US2017899A - Building structure - Google Patents

Description

Gct. 22, 1935. J. GIBSON BUILDING STRUCTURE 2 Sheets-Sheet 1 Filed June 13, 1933 ED INVENTOR BY JOSIAH 6155011 v ATTORNEY Get. 22, 1935. J. GIBSON BUILDING STRUCTURE- Filed'June 15, 1955 '2 Sheis-Sheet 2 I INVENTOR 51.42! 61550N A TTORNE Y Patented Oct. 22, 1935 ITED STATES PATENT OFFIE 2 Claims.

This invention relates to a building structure, and particularly pertains to the construction of dams, grain elevators, dock walls, break waters, and the like.

In building dams and structures of like character designed to resist lateral pressures, the dc signers are concerned with problems relating to the solidity and permanence of the structure as it resists the pressure of impounded water, and they are also concerned with problems having to do with the flexibility of the dam whereby its structurewill not become weakened due to excessive strains and shock, such for example as might be produced by an earthquake.

In building dams requiring great strength it is usual to build the dam of concrete suitably reinforced. Such structures require considerable complicated form work and a large amount of concrete. It is the principal object of the present invention to provide a concrete dam structure which will have all of the features of strength of concrete dams of conventional design but will require a lesser amount of concrete in its construction and will dd features of flexibility which will insure that the dam will not only withstand excessive water pressure but will resist earth shock normally tending to fracture the structure.

The present invention contemplates the construction of a dam of vertically extending cellular construction formed of cementitious material, and which structure receives material in permanent granular form adapted to give weight and stability to the relatively light cement skeleton of the dam.

The invention is illustrated by way of example in the accompanying drawings in which:

Figure 1 is a view in plan showing the cellular structure of the dam and a typical method of placing it in a gorge to be obstructed.

Fig. 2 is a view in front elevation showing the dam indicating the manner in which its footings are built. and indicating by horizontal dotted lines the courses of the cellular structure as integrally cast.

Fig. 3 is a view in central vertical section through the dam as seen on the line 3-3 of Fig.2 and indicates the bater given to the upstream face of the dam and the manner in which the horizontal thickness of the dam is progressively increased toward the base thereof.

Fig. 4 is a view in horizontal section through the dam as seen on the line 44 of Fig. 3, showing the hexagonal shape of the cells, the elongation of the cells on the upstream side of the dam, and a portion of the drain system.

uniform in sectional dimensions.

Fig. 5 is an enlarged fragmentary view in one of the cell structures, disclosing its reinforcement.

Referring more particularly to the drawings, it will be seen that the cellular structure of the 5 dam is formed of a plurality of hexagonal cells l0 which have a central hollow portion l I unobstructed throughout the length of the cell and extending vertically from the bed rock indicated at l2 in Fig. 3 to the top of the dam. These cells are cast in horizontally arranged courses, and it will be seen in Fig. 3 that these courses are indicated as I3 to l8, inclusive. The vertical heighth of each horizontal course progressively increases from the relatively short course l8 to the course I3 of extreme heighth. The course of cells l3 which forms the upstream face of the dam comprises front wall sections I9 and of each cell disposed at an angle to each other and forming angular corrugations continuing across the width 20 of the dam face, and each corrugation extending the full heighth of the dam. These walls progressively decrease in thickness toward the top of the dam. This may be done by a gradual continuous taper of the wall or by progressively stepping the wall in as the various courses of the dam are cast. In Fig. 3 of the drawings the upstream face of the dam is shown as formed with the wall battered from the toe 2| of the dam and gradually tapering as the wall progressively decreases in thickness at each course. The upper end of the cells I 0 in each course are substantially The sectional formation of the cells in the upstream facing course l3 progressively elongate toward the base of the dam, as shown in Figs. 3 and 4 of the drawings. This gives added strength to the dam towards its base. The lower portions of the cell structure are embedded into the bed rock 12 so that resistance to horizontal shear at the base of the dam may beadequately provided.

Referring to Fig. l of the drawings it will be seen that the cell elements not only have the angular faces formed by wall sections l9 and 20,

but also the parallel faces .22 and 23 which ex- 4b tend at right angles to the upstream face of the dam. Rear faces 24 and 25 complete the formation of the individual hexagon rings of the cells. It will be recognized that these hexagonal structures provide great strength and that when they are combined in an integral cast cementitious skeleton or frame for a dam will have an enormous amount of resistance to pressure with a minimum requirement of cementitious material. 5

The cellular structure is provided with horizontal re-enforcing elements 26 and vertically extending re-enforcing elements 21 which may be tied into a re-enforcing structure 28 occurring at the intersection of the various wall elements as indicated in Fig. 4 of the drawings. The interior faces of the cell walls are formed with horizontally extending corrugations 30. It is intended that each of these cells is to be filled with material which will maintain a permanent granular condition and thus add the pressure of this granular material to the cellular structure as it is directly imposed upon the corrugations 3B in an outward and downward direction. The theory for this use of granular material such as sand may be explained as follows. Certain substances, as water, are fluids. They cannot be piled, but must be held in retainers. The pressure in a fluid at any certain depth is the same in all directions. Other substances, such as sand, have a certain tendency to flow, but may be placed in a pile. These are called semifluids. The natural slope this pile would take is called the angle of repose. It indicates that there is a certain relation between the vertical pressure and the horizontal pressure in the sand at any depth. This relation is constant for a given material and is called the coefficient of friction. 7

When such a material as sand is placed against a. retaining wall, the triangle of sand formed between the angle of repose and the wall tends to slide against the wall and puts a pressure on it. This pressure produces friction against the back of the wall. While this friction is never taken into account in retaining walls, it is vital in the design of bins or cells.

