Q: How is anchor group resistance calculated per EN 1992-4?

For an anchor group, the projected cone area A_c,N is computed as the actual footprint of the group including edge clipping. When anchor spacing s < 3·h_ef (s_cr,N), adjacent cones overlap and the group area is less than n × A0_c,N for a single anchor. The ψ_s,N factor further reduces resistance when edge distances c < 1.5·h_ef (c_cr,N). The group utilisation is N_Ed / N_Rd,c where N_Rd,c = N_Rk,c / γ_Mc (γ_Mc = 1.5 for EN baseline).

Q: What is the design process for cast-in headed anchor bolts?

For cast-in headed anchors per EN 1992-4:2018: (1) determine h_ef from the column base plate thickness and grout layer; (2) check all five tension failure modes: steel (§7.2.1.3), concrete cone (§7.2.1.4), pull-out under head (§7.2.1.5), splitting (§7.2.1.7), and blow-out when c1 < 0.5·h_ef (§7.2.1.8); (3) check three shear modes: steel (§7.2.2.3), pry-out (§7.2.2.4), and edge failure when close to an edge (§7.2.2.5); (4) verify combined interaction §7.2.3. The governing (lowest resistance) mode determines the final utilisation.

Question 1

How do I use an anchor bolt calculator for EN 1992-4?

Accepted Answer

Enter the anchor type (cast-in headed or post-installed bonded), bolt diameter and grade, effective embedment depth h_ef, edge distances c1/c2, group layout, concrete class, cracked/uncracked condition, and design loads N_Ed and V_Ed. The calculator checks all EN 1992-4:2018 failure modes: steel §7.2.1.3, concrete cone §7.2.1.4, pull-out §7.2.1.5, splitting §7.2.1.7, blow-out §7.2.1.8 for tension; steel §7.2.2.3, pry-out §7.2.2.4, edge failure §7.2.2.5 for shear; and combined interaction §7.2.3.

Question 2

What is concrete cone failure in EN 1992-4?

Accepted Answer

Concrete cone failure (§7.2.1.4) occurs when a cone of concrete is pulled out from the base element. The characteristic resistance is N_Rk,c = N0_Rk,c × (A_c,N / A0_c,N) × ψ_s,N × ψ_re,N × ψ_ec,N, where N0_Rk,c = k1 × √fck × h_ef^1.5 is the single-anchor reference. The area factor A_c,N / A0_c,N accounts for overlapping cones in a group (when spacing s < s_cr,N = 3·h_ef). Increasing embedment depth h_ef is the most effective way to improve cone resistance as it scales with h_ef^1.5.

Question 3

How is anchor group resistance calculated per EN 1992-4?

Accepted Answer

For an anchor group, the projected cone area A_c,N is computed as the actual footprint of the group including edge clipping. When anchor spacing s < 3·h_ef (s_cr,N), adjacent cones overlap and the group area is less than n × A0_c,N for a single anchor. The ψ_s,N factor further reduces resistance when edge distances c < 1.5·h_ef (c_cr,N). The group utilisation is N_Ed / N_Rd,c where N_Rd,c = N_Rk,c / γ_Mc (γ_Mc = 1.5 for EN baseline).

Question 4

What is the design process for cast-in headed anchor bolts?

Accepted Answer

For cast-in headed anchors per EN 1992-4:2018: (1) determine h_ef from the column base plate thickness and grout layer; (2) check all five tension failure modes: steel (§7.2.1.3), concrete cone (§7.2.1.4), pull-out under head (§7.2.1.5), splitting (§7.2.1.7), and blow-out when c1 < 0.5·h_ef (§7.2.1.8); (3) check three shear modes: steel (§7.2.2.3), pry-out (§7.2.2.4), and edge failure when close to an edge (§7.2.2.5); (4) verify combined interaction §7.2.3. The governing (lowest resistance) mode determines the final utilisation.

Mode	Clause	R_d (kN)	E_d (kN)	η	Result
tension	N_Rd,s Steel failure (tension) §7.2.1.3	653.3	50.0	7.7%	PASS
tension	N_Rd,c Concrete cone §7.2.1.4	54.3	50.0	92.2%	PASS
tension	N_Rd,p Pull-out / bonded failure §7.2.1.5	326.7	50.0	15.3%	PASS
tension	N_Rd,sp Splitting §7.2.1.7	54.3	50.0	92.2%	PASS
shear	V_Rd,s Steel failure (shear) §7.2.2.3	392	30.0	7.7%	PASS
shear	V_Rd,cp Concrete pry-out §7.2.2.4	108.5	30.0	27.6%	PASS
shear	V_Rd,c Concrete edge failure §7.2.2.5	161.3	30.0	18.6%	PASS

EN 1992-4 Anchor Bolt Calculator

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