رغيد فتحي مكي المتولي

Abstract Concrete filled steel tube (CFST) columns have been increasingly used in many modern structures. Concrete filled steel tube columns offer excellent structural performance, such as high strength, high ductility and large energy axial absorption capacity and have been widely used as primary axial load-carrying members (compression members) in high rise buildings, bridged and offshore structures. In this paper, experimental works is presented to investigate the behavior of light weight concrete (No fine aggregate) filled steel tube (CFST) columns. Mild circular steel tubes are used in the construction of the specimens with different diameter /thickness ratios (D/t) and different slenderness ratios (L/r), in order to assess the effect of these variables on the strength of columns. Also the ultimate strength of concrete-filled steel tube columns have been investigated by using different strengths of light weight concrete . The experimental results show that the effect of height (the slenderness (L/r) ratio) on the ultimate strength of CFST columns will have a reverse relation. While the effect of uniaxial compressive strength and the effect of diameter /thickness ratios (D/t) on the ultimate strength of CFST columns will have an increase relation.

Abstracted- Reinforced concrete (RC) columns in buildings often need rehabilitation either due to defects in the columns themselves, having to support higher loads than those foreseen in the initial design of the structure, or as the result of ageing or accidental damage. The use of steel caging for this purpose is now a common practice in many countries throughout the world. In this paper, experimental works is presented to investigate the behavior of of reinforced concrete columns strengthened externally with steel jacket under axial loads. This experimental work comprises of twelve square reinforced concrete columns with same cross section of (120x120)mm and height of 1000mm. These columns divided to four groups, the first group (includes three columns) represents the control samples i.e without any type of strengthening, second group (includes three columns) strengthened by various sizes of four vertical steel angles at column corners linked by horizontal battens, third group (includes three columns) strengthened by constant sizes of four vertical steel angles at column corners linked by various sizes of steel plates at top and bottom of columns, while fourth group (includes three columns) strengthened by constant sizes of four vertical steel angles at column corners linked by (various sizes of steel plates at top and bottom of columns besides horizontal battens).The results show that the rehabilitation technique (strengthening) of R.C. columns by using external steel jacket can increase the ultimate load from (42.2-121.7)%. Abstracted- Reinforced concrete (RC) columns in buildings often need rehabilitation either due to defects in the columns themselves, having to support higher loads than those foreseen in the initial design of the structure, or as the result of ageing or accidental damage. The use of steel caging for this purpose is now a common practice in many countries throughout the world. In this paper, experimental works is presented to investigate the behavior of of reinforced concrete columns strengthened externally with steel jacket under axial loads. This experimental work comprises of twelve square reinforced concrete columns with same cross section of (120x120)mm and height of 1000mm. These columns divided to four groups, the first group (includes three columns) represents the control samples i.e without any type of strengthening, second group (includes three columns) strengthened by various sizes of four vertical steel angles at column corners linked by horizontal battens, third group (includes three columns) strengthened by constant sizes of four vertical steel angles at column corners linked by various sizes of steel plates at top and bottom of columns, while fourth group (includes three columns) strengthened by constant sizes of four vertical steel angles at column corners linked by (various sizes of steel plates at top and bottom of columns besides horizontal battens).The results show that the rehabilitation technique (strengthening) of R.C. columns by using external steel jacket can increase the ultimate load from (42.2-121.7)%.

Abstract: No-Fine concrete filled double steel tube columns (CFDST) are being increasingly used for structural applications. It has been used for submerged tube tunnels, nuclear containment, liquid and gas retaining structures, vessels under external pressure in very deep water and for compression members in offshore construction, this is due to the aesthetic appearance, ease of maintenance and simple of construction. The (CFDST) columns also have excellent resistance to seismic loads and fire. This paper comprises of an experimental study on the structural behavior of double steel tubular columns filled with No-Fine concrete under axial load. Eight samples of double steel circular tubes with different diameters for the inner and outer tubes are used, with different slenderness ratios (L/r), different ultimate strengths of No-Fine concrete . Also two cases are study for (CFDST) samples first with hollow inner tube and second with completely filled inner and outer tubes with No-Fine concrete. The experimental results show that the effect of height (the slenderness (L/r) ratio) on the ultimate strength of CFDST columns will have a reverse relation. While the effect of uniaxial compressive strength and the effect of fully filling the core of internal tube on the ultimate strength of CFDST columns will have an increase relation.

Abstract: In this paper, experimental works is presented to investigate the behavior of reinforced concrete beams retrofitted by ferrocement to increase the strength of beams in both shear and flexure, ten reinforced concrete beams are casted in order to study different parameters such as shear reinforcement (stirrups), different diameters of wire mesh used in rehabilitation, two types of rehabilitation are used first (strengthening) and second (repairing) the beams are initially stressed to a different prefixed percentage of the ultimate load and finally mechanical method is used to fixed the wire mesh of ferrocement (using bolts) to eliminate the debonding of ferrocementand trying to reach the full maximum tensile strength of ferrocement. The experimental results indicated that the rehabilitation technique (strengthening and repairing) of R.C. beams by using ferrocement system is applicable and can increase the ultimate load from (69.8-175% in case of strengthening) and from (50.94-125% in case of repairing), also the test results for strengthening beams showed that the effect of diameter of ferrocement wire mesh (changing from 1.2 to 2.2mm) on the ultimate strength of R.C. beams will have an increase relation from {(95-175% without steel stirrups) and (69.8-126.4% with steel stirrups)}. Also for repairing beams the results state that the effect of diameter of ferrocement wire mesh (changing from 1.2 to 2.2mm) on the ultimate strength of R.C. beams will have an increase relation from {(67.5-125% without steel stirrups) and (50.94-84.9% with steel stirrups)}.