Steel Designer''''s Manual Part 14 potx

Mobility for non-mobile cranes Non-mobile cranes can be made mobile by mounting them on rails. This has two advantages: the positioning of the crane can be more easily dictated and controlled, and the loads transmitted by the rails to the ground act in a precisely known loca- tion. Many cranes have collapsed because of insufficient support underneath. However, most rail-mounted crane failures have occurred from overloading. Where the crane is to work over complex plant foundations the rail can be carried on a beam supported, if necessary, on piles especially driven for the purpose. If the rail is supported only by a beam on sleepers in direct contact with the ground, the load can be properly distributed by suitable spreaders. In either case conditions must be properly considered and designed for. Problems often occur when too much faith is invested in the capability of the ground to support a mobile crane and its outriggers. Non-mobile cranes Non-mobile cranes are generally larger than their mobile counterparts. They can reach a greater height, and are able to lift their rated loads at a greater radius. There are two main types of non-mobile crane: the tower crane and the (now rare) derrick. Due to their great size, the cranes must arrive on site in pieces. Thus the disadvantage of a non-mobile crane is that it has to be assembled on site. Having been assembled, the crane must receive structural, winch and stability tests before being put into service. A tower crane with sufficient height and lifting capacity (see Fig. 33.11) has several advantages: (1) It requires only two rails for it to be ‘mobile’.These two rails, although at a wide gauge, take up less ground space than a derrick. (2) It carries most of its ballast at the top of the tower on the sluing jib/counter balance structure, and so very much less ballast is needed at the bottom. Indeed, in some cases, there is no need for any ballast at the tower base or portal. (3) Because the jib of a tower crane is often horizontal, with the luffing of a derrick jib replaced by a travelling crab, the crane can work much closer to the structure and can reach over to positions inaccessible to a luffing jib crane. (4) A tower crane is ‘self-erecting’ in the sense that, after initial assembly at or near ground level, the telescoping tower eliminates the need for secondary cranes. (5) As shown in Fig. 33.12 a tower crane can be tied into the structure it is erect- ing, thus permitting its use at heights beyond its free-standing capacity. There exist several types of tower crane, e.g. articulated jib, luffing and saddle cranes as illustrated in Fig. 33.13. It is essential that manufacturers or plant hirers are consulted in order to make the most appropriate choice of crane. Cranes and craneage 993 Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ 12 500 kg III V VI X L5=55.Om 2900 kg III IV V X /\A/\/\J\/\\/\V\7\J\/'\ L450.Om 3600 kg V X /\J\/\/\/\/\J/\/\/\/\(\ L345.Om III IVX /\/V\/\/\/W\/ L2.40.Om III X /\A/\/V'\ 6300 kg 4 400 kg 300 kg L I 35.0 m Cranes for the stockyard Stockyard cranes have to work hard. The tonnage per job has to be handled twice in the same period of time, often with many fewer cranes. It is therefore important that cranes be selected and cited carefully to ensure maximum efficiency. 33.8.3 Other solutions If there is no suitable crane, or if there is no working place around or inside the building where a crane may be placed, then consideration must be given to a special mounting device for a standard crane, or even a special lifting device to do the work of a crane, designed to be supported on the growing structure under construction. In either event, close collaboration between the designer and erector members of 994 Erection Fig. 33.11 Tower crane (courtesy of Delta Tower Cranes) Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ I_! I' 111111 II — the management team is of paramount importance. Conversely, inadequate com- munication may prove problematic. Once the decision to consider the use of a special lifting device has been made, a new range of options becomes available. The most important of these is the possibility of sub-assembling larger and heavier components, thereby reducing the number of labour hours worked at height. This is particularly true in the case of bridgework, where substantial sums would otherwise have to be expended on other temporary supports and stiffening. A major disadvantage of special lifting devices is that the apparatus being con- sidered is often so specialized that is unlikely to be of use on another job. Thus Cranes and craneage 995 Fig. 33.12 Citigroup Tower, London showing tower cranes tied into the building (courtesy of Victor-Buyck Hollandia) Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ the whole cost is targeted at the one job for which it has