QUESTION ONERaft Foundations1.1 Definition:These are used to spread the load of the super structure over a large base to reduce the load per unit area of being imposed on the ground and this is particularly useful where low bearing capacity soils are encountered and where individual column loads are heavy.2.2 Types2.2.1 Solid RaftConsists of reinforced concrete raft of uniform thickness over the whole area simple to design and construct but can be wasteful in amount of concrete used.Solid slab rafts are suitable for lightly loaded structures such as small houses. A solid slab raft consists of a reinforced concrete slab, usually slightly larger than the area of the building. Reinforcement in the form of a mesh fabric is provided on both the top and bottom faces of the slab

Figure 1.1: Shows a Solid Raft Foundation

2.2.2 Beam and Slab RaftConsists of ground beams designed as upstand beams with a precast concrete suspended floor at ground level thus creating a void space between raft and ground floor.There may be variations in ground stiffness and cause differential settlement.The solid slab raft may be further reinforced with ground beams. The columns shall be positioned at the intersection of the ground beams.

QUESTION TWO:BACK GROUNDThe information included herein was collected from two different sites. Site Number one belonged SENANA DEVELOPERS, the site is located at Buganda Road opposite Watoto Church Central (KPC). It is a commercial development of a Shopping Mall and the client SENANA.The site is in the primary stages, with the foundations, first basement slab and second slab including the columns and retaining wall erected. On the second basement slab where we were taking photos for this report, the retaining wall was being erected including the formwork for the ramp to the ground floor were being erected. The attendance at all trades was well represented. The entire site was hoarded off with G32 iron sheets and had three gates; one at Kyaggwe Road, and two at Buganda Road. The site office was located at the eastern side of Kyaggwe Road. The kitchen and mess for workers had been erected on the western part of the site.Because of the nature of the site, we could not get hold of the details of the foundation though the care taker told us that the foundation used was a wide strip reinforced foundation, with 16T32 Bars for topping and bottoms for the foundation footings.The columns were of mechanically vibrated concrete, 800mm in diameter reinforced with 8T25 R8 links placed at 200mm C/c. Marin plys were being used for formwork soffits to slab formwork and sides of beams and rectangular columns: steel formwork (moulds) was being used for circular columns. 4X2 Timber was being used for head trees and Eucalyptus Gum poles were used for propping. Different nail sizes of 2 inch, 3inch, 4inch, 5inch and 6inch, were used for joining the formwork members. Scaffolding was mainly dependant type, of gum poles. Temporary ramps of kirundu (12X1) supported with gum poles were being used for access to higher places.Materials were being damped on different points on the slab: for example steel bars, sand, aggregates, boards and timber.There were two mixers present at site, one container for storage of valuables, temporary shade to house the kitchen and mess for workers had been erected. SITE No. 2PROPOSED CONSTRUCTION OF INTER UNIVERSITY COUCIL FOR EAST AFRICA HEAD QUARTERS AT SEZIBWA ROAD KYAMBOGO

The site is located right behind kyambogo, 2KM from Ntinda, 1km from Kabakas palace at the Northern gate.The main contractor is China Nanjing, project duration is 1year. The consultants are Symbion Uganda LTD (Project Managers), Dudley Kasibante and Partners (Quantity Surveyors), Multi-Konsults (Mechanical and Electrical Engineers) and Kaburu Okello Consulting Engineers (Structural Engineers).

2.0 Site LayoutDefinitionSite layout is the positioning of the right material, plant, services and other site components in the right place at the right time so as to ensure maximum output on siteGeneral Considerations ~ before any specific considerations and decisions can be made regarding site layout a general appreciation should be obtained by conducting a thorough site investigation at the pre-tender stage and examining in detail the drawings, specification and Bill of Quantities to formulate proposals of how the contract will be carried out if the tender is successful. Access Considerations ~this considered both on- and off-site access. Routes to and from the site were placed for the suitability for transporting all requirements for the proposed works. Access on site for deliveries and general circulation were carefully considered.Site No.1 The site was fully utilized, with provisions for access routes provided for the constructions area as passersby wheel barrows kept on ferrying concrete from the mixers.Provisions of routes for supplies like cement were placed at different points: for example sand and aggregate for the top slab at southern gate, cement at western gate.

