Performance of lapped splices in reinforced concrete loaded beyond yielding of the steel

Eighteen beams designed to fail in the lap splice after reaching yield of the reinforcing steel were tested under either a single load application or low cycle repeated loading. Splice lengths were varied from well below code requirements up to approximately those required by current codes and design methods. Performance was studied on the basis of the ductility exhibited prior to failure and the influence of load cycling and stress–strain characteristics of the reinforcing steel. No confinement (stirrups or a spiral) was provided to the splice.Comparison is made with common lap splice design methods. These assume that the beam will respond adequately and the splice will not fail prematurely if the splice length is made long enough to withstand a steel stress 25% above the normal yield strength of the reinforcing steel. The detrimental effects on ductility of higher than nominal yield stress and of strain hardening at relatively low strains for the grade 60 (nominal yield stress = 60 ksi (414 MPa)) deformed reinforcing steel used are noted. The possible weakness of using nominal yield strengths for the reinforcing steel with current design methods is emphasized.

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Effectiveness of concrete confinement on lap splice performance in concrete beams under reversed inelastic loading

Canadian Journal of Civil Engineering ◽

10.1139/l89-005 ◽

1989 ◽

Vol 16 (1) ◽

pp. 36-44

Author(s):

B. MacKay ◽

D. Schmidt ◽

T. Rezansoff

Keyword(s):

Reinforced Concrete ◽

Seismic Design ◽

Concrete Beams ◽

Reinforced Concrete Beams ◽

Repeated Loading ◽

Transverse Reinforcement ◽

Cornell University ◽

Lap Splice ◽

Concrete Confinement ◽

Load Cycling

Proposals from Cornell University for seismic design of lap splices, where the strength provided to the lap splice by the concrete confinement is considered insignificant, were evaluated. The concrete confining the splice length is assumed to deteriorate after high-intensity (inelastic) reversed load cycling so that the performance is mainly dependent on the amount of transverse reinforcement provided to confine the lap splice. Lap lengths of 30–40 bar diameters are proposed, along with heavy transverse reinforcement. Longer lap lengths are considered to be less effective. By contrast, for static loading the concrete confining the splice is known to play a major role in transferring load between the bars along the splice.The current program consisted of testing six reinforced concrete beams under fully reversed cycled loading. The three similar beams in each of the two series contained equal stirrup confinement (number of stirrups) along the lap length to satisfy the Cornell University recommendations for seismic loading for the measured reinforcing yield strength, while the splice length was varied. Splices were located in the bottom face of the test beams and were positioned in a region of maximum moment to ensure severe stressing. Each series of specimens exhibited only small strength gains with increasing splice lengths; however, the performance, when evaluated on the basis of the ductility achieved and the hysteretic energy absorbed prior to failure, was superior with long splices. Since the main reinforcement in the test beams was loaded past yielding, large increases in deformation capacity resulted in only small increases in load.Full reversal inelastic load cycling is very detrimental to the concrete that confines the splice region when compared to static (monotonic) loading or one-directional repeated loading to failure. Splice failure loads under reversal loading in the current study were below predicted static strengths for the same beam configurations, and with the longer lap lengths, static failure would have been flexural rather than in the splice. Key words: reinforced concrete, beams, splices (lap), confinement, seismic design, cycled loading, ductility, strength.

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Effects of strain-ageing on New Zealand reinforcing steel bars

Bulletin of the New Zealand Society for Earthquake Engineering ◽

10.5459/bnzsee.42.3.179-186 ◽

2009 ◽

Vol 42 (3) ◽

pp. 179-186 ◽

Cited By ~ 2

Author(s):

A. Momtahan ◽

R.P. Dhakal ◽

A. Rieder

Keyword(s):

