Bridges

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Across
  1. 4. Passage over obstacle
  2. 5. Weight of structure itself
  3. 6. Twisting force
  4. 8. First to use rope bridges
  5. 9. Strongest shape
  6. 11. Added to strengthen against earthquakes
  7. 13. Sliding on past
  8. 17. One of the main types of bridges
  9. 18. Bridge that collapsed resulting in new laws
  10. 19. Bridge that uses triangles
  11. 20. Pull apart
Down
  1. 1. Changing weight on the structure
  2. 2. Added to strengthen against unstable soil
  3. 3. Support in an arch bridge
  4. 7. First to use arch bridges
  5. 10. Added to strengthen from temperature changes
  6. 12. Has a keystone
  7. 14. Squeeze
  8. 15. Bridge that has a main cable
  9. 16. Mrs. Wink's favorite