KR100804548B1 - Repair and strengthening method of steel bridge - Google Patents

Abstract

The present invention relates to a steel bridge repair reinforcement method. Steel bridge repair reinforcement method according to the present invention is to reinforce the steel bridge including a girder made of steel (절단), cutting step of forming a cut by cutting the damaged portion of the girder in a predetermined shape; Reinforcing material preparation step of manufacturing a reinforcing reinforcement made of steel (鋼材) to the same shape as the cut portion; When the reinforcing reinforcement is placed in the cutting section of the girder, the welding groove for welding is formed in a portion where the cut surface of the girder and the cross section of the reinforcing reinforcement are in contact with each other, but the welding groove is formed in at least one of the reinforcing reinforcement and the girder. Groove forming step; And a welding step of placing the repair stiffener on the cut portion of the girder and welding the repair stiffener to the girder along the welding groove.

Girder, steel bridge

Description

Repair and strengthening method of steel bridge

1 is a schematic perspective view of a steel bridge in which an 'I' type girder is employed.

2 is a photograph showing an example of a damaged steel bridge.

Figure 3 is a flow chart for explaining the steel bridge repair reinforcement method according to a preferred embodiment of the present invention.

4 is a schematic perspective view of a steel bridge to implement the steel bridge repair reinforcement method shown in FIG.

Figure 5 is a schematic perspective view for explaining the steel bridge repair and reinforcement method shown in Figure 3, Figure 5a is a view for explaining the cutting step, Figure 5b is a view for explaining the reinforcing material preparation step and the welding groove forming step, 5C is a view for explaining a welding step.

Figure 6 is a schematic perspective view of a model bridge installed for the applicability and effectiveness of the steel bridge repair reinforcement method according to a preferred embodiment of the present invention.

7 is a photograph showing an actual installation scene of the model bridge of FIG.

8 is a graph showing the behavior characteristics of the steel bridge shown in the experiment of Figure 6, Figure 8a is a graph showing the deformation amount of the steel bridge with the cutting, Figure 8b is a graph showing the welding deformation amount of the steel bridge by welding, 8c is a graph showing the cutting stress of the steel bridge according to the cutting.

FIG. 9 is a photograph showing a panoramic view of Seohwacheon Bridge, which is the actual bridge of the closed bridge where the field test of the steel bridge repair and reinforcement method according to the preferred embodiment of the present invention was performed.

10 is a longitudinal sectional view of the Seohwacheon bridge of FIG.

FIG. 11 is a schematic perspective view showing an implementation part of a repair reinforcement method of Seohwacheon Bridge of FIG. 9.

FIG. 12 is a diagram showing an arrangement of strain gauges provided for measuring the stress behavior at a steel bridge 14m point.

13 is a graph showing the behavior characteristics of the steel bridge shown in the field experiment of Figure 9, Figure 13a is a graph showing the amount of deflection strain at the bridge 7m point, Figure 13b is a graph showing the amount of deflection strain at the bridge 14m point, 13c is a graph showing the axial stress behavior of the 14m point web, Figure 13d is a graph showing the axial stress behavior of the 14m lower flange, Figure 13e is a graph showing the principal direction stress behavior of the 14m point web, Figure 13f Is the graph showing the principal stress behavior of the lower flange at 14m.

<Description of the symbols for the main parts of the drawings>

100 ... steel bridge M100 ... steel bridge repair reinforcement method

M10 ... safety assessment step M20 ... cutting stage

M30 ... reinforcement stage M40 ... weld groove formation stage

M50 ... welding step M60 ... welding step

M70 ... inspection step g ... girder

f ... flange w ... web

d ... damage 10 ... cut

11w ... web cutting edge 11f ... flange cutting edge

30 ... repair reinforcement 31 ... flange reinforcement

32 ... Web Reinforcement 200 ... Model Bridge

300 ... Seohwacheon Bridge

The present invention is a steel bridge repair and reinforcement method for repairing and reinforcing a damaged part when a portion of a steel bridge such as an 'I' type girder bridge, a box type girder bridge, or the like is damaged by corrosion or damage caused by an impact.

Since steel is superior to other materials in terms of load capacity, earthquake resistance and fatigue, structures using steel have been increasing in recent years. When the steel is applied to the bridge, because the durability of the bridge is excellent, the installation of steel bridges such as 'I' type girder bridge, box-type girder bridge, etc. using the steel is also increasing.

Box-shaped girder bridges among the steel bridges are shown in FIGS. 1 and 2. 1 is a schematic perspective view of a steel bridge employing a box-shaped steel girder, Figure 2 is a photograph showing an example of a damaged steel bridge. Referring to FIG. 1, the steel girder bridge 9 includes a plurality of piers 1 supported on the ground and disposed vertically. The box-shaped girder 2 is provided on the upper part of the pier 1 at regular intervals to the left and right sides. Moreover, the slab 3 is arrange | positioned in parallel in the upper part of this girder 2. The girder 2 serves to transfer the load of the upper portion of the bridge to the pier (1), in the case of a girder made of steel can be damaged when used for a long time. That is, as shown in Figure 2, the cross-sectional area due to the corrosion of the web, flange, splice of the girder, the vertical stiffener and the girder deformation due to the action of the unexpected load in the design, weld leakage, external unwanted impact Damage such as breakage may occur. If the girder is damaged in this way, the load capacity of the bridge is reduced, which can seriously affect safety.