been initially designed (see Fig. 33.14). Where the frame is single-storey, and at the cost of only a slight increase in time and labour, it is possible to do without an on-site crane. With the help of a winch (powered by either compressed air or an internal combustion engine, and some blocks and tackle), a light lattice-guyed pole can be used to give very economic erec- tion (see Fig. 33.15). In this instance the pole is carried in a cradle of wires attached at points on the tower. These connection points need to be carefully designed to ensure that they will carry the load without crippling the tower structure. It is vital that all poles are used in as near a vertical position as possible, since capacity drops off severely as the droop increases. This requires careful planning and the employment of a gang of men experienced in the use of the method. In a different context, pairs of heavier poles provided with a cat head to support the top block of the tackle can be used inside existing buildings to erect the com- ponents of, for example, an overhead travelling crane, or to lift in a replacement girder. The arrangements for a pole and its appurtenances take up much less floor space in a working bay than a mobile crane. This is because a mobile crane needs a wide access route and adequate space to manoeuvre itself into position – particu- larly useful where headroom is restricted. 996 Erection Fig. 33.13 Tower cranes used in the construction of Citigroup Tower, London (courtesy of Victor-Buyck Hollandia) Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ '4 33.8.4 Crane layout It is important to decide on the type, size and number of cranes that are required to carry out the work, since each has a designated range of positions relative to the work it is to perform. These positions are then co-ordinated into an overall plan which enables each crane to work without interfering with its neighbours, and at the same time enables each to work in a position where adequate support can safely be provided (see Fig. 33.16). This plan will then form the basis of the erection method statement documentation. A major factor in planning craneage is to ensure that access is both available and adequate to enable the necessary quantity and size of components to be moved. On large greenfield developments these movements may often have to take place along common access roads used by all contractors and along routes which may be subject to weight or size restrictions. On a tight urban site the access may be no more than a narrow one-way street subject to major traffic congestion. 33.8.5 The safe use of cranes Mention has already been made of the UK Statutory Regulations. These lay down not only requirements for safe access and safe working but also a series of test requirements for cranes and other lifting appliances. Cranes and craneage 997 Fig. 33.14 A purpose-made lifting beam for cantilever erection Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ 1 998 Erection Fig. 33.15 An erection pole used to build a transmission tower Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ It is the responsibility of management to ensure that plant put on to a site has a sufficient capacity to do the job for which it is intended, and that it remains in good condition during the course of the project. Shackles and slings must have test cer- tificates showing when they were last tested. Cranes must be tested to an overload after they have been assembled. The crane test is to ensure that the winch capacity, as well as the resistance to overturning and the integrity of the structure, is adequate. British Standards lay down the various requirements for safe working. Lists of those standards, and the necessary forms to enable each of the tests to be recorded, must be provided by management, often in the form of a ‘site pack’ which the site agent must then display and bring into use as each test is carried out. It is the site agent’s responsibility to ensure that these requirements are fulfilled. The site agent may also be required to produce them from time to time for inspection by the factory inspector during one of his periodic visits to the site. A crane which has been tested and used safely in many locations might overturn at its next location. Failure is often caused by inadequate foundation provision under the tracks or outriggers of the crane. In other words adequate support under the tracks or outriggers is an essential requirement. It is equally important that the crane should work on level ground, since an overload can easily be imposed, either directly or as a sideways twist to the jib, if the ground is not level. 