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Brace footing installations on concrete

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					   Alert

   Brace footing installations on concrete
   This Alert highlights the precautions that need to be taken when installing brace
   footings on concrete slabs at an early age.
                                                                                                             September 2010


This Alert provides practical advice for builders, formworkers,          Where a specific design is undertaken for a brace footing to be
panel erectors and erection design engineers (designers). It will        fixed into concrete at low strength, the designer in conjunction
also be useful for health and safety representatives.                    with the builder, formwork company and panel erector, need to
                                                                         consider the following variables that may reduce safety of the
The information and advice relates to the design of brace footings
                                                                         designed brace footing:
(including anchors and concrete) where concrete panel braces
are to be fixed to floor slabs or independent pad footings of            • how the required minimum concrete strength can be achieved
150mm or greater thickness.                                                 prior to the erection of the panels
                                                                         • concrete curing method to be used onsite
If the concrete footing thickness is less than 150mm thick, other
safety factors must be considered by an engineer.                        • ferrule placement tolerances
                                                                         • dislodgement/misalignment of ferrules during concrete
There is also a checklist on the reverse which should be used
                                                                            placement.
before each concrete pour. It will assist with your health and safety
management of the site (consider incorporating it into your safe         In addition, the designer needs to give consideration to:
work method statement or site OHS plan).                                 • ensuring panel braces, fixings and footings are designed to
                                                                            have a minimum capacity of 10kN
Background                                                               • ensuring any modifications to ferrules, including the welding of
For the last 10 years, to improve construction productivity, builders       base plates, is done in accordance with an engineer’s design
have started erecting precast concrete wall panels on floor slabs           and relevant Australian Standards
within 24 hours of pouring the slab.                                     • designing the ferrule inserts to have a minimum embedment
Concrete strength at any time is greatly influenced by the age             depth of 150mm.
and method of curing. For example, after 24 hours air-cured              Note: Ferrules should also be designed and manufactured to
concrete, without admixtures, may only achieve about 10 per cent         ensure their designed failure mode is via cone failure of the
of its specified characteristic strength.                                concrete, not via direct pullout. This will usually require some form
The anchors used for fixing brace footings consist of a cast-in          of enlarged base of the ferrule.
ferrule into which the brace is later bolted. When anchors are           The builder, formwork company and panel erector should:
installed in concrete slabs that have not achieved the required
                                                                         • implement and maintain a documented sign-off system by a
strength, they may fail by pulling out under moderate loads. This
                                                                           competent person on all slab and anchor details before each
may lead to catastrophic failure of the wall panel, resulting in death
                                                                           pour (see checklist)
or serious crush injuries to workers.
                                                                         • verify the minimum concrete strength required before panel
Control measures                                                           erection has been achieved under site conditions.
To ensure anchors achieve the required pull-out capacity, the
concrete must attain a minimum strength as determined by the
designer (based on manufacturer and supplier specifications).
                                                                          Further information
                                                                          WorkSafe Industry Standard – Precast and tilt-up concrete
The required concrete strength to be achieved at erection must
                                                                          for buildings
be specified. Unless designated otherwise, the concrete strength
of the brace footing should be at least 20MPa at the time of              Australian Standard – AS3850-2003: Tilt-up concrete
fixing of the bracing.
                                                                          Contact details
Note: Projects specifically designed and documented by the                Call on: 1800 136 089 Email: info@worksafe.vic.gov.au
designer may use a lower strength of concrete for erection of
                                                                          For more information on occupational health and safety,
braces.
                                                                          go to WorkSafe’s website: worksafe.vic.gov.au



ALE0130/01/09.10
                                                            Alert Brace footing installations on concrete




Cast-in ferrule checklist
This checklist applies to concrete designed for less than 20MPa compressive strength at the time of precast installation.

Project: __________________________________________ Principal/head contractor: ___________________________

Subcontractors responsible: ____________________________________________________________________________

Designing engineer: ________________________________ Designated pour area inspected: ______________________

                                                                                                                           Yes         No        N/A
 1.            Is there a project-specific engineered design in place?
 2.            Is cast-in ferrule assembly embedment depth in concrete minimum 150mm?
 3.            Is all welding to cast-in ferrules to engineer’s specifications?
 4.            Are cast-in ferrules in correct position for propping arrangement?
 5(a)          Is cast-in ferrule reinforcement steel configuration to design?
 5(b)          Has reinforcement been checked? For example, N12 through-bar, mesh,
               baseplate etc or combinations (as per drawings)?
 HOLD          Above details checked and verified by competent person:
 POINT
               Sign:                                                  Date:     /       /
 6.            Has concrete testing been conducted?
               Testing laboratory verified minimum concrete strength (as per design) has been
               achieved:
 HOLD          Actual MPa achieved: _______________________________________________
 POINT
               Subcontractor sign:                                   Date: /        /
 7             Has this checklist been made available to all relevant parties (eg HSR, panel
               erector and formworker)?
 HOLD          Principal/Head contractor verified all above details:
 POINT
               Sign:                                                  Date: /       /


Note: This checklist recommends hold points when a competent person should verify the actions before proceeding to the
next point on the checklist.
All items on this checklist should be completed and verified as compliant before precast placement to designated pour area.
Subcontractor responsible /authorised representative

Name (print): ________________________________________________________________________________________


Signature: ___________________________________________________________________________________________


Disclaimer: This Alert contains information following WorkSafe’s inquires into the incident at the date of this report. The information contained in this
report does not necessarily reflect the final outcome of WorkSafe’s action with respect to this incident. WorkSafe does not warrant the information in
this report is complete or up-to-date and does not accept any liability to any person for the information in this report or as to its use.




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