US2360285A - Arched construction and method for erecting same - Google Patents

Description

Oct. 10, 1944. 5. SHERMAN 2,360,285

ARCHED CONSTRUCTION AND METHOD FOR ERECTING SAME Filed July 16, 1943 2 Sheets-Sheet 1 IN VEN TOR. 10/111 .53 Jlzqrmam BY yd ftm Oct. SHERMAN I ARCHED CONSTRUCTION AND METHOD FOR ERECTING SAME Filed July 16, 1343 2 Sheets-Sheet 2 IN VEN TOR.

fakn J. JZermaw- HTTOlP/VE) Patented Oct. 10, 1944 ARCHED CONSTRUCTION AND METHOD FOR ERECTIN G SAME John S. Sherman, South Orange, N. 3.

Application July 16, 1943, Serial No. 494,955

8 Claims.

This invention relates to arched constructions and to methods for erecting arched constructions which are formed from individual elements assembled together in arched formation before erection.

Among the objects of the invention is to provide a novel method for erecting an arched structure assembled from individual segments or slabs which are shaped to be fitted together in the pattern of an arch and which are erected in their assembled arch relationship as a composite structure and placed in position on piers, sustaining walls or other supports.

Another object is to effect savings in costs in the building of a variety of arched spans of concrete or of other plastic but subsequently hardened material by considerably reducing the amount of steel ordinarily required in such structures and by eliminating the labor which otherwise would be needed for fabricating and placing reinforcement. The only steel which need be required in a completed structure wherein the present invention is employed would be that which might be used to resist the thrust created by the arched span and to support the weight of the span and the load which might come upon it. The invention enables reduction in the dead Weight of an arched structure through the elimination of reinforcing steel and the use of a less amount of concrete, particularly in the building of a roof and other structures wherein covering protection is paramount to load-sustaining capability.

It is common practice to construct roofs for large storage buildings and factories of reinforced concrete in the form of a monolithic arch extending from support to support. For such roofs the concrete is placed over barrel arch forms.

' These forms entail complications incident to building, erecting and moving them and to delays in the placing of steel reinforcing and pouring operations as the building of the roof progresses.

Sometimes a monolithic roof structure is continuous over several spans and in such cases additional reinforcing provision must be made for withstanding negative bending moments and for expansion. Ribs of structural steel are sometimes provided to stiffen the arch. The present invention makes it possible to eliminate many of the costly adjuncts to monolithic structures and to build a roof wholly from materials which have high compressive strength and relatively low tensional strength.

In addition to these and other objects and advantages which tenable savings through the reduction of steel and concrete, and savings of time and expense for the usual form work and centering, including the cost and time involved in the erection and removal'of forms and time required for curing concrete poured into place, the invention enables the expeditious erection of a roof or other arched structure since it provides a method for utilizing slabs which can be precast in quantities and cured long in advance of their need; also, standard sizes of slabs may be made in quantities from a small number of molds and these may be used for erecting roofs and other arched structure having diiierent spans and rises merely by varying the number and choice of slabs in a single arch or span; the same molds and erecting equipment may be employed for fabricating individual elements and for erecting successive sections of a roof and roofs can be progressively built without entailing loss of time and expense which ordinarily attach when following operations have to be delayed until the completion of preceding operations, all to the end of economizing on the cost of building and erecting a roof by effecting savings in labor, materials and the amount of equipment ordinarily required when concrete is poured in place as, for example, in building a roof or other arched structure in situ.

In brief, the invention contemplates assembling an arch or section of a curved roof made up of pre-shaped roof elements laid on edge upon the ground or otherwise supported in continuation of one another with the joint ends of adjacent elements in the abutting relationship they are to maintain when erected. The individual elements may be, though not necessarily, of the same dimensions. Two tension tie-members are thenattached to the end or base elements of the assembled arch, one being applied as a chord of the arch formed by the assembled elements and the other overlying the extrados orback of the arch. Tension is applied to the respective tie-members to draw the series of assembled arch elements into tight abutting relationship and to create compressional stresses therein approximating stress conditions that will obtain when the arch is in use as a section of a roof. The arch of assembled elements is then lifted as a stable unit and placed on prepared abutments in walls or on other supports, in the position it is intended to remain as a partof a supporting structure or roof. The back tie-member may then be removed and usually would be, and the chord tie-member may be retained if needed,

or removed should the wall or other support be so constructed as to be able to assume the full thrust of the seated arch. In the drawings I have illustrated by way of example, an application of my invention in the building of a roof, and it is to be understood that other uses are contemplated.

