Constructing Environments Log Book
QIULIANG LI 621722 TUTORIAL 18
W01: Loads.………………...2 Basic structural forces and materials…………………3 W02: Structural forms…………………5 Structural joints…………………7 Glossary: Key terms…………………8 Referencing: Reference list…………………9
The structural system of a building must be able to support dynamic and static loads. (Ching, 2008) Dynamic loads: Applied suddenly to a structure with rapid change in magnitude and point of application. The structure will develop inertial forces in relation to its mass. Maximum deformation does not necessarily correspond to the maximum magnitude of the applied force (Ching, 2008). Wind loads: forces exerted by the kinetic energy of a moving mass of air, coming from horizontal directions. Roof angle >30 degrees exerts positive pressure horizontally from wind. <30 degrees exert negative pressure. Earthquake loads: more critical to the structure with horizontal forces. Static loads: Applied slowly to a structure until the static force is maximized without fluctuating rapidly in magnitude or position (Ching, 2008). Live loads: moving or movable loads on a structure, such as collected snow and water. Live loads can act both vertically and horizontally due to the dynamic nature. Occupancy loads: weight of people, furniture and stored materials. Snow loads: weight of snow accumulating on the building. Rain loads: weight of water accumulating in the building. Impact loads: kinetic loads of short duration, such as vehicles. Dead loads: static loads acting vertically downwards on a structure, comprising the weight of the structure. Settlement loads: imposed on a structure by subsidence cause by the differentiation in supporting soil. Ground pressure: horizontal force of a soil mass acting on a vertical retaining structure. Water pressure: hydraulic force of ground water exerting upon the foundation. Thermal stresses: compressive or tensile stresses in materials caused by thermal expansion or contraction.
W01 Basic structural forces and materials Activity: compression Force: It is any influence that produces a change in the shape or movement of a body. It is a vector quantity possessing both magnitude and direction. Force can be represented by an arrow whose length is proportional to the magnitude and whose orientation represents the direction (Newton, 2014).
Initial structural concepts:
Tension forces: When an external load pulls on a structure member, the particles composing the material move apart and undergo tension. The amount of elongation depends on the stiffness of the material, cross section area and the magnitude of the load (Newton, 2014).
The above structures have weak horizontal links , thus, weight cannot be widely distributed to the blocks. As a result, increases compression vertically downwards.
Compression forces: Produces the opposite effect of a tension force. When an external load pushes on a structural member, the particles of the material compact together (Newton, 2014).
This concept inter-locks each block together, which enhances the dispersion of dead load and static loads. Therefore, creating a dependent and very stable structure as a whole.
W01 Basic structural forces and materials Activity: compression continued… Disadvantages: the constructing process of the structure is very time and material consuming. During the demolition phase, there were fewer blocks we could take out as the blocks were dependent on another compared to the other groups, such as below:
The material used for construction is MDF, which is relatively lighter compared to steel and timber. Thus, it does not need a complex structure to support its loads and will still be able to be compressed.
Taking out blocks in our structure caused the forces to become unequally distributed and acting onto one direction. This led to the separation of the tower and ultimately caused it to collapse.
Material properties: • • • • • •
Strength Stiffness Shape Material behaviors Economy/cost Sustainability
Note: Melbourne is built using mostly basalt rock due to the volcanoes that surround Melbourne (Melbourne’s Bluestone 2014).
W02 Structural forms Structural systems: Solid: used in early architecture, such as Egypt. Compression is the main structural action. Surface: plain structure, such as Sydney opera house’s shell structure. Skeletal: most common structure as it is very efficient in transferring loads down to the ground. Membrane: often used to enclose large areas efficiently and cheaply, such as stadiums. Hybrid: structural frames including cladding, skeletal, membrane, etc. Constructing systems: Considerations: • Performance requirements • Aesthetic qualities • Economic efficiencies • Environmental impacts
Enclosure systems: cover of the building, consisting of the roof, exterior walls, windows and doors.
Structural system: to support and transmit applied gravity and lateral loads safely to the ground without exceeding the allowable stresses in its members. • Superstructure: vertical extension of the building above the foundation. • Substructure: foundation. Service systems: provide essential services to the building. • Water supply. • Sewage disposal. • Heating, ventilating and air conditioning. • Electrical systems. • Transport systems. • Fire fighting system. • Recycling system. (Ching, 2008)
Source: (Ching 2008, p. 2.03)
W02 Structural forms Environmentally sustainable design (ESD) considerations (Newton, 2014):
• The utilization of natural elements, such as sun light to save electricity consumption. • Embodied energy: the total energy (oil, water, power) used during all stages of a material’s life. • Recyclability. • Use of materials, such as using wood instead of steel allows less CO2 to be produced. Thus, wood has a more positive carbon footprint. • Carbon footprint: a measure of the amount of greenhouse gases generated during the fabrication, transportation and use of a particular product. Activity: frame With a limited amount of balsa wood available for tower constructing, we limited ourselves into using a triangular structure. This is because it is both material efficient and strong. On the left shows the full height of the tower, however, it was unable to support itself due to the bent supporting columns. Thus, a diagonal supporting column was constructed:
The picture above is the collapsed tower after the demolition process.
This single column allowed the whole structure to support itself upright.
The vertical support columns were cut apart, as a result, the only supporting column could not support the load on top.
W02 Structural joints
Pin joint (W02 s2 Structural joints 2014): Rotation allowed
Fixed joint (W02 s2 Structural joints 2014): No movement allowed
Roller joint (W02 s2 Structural joints 2014): Horizontal movement allowed
Glossary Key terms
Beam Bracing Column Compression Frame Load path Masonry Point load Reaction force Stability Structural joint Tension
Reference list: Ching, FDK 2008, Building Construction Illustrated, John Wiley & Sons, Hoboken, N.J. Melbourneâ€™s Bluestone 2014, video recording, University of Melbourne ENVS 10003, Melbourne. Newton, C 2014, Basic structural forces, Online recording, University of Melbourne, Melbourne. Newton, C 2014, Environmentally Sustainable Design (ESD) considerations , Online recording, University of Melbourne, Melbourne. W02 s2 Structural joints 2014, video recording, University of Melbourne ENVS 10003, Melbourne.