Ultra-high performance concrete (UHPC) is a developing concrete and today is increasing to interest using it in structures due to its advantages such as high-compressive strength, modulus of elasticity, highly durability and low-permeability. Therefore, it is necessary to provide models for prediction of nonlinear behavior of this material. This study is aimed to investigate the tension-stiffening phenomenon for UHPC and to propose a model for the post-cracking behavior of the reinforced concrete members under tension. For this purpose, in this study, 24 cylindrical concrete specimens reinforced with a rebar in its center were prepared using UHPC and Two rebar types including steel and GFRP (Glass Fiber Reinforced Polymer). Three specimen diameters (65 mm, 100 mm, and 125 mm), and two rebar diameters (12 mm and 16 mm) were considered. All specimens were tested under direct tension. According to the experimental data, a tension-stiffening model was proposed for UHPC. The proposed model has suitable correlation with experimental results.

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