Design of transverse reinforcement to avoid premature buckling of main bars

Dhakal, Rajesh; Su, Junsheng

doi:10.1002/eqe.2944

Cited by 45 publications

(9 citation statements)

References 30 publications

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“…Transverse reinforcement in the central portion of the wall shall satisfy the anti-buckling requirements of NZS3101:2006 [17], All modern design codes agree on providing transverse reinforcement in the form of stirrups/ties to provide shear resistance and confinement to the core concrete, and design provisions for these two purposes have been developed based on extensive research carried out on RC members [22][23][24][25]. However, the provisions for anti-buckling reinforcement are somewhat vague and have been developed based on experience and intuition rather than a robust theoretical backup [26].…”

Section: Design Of Transverse Reinforcement In Rc Wallsmentioning

confidence: 99%

Section: Mechanics-based Design Of Anti-buckling Transverse Reinforcementmentioning

confidence: 99%

“…To overcome the aforementioned limitations of modern design codes, researchers in the past have investigated the effectiveness of transverse reinforcement on restricting bar buckling in RC members [12,[26][27][28][29][30]. Of these reported studies, the most widely-accepted research was carried out by Dhakal and Maekawa [12], from which a methodology for the design of anti-buckling transverse reinforcement for RC columns was recently proposed [26]. Dhakal and Maekawa [12] conducted extensive analytical studies on a beam-on-springs model, where the beam represented the longitudinal reinforcing bar, and elasto-plastic springs represented the tie legs restraining the bars against buckling.…”

Section: Mechanics-based Design Of Anti-buckling Transverse Reinforcementmentioning

confidence: 99%

“…Although modern standards recommend guidelines for the design of anti-buckling transverse reinforcement, experimental research on RC walls has highlighted their shortcomings in restricting buckling of longitudinal reinforcing bars to single tie spacing. Further, in modern design methodologies, including the recent mechanics-based design procedure proposed by Dhakal and Su [26], the effect of cyclic loading on bar buckling has not been incorporated. These design methodologies assume that bar buckling initiates under high compressive strain demands.…”

Section: Recommendations For the Design Of Anti-buckling Tiesmentioning

confidence: 99%

“…In the current methodology for the design of RC structures [17], it is assumed that bar buckling initiates under the influence of compressive strains, and therefore anti-buckling reinforcement is only required in regions susceptible to compressive yielding and limits the spacing of transverse reinforcement to 6db. Bar buckling results in a sustained reduction of the compressive stress capacity of reinforcing bars; therefore, in the mechanicsbased design procedure proposed by Dhakal and Su [26] the strain corresponding to 15% reduction in compressive stress capacity was used as a criteria for the design of anti-buckling ties. Although it appears to be a logical design procedure, the effect of cyclic loading on the premature buckling of longitudinal bars was not considered in the formulation.…”

Section: Limiting Compressive Stress Deterioration In Reinforcing Barsmentioning

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: Design Of Transverse Reinforcement In Rc Wallsmentioning

confidence: 99%

Section: Mechanics-based Design Of Anti-buckling Transverse Reinforcementmentioning

confidence: 99%

Section: Mechanics-based Design Of Anti-buckling Transverse Reinforcementmentioning

confidence: 99%

Section: Recommendations For the Design Of Anti-buckling Tiesmentioning

confidence: 99%

Section: Limiting Compressive Stress Deterioration In Reinforcing Barsmentioning

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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The analytical curvature distribution model of columns and mathematical solution for pushover analysis

Zhong,

Zhu,

Wang

2024

Earthq Engng Struct Dyn

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The acquisition of a flexural backbone curve for columns primarily relies on finite element analysis and experiments, of which the complexity and high cost are significant challenges. Hence, this study proposes an analytical curvature distribution model (CDM) along the full height of the column, which is the key point of formula derivation and theoretical solution of the column backbone curve. The proposed CDM is a piecewise function model composed of linear and quadratic functions, with the characteristics of continuity and differentiability at the intersection point. The deformation compatibility equations, equilibrium equations, and material constitutive equations based on the variables of CDM are constructed to form an equation system, the solution of which can be theoretically determined by an iterative algorithm. Furthermore, 155 test specimen columns of different materials, for example, reinforced concrete, high‐strength reinforced concrete, and shape memory alloy are used to validate the proposed CDM and mathematical solutions of pushover analysis through three crucial indicators, that is, goodness of fit of backbone curve, ultimate displacement, and peak force, indicating strong practicability, high accuracy, and wider applicability. This theoretical method can be applied to deal with the key issues of interest during pushover analysis, that is, predicting the flexural backbone curves with different materials, determining the curvature distribution throughout the entire process of pushover analysis, and characterizing the evolution process of the plastic region.

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A simplified procedure for seismic collapse probability assessment of RC frame buildings

Koopaee,

Dhakal

2024

Structural Concrete

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This paper presents a procedure for simplified collapse probability prediction of RC frame buildings when subjected to ground motion intensities commonly used in designing buildings. For this purpose, seismic collapse probability of a range of RC moment resisting frame buildings are assessed at the design basis earthquake (DBE) and the maximum considered earthquake (MCE) levels of seismic intensity by conducting more than a thousand nonlinear response history analyses (NRHA) using a suite of 40 seismic ground motion records. The 13 buildings included in the investigation have different heights (5–15 storeys) and footprints (3–6 bays), are designed to different target maximum inter‐storey drifts (within the code specified limit), and have critical members detailed to sustain different levels of confinement and anti‐buckling demands. The NRHA results consistently demonstrate that the design inter‐storey drift and the anti‐buckling detailing of longitudinal rebars in the critical frame members strongly influence the collapse probability of RC frame buildings. The results also show that while RC frame buildings designed to reach 2.5% (or less) inter‐storey drifts and detailed for ductile seismic performance can successfully avoid collapse at DBE, avoidance of collapse at DBE cannot be guaranteed if RC frames are designed to reach a target drift of more than 2% and not detailed for full ductility. At MCE, collapse probability is found to consistently exceed 10% unless the building is designed to incur no more than 1% plastic drift and the frame members have ductile detailing. Based on the NRHA results of the 13 case study buildings, easy‐to‐use equations relating their seismic collapse probability at MCE with the design drift and a quantifiable measure of ductile detailing are generated and validated by comparing with the collapse probability obtained by NRHA of an independent RC frame building. The proposed equations provide a rapid, yet reasonably reliable tool for performance‐based seismic design of RC frame buildings, and enable designers to estimate seismic collapse probability of RC frame buildings without having to conduct cumbersome NRHA.

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Design of transverse reinforcement to avoid premature buckling of main bars

Cited by 45 publications

References 30 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

The analytical curvature distribution model of columns and mathematical solution for pushover analysis

A simplified procedure for seismic collapse probability assessment of RC frame buildings

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