US2079095A - Bridge construction - Google Patents

Description

May @19 E. M. WICHERT BRIDGE GONSI'RUGTION Filed June 15, 1954 8 Sheets-Sheet l y 1937; E. M. WICHERT BRIDGE CONSTRUCTION a Sheet-Sheet 2 Filed Juhe 15, 1934 km IIIIIII'II MAYA, 1937. E. M. wlcl-lsl r BRIDGE CONSTRUCTION Filed June 15, 1934 8 Sheets-Sheet 3 wN wM E. M. WICHERT 2,079,095

BRIDGE CONSTRUCTION May 4, 1937.

Filed June 15, 1934 a sheets-sheet 4 l lllll'llll w Hm m W% Mm .D m B May 4, 1937.

Filed June 15, 1934 8 Sheets-Sheet 5 May 4, l937 E. M. WICHERT 2,079,095

BRIDGE CONSTRUCTION Filed June 15, 1954 s Sfieets-Shet 6- INVENTOR May 4, 1937; M. WICHERT Q,

BRIDGE CONSTRUCTION Filed June 15, 1934 8 Sheets-Sheet 8 a w 3 W ra E v r 1,. \3

INVENTOR Patented May 4, 1937 UNiTED STS 1 1T FFICE BRIDGE CONSTRUCTION Application June 15,1934, Serial No. 730,757

10 Claims.

This invention relates broadly to bridge construction, and more particularly to the construction of non-rigid continuous bridges. It relates still more particularly to the construction of 5 bridges employing the now well known Wichert truss such as are described and claimed in my United States Reissue Letters PatentNo. 18,973, reissued October 24, 1933. The present invention has to do primarily with methods of constructing or erecting non-rigid continuous bridges and structures useful in the erection of such bridges.

The invention will be described as applied to and embodied in the construction of bridges employing the Wichert truss. Such bridges may take a variety of specific forms, and only a few of such forms have been selected for the. purpose of illustrating the present invention.

The Wichert bridge is a non-rigid continuous bridge having certain advantages described in my reissue patent above referred to, among which are the properties of being automatically adjustable. and statically determinate. However, certain problems arise in the erection of such bridges, which are particularly acute where high intermediate spans are employed or where intermediate spans pass over deep water, highways, railroads, etc. Ordinary methods of construction would require that such spans be built substantially entirely on falsework, but the provision of falsework for intermediate spans under conditions such as those mentioned wouldbe diflicult or impossible in many cases and would at least unduly increase the cost of construction. However, as a non-rigid continuous bridge cannot be constructed as such by the cantilever method, the diificulties incident to economical erection have presented a serious problem,

My invention provides a method whereby nonrigid continuous, bridges can be initially erected as rigid bridges and thereafter rendered nonrigid. This greatly simplifies the erection problem. For example, it makes it possible to erect intermediate spans without the use of falsework. The usual cantilever method may be employed,

the bridgework being rendered rigid during erection and thereafter being rendered non-rigid.

For the purpose of rendering non-rigid continuous bridgework temporarily rigid during erection various means may be employed. For ex- 1;.- non-rigid continuous characteristics. Oneor more such members may be used to render temporarily rigid the normally non-rigid quadrilateral of a Wichert truss over an intermediate pier or support.

Other details, objects and advantages of the invention will become apparent as the following description of certain present preferred embodiments thereof proceeds.

In the accompanying drawings I have shown, purely for the purpose of illustration, certain present preferred embodiments of the invention, in which Figure 1 is a diagrammatic elevational view of a portion of a Wichert truss bridge showing the application of a horizontal erection member across the quadrilateral over an intermediate pier;

Figure 2 is a diagrammatic elevational view of a portion of a Wichert truss bridge showing the application of a vertical erection member across the quadrilateral over an intermediate pier, and also showing a modified type of support;

Figure 3 is a diagrammatic elevational view of a portion of a Wichert truss bridge showing the application of both horizontal and vertical erection members across the quadrilateral over an intermediate pier, and also showing a further modified type of support;

