Experimental and FE study on RC one-way slabs upgraded with FRP composites

The use of externally bonded Fiber Reinforced Polymer (FRP) composites as a means of upgrading the flexural capacity of Reinforced Concrete (RC) one-way slabs is experimentally and numerically investigated in this study. A total of four groups of eight slabs were tested under four-point bending. The two slabs of the first group were left unstrengthened to be used as control specimens. The two slabs of the second group were externally strengthened with adhesively bonded pultruded, pre-cured CFRP plates. The four slabs of the last two groups were externally upgraded with unidirectional carbon (or E-glass) fiber fabric impregnated with an epoxy resin. In addition to the experimental program, a numerical investigation utilizing nonlinear Finite Element (FE) analysis was conducted using LS-DYNA software. Besides the eight slabs tested in this study, another eleven slabs were collected from the literature for the purpose of finite element validation. A comparison was made between the experimental and numerical results and good agreement was achieved. Based on FE validation, the numerical analysis was extended to include additional cases to study the effect of axial FRP stiffness and FRP-to-concrete width ratio on the flexural performance of upgraded slabs. As a result of the numerical study, new stiffness and reinforcement parameters were introduced in this research. These parameters were employed in the development of two new formulas for predicting the FRP debonding strain and percent gain in flexural capacity of FRP-strengthened slabs.

[1]  K. Mosalam,et al.  Strengthening of two-way concrete slabs with FRP composite laminates , 2003 .

[2]  Hsuan-Teh Hu,et al.  Nonlinear finite element analysis of reinforced concrete beams strengthened by fiber-reinforced plastics , 2004 .

[3]  Jian fei Chen,et al.  Anchorage strength models for FRP and steel plates bonded to concrete , 2001 .

[4]  Y. J. Kim,et al.  Flexural Strengthening of RC Beams with Prestressed CFRP Sheets: Using Nonmetallic Anchor Systems , 2008 .

[5]  Jerry I. Lin,et al.  Explicit algorithms for the nonlinear dynamics of shells , 1984 .

[6]  Guangming Chen,et al.  On the finite element modelling of RC beams shear-strengthened with FRP , 2012 .

[7]  Susanne Heyden,et al.  The effect of CFRP and CFRP/concrete interface models when modelling retrofitted RC beams with FEM , 2010 .

[8]  A. Nanni,et al.  Performance of One-Way Reinforced Concrete Slabs with Externally Bonded Fiber-Reinforced Polymer Strengthening , 2004 .

[9]  Scott T. Smith,et al.  FRP-strengthened RC slabs anchored with FRP anchors , 2011 .

[10]  U. Ebead,et al.  Interfacial Behavior and Debonding Failures in FRP-Strengthened Concrete Slabs , 2007 .

[11]  F. Chang,et al.  A Progressive Damage Model for Laminated Composites Containing Stress Concentrations , 1987 .

[12]  J. Teng,et al.  Intermediate Crack Debonding in FRP-Strengthened RC Beams: FE Analysis and Strength Model , 2007 .

[13]  U. Meier.  STRENGTHENING OF STRUCTURES USING CARBON FIBRE/EPOXY COMPOSITES , 1995 .

[14]  Tarek H. Almusallam,et al.  Flexural strengthening of RC beams using textile reinforced mortar – Experimental and numerical study , 2013 .

[15]  Wendel Michael Sebastian,et al.  SIGNIFICANCE OF MIDSPAN DEBONDING FAILURE IN FRP-PLATED CONCRETE BEAMS , 2001 .

[16]  Thomas Olofsson,et al.  Numerical analysis of concrete beams strengthened with CFRP: a study of anchorage lengths , 2005 .

[17]  Jin-Guang Teng,et al.  Bond-slip models for FRP sheets/plates bonded to concrete , 2005 .

[18]  O. Buyukozturk,et al.  FAILURE BEHAVIOR OF PRECRACKED CONCRETE BEAMS RETROFITTED WITH FRP , 1998 .

[19]  K. Tan,et al.  Evaluation of externally bonded CFRP systems for the strengthening of RC slabs , 2003 .

[20]  Omar Chaallal,et al.  FLEXURAL STRENGTHENING WITH CARBON-FIBER-REINFORCED POLYMER COMPOSITES OF PRELOADED FULL-SCALE GIRDERS , 2001 .

[21]  Deric J. Oehlers,et al.  A structural engineering approach to adhesive bonding longitudinal plates to RC beams and slabs , 2003 .

[22]  H. Saadatmanesh,et al.  Shear and Flexural Strengthening of R/C Beams with Carbon Fiber Sheets , 1997 .

[23]  Luciano Feo,et al.  Concrete cover rip-off of R/C beams strengthened with FRP composites , 2007 .

[24]  Hsuan-Teh Hu,et al.  Parametric analyses of square reinforced concrete slabs strengthened by fiber-reinforced plastics , 2014 .

[25]  A. Nanni,et al.  BRITTLE FAILURE IN FRP PLATE AND SHEET BONDED BEAMS , 1997 .

[26]  C. Mazzotti,et al.  An experimental study on delamination of FRP plates bonded to concrete , 2008 .

[27]  Frieder Seible,et al.  External FRP Poststrengthening of Scaled Concrete Slabs , 2001 .

[28]  Urs Meier,et al.  Carbon Fiber-Reinforced Polymers: Modern Materials in Bridge Engineering , 1992 .

[29]  Mohsen A. Issa,et al.  Performance of reinforced concrete slabs strengthened with different types and configurations of CFRP , 2012 .

[30]  Stephanie L. Walkup,et al.  Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures (ACI 440.2R-02) , 2005 .

[31]  Scott T. Smith,et al.  Interfacial stresses in plated beams , 2001 .