METHOD FOR THE MANUFACTURE OF A BRIDGE MADE OF LONGITUDINAL BEAMS AND DECK SLAB ELEMENTS

BACKGROUND

[0001]The invention relates to a method for manufacturing a bridge made of reinforced concrete or pretensioned concrete with a deck slab having at least one cantilever. Underneath the deck slab, there are arranged longitudinal beams. The longitudinal beams are arranged approximately in parallel to the longitudinal axis of the bridge. In a cross-section through the completed bridge, there are arranged two longitudinal beams that are spaced apart from one another, which are connected to one another by the deck slab. The bridge, in its finished state, has the static system of a continuous beam or a frame with at least two spans.

[0002]A widely used method for the manufacture of bridges is the segmental construction technique. In the segmental construction technique, prefabricated segments made from reinforced concrete are connected by tendons to form a bridge girder. According to Max Meyer's publication on “Under-Slung and Overhead Gantries for Span by Span Erection of Precast Segmental Bridge Decks,” Structural Engineering International, Vol. 4, 2011, pages 399-405, https://doi.org/10.2749/101686611X13131377725361, there is mentioned that the segmental construction technique is employed with a field-wise assembly of the segments for span widths ranging from 20 to 60 metres, preferably between 30 and 50 metres. Each segment weighs between 30 and 150 tonnes, with a width ranging from 5 metres to 24 metres and a length of 2 metres to 3 metres. Each segment has a single-cell or multi-cell hollow box. The segments are typically produced using the match-casting technique. The weight of the segments for a construction section ranges from 200 to 2000 tonnes, preferably between 200 and 1000 tonnes. For the manufacture of a construction section of a bridge, the segments are assembled using a positioning device. The positioning device must be capable of supporting the weight of the segments of a construction section. Positioning devices are fabricated from steel and, according to the aforementioned publication by Meyer, are among the heaviest construction devices used in bridge construction. The manufacturing of a positioning device for a bridge constructed using the segmental technique with field-wise assembly results in high resource consumption.

[0003]The joint gaps between the segments are either coated with epoxy resin or executed as dry joints during assembly. Longitudinal reinforcement that crosses the joint gaps cannot be installed in-between these joints. The joint gaps between the segments are over-pressed by the tensioning of tendons. In order to over-press the joint gaps under the relevant load states, there has to be installed a high number of tendons. The objective in developing the segmental construction technique from the 1960s onwards was not to achieve material savings for the completed bridge, but rather to create an industrialised construction method with reduced construction times. Consequently, segmental bridge construction involves significant resource consumption.

[0004]A method for manufacturing a bridge beam of a bridge from thin-walled segments is described in WO 2019090374 A1. Four thin-walled plates, having ribs, are assembled into a segment with a single-cell hollow box cross-section. The stiff and force-locking connection of the ribs forms a transverse frame within each segment, which serves to stiffen the segment. At the installation site, the segments are combined to form a bridge beam. Reinforced concrete layers are applied onto the plates of the segments. The deck slab of the bridge is then manufactured in a later working step.

[0005]The length of the segments measured in the longitudinal direction of the bridge ranges from 2 m to 3.5 m to facilitate the transport of the segments or individual plates on the road. A segment produced using this method is illustrated in FIG. 10 of the publication by Stephan Fasching, Tobias Huber, Michael Rath, and Johann Kollegger titled “Semi-precast segmental bridges: Development of a new construction method using thin-walled prefabricated concrete elements,” Structural Concrete, 22(3), pages 1561-1573, 2021, https://doi.org/10.1002/suco.202000474.

[0006]The production of the segments described in WO 2019090374 A1 using the match-casting method has proven to be impractical in construction practice due to the ribs arranged in the plates. For this reason, the above-mentioned publication by Fasching et al. recommends forming the joint gaps between the segments as filling joints. Due to the short length of the segments, there is present a high number of filling joints in each construction section. The process of filling the numerous filling joints with a filling mortar constitutes a time-consuming step that is disadvantageous for the rapid completion of a construction section.

[0007]In WO 2019090374 A1, FIGS. 4 to 14 illustrate the manufacturing of an incremental launching bridge with segments that exceed 3.5 m in length. Using the method described in WO 2019090374 A1, segments longer than 3.5 cannot be transported on the road anymore. Therefore, the base plate of the segments must be produced at an assembly area on the construction site. Since the reinforcement and concreting of the base plate is a lengthy process, and the production of the deck slab can only start after the base plate has been cast and the curing of the concrete in both the base plate and the deck slab must be awaited prior to the transport of the segment, rapid progress in construction is not feasible with the method described in WO 2019090374 A1.

[0008]The production of a bridge having a lower number of joint gaps in a construction section is described in WO 2022256851 A1. When two longitudinal beams are used to create a construction section, the number of joint gaps within a construction section can be reduced to two. The longitudinal beams with a trough-shaped cross-section are installed at the installation site, and the joint gaps are filled with a filling mortar, followed by the introduction of filling concrete into the longitudinal beams. Subsequently, deck slab elements are placed on the longitudinal beams. For the production of the deck slab, there is applied a reinforced topping concrete to the deck slab elements. The longitudinal reinforcement embedded in the filling concrete crosses the joint gaps between the longitudinal beams. In this way, the number of tendons may be reduced. A disadvantage of the method described in WO 2022256851 A1 is the large volume of concrete introduced as filling concrete into the longitudinal beams. The method described in WO 2022256851 A1, hence, has a rather high resource consumption.

