ENVS10003 CONSTRUCTING ENVIRONMENTS A01 LOGBOOK WEEK 2 Studio Report The main task in this week’s studio is about building a bridge long enough to span across a 1500mm gap using a piece of balsa, glue and tape. The basic concept of our design is ‘I’ form. Two ends are connected to table and one strip is set in the centre to hold on the item just as the sketch shows. The problem of this basic design is that one strip may not be wide and strong enough to hold a big and heavy item. Thus setting two main strips and leaving some space between those two pieces may be more appropriate. Reason to choose ‘I’ form:
Simple structure, easy to cut and build, beneficial for saving materials Reduce connection points to increase the strength of the bridge
The width and length of the main strips are important because two strips are used to load an item (ignore height, only one layer). They also have to be long enough to span across the table but not just touch the two ends of tables. Each long strip consists of three short strips (600mm×12mm×2mm). They are connected by tape, one strip is overlapped by another as the photo shows. The overlapped length is about 60mm. Therefore the actual size of the long strip is 1680mm×12mm×4mm.
Connection of 2 short strips Unit: mm
The sketches above show a detailed structure of the whole strip. Structures of the two main strips are the same. The distances between two strips at two ends are not equal due to limited time, one is about 80mm, and the other one is about 100mm.
During actual building process, we start to doubt whether the two strips are strong enough to load certain force. Therefore we use the remaining material to complete internal structure instead of breaking them into two parts and setting them at ends of the bridge. There are several variations in construction process as shown in the figure. The first design is the simplest one, while compared to second design, a triangle internal structure is more stable and stronger. Actually when building the bridge, the remaining material is not enough to set too many triangles, therefore they are only set at the centre and two ends of the bridge. Equilateral triangles turn to be isosceles triangle in order to expand the triangle area. All the connection points are wrapped with tape.
Wrap tape for connection point
Central part of the bridge
Final internal structure of triangle form
As shown in the sketch, the strips are connected to the table by horizontal tape.
Because of limited time and no extra pieces of balsa, we just wrap tape in a hurry. However it can be further improved.
When tutor started to press the bridge by a piece of balsa, the bridge started to bend, it is obvious in the photo. Withstanding bigger force, the bridge broke at where the two short strips were connected. Then tutor press another unbroken bridge at where has no triangle (circled area as shown). Finally the connection point to the table broke. Two fractures happened due to weak connection points (both strip connection and connection to table). Tape may not be strong enough to withstand large force. Another reason is that only one layer is not enough to load vertical force. The advantage of this bridge is that there is no rotation force and the internal triangle structure is stable enough to disperse the horizontal force.
Group 1’s design looks elegant and creative. Internal joints are wrapped by tape, connection to table is fixed joint therefore it is very stable. The whole structure is flexible due to rotation force, this design shows the characteristic of balsa which is soft. However it breaks at one end that has only one fixed joint, which may be less strong than the other end.
Group 2 design
Connection to table
Group 2’s design is quite simple, connection to table needs to be paid attention to because the strip just touches table there’s almost no space left as the photo shows. When pressing that bridge, it broke in a sudden due to weak connection to table.
Compared to all the groups, group 3 may have the strongest joints because both pins and tape are used to combine four pieces of balsa together.
Sketch of group 3 joint According to other groups’ design and tutor’s suggestion, connection to table and internal joints can be strengthened by adding one more layer, vertical tape and pins. Then the structure will be stronger to withstand larger force.
Learning Loop Structural Systems:
Solid: has a certain structure (e.g. bricks, stones) Surface: e.g. Sydney Opera House Skeletal (frame system): efficient way to transfer loads down through Membrane: least common, efficient and cheap, e.g. sports (large area) Hybrid: efficient, e.g. birds structure in Beijing Olympic
Construction Systems: Enclosure system Structure system Service(mechanical) system
The shell or envelope of a building, consisting of the roof, exterior walls, and doors. Support and transmit applied gravity and lateral loads safely to the ground without exceeding the allowable stresses Provide essential services to a building (e.g. water supply, sewage disposal system, heating, ventilating, air-condition, electrical system, vertical transportation system, firefighting system, waste disposal and recycling system).
Consideration of construction systems
Performance requirements: e.g. structural compatibility, integration and safety, fire resistance, allowable thickness of construction assemblies, control of heat and air flow, water vapour, accommodation of building movement, noise reduction and sound isolation, resistance to wear, corrosion, and weathering. Aesthetic qualities: Desired relationship to neighborhood, preferred qualities. Economic efficiency: Initial costs (budget), life-cycle costs (e.g. maintenance and operating costs, energy consumption, and investment) Environmental impacts: Energy and resource efficiency.
Environmentally Sustainable Design Embodied energy is the total energy used during all stages of a material’s life. Common ESD strategies: Local materials Thermal mass Insulation Wind energy Solar energy Material Cross Smart sun Night Air Water efficiency ventilation deign Purging harvesting
Structural joints: Roller joints: sliding doors
Pin joints: door handles
Fixed joints: table corner
In the studio practice we understand more about the structural joints, the joints may cause collapse of the whole bridge, therefore it is very important to complete every connection point well. A good structure must load both horizontal and vertical force well. We should have a complete design first, vary according to actual situation, and reflect on the reason of collapse and potential development of the design.
Glossary Appendix Structural Joint: ‘the different configurations in which two different pieces of material can be attached to each other, generally by welding in the case of metal or an epoxy in the case of plastic or wood (Campbell, n.d.)’ Frame: ‘the skeleton which is usually made of steel, wood or reinforced concrete, which is designed to withstand a load in a lightweight economic manner. Some of the structures that use frames are folding ladders, suspension bridges and the roof of a house (Ask, n.d.).’ Column: ‘a vertical element, usually a slender shaft, that provides structural support by carrying axial loads in compression; columns are also subject to buckling. Columns may be exposed or hidden in walls; constructed of precast concrete, masonry, stone, or wood or of steel wide-flange, pipe, or tubular sections; they may be plain, fluted, or sculpted, with or without a capital and base. Columns may also be nonstructural, used for decorative or monumental purposes (Merriam-webster, n.d.). ’ Bracing: ‘ties & rods used for supporting and strengthening various part of a building used for lateral stability for columns and beams (NCRS Construction Dictionary, 2008).’ Tension: the influence of pulling the particles of material to stretch and elongate the material. Span: ‘the entire horizontal distance between structural supports or the width of a house (NCRS Construction Dictionary, 2008).’
REFERENCE Ask (n.d.) What are some examples of frame structures? Retrieved August 11, 2014 from http://www.ask.com/question/what-is-a-frame-structure Campbell, C. (n.d.) Types of Structural Joints, retrieved August 11, 2014 from http://www.ehow.com/list_6819340_types-structural-joints.html Merriam-webster (n.d.) Column, retrieved August 11, 2014 from http://www.merriamwebster.com/dictionary/column?show=0&t=1355360075 NCRS Construction Dictionary (2008) Definition of BRACING, retrieved August 11, 2014 from http://www.engineering-dictionary.org/NCRS-ConstructionDictionary/BRACING NCRS Construction Dictionary (2008) Definition of SPAN, retrieved August 11, 2014 from http://www.engineering-dictionary.org/NCRS-Construction Dictionary/SPAN