US3209508A

US3209508A - Device for installing and removing truss frames, girders, and the like

Info

Publication number: US3209508A
Application number: US189481A
Authority: US
Inventors: Hunnebeck Emil Mauritz
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-04-27
Filing date: 1962-04-23
Publication date: 1965-10-05
Anticipated expiration: 1982-10-05
Also published as: FR1320609A; GB1006667A; CH395163A; AT238756B; DE1434341A1

Description

Oct. 5, 1965 E. M. HUNNEBECK 3,209,508

DEVICE FOR INSTALLING AND REMOVING TRUSS FRAMES, GIRDERS, AND THE LIKE Filed April 25, 1962 3 Sheets-Sheet 1 I FIG. 5 1 Y 22 MAM/70E err/4 mum/i2 Jinn/86m er A/ar 1965 E. M. HUNNEBECK 3,209,503

DEVICE FOR INSTALLING AND REMOVING TRUSS FRAMES, GIRDERS, AND THE LIKE Filed April 25, 1962 a Sheets-Sheet 2 FIG. 6

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Oct. 1965 E. M. HUNNEBECK 3,209,508

DEVICE FOR INSTALLING AND REMOVING TRUSS FRAMES, GIRDERS, AND THE LIKE Filed April 23, 1962 3 Sheets-Sheet 3 FIG. 9 FIG. 70

m'meyag United States Patent H ,43 12 Claims. (Cl. "52-632) The present invention relates to a device for the installation and removal of truss frames, girders, or the like either of a straight or arched shape and either with or Without a lower trussing, and especially of such truss frames or girders which are assembled of several structural units and may be used either directly for the construction of bridges, removable hangars, or other larger buildings, or as supporting means in the construction of bridges, underpasses, and the like of reinforced concrete. More particularly, the invention relates to a device which is connected to an end support of such a truss frame or girder and consists of a bearing unit for such an end support which is composed of several members and provided with a bearing member which is adjustable so as to permit the distance between its bearing point, for example, on a stationary abutment, and the truss frame itself to be varied. Such devices are used for solving many of the difiiculties occurring when mounting or seating a truss frame and also when removing it.

In the art of truss frames, girders, or the like, it is known to provide such frames with end supports forming bearing elements which are adapted to be telescoped into the upper booms of the frame in order to vary the total length of the structure and are to be locked in the adjusted position. These end supports are usually also connected to the lower boom of the truss frame by means of inclined rods or bars which may likewise be adjustable in length. These prior bearing elements do, however, not permit the truss frame to be accurately leveled and they cause considerable difficulties when the frame is to be lowered under a load, for example, when it is used for supporting a concrete bridge during its construction and when after the concrete has set, the truss frame is to be lowered under the weight of the concrete and is then to be disassembled or shifted laterally to another part of the structure to be erected, for example, to another lane of the bridge to be built.

There are other known constructions of end supports for truss frames or girders, the bearing elements of which are removable. These bearing elements are sometimes designed so as to be adjustable in height in order to permit the truss frame to be leveled or to be removed under a load. Such bearing elements are, however, very expensive and also require special means in the event that the abutment on which the truss frame is to be supported does not extend vertically to the longitudinal direction of the truss frame as is the case, for example, in inclined bridges.

In the erection of steel concrete structures, the supporting truss frame or girder which is first required therefor is elastically bent when the load of the concrete structure is applied thereon. At the subsequent removal of such a frame, it is therefore necessary to lower the same to such an extent that it will be free of stresses so that the transverse fiexure of the truss frame which is caused by the load thereon is eliminated since it is otherwise not possible to remove the frame. In the known truss structures this is accomplished by the operation of a large number of turnbuckles. When the truss frame is to be used again after it has been lowered and shifted laterally, all of the turnbuckles must again be reset to their original positions in order to return the truss frame to its proper ice shape. This obviously requires a great length of time and also involves the danger that the truss frame may not regain exactly its original shape.

