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

  • Mayank Tripathi University of Canterbury, New Zealand
  • Rajesh Dhakal University of Canterbury, New Zealand

Abstract

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.

References

Wallace JW, Massone LM, Bonelli P, Dragovich J, Lagos R, Luders C and Moehle J (2012). "Damage and implications for seismic design of RC structural wall buildings". Earthquake Spectra, 28: S281-S299. https://doi.org/10.1193%2F1.4000047 DOI: https://doi.org/10.1193/1.4000047

Sritharan S, Beyer K, Henry RS, Chai YH, Kowalsky M and Bull D (2014). "Understanding poor seismic performance of concrete walls and design implications". Earthquake Spectra, 30(1): 307-334. https://doi.org/10.1193%2F021713EQS036M DOI: https://doi.org/10.1193/021713EQS036M

Thomsen JH and Wallace JW (2004). "Displacement-based design of slender reinforced concrete structural walls-experimental verification". ASCE Journal of Structural Engineering, 130(4): 618-630. https://doi.org/10.1061/(ASCE)0733-9445(2004)130:4(618) DOI: https://doi.org/10.1061/(ASCE)0733-9445(2004)130:4(618)

Dashti F, Dhakal RP and Pampanin S (2017). "Tests on slender ductile structural walls designed according to New Zealand Standard". Bulletin of the New Zealand Society for Earthquake Engineering, 50(4): 504-516. https://doi.org/10.5459/bnzsee.50.4.504-516 DOI: https://doi.org/10.5459/bnzsee.50.4.504-516

Tripathi M, Dhakal RP and Dashti F (2019). "Bar buckling in ductile RC walls with different boundary zone detailing: Experimental investigation". Engineering Structures, 198. https://doi.org/10.1016/j.engstruct.2019.109544 DOI: https://doi.org/10.1016/j.engstruct.2019.109544

Tripathi M, Dhakal RP and Dashti F (2020). "Nonlinear cyclic behaviour of high-strength ductile RC walls: Experimental and numerical investigations". Engineering Structures, 222. https://doi.org/10.1016/j.engstruct.2020.111116 DOI: https://doi.org/10.1016/j.engstruct.2020.111116

Dashti F, Tripathi M, Dhakal RP and Pampanin S (2020). "A parametric study on out-of-plane instability of doubly reinforced structural walls. Part II: Experimental investigation". Bulletin of Earthquake Engineering, 18(11): 5193-5220. https://doi.org/10.1007/s10518-020-00898-w DOI: https://doi.org/10.1007/s10518-020-00898-w

Birely AC (2012). "Seismic Performance of Slender Reinforced Concrete Structural Walls". PhD Dissertation, University of Washington, Seattle. http://hdl.handle.net/1773/22577

Tripathi M, Dhakal RP, Dashti F and Gokhale R (2020). "Axial response of rectangular RC prisms representing the boundary elements of ductile concrete walls". Bulletin of Earthquake Engineering, 18(9): 4387-4420. https://doi.org/10.1007/s10518-020-00868-2 DOI: https://doi.org/10.1007/s10518-020-00868-2

Dhakal RP and Maekawa K (2002). "Modeling for postyield buckling of reinforcement". ASCE Journal of Structural Engineering, 128(9): 1139-1147. https://doi.org/10.1061/(ASCE)0733-9445(2002)128:9(1139) DOI: https://doi.org/10.1061/(ASCE)0733-9445(2002)128:9(1139)

Dhakal RP and Maekawa K (2002). "Path-dependent cyclic stress-strain relationship of reinforcing bar including buckling". Engineering Structures, 24(11): 1383-1396. https://doi.org/10.1016/S0141-0296(02)00080-9 DOI: https://doi.org/10.1016/S0141-0296(02)00080-9

Dhakal RP and Maekawa K (2002). "Reinforcement stability and fracture of cover concrete in reinforced concrete members". ASCE Journal of Structural Engineering, 128(10): 1253-1262. https://doi.org/10.1061/(ASCE)0733-9445(2002)128:10(1253) DOI: https://doi.org/10.1061/(ASCE)0733-9445(2002)128:10(1253)

