Week 2 logbook

Week 2 Learning Summary Basic Structural Joints

Structural Systems The below image shows examples of structural systems introduced this week excluding hybrid systems which is a system that has a combination of skeletal and another system, for example the Beijing Olympic swimming cube that is a hybrid of a skeletal frame system and a membrane system made of ETFE ( see image below of building during construction).

Three basic structural joints were introduced to us this week including pin joints, fixed joints and roller joints, as shown on the right. The image depicts each joint and their representation form used by engineers in their drawings.

Pin joints -

allows rotation Resists vertical and horizontal motion Often used in truss systems

Fixed joints - resists all motion - Most complex to calculate-subject to bending Roller joints resists motion perpendicular to rollers - Not as common in construction as pin or fixed joints - Useful when a joint needs to expand or contract (Ching, 2008,pp2.30)

Jessie Angus 698736 ENVS10003

Construction Systems There are three main systems in construction, the enclosure system, structural system and the service/mechanical system.

Enclosure system consists of the outer shell of the building (roof, exterior walls, doors and windows) - Protection from the weather - Dampen noise - Provide security and privacy - Windows provide light and air - Doors provide access Structural System -

Frame and foundation of the building Includes but not limited to columns, beams, floors, roof structures

Service system -

Provides utilities Includes but not limited to, potable water supply, sewage system, heating and cooling systems, electrical systems (Ching, 2008, pp.2.03)

Week 2 Studio This weeks activity was to construct a structure/frame that could bridge across a 1500mm gap with 600 x 100 x 2mm piece of balsa wood. My group gathered and discussed what the best solution would be and all agreed to do a truss like structure. We sketched out a few possibilities and the outcome we hoped for looked something like the top truss below ((a)). Although as time progressed and material ran short our truss ended up looking more like the truss labelled (b).

Another thing we discussed as a group before we began constructing was how we were going to get such a long stable structure with as little material as possible. We came up with a plan to overlap the base of the structure with the middle piece overlapping the two base side pieces (as shown below). This would enable the structure to become longer but would also help distribute the load making the structure stronger.

As you can see in the above image the structure was not as strong as originally thought and failed after 11 blocks were applied. The structure failed directly under the load as the triangles snapped, bent and gave way to the applied load. There could be several elements to why this failed some namely being that there were not enough supports running along the bottom and top to better distribute the loads weight, the fragile material, the unevenness of the triangles and the joints we created out of blue tack and tape.

As truss (b) shows it didn’t have many (or no) supports running along the top and bottom making it more venerable when a load was added.

(a)

(b) During the building process when everything began to be stuck together we were faced with the problem of the triangles snapping due to fragile size and material.

Although after some patch ups it was time for the structure to be tested.

Although after looking more closely at the structure post test all the joint remain relatively intact and the most obvious fault shown is the snapped triangles which is most likely due to inadequate support and fragility.

Week 2 Studio Looking at other group’s structures The below structure proved to be the strongest after assisted help (weighting/holding down the ends) although, without the help, the structure failed after only 6 blocks due to twisting the load off. The structure remained in tack and bent back to its original position after the load was removed.

The strength of the structure may have come from the decision to use the balsa wood on its side for the rails along the sides, By using the balsa wood on its side it puts the weight on the strongest part of the material as underneath the top layer is several other layers making it stronger. Whereas, by using the balsa wood flat down it is more likely to bend and snap along the grain as the material is thinner and more fragile in this state.

Because of this feature it became stronger than a truss structure which was a surprise. Although, after looking at why it was stronger (strongest side of material used) it is easy to understand why.

Another group’s structure which was constructed by heavily sticky taping balsa wood slats together in a straight line posed to be one of the weakest.

Although the structure on its own was strong due to it being wrapped in tape, it failed with only a few blocks by a massive bend in the middle. This was due to the structure having no supports leaving the applied loads weight to head sideways but mostly down.

Glossary Ethylene Tetrafluoroethylene or ETFE: a transparent polymer that is used instead of glass and plastic in some modern buildings (Craven, 2014).

Membrane: any thin pliable sheet of material (the free dictionary, 2014) Bracing: Make (a structure) stronger or firmer with wood, iron, or other forms of support (Oxford Dictionaries, 2014)

References Ching, F. D.K. (2008). Building Construction illustrated.

Hoboken, NJ: John Wiley & Sons, Inc. Craven, J. (2014) What is ETFE?. Retrieved from http://architecture.about.com/od/construction/g/ETFE. htm Oxford Dictionaries. (2014). Brace. Retrieved from http://www.oxforddictionaries.com/definition/english/br ace SIAP Architectural Discourse. (August 22, 2008).

Beijing National Swimming Centre: Blue Cube. Retrieved from http://siap.org/goftman/2008/08/beijingnational-swimming-cent.html The Free Dictionary. (2014). Membrane. Retrieved from http://www.thefreedictionary.com/membrane