Fig. 1 is a section of a roof erected in accordance with the present invention.

Fig. illustrates the aligning on the ground of the individual arch elements or slabs of an arch.

Fig. 3 shows the assembly of slabs on the ground and applied tie-members.

Fig. 4 shows a manner of placin an aSSeHP led arch on its supports.

Fig. 5 is a bottom view of the arch shown in Fig. 4.

Fig. 6 illustrates a section of the support of a roof which retains the chordal tie-member as a permanent member.

Fig. '7 is a vertical section on line l l of Fig, 6.

Fig. 8 illustrates how wedges may be used to compensate for irregularity in wall alignment before bedding mortar is placed.

Fig. 9 is a section on line 9-9 of Fig. 11.

Fig. 10 illustrates part of the underside of a form of slab,

Fig. 11 is a section on line H-ll of Fig. 10.

Figs. 12 and 13 show forms of clamping members attached respectively to the tie-member overlying the back of the arch and to the chordal tie-member.

In accordance with my invention the walls or other supports would be designed and built with the View of supporting an arch construction of a predetermined weight and desired curvature. The skewbacks or the bearing surfaces for the arch and the abutting ends of the arch provide for the transmission of oppositely acting forces which are commonly augularly disposed with respect to the horizontal. The vertical and horizontal components of the forcestransmitted by an arch can be counteracted by a vertical wall or other support and a tension tie-member extending between the ends of the arch in the event that the supports are not sufficiently rigid unto themselves to withstand the horizontal thrust. A variety of forms of arches and arched roofs isavailable from established engineering designs, including arches in the form of circular arcs, parabolas, inverted catenary curves and other approved forms.

The roof illustrated in the drawings is formed from a seriesof arch elements, and having determined upon a given span and roof curvature, the number and shapes of the various arch elements required for a given span are fabricated. These are required to meet certain conditions respecting the joints which in general would require: (l) The limits within which the resultant pressure acts should be such that the pressure will be distributed over the entire surface of each joint; (2) the direction of the resultant pressure should be nearly at right angles to the surface of the joint; and (3) a maximum intensity of compression on each joint, including the base, must not exceed the safe compression strength of the material. It is desirable that the lines of action of the resultant pressures on the successive joints of an arch act within the middle third of the depth of the joints.

Having designed the roof or other arched structure in accordance with well-established engineering principles, the required number of arch elements may be fabricated or obtained from stock, should a standard design be adopted. The

use of slabs cast or molded of concrete in any of its commercial forms, including asbestos-cement and mortar, and also to the use of such materials as clay, tile, glass, plastics, artificial and natural stone, and other materials having sufficient compressive strength, it will be understood that the method of erecting the arch has applications irrespective of the nature of the materials of which the arch elements are made. In this connection slabs suitably reinforced with a light steel structure could be employed to meet stress conditions within a slab due to the design of a particular arch. V

The individual arch elements IE, I I, I2, etc., are preferably assembled on their sides in end to end abutting relationship, as shown in Fig. 2. This may be accomplished by laying them along a curved line or template laid upon the ground. .A chordal tie-member I5 is secured by means of the clamping members [6, ll, to the ends of the string of assembled arch elements. These clamping members may be formed as hooks to overlie the joint ends of the base elements, as shown in Fig. 13. or any other suitable form of clamping element may be provided. A similar tension tiemember I8 is placed to overlie the back or extrades of the assembled arch. This tie-member also has attached to its ends clamping members [9, 20, which engage the joint surfaces of the end arch elements. These clamping elements may also be in the form of hooks, as illustrated in Figs. 12 and 13.

The tie-members are preferably steel rods which are sufiiciently strong to be practically inextensible under the stresses applied. Tie-member I8 is preferably disposed centrally of thestring or course of individual arch elements constituting the'arch on an even keel.

