Browsing by Author "Lewangamage, CS"

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item: Conference-Extended-Abstract
A Study on present situation, construction procedures, sensitivity towards the fill height and possible failure scenarios of corrugated soil-steel bridges using PLAXIS
(2010) Gunathilaka, WMS; Shanaka, KBK; Lewangamage, CS; Jayasinghe, MTR
The Southern Highway Project introduced the technology of using Soil-Steel Bridges to Sri Lankan construction industry for the first time. Because of the fact that the technology is still new and less familiar, therefore, it is very important to look at the suitability of the Soil-Steel structures in the Sri Lankan context. The corrugated Sail-Steel Bridges hare been used as underpass and drainage structures in the Southern Highway Project. Corrosion of the metal structure highly depends on the soil types and the ground water conditions of the region where the structure is to be constructed. Already constructed soil-steel structures were closely examined in-order to collect the information on corrosion The loading and unloading procedures given in the guidelines are questionable and there is a need to establish proper guidelines for loading and unloading process for the safety during construction and while the structure is functioning. The actual construction sequence followed in the soil-steel structure construction was modelled using Finite Element Computer Modelling and the stresses and deformations of the structure were obtained. The stresses of the steel structure under different fill heights and the HA loading was also modelled using Unite element computer modelling: Using FEM model, possible failure scenarios n ere identified.
item: Conference-Extended-Abstract
A study on structural behaviour of corrugated soil-steel bridge structure (long span) in Southern highway for different depth of soil cover
(2010) Shanaka, KBK; Gunathilaka, WAS; Lewangamage, CS; Jayasinghe, MTR
Corrugated Soil-Steel Bridges have been used as underpass and drainage structures in the Southern Highway Project. This design and construction process is novel to the Sri Lankan context. The Ring Compression theory, which is based on two dimensional plain strain idealizations, has been used in the design of the structures. However due to the presence of the ring walls, the effect of uneven loading in the longitudinal direction due to load combinations of HA and HB loads, these assumptions are in question. The maximum and minimum depths of soil covers have been defined according to the results obtained by the Ring Compression theory. The effects of depth of cover in Soil-Steel bridges were evaluated using finite element computer modelling according to the US 5400 The original design results and the results of finite element analysis were compared. The structural stability of the existing bridges with respect to the different fill heights was determined. The Ring Compression and Finite Element Methods results are compatible for higher depth of covers The stresses of the steel structure for defined maximum and minimum depth of cover, at the ultimate limit state conditions are less than the crushing strength of the steel. Butt further buckling analysis should be considered because the corrugated steel structure vulnerable to buckling failure
item: Conference-Abstract
Advanced structural health monitoring system for bridges in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, Sri Lanka., 2021-11) Rajapaksha, D; Lewangamage, CS; Vishnu, P; Hettiarachchi, P
Bridges are a critical component of the transportation infrastructure system because a failure in a particular bridge may affect a wide range of areas adversely. Also, the intensity and frequency of natural shocks and stresses that can affect the performance of the bridges, such as earthquakes, floods, and tsunami have rapidly increased during the past few years, which increases the vulnerability of bridges by combining with aging. Hence it is crucial to monitor the current health of bridges so that devastating failures could be avoided by following a structured maintenance program. In that case, advanced Structural Health Monitoring (SHM) systems that are rapidly developing for past decades with the development of IoT, have been used for bridge monitoring purposes in other countries. However, the condition of the bridge monitoring system is not so developed in Sri Lanka yet. Also, the commonly used methods such as visual inspection and traditional tethered methods are incorporated with some drawbacks. Therefore, the requirement for an advanced SHM system for bridge monitoring in Sri Lanka has been raised. In this study, a low-cost wireless synchronous sensor network developed by the Department of Civil Engineering, University of Moratuwa was applied and monitored on a bridge as a pioneering step of implementing an advanced online SHM system for bridges in Sri Lanka. Here, the synchronous vibration time history of the structure was measured using the sensor network with high accuracy. After a filtration process, the data was applied for calculating the experimental modal parameters such as natural frequencies and mode shapes using Fast Fourier Transformation (FFT) and peak picking method. Finally, the experimental results were compared with the results of Finite Element Analysis (FEA) through the Modal Assurance Criteria (MAC). The MAC analysis showed values greater than 0.84 for the first four modes shapes which indicates a good correlation with the experimental results and the FEA results. Furthermore, the measured acceleration data was used to assess the serviceability state of the bridge as well.
