Browsing by Author "Wijesundara, K"

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Engineering surveys of Sri Lankan schools exposed to tsunami
(2023) Cels, J; Rossetto, T; Dias, P; Thamboo, J; Wijesundara, K; Baiguera, M; Del Zoppo, M
The 2004 Indian Ocean tsunami affected 5% of Sri Lanka’s schools, severely damaging 108 and destroying 74. The catastrophe highlighted the critical role of schools in providing educational continuity during community recovery. Sri Lanka has since rehabilitated and rebuilt most of the destroyed schools along the coastline. However, there is a limited understanding of current levels of school exposure to tsunami. This hampers preparedness and risk reduction interventions that can improve community and educational tsunami resilience. This paper presents a multi-disciplinary school exposure database relevant to both vulnerability and loss modelling. The repository includes data on 38 schools and 86 classroom buildings, surveyed across the coastal districts of Ampara, Batticaloa and Galle in Sri Lanka, which were heavily affected by the 2004 tsunami. A new engineering rapid visual survey tool is presented that was used to conduct the physical assessment of schools for the exposure repository. School damage mechanisms observed in past tsunami inform the survey forms, which are designed to capture information at both school compound and building levels. The tsunami engineering survey tools are universally applicable for the visual assessment of schools exposed to tsunami. The surveys show that most Sri Lankan school buildings can be classified into three building archetypes. This means that future risk assessments can be conducted considering a small number of index buildings that are based on these archetypes with differing partition arrangements and structural health conditions. The surveys also raise three significant concerns. Firstly, most schools affected by the 2004 tsunami remain in the same exposed locations without any consideration for tsunami design or strengthening provisions. Secondly, Sri Lankan schools are fragile to tsunami loading and many of the schools in the Galle district suffer from severe corrosion, which will further affect their tsunami vulnerability. Thirdly, schools do not appear prepared for tsunami, and do not have adequate tsunami warnings nor evacuation protocols in place. These observations raise the urgent need to mitigate tsunami risk, including a holistic plan for tsunami retrofitting and for interventions to improve the tsunami preparedness of schools in Sri Lanka.
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Influence of exterior infill walls on the performance of RC frames under tsunami loads: Case study of school buildings in Sri Lanka
(Elsevier, 2021) Zoppo, MD; Wijesundara, K; Rossetto, T; Dias, P; Baiguera, M; Ludovico, MD; Thamboo, J; Prota, A
This paper assesses the structural performance of RC frame buildings subjected to tsunami-induced loads, accounting for the influence of exterior masonry infill walls on the overall structural performance. Both the in-plane and out-of-plane contributions of masonry infill walls are considered in the analysis. To illustrate the importance of accounting for exterior infill walls in the response of structures to tsunami, two case study buildings are considered and modelled in 3D. The first case study is a typical two-storey school building in Sri Lanka, and the second is a modified version of this design configuration proposed in Sri Lanka after the 2004 Indian Ocean Tsunami to provide more redundancy against scour. Through these case studies, the effect of the non-uniform distribution of infill walls in the building and their failure (or “breakaway”) on building performance is considered. The building performance is characterized by a number of response parameters (i.e., first yielding, development of two hinges, and shear failure in ground floor columns). The paper shows that the in-plane behaviour of exterior infill walls increases the flexural capacity and lateral stiffness of the structure, as would be expected. However, it also shows that an assumption of non-breakaway infill walls consistently leads to premature structural failure mechanisms, associated with the concentration of drag forces on seaward columns only. The results demonstrate that a good estimation of the location and occurrence of shear failure in structural elements can only be achieved by explicitly considering the out-of-plane behaviour and failure of exterior infill walls during an incremental tsunami load analysis. Finally, the Froude number assumed for the analysis is seen to strongly affect the performance of both structural and non-structural components, highlighting the importance of choosing realistic tsunami properties to perform a reliable capacity assessment.
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Rapid seismic visual screen method for masonry infilled reinforced concrete framed buildings: Application to typical Sri Lankan school buildings
(Elsevier, 2023) Sathurshan, M; Thamboo, J; Mallikarachchi, C; Wijesundara, K; Dias, P
Seismic rapid visual screening (RVS) methods are used when a large stock of structures is to be evaluated for seismic risk. Although several RVS methods are available, applications of those methods to appraise the seismic risk of reinforced concrete framed (RC) buildings with irregularities in masonry infill walls (MIWs) are limited. School buildings constructed in Sri Lanka are built with certain RC frame typologies; however, they vary in terms of MIW arrangements used. Therefore, a new RVS method is proposed to evaluate the seismic risk of masonry infilled reinforced concrete (RC-MIW) buildings, particularly for the typical RC-MIW school buildings in Sri Lanka. The proposed RVS method incorporates irregularities of MIW arrangements in the typical RC buildings, the attributes of which are not well accounted in the available RVS methods. The vulnerability attributes such as short column and soft storey effects, arise due to the irregularities of MIW arrangements in the buildings, are explicitly incorporated in the proposed RVS method. The FEMA P-154 guidelines were followed to develop basic scores, score modifiers and minimum scores in the proposed RVS method. For that purpose, seismic performances of RC-MIW schools with various MIW irregularities were numerically analysed. The effectiveness of the proposed RVS method is compared with the existing RVS methods to evaluate the seismic risk of typical RC-MIW school buildings in Sri Lanka. It is shown that the proposed RVS method is capable of capturing the seismic risks of such typical RC-MIW Sri Lankan school buildings
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Seismic fragility of lightly reinforced concrete school building typologies with different masonry infill configurations
(Elsevier, 2023) Sathurshan, M; Thamboo, J; Mallikarachchi, C; Wijesundara, K
This paper presents the outcome of a research study conducted to establish seismic fragilities of school building typologies in Sri Lanka. The school buildings in Sri Lanka can be characterised as lightly reinforced concrete (RC) buildings, infilled with masonry walls (IMW). However, they are categorised into two typologies based on the structural layouts used (1) Type 1 (T01) and (2) Type 2 (T02). Although, the school buildings can be grouped into two typologies, variabilities in terms IMW configurations and their arrangements are observed among those school buildings. These variabilities in terms of building typologies as well as IMW arrangements were taken to establish seismic fragility curves. The seismic performances of the school buildings were numerically assessed, where in total 640 building cases were analysed by varying typologies, IMW configurations, and stochastic material properties. Since, the RC school buildings are lightly reinforced, a simplified, yet a novel approach was followed to account the shear failure of RC columns under seismic actions. Then, four damage thresholds were established (slight, moderate, severe and collapse) and the corresponding fragility curves are presented in terms of school building typologies considered. Finally, based on the fragility curves, damage probability matrices of the building typologies were established.