Design of FRPs in circular bridge column retrofits for ductility enhancement

Abstract Retrofit design of existing columns in buildings and bridge piers necessitates the accurate prediction of the deformation capacity of structures. In this study, an analytical model is proposed to estimate the ductility of potential plastic hinge regions of RC columns after a fiber reinforced polymer (FRP) retrofit. A simple bilinear stress–strain model that is capable of representing an FRP concrete response exhibiting softening at low confining pressures and hardening at higher confinement is proposed. This model is then employed in an approximate closed form sectional analysis of circular columns subjected to axial force and bending moment. Section ductilities that can be obtained as a result of FRP retrofit are expressed in terms of non-dimensional column parameters and confining pressure supplied by FRPs. The accuracy of the model to estimate the ductility of FRP retrofitted columns is verified by comparing model estimations with sectional analysis and test results. Subsequently, a simple non-iterative seismic retrofit design procedure using FRPs is established for circular bridge columns. Finally, parametric studies are conducted on a typical bridge column for different axial loads, reinforcement ratios and FRP amounts. Results are presented in the form of non-dimensional plots to aid engineers in the FRP retrofit design of columns for ductility enhancement.

[1]  J. Teng,et al.  Design-oriented stress–strain model for FRP-confined concrete , 2003 .

[2]  Ying Tian,et al.  A Seismic Retrofit Design Methodology for R/C Bridge Columns Using Fiber Composites , 2004 .

[3]  S. Sheikh,et al.  Retrofit of Square Concrete Columns with Carbon Fiber-Reinforced Polymer for Seismic Resistance , 2003 .

[4]  Amir Mirmiran,et al.  Model of Concrete Confined by Fiber Composites , 1998 .

[5]  Silvia Santini,et al.  Design of FRP jackets for upgrade of circular bridge piers , 2001 .

[6]  Robert Park,et al.  Confining Reinforcement for Concrete Columns , 1994 .

[7]  Hamid Saadatmanesh,et al.  Seismic Strengthening of Circular Bridge Pier Models with Fiber Composites , 1996 .

[8]  Hamid Saadatmanesh,et al.  STRENGTH AND DUCTILITY OF CONCRETE COLUMNS EXTERNALLY REINFORCED WITH FIBER COMPOSITE STRAPS , 1994 .

[9]  Kent A. Harries,et al.  Experimental investigation of the behavior of variably confined concrete , 2003 .

[10]  Scott T. Smith,et al.  FRP: Strengthened RC Structures , 2001 .

[11]  M. Saatcioglu,et al.  Inelastic analysis of reinforced concrete columns , 2000 .

[12]  M. R. Spoelstra,et al.  FRP-Confined Concrete Model , 2001 .

[13]  Kazuhiko Kawashima,et al.  A STRESS-STRAIN MODEL FOR CONCRETE CYLINDERS CONFINED BY CARBON FIBER SHEETS , 1998 .

[14]  M Saiid Saiidi,et al.  SIMPLE CARBON-FIBER-REINFORCED-PLASTIC-CONFINED CONCRETE MODEL FOR MOMENT-CURVATURE ANALYSIS , 2005 .

[15]  Shamim A. Sheikh,et al.  SEISMIC BEHAVIOR OF CONCRETE COLUMNS CONFINED WITH STEEL AND FIBER-REINFORCED POLYMERS , 2002 .

[16]  Sidney Mindess,et al.  ANALYTICAL MODEL FOR CONCRETE CONFINED WITH FIBER REINFORCED POLYMER COMPOSITE , 2004 .

[17]  Mervyn J. Kowalsky,et al.  DEFORMATION LIMIT STATES FOR CIRCULAR REINFORCED CONCRETE BRIDGE COLUMNS , 2000 .

[18]  Khalid M. Mosalam,et al.  Analysis of reinforced concrete columns retrofitted with fiber reinforced polymer lamina , 2007 .

[19]  F. Seible,et al.  Seismic Retrofit of RC Columns with Continuous Carbon Fiber Jackets , 1997 .

[20]  Pierre Labossière,et al.  Axial Testing of Rectangular Column Models Confined with Composites , 2000 .

[21]  Khalid M. Mosalam,et al.  A computational model for reinforced concrete members confined with fiber reinforced polymer lamina: Implementation and experimental validation , 2007 .

[22]  J. Teng,et al.  Strength Models for Fiber-Reinforced Plastic-Confined Concrete , 2002 .

[23]  A. Mirmiran,et al.  Effect of Column Parameters on FRP-Confined Concrete , 1998 .

[24]  Yan Xiao,et al.  Compressive Behavior of Concrete Confined by Carbon Fiber Composite Jackets , 2000 .

[25]  W. J. Hall,et al.  Earthquake spectra and design , 1982 .

[26]  Baris Binici,et al.  An analytical model for stress–strain behavior of confined concrete , 2005 .

[27]  Zhishen Wu,et al.  Strength and ductility of concrete cylinders confined with FRP composites , 2006 .

[28]  Yong Lu,et al.  Probabilistic Drift Limits and Performance Evaluation of Reinforced Concrete Columns , 2005 .