It was reported that the rear side of the Excellency Reception Hall in Wellewatta Collapsed on 18^th May 2017 around 11.00 a.m. “Daily News” Newspaper published on 19.05.2017  reported that it has caused 1 death, injuries to 27 construction workers while six others were reported missing and another believed to be trapped under the rubble.

Google Map of the Location	Drone image of the location after building collapsed

This building is situated within the Municipality Limits of Colombo in Palle Pattu of Salpiti Korale in Colombo District, Western Province.

A team of National Building Research Organisation (NBRO) consisting with Civil Engineers, Geotechnical Engineers, Material Engineers, and Geologists visited the above building failure site on 18^th and 19^th May 2017.

According to the observations made by NBRO team, front part of the building named as   “Excellency” remains without failure. This part of the building consists with 03 fully completed floors above the ground level plus another partially completed 02 floors.

According to the visual observations, collapsed part of the building was a reinforced concrete structure with columns, beams and slabs. Steel roof was provided for part of the building and partially completed columns were noted over the top slab panel.

The debris of the collapsed building shows slab panels were fallen and jammed together demolishing vertical columns. Beam- column joints were completely broken.

Collapsed of Structural Elements

Remarks

A relationship with foundation type with its founding depth and geology of founding depth could not be interpreted due to lack of adequate technical information available on sub soil layers. Therefore, a proper interpretation cannot be made with regard to a possible foundation failure.

The floor slabs of the building were supported with horizontal beams and vertical columns and it is clear that the structure was not strong to support the loads at the time of failure. Failure occurs when the overstressed elements reaches an ultimate stress level.

Mr. K.K.J.S.Fernando, Consultant Structural Engineer addressed to Director City Planning, Municipal Engineer’s Department, Colombo Municipal Council has stated that building structure has been designed for 05 storey. However, another 02 floors have been added without getting the consent of the design engineer. Design alternations had been carried out time to time adding extensions horizontally as well as vertically to the original structure.

In general building elements can be overstressed due to one of the following or combinations:

1. Violation of building code when designing;

2. Bad workmanship; Removal of form works of columns, slabs, beams of immature concrete at upper floors;

3. In correct size, shape or the bad quality of material of which did not comply with the design requirement during construction;

4. Adding of extra storey than the original design. It could be a case of weak columns and foundation;

5. Failure of underground soil strata.

NBRO is of the opinion that column/s at upper floor level have been reached their ultimate failure state due to reason/s one or combinations given above. Once reaching the ultimate failure state they would have crushed and failed to support the loading of upper slab. This would have caused to collapse of next lower floor due to impact force and additional weight of collapsed material. This can be happened progressively from top to bottom collapsing all the structural elements in one bay within very short time period. This would have caused the collapse of one bay (near cannel) first and the full-down force forming lateral movement would have then caused collapse of remaining structure. Some more investigations/ information such as geotechnical parameters of sub soil layers, structural drawings, workmanship, etc are required to find out the origin of failure.