WO2013104833A1

WO2013104833A1 - A method and an apparatus for building a bridge cast on site

Info

Publication number: WO2013104833A1
Application number: PCT/FI2013/050032
Authority: WO
Inventors: Risto KULMALA
Original assignee: Kulmala Risto
Priority date: 2012-01-13
Filing date: 2013-01-11
Publication date: 2013-07-18
Also published as: FI123603B; FI20125044A; EP2802712A1

Abstract

The invention relates to a method for building a bridge cast on site, in which method a formwork (1) is formed on the bridge construction location, the formwork (1) is reinforced, concrete is cast in the formwork (1), the concrete is allowed to dry, and after the drying the formwork (1) is removed from around the concrete structures of the bridge. In the method according to the invention, the formwork (1) of the bridge is formed of at least two formwork modules (2) whose height is adjustable by actuators, which modules (2) are brought to the bridge construction location and, adjusted to a suitable height and connected to each other in order to construct an integral formwork (1)

Description

A METHOD AND AN APPARATUS FOR BUILDING A BRIDGE CAST ON SITE

Field of the invention

The invention relates to a method for building a bridge cast on site. The invention also relates to an apparatus for applying the method according to the invention. Background of the invention

Building a bridge by casting from concrete is, at present, still started by making a wooden formwork at the bridge construction site. The formwork is reinforced, and it can be provided with pipe systems for water supply, sewage and/or district heating, as well as electric and/or communication lines (electricity is needed at least when lighting columns are erected on the bridge) to be embedded in the concrete. In many cases, particularly when the bridge is built on flat land, bridge abutments have to be constructed from suitable soil materials and concrete at both ends of the bridge, for raising the passage across the bridge to a suitable height so that the necessary height difference is achieved at the front and rear ends of the bridge, for e.g. a passage, a railway or a body of water below the bridge. The bridge abutments, or sometimes one of them, can also be made after casting the deck of the bridge. In case the bridge spans across a valley and the span of the bridge extends across this terrain point, there is no need to build bridge abutments, but the contours of the terrain and, if necessary, supporting below the deck of the bridge in a suitable way may be sufficient. After the wooden formwork has been finished, a large amount of concrete is cast in it, normally by transporting the concrete to the site by pump vehicles. After the casting, the concrete is allowed to dry until the cast concrete has reached a sufficient strength for removing the formwork, before the wooden formwork is disassembled.^" After the disassembly of the formwork, the concrete structures of the bridge are allowed to dry further before the next steps. Finally, the bridge is finished by laying down the pavings for the future driveway and/or pedestrian and bicycle way as well as by mounting the railings and lighting columns on the bridge floor. The most laborious step in the present method is normally the assembly and disassembly of the wooden formwork. The formwork which is built up of planks and boards on site is for single use, and therefore it normally requires a very large quantity of sufficiently heavy timber which is worked primarily manually to the dimensions of the bridge according to the drawings, taking into account the contours and load-bearing capacities of the terrain at the time. Consequently, the assembly and disassembly of the formwork require a lot of manual work and thereby also a lot of time and labour, which makes the construction of a bridge by the present method very expensive and time consuming.

Brief summary of the invention It is an aim of the invention to present a novel method for building a bridge to be cast on site, the method reducing the amount of work and costs involved in building the bridge to be cast on site, and reducing the time required for the construction. Further, it is an aim of the invention to present an apparatus for building a bridge to be cast on site by applying the method according to the invention.

The principle in the method according to the invention is that the formwork for a bridge to be cast on site is formed of at least two formwork modules which can be re-used several times and whose height can be adjusted by actuators, and which are fastened to each other by removable fastening members, and which are transported to the construction site, adjusted to a suitable height, and connected to each other before casting the bridge, in such a way that the formwork formed of the modules is uniform and sufficiently leak-proof. The formwork is advantageously also such that after the concrete has dried, the formwork modules can be disassembled and moved downwards by actuators so that the formwork is removed from the dried concrete structure and is moved to such a distance from the structures of the bridge that the formwork modules can be transported away from the construction site. In this application, adjustment in the height direction refers to such adjustment that the formwork modules can simultaneously also move, upon adjusting, slightly in the horizontal (oblique) direction; in other words, the direction of the adjustment is not necessarily the upwards direction perpen- dicular to the ground surface.