[0009]Additionally, the use of trough-shaped longitudinal beams in the construction method shown in WO 2022256851 A1 is disadvantageous because their low centroid position at the top results in a low moment of resistance. The significantly less favourable load behaviour of longitudinal beams with a trough-shaped cross-section compared to longitudinal beams with a hollow box-shaped cross-section is explained in FIGS. 1 and 2 of WO 2022256851 A1.

[0010]Trough-shaped beams with thin-walled plates must be braced at the top of the wall plates with a network to avoid stability issues, as illustrated, for example, in the FIGS. 29 to 34 of WO 2022256851 A1. In the publication by Johann Kollegger, Dominik Suza, Clemens Proksch-Weilguni, and Wolfgang Träger titled “First application of the balanced lowering method to build two bridges in Austria,” Structural Concrete, 23 (3), pages 1413-1425, 2022, https://doi.org/10.1002/suco.202100629, FIGS. 10 and 11 show a network for the bracing of thin-walled longitudinal beams with a trough-shaped cross-section. The production of such a bracing in the precast plant is elaborate due to the extensive welding required. The bracing is embedded in the filling concrete in the final state and serves no structural function.

[0011]Construction methods, in which longitudinal beams with a trough-shaped cross-section and deck slab elements are used to produce a construction section are described in DE 2520105 A1, AT 285663, and EP1780338 A1.

[0012]The drawings in FIGS. 11 and 21 of DE 2520105 A1 show trough-shaped longitudinal beams with wall plates having a large thickness. The longitudinal beam depicted in FIG. 21 is produced using a supporting framework and formwork using the cast-in-place method. There is no information in DE 2520105 A1 regarding the manufacture of the longitudinal beam depicted in FIG. 11. If this longitudinal beam is produced as a precast element, it will have a high weight per meter due to the thick wall plates and the thick base plate. This will be unfavourable for positioning the longitudinal beam at the installation site, as, for this reason, it will be necessary to use mobile cranes with high load capacities. Due to the substantial thickness of the wall plates, there will not be required bracing at the upper ends of the wall plates in this example. With the longitudinal beams made of reinforced concrete depicted in DE 2520105 A1, either rapid manufacturing of a construction section is not possible because the longitudinal beams are produced using the cast-in-place method, or only bridges with small spans can be constructed as statically unfavourable trough-shaped longitudinal beams with final cross-sectional dimensions will be installed.

[0013]AT 285663 shows trough-shaped longitudinal beams in the drawings FIGS. 6 and 7. The wall plates of the longitudinal beams have thickened areas at the upper end to improve their stability behaviour during construction phases. The deck slab is constructed using deck slab elements and a layer of topping concrete. Using the longitudinal beams depicted in AT 285663 will only allow for the construction of bridges with small spans, as statically unfavourable trough-shaped longitudinal beams with final cross-sectional dimensions will be installed.

[0014]EP 1780398 A1 describes the manufacture of a bridge using deck slab elements and trough-shaped longitudinal beams. The deck slab elements are manufactured with a significant height to increase the internal height of the hollow box of the completed bridge. From a static point of view, this is particularly unfavourable, as it reduces the height of the trough-shaped longitudinal beams during construction phases. Thus, the method described in EP 1780338 A1 may only be used for the construction of bridges with small spans.

[0015]The drawings in FIGS. 5 and 6 of U.S. Pat. No. 3,788,023 show a method for manufacturing a bridge using prefabricated longitudinal beams. In order to create a construction section, there is placed a longitudinal beam on the cantilevered part of the preceding construction section and on the pier located at the front in the direction of the bridge's construction. Since the longitudinal beam has the final cross-sectional dimensions, the longitudinal beam cannot be produced in a precast plant and must rather be manufactured close to the installation site. The positioning of the longitudinal beam requires a very large positioning device or cranes with extremely high load bearing capacities, which in both cases will be associated with significant resource consumption. There will not be arranged any continuous longitudinal reinforcement that crosses the joint between the longitudinal beam and the preceding construction section. For this reason, there have to be installed additional tendons to accommodate stresses from traffic load and temperature effects on the individual spans. Due to the complex joint formation and the use of large lifting devices, the method described in U.S. Pat. No. 3,788,023 has a high resource consumption.

[0016]In EA 201201135 A1 there is shown a method for manufacturing a bridge with prefabricated longitudinal beams for spans of up to 24 m. For the production of a construction section, the longitudinal beam is placed on the cantilevered steel console of the preceding construction section and on the pier located at the front in the direction of the bridge's construction. A steel structure is formed in the joint between the longitudinal beam and the preceding construction section in order to transfer shear forces. The longitudinal reinforcement of the preceding construction section is welded to the longitudinal reinforcement of the longitudinal beam. Concrete is then introduced into the joint. The dimension of the joint in the longitudinal direction of the bridge is approximately equal to the height of the bridge cross-section, as the formation of the steel consoles and the working space required for welding will require a large joint dimension in the longitudinal direction of the bridge (see drawings FIGS. 1 to 3 in EA 201201135 A1). Since the longitudinal beam has the final cross-sectional dimensions, the longitudinal beam cannot be produced in a precast plant and must rather be manufactured close to the installation site. For the positioning of the longitudinal beam there is required a very large positioning device or cranes with extremely high load capacities, which in both cases will be associated with significant resource consumption. Due to the complex joint formation and the use very large lifting devices, the method described in EA 201201135 A1 has a high resource consumption. Because of the large joint dimensions there has to be used significant quantity of in-situ concrete on site. Because the curing of the in-situ concrete in the joint must be awaited before the next construction section can be produced, the method shown in EA 201201135 A1 does not allow for rapid construction progress.