When steel bridges are damaged, conventional methods for repairing and reinforcing steel bridges can be largely classified into repairing and reinforcing methods. Repair methods include calibration method, stop hole installation method, and reinforcement methods include replacement method, reinforcement method, girder extension method, column extension method, and reinforcement plate fastening method. However, these methods can be applied in the case of relatively small damage, but in the case of relatively large damage, there was a clear limitation in its application. In the case of steel bridges with a large degree of damage, the conventional repair and reinforcement methods cannot be applied, and thus, the damaged bridge itself must be completely replaced or the entire bridge must be rebuilt, thereby causing a very uneconomic problem. In addition, when replacing the span of the bridge or the entire bridge as described above, and if you want to implement a specific construction method of the conventional reinforcement reinforcement method, it is necessary to control the traffic of the bridge has caused a lot of problems, such as traffic jams. On the other hand, the theoretical and experimental verifications and norms on the safety, repair and reliability of steel bridges are still insufficient in the case of steel bridges compared to concrete structures. There is an urgent need for evaluation criteria for reliability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a steel bridge repair and reinforcing method which is very economical in terms of air or construction cost while improving durability of an aging or large damage steel bridge. In addition, in one embodiment of the present invention, the steel bridge repair and reinforcement method that can secure the stability of the bridge during construction as well as during the construction of the public while not being able to repair and repair in the public state that does not control the traffic of the damaged steel bridge The purpose is to provide.

Steel bridge repair and reinforcing method according to the present invention for achieving the above object is to repair and reinforce the steel bridge including a girder made of steel, cutting to form a cut by cutting the damaged portion of the girder in a certain shape step; Reinforcing material preparation step of manufacturing a reinforcing reinforcement made of steel (鋼材) to the same shape as the cut portion; When the reinforcing reinforcement is placed in the cutting section of the girder, the welding groove for welding is formed in a portion where the cut surface of the girder and the cross section of the reinforcing reinforcement are in contact with each other, but the welding groove is formed in at least one of the reinforcement and the girder Groove forming step; And a welding step of arranging the repair stiffener in the cut portion of the girder and welding the repair stiffener to the girder along the welding groove, wherein the cutting step and the welding step are common to the bridge. It is desirable to be done during 共用).

According to the present invention, when performing the cutting step and the welding step of the common use of the steel bridge further comprises a safety evaluation step of determining whether the safety of the steel bridge before the cutting step by the common load capacity formula, the common Load capacity determination formula P '= P × K _s × K _r × K _t × K _o × K _H , where P is the basic load capacity, P = 24 × (σ _a -σ _d ) / σ ₂₄ , and σ _a is allowed Stress, σ _d is dead load stress, σ ₂₄ is stress due to DB-24 load, K _s is correction factor for stress, K _r is correction factor for road condition, K _t is correction factor for traffic condition, K _o is the correction factor for other conditions, K _H is the correction factor according to the heat input, and if the common load capacity of the steel bridges in common use obtained by the common load capacity formula is more than the specified safety standard value in the standard specification, It is preferable.

Hereinafter, with reference to the accompanying drawings, a steel bridge repair reinforcing method according to a preferred embodiment of the present invention will be described in more detail.

3 is a flowchart illustrating a steel bridge repair reinforcement method according to a preferred embodiment of the present invention, Figure 4 is a schematic perspective view of the steel bridge to implement the steel bridge repair reinforcement method shown in Figure 3, Figure 5 is a 5A is a schematic perspective view for explaining the steel bridge repair and reinforcement method shown, Figure 5a is a view for explaining the cutting step, Figure 5b is a view for explaining the reinforcing material preparation step and the welding groove forming step, Figure 5c is a welding step It is a figure for demonstrating.

Prior to implementing the steel bridge repair reinforcement method (M100) according to a preferred embodiment of the present invention, the damaged portion (d) of the steel bridge is clearly identified. The damage causes of the steel bridge 100 are roughly classified as damages due to the action of the load which is unexpected in design, reduction of the cross-sectional area due to corrosion, unexpected damages due to unwanted external force, and damages due to the manufacturing and construction causes such as weld leakage. Can be. In order to accurately understand the cause of damage of the damaged part (d) of the steel bridge 100, the design drawing of the target steel bridge 100, including the design statement, design, and completed drawings, the actual working load of the target steel bridge 100 (past and present Traffic volume survey, large car entry rate calculation), construction and inspection records for the construction and repair of the target steel bridge (100), etc., and the stress inspection of the damaged part (d) and the welding of the damaged part (d) and the use of the base metal See examples of similar damage and data from similar repair work. If the material used or the welding material of the steel bridge 100 is unclear, it is preferable to perform a separate analysis by drilling a portion where stress concentration does not occur. After identifying the cause of damage of the damaged portion (d) with reference to the above data to determine the degree of damage of the damaged portion (d). To do this, nondestructive testing should be performed according to the type of damage as well as the naked eye. For example, the reduction of the cross section due to corrosion requires the measurement of thickness using ultrasonic inspection, and the crack inspection needs to be subjected to nondestructive inspection such as penetration inspection and ultrasonic inspection. After determining the damage portion (d), the cause of the damage and the degree of damage through the above process, if the damage degree is large, determine the implementation of the steel bridge repair reinforcement method (M100) according to a preferred embodiment of the present invention, as will be described later Steel bridge repair and reinforcement method (M100) is to be carried out during the public use of the bridge, so that the safety load during the work in advance to determine the load-bearing load of the steel bridge 100 in advance.

Steel bridge repair and reinforcement method (M100) according to a preferred embodiment of the present invention may control and enforce the traffic of the damaged steel bridge (100), but is preferably carried out in common. 3 to 5, the steel bridge repair reinforcing method (M100) is performed in the order of cutting step (M20), reinforcing material preparation step (M30), welding groove forming step (M40) and welding step (M60).

