Bridge Over Corace River in Gimigliano Municipality: Urgent Traffic Rehabilitation
This work was one of the boldest kind of Maillarts ever made by Adriano Galli. This is the first example of arched road bridge, made of reinforced concrete and with stiffening deck in the South of Italy. This is over 170m length with two access viaducts, consisting of three-deck continuous beams on four sturdy supports and a very solid slender central arch of 80m. The disruption that caused the unavailability of the bridge had posed forcefully two essential questions: the first one purely functional and "utmost urgency," the second one of cultural and philosophical nature for the need of seismic rehabilitation increasing its functions. The urgency was to resolve at an early stage to quickly make the bridge fit for use again, at least for traffic of light vehicles. The re-functionalization, carried out in the second phase was aimed at adjusting the crossing to the new task, eliminating the mixing of pedestrian and vehicular traffic while simultaneously performing seismic retrofitting of the bridge.
Limited transit to light vehicles was ensured even during seismic retrofitting of the bridge which needed its temporary closure to traffic.
Enzo Siviero,
Professor, member of Progeest s.r.l. Padua, Italy, IUAV University of Venice, Italy,
Alessandro Stocco,
Architect, member of Progeest s.r.l. Padua, Italy, Phd student, ETCAEH University of Nova Gorica, Italy, and
Andrea Totaro,
Engineer, PhD student, University of Brescia, Italy.
The static approach on the structural aspects of architectural design, in this case, was characterized by the binomial form and function maintained, even after rehabilitation. These binomial features were clear formal lightness of original work of Galli.
The two phases of general project provided the measures needed to reopen the bridge to traffic as a first stage, and later, the functional enlargement of two walkways to the central lane. The overall intervention was planned in two coordinated phases of execution, subsequently linked by a dichotomous relationship within very compelling logic.
The first phase of the project involved the construction of new hydraulic right shoulder, already prepared to receive pedestrian enlargements, in addition to general strengthening and lifting of the deck. This was to avoid substantial interruptions of traffic, in the second phase of the intervention.
The second phase of the intervention consisted of creation of a box-shaped/metal mesh structure with piers. This offered metal spatial network structure with a new deck supports, in lieu of abandoned piers of the viaduct and simultaneously resisted the thrust of concrete arch and also supported the development and enlargement of the pedestrian area.
These two new bridge decks supported by longitudinal trusses, alongside the existing bridge, and supported by a pair of "powerful arms" as if to reinterpret the Athlas’s myth. Their function is twofold, first allowing the passage of light vehicles during the work of consolidation of the existing bridge, thus maintaining the continuity of vehicles. Finally when completed, served as a wide pedestrian path, to allow the pedestrian facing upstream and downstream to enjoy breathtaking panoramic views from a kind of bridge-square and place of rest.
Starting from these considerations, the project had found a preliminary delineation after some pre-configuration steps in order to achieve a satisfactory and accepted result which were in compatibility with the existing work that needed to be preserved not only in its formal geometry of the beautiful arch that characterizes its pathos, but also possibly enhanced by a vision set almost as jewel in a frame that can carry the look directly at the center of a work that lives, shining its light.
The two symmetrical enlargements, in addition of allowing the limited transit to passenger cars while performing on the main work, also permitted possibility of supporting the deck after elimination of piers at least on the side of the landslide not yet fully stabilized. Secondly, this also made it possible to allow for the full enjoyment of extraordinary emotional views of both upstream and downstream.
Another element of analysis is study of chromatism of white ice that could address a surface protection of concrete, in partial contrast/dialogue with the metal elements that could be expressed in gray or other colors at level of final finishing. Finally, we proposed a study on lighting using variable chromatism LED in order to articulate in different ways the relationship between the object and its enjoyment, even in the night suggestions. Thus, it could allow for further development of the two small villages as attraction for tourists so that it could receive curious visitors in future.
