US3530676A - Concrete wall construction with tension-loaded external reinforcing element and method - Google Patents

Description

Sept. 29, 1970 p YORK 3,530,676

CONCRETE WALL CONSTRUCTION WITH TENSION-LOADED EXTERNAL REINFORCING ELEMENT AND METHOD Filed Feb. 19, 1969 2 Sheets-Sheet 1 PM L.. Q

INVENTOR. PHILIP J. YORK ATTORNEYS 3,530,676 LOADED EXTERNAL REINFORCING ELEMENT AND METHOD Sept. 29, 1970 P. J. YORK CQNCRETE WALL CONSTRUCTION WITH TENSION Filed Feb. 19, 1969 2 Sheets-Sheet 2 INVENTOR. PHILIP Jj YORK ATTORNEYS F/G. a

3,530,676 CONCRETE WALL CONSTRUCTION WITH TENSION-LOADED EXTERNAL REINFORC- ING ELEMENT AND METHOD Philip J. York, Mill Valley, Calif., assignor to J. H.

Pomeroy & Co., Inc., San Francisco, Calif., a corporation of Washington Filed Feb. 19, 1969, Ser. No. 800,525 Int. Cl. E02d 5/20 U.S. Cl. 61-39 6 Claims ABSTRACT OF THE DISCLOSURE A concrete wall construction with tension-loaded external reinforcing element serves to carry the major tens1on forces experienced by a concrete wall on the excavated side of a wall when subjected to earth pressure from the opposite side. Struts then act against the unexcavated side of the wall to apply and develop compressive forces in the subsurface region adjacent the unexcavated side face of the wall.

BACKGROUND OF THE INVENTION This invention pertains to concrete wall structures and a method of constructing same. More particularly, this invention pertains to such wall structures as employed in excavations, for example, as in the forming of a foundation for a building, subway, or the like. The invention is particularly useful in constructing wall structures of a type, for example, as shown in U.S. Letters Patent 3,412,562.

Heretofore, in many instances, wall structures have re- "quired supplemental support applied from the excavated side of the wall. A common approach in the supplying of such supplemental support has been to employ elongated wale members disposed horizontally along the face of the foundation wall while horizontal struts, extending for great distances across the entire excavation, are jacked in their longitudinal direction against the wale members of the opposed walls.

These wale members are typically quite bulky, extending for great lengths, are hard to work with and position, and are quite expensive. Further, in many instances, where the use of wale members and transversely extending struts is objectionable from a practical point of view, tie-backs may be used. However, during the construction process, should an accident or loss in the tie-back footing dislodge the tie-back, a portion of the wall structure will then be unsupported in a manner heretofore demanding the utilization of such wale members, with their attendant objectionable aspects.

Thus, there has long been a need for the provision of means serving to provide support to the wall against the action of earth pressure from the unexcavated side thereof without requiring the introduction of the sometimes objectionable wales.

In addition to the above circumstances, it is sometimes necessary for the architect on a construction job to change the plans after excavation has begun and, accordingly, in such instances, and at limited locations, a need may arise not previously anticipated for the application of suitable localized support to the excavated face of the wall acting against counter-forces of earth pressure on the excavated side.

Heretofore, as described in the above identified patent, concrete walls have been constructed taking advantage of arch action support wherein the upstanding wall comprises a number of upstanding soldier beams between which slabs of concrete have been formed. In each of the slabs, the dimensions are such as to generate arch action i nited States 3,530,676 Patented Sept. 29, 1970 support of a type wherein the concrete slab is characteristically subjectel mainly to compressive forces under the earth pressure acting against the unexcavated side of the wall.

SUMMARY OF THE INVENTION AND OBJECTS In general, a wall construction and method have been provided herein for establishing improved lateral support to unexcavated earth bearing against one side of the wall where earth on the other side of the wall is excavated away from the wall. The wall construction in general comprises spaced soldier beams, preferably such as structural steel H-beams disposed upright in a plane and formed with spaced parallel flange portions. A slab of concrete is flanked by the soldier beams and a relatively broad, thin, substantially non-stretchable band, such as of structural steel, is secured to two soldier beams. Means serving to stress the band and place it under tension subjects concrete of the slab to compressive forces on the un excavated side of the wall. Thus, a preloading element, e.g. a wedge, cooperates with struts disposed to act upon the opposite ends of a length of the band. The struts are forced thereagainst in a direction to counteract the earth pressure bearing upon the unexcavated side of the wall.

