Academic Staff

Department of Civil and Environmental Engineering, Faculty of Engineering, University of Ruhuna, Hapugala, Wakwella, Galle.

Telephone :

• PhD in Civil and Environmental Engineering from Saitama University, Japan (2008)
• M. Eng in Structural Engineering from Saitama University, Japan (2005)
• PG. Dip in Structural Engineering Design from University of Moratuwa, Sri Lanka (2002)
• B.Sc. with First Class Honours Degree in Civil Engineering from University of Moratuwa, Sri Lanka (2000)

• Senior Lecturer Grade I, Department of Civil and Environmental Engineering, University of Ruhuna (April 2014 to date)

• Senior Lecturer Grade II, Department of Civil and Environmental Engineering, University of Ruhuna (April 2008- to April 2014)

• Charted Engineer, Institution of Engineers Sri Lanka

• Research Assistant, Department of Civil and Environmental Engineering, Saitama University, Japan (April 2005 - March 2008)
• Postgraduate (PhD) student at Graduate School of Science and Engineering, Saitama University, Japan (April 2005 - March 2008)
• Postgraduate (M. Eng) student at Graduate School of Science and Engineering, Saitama University, Japan (April 2003 - March 2005)
• Postgraduate (PG Diploma in Structural Engineering Design) student at Department of Civil and Environmental Engineering, University of Moratuwa, Sir Lanka (November 2001 - December 2002)
• Lecturer, Department of Civil and Environmental Engineering, University of Ruhuna, Sri Lanka (March 2001- March 2008)
• Assistant Lecturer, Department of Civil and Environmental Engineering, University of Ruhuna, Sri Lanka (September 2000- March 2001)
• Instructor, Department of Civil Engineering, University of Moratuwa, Sri Lanka (July 2000- August 2000)
• Trainee Engineer at Millennium City Housing Project, Athurigriya, Malabe, Colombo at Jayarathne Construction Company (1999)
• Undergraduate Engineering Trainee at the Surath Wickramasinghe Associates (October - December 1998)
• Undergraduate Engineering Trainee at Maga Engineering Ltd (October- December 1997)
• Management Trainee at D. Samson Industry (Pvt) Ltd (July 1993 - September 1995)

• KUBOTA Scholarship awarded by Nippon Koei Co. Ltd , Japan (2007)
• TAKASE Scholarship awarded by Takase Co-operation Ltd, Japan (2006)
• Honors Scholarship awarded by The Association of International Education, Japan (2005)
• TAKASE Scholarship awarded by Takase Co-operation Ltd, Japan (2003)
• Mahapola Scholarship granted by the government of Sri Lanka (1995 )

• Member, Institution of Engineers Sri Lanka
• Member, Society of Structural Engineers Sri Lanka
• Member, Japan Concrete Institute

• Durability of Reinforced Concrete and Prestressed Concrete Structures
• Research on High Strength Concrete and High Performance Concrete
• Research on Bridge Management Systems for RC and PC Bridges
• Structures using Innovative Materials
• Structural Assessment and Repair & Retrofitting

• Mechanics of Materials
• Fundamentals of Civil Engineering (Building and Materials section)
• Infrastructure and Environment
• Structural Analysis
• Concrete Technology
• Quantity Surveying and Construction Process
• Design of Structural Elements
• Building Engineering
• Advanced Concepts of Civil Engineering Design

Research Projects

• Investigation on Techniques to reduce damages due vibration induced on Construction Sites (co-supervised) (2013-2014)
• Exposing level of noise & vibration among construction workers and their health effects (co-supervised) (2013-2014)
• Development of FEM model to investigate performance of Un-Reinforced Masonry (URM) & Retrofitted Walls  against Seismic Activities (2013-2014)
• Development of Bridge Management Tool (Phase 2: In-cooperating deterioration prediction model ) (2013-2014)
• Investigation on methods to improve health and safety practices in construction sites (2012-2013)
• Development of Bridge Management System for Sri Lanka (2012-2013)
• Use of Structural Optimization for Earthquake Resiliency of Masonry Buildings (2012-2013)
• Investigation on relation between industrial noise and peoples response (2011-12)
• Investigation on Performance of structures for blast induced vibration and application of Control techniques (2011-12)
• Pervious Recycled Aggregate Concrete Materials for Sustainable Built Environment (2011-12)
• Strengthening Load Bearing Masonry Wall Panels using Locally available Materials (2011-12)
• Condition Assessment, damage detection, life cycle evaluation and 
• repair of existing Structures in Sri Lanka due to Chloride Attack (2011-12)
• Use of Recycled Short Fibers in Structural Concrete to Enhance Mechanical Properties (2011-12)
• Service Life Prediction of RC Structures Exposed to Chloride Environments (2010-11)
• Investigation of Optimum Utilization of Rice-Husk-Ash to enhance the Mechanical Properties of Concrete (2010-11)
• Investigation into Time-dependent Deformation and Drying Shrinkage in Concrete with Composite Mineral Admixtures (2010-11)
• Investigation of the Threshold for Surface Cracks due to Blast Vibrations (2010-11)
• Investigation of use of Wall Surface Materials to reduce Industrial Noise (2010-11)
• Investigation of Mechanical Properties and Durability of Concrete Containing Rice Husk Ash (June, 2010)
• Condition Assessment of Reinforced Concrete Structures Exposed to Chloride Environment and Service Life Prediction (June, 2010)
• Evaluation of a Bridge Management System for Reinforced Concrete and Prestressed Concrete Bridges (May, 2009)
• Structural aspects of post-tsunami construction (buildings) against natural disasters (May, 2008)
• Review on existing methods of masonry construction (buildings) against earthquakes and their application to Sri Lanka (May, 2008)