{After the tie-members have been properly placed, tension is applied thereto by tightening members such as boomers or load binders'or' any adjustable tighteners, such as a turn-buckle 21 or a bolt 22, as shown in Fig. 3, for example. The tensional stresses applied to the tie-members'are in such magnitudes as to impose compressional stress in the assembled arch elements and maintain them as a stable unit during carriage. I he stress in the chordal tie-member l5jopposes the stress set up by tightening the other or overlying tie member prior to lifting the assembled elements and compensates in part for the horizontal thrusts at the ends of the arch. Thetie-member l8 overlying the extrados of the arch contributes to the compressional forces imparted to the arch elements and to preventing the assembled arch elements from deflecting from their abuttingrelationship.

As thus assembled the arch may be carried as a unit. For erecting the archa bridle 24 or other lifting means is attached to tie-member i8 for engagement with the hook 25 of a hoist, Fig. 4.v

lowered onto previously prepared bearings ori skewbacks 28, 29. After it has come to restin its final position, thetie-membens I'Ea'nd l8 may be removed and the walls will support the arch as intended. Should the walls not have been desighed to Withstand the thrust of the arch, beams or rods such as 30 may be anchored as at 3| and 32 in the supporting walls or whatever bearings are provided before the arch is lowered into place.

When suspended from a hoist the resultant pressures on the successive joints between the assembled arch elements approximate the pressures which will obtain when the arch is erected. The forces exerted by the tie-members maintain the arch elements in arch-supporting relationship. Consequently there is no appreciable change in the condition and dimensions of the arch when it is set upon its bearings or skewbacks and the binding tie-members are removed.

In order to enable the removal of the clamping means at the ends of the carrying tie-members l and 18, slots or grooves 33, 34 will be provided in the skewbacks or, as an alternative measure, the joint surfaces in the ends of the end arch elements may be recessed to receive the hooks IS, IS, and H, 23. For removing these hooks, the tie-members may be loosened at 2| and 22 so that the hooks can be turned through 90 degrees and withdrawn from slots 32, 33.

The roof may be progressively built by the successive placing of individual arches side by side, as illustrated in Fig. 7.

Should it be desired to avoid the use of tiemembers anchored permanently to the walls of a building, the chordal tie-members may be used as construction elements. A part of a roof employing this construction is shown in Figs. 6 and 7. In this modification the tie-member 35 balances the horizontal thrust of the arch. The arch rests in place upon skewbacks 36, and grooves 37 are provided in the skewbacks for accommodating the clamping hooks 38. The recesses 31 may be filled with mortar which, if desired, may also fill the trough 39 between the supporting wall and back of the arch.

It is appreciated that in some cases mis-align ment will occur between the supporting walls, and when this happens some expedient, such as wedges 40, 4|, Fig. 8, may be employed for backing up the bases of the arches. In such case the wedges would be positioned before the binding tie-members are removed from the arch. The space between the skewback and the abutting surface of the arch could be bedded with mortar or other material. I

An important attainment of the present invention is the saving of weight and material. The thickness of the arch or the depth of the individual arch elements may be computed to attain the greatest saving in weight, and it will be appreciated that the stronger the material, the lesser the required thickness of the arch elements. Although the thickness may be uniform throughout the length of each arch element, in some cases it is desirable to provide enlargements at the joints of the arch elements to provide footings having greater depth than the thickness of the slab between joints. Such a slab is illustrated in Figs. 9, and 11. The effect of the enlarged footing 44 is to provide a joint surface 45 having areas greater than the mean crosssectional area of the slab. between footings so as to assure sufficient strength at the joints and also provide increased frictional grip between the joinder surfaces. The slab can be further lightened by the provision of grooves 46 leaving ridges running parallel to the arch-ring.

The lines of joinder between adjacent courses and between the individual slabs within arches may be caulked with pitch or other sealing material, if desired.

It will be appreciated that mortise and tenon connections may be provided in the abutting surfaces of the slabs, and that other forms for connecting the slabs together may be employed, such as dowels, aligning lugs, overlapping reinforcing, wire screening or other devices or materials embedded in the slabs, but all such appurtenances are auxiliary features not required for the practice of the present invention. Such appurtenances might be availed of for improving the weather-proofing of the joints and for facilitating the assembling operation, but are not indispensable.

