US 3239913 A
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Description (OCR text may contain errors)
March 15, 1966 G. R. RICHMOND 3,239,913
METHOD OF SECURING A CONNECTING MEANS IN A CONCRETE STRUCTURAL MEMBER Filed Aug. 17, 1962 IN VEN'TOR. GORDON R. RICHMOND aya 70 1 ATTORNEYS United States Patent 3,239,913 METHOD OF SECURING A CONNECTING MEANS IN A CONCRETE STRUQTURAL MEMBER Gordon R. Richmond, Westlake, Ohio, assignor to Concrete Masonry Corporation, Elyria, Ohio, a corporation of Ohio Filed Aug. 17, 1962, Ser. No. 217,626 2 Claims. (Cl. 29155) This invention generally relates to a process for making concrete beams or columns and contemplates embedding a plate means or a multiplicity of plate means in a concrete structural member extending in any direction therefrom. Further, the invention contemplates providing plate means positioned at right angles to each other through a beam or column, such beam achieved in a form which is of conventional design; that is, an open topped steel form.
More particularly, this invention relates to providing a transverse joint plate means in a concrete structural member and a method for performing the same without requiring form modification to allow the transverse member to project therefrom during the casting operation.
More specifically, the instant invention contemplates embedding a plate means in a structural component within the limits defined by an open-topped boxlike steel form. Prior to the pouring operation, the structural member is coated with a suitable retarding substance to delay the bonding of the concrete thereto, without affecting the quick setting properties of the concrete in the remainder of the member in proximity thereto. After the cast member has set, the form may be removed and the plate, due to the incomplete bond with the concrete, is now available for welding other structural members thereto.
As will become apparent hereinafter, many variations in the structure and techniques .of the instant disclosure can be had. If plates projecting from a plurality of sides of the column are desired, such structure can readily be achieved by employing the technique disclosed herein.
A further variation of this technique is embodied in the welded joint. In general, a plate or angle having a portion thereof coated with a retarding substance is cast flush with the surface of the structural member. Form removal is effected after the concrete has set but before the retarding action has been overcome. A further plate or angle means then is welded to the embedded plate or angle. Since the concrete adjacent the embedded plate is still elastic, the usual cracking and spalling will not occur. Subsequently, the delaying action of the retarding substance is overcome and the bond between the plate and concrete is perfected.
The problem and prior art solutions Modern construction techniques dictate preforming as many structural units as possible, transporting them to the job site, and thereupon assembling them. Such practice has given rise to large quantities of columns, beams, and the like being formed at a plant where a ready mix or batch plant is available, and thereafter transporting the precast units to the site for erection. Several difficulties arise where transverse joint members which project from the sides of the structural member are to be provided. Firstly, the subcontractor who provides the structural units, such as beams, columns, and the like, must spend considerable sums to provide forms to meet the needs of a wide variety of customers. Since the particular need will vary from one job to the next, it is not economically feasible to use a form for a single job and then discard it in favor of a different form for the next job. The forms, in essence, should be versatile to permit a wide range of uses with consistently fine results.
Prior art devices suggest that the forms be made of wood, which allows modification at any point to provide openings for bearing plates, haunches, fin plates, and like transverse members. However, the use of wood forms for beams, columns, and the like, is objectionable in that a great deal of work is required after the concrete has set in order to work the finish of the exterior of the column or beam to a surface finish smooth enough to be suitable for use as an exposed architectural unit. Further, wooden forms require considerable labor to construct and maintain. The useful life of wooden forms is short when contrasted to that of steel or the like.
To this end, steel forms have found extensive use, generally being of the configuration of an elongated box with the top open and are up to feet or more in length. The use of steel forms provides an exceedingly smooth finish on the exterior of the concrete, in some cases superior to hand finishes, requiring no subsequent finishing after the concrete sets. However, it is readily apparent that steel forms would be costly initially and could not be modified readily to receive transverse joint members. By modified it is meant that the form could not easily be cut to receive, for example, a plate extending transversely of the column or beam. A plate which extends out of one side only could be cast without difficulty since the form is open at the top. However, the requirements are such that if the plate was to extend equidistant from opposite sides of the structural unit, it would require form modification so as to allow the plate to extend therethrough. A subsequently order for a structural member, which required that the transverse plate be positioned in a different location, would necessitate either patching of the form, which would be difficult at best, or a new steel form. Obviously, the cost of the latter alternative would be prohibitive. The former alternative would be unsatisfactory both from the standpoint of cost and the effect a patch would have on the surface finish.
