Windows & Doors
Week 7 Detailing for Heat and Moisture Drainage Walls Overview, Prevent water from flowing through roof sheeting panels Basement and expanding and contracting of gutters to be designed for this. Moisture penetration points Rood$ing Figure 1: Moisture Penetration Points • Water can enter through gaps and splash-‐back from hitting another object. Strategies for stopping water from entering • Remove openings: However if openings cant be removed, Waterproofing can be done by using sealants such as silicone or gaskets made of artificial rubbers. These are both flexible and waterproof materials that can allow for tolerances that cause unplanned openings. These materials wear out and need to be maintained. • Keeps water away: Eves, sloping roofs and roof/wall flashings can do this. Overlaps can be used to on tiles, roof sheeting and weatherboard cladding systems, this works by allowing water to slope away from the building. • Neutralize the forces that move water through openings: The forces consist of gravity, momentum, surface tension and air pressure. Again slopes and overlaps with double cavity brick walls with a membrane and flashing allowing moisture to flow out. At doors there are thresholds and a sloping pavement to direct the flow away form the door. Only a 1% slope is needed and it will prevent water penetration. Capillary action can be broken with gaps and openings which prevent the flow of water and hence water entering. • Air barriers are used to prevent the problems of air pressure, with the tendency for water to be pumped in to the building.
Detailing for Heat Controlling heat aims to, in summer: Reduce heat gain and use cool sea breezes to cool down, while in winter, maximize heat from sun and reduce heat loss. Conduction Thermal insulation: Reduces conduction, bulk insulation has high R values and can be fitted into wall frames. Thermal Breaks: Low conductive rubber materials reducing heat transfer. Double Glazing: Glass is very poor at retaining heat and is where most of the heat is lost in a building. By allowing air spaces between the glass panes it reduces heat loss considerably well, while still letting natural light in. Radiation Reflective surfaces can reduce heat Shading verandahs, eaves, screens, roof gardens Thermal mass Stores heat gained from the sunlight during the day and releases it slowly at night. Best materials for thermal mass are Brick masonry and concrete, water around the building such as a pond or close to the beach can help provide this benefit. Reducing air leakage Building wrap in polyethylene can be both an air barrier and for waterproofing. This can reduce heat loss dramatically when air leakages are all found and controlled.
Materials Rubber • Flexible, elastic, waterproof are good insulators, cost effect and durable. hi • Used for seals at control joints and around openings, $loor lining as they provide grip, electrical insulation and hosing and piping.
Plastic
Paint
• Light, medium-‐low hardness, easily molded into desired shape, can be both ductile and brittle.
• Are liquid untill applied and dry when in-‐contact with air. Can have different colours and applications
• Different types are Thermoplastics, Thermosetting plastics or Elastomers.
• Finishes used to colour or protect a surface. Gloss can be used to waterproof the surface as are non soluble, it is also easier to clean. Needs to be resistant to chipping, cracking and peeling.
• Tend to be waterproof, good insulators, cost effective and can be recycled, meaning low embodied energy. Used for piping and substitute for glass.
Week 9 This week, Kane Construction was so kind enough to let us view their 5 floor extension of the Owen Dixon Chambers which was a commercial building with offices for barristers called “chambers”. The construction process was quite different from a usual building as it was an extension as well as there being limited storage areas and loading bays. The extension consisted of light weight concrete panels (Hebel) and steel structure, due to needing to reduce weight as much as possible as it was sitting on top of an existing building. The structure of the existing building was not to be strengthened. Around the plant area where there was heavy machinery, Bondek was used as a concrete slab system. Construction Program 1. Set up appropriate site accommodation, signage, gantries and hoardings. 2. Erect tower crane off existing top roof. 3. Create a loading bays, storage and hoisting zones. 4. Start erecting steel structural framing system and lightweight concrete planks were placed then grouted up. 5. Internal walls and services placed 6. Glass Façade panels. 7. Finishes, painting, carpets etc. Hebel Hebel panels came in 600Wx 180D and were aerated and lightweight. Being small dimensions it made it easier for lifting it into the building where it was narrow. It had steel reinforcement mesh both top and bottom and inbetween panels to connect them structurally. They would sit on top of steel UB sections and have intermediate supports allowing it to span 5-‐7metres.
