Lecture 3B_building Materials

Lecture XX: Design Technology, ARCHTECH 312

DESIGN TECHNOLOGY OF

BUILDING MATERIALS

Course Coordinator: Prof. Alessandro Melis 31/07/2014

Design Technology of Building Materials

Building Materials:

Evaluation of Structural

Materials


Evaluation of Structural Materials

Basic loading on building structure leads to the occurrence of the following phenomena: 1. Stress: Application of force per unit area (N/m2 or Pa). Depending on direction of

force, it is of the following kinds: • Compression • Tension • Shear Stress

2. Strain: is the possible deformation in length, cross section area and/ form of the material on application of stress. It is calculated as a ratio of change in length or area of the material. It describes the plasticity or elasticity of the material, its possibilities and flexibility under various loading conditions.



Therefore, a material is tested for the following strengths to ascertain its potency and performance before its application as a structural element in construction: •Yield strength: The minimum stress required to cause the first smallest deformation of the material. •Compressive strength: The maximum compressive or shear stress required to cause failure of material. •Tensile stress: The maximum tensile stress required to cause failure of material.

Stress- strain ratio or Young’s modulus: is another method used to ascertain the strength of a material, i.e. its property of Elasticity, or the capability of a material to re-attain its shape after being deformed due to application of any kind of stress. A graph is usually plotted to chart the maximum stress up to which the strain beard by the material does not cause permanent deformation.



Ductile material: Ex. Structural steel, that bends and yields to a high stress level without being damaged.

Brittle material: Ex. Timber, that cracks immediately on application of excessive stress


Building Materials:

Examples of Structural

Materials


Brick Masonry

Brick Masonry: Use of Bricks joined together by Cement Mortar. Details as follows: •Brick Composition– Modern fired clay bricks comprising of silica, alumina, lime and even reusable materials such as fly-ash. •Mortar Composition– 1:5-Cement: coarse sand ratio Design Details •Each coarse of brick shall be interspersed by a binding mortar layer of 10-12mm (maximum), there should be no vertical joints. •Depending on Architecture detail, the elevation may be plastered in 12mm cement plaster or be raked-in 10mm to create aesthetic grooves. •They can be single or double brick walls depending on climatic requirements and may be interspersed with cavity or insulation accordingly.

Fly ash brick: Comprising of Flyash which is otherwise a polluting material, this is easier to manufacture as it is self cementing, and does not require firing. Allows lesser moisture seepage and is stronger than regular bricks. Moreover it is an energy saving material.


Brick Masonry

Example: London School of Economics, Student Centre. Architects: Odonell- Tuomey For full video refer: http://www.odonnell-tuomey.ie/webpage/process.htm Architect is explaining how they achieved the complex effect of slanting walls in brick masonry by simply stacking them at the corners, hence none of the bricks had to be cut to give this sloping effect.

http://www.odonnell-tuomey.ie/webpage/process.htm












Brick Masonry

Brick is also used to construct the foundation of the load bearing brick-wall. A. Concrete Base B. Stepped brick footing C. Foot resting for flooring at internal Plinth

level D. Damp proof course, preventing moisture to

travel upwards into building from the ground

E. Wall plate F. Floor joist G. Concrete plinth-base

•Brick is also used to construct structural arches for door and window openings or as architectural design elements. •It allows equal distribution of load from the top centre. •The most important is the keystone that holds the arch together in place.


Timber

Timber: Wood undergoes treatment and seasoning to produce timber for building construction. Timber is structurally as the following elements: •Beams •Columns •Trusses •Framing and bracing •Timber Staircase Example: A complex modern example is the Tamedia office building in Zurich by architect Shigeru Ban. Timber was largely proposed as the main structural system from a technical and environmental point of view.


Timber

Timber Structure: beam and column joint detail for a 7storey building Tamedia office building in Zurich by architect Shigeru Ban Refer: http://www.shigerubanarchitects.com/

http://www.shigerubanarchitects.com/









Timber

Design Details for timber structures: •The minimum dimensions of the timber cross section are calculated using the limit state method which is based on yield strength and young’s modulus of the material, along with the expected loading and design span of the timber member. •Timber is a brittle material hence it is designed for short spans. •Timber joineries can be simple tongue and groove/ butt joints or complex depending on the purpose. Members can be nailed or bolted. •Incorporation of steel bolting systems in the joineries helps and otherwise brittle material attain flexibility, making the joints stronger towards shear and lateral loads. •Screw sizes for bolts need to be decided carefully so as not to crack the timber. •Timber is not a fire safe material, hence more modern and engineered prototypes that are tested as fireproof timber should only be used in fire safety zones.


Concrete (including R.C.C.)

Structural formwork: •Columns •Beams •Lintels •Large span Slabs •Retaining walls and basement works •Column footing and foundations •Staircase support

Example: Sir Paul Reeves building, AUT by Jasmax Architects Structural solutions for this building reflect the need for flexibility in internal planning, and include concrete shear walls around the central core and perimeter columns supporting long-span castellated floor beams to yield large open floor plates.

(left) the tri-column of Reinforced concrete on the

corner building junction (right) reinforcement of

the RCC tri-column during construction.


Concrete (including R.C.C.)

Design details for Concrete and RCC structures: •Concrete performs well in compression and cracks in tension. Hence, steel is used in the tension zone to combat this stress in both beams and slabs. •Spans and cross sectional dimensions are designed as per limit state method that calculates these according to loading and bending moment. •For lateral forces due to wind and earthquake, shear walls are designed in complex buildings. Shear walls are RCC slender walls extending through the vertical rise of the building. It cannot have any openings and its thickness is designed as per loading stress. •The material can withstand high temperatures due to fire, unlike steel and timber, hence can be used in fire staircase and refuge enclosures that are safety zones. •Waffle slabs can be used to decrease overall beam depth and increase span of spaces between columns.

