Abstract:
A method and apparatus for tensioning a staggered anchorage comprised of a plurality of tension members, which are anchored in a bore hole at various depths, thus having different free steel lengths. For each staggered anchorage, each tension member is tensioned up to a predetermined maximal load and is then subsequently adjusted to the working load. To achieve a consistent elongation reserve of the individual tension member and thus to increase the security of a staggered anchorage, the staggered anchorage is adjusted to the working load, all tension members are adjusted to a reduced elongation (ΔI w ) by a uniform elongation difference (ΔI max −ΔI w ) relative to the respective elongation (ΔI max ) of the predetermined maximal load. An arrangement for performing the method has a single tensioning plane, which is force interconnected with defined locking elements that are arranged on tension members in clamping planes.

Description:
This nonprovisional application claims priority under 35 U.S.C. § 119(a) on German Patent Application No. DE 2005 010 957.8-25, which was filed in Germany on Mar. 10, 2005, and which is herein incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method and an arrangement for tensioning a staggered anchorage. 
   2. Description of the Background Art 
   Pressure-grouted anchorages are known, for example, as ground or rock anchorages. They are generally comprised of a plurality of axis-parallel tension members of steel rods, steel wires, or steel wire strands, which are guided into a bore hole. By grouting at the furthest end of the bore hole, a grouted body is formed, which bonds the tension members with the surrounding ground for transmitting a load to the underground. The longitudinal segment of a tension member, which facilitates load transfer, is referred to as an anchorage length L tb . At their opposite end, the tension members are anchored, with the aid of anchorage wedges, in an anchorage disk, which rests on an above-ground bore hole end. During the tensioning of the pressure-grouted anchorage, the tension members in the area between the anchorage disk and the grouted body can elongate freely. Therefore, this area is also referred to as a free steel length L tf . 
   A staggered anchorage is a special embodiment of a pressure-grouted anchorage, wherein the load transmission area is not concentrated at an end of the pressure-grouted anchorage, but instead is distributed over a larger longitudinal section of the pressure-grouted anchorage. By distributing the anchorage force over an extended load transmission area, a more balanced loading into the underground takes place, thus improving the anchorage effect. The distribution of the load is achieved by utilizing tension members of varying length, the ends of which terminate at various bore hole depths. The result thereof is an axial staggering of an anchorage length L tb  in the bore hole. 
   When tensioning a pressure-grouted anchorage, industrial standards require that, for security reasons, the tension members are tensioned to a defined test load F p  before subsequently being impacted, by repeated de-tensioning and re-tensioning, with the required working load. For the tensioning operation, it is common for pressure-grouted anchorages with tension members of identical length to use a multistrand jack, whereby with one hoist of the jack, all tension members are elongated simultaneously and to the same extent. Thus, all tension members are in the same state of tension during the tensioning process. 
   In contrast, the problem with tensioning staggered anchorage is that with uniform elongation of all tension members, varying states of tension would occur due to their different free steel lengths L tf . Shorter tension members would be subjected to more stress as compared to longer tension members so that in shorter tension members, the test load F p  would already be reached at an elongation, at which longer tension members would still be far below the test load F p . 
   For this reason, staggered anchorages are tensioned with hydraulically interconnected monojacks, that is, there is one dedicated jack for each tension member, which tensions the tension member until the test load F p  is reached. As a result of the varying free steel lengths L tf  of the tension members, different elongation values are obtained. Once the test load F p  is reached, the individual tension members are adjusted to a uniform working load, that is, after the tensioning operation is completed, all tension members, regardless of their length, have the same working load. 
   The necessity to have on hand and to operate multiple monojacks, has proven to be extremely costly, both technically and economically. In addition, using multiple monojacks entails considerable expenditures for the required measuring and logging labor. Although, from a technical viewpoint, applying a uniform working load to the individual tension members helps achieve a high anchorage force, however, it has the disadvantage that in the event of unexpected elongation of the anchorage, for example, due to deformations below ground, the elongation reserves of the individual tension members are different. With tension members of shorter free steel lengths, the reserves will be used up after a short overelongation, thus running the risk that these tension members fail. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a method and an arrangement for tensioning staggered anchorages that simplifies the tensioning operation and improves the load behavior of a staggered anchorage when overelongated. 