Kashani MM, Lowes LN, Crewe AJ and Alexander NA (2015). "Phenomenological hysteretic model for corroded reinforcing bars including inelastic buckling and low-cycle fatigue degradation". Computers and Structures, 156: 58-71. https://doi.org/10.1016/j.compstruc.2015.04.005 DOI: https://doi.org/10.1016/j.compstruc.2015.04.005

Tripathi M (2020). "Bar Buckling in Ductile Reinforced Concrete Walls: Causes, Consequences and Control". PhD Dissertation, University of Canterbury, Christchurch. http://dx.doi.org/10.26021/1859

Tripathi M, Dhakal RP, Dashti F and Massone LM (2018). "Low-cycle fatigue behaviour of reinforcing bars including the effect of inelastic buckling". Construction and Building Materials, 190: 1226-1235. https://doi.org/10.1016/j.conbuildmat.2018.09.192 DOI: https://doi.org/10.1016/j.conbuildmat.2018.09.192

Tripathi M, Dhakal RP, Dashti F and Massone LM (2019). "Low-cycle fatigue damage of buckling prone reinforcing bars". Pacific Conference on Earthquake Engineering and Annual NZSEE Conference, Auckland, New Zealand. http://db.nzsee.org.nz/2019/Oral/11A.02%20Dhakal.pdf

SNZ (2006). " NZS 3101: Concrete Structures Standard- The Design of Concrete Structures". Standards New Zealand, Wellington. https://shop.standards.govt.nz/catalog/3101.1%7C2%3A2006%28NZS%29/view

ACI (2014). " Building Code Requirements for Structural Concrete (ACI 318–14)". American Concrete Institute, Farmington Hills, MI.

ACI (2019). "Building Code Requirements for Structural Concrete (ACI 318–19)". American Concrete Institute, Farmington Hills, MI. https://www.concrete.org/store/productdetail.aspx?ItemID=31819HC&Format=HARD_COPY&Language=English&Units=US_Units

CEN (2005). "Eurocode-8: Design of Structures for Earthquake Resistance-Part 1: General Rules, Seismic Actions and Rules for Buildings". European Committee for Standardisation, Brussles.

SESOC (2013). "Design of Conventional Structural Systems following the Canterbury Earthquakes: Interim Design Guidelines". https://www.sesoc.org.nz/library/guidelines/sesoc-interim-design-guidance-design-of-conventional-structural-systems-following-the-canterbury-earthquakes/

Sheikh SA and Uzumeri SM (1980). "Strength and ductility of tied concrete columns". 106(ASCE Proceeding). https://www.researchgate.net/publication/279577120_Strength_and_Ductility_of_Tied_Concrete_Columns DOI: https://doi.org/10.1061/JSDEAG.0005416

Mander JB, Priestley MJN and Park R (1988). "Theoretical stress-strain model for confined concrete". ASCE Journal of Structural Engineering, 114(8): 1804-1826. https://doi.org/10.1061/(ASCE)0733-9445(1988)114:8(1804) DOI: https://doi.org/10.1061/(ASCE)0733-9445(1988)114:8(1804)

Mander JB, Priestley MJN and Park R (1988). "Observed stress-strain behavior of confined concrete". ASCE Journal of Structural Engineering, 114(8): 1827-1849. https://doi.org/10.1061/(ASCE)0733-9445(1988)114:8(1827) DOI: https://doi.org/10.1061/(ASCE)0733-9445(1988)114:8(1827)

Saatcioglu M and Razvi SR (1992). "Strength and ductility of confined concrete". ASCE Journal of Structural Engineering, 118(6): 1590-1607. https://doi.org/10.1061/(ASCE)0733-9445(1992)118:6(1590) DOI: https://doi.org/10.1061/(ASCE)0733-9445(1992)118:6(1590)

Dhakal RP and Su J (2018). "Design of transverse reinforcement to avoid premature buckling of main bars". Earthquake Engineering and Structural Dynamics, 47(1): 147-168. https://doi.org/10.1002/eqe.2944 DOI: https://doi.org/10.1002/eqe.2944

