iosr-JMCE   Volume-11 ~ Issue-5 ~ Sep-Oct 2014

Abstract: External prestressing is commenly used with notable effectiveness to increase and upgrade the flexural capacity of Reinforced Concrete (RC) beams and slabs. However, the major practical difficulty associated with external prestressing is that, it must be applied to relatively high strength concrete elements which may not be met in many cases where geometry and properties of concrete and steel reinforcement of existing member can't be modified. Hence the designer has no control on the existing structural elements that need repair. This research is aims to develop and evaluate an innovative strengthening technique for low strength concrete slabs.

[1]. El-Habbal, I., Abdalla, H., and El-Zanaty, A. (2003). "Strengthening of Reinforced Concrete Beams Using External Prestressing", Tenth International Colloquium on Structural and Geotechnical Engineering, Cairo, Egypt.
[2]. Gallab, A., (2005). "Factors Affecting the External Prestressing Stress in Externally Strengthened Prestressed Concrete Beams", Journal of Ain Shams, Vol. 27, Issue 9, pp. 945–957.
[3]. Virlogeux, M. (1982). "External Prestressing", Proceeding of IABSE, Zurich, Switzerland, pp 101-108.
[4]. Tan, K., Ng, C. (1997). "Effects of Deviators and Tendons Configuration on Behaviour of Externally Prestressed Beams", ACI Struct J, Vol. 94, No. 1, pp. 13–22.
[5]. Ibrahim, M. (2010). "Parametric Study of Continuous Concrete Beam Prestressed with External Tendon", Jordan Journal of Civil Engineering, Volume 4, No. 3.

Abstract: Wind induced load is an important issue for tall buildings, cable suspension bridges, electricity transmission towers, telecommunication towers and chimneys during natural disasters like strong winds of cyclone and earth quakes. One way to minimize wind-induced vibrations of tall buildings is to focus more on their shapes in the design stage. Important design aspect is that rather complicated sectional shapes are basically good with regard to aerodynamic properties for crosswind responses, which is a key issue in tall building wind-resistant design. Four models of non-circular high rise buildings were made and tested in a low speed wind tunnel. Triangular, taper square, square steps with sharp corners and square steps with filleted corners models are prepared. The study investigates the drags force and pressure distribution at the center of different models at different velocities with different orientations.

[1] Y.Tamura et al (2010), Aerodynamic characteristics of tall building models with various unconventional configurations, Proceedings of the 2010 Structures Congress.
[2]. J-A., Amin, A-.K.,Ahuja, 2008, Experimental study of wind pressures on irregular plan shape buildings, BBAA VI, 20-24.
[3]. Y.C., Kim, J., Kanda, 2010, Characteristics of aerodynamic force and pressures on square plan buildings with height variations, Journal of Wind Engineering and Industrial Aerodynamics 98, 449-465.
[4]. Hayashida, H.,Iwasa,Y.,1990.Aerodynamicshapeeffectsoftallbuildingforvortex induced vibration. Journal of Wind Engineering and Industrial Aerodynamics 33,237–242.
[5]. N., Lin, C., Letchford, Y., Tamura, B., Liang, O., Nakamura, 2005, Characteristics of wind forces acting on tall buildings, Journal of Wind Engineering and Industrial Aerodynamics 93, 217-242.
[6]. Y.C., Kim, J., Kanda, 2010, Characteristics of aerodynamic force and pressures on square plan buildings with height variations, Journal of Wind Engineering and Industrial Aerodynamics 98, 449-465.
[7]. Chien, C.W., Jang, J.J., Li, Y.C. (2010), "Wind-resistant design of high mast structures", Journal of the Chinese
Institute of Engineers 33 (4), 597-615.

Abstract: Flow over skewed steps is an interesting practical problem with wide range of applications such asaerodynamic vehicles and structures. A closed view of any automobile gives an idea that it has been derived from step pattern. Now a day's researchers are concentrating on increasing of fuel economy and minimization of noise by eliminating undesirable drag forces and aerodynamic instabilities particularly in high speed vehicles. Fuel economy is mainly depends on induced drag which is a dependent of step inclination angle. This study investigates the variation of flow behavior with step inclinations on different models at different velocities. Based on the literature review nine models were designed by using CATIA.

[1] R.B.Sharma et al (2014), Drag Reduction of Passenger Car Using Add-On Devices, Hindawi Publishing Corporation.
[2] Ram Bansal et al (2013), CFD Simulation for Flow over Passenger Car Using Tail Plates for Aerodynamic Drag Reduction, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE).
[3] B.F.Armaly et al(1983), Experimental and theoretical investigation of backward-facing step flow, J . Fluid Mech. (1983), vol. 127.
[4] Olivier Cadot et al (2004), Three-dimensional stationary flow over a backward-facing step, European Journal of Mechanics B/Fluids 23 (2004) 147–155.
[5] Bahram Khalighi et al, Unsteady Aerodynamic Flow Investigation around a Simplified Square-Back Road Vehicle with Drag Reduction Devices
[6] Young J. Moon et.al (2005), Investigation of Flow-Induced Noise from a Forward Facing Step, Japan Society of Fluid Mechanics
[7] Durst. F, and Peireira (1993) the plane symmetric sudden-expansion flow at low Reynolds numbers, J. Fluid Mech., 248, pp. 567–581.

Abstract: Friction stir welding (FSW) is a latest solid state joining process for similar or dissimilar metals. It has wide application in several industries. In friction stir welding, selection of tool material and design of tool plays an important role for weld quality. In this experimental work, two different tool materials were used with straight cylindrical pin profile i.e. High carbon High chromium Steel (D3) (HcHcr) and High Speed Steel (H.S.S).The aim of this work is to analyze the effect of each tool on mechanical properties of weld metal. Keywords: Friction Stir Welding, Tool material, Mechanical Properties.

[1]. Thomas WM, Nicholas ED, Needham JC, Murch MG, Temple-Smith P, Dawes CJ. Friction stir butt welding. International Patent Application No. PCT/GB92/02203; 1991.
[2]. Xiaocong He, Fengshou Gu, Andrew Ball "A review of numerical analysis of friction stir welding" Progress in Materials Science 65 (2014) 1–66
[3]. El-Danaf EA, El-Rayes MM. Microstructure and mechanical properties of friction stir welded 6082 AA in as welded and post weld heat treated conditions. Mater Des 2013; 46:561–72.
[4]. Sonne MR, Tutum CC, Hattel JH, Simar A, De Meester B. The effect of hardening laws and thermal softening on modeling Residual stresses in FSW of aluminum alloy 2024-T3. J Mater Process Technol 2013; 213:477–86.
[5]. Kitamura K, Fujii H, Iwata Y, Sun YS, Morisada Y. Flexible control of the microstructure and mechanical properties of friction stir welded Ti–6Al–4V joints. Mater Des 2013; 46:348–54.