Browsing by Author "Wijesundara, KK"

Now showing 1 - 7 of 7

item: Conference-Full-text
Application of continuous wavelet transformation method in estimation of model properties
(2013-11-12) Wijesundara, KK
Continuous wavelet transform (CWT) has recently emerged as a promising tool for identification of modal properties such as natural frequencies, damping ratios and mode shapes through ambient excitation measurements of structures. This paper mainly discusses the capability of CWT method to identify the modal properties accurately using a practical application in a five storey reinforced concrete structure with masonry in-fills. Natural frequencies are identified by extracting windows paralleled to the frequency axis at wavelet ridges. Damping ratios are estimated using the wavelet-based logarithmic decrement method. They are further compared with the damping ratios obtained from the random decrement (RD) method. Furthermore, the mode shapes extracted using CWT method is compared with the results of the modal analysis. Finally, a conclusion can be drawn that the CWT used for the output-only system identification of ambient excitation structures yields a good agreement with results of the RD method and the finite element models.
item: Conference-Abstract
Applications of finite element method in structural engineering
Randiligama, SMCM; Jayathilake, RGSN; Wijesundara, KK
It is a challenge for structural engineers to analyze complicated structural forms effectively using conventional analytical methods. Therefore, structural engineers prefer to use a commercial finite element software rather than using analytical methods. Many finite element software are based on the displacement based finite element method. As it is an approximate method, many drawbacks have been identified in applications in structural engineering due to misconceptions of users. Therefore, the objective of this study is to identify the limitations of using different finite elements to model structural components in buildings such as trusses, beams, slabs, foundations and their connections. To achieve the above objective, several case studies are selected and analysed using SAP2000 software. Based on the results, proper guidelines have been proposed for structural modelling. It is important to note that this study was limited to materials in linearly elastic behaviour.
item: Conference-Abstract
Finite difference approximation to wave equation to simulate sloshing of ground supported tanks for earthquake loadings
Majeed, ZZA; Baskaramaharajah, M; Wijesundara, KK
Sloshing is a liquid vibration physical phenomenon which causes when liquid storage tank is subjected to external loading. Major effects due to sloshing are higher impact pressure on tank walls and over spillage of liquid. Therefore, this study was aimed to investigate the sloshing pressure of ground supported rigid cylindrical tanks under earthquake loading. In this study, wave equation was used to convert the physical phenomenon to a mathematical model and nonlinear terms were approximated. Finite difference method was used to solve the mathematical model for the simulation of sloshing in frequency domain for 2D analysis. Input motions of earthquake loading were obtained from the average Fourier spectrum of seven earthquake records. Here, the liquid was assumed to be inviscid, incompressible and irrotational. Based on the results obtained using the generated finite difference code, the aspect ratio of the tank and frequency of ground motion affects the sloshing pressure.
item: Conference-Abstract
Numerical simulation of prediction of shear strength of reinforced concrete beam using total crack strain model
Bandara, NMSH; Bandara, IMLR; Wijesundara, KK
Despite significant experimental, numerical and analytical research, the shear behaviour of reinforced concrete members remains one of the least understood mechanisms in reinforced concrete. Due to the complexity of shear behaviour, empirical or semi-empirical analysis approaches have typically been developed and these are widely employed in codes of practice. With the development of concrete construction industry, now it is common in construction of reinforced concrete moment resisting frames that some columns supported on beams as floating columns resulting a shorter shear span to depth ratio to beams. Furthermore, longer spans as well as shorter spans are in a single frame of multi bays to get the architectural appearance. However, the beam section designed for a longer span is continued even in the shorter span of the frame resulting shorter span to depth ratio in shorter bays. In the design stage of such elements, as a consequence that less attention paid in predicting the shear capacity than moment capacity, the brittle failures mode of beams in shear is observed before the ductile failure mode in moment. This actually violates the concept of ultimate limit state design. Therefore, the objective of the research study is to predict the shear strength of reinforced concrete beams using the total crack strain constitutive model and to validate the prediction with available experimental data in the literature. Simply supported beams are modelled with Midas FEA using Total crack strain model and their results are compared with the experimental results. Then the validated model is used to predict the shear strength of beams in monolithic construction. It was concluded that when predicting the shear failure of reinforced concrete members by total crack strain model, results were very sensitive to the defined shear stress strain relationship.
