in the stressing anchorage 1 according to fig1 each end of a prestressing element 2 , formed as strand , is led through one of the bores 3 of an anchor head 4 . anchor head 4 lies with one face 5 on a bearing plate 6 . each bore 3 of anchor head 4 has a conical extension 7 toward the second face which is turned away from bearing plate 6 . a frustoconical wedge 8 is placed in this conical extension 7 of bore 3 of anchor head 4 . frustoconical wedge 8 , which is bipartite or tripartite , and which has moreover longitudinal slots , holds the end of prestressing element 2 , formed of strands , in the prestressed position . wedge 8 is pulled via prestressing element 2 into bore 3 ; the conical extension 7 of bore 3 presses wedge 8 on prestressing strand 2 , by means of which prestressing element 2 is held . in the case presented in fig1 anchor head 4 consists of a mortar - like mass , which is hardened . since this mortar - like mass is more ductile , i . e . more workable than the steel of the frustoconical wedge 8 , the surface of extension 7 of this anchor head 4 adapts to the frustoconical surface of wedge 8 . the surface of extension 7 which accepts the frustoconical wedge 8 is impregnated , sealed or coated . the mortar - like , hardening mass can be , for example , a concrete , which has a firmness of at least 60 n / mm2 after hardening . bearing plate 6 is provided with a trumpet 9 , which is made of sheet metal or high - strength pe , and which is concreted as a unit into a part of the structure 10 . trumpet 9 , with its inner part 11 , runs into a jacket tube 12 , which is fabricated of steel or high - strength pe in the form of a corrugated pipe , in which the prestressing elements 2 are placed over the whole length of the part of the structure 10 . a spiral 13 of reinforced steel is mounted on bearing plate 6 , through which spiral the tension forces , arising from prestressing elements 2 , can be better transferred from bearing plate 6 to the part of the structure of concrete . fig2 shows a view of anchor head 4 according to fig1 . disposed distributed over anchor head 4 are several bores 3 to receive and hold prestressing elements 2 by means of frustoconical wedges 8 . here it can be seen that the frustoconical wedges 8 consist of two half shells 14 and 15 , and have in addition longitudinal slots 16 . in the upper half of the section according to fig3 shown through a bore 3 of anchor head 4 , is the position of wedge 8 before setting , and in the lower half the position of wedge 8 is shown after stressing of the prestressing elements ( not depicted ). conical extension 7 , essentially corresponding to the frustoconical form of wedge 8 , has in its end area 17 a second conical extension 18 , whose angle of opening is larger than that of conical extension 7 . in inserting wedge 8 into conical extension 7 , the surface of wedge 8 in end area 17 does not come into contact with the mortar - like mass of anchor head 4 . the depth of second conical extension 18 is selected in such a way that wedge 8 even after stressing , as shown in the lower half of fig3 still has an outside end area 19 which still lies in the area of the second conical extension so that wedge 8 in this end area 19 does not come into contact with the mortar - like mass of anchor head 4 . achieved thereby is that the edge of the bore in end area 17 remains undamaged during repeated stressing procedures of the prestressing elements during which wedge 8 is pulled at least partially out of bore 3 of anchor head 4 . fig4 shows a section through the conical extension 7 of bore 3 of anchor head 4 . the solid line 20 shows the conical extension which essentially corresponds to the frustoconical form of wedge 8 . depending upon the type of load on the prestressing elements and consequently on the frustoconical wedge 8 , cone angle α is adapted in the production of anchor head 4 with bores 3 . achieved with a smaller cone angle α , indicated by broken line 21 , is that the main load is transferred more to the rear , i . e . in the fatter area of the wedge to the clamped strand part of prestressing element 2 . this is desired in particular when the prestressing elements and consequently the wedge are subjected to a static load . achieved with a larger cone angle α , indicated by broken line 22 , is that the main stress of the load , affecting the prestressing elements , is transferred more toward the frontal area of wedge 8 to the clamped strand part of prestressing element 2 . this is especially desired when a dynamic load acts upon the prestressing elements and consequently upon the anchor head 4 . the changes in the cone angle α with respect to the frustoconical form of the wedge lie within an range of ± 1 degree . apparent from fig5 is how the main load , having an effect from the frustoconical wedge 8 upon the clamped strand part of prestressing element 2 , can be transferred distributed differently . presented here by a solid line 23 , as in fig4 is the conical extension of bore 3 of anchor head 4 which corresponds to the frustoconical form of wedge 8 . the change in the cone angle of conical extension 7 occurs outwardly starting from the middle of conical extension 7 . with a reduction of the cone angle represented by the broken line 24 , the main load is