Figure 4 is a diagrammatic elevational view of a portion of a Wichert truss bridge of the tower type showing the application of a vertical erection member below the quadrilateral over an intermediate pier;

Figure 5 is a vertical transverse cross sectional view taken on the line VV of Figure 4 and to enlarged scale;

Figure 6 is a diagrammatic elevational View of a portion of a Wichert truss bridge of the tower type showing the application of a horizontal erection member across the quadrilateral over an intermediate pier;

Figure '7 is a diagrammatic elevational view of a, portion of a Wichert truss bridge of the tower type showing the application of a vertical erection member across the quadrilateral over an intermediate pier;

Figure 8 is a diagrammatic elevational view of a portion of a Wichert truss bridge of the tower type showing the application of both horizontal and verticalerection members across the quadrilateral over an intermediate pier;

Figure 9 is a, diagrammatic elevational View of three spans of a Wichert truss bridge illustrat- Figure is a vertical transverse cross-sectional view taken on the line XVXV of Figure 13;

Figure 16 is a detail elevational view showing the construction and application of a vertical erection member;

Figure 17 is an elevational view, partly in vertical transverse cross section, of a portion of the construction shown in Figure 16;

Figure 18 is a detail elevational view showing the construction and application of horizontal and vertical erection members in combination;

Figure 19 is a detail elevational view showing the construction and application of a vertical erection member below the quadrilateral;

Figure 20 is a detail elevational view illustrating a further method of erection;

Figure 21 is a detail plan view of a portion of the construction shown in Figure 20;

Figures 22, 23, 24 and 25 are diagrams illustrating a method of erection;

Figures 26 and 27 are, respectively, detail elevational views of mechanism adapted for use in the method of erection illustrated in Figures 20 to 25, inclusive; and

Figure 28 is a horizontal cross-sectional view taken on the'line XXVIIIXXVIII of Figure 2'7 and to enlarged scale.

Referring now more particularly to the drawings, Figure 1 illustrates diagrammatically a portion of a Wichert truss bridge mounted over an intermediate pier 30. A supporting member 3! is permanently and fixedly connected with the pier 30 and carries a pin 32 to which the lower members 33 of the quadrilateral are pivoted. Pivoted to each of the members 33 at its opposite extremity at 34 is one of the upper quadrilateral members 35. The upper quadrilateral members are pivoted together by a pin 36. Normally the quadrilateral made up of the two members 33 and the two members 35 is non-rigid. Such quadrilateral is, however, rendered temporarily, rigid by the use of an erection member 31 joining the two pins 34. Such erection member transforms the bridgework into a rigid construction during erection and enables the use of the cantilever method to build out beyond the pier 30. The erection member 37 is preferably longitudinally adjustable so that when the opposite portions of the span have been constructed as cantilevers adjustment of the member 37, together with whatever slight longitudinal movement of one of the spans may be necessary, will enable connecting of the two halves of the span. After such connection has been effected the member 31 may be entirely removed, or it may be so adjusted as to impart to the bridgework non-rigid continuous characteristics. This may be done without removing the member 31 if it is adjusted so as not to carry any load either in tension or in compression.

The construction shown in Figure 2 is similar to that of Figure 1 except that the erection member 38 extends vertically instead of horizontally as is the case with the erection member 3? of Figure 1. In each case, however, the erection member is adapted to withstand both tension and compression and thereby renders the quadrilateral temporarily rigid during erection. Figure 2 also illustrates a modified form of support, the supporting member 39 being mounted on the pier 40 for movement longitudinally of the bridge. Roller bearings are indicated diagrammatically at ll. Longitudinally movable supports will ordinarily be used over all piers but one to allow the bridge to take full advantage of its non-rigid continuous characteristics.

A similar construction is shown in Figure 3 except that in this figure two erection members 42 and 43 are provided. Each of the erection memers 42 and 33 may be adapted to withstand tensile stresses only, in which case both members are necessary to render the quadrilateral temporarily rigid. In Figure 3 there is also shown a further modified form of support in which the supporting member 44 is permanently and fixedly connected with the pier 45. A link 46 pivoted to the supporting member 44 at 41 and to the lower members of the quadrilateral at 48 supports the structure but at the same time permits limited longitudinal movement thereof similarly to the supporting structure shown in Figure 2.

