Joint reinforcement design method for tension member and joint of tension member

Abstract

To provide a method for designing a reinforcing plate bonded to a tension member bolt joint part.SOLUTION: The method comprises: Inputting a member size, a bolt diameter, and the number of bolts into an input device of a computer; Calculating, by an arithmetic device, a strength sufficiency rate S of a bolt joint portion from a database DB1 in a storage device; In the case of S ≥ 1.0, no reinforcement is required, and the calculation is ended; In the case of S < 1.0, reinforcement is required, and the minimum plate thickness t satisfying the ratio TB / TS > 1.0 of the reinforcing plate yield strength TB to the necessary yield strength shortage TS is determined from the database DB2; Calculating a peel strength TA for a plate length L of a reinforcing plate having a minimum plate thickness t from a DB3 portion of a database and having no tip end inclined portion; When the ratio TA / Tun with respect to the allowable proof stress Tun is 1.0 or more, the calculation ends with the determination of the sheet length L; In the case of TA / Tun < 1.0, the peel strength TA is calculated for the plate length L of the reinforcing plate with the tip end inclined portion from the database DB4; For ramp shapes with TA / Tun ≥ 1.0, determining the plate length L; and, In the case of TA / Tun < 1.0, adhesion reinforcement is impossible, and the calculation is ended.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a design method for adhesively reinforcing bolted joints of tension members, which are often used as braces in the web members of power transmission towers, communication towers, and substation steel structures (hereinafter referred to as steel towers, etc.), or in the bracing of steel structure buildings such as steel-framed gymnasiums, and to an adhesively reinforced joint. [Background technology]

[0002] Open-section steel members such as angle steel, channel steel, and flat steel are sometimes used as tension members. When bolting these members together, for example, in an angle member, where only one flange is attached to the other, the effective cross-sectional area of ​​the bolted joint is calculated by deducting not only the cross-sectional area due to the bolt holes but also a portion of the other flange's cross-section, which forms the protruding leg, from the other flange, as an ineffective stress transmission area. This portion is then deducted in proportion to the number of bolts, resulting in a much smaller effective cross-sectional area than the shaft of the member. Therefore, it is known that the tension member is prone to fracture at the bolt holes before the entire shaft cross-section reaches tensile yield (below the elastic limit).

[0003] In the case of tension braces used in steel structure buildings such as steel-framed gymnasiums, the required strength T is required to prevent the bolt hole position or bolt shaft from breaking before the entire cross section of the shaft yields. un Tensile strength T of bolted joint against e is required to satisfy the joint strength requirement of the following formula 1. T e ≧T un = α × A g ×F(α: safety factor 1.2, A g : total cross-sectional area of ​​the shaft of the member, F: material yield strength)...Equation 1

[0004] In the frames of steel towers and other structures, both the columns and the web members are often constructed with angle members, and the columns and the web members are generally connected by bolt-support joints. The web members, like the tension braces, function to transmit shear forces acting on the frame through tensile resistance, but until now, the joint design of the web members has not been required to satisfy the condition of Equation 1 above. However, if the joint breaks before the axial tensile resistance of the web members is fully exerted, there is a high risk that the columns, even if they are sound, will not be able to adequately resist external forces such as earthquakes.

[0005] Furthermore, there is an increasing need to confirm the structural safety of the approximately 250,000 existing transmission towers across the country. When considering screening the huge number of tower bodies to determine whether they require reinforcement, it would be inefficient to evaluate strength if components that are prone to joint fracture were mixed in, so it would be practically beneficial to be able to assume that the bolt joints of the web members, which are prone to fracture, are reinforced.

[0006] Furthermore, when existing steel towers, etc., contain components with insufficient strength, measures such as replacing those components are usually taken. However, even in the case of web members where the tensile strength of the shaft cannot be fully exerted due to cross-sectional defects at the bolt joints, if the bolt joints can be easily reinforced, there is a significant advantage in that there is no need to replace the components.

[0007] On the other hand, in steel-framed buildings such as steel-framed gymnasiums, which often use open-section steel components such as angle steel, channel steel, or flat steel, the bolt connections of the braces are required to satisfy the required strength connection conditions (Equation 1) as mentioned above. However, the braces of older steel-framed buildings built before the implementation of the so-called New Earthquake-Resistant Design Law often do not satisfy these conditions and are therefore thought to be prone to tensile fracture.