In an effort to escape the high cost of steel form modification and the subsequent costly and laborious finishing when wooden forms were used, several solutions were proposed. One solution entailed embedding metallic plates flush with the exterior surface of the structural member and welding fin or angled members thereto after removal of the forms. Although, at first blush this would appear to solve the problem, it has shortcomings also. The high heat attendant to the welding operation caused spalling and cracking in the vicinity of the embedded plate member. Obviously, the bond was weakened severely and the concrete adjacent the plate was deteriorated to such a degree that the load bearing characteristics were reduced severely. Of no less importance was the unsightly appearance presented by the structural unit, thereby rendering it worthless as a finished exposed architectural unit.
A second solution involved the casting of a tubular member within the limits defined by the surfaces of the structural member. This was unsatisfactory in that it reduced the cross-sectional area thereof with an attendant reduction in the load-carrying ability of the member.
The solution The search for a solution to these pressing problems resulted in the instant invention. The novel structure and method of the embodiment shown is achieved through the use of an unmodified form. That is to say, the steel forms, which are the most desirable to obtain an excellent surface finish, can be used for either unmodified structural units or modified structural units with joining means projecting therefrom. The present invention allows plates, connections, joints, and similar transverse members to be placed at any point in the unit, with the result that the ultimate end product will permit welding of a joint member to an embedded angled member with out spalling or cracking of the concrete adjacent thereto.
For example, a column that would be used centrally of a structure would have as many as four connecting portions projecting from the side faces of the column. In order to achieve such structure, it is necessary either to modify the form so as to permit the connecting portions to project from the form and cast in situ or cast flush plate members in an unmodified form and subsequently weld an angle plate to the flush plate. The former method was virtually impossible when steel forms Were used. The latter practice caused objectionable spalling and cracking of the concrete adjacent the plate member, as heretofore noted. If the welding operation could be performed when the concrete was in an elastic state, the objectionable cracking and spalling could be avoided. The subsequent bond between the plate member and the concrete, therefore, would be of expected strength. A further advantage of the welding method disclosed resides in the unblemished appearance of the surface adjacent the plate member, which gives a finished appearance to the structural member so that it is suitable for use as an exposed architectural unit.
The novel solution to the above-enumerated problems and the remarkable advantages of the novel joint structure and method will become apparent more readily in the attendant description to achieve the objects set forth below.
It is, therefore, an object of this invention to provide a novel joint means and method.
It is a still further object of this invention to provide a novel method whereby a joint or plate member may be welded to an embedded plate member without causing spalling or cracking of the concrete adjacent the embedded plate.
It is a still further object of this invention to provide a novel method for joining plates or the like to an embedded plate member without impairing the expected strength of the connection between the concrete and the embedded plate member.
Further and fuller objects will become readily apparent when reference is made to the accompanying drawings wherein like reference characters refer to like parts.
In the drawings:
FIG. 1 is a fragmentary cross-sectional view in elevation of a structural member having a retardant coated angle embedded therein and a further angled member welded to the first angle;
FIG. 2 is a view taken along the line 2-2 of FIG. 1.
Most commercial cement compositions, such as Portland cement, are calcium-aluminum-silicate mixtures having various amounts of magnesium oxide and still smaller proportions of sulfur trioxide, which is purposely added as a retarding agent to the finished product.
The presence of the sulfur trioxide is in the form of calcium sulfate or the dihydrate, otherwise known commercially as gypsum. The sulfur trioxide ion from the calcium sulfate hydrate inhibits hydration of the aluminum in the cement by forming a film on the tricalcium aluminate, preventing it from crystallizing which causes the cement to set.
Accordingly, the type and amount of retarder to be used in each instance will depend upon the particular composition of cement. Since each cement differs in its aluminum content, the proportion of retarder needed will vary to the extent required to prohibit the aluminum from crystallizing or to keep the aluminum compounds in the amorphous state. It is known, for example, that cements having high calcium aluminate content are quick setting and are retarded readily by the addition of gypsum or mixtures or gypsum with calcium hydroxide.
