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Construction Technologu and. Building Materials Learning Limit º. º Training Module for Barefoot Work Book. Exercisel: Identify the construction materials. The books have gained a worldwide readership, and their success – and their impact on construction education – is a tribute to Roy Chudley's experience in. The Building Construction Handbook is THE authoritative reference for all No part of this book may be reprinted or reproduced or utilised in any form or by any .
According to this, the rocks are classified into three types a. Stratified Rocks: These rocks posses planes of stratification or cleavage and such rocks can be easily split along these planes Ex: sedimentary rocks b.
An stratified rocks: The structure may be crystalline granular or compact granular. Examples: Igneous rocks and Sedimentary rocks affected by movements of the earth. Foliated Rocks: These rocks have a tendency to split up in a definite direction only. Ex: Metamorphic rocks. Chemical Classification: According to this classification rocks are classified into three types.
Siliceous rocks: In these rocks, silica is predominates. The rocks are hard; durable and not easily effected by weathering agencies. Ex: Granite, Quartzite, etc. Argillaceous Rocks: In these rocks, clay predominates. The rocks may be dense and compact or may be soft. Ex: slates, Laterites etc. This requires that people are provided with properly maintained safe surroundings in which to work, along with safe means of accessing and leaving that place of work.
It is an overall requirement for reasonable precautions to be taken, with the perceived and varying risk associated with every place of work. Sufficient and suitable working space should be provided with regard to the activity being undertaken.
Regulation 7: Precautions against falling through fragile material. This applies mainly to work at heights in excess of 2 m, although potential for falls from any height must be assessed. Requirements for sufficient and adequate means of guarding persons from fragile material must be in place, with a prominence of warning notices displayed in the vicinity see also Work at Height Regulations.
Regulation 8: Falling objects. This requires sufficient and suitable means for preventing injury to persons from falling objects. Provisions may include guard rails, toe boards and protective sheeting to scaffold systems. No material to be tipped or thrown from height see rubble chutes, Chapter 5. Material to be stored or stacked in a stable manner to prevent collapse or unintentional movement.
Regulations 9 to Work on structures. A large amount of work associated with the construction of buildings is essentially temporary. Therefore potential for structural collapse, e. The necessary precautions must be taken to prevent danger.
Demolition and dismantling are also high-risk 10 n n n n n n n Advanced Construction Technology areas, justifying thorough planning and risk analysis before and as work proceeds.
Regulations 12 and Excavation, cofferdams and caissons. Substructural work has an inherent danger of collapse. Suitable provision to prevent collapse of trenches etc. Awareness of water-table levels and possible variations, e. Regulation Prevention of drowning. This is not applicable to all sites, but if there is a danger from water or other liquids in any quantity then every practical means possible must be taken to prevent people falling into it.
Personal protective and rescue equipment must be available, maintained in good order, and water transport must be provided under the control of a competent person.
Regulations 15 to Traffic routes, vehicles, doors and gates. These make provision for segregation of vehicles and pedestrians, with definition of routes.
The regulations require adequate construction and maintenance of temporary traffic routes, control of unintended traffic movement, warnings audible or otherwise of vehicle movements, prohibition of misuse of vehicles, and safeguards for people using powered doors and guards such as that on hoist facilities.
Regulations 18 to Prevention and control of emergencies. These make provision for emergency routes, means of escape, evacuation procedures, adequate signing, firefighting equipment, emergency lighting and associated training for dealing with emergencies.
Welfare facilities. Minimum requirements apply even to the smallest of sites. These include an adequate supply of drinking water, sanitary and washing facilities, means to heat food and boil water, adequate outdoor protection including personal protective equipment PPE , rest accommodation and facilities to eat meals, first-aid equipment under the control of an appointed person, and accommodation to change and store clothing.
Regulations 23 to Site-wide issues. General requirements to ensure fresh air availability at each workplace, reasonable temperatures maintained at internal workplaces, protection against inclement weather, adequate levels of lighting including emergency lights , reasonably clean and tidy workplaces, well-defined site boundaries, and maintenance of site equipment and plant for safe use by operatives. Regulations 28 to Training, inspection and reports.
Supervision of others by those suitably qualified may be acceptable. Places of obvious danger and risk, such as excavations, cofferdams and caissons, to be inspected regularly at least daily and when changes are effected by a competent person. The principal considerations under the Work at Height Regulations apply to any place at or below ground level as well as above ground. They also include the means of gaining access and egress from that place of work.