33.8.6 Slinging and lifting Components, whether they are on transport or are lying in the stockyard, should always be landed on timber packers. The packers should be strong enough to Cranes and craneage 999 Fig. 33.16 Typical crane layout Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ hand me support the weight of the steel placed above them, and thick enough to enable a sling to be slipped between each component. When lifting a component for transport only, the aim is to have it hang horizon- tally. This means that it is necessary to estimate its centre of gravity. Although this calculation may be easy for a simple beam, it may prove more problematic for a complex component.The first lift should be made very slowly in order to check how it will behave, and also to check that the slings are properly bedded (see Fig. 33.17). Most steelwork arrives on site with some or all of its paint treatment. Since the inevitable damage which slinging and handling can do to paintwork must be made good, it is therefore important to try to minimize that damage. The same measures that achieve this also ensure that the load will not slip as it is being lifted, and that the slings (chain or wire) are not themselves damaged as they bend sharply around the corners. Softwood packers should be used to ease these sharp corners. Packers to prevent slipping are even more necessary if the piece being erected does not end up in a horizontal position.The aim should always be to sling the piece to hang at the same attitude that it will assume in its erected position. Pieces being lifted are usually controlled by a light hand line affixed to one end. This hand line is there to control the swing of the piece in the wind, and not to pull it into level. Wherever possible non-metallic slings should be used. They will reduce damage to paintwork and are less likely to slip than chain or wire slings. In extreme cases two pieces may have to be erected simultaneously using two cranes. Staff, working back at the office, should account for this in the site erection method statement. It is too late to discover this omission when the erection is attempted with only one crane, or with no contingency plan to pull back the head of the column. As discussed above, it is important to consider both the stiffness of large assem- blies such as roof trusses as they are lifted from a horizontal position on the ground, 1000 Erection Fig. 33.17 Typical slinging of a piece of steelwork Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ and the need to build assemblies in a jig to represent the various points at which connection has to be made in the main framework. An additional jig for lifting can be particularly useful if there are many similar lifts to be made. This can be made to combine the need to stiffen with the need to connect to stiff points in the sub- frame, and the need to have the sub-frame hang in the correct attitude on the crane hook. The weight of any such stiffening and of any jig must of course be taken into account in the choice of crane. Some temporary stiffening may be left in position after the initial erection until the permanent connections are made. This eventuality should also have been fore- seen, and sufficient stiffeners and lifting devices should be provided to avoid an unnecessary bottleneck caused by a shortage of a device for erection of the next sub-frame. Where a particularly awkward or heavy lift has to be made, slinging and lifting can be made both quicker and safer if cleats for the slings have been incorporated in the fabrication. Each trial lift made after the first one wastes time until the piece hangs true. The drawing office should determine exactly where the centre of gravity is. A chart giving details of standard hand signals is illustrated in Fig. 33.18. Their use is essential when a banksman is employed to control the rear end of the trans- port, thereby bringing the component to the hook as it is reversed. The banksman is needed to relay the signal from the man directing the movements of the crane if he is out of sight of the crane driver.A clear system of signals should be agreed for the handover of crane control from the man on the ground to the man up on the steel who controls the actual landing of the component. A banksman may also be needed up on the steel if the crane driver cannot clearly see the top man who is giving the control instructions: it is vital that there is no confusion over who is giving instructions to the crane driver. 