Materials

Formulating Constitutive Stress-Strain Relations for Flexural Design of Ultra-High-Performance Fiber-Reinforced Concrete

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Abstract

Ultra-high-performance fiber-reinforced concrete (UHP-FRC) has high compressive strength (> 22 ksi [150 MPa]) and exceptional compressive ductility. The use of UHP-FRC provides new opportunities for future infrastructure. However, structural design criteria have not been developed to fully utilize UHP-FRC’s excellent mechanical properties. Maximum useable compressive strain, εcu, specified in the current design codes (ACI 318 Building Code and AASHTO LRFD Bridge Design Specifications) are limited to 0.003 for conventional plain concrete with little ductility and a maximum compressive strength of about 10 (69 MPa) and 15 ksi (103 MPa) for ACI 318 and AASHTO LRFD Specifications, respectively. This maximum concrete compressive strain directly limits the amount of longitudinal reinforcement that could be used in flexural members, which in turn limits the flexural capacity of the members. Since the maximum useable strains of UHP-FRC are 5 to 10 times of that of plain concrete, it is apparent that the maximum compressive strain used for the current design needs to be reevaluated for UHPFRC. In addition, unlike plain concrete, the tensile strength of UHP-FRC can also contribute to its bending capacity. This research investigated the flexural behavior of a UHP-FRC beam reinforced with flexural reinforcement five times greater than that allowed by ACI or AASHTO provisions for tension-controlled conventional reinforced concrete beams. The large amount of reinforcement also significantly affected the tensile behavior of UHP-FRC due to the tension-stiffening effect.

Keywords: beam, tension-stiffening effect, maximum concrete compressvie strain, tension-controlled, UHP-FRC

How to Cite:

Chao, S., Kaka, V. & Kim, J., (2016) “Formulating Constitutive Stress-Strain Relations for Flexural Design of Ultra-High-Performance Fiber-Reinforced Concrete”, International Interactive Symposium on Ultra-High Performance Concrete 1(1). doi: https://doi.org/10.21838/uhpc.2016.46