While I have described herein the principle of my invention in connection with the construction of arched roofs, it is to be understood that this is only one mode of embodying that principle and that I contemplate other uses and constructions within the scope of the appended claims.

What is claimed is:

1. The method of constructing a curvilinear arch from individual arch elements including the steps of assembling an arch by placing individual arch elements on their sides on a substantially horizontal surface and with their ends in abut-- ting relationship in the respective positions they are to occur in the arch, subjecting the arch elements at each end of the assembled arch to forces of such magnitudes and directions as to create resultant pressures on the successive joints at the abutting ends of the assembled arch elements while constraining the back of the arch in its assembled form to thereby hold the assembled arch elements against deflecting from their assembled relationship, and erecting the arch as a unit with the arch elements at each end of the arch resting on prepared abutments.

2. The method of constructing a curvilinear arch from individual arch elements including the steps of assembling an arch by placing individual arch elements on their sides on a substantially horizontal surface and with their ends in abutting relationship in the respective positions they are to occur in an arch, applying tie-members over the back and opposite the intrados of the arch and extending between the arch elements disposed at the ends of the assembled arch, subjecting the tie-members t'o tension to hold the assembled arch elements as a rigid body, and erecting the arch by carrying the arch and placing it as a unit on prepared abutments.

3. The method of constructing a curvilinear arch including the steps of assembling a number of pre-cast arch elements in the relation they are to remain in when erected, binding the arch elements in their assembled relationship by tiemembers extending from and between the arch elements at the ends of the string of assembled arch elements and over the back and under the arch of assembled arch elements, tensioning said tie-members to hold the assembled arch elements in their intended relationship, carrying the asthe ends of the assembled arch'elements, over the 1 back and opposite the intrados of the assembled arch elements, tensioning the tie-members tohold the assembledarch elements as a rigid body, and placing the assembled arch elements as a'unit on prepared abutments.

5. The method of erecting an arch including the steps of assemblinga number of arch :elements in the relation they are to remain as parts of an arch, binding the arch elements in their assembled relationship by tie-members extending from and between the arch elements at the ends of the string of assembled arch elements and over the back and under the arch of assembled arch elements, tensioning said tie members to hold the assembled arch elements in their intendedrelationship, lifting the thus assembled arch as a stable unit and depositing it on previously prepared bearings, and removing the tiemembers which bound the arch elements as a stable unit during erection.

6. The method of constructing a curved roof from individual arch elements including the steps of assembling individual arch elements in the respective positions they are to occur in an arched roof, fastening the ends of tie-members to the arch elements at each end of the arch,one of said tie-members extending between the arch elements at the ends of the arch and overlying the extrados of the arch and another of said tiemembers extending as a chord between said end arch elements, tensioning said tie-members to create resultant pressures on the'successive joints between the assembled arch elements and to hold the assembled arch elements as a rigid body, carrying the arch thus assembled and placing it upon prepared abutments, and removing the tiemember overlying the extr'ados.

7. An arched unit for use in constructing an arched roof comprising in combination, a course of individual prefabricated arch elements ,arranged in series with joint surfaces of adjacent arch elements abutting one another, a tensioned tie-member overlying the extrados of the assembled arch elements and secured at its ends to the arch elements at the ends of the course, and a tensioned tie-member also secured to the arch elements at the ends of the course and extending between the same beneath the intrados of the arch, the tensional stresses in said tie-members being of such magnitudes as to maintain the course of individual arch elements in equilibrium.

8. In a roof, the combination comprising a plurality of individual curvilinear arches forming a roof covering, each of said-arches consisting of a course of individual-arch elements held together and supported as an arch independently of its supporting members underlying its ends, the individual arch elements being arranged in series with joint surfaces of adjacent arch elements abutting one another, each arch in said series of arches having a tensioned tie-member connected at its ends-t0 the arch elements at the ends of the arch and extending as a chord of the arch whereby the reactions of the arch at its ends are counteracted and the arch is sustained in erected position, and bearing supports underlying the arch elements at the ends of each arch, said bearing supports having slots in their bearing surfaces for providing space for the passage of said tensioned tie-member and for enabling its disconnection and emoval from the arch, if desired.

JOHN S. SHERMAN.

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