BRIEF SUMMARY

[0017]Therefore, the object of the present invention is to provide a method for the rapid construction of a bridge that enables a faster construction process than the method described in WO 2019090374 A1 using thin-walled segments, which has a lower resource consumption compared to the segmental construction method, the method described in WO 2022256851 A1 using trough-shaped longitudinal beams and filling concrete, and the methods described in U.S. Pat. No. 3,788,023 and EA 201201135 A1 using prefabricated longitudinal beams, and which is suitable for the production of bridges with larger span widths than the methods described in DE 2520105 A1, AT 285663, and EP 1780338 A1 with trough-shaped longitudinal beams.

[0044]The method according to the invention is suitable for the manufacture of bridges with spans widths ranging from 25 m to 60 m, and preferably from 30 m to 50 m.

[0051]An advantageous application of the method according to the invention is made possible when the reinforcement bars of the connecting reinforcement are connected in the layer of concrete arranged above the base plate of a longitudinal beam through reinforcement sleeves with the longitudinal reinforcement of an already installed longitudinal beam and, optionally, with the longitudinal reinforcement embedded in the at least one pier segment.

[0052]In the method according to the invention, it may be advantageous if longitudinal reinforcement is installed over the entire length of a construction section on the base plate of at least one longitudinal beam, and a layer of concrete is applied.

[0053]An advantageous application of the method according to the invention is made possible if the width of a longitudinal beam is at most 3.5 m and preferably at most 2.5 m, and the thickness of the base plate and/or the cover plate is at most 150 mm and preferably at most 100 mm.

[0054]When using the method according to the invention, it may be beneficial if at least one longitudinal beam and/or at least one deck slab element and/or at least one pier segment is made from high-strength or ultra-high-strength concrete.

[0055]Advantageously, when using the method according to the invention, the at least two longitudinal beams may be installed using at least one crane or using a positioning device or using an incremental launching method.

[0056]If a positioning device is used for installing the at least two longitudinal beams at the installation site, it can be advantageous if the positioning device has at least one frame support that is arranged next to the pier and that is located at the front in the direction of manufacture of the bridge.

[0057]An advantageous use of the method according to the invention is made possible when the topping concrete is applied in two layers, wherein the top of the first layer of the topping concrete is approximately at the same height as the upper surface of the plates of the deck slab elements after the deck slab elements have been placed on the longitudinal beams.

[0058]In order to reduce the number of wear-prone bridge bearings, it is advantageous if at least one longitudinal beam or at least one pier segment is rigidly and, optionally, bend-stiffly connected in the longitudinal and transverse directions with the pier arranged underneath.

[0059]In order to absorb bending, shear, and torsional stresses, it may be advantageous if a pier segment is manufactured with a greater height and/or greater width than the adjacent longitudinal beams.

[0060]In order to reduce on-site work, it may be advantageous if at least one pier segment is prefabricated and installed on a pier using a crane or a positioning device after the concrete has cured.

[0061]Two adjacently arranged pier segments, which are supported on bridge bearings, may be connected in a force-locking manner by a transverse beam to enable the absorption and transfer of torsional moments into the bridge bearings.

[0062]A further optimization of the method according to the invention is made possible when two pier segments and a transverse girder, which connects the two pier segments in a force-locking manner, are prefabricated as a single piece and installed on one or two piers after the concrete has cured.

[0063]It may be advantageous if at least one joint gap between two adjacent longitudinal beams or, optionally, between a pier segment and an adjacent longitudinal beam is formed as a filling joint with a width of 5 mm to 300 mm and preferably 10 mm to 30 mm, or as a ground dry joint or as a match-cast joint.

[0064]In the method according to the invention, it may be advantageous if at least one tendon with subsequent bonding is installed above the base plate of a longitudinal beam prior to the installation of the longitudinal beam, tensioned, and grouted, and is embedded in a layer of concrete that is formed over the base plate of the longitudinal beam. after the installation of the longitudinal beam. The at least one tendon is made with a sleeve made of steel sheet or plastic, for example, polypropylene. A grout mortar based on cement may be used for grouting.

[0065]An advantageous use of the method according to the invention is made possible if a portion of a tendon is embedded in a layer of concrete applied on the base plate of a longitudinal beam, and at least one other portion of the tendon is installed within the longitudinal beam and outside the concrete cross-section, the tendon is pre-tensioned, and the tendon is grouted with a grouting mortar.

[0066]In each span of the bridge constructed using the method according to the invention, at least two longitudinal beams are installed. For example, in a bridge with three spans and two adjacent longitudinal beams, a total of six longitudinal beams are installed.

[0067]If bridge bearings are arranged between the longitudinal beams or, optionally, between the pier segments and the tops of the piers, the bridge constructed using the method according to the invention has, in its completed state, the static system of a continuous beam. If the longitudinal beams or, optionally, the pier segments are rigidly and, optionally, bend-stiffly connected to the piers arranged underneath, the bridge in its completed state has the static system of a frame.

