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Self-supporting lattice towers, which are having quite a few unique structural features, play a vital role in communication networks. Ensuring structural stability of these giant structures under all possible natural and human threats are vital as failures of such structures may cause a catastrophic human & property damages. Further, possible communication outages caused by failure of tower/towers in disaster situation are a critical as it may hamper rescue and other emergency operations. This was experienced by South and South East Asian countries during 2004 Tsunami. Hence, need of mitigating these situations have been highlighted by various reports. Therefore, ensuring structural integrity of self-supporting lattice towers under seismic forces is an essential and timely need. This paper discusses a seismic performance of four leg and three leg lattice towers under Response Spectrum analysis under different sub soil conditions. Results of seismic analyseshas also been compared with wind analyses results.

Corrugated Soil-Steel bridges have been used as drainage structures and underpasses in the ongoing Southern Highway project. Because the Soil-Steel bridges are novel to Sri Lankan context and the catastrophic bridge failure at Poddala, 2009 led to a controversy about the suitability and the stability of Soil- Steel bridges. The structure safety against crushing failure of the corrugated steel arch was determined using finite element methods. Furthermore, even though the Soil-Steel bridges failed mainly due to the buckling of the corrugated plates and AISI guidelines, which had been used to design bridges in Sri Lanka, doesn’t cooperate versatile design procedure for the buckling failure. Therefore, the structural stability against crushing and buckling failure of the existing bridges (Long Span Type) with respect to the different fill heights were determined using finite element analysis.