Measures taken by these regulations are designed to protect a person from injury caused by falling any Site layout 11 distance. This may be from plant and machinery or from equipment such as scaffolding, trestles and working platforms, mobile or static. In summary: Organisation and planning.
This includes provisions for emergencies and rescues, and regard for assessing risk to persons working during inclement weather. Regulation 5: Any person being trained to be supervised by a competent person. Regulation 6: Risk avoidance.
This is concerned primarily with appraisal of the work task relative to its situation: Provisions to be in place for preventing persons sustaining injury from falling. Work at height equipment.
Further requirements for assessment of risk relative to the selection of plant and equipment suitable for collective rather than individual use. Specific work equipment. Scaffold and working platforms: Generally taken as mm min.
For practical purposes a mm wide scaffold board secured vertically. Means to prevent physical access also required. Nets, airbags or other safeguards for arresting falls: A safeguard and its means for anchoring must be of adequate strength to arrest and contain persons without injury, where they are liable to fall. Persons suitably trained in the use of this equipment, including rescue procedures, must be available throughout its deployment.
Generally, this applies to work of a short duration. Position to be secured by rope lashing or other mechanical fixing. Regulation 9: Fragile surfaces. Where it is impossible to avoid, then sufficient protection, e. Location of fragile surfaces is to be indicated by positioning of prominent warning signs.
Suitable provisions, e. Facilities are to be provided for safe collection and transfer of materials between high and low levels, e. No objects to be thrown. Materials to be stacked with regard to their stability and potential for movement.
Dangerous areas. Areas of work of specific danger, e. Warning signs to be displayed. These regulations specifically apply to scaffolding, ladders and fall protection equipment. After installation or assembly, no equipment may be used until it has been inspected and documented as safe to use by a competent person. Further inspections are required where conditions may have caused deterioration of equipment, or alterations or changes have been made.
Following an interval, every place of work at height should be inspected before work recommences. Personnel duties. Persons working at height should notify their supervisor of any equipment defect. Under the Health and Safety at Work etc. Act employers must have defined duties, which include providing: Employees and the self-employed have duties to ensure that they do not endanger others while at work. This includes members of the public and other operatives on site. They must cooperate with the health and safety objectives of their employer the main contractor , not interfere with any plant or equipment provided for their use, other than its intended use, and report any defects to equipment and dangers relating to unsafe conditions of work.
The preceding section on provision of facilities under the Construction Regulations, the Work at Height Regulations and the Health and Safety at Work etc. Act is intended as summary comment for guidance only. For a full appreciation, the reader is advised to consult each specific document. These are published by The Stationery Office, www. Mess huts These are for the purposes of preparing, heating and consuming food, which may require the following services: To provide a reasonable degree of comfort a floor area of 2.
This will provide sufficient circulation space, room for tables and seating, and space for the storage of any utensils. Consideration can also be given to introducing a system of staggered meal breaks, thus reducing space requirements. On large sites where full canteen facilities are being provided this will be subcontracted to a catering firm. Mess huts should be sited so that they do not interfere with the development of the site but are positioned so that travel time is kept to a minimum.
On sites that by their very nature are large, it is worthwhile considering a system whereby tea breaks can be taken in the vicinity of the work areas. Siting mess huts next to the main site circulation and access roads is not of 14 Advanced Construction Technology major importance. Drying rooms Used for the purposes of depositing and drying wet clothes.
Drying rooms generally require a lighting and power supply, and lockers or racks for deposited clothes. A floor area of 0. Drying rooms should be sited near or adjacent to the mess room. Toilets Contractors are required to provide at least adequate washing and sanitary facilities as set out in Regulation 22 of the Construction Health, Safety and Welfare Regulations. All these facilities will require light, water and drainage services.
If it is not possible or practicable to make a permanent or temporary connection to a drainage system, the use of chemical methods of disposal should be considered. Sizing of toilet units is governed by the facilities being provided, and if female staff are employed on site separate toilet facilities must be provided.
Toilets should be located in a position that is convenient to both offices and mess rooms, which may mean providing more than one location on large sites. First-aid rooms Only required on large sites as a specific facility, otherwise a reasonably equipped mess room will suffice. The first-aid room should be sited in a position that is conveniently accessible from the working areas, and must be of such a size as to allow for the necessary equipment and adequate circulation, which would indicate a minimum floor area of 6 m2.
