Fiber Reinforced Polymers

This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed ...

It is well known that the strength and ductility of concrete are highly dependent on the level of confinement provided by the lateral reinforcement. The stiffness and the constitutive behavior of the confining reinforcement (elastic, elastoplastic, etc.) are the important factors affecting the behavior of concrete. In this study, a new simple confined concrete model is developed for describing the axial and lateral deformation characteristics of concrete under triaxial compression. The stress-strain relationship of confined concrete in the axial direction is defined with an elastic region followed by a nonlinear curve. The descending region of the stress-strain curve is defined using a constant failure energy criterion. The elastic limit, ultimate strength, and residual capacity of confined concrete are determined using the Leon-Pramono criterion. The lateral deformation of confined concrete is described using a function that provides a smooth transition from elastic to inelastic behavior and satisfies the zero volumetric strain condition at ultimate strength. The model estimations are compared with the results of triaxial concrete compression tests, and fiber reinforced polymer (FRP) and steel confined concrete tests reported in the literature. A good agreement was observed in terms of ultimate strength, residual strength, and axial and lateral deformation behavior. It was observed that the model can be successfully applied for FRP and steel confined concrete, removing the need to adjust parameters for different lateral reinforcement types. Finally, a parametric study was conducted to investigate the effect of the lateral reinforcement ratio, concrete strength, and compressive failure energy on the behavior of steel and FRP confined concrete.

The premature failure problem of  beams strengthened with external plates reduces  its  efficiency.  Although  this  problem  is considered  in  different experimental and analytical studies, more effort is required to increase the efficiency  of  such  expensive  strengthening  technique.  As  part  of  a comprehensive  program,  this  experimental  study  i s  applied  on  eleven continuous  reinforced  concrete  (R .C )  beams  and  nine  full -scale  simply supported R.C beams. The effect of using different materials and schemes for  external  reinforcing  was  investigated  on  the  overall  behavior  of  the strengthened  beams.  Behavior  of  beams  strengthened  with  the  proposed  schemes was  explored  considering  its practicality and cost of strengthening. The  ultimate load  of the tested beams were compared with the design load
calculated using the ACI 440-02 guidelines for external flexure and shear
strengthening of beams. Generally,  controlling the shear cracks propagation by using web plates and  reducing stress concentration and crack propagation along  the  strengthening  plate  delays  the premature  mode  of  failure and correspondingly  enhances  significantly the strengthened  beam’s  capacity and ductility.  Due to their significant  effect, different common  strengthening schemes need to be considered in any proposed design guidelines for more economic and reliable applications.

This paper deals with the shear strengthening of RC beams using externally bonded ͑EB͒ fiber-reinforced polymers ͑FRP͒. Current code provisions and design guidelines related to shear strengthening of RC beams with FRP are discussed in this paper. The findings of research studies, including recent work, have been collected and analyzed. The parameters that have the greatest influence on the shear behavior of RC members strengthened with EB FRP and the role of these parameters in current design codes are reviewed. This study reveals that the effect of transverse steel on the shear contribution of FRP is important and yet is not considered by any existing codes or guidelines. Therefore, a new design method is proposed to consider the effect of transverse steel in addition to other influencing factors on the shear contribution of FRP ͑V f ͒. Separate design equations are proposed for U-wrap and side-bonded FRP configurations. The accuracy of the proposed equations has been verified by predicting the shear strength of experimentally tested RC beams using data collected from the literature. Finally, comparison with current design guidelines has shown that the proposed model achieves a better correlation with experimental results than current design guidelines.

The noncorrosive fiber-reinforced polymer (FRP) composite bars are an excellent alternative reinforcement. In this paper, a review of the available punching load equations of two-way FRP-reinforced slabs and shear strength equations of one-way FRP-reinforced slabs are provided. All the models were verified against results for test specimens from the literature. The equivalent steel ratio model of Theodorakopoulos and Swamy produced the best estimates for the punching load while the model of Deitz, Harik, and Gesund yielded the best predictions of shear capacity. One of the punching strength models was modified in the current research and it gave excellent results. Using this modified model it is proved that the increase in the reinforcement ratio is accompanied by an increase in the punching strength.

The objective of this project is to evaluate the long-term effectiveness of fiber reinforced plastic (FRP) composite wraps in preventing corrosion of reinforced concrete elements in severe environments. The experimental program was established to help determine if FRP wraps provide barriers against the transportation of chlorides into the concrete or if impermeable wraps trap chlorides and moisture beneath the wrap and thereby accelerate the corrosion process. The focus of this report is on the development of procedures for understanding data collected from 13 specimens that were removed from exposure testing and studied in detail. The specimens represent typical rectangular (beam) and cylindrical (column) elements in reinforced concrete bridges. Partially wrapped versus unwrapped elements were studied. Other parameters of interest in design and construction included: cast-in chlorides to represent specimens already exposed to a corrosive environment prior to wrapping, cracked versus uncracked elements, addition of corrosion inhibitors, and materials of repair for damage to concrete due to corrosion or to construction traffic prior to wrapping.

