Discussions
- This type of structure is not common in Nepalese context.
- Heavy dead load was acting on the space truss.
- The design report and drawing are not available with the hospital management at the time of the site visit.
- The existing post accident site scene indicates that the cause of the failure may not have been due to failure of supports. The top tie beam, columns and base plates are intact.
- It seems that base plates were not properly anchored to the RC beam.
- There was not an instantaneous overloading to the roof structure owing to earthquake, strong wind, overcrowding or thunderbolt etc.
- The collapse was almost sudden giving very short time though there could have been some unnoticed yielding.
- Sliding supports may not have worked properly as envisaged in design owing to corrosion or lack of regular greasing.
- No regular monitoring or maintenance was carried out.
Conclusions
- It is difficult to draw specific conclusions based on a day visit to the accident site.
- Though there could be a design deficiency, most likely shortcomings could have happened during construction time. There are various possibilities, for example, material quality as per designer’s specification, various confirmatory destructive or non-destructive tests before or during or after construction, workmanship, supervision quality, ad hoc design alteration and so on.
- There should be some yielding of joints/members before failure but that could have been missed because of the height at which the roof rested, its inaccessibility and lack of regular monitoring or maintenance.
- Most likely failure could have started from failures of joints at critical places. This caused first pushing of sliding support and block walls along that line. Later when most of the roof members fell the sliding plates were pulled and only two sliding plates were left because of their non-sliding position
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