COMPUTER AIDED ANALYSIS AND DESIGN OF PIPELINE TRUSS BRIDGES

Abstract

Ever increasing demand of fuel has brought great pressure on the transportation of refined petroleum as well as the crude oil. The existing roads and railways have proved to be not only inadequate but also unsafe, uneconomical and prone to delays. Pipelines offer a viable and much cheaper alternative while at the same time ensuring an almost uninterrupted supply. In the offshore, arctic and hilly regions, they are the only means of efficient and economic petroleum transportation.• Very often a pipeline needs to be taken over obstacles by erecting bridges solely for the pipeline. Truss bridges offer an efficient solution in the span range of 10 m' to 60 m.. Since a large number- of such bridges would be required'. in a vast country like ours, it may be worth t.o develop an . efficient computer software for analysis and design of pipeline bridges. Such a package offers advantage of economical -design besides accuracy of computations and saving of Lime. This thesis-has been devoted t.o the development of a package for the analysis and design of simply. supported truss bridges for pipelines using personal/main frame computers. A more accurate 3-D analysis has been used, which is not feasible if the computations are done manually. The. package has built-in geometric data generation for a particular type of truss along with the generation of member forces for the first trial of design. Any number of analysis and design cycles can be opted by the user, but the convergence usually occurs within two to four cycles. A case of 30 m span has been taken up for illustration of the use and application of the software package. Using the developed software other spans of 40, 50 and 60 m maintaining the same bridge cross-section are also analysed and forces in typical members and also the maximum deflections and total weight of steel work are tabulated. The deflection to span ratio varies almost linearly with span while the steel weight increases somewhat non-linearly. In order to investigate the effect of joint rigidity the 30 m span bridge is also analysed considering it as rigid jointed and significant alteration in the moments in the end portals and sway bracings is obtained. The member forces obtained from the computer analysis have also been compared with those from the analysis carried out manually and though showing a general agreement, highlight some obvious differences.