The study of the network structure articulated through different significant stages of the project. Starting from an initial proposal for ‘needle’ which are both physically and formally concentrated forces down in one place, then to the possibility of creating a portal forming real static channels that could accommodate the flow of forces determined by the thrust of the central arch. This means highlighting of exchange of stresses between old and new structure.
The next proposal was of a molten metal box, articulated by the introduction of a second arm. Thus, forming an architectural plasticity to convey the set of forces related to each other in various ways.
The final proposal was structured with a transformation of box spindle by virtual excavation that mimic the evolution from full to empty gradually reducing the size of rods until you get to the actual truss connecting via a special joint to the longitudinal beam. In this solution, we wanted to dispel the most of the rods along the wall to articulate as much as possible the full visual permeability. Thus, the historic bridge would only have been partially filtered by the new work.
The analysis covered the approach viaduct on the right shoulder, because this portion was actually damaged by landslides and damaged on the side. The plan shows a driveway on failure due to the translation. Lower first pile suffered after the complete detachment of the section from the deck.
Actually it was difficult to assess the state of the shoulder (because some areas are covered with debris) and the attack of the piers and on to foundation. As all three piers are damaged by crushing and complete detachment of the concrete, the first pillar was completely damaged.
The second pillar, completely visible, clearly showed the sequence of the actions which caused the displacement of the structure. All the piers are clockwise rotated. These present damages along the outside of the stretched fibers and torn down in the support side.
The third pillar, visually, seems to have minor damages as well but the fourth, appearing less damaged.
The first span measure 10.35 metres and the beams are still undamaged and without injury, second one measure 12.50 metres and has visible lesions, the third one and the fourth one measuring 11.60 metres. The third span has some damages in the middle, especially at the backbone for exceeding maximum stress due to the maximum moment.
As visually analyzed and described above the process that originated damages was due to a failure of the land. Thus giving rise to the cutting of the pillars of the first stack and relative failure of the beams of the deck causing damages of the beams.
To make the bridge safe, prevention of further displacement of the foundation and restoration of the initial static configuration of the structure needed to be done in the succession for intervention at the foot of the piles, the intervention of producing the two semi-abutments and support would ensure finally getting integrated with the lifting and repositioning of the concrete beams.
For the reopening of the bridge to traffic, the existing structure, more specifically in the node deck -right shoulder should be put in safety. An active monitoring system was still maintained, which was developed in the days immediately following the landslide.
Intervention at the foot of piles
In order to permanently block foundations of pillars 1, 2, 3 and 4, the construction of reinforced concrete slab, joining foundations and fixed to this side with tie rods that allowed stitching of potential sliding surfaces, which were still present. This stitching comprised the soil to the slope, stabilized the slope in the area.
The reinforced concrete slab developed to "terraces" and followed the inclination of the slope and at the same time, allowed the formation of flat areas on which could be accessed for tie rods.
After the realization of concrete stitching slab, a coverage was made with stones and earth in order to renaturalize the area.
Realization of the new right abutment
The construction of the new shoulder on right abutment was planned with micropiles and tie rods, made at the height of the first pillar of the existing bridge and of two semi-abutments: one upstream and one downstream of the pillar jointed by a crosspiece.
The function of this new system "abutment" is to replace pillar 1 of the existing bridge, which had been significantly damaged. The disruption caused by landslide and natural deterioration caused by aggressive weather effects on the right shoulder made the recovery difficult or even impossible, considering the extremely urgent nature of the intervention.
The aforesaid semi-abutments had been designed and sized for a double purpose: to replace pillar 1 of the existing bridge, supporting the bridge and sustaining the two ends of the footbridges that in a second and subsequent design phase was proposed to be built.
Considering the historic and architectural importance, as a boundary condition in the basic design of the products, a design solution was to be implemented, which was able to respect the pre-existing values and at the same time those characters that formed the architectural, environmental and landscape point of view to qualify this area.
In order to optimize the placement of the work in the natural and environmental context, the elevations of the construction (the new shoulder) and slabs, were planned to be lined with local stone such as that coming from the caves of the Capo dell’Armi close to Lazzàro, from which the rock is called "Reggina" or "di Lazzaro."
