Abstract:
A corrosion-resistant tension member, particularly an inclined cable of a cable stayed bridge, is comprised of a bundle of individual elements, for example, steel wire strands, which in its open area is encapsulated by sheathing, and which within the structure extends inside a guide canal that is formed by a recess pipe. The sheathing—sealing off the front side of the guide canal—is thereby directly or indirectly connected to the structure. Between the sheathing and the entrance point of the tension member into the structure, a connecting pipe is arranged, which on the one hand is detachably connected to the sheathing and on the other hand is connected to the structure by a flange plate.

Description:
[0001]     This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. DE 20 2004 008 621.2 filed in Germany on Jun. 1, 2004, which is herein incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention is directed to the construction of a corrosion-resistant tension member in an area where it enters a structure, particularly an inclined cable at a pylon of a cable-stayed bridge.  
         [0004]     2. Description of the Background Art  
         [0005]     It is known with cable stayed bridges to load-transmittingly connect inclined cables with a pylon, with the inclined cables extending at an angle to one another and with which the roadway pillar is stayed against the pylon and which are primarily comprised of a bundle of individual elements, for example, steel wire strands. This for one can be accomplished with the stays coming from different directions all converging to the pylon there to be anchored, at times in a crisscross fashion; this requires a plurality of anchoring devices. Another option is to run the stays over the pylon in a saddle-like fashion, whereby the load-bearing forces extending at a right angle to the stay cable axis are transferred via the saddle to the pylon.  
         [0006]     If such an inclined cable is damaged, for example, by the presence of corrosion on the steel tension members, it must be possible to replace such an inclined cable. In a conventional solution, a saddle-shaped canal is formed in the pylon for this purpose, into each of which one inclined cable can be inserted (DE 88 10 423 U). The lower area of the canal is comprised of a half tube forming a support trough with a saddle bearing at the vertex, where a saddle pipe sheathing the bundle of individual tension members in this area can be locked into place to avoid longitudinal offset. This is done with a bearing sleeve that is arranged in the vertex of the reversing point along the support trough, which is fitted with a bearing ring that is attached to the saddle pipe.  
         [0007]     For stabilization purposes and to bond the individual tension members of the bundle with the saddle pipe, the remaining interstices are filled with a hardening material, for example, cement mortar. To improve the adhesion to the hardening material, the tension members, that is, for example, the steel wire strands, can preferably be roughened by sandblasting, at least in the area of the vertex.  
         [0008]     In the conventional solution, the saddle pipe is directly connected with the sheathing of the bundle in the open area of the inclined cable outside the pylon by flange rings. As a result, the canal formed in the pylon, which must have a relatively large diameter, at least a greater height than the diameter of the bundle to make it possible to replace the bundle with the saddle pipe, is open on the front entry and/or exit point of the inclined cable. This opening is a disadvantage, because it is exposed to environmental influences and accessible to animals, particularly birds, which can cause dirt buildups and corrosion.  
       SUMMARY OF THE INVENTION  
       [0009]     It is therefore an object of the present invention to provide a simple and economical method, which also foremost takes statical requirements into consideration, to close the openings in the guide canal for the inclined cable of a cable stayed bridge without compromising the conditions for the exchangeability of the inclined cable.  
         [0010]     Essentially, the invention is based on the idea that with a tension member of the previously described kind, particularly with stay cable of a cable stayed bridge, the transition from the sheathing in the open area of the tension member to its connection to the structure, in the case of a cable stayed bridge to the pylon, is accomplished via a connecting pipe, which on the one hand can be tightly connected to the structure, for example, via a flange plate, and on the other hand can be connected to the sheathing in the open area such that a future replacement of the inclined cable is not impeded. By adding an elastic intermediate layer in the area of this connection, a tolerance adjustment can be achieved, and angle movements due to traffic loads, wind action, or the like and, to a certain degree, temperature-induced movements can be absorbed so that bending moments need not be considered in the construction. The result is a simple and economical solution for the connection of the sheathing of an inclined cable to the structure with advantages with regard to construction and installation and to a potentially required replacement of the inclined cable.  
         [0011]     It is irrelevant for the application of the invention whether the tension member, particularly the inclined cable, is in the process of being inserted and anchored in the pylon, or whether it is rerouted thereupon via a stay saddle.  
