THESIS
2019
xiii, 119 pages : illustrations (chiefly color) ; 30 cm
Abstract
Reinforced concrete has been established as a major construction material since the
last century. Some existing structures that no longer meet current standards and or
even become functionally obsolete require immediate repair and strengthening.
Strain-hardening cementitious composite (SHCC) was a class of high performance
materials developed under the guidance of micromechanics theory. Its superior
properties include high ductility and energy absorption with multiple cracking
behaviour and high durability through tight crack control. With proper mix design,
high tensile strength can also be achieved. In the literature, SHCC have been
considered as a potential material for strengthening of reinforced concrete (RC)
structures due to their compatibility in both physical and mecha...[
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Reinforced concrete has been established as a major construction material since the
last century. Some existing structures that no longer meet current standards and or
even become functionally obsolete require immediate repair and strengthening.
Strain-hardening cementitious composite (SHCC) was a class of high performance
materials developed under the guidance of micromechanics theory. Its superior
properties include high ductility and energy absorption with multiple cracking
behaviour and high durability through tight crack control. With proper mix design,
high tensile strength can also be achieved. In the literature, SHCC have been
considered as a potential material for strengthening of reinforced concrete (RC)
structures due to their compatibility in both physical and mechanical properties. This
study focuses on the shear strengthening of beams with high strength SHCC. Direct
shear test was performed to show that the bond strength between RC and SHCC under
shear load was satisfactory, even without any anchoring system. Reinforced concrete
beams designed with different shear span-to-depth ratio (1.5:1 and 2.5:1) were then
cast. Thin layers of high strength SHCC were patched on both sides of the RC beams
as a strengthening system. The results showed that the shear capacity of certain
strengthened groups significantly increased compared to the reference group. Upon
ultimate failure, the stable propagation of multiple cracking on the strengthening layer
restrained surface concrete from spalling. In terms of repairing damaged RC beams, it
was found that SHCC patches can effectively recover capacity loss. However, the
level of recovery depends on the damage conditions. A finite element model was
constructed to simulate the experimental tests, and satisfactory agreement between
numerical and test results was achieved. A simple design equation for SHCC patching
strengthening system was proposed according to the numerical parametric study using
ABAQUS. This study demonstrated the feasibility of using high strength SHCC in shear strengthening and repair of RC beams. It also presented a simple design method
for the strengthening system to lay the foundation for its practical use.
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