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Steel-FRP composite structural systems
... The present study is carried out to investigate a variety of strengthening approaches based on the available research recommendations and to propose an appropriate strengthening method for built-up steel C channels. The available investigations in the area of strengthening approaches for improving the structural performance of the open cross-section structural steel members are sufficient and the recommendations provided[14][15][16][17][18][19][20][21][22][23][24][25]were used to arrive at an optimal strengthening mechanism for structural steel C channels. The recommendations are: 1. Depending on the accessibility, CFRP strengthening can be provided by partial or by a full wrap of the structural elements. ...
Highlights
• A test program on CFRP strengthened long steel built-up beams is presented.
• Two different strengthening approaches were examined: flange and modified cross section strengthening.
• Remedy to overcome the CFRP wrinkles is addressed.
• The effective strengthening technique for long steel built-up beam is proposed.
Abstract
Test study on simply supported built-up beams (plate on top of a channel section) with two different strengthening approaches using carbon fiber reinforced polymer (CFRP) fabrics by external bonding namely flange strengthened and modified cross section strengthened has been conducted. The study specimens simulated the flange restrained C-channel sections in lateral bracing of steel bridge superstructure and steel storage structures. A total of seven different strengthening configurations were made based on the two strengthening approaches. The results indicate that the flange strengthening approach is not an efficient method of retrofitting open cross section specimens with longer length compared to the modified cross section strengthening method with infilled core which significantly improved the flexural strength. In addition, the results indicate that with an increase in a number of confinement wrap using bidirectional CFRP fabrics the wrinkling can be prevented. The results also indicate that depending on the magnitude of camber imperfection (initial bent about major axis) different failure modes of CFRP can be observed.
... Strengthening steel structures using adhesively bonded fiberreinforced polymer (FRP) plates has been extensively studied in recent years because of the advantages this method offers; primarily the ease and speed of installation, and it is lightweight compared to welded or bolted steel plates. The majority of studies focused on the use of carbon FRP (CFRP) plates because of their higher Young modulus, which can approach or exceed that of steel (Miller et al. 2001;Zhao and Zhang 2007;Harries and El-Tawil 2008;Fam et al. 2009). Conversely, glass fiber-reinforced polymer (GFRP) plates are considerably lower in cost than CFRP plates and their lower elasticity modulus can be compensated for by the fact that GFRP plates are typically thicker (El) than CFRP sheets. ...
The present study develops a theory for the elastic analysis of a preloaded wide flange steel beam, strengthened with two glass fiber-reinforced polymer (GFRP) plates bonded to both flanges, then subjected to additional loads. Starting with the principle of stationary potential energy, the governing equilibrium equations and corresponding boundary conditions are formulated prior to and after GFRP strengthening. The resulting theory involves four coupled equilibrium equations and 10 boundary conditions. A general closed form solution is then provided for general loading and boundary conditions. Detailed comparisons with three-dimensional finite-element solutions show that the theory provides reliable predictions for the displacements and stresses. A parametric study is then developed to quantify the effects of strengthening, GFRP plate thicknesses, and preexisting loads on the capacity of the strengthened beam
... Studies Involving Steel Beams Reinforced with FRP Miller et al. (2001), Zhao and Zhang (2007) , and Harris and Tawil (2008) investigated the mechanical properties of fiberreinforced plastic (FRP) and adhesive materials. Taljsten (1997) adopted two elastic analytical models to determine the shearing and peeling stresses of the adhesive layer in a beam strengthened by a plate bonded to its bottom surface. ...
The present study complements recent published work by developing a general closed-form solution for the analysis of steel beams reinforced with glass-fiber-reinforced plastic (GFRP) plates under general loading and boundary conditions. Comparisons against three-dimensional (3D) finite-element (FE) solutions indicate that the solution accurately captures the transverse-longitudinal and predominantly lateral responses. For predominantly torsional responses, the solution is shown to provide good predictions when the shear modulus of the adhesive layer is weak. For cases where the shear modulus is stiff, the present theory is found to lead to an overly stiff response. Careful examination of strain profiles as predicted by the 3D FE analyses provides valuable insight on the reason for the overly stiff behavior in such cases and shows the necessity of incorporating transverse shear deformation effects into the formulation.
... The research findings showed that CFRP plates can cause significant increasing of normal composite beam's ultimate load carrying capacity, returning the ultimate load bearing capacity and hardening of the damaged composite beam [7]. FRP sheets/strips are also effective in the strengthening of steel structural elements to extend their fatigue lifetime and reduce crack propagation8910 if galvanic corrosion is prevented and sufficient bond is provided [11, 12]. Kim and Harries, developed a three-dimensional (3D) non-linear finite element model for predicting the fatigue strength of notched steel beams using ANSYS software. ...
