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

Karkarna, Yakubu Mustapha (2023) INVESTIGATIONS INTO THE DUCTILITY OF LAP JOINTS IN LOW�STRENGTH REINFORCED CONCRETE BEAMS. Doctoral thesis, University of West London.

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Abstract

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.

Item Type: Thesis (Doctoral)
Subjects: Construction and engineering > Civil and structural engineering
Depositing User: Marc Forster
Date Deposited: 20 Sep 2023 09:00
Last Modified: 20 Sep 2023 09:00
URI: https://repository.uwl.ac.uk/id/eprint/10384

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