• Conference Co-chair, 3rd International Symposium on Advances in Civil and Environmental Engineering Practices for Sustainable Development (ACEPS-2015), Faculty of Engineering, University of Ruhuna, 9th March 2015  
• Member, International Conference Committee, International Conference on Structural Engineering-2015, Colombo, 24th to 26th August 2015  
• Member, Scientific Committee, 5th International Conference on Sustainable Built Environment (ICSBE), 12th to 15th December, 2014
• Member of the Committee appointed by DG/ICTAD for Reviewing and updating of Guide Book on Disaster Resilient Building Design and Construction Practices, April 2014
• Chairman, Organizing Committee of the First Annual Research Symposium, Faculty of Engineering, University of Ruhuna, January 2014
• Invited Lecture on “Guidance to Select Science Stream for Advanced Level”, at Ga/ Dorepe Maha Vidyalaya, Navodya College, Angulugaha on 30th April 2013 
• Consultant (Structural Engineering), Research and Development programme, National Building and Research Organization (NBRO) under Government Research Grant 2013
• Member of Judge Panel for the Competition organized by Hambantota District Chamber of Commerce, 2013
• Member, Scientific Committee, 4th International Conference on Structural Engineering and Construction Management (ICSECM), 13th to 15th December, 2013
• Committee Member (Senate appointment), Preparation of Rules and Regulation for Conducting Examinations at University of Ruhuna (2013)
• Executive Member, Programme Committee, Staff Development Centre, University of Ruhuna (November 2012 – 2014)
• Team Member, Programme Review on HND in Civil Engineering at ATI, Mattakkuliya by HETC Project
• Member, Senate Sub-committee to prepare University orientation programme
• Chairman, Review of Academic Rules and Regulations and Revision of Curriculum, Faculty of Engineering, 2012-2013
• Committee Member (Senate appointment), Establishment of a Centre for International Relation, Tourism and Modern Language Studies at Hambantota. 
• Committee Member, Internal Quality Assurance Cell – Faculty of Engineering (May 2012 – 2013)
• Symposium Coordinator, “Second Engineering Graduate Symposium on Recent Advances in Civil Engineering”, on 11th January, 2013 at Faculty of Engineering, University of Ruhuna
• Symposium Coordinator, “Second Civil Engineering Research Exchange Symposium 2012 (CERES’ 12)” with collaboration of University of Peradeniya and University of Moratuwa on 02nd July, 2012 at the Faculty of Engineering, University of Ruhuna  
• Symposium Coordinator, “First Engineering Graduate Symposium on Recent Advances in Civil Engineering”, on 26th September, 2011 at Faculty of Engineering, University of Ruhuna 
• Liaison Officer of IESL – Faculty of Engineering, University of Ruhuna (December, 2011 –2013) 
• Executive Committee Member, Society of Structural Engineers Sri Lanka (November, 2011 - 2013)
• Member, Selection Committee for Best Entrepreneur Awards 2011, Hambantota District Chamber of Commerce (HDCC), Appointed by Vice Chancellor, University of Ruhuna
• Chartered Engineer
• Sector Expert (Construction), Tertiary and Vocational Education Commission (TVEC), Ministry of Youth Affairs, Appointed by Director General TVEC.
• Chairman/ Member of Technical Evaluation Committees, University of Ruhuna (December 2010 to date)
• Member, Hambantota Development Plan, Hambantota District Chamber of Commerce (HDCC), Appointed by Vice Chancellor, University of Ruhuna
• Team Member of Community Development and Livelihood Improvement “GEMIDIRIYA” Project: Representing Department of Civil and Environmental Engineering, Faculty of Engineering, University of Ruhuna
• Coordinator, Engineering Education Unit, Faculty of Engineering, University of Ruhuna (December 2010 – 2013) 
• External Examiner, PhD, M. Phil, M. Eng., Degrees at University of Moratuwa
• Advisor, Civil and Environmental Engineering Society, Faculty of Engineering, University of Ruhuna (November 2010 – February 2013)  
• Member of the Senate, University of Ruhuna (November 2010 to 2013)
• Member, Faculty Sub-Committee for Enhancing ICT skills of Undergraduate Students
• Coordinator and resource person short course on Computer Based Structural Analysis for Engineers attach to National Water Supply and Drainage Board (NWS&DB), Regional Support Centre – Southern & Uwa, from 06th March to 09th April, 2010
• Chairperson, Souvenir Sub-Committee, 10th Anniversary Celebration of the Faculty of Engineering
• Symposium Coordinator, “International Exchange Symposium 2009 on Sustainable Infrastructure Development in Asia”  with collaboration of Saitama University, Japan, University of Peradeniya and University of Moratuwa on 14th to 15th September, 2009 at the Faculty of Engineering, University of Ruhuna
• Executive Committee Member, Staff Development Centre (2009 –2012) 
• Faculty Coordinator, 6th Academic Session and 5th Vice Chancellor’s Award Ceremony (2009)
• Faculty Coordinator,  Dayata Kirula Exhibition, BMICH, Colombo (2009)
• Faculty Coordinator, TECHNO Exhibition, October 2008, 2009, 2010, 2011
• Coordinator, Surveying Camp 2008
• Committee Member, Engineering Program Accreditation 
• Faculty Coordinator, “Rohana”, The Journal of University of Ruhuna (2001 – 2002)

