INVESTIGATION OF RECTANGULAR CONCRETE COLUMNS REINFORCED OR PRESTRESSED WITH FIBER REINFORCED POLYMER (FRP) BARS OR TENDONS

Fiber reinforced polymer (FRP) composites have been increasingly used inconcrete construction. This research focused on the behavior of concrete columnsreinforced with FRP bars, or prestressed with FRP tendons. The methodology was basedthe ultimate strength approach where stress and strain compatibility conditions andmaterial constitutive laws were applied.Axial strength-moment (P-M) interaction relations of reinforced or prestressedconcrete columns with FRP, a linearly-elastic material, were examined. The analyticalresults identified the possibility of premature compression and/or brittle-tension failureoccurring in FRP reinforced and prestressed concrete columns where sudden andexplosive type failures were expected. These failures were related to the rupture of FRPrebars or tendons in compression and/or in tension prior to concrete reaching its ultimatestrain and strength. The study also concluded that brittle-tension failure was more likelyto occur due to the low ultimate tensile strain of FRP bars or tendons as compared to steel.In addition, the failures were more prevalent when long term effects such as creep andshrinkage of concrete, and creep rupture of FRP were considered. Barring FRP failure,concrete columns reinforced with FRP, in some instances, gained significant momentresistance. As expected the strength interaction of slender steel or FRP reinforcedconcrete columns were dependent more on column length rather than material differencesbetween steel and FRP.Current ACI minimum reinforcement ratio for steel (pmin) reinforced concretecolumns may not be adequate for use in FRP reinforced concrete columns. Design aidswere developed in this study to determine the minimum reinforcement ratio (pf,min)required for rectangular reinforced concrete columns by averting brittle-tension failure toa failure controlled by concrete crushing which in nature was a less catastrophic and moregradual type failure. The proposed method using pf,min enabled the analysis of FRPreinforced concrete columns to be carried out in a manner similar to steel reinforcedconcrete columns since similar provisions in ACI 318 were consistently used indeveloping these aids. The design aids produced accurate estimates of pf,min. Whencreep and shrinkage effects of concrete were considered, conservative pf,min values wereobtained in order to preserve an adequate margin of safety due to their unpredictability

Structural Evaluation of the John A. Roebling Suspension Bridge

The primary objective of the structural evaluation of the John A. Roebling Bridge is to determine the maximum allowable gross vehicle weight (GWV) that can be carried by the bridge deck structural elements such as the open steel grid deck, channels, standard sections, or built-up sections. To achieve this objective, four levels of analysis are carried out: Element Level , Sectional level 1 , Sectional level II , and Global level analysis. The four levels of analysis yield a load envelope that encapsulates the maximum and minimum allowable loads. The maximum allowable gross vehicle weight (GWV) for different truck and bus types are presented for different levels of structural elements sectional loss. The loss or reduction in element sectional properties is due to rust, cracks, etc. The Element Level Analysis is the most critical and yielded the maximum allowable gross vehicle weights. The critical member in the bridge deck is the built-up 36 inch deep section. Its allowable bending strength controls the maximum Gross Vehicle Weight (GVW) that can be permitted on the bridge. Results are presented for different levels of sectional losses (10% to 40%, in 10% increments). In the event that replacement of the open grid deck will take place in the future, results are presented for different deck weights (10 psf to 50 psf in 10 psf increments). The current open grid deck weight is 20 psf

Inspection and Evaluation of a Bridge Deck Reinforced with Carbon Fiber Reinforced Polymer (CFRP) Bars

Cracking in reinforced concrete decks is inevitable. It leads to the corrosion and eventual deterioration of the deck system. The use of non-corrosive reinforcement is one alternative to steel in reinforced concrete construction. This report deals with the field evaluation and performance of a concrete bridge deck reinforced with carbon fiber reinforced polymer (CFRP) bars. The bridge is identified as the Elkin Station Road Bridge on route CR1210 over the Two Mile Creek in Clark County, KY. The CFRP bars were placed in the top and bottom mats of the bridge deck in both the transverse and longitudinal directions. The results of the laboratory tensile tests of the CFRP bars used in the deck are presented in this report. The bridge was opened to traffic in May 2002. Monitoring of crack formation and location, and maximum crack width and length in the deck initiated in June 2002and continued until September 2005. The cracks in the deck were not measurable since the maximum observed crack width was less than the smallest unit (1/100 inch) on the crack comparator. This indicates that the cracks are well below the maximum allowed crack width of 0.013 inch per AASHTO Standard Specification for exterior exposure

Seismic Evaluation of I-24 Bridges and Embankments in Western Kentucky–Summary Report

I-24 is considered as one of the high priority and emergency routes in the region. Hence, it is essential that I-24 remains functional and operational after an earthquake event. The objective of this study is to perform seismic evaluation and risk assessment of bridges and embankments along I-24 in western Kentucky. The assessment assists identifying and prioritizing bridges that are susceptible to failure. The study aims at evaluating the seismic risk for 127 bridges, of which 82 bridges lies on I-24 and 45 bridges cross over I-24. This report is the first (1st) in a series of seven reports for Project SRP 206: “Seismic Evaluation of I-24 Bridges”. The seven reports represent a comprehensive study evaluating the seismic vulnerability of bridges and embankments along I-24 in western Kentucky. This report is intended to provide a summary of the results of the comprehensive study. Basic ranking results and/or deficiencies of the seismic performance of the 127 bridges are documented, and retrofit recommendations, if any, are presented in this report. However, all details and records for Project SRP 206, “Seismic Evaluation of I-24 Bridges”, are presented in the accompanied six reports