item: Conference-Abstract
An experimental study on flexural strengthening of reinforced concrete beams using externally bonded FRP
(2010) Perera, PDR; Jayasinghe, MTR; Lewangamage, CS
The strengthening technique of Ffiber Reinforced Polymer (FRP) bonding externally is now established as a simple and convenient repair method for enhancing the flexural performance of concrete beams. In order to increase the stiffness and the flexural carrying capacity of beams under specific service conditions, FRP bonding has become very effective method. This paper presents the structural performances of FRP bonded beams. Experiment was conducted to find out the flexural strength increment which can he obtained by bonding F RP externally and identified the deflection pattern am! failure modes.
item: Conference-Abstract
Analysis of four leg telecommunication towers for seismic loading using response spectrum method
Gunathilaka, AMLN; Lewangamage, CS; Jayasinghe, MTR
Telecommunication towers are common sight even in very remote areas of Sri Lanka with the revolutionary development in this sector during last few decades. These towers play a vital role especially in wireless communication. Hence, a failure of such tower in a disaster like an earthquake is a major concern since it hampers communication needs in rescue operations during the disaster. Further, since these are usually tall structures, failure of tower may itself cause a significant damage. However, almost all existing telecommunication towers in this country have not been checked for seismic loading since Sri Lanka was considered as a country free from earthquakes until recently. But, now most of the structural engineers consider seismic effects for their designs of important structure such as high rise buildings, dams, etc. Still, this practice has not been implemented regarding telecommunication tower designs. This paper discuss the structural performance of selected existing four legged Greenfield towers which were analyzed under seismic loadings using Response Spectrum method given in ANSI/TIA-222-G. Approach of analysis and comparison of analytical results under different seismic analytical techniques as well as with results under wind loading are presented in this paper.
item: Article-Abstract
An Approach to seismic analysis of (Engineered) Buildings in Sri Lanka
Lewangamage, CS; Kularathna, HGSR
Even though, Sri Lanka was believed to have no seismic threats, it is now realized that Sri Lanka can no longer be considered as a country safe from seismic threats following the recent events that occurred in and around the island. The present study is therefore aimed at providing guidance on suitable analysis procedure for buildings in Sri Lanka where the seismic consideration is explicitly warranted for a structure. The proposed guidelines in this study are based on Euro Code 8 (EN 1998-1: 2004): “Design of Structures for Earthquake Resistance”. Euro Code 8 was selected for this purpose as it allows national choices in defining seismic characteristics such as peak ground accelerations, response spectra, etc. in seismic design procedure. This study mainly focuses on these national choices and suitable values are proposed and discussed, depending on the available seismic data in Sri Lanka. Whenever there is a lack of data, suitable approaches are suggested comparing similar seismic codes such as IS 1893-1: 2002 and AS 1170.4: 2007. Finally, two case studies are carried out in order to illustrate how the developed guidelines can be used in the seismic design procedure of buildings particularly in Sri Lanka.
item: Conference-Full-text
Behavior of reinforced concrete columns confined with CFRP (Carbon fibre reinforced polymer)
(2013-11-11) Rankoth, CK; Lewangamage, CS; Jayasinghe, MTR
In modern world the retrofitting of structures is promoted rather than demolishing and reconstruction of deteriorated structures.Attentionhas also given to increase the load carrying capacity of existing structures to increase the usage capacity or to change the intended usage. Retrofitting of structures using Carbon Fibre Reinforced Polymer materials is accepted as a sustainable and effective method comparatively to most of other well-known methods like steel plate bonding and external post tensioning. This paper presents anexperimental study carried out to understand the effectiveness of external CFRP confinement for square reinforced concrete columns and validation of ananalytical stress strain model,using experimental results. Four reinforced concrete columns, one control specimen without external confinement and three specimens with full external confinement were tested for compression to monitor the strength gain against axial loading. The results showed a considerable increase of the axial strength, about 50% and improved ductility, up to about 20% for the columns with external confinement. The analyticalstress stain modelpresented anacceptable agreement with obtained experimental results.