First-aid equipment must be under the charge of a suitably trained, appointed person, with responsibility for accounting for the contents and their use. Before the proposed site layout is planned and drawn, the contracts manager and the proposed site agent should visit the site to familiarise themselves with the prevailing conditions.
During this visit the position and condition of any existing roads should be noted, and the siting of any temporary roads considered necessary should be planned. Information regarding the soil conditions, height of water table, and local weather patterns should be obtained by observation, site investigation, soil investigation, local knowledge or from the local authority. The amount of money that can be expended on this exercise will depend upon the size of the proposed contract and possibly upon how competitive the tenders are likely to be for the contract under consideration.
Figure 1. Subsoil is a firm sandy clay with a water table at a depth that should give no constructional problems. Possession of site is to be at the end of April, and the contract period is 18 months.
The work can be programmed to enable the foundation and substructure work to be completed before adverse winter weather conditions prevail. Development consists of a single five-storey office block with an in-situ reinforced concrete structural frame, in-situ reinforced concrete floors and roof, precast concrete stairs, and infill brick panels to the structural frame with large hardwood timber frames fixed into openings formed by the bricklayers. Reduced-level dig is not excessive, but the topsoil is to be retained for landscaping upon completion of the building contract by a separate contractor; the paved area in front of the office block, however, forms part of the main contract.
The existing oak trees in the north-east corner of the site are to be retained and are to be protected during the contract period. Estimated maximum number of staff on site at any one time is 40, in the ratio of 1 supervisory staff to 10 operatives plus a resident clerk of works. Main site requirements are as follows: Storage compound for major materials. Timber store and formwork fabrication area. Reinforcement store and fabrication area. Scaffold store. Car parking areas.
Sizing and location of main site requirements can be considered in the following manner: Using plastic-coated galvanised steel prefabricated cabins based on a 2. Other standard internal widths are 2. Two positions on the site in question seem to meet these requirements: Office for reception and materials checker A hut based on the requirements set out above for the clerk of works would be satisfactory.
The office needs to be positioned near to the site entrance so that materials being delivered can be checked, directed to the correct unloading point, and — most important — checked before leaving to see that the delivery has been completed. It also needs to be easily accessible for site visitors, thus preventing unsupervised wandering onto the site.
Lock-up store This needs to be fitted with racks and storage bins to house valuable items, and a small unit of plan size 2. This will enable the issue of stores only against an authorised and signed requisition to be carefully controlled, the assistant site agent fulfilling the function of storekeeper.
Perhaps 3 modules of The mess room needs to be sited in a fairly central position to all the areas of activity, and the east end of the paved area has been selected. The drying room needs to be in close proximity to the mess room and has therefore been placed at the east end of the mess room.
Consideration could be given to combining the mess room and drying room into one unit. Toilets On this site it is assumed that connection can be made to existing drains. If this is not convenient, temporary or preferably permanent drain branches can be connected to a main sewer. Two such units are considered to be adequate, one to be sited near to the mess room and the other to be sited near to the office complex.
Adequate sanitary conveniences are required in the Construction Health, Safety and Welfare Regulations For the mess toilet unit catering for 36 operatives two conveniences are considered minimum, but a Site layout 19 n n n n n n n three-convenience toilet unit will be used, having a plan size of 2. Similarly, although only one convenience is required for the office toilet unit, a two-convenience unit will be used with a plan size of 2. Materials storage compound An area to be defined by a temporary plywood hoarding 2.
Plan size to be allocated Timber storage Timber is to be stored in top-covered but open-sided racks made from framed standard scaffold tubulars.
Maximum length of timber to be ordered is unlikely to exceed 6. This area has been sited to the south of the paved area, giving good access for delivery and within the reach of the crane.
Reinforcement storage The bars are to be delivered cut to length, bent and labelled, and will be stored in racks as described above for timber storage. Maximum bar length to be ordered assumed not to exceed This area has been sited to the north of the storage compound, giving reasonable delivery access and within reach of the crane.
Scaffold storage Tube lengths to be stored in racks as described for timber storage, with bins provided for the various types of coupler. Assuming a maximum tube length of 6. This storage area has been positioned alongside the west face of the proposed structure, giving reasonable delivery access and within reach of the crane if needed.
Tower crane To be sited on the paved area in front of the proposed building alongside the mixer and aggregate storage position. A crane with a jib length of Car parking Assume 20 car parking spaces are required for operatives, needing a space per car of 2.
