File Folder Bridge Construction

We began investigating bridge structure and design with the ultimate goal of designing our own bridge on a bridge simulation software. We used a series of plans from West Point Bridge Design to build a model truss bridge. After we completed this first activity, we embarked on learning how to test structural members (Activity #2) and how to analyze and evaluate a truss (Activity #3).

Activity #1: BUILD A MODEL OF A TRUSS BRIDGE

*I put the pdf file of activity #1 in the google drive folder above along with the svg/pdf files we created to laser cut the members of the bridge*

Materials:

• Standard manila file folder
• Building board made of foam
• Wax paper
• Pins
• Scissors
• Razor blade
• Superglue
• Accelerant
• Ruler
• Pencil

1. Cut out gusset plates from card stock.
2. Prepare foam board by covering building outline with a sheet of wax paper and hold it down using pins.
3. Lay out gusset plates in correct positions, but do not glue them down .

1. Laser cut top chords, end posts, floor beams, verticals, and struts or hand-draw lines with ruler and cut using razor blade.

1. Crease dotted lines (shown in plans) to form bars and glue end flaps together using superglue.

1. To make the bars for the bottom chords, diagonals, verticals, top lateral bracing, and portal bracing, slice 4 mm wide strips from the manilla file folder (or use laser cutter).
2. After all of the members are constructed, place bars on template for one side of the bridge. Trim as needed and do for both sides of the bridge. Glue them only to the gusset plates, not the wax paper.

1. On only one side of the bridge, position 10mm x 10mm tube. For the top chords, cut the outer end at an angle to make the connection with the end post better. Then, glue to gusset plates.

1. Position and glue verticals (10mm x 6mm tubes) with the shorter (6mm) side flat on board and longer (10mm) side upright.

1. Carefully peel the upper half of the truss from the wax paper and glue it to the bottom half. Also glue the final gusset plate at connection K.

1. Repeat steps 7-10 for second truss.
2. To construct the lateral bracing subassembly, which connects the two trusses at the top, start by pinning gusset plates to board. Then, glue single 4mm bars to form lateral bracing and glue the struts (6mm x 6mm) to gusset plates.

1. Apply glue to all five gusset plates and position one truss in place so that it's upside down and aligned with the lateral bracing. Do the same for the second truss.

1. To connect the trusses together at the bottom, use the floor beams. On the 6mm x 15mm tubes, mark off 5mm from each end (the middle section should measure 9 cm in length). Since there are no gusset plates to glue the floor beams to, cut the corners of the tubes to form four flaps where glue will be applied.

1. Glue the beams at the center of the bottom chords with the 15mm side vertical.
2. Cut out two 11cm x 13mm rectangles from manilla file folder to make end floor beams and glue to each end of truss.

1. Glue down the portal bracing and you have just finished the bridge!

1. Top:
1. Perform quality inspection.
2. RESULTS: Our bridge held 5 kg. of books, but it collapsed when we tried to add one more. Below is a video of us testing our bridge.