1. Royal Plaza Hotel Collapse Thailand Group 24

2. Summary on Collapse Collapsed on Fri 13th August 1993 in less than 10 seconds 379 people in the Hotel were buried, 137 killed and 227 badly injured Collapse was compare to that of a demolition with the use of explosives

3. Structural History Original building, constructed in 1983, was 3 stories high with 1 underground level Original use was as a massage parlour, changed to a hotel in 1985 Building was modified in 1990, adding 3 extra stories Soil bearing strength was measured, but no foundation or column strengthening carried out

4. Unusual Collapse Most buildings collapse during or just after construction Royal Plaza collapse 3 years after modifications There were no extreme environmental factors, e.g., earthquakes or floods No misuse of the building

5. Investigation Tests Concrete Stress Test - Concrete compressive strength was between 10- 15MPa, within reliability limits Rebar Tests - Rebar samples found to conform to standards Soil Bearing Capacity - Soil able to carry loads even after modification Process of elimination - creep deformation in columns cause of collapse

6. Investigation Findings Original structure adequately overdesigned with a large Factor Of Safety, explaining delay in collapse Additional floors added to dead and live loads, reducing original margins for safety to zero Columns carrying dead loads at 70-80% capacity, causing micro-cracks When one column close to failure, its loads would be redistributed to the others Called “Progressive Failure” as a collapse of one column leads to the rest failing

7. Lessons learned Outlooks changed: Buildings that withstood construction without collapse were not only in danger in events of misuse or environmental disaster Change in practices: Buildings could not be constructed with saving money over people’s safety as a priority any more

8. Procedures Implemented All buildings that were under suspicion of lacking safety in the country were reviewed. 218 were renovated as a result. All engineers were required to register with a newly established Council of Engineers and their work was more closely monitored

9. Thank you! Questions…