Behavior of reinforced concrete beams strengthened with CFRP rod panels CRP 195

As a result of construction problems with curved I-girders, increased tub girder research, and improved fabrication techniques, twin steel tub girder superstructures are increasingly more common for curved highway ramps. Historically, however, choosing a twin tub girder bridge instead of a bridge composed of three or four I-girders has resulted in a nonredundant or “fracture critical” designation for the bridge. This paper presents results from an analytic investigation of the redundancy of twin steel tub girder bridges. Parametric nonlinear finite-element analyses are used to determine the role of different bridge components in developing load transfer from a damaged girder to an undamaged girder. The key parameters of span length, bridge continuity, curvature, location of girder damage, and type and spacing of external bracing are investigated. The results of this study indicate that twin steel tub girder bridges can be classified as redundant if the bridge is designed in accordance with the AAS...

Structural Redundancy Evaluation of Steel Tub Girder Bridges

CFRP Rod Panels (CRPs) have been recently developed to externally strengthening concrete structures in flexure, especially over multi-lane highways. Both exterior beams of a reinforced concrete (RC) bridge traversing southbound Interstate 71 (I-71) in Kentucky were damaged by an over-height truck impact. Rebars within the bottom mat of each exterior beam were severely bent due to the impact. CRP 195, with CFRP rods 3.96-mm (0.156 in) in diameter, and having a capacity of 870 kN (195.6 kips) per 300 mm (12 in) width of panel, were selected for flexural strengthening. CRPs were chosen due to their modular construction capability permitting a smaller work crew to carry out the retrofit construction while requiring closure of only a single lane of traffic on I-71. As current codes do not address CRPs, the retrofit design was based on American Association of State Highway and Transportation Officials (AASHTO) guidelines for externally bonded FRP. A load rating of the impacted girders was carried out for the as-built, damaged, and retrofitted stages. This paper details the retrofit construction of the bridge girders, highlighting the advantages of the CRPs.

https://www.mdpi.com/2504-477X/2/3/40/pdf

Design and Construction of CFRP Rod Panel Retrofit for Impacted RC Bridge Girders

/pdf/investigation-of-rectangular-concrete-columns-reinforced-or-52q0insdue.pdf

Investigation of rectangular concrete columns reinforced or prestressed with fiber reinforced polymer (frp) bars or tendons

Two long-term loads concrete stress/strain models are introduced. One model, the typical long-term model, uses modified parabolic and linear equations to include creep and shrinkage effects. The other, a realistic long-term model, incorporates a realistic load path for concrete in compression as well as creep and shrinkage phenomena. The proposed models were used to study the influence of their constituents on the ultimate strength of reinforced concrete-column cross sections under long-term loading. An analytic procedure was used to generate the strength-interaction relationships of the column cross sections. A series of calculations was performed for 2 selected column cross sections, and the short- and long-term results are compared. The short-term model strengths computed using the same procedure compare well to the strengths computed according to ACI 318. Small differences are discernible between the strengths obtained using the typical long-term model and the short-term model at low reinforcement ratios. The differences increase at large reinforcement ratios. A noticeable reduction in strength can be observed above the balance point when using the realistic long-term model.

Influence of Long-Term Loads on Concrete Column Strength

This paper reports tests of nine model cantilever columns. The objectives of this phase of a study of the deformation capacity of columns in structural systems were to experimentally determine and analytically predict the complete axial load-moment-curvature (PM-4) relationships for columns with large axial loads and minimal ties. The controlled lateral deformation loading method used maintained stability after the maximum moment resistance was reached and allowed the descending branch of the P-M-+ relationships to be measured. This bracing against instability is similar to the lateral resistance which stronger members in an unbraced frame can provide. The measured P-M-+ relationships were not as brittle as previously indicated, but were nearly flat-topped and exhibited significant ductility. An analytical procedure was developed which closely agreed with the relationships observed. Concrete crushing strains ranged between 0.0096 and 0.0160 in./in. Predictions of an ultimate ltrain equation indicated that the values greater than 0.003 in./in. ,here due to the appreciable moment gradients. The results indicate ;,at the ACI Building Code limiting strain criteria can be safely inn-eased to 0.004 in./in. for columns with moment gradients which produce reversal of moments in the column length. Such an increase could have substantial benefits by allowing economical usage of higher strength reinforcement (f, of 80 to 90 ksi) in many columns.

J. S. Ford

Papers

Behavior of Concrete Columns UnderControlled Lateral Deformation