   An embodiment of the invention provides for an adjustment of the tension members of a staggered anchorage, starting at their respective elongation at a predetermined maximal load, to the operational state of the staggered anchorage such that all tension members in the operational state are less tensioned by a uniform length value than at a predetermined maximal load. The elongation difference of the tension members between pre-tensioning at the predetermined maximal load and the working load is thus an identical value for all tension members. However, due to varying free steel lengths of the individual tension members, the uniform length alteration of the tension members leads to varying states of tension of the individual tension members at a transition to the state of operation. 
   The predetermined maximal load is thereby freely selectable in accordance with specific requirements of the respective application, and beneficially is equal to the test load F p  of the tension members to fully utilize their potential bearing capacity. 
   The great benefit derived therefrom is such that when tensioned beyond the working load until the maximum allowable load of the staggered anchorage is reached, all tension members have the same bearing reserves, irrespective of their lengths. The maximum allowable load thereby corresponds to the state of tension of the staggered anchorage, whereby all tension members are impacted with the predetermined maximum load, preferably the test load F p . Thus, a beneficial feature of a staggered anchorage of the present invention is great safety from failure. 
   The tension members of the staggered anchorage can be tensioned with monojacks to a predetermined maximum load, then de-tensioning them, either path-dependently or force-dependently. The de-tensioning of the tension members can thereby be done individually or simultaneously. Thereafter, all tension members of the staggered anchorage have a uniform load reserve. 
   Since this still requires expenditures not to be neglected when tensioning the tension members, an embodiment of the invention goes a different route. Starting with the varying free steel lengths L tf  of the individual tension members, the elongation value to reach a predetermined maximal load, preferably the test load F p , is thereby calculated for each tension member. Based thereon, all tension members are tensioned in only one tensioning plane, whereby tension members with different free steel lengths are tensioned successively and with different, previously calculated elongations until the predetermined maximum load is reached. A result of the elongation differences in the steel elongation of various tension members is that only when the predetermined maximal load is reached is the same state of tension present in all tension members at the same time. 
   The initial advantage of this method is that only one jack is needed for the tensioning operation. This can be a commercially available multistrand jack, whereby the user of a method of the present invention is merely faced with minor investment expenditures as compared to the use of monojacks. The tensioning of a staggered anchorage is limited to only one stroke and is thus quickly accomplished. Since only one jack is utilized, there is little expenditure for measuring and logging tasks. The benefit of the invention is a simple operation and quick execution of the tensioning procedure, which last but not least increases its economic efficiency. 
   After tensioning the tension members to the predetermined maximum load, the staggered anchorage is adjusted to the service load state. Again, a state is thereby generated, whereby the individual tension members are all less elongated at the identical value, as compared to the elongation under the predetermined maximal load. Thus, under the working load of the staggered anchorage, all tension members have identical elongation reserves before reaching the predetermined maximal load. If the staggered anchorage is overelongated in the service state, the anchorage force can therefore be increased without overtensioning the anchorage. The highest efficiency and thus maximum load capacity is achieved when the predetermined load is reached simultaneously in all tension members. Thus, a pretensioned staggered anchorage according to the present invention provides optimum safety from overelongation while allowing a simple and quick execution of the tensioning operation. 