• Participant of Seminar on “Transportation Structures: Design, Construction and Maintenance”, organized by Society of Structural Engineers, Colombo, Sri Lanka on 12th August, 2014
• Participant of workshop on “Outcome Based Curriculum Development for Engineering Faculties”, by the HETC Project, Ministry of Higher Education at the Hotel Renuka, Colombo on 23rd and 24th August, 2013
• Participant of Seminar on “Modern Bridges & Urban Flyovers”, organized by Society of Structural Engineers, Colombo, Sri Lanka on 2nd July, 2013
• Participant of workshop on “Initiatives in Quality Assurance and Strengthening Internal Quality Assurance” conducted by Quality Assurance and Accreditation Council Division of the University Grants Commission and at the University of Ruhuna on 8th May 2013
• Participant of workshop on “Cooperate Plan for IESL”, conducted by the Institution of Engineers, Sri Lanka at the Blue-Water Hotel, Wadduwa on 20th January 2013
• Participant of training programme on “Outcome Based Education and Accreditation as per Washington Accord Guidelines” conducted by the Institution of Engineers, Sri Lanka at the IESL Headquarters from 25th to 27th June, 2012
• Participant of workshop on “Research Commercialization of Universities Projects and Innovations”, by the HETC Project, Ministry of Higher Education at the Hotel Janaki, Colombo on 2nd November, 2011
• Participant of workshop on “Outcome Based Approach to Modern Engineering Education” conducted by the Institution of Engineers, Sri Lanka at the Hotel Taj Samudra, Colombo, 22nd October, 2011
• Participant of workshop on “Operation and Maintenance of Southern Expressway” jointly organized by Road Development Authority and Japan International Cooperation Agency (JICA) at the Ceylon Continental Hotel, Colombo on 15th September, 2011 
• Participant of training programme on “Accreditation of University Degree Programme” conducted by the Institution of Engineers, Sri Lanka at the IESL Headquarters from 11th to 12th May, 2011 
• Participant of Civil Engineering Research Exchange Symposium  (CERES '2010 ) was held on 27th February 2010 at University of Peradeniya
• Participant of International Exchange Seminar on Current and Future Collaborations in Education and Research between Sri Lankan Universities and Saitama University was held on 17th February 2010, Saitama University, Japan. Presented paper title: Research Activities at Ruhuna Engineering Faculty: Past-Present-Future
• Participant of International Exchange Symposium on International Collaboration in Education and research between Sri Lanakan Universities and Saitama University  was held on  16th February 2010, Saitama University, Japan
• Participant of training program on Static and Dynamic Analysis and Structural Design of Highway Bridges by University of Moratuwa on November, 2009
• Participant of seminar on Advances in Tall Buildings and Green Building Technology organized by Society of Structural Engineers, Colombo, Sri Lanka on 24 November, 2009.
• Participant of workshop on Strategies and Engineering Solutions for North – East Development organized by IESL on October, 2009
• Participant of workshop on the use of Portland Limestone Cement in Concrete organized by Holicm (Lanka) Ltd on September 2009
• Participant of workshop on Planning the New Higher Education Project organized by University of Ruhuna on April 2009
• Participant of workshop on Innovative and Interactive Teaching Method organized by Quality Assurance and Accreditation Council, Colombo on February 2009
• Participant of Seminar on Construction of Flood Damaged Bridges in Southern Province, organized by Southern Provincial Road Development Authority, Galle, Sri Lanka on December, 2008
• Participant of workshop on Vision for High-rise Building organized by Society of Structural Engineers, Colombo, Sri Lanka on 23 September, 2008.
• Invited Lecture for “Question Time” organized by the Society of Structural Engineers, Sri Lanka on August 2008, Presentation Title: “Durability of Concrete Structures”, 
• Presented a paper in the International Collaborative Graduate Program between Saitama University; Japan, Hawaii University, USA, Thammasat University; Thailand, and University of Moratuwa; Sri Lanka at Saitama University, March 2008
• Participated in a workshop on fib Task Group Meeting (Durability of PC Bridges), May 2007, Shizuko, Japan 
• Participated in a workshop on Cost Effective Methods of Road Construction and Maintenance, Transportation Engineering Division, Department of Civil Engineering, University of Moratuwa Sri Lanka (March, 2002)

Professional Experiences

• Senior Lecturer Grade II, Department of Civil and Environmental Engineering, University of Ruhuna (April 2008- to date)
• Research Assistant, Department of Civil and Environmental Engineering, Saitama University, Japan (April 2005 – March 2008)
• Postgraduate (PhD) student at Graduate School of Science and Engineering, Saitama University, Japan (April 2005 - March 2008) 
• Postgraduate (M. Eng) student at Graduate School of Science and Engineering, Saitama University, Japan (April 2003 - March 2005)
• Postgraduate (PG Diploma in Structural Engineering Design) student at Department of Civil and Environmental Engineering, University of Moratuwa, Sir Lanka (November 2001 - December 2002)
• Lecturer, Department of Civil and Environmental Engineering, University of Ruhuna, Sri Lanka (March 2001- March 2008)  
• Assistant Lecturer, Department of Civil and Environmental Engineering, University of Ruhuna, Sri Lanka (September 2000- March 2001) 
• Instructor, Department of Civil Engineering, University of Moratuwa, Sri Lanka (July 2000- August 2000)

Refereed Publications

• Vitharana V. H. P., Subashi De Silva G.H.M.J. and Sudhira De Silva, “Health hazards, Risk and Safety practices in construction sites –A Review Study”, “ENGINEER”, Journal of the Institution of Engineers, Sri Lanka (IESL) Vol. XXXXVI, No. 2, 2014, pp. xx-xx. (to be published)
• Mendis W.S.W., De Silva G.S.Y. and De Silva G.H.M.J.S., “Performance and retrofitting of un-reinforced masonry buildings against natural disasters – A Review Study”, “ENGINEER”, Journal of the Institution of Engineers, Sri Lanka (IESL) Vol. XLVII, No. 3, July 2014, pp. 71-82
• Pushpakumara B.H.J., Sudhira De Silva and Subashi De Silva G.H.M.J., “A non-destructive test based condition rating method for concrete bridges”, International Journal of Advanced Structural Engineering (under review)
• Pushpakumara B.H.J., Sudhira De Silva and Subashi De Silva G.H.M.J., “Investigation on Efficiency of Repairing and Retrofitting Methods for Chloride induced Corrosion of Reinforced Concrete Structures”,  “ENGINEER”, Journal of the Institution of Engineers, Sri Lanka (IESL) Vol. XXXXVI, No. 4, 2013, pp. 19-30.
• De Silva S., Mutsuyoshi, H., and Witchukreangkrai, E., Evaluation of Shear Crack Width in I-shaped Prestressed Reinforced Concrete Beams, Journal of Advance Concrete Technology (ACT), Vol. 6, No. 3, October 2008, pp. 443-458