33.9 Safety 33.9.1 The safety of the workforce The health and safety regulations require a project safety plan to be drawn up,which should include a detailed assessment of anticipated risks. There are a number of standards, regulations and guidance notes for the safety of the workforce during construction, as referenced in the further reading. Site safety of the workforce is subject to statutory regulation and inspection by the Health and Safety Executive. Regulations lay down minimum acceptable standards for the width of working platforms; the height of guard-rails; the fixing of ladders; and so on. They refer to the use of safety belts and safety nets. They lay down the frequency with which a shackle or chain sling must be tested and the records that must be kept to show that this was done. Reference should be made to the appropriate regulation for the details of these requirements. Safety 1001 Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ clench and unclench fingers to signal take the strain signal with one hand other hand on head signal with both hands clench and unclench fingers to signal inch the load TRAVEL FROM ME JIB UP JIB DOWN DERRICKING JIB TRAVEL TO ME HOIST LOWER SLEW LEFT SLEW RIGHT EXTEND JIB RETRACT JIB TELESCOPING JIB TROLLEY OUT TROLLEY IN HORIZONTAL JIB STOP EMERGENCY STOP 1002 Erection Fig. 33.18 Standard hand signals for lifting Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ [...]... all rights reserved Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ Steel Designers' Manual - 6th Edition (2003) Safety I Fig 33.20 — S A prefabricated working platform slung over a convenient beam 1005 Steel Designers' Manual - 6th Edition (2003) 1006 Erection Proper consideration... licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ Steel Designers' Manual - 6th Edition (2003) Safety Fig 33.21 1007 Bridge failure during cantilever erection Fig 33.22 Typical splice detail that is adequate in tension but would fail if subject to significant compression Steel Designers' Manual - 6th... (1984) Guidance Note 28 (Parts 1–4), HMSO 3 The British Constructional Steelwork Association (2002) National Structural Steelwork Specification for Building Structures, 4th edition, BCSA/SCI 4 British Standards Institution (1990) Building setting out and measurements Part 1: Methods of measuring, planning and organisation and acceptance criteria Part 2: Measuring stations and targets, Part 3: Check-lists... publication Design of steel framed buildings without applied fire protection.4 Partial Steel Designers' Manual - 6th Edition (2003) Structural performance in fire 1019 Concrete floor slab This material is copyright - all rights reserved Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ (a)... call 01344 872775 or go to http://shop.steelbiz.org/ 1012 Erection 7 Couchman G.H., Mullett D.L & Rackham L.W (2000) Composite slabs and beams using steel decking: best practice for design and construction The Metal Cladding & Roofing Manufacturers Association/The Steel Construction Institute, Ascot, Berks 8 British Standards Institution (1993) Quality systems Part 14: Guide to dependability programme... practice for safe use of cranes Part 3: Mobile cranes BS 7121, BSI, London British Standards Institution (1997) Code of practice for safe use of cranes Part 5: Tower cranes BS 7121, BSI, London British Standards Institution (1998) Code of practice for safe use of cranes Part 11: Offshore cranes, BS 7121, BSI, London The Steel Construction Institute (1993) A Case Study of the Steel Frame Erection at Senator... Publication 136, Ascot, Berks The Steel Construction Institute (1994) The Construction (Design and Management) Regulations 1994: Advice for Designers in Steel SCI Publication 162, Ascot, Berks Steel Designers' Manual - 6th Edition (2003) Chapter 34 Fire protection and fire engineering by JEF ROBINSON This material is copyright - all rights reserved Reproduced under licence from The Steel Construction Institute... methods 1013 Steel Designers' Manual - 6th Edition (2003) 1 014 Fire protection and fire engineering The fire-resistance requirements of Document B apply only to structural elements used in: This material is copyright - all rights reserved Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/... the limiting temperature derived from BS 5950 Part 8 This material is copyright - all rights reserved Reproduced under licence from The Steel Construction Institute on 12/2/2007 To buy a hardcopy version of this document call 01344 872775 or go to http://shop.steelbiz.org/ 34.3 Structural performance in fire 34.3.1 Strength of steel at elevated temperatures Steel begins to lose strength at about 200°C... than in normal structural tests 0.9 0.8 H\ BS 5950: Part 8 U i1.5 strain 0.6 —0.5 strain 0.5 Eurocode 3 proposal a) L 4-, V) 0.2 _ 200 400 teniperature Fig 34.3 strain) 600 800 (°C) Strength retention factor for grade 43 steel at elevated temperatures Steel Designers' Manual - 6th Edition (2003) Structural performance in fire 1017 BS 5950 Part 8 specifies the use of 2.0% strain values for design . 33 .14 A purpose-made lifting beam for cantilever erection Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel. slinging of a piece of steelwork Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute. (courtesy of Victor-Buyck Hollandia) Steel Designers' Manual - 6th Edition (2003) This material is copyright - all rights reserved. Reproduced under licence from The Steel Construction Institute