   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 
     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: 
       FIG. 1   a  is a longitudinal cross section of a tensioned staggered anchorage; 
       FIG. 1   b  shows the load transfer zone of the staggered anchorage illustrated in  FIG. 1   a;    
       FIG. 2  is a longitudinal cross section of an arrangement of the present invention for tensioning the staggered anchorage illustrated in  FIG. 1 ; 
       FIGS. 3   a  and  3   b  are lateral and top views of a fixing segment of a tensioning wedge of the arrangement illustrated in  FIG. 2 , according to an embodiment of the invention; 
       FIGS. 4   a  and  4   b  are lateral and top views of a clamping segment of a tensioning wedge of the arrangement illustrated in  FIG. 2 , according to an embodiment of the invention; 
       FIGS. 5   a  and  5   b  are lateral and top views of an adjustment element for a tensioning wedge of the arrangement illustrated in  FIG. 2 , according to an embodiment of the invention; 
       FIG. 6  is a partial cross-sectional lateral view of a tensioning wedge in combination with an adjustment element according to an embodiment of the present invention; 
       FIG. 7  is a longitudinal cross section of a staggered anchorage in the area of the tensioning plane during the setup of the tensioning wedges; 
       FIG. 8  illustrates a further embodiment of an adjustment element of the present invention; and 
       FIG. 9  is a diagram of the load-elongation behavior of the individual tension members. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a ground anchorage as a staggered anchorage  1  in a service state. The staggered anchorage  1  is guided into a bore hole  2 , the top opening of which is enclosed by a base plate  3 . The base plate  3  has a central opening, through which the staggered anchorage  1  extends with its above-ground end. A longitudinal axis of the staggered anchorage  1  has the reference numeral  14 . 
   The staggered anchorage  1  includes a plurality of axis-parallel tension members  4 ,  5 , and  6 . Each tension member  4 ,  5 , and  6  has a steel wire strand  7 , which along most of its length is provided with a sheathing  8 . In contrast, the end  9  of the steel wire strand  7  assigned to the bottom of the bore hole remains bare. Due to the different lengths of the tension members  4 ,  5 , and  6 , an arrangement of the ends  9  of the steel wire strands  7  in the bore hole  2  is formed that is staggered in the longitudinal direction  14  of the staggered anchorage  1 . 
   The opposite, above-ground ends of the tension members  4 ,  5 , and  6  are threaded through bores in an anchorage disk  10 . In order to form a receptacle  11 , the bores expand conically in the direction of the open ends of the tension members  4 ,  5 , and  6 . In the receptacles  11 , three-part segment-shaped anchorage wedges  12  are arranged in a conventional fashion, which rest upon the anchorage disk  10 , thus exerting a clamping effect on the steel wire strands  7 , which causes an anchorage of the steel wire strands  7  in the anchorage disk  10 . 
   To transmit the anchorage force underground, the bore hole  2  is grouted with an injection mortar  13 . In the area of the free ends  9 , a bonding takes place of the strands  7  with the injection mortar  13  so that the anchorage force is transmitted to the walls of the bore hole  2 , and furthermore, to the surrounding ground. The area of the tension members  4 ,  5 , and  6 , which is effective in the load transfer to the underground, is referred to as anchorage length L tb . 
   In the area of the sheathing  8 , on the other hand, the sheathing  8  prevents the forming of a friction-locked bond between the strands  7  and the injection mortar  13 . Despite the injection mortar  13 , the strands  7  are quite flexibly arranged in the sheathing  8  so that in the area of the sheathing  8  no load transfer below ground takes place. The area of the free expandability of the strands  7  is referred to as a free steel length L tf , and is only shown for the tension member  6  in  FIG. 1   b.    
   As can be seen in  FIG. 1   b , with a staggered anchorage  1 , the load transfer to the underground is done in accordance with the staggered arrangement of the free ends  9  of the steel wire strands  7  in the bore hole  2 . Thus, the anchorage force is not transferred to the underground concentrated in one anchorage plane, but via a longitudinal segment that is definable by selecting the staggering of the tension members  4 ,  5 , and  6 , which in the instant embodiment is three times the anchorage length L tb . 
     FIG. 2  shows a longitudinal cross section of an arrangement for tensioning the staggered anchorage  1  described in  FIG. 1 . On the right side of the illustration, the above-ground end of the staggered anchorage  1 , including base plate  3 , anchorage disk  10 , and anchorage wedges  12  can be seen. At the time the staggered anchorage  1  is being tensioned, the strands  7  of the tension members  4 ,  5 , and  6 , do not yet terminate behind the anchorage wedges  12  (see  FIG. 1 ) but extend in the longitudinal axis  14  of the staggered anchorage  1  to allow the setup of a tensioning arrangement. 