In the cutting step (M20) to cut the damaged portion (d) of the steel bridge (100). The cutting range is a minimum area where damage has occurred, and there is no particular limitation on the cutting shape, but as shown in FIG. 5A (a), the cutting range is cut into a rectangular shape for ease of cutting and welding operations to be described later. The cutting of the damaged part (d) uses gas cutting, and preheats the cutting start at 850 to 900 ° C. for about 10 seconds prior to gas cutting, and preferably maintains the cutting speed at about 200 to 300 mm / min. On the other hand, most of the damage of the steel bridge 100 is generated in the girder (g), the girder (g, girdir) is a web (w, web) and the web (w) in a direction orthogonal to the web (w) Consists of a flange (f, arranged) at the top and bottom of each. If the damaged part (d) of the girder girder (g) is only on one of the web (w) or the flange (f), only the part may be cut, but when the web (w) and the flange (f) are present together, As shown in (a) to (c) of 5a, the cutting order of the girder g first cuts the web w and then the flange f.

The reinforcing material preparation step (M30) is carried out after completion of the cutting step (M20). In the reinforcing material preparation step (M30) to prepare a reinforcing reinforcement material 30 having the same shape and specifications as the damaged portion (d) cut in the cutting step (M20). The reinforcing stiffener 30 is selected and manufactured by selecting the same material as that of the cut damaged portion d. When the cross section of the damaged part d cut by cutting both the flange f and the web w of the girder g in the cutting step M20 is a 'ㅗ' shape, the flange part and the web part are integrally formed. The repair reinforcement may be manufactured to form a cross-section of the repair reinforcement in a 'ㅗ' shape in the same manner as the cut part d, but as shown in FIG. 5B, the flange reinforcement 31 and the web reinforcement having a plate shape may be formed. (32) can also be manufactured, respectively. As such, when the flange reinforcement 31 and the web reinforcement 32 are separately manufactured, the flange reinforcement 31 and the web reinforcement 32 are welded to each other in the welding step M60 to be described later.

The welding groove forming step (M40) is carried out after completion of the reinforcing material preparation step (M30). In the welding groove forming step M40, when the repairing reinforcement material 30 manufactured in the reinforcing material preparation step M30 is disposed at the cutout portion 10 of the girder g in which the damaged part d is cut, the girder ( g) is a step of forming a welding groove 33 for welding, which will be described later, at a portion where the cut surfaces 11w and 11f and the cross section of the reinforcing reinforcement 30 are in contact with each other. In order to form the welding groove 33, a cross section of the cross section of the repair reinforcement 30 that contacts the cut surfaces 11w and 11f of the girder g is cut at a predetermined inclination angle α. That is, in the case of the flange reinforcement 31, both longitudinal cross sections are cut at a predetermined inclination angle α with respect to the direction perpendicular to the ground, and in the case of the web reinforcement 32, both cross sections in the longitudinal direction are perpendicular to the ground. It cuts with respect to the predetermined inclination angle (alpha), and cuts both end surfaces of the width direction by the predetermined inclination angle (alpha) with respect to the ground surface. When the reinforcing reinforcement material 30 cut in this manner is disposed on the cutout portion 10 of the girder g, a triangular shape is formed between the cut surfaces 11w and 11f of the girder g and the cut end surface of the reinforcing reinforcement material 30. Welded grooves 33 are formed. Further, a triangular weld groove 33 is formed between the upper surface of the web reinforcement 32 and the lower surface of the flange reinforcement 31. On the other hand, in order to form the welding groove 33, it is not necessary to cut the cross section of the reinforcement reinforcement 30, and the reinforcement reinforcement 30 does not cut, but reversely cut the cut surfaces 11w, 11f of the girder g You may cut at the inclination angle α. In addition, you may cut together the cut surface 11w, 11f of the maintenance reinforcement 30 and the girder g. When the end face of the reinforcement material 30 and the cut surfaces 11w and 11f of the girder g are simultaneously cut, the cut end surface of the reinforcement material 30 and the cut cutting surfaces 11w and 11f of the girder g are cut. When placed in contact with each other, the angle formed between these cross sections is such that the predetermined inclination angle α is obtained. The predetermined inclination angle α may be variously set according to welding conditions.

When the welding groove forming step (M40) is finished, the weld welding step (M50) is performed. The welding step M50 is performed before the welding step M60, which will be described later, and tack welding the repair reinforcement 30 to the cut portion 10 of the girder g. That is, the repair reinforcement 30 is placed on the cutout 10, and then the repair reinforcement 30 and the girder g are welded to each other at regular intervals along the welding groove 30. ). Fusible welding welds approximately 10 to 20 mm per its welding point (t). Steel bridge repair reinforcement method (M100) according to the present invention is to perform the bridge in common, so that the bridge according to the progress of the vehicle when welding the reinforcement material 30 and the girders (g) in the welding step (M60) to be described later The welding environment is not favorable due to vibration of work table and vibration caused by wind. Accordingly, it is desirable to facilitate the welding once the maintenance reinforcing material 30 is fixed to the girder g through the temporary welding.

