Assessment of structural vulnerability of Sri Lankan hospitals under natural hazards – Tsunami as a case study

Abstract

Hospitals are considered critical service units of a society that need to operate before, during, and after disasters. The Ministry of Health of Sri Lanka has embraced the “Safe Hospitals” Initiative promoted by the World Health Organization (WHO), as a strategic priority for health sector Disaster Management to strengthen the resilience of the hospitals. WHO has developed a toolkit for the assessment of the safety of hospitals including structural, non-structural, and functional aspects. This toolkit consists of four modules that are; hazard identification, structural safety, non – structural safety, and emergency and disaster management. A review of this toolkit has pointed out the need for major alterations to the structural safety module of the Safe Hospital Toolkit to Sri Lanka since the Sri Lankan disaster profile is quite different from that of the Latin American countries in which the toolkit was developed; where earthquakes and cyclones are predominate. The objective of this assessment was to develop a toolkit to assess the structural safety of hospitals in Sri Lanka addressing the structural vulnerability/robustness of buildings considering natural hazards; high winds, floods, tsunamis, and landslides. Accordingly, a draft Structural Safety of Hospitals assessment Sri Lanka (draft SSH – SL) has been developed based on the Safe Hospital Toolkit and the available Sri Lankan guidelines for hazard resilient constructions. Then, the draft SSH – SL has been used in a pilot study to identify its limitations, on two hospitals based on their functionality, namely the District General Hospital Gampaha and the Teaching Hospital, Kegalle. To further develop the SSH - SL, field data of another pilot study conducted on six hospitals on the southern coast are used along with a thorough literature review. Moreover, expert surveys were conducted to further improve the toolkit and to obtain the weights using the Analytical Hierarchy Process (AHP), for all the criteria in the SSH – SL, and a Structural Robustness Index (SRI) is defined. Finally, the developed tool under tsunamis is checked for applicability based on the data obtained from the second pilot study and is validated by comparing the actual damage occurred in 2004 Indian Ocean Tsunami with the obtained SRI scores. However, the developed tool for other assessments require validation through more case studies. According to the relative weights obtained through AHP, two main attributes; construction material and the foundation system were found to be significantly important. The assessments of tsunamis and floods share the same building attributes with different weights; the attributes of the lateral load resisting system and the number of stories get a higher weight under the tsunamis compared to floods, as the impact loads applied by the tsunamis are higher than that of the floods. Considering the SRI scores, it was found that the median score for the general assessment is 3 whereas it is 2.33 for all the other assessments. This gives a clear idea of the robustness of buildings as the SRIs above the median score are tend to be robust and the SRIs below the median tend to be vulnerable. The case study carried out focussing on the assessment developed for tsunamis suggests that the Structural Robustness Index (SRI) method is a more nuanced and improved method for assessing the structural robustness compared to the PTVA method. It is highlighted that the SRI method identifies structures that are above the median level in terms of structural robustness than that of the PTVA method. As far as the intra-hospital variation is concerned, the SRI variation mostly depends on the building attributes such as the number of storeys and the construction material. It is also identified that there is a coupling effect between building attributes such as the construction material and the number of storeys as the buildings with a higher number of storeys are also tend to be made of reinforced concrete frames whereas the single storey buildings are made of masonry. The inter-hospital variation of SRIs mostly depends on the surrounding attributes as they change with the geographical location. These results are valid for the buildings up to four storeys including unreinforced masonry, reinforced concrete structures with masonry infills, and reinforced concrete framed structures that were assessed during the field survey. The SSH - SL could be further improved by incorporating the level of exposure and functional attributes and emergency and disaster management attributes to develop a comprehensive risk index, which is beneficial for the disaster management decision-making stage of hospitals.