PCI 124 Specification for Fire Resistance of Precast/Prestressed Concrete-PCI 124 Specification for Fire Resistance Webinar Presenter Q&A

PCI 124 Specification for Fire Resistance Webinar Presenter Q&A

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During a PCI 124 Specification for Fire Resistance of Precast/Prestressed Concrete webinar presenter Q&A session, several questions were addressed. One question asked if there were plans to develop fire code language for UHPC building elements. The response stated that while there are no plans in the short term, as UHPC evolves within the body of knowledge for PCI, consideration will likely be given to including language for its inclusion in building codes and PCI 124.<br /><br />Another question asked about analyzing the fire resistance of composite insulated sandwich wall panels. The answer explained that currently, building codes only address heat transmission criteria and not structural strength for walls. The controlling end point criteria during testing was found to be heat transmission and not structural failure. However, PCI 124 does cover wall panels, including insulated sandwich walls, in Section 3.2.4.<br /><br />The topic of fiber reinforced precast concrete was also discussed. It was clarified that when steel fibers are used, they are primarily for crack control or shear resistance, which does not affect fire design. There are no specific provisions in PCI 124, ACI 216.1, or the IBC for determining the fire resistance of fiber reinforced precast concrete. However, for concrete reinforced with FRP, Section 4.4.5 of ACI 440.1R provides guidance.<br /><br />The webinar also addressed whether PCI 124 applies similarly to unbonded post tensioned prestressed concrete slabs as pretensioned slabs. The answer referred to Entry Item No. 4 in Table 721.1(1) in the 2018 IBC, which covers this condition. In earlier editions of the IBC, the table can be found in Section 719 or 720.<br /><br />Regarding minimum concrete cover on wall panel reinforcement, the response explained that due to extensive testing of concrete walls over the years, the main failure mode is thermal transmittance of heat through the wall. Therefore, fire resistance provisions in PCI 124, ACI 216.1, and the IBC do not specify any cover requirement for reinforcement steel. The need for reinforcement steel is typically for addressing flexure from lateral loads, and there is no requirement for a wall to meet a fire incident simultaneously with a wind or seismic event. However, if reinforcement is needed to support gravity loads, cover requirements should be examined where fire resistance is required. The cover requirements for reinforcement in concrete slabs can be followed.<br /><br />Other questions addressed topics such as strength reduction factors in PCI 124, weep holes in hollow core slabs, and the reasoning behind cover requirements for corner bars and tendons in beams. The webinar provided explanations and guidance for these topics.

Keywords

PCI 124

fire resistance

precast concrete

UHPC

building codes

insulated sandwich wall panels

fiber reinforced precast concrete

steel fibers

FRP

post tensioned prestressed concrete slabs