In applying these retarders aqueous solutions, i.e., calcium sulfate dihydrate and calcium hydroxide, are prepared and uniformly coated over the plates prior to being positioned in the concrete structure. The concentration of the aqueous solutions is usually sufiicient so that the retarder will range up to about two percent by Weight of the cement. The concentration will vary, however, depending upon the aluminum content of the cement and the particular retarder being used. Thus, for example, where a carbohydrate is used, amounts less than one-half percent by weight of the cement have been found to be satisfactory. A particularly outstanding carbohydrate retarder is sucrose or sugar which, in very small amounts, has been found to be a very satisfactory retarding agent, and can be used without detrimental effect on the ultimate strength of the cement. These retarders will, however, reduce the green strength in that it is a natural consequence of delaying hydration which prevents the cement from hardening. These decreased green strengths, however, are not carried over to the ultimate strength when hydration and hardening are complete. Other carbohydrates which have been noted to be satisfactory are, for example, calcium lignosulfonates, casein, cellulose and other metal sulfates, such as copper, boron, and the like.
Among the commercial retarders available on the market are the types C and F sold by the Sika Chemical Corporation. The xylol base type has been found most satisfactory since its presence is readily detectable upon inspection due to its color. The water base type retarder has been used with good results; however, due to the absence of color it is not readily discernible upon visual inspection.
The welded joint and method The novel method of welding a joint plate member to a column will now be explained with particular reference to FIGS. 1 and 2. Although a single joint connection is shown, it is contemplated that connections could be made on all four sides of the column 60. It is obvious that any desired number of angled plates could be provided on a single side depending on the load requirements of the structural system. For ease of description, only a single connection will be described.
An angled member 61 is notched as at 62 and 63 in the leg 64 of the angle. The notching of the leg 64 allows the angle member 61 to be inserted between the reinforcing rods 65, where it is tack welded or secured to the reinforcing rods by other suitable means. The downwardly extending leg 66 of the angled member 64 is coated on the inner face 74 and ends with a suitable retarder substance 70, such as those alluded to hereinbefore. The concrete then is poured in the form after reinforcing rods have been spaced the required distance from the bottom and sides of the form. The concrete flows evenly about the angled member 61 grippingly to engage the leg 64. The concrete adjacent the leg 66 and the ends thereof is delayed in setting and, as a consequence, while the remainder of the beam has set up firmly enough to strip the forms, the concrete adjacent the leg 66 and the ends thereof remains somewhat plastic. The forms are stripped and the angled member 67 then is welded to the leg 66, as shown at 68 and 69. Since the concrete in the region of the retarder coating '70 is in a plastic state, the expansion of leg 66 during the welding operation will have negligible deleterious effect on the concrete. Upon the completion of the welding operation, in a matter of a short period of time, the delaying action characteristic of retarders is overcome and the concrete sets so as to grip the leg 66 firmly. The angled member 67 provides a bearing point for connection to the beam running transverse to the structural member 6%).
It is to be appreciated that four such members could be provided around the four sides of the structural member 60 so that it may be used as an internal column with four transverse members to be connected thereto. This is possible since the angled member 61 and similar angled members can be placed flush with the surfaces 71, 72, and 73 of the structural member 60 during the casting operation without modifying the form. This is possible since all the embedded angle plates are flush with the surfaces 71, 72 and 73 of the structural member 60. Each of the angled members so placed can be joined to an angled member, such as the one indicated at 67.
It has been found that the inner face 74 and ends 75 need to be coated to protect the concrete from the heat of the welding operation. Heat, which by the inherent thermal conductivity of the angle member is transmitted to the leg 64, is less intense than at the leg 66 and is quickly dissipated through the angle reinforcing members 65 and the concrete without any deleterious efiects on the strength of the joint or appearance of the member.
For ease of description only a few of the anticipated embodiments of the instant invention have been shown. It is contemplated that other forms could be made without departing from the true spirit of the invention. Accordingly, I intend to be limited only by the scope of the appended claims.
1. The method of providing a transverse connecting means in a concrete structural member without requiring form modification comprising the steps of providing form means to contain said concrete, placing a reinforcing network having an angled plate attached thereto in said form, coating said angled plate on a portion thereof with a retarding substance, pouring concrete in said form, permitting said concrete to set sufiiciently to remove said form means, removing said form means and welding an References Cited by the Examiner UNITED STATES PATENTS 1,052,696 2/1913 Sloan -181 1,783,609 12/1930 Forssell 50181 1,796,048 3/1931 Robinson a- 50181 2,271,089 1/1942 Neptune 25-131 2,886,370 5/1959 Liebert 50465 3,086,273 4/1963 Welborn 50128 FOREIGN PATENTS 376,308 7/1932 Great Britain.
ROBERT F. WHITE, Primary Examiner.
HENRY C. SUTHERLAND, ALEXANDER H. BROD- MERKEL, Examiners.