   The tensioning arrangement illustrated in  FIG. 2  also includes a multistrand jack  15  having a cylinder  16 , which is oriented in the longitudinal axis  14  of the anchorage and forms a housing of the multistrand jack  15 , and a piston  17  that is slidably arranged inside the cylinder. For easier handling, the cylinder  16  is provided with handles  18 . The piston  17  has a central passage for the strands  7  of the tension members  4 ,  5 , and  6 . 
     FIG. 2  shows the multistrand jack  15  in an initial position for the tensioning operation, whereby the piston  17  is completely retracted in the cylinder  16 . To tension the staggered anchorage  1 , the piston  17  is extended. The tensioning path followed by the piston  17  thereby defines a tensioning axis  26  as well as a tension direction  27 . 
   At the bore-hole side, the multistrand jack  15  rests on a hollow cylindrical component  19 , the purpose of which is to retain the anchorage wedges  12  in the receptacles  11  of the anchorage disk  10  during the tensioning of the tension members  4 ,  5 , and  6 . The component  19  is therefor positioned on the anchorage disk  10 , and is thus force-transmittingly inserted between the multistrand jack  15  and the anchorage disk  10 . The retaining of the anchorage wedges  12  is done by wedge retaining disk  20 , which seals the face side of component  19 . During the test procedure, when the tension members  4 ,  5 ,  6 , are being detensioned, it moves with the anchorage wedges  12 . Only after the last detensioning operation and prior to the retensioning of the tension members  4 ,  5 ,  6 , to the working load F w  is the wedge retaining plate  20  fixed in the component  19 . 
   At its free end, the piston  17  carries a clamping plate  21 , which also has the shape of a perforated disk and in design is almost identical to the anchorage disk  10 . Thus, the clamping plate  21  has passage bores, which expand conically towards its face side  23  to form receptacles  22 . Running through each receptacle  22  is the bare strand  7  of tension members  4 ,  5 , and  6 , thus extending beyond the face side  23  of the clamping plate  21  with its free end. 
   On the projecting ends of the strands  7 , locking elements in form of clamping wedges  25  are mounted, which serve the purpose of fixing the strands  7  into place against the clamping plate  21  in a tension direction  27  for the tensioning operation. This is done by wedging the strands  7  in with a clamping wedge  25 , which in turn rests on the walls of the receptacle  22  of the clamping plate  21 . The clamping force is transmitted across the entire length of the clamping wedge  25  into the strands  7 . However, to simplify the appreciation of the invention, henceforth, the clamping force is reduced to an idealized clamping plane A, B, C, which is oriented radially to the tensioning axis  26  and is clamping wedge-specific. 
   As can be seen in  FIG. 2 , prior to tensioning, the clamping wedges  25  are in a staggered arrangement in the tensioning direction  26 . The clamping wedge  25  for the strand  7  of tension member  4  thus defines the clamping plane A, the clamping wedge  25  for the strand  7  of tension member  5  defines the clamping plane B, and the clamping wedge  25  for strand  7  of the shortest tension member  6  defines the clamping plane C. In  FIG. 2 , the distance of clamping plane B to clamping plane A is referenced as ΔI 1 , the distance of clamping plane C to clamping plane A is referenced as ΔI 2 . 
   In contrast thereto, referred to as tensioning plane  24  is the plane that extends radially to the tensioning axis  26 , which, during the tensioning procedure of the staggered anchorage  1 , moves in tensioning direction  27 , thus transferring the tensioning force to the tension members  4 ,  5 ,  6 . Consequently, an impacting of a strand  7 , and thus a tension member  4 ,  5 ,  6 , with tensioning force, does not occur until the tensioning plane  24  is congruent with one of clamping planes A, B, C. 