Façade Figure 2 Facade Panels, Left: Fixing Plate bolted to slab Facades are imported from China and are glass with a metal frame and tinted. Each panel connects to the slab where there is a rebate and an angle bracket as a fixing plate which bolts the panels in structurally. The panels connect to each other through a male and female joints allowing easy installation and overlapping allowing waterproofing. Hoardings: A high temporary fence or structure enclosing a demolition or a building site during works. Restricts access and provides side protection to the public. Gantry: A structure, which covers a public way and provides protection from both the side and overhead. Hoisting Zone: A zone of the gantry dedicated for the craning or hoisting of materials from the road to the building site. Has to be able to fit large semi trailers and take the point loads.
People involved in Construction of Owen Dixon Chambers Client (Owen Dixon Chambers) Contractor (Kane Construction)
Employees
Construction Manager
OH&S Of$icer
Site Manager
Consultants
Subcontractors
Quantity Surveyors
Engineers
Environmental Engineers
Carpenters
Crane operators
Architect
Electrician
Plumbers
Suppliers
Week 10 Lateral Loads Lateral loads are mostly due to wind and earthquakes. With large structures and being tall and slender there are large amount of surface area and hence large lateral forces. A strong base is needed for earthquakes. Bracing or shear walls as well as rigid connections can be used to resist lateral loads. Shear walls transfer the horizontal forces, vertically down to the footings and rigid connections. Columns and slab connections can be moment resisting (rigid) and prevents a structure from overturning when effected by lateral forces. Roofing needs to be secured as well as it gets uplift and suction from lateral loads travelling over it. In earthquakes if buildings are not symmetry, structural isolation is needed as the buildings will vibrate at different rates. Wind forces on the roof are carried to the ceiling sheeting/diaphragm through the roof and ceiling framing Wind forces on the top half of the wall are carried to the ceiling diaphragm. Wind forces on the bottom half of the wall are carried to the ground through wall framing, slab and footing. Bracing is used to support the wall framing and increase its structural capacity.
Durability issues of Reinforced Concrete Steel reinforced concrete is not immune to the effects of environment. There are environmental factors such as temperature. Durability is attracting more and more world attention and increasing being studied. This review aims to give a brief description the known factors in scientific literature that can influence the durability on concrete. Temperature Daily and seasonal temperature variations will cause changes in the concrete volume. Temperature raises causes concrete to expand and the concrete to contracts when temperature falls and effects are at freezing and thawing. Volume changes in concrete can produce significant stresses in the concrete and these tensile stresses can cause the concrete to crack. Fire Fire around concrete structures can weaken the superstructure and decrease the concrete strength. The heat can cause distortion, excessive deflection and expansion, buckling of the steel reinforcement. Moisture Changes in the moisture content in concrete will result in either concrete expansion as the concrete gains moisture or contraction when concrete loses moisture. As concrete is being cured the surface of the concrete will dry and shrink at different rates to the inner regions of the concrete. If left unrestrained cracking can occur. Contaminants Contaminants in water that were absorbed into the concrete may cause staining, steel corrosion, or sulphate attack. Contaminants include chloride and sulphate salts and carbonates. An increase in the size of salt crystals in the capillaries near the evaporating surface can cause cracking.
Carbonation Concrete undergoes shrinkage due to carbonation. Carbon dioxide in the atmosphere reacts in the presence of moisture cement minerals usually being the carbonic acid. If the steel reinforcement is placed too close to the surface, corrosion can occur as a result. Acid attack Portland cement paste has a high pH value of around 12.5 to 13.5.When it comes in contact with an acidic environment acid attacks the concrete. The reaction dissolves cement matrix into a soft mush. The steel reinforcement depassivates leading to corrosion. Chloride Attack Common sources of chloride are salt spray in marine conditions, chloride contaminated water such as beach sand, admixtures such as Calcium Chloride and the de-‐icing salt. Concentrations of chlorides in the concrete will cause the reinforcing steel to corrode and will also cause the concrete to crack and disintegrate . Sulphate attack Some soils contain alkali, magnesium and calcium sulphates. When these sulphates come into contact with groundwater, they form a sulphate solution. Seawater may also contain significant sulphate content . The sulphate attacks the hardened cement paste. This results in expansion and disruption of concrete and depassivates steel reinforcement . Recommendations to allow structurally stable concrete and reduce collapses and failures. • More concrete cover to prevent carbonation • Increasing the cement water ratio as cement is alkaline and neutralizes acid attack. • Install fire proofing measures to prevent extreme heat transfer • Ensure proper vibrating to make sure no honey combing occurs. • Increase concrete to reinforcement cover so that there is more cement neutralizing the acidic outside environment.