Our problem in getting at the loads in the cell walls would be the same as for retaining walls if the cells were large enough that the angle of repose from the different sides did not intersect before the top of the cell was reached. Therefore another term is introduced. This is called the hydraulic ratio. It is the result of dividing the area of the cell at any point by its perimeter.

One of the best ways to learn how sand will act in a cell is to study the hour glass. A small pile forms in the lower glass where the sand drops on its highest point. Here the slope soon exceeds the angle'of repose and a slide occurs, spreading itself out on the side of the pile. All the agitation in the upper glass is at its center. Here a crater is formed which has a slope of the angle of repose and similar slides occur, but in this case to the center. No material slides against the glass sides if it is under pressure from sand above.

It is concluded from a study of the hour glass that the sand forms a dome from the walls of the glass and that the'center of this dome breaks first, thus the agitation at the center of the upper glass. A formula is developed on this assumption called the Janssens formula. The formula is rather involved andneed not be discussed here. The horizontal pressure at the bottom of a cell may be obtained from this formula. The vertical pressure on the floor of the cell can be found as there is a constant relation between these two pressures.

The vertical pressure times. the area of the floor of the cell gives the total load carried on the floor of the cell. The total weight of the sand in the cell less that carried by the floor of the cell is the load carried by the walls of the cell. It is reasonable to assume that this load is divided according to the perimeter of the cell. This gives the vertical load carried in eachwall due to the sand fill. The horizontal tension at any level in these cell walls and also the bending moment at that level can be found as the Janssens formula gives the horizontal pressure at any level.

Based on the premises previously outlined, it will be evident that the granular material will provide a desired weight and resistance in a structure of this particular kind without sacri- 1 ficing. flexibility, and while the invention is here shown as embodied in a dam, it will be understood that principles here set forth will be equally applicable in the construction of grain elevators,

dock walls, break waters, and the like.

When a dam is being built within which the present structure is employed, it is not difficult to ascertain the area at which the dam may leak and to make it possible to readily explore and repair this area. This is accomplished by providing drains 3| which extend through the walls of the cells of the various horizontal courses as indicated in Figs. 1 and 4 of the drawings, and which drains are subtended by lateral drains 32. The drains are preferably tile set end to end and placed in gravel. The drains are arranged systematically so that each drain accommodates a particular area of the dam, thus making it possible toreadily ascertain which portion 01' the dam may have developed a leak.

In the construction of the dam it will'be understood that the cellular skeleton or frame of the dam may be cast by the use of any preferred method or form of construction and operation, and that the present invention is not concerned with the particular method of forming the dam. It will be recognized, however, that the dam has been especially designed with the idea of providing as much duplication of form work as possible. The interior of each cell i0 is a perfect hexagon. The rear cell on each horizontal course is a duplicate of the rear cell in the next horizontal course. This is likewise true of the second cell from the downstream side, and so on. This is true except for the difference caused by the elongation of the cells in the course I3 which provides the upstream face for the dam. By this arrangement and by filling the cells with granular material, such as sand, the friction of the sand upon the corrugated wall will tend to direct the pressure of the weight of the sand outwardly, and it is proposed to carry as much as possible of this weight upon the cell walls. It will also be evident that the structure will insure that the dam will be quite flexible and that it will not be necessary for expansion joints to be required to accommodate temperature changes and to withstand sudden and severe earth shock.

The dam may be designed and built in accordance with well defined engineering practice to embody the principles of the present invention.

The dam may be provided with a walk or roadway, such for example as indicated at 35 in Fig. 3 of the drawings. This roadway is here shown as being superimposed upon the course of cells l3, and is bounded along opposite sides by the angularly arranged pairs of walls of the cells.

It will thus be seen by a careful analysis or the data presented in the preceding portion of the specification that the dam or other structure built by this method will present a maximum resistance to lateral pressures, and at the same 15 time will have a desirable flexibility, so that the best features of a rigid concrete structure and a gravity dam may be obtained.

While I have shown the preferred form of my invention, as now known to me, it will be understood that various changes may be made in combination, construction, and arrangement of parts by those skilled in the art without departing from the spirit of my invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. A structure designed to resist lateral pressure which consists of a honeycomb cementitious skeleton forming a plurality of vertically extending hollow cells of hexagonal section, said cells ,7

angles to the longitudinal axis of the cell, and said hollow portions being filled with material of permanent granular character.

2. A dam structure comprising a monolithic cementitious skeleton which includes a plurality of vertically extending horizontally parallel rows of cells, said rows progressively decreasing in heighth from the upstream side of the dam and the walls of said cells progressively decreasing in thickness from the base of the dam, the foremost walls of the first row of cells on the upstream side of the dam being battered, the inner faces of said cells being formed with ver-' tically arranged horizontally extending corrugations, the vertical openings in said cells bound by said corrugated walls being filled with gran-

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