Behaviors of New RC Bridge Columns Made of Highly Flowable Strain-Hardening Fiber-Reinforced Concrete (HF-SHFRC) under Cyclic Loads

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Abstract
Remarkable development of high-strength concrete and reinforcement has been achieved nowadays. The purpose of the New Reinforced Concrete (New RC) project is aimed to reduce member section size by using high-strength concrete (f′c > 70 MPa) and high-strength rebars (fy > 685 MPa). Material consumption can be further reduced owing to the upgrade of strength. However, the brittle nature of high-strength concrete may also cause early cover spalling and other ductility issues. The addition of steel fibers is an alternative transverse reinforcement in New RC infrastructure systems. Highly flowable strain-hardening fiber-reinforced concrete (HF-SHFRC) has excellent workability in the fresh state and exhibits the strain-hardening and multiple-cracking characteristics of high-performance fiber-reinforced cementitious composites (HPFRCC) in their hardened state. This study aims to investigate the cyclic behavior of New RC bridge columns made of HF-SHFRC. Five large-scale bridge columns are subjected to cyclic lateral loading to verify their responses and deformation capacity. The test results show that by adding 1.5 % of high-strength hooked steel fibers, great deformation capacity is developed, in which either the stirrups spacing is increased to two times that of the control specimen or all tires are eliminated in New RC bridge columns. In addition, the accuracy of the proposed concept of equivalent lateral reinforcement is verified by the test results. Implementation of HF-SHFRC in New RC infrastructure offers opportunities to significantly simplify the design and construction of members for sustainable urbanization while ensuring adequate ductility and damage tolerance.

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