• V.H.P.Vithrana, G.H.M.J. Subashi De Silva and G.S.Y. De Silva, “ Noise and Vibration exposure levels of workers in building construction sites,  ICTAD Journal, Journal of the Institution of Construction, Training and Developments (ICTAD) issue 12, 2014

Refereed Transactions and Conference Publications

• Jayawardhana W.A.P.D.,  Jayawardhana B.M.B.H., Subashi De Silva G.H.M.J. and De Silva G.S.Y., “Use of Waste Materials as Damping Layer to reduce Ground Vibration”, Second Annual Research Symposium (ARS), Faculty of Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, January 2015, pp. 5
• Ranatunga S.P., Pathirana H. P. C. P., Subashi De Silva G.H.M.J. and De Silva G.S.Y., “Effect of Whole body Vibration on the Health of Operators in Construction Sites”, Second Annual Research Symposium (ARS), Faculty of Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, January 2015, pp. 4
• Abeygunawardana N.T., Azam M.N.M., De Silva G.S.Y. and Subashi G.H.M.J., “Investigation of the Performance of Un-Reinforced Masonry Walls against Reversed Cyclic Loads”, Second Annual Research Symposium (ARS), Faculty of Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, January 2015, pp. 3
• Ravishanka B.W.C., Shanaka M.M., De Silva G.S.Y. and Subashi G.H.M.J., “Assessment of Existing Bridges Using Bridge Management System”, Second Annual Research Symposium (ARS), Faculty of Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, January 2015, pp. 2
• H.P.C.P. Pathirana, S.P. Ranatunga, G.H.M.J. Subashi De Silva, and G.S.Y. De Silva, Exposure Level of Noise and Vibration among Construction Workers and Their Health 
• Effects, The Proceedings of the 3rd International Symposium on, Advances in Civil and Environmental Engineering Practices, for Sustainable Development (ACEPS-2015), Faculty of Engineering , University of Ruhuna, Hapugala, Wakwella, Galle, 09th March 2015 pp. 287-293
• V.H.P.Vitharana, G.H.M.J. Subashi De Silva, and Sudhira De Silva, Comparing Health Risks among Vehicle Operators in Construction Sites exposed to Whole-Body Vibration Using EU directive 2002/44/EC and ISO 2631-1, The Proceedings of the 3rd International Symposium on, Advances in Civil and Environmental Engineering Practices, for Sustainable Development (ACEPS-2015), Faculty of Engineering , University of Ruhuna, Hapugala, Wakwella, Galle, 09th March 2015 pp. 349-356
• W.S.W. Mendis, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Post-Strengthening of Un-Reinforced Masonry Structures with Seismic Belts, The Proceedings of the 3rd International Symposium on, Advances in Civil and Environmental Engineering Practices, for Sustainable Development (ACEPS-2015), Faculty of Engineering , University of Ruhuna, Hapugala, Wakwella, Galle, 09th March 2015 pp. 349-356
• W.S.W. Mendis, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Dynamic In-Plane Behaviour of Seismically Strengthened Un-Reinforced Masonry Walls, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. xx-xx
• Ranatunga S.P., Pathirana H. P. C. P., Subashi De Silva G.H.M.J. and De Silva G.S.Y., “Effect of Noise and Vibration on Health of Workers in Road Development Sites”, Special Session s on Climate Change, Community - Environment and Ecosystem and Environmental Pollution and Chronic Kidney Disease in North Central Province of Sri Lanka, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. 127-133
• Jayawardhana W.A.P.D.,  Jayawardhana B.M.B.H., Subashi De Silva G.H.M.J. and De Silva G.S.Y., “Investigation on Characteristics of Vibration Induced by Soil Roller Compaction and Effectiveness of Damping Layer to Reduce the Vibration”, Special Session on Design & Construction, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. 129-136
• Abeygunawardana N.T., Azam M.N.M., De Silva G.S.Y. and Subashi G.H.M.J., “Performance of Ferrocement Strengthened Unreinforced Masonry Walls Against Reversed Cyclic Loading”, Special Session on Design & Construction, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. 121-128
• Ravishanka B.W.C., Shanaka M.M., De Silva G.S.Y. and Subashi G.H.M.J., “Strategically Rehabilitation of Existing Concrete Bridges and Application Of Bridge Management System for RC Bridges in Sri Lanka”, Special Session on Design & Construction, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. 113-120
• Vitharana V.H.P., Subashi De Silva G.H.M.J. and De Silva G.S.Y., “Method to Assess Comfort Level and Potential Health Risks of Construction Workers Exposed to Whole Body Vibration”, Special Session on Sustainable Buildings and Infrastructure, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. 81-88 
• Pushpakumara B.H.J., De Silva G.S.Y. and Subashi De Silva G.H.M.J., “Condition Assessment based Approach for Identifying Remediation Plan of Concrete Bridges in Sri Lanka”, Special Session on Design & Construction, Proceedings of 5th International Conference on Sustainable Built Environment (ICSBE-2014), Kandy, Sri Lanka, December 2014, pp. 100-108 
• M.M.M. Samanpriya, V.P. Sonnadara, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Evaluation of the Performance of Unreinforced Masonry Buildings against Earthquakes and Selection of Suitable Retrofitting Method, Proceedings of International Conference on Structural Engineering and Construction Management, 13-15 December 2013, paper no. SBE/13/138.
• W.A.M. Wanniarachchi, C.M. Welhena, G.H.M.J. Subashi De Silva and G.S.Y. De Silva, Investigation of Characteristics of Vibration induced by Construction Activities and its Effects on Structural Responses, Proceedings of International Conference on Structural Engineering and Construction Management, 13-15 December 2013, paper no. SBE/13/141
• Lahiru Galappaththi, G.H.M.J. Subashi De Silva and G.S.Y. De Silva, Investigation on Methods to improve Health and Safety Practices in Construction Sites, Proceedings of International Conference on Structural Engineering and Construction Management, 13-15 December 2013, paper no. SBE/13/142
• K.K.G.D.D.L  Kariyawasam, U.B.H.U Hemapala, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Development of a Bridge Assessment Tool to identify Current Condition of Reinforced Concrete and Pre-Stressed Concrete Bridges, Proceedings of International Conference on Structural Engineering and Construction Management, 13-15 December 2013, paper no. SBE/13/139