The method according to the invention has the advantage that, thanks to it, when constructing a bridge to be cast on site, it is no longer necessary to build a wooden formwork which is expensive and slow to make, but the formwork can be assembled on site from formwork modules whose height can be suitably adjusted by actuators and which can be connected to each other. By using these modules, constructing the formwork needed for casting the bridge takes significantly less time, and using it as the formwork for the bridge requires considerably less labour than the conventional wooden form- work. Moreover, the method according to the invention has the advantage that casting the bridge no longer requires a large quantity of expensive timber which, after the use, becomes waste wood that is unfit for use in e.g. other construction. Also, traffic beneath the bridge can be started earlier than by using the conventional method, because the formwork used in the method does not fill all the space left beneath the deck of the bridge, but free spaces are left beneath the bridge where the traffic can in most cases be arranged without modifications in the support of the formwork.

Description of the drawings

In the following, the invention will be described in more detail with reference to the appended drawings, in which

Fig. 1 shows an apparatus according to the invention seen from the side, shows the apparatus according to Fig. 1 , seen from the front,

Fig. 3 shows the lower part of a frame beam of a supporting element in the apparatus according to the preceding figures, seen from below, Fig. 4 shows a joint between an extension element in the upper part of a frame beam, and the frame beam, and Fig. 5 shows a casting support for a framework element, as well as devices for turning and locking an edge piece, seen from the front.

Detailed description of the invention

Figures 1 to 5 show an apparatus according to the invention, by means of which a bridge to be cast on site can be built according to the principles of the method according to the invention. As shown in Figs. 1 and 2, this apparatus comprises formwork modules 2, which can be adjusted by actuators in the height direction and which can be connected to each other afterwards by easily removable fastening members, to form a single integral formwork 1. The formwork modules 2 may be available in different lengths, wherein a formwork of a suitable length can be assembled by suitably combining these formwork modules 2 of different sizes. In this case, however, all the formwork modules 2 are equal in width, because the bridge to be cast has a constant width over its whole span. Figure 2 shows that in this embodiment, two lines of formwork modules 2 are placed next to each other in the width direction so that the first line forms the left side of the formwork 1 and the second line forms the right side of the formwork 1. Consequently, such an embodiment can be used for building the deck of a bridge to be made for even quite a wide driveway.

The formwork modules 2 constitute a supporting element 3 having a tubular girder structure, and a formwork element 4 formed of a reinforced plate structure. The formwork element 4 with a plate structure is fastened onto the supporting element in such a way that by adjusting the height of the supporting element 3 having an adjustable height, the formwork element 4 can be lifted up and lowered down. The formwork elements 4 of adjacent formwork modules 2 are in this case mirror images of each other, because the side edge of the formwork elements 4 on the left hand side is connected to the left side edge of the formwork elements on the right hand side at the symmetry axis of the bridge deck as shown in Fig. 2. As a result, no vertical casting support is connected to the abutting side edges in the same way as to the edges of the bridge. These casting supports 18 are elements that can be fastened at different points to the edge pieces 12 of the formwork element 4 that constitute the side edges in an adjustable way as shown in Fig. 5. Consequently, even though the formwork modules are equal in size with respect to their supporting elements, the width of the formwork formed on their form- work elements 4 can be adjusted to some extent, thanks to the adjustable casting supports 18. Therefore, adjacent and successive formwork modules 2 do not necessarily need to be exactly equal in width.

The supporting element 3 is preferably a truss structure formed of tubular girders comprising at least four vertical frame beams 6 and intermediate struts 7, some of which are perpendicular to the frame beams 6 and some are at an angle of 45° to them, to achieve the rigidity and strength required for bearing the casting of concrete. The structure of the intermediate struts 7 shown in Figs. 1 and 2 is exemplary; in other words, in the different applications the intermediate struts 7 may be placed between the frame beams 6 in a way deviating from this. The joints between the frame beams 6 and the intermediate struts 7 can be, for example, welded, screw, riveted, or clinched joints, or combinations of these. The material of the frame beams 6 of the supporting elements 3 and the intermediate struts 7 is metal, such as steel, stainless steel, or aluminium. The lower ends of the frame beams 6 of the supporting elements 3 are provided with wheels 8 mounted on bearings, as shown in Fig. 3, on which wheels the formwork module 2 can be moved. Inside the lower end of each frame beam 6, a lifting actuator 9 is provided, which is an actuator with a linear movement, having a supporting member 92 (e.g. a piece of a steel sheet) provided at the end of a moving head 91 and supported to the ground. The lifting actuator 9 is placed in such a way that its moving head 91 and the supporting member 92 therein can be pushed the travel distance of the lifting actuator 9 outwards from the end of the frame beam 6 and inwards in such a way that the supporting member 92 moves back above the outer rim of the wheels 8 as shown in Fig. 3. In this way, the frame beams 6 and thereby the whole formwork module 2 can be moved up and down by the actuators so that the wheels 8 at the lower end of the frame beam 6 can be lifted off the ground or lowered back onto the ground.