In Figure 4 there is illustrated a Wichert truss bridge of the tower type in which a supporting member 49 is permanently and fixedly connected with the pier 50. A tower member 5| is pivoted to the supporting member at 52 and is pivoted to the upper members of the quadrilateral at 53. Thus the quadrilateral is normally non-rigid. However, for erection purposes an erection member 54 is utilized which is connected with the lower members of the quadrilateral at 55 and with the pier at 55. As each of the members 5| and 54 is connected with the pier and with the quadrilateral, the quadrilateral is rendered rigid so long as the member 54 is effective.

Figure 5, being a transverse cross section through the construction of Figure 4, shows such construction as applied to both sides of the bridge. The construction above described for one side is duplicated on the opposite side.

Figure 6 also discloses a tower type Wichert truss bridge having a horizontally extending erection member 51 within the quadrilateral, and Figure 7 is similar but showing the use of a vertically extending erection member 58 within the quadrilateral. Figure 8 is likewise similar but discloses the use of two erection members 59 and 60 within the quadrilateral. Each of the members 59 and 60 may be adapted to withstand tension only, whereas each of the members 51 and 58 will normally be adapted to withstand both tension and compression.

In Figure 9 there are shown diagrammatically three spans of a Wichert truss bridge. The central span extends between piers GI and 62 over each of which is a typical normally non-rigid quadrilateral. The bridge is anchored to the pier 6|,that is to say, it is permanently and fixedly connected with such pier through the agency of a supporting member 63. Thus there is no longitudinal movement at the pier 6|, such movement being provided for at each of the other piers. i

The outer piers are shown at 64 and 65 and above each of these piers, as well as above the pier B2, is a link supporting member 66.

Each of the outer spans of the bridge is first constructed in conventional manner upon the usual falsework 61. As each of the quadrilaterals overlying piers 6| and 62 is constructed there is inserted therein an adjustable erection member 68 capable of withstanding both tensile and compressive stresses. The respective erection members 68 render the quadrilaterals rigid during erection so that the intermediate span may be constructed from opposite sides by the usual cantilever method and without the necessity of using any falsework thereunder. During such construction the bridge is in efiect and has the characteristics of a rigid bridge. When the construction has progressed to the point when connection of the opposite cantilever portions. is ready to be effected such portions can be raised and lowered by adjustment of the respective members 68. Likewise, the right-hand half of the bridge may be moved longitudinally by an adjustable tie member 69 so that the opposite halves of the bridge may be brought into proper cooperative relationship in an extremely simple manner. After the opposite'halves of the bridge have been joined at the center of the intermediate span the members 68 are either entirely removed or relieved of any stress, thereby transforming the bridge into a non-rigid continuous bridge.

In Figure 10 there is shown a modified construction in which the quadrilateral ismounted upon a pierlll by a link H. The left-hand extremity of the outer span is mounted upon a pier 12 by a link it. The outer span is constructed on falsework 14. Such span is maintained in fixed position by an adjustable tie member 15. The quadrilateral is rendered temporarily rigid during erection by erection members l6 and 1'! each of which may be adapted to withstand tension only. The remainder of the bridge is constructed as above described in connection with Figure 9.

A further modificationis shown in Figure 11. In this case the quadrilateral is mounted over a pier 18 by a link 19. The left-hand extremity of the outer span is mounted over a pier 89 by a link BI and an adjustable tie member 82 is provided to fixedly position the span. No erection members are utilized within the quadrilateral in this construction, but an erection member 83 anchored to a temporary pedestal 83a fixedly connects one corner of the quadrilateral with the ground. Such member 83 in combination with the tie member 82 insures rigidity of the quadrilateral during erection.

