Establishment and development of non-state narrow-gauge railways (called “third-order” ones) in Pomerania occurred at the turn of the 19th and 20th centuries, as a result of numerous factors, including: transport needs, new technical solutions and two laws of 1892 and 1895.
The first of them concerned the principles of construction of narrow-gauge railways, the second one – the rules for financing projects related to the construction of railway infrastructure / narrow-gauge railways. In order to bear so large investments, local joint stock companies were established, which were raising funds for the needs of building particular lines.
The entire Pomeranian network was created between 1892 and 1914. In the initial period, there were no resources for such a challenge. The provincial authorities concluded a contract with the Lentz und GmbH association from Szczecin (later moved to Berlin), headed by Friedrich Lentz. The company was in charge for both design and construction works. However, when performing specialist works, such as construction of bridges or viaducts, the company cooperated with subcontractors.
The narrow-gauge railways were subordinate to district authorities. Their task was to support agricultural facilities of large estates and to provide public transport by supplementing the standard-gauge railway network.
This article presents four exceptionally interesting bridges, that show several solutions used in Pomeranian narrow-gauge railways.
Bridge parameters as the height, length and width of individual elements, in relation to the anticipated load, were regulated by specific state laws. The turn of the 19th and 20th centuries, however, was a time of searching and experimenting both in terms of construction and the use of new materials such as ferroconcrete and reinforced concrete, which were supposed to be an answer to the growing demands faced by creators of engineering structures.
Bridge in Żarowo – a Steel Truss
The Ina river, Stargard–Trzebiatów–Gryfice line, 45.547 km
The earliest beginnings of the construction of the Stargard line (in fact it was called the Szadzko line – German Saatzig) were related to the initiation of building Stargard-Storkówko (German Saatzig) and Stara Dąbrowa (German Alt Dammerow)-Ińsko (German Norenberg) routes by local authorities in May 1893. At the end of that month, the local assembly of the Stargard district approved the construction of the railway and made out the statute of a joint stock company, the main body of which was to be the general assembly. The board of directors was to be in charge of the company’s management. In July 1893, the formulating of the society’s operating principles began. The cost of the future investment has been estimated at 2,181,000 marks. Apart from the construction of the Stargard-Storkówko and Stara Dąbrowa-Ińsko lines, the works were to include the construction of two side routes: from Storkówko to the border of the district towards Maszewo (German: Massow) and Nowogard (German: Neugard) and from Stara Dąbrowa (German Alt Damerow) to Kania (German: Kannenberg), with the possibility of further expansion to Dobra Nowogardzka (German: Daber) and Łobez (German: Labes). In August 1893, the district authorities changed the planned track gauge from 600 mm to 1000 mm, with a maximum speed of 20 to 30 kph. In November, the company was registered.
The narrow-gauge railway bridge near the village of Żarowo (German: Saarow) is located approx. 7 km north-west of Stargard, over the Ina river. It was built on the Stargard-Dobra Nowogardzka-Łobez and Ińsko-Drawsko Pomorskie routes, between Żarowo and Małkocin stations. It was put into use in 1894 or 1895. The contractor for the facility and the whole line was Lentz und GmbH. The steel elements and rails were ordered at the Krupp plant in Essen, which was one of the partners of Lentz und GmbH.
In 1955, the bridge underwent a major renovation. The 1950s and 1960s were the peak period in the operation of this line, both in terms of passenger and cargo traffic. However, after that time, the traffic began to decrease. Through the 1980s, the use of particular sections of the line was gradually reduced. Finally, the bridge in Żarowo, along with the section on the Stargard-Dobra Nowogardzka route, was taken out of service in 2001. A year later, it was entered in the register of objects of cultural heritage (number A-111 21.12.2002).
The three-span bridge in Żarowo is a fixed, steel, truss, through bridge. The design is quite typical for the period when the best solutions and applications for new materials such as steel and concrete were still being sought.