Also, the upper part of the frame beams 6 of the supporting element 3 are provided with extension elements 1 1 movable upwards from the frame beams 6 and back down by means of control actuators 10 with linear movements, placed at the side of the frame beams 6, the formwork element 4 being fastened to the ends of the extension elements 1 1 . As shown in Fig. 4, the extension elements 1 1 are beam girders which are otherwise similar to the frame beams 6 but they have such outer dimensions that they can be fitted inside the frame beams 6. By moving the extension elements 11 out from the inside of the frame beams 6 and back in again, the frame beams 6 can be extended and shortened; in other words, the framework element 4 fastened to the ends of the extension elements 1 1 can thus be lifted and low- ered. In this case, the extension elements 1 1 are rigidly fastened (e.g. by welding) to the framework element 4, wherein the control actuators 10 by the side of the frame beams 6 are controlled to move simultaneously and the same distance. The fastening of the frame beams 6 to the framework element 4 can also be removable (e.g. a screw fastening) or formed by articulation. The travel distance of the extension elements 1 1 is substantially greater than the travel distance of the movable ends 91 of the lifting actuators 9, but the extension elements are moved by the control actuators 10 which are telescopic actuators with a linear movement and produce a lower power than the lifting actuators 9 at the lower end of the frame beams 6. In this way, the adjustment of the extension elements 1 1 provides the coarse adjustment in the height direction of the supporting element 3, and the adjustment implemented by the lifting actuator 9 in the lower part of the frame beams 6 provides the fine adjustment. Because the control actuators 10 of the extension elements 1 1 are actuators with linear movements and produce lower power than the lifting actuators 9 at the lower parts of the vertical beams, the extension elements 1 1 are also provided with locking elements, shown in Fig. 4, for locking them in a desired position with respect to the frame beams 6 for the time of concrete casting. In other words, the control actuators 10 of the extension elements 1 1 are not, in this embodiment, intended to be used for moving the formwork elements when concrete has been cast, but only for adjusting the height of the formwork during its assembly and disassembly. The locking means are, in this case, for example locking pins 1 12 to be fitted in holes formed at regular intervals in the frame beams 6 and the extension elements 1 1 , and to be locked in place by locking rings 1 1 1 , as shown in Fig. 4.

The formwork elements 4 are made of sufficiently thick and rigid metal sheets (e.g. steel or aluminium sheets), to be capable of carrying the weight of wet concrete. The formwork elements 4 can also be reinforced by suitable braces fastened underneath the metal sheets, such as sheet or beam braces 41 . The formwork elements consist of a frame element 12 and edge pieces 13 provided on both sides of the frame element 12 to be turned and locked in a desired position. Between the edge pieces 13 and the extension elements 1 1 of the supporting element 3, side struts 14 are provided, which are pivotally connected at their first end to the extension elements 1 1 of the supporting element 3, and at their second end to the edge pieces 13 in such a position that the edge piece 13 can be turned and locked by means of the side strut 14 either in such a way that it extends in parallel with the plane formed by the top surface of the frame part 12 or forms a suitable angle to it (an angle of, for example, about 10 to 20°) so that the cast bridge deck is provided with an upwards bevel having the length of the edge piece 13. For providing different positions in this embodiment, the side struts 14 are also formed by tubular beams fitted inside each other as shown in Fig. 5 so that a swivelling actuator 131 having a linear movement is fastened between the extension element 1 1 and the edge piece 13 in the way shown in Fig. 5, wherein the edge piece can be swivelled to different positions by moving the movable end of this swivelling actuator inwards and outwards. Furthermore, the side struts 14 are provided with a locking device for locking them into given lengths; thus, the edge pieces 13 can be mechanically locked into a desired position. The locking device can be, for example, a locking pin similar to that used for locking the extension elements, which is fitted through holes in the parts of the side strut 14 when the side strut 14 is to be locked in an adjusted position. The locking and unlocking can be implemented by an actuator or manually. Locking by an actuator facilitates the use, because the side struts 14 are underneath the formwork element in a place which is difficult to access with- out using an aerial work platform or the like. Figure 5 also shows the mechanism for adjusting the casting supports 18 on top of the edge pieces 13. In this case, it is implemented by means of adjusting pieces 182 fastened in an articulated manner on the rear side of the casting support 18. As the casting support 18 is an elongated, plate-like piece (usually having the length of one formwork module) reinforced with braces 181 , at least two adjusting pieces 182 are often provided in succession at regular intervals in the longitudinal direction of the formwork element 4. The adjusting piece 182 comprises several longitudinal successive holes 183, through which it can be fastened by bolts 184 in the width direction of the formwork element to different points of the edge piece 13; in this way, the casting supports 18 are made adjustable in the width direction of the form- work element. The casting supports 18 can also be tilted, because tilting supports 185 are provided between the casting supports 18 and the adjusting pieces 182 behind them, fastened at their first end in an articulated 186 manner to the upper part of the brace 181 in the casting support 18, and their second end being provided with a fastening hole 187, through which the tilting support 185 can be fastened to different points of the adjusting piece 182 through the horizontal holes 188 therein. Thanks to the adjustment of the casting supports 8 in the width direction, the width of the formwork surface 17 of the formwork element 4 can be adjusted; in this way by using the formwork elements 4 shown in Figs. 1 to 5, the width of the formwork surface 17, i.e. the width of the finished bridge, can be adjusted as desired, without replacing the formwork elements 4 used. Thanks to the possibility of tilting the casting supports 18, the edges of the deck of the finished bridge can be made bevelled, if desired.

