Design method for reinforcing joints of tensile members and joints of tensile members

Abstract

A method for designing a stiffener plate to be bonded to a tension member bolted joint is provided. The method involves inputting the member size, bolt diameter, and number of bolts into a computer input device, and the calculation unit calculates the strength fulfillment rate S of the bolted joint from database DB1 in the storage device. If S≧1.0, reinforcement is not required and the calculation ends. If S<1.0, reinforcement is required, and the calculation is completed. B and the required strength deficiency T S Relative to T B / T S The minimum plate thickness t that satisfies the requirement of >1.0 is determined, and the peel strength T is calculated from the database DB3 for the plate length L of the reinforced plate with the minimum plate thickness t and no inclined tip. A Calculate the required strength T un Relative to T A / T un If ≧1.0, the calculation ends with the plate length L determined, and T A / T un When <1.0, the peel strength T for the plate length L of the reinforced plate with a sloped tip is calculated from the database DB4. A Calculate and T A / T un In the case of a slope shape of ≧ 1.0, determine the plate length L and T A / T un If it is <1.0, adhesive reinforcement is not possible and the calculation ends.

Description

[Technical Field]

[0001] The present invention relates to a design method for reinforcing bolted joints of tensile members, which are often used as bracing members in transmission towers, communication towers, or substations (hereinafter referred to as "towers, etc."), or as bracing members in steel-framed buildings such as steel-framed gymnasiums, using adhesive, and to adhesively reinforced joints. [Background technology]

[0002] While open-section steel members such as angle steel, channel steel, or flat steel are sometimes used as tension members, in the bolted joints of these members, for example, in the case of angle members, if only one flange is attached to the mating material, when calculating the tensile strength of the bolted joint, not only is the cross-sectional loss due to the bolt holes considered, but a portion of the cross-section of the other flange, which becomes a protruding leg, is considered to be ineffective in terms of stress transmission. This portion is deducted in proportion to the number of bolts, so the effective cross-sectional area becomes considerably smaller than that of the member's shaft. Therefore, it is known that the tension member is prone to fracture at the bolt hole location before the entire cross-section of the shaft yields in tensile strength (below the elastic limit).

[0003] In the case of tensile bracing members used in steel-framed buildings such as steel-framed gymnasiums, the required strength T must be such that the entire cross-section of the axial portion does not fracture at the bolt hole location or the bolt shaft before tensile yielding. un Tensile strength T of the bolted joint e It is required that the load-bearing capacity connection conditions in Equation 1 below be met. T e ≧T un =α×A g ×F(α: safety factor 1.2, A g : Total cross-sectional area of ​​the member shaft, F: Yield strength of the material) ... Equation 1

[0004] In steel towers and similar structures, both the column members and the web members are often made of angle members, and the connection between the column members and the web members is generally made by bearing connections using bolts. The web members, like the tensile bracing members, transmit the shear force acting on the structure through tensile resistance, but conventionally, it has not been required that the connection of the web members satisfy the conditions of Equation 1 above. However, if the connection breaks before the tensile resistance of the axial portion of the web member is fully exerted, there is a high risk that the structure will not be able to adequately resist external forces such as earthquakes, even if the column members are sound.

[0005] Furthermore, with approximately 250,000 power transmission towers existing nationwide, the need for structural safety verification is increasing. When considering screening these vast number of towers for reinforcement needs, the presence of members with pre-existing joint failures makes performance evaluation inefficient. Therefore, it would be practically beneficial to assume that bolted joints of easily fractured bracing members are reinforced.

[0006] Furthermore, if existing steel towers or similar structures contain members with insufficient strength, measures such as replacing those members are usually taken. However, even in the case of bracing members where the tensile strength of the shaft cannot be fully exerted due to cross-sectional defects at the bolted joints, if the bolted joints can be easily reinforced, there is a significant advantage in that the need to replace the members is eliminated.

[0007] On the other hand, in steel-framed buildings such as gymnasiums, where open-section steel members such as angle steel, channel steel, or flat steel are often used, the bolted connections of bracing members are required to satisfy the load-bearing capacity connection conditions (Equation 1) as described above. However, bracing members in older steel-framed buildings constructed before the so-called New Seismic Design Law came into effect often do not meet these conditions and are therefore prone to tensile fracture.

[0008] Therefore, reinforcement of the bracing members is necessary when designing for seismic reinforcement. However, unlike newly constructed buildings, in the case of older existing buildings, it is often difficult to reinforce them because it is not possible to weld to the bolted joints of the bracing members or to attach reinforcing members with bolts. If it were possible to reinforce the joints in a simple way while leaving the existing bracing members in place, it would contribute to promoting seismic reinforcement of older existing buildings.

[0009] Regarding the reinforcement of joints in members subjected to tension, reinforcement methods using adhesives have been studied in recent years, for example, as seen in Patent Documents 1-2 and Non-Patent Documents 1-4.

[0010] Patent Document 1 discloses a reinforcing laminate material for reinforcing a structure, which is used to reinforce a structure by adhering to and integrating it with the reinforced surface of the structure, and is characterized by comprising a fiber-reinforced composite material, a high-elongation elastic resin layer formed on the side of the fiber-reinforced composite material that is adhered to the structure, and an intermediate resin layer disposed between the fiber-reinforced composite material and the high-elongation elastic resin layer.

[0011] Patent Document 2 discloses a backing plate used to reinforce a base material or to connect two or more base materials by being bonded to the base material with an adhesive, characterized in that a thin-walled portion is provided at the end of the main body of one backing plate, and the thin-walled portion is thin on the side that is bonded to the base material, from the end surface side.

[0012] Non-patent document 1 introduces previous research on joint reinforcement, which involves using FRP (fiber-reinforced plastic) sheets to bond existing bolt or rivet joints in structures with adhesive.