Reinforced Concrete ◽

New Zealand ◽

Yield Strength ◽

Seismic Design ◽

Reinforcing Steel ◽

Reinforcing Bars ◽

Capacity Design ◽

Plastic Hinges ◽

Strain Ageing ◽

Steel Bars

Modern seismic design codes, which are based on capacity design concepts, allow formation of plastic hinges in specified locations of a structure. This requires reliable estimation of strength of different components so that the desired hierarchy of strength of the structural components can be ensured to guarantee the formation of plastic hinges in the ductile elements. As strength of longitudinal reinforcing bars governs the strength of reinforced concrete members, strain-ageing, which has significant effect on the strength of reinforcing bars, should be given due consideration in capacity design. Strain-ageing can increase the yield strength of reinforcing steel bars and hence the strength of previously formed plastic hinges, thereby likely to force an unfavourable mechanism (such as strong beam-weak column leading to column hinging) to take place in subsequent earthquakes. In this paper, the strain-ageing effect of commonly used New Zealand reinforcing steel bars is experimentally investigated. Common New Zealand steel reinforcing bars are tested for different levels of pre-strain and different time intervals up to 50 days, and the results are discussed focussing on the extent of strain-ageing and its possible implications on seismic design provisions. The results indicate that designers need to use a higher flexural strength (in addition to overstrength) for the weaker member in checking the strength hierarchy in capacity design of reinforced concrete frames. Similarly, in designing retrofit measures to restore a damaged reinforced concrete member engineers need to take into account an increase of yield strength of the reinforcing steel bars employed in the member due to the strain-ageing phenomenon and the extent of increase in the yield strength depends on the level of damage.

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Flexural performance of reinforced concrete beams strengthened with strain-hardening cementitious composite and high strength reinforcing steel bar

Composites Part B Engineering ◽

10.1016/j.compositesb.2013.08.069 ◽

2014 ◽

Vol 56 ◽

pp. 512-519 ◽

Cited By ~ 23

Author(s):

Yun Yong Kim ◽

Bang Yeon Lee ◽

Jin-Wook Bang ◽

Byung-Chan Han ◽

Luciano Feo ◽

...

Keyword(s):

Reinforced Concrete ◽

Strain Hardening ◽

Concrete Beams ◽

High Strength ◽

Reinforced Concrete Beams ◽

Reinforcing Steel ◽

Cementitious Composite ◽

Flexural Performance ◽

Steel Bar

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Strength & Conduct of Reinforced Concrete Corner Joint under Negative Moment Effect

Journal of Architectural Environment & Structural Engineering Research ◽

10.30564/jaeser.v4i4.3607 ◽

2021 ◽

Vol 4 (4) ◽

Author(s):

Rasha A Waheeb

Keyword(s):

Reinforced Concrete ◽

Yield Stress ◽

Steel Reinforcement ◽

Reinforcing Steel ◽

Steel Ratio ◽

Negative Moment ◽

Concrete Joints ◽

Moment Effect ◽

Joint Shape ◽

Types Of Faults

The aim of our study is to reveal the effect of steel reinforcement details,tensile steel reinforcement ratio, compressed reinforcing steel ratio,reinforcing steel size, corner joint shape on the strength of reinforcedconcrete Fc' and delve into it for the most accurate details and concreteconnections about the behavior and resistance of the corner joint ofreinforced concrete, Depending on the available studies and sources inaddition to our study, we concluded that each of these effects had a clearrole in the behavior and resistance of the corner joint of reinforced concreteunder the influence of the negative moment and yield stress. A studyof the types of faults that can be reinforced angle joints obtains detailsand conditions of crushing that are almost identical for all types of steelreinforcement details and the basic requirements for the acceptable behaviorof reinforced concrete joints in the installations and the efficiency of thejoint and this may help us to prepare for disasters, whether natural or other,as happens with tremors The floor and failure that may occur due to wrongdesigns or old buildings and the possibility of using those connections totreat those joints and sections in reinforced or unarmed concrete facilitiesto preserve the safety of humans and buildings from sudden disasters andreduce and reduce risks, as well as qualitative control over the productionof concrete connections and sections free from defects to the extreme.

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REINFORCED CONCRETE BEAMS USING LOCALLY MANUFACTURED STEEL BARS: INVESTIGATION OF FLEXURAL BEHAVIOR

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2015.170 ◽

2015 ◽

Vol 2 (1) ◽

Author(s):

Shehab Mourad ◽

Abdelhamid Charif ◽

Iqbal Khan

Keyword(s):