BRIEF SUMMARY OF THE DRAWINGS

[0068]Further details, features, and advantages of the invention are obvious from the following explanations of exemplary embodiments schematically illustrated in the drawings FIG. 1 to FIG. 19. In the drawings, the following is shown:

[0069]FIG. 1 shows a view of the installation site of a first embodiment according to the invention after the installation of two longitudinal beams;

[0070]FIG. 2 shows a view of the installation site of the first embodiment according to the invention after the placement of seven deck slab elements;

[0071]FIG. 3 shows a view of the installation site of the first embodiment according to the invention after the application of a topping concrete layer on seven deck slab elements;

[0072]FIG. 4 shows a longitudinal section of the first embodiment according to the invention along the intersecting line IV-IV indicated in FIG. 3;

[0073]FIG. 5 shows a cross-section of the first embodiment according to the invention along the intersecting line V-V indicated in FIG. 4;

[0074]FIG. 6 shows a view of the installation site of a second embodiment according to the invention after the installation of four longitudinal beams;

[0075]FIG. 7 shows a plan view of the installation site of a third embodiment according to the invention during the installation of the longitudinal beams using the incremental launching method;

[0076]FIG. 8 shows a plan view of the installation site of the third embodiment according to the invention after the placement of five deck slab elements on the longitudinal beams;

[0077]FIG. 9 shows a plan view of the installation site of the third embodiment according to the invention after the application of the topping concrete on the deck slab elements and the cover plates of the longitudinal beams;

[0078]FIG. 10 shows a cross-section of the third embodiment according to the invention along the intersecting line X-X indicated in FIG. 7;

[0079]FIG. 11 shows a cross-section of the third embodiment according to the invention along the intersecting line XI-XI indicated in FIG. 8;

[0080]FIG. 12 shows a view of the installation site of a fourth embodiment according to the invention after the application of a first layer of topping concrete on the cover plates of the longitudinal beams;

[0081]FIG. 13 shows a vertical section of a fifth embodiment according to the invention along the intersecting line XIII-XIII indicated in FIG. 14;

[0082]FIG. 14 shows a vertical section of the fifth embodiment according to the invention along the shifting line XIV-XIV indicated in FIG. 13;

[0083]FIG. 15 shows a view of the installation site of a sixth embodiment according to the invention after the positioning of two pier segments;

[0084]FIG. 16 shows a view of the installation site of the sixth embodiment according to the invention after the installation of two longitudinal beams;

[0085]FIG. 17 shows a view of the installation site of the sixth embodiment according to the invention after the application of the topping concrete on three deck slab elements and a part of the cover plates of the longitudinal beams;

[0086]FIG. 18 shows a vertical section of a seventh embodiment according to the invention; and

[0087]FIG. 19 shows a vertical section of an eighth embodiment according to the invention.

DETAILED DESCRIPTION

[0088]A first embodiment of the method according to the invention is illustrated in FIGS. 1 to 5.

[0089]The individual working steps for the manufacture of a construction section of a multi-span bridge 21 are schematically depicted in FIGS. 1 to 5. For the sake of clarity, these drawings do not depict the complete reinforcement, tendons, mounting bearings, positioning devices, working scaffolds, and fall protection.

[0090]In the first step, as shown in FIG. 1, two longitudinal beams 11 are transported to the installation site 23 using a positioning device and installed in their final position. The joint gaps 24 between the longitudinal beams 11 and the preceding construction section are filled with concrete or a grouting mortar. The width of the joint gaps 24 may range between 5 mm and 300 mm. In the first exemplary embodiment, the 20 mm wide joint gaps 24 are filled with a grouting mortar. In a joint gap 24 arranged between the wall plates 12, base plates 13, and cover plates 14 of adjacent longitudinal beams 11, there is not existent any longitudinal reinforcement 32 that crosses the joint gap 24.

[0091]In the second working step, as shown in FIG. 7, seven deck slab elements 2 for the entire construction section are placed on the longitudinal beams 11 using the positioning device 47. In the next working step, a connecting reinforcement 33 with reinforcement sleeves 35 is attached to the preceding construction section. Subsequently, a layer 10 of concrete is applied on each of the two longitudinal beams 11 on the part of the base plate 13 that is arranged adjacently to the preceding construction section.

[0092]Next, the connecting reinforcements 33 for the lower longitudinal reinforcement 32 are first laid, followed by the upper longitudinal reinforcement 32 of the deck slab 1. In order to ensure a rapid construction process, it is in particular advantageous to minimise the reinforcement work at the installation site 23. For this reason, the lower transverse reinforcement 34 and the lower longitudinal reinforcement 32, a part of the upper transverse reinforcement 34, and the shear reinforcement are preferably already incorporated into the deck slab elements 2 during their production in the prefabrication plant.

[0093]In the third working step, as shown in FIG. 3, a layer of topping concrete 9 is applied on the deck slab elements 2.

[0094]FIG. 4 shows that longitudinal reinforcements 32 are installed in the base plates 13, wall plates 12, and cover plates 14, which do not cross the joint gap 24. The joint gap 24 is only crossed by the connecting reinforcement 33 in the layer 10 of concrete above the base plate 13 and the longitudinal reinforcement 32 of the deck slab 1.

[0095]FIG. 5 shows a cross-section of the completed bridge 21, which is arranged directly next to the joint gap 24. The only longitudinal reinforcements 32 present in this cross-section consist of the connecting reinforcement 33, which is embedded in the layer 10 of concrete above the base plate 13, and the longitudinal reinforcement 32, which is arranged in the topping concrete 9 of the deck slab 1.

