Abstract
It is easy to think of using sawtooth steel plate on the surface of column to increase the interfacial friction in the temporary RC column underpinning structure. However, there is little research on the friction properties between sawtooth steel plate and concrete. 108 working condition of double interface shear tests were conducted for measuring the friction coefficient between the sawtooth steel plate and the concrete, and the effects of concrete strength, sawtooth size, interface contact method and interface normal pressure on the friction coefficient were also analyzed. The results show that concrete strength on the friction coefficient is not significant when the interface normal pressure is less than 6MPa. After the use of sawtooth steel, the coefficient of friction is greatly improved, and the friction coefficient is approximately linearly related to the aspect ratio of the sawtooth. Damage on the concrete surface will be reduced after adding a flexible material at the contacting interface, but at the same time, it will reduce the friction coefficient. When the sawtooth steel is in direct contact with the concrete, the friction coefficient increases with increasing normal pressure at the interface, however, when the interface is added with flexible material, the friction coefficient is almost irrelevant to the normal pressure.
Highlights
Over the past decades, the renovation of existing buildings is booming in many countries
(3) The damage of the concrete surface will be reduced after the interface material is added, the friction coefficient between steel plate and concrete will decrease
When adding felt and carpet at the contact interface, the average friction coefficient was reduced by 24.4% and 14.3% compared with the average friction coefficient of direct contact
Summary
The renovation of existing buildings is booming in many countries. Try to develop little damage underpinning methods for RC column, Hohai University[9] proposed a new type underpinning joint for concrete column that load underpinning by friction of sawtooth steel plate and column face. BG Rabbat(1985)[11] studied the friction coefficient of the interface between steel plate and concrete with wet and dry conditions. The friction coefficient is too small, which limits the application of steel-concrete contacting underpinning method in engineering. The author proposed the application of the sawtooth steel plate to contact with concrete, expecting to greatly increase the friction coefficient under the condition that micro-damage occurs on concrete surface. Tests to study the friction coefficient between the sawtooth steel plate and concrete were carried out systematically
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