This area can be provided to the south of the mess room and drying room complex. Fencing The north and south sides of the site both face onto public footpaths and highways.
Therefore a close-boarded or sheet hoarding in accordance with the licence issued by the local authority will be provided. A lockable double gate is to be included in the south-side hoarding to give access to the site. The east side of the site faces an undeveloped site, and the contract calls for a 2. This fence will be 20 n n n Advanced Construction Technology erected at an early stage in the contract to act as a security fence during the construction period as well as providing the permanent fencing.
The west side of the site has a 2. Services It has been decided that permanent connections to the foul drains will be made for convenient site use, thus necessitating early planning of the drain-laying activities. The permanent water supply to the proposed office block is to be laid at an early stage, and this run is to be tapped to provide the supplies required to the mixer position and the office complex. A temporary connection is to be made to supply the water service to the mess room complex, because a temporary supply from the permanent service would mean running the temporary supply for an unacceptable distance.
An electrical supply is to be taken onto site, with a supply incoming unit housed in the reception office along with the main distribution unit. The subject of electrical supplies to building sites is dealt with in Chapter 1. It has been decided that a gas supply is not required. As a further public relations exercise it might be worthwhile considering the possibility of including public viewing panels in the hoarding on the north and south sides of the site.
Some examples of the standard images that could be used are shown in Fig. Sign colours Geometric shape Indication Red on white background, black image Yellow with black border, black image Blue with white image Green with white image Circular with a diagonal line Triangular Circular Oblong or square Prohibition Warning Mandatory Safe condition References: Health and Safety at Work etc.
Management of Health and Safety at Work Regulations. The extent to which the above exercise in planning a site layout would be carried out in practice will depend upon various factors, such as the time and money that can reasonably be expended and the benefits that could accrue in terms of maximum efficiency compared with the amount of the capital outlay. The need for careful site layout and site organisation planning becomes more relevant as the size and complexity of the operation increase.
This is particularly true for contracts where spare site space is very limited. It may also be needed to provide the power to drive small and large items of plant. Two sources of electrical supply to the site are possible: As a supply of electricity will be required in the final structure the second source is usually adopted, because it is generally possible to connect a permanent supply cable to the proposed development for construction operations, thus saving the cost of laying a temporary supply cable to the site.
To obtain a metered temporary supply of electricity a contract must be signed between the main contractor and a local area electricity marketing company. They will require the following information: Site location plan. Maximum anticipated load demand in kW for the construction period.
Final load demand of the completed building to ensure that the correct rating of cable is laid for the permanent supply. Date on which temporary supply will be required. Name, address and telephone number of the building owner or their agent, and of the main contractor. Electricity on building sites 23 To ensure that the supply and installation are available when required by the builder it is essential that an application for a temporary supply of electricity is made at the earliest possible date.
On any construction site it is possible that there may be existing electricity cables, which can be advantageous or may constitute a hazard or nuisance. Overhead cables will be visible, whereas the routes and depths of underground cables can be ascertained only from the records and maps kept by local area supply companies.
Overhead cable voltages should be checked with the local area suppliers, because these cables are usually uninsulated and are therefore classed as a hazard due mainly to their ability to arc over a distance of several metres.
High-voltage cables of over 11 kV rating will need special care, and any of the following actions could be taken to reduce or eliminate the danger: Apply to have the cable taken out of service.
Erect warning barriers to keep site operatives and machines at a safe distance. These barriers must be clearly identified as to their intention, and they may be required to indicate the safe distance in both the horizontal and vertical directions. The local area supplier will advise on suitable safe distances according to the type of cable and the load it is transmitting. The position and depth of underground cables given by electricity suppliers must be treated as being only approximate, because historical records show only the data regarding the condition as laid, and since then changes in site levels may have taken place.
When excavating in the locality of an underground cable extreme caution must be taken, which may even involve careful hand excavation to expose the cable. Exposed cables should be adequately supported, and suitable barriers with warning notices should be erected. Any damage, however minor, must be reported to the electricity supplier for the necessary remedial action. It is worth noting that if a contractor damages an underground electric cable that was known to be present, and possibly caused a loss of supply to surrounding properties, the contractor can be liable for negligence, trespass to goods and damages.
These impose duties and expectations on employers, employees and the self-employed, for health and safety responsibilities with regard to the use of electricity. Risk assessment and suitable precautions relating to particular hazards, such as overhead lines and underground cables encountered on site, are contained by the Health and Safety at Work etc. Installations should follow rules given in BS Section details provision for temporary installations and installations on construction sites.