         [0012]     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:  
         [0014]      FIG. 1  is a vertical cross section of a connecting point of a sheathing of a tension member according to the present invention, illustrating an inclined cable, which is rerouted on a pylon via a cable saddle, in the area of its entrance into the construction;  
         [0015]      FIG. 2  is a cross section of the sheathing along the line II-II in  FIG. 1 ;  
         [0016]      FIG. 3  is a cross section of the sheathing along the line III-III in  FIG. 1 ;  
         [0017]      FIG. 4  is the detail IV in  FIG. 1  at a larger scale;  
         [0018]      FIG. 5  is the detail V in  FIG. 4  at a larger scale; and  
         [0019]      FIGS. 6 and 7  illustrate further embodiments of the connection according to  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]      FIG. 1  illustrates an embodiment of the invention in a vertical cross section, showing an inclined cable  1  that is rerouted on a pylon  2  made of steel-reinforced concrete. The inclined cable  1  is comprised of a bundle  3  of individual tension members like steel wires, steel rods, or steel strands, which in their open areas are arranged inside a sheathing  4 , for example, a pipe sheath made of PE (polyethylene).  
         [0021]     In the pylon  2 , a saddle-shaped canal  6  having an oval cross section, an open front side, and a radius R, into which the inclined cable  1  can be inserted from the outside in, is formed by a recess pipe  5 . In the area of its passage through the pylon  2 , the bundle  3  itself, is also guided in a steel saddle pipe  7  in the shape of a circular arc, inside of which the individual tension members of the bundle  3  are bonded with the saddle pipe  7  by grouting mortar  8 .  
         [0022]     In the vertex area  9  of the rerouting point, a recessed saddle bearing  10  with a recess  11  is located, with which a cleat  12  that is firmly attached to the saddle pipe  7  by welding, for example, engages. This type of anchoring, while allowing complete exchangeability of the stay cable  1 , reliably ensures the prevention of longitudinal movements during the installation of the inclined cable and at the same time allows the absorption of differential forces that occur in the longitudinal direction of the inclined cable  1 . During the replacement process, this construction allows for the entire inclined cable  1  to be lifted with the saddle pipe  7  until the cleat  12  disengages from the recess  11 ; the oval shape of the recess pipe  5  ( FIG. 3 ) leaves enough upper space to do this. Thereafter, the inclined cable  1  with the saddle pipe  7  along the circular bend of the rerouting area per radius R can be pulled from the canal  6 . A new stay cable can be installed by reversing the steps.  
         [0023]     The construction of the connection of the sheathing  4  of the inclined cable  1  to the structure, namely to the pylon  2 , according to the present invention, in a way that the canal  6 , which is formed by the recess pipe  5 , is closed on the front side, is illustrated in FIGS.  2  to  5 .  
         [0024]     As is shown in  FIG. 1 , a connecting pipe  14 , which is made of steel, is located between the sheathing  4  of the inclined cable  1  in the open area and the outer wall  13  of the pylon  2 , which is detachably connected to the sheathing  4  on the one hand and with the pylon  2  on the other hand. In order to overcome potential diameter differences more easily, a transition pipe  15  can be arranged between the sheathing  4  in the normal area and the connecting pipe  14 , which, like the sheathing  4 , is most often made of plastic, particularly of PE.  FIG. 2  shows a cross section along the line II-II of the transition pipe  15 . The diameter difference between the sheathing  4  in the open area of the inclined cable  1  and the transition pipe  15  can be compensated for by a transition piece  15   a.    
         [0025]     As can be particularly seen in  FIG. 4 , which shows an enlarged illustration of the detail IV of  FIG. 1 , the connecting pipe  14  has a flange plate  16  on the end facing the structure.  
         [0026]     This flange plate  16  can have a rectangular shape since the oval opening of the recess pipe  5  has to be covered ( FIG. 3 ). The flange plate  16  is detachably connectable to the structure  2  by a screw connection  17 , for example, opposite a concrete-cast anchor plate  18 . The anchor plate  18  conforms to the flange plate  16 , at least in its peripheral shape. The flange plate  16  also takes into account the transition from the oval diameter of the recess pipe  5  to the circular diameter of the inclined cable  1 , illustrated by the cross section of the connecting pipe  14  and that of the saddle pipe  7 . An illustration of the bundle  3  comprised of the individual tension members was omitted in  FIGS. 2 and 3  for reasons of clarity.  