In addition to the technical qualities of the stone (very low porosity, high hardness and strength, frost-proof) and the particular gray-brown with pale blue colour, the use of this stone allowed to retain the aesthetics, especially in natural environments as must be safeguarded.
It may also be choosing a different local type or otherwise compatible stones with the characteristics of the site.
Deck lifting
The lifting of the deck was to be accomplished by use of pair of hydraulic jacks, mounted on a special metal frame (sling) made at each pier of the viaduct.
On pillars 2 and 3 was planned to build a harness to the head of the pillars with steel sections linking the three pillars forming piles.
Hydraulic jacks needs to be placed on these profiles for lifting the deck.
When the jacks placed on the shoulder at correspondence of the pillar 1 and on pillars 2 and 3, will be loaded and then proceed to cut the head of the pillars to a height of about 70 to 80 cm (height presumed necessary to remove all c.c. parts that have deteriorated because of the landslide event to be verified on construction site).
The construction is lifted until the jacks reach theoretical stresses due to bending action of the beams. This was calculated considering it to be a continuous beam scheme over several supports as a function of self-weight and permanent loads.
The steel harnesses will not be removed as they were useful in the construction phase of footbridges for the support of the footbridges during assembly phase.
This work, as well as to restore and expand the existing road blocks the side of the mountain in the area where the landslide originated. All the preparatory work described in this report is the knowledge of the system of disposal of storm water that must be intercepted, so as to divert the waters and regiment in order to prevent any problem in case of any further future flood events.
From the technical point of view, this part of the slope is in better condition than in the south: the south side of the bridge is in fact where the landslide occurred.
From the landscape point of view of a construction site road on the southern side would give rise to far greater environmental impact than that expected in the north: in fact, it should have started much further south to link up the existing road, and then with a length higher than that expected (400m approx. compared to 300m assumed.). In addition, this would have been most visible from the town of Gimigliano both from the provincial road on the opposite side.
The main track follows an existing path north of the bridge for a distance of approx. 120m, then returns to the bridge with a bend to get to the main pad site around the pillar 3: measure around the track approx. 315 m.
A Prog. 245 approx. disconnecting the first branch on the right and uphill to reach the pad site provided upstream of the pile 2. From this still climbing is possible to reach the pillar 1 and the area for the construction of the new shoulder designed.
A Prog. 290 comes off the track that comes down & reaches the pillar 4 and arch attack.
The tracks designed exceed a total climb of approx. 29m. The slopes are maintained always below 16%. The section of the track width of 4.00 m is expected.
These tracks will be maintained and used for future maintenance of the shoulder tie rods and bolts of the project for the stitching of the linking slab between the existing foundations, and for the monitoring of the existing bridge and future soil tests.
But there is more, using a pedestrian path to edge shoulder. There is also access to the public to admire the bridge in its "intimacy" with the direct and very unusual "vision" of the intrados of the deck, as well as to enable the transition from upstream to downstream in safe conditions without crossing the street.
In this way, the work amplifies its perceptive coherence. From the outside, for its majesty with significant historical and landscape excellence. From the inside, overcoming the mere traffic function "necessary" to make it a real "place" to fully live It goes without saying that this would open up interesting prospects for further enhancement and unpublished work in the landscape as a place of particular tourist attraction.
Limited transit to light vehicles was ensured even during seismic retrofitting of the bridge which needed its temporary closure to traffic.
Enzo Siviero,
Professor, member of Progeest s.r.l. Padua, Italy, IUAV University of Venice, Italy,
Alessandro Stocco,
Architect, member of Progeest s.r.l. Padua, Italy, Phd student, ETCAEH University of Nova Gorica, Italy, and
Andrea Totaro,
Engineer, PhD student, University of Brescia, Italy.
Introduction
The bridge built by Adriano Galli, though damaged, still appears today sleek and majestic connection of the two top sides of Corace river. The work is characterized by its clear and simple light shape.The static approach on the structural aspects of architectural design, in this case, was characterized by the binomial form and function maintained, even after rehabilitation. These binomial features were clear formal lightness of original work of Galli.