[0013] Non-patent document 2 states that, regarding a method of repairing and reinforcing steel structures by bonding backing plates, experiments were conducted to clarify the fatigue durability of steel plate joints bonded with epoxy resin, for both steel plates and CFRP (carbon fiber reinforced plastic) plates used as backing plates, and that insights toward establishing a design method for joint reinforcement were obtained.

[0014] Non-patent document 3 describes an analytical study of the stress generated in the adhesive when a single-ply bonded steel sheet is subjected to uniaxial tension, and the results of a uniaxial tensile test of the single-ply bonded steel sheet. It clarifies the stress state, including the stress generated in the adhesive of the single-ply bonded steel sheet, and states that the shear force, normal stress, and energy release rate at the time of delamination of the plywood can be used to evaluate delamination failure of the bonded surface.

[0015] Furthermore, Non-Patent Document 4 proposes a method to compensate for the insufficient load-bearing capacity of tensile brace joints in steel structures such as school gymnasiums. This method involves attaching a carbon fiber sheet to the joint with an impregnating adhesive resin, and then impregnating and curing the carbon fiber sheet with the impregnating adhesive resin by vacuum resin impregnation molding (VaRTM method) under vacuum.

[0016] Non-patent documents 1 to 3 concern the evaluation of the mechanical properties and peel failure of adhesive joints between plates bonded together with adhesive. While these may be useful as references when individually evaluating the load-bearing capacity of adhesively reinforced bolted joints of tensile members targeted by the present invention, they do not describe or suggest any useful technical information for efficiently reinforcing the enormous number of bracing members of the approximately 250,000 power transmission towers currently existing throughout Japan.

[0017] Furthermore, Non-Patent Document 4 describes a new method for adhesively reinforcing bolted joints of tensile brace members in steel structures. However, this method involves extending a carbon fiber sheet, which is the reinforcing material, not only to the bolted joints at the ends of the brace members but also to the gusset plates, covering the carbon fiber sheet with auxiliary materials for the VaRTM method, and then creating a vacuum to impregnate it with an impregnation adhesive resin. This method requires equipment such as a vacuum pump and its power supply, and therefore cannot be said to be suitable for high-altitude outdoor work environments such as steel towers. [Prior art documents] [Patent Documents]

[0018] [Patent Document 1] Japanese Patent Publication No. 2019-150953 [Patent Document 2] Japanese Patent Publication No. 2018-071310 [Non-patent literature]

[0019] [Non-Patent Document 1] Composite Structure Committee, Research Subcommittee on Joining Methods for FRP and Steel, "Advanced Technologies for Joining FRP Members and Adhesive Joining of Steel and FRP," 2014, Journal of Japan Society of Civil Engineers, Series A1 (Structural and Earthquake Engineering), Vol. 70, No. 5, pp. II_120-II_133. [Non-Patent Document 2] Thai Wisal, Kazufumi Nakamura, Ho Hayashi, and Hisakazu Horii, "Evaluation of Fatigue Strength of Adhesive Joints of Steel Plates with Backing Plates Adhered with Epoxy Resin," 2018, Journal of Japan Society of Civil Engineers, Series A1 (Structural and Earthquake Engineering), Vol. 74, No. 5, pp. II_56-II_66. [Non-Patent Document 3] Takeshi Mizutani, Takahiro Sakamoto, Toshiyuki Ishikawa, and Hisakazu Horii, "Mechanical Properties of Single-Sided Bonded Steel Sheet Subjected to Uniaxial Tension," March 2019, Journal of Structural Engineering, Vol. 65A, pp. 755-768. [Non-Patent Document 4] Takahiro Matsui, Kohei Suzuki, Sota Sato, Yuki Kubokawa, Daiki Nakamoto, and Kota Matsumoto, "Reinforcement Method for Steel Structural Brace Joints by VaRTM Forming and Bonding of Carbon Fiber Sheets," October 2021, Journal of the Architectural Institute of Japan, Vol. 27, No. 67, pp. 1279-1284. [Overview of the Initiative] [Problems that the invention aims to solve]

[0020] From the above perspective, the present invention provides a design method for reinforcing bolted joints of tensile members, which are often used as bracing members for steel towers and other structures used in high-altitude outdoor work, and as bracing members for steel-structured buildings such as old steel-framed gymnasiums, by bonding reinforcing plates to them; a design method for reinforcing joints of tensile members that can efficiently determine the dimensions and shape of the reinforcing plates necessary to secure the required load-bearing capacity of the bolted joint; and a joint reinforced using the said reinforcement design method. [Means for solving the problem]

[0021] The solution means of the present invention for solving the above problems is a bonding method for bonding a reinforcing plate to a bolt joint of a tensile member with an adhesive, and is a design method for determining the required cross-sectional dimension and required length of the reinforcing plate, (Step 1) The member size of the tensile member to be reinforced and the bolt shaft diameter and number of bolts of the bolt joint of the tensile member are input by the input device of the computer. (Step 2) Based on the information of the tensile member input in Step 1, the arithmetic unit of the computer searches the list in the database stored in the storage device of the computer, and the tensile strength T of the bolt joint of the tensile member e and the required strength T of the bolt joint set as a predetermined value that exceeds a certain ratio of the tensile yield axial force of the shaft portion of the tensile member un and the ratio T of e / T un The strength adequacy ratio S of the bolt joint of the tensile member defined by is calculated.

[0022] (Step 3a) The value of the strength adequacy ratio S calculated in Step 2 is automatically determined by the arithmetic unit of the computer. When S≧1.0, it is determined that the bolt joint of the tensile member does not require reinforcement, and the calculation is terminated. (Step 3b) The By the computer's arithmetic unit automatic determination done If the result is S<1.0, proceed to Step 4. (Step 4) A reinforcing plate for reinforcing the bolt joint having a plate width set according to the member size of the tensile member to be reinforced, with the necessary condition: T B / T S >1.0 {where T B : reinforcing plate strength, T S : insufficient required strength = (1 - S)×T un}, the plate thickness of candidates are searched and selected from the list in the database stored in the storage device by the arithmetic unit of the computer. (Step 5) Among the plate thickness of candidates of the reinforcing plate searched in Step 4, the one with the minimum of plate thickness is determined.

