Project not implemented
Mrtvi kanal (Dead Canal),
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Juraj Šekulja (†), Marin Franolić, Vladi Bralić, Zvonimir Kamenar
Model: Milivoj Hrelja
Photography: Ranko Dokmanović
The basic conception of this competition work and the suggested urban-architectural (sculptural) solution is based on forming a spatially autonomous memorial complex for Croatia’s national defenders, consisted of distinguished urban elements: a memorial bridge, a sculpture and an on-board museum. The elements of the complex are connected into a functional, esthetic and symbolic entirety, spatially articulated to respect the historical, cultural and urban values and characteristics of the Rijeka’s Mrtvi kanal (Dead Canal) and its coast.
MEMORIAL BRIDGE FOR CROATIAN NATIONAL DEFENDERS: The authors tried to accomplish the bridge solution as fitting to its memorial and its necessary utility functions – correct distribution of pedestrian traffic, quality of the baring assembly, adherence and logics of the force(s) path, cost effective and the simplicity of the construction – as well as fitting an important function of harmonious integration into the valuable city landscape. The free movement of pedestrians across the bridge has been secured by adequate width of the modularly composed pedestrian path (the module of 60cm). The bridge is accessed by two 6 meters wide entrances, and it then continues to widen to the levels of its horizontal and vertical culmination. The cross section of these two (horizontal and vertical) planes in its culminating point is placed asymmetrically to the total length of the bridge and according to the Golden Ratio. On this culminating point, its widest part, the bridge is 8.40m long and the vertical alignment reaches 1.5m from the strand of the canal. The total length of the bridge is 35m. The ground plan and altitudinal figuration result from an appetite to enable average pedestrians to walk straight and fast over the bridge, but simultaneously allow others to rest and take in the urban scenery it introduces (the memorial complex, Rijeka and Sušak characteristic city facades, Rijeka coast and waters, the sea, Trsat Tower and Canyon of Rječina).
Additionally, lenient and continuous, camber of the convex line, a walking surface of only 1.5m enables comfort and overview of the zebra for both pedestrians as well as physically disabled users (the maximum incline of the floor surface is 5°), and this benefits to the undisturbed movement of small vassals through the canal and under the bridge. From the formalist point of view, the bridge in planning contains its set of qualities which differ from those of the existing bridges on the Mrtvi kanal (Dead Canal) and on the River Rječina. The ground plan of the bridge shows widening from the entrance to the horizontal and the vertical culminating level in a manner of a lenient camber thus enabling the users to recess on the bridge and not be in the way to those crossing the bridge in heed.
However, from the viewpoint of an average pedestrian, the curved, convex margins of the bridge look completely equal and parallel (due to entasis – an optical illusion sporadically used in building temples in ancient Greece).
For the sight of the bridge there are three basic determination lines that are actually a reflection of the traffic surface and the span construction: the level line (a traffic surface line when looking from the sideway angle), intrados (the lower margin of the master carriers) and suprados (upper margin of the master carriers). The level line of the bridge, as a basic transition line, is convexly curved and consists of two simple curves, proper circles of a differently curved radius, and share a tangent in their culminating point.
The line of the level line is conceived as a visible line which appropriately functions when looking from the sideway angle and thus suits the eye of the beholder. The convex shape of the level line with extremely mild ups and downs was chosen as optimal, and for functional purposes of comfortable crossing, visibility of the pedestrian traffic on the entire environment area, as well as sailing under the bridge.
The line of the suprados, as second marking line of the bridge, completely follows the level line. The intrados line, as third marking line of the bridge, comes forth, very slowly to the lines of the level line and the intrados.
A structurally and economically optimal line has been chosen, a line that adjusts to the schedule of internal forces and stresses in the carrier. However, with respect to the side, in the optical and physiological perspective, due to the optical illusion of distorted directions (produced by the mutual position of the curved level lines, suprados and intrados) and optical illusions play of light and shadow (produced by continuously arched cantilever projection of an extended walking surface), all three marking lines of the bridge resemble in harmonious and mutually parallel way (one should observe the model of the bridge so that one’s watching point can be that of an average pedestrian approaching the bridge sideways).
It should be noted that the level lines, lines of suprados and intrados of the bridge have a point of culmination, which is located asymmetrically to their roundness that is to the overall width of the bridge and the banks of the canal. The culmination point is located at the position of the Golden Ratio (SectioAurea, A: B = B: C) in relation to the total width of the bridge and the canal (C). In such circumstances, the rise line and fall line of the bridge varies, and according to the authors, the proportions of the cuts and the entirety of the bridge are visually most appropriate.
Particularly appropriate, from the authors’ perspective, are the relationships of mass distribution of the bridge on the Mrtvi kanal (Dead Canal). From the formal perspective, it is important to highlight that the authors, when selecting materials for production, have conceived the bridge as made of glulam wooden structure with azobé. The wooden bridge on the Mrtvi kanal (historical territory of the old harbor), is surrounded by small wooden boats, causing an intense physical sensations of comfort, contentment, serenity, warmth and even suppression of contrasting effects with simultaneously adapting to them. It confronts the experience of the impersonal, the cold and the monotonous and rather resembles a historical experience. In addition, there are significant aesthetic phenomenon and exotic beauty of the glulam.
