Reinforced concrete block masonry (RCBM) is commonly used in seismic regions instead of unreinforced masonry due to its better load resistance and ductility characteristics. The RCBM assemblages are conventionally provided with single layer of reinforcement at the centre of the walls. Due to this arrangement, providing confinement and lateral restraint to the vertical reinforcement bars in RCBM is challenging. In this study, twenty-one RCBM panels were constructed and tested under cyclic compression loading to evaluate the buckling characteristics of vertical reinforcement bars and effectiveness of different lateral ties configurations. The grout properties were also varied to study its influence on the cyclic compression behaviour of RCBM panels. The outcomes of the testing revealed that the single layer of vertical bars restrained with or without lateral ties did not exhibit any axial buckling under cyclic compression loading, leading to an inference that the surrounding grout has provided adequate restraint to these vertical bars. Using the experimental data, cyclic stress-strain curves and associated engineering parameters were derived for the tested RCBM panels.

Compressive strength of grouted concrete masonry is an important parameter to design reinforced/grouted concrete masonry walls. The design standards stipulate two methods to determine the compressive strength of masonry (1) using tabulated unit strength and mortar type, and (2) testing representative masonry prisms. The compressive strength prediction of grouted concrete masonry is influenced by compressive strength values of hollow blocks, mortar and grout, and their geometries. Therefore, a multi-level approach was employed in this study to improve the existing unit strength correlations of the standards for more reliable prediction of compressive strengths of grouted concrete masonry. The existing methods to determine the compressive strength of grouted masonry were critically appraised and a database of compression tests of grouted concrete masonry prisms/wallettes was developed. This database was then used to evaluate the correlations between the compressive strengths of block, mortar, grout and masonry. The applicability of existing unit strength correlations from the design standards and literature were assessed and their relevancy and limitations are highlighted. Subsequently, updated sets of unit strength correlations are proposed in this study, through statistical reliability analyses of the predictions against the experimental results included in the database. The proposed unit strength correlations were classified according to the mortar type/strengths (≤ 10 MPa and > 10 MPa). It has been shown that the new correlations are more structurally reliable than the existing unit strength correlations through comparing the 95th percentile error values.

Seismic retrofitting solutions for reinforced concrete (RC) school building types in high-seismic regions are extensively reported in the state-of-the-art. Conversely, limited studies have focused on the extent of retrofitting needed for RC school buildings in low- to moderate-seismic regions. To explore this aspect, seismic retrofitting options for RC school buildings in Sri Lanka are investigated. Three retrofitting options are examined: (1) adding/altering masonry infill walls (MI walls) to reduce irregularity in buildings, (2) RC jacketing of columns and (3) a combination of adding/altering MI walls and RC jacketing. These retrofit options are applied to a common typology of Sri Lankan MI-RC school buildings, considering two and three storey height variations. A simplified numerical modelling approach that accounts for the contribution of MIs, the shear failure of RC column and torsional effects is adopted to analyse the performance of the school buildings with and without retrofit. Based on the analyses, three damage states are defined: damage limitation (DL), significant damage (SD) and near collapse (NC). Finally, a multi-criteria decision making (MCDM) method is used to determine the optimal retrofitting option for the considered school building typology, considering engineering and economic parameters. The optimal retrofit solution for the three-storey MI-RC school building is found to be jacketing of ground floor columns. Conversely, for the two-storey MI-RC school building, alteration of infill walls (MI walls) is deemed optimal. Finally, a sensitivity analysis is carried out on the MCDM method.

Resilience of systems to natural hazards has become an interesting concept in civil engineering and it is based on the determination of the losses due to the impacts of natural hazards. In the last decades, many contributions have focused on the assessment of losses that may occur at the time of the event, as generally assumed for earthquakes. However, this assumption may be incorrect when the interval between the time of occurrence and the time when the system functionality reaches the minimum value needs to be considered. This paper aims to propose a novel method to quantify this interval, which is called disruption time, by proposing a novel formulation of the loss model based on infrastructure redundancy. The proposed method was herein applied to a case study that considers landslides in Sri Lanka. The main goal of the paper is to propose a formulation that can be implemented in a more comprehensive framework to calculate more realistically the resilience of systems to natural hazards.

In-plane behaviour of reinforced concrete masonry walls (RCMW) is complex, as the shear resisting mechanism is influenced by the characteristics of concrete masonry assemblage, steel reinforcement (vertical and horizontal), and internal grouting used. Rational design guidelines are given in the masonry design standards to determine the in-plane capacities of RCMWs. However, the structural reliability of design guidelines provided in the standards, particularly in the Australian masonry standards (AS 3700, 2018) is not well examined. Therefore, the reliability of in-plane shear design provisions of AS 3700 (2018) has been evaluated in this study. An experimental database of RCMWs was developed for this purpose; subsequently, First-Order reliability method was used to verify the reliability of in-plane shear design. The reliability analysis revealed that the existing design provisions in AS 3700 (2018) are marginally failing to satisfy the target reliability index of 4.0 set in this study, however further sensitivity analyses are needed to verify appropriate capacity reduction factor for the design.

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.

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.

Critical infrastructures such as transportation, power, telecommunication, water supply, and hospitals play a vital role in effectively managing post-disaster responses. The resilience of critical infrastructures should be incorporated in the planning and designing phase based on the risk assessment in a particular geographic area. However, the framework to assess critical infrastructure resilience (CIR) is variably conceptualised. Therefore, the objective of this study was to critically appraise the existing CIR assessment frameworks developed since the adoption of the Sendai Framework in 2015 with the hazard focus on earthquakes. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) method was used for the selection of the 24 most relevant studies, and these were analysed to delineate existing frameworks, models, and concepts. The study found that there are wide-ranging disparities among the existing frameworks to assess the infrastructure resilience, and it has become a key challenge to prioritise resilience-based investment in the infrastructure sector. Furthermore, key attributes such as performance indicators, emergency aspects, and damage assessment need to be considered for different disaster phases—ex-ante, during, and ex-post—to improve the long-term resilience of critical infrastructure. Subsequently, an integrated and adaptable infrastructure resilience assessment framework is proposed for proper critical infrastructure planning and resilience-based investment decision making.

The suitability of untreated rice husk ash (URHA) as a supplementary to the ordinary Portland cement (OPC) and fine aggregates (FA) in high strength self-compacting concrete (SCC) was investigated in terms of mechanical properties as well as environmental impact assessments (EIA). In total, nine SCC mixes were prepared and investigated with various levels of URHA replacements to OPC and FA. Initially, the fresh and hardened properties of URHA incorporated SCC were determined. Further, EIAs were carried out considering eighteen different environmental impact indices for the optimum URHA incorporated SCC mixes to determine the most appropriate mix in terms of mechanical properties along with their environmental impacts. The experimental results reveal, URHA in the range of 10–15% can be used without compromising the fresh and hardened properties of SCC. The results of the EIAs are presented and discussed in terms of compressive strength to environmental indices ratios to normalise the comparison. The EIAs disclose that even through some of the mixes provide better performance in terms of certain environmental impact categories; especially CO2 emission, water pollution (fresh and marine) and ecotoxicity, their strength to environmental impact ratios are relatively low. Thus, it is recommended to select the optimum mix design of URHA incorporated high strength SCC in terms of mechanical properties and as well as EIA.