Volume 05 Issue 02
Investigation of Efficiency of Different Ground Motion Scaling Methods for Estimating Seismic Demands of Steel Moment Frames
Morteza Razi | pp: 52-61 | Download Paper | Show Abstract
Abstract: There are different methods in seismic design codes for scaling earthquake ground motion records for the purpose of performing nonlinear time history analysis. The main objective of this study is to evaluate how different scaling approaches affect the results of nonlinear time history analysis. Reduced the scatter in estimated drift angles was the main criteria to measure the effectiveness of different scaling methods. For this purpose, three steel moment resisting frames with different height (3, 6, and 10 stories) were subjected to Incremental Dynamic Analysis under a suite of twenty near-fault and far-fault ground motions. The results indicate that the scaling method based on UBC 97 causes a more significant dispersion in the responses compared to the other considered methods.
Experimental Study of Delamination in GFRP during Drilling using Single AE Sensor
J. Sudha, S. Sampathkumar | pp: 62-65 | Download Paper | Show Abstract
Abstract: A Non-destructing testing (NDT) and an unconventional method that is being used for identifying the location and detection and determining the various characteristics of defects in products is Acoustic Emission Technology (AET), which can be applied for understanding the various events associated with drilling process, that occurs from the time when the drill bit comes into contact up to the completion of the drilling process. This paper focusses in finding the maximum thickness to detect drilling related delamination using single AE sensor. Delamination has been artificially induced by placing non-adhesive Teflon tape between the layers at the exit. Various AE parameters are analyzed to find its relation with the thickness of the composite material. Peak amplitude and slope of the cumulative RMS curve decreases with the increase in thickness of composite. Hence, the range of the thickness has been found out beyond which a single AE sensor cannot be used effectively to analyze different events that occur during drilling.
Modeling & Numerical Analysis of Supersonic Combustor with Double Inclined Ramp-Cavity Fuel Injector
G. Hariharan, N. SenthilKumar, S. Gopalakannan | pp: 66-70 | Download Paper | Show Abstract
Abstract: Sustaining the Supersonic Combustion in Scramjet engine is a very challenging topic of research nowadays. ‘Single-stage-to-orbit’ aerospace vehicles incorporating scramjet engine, is being contemplated to cut down space transportation costs. Propulsion and airframe unit integration, where the vehicle body adds to the thrust generating capacity of the engine besides providing aerodynamic lift, forms an integral part of the design philosophy. This Paper describes some challenges in the modeling of the Supersonic Combustor for proper mixing of air-fuel. Fuel Injectors are a critical component and their design has important effects for sustaining the flame in supersonic combustion as well as overall performance of the engine. Ramp injectors are considered to be a key feature to generate axial vortices. Generation of acoustic oscillations by the cavity injector is also considered to be a better candidate to achieve optimum mixing. Improvement in the performance of ramp and cavity injectors can be improved overall, by combining these injectors properly. Generation of turbulence and 3D flow field for better mixing and proper combustion relies on the combination of cavities and ramps. Ramps will improve the penetration of fuel in to the core and cavities will improve the flame holding characteristics. The ramp generated axial vortices can be utilized to scoop out the hot gases generated at cavities to improve the combustion efficiency. Thus Ramp and cavity combination shows promising characteristics for better scramjet combustor performance. Instead of having a long single inclination in the ramp, two short double inclinations can be made. By this we can prevent the sudden loss of energy. This in-turn increases the flame stabilization during Combustion.
Seismic Performance Evaluation of Knee and EBF Braced Frames using Nonlinear Static Analysis
Amin Moshtagh, Vahid Saberi, Hamid Saberi | pp: 71-77 | Download Paper | Show Abstract
Abstract: Earthquake-resistant structure systems should be designed to stand large deformation to absorb and attenuate imposed energy due to an earthquake while providing sufficient stiffness to transfer the forces to the base without collapse. Knee Braced Frames (KBF), which involves added additional diagonal elements to a frame to increase its ability to withstand lateral loads, is suggested by several researches. In this study, the seismic performance of KBFs are evaluated and compared with Eccentric Braced Frames (EBF). Nonlinear static analyses were utilized for seismic evaluation and comparison between the mentioned frame systems. Three steel structures of 5, 10, and 15-story were numerically modeled, and the seismic parameters such as lateral stiffness, inter-story drift, ductility, and response modification factors were calculated for each structure system. It was observed that using KBF systems resulted in a reduction in intersotry drifts compared to EBFs. KBF systems show more stiff responses in comparison with EBFs and they presented much more stiff response by reducing the knee element length. The KBFs have more ductile behavior in comparison with EBFs, although base shear in KBFs is less than EBFs.