Probabilistic Sensitivity Analysis of Reinforced Concrete Bridge Deck Strengthened with Carbon Fibre Reinforced Polymers (CFRP) (original) (raw)
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The strength of reinforced concrete elements retrofitted in flexure by means of externally bonded Carbon Fibre Reinforced Polymers (CFRP) has attracted the attention of researchers due to many advantages highlighted by a wide set of experimental results. This research presents reliability study on reinforced concrete (RC) bridge deck strengthened with externally bonded CFRP subject to corrosion. The deck was subjected to reliability analysis, using First Order Reliability Method (FORM), enhanced with genetic algorithms and the inherent safety was found to yield safety index of 3.8, this agreed with the recommendation of the Joint Committee of Structural Safety Code (JCSS 2001) for structures with moderate consequence of failure. The reliability analysis for the intact and the corrosion affected deck were executed through a developed program, written using MATLAB Simulink and the result showed the detrimental effect of corrosion on reinforcement of steel in the bridge deck. Flexural capacity restoration was also undertaken for the bridge deck using Carbon Fibre Reinforced Polymer (CFRP) with the adoption of adhesive bonding technique. The results of the reliability-based analysis of the strengthened deck with Carbon Fibre Reinforced Polymer (CFRP) yielded a flexural capacity restoration up to 100%. Sensitivity analysis for the bending mode of failure were also conducted and it was observed that the critical mode of failure to be strengthened is flexure.
Safety factors for CFRP strengthening in bending of reinforced concrete bridges
Composite Structures, 2015
Concerning the strengthening in bending of reinforced concrete bridge decks, the use of fiber reinforced polymers (FRP) has increased due to its easy application and excellent mechanical and chemical properties. However, due to the lack of codes and standards and the lack of experience in the long term behavior, uncertainties exist in the calculation bases along the dimensioning of this reinforcement and more precisely in the partial coefficients of safety to be adopted for the material properties. As a consequence, bridge engineers are reluctant to use composite materials in the strengthening of damaged reinforced concrete bridge decks. To try to overcome this problem, this paper describes the methodology for a reliability-based calibration of the partial safety factors to be used for the CFRP material in the design of strengthening to bending. The method requires the definition of a response model jointly with the statistical definition of the model error. This is discussed in the first part of the paper. The reliability-based procedure is developed based on the design equation and the corresponding model. A simple set of partial safety factors is finally proposed for a representative population of RC bridges. The conclusions highlight the importance of incorporating the model error in the calibration. In addition, the paper shows how in some cases it is not feasible to design a flexural strengthening by using CFRP.
Predictable Behavior of GFRP-Reinforced Bridge Decks: Formulation of a Strain-Based Capacity Model
International Journal of Polymer Science, 2019
This paper proposes a reliability analysis framework for glass fiber-reinforced polymer- (GFRP-) reinforced concrete systems with uncertain capacities and demands over time. Unfortunately, there has been limited discussion or research done related to the potential change of failure modes over time. Therefore, a rational approach is needed to integrate multiple failure modes in a single analysis framework, considering uncertainties of time-variant demands and capacities. To account for multiple failure modes, this study proposes the limit state function to estimate the safety margin, based on strain values of GFRP-reinforcing bars. A proposed limit state function can capture the likelihood of both shear and flexural failure modes, simultaneously. In this study, seven typical bridge deck configurations (e.g., varied deck thickness, girder spacing, and bar size) were exposed to various ambient temperatures. Simulation results show that reliability indices of 100-year exposure exhibit s...
Reliablity analysis of bridge beams retrofitted with fibre reinforced polymers
Composite Structures, 2008
This paper presents a study of reliability of RC beams retrofitted with FRP. The beams' variables and their variability are assessed. Three common failure modes are considered, i.e. flexural failure, intermediate span debond and end debond. The prediction models used in this study were developed previously by the authors. Monto Carlos simulation is carried out to study the variability of the capacity of CFRP-strengthened beams for each failure modes. A reliability analysis is carried out based on the guidance provided by Eurocode 2. The analysis provides the bases for recommendation of capacity reduction factors for different failure modes. It is found that a factor of 0.6 is needed for flexural failure and intermediate span debond; whereas a factor of 0.5 can be applied for end debond.
2004
This paper compares and reviews the recommendations and contents of the guide for the design and construction of externally bonded FRP systems for strengthening concrete structures reported by ACI committee 440 and technical report of Externally bonded FRP reinforcement for RC structures (FIB 14) in application of carbon fiber reinforced polymer (CFRP) composites in strengthening of an aging reinforced concrete headstock. The paper also discusses the background, limitations, strengthening for flexure and shear, and other related issues in use of FRP for strengthening of a typical reinforced concrete headstock structure such as durability, de-bonding, strengthening limits, fire and environmental conditions. A case study of strengthening of a bridge headstock using FRP composites is presented as a worked example in order to illustrate and compare the differences between these two design guidelines when used in conjunction with the philosophy of the Austroads (1992) bridge design code.
