Method for erecting a suspension bridge and device therefor

The present invention relates to a method for mounting prefabricated deck sections of a suspension bridge wherein deck sections positioned below the suspension cables of the suspension bridge essentially at surface level (ground or sea level) are lifted consecutively to their respective final elevated position in which position hangers depending from the suspension cables are secured to the lifted deck section and the latter is at least provisionally connected to the adjacent deck section previously mounted.

Methods of this type are generally known. FR-A-2580687 discloses such a method in which the deck sections are lifted by cranes travelling on the suspension cables of the suspension bridge. Furthermore it is known to lift the deck sections by means of winches winding on lifting wires deflected at trolleys travelling on the suspension cables; the winches are located on the ground (WO 91/08344, Fig. 1). Furthermore the deck sections may be lifted by means of a floating crane (WO 91/08344, Fig. 2). WO 91/08344 finally discloses a method for lifting a deck section wherein lifting device yokes are secured to the deck sections while corresponding lifting wire yokes are secured to the hangers depending from the suspension cables; each lifting device yoke comprises two lifting devices, and lifting wires are secured to the lifting wire yokes (Fig. 16). The disclosure is silent about the question how to secure the lifting wire yokes to the hangers; apparently they are mounted at the hangers before the latter are secured to the suspension cables.

The above mentioned method employing a floating crane is very expensive where very heavy prefabricated deck sections shall be mounted due to the enormous costs for a suited floating crane. The method employing winches located on the ground is costly due to the requirement for very long lifting wires. The method using lifting cranes requires corresponding long wires to secure the cranes in their position. The last mentioned method employing lifting cable yokes at the hangers and lifting device yokes at the deck sections is very costly as well since a proper lifting wire yoke is required for each hanger; a further shortcoming is that the freely dangling lifting wires not in use may damage each other. A shortcoming common to all prior art methods is that they are very time consuming; this is since the deck sections must be lifted very slowly otherwise the lifted deck section could clash with the adjacent one.

It is an object of the present invention to provide for a method for mounting prefabricated deck sections of a suspension bridge which method allows the mounting of very heavy deck sections rapidly and at low costs.

In accordance with the present invention this object is solved in that a lifting device platform is employed which platform during each lifting step is supported by the hangers to be fixed to the deck section to be lifted momentarily and is advanced between two successive lifting steps from a position above the deck section just mounted to a position above the adjacent deck section to be lifted next. The lifting devices are provided at the lifting device platform. The lifting device platform during each lifting step is immediately secured to hangers relating to the deck section to be lifted. After the hangers have been secured to the deck section after it has been brought into its final elevated position the lifting device platform is detached from the hangers such that it may be advanced to its next position where it is secured to the hangers again.

The inventive method is applicable for all known types of suspension bridges independently whether each deck section is supported by two hangers, four hangers, two pairs of hangers, four pairs of hangers or the like.

Preferably the lifting device platform, during each lifting step, is connected to the deck section mounted in the foregoing step. Together with the lifting device section the lifting devices mounted thereon may be very accurately positioned in this instance. This allows by a very simple way an exact positioning of the deck section to be lifted with respect to the adjacent deck section already mounted. Thus lifting of the deck sections may be accelerated since there is no risk that the two adjacent deck sections clash with one another and damage each other while one of them is lifted. The fact that relatively short lifting wires may be employed in the inventive method as compared with prior art methods contributes to reduce the tendency of the deck section to be lifted to swing.

A lifting device platform to be employed in the inventive method comprises at least one longitudinal beam and at least one transversal beam displacably connected to the longitudinal beam(s) wherein the transversal beam(s) are adapted to extend between two opposing hangers (pairs of hangers) and are provided at each extremity with at least one lifting device as well as fixing means to secure said extremity to the respective hanger(s). The displaceable connection between the at least one longitudinal beam and the transversal beam(s) allows that they may be advanced independently; the at least one longitudinal beam may be advanced while the transversal beams are secured to the hangers or rest on the deck section respectively, and the transversal beams may be advanced to the next hangers travelling along the at least one longitudinal beam while the latter is fixed to the deck section just mounted for example by means of auxiliary beams. The advantages of such construction of the lifting device platform will become more apparent from the description of the drawings annexed hereto.

Where the deck sections are supported by four hangers or pairs of hangers respectively the lifting device platform comprises at least two transversal beams.

