Abstract
Ultra-High Performance Concrete (UHPC) has been a material of interest for retrofitting reinforced concrete elements because of its pioneer mechanical and material properties. Numerous experimental studies for retrofitting concrete structures have shown an improvement in durability performance and structural behaviour. However, conservative and sometimes erroneous estimates for bond strength are used for numerically calculating the strength of the composite members. In addition, different roughening methods have been used to improve the bond mechanism; however, there is a lack of numerical simulation for the force transfer mechanism between the concrete substrate and UHPC as a repair material. This paper presents an experimental and numerical programme designed to characterize the interfacial properties of concrete substrate and its effect on the bond strength between the two materials. The experimental programme evaluates the bond strength between the concrete substrates and UHPC with two different surface preparations while using bi-surface test and additional material tests, including cylinder and cube tests for compression property, direct tension test, and flexural test to complement UHPC tensile properties. Non-linear finite element analysis was conducted, which uses a numerical zero thickness volume model to define the interface bond instead of a traditional fixed contact model. The numerical results from the zero thickness volume model show good agreement with the experimental results with a reduction in error by 181% and 24% for smooth and rough interface surfaces if compared to the results from the model with a fixed contact.
Highlights
Ultra-high performance concrete (UHPC) has been in the interest of research with different range of applications for bridge construction, repair and rehabilitation, overlays, building, petroleum industry, hydraulic structures, and architectural components [1,2]
UHPC is developed by the inspiration of three concrete technologies: self-compacting concrete (SCC), high-performance concrete (HPC), and fibre reinforced concrete (FRC) with a high compressive strength that is higher than 126 MPa (18 ksi) and post-cracking tensile strength of more than 5 MPa (0.7 ksi) [1,3,4,5,6,7]
Normal strength concrete (NSC) [12,13] and the key factor of UHPC production is the enhancement of material density, mechanical homogeneity, and particle packing by improving macro and micro properties [12,13,14,15,16,17,18,19,20], which help the durability of UHPC against chloride diffusion
Summary
Ultra-high performance concrete (UHPC) has been in the interest of research with different range of applications for bridge construction, repair and rehabilitation, overlays, building, petroleum industry, hydraulic structures, and architectural components [1,2]. Harris et al, [45] and Azizinamini et al, [46] presented an approach to solve this challenge using simple fix contact surface or tie model between two layers Such an approach might cause the overestimation of bond strength and global structural performance. Mechanical properties of UHPC are investigated to achieve this goal, and the test results are used to simulate the behaviour of UHPC in ATENA software
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