US3226904A - Method of assembling plate-shaped stereo truss for roof or floor - Google Patents

Description

- Jan. 4, 1966 TAKAO ITOH METHOD OF ASSEMBLING PLATE-SHAPED STEREO TRUSS FOR ROOF OR FL Filed April 23, 196

6H6 A A United States Patent 3,226,904 METHOD OF ASSEMBLING PLATE-SHAPED STEREO TRUSS FOR ROOF R FLOOR Takao Itoh, Tokyo, Japan, assignor to Kajima Construction Co., Ltd., Tokyo, Japan, a corporation of Japan Filed Apr. 23, 1962, Ser. No. 189,446 1 Claim. (Cl. 52-655) The present invention relates to plate-shaped solid trusses to be used for roof.or floor construction etc. for buildings, and more particularly to such trusses which are characterized in that at the apex of a right angle equilateral triangle having as a base the line connecting two parallel upper cords, a lower cord is arranged in parallel to the upper cords, and the upper and lower cords are connected together to form a truss with diagonals which join at the same point on the lower cord, and the joint points of the diagonals with the two upper cords or the middle points of each pitch of the joint points are connected with transverse members in the form of a ladder to form a unit truss beam of triangular section, and a number of such unit truss beams are connected in parallel to form a unit in such manner that the connecting points of the diagonals and the upper cords of a unit truss beam are shifted one-half phase with the corresponding points of the adjacent truss beam.

For a better understanding of the invention, reference is taken to the accompanying drawings, in which FIG. 1 is a perspective view of a unit truss beam of triangualr section embodying the invention;

FIG. 2-a, -b and -c are a sectional view, a side view and a plan view of FIG. 1, respectively;

FIG. 3 is a plan view of a plate-shaped solid truss illustrating the assembled condition of unit trusses;

FIG. 4 is a partial sectional view of FIG. 3; and

FIG. 5 is a side View of FIG. 3.

Referring to the drawings, which show an embodiment of the invention, 1 represents an upper cord consisting of an angle shaped steel member, a steel pipe or other shaped steel member, and 2 illustrates a lower cord using the same steel.

According to the invention two parallel upper cords 1, 1 are connected together at points a and b at equal spacing by means of transverse members 4 in the form of a ladder, and a lower cord is arranged at an apex of an equilateral triangle with respect to the two upper cords and in parallel relationship thereto. The adjacent points a of the upper cords 1 are connected by means of four diagonals 3 to a common point 0 on the lower cord 2 to constitute a unit truss beam A of triangular section, and a number of such unit trusses A are connected together in such manner that the joining points a of diagonals 3 are shifted to points a, i.e., to one-half spacing between the points a--a'.

When load is applied to the unit truss beam A of triangular section the lower cord usually acts as a tension member, while the upper cord 1 supports compressive load, and the upper and lower cords made of angle or other formed steel members used under such condition are strong against the tension while liable to be collapsed by compression. The buckling strength of upper cords 1 varies in inverse proportion to the span length 1 between the two adjacent points a and a for connecting the upper cords 1 and diagonals 3, so that in order to increase the strength of such truss it is desirable to minimize the span length I. On the other hand, increasing the number of diagonal members 3 in order to shorten the span length 3,226,904 Patented Jan. 4, 1966 results in an increase of the material used and also the weight of the truss itself, so that it is not a desirable solution. From such point of view the invention was developed in order to increase the strength of the truss beam Without increasing the number of diagonal members 3 in such manner that unit trusses A are connected together as a unit in parallel by shifting /2 phase with each other, i.e., the joints a of the diagonal members 3 of a unit truss beam coincide with the middle points b of the pitch 1 of the adjacent unit truss beam so that the pitch between two adjacent points a and a of the upper cord of a plate-shaped solid truss formed according to the invention will become /2. This means a decrease of the span length of a unit truss A to one-half, and accordingly the strength of the plate-shaped solid truss can be substantially increased without increasing the material. In other words, the minimum material may be used for obtaining a plateshaped solid truss having the same strength.

According to the invention, the points a joining the upper cords 1 and the diagonal, and the middle points b between the points a are connected by means of transverse members 4 so that when a plate-shaped solid truss is formed the joints a of each upper cord 1 and diagonal 3 are restricted by the transverse member 4 in the transverse direction so that the upper cords can resist buckling in the transverse direction.

The invention as above described has the following merits:

(l) A unit truss beam of triangular section can be erected on the ground level, and these truss beams are joined together in parallel at a high level so that the operating quantity at high places can be reduced and the process can be accelerated.

(2) A number of unit truss beams of triangular section are arranged in parallel, and all the upper cords are joined together so that the collapse of the truss beamcan be prevented different from the case when roof or floor structure is supported by means of a number of unit truss beams of I-shaped section.

(3) The buckling length of the upper cords as above described is restrained at each /2 pitch of the joints of the lower cord with each end of the diagonals connecting the both cords and each end of the transverse member for connecting the upper cords with each other and the lower cord so that the buckling length for calculation can be taken to be A2 of the lower cord, and thus the sectional area of the members can be saved.

(4) As above described the invention consists of a plateshaped solid truss structure so that all members are subject to the longitudinal stress only for external forces without accompanying bending and thus the sectional area of the member can be saved from this point also.

(5) By rendering the pitch of transverse members for connecting the upper cords with each other to coincide with the spacing between the purlins or floor joists the weight of the members can be economized.

What I claim is:

A truss-like structural assembly for use in roof or floor construction, comprising: a plurality of unit truss beams connected together in substantially abutting relationship; each unit truss beam comprising two parallel upper chord members, a plurality of transverse members extending between and connecting together said upper chord members at substantially equal spacings to form a ladder-like structure, a lower chord member parallel to said upper chord members and spaced therefrom so as to form an equilateral triangle with said upper chord members when viewed in transverse section, and diagonal members connecting saidupper chord members to said lower chord member, said diagonals extending from each end of alternate transverse members to points located on said lower chord member substantially equidistant from the ends of adjacent alternate transverse members, said points being spaced along said lower chord at spacings substantially equal to the spacing between alternate transverse members; a number of said unit truss beams being connected together such that the joints between the diagonal members and the upper chord members of each unit truss beam are located between and substantially equidistant from the joints between the diagonal members and the upper chord members of adjacent unit truss beams.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 9/1953 Germany.

RICHARD W. COOKE, JR., Primary Examiner.

WHITMORE A. WILTZ, Examiner.

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