BS 5531:1988 download free.Code of practice for Safety in erecting structural frames.
1 Scope
This code of practice makes recommendations concerning safety in erecting the principal types of structural frames, mainly in precast concrete and steel. Consideration is also given to the following:
a) space frameworks
b) timber frameworks
c) aluminium frameworks
d) plastics frameworks
This code does not include recommendations on work involved in the erection of in situ concrete frames (see BS 5975).
This code does not deal with those aspects of site safety which are generally applicable to all construction operations and for which guidance and information are readily available elsewhere (e.g. use of hand tools, ladders, etc.).
NOTE The titles of the publications referred to in BS 5531 are listed on the inside back cover.
2 Definitions
For the purposes of this code the following definition applies.
method statement
a document setting out a safe system of work, in detail dependent on the complexity of the work involved
NOTE Other terms used in this code are those in common use during construction operations.
13 Site preparation
13.1 General
The contractor should check the site for hazards before starting work, and should note any special features. There should be suitable unobstructed safe access for delivery vehicles, cranes and other plant. The position of overhead services, particularly live electric cables, should be checked, as should the positions of any buried services which may be vulnerable to damage by traffic. Movement about the site should be planned with the provision of sound access ways. This may require the formation of temporary roads and hard standings designed for the loads involved. Separate clean and clear pedestrian access ways may be necessary.
The increasing use of access equipment requires the provision of a higher standard of site preparation. The control of other site activities, such as trench excavation, may he necessary so that the use of access equipment is not hindered.
13.2 Storage area
Sufficient area should be allocated for the stacking, storage and handling of materials and components. This area should be clean, even, firm and reasonably level and of adequate size, clear of any of the hazards mentioned in 13.1.
Stacking should be such that no overloading either of the storage area or of the individual units occurs. Bearers will need to be used between units and the height of the stack should be limited as far as possible. The need to climb on to the stack should be avoided.
If frames are used for storage, it is essential that they are stable and that they are loaded and unloaded so as to minimize eccentric loading.
13.3 Above ground storage
Components may need to be stored on the framework. Positions, layout and loading have to be determined before the commencement of work and loads should be placed without impact.
14 Setting-out, levelling and alignment
14.1 Precautions in setting-out
The required degrees of accuracy should be clearly determined before setting-out is begun. The limiting tolerances should be stipulated if they have not already been included in the specification. Failure to achieve these tolerances may result in dangerous improvisations.
14.2 Levelling and alignment Levelling and alignment is a potentially dangerous stage in the erection sequence, when temporary instability may occur.
21.3 When two or more traversing jacks are being used, considerable resistance to traversing may be experienced. This may be the result of the traversing of the jacks not being absolutely synchronized, thus causing the arrangement to act like a large scale lock-nut device. Visually the phenomenon is not immediately obvious: neither is the direction in which further traversing (to or fro) will release the “lock”.
21.4 In multi-jacking systems care should be taken to coordinate the jacking so that no single jack becomes overloaded. Otherwise damage may result to the jack in question, or the member it is jacking against.
22 Working arrangements
22.1 A prerequisite of safe working arrangements is to minimize the time when men have to work at a height. This can be done by pre-assembling as much of the structure as possible at ground level. Work on open structures should be kept to an absolute minimum, since most serious accidents to erectors result from falls. Working platforms, gangways, ladders, etc. should be provided whenever practicable.
22.2 Vertical access should normally be by ladders, or, preferably, staircases, temporary or permanent. Provision should be made for the ascent or descent of ladders to start from a landing place which should be provided with an edge protection if there is a risk of falling. Ladder access should be provided by pre-locating the ladders on a frame member prior to lifting. Attachments may be by cleats or clamps so designed that the ladder can be lifted clear after the erector has descended.
22.3 In appropriate cases a man-carrying skip suspended from a crane may be used for vertical access. The Construction (Lifting Operations) Regulations 1961, Regulations 44 and 47 are particularly relevant on these occasions.
22.4 Horizontal access on open frameworks should be provided by gangways constructed at ground level and lifted into position. Fixing details should be simple and aimed at minimizing the number of work operations performed at a height. A working platform should if possible be pre-located on the appropriate frame member prior to erection. Fixings should be as few as possible and should be easily removable at a height.
22.5 Mobile scaffolds. hydraulic access equipment and static scaffold towers can be used when ground conditions are suitable. The early provision of the floor will promote the use of such equipment.
35.5.2 Erection sequence. A recommended erection sequence is given below (this assumes a socket base fixing as in Figure 12 and Figure 13).
a) Erection should commence with the corner column of a braced bay (see Figure 7), the erection packs having previously been levelled. The preferred method of lifting is by means of a shackle using a lifting hole near the top of the column.
b) The socket to receive the foot of the column should be completely clear of obstruction before the lifting of the column commences.
c) When placed in the socket, the column should be made secure by inserting wedges at the base and by propping the column in position. At this stage care should be taken to ensure that the column is located as near as practicable to its final position before release of the crane. The wedges should be used on all four sides. If wooden wedges are used they should have adequate contact area (i.e. there should only be a small degree of taper, preferably not more than 1 in 14). The props should be of the push-pull type to facilitate alignment operations and should be positively fixed to the column and to the ground or floor slab.
d) The remaining columns to form the braced bay should then be erected in the same way.
e) Cross bracing may then he fixed between the columns followed by eaves beams.
i) Depending on the span, it may be appropriate to lift the first rafter in one piece and fasten it to the columns, propping and guying it before releasing the lifting tackle.
If the rafter has to be erected in two portions the same principles will apply and the method is illustrated in Figure 12.
g) The rafter to complete the second portal should be erected in the same way. Permanent rafter bracing should be installed.
h) Any single span purlins in this bay should now be fixed.
1) Final alignment of the columns in the completed portion of the framework can now take place. This may be achieved by using pilot columns or profiles in advance of the erection. When columns are in their correct position the bases should be grouted or concreted as appropriate. Care should be taken not to disturb the wedges or props.