Ibrisam Akbar

Strengthening Schemes for Flexure and Torsion Using FRP Laminates: A State of Art Review

RC beams as a structural member contain a variety of non-uniform loads. These non-uniform loads caused combined effects of flexure and torsion. There are numerous studies available, that suggests different strengthening schemes using FRP laminates, as a solution for flexure and torsion deficient beams. Most of the experimental studies suggested individual strengthening schemes for flexure or torsional deficiency RC beams. However, the combined effects were not studied due to difference in experimental setup, testing procedure and specimen detailing. Therefore, the outcome of previous studies was needed to combine together to facilitate the strengthening process as a guideline case of such deficiency. Therefore, a combined review is presented by suggesting different configuration for flexure and torsion deficient RC beams. Most of the studies suggested that the application of FRP laminates at the soffit of beam is suitable for flexural strengthening. The application of U-shape or full wrap are suitable for strengthen torsion deficient beams. Similarly, 45° wraps are more effective than 90°wraps for improving ductility of torsion deficient beams.

An Experimental Study on the Effects of Biaxial Bending due to Eccentric Load on RC Beam

Eccentric loads are very common in structures due to building configuration. Unequal slab length, circular ramp, large cantilevers are very common in modern architecture. The RC beams in previous studies were tested under the three and four point uniform loads. Therefore, a simple testing setup was arranged to understand the behaviour of RC beam under eccentric load applied at mid span. In this study the single point load applied eccentrically on RC beam. The beams were tested at different eccentricity and compared with control beam tested under the uniform load or zero eccentricity. Results have shown a drastically reduced crack load up to 54% compared to control beam as the eccentricity increased. However, small changed in ultimate load carrying capacity was observed up to 60mm eccentricity. Eccentric load caused biaxial bending due to high concentration of load on one side of beam, which change failure mode of RC beam from ductile to brittle.

Effects of Eccentric Load on Un-Strengthen and CFRP Strengthened RC Beams

CFRP strengthened reinforced concrete (RC) beams are usually tested under either three points or four point concentric loads; the effect of eccentricity is neglected in many studies. In this experimental program eight RC beams tested in two groups, GROUP ‘A’ & ‘B’. In group ‘A’ four RC beam tested, one control beam tested under concentric load and three under the eccentricity of 40, 60 and 80 mm respectively. The remaining four RC beams in group ’B’ strengthened using carbon fibre reinforced polymer (CFRP) strip and tested under the 60mm eccentricity. The experiment has confirmed the behaviour transformation from flexure failure to local failure due to variation in eccentricity. Therefore, the effects of eccentricity cannot be neglected and required special consideration before applying strengthening scheme on RC beam. The RC beams strengthen using CFRP have the ability to enhanced the load carrying capacity of beams tremendously, but the eccentric load effect on ductility, and failure mode of RC beams.

A Review of Combined Flexure, Shear & Torsion Strengthening of Reinforced Concrete Beam

Strengthening of reinforced concrete (RC) beam using fibre Reinforced Polymer (FRP) revealed as the most efficient strengthening material due to its numerous mechanical properties. From literature, different experiment conducted to discuss strengthening options for RC beam, based on the observed crack pattern and failure mechanism. The appearance of crack formation on RC beams under loading identifies the mode of failure. For example, to increase the flexural capacity of RC beam, FRP is applied at the tension zone. Similarly, for shear and torsion strengthening FRP wraps is being applied at the both faces of the beam. In previous studies the achievement of high strength in shear and torsion is attributed by applying full wrap. Practically the application of full wrap on RC beam is impossible and required more indepth study to propose practical solutions. However, the combined effects of flexure, shear and torsion have not been discussed yet. Therefore, the strengthening schemes from literature are combined to propose new strengthening scheme for RC beam under combine the action of flexure, shear and torsion. However, experimental data are required to validate the proposed scheme KeywordsCrack Pattern; Reinforced Concrete; Flexure; Shear; Torsion; FRP Strengthening scheme.

Effect of Flexural Static Load on the Strength of GFRP Gratings

– The usage of steel in offshore deep water area contributes to the massive load of the offshore platform which will lead to the massive operational cost. Therefore, the reduction of weight of platform is the major issue that need to be tackled properly. The great improvement in strength to weight ratio compare to steel and high resistivity to corrosion makes Glass Fibre Reinforced Polymer (GFRP) grating preferable. GFRP gratings are normally made of two types of processes which are moulded and pultruded and it is usually consists of glass fibre and bonding matrixes of vinyl ester (VE), polyester (PE), or phenolic (PHE). However there is still doubt on GFRP grating application for offshore due to no consensus guidelines for the design of GFRP grating and there are many several types of GFRP grating available to be chosen. This paper presenting the study on two types of GFRP grating strength with variation of bonding matrixes under flexural static load. A total of six specimens of GFRP grating which consist of 1 each of molded vinyl ester, molded polyester, molded phenolic, pultruded vinyl ester, pultruded polyester and pultruded phenolic were tested to failure in flexure. The main parameters concerns in this study are 1) max load vs. mid-span deflection and 2) failure mode of the specimens.

The Bond Strength of CFRP Plated Steel Member Submerged in Saltwater

This paper presents the experimental results of CFRP plated steel blocks in wet and dry conditions using saltwater. A total of 9 pull test specimens were tested that was divided into two groups; normal and heated saltwater at room temperature and 50°C, respectively. The purpose of this test is to investigate the changes in the debonding capacity of the CFRP plated steel blocks. It was found that both systems showed insignificant increase in bond strength. However, the stiffness of the bonding system increased as the temperature of the saltwater was increased, suggesting the effect of post curing of the adhesive.

The Strength of GFRP Gratings under Accelerated Ageing Process

Glass Fiber Reinforced Polymer (GFRP) gratings are normally made of two types of processes which are molded and pultruded. It consists of glass fiber and bonding matrixes of vinyl ester (VE), polyester (PE), or phenolic (PHE). The great improvement in strength to weight ratio compare to steel and high resistivity to corrosion makes GFRP grating preferable. However, the use of GFRP grating in offshore is scarce due to issues related to durability and the harsh environment Based on the observation, the accelerated ageing process affects the performance of GFRP gratings by reducing its strength in flexural static load test. Therefore; this study concentrates on the effect of accelerated ageing on GFRP grating. A total of 18 GFRP grating specimens which consist of 6 each of molded Vinyl Ester, molded Polyester and pultruded Phenolic. The entire specimens were aged by immersion in seawater at elevated temperature (60 °C) for the period of 2 month. The main parameters concerns in this study are 1) Max Load vs. Immersion Period, 2) Max Load vs. Deflection graph of results.