item: Thesis-Abstract
Behaviour of reinforced concrete columns confined with CFRP
(2015-02-08) Rankoth, CK; Lewangamage, CS
In worldwide reinforced concrete is the major construction material used for buildings and general structures. The requirement of strengthening of reinforced concrete structures may emerge not only due to timed degradation but also due to various reasons like construction faults, increased loads and changes in utilization purpose etc. Rehabilitation of reinforced concrete structures using Carbon Fiber Reinforced Polymer materials is recognized as a very effective retrofitting method in all over the world and provides advantages like durability, water proofing capability, ease of application due to less weight etc. CFRP materials can be used for strengthening of almost all the components of a RC structure like beams, slabs columns, beam column joints etc. Among these, strengthening of columns should be done with greater care because of failure of a major column may lead to failure of complete structure. In this research attention was given to study the behavior of short RC columns strengthened with CFRP composites. The current practice on strengthening reinforced concrete columns with external CFRP jacketing is to provide full confinement all over the column with less care on the required strength increment. As CFRP is a costly material providing partial confinement where necessary may be a viable option for cost reduction, rather than providing full confinement. The numbers of studies that have been carried out on partially confined rectangular columns are relatively less and only some available design guidelines provide design process for providing partial confinement using CFRP. It is obvious that the best way to identify the structural behavior is through a thorough experimental study. But behaviour CFRP confined columns depends on many parameters such as, failure stresses and strains of CFRP jacket, jacket thickness, number of CFRP layers, percentage of steel reinforcement etc. Studying of all those parameters experimentally is not a cost effective option as the structural form and load sharing will be specific for a single case. Finite element modeling is the best way to study a criterion that depends on this kind of large number of input variables. But still the finite element modeling of confined concrete column is in evolving stage and there is no globally accepted finite element model to predict the behavior of CFRP confined columns. The experimental and theoretical studies available in Sri Lanka regarding CFRP strengthening are next to zero. When design guidelines available for CFRP design are considered, there are various design codes for different countries like USA, Japan, Canada and Switzerland. Under this background designers and contractors in Sri Lanka are in a fuzz regarding which design guideline system will provide adequate safety factor while maintain the feasibility of the project Three major objectives were setup under this study. An experimental study was carried out to investigate the ductility and ultimate load carrying capacity increment of both reinforced and unreinforced square columns due to full confinement and to understand the behaviour of reinforced concrete columns with partial confinement. Second objective was to develop a finite element model using ANSYS software to simulate the behavior of confined concrete columns and study an analytical model capable of predicting stress strain behaviour and ultimate load carrying capacity of CFRP confined columns. Also a study was carried out about different available guidelines and attempt was made to identify the factor of safety provided for each design methods against obtained experimental results. Under experimental study total number of 17 columns with dimensions of 150  150  350 mm was tested. The test specimens consist of 6 plain concrete columns with 3 control specimens and 3 fully confined columns. 11 reinforced concrete columns with 3 control specimens, 3 columns with full confinement and 5 columns with partial confinement. Two wrapping patterns were used for partially confined columns, three specimens with two sets of 75mm width wraps at top and bottom of the column and two specimens with three 50mm wraps at top bottom and middle of the column. The volumetric ratio of CFRP for partially confined column specimens were kept constant to study the effect of wrapping pattern and jacket location for strength and ductility increment. All the columns were tested for axial compression. Under analytical study the model proposed by “Harajli” was studied. CFRP design specifications published by American Concrete Institute (ACI) and International Federation for structural concrete (fib), Switzerland were reviewed against the experimental results to identify the factor of safety against ultimate load carrying capacity estimation. The results of experimental study revealed that any kind of external confinement, full or partial with external CFRP jacketing is capable of increasing the load carrying capacity and ductility of a column to a considerable extent. The load carrying capacity increment for fully wrapped reinforced concrete columns were 100% while for plain concrete columns it was 47%. When load carrying capacity increment of partially confined columns considered, the specimens with two 75mm wraps showed a capacity increment of 59% while specimens with three 50mm wraps showed an increment of 83%. From above observation it was realized that for partially confined columns not only the volumetric ratio of the CFRP wrapping but also the wrapping pattern have a large influence on load carrying capacity. When ductility increment is considered it was observed that ductility increment is proportional to the strength increment, more the strength increment more the ductility increment. The finite element model based on Extended Drucker Prager plasticity model for concrete showed a good prediction of horizontal strain vs. vertical stress variation for fully confined models and could predict the failure load with an error of 1.8% hence the developed finite element model can be treated as an acceptable model. The analytical model proposed by Harajli showed a considerable variation of stress strain behaviour prediction but the ultimate failure load prediction according to above analytical model showed a good agreement with experimental failure loads with an error of 1.1% The estimated failure loads from ACI guidelines showed a factor of safety of 3.5 against experimental results while fib guidelines showed a factor of safety of 1.6 for fully confined reinforced concrete specimens. Only fib guidelines gives a method to estimate failure load of partially confined columns and showed a factor of safety of 2 for specimens with 75mm wrappings and 2.1 for specimens with 50mm wrappings. As the current practice is to provide full confinement for columns and two guidelines shows a considerable variation of factor of safety the designers are advised to select the suitable design system based on the risk level associated with a specific project. Keywords: CFRP, reinforced concrete columns, partial confinement, strength, ductility, finite element modeling