Inspection and Evaluation of a Bridge Deck Partially Reinforced With GFRP Rebars

The corrosion of steel can be a significant problem in bridge decks in which the reinforcing and prestressing steel are accessible to deicing salts and combinations of moisture, temperature and chlorides through cracks, leading to concrete deterioration and loss of serviceability. Fiber Reinforced Polymer (FRP) rebars have emerged as one alternative to steel reinforcement in corrosive environments. The objective of this study is to evaluate the cracks formed on a bridge deck that is partially reinforced with glass fiber reinforced polymer (GFRP) rebars. The bridge constructed in 1997 is in Bourbon County, KY, on US460 over the Rogers\u27 Creek. Its deck is partially reinforced with GFRP rebars in place of epoxy coated steel rebars. The bridge has been monitored for cracks over a period of two years from June 1998 to July 2000. The maximum measured crack width of 0.013 in (0.3 mm) in the GFRP reinforced section meets the maximum allowed by ACI (Section 10.6) and AASHTO (Section 8.16.8.4) specifications in steel reinforced structures for exterior exposure

Structural Evaluation of the John A. Roebling Suspension Bridge – Element Level Analysis

The primary objective of the structural evaluation of the John A. Roebling Bridge is to determine the maximum allowable gross vehicle weight (GVW) that can be carried by the bridge deck structural elements such as the open steel grid deck, channels, standard sections, or built-up sections. To achieve this objective, an “Element Level Analysis” is carried out. The maximum allowable GVW for different truck and bus types are presented for different levels of structural elements sectional loss. The loss or reduction in element sectional properties is due to rust, cracks, etc. The critical member in the bridge deck is the built-up 36 inch deep section. Its allowable bending strength controls the maximum GVW that can be permitted on the bridge. Results are presented for different levels of sectional losses (10% to 40%, in 10% increments). In the event that replacement of the open grid deck will take place in the future, results are presented for different deck weights (10 psf to 50 psf in 10 psf increments). The current open grid deck weight is 20 psf

Performance Evaluation of Concrete Bridge Decks Reinforced with MMFX and SSC Rebars

This report investigates the performance of bridge decks reinforced with stainless steel clad (SSC) and micro-composite multistructural formable steel (MMFX) rebars. The two-span Galloway Road Bridge on route CR5218 over North Elkhorn Creek in Scott County, KY, was reinforced with SSC rebars in one span and MMFX rebars in the second span. The reinforcements are intended to prolong the service life of the newly constructed bridge decks due to the expected corrosion-resistance capability. Moment-curvature analyses indicated that MMFX RC decks had 57% and 85% higher strengths than SSC RC decks in positive and negative moment regions, respectively. The areas under the moment-curvature curves, a ductility indicator, of the MMFX RC decks, however, were 5% and 14% less than that of SSC RC decks in similar regions. Field performance of the bridge decks was monitored beginning in August 2001, following its completion in July 2001. Field evaluation consists of locating and measuring crack formation. As of September 2005, the cracks in the deck were not measurable since the maximum observed crack width was less than the smallest unit (e.g. 1/100 in.) on the crack comparator. This is also less than the maximum crack width (0.013 in.) allowed by the AASHTO Standard for exterior exposure

Shear Strength of R/C Beams Wrapped with CFRP Fabric

The emergence of high strength epoxies has enhanced the feasibility of increasing the shear strength of concrete beams by wrapping with carbon fiber reinforced polymer (CFRP) fabric. The objective of this investigation is to evaluate the increase in shear strength of concrete beams wrapped with different configurations of CFRP fabric. Shear tests are conducted up to failure on two reinforced concrete control beams and twelve reinforced concrete beams wrapped with four different configurations of CFRP fabric. An analytical procedure is presented to predict the shear strength of beams wrapped with CFRP fabric. Comparisons are made between the test results and the analytical calculations. The shear strength is increased up to 33% on concrete beams wrapped with CFRP fabric at an angle of ± 45° to the longitudinal axis of the beam

Retrofit of the Louisa-Fort Gay Bridge Using CFRP Laminates

This report details the processes pertaining to the repair and strengthening of the Louisa-Fort Gay Bridge, Lawrence County, KY, using advanced composite materials. Site inspections revealed flexural cracks in the reinforced concrete girders of the continuous bridge structure. To determine the cause of these cracks, an evaluation was initiated based on vehicle classification and truck weight data. The results confirmed that certain reinforced concrete girders were stressed beyond the limits allowed by the AASHTO Code. A retrofit scheme using carbon fiber reinforced polymer (CFRP) composite was devised and the amount of CFRP laminates needed for flexural strengthening was determined from moment-curvature analyses. Retrofitting work began in September of 2003, and the project was completed in October of 2003. Crack gauges were installed at the affected areas to monitor the effectiveness of the retrofit. The bridge was inspected on a number of occasions and, as of September 28 2006, no movement in the crack gauges has been observed