A further modification is shown in Figure 12. The quadrilateral is mounted over a pier 84 by a link 85. The left-hand extremity of the outer span is mounted over a pier 86 by a link 8! and an adjustable tie member 88 is provided. A predetermined weight 89 is suspended from the top pin of the quadrilateral, this having substantially the same effect as the various provisions above described for maintaining the quadrilateral temporarily rigid. The same effect can be obtained by placing a flooring crosswise between the lateral pins of the quadrilateral and placing the weight on such flooring.

Several specific constructions for performing the functions above described will now be .ex plained. These specific constructions simply represent possible ways. of effecting the desired results and are purely illustrative.

. reference numeral 98.

In Figures 13, 14 and 15 there is shown in detail a horizontally extending erection member adapted to withstand both tension and compression and suitable for use in constructions such as those of Figures 1 and 6. In Figure 13 the lower extremities of the upper members of the quadrilateral are shown at 90. Each of these is rigidly connected to a pair of matching gusset plates. In Figures 13 and 14 the pair of gusset plates to which the left-hand member 90 is connected is shown at 9m, 91?), and the pair of gusset plates to which the right-hand member 90 is con-- nected is shown at 92a, 92b. The gusset plates 9m, Mb areconnected through angles 94 to a thrust plate 95. A hydraulic jack 9! has its lefthand portion 96 bearing against the thrust plate 95 and its right-hand portion l 05 bearing against another thrust plate N14 to be presently described.

The erection member is designated generally by It comprises a pair of oppositely disposed channels 99 connected in spaced apart relationship with their flanges extending outwardly and adapted to receive the parts of gusset plates therebetween, as shown in Figure 14. The erection member is shown as being bolted to the gusset plates 9m, Bib by bolts mu. Also passing through the gusset plates 9la, 9th and the erection member 98 is a relatively large bolt NH. The gusset plates are drilled to snugly receive the bolt NH, but the channels 99 of the erection member are provided with elongated slots N12 to permit relative movement between the erection member and the bolt lill, as will presently be described.

Connected With the respective channels 99 are angle members Hi3 and connected with the outwardly extending arms of such angle members is a thrust plate I04 against whichthe right-hand end I95 of the hydraulic jack 9? is adapted to bear. The erection member is stifiened behind the angle members H13 by a cross plate I05 held in place by angle members lill. A plate N18 is connected with and extends across between the respective channels below the jack to serve as a support for the jack when notin operative position. The right-hand extremity of the erection member 93 is pivotallyconnected to the gusset plates 92a, 9% by a. bolt Hi9.

When the parts are in the position shown in Figures 13 and 14 the erection member 98 acts either in tension or in compression between the respective pairs of gusset plates 91a, 9H) and 92a, 92b and hence between the respective lateral pivots Ill and l l i of the quadrilateral. The erection member thus renders the quadrilateral rigid during erection, making it possible to erect the bridge by the cantilever method as above described; When the opposite halves of the span have been constructed by the cantilever method and are readyto be connected togethersome adjustment of the erection member 98 will probably be desirable. The jack ill is placed in operative position and pressure applied thereto so as to relieve the bolts Hill of substantial shearing stress. The bolts Hill are then removed and the nut on the bolt It]! is somewhat loosened, whereupon the erection member is ready for longitudinal adjustment, which is efiected by increasing or decreasing thepressure in the jack to extend or retract the same. After the ends of the span have been connected together the'pressure in the jack is relieved and the jackrendered inoperative. As the bolts lllfl have been removed and the nuts on the bolt lfll have been loosened, the erection member 98 is also rendered inoperative. Any relative movement between the erection member and the gusset plates 9Ia, 9Ib, either during the adjustment or upon rendering the erection member inoperative, is provided for within predeterminate limits by the elongated slots I02 in the erection member in which the bolt IBI slides. The erection member 98 may be either removed entirely or left in place but without taking any stress. In either event the bridge will assume non-rigid continuous characteristics.

The construction of the erection member 98 is such that during the adjustment such member will be under compression and not under tension. The member is not designed to be adjustable under tension and will always be used in places where adjustment will be effected with the erection member under compression. As the horizontal erection member, when used alone, as in Figures l and 6, is always under compression during the adjustment the erection member 98 is used as such a horizontal erection member.

