Structural Engineering, Steel Structures, Earthquake Resistant Design, Cold Fromed Steel, Steel Bolted and Welded Connections

Structural optimisation is a topic which gathers the interest of many research teams and engineers. Its purpose is to minimise an objective function, such as the weight of a structure, subjected to certain constraints (e.g. compliance of structural members with code requirements). In this paper, optimal design (in terms of shape and sizing) of through-truss steel bridges is performed. Several cases of simply supported bridges with different spans (40m, 50m and 60m) and varying width, corresponding to one or two traffic lanes, were examined. For the aforementioned bridges, the effect of three deck types (reinforced concrete deck, fiber reinforced polymer deck and steel deck) on the weight of the truss and the total weight was investigated. Least-weight shape and sizing optimal design was executed, with the height of the truss and the cross-section areas of its members constituting the design variables of the problem. The structural analysis and design were conducted in accordance with the specifications of the Eurocodes. The influence of both the height-to-span ratio and the deck type on the weight of the truss, the total weight and the cost is discussed based on the results obtained from the optimisation procedure.

Since 18th century, progresses in iron industry allowed the spread of metal bridges in UK, US and France. These bridges were characterized by various construction types. In Italy, apart from some rare previous example, metal bridges spread only after 1860s. In a first phase, financial capital, materials, and designers were mainly foreigners; only since the end of the century Italian enterprises developed. Most of the bridges were continuous beam bridges on masonry piers; initially the most common type was the lattice truss bridge, subsequently trusses made of square panels with double bracing prevailed. Many bridges built before World War II were demolished and rebuilt because they no longer met the needs of traffic and safety, or because damaged by exceptional events. The Ponte della Becca –  at the confluence of Po and Ticino rivers, next to Pavia – is a 1040 m long continuous-beam trussed bridge. The bridge was inaugurated in 1912, but bombings of 1944 made him unfit for use until 1950. Nowadays the state of preservation of the bridge is poor: in addition to widespread oxidation, some piers suffered settlements. In November 2010, a pier underwent a major settlement and the bridge was strengthened building two new piers adjacent to the settled one, which collapsed in March 2011. Since then, heavy vehicles are prohibited from passing on the bridge. Conservation, strengthening and use of the Ponte della Becca are complex issues. The bridge has a fundamental role in the local transport. A performance adjustment would involve significant investments, but also invasive interventions without solving the problems due to poor track width; the Provincial Administration has intention to build a new bridge parallel to the existent, which would be preserved for pedestrian use; the limitation of the importance of the bridge as a transit route is likely to limit the possibility of access to adequate funding for its conservation. The article presents some critical reflections on the issue

A corrugated web beam is a built-up beam with thin walled corrugated web. T RI WP, designed as a web profiling to avoid the failure of the beam due to loss of stability before the plastic limit loading of the web is reached. The web profile is a modified section of a trapezoid web profile steel section which is the eccentric stiffeners of the trapezoidal section; that is eliminated and changed to the slanting stiffeners. This paper develops a three-dimensional finite element model using LUSAS 14.3 to study on the effect of the triangular steel beam web profile (T RI WP), box beam in deflection and stress compared to that of the normal flat beam (FW). All specimens are cantilever beam which are fixed at one ends. The flange is constant with variable web profiled. Nonlinear analysis was used in analysing the deflection and stress of the flat plate model, box beam and triangular web profile (T RI WP). The FEA throw LUSAS 14.3 program can be used as a very useful tool in predicting the deflection of cantilever beams and can provide very detailed information for the distribution of stress in beams with different profile web.

Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one.