   In the example embodiment, the clamping plate  21  embodies the tensioning plane  24 . The tensioning plane  24  and one of clamping planes A, B, C. are congruent as soon as the clamping wedge  25  is firmly positioned in the receptacle  22  of clamping plate  21 . This state is illustrated in  FIG. 2  for tension member  4 . In addition, as a result of the geometric adaptation of the receptacles  22  of clamping plate  21  to the geometry of the clamping wedges  25 , the tensioning plane  24  is located in a plane of a side face  23  of the clamping plate  21 . 
   The function of the described arrangement as well as the procedure of the tensioning operation will be explained in more detail below with reference to  FIG. 9 . 
   The more detailed construction of the clamping wedge  25  of the tensioning arrangement is shown in its entirety in  FIG. 6 , and its individual components in  FIGS. 3   a ,  3   b ,  4   a ,  4   b .  FIGS. 3   a  and  3   b  illustrate the fixing segment  30  of the clamping wedge  25  in plan and top view. The fixing segment  30  is formed by a thick-walled hollow cylinder  31 , in the lower region of the outer shell of which an annular slot  32  is milled in. In this way, an annular flange  33  is formed on the lower front face, which features an outer diameter that is smaller than that of the hollow cylinder  31 . Half-way up the fixing segment  30 , there is also a threaded bore  34  extending radially through the cylinder walls, which serves as a receptacle for a stud screw  35  ( FIG. 6 ). 
   In the operational state, the fixing segment  30  is axially united with the clamping segment  36  illustrated in  FIGS. 4   a  and  4   b , to form a complete clamping wedge  25  according to the invention. The clamping segment  36  is essentially comprised of three identical wedge segments  37 , which, assembled cylindrically, have the shape of a truncated cone with axial passage bores. To improve the transfer of the clamping force, the walls of the passage bores have a profiled surface. On their outer periphery, the segments  37  are provided with an annular slot  38 , in which an annular spring  39  is arranged that holds the three segments  37  together. 
   A further feature of the invention is that in the thick-walled area, the segments  37  extend axially with a constant thickness to mutually form a connecting shaft  42 . In this area, the segments  37  are provided with an interior annular slot  40  so that an annular flange  41  ( FIG. 6 ) is formed at a face-side end of the connecting shaft  42 . 
   In  FIG. 6 , a complete clamping wedge  25  is illustrated, partly in lateral view, partly in longitudinal view. It can be seen how a form-fitting connection is formed by positioning the fixing segment  30  and the clamping segment  36  side-by-side axially, whereby the annular flanges  33  and  41  engage with the annular slots  32  and  38 , respectively, for forming a gearing. 
   In the longitudinal axis of the clamping wedge  25 , the fixing segment  30  and the clamping segment  36  form a continuous hollow cavity so that an axial sliding of the clamping wedge  25  onto the open end of strand  7  (only indicated with dotted lines in  FIG. 6 ) is possible. When the stud screw  35  is screwed in, it penetrates the continuous hollow cavity, thereby encountering the strand  7  extending therein. Thus, by using the set screw  35 , it is possible to fix the fixing segment  30 , and thereby the entire clamping wedge  25 , into place against the strand  7 . 
   Because the clamping wedges  25  define the clamping planes A, B, C, it is essential for the invention that the clamping wedges  25  are attached on the strands  7  in their proper position. For their proper position, the previously calculated axial distance ΔI in between the clamping wedges  25  is relevant. The axial distance ΔI between the clamping wedges  25  and the tension members  4 ,  5 , or  6 , according to the invention, respectively equals the difference of the elongations of the individual tension members when the predetermined ultimate load is applied to each tension member, relative to their untensioned initial state. This elongation difference ΔI can be mathematically calculated if the free steel length L tf  and the predetermined maximal load, or the test load F p , are known. 
   To set up the clamping wedges  25  on the strands  7  of the tension members  4 ,  5 , and  6  at the correct mutual distance in accordance with the invention, a mutual reference plane is beneficial, whereby its axial distance to the individual clamping planes A, B, C, are determined, and from there, the clamping planes A, B, C. are measured in. 