• A.U. Senaratna, W.P.N. Weerasinghe, G.H.M.J. Subashi De Silva and G.S.Y. De Silva, Utilization of Bottom ash as a Construction Material, Proceedings of International Conference on Structural Engineering and Construction Management 13-15 December 2013, paper no. SBE/13/140
• B.H.J. Pushpakumara, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Calcium Nitrate mixed mortar for repairing corroded RC structures, Proceedings of International Conference on Structural Engineering and Construction Management, 13-15 December 2013, paper no. SBE/13/100
• W.S.W. Mendis, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Seismic Resistant Techniques for Retrofitting of Existing Masonry Dwellings in Sri Lanka, Proceedings of International Conference on Structural Engineering and Construction Management, 13-15 December 2013, paper no. SBE/13/101
• V.H.P.Vithrana, G.H.M.J. Subashi De Silva and  G.S.Y. De Silva, Risk associated with Noise and Vibration exposures and their effects on Health of Workers in Construction sites, Proceedings of International Conference on Structural Engineering and Construction Management 13-15 December 2013, paper no. SBE/13/113
• B.H.J. Pushpakumara, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Repair of Corrosion Cracks using Cement based Mortars, Annual Transactions of the Institute of Engineers Sri Lanka (IESL), Institution of Engineers Sri Lanka, Vol. 1, Part B, October, 2013, pp. 135-139
• W.S. Wasundara Mendis, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Earthquake resistance of Un-reinforced Masonry Walls retrofitted with Bamboos, Annual Transactions of the Institute of Engineers Sri Lanka (IESL), Institution of Engineers Sri Lanka, Vol. 1, Part B, October, 2013, pp. 135-139
• V.H.P.Vithrana, G.H.M.J. Subashi De Silva and G.S.Y. De Silva, Health Hazards, Risk Factors and Safety Practices in Construction sites: Review Study, Advanced Civil Engineering Practices for Sustainability. ACEPS 2013, September, 2013, pp 17-24.
• W.S. Wasundara Mendis, G.S.Y. De Silva and G.H.M.J. Subashi De Silva, Experimental Study on Diagonal shear behavior of Un-reinforced Masonry walls retrofitted with Low cost materials: Bamboo strips and Poly-Propylene bands, Proceedings of the 3 rd Annual Sessions of the Society of Structural Engineers, Sri Lanka, pp 35-39, September, 2013.
• V.H.P.Vithrana, G.H.M.J. Subashi De Silva and G.S.Y. De Silva, Workers; awareness of risk factors and safety practices in building Construction sites, Proceedings of the 3 rd Annual Sessions of the Society of Structural Engineers, Sri Lanka, pp 47-52, September, 2013.
• Mendis W.S.W., De Silva G.S.Y. and De Silva G.H.M.J.S, An economic technique for seismic retrofitting of existing masonry dwellings in Sri Lanka, Proceedings of 10th Academic Sessions of University of Ruhuna, 20 March 2013, pp. 57-58
• Vitharana V.H.P., De Silva G.H.M.J.S. and De Silva G.S.Y., Safety practices among construction workers and contractors in Sri Lanka, Proceedings of 10th Academic Sessions of University of Ruhuna, 20 March 2013, pp. 56.
• Pushpakumara B.H.J., De Silva G.S.Y. and De Silva G.H.M.J.S., Use of repaire mortars for corrosion prevention of existing reinforced concrete structures, Proceedings of 10th Academic Sessions of University of Ruhuna, 20 March 2013, pp. 52.
• Priyadarshani S.T.A, Sanjeewa W.S.M., Mendis W.S.W., De Silva G.S.Y and De Silva G.H.M.J.S., Strengthening Load bearing Masonry Wall Panels using Locally available Materials, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/206.
• Ranawaka P.M., De Silva G.S.Y. and De Silva G.H.M.J.S., Ground Vibration due to Precast Pile Driving in Mega Construction Projects, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/201. (Abstract submitted)
• Perera1 B.B.L., Priyadarshana R.D.S.I., De Silva G.S.Y. and De Silva G.H.M.J.S., Development of Repairing Methods for Damaged Structures due to Chloride Attack in the Marine Environment, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/169
• Godevitharana A.G.D.N., Jayaweera P.A.P.S. and De Silva G.S.Y., Selection of Aggregate Suitable to Produce Pervious Concrete for Sustainable Built Environment, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/168.
• Priyankara K.M., Rajakaruna R.M.O.B., De Silva G.S.Y. and De Silva G.H.M.J.S., Resistance to Shrinkage Cracking of Mineral Compound Mix Concrete under Actual Environmental Conditions, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/167. (Abstract submitted)
• Pushpakumara B.H.J., De Silva G.S.Y. and De Silva G.H.M.J.S., Evaluating Mitigation Methods for Chloride Induced Corrosion of Reinforced Concrete Structures, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/153.
• Mendis W.S.W., De Silva G.S.Y. and De Silva G.H.M.J.S., Performance of Un-Reinforced Masonry Buildings against Natural Disasters - Review Study, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/135.
• Sandaruwini A.H.W.E, Bandara K.A.J.M and De Silva G.S.Y., Investigation on Mechanical Behavior of Concrete with Fibers Made of Recycled Materials, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/81.
• Hemantha Dedigama K.N., Shyaman Premarathne S.M.P., De Silva G.H.M.J.S., De Silva G.S.Y. and Jayasundara N.D., Investigation of Natural Material to Reduce industrial Noise, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/78.
• Ranasinghe P.V.R., Shantha H.P.P., De Silva G.H.M.J.S and De Silva G.S.Y., Investigation on Techniques to Control Structural Damage due to Blasting Activities, Proceedings of International Conference on Sustainable Built Environment (ICSBE-2012), 14-15 December 2012, paper no. SBE/12/77
• Pushpakumara B.H.J., De Silva G.S.Y. and De Silva G.H.M.J.S., Service Life Evaluation of Reinforced Concrete Structures in Sri Lanka, Proceedings of 10th Annual Sessions of the Institute of Engineers Sri Lanka (IESL), 23 October 2012, pp..
• Pushpakumara B.H.J., De Silva G.S.Y. and De Silva G.H.M.J.S., Condition Assessment and Service Life Prediction of Reinforced Concrete Bridges Exposed to Chloride Environment, Proceedings of 2nd Annual session of the Society of Structural Engineers' Sri Lanka (SSE-SL), 25 September 2012, pp. 63 – 70