The casting supports 18 are also provided with safety fences 19 which are in this embodiment fastened to the casting supports 18 but which may, in an embodiment, also be fastened directly to the edge pieces 13. The safety fences 19 secure that working on top of the formwork element is as safe as possible right from the beginning.

In the edge areas, the frame element 12 is provided with horizontal parts 15 and a U-shaped part 16 in the middle between them, for forming a load- bearing beam underneath the deck of the bridge. As seen in the figure, corresponding parts are also provided in the formwork element 4 of the adjacent formwork module 2, namely horizontal parts 15 in both edge areas of the frame element 12 and a U-shaped part 16 between them for forming a second load-bearing beam underneath this half of the bridge and thereby to make the structure, with the other half, as symmetrical as possible in view of the square torque of the cross-sectional surface and thereby uniform in view of its bending stiffness. Normally, the U-shaped part 16 has a shape that opens up slightly upwards, to facilitate the removal of the formwork element 4 from the dried concrete. The formwork element 4 may also be provided with U-shaped or corresponding parts which are transverse or oblique to the lon- gitudinal direction, for forming reinforcing beams in different directions in the bridge deck. On the other hand, in some cases the formwork element may also be level over its whole width. Thus, the rigidity requirements of the structure are taken into account in the uniform structure (suitable thickness, or the like).

The upper and lower surfaces of the frame part 12 and the edge pieces 13 of the formwork element 4 constitute the formwork surface 17 which determines the shape of the deck of the bridge to be cast, and of the bracing structures underneath it. The formwork surface 17 can be a pure metal surface which is, for example, lubricated with formwork oil before casting the concrete. The formwork surface 17 can also be a metal surface coated with a suitable coating or paint. The painted surface is advantageously painted with e.g. powder paint, to which concrete is known to adhere poorly. The shape of the formwork surface 17 may be straight, angled or curved in a desired way, for example upwards convex so that the road surface to be paved on the bridge can be more easily made upwards convex. Furthermore, the formwork surface can be embossed or coated in such a way that the surface of the finished concrete has the same appearance as if a formwork made of planks had been used. The front and rear end edges of the formwork elements 4 are provided, on the side of the lower surface of the formwork elements 4, with fastening members 5, by means of which the formwork elements can be fastened to each other in a disengageable way. The fastening members 5 are, in their simplest form, lugs provided slightly (for example about 5 to 10 mm) spaced from the formwork element 4 in the direction of the inner parts, equipped with a hole, from which the lugs can be fastened to the edge of the end of the adjacent formwork element. Thus, the end edges of the formwork elements 4 can be tensioned closely against each other by the fastening members 5. Furthermore, in this way the fastening members 5 are brought outside the formwork elements 4 in such a way that no concrete can leak into them, which could make it more difficult to unlock them when disas- sembling the formwork 1.