[0008] Therefore, when designing earthquake-resistant reinforcement, it is necessary to reinforce the diagonal braces. However, unlike newly constructed buildings, in the case of old existing buildings, reinforcement is often difficult because it is not possible to weld the bolt joints of the diagonal braces or to attach reinforcing members with bolts. Therefore, if it is possible to reinforce the joints in a simple manner while leaving the existing diagonal braces in place, it will contribute to promoting the earthquake resistance of old existing buildings.

[0009] In recent years, research has been conducted into reinforcement methods using adhesives for reinforcing joints of members subjected to tension, as can be seen in Patent Documents 1-2 and Non-Patent Documents 1-4, for example.

[0010] Patent Document 1 discloses a reinforcing laminate material for a structure that reinforces the structure by adhering and integrating it with the surface of the structure to be reinforced, characterized in that it has a fiber-reinforced composite material, a high-elongation elastic resin layer formed on the surface of the fiber-reinforced composite material that is attached to the structure, and an intermediate resin layer arranged between the fiber-reinforced composite material and the high-elongation elastic resin layer.

[0011] Patent Document 2 discloses a backing plate that is adhered to a base material with an adhesive to reinforce the base material or to connect two or more base materials, characterized in that the end of the main body of one backing plate has a thin-walled portion that is thinner than the thickness of the main body, and the thin-walled portion is thinner from the surface side of the end to the adhesive surface that is adhered to the base material.

[0012] Non-Patent Document 1 introduces previous research into joint reinforcement, in which FRP (fiber reinforced plastic) plates are spliced ​​with adhesive to bolted or riveted joints in existing structures to create a combined joint.

[0013] Non-patent document 2 reports that, regarding a method of repairing and reinforcing steel structures by adhesively bonding backing plates, an experiment was conducted to clarify the fatigue durability of steel plate joints reinforced with epoxy resin when steel plates and CFRP (carbon fiber reinforced plastic) plates were used as backing plates, and that this resulted in knowledge that could be used to establish a design method for reinforcing joints.

[0014] Non-patent document 3 describes an analytical study of the stress that occurs in the adhesive when a steel plate bonded with a single backing plate is subjected to uniaxial tension, and the results of uniaxial tensile tests on the steel plate bonded with a single backing plate. The study clarifies the stress state, including the stress that occurs in the adhesive when the steel plate is bonded with a single backing plate, and states that the shear force, normal stress, and energy release rate when the backing plate is peeled can be used to evaluate peel failure at the adhesive surface.

[0015] Furthermore, Non-Patent Document 4 proposes a method for compensating for the lack of bearing capacity of tension brace joints in steel structures such as school gymnasiums by attaching a carbon fiber sheet to the joint with an impregnating adhesive resin, creating a vacuum using the Vacuum Resin Impregnation Molding Method (VaRTM method), and impregnating and curing the impregnating adhesive resin into the carbon fiber sheet.

[0016] Non-patent documents 1 to 3 relate to the evaluation of mechanical properties and peeling fracture of adhesively bonded joints between plates bonded with adhesive, and are useful as references for individually and specifically evaluating the strength of adhesively reinforced bolted joints of tensile members, which are the subject of this invention. However, they do not describe or suggest any useful technical information for efficiently reinforcing and designing the numerous web members of the approximately 250,000 existing transmission towers nationwide.

[0017] Furthermore, Non-Patent Document 4 describes a new method for adhesively reinforcing the bolted joints of tension brace members in steel structures. In this method, a carbon fiber sheet, which serves as a reinforcing material, is attached not only to the bolted joints at the ends of the brace members but also to the gusset plates, and the carbon fiber sheet is then covered with auxiliary materials for the VaRTM method, after which a vacuum is created to impregnate the sheet with an impregnating 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 on steel towers. [Prior art documents] [Patent documents]

