阅读说明：本技术 一种钢结构疲劳裂纹加固结构及其加固方法 (Steel structure fatigue crack reinforcing structure and reinforcing method thereof ) 是由 柯璐 姚剑伦 陈正 冯峥 李传习 朱夫瑞 李友林 李静 于 2021-08-06 设计创作，主要内容包括：本发明公开了一种钢结构疲劳裂纹加固结构,包括钻设于被加固钢结构裂纹前端的冷扩止裂孔以及固定于被加固钢结构两侧的两个形状记忆合金补强板。本发明还提供了一种钢结构疲劳裂纹加固方法,具体按照以下步骤实施：在被加固钢结构上的裂纹延伸处开设止裂孔；于室温下采用冷扩专用设备对止裂孔进行扩充,得到冷扩止裂孔；于室温下对两个形状记忆合金补强板分别进行预拉使之产生塑性变形；采用螺栓将预拉后的形状记忆合金补强板分别固定于被加固钢结构板件两侧,确保覆盖冷扩止裂孔和裂纹；对已固定的形状记忆合金补强板进行加热,使其产生塑性收缩变形；让加固后的结构于室温下自然冷却,清理表面,之后进行表面涂装。(The invention discloses a steel structure fatigue crack reinforcing structure which comprises a cold expansion crack stop hole drilled at the front end of a reinforced steel structure crack and two shape memory alloy reinforcing plates fixed on two sides of the reinforced steel structure. The invention also provides a steel structure fatigue crack reinforcing method, which is implemented according to the following steps: forming crack stop holes at the crack extending positions on the reinforced steel structure; expanding the crack-stopping hole by adopting special cold-expanding equipment at room temperature to obtain a cold-expanding crack-stopping hole; pre-stretching the two shape memory alloy reinforcing plates at room temperature to generate plastic deformation; respectively fixing the pre-stretched shape memory alloy reinforcing plates on two sides of the reinforced steel structure plate by using bolts to ensure that cold expansion crack-stopping holes and cracks are covered; heating the fixed shape memory alloy reinforcing plate to generate plastic shrinkage deformation; and naturally cooling the reinforced structure at room temperature, cleaning the surface, and then coating the surface.)

1. The utility model provides a steel construction fatigue crack reinforced structure which characterized in that, locates the cold expansion crack arrest hole of being consolidated steel construction crackle front end and is fixed in two shape memory alloy stiffening plates of being consolidated steel construction both sides including boring.

2. The steel structure fatigue crack strengthening structure of claim 1, wherein the cold expansion crack arrest hole drilled at the front end of the crack of the strengthened steel structure is obtained by cold expansion of the crack arrest hole at room temperature by using a special cold expansion device. The special cold expanding equipment mainly comprises a steel bar with the diameter being slightly larger than the aperture of the crack arrest hole, and the steel bar penetrates through the crack arrest hole under the powerful action of a mechanical device, so that cold expansion of the crack arrest hole is realized.

3. The steel structure fatigue crack reinforcing structure of claim 1, wherein the two shape memory alloy reinforcing plates are respectively fixed on two sides of the reinforced steel structure, specifically: pre-tensioning the two shape memory alloy reinforcing plates at room temperature to generate plastic deformation, and then relieving the tensioning force; fixing two shape memory alloy reinforcing plates on two sides of the reinforced steel structure by using bolts to ensure that the cold expansion crack stop hole and the crack are covered; then, a heating device is adopted to carry out thermal excitation on the two shape memory alloy reinforcing plates so as to enable the inner parts to generate plastic shrinkage deformation; and finally, naturally cooling the reinforced structure at room temperature.

4. A steel structure fatigue crack reinforcing method is realized according to the steel structure fatigue crack reinforcing structure of claim 1, and is characterized by being implemented according to the following steps:

step 1, drilling a crack stop hole at a crack extension part on a reinforced steel structure;

step 2, expanding the crack-stopping hole by adopting cold expansion special equipment at room temperature to obtain a cold expansion crack-stopping hole;

step 3, respectively pre-stretching the two shape memory alloy reinforcing plates at room temperature to generate plastic deformation;

step 4, fixing the pre-stretched shape memory alloy reinforcing plates on two sides of the reinforced steel structure plate respectively by using bolts to ensure that cold expansion crack stopping holes and cracks are covered;

step 5, heating the shape memory alloy reinforcing plate fixed in the step 4 to generate plastic shrinkage deformation;

and 6, naturally cooling the reinforced structure at room temperature, cleaning the surface, and then coating the surface.

5. The method for strengthening fatigue cracks of steel structure according to claim 4, wherein the step 5 is repeated when the shape memory alloy stiffening plate has stress relaxation.

