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
Application of Response Surface Methodology in Finite Element Analysis of Deflection of Pretensioned Inverted T-Beam with Web Openings Strengthened with GFRP Laminates
A precast, prestressed concrete girder with circular web openings allows building service systems (mechanical, electrical, communications, and plumbing) to cross the girder line within the member’s depth, reducing a building’s floor -to-floor height and the overall height of the structure. These height reductions have the potential to improve the competitiveness of total precast concrete structures versus other types of building systems. The experimental program reported in this paper tested three inverted -tee girders with circular web openings strengthened with GFRP to failure to evaluate the openings’ effect on girder behavior. The test girders were designed using available recommendations in the existing literature. Using ANSYS, finite element models were developed to simulate beam deflection behavior. Accuracy of the model is assessed by applying it to prestressed beam tested in this research. Comparison of analytical results with the available experimental results for load–deflection relationships show good agreement between the finite element and experimental results. Polynomial mathematical model, generated using various combination parameters using multiple regression analysis were found to be statistically significant. Parametric study using response surface methodology through finite element analysis may form efficient approximation to immediate deflection.
Mathematical Modeling of Scour and Deposition
Electronic computers are opening up the field of sedimentation engineering by permitting the analysis of problems which heretofore have required too much time and effort. Movable stream bed profiles are being calculated in addition to water surface profiles. The initial gradation of sediment material in the stream bed may be prescribed to facilitate the calculation of an armor layer. This gradation is continually changed by the computer program in response to sediment particles being deposited on the stream bed and material on the stream bed being removed to satisfy transport capacity. Hydraulic sorting of sediment by grain size is accomodated. The stream bed does not have to be represented by a single grain size. Retardance of motion because of armor layer is calculated.