LockwoodSTEM
PRINCIPLES OF ENGINEERING
UNIT 2 · BRIDGE STRUCTURES & MATERIALS
POE 2.1 · Student Resource

Bridge Mission Analysis

Translate the bridge challenge into criteria, constraints, questions, and initial structural concepts.

Name: ______________________________
Period: ______
Date: ____________
1

Mission Requirements

Span

400 mm

Width

65 mm maximum

Design Load

100 N at midspan

Deflection

≤ 10 mm at 100 N

Mass

≤ 150 g

Mounting

Standard two-support test fixture
2

Criteria & Constraints

RequirementCriterion or Constraint?Why It Matters
Carry 100 N centered
≤ 10 mm deflection
≤ 150 g mass
400 mm span
Approved materials / manufacturing
Standard two-support interface
3

Initial Structural Concepts

Concept A

Label chords/girders, verticals, diagonals, deck/cross members, and joints.

Concept B

Label chords/girders, verticals, diagonals, deck/cross members, and joints.

4

Need-to-Know Questions

1.
2.
3.
4.
5

Mission Check

□ I can explain strength vs. stiffness.□ I identified the major constraints.□ I created two structural concepts.□ I have questions to investigate.
Return to Lesson 2.1

Current Bridge Challenge Manufacturing Limits

400 mm clear span; 65 mm maximum width; 100 N centered load; deflection ≤ 10 mm; total mass ≤ 150 g. Primary structure: approved wood or plywood, including one-piece laser-cut open-web plywood side trusses. No acrylic, solid side plates or fully printed bridges.

Joints: PVA/CA glue, interlocking plywood, plywood gussets, PLA/PETG printed fittings, or M3 nuts/bolts (M3 washers permitted); no screws, epoxy or hot glue. Plywood ≤ 3.2 mm thick; joint gussets ≤ 40 × 25 mm, ≤ 800 mm², ≤ 20 mm overlap on members, and at most two layers (one per side).

Printed connectors only (not primary members): PLA/PETG, ≤ 35% infill, ≤ 4 walls, ≤ 5 top/bottom layers each, ≤ 0.28 mm layer height, 0.4 mm nozzle, ≤ 50 mm long and ≤ 15 g per part, ≤ 40 g printed total. Submit CAD, print settings and measured masses when printed parts are used. Full unit specifications.