CFRP Composites for Strengthening of Reinforced Concrete Walls with Openings
This paper presents the results of a research work aimed at investigating the potential used of externally bonded Carbon Fiber Reinforced Polymer (CFRP) composite sheets as a strengthening solution for uniaxial rectangular concrete walls with central rectangular in-plane openings. Seventeen of 1/3 scale rectangular concrete walls with and without central rectangular in-plane openings of different sizes (5%, 10%, 20% and 30% of wall areas) are tested. In thickness direction, one central layer of steel fabrics was used to reinforce the concrete walls. The walls were subjected to uniaxial loading aligned with the longest edge of the concrete walls. The loading was applied eccentrically (t/6) with respect to the mid-plane of the walls. Two different patterns were used to fix the CFRP to both surfaces of the walls which are parallel to the midplane of the wall segments. The first pattern consisted of applying four strips of CFRP parallel to the four edges of the opening such that they framed the opening. In the second pattern, CFRP strips were used to reinforce the walls in the vicinity of the opening edges only, i.e. four CFRP strips were applied close to the corners of the openings, in an angle of 45 degrees with both adjacent edges of the opening. From the results of the research work, it was found that CFRP strips applied at an angle of 45 degrees to both adjacent edges of the opening yielded a better compressive strength compared to the CFRP strips that framed the openings. Keywords-Reinforced concrete wall, opening, ultimate load, Carbon Reinforced Polymer, CFRP, stress concentration, strengthening
Parametric Study for Performance of R.C. Wall with Opening using Analytical F.E. Model
Earthquake is a catastrophic event, which makes enormous harm to properties and human lives. R.C. walls are provided in structures to decrease horizontal displacements under seismic load. R.C walls in residential buildings might have openings that are required for windows, doors or different states of openings due to architectural purposes. Size, position, and area of openings may fluctuate from an engineering perspective and might have an impact on stiffness of R.C wall and on the structures seismic reaction. F.E. modeling approach has been conducted to study effects of opening shape, size and position in RC wall with different thicknesses under axial & lateral static loads. F.E. Method using “ANSYS” becomes an essential approach in analyzing civil engineering problems numerically. Now we can make various models with different parameters in short time by using ANSYS instead of examining it experimentally, which consumes much time and money. The proposed F.E approach has been verified with experimental programs conducted by other researchers and gives a perfect correlation between the model and experimental outputs including load capacity, failure mode, crack pattern and lateral displacement. A parametric study is applied to investigate effects of opening size, shape, orientation, aspect ratio, position with different R.C. wall thicknesses. After verifying the proposed F.E approach with other mathematical design models conducted by other researchers, a statistical analysis was performed on 38 F.E. specimens and is presented in this paper. Outcomes of this statistical analysis provide an overview of the performance of current design models and identify research gaps. The findings presented herein will be used to define a new mathematical formula to provide the ultimate axial load of R.C. wall with circular opening. This research may be useful for improving existing design models and to be applied in practice, as it satisfies both architectural and structural requirements.
Physical Principles of Wind Energy Conversion
The primary component of a wind turbine is the energy converter which transforms the kinetic energy contained in the moving air, into mechanical energy. For the initial discussions of principles, the exact nature of the energy converter is irrelevant. The extraction of mechanical energy from a stream of moving air with the help of a diskshaped, rotating wind energy converter follows its own basic rules.