Browsing by Author "Karunarathna, WWN"

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item: Conference-Abstract
Finite element analysis of truss type steel bridges
(2016-08-11) Baskaran, K; Karunarathna, WWN; Gamage, HDH
This work aims towards 3-D finite element analysis of truss type steel bridges using SAP2000 software. Some of the recent bridge failures which happened in Sri Lanka were analyzed using SAP2000 software. Failure loads and failure modes of the failed bridges were compared with the finite element analysis results. Scaled down models of a Pratt type truss bridge were tested in the structural laboratory, and then failure loads and failure modes of the test models were compared with the finite element analysis predictions. Models with portal and without portal were tested separately to see the effect of end portals with the introduction of the lateral load. Scaled down model of a Tied Arch bridge was also tested to observe the failure mode and the test results were also compared with the finite element analysis results. Span vs. tonnage graphs were developed for different truss type bridges, such as Pratt, Modified Warren, Tied Arch, Inverted Arch and the Parker truss, considering them being used by pedestrians and light vehicles. The weights of the existing bridges were also compared with the obtained graphs for some of the selected truss types.
item: Thesis-Abstract
Optimization of truss type steel bridges
(2016-05-02) Karunarathna, WWN; Baskaran, K
This work aims towards analyzing truss type steel bridges by 3-D finite element modelling using SAP2000. Details of different truss type steel bridges are discussed together with gathered information on such bridges found in Sri Lanka. State of the art, regarding design and assessment of truss type steel bridges were also reviewed. Scale-down model bridges were tested in the Structural Laboratory (UOM) and the test results were used to validate the SAP models and observe the overall behaviour. The actual failure loads and failure patterns were observed and compared with SAP analysis results. 3-D [mite element modelling gives a clear image in modelling of truss type bridges, than 2-D finite element counterparts due to the facilities available to check the lateral stability of the bridges. This research contains some methods to improve the lateral stability of truss type steel bridges too. Failure study and analysis were done for some failed bridges in Sri Lanka using SAP 2000. Results predicted by SAP 2000 are compared with actual failure modes, loads and deflections. Span vs. tonnage graphs were obtained with optimum steel usage, for the selected truss type steel bridges which include common truss types used in the country and some of other efficient truss types. It contains span vs. tonnage graphs which were obtained for Modified Warren, Parker, Inverted Arch, Pratt and Tied Arch bridges which are used for pedestrians and light vehicles. The weights of the actual existing bridges are presented in the same graph (if applicable) and the reasons for deviation from the graph are also discussed. Set of span vs. tonnage curves were plotted for different truss types in same graph, for comparison purpose which shows tonnage required for each selected truss type, for given range of spans. Finally, some guidelines for local bridge designers, and some suitable truss types are recommended by considering minimum steel usage.