Subsequent to the formation of a concrete wall of the type comprised of upright soldier beams having contiguous slabs of concrete disposed therebetween, the above wall construction is provided by pursuing the general addition steps of a method comprising attached a stiff, flexible band to each of two of the soldier beams and conditioning the band so as to tend to retain the spacing between the two beams thereby permitting earth pressure to apply compressive forces to the concrete of the slabs in a subsurface portion along the backside of the slabs following the next step of further excavation of earth below the band on the excavated side of the slab while tension forces on the front of the wall are primarily accepted to be carried by the band.

A more specific preferred method includes further steps of preloading the band so as to introduce stress into the band prior to commencing the above mentioned further excavation below the level of the applied band. Struts or other means are employed for applying laterally spaced apart forces to the plane of the wall construction in a direction transversely of the plane and extending away from the excavation after the band has been applied. These forces are suflicient to counteract at least a major portion of the load of earth pressure anticipated to be developed against the opposite side of the wall upon continuing the excavation below the level of the band applied above.

It will be apparent from the above that it is a general object of the invention to provide an improved wall construction and method.

It is another object of the invention to provide a wall construction wherein the arduous task and expense involved in providing elongated wale members externally of the face of the wall is eliminated while retaining substantially the same function achieved in localized areas, or across the entire wall dimension, by means of a unique cooperation of the application of relatively thin, broad inelastic straps working in conjunction with the compressive forces developed in the concrete slabs of the wall itself.

The foregoing and other objects of the invention will be readily apparent from the following detailed description of preferred embodiments of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a portion of an excava- 3 tion incorporating a wall construction according to the invention;

FIG. 2 shows, in plan, a schematic diagram of five (prior art) preliminary steps (2A-2E) pursued in forming a wall construction according to the invention;

FIG. 3 is a diagrammatic plan view disclosing an addition step in the method according to the invention;

FIG. 4 diagrammatically shows in side elevation section a further step in accordance with the invention;

FIG. 5 is a diagrammatic plan view demonstrating another step in the method of constructing a wall construction according to the invention;

FIG. 6 is a diagrammatic plan view disclosing a still further step in the sequence of steps forming a wall construction according to the invention;

FIG. 7 is a diagrammatic side elevation section view demonstrating yet additional steps in accordance with the method of the invention; and

FIG. 8 is a perspective view of a portion of an excavation incorporating a wall construction according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An excavation 10 (FIG. 1) is diagrammatically shown utilizing a wall construction 11 according to the invention. The wall construction 11 is of a type suitable for forming a portion, for example, of a building foundation or other foundation wall and, as disclosed in FIG. 1, is shown in that state of development wherein additional work is continuing and before transverse beams of the building structure itself take the load of earth pressure acting against the unexcavated side of the wall 11.

Wall structure 11 includes a series of upstanding soldier beams 12 which are positioned in the ground so that their lower ends penetrate the ground suitably beneath the lowest anticipated depth of the excavation, e.g. indicated by the line 13.

Slabs of concrete 14 are formed, as described further below, in a manner whereby they are contiguous to the webs and flanges of soldier beams 12 flanking the upstanding sides of each slab 14.

Means are provided, as now to be described, for locally strengthening wall 11 in a manner serving to reinforce those subsurface slab portions which might otherwise be subjected to destructive tension forces in the absence of such reinforcement means.

Accordingly, a relatively broad, thin, substantially nonstretchable band 16 of suitable material, such as structural steel, is secured at its ends (as by welding) to the two soldier beams 12a, 12b. Subsequently, means serving to tighten or place band 16 under tension so as to apply a stress thereto includes the pair of wedges 17, 18 which are driven by suitable known means between band 16 and the plane of wall 11. Preferably, wedges 17, 18 are located to coincide with the position of an intermediate H-beam 120 which permits greater flexibility in correcting unanticipated support requirements at other levels on the wall 11.

As shown in FIG. 1, the means for reinforcing wall construction 11 at the local region above referred to further includes a pair of horizontally disposed struts 19 arranged in known fashion to be jacked longitudinally against the anchored ends of band 16 in a manner to counteract the load of earth pressure acting against the unexcavated side of wall construction 11.