In Figures 16 and 17 there is shown a vertical erection member such as may be used in constructions of the type shown in Figures 2 and '7. In Figure 16 the pier is shown at H2 and is provided with a bearing plate I I3 and an upwardly projecting pin I I3a. A rocker I I4 is mounted atop the bearing plate and is centeredby the pin I Illa which enters a cavity H5 in the rocker. The lower pivot pin II 5 of the quadrilateral is carried by the rocker and the lower members I H of the quadrilateral are pivotally connected by the pin H5. The upper members I13 of the quadrilateral are connected by the upper pivot pin H9 to which are also connected the upper members I20 of the adjacent spans. The erection member is designated by reference numeral I2I and comprises two sets of telescoping channels. The upper channels I22 are connected with the pivot pin I I9, and the lower channels I23 are connected with the pivot pin H6. The channels I22 telescope within the channels I23. Held by the inner channels I22 is a bolt I24 which passes through elongated slots I25 in the outer channels I23. Held by the outer channels I23 is a bolt I23 which passes through elongated slots I27 in the inner channels I22. Each of the bolts I24 and I25 is provided with nuts I24ct.

A hydraulic jack I28 extends between and bears against the respective bolts I24 and I26. When it is desired to adjust the erection member I 2i, pressure is applied to the jack, thus enabling the erection member to be longitudinally adjusted as required. During adjustment the erection member is always under tension, and as the vertically extending erection member, when used as in Figures 2 and 7, is always subjected to tension during adjustment, the erection member I2I is used for this purpose. When it is desired to maintain the erection member I2I in a fixed adjusted position the respective channels I22 and I23 may be bolted together by bolts I 29, as shown in Figure 16. The nuts I24a will normally be designed for the purpose only of maintaining the bolts I24 and I26 in place and will not ordinarily be relied upon to exert substantial friction on the channels I22 and I23.

In Figure 18 there is shown a construction such as would be suitable for use in the modifications of Figures 3 and 8. In Figure 18 the pier is shown at I30 and a rocker I3I is mounted thereon as in Figure 16. The rocker carries the lower pivot pin I32 to which the lower members I33 of the quadrilateral are connected. The upper members I34 of the quadrilateral are pivoted to the respective lower members I33 by pins I35 and to each other by the upper pivot pin I 36.

In this modification two erection members I3! and I38 are utilized, each of such members simply comprising a pair of saddles having the opposite ends thereof connected by turnbuckles I39. Of course the erection members in this construction can withstand tension not only during adjustment but at all other times.

In Figure 19 there is shown a construction suitable for use in the form of Figures 4 and 5. The pier is shown at I40 and the tower at I 4|. The tower is pivoted at I42 to a supporting member I43 permanently and fixedly connected with the pier. The upper members I44 of the quadrilateral are pivoted at I45 to the top of the tower MI. The lower members I46 of the quadrilateral are pivoted to the respective members I44 at I41 and are connected respectively with gusset plates I48 which are pivoted together at I49. The quadrilateral is thus normally non-rigid.

An eye I58 is connected with the pier I40 at I5I and contains a pin I52. An erection member I53 connects the pin I49 and the pin I52. The erection member I53 comprises upper and lower eye members I 54 and I 55, respectively, each having a threaded shank and a turnbuckle I56 cooperating therewith. The erection member I 53 may be relatively short and of substantial cross-section so as to withstand either tension or compression at all times, both during adjustment and otherwise. However, the erection member I53 will normally be designed for tension only, and in such case blocks I53a cooperating with wedges I53b resting on the pier I40 and underlying the respective gusset plates are used to sustain the weight of the bridgework during erection.

A somewhat different method of construction is illustrated in Figures 20 to 28, inclusive. The method illustrated in such figures is for the construction of an over-Water bridge in which the respective spans are separately constructed on barges and floated into place. Each span is preferably constructed on a separate barge, the construction being effected in usual manner, such as on falsework. The quadrilaterals at the ends of the spans are maintained rigid during erection. A selected span is first set in place on its piers. This may be either an end span or an intermediate span. It is preferably the anchored span, although another span may be uti lized if desired and temporarily anchored.

