Browsing by Author "Lewanagamage, CS"

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item: Conference-Full-text
Analysis and design of telecommunication towers for earthquake loading in Sri Lanka for sustainability
(2013-11-12) Gunathilaka, AMLN; Lewanagamage, CS; Jayasinghe, MTR
Large number of telecommunication towers has been constructed in Sri Lanka during last few decades with the rapid development of telecommunication sector in the country. These towers play a significant role especially in wireless communication and failure of such tower in a disaster like an earthquake is major concern mainly in two ways. One is the failure of communication facilities will become a major setback to carry out rescue operations during disaster while failure of tower will itself cause a considerable economic loss as well as damages to human life in most of the cases. Therefore, design of telecommunication towers considering all possible extreme conditions is of utmost importance and a good design can be considered as a step towards a greater degree of sustainability. However, almost all telecommunication towers in this country have not been checked for earthquake loading since most of people believe that earthquake threats are not that much of significance to Sri Lanka until recently. With many tremors recorded in recent past, designers have started to rethink about earthquake design of structures and main objective of this research is assessing the performance of exiting towers (which were not initially designed considering earthquake loading) under possible earthquake loading and find cost effective strategies for retrofitting in case such action has to be effected. Accordingly, behaviour of existing four legged Greenfield towers under seismic loadings appropriate for Sri Lankan conditions were analyzed using equivalent static load method given in ANSI/TIA-222-G. This can be considered as an initiative in this research area under local conditions. Results and conclusions based on this analysis are discussed in this paper.
item: SRC-Report
An assessment of wind loading and wind energy potential for Sri Lanka
(2016) Lewanagamage, CS; Maduranga, WLS
It was more than 40 years ago that Sri Lanka last established a wind loading map after the severe cyclone that struck the country in 1978. It is strongly believed that statistical methods had not been used in developing this wind loading map. I lence. the map can either overestimate or underestimate the wind speeds at least in some of the regions ol the country. Therefore, on updated map which suits the changing climate patterns experienced in the country has become a necessity. In Sri Lanka, different wind codes arc being used when structures are designed to withstand wind actions. Moreover, (here is no suitable wind loading map that can be used with the Eurocode 1 or BS 6399-2. I he existing wind resource mops for Sri Lanka have been developed in macro scales with low resolutions which is not adequate for effective decision making in wind power generation. Moreover, most of them represents wind speed distributions except for wind power distribution. Therefore, the industry always uses expensive methods to identify the suitable regions for the establishment of wind turbines. As the initial stage of this study a wind loading map for Sri Lanka was developed for different return periods (5, 10, 50, 100, 200, 500 and 1000 years) and for different averaging time periods (3-$econd gust, 10-minute average and hourly mean) using the wind data obtained from 24 weather stations. The data used were the monthly maxi mums of 3-minute average and instantaneous maximum wind speeds, recorded over a period of about 35 years. Extreme value distributions called Gringorten and Gumbel methods were tested to predict the extreme wind speeds. Finally, the Gringorten methods was adopted due to its unbiased nature. The generated wind contours for both 3-second gust and 10-minute average basic wind speeds were analyzed for delining the wind loading zones for Sri Lanka. Altogether a new wind power distribution map was proposed for Jaffna Peninsula region in Sri Lanka which has been previously identified as a region with a higher wind energy potential. The required data was obtained from SLSEA (Sri Lanka Sustainable Energy Authority) and the Survey Department of Sri Lanka. Computational Fluid Dynamics based model has been used for the generation of wind power distribution map. The resolution of the map has been increased up to 150 m x 150 m (5” x 5”)- Coastal regions such as Vcravil, Pooneryn, Ampan, Punkudulivu, Kayts, Kankcsanlurai. Ponnalli Khadu, Karainagar, Mandaitivu and Alvai were identified as the regions which have the highest wind energy potential in Jaffna Peninsula.
item: Conference-Full-text
Condition assessment of steel bridges in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2014-03) Chathuranga, KADK; Lewanagamage, CS; Hettiarachchi, MTP
The majority of steel bridges in Sri Lanka have been built more than 100 years ago. Most bridges have been subjected to changes such as deterioration due to corrosion, mechanical damage due to fatigue and repair due to maintenance. Therefore condition evaluation of such bridges is vital to ensure public safety. This paper presents condition assessment of selected steel bridges in Kaluthara district. The task is pursued through visual observations. Two mathematical models have been developed in this research to evaluate the condition of bridges. The Analytical Hierarchy Process was applied to obtain the priority vector of bridge elements and important factor of bridge elementswere used to obtain the overall bridge condition index. The modified overall bridge condition index is employed to assess the bridge condition. The results obtained from four selected steel bridges are presented in this paper.
item: Conference-Full-text
Condition Assessment Of Steel Bridges In Sri Lanka
(2014-06-10) Chathuranga, KADK; Lewanagamage, CS
The majority of steel bridges in Sri Lanka have been built more than 100 years ago. Most bridges have been subjected to changes such as deterioration due to corrosion, mechanical damage due to fatigue and repair due to maintenance. Therefore condition evaluation of such bridges is vital to ensure public safety. This paper presents condition assessment of selected steel bridges in Kaluthara district. The task is pursued through visual observations. Two mathematical models have been developed in this research to evaluate the condition of bridges. The Analytical Hierarchy Process was applied to obtain the priority vector of bridge elements and important factor of bridge elementswere used to obtain the overall bridge condition index. The modified overall bridge condition index is employed to assess the bridge condition. The results obtained from four selected steel bridges are presented in this paper.