[0096]In segmental bridge construction, there is no continuous longitudinal reinforcement 32 in the joint gaps 24 between the individual segments. Therefore, the joint gaps 24 must be kept under pressure through post-tensioning. Bridges 21 with a hollow box-shaped cross-section made using cast-in-place methods have a continuous longitudinal reinforcement 32 in the construction section joints, which is arranged in both the base plate 13 and the cover plate 14 as well as in the wall plates 12. However, experimental tests on longitudinal beams 11 having a hollow box cross-section have shown that torsional moments may also be absorbed if the continuous longitudinal reinforcement 32, as shown in FIG. 5, is only arranged in a layer 10 of concrete arranged above the base plate 13 and in the topping concrete 9.

[0097]With the configuration of the connection of the construction section to be built to the preceding construction section according to the invention, a rapid construction of the construction section is possible, as the time-consuming reinforcement and formwork work in the hollow boxes of the longitudinal beams 11 is minimised. The reinforcement work is limited to screwing the connecting reinforcement 33 into the reinforcement sleeves 35 installed in the base plate 13 of the preceding construction section, and, optionally, laying transverse reinforcement 34 over the connecting reinforcement 33. The effort required for formwork is very small, as formwork must only be produced for the front face of the layer 10 of concrete and the joint gaps 24.

[0098]FIG. 5 shows that the longitudinal beam 11 is directly supported on the pier 22. The longitudinal beam 11 may be connected rigidly and with bending stiffness to the pier 22 through connecting reinforcement 33 and grouting mortar. Alternatively, bridge bearings 29 could also be arranged between the longitudinal beams 11 and the pier 22.

[0099]For the manufacture of the longitudinal beam 11, there are several possibilities. In the first exemplary embodiment, the base plate 13 is produced with its final width in the first step. Subsequently, the wall plates 12 are produced on the base plate 13. In the last working step, the cover plate 14 is produced. The base plate 13 and the wall plates 12 could also be produced in a single working step. It would also be possible to manufacture the wall plates 12 in a horizontal position during a first working step and then rotate them into a vertical position after the concrete has cured. In this case, the base plate 13 would be cast between the wall plates 12.

[0100]The longitudinal beam 11 and the deck slab elements 2 of the first exemplary embodiment are made from high-strength concrete. Alternatively, the longitudinal beam 11 and the deck slab elements 2 could also be made from ultra-high-strength concrete. The use of self-compacting concrete may also be considered, especially for the production of thin-walled wall plates 12.

[0101]The first exemplary embodiment shows the manufacture of a construction section of a multi-span bridge 21. A multi-span bridge 21, for example with three spans, could also be produced in a single construction section.

[0102]In the drawings FIG. 1 to FIG. 5, there is described the construction of a bridge 21, in which the joint gaps 24 between adjacent longitudinal beams 11 are arranged near the piers 22. Using the method according to the invention, it would also be possible to position the joint gaps 24 at different locations, such as at the points of zero moments occurring under dead load.

[0103]A second embodiment of the method according to the invention is illustrated in FIG. 6.

[0104]In order to manufacture a construction section, longitudinal beams 11 are installed in the first working step. Unlike the first embodiment example, in which, according to FIG. 1, there are installed two longitudinal beams 11, each approximately the length of the construction section, in the second exemplary embodiment, four longitudinal beams 11 are installed for the construction section. The length of each of the four longitudinal beams 11 corresponds to approximately half the length of the construction section. Each longitudinal beam 11 is supported at one end on a pier 22 and at the other end on a scaffold tower 17.

[0105]Each longitudinal beam 11 is produced from four wall plates 12, a base plate 13, and a cover plate 14. The wall plates 12 are pre-manufactured in a horizontal position and then set up after the concrete has cured. Due to this manufacturing process, the length of the wall plates is limited to between 9 m and 12 m. In this exemplary embodiment, the four wall plates 12 of one longitudinal beam 11 have the same thickness. It would also be possible to produce the wall plates 12 arranged next to a pier 22 with a greater thickness to account for the higher shear forces near the piers 22. Additionally, it would also be possible to manufacture wall plates 12 with variable thickness.

[0106]The base plate 13 and the cover plate 14 are produced after the wall plates 12 have been erected. FIG. 6 shows that there are given joint gaps 24 between the wall plates 12 in the centre of the longitudinal beam 11. In the joint gaps 24 of the wall plates 12, there is no longitudinal reinforcement 32 that crosses the joint gaps 24. The joint gaps 24 are formed as ground dry joints.

[0107]The further working steps will proceed similarly to the first exemplary embodiment. Due to the scaffold towers 17, which are arranged approximately in the centre of the construction section, lower stresses will occur in the longitudinal beams 11 in the subsequent working steps compared to the first exemplary embodiment. However, in the second exemplary embodiment there will arise additional effort for the assembly and disassembly of the scaffold towers 17.

[0108]A third embodiment of the method according to the invention is illustrated in FIGS. 7 to 11.

[0109]In this embodiment, the longitudinal beams are installed using the incremental launching method. The entire bridge 21 is constructed in a single construction section. The device for positioning the longitudinal beams 11 is usually arranged on or behind an abutment 19.

