US2908139A - Prestressed masonry structures - Google Patents

Description

United States Patent F HYDRAULIC IMPACT PULSATOR TRANSMISSION SYSTEM Charles F. Warren, deceased, late of Paragould, Ark., by Kathleen Warren, executrix, Paragould, Ark., assignor to Charles F. Warren, Jr.

Original application April 12, 1946, Serial No. 661,542,

now Patent No. 2,676,464, dated April 27, 1954. Divided andthis application April 2'1, 1954, Serial No. 424,629

6 Claims. (Cl. 6054.6)

The invention relates generally to hydraulic impact pulsator transmission systems and more particularly to a system adapted to transmit impacts by means of a reciprocating column of fluid. It is the general object "of the invention to provide a new and improved system of this character.

This is a division of application Serial No. 661,542, filed April 12, 1946, for Patent 2,676,464, upon a Hydraulic Impact Pulsator Transmission System.

Another object is to provide ahydraulic impact transmission system for use with portable impact tools; and particularly one having a conduit between an impact producing unit and an impact tool unit, means in the impact unit for filling the conduit with a fluid (as for example, oil or other suitable liquid) and for maintaining a column of fluid in the conduit under static pressure, means for imparting rapid reciprocating movement to the rigid column so formed, and means at the impact to'ol unit end of the conduit forminga restricted return outlet for excess fluid supplied to the conduit. A further object is to provide such a system with manually operable means at the impact tool unit for enlarging the return outlet for the fluid so as to relieve the pressure on the column and stop the operation of the tool.

Another object is to provide an impact transmission system with an impact producing unit, an impact tool unit and pressure fluid supply and return conduits con- :necting the impact unit with the impact tool unit, together with control means carried on the tool unit for starting :and stopping the operation of the tool when the impact unit is in operation.

Another object is to provide a new and improved impact tool unit for transmission system.

A further object is to provide a new and improved Ihydraulic impact transmission system embodying a reciprocable rigid column of fluid, means for reciprocating the column, means connected to one end of the column :for supplying fluid thereto at a rate in excess of the leakage therefrom, and means at the other end of the column for controlling the discharge of excess fluid :therefrom.

Other objects and advantages will become readily apparent from the following detailed description taken in connection with the accompanying drawings 'in which:

Fig. 1 is a perspective view of a preferred form of the invention.

Fig. 1a is a perspective view thereof ona reduced scale with two impact tool units.

Fig. 2 is a vertical section approximately along the line 22 of Fig. 3 of the pumping unit thereof.

Fig. 3 is a plan section along thelin'e 3-3 of'Fig. 2 i Fig. 4 is a vertical section on a reduced scale'along the line 44 of Fig. 2. i

Fig. 5 is a vertical central section through the impact 1001 Unit.

.Fig. 5a is'anenlarged fragmentary view of'ap'ortion 'Of Fig. 5.

Patented Oct; 13, 1959 Fig. 6 is a fragmentary section along the line 6- -6 of Fig. 5.

Fig. 7 isa similar fragmentary section with the control valve in an alternative position.

While the invention is susceptibleof embodiment in many difierent forms, there is shown in the drawings and will herein be described in detail one such embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

In the form selected for purposes of disclosure this invention is embodied in a hydraulically actuated impact tool system comprising generally a pumping or impact producing unit A (Fig. 1), an impact tool B, a supply conduit C connecting the pumping unit to the impact tool for conducting a fluid (such as oil) under'pressure to operate the impact tool and a return conduit DIfO'I returning excess operating fluid to the pumping unit. As shown in Fig. 1a a pair of impact tool units B are connected to an impact producing unit A,.the unit A and a drive motor E therefor being mounted on a common frame F. As shown, a belt G runs from a pulley on the motor to a pulley H on the drive shaft of the unit A.