This procedure is especially difiicult if the truss frame is assembled of a plurality of structure units and provided with a trussing underneath it. Such truss frames are statically uncertain since the necessary adjustment of the various turnbuckles produces internal stresses in the frame which cannot be controlled. Even such constructions in which the compression rods of a trussing are adjustable in length so as to permit the truss frame to be adjusted to a super-elevation thereof and also to permit the truss frame to be lowered when it is to be removed from the concrete structure which it has supported while being built, do not facilitate the above-mentioned procedure since not only these turnbuckles, but also those of the lower booms of the truss frame must be loosened and.

again be tightened to the exact original setting after the truss frame has been shifted.

There are also end elements known for truss frames which serve as horizontal form supports or the like, each of which consists of upper tension and compression rods which are arranged in a triangular formation and in which the upper end of the compression rod is butt-jointed to the upper boom of the truss frame, while the lower end of this compression rod is flexibly connected by a turnbuckle to the lower boom of the truss frame. By means of this turnbuckle it is impossible to lower the entire truss frame in a continuous movement since the compression rod of the triangular end element is butt-jointed to the upper boom of the truss frame. Apart from this, such an end element is rather expensive since it is made of four parts.

It is an object of the present invention to overcome the above-mentioned deficiencies by providing a device of the type as described at the beginning which is designed so as to permit the end or bearing unit which is connected to the upper boom of the truss frame to be pivoted relative to this upper boom within the plane of the truss frame and also relative to the bearing plate.

It is also advisable in the structure according to the invention to provide the end unit which may be connected to the upper boom of the truss frame so as to be adjustable in length and in a manner so that the joint which connects the upper and lower parts of this end unit to each other as well as the joint which connects the upper part to the truss frame are both provided on an upper part of the end unit and both end units are adjustable relative to each other in various adjusted positions.

The lower part of the device according to the invention which is connected to the compression area of the truss frame and usually comprises a turnbuckle should be designed so as to permit the end unit to be adjustable to a sufficient length. At any horizontal adjustment of the bearing member of theend unit, this member should be pivotable upwardly at least to the extent to the flexure of the truss frame when it is subjected to a full load, and downwardly to approximately one half the height of the truss frame and at least to one half the height of the associated end girder. This permits not only a proper lowering of the truss frame when not under stress, but when using an arched truss frame it also permits by means of lowlying bearing elements a transmission of the reactionary bearing force to the neutral axes of the truss frame. For carrying out the lifting and lowering adjustments of the truss frame it is therefore merely necessary to vary the length of the lower part of the device according to the invention which may be called a bearing end unit. It is therefore no longer necessary to loosen the turnbuckles which are provided in the lower boom of the truss frame and in the trussing underneath the latter. It is also no longer difiicult to shift such truss frames latea ally to a new position and it is therefore now possible by means of one or several truss frames first to encase and build, for example, one lane of a bridge and then to shift the frame or frames laterally for also building the other lane. The present invention also permits hounches to be encased without additional means. A further advantage of the invention is that it facilitates considerably the removal of arched truss frames after building concrete structures since prior to this invention and arched truss frame required the operation of additional means for relieving it of stresses in order to permit its removal. The device according to the invention permits the bearing members to be drawn inwardly by reducing the length of the lower parts of the end unit so that the truss frame will then disengage from the encased concrete structure after it has set. The flexible connection of the lower part of the end unit to the upper part thereof is preferably designed so as to lie within the point of intersection of the neutral axes of both parts, and it is then very advisable to insure that this point of intersection lies above the point of engagement of the bearing force so that a plane extending in the direction of the latter intersects with the point of intersection of the neutral axes of the two parts of the end unit. By means of such an arrangement it is possible to avoid any additional bending stresses in both the upper and lower parts of the end unit.

According to the invention, it is further advisable to provide the free end of the upper part of the end unit with a rounded bearing member which is adapted to rest on a plate which, in turn, is rested on an abutment. The pivoting movement of the upper part of the end unit for raising and lowering the truss frame results in a horizontal movement of the free end of this upper part. If the bearing member is made of a rounded shape, it will be able to roll over the bearing plate and will thus facilitate the horizontal movement. The rounded bearing member is preferably provided with a bore or an elongated aperture or the like through which a pin is inserted which is prevented from becoming entirely disconnected from the bearing member and the end unit by being provided on its upper end above the bearing member with a disk, while the lower end of this connecting pin is secured to the bearing plate. In this manner, the bearing plate is irremovably connected to the bearing member, although it permits the plate to be shifted and turned relative to the bearing member. By being able to turn this hearing plate relative to the bearing member the advantage is attained that the plate may also be mounted on an abutment at an inclination to the plane of the truss frame, for example, for the erection of a bridge which extends at an angle. Finally, it is also advisable that the bearing plate is made adjustable in the longitudinal direction of the truss frame.