The two phases of general project provided the measures needed to reopen the bridge to traffic as a first stage, and later, the functional enlargement of two walkways to the central lane. The overall intervention was planned in two coordinated phases of execution, subsequently linked by a dichotomous relationship within very compelling logic.
 |
| Figure 1: Bridge over Corace at the end of works |
 |
| Figure 2: Re-functionalization of the crossing |
The first phase of the project involved the construction of new hydraulic right shoulder, already prepared to receive pedestrian enlargements, in addition to general strengthening and lifting of the deck. This was to avoid substantial interruptions of traffic, in the second phase of the intervention.
The second phase of the intervention consisted of creation of a box-shaped/metal mesh structure with piers. This offered metal spatial network structure with a new deck supports, in lieu of abandoned piers of the viaduct and simultaneously resisted the thrust of concrete arch and also supported the development and enlargement of the pedestrian area.
These two new bridge decks supported by longitudinal trusses, alongside the existing bridge, and supported by a pair of "powerful arms" as if to reinterpret the Athlas’s myth. Their function is twofold, first allowing the passage of light vehicles during the work of consolidation of the existing bridge, thus maintaining the continuity of vehicles. Finally when completed, served as a wide pedestrian path, to allow the pedestrian facing upstream and downstream to enjoy breathtaking panoramic views from a kind of bridge-square and place of rest.
Research, Form, Function
The new and different technologies available today, allow to evolve the crossings as an object, composed by multi-parts, both as a combination of materials used and an interactive mechanical systems. This combination of form and function means its development path using necessary tools for the realization of this bridge, creating static universal metaphor: the bridge made to join. |
| Figure 3: Different chromatic simulations of bridge contextualized |
Starting from these considerations, the project had found a preliminary delineation after some pre-configuration steps in order to achieve a satisfactory and accepted result which were in compatibility with the existing work that needed to be preserved not only in its formal geometry of the beautiful arch that characterizes its pathos, but also possibly enhanced by a vision set almost as jewel in a frame that can carry the look directly at the center of a work that lives, shining its light.
The two symmetrical enlargements, in addition of allowing the limited transit to passenger cars while performing on the main work, also permitted possibility of supporting the deck after elimination of piers at least on the side of the landslide not yet fully stabilized. Secondly, this also made it possible to allow for the full enjoyment of extraordinary emotional views of both upstream and downstream.
Another element of analysis is study of chromatism of white ice that could address a surface protection of concrete, in partial contrast/dialogue with the metal elements that could be expressed in gray or other colors at level of final finishing. Finally, we proposed a study on lighting using variable chromatism LED in order to articulate in different ways the relationship between the object and its enjoyment, even in the night suggestions. Thus, it could allow for further development of the two small villages as attraction for tourists so that it could receive curious visitors in future.
 |
| Figure 4: Localization with ortophoto and image of landslide |
The study of the network structure articulated through different significant stages of the project. Starting from an initial proposal for ‘needle’ which are both physically and formally concentrated forces down in one place, then to the possibility of creating a portal forming real static channels that could accommodate the flow of forces determined by the thrust of the central arch. This means highlighting of exchange of stresses between old and new structure.
The next proposal was of a molten metal box, articulated by the introduction of a second arm. Thus, forming an architectural plasticity to convey the set of forces related to each other in various ways.
The final proposal was structured with a transformation of box spindle by virtual excavation that mimic the evolution from full to empty gradually reducing the size of rods until you get to the actual truss connecting via a special joint to the longitudinal beam. In this solution, we wanted to dispel the most of the rods along the wall to articulate as much as possible the full visual permeability. Thus, the historic bridge would only have been partially filtered by the new work.
