Bridges: rivets; corrosion, vibration and shock

Bridges, buildings and ships use rivets for connecting plates and juctions. Rivets allow some movement that relieves stress in ways welding can not. A wave threaded nut can be heated a small amout to get enough expansion to clamp onto the bolt with characteristics similar to a rivet. The distribution of stress through the bolt is even and the plates will be able to move like a rivets. The advantage is lower cost and ease of use.

Two aspects of the wave thread can be used: It can be designed to evenly distribute stress across the threads; and there is no high torque tightening, only full engagement. Normally bridge bolts are tightened to a bolt stretching limit with stress induced. The wave threads can be designed to include some bolt stretching, but reducing pre-loaded stress means they can withstand more shock. This is a consideration for earthquakes. The even distribution of stress adds over 20% more strength and also contributes to withstanding shocks. All preloaded stress contributes to long term fatigue. Cold rolling them will be challanging, but not impossible. This will take a dedicated team to certify the capabilites of improving the strength and durability of bridge appications.