Impact tools of the character to which this invention relates are in the nature of hammers, drills and tamper's, which are similar in function to corresponding pneumatically driven tools. However, such tools of thepneumatic type require the provision of an air compressor unit accompanied by an internal combustion motor or other prime mover of substantial power, Whereas the combination ofan impact unit or pump and an impact tool directly connected to the pump'by means of .a flexible conduit which confines a continuous and rigid column of fluid under pressure extending from the pump to the tool, constitutes a much more efficient mechanism and employs only a fraction of-the .power of the pneumatic system for driving the pump and operating the tool. The present invention is an improvement in by: draulic impact transmitting systems of the type embodying a rigid reciprocable columnof oil (or other liquid) and constitutes an improvement in the system of Patent No. Re. 22,122, issued to Charles F. Warren and William R. Smith, dated lune-16, 1942. A

In the form illustrated the pumping unit is adapted to operate two impact tool units. The operating elements of the pumping unit are mounted in a housing 1 which serves also as a reservoir for the hydraulic fluid, and as seen in Fig. 1 isof substantially rectangular form except that the top wall 2 and one end wall 3 are con nected by a curved portion 4 substantially concentric with the axis of a drive shaft 5. This shaft extends through a hollow boss 6 in one side Wall of the housing, and the boss 6 provides a pocket or recess 6a which seats theroller bearing 7 for the shaft together with a packing element 8. A circular opening 9. in the =opposite side wall of the housing is large enough to, permit insertion or withdrawal of the shaft 5 with itsfdriving eccentrics 10, 10 together with the bearing assembly; and this opening 9 is closed by a cover plate '11-, which includes an inwardly open pocket or recess 11a to support a roller bearing '12 for the inner end of the shaft 5. Each.

' as a-unitthroughthe opening. 9, and its mounting'in the housing will be completed by application of the cover Oct. 13, 1959 w, o -rofl m- I 2,908,139

PRESTRESSED MASONRY STRUCTURES Filed July 23, 1957 4 Sheets-Shae; 3

F167 62. 64: FIG-8 INVENTORS I BY Q7? 8.7 61- ATTORNEY United States Patent- ,908,1 9 g N PREQTRESSED MASONRY STRUCTURES w liaut -fi mm Conc r s pb: a l W stfo d, s

This invention relates to masonry structures and. to,.

methods: of producing structural membersfrom .monolithic stone. bodies.,of the-class including granite and other, natural stones which areremoved from their origi-.

nal; geological formations.

Structural materials ofthe natural stone class, such as are exemplified by granite in particular, although charactel zed by great-inherent. compressive strength, exceeding1y, fine.-Weatheri,ng characteristics, and complete absencegof.,compressiyeicl' ep;and shrinkage, do not have the tensilestrength characteristics which may be desired inv some ;'st1 "uctural members.. Therefore, it has not been practical to. .utilize granite, in-- structures which are subjecte i,,to. .bending momentsthatproduce a net tension. aeross a mpnolithic body or across joint..planes of abutment of a composite stone structure.

It, is the object of the present invention ,to provide improyed load bearingpharacteristics .in structural. members ,ofifmpnolithie. stone. and .to devise improved .methodsEof forming structural members of. the natural stone class. Specifically, it object to provide monolithic stqnesquctllral members which characterized by the utiliiation ofithe superior.compression properties of the naLHraLstOne. Without the introduction of .major tensile esses: nat enauu le m e- It'islalso an object pi theinyention to devise composite structural inember ssmade-uppf a plurality ofmonolithic pieces of. naturahstonewherein the combined-mass is subjected .to mechanically induced compression forces.

These. andotherobjects .will; be more fully understood from,;the.,following.;discussion and disclosure ofi the in-' vention,v

From a study of the inherent tensile strength limita Q =f Ammmh Q-B ne bodyernployed :as a structural member, and,' .havin 'n .mindtheforegoing objectives, there. .,has.,evolved .theinventive concept of re-establishi fi.monolithiestone bodya part of the compression- Originally, P1ZSD L n the bodyas it occurred natuv geolo'gicahformation. This concept further;

includes, the idea 1 of. exerting .compression forces within thepmonolithicstone, body of a predetermined value so as .to.obtain,.a. structural member whose load bearing capacity is a direct function of the total recompression in troducedjnto .thQ monolithic. stone body.