Technical Field

The invention belongs to the technical field of bridge engineering, and particularly relates to a steel structure fatigue crack reinforcing structure and a steel structure fatigue crack reinforcing method.

Background

The steel structure has the advantages of small self weight, rapid assembling construction, large safety storage and the like, so the steel structure is widely applied to infrastructure. Fatigue and fracture are considered to be one of the most important causes of failure of steel structures. According to incomplete statistics, 80-90% of steel structure damage is related to fatigue fracture; for example, a great deal of fatigue cracks appear after five years of the open bridge vehicle of Severn in England, and a great deal of fatigue cracks are found after two years of the open bridge vehicle of Tiger door. Similarly, a large number of fatigue cracks were found in six years by turning on the large bridge of Yangtze river and the large bridge of the pond sea river. The crack detection of the steel structure is difficult, and the crack is usually found to be in a medium-high speed propagation stage, so that the rapid reduction of the using performance of the structure is easily caused, and the structure collapse is even caused. It can be seen that the fatigue cracking phenomenon of the bridge steel structure is common and has great harm.

Common steel structure crack arrest repair methods include a crack arrest hole method, a crack filling method, an optimization structure design method, a bolting/welding steel plate reinforcement method, a steel sticking reinforcement method, a CFRP (cement fly-ash radical) sticking reinforcement method and the like. Of these, the stop-hole method is simple to construct, but is not effective in some cases (e.g., fatigue cracks caused by torsion), and cracks may continue to develop through the stop-hole. The crack filling method has high requirements on the performance of the filling material and the construction process, and the filling depth of the filler has great influence on the crack control effect. The optimization of the structural design method is helpful for reducing the geometric discontinuity and relieving the stress concentration, but the rigidity and the ultimate bearing capacity of the structure can be reduced; the use of hot cutting to optimize the construction may also introduce undesirable residual stresses, and high temperatures may cause the material to harden, reduce toughness, and even reduce fatigue resistance once improperly designed. The steel plate reinforcement method can greatly improve the local rigidity of the structure, but the construction is relatively complex, the self weight is greatly increased, if bolting or riveting is adopted, new damage can be caused to the structure by drilling, adverse residual stress can be introduced and material hardening can be caused if welding is adopted, and new potential fatigue vulnerable points can be introduced by the connection methods. The steel adhesion reinforcing method avoids the adverse effects of bolting and welding, but the steel plate has overlarge rigidity, the end part is easy to peel off, and the method is not suitable for reinforcing a complex structure. The CFRP reinforcement method has a disadvantage in that the CFRP interface is at risk of peeling, and the construction process is complicated if a prestress is applied. In summary, the conventional steel structure fatigue crack repairing and reinforcing technology has defects in the aspects of crack arrest effect, construction process and the like. Therefore, it is urgently needed to develop a steel structure fatigue crack repairing structure and method with simple construction and better crack-stopping effect to effectively inhibit the fatigue crack from expanding, greatly prolong the service life of a steel structure bridge and further save the maintenance cost of infrastructure.

Disclosure of Invention

In order to solve the problems, the invention discloses a steel structure fatigue crack reinforcing structure which is used for effectively inhibiting the fatigue crack from expanding and greatly prolonging the fatigue life of a steel structure.

In order to achieve the purpose, the invention discloses a steel structure fatigue crack reinforcing structure, which comprises the following components: the utility model provides a steel construction fatigue crack reinforced structure, includes bores the cold expanding crack arrest hole of locating by reinforced steel construction crackle front end and is fixed in two shape memory alloy stiffening plates by reinforced steel construction both sides.

The invention discloses a steel structure fatigue crack reinforcing structure, which also has the following characteristics:

as the steel structure fatigue crack reinforcing structure disclosed by the invention, the cold expansion crack arrest hole drilled at the front end of the reinforced steel structure crack is obtained by cold expanding the crack arrest hole at room temperature by adopting special cold expansion equipment. The special cold expanding equipment mainly comprises a steel bar with the diameter being slightly larger than the aperture of the crack arrest hole, and the steel bar penetrates through the crack arrest hole under the powerful action of a mechanical device, so that cold expansion of the crack arrest hole is realized.

As the steel structure fatigue crack reinforcing structure disclosed by the invention, the two shape memory alloy reinforcing plates are respectively fixed on two sides of the reinforced steel structure, and the structure specifically comprises the following components: pre-tensioning the two shape memory alloy reinforcing plates at room temperature to generate plastic deformation, and then relieving the tensioning force; then fixing the two shape memory alloy reinforcing plates on two sides of the reinforced steel structure by adopting bolts and gaskets to ensure that the cold expansion crack-stopping holes and cracks are covered; then, a heating device is adopted to carry out thermal excitation on the two shape memory alloy reinforcing plates so as to enable the inner parts to generate plastic shrinkage deformation; and finally, naturally cooling the reinforced structure at room temperature.