As will be explained further below, the foregoing arrangement serves to subject the intervening concrete of slabs 14 defined between beams 12a and 12b to compressive forces acting in subsurface portions thereof beneath the face 21 of wall 11, i.e. the wall face remote from strap 16. In this manner, the near face (on the excavated side) tends to experience tension forces whereby strap 16 serves to accept or carry these tension forces which the wall construction 11 would otherwise be forc d to carry. As is known, concrete under tension exhibits less strength than under compression and is unsuitable for carrying tension forces.

Another embodiment of the wall construction 11 is shown in FIG. 8 of the drawing. In FIG. 8, the embodiment disclosed provides an elongated strap 22 which extends along a substantial length of wall structure 23 so as to provide reinforcing along a substantial portion thereof.

As disclosed above, wedges 24 are driven between strap 22 and the plane of the wall in order to preload the strap before struts 26 are jacked in the direction of arrows 27. In this manner, the reverse surface of slabs 28 will be subjected to compressive forces as described further below while strap 22 will have accepted the tension forces which would normally be applied to the subsurface portions of slabs 28 on the excavated side face of wall 23.

The foregoing types of wall constructions are preferably formed by pursuing the method now to be described. Thus, the sequence of steps depicted by FIGS. 2A-2E discloses preliminary steps in forminga concrete wall construction comprised of slabs of concrete and H-beam members formed in the ground prior to excavation from one side of the wall. Accordingly, a number of holes 29 may be drilled or otherwise formed in the earth (FIG. 2A). Next, H-beams 12 are snugly inserted into the holes 29. Thereafter, a weakly cemented grout material of conventional composition 32 is introduced into holes 29 so as to surround members 12 whereby upon hardening a moderate earth seal is created about each of H-beam members 12. Subsequently, earth is excavated from betwen members 12 so as to form trench portions 33 defined between each adjacent pair of members 12. Concrete 34 is thereafter placed in trench portions 33 whereby upon p rmitting concrete 34 to harden, arch action support, as designated by the phantom lines 36, will be provided by virtue of the lateral spacing relative to the thickness of the wall.

The above procedure is outlined clearly in the above identified patent.

Subsequent to the above steps, the method then proceeds with the further steps of excavating downwardly to a level 37 at which the band of strap 16 is to be applied. At level 37 beam 12 'will, of course, be subjected to a load of earth pressure as indicated by the arrows 38. After affixing the ends of strap 16 to the two soldier beams 12a, 12b, strap 16 is tightened and preloaded to introduce stress into strap 16 by driving a pair of wedges 17, 18 between strap 16 and the plane of the wall.

From inspection of FIG. 5, it will be readily apparent that this preloading of strap 16 serves to tend to pull the outer ends of straps 16 and their associated beams 12a, 12b toward the excavated side of the wall. This attempted bending of the concrete slabs 14a, 14b introduces, if successful, modest compressive forces in the subsurface region adjacent the excavated side of the wall as indicated in FIG. 5 by the small cs. At a minimum, wedges 17, 18 ought to introduce sufiicient stress into strap 16 so as to maintain at least an equilibrium in the forces within slabs 14a, 14b.

After having preloaded strap 16 as above described, struts 19 are then positioned to bear against the anchored ends of strap 16 and jacked by conventional means such as hydraulic jacks in order to apply forces acting in the direction of arrows 39. These forces, accordingly, constitute laterally spaced apart counterforces applied to the plane of wall construction 11 in a direction transversely of the plane and extending away from the excavation. These forces are applied in an amount so as to counteract that amount of earth pressure which is anticipated to be developed against the opposite side of the wall upon continuing the excavation to a further depth, such as down to the level of line 41 (FIG. 7).

Thus, after positioning struts 19 and applying a major portion of the anticipated earth load expected to be encountered, the excavation is continued down to the level of line 41 or thereabouts which in turn develops the load of earth pressure acting against both the struts and the wall.

From inspection of FIG. 6, it will be apparent that the jacking of struts 19 against soldier beams 12a, 12b causes the unexca'vated side of the wall to be subjected to compressive forces. While the excavated side of the wall would normally contain tension forces indicated by the small ts the tensioning action of strap 16 serves to pick up and carry these forces in tension to relieve the concrete. In this manner, strap 16 serves to accept the tension forces otherwise demanded of the concrete wall.

