Browsing by Author "Dias, P"

Now showing 1 - 6 of 6

Open Access
A cross-category analysis of high impact low occurrence (HILO) disasters
(Elsevier Ltd, 2026-03-19) Samaraweera, U; Kulatunga, U; Dias, P
This paper explores six High Impact Low Occurrence (HILO) disasters, generating insights from five different categories associated with them, namely causes (geophysical, technological, biological, sociological), phases (preparedness, response, recovery), dimensions (socio-economics, governance, equity), sectors (health, education, infrastructure, economy) and national contexts with differing levels of economic development. The process involved the generation of a questionnaire, based on a literature review; and the subsequent analysis and discussion of the questionnaire responses made by six experts nominated by six academies of science in Asia. The findings highlight the limitations of probabilistic, frequency-based risk models for HILO disasters and instead emphasise the importance of scenario-based (worst-case) analyses; mechanisms that preserve inter‐generational knowledge, institutional continuity and community‐based early‐response networks; strengthening community resilience while ensuring equity; and making appropriate investments for increasing preparedness, if not through structural interventions, at least through sustained awareness programs and periodic drills. Theoretical contributions include arguments that institutional capacity, governance quality, and social resilience are more decisive determinants of HILO event outcomes than probabilistic risk analyses; and that effective preparedness depends more on anticipatory planning, scenario-based training and institutionalised memory rather than experiential learning; thus advancing HILO theory beyond event-centred and frequency-driven interpretations towards a more governance- and resilience-oriented understanding.
Open Access
Aspects of Structural Vulnerability against Tsunamis
(SLIIT, Faculty of Engineering, 2022-02-11) Dias, P
Using historical data, it is shown that tsunamis may not occur for earthquake magnitudes even up to Mw = 8. Field data can be used to arrive at generalized fragility curves for different materials of construction as functions of inundation depth. Such curves can also be integrated into vulnerability curves that can be characterized by simple negative exponential equations. It is also possible to create synthetic fragility curves generated by Monte Carlo simulation, which were found to have a reasonable fit with the empirical ones. While most simulations focus only on the structural frames in buildings, partitions can also play a significant role in damage mechanisms. There is also a role for simplified indices of either risk or robustness, based ideally on physics rather than expert opinion. Such indices can also be used to consider risk to an entire system, for example buildings, functions and backup services that are spread across adjacent coastline hospitals.
Embargo
Infill Masonry Strut Models in Reinforced Concrete Frames: Multilevel Reliability Analyses for Predicting In-Plane Responses
(John Wiley and Sons Inc, 2026-03-10) Raheem, S; Thamboo, J; Mallikarachi, C; Wijesundara, K; Dias, P
The moment-resisting reinforced concrete (RC) frame infilled with masonry walls is a common form of construction for low- to medium-rise buildings. The importance of considering the infill masonry walls (IMW) in seismic analysis is accentuated due to the interaction between infills and the surrounding frame. Several analytical IMW models have been proposed to model IMW as equivalent diagonal struts, and the appropriateness of those models has been justified through experimental and numerical calibrations. However, the reliability of those analytical models is not well substantiated. Therefore, the reliabilities of five different analytical models have been evaluated herein using the First-Order Reliability Method (FORM). The stochastic uncertainties involved in predicting the in-plane capacities of IMW-RC frames have been incorporated in the reliability analyses. Subsequently, reliabilities of IMW models have been ascertained using experimental data sets compiled at two different scales, namely (1) single story–single bay and (2) multistory IMW-RC frames. 120 experimental data sets of single story–single bay IMW-RC frames tested under in-plane loading and three multistory IMW-RC frames tested on shake-tables were used to assess the reliabilities of IMW models. The results showed that the IMW models considered have predicted the in-plane behavior of IMW-RC frames (single or multistory) to certain levels of accuracy. The predicted reliability indices (β values) of the models vary between 1.03 and 4.13. The reliabilities differ when different aspects of the predictions are being considered, such as peak or ultimate load and drift capacities of single story–single bay frames or base shear and story drift of multistory frames. Therefore, depending on the requirement (strength- or displacement-based design), the IMW models should be selected appropriately to carry out the seismic analyses of IMW-RC buildings.
