starting situation
the redesign of the intersection of ennstal state road b320, salzkammergutstraße, and glattjochstraße in the municipality of stainach-pürgg is defined by its sensitive location between grimming and trautenfels castle, embedded in a cultural landscape with fish ponds and iris meadows. the client requires a grade-separated solution, with the ennstal road passing over an underlying roundabout. the existing road planning appears not further optimizable given the road junctions into the roundabout and the location of third-party land with a gas station. free sightlines over the roundabout are not desired for traffic safety reasons. the large radius of the roundabout ensures sufficient visibility at entries and exits. from the traffic planners’ perspective, a minimal-diameter embankment for the roundabout would also be feasible. this means that a large, column-free span of the roundabout is functionally unnecessary.
design
in the immediate vicinity, trautenfels castle serves as the landmark of the area. the bridge is not intended to compete with it; there is no need for a second landmark. the bridge is designed as a simple, easily constructible structure with economical spans of approximately 18 to 8 meters.
support spacing responds to the bridge height: largest at the roundabout, tapering toward the lateral supports. the bridge girder adapts to varying spans via changes in cross-section thickness. the supports are always perpendicular to the road slope in longitudinal view and taper toward the lateral supports, emphasizing the gentle incline. where the bridge is highest, it appears most massive; near the ground, it appears most delicate. this effect is accentuated by a semi-transparent spray shield, higher at the apex than at the side supports. at the roundabout center, the supports are replaced by a fixed bearing both longitudinally and transversely. structurally, the bridge is restrained horizontally in both directions at this point, while longitudinal expansion is allowed at the lateral bearings (see structural concept).
bridge shadow
the necessary foundations for supports and bearings are covered with concrete panels, widening toward the roundabout in accordance with the greater spans and increasing structural mass. simultaneously, they shorten in the longitudinal direction, roughly mimicking the bridge’s shadow. the panels accommodate ground-level lights, illuminating the bridge underside. the higher the bridge, the brighter the underside. the light-colored exposed concrete reflects and gently lights the surroundings, aiding nighttime orientation.
the redesign of the intersection of ennstal state road b320, salzkammergutstraße, and glattjochstraße in the municipality of stainach-pürgg is defined by its sensitive location between grimming and trautenfels castle, embedded in a cultural landscape with fish ponds and iris meadows. the client requires a grade-separated solution, with the ennstal road passing over an underlying roundabout. the existing road planning appears not further optimizable given the road junctions into the roundabout and the location of third-party land with a gas station. free sightlines over the roundabout are not desired for traffic safety reasons. the large radius of the roundabout ensures sufficient visibility at entries and exits. from the traffic planners’ perspective, a minimal-diameter embankment for the roundabout would also be feasible. this means that a large, column-free span of the roundabout is functionally unnecessary.
design
in the immediate vicinity, trautenfels castle serves as the landmark of the area. the bridge is not intended to compete with it; there is no need for a second landmark. the bridge is designed as a simple, easily constructible structure with economical spans of approximately 18 to 8 meters.
support spacing responds to the bridge height: largest at the roundabout, tapering toward the lateral supports. the bridge girder adapts to varying spans via changes in cross-section thickness. the supports are always perpendicular to the road slope in longitudinal view and taper toward the lateral supports, emphasizing the gentle incline. where the bridge is highest, it appears most massive; near the ground, it appears most delicate. this effect is accentuated by a semi-transparent spray shield, higher at the apex than at the side supports. at the roundabout center, the supports are replaced by a fixed bearing both longitudinally and transversely. structurally, the bridge is restrained horizontally in both directions at this point, while longitudinal expansion is allowed at the lateral bearings (see structural concept).
bridge shadow
the necessary foundations for supports and bearings are covered with concrete panels, widening toward the roundabout in accordance with the greater spans and increasing structural mass. simultaneously, they shorten in the longitudinal direction, roughly mimicking the bridge’s shadow. the panels accommodate ground-level lights, illuminating the bridge underside. the higher the bridge, the brighter the underside. the light-colored exposed concrete reflects and gently lights the surroundings, aiding nighttime orientation.