Preferably the fixing means to secure the transversal beams to the respective hangers are provided at end portions of the transversal beams which are moveable with respect to center portions of the transversal beams. In particular the end portions of the transversal beams may be hingedly connected to their respective center portions. This allows that the end portions of the transversal beams may be displaced such that the transversal beams may be advanced between two opposing hangers (pairs of hangers) without interfering with the latter after they have been secured to the lifted deck section. In another embodiment the end portions are telescopically fixed to the center portions of the transversal beams.

In a preferred embodiment of the inventive lifting device platform the fixing means comprise tubes which are composed of two half-shells clamped together so as to enclose the lower ends of the respective hangers and to rest on the hanger heads. Such tubes allow in particular that the hanger heads may be inserted through bores into the inner of the deck section where they may be secured to the deck section.

When a suspension bridge having hangers by pairs shall be erected the lifting devices are preferably located intermediate between a pair of tubes adapted to be fixed to the pair of hangers as setforth above. The tubes of each pair of tubes are connected with each other and finally with the transversal beam by means of a stiff connecting member at which the lifting device may be mounted. Such a construction avoids the risk that the equipment overturns under the load of the deck section.

If the suspension bridge to be erected comprises single hangers instead of pairs of them preferebly two lifting devices are provided adjacent each hanger in a symmetrical configuration.

Further aspects of the present invention as well as their various benefits will become more clear from the subsequent description which refers to the drawing illustrating a preferred embodiment of the invention.

Fig. 1 shows a suspension bridge to be erected wherein two deck sections are just to be lifted.

Fig. 2-6 illustrate subsequent steps of advancement of the lifting device platform between two sucessive lifting steps of the inventive method.

Fig. 7 is a cross sectional view of a preferred lifting device platform and the deck section to be lifted.

Fig. 8 shows a detail of the lifting device platform according to fig. 7.

Fig. 9 is a view similar to fig. 7 but shows the deck section in its entirely lifted position after the hangers have been secured to the deck section and after the transversal beams have been prepared for being advanced.

Fig. 10 shows a detail of fig. 9.

Fig. 11 and 12 illustrate a preferred embodiment of the fixing means to secure the transversal beams to the hangers.

Fig. 13 is a schematic perspective view illustrating a preferred general design of the lifting device platform of the invention.

The suspension bridge according to fig. 1 comprises two pylons 1 over which two suspension cables 2 are stretched. Hangers 3 depend from the suspension cables 2. Every mounted deck section 5b, 5c is supported by four hangers 3.

A platform 4 is supported by the hangers 3a, 3b belonging to the deck section 5a to be lifted. The platform 4 is secured to the deck section 5b adjacent to the deck section 5a to be lifted.

The platform 4 comprises two longitudinal beams 6 and two transversal beams 7a, 7b. The transversal beams 7a, 7b are displaceably connected to the longitudinal beams 6 such that they may be displaced with respect to the longitudinal beams in the longitudinal direction of the latter. At each extremity of the transversal beams 7a, 7b lifting devices are provided pulling lifting wires 8 secured to the deck section 5a to be lifted.

The lifting device platform and its function is explained in Fig. 2-6 in greater detail. Fig. 2 shows the deck section 5b mounted previously; the pairs of hangers 3c, 3d are secured to the deck section 5b at their lower extremities after termination of the previous lifting step. Now (fig. 3), the longitudinal beams 6 are advanced by being displaced on the transversal beams 7a, 7b which remain for the present in their position. Together with the longitudinal beams 6 the rear auxiliary ballasted beam 10 is advanced. After that, the transversal beams 7a, 7b are advanced to the free end of the deck section 5b mounted previously and an auxiliary support 9 is installed; then the longitudinal beams 6 (self-launching) again are advanced (fig. 4) together with the rear auxiliary beam while the transversal beams 7a, 7b and the auxiliary support 9 are kept in their position. Now (fig. 5) the transversal beams 7a, 7b are advanced travelling along the longitudinal beams 6 from which they depend while the latter rest on the auxiliary support 9 and the auxiliary beam 10; to compensate for the weight of the transversal beams 7a, 7b the auxiliary beam 10 is provided with a counterweight 11. When the transversal beam 7b reaches the next pair of hangers 3b it is secured to the latter as described in greater detail below; it is also secured by wires 25 to the deck section 5b previously mounted. Now (fig. 6) the auxiliary support 9 is advanced to the end of the deck section 5b previously mounted and is secured in this position; then the longitudinal beams 6 together with the auxiliary beam 10 are advanced until the transversal beam 7a located at their front end reaches the pairs of hangers 3a. The auxiliary beam 10 is secured to the previously mounted deck section and the transversal beam 7a is secured to the pairs of hangers 3a. Now, the lifting wires 8 depending from the lifting devices may be secured to the deck section to be lifted and the lifting devices provided at the extremities of each transversal beam 7a, 7b may lift the deck section 5a by means of the lifting wires 8. During the lifting step the lifting device platform remains connected to the deck section 5b mounted previously by the auxiliary support 9 and the auxiliary beam 10.