When the temporary welding step M50 is completed, the welding step M60 is performed. In the welding step M60, the girder g and the reinforcement 30 are mutually formed along the welding groove 33 between the cross section of the repair reinforcement 30 and the cut surfaces 11w and 11f of the girder g cut 10. Weld When the flange reinforcement material 31 and the web reinforcement material 32 are manufactured separately in the reinforcing material preparation step (M30), as shown in FIG. 5C, the flange reinforcement material 31 is welded first, and then the web reinforcement material 32 is later produced. It is preferable to weld. In addition, it is preferable to remove moisture remaining in the welded portion before welding, for example, by thermal drying due to an oxygen frame. Since water is composed of oxygen and hydrogen, when hydrogen exists in the form of pores in the welding part, the hydrogen pores are in an unstable state immediately after welding, and when the external factors such as heat or external stress fatigue are given, This results in serious welding problems such as cracking. To prevent this, preheat the welded area with a torch to remove moisture. In addition, by using a welding material as a low hydrogen electrode, welding cracks that may occur when the girder g and the repair reinforcement 30 are welded to each other may be reduced. On the other hand, the welding of the high-tensile steel is limited in the heat input to ensure toughness, but in the welding during the common use of the steel bridge 100, it is good to suppress the heat input for the following reasons. That is, when welding, the temperature of the peripheral member also rises and the load capacity decreases, so there is a fear that buckling and deformation occur under static stress. If the heat input is excessive, it is preferable to limit the heat input because the area where the load capacity decreases from the temperature rise becomes large. In addition, even if the interpass temperature is high, the area reaching the temperature range where the load capacity decreases is large. Therefore, it is better to keep the interpass temperature lower than the limit temperature necessary for the prevention of low temperature cracking. In welding, preheating and interpass temperature requirements are to be preheated in accordance with the provisions of bridge specifications, for example, road bridge specifications. For example, if the carbon equivalent of SM520 and SM570 is low in the range of 0.3 to 0.47, preheating may be omitted. However, if the carbon preheating is omitted for steels having a high carbon equivalent, the risk of cold welding cracking increases. In consideration of these conditions, it is preferable to perform lamination welding when the neck thickness of the welding is 5 mm or more to prevent excessive heat input during welding, in which case the bead thickness per layer should not exceed 3 mm. The temperature between passes should not exceed 150 ℃, and the thickness of the electrode should not exceed 4mm. However, it is necessary to increase the preheating temperature in situations of increased restraint, increased hydrogen content, low weld input heat or steel composition at the upper limit of the road bridge specification. Conversely, it is appropriate to reduce the preheat temperature to prevent cracking due to confinement and hydrogen levels, actual steel composition or high weld heat input.

When the welding of the reinforcing reinforcement 30 and the girder g is completed in the above manner, an inspection step (M70) of inspecting weld defects of the weld portion is performed, and the inspection of the weld defects is performed through non-destructive inspection. Defects in the weld create localized stress concentrations by forming notches in the material. In addition, weld defects may cause buckling and fatigue strength reduction of the entire steel structure. For this reason, it is important to conduct a complete inspection and repair of the weld. In the steel bridge repair reinforcement method (M100) according to a preferred embodiment of the present invention, a non-destructive test of a welded part may adopt a radiographic test and an ultrasonic flaw test. Radiation penetration test is a non-destructive test method in which X-rays or gamma rays are transmitted through an object, and the presence of defects is judged by an image such as a film. In order to apply the radiographic test to spot welding, a portable X-ray generator or mobile gamma ray is used. The transmittance meter (IQI) uses an IQI defined in KS B 0848. The structure and size of the gradation system is in accordance with KS B 0845. There are a number of weld defects that can be detected by the radiographic test, and representative examples are cracks, undercuts, penetration defects, craters, penetration excesses, pores, slag, penetration defects, overlaps, and the like. The inspection results are determined in accordance with the regulations. The most important aspect in the application of radiological technology is the orientation of the radiation source and the placement of the specimen. When photographing edge joints, it is necessary to be able to include all welded structures in order to be most advantageous on the film. The deciding factor of this criterion depends on the weld criterion, the construction of the joint and the design stress. The imaging method of the heat affected zone HAZ should be set at a position where two focal points have an angle of incidence of 90 ° with respect to the heat affected zone. The standard of the transmission test is KS B 0845-1976, which is a radiographic test method for steel welds and a classification method for transmission pictures. Ultrasonic flaw detection is a non-destructive test that uses the physical properties of ultrasonic waves to detect defects in materials such as metals and their bonding members, and to investigate the nature and condition of the detected defects. Ultrasonic transducers are classified into vertical and rectangular types, based on KS B 0817. Weld defects that can be detected by ultrasonic flaw testing include interlayer fusion defects, internal penetration defects, root penetration defects, and cracks. Due to the nature of the examination, the location of the defect is known, but the shape is difficult to implement accurately, so it is necessary to use it together with the radiographic test. The specification of the ultrasonic flaw test is based on KS B 0896-1977, the ultrasonic flaw test method for steel welds and the classification method of test results. If a defect in the welded portion is detected in the inspection step (M70), the quality of the welded portion can be ensured by performing repair.

On the other hand, the steel bridge repair reinforcement method (M100) according to a preferred embodiment of the present invention is to cut and weld the damaged portion (d) of the girder (g) during the common use of the steel bridge 100, so before the cutting step (M20) By performing the evaluation step (M10), the step of evaluating and predicting the load capacity of the bridge in common. According to the result of the safety evaluation step (M10) it is determined whether to implement the construction method according to the present invention in the repair and reinforcement of the steel bridge. Since the steel bridge 100 was constructed according to various design criteria at the time of design, there are many variations in live load performance. In addition, the structural conditions for the bridge are changed by various factors such as the shape and weight of the traffic vehicle, the aging and damage of the steel bridge, the amount of traffic. As such, the live load effect and the resistance of structural members are variables composed of various factors with uncertain characteristics, so accurate evaluation of them must be preceded for safety evaluation of damaged bridges.