The objects, features, and advantages of the present invention will become more clearly apparent from the following detailed description of several preferred embodiments thereof which is to be read with reference to the accompanying drawings, in which FIGURE 1 shows a diagrammatic side view of a truss frame which is composed of several structural elements and is provided with a trussing and with two of the devices according to the invention for raising and lowering the truss frame which is herein shown in a raised position;

FIGURE 2 shows the truss frame according to FIG- URE l in an intermediate position;

FIGURE 3 shows the truss frame according to FIG-

URES

1 and 2 in a lowered position;

FIGURE 4 shows the truss frame according to FIG- URE 2 in a position in which only one end of the frame is lowered;

FIGURE 5 shows a detail side view of one of the de vices according to the invention which is connected to an end girder of a truss frame which is composed of 4 several parts and is partly shown in the same position as in FIGURE 2;

FIGURE 6 shows a side view similar to that of FIG- URE 5 but of a modification of the device according to the invention in connection with a truss frame;

FIGURE 7 shows a plan view of the device and the truss frame according to FIGURE 6;

FIGURE 8 shows an enlarged side view, partly in section of the device according to FIGURE 6, but without the lower part of the end unit;

FIGURE 9 shows a side view of a further modification of a part of the device according to the invention;

FIGURE 10 shows a cross section taken along line XX of FIGURE 9;

FIGURE 11 shows a side view of a part of an arched truss frame with the device according to the invention; while FIGURE 12 shows a side view of still another modification of the invention.

The truss frame or girder as illustrated in FIGURES 1 to 4 consists of two structural elements or units which as seen in a side view, form trapezoids with equal upper and lower sides and of two structural elements 2 which in a side view have substantially the shape of parallelograms and form the end girders of the truss frame. The upper booms 3 and '4 of

units

1 and 2 are connected to each other in a conventional manner by means of bolts 5 or the like, while the

lower booms

6 and 7 are indirectly connected by means of turnbuckles 8. By tightening the turnbuckles 8, the truss frame which is composed of four structural units may be given the required superelevation. The truss frame is trussed at the lower side by tension rods 9 of a constant length, tension rods 9' which may be adjusted in length by means of a turnbuckle 11, and compression rods 10 and 10'. The tension rods are pivotably connected to each other and the two outer tension rods 9 are in addition pivotably connected to the lower booms 7 of the end supports 2. The

compression rods

10 and 10 are pivotably connected to the tension rods and also to the upper booms of the

structural units

1 and 2. The entire framework which is preferably superelevated in order to compensate for the load which it has to take up, for example, in the construction of a concrete bridge constitutes a unit which is rigid in itself.

The upper members 13 of the bearing device according to the invention which is capable of being raised or low ered are pivotably connected to the upper booms 4 of the end girders 2 by means of bolts 12 or the like. This upper member 13 may consist either of one or two parts. Thus, for example, in the case of the truss frame according to FIGURE 5 it is assumed that this upper member 13 consists of two parts which are slidable relative to each other and may be locked to each other in the particular adjusted position by a bolt 14 or the like, while in the case according to FIGURES 6 and 7 it is assumed that each upper member 13 consists of only one piece, even though it may be composed of several rigidly connected parts. A number of apertures 15 and 16 as shown in FIGURE 5, or 17 as shown in FIGURE 6 permit the upper member of the bearing unit to be adjusted in length.

The lower boom 6 of each end support 2 has a turnbuckle 18 pivotably connected thereto which serves as the lower member of the bearing unit. The joint is formed by a bolt 19 or the like which may also serve at the same time for securing a tension rod 9 if the truss frame is to be provided with a lower trussing. The other end of each trunbuckle 18 is pivotably connected by means of a bolt 20 or the like to the associated upper member 13, that is, in the embodiment according to FIGURE 5 at a point vertically above the point where the reactive bearing force A engages. In the embodiment according to FIGURE 6, the pivot point is spaced from the bearing point and the turnbuckle 18 on the lower boom is connected by a bolt 21 or the like to the upper member 13.

