US2152896A - Structure - Google Patents

Description

April 4, 1939.

FIG. I

T. MADDOCK STRUCTURE Filed Sept. 4, 1936 INVENTOR Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE 3 Claims.

The improvement relates to expanding spans in structures.

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

Expansion and contraction are provided for in simple or multiple spans of all kinds in order to reduce secondary stresses, to reduce thrusts on columns and piers, to utilize the advantages of continuous spans of unlimited length, to increase the rigidity of spans, to increase resistance to wind stresses, to increase ease of erection and decrease the amount of false work.

Several forms of expanding continuous spans are illustrated by the accompanying drawing.

Figure 1 is a side elevation of an eight panel truss with an expanding continuous mechanism.

Figure 2 is a side elevation of two eight panel continuous trusses connected by an expanding continuous mechanism.

Figure 3 is a side elevation enlargement of the mechanism shown in Figure 1.

Figure 4 is a plan of the mechanism as used to secure continuity in lateral systems to resist wind loads, etc;

Figure 5 is a side elevation enlargement of the mechanism shown in Figure 2.

The side elevation shown in Figure 1 includes a truss and part of the adjoining continuous trusses. The central four panels are directly connected to the left two panels but are connected to the right two panels by an expanding and contracting mechanism.

The mechanism as shown enlarged by Fig ure 3 consists of two toggle joints |-2--3 and ||-|2|3 which connect the top and bottom chords respectively. Numbers 20 and 2| are top and and 3| are bottom chord members. Numbers 4|], 4| and 42 are vertical members. Numbers 50, 5| and 52 are diagonal members. Number 54 is a strut tie to prevent bending in member 4|.

The toggle lever arm 3--2 is extended in length to 4 and increased in width to resist bending. This lever arm is connected by the strut-tie 4-1 to a rocker arm 5| at the pin 1. The opposite end of the rocker arm is connected at pin 5 to the strut-tie 5-|4 in turn connected to the lever arm |4-|3. The rocker arm turns on pin 6 which is midway between pins 4 and H on 4|.

The distance between pins and 2, 2 and 3, 2 and 4, 4 and and 1 and 6 are respectively equal to II and l2, l2 and I3, I2 and l4, l4 and 5 and 5 and 6.

In order to relieve the mechanism from shear stress the right end of the central four panels is supported on the left end of the right two panels, i. e., as illustrated, II is supported on 8. Horizontal movement is secured on rollers. Rookers or sliding plates also may be used.

The toggle members I2 and |--|2 may be made similar to 43 and two additional strutties connected to a second rocker arm pivoted on 42 to provide double action if so desired.

Figure 4 differs from Figure 3 in no essential particular. The size of members is reduced as lateral forces from wind etc., are less than vertical forces. Numbers |2|l--|2||30 and |3| are the chords, numbers 4|l--|4|l42--| 43 are transverse members, and numbers |5| and 53 are .diagonal members as customarily used. Numbers |5|||5| are diagonal members placed to strengthen |4| against bending when the toggles are connected thru a rocker arm as shown by |5--|6|'|. The toggle 8|--8283 and 84 and 9|--9293 and 94 and the connecting strutties 84-|1 and 94-| 5 are similar to those shown in Figure 3. No detail is shown to independently care for the small shear stress resulting from lateral forces of wind loads, etc.

Figure 5 shows two separate modifications from Figure 3. The mechanism is located over point of support and the toggles operate in the same instead of opposite directions. As shown the member 43 is subject to compression. With toggles inverted it is subject to tension. Additional toggles may brace 4|, 42 and 43 if desired.

When mechanism is located at point of support the ends of the span move horizontally on rollers, etc., as customary.

The greater the angles |-23 and ||--|2|3 the less stress in the mechanism and members 4| and 42, etc.

In operation as illustrated, tension between pins I and 3 creates an equal compression between pins II and |3 while compression between pins and 3 creates equal tension betweenpins H and I3; and as the mechanism provides for equal horizontal movements between pins I and 3 and H and I3, expansion and contraction of the entire span takes place without altering the tension and compression in the upper and lower chords.

I claim:

1. A mechanism in spans of structures consisting of a toggle joint in each chord with an extended lever arm of each toggle connected by a strut-tie to a rocker, said strut-ties being connected to opposite ends of said rocker, insuring the simultaneous movement of the toggles to control the lengths of the chords.

2. A mechanism in spans of structures located other than at piers or supports, consisting of a toggle joint in each chord with the elbows of each toggle connected by a strut-tie to a rocker, said strut-ties being connected to opposite ends of said rocker, insuring the simultaneous move ment of toggles to control the length of the 10 chords; together with a member maintaining the alignment of the chords and sustaining the shear stresses.

3. A mechanism in spans of structures, located other than at piers or supports, consisting of toggle joints in each chord, said toggles being connected, insuring their simultaneous movement to control the length of the chords; together with a member maintaining the alignment of the chords and sustaining the shear stresses.

. THOMAS MADDOCK.

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