The initial span above referred to has adjustable vertical erection members over the supports at both ends and has both of the inner members of each quadrilateral in place. The outer lower quadrilateral member at each end is also held in place, as will presently be described, but the outer upper quadrilateral members are omitted, these later being set in place upon connection of the initial span with adjacent spans.

The erection of a bridge by this method is shown diagrammatically in Figures 22, 23, 24 and 25. In Figure 22 there is shown an initial span I51 mounted upon piers designated diagrammatically at I58. The inner quadrilateral members I59 are in place and at each end an adjustable vertical erection member IBIJ is provided. The lower outer quadrilateral members I6I are held loosely in place and the upper and outer quadrilateral members, whose position will ultimately be as indicated by the dotted lines I52, are missing. Male guide members I63 are provided at the opposite ends of the span I51 above the respective erection members I60 to assist in positioning the adjacent spans in place.

Referring now to Figure 23, a span lo l is separately constructed on a barge with an erection member I inplace in one end thereof, which end is in all respects similar to the lefthand end of the span I51! above described. The right-hand end of the span ltd, however, has only the member I 56 for closing the quadrilateral at the left-hand end of the span I57 and adapted to assume the position indicated bythe dotted line I62. The span I 64 is floated out into. position on its barge and is moved laterally into place in end to end relationship with the span I51. At the right-hand extremity of the span IE4 is a female guide member I67 adapted to receive the male guide member IE3 to assist in properly positioning the two spans. Likewise the erection member I66 at the left-hand endof the span I5? is longitudinally adjustable and may be operated as necessary to enable the two spans to be connected. The member Ifili is connected into the quadrilateral, after which the erection member I60 at the'junction of the two connected spans may be removed or rendered inoperative.

Another span I68 may be connected with the right-hand extremity of the'span I5? as indicated in Figure 23. In Figure 24 the spans I64, I51 and IE8 are shown as being completed except for the outer extremities of the spans its and I68 .and removal of the guide members. Figure 25 shows the spans Hid, I57 and IE8 entirely completed and the guide members removed and additional spans being added.

' The temporary erection members must remain in place in the outer or unfinished ends of the spans until other spans are connected therewith. However, as soon as a new span is added to the existing structure the erection member at the junction may be dispensed with. Thus a nonrigid continuous bridge may be constructed by the flotation method by rendering the respective spans rigid during erection and thereafter transforming the construction into a non-rigid continuous bridge.

In Figure 20 the connection of two spans by the method just described is illustrated. It may be assumed that the left-hand span, viewing Figure 20, is in place and the right-hand span is being connected therewith. The erection member I69 is in place and the outer lower quadrilateral member IIII is loosely connected with the lower pivot pin III and is held up by a cable I12. The right-hand span is then moved into place. This is assisted by the guide device I'Ib, as above explained. During movement of the right-hand span into place the stringer I'IIi is temporarily held up by a hanger III to allow the same to drop into place in proper co0perative relationship with the corresponding stringer after the right-hand span is in place. When the guide device H5 has brought the holes for the pin I'M into alignment such pin is inserted. The erection member IE9 is then adjusted as necessary to enable the pin I13 to be inserted in the holes provided in the members connected thereerally by reference numeral IIII.

to which are pivoted the lower quadrilateral members I80. Other portions of the construction clearly shown in Figure 20 areomitted in Figures 26 and 27. The adjustable erection member shown in Figures 26 and 27 is designated gen- It comprises telescoping members made up of channels, the lower of such members comprising the channels I82 and the upper thereof comprising the channels I83. The upper member telescopes within the lower member. H-beams I84 are provided outside the channels I82 to stiffen. the structure. Thrust plates I85 and Idfi are connected, respectively, with the channels I82 and I83. This connection may be effected in any appropriate manner as, for example, by the method shown in Figure I5. A jack, illustrated purely diagrammatically at I8'I, bears between the thrust plates I85 and I33 to raise and lower the upper portion of the erection member. Strengthening mem bers I88 are connected with the channels I83 and supports I85 are adapted to be interposed between the members I88 and the tops of the H-beams I36 to maintain the erection member in desired adjusted position. Bolts Ififl passing through portions of the members I88 and through the spacers I89 and also connected with the upper portions of the H-beams I84 may also be used so that the erection member I8! will withstand both tensile and compressive stresses when in adjusted position. The erection member I8I is adjustable under compression.