Truss bridges originate from brace and roof truss constructions. They belong to the type of beam bridges. They come directly from the skeletal architecture and use the same solutions to carry as much weight as possible at maximum distances, while reducing the amount of material used.
The entire bridge is 69.5 m long. It consists of three steel, riveted spans. It is a through bridge, which means that the carriageway is bounded on the sides, e.g. by a truss; unlike the so-called deck bridge where the truss is underneath.
Extreme spans are 15 m long, 1.6 m high and 3.5 m wide. They consist of two parallel, single-wall trapezoidal trusses connected at the bottom with I-beams. The central span has an elliptical shape, 19 m long, 4.5 m wide and has the height of 4.5 m in the lowest point and 6 m in the highest one. It is made of two, double-walled trusses connected with I-beams at the bottom, and with angle bar construction in 1/3 of the length of the span at the top. Trusses are made of rolled elements, so-called shapes, of varied cross-sections. The weight of the supporting structure alone is 76.7 tons.
All three spans are independently placed on bearings that transfer the load to the supports. In multi-span bridges, expansion joints were usually used. This means that there were gaps between the spans. This solution ensured independent work of each span.
The carriageway consists of steel beams lying along supporting structures. Directly on them, there are wooden sleepers, bearing the track. The bridge in Żarowo is a monorail one. Initially, the track gauge was 750 mm, and after the war it was changed into 1000 mm. For this purpose, additional tracks have been added without removing the original ones.
The bridge in Żarowo is set on supports that are 3.5 m high. The two boundary pillars are mounted on concrete foundations, on which brick stems were erected, covered with a thick reinforced concrete coat, giving them the shape of an elliptical cylinder with dimensions of 5.5 ˣ 2 m. The bridge heads, sunk in the embankment, built on a rectangular plan, 5.12 m wide and 4.5 m long, have analogical construction.
Bridge in Nowielice – The Gryfice Line
The Rega river, Popiele–Trzebiatów–Gryfice line, 45.547 km
Several kilometres north of Trzebiatów, near a small town of Nowielice, there is a bridge over the Rega river. The decision to create the railways in the Gryfice district was made in March 1893. The authorities of the district decided to establish a joint stock company (Genosenschaft zum Bau einer Kleinbahne von Greifenberg as Horst, transformed into Greifenberger Kleinbahn Aktiegesellschaft in 1895), which took over a large part of the costs associated with the investment and its supervision. The work was commissioned to Lenz GmbH, which became the most important shareholder and investor. After numerous deliberations, it was decided that the line would have a spacing of 750 mm. The line to Niechorze was put into use in 1896. On this basis, it can be concluded that the bridge over the Rega in Nowielice was built between 1895 and 1896. In the post-war period, the bridge was renovated only once, in 1955. The object was entered in the register of objects of cultural heritage, number 1253.
The construction of the three-span railway deck bridge refers to steel truss bridges. The period when it was created was a time of search for various solutions for a new material – reinforced concrete. It is made of reinforced concrete prefabricated units manufactured by ELLMER company from Szczecin.
Reinforced concrete Howe truss is composed of elements joined with bolts, which turned out to be not a successful experiment. To join the elements, special formwork had to be built, which complicated and extended the construction process. This solution appeared for further several times on the Gryfice line, e.g. between Mrzeżyno and Roby stations. However, due to its faults, it was not widely used afterwards.
The entire bridge is almost 55 m long. Spans with a length of 16.95 m and a width of 3.25 m are made of three pairs of reinforced concrete truss girders, joined below with a reinforced concrete beam. The construction height of the spans is 2.7 m and the bridge clearance is 4.0 m.
On the trusses there is a reinforced basin-profiled construction filled with crushed stone. On the aggregate, sleepers and 1000 mm-gauge tracks are placed. A reinforced concrete pavement runs along the tracks. Each span is put independently and separated by expansion joints, covered with belts made of galvanized metal. The gauge of the bridge was limited by a massive concrete balustrade made on-site with the use of formwork, i.e. forms that gave it a specific shape. On the headwater side, over the pillars, small balconies are hung. The detail on the bridge reflected the rhythm of the balusters, pillars and an Art Nouveau motif of a horizontal wave – a symbol of water, placed both inside and outside. These motifs were also used in other reinforced concrete bridges on this line. From the top, the balustrade is finished with a semicircular cornice.
