Shear behavior of fiber-reinforced concrete hollow-core slabs under elevated temperatures. (15th March 2021)

• Record Type: Journal Article
• Authors: Nguyen, Hang T.N.; Li, Ye; Tan, Kang Hai
• Is Part Of: Construction & building materials. Volume 275(2021)
• Publication Date: 2021-03-15
• Subjects: Concrete hollow-core slabs -- Polypropylene fibers -- Steel fibers -- Shear behavior -- Elevated temperatures -- Finite element modeling -- Abaqus/explicit; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2020.121362
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Hollow-core slabs might fail in shear before achieving their designed fire resistance. The use of steel fibers enhances shear capacity of hollow core slabs subjected to fire. Brittle failure under fire effects can be avoided with the use of steel fibers. Fire-exposed slabs with hooked steel fibers exhibit better performance compared to those with straight steel fibers. ABAQUS and the Concrete Damage Plasticity Model can predict behavior of fire-exposed slabs with and without fibers. Abstract: Experimental results of shear investigations on six hollow-core slabs with and without fibers cast by the extrusion method and tested under elevated temperatures are presented here. The purpose is to investigate shear behavior of precast/prestressed concrete hollow-core (PCHC) slabs using different types of fiber and fiber contents to resist fire effects. Three types of fiber including polypropylene (PP), hooked steel, and high-strength/straight steel fibers were employed. Two volume fractions of PP fibers (0.11 and 0.22%) and of steel fibers (0.51 and 0.89%) were examined. The effectiveness of PP fibers and steel fibers with different contents on structural performance of fire-exposed hollow-core slabs was quantified. Experimental results showed that the use of PP fibers increased resistance of concrete to explosive spalling, while resistance to load and elevated temperatures was substantially enhanced with the use of steel fibers. In addition, web-shear failure at an early stage of fire exposure was observed in all specimens without fibers and those with only PP fibers, exhibiting premature/brittle behavior. However, with the use of steel fibers, failure mode shifted from web-shear to flexural-shear or even flexural failure. Ductility and toughness of steel-fiber specimens subjected to elevated temperatures were also significantly enhanced. Test results from the experimental studies were then used to verify finite element (FE) models that simulated fire behavior of PCHC slabs with and without fibers. Good agreement between the test results and the FE models in terms of furnace temperature at failure, maximum deflection, and failure mode was obtained, thus verifying the numerical models. The verified FE models were then used to investigate web-shear mechanism of PCHC slabs exposed to fire. It is shown that temperature-induced tensile stresses in concrete webs (instead of temperature-induced reduction in strength of concrete and strands) governed web-shear behavior of PCHC slabs under elevated temperatures.