Influence of loading condition and reinforcement size on the concrete/reinforcement bond strength (original) (raw)
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Techniques Used for Bond Strengthening of Sub-Standard Splices in Concrete: A Review Study
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Bar splicing is considered an essential part of the construction process of reinforced concrete (RC) due to the ease of installation in construction, transportation constraints, and restricted length of reinforcing bars. Splices serve the primary role of joining reinforcement bars in standard RC elements such as columns, walls, beams, slabs, and joints. Bond behavior between the bars and the concrete is one of the fundamental qualities required for appropriate RC structure design and analysis, as it affects serviceability and ultimate limit states. The most common failure found in lap splice locations is debonding, which occurs at the splice region and insufficient lapped length is considered as the primary cause because of design or construction mistakes, design by outmoded code, and natural catastrophes. As a result, strengthening existing substandard splices in RC structures is critical. The purpose of this research is to analyze and summarize experimental strengthening solutions...
Bond strength of reinforcement in splices in beams
Structural Engineering and Mechanics, 2003
The primary aim of this study was to investigate the bond strength between reinforcement and concrete. Large sized nine beams, which were produced from concrete with approximately f c ' = 30 MPa, were tested. Each beam was designed to include two bars in tension, spliced at the center of the span. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. In all experiments, the variable used was the reinforcing bar diameter. In the experiments, beam specimens were loaded in positive bending with the splice in a constant moment region. In consequence, as the bar diameter increased, bond strength and ductility reduced but, however, the stiffnesses of the beams (resistance to deflection) increased. Morever, a empirical equation was obtained to calculate the bond strength of reinforcement and this equation was compared with Orangun et al. (1977) and Esfahani and Rangan (1998). There was a good agreement between the values computed from the predictive equation and those computed from equations of Orangun et al. (1977) and Esfahani and Rangan (1998).
Performance of Tension Lap-Splice in Lightweight Concrete
International Journal of Engineering and Advanced Technology, 2020
The use of Light-Weight Concrete (LWC) in modern construction has resulted in efficient designs and considerable cost savings by reducing structural own weight and supporting footings sections. The purpose of this paper is to investigate the Lap-Splice behavior between LWC and steel reinforcement (RFT). The tested specimens were divided into four groups to study the effect of main variables: steel reinforcement bar size, internal confinement (stirrups), splice length and concrete cover thickness. Four-point bending tests were carried out on test specimens to evaluate the performance of lap splices under pure bending. Bond behavior and failure modes were noted to be similar in the normal concrete and in the LWC. In tested beams, it was observed that the bar size has a significant influence on the mean bond stress in the splice. Improving radial tensile strength by using increasing stirrups number improves the bond behavior. The splice length up to 35 times bar diameter decreased the ...
Behavior of Fibrous Reinforced Concrete Splices
The Open Civil Engineering Journal
Background: The tangent of the relationship between bond stress and displacement (slip) is called the modulus of displacement and gives the basis for the theory. This theory is used to determine the stress distribution along the spliced reinforcement bars. Objective: This research presents a modification on the theory of the modulus of displacement to determine the stress distribution along the spliced reinforcement bond for fibrous reinforced concrete. Methods: 1- General differential equations are derived for concrete stress, stress in reinforcement bars and bond stress between reinforcement bars and surrounding concrete. 2-The general solutions of these D.E. are determined and Excel data sheets are prepared to apply these solutions and determine the concrete, steel and bond stresses. Results: Excel data sheets are prepared to determine the concrete, steel and bond stresses. The stresses are determined along the bar splice length considering the effect of steel fiber content. Conc...
Effect of tension lap splice on the behavior of high strength self-compacted concrete beams
Construction using concrete is spreading widely and there is a need for concrete that is capable of flowing under its own weight without mechanical vibration or compaction and fill the places between reinforcement and the complicated form shapes. From here, Self-Compacted Concrete (SCC) appears for the first time. Limited attention has been directed toward the bond between High Strength Self-Compacted Concrete (HSSCC) and spliced bars in beams [1–8]. This research studies the bond between HSSCC and spliced tension bars in beams. It is focused on observing the effect of some factors such as; reinforcement bar diameter and ratio, splice length and casting position on the beam flexural behavior. An experimental program consisting of sixteen simply supported beams divided into four groups is considered. All beams are of 1800 mm span and 200 · 400 mm cross-section cast with HSSCC. In twelve beams, the tensile steel was spliced in the constant moment zone, and four control beams without splice for comparison purpose. During testing; ultimate capacity, deflection, crack pattern and mode of failure have been recorded. Test results had been compared with proposed values in the Egyptian code of practice, other international design codes and recorded values of other researchers.
