Envs10003 w 02 logbook

ENVS10003 CONSTRUCTING ENVIRONMENTS WEEK 02 LOGBOOK CONTENTS

01_ Studio Report

02_Learning Loop

03_Grossary Appendix

04_Referenc e List

Bridge truss-pratt, M Franzen, 2012

01_Studio Report Activity ‘Frame’ (Build a stable structure to bridge across a 1500mm gap) PROCESS 1 Construction Concept Design Plan A: Build the bridge in a shape of arch with parker truss.

Constraints: Constraints of material. It’s hard to find a spot to put any objects on to test the variety of stresses and loads.

Plan B: Build the bridge with bendy wood sticks on both side in warren truss, and the platform on the top of the middle constructed by another horizontal wood stick underneath.

Constraints: Even though the material might be enough, the warren truss structure is not as strong as the parker truss structure.

2mm 600mm 100mm

Consideration: As the wood material is made of a 600mm x 100mm x 2mm piece of soft balsa wood, it’s good in tension but not good in compression. Thus, we need to consider how to organize the existing material, how to join the members together and if we need to make any changes.

PROCESS 2 Construction System LOAD

As the object sitting on the bridge would apply loads on the soft wood stick which is good in tension, the wood would not be able to hold the weight so that it would bend downwards. Inspired by the e-learning session of Construction Joints, we decided to use the warren truss structure to help to transfer the loads through the truss in order to undertake the weight of the object.

Instead of using single weak joint such as the mitre or butt joints to hold the members together, we decided to use pins and tape combination to make the joints stronger for maximum support in order to avoid collapsing.

As the length of the balsa wood is not long enough to build a single bridge beam, we cut 3 species of wood stick to tape them together in folding way in stead of gluing.

It can allow the load pass through the wood stick underneath without collapsing.

PROCESS 3 Deformation & Stability After the bridge was built, we started to add a wood block on the top of the bridge (the rectangle platform). When the object landed on the surface of the platform, the load was applied. As shown as the graph below, it shows the load paths through the bridge structure. Eventhough the compression is directed downwards eventually, the support of the warren truss allowed the load transfer through it.

LOAD PATH

Next step, instead of putting light weight object on the platform, we started to put a heavier object such as a iPhone up the top. As the truss structure we used is a method of fixed joints. The weakness is that it would allow the bending occur as the magnitude of the load increases.

As shown in the graph above, when we put a heavy brick on the top of the bridge, the magnitude of the load stremely increased. Besides, the soft wood stick is good at tension, when it can not afford the forces transferred from the load and the fixed joint, it started bending badly. Eventually, the compression is overweight in order to break the wood stick. Then the bridge started collapsing.

PROCESS 4 Comparison Comparing to the bridge built by other groups, I found that they used different types of jointing method, truss and ways of using materials. For instance, in the graph on the left hand side, the group used butt butt joints. As shown

as above, the load transferred through the vertical truss downwards. Since, they cut the wood in about 3cm width, the affordability of the wood is larger in order to undertake the weight of the compression coming from the blocks on the top.

In the graph shown on the right- hand side on the bottom, the group also used warren truss as our group did. However, the difference is that they glued bunch of pieces of rectangular wood sticks on the top. In which, it allowed the object to load on the flat and wide surface in order to reduce the compression force. However, the bottom is only constructed by two thin wood sticks without any truss. It would result in the bridge leaning towards both side when the magnitude of load applied becomes bigger.

02_Learning Loop CHING: 02 the Building (2.08-2.11)

Construction Joints E-learning, 2014

There are 3 basic construction joints.

Truss system (Pin joints)

- Pin joints - Roller joints - Fixed joints

A Framework for analysing Form E-learning, 2014

As the load applied on the beam, the compression force would be transferred through the columns and beams in horizonttal or vertical direction. However, when the force transferred to the beam on the left hand side, the load would be directed upwards as the compression of the beam on the right hand side causes to rotation.

Therefore the reaction forces would be directed downwards.

Load occur in one member. If it’s fixed joints, the bending would occur.

Assimilating Knowledge Referred to the studio activity. When a live load coming from the object applied on the top of the bridge. The compresson force would be transferred through the truss. However, the collapse points is also depended on the effieciency of material and the types of the truss. Through the activity, we need to consider that when we are constructing or designing a building, it is necessary to consider about the budgets contraints, initial cost and the allowable tolerance etc. This time, we can see the constraints of the material is a problem for us when we try to frame a stable strucutre.

03_Glossary Appendix 1. Structural Joint- There are many types of strucural joints using in the building construction. Such as fixed joints, pin joints and roller joints.

PIN JOINTS

2. Frame - a rigid structure that surrounds something such as a picture, door, or windowpane.

3. Column- it is used to support floor and rood stucture. In architecture or structural engineering, it is a structural element that transmits, through compression, the weight of the structure above to other structrual elsments.

4. Bracing- (Truss) It is a system of braces used to strengthen or support the building. It ought to be perfectly adequate.

5. Tension- it applys a force to (something) which tends to stretch

6. Span -a section between two intermediate supports

it.

04_Reference List A frame for analysing form, e-learning, 2014, viewed 8th August 2014. Retrieved from, https://www.youtube.com/watch?v=KJ97Whk1kGU&feature=youtu.be

Bridge truss-pratt, M Franzen, 2012, viewed 8th August 2014. Retrieved from, http://mfranzen.ca/images/pics/classes/des/bridge_truss-pratt-l.jpg

Ching, F. (2014). Building construction illustrated / Francis D. K. Ching. Hoboken, New Jersey: John Wiley & Sons, Inc., 2014, pp. 2,02-2,04 Construction Joints, e-learning, 2014, viewed 8th August 2014. Retrieved from, https://www.youtube.com/watch?v=kxRdY0jSoJo&feature=youtu.be

ESD &Selecting Materials, e-learning, 2014, viewed 8th August 2014. Retrieved from, https://www.youtube.com/watch?v=luxirHHxjIY&feature=youtu.be

Structural systems and forms, e-learning, 2014, viewed 8th August 2014. Retrieved from, https://www.youtube.com/watch?v=l--JtPpI8uw&feature=youtu.be