US 3750210 A
Apparatus for the construction of bridges incorporating piers pivoted to a transverse structure which may be an integral part of a bridge span or a cross-beam on which a span is supported. The piers can pivot in a plane transverse to the bridge and are normally maintained at a predetermined angle to the transverse structure by hydraulic articulators connected to piers and transverse structure across the angle therebetween. The articulators incorporate a valve actuable when the articulators are subjected to a predetermined load to permit a change of length of the articulator and a consequent variation of the angle between piers and transverse structure and thus to relieve excessive stresses on the bridge structure.
Description (OCR text may contain errors)
United "States Patent 1 1 Barnard et al.
1 1 APPARATUS FOR THE CONSTRUCTION OF BRIDGES I75] inventors: John Marlee Herbert Barnard,
Milford-on-Sea; omit lan Knight; 1
Eric Longbottom, both of Bounemouth, all of England 221 Fiiedz 1111;.4, 1971 211 Appl.No.: 168,965
 I Foreign Application Priority Data 1451 Aug. 7, 1973 3,l7l,259 3/1965 Roussel 6l/46.5 2,687,617 8/1954 Neweli l4/l X 1,358,95l ll/l920 Helmich 6l/48 2,367,29l l/l945 Le Tourneau l4/l 2,997,852 8/l96l Sudcrow 6l/46.5 3,392,534 7Il968 Blenkarn til/46.5 3,323,l57 6/l967 Vaugoyeau l4/l 3,367.l l9 2/l968 Rybicki (ii/46.5
Primary Examlner--Nile C. Byers, Jr. Attorney-Gordon W. Daisley [5 7 1 ABSTRACT Apparatus for the construction of bridges incorporating piers pivoted to a transverse structure which may be an integral part of a bridge span or a cross-beam on which a span is supported. The piers can pivot in a plane transverse to the bridge and are normally 'maintained at a predetermined angle to the transverse structure by hydraulic articulators connected to piers and transverse structure across the angle therebetween. The articulators incorporate a valve actuable when the articulators are subjected to a predetermined load to permit a change of length of the articulator and a consequent-variation of the angle between piers and transverse structure and thus to relieve excessive stresses on the bridge structure.
7 Claims, 3 Drawing Figures Aug. 13,1910 1 Great Britain 39,041/70 s21 11.s.c1. ..14/1, 6l/46.5, 14/15 1511 1111. E0111 1/00  Field of Search ,14/1, 42, 58, 7s; t 61/466 [561 v References Cited unmzo STATES PATENTS 3,074,239 1/1963 Mustard"; 14/1 X lib j 1 l a I 4 I i g PATENTEU AUG 71975 SHEEY 1 [IF 3 APPARATUS FOR THE CONSTRUCTION OF BRIDGES This invention relates to apparatus for the construction of bridges and is particularly concerned with devices for supporting a bridge span.
When a bridge is mounted on piers or on a frame or frames incorporating piers, it may happen that two laterally spaced piers rest on different types of ground and may be subject to differential settlement under load. If the bridge structure is flexible enough to move laterally the differential settlement can sometimes be catered for by tilting of the piers, accompanied by lateral movement of the bridge, until both piers are footed on firm ground. If, however, the bridge structure is laterally stiff and is firmly anchored at its ends, for example to the banks of a stream or other obstacle, the bridge can only move vertically and the pier on the softer ground may be unable to bed down onto a firm foundation. In such a case the load on the transverse structure and the firmly footed pier or piers will be considerably increased and when these are rigidly connected, as they usually are in known arrangements, some of the structural members may well become overstressed and sustain damage.
This invention aims at avoiding such overstressing and consequent damage by providing an arrangement whereby the angle, measured in a plane transverse to the bridge, between a pier andthe transverse structure to which it is attached, can change when a predetermined critical loading is reached so that differential settlement can be accommodated without substantial lateral movement of the bridge.
The invention therefore comprises apparatus for the construction of a bridge incorporating piers pivotally connected to a transverse structure for articulation in aplane transverse to the bridge, the angles between the piers and the transverse structure being normally maintained at predetermined values by hydraulic articulators each connected to a pier and to the transverse structure and extending obliquely across the angle therebetween, each such articulator having a release valve operative, when a predetermined critical load on the articulator is exceeded, to permit change of length of the articulator and variation of the angle between the associated pier and the transverse structure.
It is to be understood that the connections between the transverse structure'and the piers and between the hydraulic articulators and, on the one hand, the piers and on the other hand, the transverse structure, may be either direct attachments or indirect attachments through an intermediate member or members.
The transverse structure may be an integral part of a bridge span or an attachment thereto or may be a separate member, for example a cross beam upon which a bridge span is or will be supported. The invention is, of course, particularly useful in the construction of temporary bridges where it is not possible to prepare or to select adequately solid footings for the piers. One especially useful application occurs in the construction of abridge in the manner described in our copending Patent Application Serial No. 859,622, filed September 22, 1969, now abandoned, in which the piers are lowered from a bridge sparrwhich has been projected over an obstacle and the pier footings, fol-example on a river bed, may be quite unpredictable.
