engleski

New Timber bridges in Croatia

Abstract The paper presents two new timber bridges planned for construction in 2008 in Croatia. Their sites are near Ivanec and in the town of Samobor. The first one is a pedestrian bridge for light traffic with agricultural vehicles (mostly combine harvesters) and the latter is for pedestrian and bike traffic only. The bridge near Ivanec is a three-hinged arched structure with suspended transversal girders on a steel suspension. The axial span of the bridge is 23.80 m, which is the distance between the supporting reinforced concrete piers on the river banks. The static structure is a three-hinged arched one, so that the axial arrow of the circular arches in the mid-span is 502 cm. The radius of an arch per axis is 16.61 m. Cross sections of the arches are 20/60 cm and are made of 1st class European spruce glulam, according to EC5 class BS 14. On the arches, at an axial distance of 260 cm there are suspended steel elements of 60/60/6 mm rectangular pipe sections, connected according to the details in the design project to the transversal glulam girders with 18/40 cm cross section. In the bottom tensile zone, the transversal girders are connected at the level of arches by steel pipe elements of 80/80/8 mm rectangular cross section, from one bearing to another. The transversal girders and such steel elements in the tensile zone with the steel cross diagonals form a bracing in the bottom zone providing a lateral stabilisation for the walking and carriageway structure. The carriageway structure consists of continuous beams with 16/16 cm cross section, supported by cross girders and connected with screws according to a detail in the design project. The walking surface of the carriageway from one railing to another is of 356 cm clear width and has been adjusted for the width of combine harvesters, i.e. up to 310 cm, which is by 46 cm less than the total width of the carriageway surface. The bridge has no special pedestrian walking surfaces as they were not required. The carriageway surface of 16/16 cm small beams will be done by leaving 1 cm distance between two beams. The reason is primarily the durability of the bridge structure and by application of protective agents the expected bridge lifespan would exceed 50 years. The timber bridge in the town of Samobor will be a beam structure made of glulam girders of pine or spruce tree, class BS 14 according to EC5. All steel bearing elements will be of S235 steel for structures on open and the handrail will be made of 1.4301 stainless steel. The main girders of 18/60 cm cross section are made at an axial distance of 192 cm. The axial span of the bridge will be 10.2 m from one pier bearing to another. On the main girders, at an axial distance of 92 cm, transversal girders will be placed of 10/14 cm cross section, and they will support the secondary girders of the same cross section, parallel to the main girders at an axial distance of 58 cm. A grid consisting of the main, transversal and secondary girders will form a base of a walking surface to be made of a 9-mm wide water-resistant veneer board placed across a 25-mm wide water-resistant OSB board. The water-resistant veneer board has a roughly processed anti-sliding surface that will serve as a walking surface. More details on the bridges in the paper – WCTE 2008 CD presentation.

timber bridges; calculating structures; COSMOSM; details

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