Materials and Structures, 2002
Reports on the very brittle and splitting mode of failure of tension lap splices anchored in high strength concrete (HSC) specimens and the lower normalized bond stress [u/~) for high strength than for normal strength concrete, instigated several research projects aiming at recommending mechanisms to provide confinement and ductility for bars or splices anchored in HSC. The stateof-the-art report of ACI Committee 363, ACI 363R-84, defines high strength concrete as concrete with compressive strength above 6,000 psi (41.4 MPa).
A study on the bond strength of tension lap splices in self compacting concrete
Materials and Structures, 2009
The primary objective of the research reported in this paper was to evaluate the effect of using self compacting concrete on the bond strength and mode of bond failure of tension lap splices anchored in normal strength concrete (NSC). Studies on the effect of transverse reinforcement on anchored reinforcement in self compacting concrete to prevent brittle mode of failure is limited. To meet this objective, full-scale NSC beam specimens were tested. Each beam was designed with bars spliced in a constant moment region at mid-span with various levels of stirrup confinement. The slip of the reinforcement with respect to concrete is also measured by providing notches at the end of the splices. Test results indicated that there is an increase in the bond strength when self compacting concrete is used in place of vibrated concrete. Ductility and splice strength increased as the confinement increased. When the stirrup spacing is less than 150 mm, the failure in the splice region was by yielding of steel. The influence of confinement on the crack formation of the beams is also reported. Keywords Bond (reinforcement to concrete) Á Self compacting concrete Á Confinement Á Splice Á Bond stress-slip Á Crack-width Á Ductility
Bond Strength of Tension Lap-Splices in Full Scale Self-Compacting Concrete Beams
Turkish Journal of Engineering and Environmental Sciences, 2008
Twelve full-scale beam specimens (2000 × 300 × 200 mm) were tested in positive bending with the loading system designed to determine the effect of self-compacting concrete (SCC) and the diameter of reinforcement on bond-slip characteristics of tension lap-slices. The specimens of lap-splice series were tested with lap-spliced bars centred on the midspan in a region of constant positive bending. The splice length of the deformed bars was set at 310 mm in all beam specimens. This value was selected to develop a steel stress less than yield to ensure splitting mode failure in all beam specimens. The beams were cast with the 16 and 20 mm bars (the tension lap-splices) in the bottom position. The casting procedure was the same for all beams. Two types of concrete were used in the experimental programme, including normal concrete (NC), with a slump less than 68 mm, as the comparatively low-slump concrete, and SCC as an extremely high-workability concrete. The variables used in this study were the concrete type (SCC and NC) and reinforcing bar size (16 and 20 mm). It was found that as the diameter of the steel bar increased from 16 to 20 mm the bond strength decreased regardless of concrete type. Finally, although the compressive strength of concretes was almost the same and there were slight differences between the diameters of lap-spliced bars, the normalised bond strengths of the SCC mixes were about 4% higher than those of the NC mixes for both bar diameters, indicating that the reinforcing bar was completely covered by SCC due to its filling ability.
Materials and Structures, 2009
In this study, nine different types of concrete were adopted: normal concrete (NC) with low slump (68 mm) and eight types of self-compacting concrete (SCC) in which cement was partially replaced by four kinds of replacements (25%, 30%, 35% and 40%) of class F fly ash (FA) and by four kinds of replacements (5%, 10%, 15% and 20%) of silica fume (SF). The main objective of this research was to evaluate the effect of different types and dosages of mineral additions on the moment capacities and stiffnesses of the beam specimens and the bond strength of tension lap-spliced bars embedded in NC and self-compacting concretes (SCCs). To achieve these objectives, 27 full-scale beam specimens (2000 9 300 9 200 mm) were tested. In all beam specimens, 20 mm reinforcing bars were used with a 300 mm splice length as tension reinforcement. The variable used was the amount of FA and SF incorporated into SCC. Each beam was designed with bars spliced in a constant moment region at midspan. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point.