The Bridge and the Disruption
The bridge essentially is made of an arched structure and two viaducts on which stands a concrete structure with stiffening beams, the slab and the road box rest on top of them. The deck consists of three continuous L-shaped beams starting from the shoulder and come to the fourth pillar, has a depth of 2.00ms and a width of 0.30m, each one download on its pillar is part of the pilastrade. The three pillars are of two types: the first measuring a width of about 0.80m, and the other measures about 1.25m. In both cases, the thickness is about 0.35m. |
| Figure 5: Effects on pilastrades |
The analysis covered the approach viaduct on the right shoulder, because this portion was actually damaged by landslides and damaged on the side. The plan shows a driveway on failure due to the translation. Lower first pile suffered after the complete detachment of the section from the deck.
Actually it was difficult to assess the state of the shoulder (because some areas are covered with debris) and the attack of the piers and on to foundation. As all three piers are damaged by crushing and complete detachment of the concrete, the first pillar was completely damaged.
The second pillar, completely visible, clearly showed the sequence of the actions which caused the displacement of the structure. All the piers are clockwise rotated. These present damages along the outside of the stretched fibers and torn down in the support side.
The third pillar, visually, seems to have minor damages as well but the fourth, appearing less damaged.
The first span measure 10.35 metres and the beams are still undamaged and without injury, second one measure 12.50 metres and has visible lesions, the third one and the fourth one measuring 11.60 metres. The third span has some damages in the middle, especially at the backbone for exceeding maximum stress due to the maximum moment.
As visually analyzed and described above the process that originated damages was due to a failure of the land. Thus giving rise to the cutting of the pillars of the first stack and relative failure of the beams of the deck causing damages of the beams.
To make the bridge safe, prevention of further displacement of the foundation and restoration of the initial static configuration of the structure needed to be done in the succession for intervention at the foot of the piles, the intervention of producing the two semi-abutments and support would ensure finally getting integrated with the lifting and repositioning of the concrete beams.
Reopening to Traffic of Bridge Over Corace River
The structural intervention designed in the executing project. In the first step, it aims to reopen to traffic, connecting Gimigliano with Tiriolo. |
| Figure 6: Longitudinal section of the slab |
For the reopening of the bridge to traffic, the existing structure, more specifically in the node deck -right shoulder should be put in safety. An active monitoring system was still maintained, which was developed in the days immediately following the landslide.
Intervention at the foot of piles
In order to permanently block foundations of pillars 1, 2, 3 and 4, the construction of reinforced concrete slab, joining foundations and fixed to this side with tie rods that allowed stitching of potential sliding surfaces, which were still present. This stitching comprised the soil to the slope, stabilized the slope in the area.
The reinforced concrete slab developed to "terraces" and followed the inclination of the slope and at the same time, allowed the formation of flat areas on which could be accessed for tie rods.
After the realization of concrete stitching slab, a coverage was made with stones and earth in order to renaturalize the area.
Realization of the new right abutment
The construction of the new shoulder on right abutment was planned with micropiles and tie rods, made at the height of the first pillar of the existing bridge and of two semi-abutments: one upstream and one downstream of the pillar jointed by a crosspiece.
 |
| Figure 7: Contextualization and view of new shoulder |
The function of this new system "abutment" is to replace pillar 1 of the existing bridge, which had been significantly damaged. The disruption caused by landslide and natural deterioration caused by aggressive weather effects on the right shoulder made the recovery difficult or even impossible, considering the extremely urgent nature of the intervention.
The aforesaid semi-abutments had been designed and sized for a double purpose: to replace pillar 1 of the existing bridge, supporting the bridge and sustaining the two ends of the footbridges that in a second and subsequent design phase was proposed to be built.
Considering the historic and architectural importance, as a boundary condition in the basic design of the products, a design solution was to be implemented, which was able to respect the pre-existing values and at the same time those characters that formed the architectural, environmental and landscape point of view to qualify this area.
 |
| Figure 8: Position of new shoulder |
In order to optimize the placement of the work in the natural and environmental context, the elevations of the construction (the new shoulder) and slabs, were planned to be lined with local stone such as that coming from the caves of the Capo dell’Armi close to Lazzàro, from which the rock is called "Reggina" or "di Lazzaro."