The neutral axes of the mentioned part are indicated at 13 and 18'.

In both embodiments according to FIGURES 5 and 6, the outer end of each upper member 13 is rigidly secured to a

rounded bearing member

22 or 22, respectively. As illustrated particularly by the bearing member 22' in FIGURES 7 and 8, each bearing member 22 or 22' is provided with a bore or elongated aperture 23 through which a pin 24 passes, the lower end of which is secured to a plate 25, for example, by being screwed therein, while its upper end is rigidly secured to a disk 26 which prevents the bearing plate 25 from falling off the upper member 13 when the latter is raised. Plate 25 which is adapted to rest on an abutment 27 and is slidable relative thereto is in this manner not only fixed in position relative to the upper member 13 but can also be turned relative to the bearing member and the truss frame. Since when the truss frame is lifted, each bearing member will shift from the position as shown in FIGURE 2 to the position as shown in FIGURE 1 or when the truss frame is lowered from the position according to FIGURE 2 to the position according to FIGURE 3 or FIGURE 4, the elongated aperture 23 extends in the direction of the plane of the framework. The distance 1 between the bearing points of the super-elevated framework therefore changes, and it decreases by the amount of A1 or A1 if only one end of the framework is lowered or raised. In order to show this more clearly, it is indicated in dotted lines in FIGURES 1, 3, and 4 not only in which position the upper and lower members of the bearing unit will be when the truss frame is neither raised nor lowered, that is, when they will be in the position according to FIG- URE 2, but it is also indicated in FIGURE 6 in dot-anddash lines in which positions the bearing member will be after the frame has been raised and lowered. In order to illustrate the horizontal displacement of the bearing member as clearly as possible, it has been assumed in FIGURE 6 that the truss frame is stationary and the bearing member 22 together with the bearing plate 25 and the abutment 27 are raised or lowered. It may be clearly seen from FIGURE 6 that by reducing the distance between the connecting points of turnbuckles 18, the truss frame may be raised relative to the stationary abutment 27, while by increasing the distance between the connecting points of turnbuckles 18, the truss frame may be lowered from the position as shown in full lines. The change in span in the first case is indicated in FIGURE 6 as amounting to A1, and in the second case to A1 The movement of the bearing member 22 which corresponds to the change in length Al or A1 is made possible by the elongated aperture 23 or the like which lies within the perpendicular plane of the truss frame.

As indicated in FIGURE 4, it is not even necessary to change the setting of the two turnbuckles 18. The raising and lowering of the truss frame can therefore be carried out not only quite easily and simply, but also very quickly and without changing the shape of the truss frame itself.

A modification of the bearing member which is secured to the upper member 13 is illustrated in FIGURES 9 to 11. The curved surface 28 of the rounded bearing member 22' according to FIGURE 8 is in this case subdivided into two surfaces 28' which are spaced at a distance e from each other and extend upwardly approximately to the upper edge 29 of the upper member 13 of the bearing unit. Each of these surfaces 28' of the bearing member 22 forms the outer surface of one curved web of an L-shaped section member, the other web of which is secured to the upper member 13. The inner surfaces of the two webs of the L-shaped section members which extend parallel to the curved surfaces 28' are partly covered by but spaced from a mushroom-shaped hollow member 30 which is secured to plate 25', for example, by being welded thereto. This permits a truss frame which is provided with at least one end bearing unit con- -member 22 which is pivotably secured to the upper member 13.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1. A device for installing and removing a truss frame having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit composed of two members, a bearing plate adapted to be rested on a stationary support, means pivotally connecting one of said members to one end of the upper boom of said truss frame and to said bearing plate so as to be pivotable relative to and within the plane of said frame and relative to said bearing plate, said one member comprising several parts, and means for adjusting said parts relative to each other to vary the total length of said one member.

