Alternative wall‑to‑slab connection systems in reinforced concrete structures
Date
2017-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
South African Institution of Civil Engineering
Abstract
ENGLISH ABSTRACT: In many reinforced concrete structures the walls precede the construction of the connecting floors.
A system is, therefore, required to connect the floors to the already cast walls. There are many
different floor-to-wall connection systems available in South Africa, but their behaviour and capacity
are not always fully understood, especially when the moment capacity of the joint is to be utilised.
This study focuses on four systems: continuous starter-bars, pre-bent site-installed starter-bars, preassembled
starter-bars and cast-in anchors with mechanical couplers. The design procedure for the
continuous starter-bar system is well understood and documented in design codes, but not enough
information is available on the design procedure for the other systems. Certain practical aspects of
the installation process are also not fully understood. Cold-bending and straightening of the starterbars
are inevitable in both bend-out systems. Previous research shows that this cold-working of the
reinforcement can reduce the yield stress and E-modulus of the steel. In order to investigate these
findings, a series of tensile tests are conducted. The results indicate that a significant reduction can
be expected in both the yield stress and modulus of elasticity of the steel. Low-cycle fatigue tests
further suggest that cold-bent steel also has a reduced ductility. The tensile tests are followed by the
construction and testing of the systems in full-scale wall-to-slab connections. The effect of the coldbending
on the starter-bars is clearly visible, as both the responses of the bend-out systems are less
satisfying than the results from the continuous starter-bar system. The experimental phase is followed
by numerical analysis of the connection systems. The finite element analyses show that the structural
performance is significantly more sensitive to a reduction in the yield stress of the starter-bars, than
to the use of a lower concrete grade. It is concluded that all the alternative connection systems can be
implemented successfully in a moment-fixed wall-to-slab connection, but that the site-installed bendout
system is the preferred method. However, in order to ensure that the system performs on the
same level as conventional systems, it is recommended that the design should be conducted with a
set of modified steel properties to allow for the negative effect of the cold-working on the starter-bars.
Description
CITATION: Gerber, J. D. & Van Zijl, G. P. A. 2017. Alternative wall‑to‑slab connection systems in reinforced concrete structures. Journal of the South African Institution of Civil Engineering, 59(3):36-47, doi:10.17159/2309-8775/2017/v59n3a5.
The original publication is available at http://www.scielo.org.za
The original publication is available at http://www.scielo.org.za
Keywords
Reinforced concrete, Reinforced concrete construction, Concrete construction -- Joints, Reinforced concrete construction -- Testing
Citation
Gerber, J. D. & Van Zijl, G. P. A. 2017. Alternative wall‑to‑slab connection systems in reinforced concrete structures. Journal of the South African Institution of Civil Engineering, 59(3):36-47, doi:10.17159/2309-8775/2017/v59n3a5