Prestressed composite pile

Aug. 25, 1964

J. R. BAITTINGER

3,145,540

PRESTRESSED COMPOSITE PILE

Filed March 14, 1962

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ATTORNEY

Aug. 25, 1964 j. _R. baittinger 3,145,540

PRESTRESSED COMPOSITE PILE

Filed March 14, 1962 2 Sheets-Sheet 2

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United States Patent Office

3,145,540

Patented Aug. 25, 1964

3,145,540

PRESTRESSED COMPOSITE ΡΠΕ

Jack R. Baitanger, 2 Wheatley Court, Scotch Plains, N.J., assignor of one-half to John J. Dougherty, Cedar Grove, NJ. 5

Filed Mar. 14, 1962, Ser. No. 179,700

Claim. (CL 61—53)

This invention relates generally to the art of piling and more. particularly to an improved composite pile, the jo upper part of which comprises prestressed reenforced concrete and the lower part comprises wood.

Piles are used to support or to form foundations for structures such as buildings, tanks, bridges, conduits, piers, wharves, etc. by inserting them into or through the yield- 15 ing surface strata far enough to obtain a solid support for the principal structure.

As is well known, untreated wooden piles are frequently unsatisfactory when exposed to salt or brakish water, or when exposed to changing tides or changing water 20 tables. In free water such piles are attacked by marine borers and other insects and are liable to rot. In earth above the lowest level of the water table, they are subject to termites, fungi, mold and rot. Because concrete is not unduly affected by the above destructive forces, it 25 has been proposed to use a composite wood-concrete pile structure having a wooden section entirely below the area where the above destructive forces attack and a concrete section connected to the top of the wooden section.

Composite piles wherein the upper part is formed of 30 hollow cylindrical concrete sections connected by a solid concrete section and fastened together with prestressed steel cables and reenforced by longitudinal and helical wires are desirable as the hollow upper parts of the composite pile provide great point bearing area and large 35 surface area per unit weight of material. The upper part also has a large section modulus, resulting in a high bending resistance. This results in a rigid pile, well able to resist horizontal forces such as winds, waves, earthquakes and the impact of ships. Such hollow upper part of the 40 pile also has a large radius of .gyration in proportion to its weight so that its slenderness ratio is low when column action must be taken into account in the design.

It. is accordingly a principal object of the present invention to provide a composite pile based on the use of a 45 prestressed concrete hollow cylindrical upper section and a wooden bottom section.

Another object of the invention is to provide a composite pile that is especially well adapted to withstand both tensional and compressional longitudinal forces as 50 well as lateral stresses.

. The above advantages and objects are achieved by providing a composite pile that is economical in use and which does not require expensive or scarce speciallyfabricated parts. 55

For further comprehension of the invention and of the objects and advantages thereof, reference will be had to the following description and accompanying drawings and to the appended claim in which the various novel features of the invention are most particularly set forth. ⁶⁰

In the accompanying drawings forming a material part of this disclosure:

i IG. 1 is a side elevational view of a composite pile embodying my invention, only part of the bottom section being shown.

FIG. 2 is a cross-sectional view taken on the line 2—2 of FIG. 3.

FIG. 3 is a top plan view as seen from the line 3—3 Of FIG. 1. ₇₀

FIG. 4 is a cross-sectional view taken on the line 4—4 of FIG. 1.

FIG. 5 is a similar view taken on the line .5—S, of FIG. 1.

FIG. 6 is a top perspective view of a reenforcing, cage.

FIG. 7 is an enlarged cross-sectional view taken on the line 7—7 of FIG. 2.

Referring in detail to the drawings, in FIG. 1, a composite pile embodying my invention is shown and designated generally by the reference numeral 10. The composite pile as can be seen iri FIGS. 1 and '2 comprises two principal parts, a wooden lower section 12 (the lower part of which is not shown) and an upper concrete section. 14.

The wooden section 12 ordinarily will be generally round in cross-section, such as a section of log, although unlike other known structures the cross-sectional shape of the wooden section is not of .particular importance, but its top or butt end 12α must be round, the only requirement being that the dimension and cross-section of this end portion be such as to provide a tight fit in the bottom of the concrete section 14.