See also, BS The supply distribution assemblies used in the installation should comply with the recommendations of BS Specification for distribution assemblies for reduced low voltage electricity supplies for construction and building sites. This covers the equipment suitable for the control and distribution of electricity from a three-phase four-wire a. BS EN -2 specifies plugs, socket outlets and cable couplers for the varying voltages recommended for use on construction sites.
The appliances and wiring used in temporary installations on construction sites may be subject to extreme abuse and adverse conditions: Electrical distribution cables contain three line wires and one neutral, which can give either a V three-phase supply or a V single-phase supply.
Records of accidents involving electricity show that the highest risk is encountered when electrical power is used in wet or damp conditions, which are often present on construction sites. It is therefore generally recommended that wherever possible the distribution voltage on building sites should be V.
This is a compromise between safety and efficiency, but it cannot be overstressed that a supply of this voltage can still be dangerous and lethal. The recommended voltages for use on construction sites are given below: Mains voltage V three-phase: Reduced voltage V three-phase: It is worth considering the use of 50 or 25 V battery-supplied hand-lamps if damp situations are present on site. All supply cables must be earthed, and in particular V supplies should be centre-point earthed so that the nominal voltage to earth is not more than 65 V on a three-phase circuit and not more than 55 V on a single-phase circuit.
Protection to a circuit can be given by using bridge fuses, cartridge fuses and circuit breakers. Adequate protection should be given to all main and sub circuits against any short-circuit current, overload current and earth faults. Protection through earthing may be attained in two distinct ways: Insertion in the supply of a circuit-breaker with an operating coil that trips the breaker when the current due to earth leakage exceeds a predetermined value.
BS and BS EN recommend that plug and socket outlets are identified by a colour coding as an additional safety precaution to prevent incorrect connections being made. The recommended colours are: Main distribution assembly MDA Control and distribution of mains supply for circuits of V three-phase and V single-phase. Transformer assembly Transforms and distributes electricity at a reduced voltage: Socket outlet assembly SOA Connection, protection and distribution of final subcircuits at a voltage lower than the incoming supply.
Extension outlet assembly EOA Similar to outlet assembly except that outlets are not protected. A very-low-voltage current passes along these conductors between the portable plant and the fixed EMU.
A failure of the earth continuity conductor will interrupt the current flow, which will be detected by the EMU, and this device will automatically isolate the main circuit. The cubicles or units must be of robust construction, strong, durable, rain resistant and rigid to resist any damage that could be caused by transportation, site handling or impact shocks likely to be encountered on a construction site. All access doors or panels must have adequate weather seals.
The routeing of the supply and distribution cables around the construction site should be carefully planned. Cables should not be allowed to trail along the ground unless suitably encased in a tube or conduit, and even this method should be used only for short periods of time.
Recommended minimum height clearances for overhead cables are: Cables that are likely to be in position for a long time, such as the supply to a crane, should preferably be sited underground at a minimum depth of mm and protected by tiles, or alternatively housed in clayware or similar pipes.
In the interest of safety, and to enable first-aid treatment to be given in cases of accident, all contractors using a supply of electricity on a construction site for any purpose must display, in a prominent position, extracts from the Electricity at Work Regulations.
Pictographic safety signs for caution of the risk of electric shock are applicable under the Health and Safety Safety Signs and Signals Regulations Inadequate lighting also increases the risks of accidents and lowers the security of the site. The initial costs of installing a system of artificial lighting for both internal and external activities can usually be offset by higher output, better-quality work, a more secure site, and apportioning the costs over a number of contracts on a use and reuse basis.
The reasons for installing a system of artificial lighting on a construction site are as follows: Without adequate light, all activities on construction sites carry an increased risk of accident and injury.
By enabling work to proceed, losses in productivity can be reduced. Reduces the wastage of labour and materials that often results from working in poor light. Avoids short-time working due to the inability to see clearly enough for accurate and safe working. Improves the general security of the site. The following benefits may be obtained by installing and using a system of artificial lighting on a construction site: Overtime and extra shifts can be worked to overcome delays that might occur from any cause.
The amount of spoilt material and the consequent rectification caused by working under inadequate light can be reduced. It provides an effective deterrent to the would-be trespasser or pilferer. Contractual relationships will be improved by ensuring regular working hours and thus regular earnings.
