The collapse of the Hyatt Regency hotel's walkways was primarily due to a critical design flaw involving changes to the structure's steel hanger rods, which led to a catastrophic overloading of key connections.
The Root Cause: Flawed Design Modification
Investigators determined that the tragic collapse stemmed directly from changes to the design of the walkway's steel hanger rods. The original architectural plans for the hotel's suspended walkways were altered, creating a critical vulnerability in the structure.
Specifically, the design modification resulted in a problematic configuration where two walkways were suspended one directly below the other. The second-floor walkway was hanging directly under the fourth-floor walkway. Both were suspended from a set of 1.25-inch-diameter (32 mm) steel hanger rods. This arrangement meant that the connections supporting the upper, fourth-floor walkway were inadvertently forced to bear the combined weight of both the fourth-floor walkway and the second-floor walkway. This significantly increased the load on these critical connections beyond their intended capacity.
Understanding the Structural Failure Mechanism
The revised design transformed what should have been a distributed load into a concentrated stress point, ultimately leading to the structural failure.
- Overloaded Connections: The primary reason for the collapse was the immense stress placed on specific steel connections within the hanger rod system. These connections, designed to support a single walkway's load, were subjected to nearly double the anticipated weight due to the altered load path.
- Concentrated Stress: Instead of having separate, independent support systems or a more robust, continuous rod design, the modified structure created a "chain" where the lower walkway's weight was directly transferred through the upper walkway's supporting elements. This concentrated the entire load onto the connections at the fourth-floor level.
- Material Failure: Under this excessive and unanticipated stress, the clevis-and-rod assemblies at the fourth-floor connections failed. This led to the immediate and catastrophic collapse of both the second-floor and fourth-floor suspended walkways.
For more detailed information regarding the incident, further investigation results are available from reputable sources online, such as the Hyatt Regency walkway collapse documentation.
