a beam member constituted by a web and a first flange and a second flange, which are perpendicularly coupled to the web on both sides of the web;

an upper bracket fitted into the first flange at an upper portion of the beam member;

a lower bracket that faces the upper bracket at a lower portion of the beam member and is fitted into the first flange; and

a plurality of tensile members extending in a longitudinal direction of the beam member between the upper bracket and the lower bracket and fixedly installed on the upper bracket and the lower bracket, respectively,

wherein the upper bracket is constituted by a first bracket member and a second bracket member, which face each other with respect to the web at the upper portion of the first flange and are spaced a predetermined distance from each other, each of the first bracket member and the second bracket member comprises:

a vertical plate extending from a front surface of the first flange by a predetermined length in the longitudinal direction of the beam member;

a horizontal plate formed by being bent vertically from one end of the vertical plate; and

a hanging plate disposed on a rear surface of the first flange by being vertically bent from one end of the horizontal plate,

a first groove is defined at an edge of the other end of the horizontal plate of the first bracket member,

a second groove is defined at an edge of the other end of the horizontal plate of the second bracket member,

the first groove and the second groove are disposed to face each other to define a hollow having a predetermined size, at which the plurality of tensile members pass, between an inner surface of the first groove and an inner surface of the second groove, and

an anchoring member for anchoring the plurality of tensile members is seated on an upper portion of the horizontal plate corresponding to the hollow.