presentation on safety issues during erection of steel frame structure

8/4/2019 Presentation on Safety Issues During Erection of Steel Frame Structure

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ISSUE

• Project involved construction of a large span steel framed portal framebuilding.

• Longitudinal stability was provided by triangulated vertical sidebracings and triangulated bracings in the plane of the rafters.

• The erection method statement had been based upon the principle thatthe first bay to be erected would be the bay containing the side andrafter bracings. There would be temporary wire rope guys until thepermanent bracings has been installed and fully bolted.

• A delay occurred in the delivery of the permanent bracing to the site butit was decided to progress with the construction using the temporarywire rope guys to achieve longitudinal stability.

• After erection of several bays, purlins were lifted on to the roof.

• Longitudinal wire rope guys could not take up the eccentric loading,building collapsed.



WHAT WENT WRONG ???

• They did not stick to the construction sequence.

• Only after the agreement of the originator or any competent authority ,the construction sequence can be altered.



TRUSS ERECTING AND BRACING

• A truss rafter roof system, if properly designed fabricated erected and

braced will be a strong and economical way to frame a building roof.• There are some design assumptions which should be taken care during

erection.

Trusses have very little strength in the lateral direction



Erection of truss by lifting them upside down onto the wall plates. Then tip

into the upright position.



Temporary truss and wall bracing will be required until the bracings are

secured. These temporary braces supports the trusses against wind from eitherdirection

Temporary

truss

Wall

bracing



The permanent bracings are to be installed with bolts and subsequent

construction of bays.



After the erection of bays, the purlins are lifted to the roofs.

Cross bracings are also provided for tension web members for stressreversals (e.g. Wind uplift)

The trusses should not be used as a working platform until they are

permanently braced.

The building site should not be left without all temporary and permanent bracing

being installed.

Web member



CDM DUTIES THAT WILL ENSURE SAFETY

The main designer must ensure that they take buckling of compression

members into account and specify in the drawings wherever stiffenersare required for lateral support.

The temporary work designer should ensure stability of the temporaryworks

In words of CDM,

Eliminate – Taking care of buckling action of compression members

Reduce – By providing temporary supports and stiffeners

Inform – Giving notes in the drawing. about providing temporarysupports. Informing the contractor through construction sequence.

Control - The contractor should ensure that the construction sequenceis being followed properly.

presentation on safety issues during erection of steel frame structure

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