The invention also provides a steel structure fatigue crack reinforcing method, which is implemented according to the following steps:

step 1, drilling a crack stop hole at a crack extension part on a reinforced steel structure;

step 2, expanding the crack-stopping hole by adopting cold expansion special equipment at room temperature to obtain a cold expansion crack-stopping hole;

step 3, respectively pre-stretching the two shape memory alloy reinforcing plates at room temperature to generate plastic deformation;

step 4, fixing the pre-stretched shape memory alloy reinforcing plates on two sides of the reinforced steel structure plate respectively by using bolts to ensure that cold expansion crack stopping holes and cracks are covered;

step 5, heating the shape memory alloy reinforcing plate fixed in the step 4 to generate plastic shrinkage deformation;

and 6, naturally cooling the reinforced structure in the step 5 at room temperature, cleaning the surface, and then coating the surface.

The technical scheme of the invention also has the following characteristics:

as a preferred embodiment of the present invention, when there is stress relaxation in the shape memory alloy reinforcing plate, the shape memory alloy reinforcing plate may be thermally activated for the second time, that is, step 5 may be repeated.

Compared with the prior art, the invention has the following advantages: (1) according to the steel structure fatigue crack reinforcing structure and the reinforcing method thereof, the steel structure member or the area with the fatigue crack is reinforced, so that the stress state of the tip of the crack can be obviously improved, and the fatigue crack expansion can be effectively inhibited; (2) according to the steel structure fatigue crack reinforcing structure and the reinforcing method thereof, the reinforced steel structure is drilled without hot cutting, so that new damage to the original structure is very small, and obvious stress concentration cannot be generated at the periphery by externally pasting the shape memory alloy reinforcing plate, so that a new fatigue risk source is prevented from being introduced; (3) the steel structure fatigue crack reinforcing structure and the reinforcing method thereof have the advantages that the structure is simple and light, and the overlarge self weight of the original structure cannot be increased; (4) according to the steel structure fatigue crack reinforcing structure and the reinforcing method thereof, personalized reinforcing schemes do not need to be set one by one according to different crack lengths and different crack trends, the universality is good, great convenience is brought to reinforcing design and construction, and therefore the cost is saved; (5) according to the steel structure fatigue crack reinforcing structure and the reinforcing method thereof, the prestress loss in the shape memory alloy reinforcing plate can be compensated by thermally exciting the shape memory alloy reinforcing plate for the second time, and the reinforcing effect is improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic view of the installation of a steel structure fatigue crack reinforcing structure according to the present invention;

FIG. 2 is a schematic view of a steel structure fatigue crack reinforcing structure of the present invention after the shape memory alloy reinforcing plate is removed.

FIG. 3 is a schematic diagram of the thermal excitation of the shape memory alloy reinforcing plate by the heating device.

In the figure: 1. the steel structure to be reinforced, 2 cold-expanding crack-stopping holes, 3 shape memory alloy reinforcing plates, 4 cracks, 5 bolts, 6 gaskets and 7 heating devices.

Detailed Description

Embodiments of the present invention will be described with reference to the following embodiments, so as to describe in detail how to implement the technical means to solve the technical problems and achieve the technical effects.

As shown in fig. 1-3, the steel structure fatigue crack strengthening structure based on the cold expansion crack arrest hole and the shape memory alloy reinforcing plate of the present invention comprises a cold expansion crack arrest hole 2, a shape memory alloy reinforcing plate 3, a bolt 5 and a heating device 7.

The cold expansion crack-stopping hole 2 is drilled at a certain position at the front end of the crack 4 of the reinforced steel structure 1; and the cold expansion crack-stopping hole 2 is obtained by cold expanding the crack-stopping hole at room temperature by adopting special cold expansion equipment.

Further, the position of the crack arrest hole 2: the circle center of the crack arrest hole 2 is located at 0.5t from the crack tip, and t is the thickness of the reinforced steel structure 1. The diameter of the crack arrest hole 2: the diameter of the crack arrest hole 2 depends on the thickness of the reinforced steel structure 1 and the length of the crack 4; setting the diameter of the crack-stopping hole as d, and if the length of the crack 4 is 40mm-80mm, taking d as 10 mm; if the length of the crack 4 is 80mm-120mm, d is 14 mm; if the length of the crack 4 is 120mm-150mm, d is 18 mm.

Furthermore, the cold-expanding special equipment mainly comprises a steel bar with the diameter being slightly larger than the aperture of the crack arrest hole, and the steel bar penetrates through the crack arrest hole under the powerful action of a mechanical device, so that cold expansion of the crack arrest hole is realized.

