Constructing Environments Logbook Week 4 Summary
Construction Workshop Design Challenge: Span This week’s challenge was to construct a bridge with the capability to span a 1 meter gap whilst supporting the biggest load possible. Our bridge was to be constructed out of 4 pieces of timber, 1 piece of ply and 3 pieces of 1200 x 35 x 35 timber. A design of a truss was agreed on straight away allowing us to get construction away as soon as possible. One of the pieces of timber was cut into 6 200mm lengths, initially with a right angled joint. This was changed to a 45 degree joint after considerations were made as to how we could attach the individual supports to the main beams that run parallel on the top and bottom. The support struts were secured to the top and bottom beams by drilling screws into each connection. We discovered during testing that these screws added a weakness to the overall structure. Final truss design showing connection details Also at the end of construction we added the ply wood across several of the gaps between struts to add additional tensile strength. This was not done in a very strategic manner and probably subtracted from the trusses structural capability. Illustration of beam in compression on the top and tension on the bottom
Samuel Hill
Constructing Environments: Week 3 Logbook
Student Number: 722052
As can be seen in the photos there were several causes of failure on our truss. The top beam failed at a point close to where the load was applied due to the increasing load and the beams inability to support it. My theory that the screws had an impact in weakening the beam to a point where it lost critical bearing capacity. The screws divided the fibres within the beam limiting its bearing capacity. As can be seen in the photos there were several causes of failure on our truss. The top beam failed at a point close to where the load was applied due to the increasing load and the beams inability to support it. My theory that the screws had an impact in weakening the beam to a point where it lost critical bearing capacity. The screws divided the fibres within the beam limiting its bearing capacity.
The below photo and illustration shows both supporting beams at their point of failure. The top member was due to a weakened beam caused by the screws inserted as well as having the load applied directly at this joint. The bottom member at its failure point is carrying the vast majority of its load through 1 strut as it’s the longest still attached. The shorter struts had disconnected from either the top or bottom as the load was increased, therefore removing their ability to transfer load, shifting it to the next strut along. This huge load transferred down 1 strut put too much point load on the bottom beam causing it to fail.
Samuel Hill
Constructing Environments: Week 3 Logbook
Student Number: 722052
Samuel Hill
Constructing Environments: Week 3 Logbook
Student Number: 722052
Samuel Hill
Constructing Environments: Week 3 Logbook
Student Number: 722052
Scale; Annotations & Working Drawing Conventions The working drawings analysis centred around our ability to effectively understand and convey what we see on the page into a physical setting. Allowing us to observe the finished construction was beneficial to this comprehension. Some of us have already an understanding of working drawings which also assisted. One thing that was apparent was the drawings seemed to be in a very confusing order, from what I could ascertain was that each section of drawings was not where I expected them to be. The roof sections, details and then engineering and structural drawings were not compiled so one needed to flip back and forth between sections in order to clarify the information. The information included in the drawing set is very beneficial in order to understand how the structure is put together. Details on the curtain glazing faรงade was interesting to explore. The complex roof supports, struts, ties and beams were articulated in the plans, structural drawings as well as the isometric and 3D views. These drawings are very helpful.
Samuel Hill
Constructing Environments: Week 3 Logbook
Student Number: 722052
Glossary of terms Joist: Joists are essential component of wood and steel frame flooring systems. They span the gap between bearers; provide a platform on which flooring is laid and allow ceiling materials to be applied directly to or be suspended from.
Steel Decking: Metal decking is used as a working platform during construction and as formwork for a sitecast concrete slab. (Ching, 2014)
Bearer:
Can be concrete, steel, timber or combination of all 3. Essential to the efficient transfer of loads from a flooring system and above to the footing below.
Concrete Plank: A precast concrete panel that are one way spanning units. Spacing:
The space between each joist or beam. Standard spacing between joists on a flooring system is 600mm centres. Can be adjusted depending on the effect of the live and static loads.
The below graphic shows a number of this week’s terms.
Girder: Denotes a steel beam. Can take the form of plate girders and box girders Reference List Ching, F, D, K. (2014). Building Construction Illustrated. Hoboken, New Jersey: John Wiley & Sons.
Samuel Hill
Constructing Environments: Week 3 Logbook
Student Number: 722052