“Timber has no disadvantages, only design challenges,” said andrew dunn, chief executive of the timber development association. “a forgotten knowledge of fire and durability has limited timber use but that is changing. The key aspect for timber is that its properties are well known and very predictable.” Structural type, location and intended service life are all factors when determining the appropriate use of timber, but in general terms it is lightweight, easily worked, very adaptable to offsite manufacturing and generally cheaper than other materials. Its main market is in low-rise residential structures but there is a growing interest in the mid-rise sector for apartments, office buildings and school buildings. Timber has higher structural efficiency as carried load per unit weight compared to reinforced concrete and steel structures A common stud used in house construction has similar compressive strength to general purpose concrete Many timbers are either naturally durable or can be easily treated to make very durable. Wood, the raw material of structural structural timber products, timber products, is made from energy en ergy from the sun and carbon absorbed from the air (from the carbon dioxide in the air). Half the dry mass of timber is carbon absorbed from the air.
Timber used internally provides a healthier environment for occup ants as it helps maintain a better relative humidity The vast majority of structural timber is sourced from sustainably managed forests and plantations. Dunn argues timber offers more architectural design flexibility, which creates more design options without sacrificing structural requirements. “the natural warmth and beauty of wood is aesthetically pleasing,” he said. The metropol parasol in seville, spain, a 5,000 square metre, four-storey plaza cover, is an example of how timber has been used creatively recently. The treet or ‘the tree' shows how far timber has come. A 14-storey (49-metre) apartment building in bergen designed to comply with the passive the passive haus sustainability standard. When completed it will be the tallest modern timber apartment structure in the world.
The sky is the limit literally,” said dunn. “There “ There is a growth of timber building pushing the height limits. Canada has three tall timber buildings in the pipeline, a 13-storey quebec city project, using cross-laminated timber and glulam, a 12-storey building in ottawa and a project in vancouver targeting 18 storeys. Not to be outdone, the highest timber building planned so far is a 23 -storey office building in sweden.” “
"Concrete has been used for structures since ancient greece and rome,” said marianne fourie of the international federation for structural concrete. “Technological “Technological improvements and innovations over the centuries have refined its use. Structural concrete today allows engineers and architects to design and achieve striking edifices that are as robust as they can be aesthetic. Advanc es have also led to the more widespread use of precast concrete, which offers great benefits of cost and speed of construction.”
When it comes to larger edifices, such as tall buildings and bridges, fourie argues that nothing comes close to structural concrete for sheer strength and durability. Part of its attraction, she says, is also its versatility. “There is no reason to limit design to one material only,” said fourie. “Assimilating other materials into concrete structure design is simple. However, structural concrete is not only used in conjunction with other materials but also incorporates them, for example, with fibre-reinforced concrete.” Fourie says although other materials have become ‘trendier’ for their perceived environmental friendliness, structural concrete has made great strides in sustainability. It also has inherent ecological benefits since it is made from the most commonly available minerals (sand and limestone), and has excellent durability, thermal mass and minimal waste. She cites two projects, which both won an ‘award for outstanding concrete structures,’ as shining ex amples.The centro ovale concrete shell (chiasso, switzerland), illustrates the versatility of the material, while the bella sky hotel (copenhagen, denmark) is an example of the innovative use of precast concrete.
colours. A recent trend is the use of a pristine quality to edifices. The also continuously advances, with incorporated to enhance strength and increase the architectural possibilities.”
“The aesthetic possibilities of structural concrete are limitless,” said fourie. “One innovation is the use of pigmented admixtures that allow designers to create facades in a great variety of white concrete, which lends reinforcement of concrete all matter of material being
“steelwork in major construction is on the rise as builders become more attuned to the advantages of using the material in easing onsite risks, speeding development for earlier returns and environmental benefits,” said alan marshal, communications manager at the Australian steel institute. The us-based council on tall buildings and urban habitat recently reported the number of composite multi-level projects over 200 meters that typically comprise a steel frame with metal decking, rose 54 per cent worldwide in 2014. “Australia has experienced a similar resurgence,” said marshal. “This is particularly the case along the eastern seaboard where, during the same period, about 20 composite multi-level projects are underway, such as at 480 Queen Street, which is the first steel framed building of its size in Brisbane. It utilizes a parallel beam flooring system to achieve five-day floor cycle times, along with many other benefits gained from composite design and build programs.” Marshall argues the case for steel under three key criteria: speed and efficiency; the reduction of on-site risks; and sustainability and waste reduction. Speed and efficiency
Computer modelling before fabrication on computer numerically controlled (cnc) equipment means the components are produced right first time and there is minimal rework Earlier construction provides faster completion and payback commencement Faster construction means the builder’s staff can be released earlier to start the next project Steel is a structurally efficient building material and so buildings are lighter and often foundations c an be smaller as a result Steel is fabricated in controlled conditions driven by 3d modelling and cnc equipment increasing safety and reducing mtis and ltis A test certificate is available for all steel used and this can be made traceable through to the finished product Design for standardized bolted connections and repetitive floor plates c an increase speed of construction Reducing onsite risks