The cold expanding crack arrest hole 2 has the advantages that: the stress level of the tip of the crack 4 can be reduced by drilling the crack-stopping hole, the expansion of the crack 4 is inhibited, and the fatigue life of the reinforced steel structure is prolonged. After cold expanding is carried out on the crack arrest hole, residual compressive stress is generated around the hole, the average stress amplitude around the hole is reduced, and the tensile stress at the tip of the crack 4 is reduced; therefore, the propagation of the crack 4 can be further suppressed, and the fatigue life of the reinforced steel structure 1 can be further extended.

The two shape memory alloy reinforcing plates 3 are pre-tensioned at room temperature to generate plastic deformation, and then the tensioning force is released; respectively clinging two shape memory alloy reinforcing plates 3 to two sides of a reinforced steel structure 1 to ensure that a cold expansion crack stop hole 2 and a crack 4 are covered, and then respectively fixing the two shape memory alloy reinforcing plates 3 to two sides of the reinforced steel structure 1 by adopting a bolt 5 and a gasket 6; then, the two shape memory alloy reinforcing plates 3 are thermally excited by the heating device 7 to be restored to the initial state before pretensioning, and at this time, pre-pressure is generated on both end faces of the crack 4 of the reinforced steel structure 1. Finally, the heating device 7 is removed, the shape memory alloy reinforcing plate 3 is naturally cooled to the room temperature, and finally coating is carried out.

When the shape memory alloy reinforcing plate 3 has stress relaxation, the heating device 7 can be used for carrying out secondary thermal excitation on the shape memory alloy reinforcing plate 3, so that secondary compensation of prestress loss can be realized, and the reinforcing effect is improved.

The use of the shape memory alloy stiffening plate 3 has the advantages that: when the heating device 7 is adopted to thermally excite the shape memory alloy reinforcing plate 3, pre-tensioning stress is generated inside the shape memory alloy reinforcing plate 3 and acts on the reinforced steel structure 1 to generate pre-pressure on two end faces of the crack 4, so that the crack 4 is closed, the expansion of the crack 4 is inhibited, and the structural fatigue life is greatly prolonged. Therefore, the reinforcing effect of the shape memory alloy reinforcing plate 3 is better.

In the above operation, it is noted that:

a) the drill should be slowly drilled when the crack-stopping hole is drilled, so as to ensure uniform stress distribution around the hole, and in addition, the eccentric angle of the drill hole should be controlled to be-15-30 degrees (the eccentric angle is the deviation angle of the circle center of the crack-stopping hole relative to the propagation direction of the crack 4). According to the evaluation of the real bridge test, the stress peak value of the crack tip is reduced by the crack arrest hole, but the stress peak value is increased by the deviation of the hole position. Therefore, if the hole site is deviated, the crack arrest effect is lowered.

b) Bolt holes are drilled around the positions far away from the crack 4 and far away from the edge of the shape memory alloy reinforcing plate 3, so that a new fatigue risk source is prevented from being introduced.

c) When the surface treatment is performed on the cracking region near the fatigue crack 4, the area of the treated region should be slightly larger than the area of the shape memory alloy reinforcing plate 3. The determination of the fatigue cracking area can be made through common knowledge and engineering experience of technicians in the field, or can be obtained through structural analysis and calculation, which are common means for solving the fatigue problem of the steel structure.

d) If the crack 4 is located at the edge of the steel plate, one side of the shape memory alloy reinforcing plate 3 should be aligned with the crack edge of the reinforced steel structure 1, so that the shape memory alloy reinforcing plate 3 can better inhibit the crack 4 from expanding.

And two heating devices 7, wherein heating belts on the heating devices 7 are respectively fixed on the outer sides of the two shape memory alloy reinforcing plates 3, and cover the outer sides of the two shape memory alloy reinforcing plates 3.

Further, the heating belts on the two heating devices 7 are respectively fixed on two sides of the two shape memory alloy reinforcing plates 3, specifically: when the shape memory alloy reinforcing plate 3 is heated, the heating belt on the heating device 7 is covered on the outer side of the shape memory alloy reinforcing plate 3, the temperature regulator is switched on after the power supply is switched on, and the required temperature is regulated. The heating device 7 has the following characteristics (1) flexibility, and can be used in special occasions and in severe environments. (2) The shape memory alloy reinforcing plate is heated by converting electric energy into heat energy, and has a certain heat preservation effect. (3) Can adjust to required temperature through temperature regulator, easy operation is convenient.

While the foregoing description shows and describes several preferred embodiments of the invention, it is to be understood, as noted above, that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.