It has been shown, since the beginning of the 20 century, by many investigators that axial strength and ductility of reinforced concrete column can be significantly improved by providing sufficient lateral reinforcement. In order to improve the strength and ductility or to facilitate the construction of reinforced concrete circular columns, the PI of this proposal has developed a new confinement technique.
The proposed confinement technique is meant to increase the spacing of the confining spiral without jeopardizing the strength and ductility of the column or to improve the ductility and strength without reducing the spiral spacing and hindering the flow of concrete during construction. The new confinement technique uses two opposing spirals (cross spirals). Each of the two cross spirals is spaced twice what a single spiral is spaced to provide equivalent (same) amount of confining reinforcement. This will provide plenty of room (spiral spacing) so that the flow of concrete is not obstructed by the spiral in order to facilitate the construction of the columns. Earthquakes require the columns, which are the main supporting elements of the structure, to be adequately confined to provide sufficient ductility to dissipate energy without collapse, especially when high-strength concrete is used. The proposed confinement technique may be used to provide two opposing (cross) spirals instead of a single conventional spiral with the same spacing. This will double the amount of confinement without reducing the spiral spacing and violating the minimum allowable spiral spacing as specified by the ACI 318-02 building code. This may significantly enhance the ductility of the column.
The PI has already investigated the new confinement technique for circular columns sujected to concentric axial compressive loading. It was found that the new confinement technique may be used to improve the strength and ductility or to facilitate the construction of reinforced concrete columns and piles.
The objective of this research is to experimentally study the behavior of reinforced concrete circular columns confined using the proposed confinement technique (cross spirals) under constant axial loading and cyclic lateral loading to simulate seismic loading. This will be compared to columns confined with single conventional spiral in accordance with the ACI 318-02 concrete building code. This study includes conducting the experimental testing of 12 reinforced concrete circular columns. The columns will be subjected to constant axial load and reversed cyclic lateral load to simulate seismic loading.
The current state-of-practice in seismic design of concrete columns does not meet the increasingly demanding standard of post-earthquake serviceability, but rather only attempts to maintain life-safety. This research will open a new and wide research topic to study the effect of the new confinement technique on the behavior of R/C column subjected to different loads. The ductility of columns is a very important issue in seismic design and needs to be enhanced to reduce the seismic hazard and provide more safety during and after earthquakes. This research will also open a wide door to the PI to do more research in the topic and carefully look at the advantages and is advantages of the new idea. The application of the findings of the proposed research into practice will help change the course of current earthquake engineering workforce to concentrate more on damage minimization in structures.
