What you need to know
Steel frame erection can be a complex process using materials of substantial weight that involves rapidly changing circumstances creating significant hazards.
Key issues with steel erection are:
- Falls from height
- Materials being dropped
- Being struck by moving steel members or decking packs
- Unintended structural collapse
- Manual handling
- Cranes, MEWPs and other equipment overturning
Design and planning
It is important that risks are identified and control measures are selected during the pre-construction/planning phase. Engaging specialist contractors with the necessary skills, knowledge, experience and training will assist in risk reduction and the designer can consult with them on:
- Plant and equipment to be used
- Skills, knowledge, experience and training required of the erectors
- Structural design of the frame
- Access to the structure during construction
- Emergency arrangements
Plan where and how the steelwork will be assembled before erection and look to minimise the number and complexity of the connections to be made to reduce the time spent working at height.
Having a build sequence where edge protection is installed at ground level before steel members are lifted into position eliminates the need to work at height to install them and puts a control measure in place as early as possible.
Having stairs and handrails installed early on will also provide safe access to high levels of the structure.
Safe systems of work, training, emergency procedures and use of properly maintained equipment are necessary.
Falls from height
Workers can fall during the erection of the frame and as such you must try to either eliminate or reduce the need to work at height.
Where work at height cannot be avoided steps must be taken to prevent or at least mitigate the effects of a fall. Suitable working platforms such as scaffolding or mobile elevating work platforms (MEWPs) should be used for access for bolting-up and similar operations. The use of nets underneath the working position or twin lanyards and harnesses can mitigate the effects of a fall but must be combined with a safe method of rescue so that anyone who may fall is not left hanging for a prolonged period.
Where the work cannot be done from a MEWP or other platform, erectors may have to work from the steel, which is known as beam ‘straddling’. This is only permissible for specific short-duration jobs where the beam is of an I beam section. Workers must sit astride the flange with the sole and heel of each foot resting on the bottom flange and grasp either side of the top flange with both hands. A backup system such as harness and twin lanyard must be in place to mitigate the effects of a fall. Walking on the top flange of steel beam is dangerous and must never be undertaken.
The hazards associated with laying decking and the necessary precautions are like those required for safe working during industrial roofing.
Materials being dropped
Dropped materials and tools can cause significant personal injury and as such you should arrange your work activity to mitigate this risk by:
- Programming work to make sure other trades are not working underneath the erectors
- Ensuring there are barriers at open edges such as toeboards to prevent materials falling off
- Arranging for materials to be stored safely so they do not fall from height
Being struck by moving steel members or decking packs
Control of lifting operations is vital to avoid workers and others being struck by materials. The use of a competent person or people, exclusion zones and not lifting over people will reduce and control this risk.
Structural collapse before it is fully braced
To prevent the risk of unintended collapse of a steel erection whilst it is being built you will need to ensure that there is a sequential method of erection that is developed in consultation with the frame designer and/or a structural engineer.
Adding bracing, guys or stays into the design should ensure integral stability of the structure through all stages of erection. These arrangements need to be checked regularly to ensure stability is always maintained.
Adequate information must be passed to the erectors about special sequences that need to be followed to ensure stability so that they are able to adhere to design specifications.
The materials used in steel frame erection can be of significant weight. It is important that during the pre-construction/planning phase thought is given to both the sequence of erection and the use of manual handling aids, such as cranes and trolleys, to control the risk of injuries from lifting, carrying or handling.
Cranes, MEWPs and other equipment overturning
To allow safe use of cranes, mobile platforms and other equipment such as tower scaffolds it is important to make sure the ground is of sufficient strength and stability to bear the weight of the plant or equipment before work starts to avoid them tipping over.
Ensure that traffic arrangements on site are such that plant and equipment are not struck whilst in use as this may cause them to tip over.