         [0027]      FIG. 4  also shows the construction of the inclined cable  1  in the area of its exit from the pylon  2 . It can be seen how the individual elements of the bundle  3 , which in the area of the saddle pipe  7  are bare, that is, not sheathed, but are individually sheathed for corrosion protection in the open area of the inclined cable  1 , for example, strands  19  with PE sheathings  20 , make the tangential transition from the circular direction inside the saddle pipe  7  to the straight direction in the open area of the inclined cable  1 . This transition can be roughly localized at the exit of the inclined cable  1  from the pylon  2  in the area of line III-III in  FIG. 1 . It is beneficial to extend the length of the circular saddle pipe  7  along the radius R beyond this point to ensure that the end  21  of the saddle pipe  7  is sufficiently spaced apart from the bundle  3  in a radial direction, particularly in its lower area.  
         [0028]     In order to achieve a constant soft redirecting of the bundle  3  in this area, particularly with lateral angle deviations, which can be easily determined on site, a cushioning element  22  that is made of an elastic and/or ductile material can be arranged at the at the inner wall of the end  21  of the saddle pipe  7 . In its most simple form, this cushioning element  22  can be a piece of pipe; however, it can also be a molded part having an inner contour with rounded edges that is adapted to the behavior of the bundle  3 , as illustrated in  FIG. 4 . It is beneficial to extend this cushioning element  22  beyond the end  21  of the saddle pipe  7  to always ensure a soft support for the bundle  3  there.  
         [0029]     In order to be able to fill the complete area of the saddle pipe  7  with grouting mortar  8 , a formwork pipe (not shown) can be temporarily put over the end  21  of the saddle pipe  7 , which is sealed off against the saddle pipe  7  by a seal. After the front opening of the formwork pipe is sealed off, the entire cavity can be grouted. The formwork pipe with the lid to seal the front opening could be removed again after the grouting mortar  8  had hardened.  
         [0030]     The detachable connection between the connecting pipe  14  and the sheathing  4 , in this embodiment the transition pipe  15 , is illustrated in  FIG. 5  as detail V of  FIG. 4  at a larger scale. On its sheathing end, the connecting pipe  14  has an inner flange  23 , to which an outer flange  24  of the transition pipe  15  abuts from the outside. The outer flange  24  can be welded to the end of the PE transition pipe  15 . The friction-locked connection between the transition pipe  15  and the connecting pipe  14  is ensured by an axis-parallel screw connection  25 , which acts against a loose flange ring  26 . The installation of the sheathing is considerably simplified by the flange ring  26 , which can be attached from the outside. The force of the screw connection bears on the welded-on PE flange  24  via a ring  27  that is made of an elastic material, for example, rubber or plastic; in this way, constraint tensions due potentially occurring angle errors or movements are avoided and the registration of bending moments is minimized. Furthermore, a softer transmission of stress on the screw connection  25  due to pipe oscillations is thereby achieved.  
         [0031]     Whereas in the illustrated embodiment in  FIG. 5  the axial screw connection  25  is performed via axial bores  25   a  in the outer wall of the connecting pipe  14 , which is thicker in this area, a different embodiment is illustrated in  FIG. 6 . In  FIG. 6 , the connecting pipe  14  has, apart from the inner flange  23 , an outer flange  28  at its end, which is provided with bores for threading the screws for the screw connection  25 . This embodiment also has a ring  27  made of an elastic material to compensate for possible angle errors and movements, the ring being arranged between the loose flange ring  29  abutting from the outside and the end flange  24  of the transition pipe  15 .  
         [0032]     The inner flange  23 , which is illustrated in  FIGS. 5 and 6  as a one-piece unit with the steel connecting pipe  14 , can also be developed as a separate unit, for example, a steel ring  30  with bolts  31 , which can be loosened from the outside, for an abutment. In certain instances, this steel ring  30  can also be entirely omitted because the transition pipe  15 , which is connected to the sheathing  4 , is already pulled against the screw connection  25  by its own weight. As a result, segments of the connecting pipe  14  can be easily opened from the outside for inspection.  
         [0033]     It is obvious that the above-described embodiment of the sheathing connection of an inclined cable to the structure can be applied not only when the stay cable is rerouted in the structure, namely the pylon, as is illustrated, but as a matter of course also when the inclined cable is guided straight into the structure to be anchored there in a conventional way. When the inclined cable is guided straight into the structure, in other words, when it is in a concentric position in the recess pipe, the flange plate  16  abutting to the structure can also be a flange ring.  
         [0034]     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.