item: Thesis-Abstract
Behaviour of reinforced concrete flexural members strengthened with externally bonded carbon fiber reinforced polymers
(2015-01-06) Jayanath, BCR; Lewangamage, CS
Reinforced concrete structures often have to face modification and improvement of their performance during their service life. The main contributing factors are change in their use, new design standards, design errors, deterioration due to corrosion in the steel caused by exposure to an aggressive environment and accident events such as earthquakes. In such circumstances there are two possible solutions: replacement or retrofitting. It is desirable to repair and reuse reinforced concrete structures from the point of view of sustainability. Strengthening may also be needed to prolong the life of deteriorated members. Use of Fiber reinforced polymers (FRP) can be considered as one of efficient technique for such strengthening of reinforced concrete elements. The previous research studies show the lack of field scale experimental studies and analytical studies such as finite element models (FEM) have been carried out to complete understanding of strengthening reinforced concrete structural element using FRP with respect to failure behaviour, strength enhancement, ductility assessment and deflection behaviour. Further, no studies have been carried out in Sri Lankan context to understand behaviour of FRP strengthening reinforced concrete systems and no technical data is available. This has led to less confidence of using this technique by practicing engineers in Sri Lanka. Various design guidelines shows the different approaches to design FRP strengthening system, especially the prediction of failure strains. This has led to poor understanding of safety against ultimate failure and confidence of using the existing guidelines for the designs. This study covers the above aspects with respect to strengthening of reinforced concrete flexural elements using carbon fiber reinforced polymers (CFRP). A comprehensive experimental program has been carried out using field scale flexural strengthened reinforced concrete elements (beams and slabs) to understand failure behaviour, flexural strength enhancement, ductility assessment and deflection behaviour. A nonlinear finite element model has been developed to simulate complete experimental behaviour of CFRP strengthened reinforced concrete flexural system till failure. ACI and Japanese method of designing flexural system have been evaluated and checked with the experimental results. It was observed that CFRP strengthened beams with u-wrapping showed about 60% load carrying capacity improvement with respect to control specimens It was about 140% load carrying capacity increment for normal strengthened R6 slabs (reinforced with 6mm diameter mild steel) with CFRP at soffits. The load carrying capacity increment for T10 slabs (reinforced with 10 mm diameter tor steel) with CFRP was about 70% with normal wrap of CFRP. It was clear that gain in flexural enhancement has highly depend on the reinforcement ratio and the wrapping method of CFRP. It was observed from the experimental study, a reduction in ductility of both beams and slabs strengthened with CFRP. This reduction has considerably depended on the reinforcement ratio of the elements. However, the elements still have sufficient ductility against failure. The only failure mode observed in beam failure can be classified as cover separation with simultaneous deboning of CFRP laminates. The failure has initiated by cracks formed in the reinforced concrete elements during loading. The failure mode in the slabs is due to peeling of CFRP laminates from the slab soffit known as debonding failure. The measured strain values of CFRP for beams specimen are almost constant at failure. It was about 3570 μ. The slabs are also constant with 2540μ which is independent on the reinforcement ratio. This indicates the failure is governed by the FRP strain at failure. The difference in FRP strain at failure in beams and slabs are due to wrapping method of the laminates. It was observed that tested specimen with flexural enhancement still satisfied the serviceability deflection criterion (span/300) for reinforced concrete elements. Hence, these flexural enhancement designs for beams and slabs are governed by the ultimate limit state failure. ANSYS based non-linear finite element model has been developed to simulate experimental behaviour of FRP strengthened flexural system. It has good agreement with experimental results. The calibrated material parameters has presented in this dissertation. ACI and Japanese method of designs of flexural system are governed by the prediction of debonding strain values by empirical based formulae. It was observed that prediction of debonding strain by ACI method overestimate the value compared to Japanese method. On the other hand, it was observed that Japanese method prediction is more close to experimental CFRP strain observed at the failure in this experimental program. However, ultimate moment of resistant calculation using conventional section analysis (this method is used in both codes) indicates that both ACI and Japanese method have adequate safety margin against ultimate failure of beams whereas ACI method does not show the adequate safety margin for the slabs but Japanese method does. However, Japanese method has high safety margin against beams and less value of the slabs. This difference in strains, highly depending on the failure behaviour which is directly related to the wrapping method, has to be accounted in the prediction of the debonding strain values. Proposed Japanese method of debonding prediction formula has been modified based experimental results. This modification has led to prediction of ultimate design moment for flexural enhanced elements (both slabs and beams) with reasonable factor of safety against ultimate failure. This study has led Sri Lankan engineers to understand complete behaviour of CFRP strengthened flexural systems. Proposed methodology can be used for the design with higher confidence.
