CN109025347B

CN109025347B - Method for reinforcing shear defect steel beam by using GFRP (glass fiber reinforced plastics)

Info

Publication number: CN109025347B
Application number: CN201810786018.7A
Authority: CN
Inventors: 鲁正; 马晨智; 林嘉丽
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2018-07-17
Filing date: 2018-07-17
Publication date: 2021-02-02
Anticipated expiration: 2038-07-17
Also published as: CN109025347A

Abstract

The invention relates to a method for reinforcing a shear defect steel beam by utilizing GFRP, which is characterized in that GFRP members are symmetrically arranged on two sides of a steel beam web plate to be reinforced, wherein the GFRP members comprise a bottom plate, a pair of vertical ribs vertically arranged on the bottom plate and a plurality of horizontal ribs vertically arranged on the bottom plate, the horizontal ribs are distributed between two vertical ribs at intervals and are vertical to the vertical ribs, the vertical ribs and the horizontal ribs form a plurality of cuboid cavity structures, and the bottom plate is bonded on the steel beam web plate. By the method, when the shearing force applied to the steel beam is too large and the web plate of the steel beam starts to bend, the characteristic of the section of the web plate at the weak position is changed due to the fact that the GFRP component is attached to the outside, the bending rigidity is increased, and the web plate does not bend under the action of the shearing force, so that the bearing capacity of the web plate of the steel beam is fully utilized, and the bearing capacity and the shearing strength of the steel beam are enhanced.

Description

Method for reinforcing shear defect steel beam by using GFRP (glass fiber reinforced plastics)

Technical Field

The invention relates to the technical field of building components, in particular to a method for reinforcing a shear defect steel beam by using GFRP.

Background

The steel structure is under pressure, is bent, is cut or under complicated stress, if the width to thickness ratio of plate is too big, the phenomenon of local unstability often can appear, after taking place local unstability, partial plate buckling withdraws from work, makes the effective cross-section of component reduce, can accelerate the whole unstability of component and lose bearing capacity. Conventional methods of reinforcing steel members to avoid local buckling are often accomplished by providing stiffening ribs to alter the panel compartmentalization. The stiffeners provide greater stiffness out of the plane of the web, providing support conditions for the enclosed slab area to vary the aspect ratio and width to width ratio of the slab, thereby changing the local buckling conditions.

However, the stiffening ribs are often applied to the web by welding and tend to cause fatigue failure of the component due to stress concentrations. In the prior art, the concrete and masonry structures are reinforced by using composite materials, the concrete or masonry structures are restrained by using higher uniaxial tensile strength in the plane of the concrete or masonry structures, and the bearing capacity of the concrete or masonry structures is enhanced, but the reinforcing of the shear defect steel beams by using GFRP is not reported.

Disclosure of Invention

The invention provides a method for reinforcing a steel beam with shear defects by using GFRP (glass fiber reinforced plastics), which aims at the steel beam with the shear defects, so that a web plate is not easy to buckle under the action of a shear force any more, the material of a member can be fully utilized, and the bearing capacity and the yield strength are increased.

The purpose of the invention is realized by the following technical scheme:

a method for reinforcing a shear defect steel beam by using GFRP is to symmetrically arrange GFRP components on two sides of a steel beam web to be reinforced, wherein the GFRP components comprise a bottom plate, a pair of vertical ribs vertically arranged on the bottom plate and a plurality of transverse ribs vertically arranged on the bottom plate, the transverse ribs are distributed between two vertical ribs at intervals and are perpendicular to the vertical ribs, the vertical ribs and the transverse ribs form a plurality of cuboid cavity structures, and the bottom plate is bonded on the steel beam web.

Further, the GFRP member is made of glass fiber reinforced polymer and is manufactured through integral extrusion molding, so that a weak point at a connection interface is avoided.

Furthermore, the GFRP component is obliquely arranged on the steel beam web, the upper end of the base plate of the GFRP component is close to the stress point of the steel beam, and the lower end of the base plate of the GFRP component is far away from the stress point of the steel beam. Further, the both ends of bottom plate contact with the girder steel flange respectively, and the distance of contact surface mid point and girder steel edge is zero to between the quarter of this limit length of side of girder steel, and when the length of the web in the middle of the girder steel was less than highly, this distance was 0, and when the length of web was greater than two times height in the middle of the girder steel, this distance was the quarter, because can learn through the modal analysis to the girder steel web, this kind of arrangement mode can cover most easy warping girder steel web under the condition that the girder steel received the shear force. Further, the cuboid cavity structure formed by the vertical ribs and the transverse ribs has an aspect ratio of 2: 1, thereby avoiding buckling of the vertical and cross ribs under load.

Further, the vertical ribs coincide with the height of the cross ribs for ease of processing.

Further, the bottom plate, vertical ribs and cross ribs are of the same thickness for ease of processing.

Further, the width of the base plate is twice the height of the vertical ribs, thereby enabling GFRP to reinforce steel beam webs covering a greater range.

Further, the distance between the vertical ribs and the edge of the bottom plate is one fourth of the width of the bottom plate, so that a cuboid cavity formed by the vertical ribs and the transverse ribs can effectively reinforce a steel beam web plate within the coverage range of the bottom plate without warping.

By the method, when the shearing force applied to the steel beam is too large and the web plate of the steel beam starts to bend, the characteristic of the section of the web plate at the weak position is changed due to the fact that the GFRP component is attached to the outside, the bending rigidity is increased, and the web plate does not bend under the action of the shearing force, so that the bearing capacity of the web plate of the steel beam is fully utilized, and the bearing capacity and the shearing strength of the steel beam are enhanced.

