Precracked RC T-beams Repaired in Shear with Externally Bonded CFRP Sheets

This is the accepted version of the original publication available here: http://www.concrete.org/PUBS/JOURNALS/OLJDetails.asp?Home=SJ&ID=51683632.This study investigates the structural behavior of precracked reinforced concrete (RC) T-beams strengthened in shear with externally bonded carbon fiber-reinforced polymer (CFRP) sheets. It reports on seven tests on unstrengthened and strengthened RC T-beams, identifying the influence of load history, beam depth, and percentage of longitudinal steel reinforcement on the structural behavior. The experimental results indicate that the contributions of the external CFRP sheets to the shear force capacity can be significant and depend on most of the investigated variables. This study also investigates the accuracy of the prediction of the fiber-reinforced polymer (FRP) contribution in ACI 440.2R-08, UK Concrete Society TR55, and fib Bulletin 14 design guidelines for shear strengthening. A comparison of predicted values with experimental results indicates that the guidelines can overestimate the shear contribution of the externally bonded FRP system.This work was funded by the Engineering and Physical Sciences Research Council [grant number GR/S55101/01]

Plastic design of stainless steel continuous beams

In this paper an experimental study on eight simply-supported and four two-span continuous beams employing austenitic and duplex stainless steel rectangular hollow sections (RHS) is reported. In parallel with the tests, finite element models were developed. Upon validation against the experimental results, parametric studies were conducted to expand the available structural performance data over a range of cross-section slendernesses, structural systems and load configurations likely to occur in practice. The obtained experimental and numerical results along with collated test data were used to assess the accuracy of EN 1993-1-4 design provisions and to explore the possibility of plastic design for stainless steel indeterminate structures, simultaneously accounting for the effect of strain-hardening at cross-sectional level and moment redistribution exhibited by structures employing stocky cross-sections

Experimental behavior and design of reinforced concrete exterior beam-column joints strengthened with embedded bars

Shear-deficient reinforced concrete (RC) beam-column joints (BCJs) represent one of the main factors behind the seismic damage suffered by existing concrete infrastructure, as well as the associated loss of life. This study presents a novel technique for strengthening shear-deficient RC BCJs. The technique involves embedding carbon fiber reinforced polymer (CFRP) or steel bars into epoxy-filled holes drilled within the joint core. Six exterior RC BCJs were constructed and tested under displacement-controlled cyclic loading. Five specimens, of which four were strengthened with embedded bars, were designed with shear-deficient joints according to the pre-1980s building codes. The remaining specimen was adequately designed according to ACI 352R-02. The test parameters are the type (steel or CFRP) and number (4 or 8 bars) of embedded bars. The unstrengthened control specimen experienced joint shear failure in the form of cross-diagonal cracks. The strengthened specimens, namely those strengthened with embedded steel bars, exhibited less brittle failure where damage occurred in the beam region at the early stages of loading, suggesting the outset of a beam hinge mechanism. Additionally, the strengthened specimens exhibited enhancements in joint shear strength, ductility, dissipated energy and stiffness of 6-21%, 6-93%, 10-54% and 2-35%, respectively, compared to the control specimen. This paper also presents a mechanics-based design model for RC BCJs strengthened with embedded bars. The proposed model covers all possible failure modes including yielding of the existing steel reinforcement, concrete crushing and debonding of the embedded bars. The accuracy of the proposed model was checked against the test results. The model gave good predictions with an average predicted-to-experimental ratio of 1.05 and a standard deviation of 0.04. Keywords: Analysis; Beam-column joints; Design; Embedded bars; Fiber reinforced polymer; Reinforced Concrete; Shear strengtheningDirectorate General of Higher Education, Ministry of Research and Higher Education of Indonesi