The bridge clearance is 4 m high. Reinforced concrete monolithic supports are placed on thick, concrete piling. The bridge heads, made of wet-laid concrete with the use of wooden formworks were sunk into the embankments of the tracks. The pillars set in the main stream are set on a polygon projection, 1.7 m wide and 6.38 m long. The bridge heads have ice-aprons crowned with half-cones, adjacent to the trusses from the sides of both headwater and tailwater. The spans are based on bearings placed on ashlars made of concrete. Due to the catastrophic condition of the bridge, the section of the Trzebiatów line was closed.
Bridges in Białogard – Reinforced Concrete Giants
The Koszalin-Białogard narrow-gauge railway line was an investment of the Koslin - Bublitz - Belgarder Kleinbahnen Joint Stock Company, carried out in the years 1896-1905. As with other narrow-gauge lines, due to the cost, the line width was 750 mm. After the war, it was changed into 1000 mm.
The Białogard-Rawino section was created in the years 1908-1909, as a connection of the Koszalin line and the Gryfice line. It required building numerous engineering objects, including monumental bridges in Białogard. The facilities of the section between Koszalin and Białogard were created until 1905. This line was a kind of testing ground for new materials, such as concrete and reinforced concrete. Massive reinforced concrete bridges and arch viaducts imitating classic stone constructions were characteristic of this line. In Białogard there are three objects: a bridge over a relief channel, a bridge over the Stara Parsęta river and a standard-gauge line, and a smaller viaduct – also over a standard-gauge line. All three buildings are arch, reinforced concrete structures with apertured supports. During the construction of the Białogard bridges, in all three cases, a similar technology was used. First, a wooden arch-shaped formwork was made. Wooden centrings, covered at the bottom and on the sides, were supported by wooden shores. Then reinforcement was placed in those forms and the spans were concreted.
A characteristic feature of Białogard bridges are vaulted apertures in the supports. The very fact of using arch vaults over the apertures, that is, the use of the arch structure, as a well-known element, instead of, for example, additional reinforcement over the apertures, illustrates that reinforced concrete was an innovative material for the engineers of that time. Thanks to the use of arches or apertures, the weight of the support was reduced, while maintaining the load capacity. The tendency to reduce the size of cross-sections of pillars is still visible in bridge building, where massive pillars are rare, whereas slender ones, that even seem to be floppy posts, are much more common. The apertures had a similar function. By reducing the weight of the supports, the loads transferred to the foundations and, consequently, their size were reduced.
The COMET company from Grabowo near Szczecin (Grabower Cementsteinfabrik "Comet" GmbH) was in charge of projects and their implementation. It was responsible for all engineering facilities on the so-called the Koszalin line as well. The plans were co-created by Brauenig, a secret building advisor, who came from Koszalin. The company was founded in 1896 by the famous Topffler and Grawitz families, who were also the owners of the "Stern" cement plant in Zdroje, where cement was obtained.
To make particular elements of bridges – pillars and spans – various concrete mixtures were used, which was to ensure durability of the structure. It should be remembered that the engineers were just learning this technology at that time. The fact that reinforced concrete was such an innovative material required solving a number of issues including, for example, the method of preparing and laying the reinforcement itself, as well as its anchoring.
The reinforcing rods were placed and tied in the formwork in such a way that they formed a spatial "model" of the whole object. This solution has been adopted and is now widely used, unlike the method of anchoring concrete in the form of loops. The engineering facilities in Białogard used reinforcement up to 20 mm in diameter. After making the formwork and preparation of reinforcement, concrete was laid in phases. First, the curvatures of the main arch were made, then the curvatures of arches in the pillars were layered. Due to the time required by the concreting process, the structure was gaining its full strength quite slowly, compared to present standards.