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

[0019] [Non-Patent Document 1] Subcommittee on Research and Development of Joining Methods of FRP and Steel, "Advanced Technology for Joining FRP Members and Adhesive Joining of Steel and FRP," Journal of the Japan Society of Civil Engineers, Vol. 70, No. 5, pp. II_120-II_133, 2014. [Non-patent document 2] Taiwisal, K. Nakamura, H. Hayashi, and K. Horii, "Evaluation of fatigue strength of adhesively bonded steel plates with backing plates bonded with epoxy resin," Journal of the Japan Society of Civil Engineers, Vol. 74, No. 5, pp. II_56-II_66, 2018. [Non-patent document 3] Takeshi Mizutani, Takahiro Sakamoto, Toshiyuki Ishikawa, and Hisakazu Horii, "Mechanical Properties of Single-Sided Backing Plate-Bonded Steel Plates Subjected to Uniaxial Tension," Journal of Structural Engineering, Vol. 65A, pp. 755-768, March 2019. [Non-patent document 4] Takahiro Matsui, Kohei Suzuki, Sota Sato, Hiroki Kubokawa, Daiki Nakamoto, Kodai Matsumoto, "Reinforcement method for steel structural brace joints using VaRTM forming and bonding method of carbon fiber sheets," Architectural Institute of Japan Technical Report, Vol. 27, No. 67, pp. 1279-1284, October 2021 Summary of the Invention [Problem to be solved by the invention]

[0020] In light of the above, the present invention provides a design method for reinforcing bolted joints of tension members, which are often used as web members for steel towers and other structures used in high-altitude outdoor work, or as diagonal braces for steel structural buildings such as old steel-framed gymnasiums, by gluing reinforcing plates, as well as a joint reinforced with adhesive, a joint reinforced using this method, which can efficiently determine the dimensions and shape of the reinforcing plates necessary to ensure the necessary bearing capacity required for the bolted joint, and a joint reinforced using this reinforcement design method. [Means for solving the problem]

[0021] The solution of the present invention for solving the above problem is a design method for determining the necessary cross-sectional dimensions and necessary length of the reinforcing plate in an adhesive bonding method for bonding a reinforcing plate to a bolt joint of a tension member, (Step 1) The size of the tension member to be reinforced, the bolt shank diameter of the bolt joint of the tension member, and the number of bolts are input via the computer input device. (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 calculates the tensile strength T of the bolted joint of the tensile member. e and the required strength T of the bolted joint, which is set as a predetermined value that exceeds the tensile yield axial force of the shaft of the tension member by a certain percentage. un and the ratio T e / T un The strength fulfillment rate S of the bolted joint of the tension member defined as

[0022] (Step 3a) The value of the strength fulfillment rate S calculated in Step 2 is automatically determined by the computer's calculation device, and if 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) If the result of the automatic determination 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, and necessary conditions: T B / T S >1.0 {However, T B :Reinforcement plate yield strength, T S :Required strength deficit=(1-S)×T un The calculation unit of the computer searches and selects a candidate thickness of the reinforcing plate that satisfies the above condition} from the list in the database stored in the storage device. (Step 5) Of the thickness candidates for the reinforcing plate found in step 4, the one with the smallest thickness is determined.

[0023] (Step 6) When the reinforcing plate, which has the minimum plate thickness determined in Step 5 and a predetermined length without a tapered or stepped inclined portion at its tip, is glued to the bolt joint with an adhesive, a tensile axial force acts on the bolt joint, and the adhesive in the vicinity of the small end of the tip of the reinforcing plate peels off. A is searched by the arithmetic unit of the computer from the list in the database stored in the storage device. (Step 7a) The peel strength T A is a sufficient condition:T A / T un If ≧1.0 is satisfied, it is determined that the required length of the reinforcing plate is sufficient, and the calculation is terminated. (Step 7b)T A / T un If it is <1.0, proceed to step 8.

[0024] (Step 8) T in Step 7b A / T un <1.0, the above necessary condition: T B / T S When the reinforcing plate, which has a thickness that satisfies the above equation and has a predetermined length and a tapered or stepped inclined portion at its tip, is bonded to the bolted joint of the tensile member with an adhesive, the peel strength T is determined by the peeling of the adhesive near the small end of the inclined portion of the reinforcing plate when a tensile axial force acts on the bolted joint. A is searched by the arithmetic unit of the computer from the list in the database stored in the storage device. (Step 9a) The peel strength T A is a sufficient condition:T A / T un If ≧1.0 is satisfied, it is determined that the required length of 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 the bolted joint of the tension member cannot be adhesively reinforced with a reinforcing plate, and the calculation is terminated. This is a method for designing joint reinforcement for a tensile member, characterized by including the above steps.