2. A device for installing and removing a truss frame having upper and lower booms and used in the construction of bridges, removable hangar-like structures or the like, said device comprising at least one end bearing unit composed of two members, a bearing plate adapted to be rested on a stationary support, and means pivotally connecting one of said members to one end of the upper boom of said truss frame so as to be pivotable relative to said frame and Within the plane of said frame and means connecting said one of said members to said bearing plate so as to be rockable relative thereto, said means pivotally connecting comprising a pivot element at one end of said one member, the other of said two members comprising a lengthwise adjustable member pivotally connected at one end to said one member, pivot connecting means connecting the other end of said adjustable member to the end of the lower boom of said truss frame and means including said adjustable member for causing movement of said one of said members about said pivot element and rockable movement on said plate to effectuate movement of said truss frame in said plane.

3. A device for installing and removing a truss frame having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit, having an upper member and a lower member, a bearing plate, means pivotally connecting said upper member to one end of the upper boom of said truss frame and to said bearing plate so as to be pivotable relative to and within the plane of said frame and relative to said bearing plate, means pivotably connecting said lower member to the lower boom of said truss frame, and means for increasing the length of said lower member and thereby causing pivotal movement of said upper member to such an extent that, when said bearing plate is rested on the upper surface of said support, the truss frame may be lowered relative to said surface at least for a distance equal to the flexure of the truss frame when said frame is subjected to a maximum load.

4. A device for installing and removing a truss frame having upper and lower booms used in the construction of bridges, removable hangarlike structures or the like,

said device comprising at least one end bearing unit, having an upper member and a lower member, a bearing plate, means pivotally connecting said upper member to one end of the upper boom of said truss frame and to said bearing plate so as to be pivotable relative to and within the plane of said frame and relative to said bearing plate, means pivotably connecting said lower member to the lower boom of said truss frame, and means for reducing the length of said lower member to cause pivoting of said upper member on said one end of said upper boom to such an extent that, when said bearing plate is rested on the upper surface of a stationary support, said upper surface will be disposed substantially at a level even with the center of the height of the adjacent end of said truss frame.

5. A device for installing and removing a truss frame having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit, having an upper member and a lower member, a bearing plate, means pivotally connecting said upper member to one end of the upper boom of said truss frame and to said bearing plate so as to be pivotable relative to and within the plane of said frame and relative to said bearing plate, means pivotably connecting said lower member to the lower boom of said truss frame, means for varying the length of said upper and lower members, and means for pivotably connecting said upper and lower members to each other substantially at the point of intersection of the neutral axes of said members.

6. A device for installing and removing a truss frame having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit, having an upper member and a lower member, a bearing plate, means pivotally connecting said upper member to one end of the upper boom of said truss frame and to said bearing plate so as to be pivotable relative to and within the plane of said frame and relative to said bearing plate, means pivotably connecting said lower member to the lower boom of said truss frame, means for varying the length of said upper and lower members, and means for pivotably connecting said upper and lower members to each other substantially at the point of intersection of the neutral axes of said members, said point of intersection being disposed within a plane higher than the plane within which the reactive bearing force acts upon said bearing plate when resting on said support.

7. A device for installing and removing a truss frame, having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit composed of several members, means pivotably connecting one end of one of said members to one end of the upper boom of said truss frame, a bearing member connected to the other end of said member and having a rounded outer surface, a bearing plate adapted to be rested on a stationary support, and means connecting said bearing member to said bearing plate in a manner so as to permit said bearing member to rest with its rounded surface on said bearing plate and to roll along said bearing plate when said member of said bearing unit and said bearing plate are pivoted relative to each other, said means connecting said bearing member to said bearing plate comprising a member fastened to said plate and movably connected to said bearing member.

8. A device for installing and removing a truss frame, having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit composed of several members, means pivotably connecting one end of one of said members to one end of the upper boom of said truss frame, a bearing member connected to the other end of said member and having a rounded outer surface, a bearing plate adapted to be rested on a stationary support, and means connecting said bearing member to said bearing plate in a manner so as to permit said bearing member to rest with its rounded surface on said bearing plate and to roll along said bearing plate when said member of said bearing unit and said bearing plate are pivoted relative to each other, and also to permit said bearing member and said bearing plate to pivot relative to each other about an axis extending vertically to the upper surface of said plate, said means connecting said bearing member to said bearing plate comprising a pin member extending loosely through said bearing member and secured to said plate.