The method of evaluating the load capacity of a bridge can be largely classified into three methods, namely, the method of allowable stress theory, the method of load-resistance coefficient method, and the method of reliability index. In recent years, the evaluation of the load-bearing capacity, in particular, the concrete bridges in the evaluation of the ultimate strength theory, but a lot of the evaluation method by the allowable stress method in the steel bridge (100), so the good results in the preferred embodiment of the present invention Load capacity evaluation based on the allowable stress theory commonly used in 100). The evaluation of the load capacity of a bridge member based on the allowable stress theory is based on the allowable stress of the material used. At this time, stress due to dead load and live load should be calculated in consideration of sectional loss due to damage in the target member section. The basic load capacity is a proportional value that is proportionally expressed based on the design load, which is the magnitude of the live load that the bridge can support when the steel bridge is analyzed according to the current specification (road bridge specification, etc.). That is, the maximum value of the stress due to live load that the bridge can safely bear is the value obtained by subtracting the stress value due to dead load from the allowable stress of the member material. Common load capacity determination formula P ″ = P × K _s × K _r × K _t × K _o , where P is the basic load capacity, P = 24 × (σ _a -σ _d ) / σ ₂₄ , σ _a is the allowable stress, σ _d is the dead load stress, σ ₂₄ is the stress due to the DB-24 load on the road bridge specification, K _s is the correction factor for the stress, K _r is the correction factor for road conditions, K _t is the correction factor for traffic conditions, K _o is the correction factor for other conditions. However, the above-mentioned common load capacity determination formula is merely for evaluating the condition of a bridge damaged by aging, and as a method for evaluating a case where welding, cutting or the like is taken to the steel bridge 100 for repair and reinforcement. There are some inadequacies. Therefore, in the present invention, considering the influence of heat input by cutting and welding, multiplying a constant proportional coefficient by the common load capacity determination formula to provide a corrected load capacity determination formula. The formula for determining the common load capacity of steel bridges during cutting and welding of steel bridges is as follows.

P '= P × K _s × K _r × K _t × K _o × K _H where K _H Is a correction factor in consideration of heat input by cutting and welding, and the remaining coefficients are the same as the general load capacity determination formula. The above load capacity determination formula is applied when the steel bridge 100 is a road bridge, and in the bridge of other uses such as a railway bridge or footbridge, the basic load capacity P value is adjusted according to the specification of the bridge.

When the value of the load capacity of the steel bridge to be repaired and strengthened by the above determination formula is greater than the standard load capacity on the road bridge specification, the repair and strengthening method according to the present invention is performed. The correction coefficient according to the heat input is calculated by considering the influence of stress that may occur during repair by cutting and welding the steel bridge 100 based on the general tendency of the stress distribution under heat input. The effect of stress on the structure according to heat input is specified in proportion to the distance from the heat source, and although the degree is different, it can be judged that the influence is within a range of about 200 mm. However, ultimately, the evaluation of the load capacity is to determine the most dangerous position and state, so that the correction coefficient based on the influence of the stress due to heat input can be obtained by determining the position and magnitude of the maximum tensile and compressive stress. . Repair welding under load, i.e., the maximum tensile and compressive transient stresses that can be obtained during cutting and welding are considered to have a dominant effect on the structure when cutting is performed, rather than when welding. In the case of maximum tensile and compressive residual stresses, the influence of the welding process can be considered to be the dominant one. Steel bridge 100, such as a girder bridge may be said to occur in the case of large damage due to corrosion, the occurrence position is lower than the neutral axis of the structure. Therefore, in the case of a general damaged part that is not the central point of the continuous bridge in which the parent moment is generated, repair and reinforcement according to the damage are made at the position where the tensile stress due to bending is the main action force. This means that the additional tensile stress can greatly affect the safety of the structure. From the idealized stress distribution of the previous section in relation to the safety of the structure during the repair under welding under load, the compressive stress by cutting and welding is about 45% of the yield stress of the material, and the tensile stress by welding It can be seen that about 25% of the yield stress of the material. Therefore, it is estimated that 25% of the effects on the structure due to heat input such as cutting or welding during repair and reinforcement work can be proposed, and the above correction factor is preferably 0.75, and the range of correction factor is 0.65. ≤ K _H ≤ 0.75 can be set. If the correction coefficient exceeds 0.75, the effect of heat input is assumed to be too small, and the load capacity is high. Therefore, there is a risk of safety. If the correction coefficient is less than 0.65, the load capacity is less than necessary. As described above, it is possible to ensure safety during operation by determining whether the maintenance reinforcement method according to the present invention is performed by the common load capacity determination formula of the steel bridge in common.

Hereinafter, in order to find out the effectiveness and field applicability of the steel bridge repair reinforcement method according to the present invention, a model steel bridge was manufactured and a test was performed on the Seohwacheon bridge, which is a steel bridge to be closed. The test and results of the model steel bridge will be described in detail, and then the test and results of the Seohwacheon bridge will be described.

FIG. 6 is a schematic perspective view of a model bridge installed for an applicability and effectiveness test of a steel bridge reinforcement method according to a preferred embodiment of the present invention, and FIG. 7 is a photograph showing an actual installation scene of the model bridge of FIG. 6.

This experiment was carried out on the assumption that the damaged part was cut in the lower part of the girder of the steel bridge and the reinforcement was welded to repair the steel bridge. Figure 6 shows the shape and dimensions of the model bridge, Figure 7 is a photograph of the installed model bridge. 6 and 7, the model bridge 200 has a total length of 20 m and a two-span continuous I-girder bridge with an upper flange 210 of 16 mm, a lower flange 220 of 22 mm, and a web 230 of SM490 having a thickness of 12 mm. Steel was used. Superstructure 270 was made of reinforced concrete of 300kgf / ㎠ strength. The 6-ton aggregate and concrete block 280 was loaded with load, and a total load of 12 tons was loaded on the entire bridge. Assuming that the actual bridge is installed in the same standard as the above-mentioned model bridge 200, considering that the traffic volume, etc., considering that the various loads loaded on the actual bridge is about 12 tons in this experiment, the load of 12 tons in this experiment Loaded.

