IIRC one of the main faults in the Hyatt skywalk collapse was that the fabricator fudged on the installation. The plans called for a box beam suspended from a rod with a washer to help spread the load. Instead the fabricator used a pair of channel iron welded together, this resulted in a weaker beam than the box beam that was specified. Then to compound the error no washer or plate was used to help distribute the load forces where the nut met up with the bottom of the now welded beam. The result was that the washer pulled up through the welded joint resulting in the skywalk collpse that resuled in 110+ fatalaties and twice that number injured.
Regards
alfa6 ;>}
Kansas City Hyatt Regency Skywalk Collapse
http://em-jaturner.unl.edu/courses/em223/Group1/index.htm
Causes of Failure
1. Design Change of Walkway Supports
-single rod to double rod changed loading on joint
-occurred so rod wouldn’t have to be threaded
2. Did Not Meet Building Codes
-required that joints could support 151 kN
-designed so joints could support 91 kN
-one skywalk=288.9 kN; load on fourth floor joints=96 kN
3. Poor Construction
-improper wielding and connections
-inadequate building materials
The double channel box beam was the original design. The engineer's drawings called for a full penetration butt weld between the toes of the channels--an impossible weld to make. The rod support for this "box beam" was also an impossible detail to fabricate which is why the contractor suggested the detail change on the shop drawings he submitted to the architect and structural engineer for approval. And the shop drawings were approved.
Inspections by the Kansas City Building Department were also completely worthless---but then, those inspections usually are.