Time and environmental factors cause some problems such as rusting and decay for great constructs and buildings. Since these factors significantly contribute in reducing resistance, reducing load bearing capacity and defect created in structural components, it is required to take the necessary measures in order to improve the structure performance. This research studies the effect of CFRP strips on strengthening deficient
steel beams by modeling seven beams through ABAQUS V6.11. It is worth noting that there was created a fixed, primary defect at the mid-span of tensile flange. The size and position of CFRP strips were different. The results indicated that application of CFRP could appropriately overcome the weakness occurred due to deficiency.
... Yu et al., 2013), galvanic corrosion is prevented and adequate bond is provided (Shaat et al., 2004; Harries et al., 2011). Recent strengthening projects in Japan, the United States and United Kingdom indicated that there was great potential for using CFRP to upgrade steel structural members. ...
In some structural members, deficiency may occur due to aging and environmental factors such as corrosion which causes decrement in load bearing capacity. In this research, to improve strength and stiffness of deficient structural members, Carbon fiber reinforced polymer (CFRP) plates are proposed. Ten beams were numerically modelled utilizing ABAQUS software. The various deficiency sizes were intentionally created by notching both sides of the tension flange of the beams at the mid span. To investigate the performance of the repaired beams, different lengths and placements of CFRP strips were chosen. The results showed that the CFRP-repair caused a recovery of the static load bearing capacity of the deficient beams and prevented deficiency propagation.
Corrosion occurs to steel structures due to long life and environmental exposure, which affects the load carrying capacity (LCC) and thus life of structure. Traditional methods of repairing the corroded sections are replacement and attaching other plates to damaged section. So, strengthening steel structure with CFRP laminates is now days a popular technique to regain the lost capacity due to corrosion. In this paper, a fully corroded I beam section is considered for strengthening purpose. Two sample beams of one meter length were taken from the parent beam for experimentation. Two layers of CFRP laminates were used to all sides of beam for strengthening purpose. The model of corroded I-beam was developed in ANSYS software based on average thicknesses of section. Original strength of corroded beam is calculated by using ANSYS and then comparison is done with experimental results. Results show that LCC and yield capacity of strengthened corroded beam is improved using CFRP laminates. Hence, use of CFRP laminates can be used to corroded steel sections for strengthening purpose and it is one of the best way to improve its overall strength and LCC.
Composite structural insulated panels (CSIPs) have the potential to construct lighter large-span roof structures due to high strength-to-weight ratio. However, the drawback of large deflection severely limits their applications. Two effective methods improving the stiffness of CSIPs were investigated in this paper at first. One is the method of folding, which improves the moment of inertia of cross-section areas using the principle of folded panels. The other is the method of curving, which transforms structural bending moments into axial forces using the principle of arches. Then an innovative CSIPs folded shell structure was proposed by combining the advantages of above two methods together. The mechanical behaviors of the CSIPs folded shell structure were studied comparing with CSIPs folded panels and CSIPs thin shells. The static analysis results showed the maximum vertical displacement of the CSIPs folded shell structure under self-weight was 11.054 mm, which was much less than that of CSIPs folded panel (129.17 mm) and that of CSIPs thin shell (89.78 mm). The results of geometrical nonlinear analysis demonstrated that the CSIPs folded shell structure has 5 times larger nonlinear buckling load capacity than the CSIPs thin shell. CSIPs folded shell structures have excellent structural configurations and extensive application prospects in large-span roof structures.
There are a large number of steel buildings and bridges deteriorated due to aging and corrosion and need to be repaired. Carbon fibre reinforced polymer (CFRP) plates are proposed to fill the lack of strength lost. This research presents the flexural behavior of deficient steel beams refurbished with CFRP strips. The various deficiencies size are intentionally created by notching one side and both sides of the tension flange of the beams. Fourteen specimens were examined to evaluate the static performance of the repaired beams with emphasis on load bearing capacity and the CFRP–steel interface stress. A three-dimensional finite element analysis (FEA) by ABAQUS is utilized. Results show that CFRP-repair cause a recovery of static load-carrying capacity of the deficient beams. By using CFRP within 17% of beam length, it indicates performance as a non-deficient beam. Besides, local buckling, vertical deflection and the deficiencies influences on the beams were investigated.