item: Thesis-Abstract
Seismic analysis and design of Polwathumodara highway bridge in southern transport development project
Withanage, S; Lewanagamage, CS
The natural phenomena 'earthquakes' can not be prevented but the damage caused by earthquakes can be minimised mainly by having structures to resist earthquakes. The seismic performance of bridge is important as bridges playa key role in the transportation system. Hence this research is focused on the vulnerability of a bridge based on a major highway bridge namely Polwathumodara bridge to withstand an earthquake. Selection of a suitable code of practice to be used, selection of appropriate earthquake loading is discussed in the report as earthquake data is not available in Sri Lanka. Then both the dynamic analysis (response spectrum analysis and time history analysis) and the static analysis are performed on the three dimensional model of the bridge using SAP 2000 to evaluate the design load effects. Based on the maximum design load effects a design capacity check is performed on all superstructure and substructure elements.
item: Conference-Full-text
Seismic Analysis of Guyed Mast Towers in Sri Lanka
(2016-04-26) Kogul, S; Gunathilaka, AMLN; Lewanagamage, CS; Jayasinghe, MTR
With the rapid development of the telecommunication sector in the country, telecommunication/broadcasting towers play a vital role in telecommunication and broadcasting sectors. There are many structural forms available for towers and guyed mast is one such type commonly seen in country sides of Sri Lanka where land is available for cheaper price. Moreover, in the case of very tall tower is needed, guyed mast is more economical solution than self-supporting towers. The failure of a guyed tower especially under a disaster situation such as earthquake is a major concern in many ways. One is the failure of communication/broadcasting may hamper the communication needs to carry out rescue and other essential operations. Further, failure of a tower may itself cause a considerable economic loss as well as damages to human life. Therefore, checking of structural performance tower under seismic and other extreme weather effects is quite vital. Even though, Sri Lanka was believed to have no seismic threats, presently a strong argument 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 exiting Guyed mast towers (which were not initially designed considering earthquake loading) under possible earthquake loading was selected as the objective of this study. Accordingly, behavior of existing Guyed mast 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: Article-Full-text
Seismic Analysis of Guyed Mast Towers in Sri Lanka
(2015-12-29) Kogul, S; Gunathilaka, AMLN; Lewanagamage, CS; Jayasinghe, MTR
With the rapid development of the telecommunication sector in the country, telecommunication/broadcasting towers play a vital role in telecommunication and broadcasting sectors. There are many structural forms available for towers and guyed mast is one such type commonly seen in country sides of Sri Lanka where land is available for cheaper price. Moreover, in the case of very tall tower is needed, guyed mast is more economical solution than self-supporting towers. The failure of a guyed tower especially under a disaster situation such as earthquake is a major concern in many ways. One is the failure of communication/broadcasting may hamper the communication needs to carry out rescue and other essential operations. Further, failure of a tower may itself cause a considerable economic loss as well as damages to human life. Therefore, checking of structural performance tower under seismic and other extreme weather effects is quite vital. Even though, Sri Lanka was believed to have no seismic threats, presently a strong argument 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 exiting Guyed mast towers (which were not initially designed considering earthquake loading) under possible earthquake loading was selected as the objective of this study. Accordingly, behavior of existing Guyed mast 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
Traffic induced vibration analysis of existing steel bridge in Padeniya-Anuradhapura Road
(Department of Civil Engineering, University of Moratuwa, 2011-12) Kodikara, KATL; Morawaka, UD; GunathiIake, IAPMP; Lewanagamage, CS; Ratnayake, N
The Bridge which is located in Padeniya-Abstract: Anuradhapura road is a steel truss bridge with three spans of approximately 31m long. It is currently undergoing a development process which includes constructing a new cantilever pedestrian walkway of 1.5m in length of either side of the bridge. Because of this proposed cantilever foot walk static as well as dynamic loading will be changed. In order to ensure that the structure is safe under the additional loads, structural analysis was carried out for static condition as well as for dynamic condition to check the adequacy of structural elements.Analyses of the bridge under static and dynamic loading were done by the finite element (FE) method. The bridge model is such that the structural steel is idealized by beam elements and the deck is represented by shear flexible shell elements. The support with elastomeric bearings is idealized by using an internal element with linear springs. Modelling was carried out using commercial FE software package SAP2000. Based on the results of finite element analysis this paper suggests the effectiveness of using elastomeric bearings for enhancing vibration serviceability hence expanding life span of steel truss bridges.
item: Conference-Abstract
Traffic induced vibration analysis of existing steel bridge in Padeniya-Anuradhapura road
(2011) Kodikara, KATL; Morawaka, UD; Gunathilake, IAPMP; Lewanagamage, CS
The selected Bridge which is located in Padeniya-Anuradhapura road is a steel truss bridge with three spans of approximately 31m long. It is currently undergoing a development process which includes constructing a new cantilever pedestrian walkway of 1.5 m in width of either side of the bridge. Because of this proposed cantilever foot walk static as welt as dynamic loading will be changed. In order to ensure that the structure is safe under the additional loads structural analysis uwr carried out for static condition as well as for dynamic condition and check the adequacy of structural elements. Analyses of the bridge under static and dynamic loading were done by the finite element (FE) method. The bridge model is such that the structural steel is idealized by beam elements and the deck is represented by shear flexible shell elements. The support with elastomeric bearings is idealized by using an internal element with linear springs. Modeling was carried out using commercial FE software package SAP2000. Structural Analysis revealed that there is a kind of a vibration problem exists. As a solution for this vibration problem, this paper suggests the effectiveness of using elastomeric bearings hence expanding life span of steel truss bridges.