Browsing by Author "Dumaru, Rakesh"
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- Cost-benefit analysis of retrofitted non-engineered and engineered buildings in Nepal using probabilistic approachPublication . Dumaru, Rakesh; Rodrigues, Hugo; Varum, HumbertoThe applicability and suitability of the retrofit techniques adopted to enhance the seismic performance of the existing pre-engineered and non-engineered buildings were investigated through probabilistic cost-benefit analysis. The primary objective of the study aims to support, motivate, and encourage the decision makers, owners, investors, and concerned stakeholders to invest money for retrofitting of existing seismic deficient buildings. The study also aims to identify the best retrofit technique through the comparison of cost-benefit ratio. For this, the study investigates four existing buildings, representing two buildings for each non-engineered and pre-engineered design approaches. The selected non-engineered buildings were built in late 90's and pre-engineered buildings between late 90's to 2015. After rigorous analysis, it was revealed that the unexpected losses (in terms of monetary values) could be minimized by large extents, i.e. (2-11) times for non-engineered and (3-50) times for engineered buildings with the intervention of retrofit strategies. The attained expected annual loss for as-built and retrofit buildings evaluated through discrete distribution as a function of two intensity measures reveals that the maximum expected annual loss ensues between 0.1g and 0.2 g PGA for non-engineered buildings and below 0.1 g PGA for pre-engineered buildings. A higher cost-benefit ratio value can be attained if the service life of the building structure is increased or decreased discount rate. For most of the studied buildings, buildings retrofitted with RC shear wall found to be the most economically viable, and followed by steel bracing and jacketing, respectively.
- Seismic fragility assessment of revised MRT buildings considering typical construction changesPublication . Dumaru, Rakesh; Rodrigues, Hugo; Varum, HumbertoThe present study investigates the vulnerability assessment of the prototype revised Mandatory Rule of Thumb (MRT) buildings initially designed and detailed for three storeys bare frame building; later modified through variable number of storeys (three, four, and five) and different arrangement of infill walls (bare frame, soft-storey, irregular infilled, and fully infilled). The application of infill walls increases the fundamental frequencies, stiffness, and maximum strength capacity, but reduces the deformation capability than the bare frame building. The vulnerability was also reduced through infill walls, where the probability of exceeding partial-collapse and collapse damage reduced by 80% and 50%, respectively. Furthermore, the increased in storeys (three to five) also increases the failure probability, such that partial-collapse and collapse for fully infilled increases by almost 55% and 80%, respectively. All obtained results and discussions concluded that the structural sections and details assigned for MRT building is not sufficient if considered as bare frame and soft-storey. And increase in number of storeys causes building highly vulnerable although the infill walls were considered.
- Seismic performance of buildings in nepal after the gorkha earthquakePublication . Varum, Humberto; Dumaru, Rakesh; Furtado, André; Barbosa, André R.; Gautam, Dipendra; Rodrigues, HugoFollowing the strong earthquake of Gorkha, Nepal, on April 25, 2015, and a strong aftershock on May 12, a field reconnaissance of structural damage and structural collapses was performed around the affected areas, particularly in the region around the capital Kathmandu. The main goal was to develop detailed descriptions of the seismic performance of the Nepalese building stock. To achieve this goal, the field reconnaissance survey was carried out after the two main seismic events. In this chapter, a summary of the survey is provided, focusing on both recent reinforced concrete (RC) buildings and older substandard constructions. In addition, detailed descriptions of the observed damage to urban masonry building stock and rural vernacular constructions are provided. This chapter presents evidence from the field that justifies the observed seismic performance and enables the depiction of damage modes, which could be insightful regarding future efforts to develop earthquake-resistant constructions and strategies to improve the seismic behavior around the world.
- Seismic Vulnerability and Parametric Study on a Bare Frame Building in NepalPublication . Dumaru, Rakesh; Pinheiro Rodrigues, Hugo Filipe; Furtado, André; Varum, HumbertoThe influence of the infill masonry walls in the structural response of reinforced concrete (RC) structures when subjected to earthquakes is not considered in Nepal National Building code and Indian Standard code. Field observations carried out after the 25th April Gorkha earthquake in Nepal reinforce the importance of the infill walls, namely, through the significant increasing of the structural stiffness and by the possibility of introducing unexpected mechanisms that can cause extensive damages or even the collapse of the structure. This article focuses on the study of an existing bare frame, representative of the Nepalese RC buildings, which was modeled and calibrated with data results collected from ambient vibration tests. Initially, a parametric study was conducted with the aim of evaluating the influence of parameters, such as concrete strength and elasticity modulus, slab thickness, and columns cross section in the natural frequencies of the building. The influence of the infill masonry walls in the structural response was evaluated through the modeling of three different numerical models with different disposition of the infill panels from the calibrated existing structure. The seismic vulnerability assessment was performed through non-linear static pushover and dynamic analysis. The results will be presented and discussed in terms of base maximum inter-storey drifts and maximum base shear.