According to fig. 7-10 the longitudinal beams 6 as well as the transversal beams 7a, 7b are designed in a lightweight framework construction. Each transversal beam 7 consists from a center portion 12 and two end portions 13 hingedly connected to the ends of the center portion. The end portions 13 may pivot about horizontal axes 14 for a reason as setforth below. A box girder 22 is provided at each end portion 13 of each transversal beam. A pair of tubes 16 is secured to each other by a clamping member 15 which is welded to the corresponding box girder 22. The tubes 16 surround the respective hangers and rest on the hanger heads 17. A lifting device 18 is provided on each box girder 22; it is located intermediate between the two hangers of a pair of them. The lifting wires 8 secured to the deck section 5a are pulled upwardly by said lifting devices 18.

Fig. 8 shows the design of the extremities of the transversal beams in greater detail. It additionally illustrates the roller guide equipment 19 which allows the longitudinal beams 6 and the transversal beams 7 to be displaced with respect to each other in longitudinal direction of the longitudinal beams 6. Furthermore may be seen a roller equipment 20 provided at the bottom of the transversal beams 7 in order to allow to advance them on the surface of the deck section mounted previously (cf. fig. 2-6).

Fig. 8 furthermore shows that the tubes 16 are of a smaller diameter than the heads 17 of the hangers 3 such that the tubes 16 do not hinder to insert the lower extremities of the hangers into corresponding bores in the deck section. The heads 17 of the hangers are provided with a screw thread such that the hangers may be secured to the respective deck section by nuts.

When the hangers are secured to the lifted deck section the fixing means with which the transversal beams are secured to the hangers are removed. For this purpose the lifting wires are detached from the deck section. Then the lifting devices 18 are removed from the box girders 22. Then the clamping members and the box girders welded thereto (cf. fig. 11 and 12) are opened to allow the tubes 16 to be disassembled into their half-shells. After the fixing means have been removed from the end portions 13, the latter are pivoted about the axes 14 into an upright position (fig. 9 and 10). When both end portions are pivoted in their upright position the total length of the transversal beams 7 is less than the distance between two opposing pairs of hangers 3. Thus the transversal beams may be advanced between the hangers. When the transversal beams 7a, 7b are advanced to their next position they are firstly supported by the roller equipment 20 on the surface of the deck section just mounted and then they depend from the longitudinal beams with which they are connected by means of roller guide equipment 19 (cf. fig. 2-6).

Fig. 11-12 illustrate the fixing means which are intended to secure the transversal beams 7 to the pair of hangers 3. A pair of tubes 16 consisting of two half-shells (cf. fig. 12) surrounds the lower extremities of the hangers 3 and rests on their heads 17. The half-shells of each tube are secured to each other by means of a plurality of bolts. The clamping member 15 consisting from two similar parts is provided at the upper ends of the tubes 6. Both parts of the clamping member 15 are clamped together by means of bolts 21. The box girder 22 consisting of two similar parts being welded to the parts of the clamping member 15 is secured to the end section 13 of the transversal beam by means of bolts 23 such that when the bolts 21 and 23 are tight, it is possible to achieve a very stiff connection between the tubes 16 and the transversal beam itself. The box girder 22 as well as the clamping member 15 have a central bore to allow the lifting wire to penetrate these members intermediate between the hangers. On its upper surface the box girder 22 is provided with a seat 24 for mounting of the lifting device 18.

According to fig. 13 the lifting device platform 4 adapted to mount deck sections 5 supported by four pairs of hangers 3 comprises two transversal beams 7 and two longitudinal beams 6. The lifting devices are arranged at the ends of the respective transversal beams such that the lifting wires 8 extend intermediate between the hanger heads 17 of each pair of them.