item: Thesis-Full-text
Comparative study on seismic analysis of buildings for different code of practices commonly used in Sri Lanka
Prasanna, KPN; Lewangamage, CS
Earthquake threat has been identified by many countries and analysis and design against seismic effects have therefore become almost a basic part of their structural design process. Sri Lanka has also identified the importance of designing buildings against seismic actions, specially due to recent incidents, which took place in and around the Island. However, Sri Lanka does not have its own code of practice for designing against seismic actions. Also there are not many established guidelines available in the country for this purpose. As a result, when it is required to analyze and design buildings against seismic actions, the engineers and scientists in the country face difficulties, basically with which codes and guidelines to follow. It is obvious that all of those codes are not equally suitable for conditions in Sri Lanka and also will not give out similar results. The aim of this research is to check the performance level that a building can achieve when analyzed according to different codes of practice, which are commonly used in Sri Lanka in seismic analysis. In this context, three codes of practice were considered, taking into account their applicability over the others in Sri Lankan context, namely the Australian code (AS1170.4-2007), the Indian code (IS 1893 (Part 1):2002) and the Euro code (BS EN-1998-1:2004). The recommendations provided in the research, conducted by the University of Moratuwa, Sri Lanka, aimed at providing guidance on suitable analysis procedures for buildings in Sri Lanka, based on the euro code were also inco-operated in the analysis. First, the seismic analysis procedures outlined in those codes with respect to both static and dynamic analysis were discussed in detail. Then, the analysis procedures introduced in the respective codes of practice were compared and contrasted, considering how they handle the major effects, characteristics of the structures and geotechnical considerations etc. In order to demonstrate the analysis procedures and to make a comparison on results, three high-rise buildings, having floors between 10 to 20 were selected and analyzed according to the guidelines provided in the three selected codes of practice respectively. In this case, all the structures were analyzed for three different soil conditions, which could be found in Sri Lanka. The computer software "ETABS" has been used for finite element modeling of all the structures. Response Spectrum Analysis (RSA) was used in all the dynamic analysis purposes. Equivalent static analysis was also carried out as per requirements, established in particular codes of practice. According to the results obtained in the analysis, it has been found that, irrespective of the code of practice, which has been used in the analysis, the structures have achieved Immediate Occupancy Level (IOL)in all twenty seven cases, according to FEMA356 standards. It was also found that the Indian code has given the highest drift values in many occasions while the Euro code also has given very close or sometimes similar drift values. In contrast, the Australian code has generally resulted lowest drift values. Further, it has also been identified that the Euro code has given the highest design base shear forces in all eighteen occasions. On the other hand, the Indian code has given lowest design base shear force in many occasions. The Australian code has also shown the lowest design base shear forces in few occasions.
item: Conference-Full-text
A comparative study on the mechanical properties of concrete by substituting cement with sugarcane bagasse ash
(IEEE, 2023-12-09) Sankeeth, S; Kumara, BS; Damruwan, HGH; Herath, HMST; Lewangamage, CS; Koswattage, KR; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
This research study compares the mechanical properties of concrete by substituting Sugarcane Bagasse Ash (SCBA) at various weight ratios for Ordinary Portland Cement (OPC) and Portland Composite Cement (PCC). The study was mainly concerned with determining the consistency, setting time, workability, compressive strength, and split tensile strength of concrete mixes containing different percentages of SCBA. Three replacement scenarios were considered into account: 0% SCBA (control sample), 5% SCBA, and 10% SCBA, which would have replaced both OPC and PCC. Various tests were conducted according to relevant standards to evaluate the performance of the concrete mixes. The results revealed that replacing 10% of OPC with SCBA performed better than replacing PCC and the control samples. Higher compressive strength and split tensile strength were among the improved mechanical characteristics of the concrete mixtures with 10% SCBA. These results show the possibility of using SCBA as a partial cement substitute to enhance the overall performance of concrete, especially when replacing OPC. This research offers important insights into sustainable construction practices by identifying SCBA as a feasible cementitious material with favorable economic and environmental effects. The results may assist researchers and concrete experts in optimizing the use of SCBA in concrete mix designs to achieve desired mechanical properties and enhance sustainability in the construction industry.