The length of the formwork modules 2 can vary within the limits of transportability. If the formwork module 2 is long, it may comprise two or more supporting elements 3 one after the other in connection with the same formwork element 4 in a single formwork module 2.

The apparatus also comprises a driving power unit generating unit to be connected to the lifting and control actuators of the formwork modules, as well as a control device connected or to be connected to the same, for controlling the driving power generating unit (not shown in the figures). The driving power generating unit is, for example, a hydraulics aggregate operating in a way known as such, if the actuators having linear movements and used as the lifting actuator 9, the control actuator 11 , and the actuator for swivelling the side strut 14 are hydraulic cylinders. The driving power generating unit can be, for example, a separate movable aggregate which is brought by a suitable transport vehicle to the bridge construction site. On the bridge construction site, the driving power generating unit is coupled to the actuators of the formwork modules 2 (by means of hoses delivering pressurized medium, in the case of a hydraulic system). The control device can also be integrated in the driving power generating unit, or, for example, installed in connection with a single formwork module. The control device is equipped with the necessary controls for controlling the actuators of the formwork modules 2 in such a way that the formwork element 4 at the upper end of the supporting element 3 can be moved both upwards and downwards. If the control device is separate from the driving power generating unit, it is connected by suitable control connections to the driving power generating unit. In the case of electric connections, it is possible to use alternatively either wired or wireless connections. When a device according to Figs. 1 to 5 is used according to the method of the invention, the formwork modules 2 are brought to the bridge construction site by a suitable transport vehicle, such as a truck or a trailer truck. Before this, the soil 20 on the construction site has been shaped so that at the locations of the formwork modules 2 needed for building the formwork, the soil surface has been levelled, and/or sturdy formwork soles 21 with a relatively flat top surface have been formed at this location, on top of which the form- work modules 2 can be moved along the flat top surfaces of the formwork soles 21. When transported to the site, the formwork modules 2 can be loaded on the platforms of the vehicles in such a way that the frame beams 6 of their supporting elements 3 are on (or can be fastened to) the sides of the transport vehicle. Thus, when the transport vehicle is in the desired location, the lifting actuators 9 in the lower part of the frame beams 6 can be extended in such a way that the formwork modules 2 remain on the ground, supported by the supporting means 92 at the movable ends 21 of the lifting actuators 9, and the transport vehicle can be driven off from below the platform modules. With one transport vehicle, it is usually possible to transport several formwork modules 2 at a time. The use of the lifting actuators 9 requires that at least one driving power generating unit and a control device have also been transported to the site in advance. If allowed by the terrain on the construction site, such a technique can be applied to carry the formwork modules 2 by the transport vehicle directly to the erection location or at least to its immediate vicinity, wherein the distance of transferring the formwork modules 2, supported by the wheels 8 on them, to the final erection location remains short. In any case, there is at some point a need to transfer the formwork modules 2, supported by the wheels 8 on them, in such a way that they are brought adjacent to and after each other, as shown in Figs. 1 and 2, precisely to the bridge construction location and away from this location when the formwork 1 is disassembled. The next step is to hoist the formwork elements 4 of the formwork modules 2. Here, the procedure is to move the extension elements 1 by the control actuators 10 first upwards so that the extension elements 11 can be locked at a distance slightly shorter than the play of the lifting actuators 9 from the target height. After this, the position of the formwork modules 2 is checked so that the formwork 1 formed by them is safely placed in the planned location. Next, the formwork elements 4 are lifted up by the lifting actuators 9 in the lower parts of the frame beams 6 of the supporting ele- ments 2 so that the supporting means 92 at the ends of their movable heads 91 are supported to the supporting plates 22 mounted in this location to the ground as shown in Fig. 3, and the wheels 8 rise up in the air. The height is adjusted in such a way that the formwork elements 4 in the upper parts of the formwork modules 2 are aligned as accurately as possible in the height direction. After this, the edge pieces 13 of the formwork elements 4 are turned upwards by the swivelling actuators 131 in the side struts 14, and are locked in the position shown in Fig. 2. At this stage, the casting supports 18 are also adjusted in the width direction of the formwork element to the position determined by the width of the deck of the bridge to be cast, and are locked by the tilting supports 185 to the desired position (in this case, the upright position). Next, the formwork elements 4 are connected to each other by fastening the successive formwork elements 4 to each other by the fastening members 5 provided in them. The formwork structures belonging to the deck of the bridge, such as e.g. pier formworks, are assembled and mounted in the locations intended for them. The last step before casting the concrete into the formwork 1 formed of the formwork modules 2 and the formworks of the structures belonging to it is to install the reinforcements as well as the electric cables and/or pipeworks, such as rainwater sewers or the like, which should possibly be embedded in concrete. After these finishing steps, the formwork is ready for casting the concrete. The laying of concrete to the formwork 1 is performed in a way known as such, for example by means of pump trucks or the like suitable for transporting wet concrete. After the casting, the concrete is allowed to dry until a sufficient strength has been achieved, wherein the structures of the bridge withstand the removal of the framework 1. The time required for this will depend, among other things, on the type of the concrete, the temperature of ambient air, and the thicknesses of the cast structures.

