Construction Logbook: Week 10-References

ENVS 10003 CONSTRUCTION LOG BOOK

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Week 10: When Things Go Wrong eLearnings

• Elasticity and Stress • Lateral Loads • Strategies to Resist lateral loads • Environmental Awareness and Economic Efficiency of Materials • Unsuitable Materials


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eLearnings When things Go Wrong

Elasticity and Stress -Each material has distinct properties of strength, elasticity and stiffness, The most effective materials are those that combine elasticity with stiffness -Elasticity-the ability to deform under stress-bend, stretch or compress-and return to its original shape with the applied stress removed. -Every material has an elasticity threshold-beyond this limit it will break or permanently deform. -Materials that undergo deformation before actually breaking are termed ductile -Stiffness is a meaner of the force required to push or pull a material to its elastic limit. -A materials stiffness, along with its cross sectional stiffness are important factors when considering the relationship between span and deflection under loads Practical Considerations -The dimensional stability of a material as it responds to changes in temperature and moisture content affects the manner in which it is detailed and constructed to join with other materials -The thermal conductivity or resistance of a material determines its resistance to wear and abrasion, its durability in use, and the cost required to maintain it -The ability of a material to resist combustion or withstand exposure to fire, and not produce smoke or toxic gasses, must be evaluated before using it as a structural member or an interior finish

http://www.etomica.org/app/modules/sites/MaterialFracture/Images/SSPicture2.jpg


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Lateral Forces Wind and earthquake forces have different effects or structures: Wind Force is a function of the size of the exposed surface area to the amount of wind action -Minimum active value at the base -Maximum active value at the top -Effects cantilevered structures for severely as they have reduced vertical support Earthquakes Force is a function of the amount of mass above a foundation system -Forces become exaggerated when the structure is tall and narrow -Seismic forces act at the base and can abruptly reverse direction during quake

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Strategies to Resist Lateral Forces Structural Bracing and Sheers Diaphragms -Bracing of the structure and diaphragms/sheer walls-transmits loads to cross braced walls

http://timber.ce.wsu.edu/Supplements/nau/tutorial1/images/frame.gif

Moment joints -Flexible joints allow for increased movement and compensation for lateral forces-increases structural elasticity

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Structural Separations -Can be used for irregular construction; where one end may be effected more than the other when a lateral load is applied

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Moment Resisting Frames -Where the horizontal and the vertical reinforcing of a structure act together to resist lateral loads

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SBI -Seismic Base Isolator-separates the structure from the ground through a series of foundation plates composed of a lead core and rubber and steel plates

http://www.bridgestone.com/products/diversified/antiseismic10.gif

http://www.seismicisolation.com/sites/default/files/base-isolation-elements.jpg


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Specific Selection of Materials with Environmental Awareness and Economic Efficiency Environmental Considerations: The Material Life Cycle

• Extraction process -Renewable or nonrenewable?

• Processing of raw materials manufacturing -How much energy and water is required?

• Packaging -How much energy and water is required? -Is it over packaged?

• Transportation -Proximity to destination -Availability locally or shipped from a distance?

• Usage -Does the material perform as intended function efficiently and effectively?

• Maintenance -How durable is the material or product and does it require frequent maintenance? -How does the material affect the indoor air quality

• Recycling/disposal -Toxic by-products? -Waterborne effluents -Atmospheric emissions -Solid wastes

http://etool.net.au/wp-content/uploads/2012/11/etool-LCA-graphic.jpg


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Material Selection Relies On:

• Health and IEQ-Indoor Environment Quality -choose material that is healthy on an every day basis-more comfort equals more

productivity -reduced VOC-volatile organic compounds -minimise dust capture capabilities -minimum cleaning process • Waste/Recycling/Recycled -renewable resources-bamboo floors rather • Energy Use and Embodied Energy -low embodied energy -low transport cost-Australian made • Pollution -minimise waste-low embodied toxins -production process may be environmental damaging -organic and natural materials • Life Cycle -economic efficiency in maintenance and recycle -design with purpose and durability

http://www.glazette.com/fck/editor/userfiles/green-buildings1(4).jpg


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Unsuitable Materials Case study on Beach house -Cracking north facing fascia board due to irregular heat transfer-was painted black on one side and this caused warping and deflection -Zinc-aluminum cladding glued to a plywood base was used to resist corrosion -Glue was insufficient structural material-started to blister due to extreme heat exposure -Glue not a suitable method for construction in these circumstances-caused mass delamination between plywood and corrosive resistant coating -Structure was re-clad with marine grade plywood, -Clad over the top of old material and problems arose due to condensation and chemical reaction (galvanic reaction) between the zinc aluminum cladding and plywood Summary: Material needs to be suitable for the required performance in a particular environment Material and construction technique requires constant performance over the life and duration of the structure The Statue of Liberty -Copper oxidization of exterior -Corrosion of the Iron rib structure and the copper skin -metal compatibility- dissimilar metals react and corrode-Galvanic Reaction -Similar metal resist corrosion -Iron ribs replaced with Stainless Steel and Teflon coat Note: For non-corrosive construction, metals must be similar; close to each other on the chart. The greater the distance between the metals the greater the corrosive reaction.


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References All information was sourced and adapted from

• Ching, Francis D.K., (2008)., building construction illustrated., 4th ed., New York: Wiley.

Images are referenced individually All images that are not referenced were taken by myself on site of construction

Documents

Construction Logbook: Week 10-References