Reinforced Concrete ◽

Yield Strength ◽

Yield Stress ◽

Concrete Strength ◽

Reinforced Concrete Beams ◽

Flexural Behavior ◽

Design Stage ◽

Essential Property ◽

Nominal Strength ◽

The Moment

While much attention has been and continue deservedly to be given to the effect of the variability of concrete strength and properties on the response of reinforced concrete structures, there is little, if any, information on the effects of variability of steel strength. Steel mechanical properties, including its yield strength, can significantly exceed the minimum nominal strength values for a specific grade of steel depending on the steel manufacturing processes. Such an increase in yield strength can have negative effects on the flexural behavior of beams designed as tension controlled, and reduce their ductility, an essential property in seismic resisting structures. An experimental and analytical study of the flexural behavior of RC beams was conducted through the investigation of the Moment-Curvature relationships and the ultimate steel strains. The main variable was the level of the actual steel yield stress as compared to the nominal value. It was found that unexpectedly high values of steel yield stress reduce the beam ductility and violate the tension-control condition, which was enforced in the design stage. Appropriate design corrections are proposed to account for high yield stress values in order to achieve the desired ductility of beams while maintaining the moment capacities.

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Study on the Bending and Joint Performances of Reinforced Concrete Beams Using High-Strength Rebars

Sustainability ◽

10.3390/su13063482 ◽

2021 ◽

Vol 13 (6) ◽

pp. 3482

Author(s):

Seoungho Cho ◽

Myungkwan Lim ◽

Changhee Lee

Keyword(s):

Yield Strength ◽

High Strength ◽

Reinforced Concrete Beams ◽

High Yield ◽

Performance Tests ◽

Reinforcing Bars ◽

Joint Performance ◽

Lap Splice ◽

Reinforcing Bar ◽

Nominal Strength

High-strength reinforcing bars have high yield strengths. It is possible to reduce the number of reinforcing bars placed in a building. Accordingly, as the amount of reinforcement decreases, the spacing of reinforcing bars increases, workability improves, and the construction period shortens. To evaluate the structural performance of high-strength reinforcing bars and the joint performance of high-strength threaded reinforcing bars, flexural performance tests were performed in this study on 12 beam members with the compressive strength of concrete, the yield strength of the tensile reinforcing bars, and the tensile reinforcing bar ratio as variables. The yield strengths of the tensile reinforcement and joint methods were used as variables, and joint performance tests were performed for six beam members. Based on this study, the foundation for using high-strength reinforcing bars with a design standard yield strength equal to 600 MPa was established. Accordingly, mechanical joints of high-strength threaded reinforcing bars (600 and 670 MPa) can be used. All six specimens were destroyed under more than the expected nominal strength. Lap splice caused brittle fractures because it was not reinforced in stirrup. Increases of 21% to 47% in the loads of specimens using a coupler and a lock nut were observed. Shape yield represents destruction—a section must ensure sufficient ductility after yielding. Therefore, a coupler and lock nut are effective.

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Passive corrosion control and active corrosion prevention of the reinforced concrete structures by electrochemical chloride removal and inhibitors

Anti-Corrosion Methods and Materials ◽

10.1108/acmm-03-2012-1156 ◽

2013 ◽

Vol 61 (1) ◽

pp. 32-37 ◽

Cited By ~ 3

Author(s):

Guofu Qiao ◽

Yi Hong ◽

Tiejun Liu ◽

Jinping Ou

Keyword(s):

Reinforced Concrete ◽

Concrete Structures ◽

Concrete Cover ◽

Reinforced Concrete Structures ◽

Reinforcing Steel ◽

Corrosion Control ◽

Cell Potential ◽

Content Type ◽

Chloride Removal ◽

Active Corrosion

Purpose – The aim of this paper was to investigate the passive corrosion control and active corrosion protective effect of the reinforced concrete structures by electrochemical chloride removal (ECR) method and inhibitors approach, respectively. Design/methodology/approach – The concentration of aggressive chloride ion distributed from the reinforcing steel to the surface of the concrete cover was analyzed during the ECR processes. Besides, the half-cell potential, the concrete resistance R c , the polarization resistance R p and the capacitance of double layer C dl of the steel/concrete system were used to characterize the electrochemical performance of the concrete prisms. Findings – The effectiveness of ECR could be enhanced by increasing the amplitude of potential or prolonging the time. Inhibitor SBT-ZX(I) could successfully prevent the corrosion development of the reinforcing steel in concrete. Originality/value – The research provides the scientific basis for the practical application of ECR and inhibitors in the field.

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