[0110]FIG. 7 shows a construction state where seven longitudinal beams 11 have already been installed in their final position, and five longitudinal beams 11 are being introduced using the incremental launching method. In order to reduce bending stresses in the longitudinal beams 11, a launching nose 18 is mounted on the longitudinal beam 11 located at the front in the direction of sliding. Joint gaps 24 are arranged between the longitudinal beams 11. There is not installed any longitudinal reinforcement that crosses the joint gaps 24 within these gaps. During the introduction of the longitudinal beams 11, the joint gaps 24 are over-pressed by an approximately centric pre-tensioning. In the area of the joint gaps 24, longitudinal reinforcement 32 that crosses the joint gaps 24 may be installed either before or after installing the longitudinal beams 11 in their final position over a part of the base plates 13 of adjacent longitudinal beams 11, along with a layer of concrete 10 in the area of the longitudinal reinforcement 32. It may also be advantageous to install a longitudinal reinforcement 32 and a layer of concrete 10 over the entire length of the bridge 21 on the base plates 13 of the longitudinal beams 11.

[0111]FIG. 8 shows a construction state after the longitudinal beams 11 have been installed in their final position, after the transverse beams 27 have been constructed between the longitudinal beams 11 in the area of the piers 22, and after five deck slab elements 2 have been placed on the longitudinal beams 11. The deck slab elements 2 have an approximately trapezoidal shape in plan view because the bridge 21 has the shape of a circular arc in plan view.

[0112]After placing the deck slab elements 2, the upper longitudinal reinforcement 32 and the upper transverse reinforcement 34 may be laid on the deck slab elements 2 and the cover plates 14 of the longitudinal beams 11. In a final working step, the topping concrete 9 is subsequently applied on the deck slab elements 2 and the cover plates 14 of the longitudinal beams 11. The plan view of the completed bridge 21 is shown in FIG. 9.

[0113]FIG. 10 shows a cross-section through a longitudinal beam 11 during the insertion of the longitudinal beams 11. The longitudinal beam 11 consists of two wall plates 12, a base plate 13, and a cover plate 14. Mounting bearings 8 are installed on the piers 22 for the insertion of the longitudinal beams 11.

[0114]After the longitudinal beam 11 has been inserted, transverse beams 27 are constructed between the longitudinal beams 11 according to FIG. 8. The transverse beams 27 are arranged above the pier 22. FIG. 11 shows a cross-section directly next to a pier 22 and the longitudinal beams 11 arranged above it. A transverse frame 15 has been installed within the longitudinal beam 11. The transverse frame has a length of 1.2 m in the longitudinal direction of the bridge 21. The transverse frame is rigidly connected to the wall plates 12, the base plate 13, and the cover plate 14. The transverse beam 27 is connected to the wall plates 13 and the transverse frame 15 of the two longitudinal beams 11 in a force-locking manner. FIG. 11 shows that there are installed tendons 36 in the transverse frame 15. For the transfer of the forces from the tendons 36 to the concrete of the transverse frame 15, there are installed steel plates 40 within the transverse frame 15.

[0115]The installation of the transverse frames after the longitudinal beams 11 have been set in their final position is favourable, as the transverse frames 15 are quite heavy. The substantial weight of the transverse frames 15 would lead to high stresses in the longitudinal beams 11 during the shifting process.

[0116]Finally, the mounting bearings 8 are replaced by bridge bearings 29. The transverse frames 15 are configured in such a way as to transfer the support forces from the bridge bearings 29, which are arranged centrally underneath the longitudinal beams 11, into the wall plates 12.

[0117]A fourth embodiment of the method according to the invention is depicted in FIG. 12.

[0118]The fourth embodiment is similar to the first embodiment of the method according to the invention shown in FIGS. 1 to 5. An important difference is that after the laying of the deck slab elements 2, a first layer 10 of topping concrete 9 is applied on the cover plates 14 of the longitudinal beams 11. The application of the first layer 10 of topping concrete 9 may be realised either before or after laying the longitudinal reinforcement 32 and transverse reinforcement 34 on the deck slab elements 2 and the cover plates 14 of the longitudinal beams 11. The top surface of the first layer 10 of topping concrete 9 is approximately at the same height as the top surface of the plate 5 of the deck slab elements 2. FIG. 12 shows a construction state after the application of the first layer of topping concrete 9.

[0119]After the partial curing of the first layer 10 of topping concrete 9, when it has, for example, a compressive strength of 20 N/mm², pre-tensioning with tendons 36, which are arranged in the longitudinal direction of the bridge 21 in the longitudinal beams 11, is applied. The longitudinal beams 11 are connected to the deck slab elements 2 through the first layer 10 of topping concrete 9 and through reinforcement bars that are anchored in the longitudinal beams 11 and the deck slab elements 2. The connection of the longitudinal beams 11 with the deck slab elements 2 is favourable from a static point of view, as it significantly increases the moment of inertia compared to that of the longitudinal beam 11. The application of longitudinal pre-tensioning by tensioning the tendons 36, which are arranged in the longitudinal direction of the bridge 21 in the longitudinal beams 11, is favourable, as this may achieve that no tensile stresses and consequently no cracks occur in the longitudinal beams 11, the first layer 10 of topping concrete 9, and the deck slab elements 2 when applying the second layer 10 of topping concrete 9. After the curing of the second layer 10 of topping concrete 9, the tendons 36 arranged in the longitudinal direction of the bridge 21 in the longitudinal beams 11 may be tensioned once again.

[0120]A fifth embodiment of the method according to the invention for the manufacture of a construction section of a bridge 21 with two longitudinal beams 11 in each construction section is depicted in FIGS. 13 and 14.