With reference to the embodiment shown in FIG. 8, it is readily apparent that the ends of each length 25 of the elongated strap 22 are similarly anchored as the strap 16 in FIG. 1.

From the foregoing, it will be readily evident that there has been provided an improved wall construction and method of forming same wherein local or general rein-forcement of the wall may be obtained by relatively simple means not entailing the cumbersome and awkward problems found in the utilization of conventional wall structures.

I claim:

1. In a wall for providing lateral support to unexcavated earth bearing against one side thereof as where earth has been excavated away from the other side, a 'wall construction comprising upstanding soldier beams, a slab of concrete between said beams, a relatively broad, thin, substantially non-stretchable band secured to said soldier beams, and means serving to place concrete portions disposed between the beams to compressive forces in portions thereof underlying that face of the wall remote from said band, while said band accepts tension forces to reinforce that face of the wall adjacent the band.

2. A concrete wall construction comprising soldier beams disposed upright in the earth, concrete slabs formed between the soldier beams, an excavation for-med on one side of the wall, the opposite side being under earth pressure acting against the wall, a substantially non-stretchable resilient reinforcing strap member seoured at the opposite ends of a length thereof respectively to two of said soldier beams to anchor portions thereof at a fixed lateral spacing therebetween, means tensioning said length of said strap, and means applying laterally spaced forces to said two beams in a direction extending away from the excavation and serving to at least maintain said tension in said strap while tending to place under compression slab portions of the opposite side of the wall whereby said earth pressure acting in conjunction with said applied forces serves to place subsurface portions of said opposite side of the wall under compression while said strap accepts tension on the excavated side of the wall to provide external reinforcement of the concrete.

3. In a method of strengthening a concrete wall of a type comprised of upright soldier beams having contiguous slabs of concrete disposed between pairs of said beams, the

steps comprising attaching an inelastic band to each of two said beams on the front side of said wall, and conditioning said band to tend to retain the spacing between said two beams to permit earth pressure to apply compressive forces to said concrete in a subsurface portion of the back side thereof upon excavation of the earth from the front side of the slab while tension forces on the front of the wall are primarily accepted by said band.

4. In a method according to claim 3 wherein the last named step includes the step of driving a wedge between the strap and the plane of the wall.

5. In a method of forming a concrete wall construction of a type wherein soldier beams are disposed upright in the earth and concrete slabs are formed between the soldier beams in the earth, the steps comprising excavating the earth away from one side of the wall down to a predetermined level wherein the wall is subjected to substantial earth pressure acting from the opposite side of the wall, affixing portions of an elongated, relatively strong, non-stretchable element to at least two of the beams, applying suificient tension to said element to tighten same to a point initiating compressive forces in a subsurface portion of the slabs adjacent said element, applying laterally spaced apart forces to the plane of said wall construction in a direction transversely of said plane and extending away from the excavation, said forces being sufficient to counteract at least a major portion of the load of earth pressure anticipated to be developed against the opposite side of the wall upon continuing said excavation to a further predetermined depth, and continuing said excavation to said further depth.

6. In a method of forming a concrete wall construction of a type wherein soldier beams are disposed upright in the earth and concrete slabs are formed between the soldier beams in the earth, the steps comprising excavating the earth away from one side of the wall down to a predetermined level wherein the wall becomes subjected to substantial earth pressure acting from the opposite side of the wall, afiixing the ends of a length of an elongated relatively thin, broad inelastic band of material respectively to each of two of said beams to anchor portions of the two beams thereto, tightening said band sufliciently to tend to draw saidtwo beams toward each other, applying laterally spaced apart counterforces to the plane of said wall construction in a direction transversely of said plane and extending away from the excavation, said forces counteracting earth pressure anticipated to be developed against said opposite side of the wall upon continuing said excavation to a further depth.

References Cited UNITED STATES PATENTS 3,226,933 1/1966 White 61-'39 3,243,963 4/1966 Schnabel 6l39 3,412,562 11/1968 Doughty 6l39 DAVID J. WILLIAMOWSKY, Primary Examiner P. C. KANNAN, Assistant Examiner

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