[0023] (Step 6) The minimum determined in Step 5 of When a reinforcing plate of a predetermined length, having a plate thickness and no tapered or stepped inclined portion at its tip, is bonded to the bolt joint with adhesive, the peel resistance T is determined by the peeling of the adhesive near the tip of the reinforcing plate when a tensile axial force acts on the bolt joint. A However, the computer's arithmetic unit searches for it from the list in the database stored in the memory device. (Step 7a) The peel resistance T found A is a sufficient condition: T A / T un If the condition ≥ 1.0 is satisfied, it is determined that the required length for the reinforcing plate is sufficient, and the calculation is terminated. (Step 7b)T A / T un If the value is <1.0, proceed to step 8.

[0024] (Step 8) Step 7b T A / T un In the case where <1.0, the above necessary condition: T B / T S The above satisfying >1.0 Reinforcement plate When a reinforcing plate of a predetermined length, having a plate thickness and a tapered or stepped inclined portion at its tip, is bonded to the bolted joint of the tension member with adhesive, the peel resistance T is determined by the peeling of the adhesive near the inclined tip of the reinforcing plate when a tensile axial force acts on the bolted joint. A However, the computer's arithmetic unit searches for it from the list in the database stored in the memory device. (Procedure 9a) The peel resistance T found A is a sufficient condition: T A / T un If the condition ≥ 1.0 is satisfied, it is determined that the required length for the reinforcing plate is sufficient, and the calculation is terminated. (Step 9b)T A / T unIf the result is <1.0, it is determined that adhesive reinforcement with a reinforcing plate is not possible for the bolted joint of the tensile member, and the calculation is terminated. This is a method for designing reinforcement for joints of tensile members, characterized by including the above steps.

[0025] Furthermore, in the method for designing reinforcement of the joint of the tensile member according to the present invention, the database stored in the storage device of the computer is a database that reinforces bolt joints corresponding to each of the member sizes within the range used for the tensile member. The aforementioned Reinforcement plate Plate thickness and plate length A list of various numerical values ​​necessary for determining dimensions and shapes, "(DB1) Strength sufficiency ratio S of bolted joints in tensile members", "(DB2) Thickness t of the reinforcing plate (when S < 1.0)", "(DB3) Reinforcement plate (without inclined section): plate length L and peel resistance T" A (Requirement: T B / T S >1.0)」, "(DB4) Reinforcement plate (with inclined section): Plate length L and peel resistance T" A (Requirement: T B / T S >1.0)」, It consists of the above databases 1 to 4, The first database contains the tensile strength Te at the effective cross-section or bolt shaft fracture at the bolt hole position of the bolted joint of the tensile member to be reinforced, and the required strength T of the bolted joint. un Therefore, the bolt joint The required load capacity T in the above-mentioned case un against The strength sufficiency ratio S = T represents the excess or deficiency of strength. e / T un The defined indicators are listed for each member size within the range used for tensile members.

[0026] The second database contains the required load-bearing capacity T for the bolted joint for all member sizes where the load-bearing capacity sufficiency ratio S < 1.0. unThis is for selecting the plate thickness t of the reinforcing plate necessary to compensate for the insufficient load-bearing capacity against, and the load-bearing capacity T of the reinforcing plate at the bolt hole position of the reinforcing plate in the effective cross-section. B And the aforementioned required load-bearing capacity T un The difference in required load-bearing capacity T S T B / T S However, this is a list categorized by member size within the range of members used in tensile members.

[0027] The third database is the ratio T B / T S Plate thickness satisfying >1.0 t The reinforcing plate, which does not have a tapered or stepped inclined portion at its tip, has a predetermined plate length L In contrast, the peeling resistance T of the reinforcing plate is the limit at which peeling occurs at the tip of the reinforcing plate. A The required yield strength T is calculated by stress analysis. un For each size of the tensile member to be reinforced, T A / T un The results of determining whether the value is <1.0 have been organized and listed.

[0028] The fourth database is the T A / T un The length of the reinforcing plate is <1.0 L The peel resistance T of the reinforcing plate when a tapered or stepped inclined portion is attached to the tip of the reinforcing plate is as follows: A This is calculated by stress analysis, and the aforementioned T A / T un The results of determining whether the value is ≥ 1.0 have been organized and listed. This is a design method for reinforcing joints of tensile members, characterized by the following:

[0029] In the first database described above, the effective cross-section of the bolted joint of the tensile member to be reinforced is mainly the cross-section perpendicular to the member axis at the bolt hole position, but the tensile strength T depends on the dimension of the gap from the bolt hole position at the bolted joint. e In some cases, this is determined by the fracture of the bolt shaft, which reduces the tensile strength T.e It is possible that this may be decided.

[0030] In the second database, the reinforcing plate load capacity T of the effective cross-section at the bolt hole positions of the reinforcing plate in which bolt holes are drilled. B And the required joint strength T un The difference in required load-bearing capacity T S T B / T S Regarding T B / T S A plate thickness that satisfies >1.0 is a necessary condition for selection as a candidate for a reinforcing plate.

[0031] For example, let's consider the case shown in Figure 1, where an angle member 1 is joined to a gusset plate 2 by two bolts 3a and 3b, and a reinforcing plate 4 is bonded to it with adhesive 5. In this case, the cross section at which the angle member 1 is at risk of fracture due to tensile force P is the position of the through-hole of the first bolt, bolt 3a, i.e., the r-r cross section in Figure 1. However, the effective cross-sectional area of ​​the angle member 1 joined by two bolts 3a and 3b against tension is considered to be the remainder (the shaded area in the r-r cross section) obtained by subtracting 70% of the height h of the protruding piece of the angle member 1 and the cross-sectional area at the through-hole of bolt 3a from the total cross-sectional area of ​​the member shaft.