When building the extreme span of the viaduct, it was necessary to maintain a clearance of approx. 11.2 m in width. This requirement was dictated by the existing standard-gauge railway line, which had to remain active throughout the entire time of the viaduct construction. In order to meet that need, a different method of making the formwork was used than with the other two spans, which did not require similar treatments and therefore they were supported by shores. The chosen method consisted in hanging the formwork. For this purpose, special scaffoldings were erected near the pillars: towers made of wooden trusses, fastened with elements working like hangers, to which centrings were suspended. This allowed for making the formwork without using additional shores.
A reinforced concrete railway bridge over a relief channel of the Liśnica river was built in 1908. It is located the closest to the Białogard station, so it is visible from Koszalińska street.
The bridge has a single-span structure, a slab of a total length of approx. 23 m and an elliptical arch of a span of 15 m. The bridge heads, 3.4 m wide, are sunk in the embankment. There are two vaulted apertures in the bridge heads, which are placed on the arches of the spans. External apertures penetrate the ground and are enriched with a kind of partial vaulted haunches. Such a treatment was to additionally influence the relief and strengthening of the pillars.
The limiting outline of the track is 3.75 m wide. Its outer parts are led out beyond the supporting structure, creating overhangs on both sides. Along with the apertures of the bridge heads, they are an example of finding the optimal form of a bridge, ensuring reduction of loads while maintaining the largest possible width and carrying capacity. Similar trends visible in bridge engineering relate to, for example, road lamps often mounted on the side of the bridge, thanks to which they do not narrow the gauge of the structure itself.
A three-span viaduct-bridge is a monumental building located near Kołobrzeska Street. It runs the line over the Parsęta River and over the Poznań-Kołobrzeg standard-gauge railway line. Sources are not entirely consistent as far as the date of the construction of the object is concerned: according to some materials it was 1898, according to others – the turn of 1908 and 1909.
There were tendencies to locate bridges and viaducts perpendicularly to the obstacles they were overcoming in order to reduce span lengths. This significantly influenced the reduction of costs (shortening the facility) and the safety of the structure (e.g. reducing the impact of water current and the ice movement on bridge supports). The route of the narrow-gauge line in Białogard intersected with a standard-gauge line and with rivers. In order to reduce the spread of engineering structures, the narrow-gauge line was led along an arch so that the bridge and the viaduct-bridge were located perpendicularly to the obstacles. Thus, the optimization of bridge objects took place at the expense of increasing the amount of earthworks.
The reinforced concrete object has an arched, elliptical structure with a length of almost 92 m. It consists of three slab spans, placed on apertured pillars. The central span is 23 m and the extreme ones are 24 m long. The width of the bridge is 3.35 m. On one side there is a 60 cm wide pedestrian pavement.
The bridge is south-west/north-east oriented. The south-western span passes over the Parsęta river, the north-east one over the standard-gauge line. The culvert under the central span had a flood function.
The viaduct in Białogard was built in 1908. Its form is similar to the viaduct-bridge. The object is also a three-span one, arched with a slab placed on bridge heads and two apertured pillars. The slab protrudes slightly beyond the outline of the supports. The total length of the bridge is 52.20 m, the two external spans are 8.2 m and the middle one is 22.10 m long.
The pillars were designed in the same way as in the construction of the bridge over the Stara Parsęta river. There are elliptical apertures in them, a middle one and two pairs of side ones in each. Similarly to the other described objects in Białogard, this procedure was aimed at relieving the structure.
The track is placed on a trough filled with gravel. There is a pavement on one side. The carriageway is limited by a steel, simplified barrier.
The development of the railway coincided with the development of various forms and techniques in building engineering. The objects described above were experimental constructions, therefore errors happened in technical solutions. On the basis of such a limited area, it is possible to trace the development of the idea, the evolution of the solutions used, but also the withdrawal from ineffective concepts. The multitude of solutions tested at carrying out so ambitious assumptions is impressive.