US2030262A - Truss or bridge - Google Patents

Description

Feb M, i936. T, MADDOCK 2,030,262

TRUSS OR BRIDGE Filed Jan. 27,A 1930 Patented Feb. 11, 1936 vUNITED STATES PATENT OFFICE 4 Claims.

The invention relates to a new and useful arrangement of the members of trusses or bridges which will provide for their expansion and contraction While retaining their continuity and rigidity.

The object of the improvement is to reduce the amount of materials and cost of trusses and bridges.

Expansion and contraction are to be provided for Within a simple truss, or within or between multiple trusses and girders of all types and sizes in order to reduce secondary stresses; to reduce the lateral thrust on columns and piers; to utilize the economic advantage of continuous trusses and girders without being limited in their length by the movement due to expansion or contraction from heat or stress variation; to increase the rigidity and strength of cantilever truss and girder connections with suspended spans; to increase resistance to wind stresses and to decrease the amount of false work required in erecting trusses.

The expanding truss is illustrated by the accompanying drawing.

Figure l is a side elevation of a ten panel truss embodying one form of an expanding panel.

Figure 2 is a side elevation of two seven panel trusses with a supported expanding connection between the trusses.

Figure 3 is an enlarged side elevation of the expanding panel shown in Figure 1.

Figure 4 is an enlarged side elevation of the expanding connection shown in Figure 2.

Figure 5 is a side elevation of a variation of the type of expanding panel shown in Figure 1.

The side elevation shown in Figure 1 includes a truss and part of the adjoining continuous trusses. The central span of the truss is suspended by the cantilever arms at 8 and Ill.

The suspended span is connected to the right hand cantilever arm by an expanding panel shown enlarged in Figure 3.

The crossed members 2 9 and 3 8 are provided at their approximate center with a pin (6) to enable them to move and permit an approximately equal variation in the horizontal distance between the ends of the cross 2 and 3, and 8 and 9 in accordance with the expansion and contraction in the truss.

Ends of the members 1 2, 3 4, 2 9 and 3 8 are provided with pin connected joints. The other joints in the truss may be riveted.

The crossed member 2 9 is itself trussed by the members 2 1, 1 9 and 6 1 to resist bendspan provide expansion for the adjoining spans, v

in which case, roller bearing, rocker arms or similar arrangement for permitting longitudinal movement are necessary for the pier bearings.

The side elevation of the two trusses shown in Figure 2 include parts of the adjoining continuous trusses.

The two trusses are connected over the pier 23 by crossed members forming an expansion connection or tower which is shown in detail in Figure 4.

Movable joints or pin connections are provided at the ends of the members I 1 12, I3 i4, I2 |9 and I3 |8.

The movable arm |2 I 9 is itself trussed by the members 12-11, 11-19 and iB l 1 to resist bending moments. The member 13 18 is similarly trussed.

The pin at i6 is located so as to provide practically equal horizontal movement at Il and I8, and I4 and I9.

Bearing plates are provided with rollers to permit longitudinal movement on pier 23. Rockers may also be used.

The trusses can be rigidly attached to piers 22 and 24 unless it is desired to provide for the expansion of more than two trusses at pier 23.

The side elevation of an expanding connection shown in Figure 5 is similar to that in Figure 1 except that it does not add to the length of the bridge, but merely provides that the usual hanger 3 8 which connects the cantilever arm with the suspended span is made one of the crossed members.

In operation of the crossed members shown in Figure 1, as expansion moves pin 8 toward pin 9 pin 6 will be raised approximately half as much while pins 2 and 3 will have a vertical movement approximately equal to the horizontal movement between 8 and 9. This vertical movement at 2 and 3 results in a small additional horizontal movement which tends to vary the distance from 2 to 3 with that from 8 to 9. 'Ihis variation must be kept small. As the angle 2 6 3 of the crossmembers as constructed is decreased this varia-- tion approaches zero. Thus the more expansion to be taken care of in the trusses the less must be the angle 2-6-3. The same is true of Figure 2 where the inclination of the members ll--I2 and l3--i4 add to the Variation.

The pin at 6 in Figure 1 can be located off center to partially correct variable horizontal movements between 2 and 3, and 8 and 9. The pin at I6 can be similarly located.

Figure 5 is an illustration of an expanding -connection that will have a minimum vertical `movement in pins 6-2-8 and 9.

I am aware that methodshave long been einployed to permit expansion and contraction at the ends of trusses, also that simple hanger connections allow for the same, betweencantilever arms and suspended spans, but these do not permit of continuity in a structure.

I claim:

n 1. A continuous truss construction having an expanding and contracting panel consisting 'of crossed members, pin connected at their approximate'center with twolof the four ends of 'the crossed members directly pin connected to the chords and the other two ends pin connected'to struts or ties with the other end of such nstruts or ties pin connected to diagonally opposite chord points, the entire panel and its connections permitting the ends of 'the truss to be'xed to their supports by providing internally in the truss for longitudinal variations in length due to temperature changes and stresses.

2. A connection or tower between trusses consisting f diagonally crossed members supported by single or double piers, pin connected at their approximate center, with their bases pin connected to the ends of the lower chords of the trusses and their apices pin connected to tension members which are in turn pin connected to the ends of the upper chords, the entire tower and its connections securing continuity between the adjacent trusses Without interference with the longitudinal movement vof the ends of the trusses produced 'by stresses and temperature changes.

3. A connection between cantilever arms and lsu'spended spans consisting of diagonally crossed memberspin connected at their approximate centers with one of the crossed members pin con- *r'i'e'cted tothe cantilever arm and suspended span similar to the usual hanger and the other crossed 'member pin connected at its base to a strut in turn' p'in 'connected to the lower chord of the cantilever arm and pin connected at its apex to a tie the opposite end' 'ofwhichis in turn lpin connected l tothe'upper chord of'ithe suspended span.

' 4. A "continuous V'span construction 'having an expanding and contracting panel consisting `of two members connected at their approximate Vcenter with eachinemb'er lconnected toY diagonally i opposite 'chordpointsftwo of the end connections being made directly to the chords and the other two' 'connections being made `to strut-ties vin Aturn vcc'ynr'i'e'cted to` `I'the chords; all the lmembers being -free `to rotate at their Yconnections.

THOMAS MADDOCK.

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