[0032] In other words, since it is considerably smaller than the total cross-sectional area of ​​the shaft portion of the angle member 1, in order to satisfy the conditions of equation 1, the effective cross-sectional area of ​​the reinforcing plate 4 must be sufficient to satisfy them. That is, the plate width b of the reinforcing plate 4 is limited because it is constrained by the inner surface dimensions of the flange of the angle member 1, so in order to secure the effective cross-sectional area of ​​the reinforcing plate 4, it is necessary to have a plate thickness that is sufficient even after deducting the cross-sectional loss due to the bolt holes made in the reinforcing plate 4.

[0033] In the third database, stress analysis is performed on a pre-set plate length of the reinforcing plate of the aforementioned plate thickness, which is a candidate selected in the second database, assuming that there is no tapered or stepped inclined portion at the tip of the reinforcing plate, and the peel resistance T of the reinforcing plate is determined. A The calculated results have been organized and listed.

[0034] When a tensile member is pulled while the reinforcing plate is bonded with adhesive to the bolted joint of the tensile member to be reinforced, the adhesive is subjected to shear stress within its bonding surface and simultaneously to tensile stress out of the bonding surface that attempts to peel off the reinforcing plate (hereinafter referred to as peel stress). However, in the case of a reinforcing plate that does not have a tapered or stepped inclined portion at its tip, the peel stress increases sharply near the end of the tip of the reinforcing plate on the shaft side of the tensile member. Therefore, it is known that when the peel stress reaches its limit, the tip of the reinforcing plate peels off, limiting the maximum load-bearing capacity of the tensile member joint.

[0035] As illustrated in Figure 1, the cross-sectional shape of the angle member 1, which is formed by bonding the reinforcing plate 4 with adhesive 5, changes abruptly at the tip 4a of the reinforcing plate 4. Therefore, as shown in Figure 2, the adhesive layer of adhesive 5 has shear stress τ within the bonding surface and peel stress (normal stress) σ perpendicular to the bonding surface that tries to peel the reinforcing plate 4 off. t This acts. And the peeling stress σ t Furthermore, the magnitude of the shear stress τ increases rapidly as it approaches the tip portion 4a of the reinforcing plate 4. Therefore, the peel resistance T is the limit at which peeling occurs at the tip portion 4a before the tensile force P reaches an axial force value sufficient to satisfy equation 1. A It could reach that point.

[0036] In other words, when the tension member 1 is bonded and reinforced with a reinforcing plate 4, the bonding area increases up to a certain length of the reinforcing plate 4, thus increasing the peel resistance T of the reinforcing plate. A The value increases, but then levels off around the aforementioned certain length. This phenomenon will be illustrated in the description of the embodiments below, but to the best of the inventor's knowledge, this is the first time it has been analytically verified in a concrete example.

[0037] Therefore, the third database has the following requirement: T B / T S For the reinforcing plate having a thickness satisfying >1.0, the peel resistance T is given to the set plate length. A The required load-bearing capacity T unWhether or not it reaches is calculated by stress analysis such as FEM analysis, and T for each size of the tensile member to be reinforced. A / T un The results of determining whether the value is <1.0 have been organized and listed.

[0038] The fourth database is T in the third database. A / T un When the length of the reinforcing plate is set to a certain length or longer than <1.0, and a tapered or stepped inclined portion is attached to the tip of the reinforcing plate, the peel resistance T A This is calculated by stress analysis such as FEM analysis, and T is calculated for each size of the tensile member to be reinforced. A / T un The results of determining whether the value is ≥ 1.0 have been organized and listed.

[0039] As described above, in the case of a reinforcing plate without an inclined portion at the tip, even if the plate length is increased beyond a certain limit, the peel resistance T of the reinforcing plate remains unchanged. A Although this will eventually plateau, if a tapered or stepped inclined portion is added to the tip of the reinforcing plate on the shaft side of the tension member, the abrupt change in the cross-sectional shape at the tip of the reinforcing plate, where the cross-section switches from the shaft portion of the tension member to the thickened joint portion due to the splicing of the reinforcing plate, can be mitigated, and the peel stress near the tip of the reinforcing plate can be considerably reduced, thereby lowering the peel resistance T of the reinforcing plate. A It is known that this can increase even further.

[0040] Furthermore, the peel resistance T of the reinforcing plate depends on the shape of the inclined portion attached to the tip of the reinforcing plate. A The effect on the tapered inclined portion will be explained in the description of the embodiments below, but the peel resistance T A Similar to the verification of the plateauing phenomenon in load-bearing capacity, this is the result of the inventor's parametric analysis and examination of specific cases.

[0041] The present invention also relates to a bolt joint of a tension member, wherein a reinforcing plate for reinforcing the bolt joint of the tension member, which is determined based on various numerical values regarding the reinforcing plates for different sizes of the tension member previously stored in a database by the joint reinforcement design method of the tension member of the present invention, is adhered to the bolt joint of the tension member with an adhesive. This is the joint of the tension member.

[0042] Taking, as an example, the bolt joint of the tension member 1 reinforced by adhering the reinforcing plate 4 shown in FIG. 1, the required cross-sectional dimensions (plate thickness t and plate width b) of the reinforcing plate 4 are the reinforcing plate strength T of the effective cross-section at the bolt hole position of the reinforcing plate 4 where the bolt hole is formed B and the required joint strength T un of the bolt joint, and the insufficient required strength T S with respect to T. The ratio T B / T S Regarding this, the necessary condition: T B / T S > 1.0 can be easily obtained as a numerical value that satisfies this. However, the tensile stress of the insufficient required strength T S is transmitted from the tension member 1 to the reinforcing plate 4 by the shear stress τ acting on the adhesive layer of the adhesive 5. Therefore, next, it is necessary to obtain the peeling strength T A of the reinforcing plate that can hold the shear stress τ.