[0025] In the method for designing joint reinforcement for a tensile member of the present invention, the database stored in the storage device of the computer includes a list of various values ​​necessary for determining the dimensions and shape of a reinforcing plate that reinforces a bolted joint, corresponding to each of a range of member sizes used for the tensile member, "(DB1) Strength fulfillment rate S of bolted joints of tension members" "(DB2) Reinforcement plate thickness t (when S<1.0)" (DB3) Plate length L and peel strength T of stiffened plate (without inclined portion) A (Requirement: T B / T S >1.0)" (DB4) Plate length L and peel strength T of stiffener (with inclined portion) 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 shank fracture at the bolt hole position of the bolt joint of the tensile member to be reinforced, and the required strength T required for the bolt joint. un Therefore, the strength sufficiency rate S, which indicates the strength surplus or deficiency of the bolt joint, is calculated as follows: e / T un A list of the indices defined as follows for each member size range used for tension members:

[0026] The second database stores the necessary strength T required for the bolted joint for all member sizes for which the strength fulfillment rate S is less than 1.0. un The purpose of this is to select the thickness t of the reinforcing plate necessary to compensate for the insufficient strength of the reinforcing plate. B and the required strength T un Required strength deficiency T S Relative to T B / T Sare listed by member size range used for tension members,

[0027] The third database includes the ratio T B / T S For a reinforcing plate having a thickness that satisfies the condition of 1.0 and that does not have a tapered or stepped inclined portion at its tip, the peel strength T of the reinforcing plate is the limit at which peeling occurs at the tip of the reinforcing plate for a predetermined plate length. A is calculated by stress analysis, and the required strength T un For each size of the tensile member to be reinforced, T A / T un The results of whether or not the score is <1.0 are organized and listed.

[0028] The fourth database is A / T un < 1.0, the peel strength T of the reinforcing plate when a tapered or stepped inclined portion is added to the tip of the reinforcing plate. A is calculated by stress analysis, and the T A / T un The results of whether or not the value is ≧1.0 are organized and listed. The present invention provides a method for designing reinforcement for a joint of a tensile member, characterized in that:

[0029] In the first database, the effective cross section of the bolt joint of the tensile member to be reinforced is mainly the cross section perpendicular to the axis of the member at the bolt hole position, but the tensile strength T e In some cases, the tensile strength T e may be determined.

[0030] In the second database, the reinforcement plate strength T of the effective cross section at the bolt hole position of the reinforcement plate where the bolt hole is drilled is B and the required joint strength T un Required strength deficiency T S Relative to T B / TS About T B / T S A plate thickness that satisfies the requirement of >1.0 is a necessary condition for being selected as a candidate for a stiffening plate.

[0031] For example, as shown in Figure 1, we will explain the case 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 with adhesive 5 to reinforce the joint. In this case, the critical cross section where the angle member 1 will fracture under 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. 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 of ​​the through hole of bolt 3a from the total cross-sectional area of ​​the member shaft.

[0032] In other words, since this is considerably smaller than the total cross-sectional area of ​​the shaft of the angle member 1, the effective cross-sectional area of ​​the reinforcing plate 4 must be large enough to satisfy the condition of the above formula 1. In other words, since the plate width b of the reinforcing plate 4 is limited by the dimensions of the inner surface of the flange of the angle member 1, in order to ensure the effective cross-sectional area of ​​the reinforcing plate 4, it is necessary to make the plate thick enough even after deducting the cross-sectional loss for the bolt holes to be drilled in the reinforcing plate 4.

[0033] In the third database, a stress analysis is performed on a pre-set plate length of a reinforcing plate having the plate thickness selected as a candidate in the second database, without a tapered or stepped inclined portion at the tip of the reinforcing plate, and the peel strength T A The results of the calculations are organized and listed.

[0034] When the tension member is pulled while the reinforcing plate is adhesively bonded to the bolted joint of the tension member to be reinforced, the adhesive experiences shear stress within the adhesive surface as well as tensile stress (hereinafter referred to as peel stress) out of the adhesive surface, which tends to peel the reinforcing plate. In the case of a reinforcing plate that does not have a tapered or stepped slope at its tip, the peel stress increases rapidly near the tip end of the reinforcing plate on the shaft side of the tension member. Therefore, when the peel stress reaches its limit, the tip of the reinforcing plate peels off, and it is known that this limits the maximum strength of the tension member joint.