One form of the invention will now be more particularly described, by way of example only, with reference to the accompanying drawings in which:
FIGJ is a diagrammatic elevation of a framework on which is supported part of a bridge span and F162 is a similar view of the framework after some settlement has occurred.
FlG.3 is a diagrammatic view of an articulator.
A bridge span 1 is carried on a cross beam 2 which is slung transversely below the span by anysuitable connecting means 3 which do not form part of this invention and are not, therefore, shown or described in detail. Attached by pivots 4, one to each end of the cross-beam 2 are tubular hip members 5 of rectangular cross-section; and piers 6, each comprising a plurality of leg units 7, joined end to end, extend through the tubular hip members 5 to which they are secured to provide support for the cross-beam 2 and the bridge span 1. The lower ends of the piers are attached to foot members 9 which rest upon the ground 10 below the bridge. The hip members 5 may be provided with internal guides 8, for example pads of polytetrafluoroethylene, to form bearing surfaces for the piers 6.
Hydraulic articulators lla,1 lb extend obliquely across the angles between the piers 6 and the crossbeam 2, their upper ends being connected to the tubular hip members 5 and hence, indirectly, to the piers 6 and their lower ends being connected to the crossbeam 2. These articulators are hydraulic rams of a known type, each incorporating a release valve which will sustain a predetermined maximum load on the ram but, when that load is exceeded, will open to allow extension or contraction of the articulator and thus permit a change of angle between the associated pier and the cross-beam. Thus if the bridge is stressed to the point when the maximum load on the ram is exceeded, for example when one foot member 9 is sited on a soft foundation as at 10a and can settle differentially when the bridge is loaded, the articulator 11a will contract and the articulator 1112 will extend to allow the bridge to assume a position such as that shown in FIG. 2 without incurring lateral movement of the span 1 and without overstressing the bridge structure.
It will be clear thatthe articulators 11a, 11b could equally well be connected across the angles below the cross beam 2 and could, if desired, be connected directly to the piers 6 instead of to the hip members 5; in fact the hip members are not essential to the invention which could be applied equally well to a bridge in which the piers are directly pivoted upon the cross beam. Similarly the bridge span could be constructed in such a way that it is pivoted directly to the piers, a part of its structure constituting a cross-member thus dispensing with the separate cross-beam.
FIG. 3 shows, diagrammatically, one suitable articulator of a known type incorporating a cylinder 12, a ram 13 and a hydraulic circuit having a reservoir and pump 14, a value 15 controlling flow direction and two pressure relief valves 16.
The particular arrangement described can be used conveniently in the type of bridge construction described in our above-mentioned co-pending Patent application Ser. No. 859,662, wherein the piers are lowered through the hip members after projecting the bridge span across the obstacle. It could, however, be used equally well, where conditions permit, as a separate frame erected and supported, for example by guys,
the bridge span being subsequently manoeuvered into position thereon.
Another advantage which is obtained when using this arrangement in the method comprising lowering piers from the bridge span is that excessive stresses on the bridge structure due to the water loads on the piers being lowered into a fast flowing river can be prevented. Furthermore the invention reduces the likelihood of structural damage to a bridge due to oscillations built up by traffic using the bridge.
1. Apparatus for the construction of a bridge comprising a transverse structure; piers pivotally connected to said transverse structure for articulation in a plane transverse to the bridge; hydraulic articulators each operatively connected to a pier and to the transverse structure and extending obliquely across the angle therebetween to maintain said angle, normally, at a predetermined value; and a valve in each articulator, operative when a predetermined critical load on the articulator is exceeded, to permit change of length of the articulator and variation of the said angle.
2. Apparatus as claimed in claim 1 wherein the transverse structure is an integral part of a bridge span.
3. Apparatus as claimed in claim 1 wherein the transverse structure is a cross-beam on which a bridge span can be supported.
4. Apparatus as claimed in claim 1 incorporating tubular hip members pivoted to the transverse structure and in which the piers are mounted, each articulator being operatively connected to a hip member and through said member to a pier and to the transverse structure.
5. Apparatus as claimed in claim 4 incorporating internal guides within the hip members to form bearing surfaces for the piers 6. Apparatus as claimed in claim 5 wherein the internal guides are pads'of polytetrafluoroethylene.
7. Apparatus as claimed in claim 1 wherein each hydraulic articulator is a hydraulic ram comprising a cylinder operatively connected to one of a pier and the transverse structure; a ram incorporating a piston slidable longitudinally within the cylinder and operatively connected to the other of a pier and the transverse structure; and a hydraulic circuit connecting chambers on each side of the piston and including a release valve operative when a predetermined pressure is exceeded in one of said chambers to permit an extension or contraction of the articulator and a consequent change in the angle between the associated pier and the transverse structure.
U t k t mg I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3, 750,210 Dated August 7, 1973 l fl John Marles Herbert Barnard et a1.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Eolumn 1, line 63 "859,622" should read "859,662". Column 2, line 58, "value" should read --valve--.
Signed and'sealed this 20th day of August 197 (SEAL) Attest:
v M. GIBSON JR. C. MARSHALL DANN i ting Officer Commissioner of Patents