Compared with the prior art, the invention has the following advantages:

1. the GFRP with lower price is selected, so that the method is more economical compared with other methods, and the cost is saved;

2. compared with the traditional reinforcing method for welding the steel stiffening rib, the reinforcing method has no problems of stress concentration and fatigue.

3. Compared with the traditional reinforcing mode of sticking carbon fiber cloth, the method is simple and convenient to operate and is economical.

Drawings

FIG. 1 is an elevation view of a GFRP component of the invention positioned in a steel beam web;

FIG. 2 is a top view of a GFRP component of the invention;

FIG. 3 is a side view of a GFRP component of the invention;

FIGS. 4 and 5 show the first-order modes of the steel beam web under two aspect ratios;

in the figure: 1-a steel beam web; 2-a bottom plate; 3-vertical ribs; 4-cross ribs.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples

As shown in fig. 1, in a method for reinforcing a shear-defect steel beam by using GFRP, GFRP members are symmetrically arranged on both sides of a steel beam web 1 to be reinforced, wherein the GFRP members comprise a bottom plate 2, a pair of vertical ribs 3 vertically arranged on the bottom plate 2, and a plurality of transverse ribs 4 vertically arranged on the bottom plate, the transverse ribs 4 are spaced between two vertical ribs 3 and are perpendicular to the vertical ribs 3, the vertical ribs 3 and the transverse ribs 4 form a plurality of rectangular parallelepiped cavity structures, and the bottom plate 2 is bonded on the steel beam web 1. In practice, various parameters of the GFRP component, such as thickness, height, and width of the substrate, may be adjusted depending on the particular force conditions.

In the embodiment, the size of the steel beam web single lattice is 800mm × 500mm, the GFRP base plate 2 and the steel beam web 1 are bonded by the adhesive material, and the adhesive material is an adhesive with high viscosity and high ductility. The GFRP component is symmetrically bonded on both sides of web 1. The transverse ribs 4 and the vertical ribs 3 surround to form rectangular cavities, the length-width ratio is 1/2, the length-width ratio is 140mm and 70mm respectively, the width of the bottom plate 2 is twice the height of the vertical ribs 3, the width of the bottom plate is 140mm and 70mm respectively, the distance from the center of each vertical rib 3 to the edge of the bottom plate 2 is 1/2 of the height of each vertical rib, the distance is 35mm, the height of each vertical rib 3 is 70mm, and the thickness of each bottom plate 2, each vertical rib 3 and each transverse rib 4 is 6 mm. From left to right in fig. 1, the center of the upper end edge of the GFRP member is located at 1/4 where the steel beam is single lattice long perpendicular to the shear direction, and the center of the lower end edge is located at 1/4 where the steel beam is single lattice long. The GFRP component is made of glass fiber reinforced polymer through integral extrusion molding, the bottom plate 2, the vertical ribs 3 and the transverse ribs 4 are an integral body formed through extrusion molding, and consolidation is carried out at the connection position of the bottom plate, the vertical ribs and the transverse ribs.

When the shearing force applied to the steel beam is too large to cause the web plate 1 to be buckled, the cross section characteristic of the web plate 1 at the weak position is changed due to the action of the GFRP attached to the outer side of the web plate 1, the bending rigidity is increased, buckling is not caused under the action of the shearing force, and local buckling caused by stress concentration of the web plate is avoided. The bearing capacity of the steel beam web plate is fully exerted, the bearing capacity and the shear strength of the steel beam are enhanced, and the first-order modes of the steel beam web plate under the condition of two length-width ratios are shown in figures 4 and 5.

Claims

1. A method for reinforcing a shear defect steel beam by using GFRP is characterized in that GFRP members are symmetrically arranged on two sides of a steel beam web to be reinforced, wherein the GFRP members comprise a bottom plate, a pair of vertical ribs vertically arranged on the bottom plate and a plurality of transverse ribs vertically arranged on the bottom plate, the transverse ribs are distributed between the two vertical ribs at intervals and are perpendicular to the vertical ribs, the vertical ribs and the transverse ribs form a plurality of cuboid cavity structures, and the bottom plate is bonded on the steel beam web;

the GFRP component is obliquely arranged on the steel beam web plate, the upper end of the GFRP component is close to the stress point of the steel beam, and the lower end of the GFRP component is far away from the stress point of the steel beam.

2. The method of claim 1, wherein the GFRP member is made of glass fiber reinforced polymer and is manufactured by integral extrusion.

3. The method for reinforcing a shear-defective steel beam by GFRP according to claim 1, wherein the upper and lower ends of the base plate are respectively in contact with the flanges of the steel beam, and the distance between the midpoint of the contact surface and the edge of the steel beam is between zero and one quarter of the length of the side of the steel beam.

4. The method for reinforcing the shear defect steel beam by using GFRP according to claim 1, wherein the vertical ribs and cross ribs form a cuboid cavity structure with an aspect ratio of 2: 1.

5. the method of reinforcing a shear defect steel beam with GFRP as claimed in claim 1, characterized in that the vertical ribs are in line with cross ribs height.

6. The method of reinforcing a shear defect steel beam with GFRP as claimed in claim 1, wherein the bottom plate, vertical ribs and cross ribs are uniform in thickness.

7. The method of claim 1, wherein the width of the base plate is twice the height of the vertical rib.

8. The method of claim 1, wherein the distance between the vertical rib and the edge of the base plate is one quarter of the width of the base plate.