This paper examines the structural efficiency of fibre reinforced polymer (FRP) decks for replacing traditional concrete decks intended for bridge upgrading. The investigation, which is performed by means of finite element analysis, is demonstrated on an existing noncomposite concrete-steel bridge. The bridge had an inadequate structural capacity to bear the current traffic loads. Two alternative solutions are considered: replacing the old deteriorated concrete deck with a mechanically connected FRP (i.e. without composite action) and a solution where the deck acts compositely with the underlying steel girders. Different connection techniques between the girders and FRP deck are examined for both solutions. The finite element analysis is used to assess the overall structural behaviour of the bridge as well as the interfacial stresses between the FRP deck and the steel girders under different loading conditions. The results show that a significant stress reduction can be obtained by replacing the concrete deck with the lightweight FRP deck. This reduction is more pronounced if the deck is designed to work compositely with the existing steel girders.
2012
LIFETIME ASSESSMENT OF DETERIORATING STRUCTURES NOWADAYS FOCUSES ON THE ISOLATED EFFECTS OF THE MAIN DETERIORATION PROCESSES. HOWEVER, IT IS PARAMOUNT TO STUDY THE COUPLED EFFECTS OF VARIOUS DETERIORATION PROCESSES BECAUSE SUCH INTERACTIONS COULD REDUCE STRUCTURAL INTEGRITY ; STRENGTHING IS AN ESSENTIAL TOOL TO COMPENSATE STRENGTH LOSSES AND/OR TO SUPPORT ADDITIONAL LOADS. EXTERNALY BONDED FIBER REINFORCED POLYMER FRP COMPOSITES ARE AN INCREASINGLY ADOPTED TECHNOLOGY FOR THE RENEWAL OF EXISTING CONCRETE STRUCTURES. THREE MAIN OBJECTIVES WERE CONSIDERED IN THE PRESENT STUDY. FIRST IS TO PROPOSE TIME-DEPENDENT PROBABILISTRIC MODELS OF STEEL REINGORCEMENT AND LIVE LOAD. SECOND IS TO PERFORM PROBABILISTIC ANALYSIS IN TERM OF TIME DEPENDENT FAILURE PROBABILITY OR RELIABILITY INDEX. FAILURE MODES OF FRP STRENGTHENED RC BEAM INCLUDED IN THE SURVEY WERE PROBABILISTICALLY SIMULATED USING FORM METHOD. THESE FAILURE MODES ARE BASED ON ANALYTICAL EXPRESSIONS REPORTED IN PREVIUS STUDIES. THIRD I...
ACI Structural Journal, 2005
This paper deals with the durability of the reinforced concrete (RC) beams externally strengthened with carbon fiber-reinforced polymer (CFRP) plates and fabrics under adverse environmental conditions such as 100% humidity, saltwater, alkali solution, freeze-thaw, thermal expansion, dry-heat, and repeated load cycles. The deflections, strains, failure loads, and failure modes of strengthened beams exposed to different independent environmental conditions and repeated load cycles are presented. To determine the design strength of CFRP-strengthened beams exposed to long-term environmental conditions, strength reduction factors associated with various independent environmental conditions are proposed. In addition, the failure modes and physical changes of the beams exposed to various independent environmental condi tions were also examined. It is concluded that the long-term exposure to humidity is the most detrimental factor to the bond strength between CFRP plates and fabrics and RC beams. Beams strengthened with CFRP plates and exposed to 10,000 hours of 100% humidity (at 38 ± 2 °C) experienced an average of 33% reduction in their strength. The onset of delamination was the primary mode of failure for all of the test beams. Finally, a durability-based design approach is presented. The design approach appropriately demonstrates the evaluation of nominal and design moment strengths of the beam strengthened with CFRP plates and exposed to a 100% humidity condition.
KSCE Journal of Civil Engineering, 2017
An approach to evaluate the structural reliability taking into account the degradation of the structural capacity due to corrosion of reinforced concrete buildings at the end of a time interval is proposed. The structural reliability is expressed in terms of the confidence factor, within a Demand and Capacity Factor Design format (DCFD). A new closed-form mathematical expression that considers the non-linear structural capacity degradation due to corrosion by means of a second degree polynomial function is developed. The confidence factors are obtained under the assumption that the structural capacity degradation due to corrosion follows a linear and non-linear function over a time interval. The structural reliability is obtained for a three-story reinforced concrete building subjected to two sets of real seismic ground motions recorded in Acapulco Bay Mexico. Both, aleatory and epistemic uncertainties are taken into account into the analysis. A maximum difference of 3.5% between both functions after 83 years from the construction of the building was found.