted in the ducts and secondary tensioning is performed, which forms the staged prestressed composite beam (SPCB). Four SPCB specimens were tested to simulate construction and service conditions to evaluate flexural performance. The crack distribution patterns, deflection evolution, and reinforcement strain development during loading were then observed The experimental results revealed that cracking during the precast concrete beam-bearing stage significant-ly reduced the overall crack resistance of the SPCB. consequently affecting subsequent deflection and crack development. This paper also presents proposed design methods for determining the cracking moment midspan deflection, reinforcement effective stress, an maximum crack width of SPCBs. The internal force arm coefficient for the SPCB was derived through regression analysis based on experimental data.
This paper presents a study, including the investigation, analysis, rehabilitation, and verification through full-load testing, of two adjacent overpass bridge structures that experienced significant structural damage shortly after entering service. The bridges comprise multiple units, each having three simple-span precast, pretensioned concrete girders made continuous through cast-in-place concrete diaphragms and deck. Structural damage included flexure cracks in the deck slab and web shear cracks in girders near supports. Investigations identified several contributing factors, including discrepancies between assumed and actual construction sequences, shear strength deficiencies in girders due to excessive strand debonding, inadequate shear reinforcement, and insufficient negative moment continuity reinforcement in the deck slab. Rehabilitation involved externally bonded and bolted steel plates on debonded girder webs near supports and additional negative moment continuity reinforcement through a new concrete overlay on the existing deck. A full-load test confirmed the effectiveness of these measures under design vehicle loads. The rehabilitated bridges successfully carried the design loads, with strengthening elements effectively contributing to the load-resisting mechanism. A numerical model developed using bridge modeling software validated observed response quantities. This study illustrates a methodical and practical approach to addressing structural deficiencies in prestressed concrete girder bridges caused by excessive strand debonding and inadequate continuity reinforcement, providing insights for enhancing long-term safety and performance.
Currently, hollow-core slabs are connected to walls using dowel or welded connections. The existing research on these connections is minimal, and their design capacity is limited. This research project investigated a new slab-to-wall end-bearing connection assembly that consisted of a steel plate and stud embedded in a hollow-core slab void. The capacity of the connection assembly embedded in a hollow-core slab was established by directly loading the assembly until steel or concrete failure. Results indicated that the connection assembly had conservative failure loads compared with predicted values for load applied in various directions. Slab-to-wall subassembly testing was conducted on hollow-core slabs anchored to the tops of cast-in-place walls. The setup was representative of the loading and behavior that this connection assembly would experience in a constructed build ing. Capacity of the subassembly was established by applying load until the hollow-core slab, wall, or anchor failed. The subassembly results indicated that the wall failed first in concrete breakout. Experimental capacities were conservative compared with capacities predicted using the American Concrete Institute's Building Code Requirements for Structural Concrete (ACI318-19) and Commentary (ACI318R-19). The combined results from this experimental program indicated that the proposed embedded steel plate and stud connection assembly had sufficient capacity and was easy to install.
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.
This paper demonstrates the versatility of beam-spring modeling when calculating flexural resistance functions for precast concrete insulated wall panels. Modeling frameworks that accurately estimate the flexural strength of panels while identifying critical limit states are powerful tools for precast concrete engineers. Behavior quantification benefits panels that are designed to withstand conventional wind loading and be especially beneficial for more severe loading conditions, such as blast or seismic, where evaluating the nonlinear response of structures is pertinent. This paper provides a review of the mechanics and plausible limit states of these structures, develops the modeling framework reflecting the behavior of the components, and validates this methodology using comparisons with experimental test data and analytical case studies. Emphasis is placed on the influence of wythe connector shear resistance when determining efficient panel design configurations. This study shows that beam-spring modeling captures full nonlinear resistance functions and ductility of panels examined herein, providing insight on limiting failure modes for these structures.
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 (ACI318-19) and Commentary (ACI318R-19) or the eighth edition of the PCI Design Handbook.
