Browsing by Author "Ai, Jun"
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- ItemNumerical investigation for the fatigue performance of reinforced concrete beams strengthened with external prestressed HFRP sheet(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2020-03-20) Wang, Xiaomeng; Zhou, Chuwei; Ai, Jun; Petrů, Michal; Liu, YaoExternal FRP (Fiber Reinforced Polymer) strengthening method has been considered to be an effective way to restore or increase the capacity of RC (Reinforced Concrete) beams. This study focuses on numerical simulating the fatigue performance of HFRP (Hybrid Fiber Reinforced Polymer) strengthened RC beam. Beams are pre-cracked first, then strengthened by HFRP, and subjected to fatigue loading. The test variable is the prestress of HFRP. Stress distribution and damage development of pre-cracking, strengthening and fatigue loading process are analyzed. The user-subroutine UMAT in Abaqus is used for implementation of the constitutive models of component materials. The simulation results show good agreements with experimental data. The failure of both reference beam and strengthened beams is found caused by fatigue fracture of the longitudinal steel bar. Therefore, the stress amplitude of the longitudinal steel bar is the dominant factor of the fatigue life of RC beams. Prestressed HFRP can significantly reduce the stress magnitude of longitudinal steel bar and suppress crack propagation, thus improve the fatigue life of the strengthened RC beam. In an appropriate range, elevating prestress level can prolong fatigue life of strengthened RC beam.
- ItemParametric Study of Flexural Strengthening of Concrete Beams with Prestressed Hybrid Reinforced Polymer(MDPI, 2019-11) Wang, Xiaomeng; Petrů, Michal; Ai, Jun; Ou, ShikunThe strengthening method of using hybrid fiber reinforced polymer is an effective way to increase the strengthening efficiency and lower the cost. This paper focuses on simulating the flexural behavior of reinforced concrete beam strengthened by prestressed C/GFRP (Carbon-Glass hybrid Fiber Reinforced Polymer) with different hybrid ratios and prestress levels. An elastoplastic damage constitution is used to simulate the mechanical behavior of concrete. A cohesive zone model under mixed mode is adopted to describe the debonding behavior of the FRP-concrete and concrete-steel interface. The results show good agreement with the experiment in the load-deflection curve, load-stress curve of steel, and HFRP. Furthermore, the failure mode of concrete and FRP debonding obtained from numerical simulation is the same as the test. Considering the improvement of the bending capacity, stiffness, and ductility of the strengthened beam in this paper, the best hybrid ratio of carbon to glass fiber is 1:1, and the suitable prestress level is between 30 and 50% of its ultimate strength.