Planning the lighting requirements depends on site layout, size of site, shape of site, geographical location, availability of an electrical supply and the planned activities for the winter period.
Any form of temporary artificial site lighting should be easy to install and modify as needs change, and should be easy to remove while works are still in progress.
The supply and distribution of an electrical service to a construction site has already been covered in the previous chapter, and it is therefore necessary only to stress again the need for a safe, reliable installation, designed and installed by a specialist contractor. It is expressed in lux, which is one lumen of light falling on 1 m2 of surface, and this can be measured with a small portable lightmeter, which consists of a light-sensitive cell generating a small current proportional to the light falling on it.
The level of illuminance at which an operative can work in safety and carry out tasks to an acceptable standard, in terms of both speed and quality, is quite low, because the human eye is very adaptable and efficient. Although the amount of illuminance required to enable a particular activity to be carried out is a subjective measure, depending largely upon the task, and the age and state of health of the Table 1.
The values shown in the table do not allow for deterioration, dirt, bad conditions or shadow effects. Therefore in calculating the illuminance required for any particular situation a target value of twice the service value should be used. When deciding on the type of installation to be used, two factors need to be considered: The properties of the various types of lamp available should be examined to establish the most appropriate for any particular site requirement.
They are cheap to download but are relatively expensive to run.
Tungsten halogen lamp Compact fitting with high light output, and suitable for all general area floodlighting. They are easy to mount, and have a more effective focused beam than the filament lamp. These lamps generally have a life of twice that of filament lamps, and quartz lamps have a higher degree of resistance to thermal shock than glass filament lamps. They are dearer than filament lamps and are still relatively expensive to run but should be considered if the running time is in the region of 1, hours annually.
Mercury tungsten lamps Compact, efficient, with a good lamp life, and do not need the expensive starting gear of the vapour discharge lamps. They can be used for internal and external area lighting where lamps are not mounted above 9. These are high-cost lamps but are cheap to run. Mercury discharge lamps High-efficiency lamps with a long life; can be used for area lighting where lamps are mounted above 9.
Costs for lamps and control gear are high but the running costs are low. Tubular fluorescent lamps Uniformly bright in all directions; used when a great concentration of light is not required; efficient, with a range of colour values. These lamps have a long life and are economical to run. High-pressure sodium discharge lamps Compact, efficient, with a long life.
For the best coverage without glare they should be mounted above Cost for lamp and control gear is high but running costs are low, which makes them suitable for area lighting. Apart from the cost of the lamps and the running charges, consideration must be given to the cost of cables, controlling equipment, mounting poles, masts or towers.
A single high tower may well give an overall saving against using a number of individual poles or masts in spite of the high initial cost for the tower. Consideration can also be given to using the scaffold, incomplete structure or the mast of a tower crane for lamp-mounting purposes, each subject to earthing. These aspects can be considered under the following headings: The main objectives of area lighting are to enable staff and machinery to move around the site in safety and to give greater security to the site.
Areas of local danger such as excavations and obstructions should, however, be marked separately with red warning lights or amber flashing lamps. Tungsten filament, mercury vapour or tungsten halogen lamps can be used, and these should be mounted on poles, masts or towers according to the lamp type and wattage. Typical mounting heights for various lamps and wattages are shown in Table 1. Large areas are generally illuminated by using large, high-mounted lamps, whereas small areas and narrow sites use a greater number of smaller fittings.
By mounting the lamps as high as practicable above the working level glare is reduced, and by lighting the site from at least two directions the formation of dense shadows is also reduced. The spacing of the lamps is also important if under-lit and over-lit areas are to be avoided.
Figures 1. Dispersive lighting is similar to an ordinary internal overhead lighting system, and is suitable for both exterior and interior area lighting where overhead Table 1. Ordinary industrial fittings should not be used because of the adverse conditions that normally prevail on construction sites. The fittings selected should therefore be protected against rust, corrosion and water penetration.
To obtain a reasonable spread of light the lamps should be suspended evenly over the area to be illuminated, as shown diagrammatically in Fig. Tungsten filament, mercury vapour and fluorescent trough fittings are suitable and should be suspended at a minimum height according to their type and wattage.
Typical suspension heights are shown in Table 1. Most manufacturers provide guidance as to the choice of lamps or combination of lamps, but a simple method of calculating lamp requirements is as follows: Decide upon the service illuminance required, and double this figure to obtain the target value.