While I have shown and described certain present preferred embodiments of the invention, it is to be distinctly understood that the same is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. I

I claim:

1. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose members are relatively movable, the steps consisting in forming the quadrilateral and maintaining it rigid until the essential members forming the spans on opposite sides thereof are in place, andthereafter freeing the quadrilateral so that its members may move relatively to one another.

2. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose mem bers are relatively movable, the steps consisting in erecting a portion of the bridge to one side of the quadrilateral and temporarily supporting such portion along its length, forming the quadrilateral, rendering the quadrilateral temporarily rigid, erecting a portion of the structure on the other side of the quadrilateral, and thereafter freeing the quadrilateral so that its members may move relatively to one another.

3. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose members are relatively movable, the steps consisting in forming the quadrilateral and maintaining it rigid by exerting a force across the panel formed by the members of the quadrilateral until the essential members forming the spans on opposite sides thereof are in place, and thereafter freeing the quadrilateral so that its members may move relatively to one another. I

l. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose members are relatively movable, the steps consisting in forming the quadrilateral and maintaining it rigid by means extending across the panel formed by the members of the quadrilateral until the essential members forming the spans on opposite sides thereof are in place, and thereafter freeing the quadrilateral so that its members may move relatively to one another.

5. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose members are relatively movable, the steps consisting in erecting a portion of the bridge to one side of the quadrilateral, forming the quadrilateral, rendering the quadrilateral temporarily rigid by exerting a force across the panel formed by the members of the quadrilateral, erecting a portion of the structure on the other side of the quadrilateral, and thereafter freeing the quadrilateral so that its members may move relatively to one another.

6. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose members are relatively movable, the steps consisting in erecting a portion of the bridge to one side of the quadrilateral, forming the quadrilateral, rendering the quadrilateral temporarily rigid by means extending across the panel formed by the members of the quadrilateral, erecting a portion of the structure on the other side of the quadrilateral, and thereafter freeing the quadrilateral so that its members may move relatively to one another. I v r 7. In the construction of a. non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral whose members are relatively movable, the steps consisting in erecting a portion of the bridge to one side of the quadrilateral, forming the quadrilateral, rendering the quadrilateral temporarily rigid, erecting by the cantilever method a portion of the structure on the other side of the quadrilateral, and after the essential members forming said spans are in place freeing the quadrilateral so that its members may move relatively to one another.

8. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a guadrilateral whose members are relatively movable, the steps consisting in erecting a portion of the bridge to one side of the quadrilateral, forming the quadrilateral, rendering the quadrilateral temporarily adjustably rigid, erecting by the cantilever method a portion of the structure on the other side of the quadrilateral, adjusting the quadrilateral to bring said portion of the structure into proper position, and after the essential members forming said spans are in place freeing the quadrilateral so that its members may move relatively to one another.

9. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral Whose members are relatively movable, the steps consisting in erecting a span including two adjacent members of said quadrilateral, separately erecting another span including another portion of said quadrilateral, connecting said spans together and thereby completing said quadrilateral, during said connection maintaining said two members relatively rigid, and thereafter freeing said quadrilateral so that its members may move relatively to one another.

10. In the construction of a non-rigid continuous bridge having adjacent spans connected and supported through a quadrilateral Whose members are relatively movable, the steps consisting in erecting a span including two adjacent members of said quadrilateral, maintaining said two members temporarily in adjustably rigid relationship, separately erecting another span including another portion of said quadrilateral, relatively adjusting said two members as necessary to permit connection of said spans and completionof said quadrilateral, connecting saidspans together and forming said quadrilateral by connecting its several members together, and thereafter freeing said quadrilateral so that its members may move relatively to one another.

ERNEST M. WICHERT.

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