[0121]FIG. 13 shows a positioning device 47, which is supported on the preceding construction section on the left side of the drawing and on the pier 22 on the right side of the drawing. The positioning device 47 consists of two positioning beams 41, two supports 51, two frames 42, and two sliding beams 54. Lifting devices 53 are mounted on the positioning beams 41. A frame 42 consists of two horizontally arranged frame bars 44 and a frame support 43. Steel plates 40 are arranged between the pier 22 and the frames 42. Sliding beams 54 are attached to the supports 51 and the frames 42. Rails 55 are mounted on the sliding beams 54. The positioning beams 42 may be moved transversely to the longitudinal axis of the bridge 51 on the rails 55.

[0122]FIGS. 13 and 14 show a construction state, in which both longitudinal beams 11 are in their final position, but no filling mortar has yet been placed in the joint gaps 24.

[0123]The sliding beam 54 must have a large length so that both positioning beams 41 may be positioned on the cantilevered part of the sliding beam 54. First, the longitudinal beam 11 shown on the left side of FIG. 14 is lifted and then shifted transversely to the longitudinal axis of the bridge 21. In the next working step, the longitudinal beam 11 depicted on the right side of FIG. 14 is lifted and shifted transversely to the longitudinal axis of the bridge 21. During the transverse shifting, the longitudinal beam 11 depicted on the left side of FIG. 13 must be moved laterally past the frame supports 43. When both longitudinal beams 11 are in the planned position in the plan view, they are lowered into their final position.

[0124]During the lifting and shifting of the longitudinal beams 11, bending moments will occur in the frames 42. Before the placement of the deck slab elements 2 and the application of the topping concrete 9, supports 51 may be installed between the longitudinal beams 11 and the sliding beams 54. In this case, no further bending moments will arise in the frames 42 due to the weight of the deck slab elements 2 and the topping concrete 9. FIG. 14 shows that two supports 51 have been installed above the longitudinal beam 11 depicted on the right side of the drawing.

[0125]As an alternative to the installation of the longitudinal beams 11 at the installation site 23 using a positioning device 47 shown in FIGS. 13 and 14, at least one crane could be used for the installation of the longitudinal beams 11. For example, steel brackets could be attached to the pier 22 depicted on the left side of FIG. 13 to support the longitudinal beams 11. The eccentricities between the support points on the brackets and the central plane of the pier 22 create bending moments that are absorbed by the pier 22. On the pier 22 depicted on the right side of FIG. 13, the longitudinal beams 11 could be supported on the bridge bearings 29 or on mounting bearings 8.

[0126]A sixth embodiment of the method according to the invention is illustrated in FIGS. 15 to 17. For clarity, these drawings do not depict the complete reinforcement, the tendons, the mounting bearings, the positioning device, the scaffoldings, and fall protection.

[0127]FIG. 15 shows the situation at the beginning of the manufacture of a construction section of a multi-span bridge 21 made of pre-tensioned concrete. Two pier segments 25 have been constructed on the pier 22 located at the front in the direction of manufacture of the bridge 21. The pier segments 25 are rigidly and bend-stiffly connected to the underlying pier 22. The longitudinal beams 11 of the preceding construction section have been connected to the pier segments 25 of the preceding construction section. A topping concrete 9 has been applied on the deck slab elements 2, except for the two deck slab elements 2 arranged next to the pier 22.

[0128]In the first working step for the manufacture of a construction section, as shown in FIG. 15, two longitudinal beams 11 are transported to the installation site 23 using a positioning device 47 and connected in their final position with the preceding construction section and the pier segment 25. The longitudinal beams 11 have a hollow box cross-section. The upper surfaces of the longitudinal beams 11 are at the same height as the upper surfaces of the pier segments 25. The connection of the longitudinal beams 11 with the preceding construction section and with the pier segments 25 is realised by filling the joint gaps 24 with concrete or filling mortar and by tensioning the tendons 36.

[0129]In the second working step, as shown in FIG. 17, seven deck slab elements 2 for the entire construction section are placed on the longitudinal beams 11 using the positioning device 47. Subsequently, the connecting reinforcements for the lower longitudinal reinforcement 32 are laid first, followed by the upper longitudinal reinforcement 32, and finally the upper transverse reinforcement 34 on the deck slab elements 2. In order to speed up the construction process, it is particularly advantageous to minimise the reinforcement work at the installation site 23. For this reason, the lower transverse reinforcement 34 and the lower longitudinal reinforcement 32, as well as the shear reinforcement 31, are preferably already incorporated into the deck slab elements 2 during production in the prefabrication plant.

[0130]Next, a first layer 10 of topping concrete is applied on the cover plates 14 of the longitudinal beams 11. The application of the first layer 10 of topping concrete 9 may advantageously be realised before laying the upper longitudinal reinforcement 32 and the upper transverse reinforcement 34. The top surface of the first layer 10 of topping concrete 9 is approximately at the same height as the top surface of the plates 5 of the deck slab elements 2. FIG. 17 shows a construction state after the application of the first layer 10 of topping concrete 9.

[0131]After the partial curing of the first layer 10 of topping concrete 9, when it has, for example, a compressive strength of 20 N/mm², a pre-tensioning is applied using the tendons 36 arranged in the longitudinal direction of the bridge 21 in the longitudinal beams 11. The longitudinal beams 11 are connected to the deck slab elements 2 through the first layer 10 of topping concrete 9 and through reinforcement bars that are anchored in the longitudinal beams 11 and the deck slab elements 2. The connection of the longitudinal beams 11 with the deck slab elements 2 is favourable in a static point of view, as it significantly increases the moment of inertia compared to that of the longitudinal beams 11. The application of longitudinal pre-tensioning by tensioning the tendons 36 arranged in the longitudinal direction of the bridge 21 in the longitudinal beams 11 is favourable because this may achieve that no tensile stresses and hence no cracks occur in the longitudinal beams 11, the first layer 10 of topping concrete 9, and the deck slab elements 2 when the second layer 10 of topping concrete 9 is applied.