item: Conference-Abstract
Comparison of five major wind codes with Sri Lankan context
(2016-09-01) Weerasuriya, AU; Lewangamage, CS; Lewangamage, MTR
The design manual “Design building for high winds – Sri Lanka” is the only mandatory document available for wind load design in Sri Lanka. This document extensively covers the design and construction of low rise buildings. However, the evolution of tall building construction requires advances for Sri Lankan wind loading standards, which cannot be prepared yet due to lack of available data and technology. Therefore, designers have used different international standards for wind design for medium and high rise buildings without understanding the impact of many different standards in a particular design fully. Hence, some of these common international wind standards such as CP 3 Chapter V – Part 2:1972, BS 6399.2:1997, AS 1170.2:1989, AS/NZS 1170.2:2002 and EN 1991-1-4:2005 are evaluated in this paper by considering loads exerted at ultimate limit state on the structural members such as beam and column members, shells such as shear walls and supports of a building by wind loads to understand the suitability of these codes for Sri Lankan context. The serviceability limit state behavior of a building is also evaluated according to the methods given in wind loading standards. The effective increase of the return period due to the use of load factors for wind loads is also important in order to achieve adequate risk level for different type of buildings. Finally conclusions have been drawn about the selected wind loading standards, which can be used with Sri Lankan context until country could produce its own wind code.
item: Conference-Abstract
Detection and estimation of damage in framed structures using modal data
De Silva, WARK; Lewangamage, CS; Jayasinghe, MTR
The inevitable ageing and degradation of buildings and the structural failures that follow, have ignited a need for early prognosis of probable structural failures so that proactive measures can be undertaken. Hence, one of the important steps of structural health monitoring (SHM) process is the detection of damage location and estimation of damage severity. Modal data can be effectively used for this purpose owing to their sole dependency on mechanical characteristics of a structure. This study presents a damage detection methodology based on mode shape derivatives such as mode shape slope (MSS) and mode shape curvature (MSC) for a symmetric experimental steel frame model. Furthermore, an extended parametric analysis has been performed using a calibrated finite element model to investigate damage localization and quantify severity. The study provides key conclusions about the effect of boundaries on the damage detection method for the steel frame model. Furthermore, damage detection using MSC is identified to be more sensitive as opposed to MSS method.
item: Conference-Full-text
Development of low-cost wireless sensor network and online data repository system for time synchronous monitoring of civil infrastructures
(IEEE, 2020-07) Vishnu, P; Lewangamage, CS; Jayasinghe, MTR; Kumara, KJC; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Advances in wireless sensor networks (WSN) are well proven and commonly used in Structural Health Monitoring (SHM). SHM using WSN is the modern paradigm which incorporates automated systems for data acquisition, in monitoring, analysis, and identification of structural responses and defects. Even though currently used WSN are economical compared to tethered monitoring systems, it is still unaffordable. The costly nature of traditional data loggers and the low penetration nature of currently used networking protocols, through civil structures thus requiring dense array of sensors, increase the overall cost of a WSN. This paper discusses the development of a low cost WSN to monitor the acceleration response of civil engineering structures using off the shelf products. The developed system is capable of capturing synchronous acceleration response data with the sampling frequency of 100 Hz with a resolution of 0.5 mg. The collected data is processed and shared between peer nodes using sub 1 Gigahertz wireless protocol, and stored within an online based central data repository system replacing traditional data loggers. The developed low cost WSN is proved to be a better low cost alternative in the context of a target building with 48 floors (185 m height).