[0043] The peeling strength T A sharply increases as it approaches the tip 4a of the reinforcing plate 4 and is about to peel off the reinforcing plate 4. The peeling stress (vertical stress) σ t (see FIG. 2), the length L of the reinforcing plate 4, and the shape of the tip 4a of the reinforcing plate 4 are determined by the correlation relationship. It is important to note that

[0044] That is, as described above, the peeling strength T A reaches a peak when the reinforcing plate 4 reaches a certain length, and moreover, it changes depending on the shape of the tip 4a. Therefore, to determine the dimensions and shape of the reinforcing plate 4, set the plate thickness t and plate width b, and regarding the assumed length L, or regarding the length L and the shape of the tip 4a, repeatedly perform trial and error calculations to see if the required peeling strength T A can be obtained. This is the peeling strength TA This becomes an essential condition in the process of obtaining it.

[0045] Furthermore, in practice, it is impractical to perform trial-and-error calculations for each of the numerous and diverse types of bolted joints. Therefore, it is extremely rational to create a database of numerical values ​​related to reinforcing plates for each tensile member size in advance and utilize it with a computer. Thus, the configuration of the joint of a tensile member bonded and reinforced with the reinforcing plate according to the present invention can only be achieved through the joint reinforcement design method according to the present invention.

[0046] Furthermore, the reinforcing plate can be made of any material that can be effectively reinforced with adhesive, such as steel or fiber-reinforced plastic (FRP). [Effects of the Invention]

[0047] Since the present invention is a computer-aided design method for reinforcing joints of tensile members using the procedure described above, it has the following effects. 1) For example, in reinforcement work for power transmission towers, the work is often carried out outdoors in mountainous areas and at high altitudes. Therefore, the method of reinforcing the joints of the tower's bracing members must be as simple and reliable as possible. A method of bonding reinforcing plates such as steel plates in combination with bolt joints is considered suitable. However, there is a problem that the strength of the joint after reinforcement is limited by delamination of the adhesive surface, which is characteristic of adhesive methods. The present invention addresses this problem from a design perspective of adhesive reinforcement and provides a computer-aided design method that can streamline the process of determining the dimensions and shape of the reinforcing plates necessary to secure the required strength at the joint.

[0048] 2) When considering the need for reinforcement of the approximately 250,000 power transmission towers currently existing throughout Japan, it would be efficient and practically beneficial to evaluate the strength of the towers if it could be assumed that the bolted joints of the easily fractured bracing members are reinforced. The present invention is a useful design method that can contribute to the widespread adoption of a simple and effective adhesive reinforcement method for reinforcing the various bolted joints of such bracing members. 3) Furthermore, since the adhesive reinforcement method involves bonding new reinforcing material within the width of the existing member shaft, it requires a certain degree of space. For example, it can be universally applied even in narrow areas where gusset plates cannot be installed. Therefore, the present invention is a design method that contributes to broadening the range of construction method selection when reinforcing steel structures. 4) The widespread adoption of the aforementioned adhesive reinforcement method will lead to a reduction in reinforcement costs and construction time compared to conventional reinforcement methods such as replacement of tensile members used in steel structures, including transmission towers. [Brief explanation of the drawing]

[0049] [Figure 1] This is one specific example of a joint according to the present invention, showing a state in which a reinforcing plate is bonded with adhesive to a bolted joint of an angle member, which is a tension member, where (a) is a plan view, (b) is a cross-sectional view of (a) from I to I, and (c) is a cross-sectional view of (b) from L to L. [Figure 2] This is a schematic diagram illustrating the stress state in the adhesive layer of the adhesive surface of a reinforcing plate bonded to a tension member when the tension member is subjected to a tensile axial force. [Figure 3] This is a flowchart for determining the dimensions and shape of a reinforcing plate necessary for reinforcing a bolted joint of a tension member according to the present invention. [Figure 4] This is a cross-sectional view showing the shape of the tip portion when an inclined portion is provided on the reinforcing plate according to the present invention. [Figure 5] This is an example of FEM analysis results showing the relationship between the peeling resistance (maximum resistance) of a reinforcing plate and the length of the reinforcing plate when the reinforcing plate does not have a sloping section at its tip. [Figure 6] This is an example of FEM analysis results showing the relationship between the peeling resistance (maximum resistance) of a reinforcing plate and the length of the reinforcing plate when it is reinforced with a reinforcing plate that has an inclined tip. [Figure 7] This is an example of an analytical model for examining the effect of the tip shape of the reinforcing plate. (a) describes the parameters that define the tip shape in the case without a taper, (b) describes the parameters that define the tip shape in the case with a taper, and (c) is a table of combinations of each parameter. [Modes for carrying out the invention]

[0050] As an embodiment of the present invention, in the case where an angle member 1 as shown in Figure 1 is adhesively reinforced with a reinforcing plate 4, the procedure for determining the dimensions and shape of the reinforcing plate required to reinforce the bolted joint of the tension member will be explained with reference to Figures 3 to 7 and Tables 1 to 5.

[0051] Furthermore, the present invention is not limited to angle members; channel steel and flat steel, which are commonly used as bracing members in steel structures as tension members, also fall under the scope of the present invention because the way in which the bolted joints break is the same as that of angle members.

[0052] Figure 3 is a flowchart for determining the dimensions and shape of the reinforcing plate required to reinforce the bolted joint of a tension member. First, the member size of the tension member to be reinforced, the bolt shaft diameter, and the number of bolts used in its bolted joint are input from the computer's input device (Step 1).

[0053] Based on the data input from the input device, the computer's arithmetic unit searches the first database "(DB1) Strength sufficiency ratio S of tensile member bolt joints" stored in the memory device (Step 2).

[0054] Table 1 shows an example of a database (in the case of L-shaped steel) in which the calculation results of the load-bearing capacity sufficiency ratio S of bolted joints calculated for each size of tensile member have been organized and listed.

[0055] [Table 1]

[0056] The first database, as shown in Table 1, shows the tensile strength Te(=A) of the bolted joint before reinforcement. e ×F u , or 0.75 × n × f A× f F u) and the required load-bearing capacity T for the bolted joint. un (=1.2×A g ×F) and the load-bearing capacity sufficiency ratio S(=T) before reinforcement, which was obtained from this. e / T un ) is a list organized by tensile member size. However, A e The effective cross-sectional area of ​​the joint is F. u The tensile strength of the component material, f F u F is the tensile strength of the bolt, and F is the yield strength of the member material.