   In the example embodiment, the side face  23  of the clamping plate  21 , which represents the tensioning plane  24 , at the same time, serves as the reference plane. Because the clamping wedge  25  of the tension member  4  is firmly seated in the receptacle  22  of the clamping plate  21 , its clamping plane A is already located in the tensioning plane  24 , and thus in the reference plane. Therefore, only the distances ΔI 1  from the reference plane to the clamping plane B of the clamping wedge  25  of the tension member  5 , and ΔI 2  from the reference plane to the clamping plane C of the clamping wedge  25  of tension member  6  still have to be measured in. 
   For this process, the adjustment element  45  illustrated in  FIGS. 5   a  and  b  is particularly well suited, the application of which according to the invention is shown in  FIGS. 6 and 7 . The adjustment element  45  is essentially comprised of a ring wheel  46 , which in diameter and size corresponds to the passage opening of fixing segment  30 . On the outer periphery of ring wheel  46 , a screw nut  47  is mounted, through which a threaded rod  48  can be threaded perpendicularly to the plane of a ring wheel  46 . The position of the threaded rod  48  relative to the ring wheel  46  can be fixed by using a counternut  49 . At the top end of the threaded rod  48 , a capped nut  50  is attached. Preferably, a dedicated adjustment element  45  is kept ready for each clamping wedge  25  to be set up. 
   The application of the adjustment element  45  becomes obvious from  FIGS. 6 and 7 . Because with its upper side, a clamping wedge  25  extends beyond the clamping plane A, B, C, by the known wedge-specific value p, and the adjusting elements  45 , together with the bottom side of the ring wheel  46 , form a contact surface with upper side of the clamping wedges  25 , the threaded rod  48  of each adjustment element  45  is initially adjusted to the required projection P 1,2 +ΔI 1,2  relative to the bottom side of the ring wheel  46  (see  FIG. 6 ). ΔI 1,2  equals the previously calculated value, by which the shorter tension members  5  and  6  are less elongated as compared to the longest tension member  4  so that when the predetermined maximal load is reached, all tension members  4 ,  5 , and  6  are in the same state of tension. 
   The thusly predefined adjustment elements  45  are pushed, together with the clamping wedges  25 , onto the ends of the strands  7  of tension members  5  and  6 , in a way as is illustrated in  FIG. 7 , until each threaded rod  48  runs against the side face  23  of the clamping plate  21 . This generates the distance ΔI 1,2  in between the clamping planes A, B, C, in accordance with the invention. 
   By fastening the stud screw  35 , the clamping wedges  25  are fixed into this position on the strands  7 . Subsequently, the adjustment elements  45  can be removed from the strands  7 . The state achieved in this way corresponds to the initial state illustrated in  FIG. 2  prior to the activation of the multistrand jack  15 . 
   An alternative embodiment of an adjustment element  52  of the present invention is illustrated in  FIG. 8 . There, a ringwheel-shaped basic component  53  is illustrated, which is provided with passage bores corresponding to the number and arrangement of tension members  4 ,  5 ,  6 . On their inner shell surface, the bores are provided with internal threads, which are not visible due to the view of the illustration chosen. 
   Through each of the bores, a distance sleeve  54  extends, the outer shell of which is provided with an external thread  55  corresponding to the internal thread. In this way, the distance sleeves  54  can be screwed into the passage bores of the basic component  53 . By screwing the distance sleeves  54  into the basic component  53  at varying degrees, the position of the free end of the distance sleeves  54  can be adjusted. A counternut  56  screwed onto the distance sleeve  54  and resting on the basic component  53  fixes the location of the distance sleeve  54  into the adjusted position. 
   In this way, the distance sleeves  54  are adjusted in their mutual position such that their free ends are arranged at the distances of clamping planes A, B, C, whereby the distance sleeves  54  with the longest projections from the basic component  53  are assigned to the tension members  4 ,  5 , with longer free steel lengths L tf , and the distance sleeves  54  with shorter projections from basic component  53  are assigned to tension members  5 ,  6  with shorter free steel lengths L tf . 