item: Thesis-Abstract
Development of National guidelines for seismic analysis and design of (Engineered) buildings in Sri Lanka
(2015-02-08) Kularathna, HGSR; Lewangamage, CS; Jayasinghe, MTR
Sri Lanka was believed to have no seismic threat compared to other natural disasters such as landslides, floods, droughts which often cause widespread devastations. However, it has now been realized that Sri Lanka can no longer be considered as isolated from seismic threat following recent past events occurred in and around island. Designers of structures in Sri Lanka often used to avoid seismic consideration in the design procedure essentially of buildings as Sri Lanka is located within the Indo-Australian plate and thus, the chances of inter-plate type earthquakes which take place at the plate boundaries causing significant damages are remote. However, it is possible to take place intra-plate type earthquakes at any place within the tectonic plate. A notable example of a damaging intra-plate earthquake is the devastating Gujarat Earthquake in 2001. The only available document for the purpose of seismic design of buildings in Sri Lanka is “Earthquake resistant detailing for buildings in Sri Lanka” published by the Society of Structural Engineers, Sri Lanka. The present study is therefore aimed to provide advice on how all of these factors would affect the need for seismic design in Sri Lanka and provide guidance on suitable analysis and design procedures for buildings when the seismic consideration is explicitly warranted for a structure. The proposed guidelines in this study are based on Euro Code 8 (EN 1998-1: 2004): “Design of Structures for Earthquake Resistance”. Euro Code 8 was selected for this purpose because it allows national choices in defining seismic characteristics such as peak ground accelerations, response spectra etc. in the seismic design procedure. It also allows national choices in selecting analysis and design procedures of buildings to resist seismic events. Therefore, this study mainly focuses on these national choices and suitable values are proposed and discussed depending on the available limited seismic data in Sri Lanka. Whenever there is no enough data, suitable approaches are given comparing similar seismic codes such as IS 1893-1: 2002 and AS 1170.4: 2007. Finally, two case studies are carried out in order to present how the developed guidelines are used in the seismic design procedure of buildings specifically in Sri Lanka. The two buildings selected for this purpose represent buildings with high consequences of failure during an earthquake so that it clearly shows the significance of seismic consideration in the design procedure of buildings.
item: Conference-Abstract
Earthquake Performance of free Standing four Legged Greenfield Towers
Gunathilaka, AMLN; Lewangamage, CS; Jayasinghe, MTR;
Telecommunication/broadcasting towers play a vital role in telecommunication and broadcasting sectors by facilitating wireless data and signal transmissions. The failure of a tower especially under a disaster situation such as earthquake is a major concern mainly in two ways. One is the failure of communication/broadcasting facilities which will become a major setback to carry out rescue and other essential operations during a disaster while failure of a tower will itself cause a considerable economic loss as well as damages to human life since these are tall giant structures in most of the cases. Presently, a strong dialogue is going on amongst the professionals regarding the seismic condition of our country with the reported earth tremors in recent times. Hence, evaluating the structural performance of existing telecommunication/ broadcasting towers under seismic loads is utmost important since almost all existing towers have not been designed considering seismic forces due to traditional belief that Sri Lanka will not be subjected to earthquakes of appreciable magnitudes. Considering the above situation, assessment of structural performance of existing towers (which were not initially designed considering earthquake loading) under possible earthquake loading with different analytical techniques was selected as main objective of this study. Accordingly, behaviour of existing four legged Greenfield towers under seismic loading using ANSI/TIA-222-G tower design code was studied and results, observations and conclusions based on this analysis are presented.
item: Conference-Full-text
Embodied energy and carbon footprint of two storied refuge space with lightweight load bearing panels
(IEEE, 2020-07) Thevarajah, BE; Jayasinghe, MTR; Lewangamage, CS; Ibell, TJ; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
With the effects of climate change, natural disasters are becoming more severe and frequent. Disaster resistant structures play a vital role in preventing loss of lives and damage to the belongings. A suitable material that could resist the forces of nature needs to be selected to ensure safety while reducing the adverse effects on the environment. Turning waste material into raw material is welcomed as the scarcity of natural resources and disposal of waste are becoming major issues nowadays. Such a method of replacing coarse aggregate with 100% recycled Expanded-polystyrene (EPS) is the production of lightweight concrete wall panels. A new trend of lightweight panels can be widely seen as partitions in reinforced concrete frame buildings. Incorporating these panels as a loadbearing element would lead to a drastic change in the industry. Hence a detailed study has been carried out to find out the properties of EPS panels with respect to embodied energy and carbon footprint. A comparative study has been conducted between two-storied refuge space with lightweight load-bearing panels and conventional materials such as cement blocks and fired clay bricks, through which the potential of lightweight wall panels as load-bearing walls for a two-storied refuge space is assessed.