• S.A.N.S.Wickramasinghe, S.R.Masakorala, E.A.T.P.Jayasinghe, G.H.M.J.Subashi De
• Silva and G.S.Y.De Silva, Investigation of damage on wall panels due to blast vibration, Proceedings of the International Conference on Structural Engineering, Construction and Management  (ICSECM-2011) Kandy, Vol. 1, No.1, 15-17 December 2011, pp. xx-xx
• O.S. Chathurangani, W.J.M.K. Perera, H.M.N.S. Kumari, G.H.M.J. Subashi De Silva, G.S.Y. De Silva, Utilization of Sawdust and Coconut Coir Fiber for producing Noise reducing Wall Tile, Proceedings of the International Conference on Structural Engineering, Construction and Management  (ICSECM-2011) Kandy, Vol. 1, No.1, 15-17 December 2011, pp. xx-xx
• Gunathilaka P.D.D.G, Karunarathna E.V.D.N.D, Chathuranga T.W.A.G and Sudhira De Silva, Evaluation of Current Condition State of Reinforced Concrete Structures Exposed to Severe Environmental Condition, Proceedings of the International Conference on Structural Engineering, Construction and Management  (ICSECM-2011) Kandy, Vol. 1, No.1, 15-17 December 2011, pp. xx-xx
• Susantha K.A, Udayantha J.S.K, Weerasinghe H.M.A, Sudhira De Silva and Uduweriya R. B.Y. B, Investigation of the Optimum Percentage of RHA to obtain Maximum Compressive Strength of Concrete, Proceedings of the International Conference on Structural Engineering, Construction and Management  (ICSECM-2011) Kandy, Vol. 1, No.1, 15-17 December 2011, pp. xx-xx
• Naotunna C.N , Jayawardene E.L.A.I , Seneviratne D.A.M, Sudhira De Silva and Subashi De Silva, Influence of Actual Environmental Factors on Shrinkage Behavior of Concrete Containing Mineral Compounds, Proceedings of the International Conference on Structural Engineering, Construction and Management  (ICSECM-2011) Kandy, Vol. 1, No.1, 15-17 December 2011, pp. xx-xx
• Wickramasinghe S.A.N.S., Masakorala S.R., Jayasinghe E.A.T.P., De Silva G.S.Y., Subashi G.H.M.J., Effect of Blast Vibration, Proceedings of the Inaugural Annual Sessions, Society of Structural Engineers Sri Lanka, November, 2011, pp. 23-27
• Sudhira De Silva and R. B.Y. B. Uduweriya, Investigation of the Properties of Concrete Containing Rice-Husk-Ash, Annual Transactions of  The Institution of Engineers, Sri Lanka, October, 2011, pp. 71-79
• R. B.Y. B. Uduweriya, and Sudhira De Silva Effect of Mechanical Properties of Concrete containing Rice Husk Ash, Proceedings of the Eighth Academic Sessions, University of Ruhuna, February 2011, pp. 87-94
• Laksiri Pradeep, Sudhira De Silva and Chandana Nawarathna, Structural Assessment of Reinforced Concrete Bridge Structures Exposed to Chloride Environment, Proceedings of the International Conference on Sustainable Built Environment (ICSBE-2010) Kandy, Vol. 1, No.1, 13-14 December 2010, pp. 480-487
• R. B.Y. B. Uduweriya, C. Subash, M. M. A. Sulfy and Sudhira De Silva, Investigation of Compressive Strength of Concrete Containing Rice-Husk-Ash, Proceedings of the International Conference on Sustainable Built Environment (ICSBE-2010) Kandy, Vol. 1, No.1, 13-14 December 2010, pp. 132-137
• Sudhira De Silva, Chandana Nawarathna, and Laksiri Pradeep, Evaluation Criteria for Condition State of Reinforced Concrete and Prestressed Concrete Bridges, Proceedings of the Seventh Academic Sessions, University of Ruhuna, March 2010 (in press) 
• De Silva S., Mutsuyoshi, H., and Witchukreangkrai, E., Evaluation of Shear Crack Width in I-shaped Prestressed Reinforced Concrete Beams, Journal of Advance Concrete Technology (ACT), Vol. 6, No. 3, October 2008, pp. 443-458
• De Silva S., Mutsuyoshi, H., Asamoto S, and Maekawa, A., Cracking Behavior of Ultra-High-Strength Prestressed Reinforced Concrete Beams, Proceedings of the 8th International Conference of  High-Strength Concrete and High Performance Concrete (8HSC-HPC), September 2008, Session S2-5-4, pp. 667-674
• De Silva S., Mutsuyoshi, H., Asamoto S, and Maekawa, A., Shear Cracking Behavior of Ultra-High-Strength Prestressed Reinforced Concrete Beams, Proceedings of the Japan Concrete Institute (JCI), Vol. 30, No. 3, July 2008, pp. 823-828
• Maekawa, A., Mutsuyoshi, H., De Silva S., Asamoto S, and, Cracking Behavior of Ultra-High-Strength Prestressed Reinforced Concrete Beams, Proceedings of the Japan Concrete Institute (JCI), Vol. 30, No. 3, July 2008 (in Japanese)
• De Silva S., Mutsuyoshi, H., Asamoto S, and Takagi, M., Shear Cracking Behavior of High-Strength Prestressed Reinforced Concrete Beams, Proceedings of the Japan Concrete Institute (JCI), Vol. 29, No. 3, July 2007, pp. 679-684
• Takagi, M., and Mutsuyoshi, H., De Silva S., Asamoto S, Cracking Behavior of High-Strength Prestressed Reinforced Concrete Beams, Proceedings of the Japan Concrete Institute (JCI), Vol. 29, No. 3, July 2007, pp. 577-582 (in Japanese) 
• De Silva S., and Mutsuyoshi, H., Shear Cracking Behavior in I-shaped Partially Prestressed Concrete Beams, Proceedings of the Tenth East-Asia Pacific Conference on Structural Engineering and Construction (EASEC-10), Bangkok, Thailand, August 2006, pp. 431-436 (CD-Rom version)  
• De Silva S., Mutsuyoshi, H., Witchukreangkrai, E., and Takagi, M., Experimental Study on  Shear Cracking Behavior in I-shaped Partially Prestressed Concrete Beams, Proceedings of the Japan Concrete Institute (JCI), Vol. 28, No. 2, July 2006, pp. 817-822
• Witchukreangkrai, E., Mutsuyoshi, H., Takagi, M., and De Silva S., Evaluation of Shear Crack Width in Partially Prestressed Concrete Members, Proceedings of the Japan Concrete Institute (JCI), Vol. 28, No. 2, July 2006, pp. 823-828
• Mutsuyoshi, H., De Silva S., and Witchukreangkrai, E., Influence of Prestressing on Shear Crack Width of Partially Prestressed Concrete Beams, Proceedings of 2nd International fib Congress, Session 15, Naples, Italy, June 2006, Paper ID 15-30 (CD-Rom version)
• Takagi, M.,  Mutsuyoshi, H., Witchukreangkrai, E., De Silva S., Investigation on Shear Cracking Behavior of Partially Prestressed Concrete Beams, Proceedings of the Annual Conference of JSCE, November 2005, pp. 599-600 (in Japanese) 
• De Silva S., Mutsuyoshi, H., Witchukreangkrai, E., Uramatsu, T., Analysis of Shear Cracking Behavior in Partially Prestressed Concrete Beams, Proceedings of the Japan Concrete Institute (JCI), Vol. 27, No. 2, July 2005, pp. 865-870 .