 Cutting was used for gas cutting, and as shown in Figure 6, after cutting the web 230, the damaged portion was cut in the order of cutting the lower flange 220. In the field welding, it is practically impossible to accurately set and perform welding and cutting speed, heat input amount, and the like. Therefore, in this experiment, we tried to keep the cutting speed and welding speed as constant as possible and the cutting was done under the following conditions. The web 230 and the lower flange 220 were preheated at 850-900 ° C. for about 10 seconds prior to cutting, and then cut at the speed and width as shown in Table 1 below.

order Cutting speed v (mm / min) Web Bottom flange One 276 2 291 3 257 4 228 5 138 6 156

             Table 1 Cutting Conditions

Repair reinforcement (not shown) was made of the same material and shape as the cut damage, the repair reinforcement was formed with a welding groove.

Welding was performed using FCAW (Flux Cored Arc Welding), and the first lower flange was welded with a flange repair reinforcement (not shown), and the cut web was welded with a web reinforcement (not shown). As in the case of cutting, the welding speed and heat input were maintained as much as possible, and the welding was performed under the following conditions. In this experiment, the lower flange and the web were welded in three passes with heat input Q = 2800 (J / mm ² ) and welding speed v = 3 (mm / sec). In addition, welding was repaired by what is called one side bevel butt and T joint. Detailed welding conditions are shown in Table 2 below.

Lower Flange Web

Welding speed

1Pass 2.97 2.75 2Pass 2.95 2.21 3Pass 2.58 2.98 Current (A) 240 240 Voltage (V) 40 35 Average heat input (

) 2880 2770

              Table 2 Welding Conditions

The experimental results are shown in FIG. 8 is a graph showing the behavior characteristics of the steel bridge (model bridge) shown in the experiment of Figure 6, Figure 8a is a graph showing the deformation amount of the steel bridge (model bridge) according to the cutting, Figure 8b is a steel bridge (by welding) 8) is a graph showing the cutting stress of the steel bridge (model bridge) according to the cutting.

Referring to FIG. 8A, when only the web 230 is cut, the maximum deflection at the lower end of the cut surface (x = 600 mm) is about 1 mm, and when the cut is performed to the lower flange 220, near the cut surface (x = 200). , 800 mm) showed a maximum deflection of about 3.3 mm. In addition, the residual deflection displacement after cutting was similar to the deflection displacement appeared in the cutting process, but the maximum deflection displacement is slightly reduced by the shrinkage displacement due to heat shrinkage during cooling after heat input. And it can be seen that the displacement amount is significantly larger when the cut to the lower flange 220 than when only the web 230 is cut.

 Referring to FIG. 8B, when only the bottom flange 20 was welded, the maximum rise was 0.1 mm, and after the welding and welding of the web 230 were completed, the amount of residual rise was greatly increased. have. This is considered to increase the amount of deformation of the lower end of the flange due to heat shrinkage due to the cooling of the lower flange (220).

In addition, referring to Figure 8c, when the web 230 and the lower flange 2320 is cut, the compressive stress appears due to thermal expansion due to heat input, the tensile stress appears due to thermal shrinkage due to cooling after heat input in the remaining state I can see that there is.

From the above results, it can be seen that the amount of deflection generated in the model bridge 200 at the time of cutting and welding under the loaded load satisfies the allowable deflection value proposed by the road bridge specification. The allowable deflection values on the road bridge specifications are shown in Table 3 below.

Bridge type Maximum deflection   Plate Girder Type Kinds Between Simple support girder and continuous girder Ger Burger cantilever Plate girder with slab L ≤ 10m L / 2000 L / 1200 10m ≤ L ≤ 40m L / (20000 / L) L / (12000 / L) L ＞ 40m L / 500 L / 300 Plate girders with other slabs L / 500 L / 300

             Table 3 Permissible Deflection Value (Road Bridge Specification)

Meanwhile, the effectiveness and field applicability of the steel bridge repair reinforcement method according to the present invention were tested on actual bridges which are to be closed. Hereinafter, the present experiment and its results will be described in detail with reference to the accompanying drawings. FIG. 9 is a photograph showing a panoramic view of Seohwacheon Bridge, the actual bridge of the closed bridge, in which the field test of the steel bridge repair reinforcement method according to the preferred embodiment of the present invention is performed. FIG. 10 is a longitudinal cross-sectional view of Seohwacheon Bridge of FIG. 9 is a schematic perspective view showing an implementation of the repair and reinforcement method of Seohwacheon bridge of Figure 9, Figure 12 is a view showing the arrangement of the strain gauge (strain guage) installed to measure the stress behavior of the 14m point.

The actual bridge for this experiment was Seohwacheon Bridge (300), which is scheduled to be closed, belongs to Okcheon-gun, Chungcheongbuk-do, and was located near the Okcheon IC in Gyeongbu Expressway. As shown in FIGS. 9 and 10, the Seohwacheon Bridge 300 is composed of a total of 190m 6-lane reciprocating two lanes and is composed of a steel box girder (390) and a PC beam (380). to be. Among these, the steel box girder section 390 is divided into 100m 3 spans and the PC beam 380 is divided into 3m spans of 90m. This experiment was performed in the steel box girder 390 section and all steels such as the web 330, the upper flange 310 and the lower flange 320 of the steel box was used SWS41 (SM400) steel having a thickness of 10mm. In order to reproduce the state of public use, while driving the vehicle, the halfway web (330h) and the lower flange (320h) of the 190m long span steel box section were cut to 1000 × 300mm and weld grooves were formed. Repair reinforcement material (not shown) was welded to this cut part, and also in the quarter point, the web 330q was cut to 1000 × 300 mm size and repaired by repairing reinforcement material (not shown) as in the 1/2 point. The maintenance reinforcement was made of SM490 steel, and the thickness was set to 10mm as the cut part.