item: Thesis-Full-text
Evaluation of seismic capacity of existing highway bridges in Sri Lanka
Aluthapala, UL; Lewangamage, CS; Baskaran, K
Sri Lanka is an island located in the Indian Ocean and it lies in the large Indo-Australian plate seemingly far away from any of the plate boundaries. Therefore, many people believe that this fortuitous scenario makes Sri Lanka safe from earthquakes. But an intra-plate earthquake can occur anywhere at any time. Some geologists pointed out that the Indo Australian plate is being separated into two and its boundary lies 500km away from the southern coast of the country. Therefore, Sri Lanka has a moderate risk to face an earthquake. There are over 4000 bridges on National Road Network with length varying from 3.0m to 500.0m. These bridges have varying widths about 3.0m to 25.0m and some of these have been constructed more than 50 to 100 years back. They were constructed using steel concrete composite or steel. These bridges have not been designed for seismic loads and they have not been detailed for seismic effects. Therefore, it is a must to evaluate the seismic capacity of those bridges and retrofit those if necessary. This study was focused to develop a priority list (Bridge Rank) for the purpose of further investigation on seismic capacity. It was also focused to carry out a case study for a selected bridge from the developed priority list to find out its seismic capacity. Bridges on the “A” class roads with the overall length of the bridge is greater than 25m were considered in this study. To develop the priority list for thesebridges, the method given in the “Seismic Retrofitting Manual for Highway Bridges” published by the Federal Highway Administration (Report No. FHWARD- 94-052) was used. The parameters required to input to the above methodology were obtained from the previous research findings and the bridge inventory that is maintained by the Planning Division of RDA, Sri Lanka. The bridges considered under this study have low risk to fail due to possible earthquake loadings with local conditions since the bridge rank is between 0 to 24 on the scale of 100. Bridge No 1/1 on PeliyagodaPuttalam road (Japanese Friendship Bridge) was selected for further investigation from the developed priority list since it gives the bridge ranking 12. A response spectrum analysis was carried out to find the actions of the bridge during an earthquake. For the analysis of the bridge, a Finite Element Model was developed using SAP 2000. Codes of practices for Australian standards were used to find out the seismic capacities of the substructure and the actions of superstructure was compared with the originally designed actions. The bridges considered under this study have low risk to fail due to possible earthquake loadings since the bridge rank is between 0 to 24 on the scale of 100. It is proposed to replace the bridge bearings of the bridge no 1/1 on PeliyagodaPuttalam road based on the results of the case study.
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Evaluation of seismic performance of existing reinforced concrete buildings in Sri Lanka using pushover analysis approach - a case study
(Department of Civil Engineering, University of Moratuwa, 2014-03) Milinda, ALDN; Lewangamage, CS; Hettiarachchi, MTP
Evaluation of seismic performance of existing buildings is vital to reduce their seismic vulnerability. Performance can be evaluated by the interaction between structure's capacity and the probable seismic demands. After the evaluation, suitable retrofitting methods can be used to enhance performance by modifying the capacity. In this paper the performance of a four storied reinforced concrete building was was SAP2000 finite element analysis software package was used to obtain the capacity curve of the building. The performance was evaluated using the capacity spectrum method proposed by ATC40 under the application of seismic demands derived from ATC40 document and AS1170.4 (2007) standard.Results showed that the performance of the building is satisfactory in both X and Y directions for all seismic demands determined using ATC40 document and ASH70.4 (2007).
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Evaluation Of Seismic Performance Of Existing Reinforced Concrete Buildings In Sri Lanka Using Pushover Analysis Approach – A Case Study
(2014-06-10) Milinda, ALDN; Lewangamage, CS
Evaluation of seismic performance of existing buildings is vital to reduce their seismic vulnerability. Performance can be evaluated by the interaction between structure’s capacity and the probable seismic demands. After the evaluation, suitable retrofitting methods can be used to enhance performance by modifying the capacity. In this paper the performance of a four storied reinforced concrete building was evaluated using pushover analysis. The nonlinear behaviour of the structure was simulated using plastic hinges of which properties were determined using FEMA356. The SAP2000 finite element analysis software package was used to obtain the capacity curve of the building. The performance was evaluated using the capacity spectrum method proposed by ATC40 under the application of seismic demands derived from ATC40 document and AS1170.4 (2007) standard.Results showed that the performance of the building is satisfactory in both X and Y directions for all seismic demands determined using ATC40 document and AS1170.4 (2007).