It is,compre hended, asag'eneral proposition, that the natural compression forces originally occurring in monolithic natural stone have, When-Partially reestablished in a n10no1ithic.. na tt1ra1.stone structure, a direct bearing on thQload carrying capacity of said structural member. Hdweyer, them-6 1 magnitude ofthe original compressive stresses in thevnaturalstone in its geological formations islunknown andtherefore the limitations on reintroduction,ofjcompressive stresses are given by way offopinionbupmay wellfextendflo the ultimate compressivestrength of the, natural stone.

weihave found that thisconcept-may be implemented.

by making use of wellknown devices, such ashigh tensile 2,908,139 Patented Oct. 13, 1959 2., stonebody is, in accordance .with theinvention, formedn with an opening of predetermined sizeand location; Ins. this opening is-plaeed a stressing element, such; as :a; steel tendon, whichis ,thereai ter subjected :to, a .suitabler: tensioning force and. held in ten sionbyanchoring meanm. onopposite sides of. the stonebody. There is thcmaccomsh plished a recompressing of.-the..stone with-the; desired change in. the load bea gingpapabilitiesof the natural stone.structure.. A change is. found also in themodulus; of elasticity of thenatural stone: 7 Unlike the wellrknowng stress-strain curve for -a. mater ial 'such;as .conorete,- where. they compressive modulus 5 elasticity decreases with stress throughout a rangeeof.increasing zstressvalues, thQzl'G-r,

establishment of compression. in a compressed-natural;

stone. body which. has been-subjected, to decompression-. results in. ,the. monolithic stone body-haying a, comprese. siommodulusof. elasticity which increases. with stress throughout a range-of stress values. Similarly, othen, desirable. changes are. obtained, as. appears from. the. following detailed discussion of. the, invention.

In; the accompanyingdrawings,

Fig. 1 is.a si de eleyational. view. illustratingv astructural. membersupported, in. a transversely extending ,posi.- tion with a load supported thereon;

Fig. 2 is another sideeleyational.yiewshowinga trans, versely supported .struetu ral. member. of the inyention... and fu-rtheriindicati ng a modified form. of. .restr essing;.ele a lq' ati Fi .i a r sssstiona fl wkm on h ti e rfie of Fig. 2 and further indigatesra.bonding agent for,an,-;, chorin g. the rcstressing element, solidly. in. the structural embe Fig is a detai led .viewshoyvingthe.opening formed in thsl ms me r. qn s i nea e rss inst l e enu;

i -.5 sen thsr i l Ya i ns isi las t qslr transversely 'suppprted structuraL-member made. up rot Plurs tm risk er. mq sl t ie ts q t o e he ymsaa l t. ars t ss n filsmsnt;

Fig. 6 is agraph showing the curve .for.thestress-strain; l tionship f omprss nfismrbn t i 'i s bearing membensueh as thatillustrated in. Fig.. 1.-- figure'; also contains a comparative curve for; the stress;T Strain elstis h n P e en in t s rs e. loadl s fi s emb r m; 1 ns r sti Figs. 7, 8 'and,9"'illils t rate a. specific, adaptation -of o o this. e. oad. e ri mem r o -Ye n. m loyediua st imaw l w u Figs. 10, 1 1 an d 12 illpstrateaload bliallng rnennbgr suppprtedpn monolithic, stone columns. secured in compressed relationship; i

Fig. 13 is a diagrammatic view showing .a nionolithic. beam provided witha plurali ty ofrestressing elements extendiug in diftferent directions; and

Fig. 14 is a perspective view illustrating. a surface ..plate.- made "up of' a plurality of monolithic, stone. bodies lipid together by means of, restressing, elementsjwhich havebeen tensioned to apredetermined degree. U i