   The intended application of such an adjustment element  52  takes place after the locking elements, that is, in the instant example, the clamping wedges  25  comprised of clamping segment  36  and fixing segment  30 , have been pushed onto the individual strands  7 . Subsequently, the free ends of strands  7  of the individual tension members  4 ,  5 ,  6 , are threaded one by one through their dedicated distance sleeves  54 , and the adjustment element  52  as a unit is slid onto the strands  7  in the direction of the clamping plate  21 . Little by little, the individual clamping wedges  25  thereby come to butt against the free ends of the distance sleeves  54  with the result that a distance of the clamping wedges  25  corresponding to the distance in between the clamping planes A, B, C, is generated. 
   In order to keep the elongation path as short as possible, it is beneficial for the adjustment element  52  to be slid onto the staggered anchorage  1  such as needed to enable the distance sleeve  54  with the longest projection beyond the basic component  53  to push the clamping wedge  25  on the tension member  4 ,  5  with the longest free steel length L tf  into the corresponding receptacle  22  in the clamping plate  21 . The staggered arrangement in a longitudinal direction of the remaining clamping wedges  25  on the tension members  5 ,  6 , with shorter free steel lengths L tf  thereby comes about automatically. 
   The tensioning operation is described in more detail therebelow with reference to  FIGS. 2 and 9 . When the piston  17  is extended from the multistrand jack  15 , the clamping plate  21  is moved along the tensioning axis  26  in the direction of arrow  27 . Because the clamping wedges  25  on the strands  7  of the longest tension members  4  are already firmly seated in the receptacle  22  of clamping plate  21 , the tensioning plane  24  is located in clamping plane A. By extending piston  17 , a linearly increasing load is generated in tension member  4 . The behavior of the load corresponds to line a illustrated in  FIG. 9 . 
   After reaching a tensioning value of ΔI 1 , the tensioning plane  24  arrives at a position that is congruent with that of clamping plane B, that is, the clamping wedges  25  on the strand  7  of the second-longest tension member  5  are seated with utmost precision in the receptacles  22 . By extending the piston  17  even more, the two tension members  4  and  5  are now elongated, whereby the load in tension member  4  is further increased and a load with the behavior b is initiated in tension member  5 . 
   With further tensioning of the staggered anchorage  1 , the tensioning plane  24 , after covering the tensioning path ΔI 2 , reaches the area of clamping plane C, and thus the clamping wedges  25  on the strands  7  of the shortest tension member  6  wind up in the receptacles  22 . By further extending the cylinder  17  to a maximum tensioning path ΔI 1 , all tension members are now impacted with the predetermined maximum load. The tensioning behavior of the tension member  6  has the reference symbol c. 
   As can be seen in  FIG. 9 , the load increase in the individual tension members  4 ,  5 , and  6  at constant elongation is the steeper, the shorter its free steel length L tf  is. For this reason, shorter tension members have a tensioning behavior with a steeper incline. The distance ΔI 1  of clamping plane A from B as well as the distance ΔI 2  of clamping plane A from C is chosen such, taking into consideration the respective free steel lengths L tf , that with increasing tensioning values, the stress diffusions a, b, c, converge such that in the individual tension members  4 ,  5 , and  6 , the predetermined maximum load, preferably the test load F p , is reached simultaneously. 
   By subsequent detensioning of the staggered anchorage  1  by retracting the piston  17  by the value ΔI max −ΔI w , or by retracting the piston  17  and subsequent retensioning of the tension members  4 ,  5 ,  6 , by the value ΔI w , the individual tension members  4 ,  5 , and  6  are adjusted to the working load F w  of the staggered anchorage  1 . The arrival at the working load F w  can then be indicated by the corresponding pressure or stroke of the jack. In this state, longer tension members are more tensioned than shorter tension members ( FIG. 9 ). The result is a uniform elongation reserve for all tension members  4 ,  5 ,  6 , of the staggered anchorage  1 , namely ΔI max −ΔI w . 
   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.