ENVS10003 CONSTRUCTING ENVIRONMENTS A01 LOGBOOK WEEK 5 Studio Report This week is going to do model making of part of Oval Pavilion. Our group task is to build roof light structure. Here is the roof light 3-D digital presentation.
The first thing is to consider about materials. Because we only need to do the structure therefore this model will consist of a number of strips. Due to the limit of materials, at the very beginning, we only got pieces of balsa just as the photo shows. Although it is easing cutting, but it is too soft and light, it is hard to use that to make a structure of roof light. And then we got some cardboard which is harder than balsa, however it is too hard to cut very thin strips. Cutting strips is easy to bend and not strong in the structure. The horizontal surface can withstand large compression force due to triangle structure inside.
Easy to bend
However, as a vertical member, it may not transfer too many loads due to the small contact area (left drawing shows). It can be further improved by adding two pieces of cardboard at the top and bottom of the main strip, and then it can be expected to transfer more loads (right drawing shows). Nevertheless, it may consume more time when making models because more details need to be paid attention to such as join these three strips together and then connect to other main strips. It may be difficult to handle too much staff so we give up using cardboard. After a period of time, also by referring to other group’s work, we found that wider balsa will be the best choice because it is relatively easy to cut and also easy to be joint by pins or glue. The first thing that we do is to measure the dimension as shown.
Front part
Back part
Roof light can be briefly divided into two parts: front part and back part, we need to do model making of the part in rectangular area.
Because we are going to do the model in 1: 20 scale, and the scale shown in the graph is wrong, it should be 1:200, so we did some calculation and then got accurate data.
Cut- off ends To begin the model making, we first made the back part which is shown below. We use both glue and pins to tie them up to make sure the structure is stable and strong enough with no movement. We also carefully cut each end to make them match well because it will be convenient to combine them together tightly. We used both wide and thin strips separately to make the structure look organized as the drawing shows. Wide strips are used in external outline part to withstand more loads, internal strips are set to hold the shape, thus thin strips are enough. Then we began to do front part as the graphs show. We used pins to pin them together, some use 2 pins to combine one small strip to the main one to make sure that it is stable.
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After making the front part and back part separately, we have to combine them together using pins and glue. More pins are used to ensure the structure is stable.
Learning Loop Wall system Column: Short column—shorter and thinner, column length: smallest cross section dimension < 12:1, fail by crushing when the compressive strength is exceeded or cross section is too small. Long column—taller and slimmer, column length: smallest cross section dimension > 12:1, fail by buckling, shapes of cross section determine the direction of buckling.
Structure frame: concrete frame, steel frame, timber frame. Load bearing wall: Concrete load bearing wall: either in situ or precast. Masonry load bearing wall: Reinforced masonry—formed from cone filled hollow concrete or grout filled cavity masonry. Solid masonry—created with single or multiple skins of concrete masonry units or clay bricks. Cavity masonry—formed from two skins of masonry, better thermal performance, better waterproofing, and opportunities for insulation and to run services within the wall cavity.
Stud wall: light gauge steel framing or timber framing Components: top plate, bottom plate, vertical stud, noggin, cross bracing, PLY bracing.
Material focus: timber Timber is seasoned to remove moisture and increase stability: Air seasoning: cheap but slow; Kiln seasoning, 20- 40 to dry to ~12%; Solar kiln seasoning: less expensive to run. Quarter sawn(less common): less likely to warp, cup, slow seasoning, more prone to splitting. Back sawn (more common): rapid seasoning, less prone to splitting, shrink, warp and cup. Radial sawn: dimensional stability, less prone to warping, cupping, harder to detail and stuck.
Property: relatively low hardness, fragility, ductility, high flexibility, porosity, durability, reusability, sustainability, varied density, poor conductor of heat and electricity. Specifying: seasoned timber, moisture content< 15%, protection against water and heat.
This week we learnt a lot about choosing suitable materials when making models. It can be related to the shape and stability of the whole structure. Measuring accurate data of dimension may be the most basic and important step because the strips have to be strong enough to hold others and not too difficult to cut. The joints also need to be paid attention to, use of both pins and super glue may be effective to stabilize and strengthen the structure. This practice provides an opportunity for us to understand how a complex structure forms step by step and then to decide the sequence of making different parts of the model. Materials chosen and connection types are also necessary to be taken into consideration.
Glossary Appendix Stud: In construction, a vertical framing member in wall system. Usually studs can be metal or timber (Beneke, 2014). Nogging: short horizontal member in stud wall frame to fill the gap and hold the structure.
Lintel: ‘a horizontal architectural member spanning and usually carrying the load above an opening (Merriam-webster, 2014).’ Figure: WOOD LINTEL FOR DRY CLIMATES (EarthbagStructures, n.d.)
Axial Load: ‘Axial loading is defined as a structural frame system that is a combination of primarily vertical and horizontal members that are designed to transmit applied loads to the ground. An axial load is termed as a force with its resultant passing through the centroid of a particular section and being perpendicular to the plane of the section. In short, an axial load creates a force parallel to the axis of an object (Ask, 2014).’
Figure: Axial vs flexural loading (Wikimedia Commons, 2014)
Buckling: ‘Mode of failure under compression of a structural component that is thin (shell structure) or much longer than wide (e.g., post, column, leg bone) (Answers, n.d.).’ Seasoned Timber: Seasoned timber is timber that has moisture content less than 15% and provides increased dimensional stability, which is suitable for intended use. Figure: BUCKLING OF A COLUMN (Kingsbury, 2005)
REFERENCE Answers (n.d.). Buckling. Retrieved September 4, 2014 from http://www.answers.com/topic/buckling Ask (2014). What is axial loading? Retrieved September 4, 2014 from http://www.ask.com/question/axial-loading-definition Beneke, J. (2014). Stud. Retrieved September 4, 2014 from http://garages.about.com/od/glossary/g/StudGlossary.htm EarthbagStructures (n.d.). Openings in Walls: Reinforcement, Lintels, Window Grills, Vent Block & Pipe. Retrieved September 4, 2014 from http://www.earthbagstructures.com/details/openings/openings.htm Kingsbury (2005). BUCKLING OF A COLUMN. Retrieved September 4, 2014 from http://enpub.fulton.asu.edu/imtl/HTML/Manuals/MC108_Buckling_Column.ht m Merriam-webster (2014). Lintel. Retrieved September 4, 2014 from www.merriamwebster.com/dictionary/lintel Wikimedia Commons (2014). File:Axial vs flexural loading.png. Retrieved September 4, 2014 from http://commons.wikimedia.org/wiki/File:Axial_vs_flexural_loading.png