[0035] In the example shown in Figure 1, the cross-sectional shape of the angle member 1, which is integrated by bonding the reinforcing plate 4 with the adhesive 5, suddenly changes at the tip 4a of the reinforcing plate 4. Therefore, as shown in Figure 2, the adhesive layer of the adhesive 5 experiences shear stress τ within the adhesive surface and peel stress (normal stress) σ, which tries to peel the reinforcing plate 4 perpendicular to the adhesive surface. t Then, the peel stress σ t The magnitude of the shear stress τ increases rapidly as it approaches the tip 4a of the reinforcing plate 4. Therefore, before the tensile force P reaches an axial force value that satisfies the above formula 1, the peel strength T A It is possible that the

[0036] In other words, when the tensile member 1 is reinforced by adhesive bonding with a reinforcing plate 4, the adhesive area increases up to a certain length of the reinforcing plate 4, so the peel strength T A This phenomenon will be illustrated in the description of the examples below, but to the best of the inventor's knowledge, this is the first time that it has been analytically verified in a specific case.

[0037] So, the third database is the necessary condition: B / T S For the reinforcement plate with a thickness that satisfies >1.0, the peel strength T A is the required strength T un Whether or not the value reaches T is calculated by stress analysis such as FEM analysis, and T isA / T un The results, which have been determined to be <1.0 or not, are organized and listed.

[0038] The fourth database is the T A / T un The peel strength T when a tapered or stepped inclined portion is added to the tip of the reinforcing plate is set to the plate length of the reinforcing plate that is equal to or greater than the above-mentioned certain length, which was <1.0 A is calculated by stress analysis such as FEM analysis, and T A / T un The results of whether or not the value is ≧1.0 are organized and listed.

[0039] As mentioned 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 level, the peel strength T A However, by providing a tapered or stepped inclined portion at the tip of the reinforcing plate on the axial side of the tension member, the abrupt change in the cross-sectional shape at the tip of the reinforcing plate, which changes from the cross section of the axial part of the tension member to the joint part thickened by the splicing of the reinforcing plate, can be alleviated, and the peel stress near the tip of the reinforcing plate can be significantly reduced, and the peel strength T A is known to increase further.

[0040] The peel strength T of the reinforcing plate is determined by the shape of the inclined portion attached to the tip of the reinforcing plate. A The effect of the tapered inclined portion on the peel strength T A As with the verification of the plateau phenomenon of strength increase in (1), this is the result of the inventor's investigation into specific cases through parametric analysis.

[0041] The present invention also relates to a bolted joint of a tensile member, characterized in that a reinforcing plate for reinforcing the bolted joint of the tensile member, determined based on various numerical values ​​related to reinforcing plates for each tensile member size that have been previously compiled into a database using the tensile member joint reinforcement design method of the present invention, is adhered to the bolted joint of the tensile member with an adhesive.

[0042] Taking the bolt joint of a tensile member 1 reinforced by bonding a reinforcing plate 4 shown in Figure 1 as an example, the cross-sectional dimensions (plate thickness t and plate width b) required for the reinforcing plate 4 are determined by the reinforcing plate strength T of the effective cross section at the bolt hole position of the reinforcing plate 4 where the bolt holes are drilled. B and the required joint strength T of the bolted joint. un Required strength deficiency T S Relative to T B / T S Regarding the requirements:T B / T S > 1.0, but the required strength deficiency T S The tensile stress τ is transmitted from the tensile member 1 to the reinforcing plate 4 by the shear stress τ acting on the adhesive layer of the adhesive 5. Next, the peel strength T of the reinforcing plate that can sustain the shear stress τ is calculated. A It is necessary to seek.

[0043] Peeling strength T A is a peeling stress (normal stress) σ that increases rapidly as it approaches the tip 4a of the reinforcing plate 4 and tries to peel off the reinforcing plate 4. t It should be noted that this is determined by the correlation between the length L of the reinforcing plate 4 and the shape of the tip 4a of the reinforcing plate 4 (see FIG. 2).

[0044] That is, peel strength T A As mentioned above, the strength of the reinforcing plate 4 reaches a plateau when it reaches a certain length, and also changes depending on the shape of the tip 4a. Therefore, to determine the dimensions and shape of the reinforcing plate 4, the plate thickness t and plate width b are set, and the required peel strength T is calculated for the assumed length L, or for the length L and the shape of the tip 4a. A The peel strength TA This is a necessary condition for the process.