Steel use reduces the number of workers onsite (approximately 10 to 20 per cent of the labor needed for concrete construction), reducing accident liability for builders Preassembled steel packages can be lifted straight from the truck in sequence Offsite fabrication relieves congested and hard to access sites Reduced noise and dust and construction times ease disruption to current occupants and neighborhoods For domestic housing, steel framing, roofing and cladding offer more termite-free and fire resistant abodes than with other commonly used building materials Sustainability and waste reduction
Waste removal is significantly less than for a concrete building More than 95 per cent of all structural steel is recovered and reused or recycled Steel buildings inherently lend themselves to structural addition and modification easily Independently certified steel fabricator members of the asi’s environmental sustainability charter attract an extra green star point for projects Savings in freight and materials through not having to use and remove temporary formwork The design can be future proofed for longer life such as provision of large beam penetrations to accommodate future services
Composite construction is a method whereby a concrete floor slab is utilized as part of the beam system. The slab acts as a concrete flange to the beam. As the beam and slab are of different materials, the size of the concrete flange is scaled down using a modular ratio where the young's modulus of steel is divided by the young's modulus of concrete. When these two elements bend, the top of each element is in compression and the bottom in tension. Because the bottom of the concrete is in tension of the top of steel is in compression this causes shear along the interface of the two materials. To overcome this a steel stud is welded through the metal deck. The stud is designed to take the shear force. The composite system consists of a concrete slab cast on profiled steel decking acting compositely with gluelaminated timber beams. Composite action is achieved with coach screw shear connectors between the beams and slab. The connectors have been tested in 'push out' shear tests and a three-point bend test of a full-scale floor slab has been completed. The composite system is more than three times as stiff and almost twice as strong as the same beam/slab configuration without composite action. Richard persuade, dry dig by Symons the structural engineer - 21 February 2006 Euro codes are a full set of structural design codes for building and civil engineering that used across europe to open up trade boundaries allowing designers, and manufacturers to supply designs and products to other coun tries across the continent. Conceived over 30 years ago, the eurocodes are now landing on the desks of engineers, and are expected to be fully adopted in 2010. For this reason, the eurocodes were used for the design comparisons.
In 2004, the steel construction institute published a study comparing the costs and construction programme of various methods of steelwork and concrete framing solutions that reflect modern construction techniques to determine which is the most cost effective. The study looked at two types of buildings, costing and programming each of them. The study also looked at other aspects of the building, which can be affected by the choice of framing solution such as foundations, external elevation treatments and mechanical/electrical services. The study was motivated by the egan report, which looked at the construction industry and how to lower costs. The report encourages offsite construction to improve speed and q uality on site. People are starting to use tree planting as a way of offsetting carbon emissions. This is because of trees absorbing carbon dioxide from the atmosphere. One of the problems is that once a tree reaches maturity it stops absorbing co2, then the next problem is when it dies and decays it starts to release co2 back into the atmosphere. One solution round this is to store the carbon in materials, b y using the timber as a construction material. The way in which timber is used us also key in reducing co2 emissions. Timber should be dried before it can be used as a material, and it must be. One method is by kiln drying. Kiln drying is an artificial method of drying the timber by heating it up and in turn using fossil fuels, emitting co2. This defeats the point of the object. The sustainable alternative is to allow the timber to dry naturally under co ver. The ideal situation would be for people to use natural unaltered timber and d esign buildings within its limitations. However, due to human nature and the endeavour to improve, we are going to build higher and wider buildings that are filled with more objects and fewer supports. For this reason, we must come u p with more innovative and sustainable solutions to overcome these challenges. We must harness timbers ability to lock co2 into its structure and adopt methods to manipulate its properties. One of these engineered lumbers is glue laminated timber, commonly abbreviated to glulam in the industry. Timber in the uk as a building material is widely used, but not so much as for major building components such as beams and columns. In our history, we used to use great oak timbers for roofs and beams, but due to time it takes to grow these massive timbers, it was not long until demand outstripped supply. Moving into the 21st century with the use of high strength glues, we are able to utilise fast growing tree species and mechanically bonded the timbers to form sizes and strengths that rival the oak timbers. These mechanically glued timbers are referred to as glued laminated timber, which has been abbreviated to glulam. In sustainability, the social impact on an area cannot be discussed without also discussing the environment and economics. The introduction of an industry can create an economic wealth for the local population that can lift certain areas out of poverty. This can be balanced against the environmen tal impact on the are by such industries. Industries can create noise and vibration, dust, local climate, ecology, soils, heritage, and archaeology as a by product of the manufacturing process. Initially i thought that the timber would have a great depth of construction as compared to steel. The depth of steel beams were indeed shallower than the timber beams but because the steel beams require a concrete slab needs to span from beam to beam, the overall construction depth of the steel beam plus the slab is only marginally shallower than the overall timber floor construction. The shallowest overall floor construction is of the concrete flat slab because you do not require a beam as such; the slabs span directly to the columns. REFERENCES: Read MORE: http://www.ukessays.com/essays/construction/a-comparison-of-concrete-steel-and-timberconstruction-essay.php#ixzz3lt9y6sck Read more: http://www.ukessays.com/essays/construction/a-comparison-of-concrete-steel-and-timberconstruction-essay.php#ixzz3lt9lxajg Https://sourceable.net/timber-vs-steel-vs-concrete-structures/