[0057] Note that although Figure 1 shows two bolts, the effective cross-sectional area A of the bolted joint e Since this varies depending on the number of bolts (for example, the Architectural Institute of Japan's "Design Guidelines for Steel Structure Joints," 2021.2), Table 1 takes this into account and shows the tensile strength T of the bolted joint before reinforcement. e The required strength T is calculated, and also the required strength T un This value is calculated as a value that satisfies equation 1 above.

[0058] Next, if the calculated load-bearing capacity sufficiency ratio S ≥ 1.0 in the calculation device, it is determined that reinforcement of the bolted joint is unnecessary and the calculation is terminated (step 3a). On the other hand, if the load-bearing capacity sufficiency ratio S < 1.0, it is determined that reinforcement is necessary (indicated by * in Table 1), and the process proceeds to step 4 to determine the specifications of the necessary reinforcing plate (step 3b).

[0059] In step 4, the calculation device searches the second database "(DB2) Reinforcement plate thickness t (when S < 1.0)" stored in the memory device.

[0060] Table 2 shows an example of a database (for L-shaped steel) in which the calculation results for the required plate thickness of reinforcing plates when the strength sufficiency ratio S < 1.0 are organized and listed for each size of tensile member.

[0061] [Table 2]

[0062] As shown in Table 2, the second database has the plate width b of the reinforcing plate predetermined for each size of the tensile member, and the reinforcing plate load capacity T at the effective cross-section of the reinforcing plate. B (=A e ×F u ) and the required load-bearing capacity T for bolted joints. un The difference in required load-bearing capacity T S {=(1-S)×T un The values ​​are organized by tensile member size, and the yield strength ratio T B / T S This is a list organized by tension member size. From this list, the yield strength ratio T B / T S Reinforcement plates with a thickness t that satisfy >1.0 (indicated by * in Table 2) are selected as candidates (Step 4).

[0063] From the selected candidates for the reinforcing plate, the one with the minimum plate thickness is determined (step 5), and the process proceeds to step 6 to determine its plate length L. Strength ratio T B / T S Reinforcement plates with a thickness t of ≤1.0 are ignored.

[0064] In step 6, the calculation device calculates the third database "(DB3) Reinforcement plate (without inclined portion) plate length L and peeling resistance T" stored in the memory device. A (Requirement: T B / T S >1.0) is searched (Step 6).

[0065] Table 3 shows the required conditions for each size of the tensile member: T B / T S The plate length L of a reinforcing plate (without inclined section) that satisfies (=reinforcing plate strength / required strength deficit) > 1.0 and the peeling strength T determined by stress analysis. A The results show an example of a well-organized and listed database, displaying only one size of L-shaped steel.

[0066] [Table 3]

[0067] The third database, as shown in Table 3, has the following requirements: yield strength ratio T. B / T S For a reinforcing plate with a minimum plate thickness t determined in step 5 that satisfies >1.0 and has no inclined portion at the tip, the peel strength T of the reinforcing plate determined by adhesive peeling when the plate length L is predetermined is A However, this is a list obtained through stress analysis such as FEM analysis and organized by tensile member size.

[0068] Table 3 shows an example of the case L-45×45×4 obtained by actually performing FEM analysis. In this example, even when the plate length L is increased from 23.5 cm to 53.5 cm, the peeling resistance T of the reinforcing plate remains the same for a plate thickness of 0.6 cm. A It has been shown that it hardly increases.

[0069] Figure 5 shows a graph of the FEM analysis results described above. When a reinforcing plate bonded with an adhesive (e.g., epoxy resin adhesive) is made longer, the bonding area increases, and the peel resistance T of that reinforcing plate... A It can grow larger, but it plateaus after a certain length, and extending it further hardly increases its load-bearing capacity.

[0070] Figure 5 shows a specific example that verifies this. It shows the FEM analysis results when angle members L-45×45×4 are joined with two M16 bolts and reinforced with adhesive using a reinforcing plate with a plate thickness of 0.6 cm and no inclined section, with the vertical axis representing the maximum load-bearing capacity (peel resistance T). A The horizontal axis of the graph shows the length of the reinforcing plate (plate length L). From Figure 5, it can be seen that there is a slight increase in load-bearing capacity when the reinforcing plate length is 335 mm compared to 235 mm, but there is almost no increase in load-bearing capacity beyond that. In other words, there is an upper limit to the plate length L of the reinforcing plate.

[0071] In step 6, the search result from the calculation device is the peel resistance T, which is a sufficient condition for the plate to be an effective reinforcing plate. A and required load-bearing capacity T un The strength ratio T A / T unIf the result is ≥ 1.0, the length L of the reinforcing plate is determined and the calculation is terminated (step 7a).

[0072] Note that, as illustrated in Table 3 for the L-45×45×4 case, the peeling resistance T of the reinforcing plate is as follows. A Since the calculation of this currently relies on methods such as FEM analysis, it is considered practical to pre-calculate the plate length L of the reinforcing material using FEM analysis for several combinations of plate thickness t and plate length L, and then create a database of these results.

[0073] In step 6, the strength ratio T A / T un If the value is <1.0 (indicated by * in Table 3), proceed to step 8 (step 7b).

[0074] In step 8, the calculation device calculates the fourth database "(DB4) Reinforcement plate (with inclined portion) plate length L and peeling resistance T" stored in the memory device. A (Requirement: T B / T S >1.0) is searched (Step 8).

[0075] Tables 4, 5, and Figure 4 show the requirements for each size of the tensile member: T B / T S The plate length L and peel resistance T determined by stress analysis for a reinforcing plate (with an inclined section) that satisfies (=reinforcing plate strength / required strength deficit) > 1.0. A The results are an example of a well-organized and listed database, showing only one size of L-shaped steel.

