INVESTIGATIONS INTO THE DUCTILITY OF LAP JOINTS IN LOW STRENGTH REINFORCED CONCRETE BEAMS

The most current standardised design guidelines for tension laps originated fromthe Fib Model Code 2010. These guidelines have had a significant impact on the newly proposed version of Eurocode 2, set to be published in 2023. The existing Eurocode 2 detailing guidelines can result in significantly longer lap jointsthan earlier design guidelines, such asthe replaced British Code (BS 8110-1). Furthermore, the Model Code 2010 necessitates lengthier laps than Eurocode 2. This research describes the analytical and experimental investigations conducted at the University of West London concrete laboratory to investigate the influence of rebar laps on the ductility of lapped sections. The tests were designed specifically to evaluate the effectiveness oflonger tension lapsin transmitting forces between the two-lap splice rebars. Thework described in this thesis is conducted in two stages. The first stage is an experimentaltest conducted on simply supported reinforced concrete beams with lap splices under four points bending with varying lap lengths and two reinforcement bar types. The analyses and experimental results for all the samples are described,with the deflection at the midspan of the beam measured using a built-in AEP TC4 transducer, and the result stored in a LabVIEW-based software attached to the actuator. In addition to the in-built displacement transducer, one variable displacement transducer was placed at the centre of the bottom face of the beam to record displacementfor more accuracy. The test showed that variation in lap splice length increases the stiffness and resistance of the sample. The results demonstrated how the samples’ behaviour changed, when transverse cracks initially appeared aslap joint failure approached. The detailed examination of the modelled and experimental results entails a comparison ofthe splice length’s ultimate performance with current Eurocode design recommendations. The second section describes the numerical model,which is based on nonlinear analysis. The samples are replicas of the simply supported concrete beams. The model allows the stress-strain behaviour of structural concrete to be simulated to failure and also considers the nonlinear behaviour in compression, tension, cracking and crushing of concrete. The simulation findings were then compared to the laboratory testresults. Based on the analysis conducted, it was observed that increasing the lap splices beyond 500 has no additional benefit for increasing its strength. The findings also showed that the stainless steel reinforced concrete beam deformations, which coincide with 35% and 62% of the maximum bending moment were higher than those of mild steel reinforced concrete beam. Moreover, the research also concluded that there is sufficient ductility and rotation at lap ends. However, designing the lap with a factor of 1.2 would lead to rebar congestion and unsustainable design practices in terms of sustainability.