بررسی کامپوزیت های فروسیمان برای تقویت ستون های بتنی Ferrocement composites for strengthening of concrete columns: A review

1. Introduction The strengthening and retrofitting of reinforced concrete (RC) structures are difficult but essential construction tasks [1]. Such activities are increasingly becoming significant because of the insufficient capacity of structures that have been designed using old design codes. In addition, RC structures are often damaged by numerous factors, such as natural disasters, fire or environmental effects. As a result, structures are weakened and must therefore be either strengthened or retrofitted. Effective and constructible techniques and materials should be used to improve deteriorated or substandard structural members. Deteriorated structural members must be examined and analysed carefully to determine its in situ condition prior to strengthening work. Furthermore, strengthening measures must be determined on the basis of the in situ condition of structures. Columns are essential structural elements designed to support the vertical loads of frame-structured buildings. These elements significantly stabilise such structures vertically and laterally, especially high-rise buildings. RC columns require sufficient lateral confinement to sustain axial loads effectively. This confinement is facilitated by lateral ties in the form of individual rings or continuous spirals that run from the top to the bottom of the columns [2]. Lateral confinement is also necessary to enable large deformation during loading. In the case of a seismic event, a sufficiently confined concrete core can dissipate increased amounts of energy. Thus, the capacity of this core increases when subjected to such dynamic loading events. On the contrary, a poorly confined concrete column is brittle. As a result, a structure may fail suddenly and catastrophically [3]. Tsai and Lin [4] reported that the inadequate axial load capacity and axial ductility of columns are the fundamental factors that are responsible for the collapse of many RC buildings during the 1999 Chi-Chi Taiwan earthquake. Therefore, sufficient lateral confinement must be provided to existing RC columns. Furthermore, existing substandard or deteriorated columns should be retrofitted or strengthened through external confinement to increase ductility and load-carrying capacity.