Bresler B and Gilbert P (1961). Tie requirements for reinforced concrete columns". ACI Journal Proceedings. http://dx.doi.org/10.14359/7997 DOI: https://doi.org/10.14359/7997

Pantazopoulou SJ (1998). "Detailing for reinforcement stability in RC members". ASCE Journal of Structural Engineering, 124(6): 623-632. https://doi.org/10.1061/(ASCE)0733-9445(1998)124:6(623) DOI: https://doi.org/10.1061/(ASCE)0733-9445(1998)124:6(623)

Massone LM and Lopez EE (2014). "Modeling of reinforcement global buckling in RC elements". Engineering Structures, 59: 484-494. https://doi.org/10.1016/j.engstruct.2013.11.015 DOI: https://doi.org/10.1016/j.engstruct.2013.11.015

Dhakal RP (2006). "Post-peak response analysis of SFRC columns including spalling and buckling". Structural Engineering and Mechanics, 22(3): 311-330. http://dx.doi.org/10.12989/sem.2006.22.3.311 DOI: https://doi.org/10.12989/sem.2006.22.3.311

Sato Y and Ko H (2007). "Experimental investigation of conditions of lateral shear reinforcements in RC columns accompanied by buckling of longitudinal bars". Earthquake Engineering and Structural Dynamics, 36(12): 1685-1699. https://doi.org/10.1002/eqe.712 DOI: https://doi.org/10.1002/eqe.712

Shegay AV, Motter CJ, Elwood KJ, Henry RS, Lehman DE and Lowes LN (2018). "Impact of axial load on the seismic response of rectangular walls". ASCE Journal of Structural Engineering, 144(8). https://doi.org/10.1061/(ASCE)ST.1943-541X.0002122 DOI: https://doi.org/10.1061/(ASCE)ST.1943-541X.0002122

Priestley MJN and Kowalsky M (1998). "Aspects of drift and ductility capacity of rectangular cantilever structural walls". Bulletin of the New Zealand Society for Earthquake Engineering, 31(2): 73-85. https://doi.org/10.5459/bnzsee.31.2.73-85 DOI: https://doi.org/10.5459/bnzsee.31.2.73-85

Hoult RD, Goldsworthy HM and Lumantarna E (2018). "Plastic hinge analysis for lightly reinforced and unconfined concrete structural walls". Bulletin of Earthquake Engineering, 16(10): 4825-4860. https://doi.org/10.1007/s10518-018-0369-x DOI: https://doi.org/10.1007/s10518-018-0369-x

Dhakal RP and Fenwick RC (2008). "Detailing of plastic hinges in seismic design of concrete structures". ACI Structural Journal, 105(6). http://hdl.handle.net/10092/4190 DOI: https://doi.org/10.14359/20102

Dodd L and Restrepo-Posada J (1995). "Model for predicting cyclic behavior of reinforcing steel". ASCE Journal of Structural Engineering, 121(3): 433-445. https://doi.org/10.1061/(ASCE)0733-9445(1995)121:3(433) DOI: https://doi.org/10.1061/(ASCE)0733-9445(1995)121:3(433)

Tripathi M, Dhakal RP and Dashti F (2019). "Non-linear cyclic response of concrete walls with different transverse reinforcement detailing". 12th Canadian Conference on Earthquake Engineering, Quebec City, Canada. https://hdl.handle.net/10092/101148

Scribner CF (1986). "Reinforcement buckling in reinforced-concrete flexural members". Journal of the American Concrete Institute, 83(6): 966-973. http://dx.doi.org/10.14359/2648 DOI: https://doi.org/10.14359/2648

Moehle JP (2019). "Key changes in the 2019 edition of the ACI Building Code (ACI 318-19)". Concrete International, 41(8): 21-27. https://www.concrete.org/publications/internationalconcreteabstractsportal.aspx?m=details&i=51719093

Published
2021-09-01
How to Cite
Tripathi, M., & Dhakal, R. (2021). Designing and detailing transverse reinforcement to control bar buckling in rectangular RC walls. Bulletin of the New Zealand Society for Earthquake Engineering, 54(3), 228-242. https://doi.org/10.5459/bnzsee.54.3.228-242
Section
Articles