Objectives. This study aimed to investigate physical properties of a fiber-reinforced CAD/CAM resin disc, which included woven layers of multi-directional glass fibers. Methods. Fiber orientations of CAD/CAM specimens (TRINIA, SHOFU) were specified as longitudinal (L), longitudinal-rotated (LR), and anti-longitudinal (AL). A fiber-reinforced composite (everX posterior, GC (E)) and a conventional composite (Beauti core flow paste, SHOFU (B)) were also tested. A three-point bending test and a tensile test with notchless prism-shaped specimens were conducted using a universal testing machine (AUTOGRAPH AG-IS, Shimadzu). A water absorption test was also carried out after the specimens were stored in water for 24 h or 1 week. Flexural strength and fracture toughness were obtained by conducting a three-point bending test. Results. TRINIA L and LR groups showed significantly high flexural strength (254.2 ± 22.3 and 248.8 ± 16.7 MPa, respectively). Those were approximately 2.5 times higher than those in AL, E, and B groups (96.8-98.0 MPa) (p < 0.05, ANOVA and Tukey HSD test). No significant difference was shown in flexural modulus among the experimental groups. The fracture toughness in L group (9.1 ± 0.4 MPa/m 1/2) was found to be significantly higher than those in other groups (1.9-3.0 MPa/m 1/2 ; p < 0.05). TRINIA group demonstrated significantly lower water absorption (4.7 ± 1.9 g/mm 3) than did E (16.1 ± 3.1 g/mm 3) and B (17.3 ± 3.7 g/mm 3) groups (p < 0.05). Significance. TRINIA demonstrated distinct anisotropy. TRINIA can be used as a superior restorative material when specifying directions of its fiber mesh layers.

Steel needle gates which are being used in Kolhapur Type Weirs (K.T. weirs) need to be replaced to overcome their disadvantages like heavy weight, corrosive nature, maintenance cost etc. Fiber Reinforced Plastic (F.R.P.) having advantages like light weight, low maintenance cost, corrosion resistance, longer service life etc. can be thought of as a replacement to steel in K.T. Weirs. In the present investigation an attempt is made to analyze the FRP Needle gates using finite element method. A generalized software tool is developed using FORTRAN which gives structural responses (deflections, stresses) as a result by input of material properties

Using externally bonded Fiber Reinforced polymer (FRP) laminate has become a well established solution for strengthening Reinforced Concrete (RC) beams in flexure and shear. However, the commonly observed premature modes of failure, limits the gain of capacity for the beams strengthened in flexure. In this research work, the role of the shear strengthening existence on this premature mode of failure will be explored using different strengthening schemes and loading setups. Specimens were strengthened in flexure and shear with externally bonded fiber reinforced polymer (FRP) based on the ACI-440 guidelines for design of externally strengthened beams. In addition, numerical model -based on Finite Element Method (F.E.M) - is provided for further study of strengthening schemes. It’s found that controlling the crack propagation along the beam web by bonding shear strengthening continuous laminate, rather than narrow strips reducing the risk of the common premature modes of failure with bonding external laminate for flexure strengthening. ACI-440 guidelines need to consider more applicable and efficient shear strengthening schemes in addition to provide suitable formulation to account for the effect of loading setups, in which the interference between shear force and high bending moment (e.g. 3-point loading), on premature modes of failure exists.

This paper deals with the shear strengthening of RC beams using externally bonded ͑EB͒ fiber-reinforced polymers ͑FRP͒. Current code provisions and design guidelines related to shear strengthening of RC beams with FRP are discussed in this paper. The findings of research studies, including recent work, have been collected and analyzed. The parameters that have the greatest influence on the shear behavior of RC members strengthened with EB FRP and the role of these parameters in current design codes are reviewed. This study reveals that the effect of transverse steel on the shear contribution of FRP is important and yet is not considered by any existing codes or guidelines. Therefore, a new design method is proposed to consider the effect of transverse steel in addition to other influencing factors on the shear contribution of FRP ͑V f ͒. Separate design equations are proposed for U-wrap and side-bonded FRP configurations. The accuracy of the proposed equations has been verified by predicting the shear strength of experimentally tested RC beams using data collected from the literature. Finally, comparison with current design guidelines has shown that the proposed model achieves a better correlation with experimental results than current design guidelines.

"The random nature of the explosion load, associated with the random nature of material properties, and geometric dimensional characteristics, implies the need to consider them into the analysis in order to have a more correct estimation of the structural behavior. Therefore, when the randomness of these parameters in the analysis is considered, the response of the structure assumes probabilistic nature, and this makes it necessary to look into the reliability measure.
This paper presents results from a parametric investigation of the reliability of reinforced concrete (RC) beam subjected to blast load. The probabilistic responses of the maximum displacement for a reinforced concrete flexural member under blast loadings are evaluated by means of nonlinear dy-namic analysis with simplified equivalent single-degree-of-freedom (SDOF) system.
Results of numerical simulations have shown the response of structures, in terms of maximum dis-placement in relation also to the blast load and the geometrical and mechanical characteristics of the beams. Monte Carlo simulation of dynamic response of the equivalent SDOF system is performed to estimate the reliability."

This paper deals with the shear strengthening of RC beams using externally bonded ͑EB͒ fiber-reinforced polymers ͑FRP͒. Current code provisions and design guidelines related to shear strengthening of RC beams with FRP are discussed in this paper. The findings of research studies, including recent work, have been collected and analyzed. The parameters that have the greatest influence on the shear behavior of RC members strengthened with EB FRP and the role of these parameters in current design codes are reviewed. This study reveals that the effect of transverse steel on the shear contribution of FRP is important and yet is not considered by any existing codes or guidelines. Therefore, a new design method is proposed to consider the effect of transverse steel in addition to other influencing factors on the shear contribution of FRP ͑V f ͒. Separate design equations are proposed for U-wrap and side-bonded FRP configurations. The accuracy of the proposed equations has been verified by predicting the shear strength of experimentally tested RC beams using data collected from the literature. Finally, comparison with current design guidelines has shown that the proposed model achieves a better correlation with experimental results than current design guidelines.