State of Bond along Lap Splices

2020

The practice of splicing reinforcing bars in reinforced concrete structures to manage insufficient bar length is a common approach, which is mainly due to transportation limitations on bar length. The splicing of reinforcing bars side by side offers a simple and economical solution to the problem of continuity. This paper examines the influence of different structural parameters such as concrete cover, lap splice length, shear links confinement and concrete strength on the lap splices based on an extensive experimental database of laps and anchorage. The current study shows that increasing the lap splices beyond 50∅ has no additional benefit for increasing its strength. The results also show that relative to the measured stress, specimens with larger concrete side covers shows higher splice stress compared to the samples with smaller concrete covers.

Processes

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...

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 ...

Splicing rebar with lap splices must be done in its implementation due to the influence on the methods of implementation and the availability of existing reinforcing steel length. Lap splices length (ld) serves to channel the force borne by the steel reinforcement. Lap splices length testing conducted to determine the distribution of force occurs. The test specimen lap splice using a class B which is 1.3 ld with concrete covers at least 3 cm. By using an experimental study in which the use of reinforcing steel D-10 with a lap splices length of 1.3 ld by 43 cm, 1.2 ld by 40 cm using K-400 concrete and calculation analysis produces the lap splices length 27 cm and 30 cm use quality of concrete K-400 and K-450. Tests using the tensile test equipment (Universal Testing Machine) in laboratory B2TKS BPPT. Results from this study is the length of the lap splices of 1.3 ld and 1.2 ld use quality of concrete K-400 is able to meet the mechanical properties of reinforcing steel for the collapse occurred in the reinforcing steel. With lap splices length 27 cm and 30 cm using quality of concrete K-400 occur in lap splice collapse after passing the yield stress of reinforcing steel 40 kg/mm 2. While the lap splices length 27 cm and 30 cm using the quality of concrete K-450 collapse there are a difference between the test specimens due to the tension that occur closer to the ultimate stress of rebar's at 57 kg / mm 2

2013

The design specifications for calculating development and lapped splice lengths of reinforcement in concrete are derived from a conventional empirical modelling approach that correlates experimental test data using a single mathematical equation. This paper describes part of a recently completed experimental research program to assess the effects of different structural parameters on the development length requirements of modern high strength steel reinforcing bars, including the case of lapped splices in large-scale reinforced concrete members. The normalized average bond stresses for the different variations of anchorage lengths are assessed according to the general form of a typical empirical analytical model of bond and anchorage. Improved analytical modelling equations are developed in the paper that better correlate the normalized bond strength parameters with the structural parameters of an empirical model of bond and anchorage.

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).

The main objective of this paper is to study the behaviour of lap splice of steel reinforcement in tension zones in reinforced concrete beams. An experimental program is conducted on fifteen simply supported concrete beams. The main studied variable is splices length in the splice zone. There is an increase in ductility of beams when transverse reinforcement was used.

ACI Structural Journal, 2005

Criteria recommended by ACI Committee 408 on development and lap splice length design for straight reinforcing bars in tension are presented in code format and compared with those in ACI 318-05, Building Code Recommendations for Structural Concrete. The recommended criteria produce designs with improved reliability compared to those in ACI 318. Development lengths are longer than those in ACI 318 for conditions of low cover or confinement, but shorter for bars with higher degrees of confinement, provided by added cover and transverse reinforcement and wider spacing between bars, and for normalweight concretes with strengths between 10,000 and 16,000 psi (70 and 110 MPa). This paper is sponsored by ACI Committee 408, Bond and Development of Reinforcement.

Bonfring

Analysis and design provisions for the bond and anchorage length of deformed reinforcing bars in reinforced concrete elements are typically developed based on the assumption that the strain variations along the bar becomes approximately linear at or near the ultimate state of bond failure. Hence the assumption of the development of uniform bond stress along the anchorage length is used to calculate anchorage lengths of bars regardless of the variations in anchorage lengths or bar diameter. This paper describes an ongoing experimental research program in the Centre for Infrastructure Engineering and Safety (CIES) at the University of New South Wales, Sydney aimed at assessing the effects of different structural factors on the anchorage requirements of modern high strength steel reinforcing bars, including the cases of end development and lapped splices of deformed bars in tension. While the fundamental assumption of uniform bond stress development could be justified for relatively shorter anchorage length, the study found that an increase in anchorage length and bar diameter leads to a reduction of average ultimate bond stress which might be due to the non-uniformity in the development of bond stress along the anchorage zone. It is shown in this paper that the variability in the development of bond stress due to variable anchorage lengths is associated with the variable degree of plastic deformation in the concrete?s tensile zone. This paper outlines the importance of these effects on the development of analysis and design guidelines for anchorage of reinforcement.

2013

The aim of this research is to study flexural behaviour rectangular concrete beams with lap splice between deformed and smooth bars. An experimental program has been performed to investigate the research point, where sixteen rectangular concrete beams were tested in a four point bend configuration. Specimens were grouped into four groups to investigate influences of lap splice length, stirrups intensity and location, end shape, and concrete characteristic strength (N.S.C and H.S.C). It was concluded that distributing stirrups along the splice length increase failure load more than concentrating them at splice ends; end shaping of splices increases failure load; Increasing splice length compared with that required for transmission of tensile stresses through bond decreases ductility; linearity of strain distribution along reinforcement bars increase by the increase and uniformity of stirrups confinement; increasing splice length decreases the difference between strain in deformed and smooth bars.