Figure 1: Shows the Access routes for Supplies and WorkersStorage Considerations ~ amount and types of material to be stored, security and weather protection requirements, allocation of adequate areas for storing materials and allocating adequate working space around storage areas as required, sitting of storage areas to reduce double handling to a minimum without impeding the general site circulation and/or works in progress. Cement and other valuable materials were kept in the container, while gum poles, timber,aggregates, iron bars were damped in designated working areas on site.

Accommodation Considerations ~ number and type of site staff anticipated, calculate size and select units of accommodation and check to ensure compliance with the minimum requirements of the Construction (Health, Safety and Welfare) Regulations 1996, select sitting for offices to give easy and quick access for visitors but at the same time giving a reasonable view of the site, select sitting for mess room and toilets to reduce walking time to a minimum without impeding the general site circulation and/or works in progress. At the extreme left neighboring Buganda road flats were temporary shades for the site kitchen and a resting shade for the operatives.While at site No.2 a fully functional temporary accommodation was put in place including the guard house, site office, toilet, rest rooms were erected.

Figure 2: Shows Site Office, Rest Rooms for Site 2 Figure 3.a: Shows Kitchen shade and Rest shade for Site No.1 and Figure 3.b Shows the Guard House at Site 2

Temporary Services Considerations ~ what, when and where are they required? Possibility of having permanent services installed at an early stage and making temporary connections for site use during the construction period, coordination with the various service undertakings is essential. The site actual have such temporary services like internet installed except water and electricity for works had been installed and functional at site.

Figure 4: Shows the Electricity control area at Site 2Plant Considerations ~ what plant, when and where is it required? static or mobile plant? If static select the most appropriate position and provide any necessary hard standing, if mobile check on circulation routes for optimum efficiency and suitability, provision of space and hard standing for on-site plant maintenance if required. Two mixers were placed at different locations at Site1 and porters were ferrying concrete different places using wheel barrows. The site foreman told us that since the client had to keep costs within budgets, and the fact the structure was still in the basement, hiring plants such as hoists would be an economical.At SITE2 plant considerations were adhered to, for example the hoist, mixer, parking, steel bending equipment, were suitably fixed.

Figure 5: Shows mixer at Site 2

Fencing and Hoarding Considerations ~ what is mandatory and what is desirable? Local vandalism record, type or types of fence and/or hoarding required, possibility of using fencing which is part of the contract by erecting this at an early stage in the contract.The site foreman told us that before commencement of all the works, a gauge 32 iron sheet nailed onto 100mm x 50mm timber railing on 75mm diameter gum poles, hoarding had to be erected around the Two Sites.