Choose lamp type. Repeat stage 3 for different lamp types to obtain the most practicable and economic arrangement. Consider possible arrangements, remembering that: The calculations when using dispersive lighting are similar to those given above for mounted area lighting except for the formula in stage 2, which has a utilisation factor of 0.
Beam floodlights are used to illuminate areas from a great distance. The 36 Advanced Construction Technology Figure 1. Bulkhead fittings that can be safely installed with adequate protection to the wiring can be run off a mains voltage of V single-phase, but if they are in a position where they can be handled a reduced voltage of V single-phase should be used.
Festoon lighting, in which the readywired lampholders are moulded to the cable itself, can also be used. A standard festoon cable would be See Fig. For lighting to scaffolds of four- or five-board width 60 W lamps should be used, placed at not more than 6. LOCAL LIGHTING Clusters of pressed glass reflector floodlamps, tungsten filament lamps, festoons and adjustable fluorescents can be used to increase the surface illumination at local points, particularly where finishing trades are involved.
These fittings must be portable so that shadow casting can be reduced or eliminated from the working plane: Fluorescent tubes do not usually work at a reduced voltage, so special fittings working off a V single-phase supply that internally increase the voltage are used.
Typical examples of suitable lamps are shown in Fig. As an alternative to a system of static site lighting connected to the site mains, electrical supply mobile lighting sets are available. These consist of a dieselengine-driven generator and a telescopic tower with a cluster of tungsten iodine lamps. These are generally cheaper to run than lamps operating off a mains supply. Small two-stroke generator sets with a single lamp attachment suitable for small, isolated positions are also available.
Another system that can be used for local lighting is flame lamps, which normally use propane gas as the fuel. These lamps produce a great deal of local heat and water vapour; the latter may have the effect of slowing down the drying out of the building. Therefore any fluctuation in productivity will affect a large number of people.
A severe winter can treble the typical loss of output quoted above, resulting in loss of cash flow to the main contractor and subcontractors, plus reduced pay to employees. There will also be lower profits, or a profit loss for contractors, and many skilled operatives may leave the industry in search of more secure occupations. The building owner also suffers by the delay in completing the building, which could necessitate extending the borrowing period for the capital to finance the project or the loss of a prospective tenant or downloader.
The major factor in determining the progress of works on site during the winter period is the weather. Guidance as to the likely winter weather conditions for various areas of the United Kingdom can be obtained from maps, charts and statistical data issued by the Meteorological Office, and this is useful for long-term planning, whereas in the short term reliance is placed upon local knowledge, daily forecasts and the short-term monthly weather forecasts.
The uncertain nature of the climate in the United Kingdom often discourages building contractors from investing in plant and equipment for winter-building techniques and protective measures that may prove to be unnecessary.
Contractors must therefore assess the total cost of possible delays against the capital outlay required for plant and equipment to enable them to maintain full or near-full production during the winter period. Rain Rain affects site access and movement, which in turn increases site hazards, particularly those associated with excavations and earth-moving works. It also causes discomfort to operatives, thus reducing their productivity rate. Delays with most external operations, such as bricklaying and concreting, are usually experienced, particularly during periods of heavy rainfall.
Damage can be caused to unprotected materials stored on site and in many cases to newly fixed materials or finished surfaces. The higher moisture content of the atmosphere will also delay the drying out of buildings. If high winds and rain occur together, rain penetration and site hazards are considerably increased. High winds Apart from the discomfort felt by operatives, high winds can also make activities such as frame erection and the fixing of sheet cladding very hazardous.
They can also limit the operations that can be carried out by certain items of plant such as tower cranes and suspended cradles. Positive and negative wind pressures can also cause damage to partially fixed claddings, incomplete structures and materials stored on site. Low temperatures As the air temperature approaches freezing point many site activities are slowed down.
These include excavating, bricklaying, concreting, plastering and painting, until they cease altogether at subzero temperatures; also, mechanical plant can be difficult to start, and stockpiles of materials can become frozen and difficult to move. General movement and circulation around the site becomes hazardous, creating with the low temperatures general discomfort and danger for site personnel.
When high winds are experienced with low temperatures they will aggravate the above-mentioned effects. Snow This is one of the most variable factors in British weather, ranging from an average of five days a year on which snow falls on low ground in the extreme south-west to 35 days in the north-east of Scotland. Snow will impair the movement of labour, plant and materials, as well as create uncomfortable working conditions.