Embargo
Long-term recovery from the 2004 Indian ocean tsunami in two Sri Lankan east coast municipalities
(Elsevier Ltd, 2026-01) Thamboo, J; Josiah, R; Saja, A; Salah, P; Rossetto, T; Dias, P
Sri Lanka was the second most affected country after Indonesia, in the 2004 Boxing Day Indian Ocean tsunami (IOT). A study mission was therefore carried out twenty years after the 2004 IOT to assess the recovery of the affected regions, especially in the Eastern region of Sri Lanka, focusing on two of the most affected municipalities, i.e. Kalmunai and Batticaloa. The social and infrastructure characteristics of resettlements/relocations/new settlements in the affected regions, presence of critical infrastructure, preparedness and early warning systems installed have been assessed. It was observed that similar approaches have been adopted to plan the community relocation in both of these municipalities, while the significant reemergence of residential and commercial developments in the coastal stretches of Kalmunai municipality have been noted. Exposure analyses have revealed that there are still some critical infrastructure situated in the tsunami hazard zones. It can be construed that these municipalities have recovered from the physical losses incurred, and spatial planning is in place for future developments considering the tsunami risk. Challenges and opportunities from their differing geographical contexts appear to have been judiciously handled. However, shortcomings are noted in actual implementation due to various reasons, such as limited resources, availability of funding and preference of communities to live close to their original lands. Improving the resilience of infrastructure by designing against the expected tsunami hazard and multi-hazards, regular verification of the early warning systems and evacuation procedures are emphasized to mitigate the impacts from future tsunami.
Embargo
Rapid Risk Assessment of Sri Lankan School Buildings against Tsunamis
(IEEE, 2022-10-04) Nawanandana, C; Dias, P
Rapid assessment of building vulnerability and risk is very useful, especially if based on sound engineering principles as opposed to expert opinion alone. A tsunami relative risk index (TRRI) has recently been proposed for hospital buildings based on such an approach. This study extends the concept to reinforced concrete school buildings. Two typical plan forms of school buildings were explored, each of two and three storey height. The criterion for overall structural failure was the shear capacity of columns; for scour, the number of footings undermined; and for debris impact, the shear capacity of corner columns. Of the parameters explored, the inundation depth and flow velocity were found to have the greatest influence on TRRI, while building type, building height and flow direction had much smaller influence. Debris impact was the governing risk at low inundation depths (around 1m), with scour at medium depths (around 3m) and overall structural shear failure at higher depths (around 5m).
Embargo
Resilience of masonry infilled reinforced concrete school buildings in low to moderate seismic regions: case study of Sri Lankan schools
(Springer Science and Business Media, 2025-12-08) Raheem, S; Thamboo, J; Mallikarachi, C; Wijesundara, K; Dias, P
The resilience of school buildings in high seismic regions is widely emphasised and evaluated. However such resilience in low-to-medium seismic regions are generally overlooked due to the lower probability of occurrence and low-to-medium intensities expected. Nonetheless, nominal seismic provisions should be provided for the life safety of pupils occupying these school buildings. Therefore, this study was focused on assessing the level of seismic resilience of school buildings in low-to-medium seismic regions, where the archetypal school buildings in Sri Lanka and the seismic demand in the country were taken as the case study. A framework to quantify resilience, incorporating social recovery aspects, was adopted to evaluate the seismic resilience. The resilience of the same archetypal school buildings subjected to different nominal retrofitting methods was also assessed to verify the improvement in resilience compared to un-retrofitted buildings. The epistemic and aleatory uncertainties were incorporated by using 25 different recorded seismic accelerograms and Monte-Carlo simulation of material properties (twenty sets of randomised values), respectively; with 500 combinations (aleatoric and epistemic) being analysed for each building type considered. Seismic resilience indices (RIs) obtained indicate that the school buildings with retrofitted configurations are certainly better than un-retrofitted ones, especially for higher hazard levels. Increases in the RIs are in the range of 36.6–91.2% for the highest hazard level. Sensitivity analyses were also carried out to ascertain parameter influence on RIs. The proposed nominal retrofitting solutions for these school building archetypes generate adequate resilience against the seismic hazards demarcated for the country.