Low-cycle fatigue behaviour of reinforcing bars including the effect of inelastic buckling

Tripathi, Mayank; Dhakal, Rajesh; Dashti, Farhad; Massone, Leonardo M.

doi:10.1016/j.conbuildmat.2018.09.192

Cited by 52 publications

(19 citation statements)

References 23 publications

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“…In the proposed guideline for the design of anti-buckling reinforcement, the spacing of transverse reinforcement along the longitudinal bars shall be restricted to ensure that under cyclic loading the initiation of sustained reduction of compressive stress in bars is delayed until the strain range demand (Δɛd) at the limiting curvature is achieved (as given in Table 4). When unloaded from peak tensile strains, reinforcing bars unload almost elastically, followed by near-elastic loading of the bar in compression and subsequent yielding (as shown in Figure 8) [14,15]. In a reinforcing bar unloaded from a peak tensile strain of ɛmax, the sustained reduction in compressive stress due to buckling is initiated at ɛmin.…”

Section: Limiting Compressive Stress Deterioration In Reinforcing Barsmentioning

confidence: 99%

“…In addition to bar buckling, bar fracture due to the accumulation of low-cycle fatigue damage has also been commonly observed in RC walls and columns. Although the accumulation of low-cycle fatigue damage in reinforcing bars cannot be avoided, the detrimental effect of fatigue damage on the hysteretic response of bars and their subsequent fracture can be delayed by either limiting the strain demands at plastic hinges by designing the RC structural elements for low ductility demands or by limiting the buckling of reinforcing bars to single tie spacing [15,16].…”

Section: Introductionmentioning

confidence: 99%

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Designing and detailing transverse reinforcement to control bar buckling in rectangular RC walls

Tripathi

Dhakal

2021

BNZSEE

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Bar buckling in RC structures is a commonly-observed failure mode that adversely affects their deformation capacity. To restrict bar buckling in ductile RC walls, design codes only emphasises on restricting the spacing of transverse reinforcement and does not recognise the importance of the effective stiffness of the ties (which is a combination of the tie leg axial stiffness and spacing) to restrict bar buckling. Therefore, in this paper the design requirements for anti-buckling transverse reinforcement are summarised, and improvements to the current design methodology for anti-buckling transverse reinforcement are proposed. To ensure that the transverse reinforcement detailing in plastic hinge regions is adequate to restrict bar buckling to single tie spacing and the compressive stress deterioration in bars due to buckling is controlled, refinements to the current detailing procedures are proposed. The buckling restraining ability of transverse reinforcement depends on the axial stiffness of the tie legs, while the compressive stress reduction in reinforcing bars due to buckling depends on their unsupported length (in bare bar tests) or buckling length that can include multiple tie spacing (inside RC members). Therefore, restrictions on both the axial stiffness of the tie legs and spacing of transverse reinforcement along the longitudinal reinforcing bars are proposed. The effective axial stiffness of tie legs is controlled by ensuring that the length of the tie legs in the direction of potential buckling is well below the critical length evaluated using a mechanics-based approach. Additionally, compressive stress degradation in reinforcing bars is controlled by limiting the ratio of the transverse reinforcement spacing and the longitudinal bar diameter such that any reduction of compressive stress carried by the longitudinal bars due to buckling at the limiting curvature recommended by New Zealand Concrete Standard is within an acceptable range. Furthermore, recommendations to avoid buckling of unrestrained reinforcing bars in the boundary zone and the wall web are proposed. Using the proposed design methodology, buckling of longitudinal reinforcing bars in ductile RC walls can be delayed and the detrimental effects of buckling on the lateral response of walls can be controlled until the design drift or curvature demands are met.

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Section: Limiting Compressive Stress Deterioration In Reinforcing Barsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Designing and detailing transverse reinforcement to control bar buckling in rectangular RC walls

Tripathi

Dhakal

2021

BNZSEE

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“…Also, it should be noted that the boundary ends and corners of specimen TUC from Constantin and Beyer (2016) were heavily confined, thus a greater compression strain capacity would have been possible in the boundary ends of the flanges of TUC in comparison to the unconfined specimens TUE and TUF tested here. It has also been shown that buckling prone reinforcing bars fail much earlier in comparison to reinforcing bars with limited or no buckling due to the detrimental effect of low-cycle fatigue (Tripathi et al, 2018), which make these types of walls particularly susceptible.…”

