Structural Systems: Model Bridges

ARCH 1048 ‐ STRUCTURAL SYSTEMS PROF. M. ROSTAMI

PROJECT 2: POPSICLE STICK BRIDGE GROUP 11: SAMUEL ABRAMS, CURTIS BLAIK, JAIMIE GONZALEZ, DAPNE GUILLERMO & HARTLEY ROGERS

#101177489 #101224117 #101223276 #101225187 #101215080 APRIL 8, 2019

PROBLEM DEFINED: To construct a popsicle stick bridge spanning 2’ that can withstand a load of approximately 150 lbs.

CONSTRAINTS: ‐ materials ( popsicle, glue, dental floss) ‐ spatial (measurements, not allowed to use support of sides) ‐ efficiency of design is key: minimization of weight and cost of materials drives design

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BRIDGE REPORT

PROJECT 2: POPSICLE STICK BRIDGE

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DESIGN IDEA #1: Basic warren truss design

PROS: �

SImple and "clean" looking, easy to execute

CONS: architecturally dull (will lose points), will need to consider extra reinforcement and will add much more weight,

BRIDGE DESIGN IDEAS

PROJECT 2: POPSICLE STICK BRIDGE SCALE: NTS

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DESIGN IDEA #2 Suspension/cable bridge �

PROS

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aesthetically pleasing

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lighter weight because using less wood

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CONS

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technique used to tie both ends of cables in the arch is hard to execute, if puncture holes into the wood to tie it compromisises its strength (the wood might split)

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BRIDGE DESIGN IDEAS

PROJECT 2: POPSICLE STICK BRIDGE

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DESIGN IDEA #3 Hybrid: warren truss deck, arch support and support cable �

PROS

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incorporating a crocheted floss web as overlay to wood structure to add support and help disperse load's weight

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truss support as main portion of deck is is helping to disperse both tension and compression forces of the load; arch is helping to counteract compression forces; the reinforced floss web is helping to take additional compression forces from the load and disperse it to the sides where the bridge will be resting

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CONS

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heavy (lots of wood used in construction)

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relies heavily upon the arch, balancing it's mid section almost in a teeter totter way; weaker at the ends

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arch's footprint is potentially too small, it may have needed to have wider footing to better disperse the forces of the load down into the ground.

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BRIDGE DESIGN IDEAS

PROJECT 2: POPSICLE STICK BRIDGE

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MEETING MINUTES Mar 30 Saturday �

Two members attend

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Initial meeting to brainstorm, set up the report template and begin creating design sketches

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Discussion of beam overhang, arch support and material tensile properties discussed

April 1 Monday �

the supporting arch below the deck’s construction was discussed: to create a circular element

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Whole group meeting, continuing to brainstorm design ideas

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one member proposes reinforcing the dental floss cables by braiding or crocheting them

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group member selected to be the one to stand on bridge

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popsicle stick beams to be created as main structural elements of deck; dental floss joists to be tied perpendicular to the beams to counteract deflection of the beams from the load’s gravitational compression forces and subsequent tension forces; the wood arch below the deck would help stabilize the bridge against compression forces;

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platform to be constructed where feet will be placed: foot platforms to be placed closer to walls to disperse weight and not concentrate it on the centre of the bridge

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extra support will need to be constructed beneath the foot platforms (additional trusses added) focus on using reinforced dental floss when possible rather than wood support to minimize bridge weight

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MEETING MINUTES

PROJECT 2: POPSICLE STICK BRIDGE

05

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April 7 Sunday

April 3 Wednesday A new option is discussed: a tied arch bridge that would have a rounded popsicle stick arch above a deck with tension cables running the length of the deck below

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Bridge construction continues

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Crocheted dental floss is taken from below the top part of deck, to wrap around the exterior of the bridge deck and sides like a strong, protective mesh.

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Final dimensions determined: 4″ deck, 28″ length

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Construction of bridge starts; 3D modelling used to envision possible ideas group discusses

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The arch is attached to the underside of the deck (glued to reinforced popsicle joists)

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Small warren truss system to be run parallel to underside of beams as additional support: to be about 24″ x 2″ to fit on top of the 2″ nook of side pieces putting the bridge on. Truss pieces to be 2‐3″ apart

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Area the human load should stand is discussed: originally legs were to be spread across the 2’ span (one foot at each end) to avoid a concentrated load at the center of the bridge, but with the support of the arch strongest at the center, the human load’s location is reconsidered and it is determined the feet should be spaced slightly off‐centre.

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Crocheted web structures placement is reconsidered and the extra support for where the human load’s feet will be placed is also discussed

April 6 Saturday

April 8 Monday

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Bridge construction continues

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Final adjustments to the bridge are made

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Crocheted dental floss completed, experimentation of where to best apply rigid structure: woven through the top of the bridge deck to support lateral members of top deck and help support the human load and disperse its force along the whole structure rather and mitigate and high stress points.