Figure 6: SHOWS IRON SHEET HOARDING

Figure 7: Hoarding at site 2Safety and Health Considerations ~ check to ensure that all the above conclusions from the considerations comply with the minimum requirements set out in the various Construction Regulations and in the Health and Safety at Work etc., Act 1974.Site Security ~ the primary objectives of site security are 1. Security against theft.2. Security from vandals.3. Protection from innocent trespassers.The need for and type of security required will vary from site to site according to the neighborhood, local vandalism record and the value of goods stored on site. Perimeter fencing, internal site protection and night security may all be necessary, which was the case for the site in question.These considerations were adhered at both site since both sites had hoarding, gates, containers and guards to avoid such incidences.Electrical Supply to Building Sites ~ a supply of electricity is usually required at an early stage in the contract to provide light and power to the units of accommodation. As the work progresses power could also be required for site lighting, hand held power tools and large items of plant. The supply of electricity to a building site is the subject of a contract between the contractor and the local area electricity company who will want to know the date when supply is required; site address together with a block plan of the site; final load demand of proposed building and an estimate of the maximum load demand in kilowatts for the construction period. The latter can be estimated by allowing 10W/m2 of the total floor area of the proposed building plus an allowance for high load equipment such as cranes. The installation should be undertaken by a competent electrical contractor to ensure that it complies with all the statutory rules and regulations for the supply of electricity to building sites.Office Accommodation ~ the arrangements for office accommodation to be provided on site is a matter of choice for each individual contractor. Generally separate offices would be provided for site agent, clerk of works, administrative staff, site surveyors and sales staff.The minimum requirements of such accommodation is governed by the Offices, Shops and Railway Premises Act 1963 unless they are ~1. Mobile units in use for not more than 6 months.2. Fixed units in use for not more than 6 weeks.3. Any type of unit in use for not more than 21 man hours per week.4. Office for exclusive use of self employed person.5. Office used by family only staff.Sizing Example ~ Office for site agent and assistant plus an allowance for 3 visitors.Assume an internal average height of 2.400.Allow 3.7m2 minimum per person and 11.5m3 minimum per person.Minimum area = 5 x 3.7 = 18.5m2Minimum volume = 5x 11.5 = 57.5m3Assume office width of 3.000 then minimum length required is= =8.000 Area check 3x8 = 24 S.M which is > 18.5m2An office space of about 2.000 x 2.000 was allowed for on site to accommodate the site agent, clerk of works and quantity surveyor for site 1 while at site 2 the requirements for office space were met

Figure 8: Site office at Site 2Site Health and Welfare RequirementsThe requirements for health and wellbeing of persons on construction sites are enforced by the Health and Safety Executive, through the Health and Safety at Work etc. Act 1974 and the Construction (Health, Safety and Welfare) Regulations 1996. The following minimum requirements apply and the numbers of persons on site were established by the Construction Regulations of1996.First Aid box at office shade, disclaimer stickers, Stand by van was present at site 2: also dust screens were placed on the scaffold all round to protect operatives from falling debris and dust. At site1 these considerations were not being catered though the foreman told us they have Health and Safety meetings twice a week. Figure 9: Shows Health and Safety Stickers

TYPE OF FOUNDATION: Site 1: Wide Strip FoundationThe tensile reinforcement that is cast within the concrete base allows the width of the foundation to be increased and the loads to be distributed over a greater area: Loads are distributed over a greater area reducing the load per unit area.After the excavation of the basement which was at a depth of 20metre, the trenches for the strip foundations were set out using pegs, strings, nails, profiles, plumb bob, builders square and dumpy level. Positions for the strip trenches (1200mm wide) were marked and nailed on the profile boards. With strings tied on the front nails subsidiary lines for trenches were then transferred for the rest of the trenches to other nails on profile. Sand was then used to mark out the extent of the trenches and pick axes were then used to excavate the trenches. Excess soil was the removed from trenches, hipped and then transported to designated areas.A blinding 50mm thick, of mix 1:3:6 was mixed and poured into the trench to produce a firm base. Reinforcement bars of 2X32T25 were bend and linked with R8 tied with binding wire put on the hardened blinding while maintaining concrete cover of 25mm using spacer blocks. Concrete of mix 1:1.5:3 was then poured in stripsSite 2: Pad FoundationPad Foundations ~ suitable for most subsoil except loose sands, loose gravels and filled areas. Pad foundations are usually constructed of reinforced concrete and where possible are square in plan.Construction ProcedurePits of 1200mmx1200mmx1500mm were excavated and soil cut away and a base box (formwork) of 300mmx25mm was fabricated and secured in place for the pad concrete. A blinding of mix 1:3:6 was cast in pits and left to harden. T12 bars were then cut to size to make the base and tied using binding wire. 6T16 bars spaced at 150mm C/C for columns were and R8 reinforcements were cut to size for the links and tied using binding wire. Concrete of mix 1:2:4 was then poured and mechanically vibrated using a poker.