MEMORIAL CHARACTER OF THE BRIDGE: Memorial character of the bridge is certainly represented through the fact the bridge spans the Mrtvi kanal on the move towards Delta, the spot from which the national defenders went to the front. However, in order to emphasize the memorial character of the bridge, the authors have decided to design special fences. In this sense, the proposed visual motif was the Croatian Pleter (Hrvatski pleter), a distinctive historical geometric ornament of the Croatian folklore and its cultural sphere, as an element basic to the aesthetic, functional and symbolic forming of the city itself. The pleter, as a style element the fence work has been subjected to the principle of continuous stringing, and does not serve in this case neither to the narrative nor illustrative purpose, but rather serves the manifestation of the artistic experience, doing – in addition to the aesthetic and the functional – an extremely symbolic function of highlighting the memorial character of the entire bridge. Rhythmic stringing of the fence is followed by lighting poles. The interior of the lighting column contains hidden lamps that spread light in two directions. The rounded tip of the column contains a blue glass prism through which a blue light (color of Rijeka’s identity) is directed vertically into the sky. With using this ceremonial lighting, the authors wanted to further accentuate the memorial character of the bridge.
BRIDGE CONSTRUCTION: The important elements of the bridge, off course, primary if we concentrate on its functional and formal value, are consisted of a surface for pedestrian traffic and harmony of the entire composition, leaving secondly important the existence of these elements and their necessary attributes enabled by the master span construction. With these actions the authors have shaped the bearing assembly of the bridge as closely connected to its function and shape: a simple girder bridge solution has been decided upon. The bearing assembly of the memorial bridge on the Mrtvi kanal (Dead Canal) statically resembles a timber resting upon two immobile carriers and it consists of glulam arched trusses. The main trusses are 20cm wide and vary in height from 95cm to 115cm on the culminating point of the level line. They are interconnected with vertical, secondary trusses 12cm wide. The height of the secondary trusses is identical to that of primary trusses on the resting spot. The bearing assembly rests upon another bearing assembly inside of which there are hydraulic presses incorporated and they function to compensate for the support shift. The bearing assembly consists of steel footboards stiffened with steel NPU vertical profiles. It leans on the bearing cuboids through steel rollers and hydraulic presses.
The hydraulic presses enable compensation for eventual shifts of the layout straining inside the master trusses of the bridge, regardless of eventual support remission. For this intended span and load the chosen constructive material of the bearing assembly (glulam) enables relatively small bearing forces resulting in small strong points. This support enables building strong points behind the protection of the coast wall producible with relatively small operations during the setting of foundations. Given the fact that we are using the existing coast wall, the small vertical forces ensure no preconsolidation of the foundations is necessary.
It is important to stress out that this is the way of preserving the existing appearance of the coast in the part below the trusses of the bridge. Small strong points, of a relatively shallow basic pit and small weight of the bearing assembly are rather suitable on the grounds of challenged bearing potential as is the alluvial ground of the Mrtvi kanal’s shores. The walking surface is coated in azobé, an exotic tree (known throughout Europe as steel wood). It is a tree of exceptional durability and a large resistance to wearing off, proven by its extended usage on the pontoon carriers in marinas (for instance, marina Punat on the island of Krk). The wooden surface eliminates hydro isolation and sewerage works on the walking construction. Given the walking surface consists of narrow props bolted to the baring assembly, in case of getting damaged, they can be easily replaced.
It is clear from above that by choosing glulam wood as the master baring assembly, besides its esthetic component, we are endorsing substantial economic gain. Thanks to a speedy construction, industrial manufacturing and relatively small work on foundation and support, the chosen construction enables a competitive and rather economic building.
CROATIAN NATIONAL DEFENDERS’ MEMORIAL SCULPTURE: The sculpture is shaped resembling a leaning obelisk, and with specific modeling, it is set at a memorial spot on the Delta, as an integral part of the entire memorial complex. As a spatial accent of the lean, it extends to the tense curved line of the pedestrian surface, thus visually and symbolically, andtellspedestrians about the meaning, the memorial and the historical character of Delta. This material and geometric structure carries distinctive elements of Croatian history, and is at the top described by a stylized Catholic cross as an enduring symbol of sacrifice and belonging of the Croatian people to the Western European circle. The sculpture is 8 meters high; the base is a trapezoidal-square, 75cm wide. At the end of its formal feature, the sculpture is proportionally narrowed. It is conceived to be done in massive and single-piece oak.
MUSEUM OF CROATIAN NATIONAL DEFENDERS: The authors propose that to set, as an integral element of the memorial complex of Croatian National Defenders, together with the Memorial Bridge and the sculpture on the Mrtvi kanal, a replica of the historic Croatian ship – of specific museum purpose, containing a smaller professional exhibition dedicated to the Croatian National Defenders. The reasons for choosing a smaller (area) exhibition, located on an old Croatian ship, next to the bridge and memorial area of the Delta, are summed up in the fact that only a professional museum institution can systematically collect, preserve, exhibit and professionally process materials that then must be transferred to visitors, using the achievements of modern museology. The idea of the museum on an old Croatian ship has an extra urban-historical justification. It is well known that since ancient times, all the way to rapid urbanization, on the site of today’s Mrtvi kanal, there was an old city harbor. As a historical entity, the Mrtvi kanal with its old ships and wooden sailing ships, united and amended for the beauty of the city. This is best seen in the old drawings and paintings. Its subsequent devastation relentlessly crashed the identity of Rijeka, a Mediterranean city with an interesting influence from the continental culture. As a result of industrial and residential expansion of the urban fabric, the canal channel closed to the sea with new, low and flat bridges. Also diminished are the canal’s old wooden boats, and the inhabitants of the city were seized of soul and part of the overall beauty. By placing the old Woody, a conserved veteran, or a newly built ship modeled on original blueprints of ships once present in the old port, the old silence of Mrtvi kanal would expand through the entire ambient, from the canal and Rječina to the hotelContinental. The ship would, with its historic characteristics, become an ornament and attraction in the city, and its interior (of a modern memorial museum), would represent, together with the Memorial Bridge and the sculpture, an additional feature of the entire memorial complex.