item: Conference-Full-text
Seismic design of steel concentric braced frame structures using direct displacement based design approach
(2013-11-12) Wijesundara, KK
The direct displacement based design (DDBD) procedure is well developed and used for designing reinforced concrete moment resisting frame structures, wall structures and bridges. However, there is limited number of studies available on designing steel concentric braced frame (CBF) structures using DDBD approach. Therefore, it is necessary to develop a DDBD procedure for CBF structures. On this regards, this paper proposes a DDBD procedure for steel concentric braced frame structures. The proposed procedure utilises yield displacement shape derived on the basis of tensile yielding of the braces, and equivalent viscous damping equation of the system given as a function of system ductility and non-dimensional slenderness ratio by Wijesundara et al. (2011) for concentric braced steel frame structures. Finally, the performance of four steel CBF structures designed according to the proposed DDBD procedure is studied using nonlinear dynamic response of those structures. The results show that the performance of CBF structures is in good agreement with the design considerations.
item: Thesis-Full-text
Seismic vulnerability assessment of masonry infilled reinforced concrete school building frames in Sri Lanka
(2022) Sathurshan, M; Mallikarachchi, HMYC; Thamboo, JA; Wijesundara, KK
Sri Lanka is considered as an aseismic country, hence the seismic risk is not explicitly considered in the planning and designing of critical structures. However, current studies indicate that the seismic risk cannot be completely omitted when designing buildings in Sri Lanka, particularly post-disaster structures like schools and hospitals that should be designed to withstand any potential seismic action. Meanwhile, assessing the seismic risk of all the critical structures in depth across Sri Lanka might not be an easy task, and therefore, the creation of a rapid assessment method would help to effectively screen the buildings which are seismically vulnerable. Therefore, in this study, an attempt was made to assess the seismic vulnerability of school buildings in Sri Lanka in detail by incorporating possible variations and proposing an alternate Rapid Visual Screening method (RVS) for Sri Lankan conditions by incorporating FEMA P-154 guidance. In order to study the existing school building typologies, detailed structural surveys were carried out across Sri Lanka in selected school buildings. The survey revealed that school buildings in Sri Lanka can be characterised as reinforced concrete (RC) frames, infilled with unreinforced masonry walls (MI). Based on the structural configurations, mainly two building typologies were found as (1) Type 01 and (2) Type 02. Nonetheless, in terms of MI arrangements, it was observed that significant variations exist among the school buildings. Therefore, those variabilities were explicitly taken to assess the seismic performance of MI-RC school buildings. The seismic performance of the school buildings was analysed using the OpenSees (OS) finite element programme. The torsional effects and post-processing as shear capacity and stochastic material properties (concrete, steel, and masonry) from Monte-Carlo simulation were incorporated in this study. The modal analysis and non-linear static pushover analysis were carried out, in which a total of 640 building cases were analysed. The analyses of pushover (PO) and seismic fragility revealed that the Type 02 buildings exhibit significantly better performance than the Type 01 buildings. Also, the variation in MI arrangements significantly influences the seismic resistance of the buildings. In addition, the application of the proposed RVS method is effective to carry out the seismic screening method of school buildings in Sri Lanka. Keywords: School buildings, Non-linear static pushover, Seismic performance assessment, Seismic Fragility assessment and Rapid visual screening method
item: Conference-Full-text
Shear Strength of Precast Prestressed Concrete Hollow Core Slabs
(2013-11-27) Wijesundara, KK; Bolognini, D; Nascimbene, R
Since early eighties, the precast prestressed concrete hollow core slab cross sections with non-circular voids became gradually popular, first in 400 mm thick slabs, then in 500 mm thick slabs. However, it is evidenced that this type of deeper slab sections have subjected to initial web shear cracking when they are provided longer supports and resist for higher line loads acting close to supports. Therefore, the objective of this study is to review the equations specified in American Concrete Institute (ACI), Eurocode 2 (EC2) and Canadian Standards Association (CSA) specifications to evaluate the shear strength of a member having no transverse reinforcement as in the case of hollow core slabs. For this purpose, the experimental test data on hollow core slabs are collected from past experimental programs and detailed finite element analyses are performed. Based on experimental and numerical results, it could be concluded that the evaluation of shear strength by the equations specified in ACI, EC2 and CSA specifications are conservative for the slab cross sections with circular voids while ACI and EC2 predictions are not conservative for deeper slab sections with flat webs. However, CSA predictions for all types of hollow core slab sections are more conservative than ACI and EC2 predictions.