Originally Section 8 of F2291 listed applicable load combinations to be used for each method of design (ASD or LRFD). It was decided that it was better to eliminate these combinations so we would not have to monitor changes in the standards referred to for use in making combinations. This assumption turned out to be erroneous. Monitoring of the standards is necessary. ASCE 7, the standard used in the US for determining load combinations has changed in a way that could produce unsafe amusement rides. The ASCE 7 committee decided they wanted the load factor for wind loads to be 1 for the LRFD combinations. This necessitated a change of the load factor for ASD combinations from 1 to 0.6. Design storm wind velocities were changed so that the net effect for storm wind loads was unchanged. However, in amusement ride design we consider operational wind with a specified wind speed. Resulting wind effects for the operational wind load combinations would thus be reduced by 40% if the current ASCE 7 combinations are used. There should be no effect on current designs as F2291 currently specifies the use of the previous (XXXX) ASCE 7 standard. Due to the fact that many jurisdictions require use of the current ASCE 7 for designs being reviewed for approval, it has been decided to reinstate the load combinations required for amusement rides. Additionally ASCE 7-05 which is currently listed in F 2291 will become increasingly hard to obtain. Changes have been made to the combinations specified previously so that they now address mandated design cases for unbalanced loads. THERE WILL BE NO CHANGE IN THE DESIGN LOADS FOR ANY AMUSEMENT RIDE DUE TO THESE CHANGES TO THE STANDARD.
Keywordsacceleration limits; amusement ride or devices; anti-rollback devices; chain; clearance envelope; containment; control systems; design; electrical; emergency safety device; fasteners; fatigue; fencing; guardrails; hydraulics; impact factor; loads and strengths; mechanical systems; operational hours; pneumatics; restraints; ride analysis; welding; wire rope;;
Draft Under Development