[0045] Furthermore, in practice, it is not practical to perform trial and error calculations for each of the numerous and diverse types of bolt joints, so it is extremely rational to create a database in advance of the various values ​​related to the reinforcing plates for each tensile member size and use a computer to calculate them.It can be said that the joint configuration of a tensile member adhesively reinforced with the reinforcing plates of the present invention is only possible by the joint reinforcement design method of the present invention.

[0046] The reinforcing plate may be made of any material that is effective for reinforcement with an adhesive, such as steel or fiber reinforced plastic (FRP). [Effects of the Invention]

[0047] The present invention is a computer-based design method for joint reinforcement of tensile members according to the above-described procedure, and therefore has the following advantages. 1) For example, in reinforcement work for transmission towers, outdoor work is often carried out in mountainous areas and at high altitudes, so the method of reinforcing the tower's web joints must be as simple and reliable as possible. While a method of bonding reinforcing plates such as steel plates in combination with bolt joints is considered suitable, there is a problem in that the strength of the joints after reinforcement is limited by the adhesive surface peeling that is unique to adhesive methods. This invention addresses this problem from the perspective of adhesive reinforcement design, and provides a computer-assisted design method that can streamline the process of determining the dimensions and shape of the reinforcing plates necessary to ensure the necessary strength of the joints.

[0048] 2) When considering screening the approximately 250,000 existing transmission towers across the country to determine whether or not they require reinforcement, it would be efficient and practically useful to evaluate the strength of the towers if it were possible to assume that the bolted joints of the web members, which are prone to fracture, are reinforced.This invention is a useful design method that can contribute to the spread of simple and effective adhesive reinforcement methods for reinforcing the wide variety of bolted joints of such web members. 3) In addition, the adhesive reinforcement method requires a certain degree of space because the new reinforcement material is bonded within the width of the existing member shaft. For example, this method can be applied to narrow spaces where gusset plates or other similar devices cannot be used. Therefore, this design method contributes to broadening the range of construction methods available when reinforcing steel structures. 4) The widespread use of the adhesive reinforcement method will also lead to a reduction in reinforcement costs and construction time compared to conventional reinforcement methods that involve replacing tensile members used in steel structures, including steel towers. [Brief explanation of the drawings]

[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 adhered with adhesive to a bolt joint of an angle member, which is a tension member. (a) is a plan view, (b) is a cross-sectional view taken along the line I-I of (a), and (c) is a cross-sectional view taken along the line R-L of (b). [Figure 2] 10 is a schematic diagram illustrating a stress state in an adhesive layer on an adhesive surface of a reinforcing plate adhered to a tension member when the tension member is subjected to a tensile axial force. FIG. [Figure 3] 1 is a flow chart for determining the size and shape of a reinforcing plate required to reinforce a tension member bolted joint in accordance with the present invention. [Figure 4] 10 is a cross-sectional view showing the shape of the tip when an inclined portion is provided on the reinforcing plate according to the present invention. FIG. [Figure 5] This is an example of the results of an FEM analysis showing the relationship between the peel strength (maximum strength) of a reinforcing plate and the length of the reinforcing plate when reinforced with a reinforcing plate that does not have a slope at the tip. [Figure 6] This is an example of the results of an FEM analysis showing the relationship between the peel strength (maximum strength) of a reinforcing plate and the length of the reinforcing plate when reinforced with a reinforcing plate that has an inclined portion at the tip. [Figure 7] This is an example of an analytical model for examining the influence of the tip shape of the reinforcing plate. (a) explains the parameters that define the tip shape when there is no taper, and (b) when there is a taper, and (c) is a table showing the combinations of each parameter. DETAILED DESCRIPTION OF THE INVENTION

[0050] As an example of the present invention, in the case where an angle member 1 as shown in FIG. 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 tensile member will be described with reference to FIGS. 3 to 7 and Tables 1 to 5.

[0051] The present invention is not limited to angle members; channel steel and flat steel, which are often used as tension members and braces in steel structures, also break at bolted joints in the same way as angle members, so these tension members are also included in the scope of the present invention.

[0052] Figure 3 is a flowchart for determining the dimensions and shape of the reinforcing plate required to reinforce the bolted joint of a tensile member. First, the size of the tensile member to be reinforced, the bolt shank diameter and number of bolts used in the bolted joint are input via a computer 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 fulfillment rate S of tensile member bolt joint" stored in the storage device (Step 2).