In addition to the technical qualities of the stone (very low porosity, high hardness and strength, frost-proof) and the particular gray-brown with pale blue colour, the use of this stone allowed to retain the aesthetics, especially in natural environments as must be safeguarded.
It may also be choosing a different local type or otherwise compatible stones with the characteristics of the site.
Deck lifting
The lifting of the deck was to be accomplished by use of pair of hydraulic jacks, mounted on a special metal frame (sling) made at each pier of the viaduct.
On pillars 2 and 3 was planned to build a harness to the head of the pillars with steel sections linking the three pillars forming piles.
Hydraulic jacks needs to be placed on these profiles for lifting the deck.
 |
| Figure 9: Position of sling |
When the jacks placed on the shoulder at correspondence of the pillar 1 and on pillars 2 and 3, will be loaded and then proceed to cut the head of the pillars to a height of about 70 to 80 cm (height presumed necessary to remove all c.c. parts that have deteriorated because of the landslide event to be verified on construction site).
The construction is lifted until the jacks reach theoretical stresses due to bending action of the beams. This was calculated considering it to be a continuous beam scheme over several supports as a function of self-weight and permanent loads.
The steel harnesses will not be removed as they were useful in the construction phase of footbridges for the support of the footbridges during assembly phase.
This work, as well as to restore and expand the existing road blocks the side of the mountain in the area where the landslide originated. All the preparatory work described in this report is the knowledge of the system of disposal of storm water that must be intercepted, so as to divert the waters and regiment in order to prevent any problem in case of any further future flood events.
Road Condition Near Construction Site
The access to the construction site areas is ensured through the implementation of a series of tracks designed along the right side of Corace, north side of the bridge we are talking about. This choice is dictated by technical and landscape reasons. |
| Figure 10: Phases of lifting |
From the technical point of view, this part of the slope is in better condition than in the south: the south side of the bridge is in fact where the landslide occurred.
From the landscape point of view of a construction site road on the southern side would give rise to far greater environmental impact than that expected in the north: in fact, it should have started much further south to link up the existing road, and then with a length higher than that expected (400m approx. compared to 300m assumed.). In addition, this would have been most visible from the town of Gimigliano both from the provincial road on the opposite side.
The main track follows an existing path north of the bridge for a distance of approx. 120m, then returns to the bridge with a bend to get to the main pad site around the pillar 3: measure around the track approx. 315 m.
A Prog. 245 approx. disconnecting the first branch on the right and uphill to reach the pad site provided upstream of the pile 2. From this still climbing is possible to reach the pillar 1 and the area for the construction of the new shoulder designed.
A Prog. 290 comes off the track that comes down & reaches the pillar 4 and arch attack.
The tracks designed exceed a total climb of approx. 29m. The slopes are maintained always below 16%. The section of the track width of 4.00 m is expected.
These tracks will be maintained and used for future maintenance of the shoulder tie rods and bolts of the project for the stitching of the linking slab between the existing foundations, and for the monitoring of the existing bridge and future soil tests.
 |
| Figure 11: Planimetry of the access road at the base of piles |
But there is more, using a pedestrian path to edge shoulder. There is also access to the public to admire the bridge in its "intimacy" with the direct and very unusual "vision" of the intrados of the deck, as well as to enable the transition from upstream to downstream in safe conditions without crossing the street.
In this way, the work amplifies its perceptive coherence. From the outside, for its majesty with significant historical and landscape excellence. From the inside, overcoming the mere traffic function "necessary" to make it a real "place" to fully live It goes without saying that this would open up interesting prospects for further enhancement and unpublished work in the landscape as a place of particular tourist attraction.
Acknowledgment
This article has been reproduced from the proceeding of 'National Conference on Repair & Rehabilitation of Concrete Structures' organized by ICI western U.P Gaziabad, IA Sructural Engg, and Association of Structural Rehabilitation with the kind permission of the organisers.NBMCW September 2011
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