Innovation by Alarcon Associates


Steel

Structural Steel formwork: •Beams •Columns •Structural bracing •Staircase support •Component of R.C.C. Others: •Space frames •Exterior façade framing

Example: The Owen Glenn Building, U.O.A in Auckland, by FJMT Architects. •The building is an amalgamation of RCC and steel structural design. •Steel connections and braces provide flexibility in the structure that are important in a seismic zone. •The structure would be able to withstand strong shear and lateral forces. •Steel has also been used in order to have large span clear aesthetic spaces, allowing clear vision and movement.


Steel

Designing steel structures: •Steel performs well in tension, i.e. it is well designed for bending moment. •However, it slender members tend to buckle easily, hence require lateral bracing and supports. •Steel connections can be simply welded or bolted together. •Complex connections can be formed using web steel sections, that allow multiple members to be connected at one edge. •Gusset Plates need to be appropriately sized and marked for bolting as per design thickness and number of connections when designing trusses. •In case of Gusset plates, bolt sizes and spacing should be designed carefully to avoid torsion rotation. •Steel melts under high temperatures, hence should be given proper cover by concrete when used in fire safety zones.


Building Materials:

For Non-Structural

Components

•Doors, Windows, Glazing •Insulation •Water-proofing •Flooring and Finishing •Shading Devices


Non- Structural building components

Function: Doors, windows and glazing Materials: timber, aluminium, steel and glass Aluminium section- curtain glazing •The use of these materials requires low maintenance, they are aesthetic, offer sufficient, though not very high acoustic and thermal insulation. •Newer technology and awareness is causing architects to switch to double glazing options that not only seal the building into being thermally isolated by avoiding air leaks but is also preferred as it saves energy for constant internal thermal balance. The cavity between the two glass surfaces can vary from a few mm upto a meter in depth. Example: Swiss re building, London, Architect Norman Foster.



Function: Insulation Materials: Polyurethane panels, Urea Foam, Glass wool •Material selection and thickness depends on the climatic location of the building. •Thermal values (R-U Values) and time lag are significant in deciding this as well. •Some of these materials may be toxic and flammable like foam, hence newer materials approved by various green building certifications shall be used instead. •Materials like rock wool are recyclable, durable, non toxic and non-flammable, hence are more recommendable. Cotton insulation is another material that is non-toxic and is recognised by green building rating organisations as safe, however, it is not completely effective in sealing the building from thermal bridge phenomenon. •Another innovative material is Aerogel. A relatively new material and is known to be the least dense man material. It has an extremely low thermal conductivity 0.03W/mK.



Function: Water proofing Materials: •DPC: used as a vapour barrier between the foundation and the elevational wall •Bitumen: membranes are used on the building roofing •Polyethylene sheeting (Geotextile): in the basements along the walls, preventing water to seep through them. •Hycrete: A modern material engineered by adding mixtures to regular concrete making it waterproof in itself, protecting steel reinforcement.



Other Significant materials Function: Flooring Materials: timber, tiles, stone, cement Function: Shading devices Materials •Timber louvers •Concrete bries- soliel •Glass reinforced concrete (GRC) screen •Metal Screen •Metal reflectors


New or Advanced Building

Materials


New Building Materials

2. Phase Changing materials • Materials that change their form when impacted by the smallest change in temperature.

Usually made of metal alloys, the material form responds to rise in atmospheric temperature as the day advances.

4. Nano materials • Are materials engineered at a nano scale (109) to create new generation materials that

are self cleansing for example. Insulation material Aerogel is also a nano material 5. Low e glass • Low emissivity glass prevent excessive heat from being conducted through the glazing

into the building interiors. 6. PV glazing • Use of Photovoltaic panels to harness solar energy.

World fair Pavillion at EXPO in Hannover, Germany, 2000

1. Laminated Engineered Timber: • Man made composite wood boards designed to

precise specifications. • They are versatile and have maximised strength,

loading performance (flexibility and spanning). • They are easier to work with and can be

aesthetically moulded into fluid forms. They are designed to e fire proof as well.

These materials shall be explained in detail in

further lectures on Building Envelope)


Bibliography: List of reading books

1. Aicher, Simon; Reinhardt, H.W. and Garrecht, Herald. (2014). Materials and joints in timber structures : recent developments of technology. Dordrecht, Springer

2. Butler, Robert Brown. (2002). Architectural Engineering Design: Structural Systems. Mcgraw-Hill, USA. (Common for all topics)

3. Elkink, Alide. (2012). Building Basics: Insulation. BRANZ, Porirua, New Zealand

4. M. Hassoun A. A Al-Manaseer. (2012). Structural Concrete: Theory and Design. Hoboken, New Jersey (RCC design)

5. Mckay, William Barr. (1947). Brickwork. Longmans, London 6. Mckay, William Barr. (1971). Building Construction: Volume 1-4. Orient Blackswan,

India (Brick Masonry) 7. Pringle, Trevor. (2012). Building Basics: Steel Framing. BRANZ, Porirua, New

Zealand (Steel design) 8. Steurer Anton. (2006). Developments in Timber Engineering: The Swiss

Tradition. Basel, Birkhauser 9. Structural Engineered Timber Manufacturers Association of New Zealand.

(1982). New Zealand Timber Construction Review. Akron Consolidated, Auckland

Documents

Lecture 3B_building Materials