The upper section 14,of the composite pile 10 is:a precast prestressed cylindrical concrete body formed of three sections, a top elongated hollow cylindrical body section 20, a bottom hollow cylindrical body section 22 shorter than section 20, and an intermediate solid cylindrical bodv section 24, the intermediate section serving as a joint between the top and bottom sections. The joints between the ends of the top body section 20 and the bottom body section 22 and the intermediate body section 24 are sealed by plastic cement such as the cement known in the market as Epoxy cement. Any other suitable plastic cement may of course be used.

The top body section 20 includes the cylindrical side wall 26 formed of concrete reenforced by a wire cage 28 embedded therein and shown in detail in FIG. 6. The cage includes a continuous wire, looped around, forming helically arranged convolutions 30. The convolutions are tied to each other by means of a series of prestressed metal rods 32 extending across the inside thereof and lengthwise of the cage. The prestressing of the rods 32 was effected by placing the rods on a hydraulic jack. The rods were pulled or stretched by the jack and while under tension'the rods were welded to the inside of the convolutions of the cage.28 where the rods cross the convolutions, the cage having been placed around the rods. After the welding operation, the rods were cut and released from the jack. The rods are welded to the convolutions. The side wall has smooth outer and inner surfaces.

The bottom body section 22 is similarly constructed, including the cylindrical side wall 34 of concrete reenforced by the metal cage 36, which cage consists of the helical convolutions 38 and elongated reenforcing rods 40 therealong.

The intermediate body section 24 constituting the joint between the top and bottom body sections is constituted by a solid round block 42 of concrete formed with a central air tube 46 embedded therein and extending therethrough. Pairs of wires 48, 48 are tangentially arranged with respect to the top of the tube. The pairs of wires cross each other and are welded to the tube. The wires are embedded in the concrete. Similar pairs of wires 5®, 50 are tangentially arranged with respect to the bottom of the tube and are welded thereto. The pairs of wires 59, 50 cross each other and are embedded in the concrete. The wires 48, 48 and 50, 50 serve as reenforcements. During the assembly operation, the tube 46 serves as a vent, permitting air to escape from the bottom body section 22 to and through the top body section 20. Block 42 is reenforced by a metal cage 47 embedded therein.

A series of spaced passages 52 and 54 are formed in the side walls 26 and 34 of the top body section 2® and

3,145,540 the bottom body section 22, respectively, which passages are in line with similar passages 56 formed in the intermediate body section 24 adjacent its periphery. A prestressed cable 58 extends through each set of aligned passages from one end of the body to the other. The cables hold the body sections securely and intimately together and for this purpose the cables are post-tensioned after insertion into the passages.

A metal bushing or collar 60 with an annular flange 62 along one end of the bottom body section 22 is positioned in the bottom or free end of the bottom body section 22. The flange 62 is perforated to receive the ends of the cables 58 and is provided with a shearing edge 64. While six cables are shown any desired number may be used. After the cables are inserted and post-tensioned, grout or concrete 66 is forced through the passages 52, 54 and 56 and while the cables are still under posttensioned condition the grout or concrete is permitted to harden and set, thus anchoring the cables in position. The protruding ends of .the cables are sheared off.

When the composite pile is completely assembled, the bottom surface of the intermediate concrete block 42 will be flush with the upper flat surface 70 of the butt end 12α of the wooden pile 12. The metal bushing or collar 60 will have slid along the butt end 12α of the wooden pile 12, causing some displacement of the wood to provide an extremely snug fit between the wood and bottom concrete body section 22. The increased snugness provided by the bushing or collar 60 is a material factor in developing both tensional and lateral stress resistance.

In assembling and placing the composite pile, the wooden section 12 first is driven with a pile driver in the usual way until its butt end 12α is just above the surface of the soil or water as the case may be. The bottom body portion 22 of the assembled upper section 14 is then placed in position on top of the partially driven wooden section 12, and a suitable mandrel (not shown) is lowered until it rests upon the top of the upper body section 20. The pile driver then is used to drive the bottom body portion 22 of the upper section 14 of the pile down over the butt end 12α of the wooden section 12, shearing off any excess material and thereby fitting the bottom body portion 22 snugly onto the wood.

Under most conditions of use, this improved composite pile structure will be more than sufficiently resistant to tensional stresses.

While I have illustrated and described the preferred embodiment of my invention, it will be understood that changes in details of construction might be made without departing from the principle of the invention and I desire therefore to be limited only by the state of the prior art and the appended claim.