The Study On Mechanical Performance Of New Composite Steel-truss Travelling Bridge Structure

Steel box beam adopts high-strength materials, so it has a light weight, a high strength, a good overall performance and a nice figure. It is convenient to transport and install. It is also comfortable to travel on. More importantly, it can well adapt to reciprocate loads, hence, it is applied widely in port engineering. Recently, port engineering and logistics engineering have developed quickly in China, so the structure style of steel box beam is more and more often applied in travelling bridges in ports.However, total steel usage of steel box beam is quite large, so its cost is very high and it is uneconomic. Steel truss is a kind of display rack which has a very good stability, so it is widely adopted in exhibition booth's construction engineering, super-tonnage travelling bridge in large dockyards and bridge constructions. Steel truss has advantages as followed:low cost, less total steel usage, good stability, and is convenient to transport and install.As for travelling bridge structures under reciprocate loads, at the bearing there will be a large change in stress of structure, while at the ends and midspan, there will be simple change in stress of structure. Now various engineerings prefer structures which have large spans and light weights, so it is very important to reasonably and fully use constructing materials in structural design. Hence, in this paper, a new composite structure is put forward, which can largely reduce its self-weight and also satisfy requirements of stress change of reciprocate loads.In this paper, based on economy, applicability, features of steel box beam and steel truss, and the optimization designing of a certain travelling bridge engineering, according to the structure's factual stressing situation under reciprocate loads in practical engineering, steel box beam and steel truss are combined and reasonably distributed and used, and then a new composite structure, which is named as steel truss-steel truss box beam, is put forward. This new structure utilizes steel box beam's high stability, high bearing capacity, low deflection and deformation, and steel truss's low steel usage, to offset steel truss' poor fatigue strength, low bearing capacity, and steel box beam's large steel usage and high cost, and then on the condition of satisfying requirements of deflection, deformation and fatigue strength, it can optimize structure's steel usage, reasonably use steel materials and save resources.The new structure, steel truss-steel truss box beam, has many advantages in engineering practice, however, its research is still at the starting stage, and its theoretical research lags far behind the engineering practice. Fatigue failure and computing method of steel truss-steel truss box beam need deeper research. In this paper, according to various sizes, load positions and different structure styles (including steel truss beam, steel truss box beam, and steel truss-steel truss box beam), models' building, analysis and optimization have been done based on ANSYS. Calculating results show that, steel truss-steel truss box beam has a higher bearing capacity, a good overall performance, and a less steel usage, hence, it is the very structure style of the optimizing design plan. Meantime, steel truss-steel truss box beam can not only satisfy market's requirements of steel's economic and mechanical performances, but also inspire minds and expand styles of composite structures. It is good for innovational thoughts and can also provide references for similar composite structures' research in future.