[0132]In the fourth working step, as shown in FIG. 17, topping concrete 9 is applied on four deck slab elements 2. Once the topping concrete 9 has the required strength, the tendons 23 arranged in the longitudinal beams 11 may be further tensioned. During the production of the topping concrete 9, tension members 49 arranged between the precast beams 11 and the positioning device 47 are tensioned to partially absorb the weight of the topping concrete 9 with the positioning device 47 and transfer it to the piers 22.

[0133]In the fifth working step, topping concrete 9 is applied on the three deck slab elements 2 arranged in the centre of the construction section to be built. This topping concrete 9 is only produced in the fifth working step when the topping concrete produced in the fourth working step results in an increase in the moment of inertia above the pier 22, thus allowing the bending moments caused by the topping concrete applied in the fifth working step to be absorbed with lower stresses.

[0134]When the topping concrete 9 produced in the fifth working step has the required strength, the tension members 49 may be relaxed, and the positioning device 47 may be moved into the adjacent span for the production of the next construction section.

[0135]In this example, the pier segments 25 are rigidly and bend-stiffly connected to the piers 22. A bridge 21 without bridge bearings 29 between piers 22 and pier segments 25 is referred to as an integral bridge 21. In an integral bridge 21, the construction of a transverse beam 27 to stabilise the longitudinal beams 11 and the pier segments 25 is not required.

[0136]A seventh embodiment of the method according to the invention for manufacturing a construction section of a bridge 21 with two longitudinal beams 11 and two pier segments 25 in each construction section is depicted in FIG. 18.

[0137]FIG. 18 shows a longitudinal section through a part of the completed bridge 21 in the area of the pier 22, taken in the centre of a longitudinal beam 11.

[0138]The pier segment 25 is manufactured to a height that is less than the height of the cross-section of the bridge 21 above the pier 22 in the final state.

[0139]The longitudinal beams 11 have a hollow box-shaped cross-section and a variable height. The height of the longitudinal beams 11 next to the pier segment 25 is greater than in the areas positioned further away from the pier segment 25. The pier segment 25 also has a variable height, which is greatest above the pier 22. The base plate 13 of the pier segment 25 has a variable thickness, which is greatest above the pier 22. The pier segment 25 is rigidly and bend-stiffly connected to the pier 22.

[0140]In FIG. 18, there is schematically depicted a part of the reinforcement of the bridge 21. A reinforcement bar of the longitudinal reinforcement 32 is depicted in the base plate 13 of the pier segment 25. This reinforcement bar has reinforcement sleeves 35 at both ends.

[0141]In the topping concrete 9, the upper transverse reinforcement 34 of the deck slab 1 is depicted. The transverse reinforcement 34 is arranged above the upper longitudinal reinforcement 32 of the deck slab 1 in the first layer from the top.

[0142]Connecting reinforcements 33 are screwed into the reinforcement sleeves 35 on both sides of the pier segment 25. The connecting reinforcements 33 are arranged in the layers 10 of concrete that are produced at the installation site 23 above the base plates 13 of the longitudinal beams 11. The connecting reinforcements 33 form a continuous longitudinal reinforcement 32 at the bottom side of the bridge 21 in the area of the piers. Thus, the bridge 21 has in the area of the joint gaps 24 a continuous upper longitudinal reinforcement 32, which is arranged in the topping concrete of the deck slab 1, and a continuous lower longitudinal reinforcement 32, which is arranged in the layers 10 of concrete and in the base plate 13 of the pier segment 25.

[0143]The bridge 21 is pre-tensioned using tendons 36 arranged in the longitudinal direction of the bridge 21 and predominantly in different construction sections. The anchorages of the tendons 36 are arranged on both sides of the pier segment 25. The tendons cross within the pier segment 25.

[0144]An eighth embodiment of the method according to the invention is depicted in FIG. 19. FIG. 19 shows a longitudinal section through a longitudinal beam 11 during the construction of a construction section. A layer 10 of concrete has been applied to the base plate 13 of the longitudinal beam 11. A portion of the tendon 36 is arranged in the layer 10 of concrete. The tendon 36 is deflected at two points in the layer 10 of concrete. The end anchorage of the tendon 36 is arranged in the pier segment 25 of the preceding construction section, which is shown on the left side of FIG. 19. The tension anchorage of the tendon 36 is arranged in the pier segment 25 of the construction section to be produced, which is shown on the right side of FIG. 19. The tendon 36 is installed within the longitudinal beam 11 and outside the concrete cross-section between the pier segments 25 and where the tendon 36 is deflected in the layer 10 of concrete. The tendon 36 is formed with a sleeve made of plastic, for example, polyethylene. Such a sleeve is, for example, marketed under the product name PT-PLUS by VSL (Switzerland) AG, Bern. Compared to an external tendon, the tendon 36 according to the invention has the advantage of a greater distance from the neutral axis of the longitudinal beam 11 in the central area of the longitudinal beam 11 and the advantage of a higher load-bearing capacity in the ultimate limit state of the load-bearing capacity.

LIST OF REFERENCE NUMERALS