K. Rama Raju

Osta software—offshore/onshore structural analysis under unix system

Abstract Structural analysis of large complex structures under static and dynamic loadings uses a large number of general purpose and special purpose algorithms in different languages, and also computer graphics (as pre- or post-processor programs) to help in the efficient and convenient interpretation of final structural designs. To enhance the portability of any sophisticated software system for large scale structural analysis, what is needed is a single program shell that would coordinate the three phases, pre-processing, analysis and post-processing, with effective user interaction. This paper highlights the utility of such a shell program (called OSTA) operating under the UNIX system. The OSTA Bourne shell interacts with a structural analysis system developed in FORTRAN 77 and a GKS-based graphic system written in ‘C’, to facilitate a systematic and efficient analysis capability in a minicomputer environment. Numerical examples are presented to demonstrate the features of OSTA for static, dynamic (deterministic/ stochastic) and reliability analyses under seismic, wave-current, wind and blast loadings.

Analysis and Design of RC Tall Building Subjected to Wind and Earthquake Loads

Consideration of site specific lateral loading due to wind or earthquake loads along with vertical gravity loads is important for finding the behavior of the tall buildings. As the height of a building becomes taller, the amount of structural material required to resist lateral loads increases drastically. The design of tall buildings essentially involves a conceptual design, approximate analysis, preliminary design and optimization, to safely carry gravity and lateral loads. The design criteria are strength, serviceability and human comfort. The aim of the structural engineer is to arrive at suitable structural schemes, to satisfy these criteria. In the present study, the limit state method of analysis and design of a 3B+G+40-storey reinforced concrete high rise building under wind and seismic loads as per IS codes of practice is described. Safety of the structure is checked against allowable limits prescribed for base shear, roof displacements, inter-storey drifts, accelerations prescribed in codes of practice and other relevant references in literature on effects of earthquake and wind loads on buildings.

Elastoplastic behaviour of unstiffened and stiffened steel tubular T-joints

Abstract An offshore structure such as a jacket-type tower or a semi-submersible drilling platform consists of a very large number of steel tubular joints. Due to high stress concentration near such a joint, plastic deformation often occurs which ultimately leads to the failure. In this paper, static elastoplastic behaviour of two types of stiffened and unstiffened T-joints are studied using assumed strain degenerated shell elements. The variation of stress and flow of plasticity with the increase in load is studied for all the above cases. The results are found to be in good agreement with experimental results.