[0054] Table 1 shows an example of a database (for L-shaped steel) in which the calculation results of the strength fulfillment rate S of bolted joints calculated for each size of tensile member are organized and listed.

[0055] [Table 1]

[0056] The first database contains the tensile strength Te (=A e ×F u , or 0.75 × n × f A× f F u) and the required strength T required for the bolt joint. un (=1.2×A g × F) and the strength fulfillment rate S (= T e / T un ) is a list organized by tension member size. However, A e is the effective cross-sectional area of ​​the joint, F u is the tensile strength of the component material, f F u is the tensile strength of the bolt, and F is the yield strength of the component material.

[0057] In Figure 1, there are two bolts, but the effective cross-sectional area A e Since varies depending on the number of bolts (for example, Architectural Institute of Japan "Guidelines for Design of Steel Structure Joints" 2021.2), in Table 1, the tensile strength T of the bolt joint before reinforcement is calculated taking this into consideration. e is calculated, and the required strength T un is calculated as a value that satisfies the above formula 1.

[0058] Next, if the calculated yield strength fulfillment rate S is ≥ 1.0, the calculation is terminated (step 3a). On the other hand, if the yield strength fulfillment rate S is < 1.0, it is determined that reinforcement is required (indicated by * in Table 1), and the process proceeds to step 4 to determine the specifications of the required reinforcing plate (step 3b).

[0059] In step 4, the arithmetic unit searches the second database "(DB2) Plate thickness t of reinforcing plate (when S<1.0)" stored in the storage unit.

[0060] Table 2 shows an example of a database (for L-shaped steel) in which the calculation results for the required thickness of the reinforcing plate when the strength fulfillment rate S is less than 1.0, calculated for each size of tensile member, are organized and listed.

[0061] [Table 2]

[0062] In the second database, as shown in Table 2, the plate width b of the reinforcing plate is set in advance for each size of the tensile member, and the reinforcing plate strength T B (=A e ×F u ) and the required strength T required for the bolt joint un Required strength deficiency T S {=(1-S)×T un} are organized by tension member size, and the strength ratio T B / T S is a list organized by tension member size. B / T S Reinforcement plates with thickness t that satisfies >1.0 (indicated by * in Table 2) are selected as candidates (Step 4).

[0063] The one with the smallest plate thickness is determined from the selected candidates for the reinforcing plate (Step 5), and the next step 6 is performed to determine the plate length L. B / T S Stiffeners with thickness t ≦ 1.0 are ignored.

[0064] In step 6, the calculation device calculates the plate length L and peel strength T of the third database “(DB3) reinforcement plate (without inclined portion)” stored in the storage device. A (Requirement: T B / T S >1.0)" is searched for (step 6).

[0065] Table 3 shows the requirements for each size of tension member: B / T S The plate length L of the reinforcement plate (without inclined portions) that satisfies (= reinforcement plate strength / necessary strength shortfall) > 1.0 and the peel strength T obtained by stress analysis A The results are shown in an example of a database that has been organized and listed, and which shows only one size of L-shaped steel.

[0066] [Table 3]

[0067] The third database contains the necessary conditions: strength ratio T B / T S For a reinforcing plate with the minimum plate thickness t determined in step 5 and satisfying the condition of >1.0 and no inclined portion at the tip, when the plate length L is set in advance, the peel strength T of the reinforcing plate determined by adhesive peeling A These are the lists obtained by stress analysis such as FEM analysis and organized by tensile member size.

[0068] Table 3 shows an example of the case of L-45×45×4, which was actually obtained by FEM analysis. In this example, when the thickness of the reinforcing plate is 0.6 cm, even if the plate length L is increased from 23.5 cm to 53.5 cm, the peel strength T of the reinforcing plate does not change. A It has been shown that there is little increase.

[0069] The results of the above FEM analysis are shown in Figure 5. If a reinforced plate bonded and reinforced with adhesive (e.g., epoxy resin adhesive) is made longer, the adhesive area will increase, and the peel strength T A However, once the length reaches a certain level, the strength plateaus and there is almost no increase in strength even if the length is increased further.

