Browsing by Author "Nanayakkara, KIU"

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item: Article-Full-text
Fragility curves for structures under tsunami loading
(Springer Netherlands, 2016) Nanayakkara, KIU; Dias, WPS
Susceptibility to structural damage can be characterized by a fragility curve, which is expressed as a normal or lognormal cumulative distribution of the conditional probabilities of reaching or exceeding a particular damage state, for given values of the demand parameter. Such curves have been produced for a variety of damage states in different categories of buildings exposed to tsunami loading in different parts of the world, with the demand parameter taken as inundation depth. Harmonization was sought across these studies with respect to the median inundation depth. Three categories of single-storey buildings were identified based on construction material, namely reinforced concrete, masonry and timber. The median inundation depths for the complete damage state decreased from reinforced concrete (5.4–7.3 m) through masonry (2.3–2.5 m) to timber (*1.6 m) structures. The fairly narrow ranges above represent a number of different studies and indicate that a common family of curves or ‘‘bands’’ can be arrived at. Such ranges were identified for other partial damage states too. Our genuinely original contribution is a probabilistic model that was developed using a Monte Carlo simulation to produce synthetic fragility functions for masonry and reinforced concrete structures under tsunami loading. The probabilistic model consisted of a geometric model that captured the geometrical and wall-type variations of the building lot, a loading function and a set of failure criteria, all of which required appropriate simplifying assumptions. The resulting synthetic fragility curves matched the fragility curves based on observed tsunami damage for the complete collapse damage state reasonably well.
item:
Fragility curves for tsunami loading
(2015-05-27) Dias, WPS; Nanayakkara, KIU
Vulnerability to structural damage can be characterized by a fragility curve, which is expressed as the conditional probability of reaching or exceeding a particular damage state, expressed by a lognormal cumulative probability distribution, given a certain value of the demand parameter. Such curves have been produced for a variety of damage states in different categories of buildings that have been subjected to tsunami loading in different parts of the world, with the demand parameter taken as inundation depth. Harmonization was sought across these studies with respect to the median inundation depths. Three categories of buildings were identified based on construction material; namely reinforced concrete, masonry and timber. The median inundation depths for the complete damage state decreased from reinforced concrete (5.4-7.3m) through masonry (2.3-2.5m) to timber (~1.6m) structures. The steeper fragility curves for the weaker structures suggest that they display a single failure mode, probably sliding. The fairly narrow ranges above represent a number of different studies and indicate that a common family of curves can be used in damage assessments worldwide. Such ranges were identified for two partial damage states too.
item: Conference-Full-text
Mud-concrete slab system for sustainable construction
(Faculty of Architecture Research Unit (FARU), 2021-12-03) Jayasinghe, RR; Nanayakkara, KIU; Arooz, FR; Halwatura, RU
The urgency of global climate emergency has drawn significant attention to the building industry over the last few years. Today, the building sector is responsible for 38% of the world’s greenhouse gas emissions, according to UNEP. 60% -70% of embodied carbon in a conventional column-beam reinforced concrete building is in its floor system. This paper discusses the possibility of constructing an earthen slab system using mud-concrete. It investigates a doubly curved shell structure, working predominantly in compression, to fulfil both environmental and economical demands in the construction industry; reducing the cost and labour expenses nearly 50% compared with that of traditional reinforced concrete slab systems. A 1 m x 1 m prototype mud-concrete slab was constructed to check the potential for modular construction with a square footprint. Poured mud-concrete shell of 50 mm thickness is the primary structural component, while a non-structural mud-concrete filling to a horizontal level 50 mm from apex was used to create a usable floor surface. Masonry mould method was used as the formwork system for the construction considering its cost effectiveness and ease of construction.
item: SRC-Report
Structural behavior of the doubly curved shell structure using mud-concrete (MC)
(2020) Jayasinghe, RR; Halwatura, RU; Nanayakkara, KIU; Arooz, R
Mud-Concrete is a concrete material which uses soil as its primary binding material. Mud-concrete deviates from typical concrete mixture by replacing sand and granite coarse aggregates with a graded soil. When mud-concrete is used as a walling material, initial cost and operational cost is comparatively low compared with that of cement brick or burned bricks walls. The environmental impact of the mud concrete is significantly low compared with other building materials. This paper presents the possibility of developing a doubly curved earthen slab system using mud-concrete to achieve demands of economy, environment and aesthetics. The work presented in this paper is broadly aimed towards developing an earthen slab system for housing in Sri Lanka. The main objectives of this research are to; • Propose a feasible structural system for an earthen slab system • Develop a practical construction sequence for the proposed slab system • Evaluate economic and environmental viability of the proposed slab system To fulfil both environmental and economical demands in the construction industry; reducing the cost and labour expenses nearly 50% compared with that of traditional reinforced concrete slab systems. A I m x I m prototype mud-concrete slab was constructed to check the potential for modular construction with a square footprint. Poured mud-concrete shell of 50 mm thickness is the primary structural component, while a non-structural mud-concrete filling to a horizontal/eve/ 50 mm from apex was used to create a usable floor surface. Masonry mould method was used as the form work system for the construction considering its cost effectiveness and ease of construction.