When disassembling the formwork 1 around the dried concrete, the fastening members 5 between the formwork elements 4 are removed, wherein the formwork elements 4 can disengage from each other. Also, the intermediate struts 5 between the supporting elements 3 are removed at this stage. For access to the locations of joints between the formwork elements 4 when removing the fastening members 5, it is possible to use e.g. a suitable aerial work platform. After the removal of the fastening members 5, the formwork elements 4 are lowered downwards by first moving the lifting actuators 9 in the lower parts of the frame beams 6 slightly downwards so that the form- work elements 4 disengage from the surface of the dried concrete. After this, the extension elements 1 1 are unlocked and lowered to their lowermost position by the control actuators 10, wherein the formwork elements 4 of the formwork modules 2 are lowered entirely underneath the structures of the bridge. The lowering of the lifting actuators 9 is then continued until the wheels 8 at the lower end of the frame beams 6 are lowered onto the ground, wherein the formwork modules 2 are movable on their wheels again. The formworks of the piers and other structures relating to the deck of the bridge can be disassembled at a suitable stage so that they can be removed without hampering the removal of the formwork modules. Finally, the formwork modules 2 are moved on their wheels to such a location where they can be reloaded onto the transport vehicles. For the removal of the formwork modules 2, it is possible to use a suitable working machine, such as an excavator or a wheeled loader. After being loaded onto the transport vehicles, the formwork modules 2 can be transported e.g. to the construction site of the next bridge, for maintenance, or for storage. The loading of the formwork modules 2 can be performed, for example, by moving the lifting actuators 9 of the formwork modules 2 to be loaded from the inside out of the frame beams 6 so that the lowermost intermediate beams 7 of the supporting elements 3 are lifted above the platform of the transport vehicle, wherein the platform can be backed up underneath the formwork module 2. After this, the movable heads 91 of the lifting actuators 9 are moved back into the frame beam 6, wherein the formwork module 2 remains supported by its lowermost intermediate beams 7 on the platform of the transport vehicle. After carrying the framework modules 2 away, the bridge is finished by covering the deck of the bridge with surface materials, for example with waterproofing and heavy- duty pavement, as well as by mounting the railings, lighting columns and other possible supplementary parts on the bridge. In the embodiment of the apparatus shown in Figs. 1 to 5, the deck of the bridge is formed by applying two arrays of successive formwork modules 2. However, the formwork 1 can also be formed in such a way that there is only one array of successive formwork modules 2. In this case, the formwork elements are otherwise similar to those shown in the embodiment of Figs. 1 to 5, but vertical casting supports 18 are installed in both edge pieces of the formwork elements 4. Such a solution is suitable for building narrower bridges than the embodiment shown in Figs. 1 to 5, for example for a situation in which the bridge is to be constructed for a clearly narrower passage, such as a single-lane driveway, a single-track railway, or a pedestrian and bicycle way. Thus, the width of the formwork element is adjusted merely by adjusting the position of the casting supports. As the casting supports 18 at both edges of the formwork element 4 can now be adjusted, it is still possible to form a large variety of widths.

In other respects, building the bridge by applying the above-mentioned nar- rower embodiment of the apparatus is performed in the same way as when applying the embodiment shown in Figs. 1 to 5, but there will be only one supporting element 3 and one formwork element 4 in the width direction of the bridge. The disassembly and carrying away of the formwork modules 2 can also be performed in the above described way. Loading of the formwork modules 2 can also be performed, in all the embodiments, in such a way that they are lifted into the transport vehicle by e.g. a hoisting boom assembly in the transport vehicle. On the other hand, in some cases it is also possible to apply more formwork modules than two arrays next to each other. For example when building a bridge for a wide motorway, three or more formwork modules can be mounted next to each other, if necessary. When three form- work modules are used next to each other, the side edges of the edge pieces of the formwork elements in the middlemost formwork module are not provided with a casting support on either side, and the edges of the outermost formwork elements are provided with casting supports in the side edges at the outer edges of the bridge, as in the embodiment of Figs. 1 to 5. The formwork, or the formwork modules of which the formwork is to be assembled, can also be adjustable in their width in another way.

