Wednesday, February 19, 2014

Patent Scaffolding

Patent Scaffolding ~ these are systems based on an independent scaffold format in which the members are connected together using an integral locking device instead of conventional clips and couplers used with traditional tubular scaffolding. They have the advantages of being easy to assemble and take down using semi-skilled labour and should automatically comply with the requirements set out in the Work at Height Regulations 2005. Generally cross bracing is not required with these systems but fac ¸ade bracing can be fitted if necessary. Although simple in concept patent systems of scaffolding can lack the flexibility of traditional tubular scaffolds in complex layout situations.

Patent Scaffolding

Tubular 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 2005.

Component Parts of a Tubular Scaffold ~ 

Component Parts of a Tubular Scaffold ~

Putlog Scaffolds ~ these are scaffolds which have an outer row of standards joined together by ledgers which in turn support the transverse putlogs which are built into the bed joints or perpends as the work proceeds, they are therefore only suitable for new work in bricks or blocks.

Putlog Scaffolds ~
Independent Scaffolds ~ 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

Independent Scaffolds

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 levelmust be fittedwith a toe board and a guard rail.

Working Platforms
Tying-in ~ all putlog and independent scaffolds should be tied securely to the building or structure at alternate lift heights vertically and at not more than 6„000 centres horizontally.

Putlogs should not be classified as ties. Suitable tying-in methods include connecting to tubes fitted between sides of window openings or to internal tubes fitted across window openings, the former method should not be used for more than 50% of the total number of ties. If there is an insufficient number of window openings for the required number of ties external rakers should be used.

Mobile Scaffolds ~ otherwise known asmobile tower scaffolds. They can be assembled from pre-formed framing components or from standard scaffold tube and fittings. Used mainly for property maintenance. Must not be moved whilst occupied by persons or equipment.

Mobile Scaffolds

Some basic fittings ~

Some basic fittings

Sunday, February 16, 2014

Roads-Kerbs, Pavings and Edgings

Available sections - manufactured in 915 mm lengths from silver/grey aggregate concrete.

Concrete paving flags - BS dimensions:

Tactile flags - manufactured with a blistered (shown) or ribbed surface. Used in walkways to provide warning of hazards or to enable recognition of locations for people whose visibility is impaired. See also, Department of Transport Disability Circular DU 1/86[1], for uses and applications.

Ref. BS EN 1339: Concrete paving flags. Requirements and test methods.

Landscaping ~ in the context of building works this would involve reinstatement of the site as a preparation to the landscaping in the form of lawns, paths, pavings, flower and shrub beds and tree planting. The actual planning, lawn laying and planting activities are normally undertaken by a landscape subcontractor. The main contractor's work would involve clearing away all waste and unwanted materials, breaking up and levelling surface areas, removing all unwanted vegetation, preparing the subsoil for and spreading topsoil to a depth of at least 150mm.

Services ~ the actual position and laying of services is the responsibility of the various service boards and undertakings. The best method is to use the common trench approach, avoid as far as practicable laying services under the highway.

Roads - Footpaths

Typical Examples

Wednesday, February 12, 2014

Road Construction

Road Construction ~ within the context of building operations roadworks usually consist of the construction of small estate roads, access roads and driveways together with temporary roads laid to define site circulation routes and/or provide a suitable surface for plant movements. The construction of roads can be considered under three headings:-

1. Setting out.
2. Earthworks.
3. Paving Construction.

Setting Out Roads ~ this activity is usually carried out after the topsoil has been removed using the dimensions given on the layout drawing(s). The layout could include straight lengths junctions, hammer heads, turning bays and intersecting curves.

Straight Road Lengths † these are usually set out from centre lines which have been established by traditional means

Road Construction

Earthworks ~ this will involve the removal of topsoil together with any vegetation, scraping and grading the required area down to formation level plus the formation of any cuttings or embankments. Suitable plant for these operations would be tractor shovels fitted with a 4 in 1 bucket: graders and bulldozers. The soil immediately below the formation level is called the subgrade whose strength will generally decrease as its moisture content rises therefore if it is to be left exposed for any length of time protection may be required. Subgrade protection may take the form of a covering of medium gauge plastic sheeting with 300mm laps or alternatively a covering of sprayed bituminous binder with a sand topping applied at a rate of 1 litre per m2. To preserve the strength and durability of the subgrade it may be necessary to install cut off subsoil drains alongside the proposed road.

Paving Construction ~ once the subgrade has been prepared and any drainage or other buried services installed the construction of the paving can be undertaken. Paved surfaces can be either flexible or rigid in format. Flexible or bound surfaces are formed of materials applied in layers directly over the subgrade whereas rigid pavings consist of a concrete slab resting on a granular base.

Rigid Pavings ~ these consist of a reinforced or unreinforced in-situ concrete slab laid over a base course of crushed stone or similar material which has been blinded to receive a polythene sheet slip membrane. The primary objective of this membrane is to prevent grout loss from the in-situ slab.

Joints in Rigid Pavings ~ longitudinal and transverse joints are required in rigid pavings to:-

1 . Limit size of slab.
2. Limit stresses due to subgrade restraint.
3. Provide for expansion and contraction movements.

The main joints used are classified as expansion, contraction or longitudinal, the latter being the same in detail as the contraction joint differing only in direction. The spacing of road joints is determined by:-

1 . Slab thickness.
2. Whether slab is reinforced or unreinforced.
3. Anticipated traffic load and flow rate.
4. Temperature at which concrete is laid

Setting Out - Angles

Theodolite - a tripod mounted instrument designed to measure angles in the horizontal or vertical plane.

The theodolite in principle

Measurement - a telescope provides for focal location between instrument and subject. Position of the scope is defined by an index of angles. The scale and presentation of angles varies from traditional micrometer readings to computer compatible crystal displays. Angles are measured in degrees, minutes and seconds, e.g. 165º 53' 30''

Direct reading micrometer scale

Application - at least two sightings are taken and the readings averaged. After the first sighting, the horizontal plate is rotated through 180º and the scope also rotated 180 through the vertical to return the instrument to its original alignment for the second reading. This process will move the vertical circle from right face to left face, or vice-versa. It is important to note the readings against the facing † see below.