How does the code handle combined tension and shear on an anchor?

It uses an interaction equation: (Ns/Nn)^(5/3) + (Vs/Vn)^(5/3) ≤ 1.0, where Ns and Vs are applied loads and Nn and Vn are the capacities in pure tension and shear, respectively (Clause 5.4).

What is the primary failure mode for a standard anchor in tension?

For an anchor with adequate embedment depth, the typical failure mode is the breakout of a cone of concrete originating from the anchor head (Clause 5.2.2).

Does this code cover design for seismic conditions?

No, IS 11502 does not include specific provisions for the design of anchors under seismic loads. Specialized anchors and design methods are required for such applications.

What factor of safety is recommended for site tests?

For determining the allowable load from on-site pull-out tests, a minimum factor of safety of 3.0 should be applied to the ultimate test load (Clause 5.1.2).

IS 11502

: 1995

Code of practice for design of mechanical anchors for use in concrete

CurrentSpecializedCode of PracticeBIMStructural Engineering · Fasteners, Bolts and Anchors

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This code of practice provides design guidelines for post-installed mechanical anchors used to make connections to hardened concrete. It covers the design methodology for anchors subjected to tension, shear, and combined loads, outlining various failure modes like steel failure, concrete cone breakout, and pull-out.

Lays down the procedure for the design of mechanical anchor fasteners for use in concrete.

Quick Reference Values

Interaction formula exponent for combined loads5/3

Minimum factor of safety on ultimate test load3.0

Assumed angle of concrete failure cone from anchor head45 degrees

Coefficient for concrete cone capacity (N p)0.40

Key Formulas

(Ns/Nn)^(5/3) + (Vs/Vn)^(5/3) <= 1.0 — Interaction formula for combined tension and shear

N_p = 0.4 * A_p * sqrt(fck) — Characteristic strength for concrete cone failure in tension

Vs = 0.45 * fy * As — Design shear strength of anchor steel

Practical Notes

This code's design methods are dated and do not include provisions for seismic loading. For modern and critical applications, refer to manufacturer's technical data based on European Technical Approvals (ETA).

The performance of mechanical anchors is highly dependent on correct installation procedures, including hole diameter, cleaning, and tightening torque. On-site supervision and proof testing (as per Annex A) are crucial.

The formulas provided are generic; product-specific data from the anchor manufacturer should always be preferred as it accounts for the specific anchor's performance characteristics.