• Rathnayaka R.M.M.P., Malshan W.V.D., De Silva Sudhira and De Silva Subashi, “Incorporating Re-Cycled PET Fibres for Concrete Cylindrical Culverts”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/135

• Ruwanpathirana B.S., Rathnayaka R.M.C.P., De Silva Sudhira and De Silva Subashi, “Investigation of Strength Parameters and Physical Properties of Non-Class Timber Species in Sri Lanka”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/138

• B.V.A. Perera, K.G.S. Madhushanka,, De Silva Subashi and De Silva Sudhira, “Effect of Rice Husk Ash (Rha) on Structural Properties of Burnt Clay Bricks”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/139

• Madhushanka J.G.N., Subashi De Silva G.H.M.J., De Silve G.S.Y., “Investigation on Whole Body Vibration Exposures in Workers in Construction Industry”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/145

• P.H.D.P Chandarasiri, Subashi De Silva G.H.M.J., De Silve G.S.Y., “Investigation on Ground Vibration Induced by Construction Traffic and Normal Traffic”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/146

• R.M.K.S Karunarathna, Subashi De Silva G.H.M.J., De Silve G.S.Y., “Investigation on Hand Arm Vibration Exposures in Workers in Construction Industry”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/148

• B Thirukumaran, Subashi De Silva G.H.M.J., De Silve G.S.Y., “Investigation on Characteristics of Noise Induced by Construction Traffic”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/149

• T.M. Sooriyaarachchi, W.A.M.T.C.W. Aththanayaka, De Silva Sudhira and De Silva Subashi , “Dynamic Response of RC Bridges Due to Heavy Vehicles”, 6th International Conference on Structural Engineering and Construction Management (ICSECM), Kandy, Sri Lanka, December 2015, SECM/15/157

• Rathnyayaka R.M.M.P., De Silva Sudhira and De silva Subashi, “Application of Recycled Polyethylene Terephthalate (PET) Fibers to produce Fiber Reinforced Concrete pipes”, Advances in Civil and Environmental Practises for sustainable development(ACEPS-2016), University of Ruhuna, Hapugala, Galle, Sri Lanka, 3rd March 2016, pp. 257-264

• K.G.Sandya Kumudini, De Silva Subashi and De Silva Sudhira, “Investigation on Occupants’ satisfaction in natural ventilation in office building”, Advances in Civil and Environmental Practises for sustainable development (ACEPS-2016), University of Ruhuna, Hapugala, Galle, Sri Lanka, 3rd March 2016, pp. 265-271

