RYS - RC Reinforcement Bar Bond Stress, Anchorage and Lapping

RC Reinforcement Bar Bond Stress, Anchorage and Lapping - EC02 Code

Anchorage Bond

l_b,rqdπφf_bd = (πφ²/4 )f_s

l_b,rqd = f_sφ/4f_bd

At yield , f_s = f_yd        l_b,rqd = (φ/4)(f_yk/1.15)(1/f_bd) = f_ykφ/(4.6f_bd)
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bond stress dependant on;

1)inclination of bars 45^o to 90^o
2)inclination of bars 45^o to 90^o location of rebars to thickness of cast member is considered, see below diagram, at poor location reduction factored by 0.7
3)diameter of rebars, for ϕ≥32 mm , additional factored by (132-ϕ)/100
4)concrete grade , f_bd＝1.50f_ctk ,     f_ctk = characteristic tensile strength of concrete.

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Design values of bond stress f_bd N/mm²

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Coefficients of α

note
α₂α₃α₅ ≥ 0.7
l_bd = α₁α₂α₃α₄α₅l_bd,rqd(A_s,rqd/A_s,pvd)
suggestion
for tension in table for coefficients of α above , just use 0.7 - conservative
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Anchorage, Bends and Hooks

Internal diameter (mandrel size) for bent bars; - minimum 4ϕ for ϕ≤16 mm - minimum 7ϕ for ϕ>16 mm

The minimum design anchorage length cannot be <= 1) for tension bars : min( 0.3l_bd,rqd,10ϕ ,100mm )
2) for compression bars : min( 0.6l_bd,rqd,10ϕ ,100mm )
Bends and hooks not recommended for use as compression anchorage.

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Laps in reinforcements

Laps should be staggered and should not occurs in regions of high stress.

l₀＝l_b,rqd⋅α₁⋅α₂α₃α₅α₆
α₆ = ( ρ₁/25)^0.5 1.0≤α₆≤1.5

ρ1 = % of rebars lapped within 0.65l₀ from the centers of lap

Values of coefficient α₆:

However, absolute minimum to be provided.
l_0,min＝0.3α₆⋅l_b,rqd
l_0,min ≥ max( 15ϕ , 200mm )
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Transverse Reinforcements in Lapped Rebars
For ϕ_{lapped_rebars} ≤ 20 mm or lapped_bars < 25% , no need transverse bars, rebars e.g links should be ok

Otherwise provide transvers rebars required , A_{transverse_total} ≥ A_{area_one_splice_rebar}

Lapping Rebar Details

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