Referring first to the stru ctural member shown in..Fig 1, numeral 2 denote s a monolithic stone body, such.as. granite, which has been remo ed fro -its, original, logical formation by, quarrying and subsequent. finis ng operations. In its original state, this monolithic is toner body was under very heavy; co rnpre ssi ve,v forces ofl azi order ofn agnitude of 5000 pounds per squ a re inch greater. -It is pointedo u t that, during thep'rocess of sep arating the stonebody fromalarge mass of which itvvash a constituent part, there necessarilytook place arelieving of stressesin the. bedrock andthe stonebody, (len tfinally; removed, was, therefore, in a decompressedstatei Inaqcordanee ,with the inv ention, the structural meme:

her 2 in the decompressed state described is formed with;-

an opening 4, as by drilling or other suitable means. In this opening, there is located a restressing element 6 which may, for example, consist of a steel tendon. The tendon is then subjected to tensioning forces of some suitable magnitude and held by means of anchoring devices as 8 and 10 located on two opposite external surfaces of the structural member 2. Although not necessarily so, it may be desired to place this stressed tendon 6 in a position such that it is nearer one side of the structural member 2 than the other.

As an example of one specific tensioning force which may be used, there may be cited a force of 100,000 pounds which, in one case, was applied to a rectangular beam having a cross-sectional area of 120 square inches. This structural member may then be supported in the manner suggested in Fig. 1 on spaced-apart abutments 12 and 14 and subjected to the weight of a load 16. The binding stresses developed by this arrangement would normally induce compressive stresses at the upper surface of the natural stone component of this structural member and tensilestresses at the lower surface 2b. However, by recompressing the natural stone before any working loads are applied, the entire stress distribution is altered and the natural stone acts only in compression. By utilizing only the compressive properties of the natural stone, its loadcarrying capacity is greatly increased to a point where the application of monolithic stone for a substantial span in a beam member of this type becomes practical and capable of supporting relatively heavy loads such as are represented by the load 16 suggested in Fig. 1.

In Fig. 6, there is illustrated graphically the stressstrain curve for granite when employed in a manner such that it is subjected to compressive stresses. As will be apparent from an inspection of Fig. 6, the secantmodulus for this granite member increases with increased stress all the way through a range of stress values starting at zero and running up to a point of failure. This difiers remarkably from a similar stress-strain curve for standard concrete which, as shown in Fig. 6, falls away rapidly after a very slight rise in the stress range.

In Fig. 2, there is illustrated a monolithic stone structural member 20 in which is located a stressing element 22 which is arranged in a curved path, as shown. This arrangement is designed to provide a more favorable stress distribution at the ends of the structural member while providing adequate resistance to bending stresses which are maximum at the center of the member.

Fig. discloses another arrangement in which a plurality of pieces of monolithic stone 23, 24, 25, and 26 are secured together in abutting relationship by means of a stressing element 28. This member not only secures the pieces together but also provides a recompression force which imparts a more favorable load bearing characteristic to this structural member, particularly with respect to the load 30.

In Figs. 7-9, inclusive, We have further illustrated a somewhat more specific adaptation of the invention in the form of a prestressed granite masonry retaining wall. It will be understood that the dimensions of such a wall are, in general, governed by the height of the bank which is to be retained as well as the allowable bearing pressure of the soil in the bank. In this particular form of the invention, a plurality of granite ashlar pieces are combined with prestressed granite counterforts supported on a suitable concrete footing and preferably surmounted by a granite cap.

In the structure shown, numeral 50 denotes the concrete footing onwhich is mounted a plurality of ashlar pieces as 51, 52, 53, etc., and these ashlar pieces constitute one section of a retaining wall facing. A second tier of ashlar pieces as 54, 55, 56, also supported on the concrete footing 50, are spaced apart by the granite counterfort 58 which consists of a vertical granite body having inclined surfaces as 58a and 58b. A granite cap 60 is received on the top of the tiers of ashlar pieces,

- vducedby plotting a stress-strain factor against time is substantially a straight line indicating that there is no In accordance with the invention, we further impart stability to the counterfort 58 by the use of tensional high strength steel tendons as 62 and 64 which are embedded in the concrete footing at their bottom ends and which are located through the upper end of the counterfort 58 and anchored at points 62a and 64a. The tendons may also be arranged at an angularly disposed position, as shown. If desired, the granite cap 60 may be recessed to provide protective enclosures immediately surrounding the anchor elements 62a and 64a. The ashlar piecesare designed to act as a beam in each of the tiers with all horizontal earth forces being transmitted to the restressed counterforts by means of steel dowels as 70, 71 and 72 which are disposed in the manner suggested in Fig. 8.