[0076] [Table 4]

[0077] [Table 5]

[0078] The fourth database, as shown in Table 4, has the following requirement: yield strength ratio T.B / T S The minimum plate thickness t determined in step 5 satisfies >1.0, and the yield strength ratio T in step 6. A / T un In the case of <1.0, as shown in Figure 4, for a reinforcing plate with an inclined portion (in this case, a taper) at the tip, the peel strength T of the reinforcing plate, determined by adhesive peeling when the plate length L is predetermined, is A However, this is a list obtained through FEM analysis and organized by tensile member size.

[0079] Furthermore, the peel resistance T can be maintained even if the plate length L confirmed in step 6 (third database) is made longer. A Since this is an upper limit that does not increase, the pre-set plate length L in step 8 (the fourth database) is set to a value greater than or equal to that upper limit, and in the case where an inclined portion is attached to the tip of the reinforcing plate, the sufficient condition is: yield strength ratio T. A / T un The shape of the inclined portion that satisfies ≥1.0 is searched for.

[0080] Here, the tapered shape of the tip of the reinforcing plate and the peel resistance T A Let's explain an example of examining the relationship. As shown in Figures 7(a) and (b), when the shape of the tip of the reinforcing plate is changed and tapered, even with reinforcing plates of the same thickness and length, the maximum load-bearing capacity (peeling resistance T) is different. A The graph in Figure 6 shows that the value of ) becomes larger.

[0081] Figure 6 shows the results of FEM analysis for each tapered pattern shown in Figure 7(c) for a reinforcing plate with a plate thickness of 0.6 cm, using an angle member L-45×45×4 with two M16 bolts, similar to the case in Figure 5. The vertical axis represents the maximum load-bearing capacity (peeling resistance T). A ), the horizontal axis is the taper length L t and plate thickness t p Ratio L t / t p Reinforcement plate t shown p Its tip thickness t t Comparison with t / t p The cases of =1 / 4, 1 / 3, and 1 / 2 are shown.

[0082] From Figure 6, the ratio t t / t p The smaller the value, the longer the taper L. t Reinforcement plate t p Ratio L t / t p The larger the value, the greater the maximum load-bearing capacity (peeling resistance T). A It can be seen that the strength ratio T increases in step 6. A / T un Even in the case of <1.0, by adding a taper to the tip of the reinforcing plate, the peel resistance T of the reinforcing plate can be increased. A It can be expected to increase.

[0083] Thus, the effect of the tapered shape at the tip of the reinforcing plate is related to the thickness t of the reinforcing plate. p , thickness of the tip t t Taper length L t Since each combination can be calculated using FEM analysis, the peel resistance T of the reinforcing plate, which has been determined in advance for each shape, can be calculated. A However, these can be stored in the memory device as a list organized by the size of the tension member. Needless to say, the same applies when the inclined portion is stepped.

[0084] Therefore, in step 8, the sufficient condition is: strength ratio T. A / T un If ≥1.0 is not satisfied, the calculation device searches the fourth database stored in the storage device for the reinforcing plate with the minimum plate thickness t set in step 5 and having an inclined portion at the tip, and the sufficient condition: yield strength ratio T A / T un Once a shape of the inclined section that satisfies ≥ 1.0 is selected (indicated by * in Table 4), the plate length L of the reinforcing plate is determined, and the calculation is terminated (step 9a).

[0085] In step 8, the strength ratio T A / T unIf the value is <1.0, even if the reinforcing plate has a slanted tip, it is determined that adhesive reinforcement with a reinforcing plate as shown in Figure 1 cannot satisfy the conditions of Equation 1, and the calculation is terminated (step 9b). In this case, another reinforcement method will need to be considered.

[0086] The embodiments of the design method for reinforcing joints of tensile members according to the present invention have been described above. The peel resistance T of the reinforcing plates listed in the third and fourth databases above A Currently, calculating this requires relying on methods such as FEM analysis, but analyzing all possible combinations in advance would be time-consuming and laborious. Therefore, it seems practical to limit the analysis to bolted joints corresponding to commonly used tensile member sizes.

[0087] Furthermore, as shown in Figure 1, the bolt joint to which the reinforcing plate 4 determined by the joint reinforcement design method for tensile members according to the present invention is bonded and reinforced can be completed simply by applying adhesive to the new reinforcing material 4 and tightening the bolts within the width range of the existing angle member 1 axis, resulting in a compact installation and easy on-site construction.

[0088] In other words, it is easy to install even in narrow spaces where reinforcing bolted joints is difficult, and since no large-scale equipment is required, it offers good workability at high outdoor locations such as transmission towers. Of course, it can also be universally applied to existing steel structures other than transmission towers.

[0089] Furthermore, the reinforcing plate can be made of any material that can be effectively reinforced with adhesive, such as steel or fiber-reinforced plastic (FRP). [Industrial applicability]

[0090] The bolt joint reinforcement method using adhesive and the adhesive-reinforced joints covered by this invention do not require the replacement of existing members, thus leading to a reduction in reinforcement costs and construction time. In particular, this will greatly contribute to earthquake-resistant or wind-resistant reinforcement measures for power transmission towers, of which there are a vast number throughout Japan. Furthermore, this invention, which can significantly streamline the design work of bolt joints, is not limited to transmission towers and the like, but can similarly contribute to promoting the reinforcement of other existing steel structures. [Explanation of symbols]

[0091] 1: Angle member 2: Gusset Plate 3a, 3b: Bolts 4: Reinforcement plate 4a:Tip 5: Adhesive h: Height of the protruding piece P: Tensile force τ: Shear stress σ t : Peeling stress (normal stress)

