Local Behavior of Lap-Spliced Deformed Rebars in Reinforced Concrete Beams

Twelve full-scale reinforced concrete beams with two tension lap splices were constructed and tested under a four-point loading test. Half of these beams had shorter lap splices than that recommended by American Concrete Institute Building Code ACI 318-19; they failed by bond loss between steel and concrete at the lap splice region before rebar yielding. The other half of the beams were designed with a lap splice length slightly exceeding that recommended by ACI 318-19; they failed by rebar yielding and exhibited a ductile behavior. Several strain gauges were attached to the longitudinal bars in the lap splice region to study the local behavior of deformed bars during loading. The strain in a rebar was maximum at the loaded end of the lap splice and progressively decreased toward the unloaded end because the rebar at this end could not sustain any load. Stress flow discontinuity occurred at the loaded end and caused stress concentration. The effect of this concentration was investigated based on test results. The comparison of bond strengths calculated by existing equations and those of tested specimens indicated that the results agreed well.

Advanced Composite Retrofit of RC Columns and Frames with Prior Damages—Pseudodynamic Finite Element Analyses and Design Approaches

This study develops three-dimensional (3D) finite element (FE) models of composite retrofits in deficient reinforced concrete (RC) columns and frames. The aim is to investigate critical cases of RC columns with inadequate lap splices of bars or corroded steel reinforcements and the beneficial effects of external FRP jacketing to avoid their premature failure and structural collapse. Similarly, the RC-frame FE models explore the effects of an innovative intervention that includes an orthoblock brick infill wall and an advanced seismic joint made of highly deformable polymer at the boundary interface with the RC frame. The experimental validation of the technique in RC frames is presented in earlier published papers by the authors (as well as for a four-column structure), revealing the potential to extend the contribution of the infills at high displacement ductility levels of the frames, while exhibiting limited infill damages. The analytical results of the advanced FE models of RC columns and frames compare well with the available experimental results. Therefore, this study’s research extends to critical cases of FE models of RC frames with inadequate lap splices or corroded steel reinforcements, without or with brick wall infills with seismic joints. The advanced pseudodynamic analyses reveal that for different reinforcement detailing of RC columns, the effects of inadequate lap-spliced bars may be more detrimental in isolated RC columns than in RC frames. It seems that in RC frames, additional critical regions without lap splices are engaged and redistribution of damage is observed. The detrimental effects of corroded steel bars are somewhat greater in bare RC frames than in isolated RC columns, as all reinforcements in the frame are considered corroded. Further, all critical cases of RC frames with prior damages at risk of collapse may receive the innovative composite retrofit and achieve higher base shear load than the original RC frame without corroded or lap-spliced bars, at comparable top displacement ductility. Finally, the FE analyses are utilized to propose modified design equations for the shear strength and chord rotation in cases of failure of columns with deficiencies or prior damages in RC structures.

Experimental and Theoretical Investigation of Glass Fibre Reinforced Polymer Tension Lap Splices in Ultra High Performance Concrete

Glass fibre reinforced polymer (GFRP) reinforcements are a viable replacement for corroding steel rebars. GFRP rebar tension lap splices combined with ultra high performance concrete (UHPC) can improve the efficiency of materials and construction in bridge deck construction joints. This thesis investigates the bond performance of high modulus (HM) GFRP rebar splices using UHPC. UHPC slab/beams of 100 -170 MPa concrete having 150 - 300 mm tension splices were tested along with several beams constructed from prefabricated high strength concrete sections with central GFRP spliced UHPC joints. Theoretical analysis was also conducted to evaluate critical splice lengths. Based on comparisons with code design values, recommendations are made on potential failure modes and minimum splice lengths. The serviceability, fatigue, and environmental performance of GFRP in UHPC are also considered. Recommendations from this research will improve the safety and efficiency of GFRP tension lap joints used in bridge decks and other construction

Experimental and Theoretical Investigation of Glass Fibre Reinforced Polymer Tension Lap Splices in Ultra High Performance Concrete

Glass fibre reinforced polymer (GFRP) reinforcements are a viable replacement for corroding steel rebars. GFRP rebar tension lap splices combined with ultra high performance concrete (UHPC) can improve the efficiency of materials and construction in bridge deck construction joints. This thesis investigates the bond performance of high modulus (HM) GFRP rebar splices using UHPC. UHPC slab/beams of 100 -170 MPa concrete having 150 - 300 mm tension splices were tested along with several beams constructed from prefabricated high strength concrete sections with central GFRP spliced UHPC joints. Theoretical analysis was also conducted to evaluate critical splice lengths. Based on comparisons with code design values, recommendations are made on potential failure modes and minimum splice lengths. The serviceability, fatigue, and environmental performance of GFRP in UHPC are also considered. Recommendations from this research will improve the safety and efficiency of GFRP tension lap joints used in bridge decks and other construction