HAC_Technical-Guide

ManualsBrandsHilti ManualsCast-in Anchor ChannelsHAC Front-of-slab rebar channel

166 167

Cast-In Anchor Channel Product Guide, Edition 1 • 02/2019

1. Anchor

Channel Systems

2. HAC

Portfolio

3. HAC

Applications

4. Design

Introduction

5. Base material 6. Loading

7. Anchor Channel

Design Code

8. Reinforcing

Bar Anchorage

9. Special Anchor

Channel Design

10. Design

Software

11. Best

Practices

12. Instructions

for Use

13. Field Fixes

14. Design

Example

7.1 & 7.2 Introduction to

Anchor Channel Design

7.3 Anchor Channel Tension Design 7.4 Anchor Channel Shear Design (y) 7.4 Anchor Channel Shear Design (X)

7.5 Interaction Equations

(Combined Loading)

7.6 Seismic Design

Steel Concrete Steel Concrete Steel Concrete

The nominal strength of the channel lips to take up tension

loads transmitted by a channel bolt, N

, must be taken from

ESR 3520 Table 8-3. This value is valid only if the center-to-

center distance between the channel bolt under consideration

and adjacent channel bolts, S

chb

, is at least 2b

(see fig 7.3.1.5).

If this requirement is not met then the value N

given in table 8-3

must be reduced by the factor

ua,1

iua,

ichb,

Where the center-to-center spacing between channel bolts shall

not be less than 3-times the bolt diameter d

Figure 7.3.1.5 — Anchor channel dimensions.

Channel Bolt Strength фN

Channel bolt strength N

, and ϕ are

tabulated in ESR-3520 Table 8-11 for

HAC and HAC-T with Hilti channel bolts

(HBC-B, HBC-C, HBC-T and HBC-C-N).

ϕN

≥ N

bua

The nominal strength of the channel

bolt, N

, shall not exceed the value

determined in accordance with the

following equation:

≥ A

use,N

utb

where A

use,N

is the effective cross-sectional area in tension, in

(mm

); and f

utb

shall be taken as the smaller of 1.9f

and 125,000

psi (860 MPa)

Test No. 3 is performed to evaluate the strength of the head of

the channel bolt. All channel bolt sizes have been tested. For

test No. 3, test the channel bolts in a section of channel that is

sufficiently restrained to cause failure of the channel bolt (Figure

7.3.1.6 a). If the channel bolt is intended to be used for different

channel sizes, conduct the tests in the channel profile with the

maximum width of the slot between the channel lips. Insert

the channel bolt in the channel profile and apply the load with

a coupling nut to avoid thread failure. Alternatively, in case of

standard channel bolts, channel bolts may be tested in a steel

template (Figure 7.3.1.6 b). This template shall represent the

inner profile of the channels.

(Figures a and b taken from AC232, Figure 5.8).

Figure 7.3.1.6 — Test on channel bolts, test series No. 3.

Channel Flexural Strength, фM

s,flex

Bending strength M

s,flex

s,flex,seis

and ϕ are

tabulated in

ESR-3520 Table 8-3 for

HAC and HAC-T with Hilti

channel bolts (HBC-C,

HBC-T and HBC-C-N).

ϕM

s,flex

≥ M

u,flex

The flexural strength of an anchor channel shall be established in

accordance to Test No. 4 of AC232. The purpose of this test is to

measure the bending strength of the channel taking account of

the restraint of the deformation of the outer ends of the channel

by the concrete. The tests shall be performed with all sizes

and materials of anchor channels. Anchor channels with two

anchors with a maximum spacing and the minimum distance

between the end of the channel and the anchor axis as specified

by the manufacturer and with an anchor type that provides the

lowest anchor strength shall be tested. The channel bolt with

the smallest head size and maximum steel strength that, when

tested, still results in steel failure of a part of the anchor channel

other than the channel bolt shall be used. If the largest channel

bolt size still results in bolt failure, the bolt failure load shall be

taken as the load corresponding to bending failure. In case of

locking channel bolts in combination with non-serrated channels,

test has been performed with all channel bolt sizes.

In Test No. 4, concrete failure shall be avoided. This may be

achieved by testing anchor channels with anchors that have an

increased embedment depth.

In tension Test No. 4 the distance between the support reaction

and any loaded anchor may be smaller than 2h

to avoid

concrete failure.

Photo of an anchor channel

after test; failure by bending

of channel and distortion of

anchor flanges

Figure 7.3.1.7 — Flexural test on anchor channels.

This behavior of anchor channel in concrete is influenced by

a multitude of parameters, including the condition of the base

material (cracked or uncracked), the direction of the action

(tension, shear, combined tension and shear, or shear with

lever arm), concrete strength, embedment depth, distance

to neighboring fasteners and to edges, nature of the action

(transitory, sustained, seismic or shock load) and amount

and configuration of proximate reinforcement. In addition,

environmental factors such as corrosion, extreme temperatures,

and fire can affect anchor performance and must be properly

considered in anchor channel design.

7.3.2 CONCRETE TENSILE STRENGTHS

Pull Out Strength фN

Pull-out and pull-through failure is

characterized by the anchor being

pulled out, whereby the concrete in the

immediate vicinity of the anchor may

not be damaged.

Per ESR-3520 Section 4.1.3.2.4,

nominal pullout strength (N

) is

calculated using ACI 318 anchoring

to concrete provisions. ACI 318-11

Appendix D and ACI 318-14 Chapter 17

provisions.

ϕN

≥ N

aua

= Ψ

c,P

. λ . N

reference ACI 318-14 Eq. (17.4.3.1)

= 8 A

brg

f’

reference ACI 318-14 Eq. (17.4.3.4)

f’

= concrete compressive strength

brg

for anchor channel is found in ESR-3520 Table 8-1

λ = modification factor for lightweight concrete

λ = 1 for Normal weight concrete

λ = 0.85 for Sand Light weight concrete

λ = 0.75 for All Light weight concrete

The value calculated from Eq. (17.4.3.4) corresponds to the load

at which crushing of the concrete occurs due to bearing of the

anchor head (CEB 1997; ACI 349). It is not the load required to

pull the anchor completely out of the concrete, so the equation

contains no term relating to embedment depth. Local crushing

of the concrete greatly reduces the stiffness of the connection,

and generally will be the beginning of a pullout failure.

In lightweight concrete subjected to tensile stress, the

aggregate fractures and the surface of the crack is, compared

to the fracture process in concrete containing normal weight

aggregate, relatively smooth. Therefore, the descending (strain

softening) part of the load-deformation curve for normal weight

concrete is less steep than in the case of lightweight concrete.

Hence the strength is reduced using reduction factor λ.

Figure 7.3.2.1 — Influence of crack path on the stress-deformation behavior

of concrete. concrete.(Picture from Anchorage in Concrete Construction, R.

Eligehausen).

Cracked Uncracked

Figure 7.3.2.2 — Concrete cone in cracked (left) and uncracked (right)

concrete.

A cracked tension zone is assumed because concrete

possesses relatively low tensile strength, which may be fully

or partly used by internal or restraint tensile stresses not taken

into account in the design. The load-bearing behavior of an

anchor can be significantly influenced by the presence of a

crack passing through the anchor location. For anchor channels

located in a region of a concrete member where analysis

indicates no cracking at service load levels, the following

modification factor shall be permitted

c,p

= 1.25

Where analysis indicates cracking at service load levels ψ

c,p

shall be taken as 1.0.

Concrete ψ

c,p

Cracked 1.00

Uncracked 1.25