Laminated Veneer Lumber

Laminated veneer lumber (LVL) (Fig. 4.24), also known as microlam, is more economical than laminated timber as there is little waste in the production process. It is manufactured to three grades by laminating timber strands with polyurethane resin under heat and pressure. In one process, logs are cut into flat timber strands 300 mm long these are then treated with resin, aligned and hot-pressed into billets of Load-bearing dry (hazard class 1) LVL 1 Load-bearing humid (hazard class 2) LVL 2...

Constituents Of Timber

The main constituents of timber are cellulose, hemi-cellulose and lignin, which are natural polymers. Cellulose, the main constituent of the cell walls, is a polymer made from glucose, a direct product from the photosynthesis within the leaves of the tree. Glucose molecules join together to form cellulose chains containing typically 10000 sugar units (Fig. 4.4). Alternate cellulose chains, running in opposite directions to each other, form a predominantly well-ordered crystalline material. It...

Green roofs

Green roofs are flat or low pitched roofs which are landscaped over the waterproofing layer. The landscaping may include some hard surfaces and have access for leisure and recreational functions as well as the necessary routine maintenance. Green roofs offer not only increased life expectancy for the waterproofing layer by protecting it from physical damage, ultraviolet light and temperature extremes, but also increased usable space. Environmental advantages include reduced and delayed...

Glass supporting systems

The fixing of glazing, and particularly solar control glasses, should be sufficiently flexible to allow for tolerances and thermal movements. A minimum edge clearance of at least 3 mm is required for single glazing and 5 mm for double-glazing units. Edge cover should be sufficient to cope with the design wind loading, with a minimum normally equal to the glass or unit thickness to ensure a neat sight line. Glass thickness The Planar Assembly Fig. 7.19 Typical facade glazing system should be...

Recycling of plastics

The use of plastics within European countries is approximately 44 million tonnes per year, with products for the construction industry accounting for over a half of the consumption of PVC. Currently most waste disposal is within landfill sites. However, certain thermoplastic products can be recycled into construction products. Expanded polystyrene waste can be recycled by solvent extraction into a material, which has the appearance and many characteristics of wood. PVC bottles can be recycled...

Recycling Fibrereinforced Polymers

Currently, the majority of waste fibre-reinforced polymers (FRPs) are disposed into landfill sites. One alternative is to grind the material into powder and use this ground GRP in conjunction with other binders however, this process is difficult where embedded metal fixings were incorporated into the original components. The recyclate powder can be blended with other recycled plastics to produce GRP plastics lumber, which can be used for lightly loaded piles, decking, fencing and similar...

Intelligent glass facades

An intelligent glass building facade changes its physical properties in response to sensors detecting the external light and weather conditions, thus reducing the energy consumption necessary to maintain the appropriate internal environment. Therefore intelligent facades have ecological significance in reducing global greenhouse emissions and also in reducing operational building costs to clients and users. Truly intelligent facades capitalise on the incident solar energy striking the facade of...

Carbon Content Of Ferrous Metals

Dulctile Iron Exploted

The quantity of carbon alloyed with iron has a profound influence on the physical properties of the metal due to its significant effect on the microscopic crystal structure (Fig. 5.8). At ambient temperature a series of crystal forms (ferrite, pearlite and cementite) associated with different proportions of iron and carbon are stable. However, on increasing the temperature, crystal forms that were stable under ambient conditions, become unstable and are recrystallised into the high temperature...

Deterioration Of Timber

The major agencies causing the deterioration of timber in construction are weathering, fungi, insects and fire. The natural durability of timber is defined into five categories in relation to the resistance of the heartwood to wood-decaying fungi (BS EN 350-1 1994). On prolonged exposure to sunlight, wind and rain, external timbers gradually lose their natural colours and turn grey. Sunlight and oxygen break down some of the cellulose and lignin into water-soluble materials which are then...

Intensive Green Roofs

Intensive green roofs are generally designed to accept recreational activity and to include the widest range of vegetation from grass to shrubs and semi-mature trees. Depths of soil are typically between 200 and 300 mm, which together with the necessary minimum 50 mm of water reservoir and drainage systems generate an additional imposed load of typically 400 kg m2 on the existing or proposed structural system. Intensive green roofs may incorporate both soft and hard landscaping and slopes up to...

Manufacture Of Steel

The production of steel involves a sequence of operations which are closely inter-related in order to ensure maximum efficiency of a highly energy-intensive process. The key stages in the production process are the making of pig iron, its conversion into steel, the casting of the molten steel and its formation into sections or strip. Finally, coils of steel strip are cold rolled into thin sections and profiled sheet. The raw materials for the production of iron are iron ore, coke and limestone....

Standards

BS 144 1997 Specification for coal tar creosote for wood preservation. BS 373 1957 Methods for testing small clear specimens of timber. BS 476 Fire tests on building materials and structures Parts 3, 4, 6, 7, 10-13, 15, 20-24, 31-33 BS 644 2003 Timber windows. Factory assembled windows of various types. BS 1088 Marine plywood Part 1 2003 Requirements. Part 2 2003 Determination of bonding quality. BS 1186 Timber for and workmanship in joinery Part 2 1988 Specification for workmanship. Part 3...

Building Research Establishment Publications

BRE Digest 309 1986 Estimating daylight in buildings Part 1. BRE Digest 310 1986 Estimating daylight in buildings Part 2. BRE Digest 338 1988 Insulation against external noise. BRE Digest 346 The assessment of wind loads. Part 1 1992 Background and method. Part 2 1989 Classification of structures. Part 3 1992 Wind climate in the United Kingdom. Part 4 1992 Terrain and building factors and gust peak factors. Part 5 1989 Assessment of wind speed over topography. Part 6 1989 Loading coefficients...

Fibreboards

Fibreboards are manufactured from wood or other plant fibres by the application of heat and or pressure. They are bonded by the inherent adhesive properties and felting of the fibres or by the addition of a synthetic binder. In the wet process used for the manufacture of hardboard, medium board and soft-board, no adhesive is added to the wood fibres. In the case of medium density fibreboard MDF , a resin-bonding agent is incorporated during the production process. Forest thinnings and wood...

Chemical attack and aggressive ground

The resistance of cured concrete to acid attack is largely dependent upon the quality of the concrete, although the addition of granulated blastfurnace slag GGBS or fly ash pulverised-fuel ash PFA increases the resistance to acids. Limestone-aggregate concrete is more vulnerable to acid attack than concretes with other aggregates. The resistance of cured concrete to chemical attack is defined by the design chemical class number, ranging from DC1 low resistance to DC 4 high resistance . The...

BRE Digests

BRE Digest 293 1985 Improving the sound insulation of separating walls and floors. BRE Digest 294 1985 Fire risk from combustible cavity insulation. BRE Digest 295 1985 Stability under wind load of loose-laid external roof insulation boards. BRE Digest 324 1987 Flat roof design thermal insulation. BRE Digest 336 1989 Swimming pool roofs minimising the risk of condensation. BRE Digest 337 1988 Sound insulation basic principles. BRE Digest 338 1988 Insulation against external noise. BRE Digest...

Rammedearth and cob construction

Earth construction is one of the oldest forms of building used by mankind. Rammed-earth buildings can be found in most countries, and many have survived hundreds of years. The ideal material is a well-graded mixture of gravel, sand, silt and clay fines. The clay content should be sufficient to act as an efficient binder, but not in excess to cause large moisture movement or cracking of the finished construction. In modern rammed-earth construction Portland cement is frequently incorporated as a...