green integration toward the bridge
landscape interventions aim to integrate the bridge and its structures into the surrounding landscape. mixed tree lines of native species are planted with varying spacing, providing orientation and signaling decreasing speed, with maximum tree density in the roundabout itself. species reflect potential natural vegetation: at altitudes between 600–1400 m, the dominant forest is spruce–fir–beech, with occasional maple, elm, ash, birch, pine, and larch. trees are planted to comply with clearance requirements. near watercourses, riparian species such as willow and alder dominate.
the roundabout surface is integrated with the bridge footprint via a homogeneous layer: mechanically stabilized sub-base covered with fine gravel, resembling a roadside shoulder. the course of the small grimming is largely preserved, with cross-section adjustments to meet ecological requirements. riverbank roughening is achieved through stone elements and deadwood; willows and alders provide shading. sedimentation and infiltration basins are landscape-integrated. the iris meadow is preserved and extended eastward.
situation and structural choice
as noted in the architectural report, a large, column-free span over the roundabout is functionally unnecessary. economic considerations and task requirements quickly indicated that an elegant girder bridge with well-proportioned spans is most appropriate. the bridge extends close to the terrain to avoid long concrete abutments, which would otherwise be required due to steep embankments along nearby access roads. this allows a lighter, more transparent structure. in various design studies, a slender superstructure with relatively short spans was developed.
bridge geometry
the slightly curved bridge, approximately 200 m in total length from abutment to abutment, is a continuous girder with variable spans responding to bridge height, increasing toward the apex in the roundabout center. spans range from ~7.0 m at the eastern abutment to ~17.9 m at the bridge center, creating dynamic overall geometry. span proportions were optimized so supports under the underpasses maintain sufficient and consistent clearance from roundabout traffic. span increments follow a geometric series (factor 0.9) from the bridge center outward. increasing spans toward the center require a larger girder depth, optimized for bending moments. this results in a dynamic visual effect, emphasized by the varying cross-section height. for the load-bearing superstructure, a wide plate-girder section with flared edges toward the sides was chosen; the middle section varies in height.
landscape interventions aim to integrate the bridge and its structures into the surrounding landscape. mixed tree lines of native species are planted with varying spacing, providing orientation and signaling decreasing speed, with maximum tree density in the roundabout itself. species reflect potential natural vegetation: at altitudes between 600–1400 m, the dominant forest is spruce–fir–beech, with occasional maple, elm, ash, birch, pine, and larch. trees are planted to comply with clearance requirements. near watercourses, riparian species such as willow and alder dominate.
the roundabout surface is integrated with the bridge footprint via a homogeneous layer: mechanically stabilized sub-base covered with fine gravel, resembling a roadside shoulder. the course of the small grimming is largely preserved, with cross-section adjustments to meet ecological requirements. riverbank roughening is achieved through stone elements and deadwood; willows and alders provide shading. sedimentation and infiltration basins are landscape-integrated. the iris meadow is preserved and extended eastward.
situation and structural choice
as noted in the architectural report, a large, column-free span over the roundabout is functionally unnecessary. economic considerations and task requirements quickly indicated that an elegant girder bridge with well-proportioned spans is most appropriate. the bridge extends close to the terrain to avoid long concrete abutments, which would otherwise be required due to steep embankments along nearby access roads. this allows a lighter, more transparent structure. in various design studies, a slender superstructure with relatively short spans was developed.
bridge geometry
the slightly curved bridge, approximately 200 m in total length from abutment to abutment, is a continuous girder with variable spans responding to bridge height, increasing toward the apex in the roundabout center. spans range from ~7.0 m at the eastern abutment to ~17.9 m at the bridge center, creating dynamic overall geometry. span proportions were optimized so supports under the underpasses maintain sufficient and consistent clearance from roundabout traffic. span increments follow a geometric series (factor 0.9) from the bridge center outward. increasing spans toward the center require a larger girder depth, optimized for bending moments. this results in a dynamic visual effect, emphasized by the varying cross-section height. for the load-bearing superstructure, a wide plate-girder section with flared edges toward the sides was chosen; the middle section varies in height.
- location:
- pürgg-trautenfels, austria
- architecture:
- fasch&fuchs.architekt:innen
- structural engineering:
- werkraum ingenieure zt gmbh
- rendering:
- aberjung gmbh
- competition:
- 2015