In Figs. 10, 11 and 12, we have illustrated still another specific combination of structural components including a. girder member which may be supported on granite columns indicated by the arrows 81 and 82 made up of two tiersof ashlar pieces, as shown in Fig. 10. The tiers may be supported on a concrete footing 84. In this particular arrangement, the tiers of ashlar pieces c0n- -stituting vertical column members are prestressed bycompressive forces at opposite sides of respective ashlar pieces along lines of holding which extend externally of the granite cap.

In Fig. 13, there has been illustrated a jointed stone bean made up of sections 100, 101 and 102 which are held against one another by means of a prestressedsteel tendon 104. The beam may further be provided with transverse tendon elements as 106' and 108.

:In Fig. 6, we have illustrated still another adaptation of prestressed granite in the form of a tool consisting of a jointed natural stone surface plate which may consist of a bed for machine ways. In this form of the inven-' tion, a plurality of granite pieces as 110,112, 114, 1 16, are

secured together by means of prestressed steel tendons as 118, 120, 122, 124 and .126 l and these tendons may be stressed in some predetermined amount which will furnish a restressing of each of the granite components in a desired degree to withstand certain working loads to which the surface plate may be subjected or to resist dimensionalchange from other conditions.

The several different forms of prestressed granite structural arrangements of the invention which have been disclosed furnish a number of outstanding advantages in comparison with concrete. For example, concrete creeps. given load will, after a period of time, show a very substantial increase in the deformation which is present initially on receiving the load. As the period of time'imcreases, the amount of deformation may grow 'appreciably greater.

In the case of granite, the curve of deformation prochange in deformation at anytime.

A necessary result of so-called creep present in eoncrete is the definite tendency for a loss in the steel tendon f prestressing force which may be utilized in any given in-I stance. This loss can be directly traceable to creep to an extent of about 10% of the original tension force ex- 1 erted in the steel tendon. Thus, in the case of concrete,

For instance, a body of concrete under a proximately less steel in the tendon specifications since it does not lose its effectiveness as it does in concrete.

A further advantage of the prestressed granite of the invention is present from the degree of control which can be realized. In the case of poured concrete, it is impossible to be sure of the exact strength produced by any given mix and it is customary to wait for a period of from several days up to a month to determine the strength of any given mix. In contrast, the granite which may be thought of as having been already formed and cured in nature can be tested at anytime and its strength known precisely before its installation.

In this same connection, there is realized a further advantage in that a monolithic granite structure can take a full load as soon as it is tensioned and supported, whereas, with concrete, it is necessary to wait a considerable period of time to strip the forms in which the concrete is poured and to allow the concrete to fully set, which may take as long as a month.

For the foregoing reasons, therefore, it will be apparent that we have disclosed a novel and useful structural material and method of producing a restressed stone body made up of one or more component parts. These structural components may be embodied in various types of structural combinations to impart various advantages for each specific application.

While we have shown preferred embodiments of the invention, it should be understood that various other changes and modifications may be practiced within the scope of the appended claim.

6 Having thus described our invention, what we claim is: A monolithic natural stone structure for use as a retaining wall comprising in combination a base, a plurality of tiers of stone components mounted on the base, counterfort members of stone having a compressibility characteristic resulting from the stone members having been subjected to and relieved from earth pressure and extending vertically upwardly between each of said tiers, a plurality of prestressed steel tendons anchored on the base and secured to the upper portions of the said counterforts and means for interlocking the said tiers of stone components with the counterforts, said prestressed tendons being arranged at an angle to the vertical center line of counterforts and operating to place the counterforts in a state of compression and resist horizontally acting earth forces.

References Cited in the file of this patent UNITED STATES PATENTS 375,999 Jackson Jan. 3, 1888 1,504,816 Cummings Aug. 12, 1924 2,102,447 Whitacre Dec. 14, 1937 2,413,990 Muntz Jan. 7, 1947 OTHER REFERENCES Materials of Construction, a text book, by Mills, Hayward and Rader, published by John Wiley & Sons, i[nc., New York, 1955, sixth edition, page 310.

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