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Final location and application of crocheted web is decided on for maximum support of all structural members and to best take on the forces of the applied human load

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the bridge arch is constructed and reinforced with more popsicle sticks than planned. Bridge arch is constructed at 5″ rather than the required 6″ height and falls short an inch in length. Group members discuss options and arrive at a stepped footing solution.

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Weight of bridge is a concern and discussed.

MEETING MINUTES

PROJECT 2: POPSICLE STICK BRIDGE SCALE: NTS

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DESIGN PROCESS: CONSTRUCTION

PROJECT 2: POPSICLE STICK BRIDGE

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DESIGN PROCESS: CONSTRUCTION

PROJECT 2: POPSICLE STICK BRIDGE

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DESIGN PROCESS: CONSTRUCTION

PROJECT 2: POPSICLE STICK BRIDGE

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FINAL DESIGN RATIONALE: Hybrid Warren Truss Deck w/ Reinforced Tensile Web on Arch Support Ultimately, through extensive research, we concluded that Design #3 was the superior bridge. The hybrid bridge, as it became known in our group, combined tWo main elements: A simple warren truss deck, supported by a robust arch.

The Arch spans the length of the void offering necessary support to the centre of the deck. The arch will passively transfer compression force away to the supporting structure The Deck, which also spans 2 ft. Offers support at both ends. The Warren truss system we built throughout will aid in the transferal of compression, tension, and torsion forces.

A secondary design element was added: a webbed floss structure. with incredibly high tensile strength. Not only does it add aesthetic value to the bridge, it also served a function: additional support for the top of deck. This additional support was incorporated to transfer force from the human load laterally across the bridge towards the sides it rests upon. .

We followed the Bauhaus school of thought, that form should follow function. Our bridge was created to endure a heavy human load, with its industrial aesthetic featuring the support members and unique tensile web. The bridge's integrity was not compromised by frivolous additional details, and weight was attempted to be kept at a minimum by substituting extra wood support with the lighter weight tensile web.

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DESIGN PROCESS: FINAL

PROJECT 2: POPSICLE STICK BRIDGE

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2'-4" 4"

4"

4"

4"

2"

4"

4"

5/8"

2 1/8"

5/8"

2"

bridge beam 28"

Reinforced Tensile Web on Deck on Floss

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BRIDGE DECK PLAN

PROJECT 2: POPSICLE STICK BRIDGE

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2'-4"

4"

4"

4" 4"

4"

4"

2"

4"

2 1/8"

4"

4"

4"

1/2"

1/2"

1/2"

1/2" 3/8"

1/2"

3/8"

4"

4"

2"

1"

4"

4"

4"

4"

1"

1'-11"

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BRIDGE ELEVATION

PROJECT 2: POPSICLE STICK BRIDGE

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BRIDGE PERSPECTIVES

PROJECT 2: POPSICLE STICK BRIDGE

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PROJECT 1: BALSA BRIDGE

ARCH 1048 - STRUCTURAL SYSTEMS PROF. M. ROSTAMI GROUP 13: SAMUEL ABRAMS & HARTLEY ROGERS

#101177489 $101177489 FEB. 11, 2019

4" 5/16"

3 3/8"

5/16"

balsa arch

28" 14"

14" 28"

5"

2 3/4"

1 1/4" 1 1/4"

5"

2 3/4"

5"

1/16"

4"

5"

balsa wood long - 28" x 1/4" x 1/8"

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REVISIONS MM/DD/YY

BRIDGE DECK PLAN

PROJECT 1: BALSA BRIDGE SCALE: NTS

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REVISIONS MM/DD/YY

TRUSS BRIDGE UPPER SUPPORT

PROJECT 1: BALSA BRIDGE SCALE: NTS

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REVISIONS MM/DD/YY

TRUSS BRIDGE LOWER SUPPORT

PROJECT 1: BALSA BRIDGE SCALE: NTS

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DESIGN PROCESS: SKETCHES

PROJECT 1: BALSA BRIDGE SCALE: NTS

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DESIGN PROCESS: 3D MODELLING

PROJECT 1: BALSA BRIDGE SCALE: NTS

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REVISIONS MM/DD/YY

DESIGN PROCESS: CONSTRUCTION

PROJECT 1: BALSA BRIDGE SCALE: NTS

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REVISIONS MM/DD/YY

DESIGN PROCESS: CONSTRUCTION

PROJECT 1: BALSA BRIDGE SCALE: NTS

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REVISIONS MM/DD/YY

DESIGN PROCESS: TESTING

PROJECT 1: BALSA BRIDGE SCALE: NTS

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