Figure 10: Shows a cast Pad foundation

TEMPORARY WORKS ON SITE:1: FORMWORKBasic Formwork ~ concrete when first mixed is a fluid and therefore to form any concrete member the wet concrete must be placed in a suitable mould to retain its shape, size and position as it sets. It is possible with some forms of concrete foundations to use the sides of the excavation as the mould but in most cases when casting concrete members a mould will have to be constructed on site. These moulds are usually called formwork. It is important to appreciate that the actual formwork is the reverse shape of the concrete member which is to be cast1. Formwork to Soffits of Slabs and Beams:Procedure for erection:After the columns have gained an ultimate strength, the levels for the soffits of the slab and beam formwork are marked on the columns.4x2 inch timbers are cut to size and fixed between columns using nails: this forms the joists were the head trees are then secured using the nails (5): it is on the head trees that the sides of the beams are then secured. Using strings and nails horizontality for the side shutters is kept. The sides are then strutted using 50x50mm battens. A cleat is then nailed at the end of each strut so that it is kept taught. To avoid sagging and failure of the moulds, the props are then nailed onto the head trees to give vertical support. The props are then braced to give them more support: the props are then leveled using wedges of timber which at the same time act as sole plates.The moulds are then ready to receive concrete: but for the case of slabs the joists/ head trees are marked and nailed on sides of beam formwork to form a decking base on which the marine plywood boards are nailed and leveled.2. Column moulds:The mould is placed around the column and plumbed, it is then kept in place using a kicker.While maintaining plumb, set out positions for the props (shoring) at intervals of 1500mm and prop; peg and nail props on the pegs so that they are firm enough. The mould is then ready to receive concrete.

Figure 11: Formwork to Soffits of Slabs and Beams

Figure 12: Formwork to Concrete Ramps

Figure 13: Shows Steel Moulds for Columns

3. SCAFFOLDING Scaffolds ~ these are temporary working platforms erected around the perimeter of a building or structure to provide a safe working place at a convenient height. They are usually required when the working height or level is 1.500 or more above the ground level.All scaffolds must comply with the minimum requirements and objectives of the Work at Height Regulations 2005SITE 1: Put Log ScaffoldingThe type of scaffolding was dependent scaffolding: consisting of Eucalyptus standards, braces, ledges, handrails and 12x1 inch timber platforms fastened using nails.

Figure 14: Shows Putlog Scaffolding at Site 1SITE 2: TUBULAR SCAFFOLDINGWe found the independent scaffolding at site No. 2 as described below;These are scaffolds which have two rows of standards each row joined together with ledgers which in turn support the transverse transoms. The scaffold is erected clear of the existing or proposed building but is tied to the building or structure at suitable intervals.Working Platforms ~ these are close boarded or plated level surfaces at a height at which work is being carried out and they must provide a safe working place of sufficient strength to support the imposed loads of operatives and/or materials. All working platforms above the ground level must be fitted with a toe board and a guard rail.

Figure 15: Shows the Independent Scaffolds

4. RAMPSThe ramp was made of tubular pipes fastened using couplers and propped at intervals. A slope of 150 was then allowed to ease movement of operatives.The platform was made of boards joined with nails and fastened on the joists using bolts.

Figure 16: Shows a Ramp at Site 2 used to access the Roof of the Power house.

CHALLENGES 1. Accessibility to site since most contractors wanted a written introduction letter from the University.2. The Sites were at different stages of Construction and therefore some information could not be got.3. The design of the site visited could not allow for exploration of all the necessary information.

REFERENCES1. Handbook for Construction by R. Chudley2. Advance Construction Technology By Professor Chris Gorse licensed under the Creative Commons Attribution Non-Commercial Share Alike License3. InternetCONSTRUCTION TECHNOLOGY ASSIGNMENTPage 1