transferred from wedge 8 in the area of greater diameter to the clamped strand part of prestressing element 2 , while a smaller part of the load is conveyed from wedge 8 in the area of smaller diameter to the clamped strand part of prestressing element 2 . with an enlargement of cone angle α , represented by broken line 25 , transfer of the main load takes place from wedge 8 to the clamped strand part of prestressing element 2 in the area of the wedge having a smaller diameter . for this embodiment too , the range of change of cone angle α lies within ± 1 degree . seen in fig6 is another embodiment of anchor head 4 according to fig1 . a metallic casing designed as a ring surrounds a core 27 . core 27 consists of a mortar - like , hardened mass , for example special mortar on cement base , and has , as in fig1 bores 3 , which are provided with a conical extension 7 to receive frustoconical wedges 8 and thus to hold prestressing elements 2 . these bores 3 can be designed according to an embodiment as shown in fig3 to 5 and described above . the inner surface 28 of metallic casing 26 is conically shaped , the cone narrowing in the direction of pull of prestressing elements 2 . the mortar - like mass is poured directly as core 27 into the metallic casing 26 , which has the advantage that the inner surface 28 of metallic casing 26 has to be machined and that an optimal fit of core 27 in metallic casing 26 is achieved . pouring of the mortar - like mass into the metallic casing 26 takes place from the narrower side of the cone of the metallic casing outward . in this way the surface of core 27 , which is the visible surface in the assembled state , is flat and even with the face of the metallic casing while the inner surface of core 27 is set back from the supporting surface of the metallic casing 26 so that anchor head 4 lies only with the metallic casing on bearing plate 6 . another embodiment of anchor head 4 can be taken from fig7 . the anchor head 4 presented in fig7 has essentially the same construction as that according to fig6 . here too a metallic casing 29 in the form of a ring surrounds a core 30 , which consists of a mortar - like , hardened mass and which has bores 3 for receiving prestressing elements 2 and frustoconical wedges 8 . in contrast to the anchor head presented in fig6 the anchor head according to fig7 has a metallic casing 29 whose inner surface 31 has two conical shaped areas 32 and 33 , each of which extends conically from one face toward the central area . the mortar - like mass , which forms the core 30 , is poured into the metallic casing 29 in a way identical to that described for the anchor head presented in fig6 . through this design of the metallic casing 29 , core 30 of mortar - like mass is held optimally in metallic casing 29 . bore 3 can be made in a way such as that presented in fig3 to 5 . a further embodiment of a stressing anchorage 1 is presented in fig8 . here the bearing plate 34 consists of a metallic casing 35 , which has a ring - shaped design , and into which an insert 36 composed of mortar - like mass is inserted . this insert 36 has a cone - shaped inner surface 37 opening outwardly . inserted in the cone - shaped inner surface 37 is a trumpet - shaped transition piece 38 comprised of high - strength pe which abuts the cone - shaped inner surface 37 of insert 36 . bearing plate 34 is concreted into part of the structure 40 . inserted into the area of the trumpet - shaped transition piece 38 , which abuts cone - shaped inner surface 37 of insert 36 , is a core 41 which is composed entirely of mortar - like mass , for example concrete with a firmness of at least 60 n / mm 2 . here insert 36 acts as a load distributing and cushioning element between the abutting surfaces of the core 41 and the insert 36 . this core 41 is provided with bores 3 which can be designed in one of the ways as described under fig3 to 5 . inserted into each of the bores is a frustoconical wedge 8 , which serves to hold the prestressing element . by means of this arrangement , the connection between the stressing anchorage and the part of the structure to be prestressed becomes optimal , especially with respect to the introduction of forces in the concrete . production of this stressing anchorage is reasonable in cost due to the simple design . a further embodiment of a stressing anchorage , presented in fig9 has an insert 43 concreted into the part of the structure 42 , which in this case is composed of high - strength concrete . put into this cone - shaped insert 43 is an anchor head 44 which has a frustoconical form corresponding to the cone shape of insert 43 and which is composed of a mortar - like , hardened mass . bores 5 , which are disposed in anchor head 44 and which serve to receive the frustoconical wedges 8 for holding the prestressing elements 2 , are designed in a way described according to fig3 to 5 . used as an aid to concrete in the cone - shaped insert 43 is a body which has essentially an outer form corresponding to the inner form of the cone - shaped insert . this is done , on the one hand , for reasons of stability so that the thin - walled cone - shaped insert is not compressed , and , on the other hand , to fix the insert in an aligned position with respect to the prestressing elements 2 .