Externally stored materials will become covered with a layer of snow, making identification difficult in some cases. This blanket of snow will also add to the 42 Advanced Construction Technology load to be carried by all horizontal surfaces. High winds encountered with falling snow can cause drifting, which could increase the site hazards and personal discomfort, and decrease general movement around the site. It should be appreciated that the adverse conditions described above could have an adverse effect on site productivity, even if they are not present on the actual site, by delaying the movement of materials to the site from suppliers outside the immediate vicinity.
Inclement weather conditions can have a very quick reaction on the transportation aspect of site operations, movement of vehicles around the site and, indeed, off the site, which will be impaired or even brought to a complete standstill unless firm access roads or routes are provided, maintained and kept free of snow. These access roads should extend right up to the discharge points to avoid the need for unnecessary double handling of materials.
If the access roads and hardstandings form part of the contract and are suitable, these could be constructed at an early stage in the contract before the winter period. If the permanent road system is not suitable in layout for contractual purposes, temporary roads of bulk timbers, timber or concrete sleepers, compacted hardcore or proprietary metal tracks could be laid.
Frozen ground can present problems with all excavating activities. Most excavating plant can operate in frozen ground up to a depth of mm, but at a reduced rate of output: Prevention is always better than cure.
Therefore if frost is anticipated it is a wise precaution to protect the areas to be excavated by covering with fibre mats enclosed in a polythene envelope, insulating quilts of mineral wool or glass fibre incorporating electric heating elements for severe conditions.
Similar precautions can be taken in the case of newly excavated areas to prevent them freezing and giving rise to frost-heave conditions.
If it is necessary to defrost ground to enable excavating works to be carried out, this can usually be achieved by using flame throwers, steam jet pipes or coils. Care must be taken to ensure that defrosting is complete and that precautions are taken to avoid subsequent re-freezing.
Water supplies should be laid below ground at such a depth as to avoid the possibility of freezing. The actual depth will vary according to the locality of the site, with a minimum depth of mm for any area.
If the water supply is temporary and above ground the pipes should be well insulated and laid to falls so that they can be drained at the end of the day through a drain cock incorporated into the service. Electrical supplies can fail in adverse weather conditions because the vulnerable parts such as contacts become affected by moisture, frost or ice. These components should be fully protected in the manner advised by their manufacturer. Items of plant that are normally kept uncovered on site — such as mixers, dumper trucks, bulldozers and generators — should be protected as recommended by the manufacturer to avoid morning starting problems.
These precautions will include Winter building 43 selecting and using the correct grades of oils, lubricants and antifreeze, as well as covering engines and electrical systems, draining radiators where necessary, and parking wheeled or tracked vehicles on timber runners to prevent them freezing to the ground.
Under the Construction Health, Safety and Welfare Regulations, operatives will also need protection from adverse winter conditions if an acceptable level of production is to be maintained.
Materials too will require shelter. Such protection can be of one or more of the following types: They consist of a screen of reinforced or unreinforced polythene sheeting of suitable gauge fixed to the outside of the scaffold to form a windbreak. The sheeting must be attached firmly to the scaffold standards so that it does not flap or tear a suitable method is shown in Fig.
To gain the maximum amount of use and reuse out of the sheeting used to form the windbreaks the edges should be hemmed or reinforced with a suitable adhesive tape with metal eyelets incorporated at the tying positions. Eyelets can be made on site using a special kit; alternatively the sheet can be supplied with prepared edges. Framed enclosures should be clad from the windward end to avoid a build-up of pressure inside the enclosure. It is also advantageous to load the working platform before sheeting in the sides of the enclosure, because loading at a later stage is more difficult.
The frame must be rigid enough to take the extra loading of the coverings and any imposed loading such as wind loadings. Anchorage to the ground of the entire framing is also of great importance, and this can be achieved by using a screw-type ground anchor as shown in Fig. Two forms are available: The usual shape for an air-supported structure is semi-cylindrical with rounded ends through which daylight can be introduced by having a translucent membrane over the crown of the structure.
The anchorage and sealing of the air-supported structure are also very important, and this can be achieved by using a concrete ring beam as shown in Fig. It must be provided to satisfy the health and safety objectives of the Construction Health, Safety and Welfare Regulations. Labour costs on building sites are such that maximum utilisation of all labour resources in all weathers must be the ultimate aim, and therefore capital expended in providing protective clothing can be a worthwhile investment.