US2192269A - Structure - Google Patents

Description

March 5, 1940. T, MADDOCK 2,192,269

STRUCTURE Filed March 6, 1939 FIG. i

FIG. 3

INVENTOR Patented Ma r. 5,1940

UNITED STATES PATENT OFFICE (STRUCTURE Thomas Ma ddock, Phoenix, Ariz. Application March 6, 1939, serial No. 260,075 Claims. (01. 14-16 The improvement relates to span structures.

The object of the improvement is to reduce the weight and cost of structures.

Expansion and contraction are provided for in continuous spans of all kinds in order to reduce thrusts on columns and piers, to utilize the advantages of continuous spans of unlimited length and to increase the rigidity of spans.

' Provision is made to equate the maximum positive and negative moments in- I beams and to create initial-stress in girders, beams and trusses combining expansion, continuity and moment stress control. I

Figure 1 is a side elevation of a multiple span I beam.

Figure 2 is an enlargement of the device permitting expansion while retaining continuity.

Figure 3 is an adjustable hanger.

Figure 4 is an adjustable pin seat.

Figure 1 shows a terminal span 1 with one free and one fixed end, a span 8 with fixed ends, containing the expanding device and-part of span 9 which is similar tospan 8. The piers or supports are designated at l0-H and I2.

Figure 2 shows one method of constructing the device which consists of two hangers, 5 and 6, connected by pins 1, 2, 3 and 4 to the two I beams which are reinforced by the two bars, 20 and 2|, for bending and pin bearing. The reverse side of. the beam is likewise equipped with bars and hangers to give double shear on pins and central loading. I

Expansion is provided by the rotation of hangers while the horizontal separation of the two hangers prevents the rotation ofone beam about the pin of the other, as with a single hanger, thus resisting bending moments.

With given loadsand location of device the moment stress on pins and hangers depends upon the horizontal distance between pins l and 3,

etc.

Shear is carried by one or both hangers, the amount depending upon the loading and the location of the device between piers H and I2. I Y The longer the hangers between pins l and 2, etc., the less is the angle of hanger inclination from vertical at maximum and minimum temperatures and the resulting end thrust in beams.

n2 l2 and at center of spans and that b yond the yield point both these stresses tend to equalize at This equalization of stresses is secured below the yield point when a simple span is loaded uniformlyto of its ultimate load, then connected over supports to make a continuous structure, and the remaining 3;; of load applied. When the entire load is removed initial moment stresses remain in the span that are available to equate future moment stresses.

This initial stress is likewise secured by varying the elevation of the beams support.

Similar results with expanding continuous structures are secured, for instance, in span 8 with hanger 5, located at .1464L from pier ll, connecting the beams, the application of a uniform dead load results in equal moment stresses at span center and support. When hanger 5 is then connected continuity is provided for the live loads. By selecting the position of the hangers and the preliminary loading before the second hanger is connected the desired initial moment stress is secured and the location of the points of contra flexture in the spans under various loads is controlled.

Figure 3 shows one type of adjustable hanger composed of bearings l3, M and I5, two rods, [6, with left and right hand screw threads and nuts, ll and I8, which can be used to create the initial stress desired in the beam.

Figure 4 shows an adjustable pin seat with splitbearing, 24, and shims, 23. In lieu of preliminary loading to provide initial moment stress one hanger, as 5, may be connected and 5 adjusted to position by jacks before being connected. Hangers or pin bearingsmay be adjustable to secure pre-stress'and, toprovide for Wear or pier settlement.

In design of multiple continuous beams by reducing the length of the end spans, etc., varying the elevation of the end supports and pre-stressing the internal spans practically equal positive and negative maximum moments in all the spans is secured for dead and live loading.

The drawing shows device as applied to I beams but it is also applied to girders, trusses,

concrete beams and spans in general.

As a modification of two horizontally separated hangers, sliding hangers, sliding plates or rollers to transfer both shear and positive or negative moments across expansion joints are similarly used to secure expansion, continuity and control of moment forces. Spans 8 and 9, etc., are stable as simple beams except for a small horizontal force when hangers are inclined.

I claim:

1. A device in spans of internal expanding structures consisting of two hangers connecting the members, said hangers being separated horizontally to resist moment stresses inaddition to carrying shear stresses.

2. A device in spans of internal expanding structures consisting of two hangers connecting the members, said hangers being adjustable to create initial stress or to make corrections for pier settlement.

3. A device in spans of internal expanding structures consisting of two sets of tbearings between members and said bearings being separated horizontally to resist moment stresses in" addition to carrying shear stresses.

v 4. A device in spans of internal expanding structures consisting of. two sets of bearings between members said bearings being separated horizontally to resist moment stresses in addition to carrying shear stresses and being'adjustable vertically to create initial stress or'tomake corrections for pier setlement. I I r 5. The art of securing minimum stresses or maximum economy in continuous structures,

consisting of pre-loading or pre-stressing simple A or cantilever spans to secure initial stresses and. 10 the connecting by an internal expanding device of said spans or their members to form-saidv continuous structures.

'THOMASMADDOCKQ

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