JPH045358A - Prestressed trussed girder constitution method - Google Patents

Abstract

PURPOSE:To introduce prestress to a trussed girder by pressing the trussed girder to bent upward, placing concrete in a top chord, and removing pressing means after curing of the concrete. CONSTITUTION:Patch members 4 are arranged to both ends of a trussed girder A, below which a tension cable 5 is arranged, and both the ends are fastened by tension bolts 6. Concrete 7 is placed in the top chord 1 of the trussed girder A, and after curing of the concrete 7, the tension cable is loosened to remove the patch members 4. Thus, prestress can be introduced in the top chord 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a method of constructing a prestressed truss beam used in a low-rise large-scale structure or a road bridge.

[Prior art and the problem to be solved by this invention] Generally, when introducing prestress into a structural member, high-tensile steel wire is used. Various methods have also been developed to introduce

By the way, when designing a truss beam, the top chord, or compression material, is designed by determining the allowable compressive force based on the buckling length, and the cross section is determined by comparing it with the member's compressive stress, while the bottom chord, or tension member, is designed by determining the allowable compressive force based on the buckling length. The cross section is determined by comparing the tensile stress with the allowable tensile stress for the effective cross-sectional area.

Therefore, we developed this system with the aim of significantly improving the performance of compressed materials by reducing the compressive stress using prestressing and then filling the compressed materials with concrete.

[Structure of the invention]

This invention is a steel truss beam made by connecting upper and lower chord members with a belly member, applying force to the truss member so as to give an upward bending deformation, then filling the inside of the upper chord member with concrete, Next, after the concrete hardens, the applied force is removed and prestress is introduced into the truss beam.

〔Example〕

A steel truss beam A constructed according to the present invention consists of an upper chord member 1, a lower chord member 2, and a belly member 3.

The upper chord members 1 and 2 are formed of round steel, H-shaped steel, and square steel pipes. Further, the joint cross section of the truss beam A can also be triangular.

First, a force is applied to this truss beam A to cause it to bend and deform. As an example, a support member 4 is arranged at both ends of a truss beam A, a tension cable 5 is arranged below the truss beam A, and both ends of the tension cable 5 are connected to a tension bolt 6 passing through the support member 4. 6, the upper chord member 1 of the truss beam A is filled with concrete 7, and after the concrete 7 hardens, the tension cable 5 is loosened and the backing member 4 is removed.

As a result, prestress is introduced into the upper chord member 1.

Figure 4 shows an outline of a modification of the means for applying upward bending deformation to the truss beam A, and Figure 4 shows the tension cable 5.
In this case, the hydraulic unit 8 is arranged in the middle of the truss beam A, and if necessary, the tension cable 5 and the hydraulic unit 8 are arranged in two stages, and a bending moment is applied to the truss beam A as shown in the upper part.

5 and 6 show the case where a bundle 9 is arranged between the tension cable 5 and the truss beam A, and a bending moment is applied by a hydraulic unit as shown in the upper part.

[Effects of the Invention] This invention has the above-mentioned configuration, and pressurizes the truss so as to bend it upward, fills the inside of the upper chord with concrete, and after the concrete hardens, the applying means is removed. A prestress with a stress state in the opposite direction to the stress state at the time of vertical loading is introduced into the truss wire, making it possible to reduce the amount of steel used. In addition, by filling the upper chord with concrete, prestress can be maintained and costs can be reduced compared to the conventional case where tension members are left alone.

[Brief explanation of drawings]

Figure 1 is a front view of the construction process, Figure 2 is a completed beam, and a partial cross section is shown in Figure 3, I and II. (2) and (2) are cross-sectional views showing modified examples of the truss beam, and FIGS. 4, 5, and 6 are front views and bending moment diagrams showing modified examples of means for imparting bending deformation. A...Truss beam, 1...Top chord member, 2...Lower chord member, 3...Body member, 4...Backing member, 5...
・Tension cable, 6...Tension bolt, 7...Concrete, 8...Hydraulic unit, 9...Bundle\
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Claims (1)

[Claims] It is a steel truss beam made by connecting the upper and lower chord members with a belly member.
A force is applied so as to give upward bending deformation to the truss shell, then concrete is filled inside the upper chord, and then, after the concrete hardens, the applied force is removed and a presto truss is introduced into the truss shell. How to construct a prestressed truss beam.