TSM 1004 / 3004 A – Structures 1
Introduction to Structural Systems
Fall 2022
Project
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Assignment:
You are to design the main structure (the big stuff) for a large span roof and its supports.
Preliminary Sketch Approval Date : Tuesday, November 22, 11:59 pm. Submit on Moodle.
Final Project Due Date : Sunday, December 10, 11:59 pm. Submit on Moodle.
Description:
Design a roof covering an area of 100’ x 200’.
There are to be no supports inside the 100’x200’ footprint.
Primary Elements to be roughly 20’ to 33’ apart.
Secondary Elements to be roughly 6’ to 15’ apart.
Support a snow load of 30 psf, and a dead load of 15 psf.
Support the Primary Elements appropriately, typically with columns, solid bases, or anchorages.
Primary and Secondary elements may be designed as any type of system that we have techniques for
solving for internal forces (truss, cable, arch, cable stay). They can’t be beams; Structures 2.
Solve for internal forces of typical Primary Element, typical Secondary Element, and typical Support.
Specify (material, shape and size) typical members of each of Primary, Seconday, and Support.
Design Connection between Primary Element and Support.
Project Plan. Most of them will look something like this.
The spacings will change depending on the design of
the student.
Support (Ground Connection)(Column)
Primary
Secondary
200’
100’
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Discussion:
For our purposes it is best to keep to a strict hierarchy where each type of element directly supports
only one other kind of element. For instance, it is natural to create a design in which a column holds
up one end of a Primary Element AND one end of each of two Secondary Elements. Let’s not do that.
Secondaries are held up only by Primaries. Primaries are held up only by Columns.
Snow → Deck → Purlins → Secondary → Primary → Supports → Dirt
Do not design Design Do not design
The construction of the deck and the specifics of how the load is transferred to the Secondary Span
Elements can be ignored. Just use the right number of square feet and load your trusses only on joints.
The end elements will probably support only half the load of the interior elements. Only solve for the
typical interior element.
Size Spanning Elements, or members of Spanning Elements to avoid failure. Use a Safety Factor of 1.5.
You don’t have to size each element of a truss independently. For full credit, a truss should have inde pendent specifications for Top Chord, Bottom Chord, and Web members.
Size final support, such as : Column cross section, base area of anchor block, as suitable for your de sign.
Size Connection of a typical Primary element to a typical Support element. You can probably use some
kind of single “mouse ear” pin connection. Some designs may require further research.
Elaboration
You are encouraged to use the instructor, TA, and tutors as consultants and data resources.
Your project will be unique and interesting and this assignment sheet will not have anticipated every thing every student may want to try. So we can be creative and adaptable as a design requires.
You don’t have to use trusses for everything. See attached inspiration sketches.
The materials are your choice. For steel members, you should probably use https://www.aisc.org/
globalassets/aisc/manual/v15.0-shapes-database/aisc-shapes-database-v15.0.xlsx. Also available on
Moodle.
Remember, you can only apply load to a truss at the joints.
Most rules can be broken. At instructor discretion.
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Deliverables
Preliminary Sketch (Approved by November 22):
◌ Drawings necessary to present your proposed project. Typically, plan and two elevations. Start
submitting early so you can get approval and use your time for the project. This is just a sketch.
◌ This has to be approved before you move ahead.
Final Submittal :
◌ Paragraph describing the structure.
◌ Drawings of whole structure. Drawings should be adequate to describe the structure. Consider
your full arsenal of drawings : axonometric, perspective, plan, elevation, section, etc.; which
ones help illustrate your design? At a guess, you’ll want one perspective or axon to show the 3d
organization and two elevations or sections to illustrate the systems being analyzed.
◌ Free body diagram, with loads, reactions, and dimensions, for each sub-system analyzed. (For
example: Primary, Second, and Support.)
◌ For funicular elements, include a form diagram of the actual curve.
◌ Provide all calculations and diagrams used to solve for member forces.
◌ Provide member sizes for Primary Spanning, Secondary Spanning, and Final Support systems.
◌ Design of connection at support should include any bolt or pin sizes and counts as well as thick nesses of any penetrated materials.
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Inspiration Sketches
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Sample Design
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Some Numbers
Material Allowable Stress Modulus of Elasticity
Plate Steel: F
y
= 36 ksi E = 29,000 ksi
Steel Shapes: F
y
= 50 ksi E = 29,000 ksi
Steel Bolts: F
y
= 70 ksi E = 29,000 ksi
Steel Cable: F
y
= 250 ksi E = 29,000 ksi
Concrete: f
c
’ = 4 ksi E = 5,000 ksi
Timber: Fallow = 1.2 ksi E = 1,500 ksi
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