Cutting was performed using gas cutting, and as shown in FIG. 11, after cutting the web 330h of the one-half point 1/2 point, the lower flange 320h was cut and one-span after a series of repair welding operations were completed. The damaged portion was cut in the order of cutting the web 330q at the quarter point. In this experiment, we tried to maintain the constant cutting and welding speed as much as possible. Cutting was performed under the following conditions. The web and lower flanges were preheated at 850-900 ° C. for about 10 seconds prior to cutting, and then cut at the speed and width shown in Table 4.

location order Cutting speed v (mm / min) Web flange Lane 2 1/2 (14m) One 92 Lane 2 1/2 (14m) 2 118 1 st lane 1/4 (7 m) 3 98

                    Table 4. Cutting Conditions

Welding was performed using FCAW (Flux Cored Arc Welding) and welded the cut portion of the lower flange (320h) of 1/2 point of the interval using a repair reinforcement and then the cut portion of the web (330h). In addition, in the quarter point 1 span, repair welding was performed using the reinforcement materials in the same manner as in the case of the half point web of the 1 span. In the same manner as in the case of cutting, it was intended to maintain a constant welding speed and heat input as much as possible. Welding was performed under the conditions of Table 5 below. In this experiment, the lower flange and the web were welded in three passes with the heat input Q = 2800 (J / mm ² ) and the welding speed v = (1mm / sec). And the angle of the welding groove was formed at 30˚ and the butt repair welding. Detailed welding conditions are shown in Table 5 below.

Lower Flange Web Welding speed v (mm / sec) 1 pass 1.31 0.74 2 Pass 1.25 0.65 3 Pass 1.71 0.95 Current (A) 240 240 Voltage (V) 40 35 Average heat input amount (J / mm) 2880 2770

                    Table 5. Welding Conditions

This experiment was divided into static load test and live load test. In the static load test, 43.2 tf was loaded by truck and loaded at 1/2 (14m) and 1/4 (7m) of one and two lanes, respectively. As for the load type, 43.2tf was loaded like the static load in the one-lane two-lane section. To be more specific, the dump truck was operated to implement the live load by carrying the live load during the experiment, and the static load (dump truck) was loaded to compare the results with the stress and displacement characteristics under the static load. The resulting stress and strain were measured.

On the other hand, the construction method implemented is summarized as follows. In order to confirm the safety of the allowable live load of the bridge due to section loss during cutting, the most vulnerable part of the load capacity was selected. The cross section corresponding to the web (7 m point, 330q) of the selected portion is cut. Steel box girders 390 are difficult to join reinforcement materials by minimizing the cutting width that can be compared with the size of the heat source, that is, the nozzle size, when the amount of energy or the same energy input to the cutting surface is a factor that governs the cutting property during cutting. ), Excessive deformation and rapid stiffness decline were prevented. In addition, the cross section corresponding to the lower flange (14m point, 320p) of the web (14m point, 330p) is cut. In this case too, pay attention to the same matters as before. The cross section is arranged by gouging or grinding, and a welding groove of about 30˚ is formed in the reinforcement reinforcement and the existing girder for joining. In this case also try to suppress the deformation caused by the action of additional heat as much as possible. The cut lower flanges of 7m and 14m are replaced and welded with the reinforcement of the same shape. In this case, welding is performed after the tack welding to smoothly weld and prevent deformation between the reinforcing reinforcement and the existing girder and replace and weld the web (330p) of 14m point with the reinforcing reinforcement (not shown). In this case, tack welding is used at the bottom of the joint surface for complete penetration and ease of work. In this case, care should be taken to avoid excessive deformation of the repair reinforcement being welded in the direction perpendicular to the principal.

In this experiment, the experimental results were measured mainly on the stress change and deflection by cutting and welding in the state of common use for the steel box girder 390. Fig. 12 is a diagram showing the arrangement of strain gauges provided for measuring the stress behavior of the damaged part. As shown in FIG. 12, principal and principal perpendicular stresses were measured along the cutting line of the reinforcement weld face for the web of bridges 1/4 (7m) and 1/2 (14m) and repaired. The stress at the position 400 mm away from the cutting line of the weld surface was measured. The stresses of the lower flanges of the 1/4 (7m) and 1/2 (14m) points were divided into the upper and lower surfaces, respectively, and the stresses in the principal direction and the principal perpendicular direction were measured. In addition, in order to understand the effect of the sharp deformation near the cutting surface and the deflection of the structure due to welding, the deflection measuring device (LVDT) was installed at the bottom of the lower flanges 320h and 320q near the cutting surface to measure the real-time deflection amount. The experimental results are shown in FIG. FIG. 13 is a graph showing the behavior characteristics of the steel bridges shown in the field experiment of FIG. 9, FIG. 13A is a graph showing the deflection deformation amount at 7 m point, FIG. 13B is a graph showing the deflection deformation amount at 14 m point, and FIG. 13C is Fig. 13d is a graph showing the axial stress behavior of the 14m point web, FIG. 13e is a graph showing the axial stress behavior of the 14m point flange, and FIG. 13e is a graph of the principal direction stress behavior of the 14m point web, and FIG. 13f is 14m. This is a graph showing the principal stress behavior of the lower flange.

As a result of the experiment, as shown in FIGS. 13A and 13B, sagging displacement occurred up to about 2.9 mm when cutting the web 330q in common at the second lane 1/4 (7m), but the residual rise after the welding operation was completed. The amount of was increasing significantly. Also, at the 2nd lane 1/2 (14m), the deflection displacement of up to about 5.4 mm occurred when the web (330h) and the lower flange (320h) were cut, which is also the same as the 2nd lane 1/4 (7m) welding After this was completed the yield of its residual rises increased significantly. Therefore, it was found that the sag (41.8mm) value in the road bridge specification was satisfied in a series of repair and reinforcement works during public use, and the stability of deflection displacement could be secured by applying the reinforcement reinforcement method by new plate replacement in public use.