Furthermore, the method and the apparatus according to the invention can deviate from the above presented example embodiments in many respects. For example, the adjustment of the formwork modules in the height direction can be implemented in various ways by arrangements changing the height of the supporting elements. Part of the height adjustment can also be implemented by mechanical structures to be adjusted manually. In an embodi- ment, the coarse height adjustment is implemented by means of a screw or a gearwheel and a gear rack/a chain in such a way that a separate driving apparatus is connected to a screw in the frame beam or to a connecting member (e.g. an angular shaft end or the like) connected to the gearwheel when making the adjustment, and when making the adjustment the screw or gearwheel is rotated by a separate driving apparatus connected to the con- necting member in such a way that the formwork element at the upper end of the supporting element is lifted or lowered to a desired height level. Such an adjustment can also be provided instead of the lifting actuators having a linear movement in the lower parts of the supporting elements. In an embodiment, the height adjustment can be provided merely in the lower or upper part of the supporting element. Consequently, the method and the apparatus according to the invention are not restricted to the example embodiments presented above, but they may vary within the scope of the appended claims.

Claims

Claims:

1. A method for building a bridge cast on site, in which method a formwork (1 ) is formed on the construction site of the bridge, the formwork (1 ) is rein- forced, concrete is cast in the formwork (1 ), the concrete is allowed to dry, and after the drying the formwork (1 ) is removed from around the concrete structures of the bridge, characterized in that the formwork (1 ) of the bridge is formed of at least two formwork modules (2) , which modules (2) are brought to the bridge construction location, adjusted to a suitable height and connected to each other in order to construct an integralformwork (1 ).

2. The method according to claim 1 , characterized in that the after the adjustment the formwork modules (2) are locked in position and connected to each other so that after the casting of the bridge and the drying of the cast, the formwork modules (2) can be disassembled and lowered downwards by actuators for disengaging the formwork (1 ) from the dried concrete structure.

3. The method according to claim 2, characterized in that the formwork (1) is assembled from formwork modules (2) of at least two different sizes in such a way that the formworks (1 ) of different sizes are formable by applying various combinations of formwork modules (2) of different sizes.

4. The method according to claim 3, characterized in that the formwork modules (2) are transferred on wheels (8) provided on them, to be aligned in the width direction of the bridge and/or one after the other in the longitudinal direction of the bridge.

5. The method according to any of the claims 1 to 4, characterized in that the height of the formwork modules (2) is increased by lifting actuators (9) provided in them, in such a way that the wheels (8) of the formwork modules (1 ) are lifted off the ground and the formwork modules (2) come flush with the bridge to be built in such a way that they constitute a stable and uniform formwork ( ) having the size of the whole deck of the bridge.

6. An apparatus for building a bridge cast on site according to any of the preceding claims, characterized in that the apparatus comprises at least one formwork module (2) which can be adjusted by an actuator to a suitable height in the height direction and can be fastened to other formwork modules

(I ) to constitute a formwork (1 ).

7. The apparatus according to claim 6, characterized in that the formwork module (2) comprises a supporting element (3) provided in the lower part of the formwork module (2) and being adjustable in height, and a formwork element (4) in the upper part of the formwork module (2).

8. The apparatus according to claim 7, characterized in that the supporting element (3) is provided with at least one actuator (9, 10) arranged to move the formwork element (4) upwards and downwards in the height direction.

9. The apparatus according to claim 7 or 8, characterized in that the form- work element is provided with a frame element (11 ) and at least one edge piece (13) pivotally connected at its edge on the side of the frame element

(I I ) to the side edge of the frame element (11 ) and to be locked in at least one position, for adjusting the width of the formwork element (4).

10. The apparatus according to any of the claims 6 to 9, characterized in that the apparatus comprises a driving power generating unit, to be connected to the actuators (9, 11 ) of the formwork modules (2), and a control device connected to the same, for controlling the driving power generating unit.