Section: Tuf Observationsmentioning

confidence: 99%

“…The ductile reinforcing bars used in the boundary ends (previously discussed in Section 2.2) also allowed the walls tested here to achieve high ductilities, whereas low-ductility welded wire mesh has been used in Colombian construction practice (Blandón et al, 2018;Blandón and Bonett, 2020). Thus, a wall detailed with low-ductility steel could result in a brittle failure due to fracturing of the bars, which can also be exacerbated with the phenomenon of low-cycle fatigue (Tripathi et al, 2018).…”

Section: Bilinear Force-displacement Responsementioning

confidence: 99%

“…While this type of failure had been previously reported experimentally (Goodsir, 1985;Oesterle et al, 1976;Thomsen and Wallace, 2004), this was the first time it had been widely observed after earthquake events. Correspondingly, there has recently been a great deal of experimental and numerical investigative research focusing on the out-of-plane instability of RC walls due to in-plane loading (Dashti et al, 2018;Haro et al, 2018;Parra and Moehle, 2017;Rosso et al, 2016;Rosso et al, 2018). However, all of these recently tested specimens were either planar (i.e., rectangular) walls or idealized boundary elements.…”

Section: Introductionmentioning

confidence: 99%

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Seismic performance of slender RC U-shaped walls with a single-layer of reinforcement

Hoult

Appelle

Almeida

et al. 2020

Engineering Structures

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Reinforced concrete walls are commonly used to resist the lateral loading induced by wind and earthquake actions. While most walls include two vertical reinforcement layers, some regions of the world construct slender, non-rectangular concrete walls with a single vertical layer of reinforcement. The seismic performance of such elements is largely unknown given the paucity of experimental research. This paper presents the results of two slender reinforced concrete U-shaped walls tested at the Earthquake Engineering and Structural Dynamics Laboratory (EESD Lab), École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. Both wall specimens, designed similar to construction practice in Colombia, were tested using quasi-static cyclic loading to observe if out-of-plane instability would develop when deformations were limited to prevent the flange boundary ends crushing. Initial failure of both wall specimens corresponded with local out-of-plane buckling in the boundary ends of the flanges occurring on load reversal. The buckling lengths were approximately 700-800 mm, which corresponded to 44-50 bar diameters. The crack patterns were observed to be steepest in the web of the walls, demonstrating the increased shear demand in comparison to that of a rectangular wall. Both wall specimens reached ultimate drifts larger than 2.5-3.0% before global failure occurring in the web-flange intersection due to crushing. A small twist was subjected to one of the walls when centered and loaded diagonally, which showed that the decay in torsional stiffness is proportional to the decay in translational stiffness.

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Experimental study on the effects of bi‐directional loading pattern on rectangular reinforced concrete walls

Niroomandi

Pampanin

Dhakal

et al. 2021

Earthq Engng Struct Dyn

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In this experimental study, three identical reinforced concrete (RC) walls were tested under three different lateral loading patterns. These loading patterns were cyclic in‐plane, skewed with 45° angle and clover leaf. The main objective was to investigate the effects of these bi‐directional loading patterns on the seismic behavior of slender rectangular RC walls. The results showed significant increase in tensile and compressive strains in concrete and longitudinal bars that led to earlier cover concrete spalling and bar buckling in the specimens subjected to bi‐directional loading. The neutral axis depth and compression zone were found to be substantially larger when subjected to bi‐directional loading and this led to the occurrence of concrete crushing and bar buckling in the web. Moreover, lateral instability failure triggered earlier in the specimens under bi‐directional loading, as a result of reduction of out‐of‐plane stiffness of the wall. However, bi‐directional loading did not significantly increase out‐of‐plane buckling of the wall in terms of out‐of‐plane displacement. In‐plane and out‐of‐plane shear cracks formed in one of the specimens subjected to bi‐directional loading, whereas the same wall under in‐plane loading developed only flexural cracks. It was also found that in‐plane shear deformation was larger when the wall was subjected to bi‐directional loading. The results of this experimental study emphasize the need for further investigation of the effects of bi‐directional loading on RC structural walls.

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Low-cycle fatigue behaviour of reinforcing bars including the effect of inelastic buckling

Cited by 52 publications

References 23 publications

Designing and detailing transverse reinforcement to control bar buckling in rectangular RC walls

Designing and detailing transverse reinforcement to control bar buckling in rectangular RC walls

Seismic performance of slender RC U-shaped walls with a single-layer of reinforcement

Experimental study on the effects of bi‐directional loading pattern on rectangular reinforced concrete walls

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