Conferences and Other Publications

• O.S. Chathurangani,, G.H.M.J. Subashi De Silva, G.S.Y. De Silva, S. Jayakodi W.J.M.K. Perera, H.M.N.S. Kumari,, Utilization of saw dust, coconut coir fiber and rice straw for controlling industrial noise. Proceeding of Young members Technical conference, the 105 th Annual Sessions of Institution of Engineers, Sri Lanka, October 2011
• S.A.N.S.Wickramasinghe, S.R.Masakorala, E.A.T.P.Jayasinghe, G.H.M.J.Subashi De Silva and  G.S.Y.De Silva.  Investigation of effect of blast vibration on masonry walls. Proceeding of Young members Technical conference, the 105 th Annual Sessions of Institution of Engineers, Sri Lanka, October 2011
• C.N.Naotunna, ELAI Jayawardene, D A M Senevirathne, Sudhira De Silva and Subashi De Silva, Influence of actual environmental factors on shrinkage behavior of concrete containg mineral compounds. Proceeding of Young members Technical conference, the 105 th Annual Sessions of Institution of Engineers, Sri Lanka, October 2011
• R. B. Y. B. Uduweriya, C. Subash, M. M. A. Sulfy and Sudhira De Silva, Investigation of Compressive Strength of Concrete containing Rice-Husk-Ash, Proceedings of the Young Members Section – 2010, 104th Annual Sessions, The Institution of Engineers Sri Lanka, October, 2010
• Chandana Nawarathna, Laksiri Pradeep, Suranga Priyalal and Sudhira De Silva, Evaluation of Current Condition State of Bridges and Laboratory Investigation of the Chloride Induced Corrosion Cracking , Proceedings of the Young Members Section – 2009, 103th Annual Sessions, The Institution of Engineers Sri Lanka, October, 2009
• Chandana Nawarathna, and Sudhira De Silva, Investigation of Current Condition State of Bridges in Galle district by Simple Evaluation Method, Proceedings of the International Exchange Symposium “Sustainable Infrastructure Development in Asia”, Faculty of Engineering, University of Ruhuna, Sri Lanka, September, 2009 pp. 71-76 (ISBN 978-955-1507-12-1)
• De Silva S., Mutsuyoshi, H., and Asamoto S, Analysis of Shear Crack Width in High-Strength I-shaped Prestressed Reinforced Concrete Beams, Proceedings of the Ninth  International Summer Symposium of JSCE, September 2007, pp. 279-282
• De Silva S., Mutsuyoshi, H., Uramatsu, T., and Tagagi, M., Flexural Cracking Behavior in Prestressed Reinforced Concrete Beams, Research Report of Department of Civil and Environmental Engineering, Saitama University, Japan, Vol. **, No. **, July 2007 (in press)
• De Silva S., and Mutsuyoshi, H., Control of Shear Crack Width in Prestressed Reinforced Concrete Beams, Research Report of Department of Civil and Environmental Engineering, Saitama University, Japan, Vol. **, No. **, July 2007 (in press)
• De Silva S., Mutsuyoshi, H., and Takagi, M., Shear Cracking Behavior and It’s Design Methodology for Prestressed Reinforced Concrete Beams, Proceedings of the Joint Seminar between Saitama University and Tohoku University, Japan, August 2006, pp. 3-14
• De Silva S., and Mutsuyoshi, H., 3D Finite Element Modeling of Shear Cracking Behavior in Partially Prestressed Concrete Beams, Proceedings of the Eighth International Summer Symposium of JSCE, July 2006, pp. 67-70
• De Silva S., Mutsuyoshi, H., Witchukreangkrai, E., Takagi, M.,  Design Methodology of Shear Crack Width in Reinforced Concrete and Partially Prestressed Concrete Beams, Proceedings of the Annual Research Journal of SLSAJ, Issue 5, September 2005, pp. 71-76
• De Silva S., Mutsuyoshi, H., Witchukreangkrai, E., Takagi, M.,  Experimental Investigation on Shear Cracking Behavior of Partially Prestressed Concrete Beams, Proceedings of the Seventh International Summer Symposium of JSCE, July 2005, pp. 57-60.
• Takagi, M.,  Mutsuyoshi, H., Witchukreangkrai, E., De Silva S., Experimental Investigation on Flexural Cracking Behavior of Partially Prestressed Concrete Beams, Proceedings of the Seventh International Summer Symposium of JSCE, July 2005, pp. 61-64.
• De Silva S., Mutsuyoshi, H., Witchukreangkrai, E., Uramatsu, T., Shear Cracking Behavior of Partially Prestressed Concrete Beams, Proceedings of the Annual Research Journal of SLSAJ, Issue 4, October 2004, pp. 38-43
• De Silva S., Mutsuyoshi, H., Witchukreangkrai, E., Uramatsu, T., Effectiveness of Prestressing Force in Controlling Diagonal Crack Width of Partially Prestressed Concrete Beams, Proceedings of the Sixth International Summer Symposium of JSCE, July 2004, pp. 33-36.

• R.M.M.P Rathnayaka, W.V.D Malshan and G.S.Y. De Silva, “Application of Recycled Polyvinyl Chloride Fibers to Produce Lightweight Concrete and Investigate Their Mechanical Properties”, Fifth Undergraduate Research Symposium on Recent Advances in Civil Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, 7th January 2016, pp. 11-12

• T.M.S. Arachchi, W.A.M.T.C.W. Aththanayaka and G.S.Y. De Silva, “Structural Health Monitoring of Concrete Bridges”, Fifth Undergraduate Research Symposium on Recent Advances in Civil Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, 7th January 2016, pp. 13-14

• B.S. Ruwanpathirana, R.M.C.P. Rathnayakaand G.S.Y. De Silva, “Investigate Structureal Properties of Non-Class Timber Materials and Their Possible Applications”, Fifth Undergraduate Research Symposium on Recent Advances in Civil Engineering, University of Ruhuna, Hapugala, Galle, Sri Lanka, 7th January 2016, pp. 15-16

Thesis

• Shear Cracking Behavior and Design Methodology for Prestressed Reinforced Concrete Beams, PhD dissertation, Saitama University, March 2008, pp. 221
• Investigation of Shear Cracking Behavior of Partially Prestressed Concrete Beams, Master of Engineering, dissertation, Saitama University, March 2005, pp. 190
• Application of Artificial Neural Network in Civil Engineering, Undergraduate research thesis (Part I) submitted to Department of Civil Engineering, University of Moratuwa, Sri Lanka, July 2000, pp. 150
• Computer Based Methodology for Building Air-Conditioning Load Estimation,”AC2000”, Undergraduate research thesis (Part II) submitted to Department of Civil Engineering, University of Moratuwa, Sri Lanka, July 2000, pp. 125