9. A device for installing and removing a truss frame having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit composed of several members, means pivotably connecting one end of one of said members to one end of the upper boom of said truss frame, a bearing plate adapted to be rested on a stationary support, and means connecting said bearing plate to the other end of said member so that said plate and said member are pivotable relative to each other and said plate is also adjustable in the longitudinal direction of said truss frame, said means connecting said bearing plate to the other end of said member comprising adjustable pin and slot means.

10. A device for installing and removing a truss frame, having upper and lower booms and used in the construction of bridges, removable hangarlike structures or the like, said device comprising at least one end bearing unit composed of several members, means pivotably connecting one end of one of said members to one end of the upper boom of said truss frame, a bearing member connected to the other end of said member and having a rounded outer surface, a bearing plate adapted to be rested on a stationary support, and means loosely but irremovably connecting said bearing member to said bearing plate in a manner so as to permit said bearing member to rest with its rounded surface on said bearing plate and to roll along said bearing plate when said member of said bearing unit and said bearing plate are pivoted relative to each other.

11. A device for installing and removing a truss frame, having upper and lower booms and used for the construction of bridges, removable hangarlike structures or the like or as supporting means when building bridges or other structures of concrete and comprising at least one end bearing unit composed of several members, means for pivotably connecting one end of one of said members to one end of the upper boom of said truss frame, a hearing member connected to the other end of said member and having a rounded lower surface and an aperture extending through said bearing member substantially radially to said rounded surface, a bearing plate adapted to be rested on a stationary support, and a rod-shaped member secured at one end to said plate and having a diameter smaller than said aperture and extending loosely through said aperture, and a stop member secured to the other end of said rod and spaced from and located above the upper surface of said bearing member when said bearing member rests on said plate and having a larger diameter than said aperture.

12. A device for installing and removing a truss frame, having upper and lower booms and used for the construction of bridges, removable hangarlike structures or the like or as supporting means when building bridges or other structures of concrete and comprising at least one end bearing unit composed of several members, means for pivotably connecting one end of one of said members to one end of the upper boom of said truss frame, a bearing member connected to the other end of said member and having a rounded lower surface and an aperture extending through said bearing member substantially radially to said rounded surface and being elongated with its longitudinal axis extending in the direction of said truss frame, a bearing plate adapted to be rested on a station- References Cited by the Examiner ary support, and a rod-shaped member secured at one UNITED STATES PATENTS end to said plate and extending loosely through Said 2 9 5 2 4 5 1 Leonard 189 37 aperture, and a stop member secured to the other end of 5 3,029,913 4/62 Liesenfeld 189-37 said rod and spaced from and located above the upper FOREIGN PATENTS surface of said bearing member when said bearing mem- 1,029,850 5/58 G ber rests on said plate and having a diameter larger than RICHARD W, COOKE, JR., Primary Examiner. e width of said aperture 10 JACOB L. NACKENOFF, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,209,508 October 5, 1965 Emil Mauritz Hunnebeck It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, line 3, for "Tirol, Austria read Schloss Klamm, Post Obsteig, Tirol, Austria in the heading to the printed specification, line 4, for "Schlob Klamm" read Schloss Klamm Signed and sealed this 23rd day of August 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. A DEVICE FOR INSTALLING AND REMOVING A TRUSS FRAME HAVING UPPER AND LOWER BOOMS AND USED IN THE CONSTRUCTION OFO BRIDGES, REMOVABLE HANGARLIKE STRUCTURES OR THE LIKE, SAID DEVICE COMPRISING AT LEAST ONE END BEARING UNIT COMPOSED OF TWO MEMBERS, A BEARING PLATE ADAPTED TO BE RESTED ON A STATIONARY SUPPORT, MEANS PIVOTALLY CONNECTING ONE OF SAID MEMBERS TO ONE END OF THE UPPER BOOM OF SAID TRUSS FRAME AND TO SAID BEARING PLATE SO AS TO BE PIVOTABLE RELATIVE TO AND WITHIN THE PLANE OF SAID FRAME AND RELATIVE TO SAID BEARING PLATE, SAID ONE MEMBER COMPRISING SEVERAL PARTS, AND MEANS FOR ADJUSTING SAID PARTS RELATIVE TO EACH OTHER TO VARY THE TOTAL LENGTH OF SAID ONE MEMBER.