الفهرس 
chapter (1) : introductionOnly 14 pages are availabe for public view
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Abstract
L-shaped reinforced concrete (RC) columns are required for special structural design; it gives more indoor space than the common RC columns and decrease prominent corners in a room which increases usable space. L-shaped reinforced concrete columns loss strength rapidly after high levels of fire effects due to their large surface area. This thesis presents an experimental investigation to study the behavior of L-shaped RC columns, difference effects between elevated temperature and direct fire on L-shaped RC columns, and the efficiency of many different techniques of retrofitting L-shaped RC columns after exposing to elevated temperature and direct fire. A total of seventeen half scale L-shaped RC columns were heated, retrofitted and tested under axial compression with small eccentricity. The main studied variables were the type of exposure temperature (elevated temperature and direct fire), the level of temperature (ambient temperature, 400 oC, and 600 oC ) and the retrofitting technique (steel angles with different number of battens, Fibrous and non-fibrous self-compacting concrete jacket, Fibrous and non-fibrous Reactive Powder Concrete Jacket). Test results indicated that increasing the degree of temperature has significant effect in decreasing the ultimate capacity, deformations and strains of columns. Effect of exposure to direct fire in decreasing ultimate capacity, deformations and strains of columns was less than exposure to elevated temperature. Retrofitting L-shaped columns with studied different techniques can increase the ultimate capacity, decrease the axial deformation, lateral deformation, vertical and horizontal concrete strain. Fibrous RPC jacketing of columns exposed to 400 °C and 600 °C increased the column ultimate capacity by 33% and 14% over that of the non-heated control column, respectively. However, fibrous SCC jacketing could only restore the ultimate capacity for columns exposed to 400 °C. Steel jacketing of columns exposed to 400 °C increased the column ultimate capacity by 32% over that of the non-heated control column. In addition to, a theoretical analysis were performed to design and analyze the L-shaped RC columns using the basic equations of ultimate limit state of strength. These equations were programmed by FORTRAN program to find the depth and inclination of neutral axis and then calculating the ultimate moment capacity in both two axes.