13C to 13F show changes in stress distribution, which is a result of experiments performed by the steel bridge repair reinforcing method according to the present invention at the 1/2 point of the second lane. Among the stresses in the axial direction (x direction) and the principal direction (y) of the web and flange, the maximum stress was about 120 MPa in the x direction when cutting the flange, and the average stress value in other parts was 20-40 MPa. It could be seen that. These experimental results verify the safety and reliability of the steel bridge repair reinforcement method according to the present invention with the stress distribution within the allowable stress (140MPa). The allowable stresses of the welds on the road bridge specifications are shown in Table 6 below.

River bell SM400 SMA400 SM490 SM490 , SMA490 SM520 SM570 SMA570 Steel plate thickness ( mm ) 40 or less More than 40 100 or less 40 or less More than 40 100 or less 40 or less More than 40 75 or less Over 75 100 or less 40 or less More than 40 75 or less Over 75 100 or less ball chapter for Fold I'm only if for mouth home for Fold compression Stress 140 130 190 175 (190) ^note) 210 200 (210) ^weeks) 195 (210) ^weeks) 260 250 (260) ^weeks) 245 (260) ^Note) Seal Stress 140 130 190 175 (190) ^note) 210 200 (210) ^weeks) 195 (210) ^weeks) 260 250 (260) ^weeks) 245 (260) ^Note) shear Stress 80 75 110 100 (190) ^weeks) 120 115 (120) ^Note) 110 (120) ^Note) 150 145 (150) ^Note) 140 (150) ^Note) Fillet Welding , Partial penetration Home Welding shear Stress 80 75 110 100 (190) ^weeks) 120 115 (120) ^Note) 110 (120) ^Note) 150 145 (150) ^Note) 140 (150) ^Note) Spot welding When quality similar to factory welding cannot be obtained, it shall be said to 90% of the above. Note) For TMC steels, the value of () applies.

                         Table 6. Allowable Stress in Weld (MPa)

In order to verify the effectiveness, field applicability, and safety of the steel bridge repair reinforcement method (M100) according to the preferred embodiment of the present invention, as a result of experiments on the model bridge and the actual bridge, the damage of the steel bridge in common The safety of repairing and reinforcing steel bridges by cutting and welding parts and the safety of bridges after repairing and reinforcing were confirmed.

In particular, the safety and reliability of the steel bridge repair reinforcement method (M100) according to the present invention was clearly verified through experiments carried out under load conditions for Seohwacheon Bridge, which is scheduled to be closed.

As described above, the steel bridge repair reinforcing method according to the present invention has the advantage that it is very economical because it can be repaired and reinforced in a short time in a short time due to the aging or large damage degree.

In addition, in one embodiment of the present invention can be reinforcement in the common state that does not control the traffic of the damaged steel bridge is very advantageous in transportation and economic, and the safety of the bridge during the reinforcement as well as during the construction process is ensured .

Claims (8)

Repair and reinforcement method of steel bridge including girders made of steel, Cutting to form a cut by cutting the damaged portion of the girder in a predetermined shape; Reinforcing material preparation step of manufacturing a reinforcing reinforcement made of steel (鋼材) to the same shape as the cut portion; When the reinforcing reinforcement is placed in the cutting section of the girder, the welding groove for welding is formed in a portion where the cut surface of the girder and the cross section of the reinforcing reinforcement are in contact with each other, but the welding groove is formed in at least one of the reinforcement and the girder Groove forming step; And And arranging the repair stiffener to the cut portion of the girder and welding the repair stiffener to the girder along the welding groove. When performing the cutting step and the welding step of the common use of the steel bridge further comprises a safety evaluation step of determining whether the safety of the steel bridge before the cutting step by the common load capacity formula, The common load capacity determination formula P '= P × K _s × K _r × K _t × K _o × K _H , where P is the basic load capacity, P = 24 × (σ _a -σ _d ) / σ ₂₄ , σ _a Is the allowable stress, σ _d is the dead load stress, σ ₂₄ is the stress due to the DB-24 load, K _s is the correction factor for stress, K _r is the correction factor for road conditions, and K _t is the correction factor for traffic conditions. , K _o is the correction factor for other conditions, K _H is the correction coefficient for heat input, If the common load capacity of the steel bridges of the public bridges obtained by the common load capacity formula is more than the safety standard value in the standard specification, the steel bridges are repaired and reinforced. The correction coefficient K _H according to the heat input range is 0.65 ≤ K _H ≤ 0.75 steel bridge repair reinforcement method characterized in that. The method of claim 1, The cutting step and the welding step is a steel bridge repair reinforcement method, characterized in that performed during the common use of the bridge (교 用). delete delete The method of claim 1, The girder has a web and a flange intersecting with each other, In the cutting step, the steel bridge repair method, characterized in that first cutting the web of the girder and then cutting the flange. The method of claim 1, The girder has a web and a flange intersecting with each other, In the cutting step, cutting the web and the flange of the girder, In the reinforcing material preparation step, a web repair reinforcement corresponding to the web cut in the cutting step and a flange repair reinforcement corresponding to the cut flange are respectively provided, In the welding step, the steel bridge repair method characterized in that after welding the flange repair stiffener welds the web repair stiffener. The method of claim 1, Before the welding step, steel bridge repair method characterized in that it further comprises a tack welding step of tack welding the repair reinforcement (cut welding) on the cut surface of the girder. The method of claim 1, After the welding step, the steel bridge repair method characterized in that it further comprises an inspection step for inspecting the weld defects of the welded portion through a non-destructive test including a radiographic test and an ultrasonic flaw test.

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