This frame was designed as a braced with rigid floor diaphragms and factor K=1. However when "they prematurely removed temporarily shores of a VERY long span composite floor deck such that the deck/slab sagged so much ...", the big group of columns became unbraced with semi-rigid floor...
I think that the Designer made the same mistake as JAE in his post, he considered the whole frame as braced. The external columns located near the walls have X braces and can be considered as braced. However, the internal columns located in the middle of the building should be considered as...
This is the quote from AISC that clearly explains the cause of Hard Rock hotel collapse.
"While ordinarily the existence of masonry walls provides enough lateral support for tier building frames to control lateral deflection, the increasing use of ... wide column spacing for high-rise...
The formula is based on the following model. Axially loaded column with pins at both ends, top pin connected to a spring representing a floor support. The column has two buckling modes, with and without lateral movement, and two corresponding critical loads. If mode without lateral movement...
In my post of Dec. 26 I wrote formula:
P < E c x bc x h x H / L (1)
and got some critical comments. Here is my answer for these comments.
1) The formula belongs not to me. I got it from the theory of stability of elastic systems and implemented it to concrete floors.
2) The formula does not...
I want to simplify my points. If the Designer wanted to design a braced frame, he had to provide a strong bracing system which guaranteed that all columns are not horizontally movable. In this case effective length factor can be K=1 or less. If the Designer wanted to design an unbraced frame, he...
The picture of the building after collapse corresponds to insufficiently braced frame with columns inclined to the middle of the building. It means that P-delta effect takes place. The Designer used effective length factor K=1 or less. Since the bracing system was not rigid enough, the...
Boris Kuznetsov (structural)
Post tension constructions in general and Hard Rock hotel in particular have concrete slabs with long spans and thin thicknesses. It may change buckling mode and critical load of building. Therefore, additional column stability check, not included in standard...
After the heavy swimming pool was installed on 9th floor of Hard Rock hotel, the concrete deck supporting the pool sagged. It leads to significant drop in the floor rigidity. Sagging floor can not be qualified as rigid support for column stability, only as elastic support. The standard method...
Hard Rock hotel collapsed due to incorrect design. The presence of heavy swimming pool makes the standard frame design not applicable because the 9th floor of the building became movable in horizontal direction. All columns of 8th and 9th floors designed incorrectly. The hotel collapsed due to...
On October 12 the Hard Rock hotel collapsed in several hours after the Builder installed heavy swimming pool on 9th floor of the building.
In standard practice beams and floors are designed for bending moments and columns for compression forces. In reality beams and floors have also additional...