Claims

1. A bonding method for bonding a reinforcing plate to a bolted joint of a tension member using an adhesive, wherein the required cross-sectional dimensions and required length of the reinforcing plate are determined, (Procedure 1) The computer's input device inputs the size of the tensile member to be reinforced, as well as the bolt shaft diameter and number of bolts at the bolted joint of that tensile member. (Procedure 2) Based on the information of the tensile member entered in Procedure 1, the computer's calculation unit searches the list in the database stored in the computer's storage device and determines the tensile strength T of the bolted joint of the tensile member. e The required load-bearing capacity T of the bolted joint is set as a predetermined value that exceeds the tensile yield axial force of the shaft portion of the tension member by a certain percentage. un The ratio T e / T un The strength sufficiency ratio S of the bolted joint of the tensile member, as defined by [formula], is calculated. (Procedure 3a) The numerical value of the strength sufficiency ratio S calculated in Procedure 2 is automatically determined by the computer's calculation device. If S ≥ 1.0, it is determined that reinforcement is not required for the bolted joint of the tensile member, and the calculation is terminated. (Step 3b) If the result automatically determined by the computer's arithmetic unit is S < 1.0, proceed to step 4. Step 4: A reinforcing plate for reinforcing the bolt joint having a plate width set according to the member size of the tensile member to be reinforced, with the requirement: T B / T S > 1.0 {where T B : Reinforcing plate endurance, T S : Insufficient required endurance = (1 - S) × T un} Candidates for the plate thickness of the reinforcing plate that satisfy the above are retrieved and selected by the arithmetic unit of the computer from a list in the database stored in the storage device. (Step 5) From the candidates for the thickness of the reinforcing plate found in Step 4, the one with the smallest thickness is determined. (Procedure 6) When the reinforcing plate, which has the minimum thickness determined in Procedure 5 and a predetermined length without a tapered or stepped inclined portion at its tip, is bonded to the bolt joint with adhesive, the peel resistance T is determined when a tensile axial force acts on the bolt joint and the adhesive near the tip of the reinforcing plate peels off. A However, the computer's arithmetic unit searches for it from the list in the database stored in the memory device. (Procedure 7a) The peel resistance T found A is a sufficient condition: T A / T un If the condition ≥ 1.0 is satisfied, it is determined that the required length for the reinforcing plate is sufficient, and the calculation is terminated. (Step 7b) T A / T un If the result is 1.0, proceed to step 8. (Step 8) T in Step 7b A / T un <If it is 1.0, the above necessary condition: T B / T S > When a reinforcing plate having a thickness of 1.0 and having a tapered or stepped inclined portion at its tip, and a predetermined length of the reinforcing plate is bonded to the bolt joint of the tension member with adhesive, the peel resistance T is determined when a tensile axial force acts on the bolt joint, causing the adhesive near the inclined tip of the reinforcing plate to peel off. A However, the computer's arithmetic unit searches for it from the list in the database stored in the memory device. (Procedure 9a) The peel resistance T found A is a sufficient condition: T A / T un If the condition ≥ 1.0 is satisfied, it is determined that the required length for the reinforcing plate is sufficient, and the calculation is terminated. (Step 9b) T A / T un If the result is <1.0, it is determined that adhesive reinforcement with a reinforcing plate is not possible for the bolted joint of the tension member, and the calculation is terminated. A method for designing reinforcement for joints of tensile members, characterized by including the above steps.

2. In the method for designing reinforcement for a joint of a tensile member according to claim 1, the database stored in the storage device of the computer is a list of various numerical values ​​necessary for determining the dimensions and shape of the plate thickness and plate length of the reinforcing plate that reinforces the bolted joint, corresponding to each member size within the range used for the tensile member, "(DB1) Strength sufficiency ratio S of bolted joints in tensile members", "(DB2) Thickness t of the reinforcing plate (when S < 1.0)", "(DB3) Reinforcement plate (without inclined section): Plate length L and peeling resistance T" A (Required condition: T B / T S >1.0) "(DB4) Reinforcement plate (with inclined section): Plate length L and peel resistance T" A (Required condition: T B / T S >1.0) It consists of the above four databases, The first database contains the tensile strength T at the effective cross-section or bolt shaft portion fracture at the bolt hole position of the bolted joint of the tensile member to be reinforced. e The required load-bearing capacity T for the bolted joint. un Therefore, the strength sufficiency ratio S = T represents the excess or deficiency of the strength in the bolted joint relative to the required strength T un. e / T un The defined indicators are listed for each member size within the range used for tensile members. The second database contains the required load-bearing capacity T for the bolted joint for all member sizes where the load-bearing capacity sufficiency ratio S < 1.

0. un This is for selecting the plate thickness t of the reinforcing plate necessary to compensate for the insufficient load-bearing capacity, and the load-bearing capacity T of the reinforcing plate is the effective cross-sectional area at the bolt hole position of the reinforcing plate. B And the aforementioned required load-bearing capacity T un Ratio of the required load-bearing capacity deficit TS to T B / T S However, this is a list categorized by member size within the range of members used in tensile members. The third database is the ratio T B / T S For a reinforcing plate having a thickness t that satisfies >1.0 and having no tapered or stepped inclined portion at its tip, the peeling resistance T of the reinforcing plate is the limit at which peeling occurs at the tip of the reinforcing plate relative to a predetermined plate length L. A The required yield strength T is calculated by stress analysis. un For each size of the tensile member to be reinforced, T A / T un The results of determining whether the value is <1.0> have been organized and listed. The fourth database is the T A / T un For a plate length L of the reinforcing plate that is <1.0, the peel resistance T of the reinforcing plate when a tapered or stepped inclined portion is attached to the tip of the reinforcing plate. A This is calculated by stress analysis, and the aforementioned T A / T un The results of determining whether the value is ≥ 1.0 have been organized and listed. A method for designing reinforcement for joints of tensile members, characterized by the above.

3. A joint for a tension member, characterized in that, with respect to the bolted joint of the tension member, a reinforcing plate for reinforcing the bolted joint of the tension member, determined based on various numerical values ​​for reinforcing plates for each tension member size that have been previously stored in a database, is bonded to the bolted joint of the tension member with an adhesive, according to the tension member joint reinforcement design method described in claim 1 or 2.

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