[0070] Figure 5 shows a concrete example that verifies this. The figure shows the results of an FEM analysis of an angle member L-45x45x4 joined with two M16 bolts, when the plate is reinforced with a 0.6cm thick reinforcement plate without an inclined portion. The vertical axis shows the maximum strength (peeling strength T A ), and the horizontal axis represents the length of the reinforcing plate (plate length L). From Figure 5, it can be seen that there is a slight increase in strength at a reinforcing plate length of 335 mm compared to 235 mm, but there is almost no increase in strength 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 by the computing device is the peel strength T A and the required strength T un Strength ratio T A / T unIf ≧1.0, it is determined that the plate length L of the reinforcing plate has been determined, and the calculation is terminated (step 7a).

[0072] In addition, as shown in Table 3 for the case of L-45 × 45 × 4, the peel strength T A At present, calculation of t requires the use of methods such as FEM analysis, so it is considered practical to calculate the plate length L of the reinforcement material in advance using FEM analysis for several combinations of plate thickness t and plate length L and to create a database.

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

[0074] In step 8, the arithmetic unit calculates the plate length L and peel strength T of the fourth database “(DB4) reinforcement plate (with inclined portion)” stored in the storage unit. A (Requirement: T B / T S >1.0)" is searched for (step 8).

[0075] Table 4, Table 5 and Figure 4 show the requirements for each size of tension member: T B / T S The plate length L of the reinforcement plate (with inclined portion) that satisfies (= reinforcement plate strength / necessary strength shortage) > 1.0 and the peel strength T obtained by stress analysis A The results are an example of an organized and listed database, displayed for only one size of L-beam.

[0076] [Table 4]

[0077] [Table 5]

[0078] The fourth database is shown in Table 4, which lists the necessary conditions: strength ratio TB / T S > 1.0 and the minimum plate thickness t determined in step 5, and the proof stress ratio T A / T un In the case of <1.0, for a stiffened plate with an inclined portion (here, a tapered portion) at the tip as shown in Figure 4, the peel strength T of the stiffened plate determined by adhesive peeling when the plate length L is set in advance is A These are lists obtained by FEM analysis etc. and organized by tensile member size.

[0079] In addition, even if the plate length L confirmed in step 6 (third database) is longer, the peel strength T A is an upper limit value that does not increase, so the plate length L set in advance in step 8 (fourth database) is set to a value equal to or greater than the upper limit value, and when an inclined portion is added to the tip of the reinforcing plate, the sufficient condition: yield strength ratio T A / T un The shape of the slope portion that satisfies ≧1.0 is searched for.

[0080] Here, the tapered shape of the tip of the reinforcing plate and the peel strength T A As shown in Figures 7(a) and (b), when the shape of the tip of the reinforcing plate is changed to a tapered shape, the maximum strength (peel strength T A ) is larger, as shown in the graph in FIG.

[0081] Figure 6 shows the results of FEM analysis of the tapered patterns shown in Figure 7(c) for a 0.6cm thick reinforcing plate when using angle members L-45x45x4 with two M16 bolts, as in Figure 5. The vertical axis shows the maximum strength (peel strength T A ), the horizontal axis is the taper length L t and plate thickness t p Relative to L t / t p indicates the reinforcing plate t p The tip thickness t t Ratio to t t / t p The cases of =1 / 4, 1 / 3, and 1 / 2 are shown.

[0082] From FIG. 6, the ratio t t / t p The smaller the taper length L t Reinforcement plate p Ratio to L t / t p The larger the value, the greater the maximum strength (peel strength T A ) increases. From this result, it can be seen that the strength ratio T A / T un Even if the peel strength T A is expected to increase.

[0083] In this way, the influence of the tapered shape of the tip of the stiffener plate is proportional to the thickness of the stiffener plate t p , tip thickness t t , taper length L t Therefore, the peel strength T of the reinforcement plate obtained in advance for each shape can be calculated by FEM analysis. A However, the list can be stored in the storage device as a list organized by tension member size. It goes without saying that the same applies to the case where the inclined portion is stepped.

[0084] Therefore, in step 8, the sufficient condition: strength ratio T A / T un ≧1.0 is not satisfied, the calculation device searches the fourth database stored in the storage device for the reinforcing plate having the minimum plate thickness t set in step 5 and an inclined portion at the tip, and the sufficient condition: proof stress ratio T A / T un When the shape of the inclined portion that satisfies ≧1.0 is selected (shown with * in Table 4), the plate length L of the reinforcing plate is determined to be 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 an inclined portion at the tip, it is determined that the adhesive reinforcement using the reinforcing plate as shown in Figure 1 cannot satisfy the condition of Equation 1, and the calculation is terminated (Step 9b). In this case, another reinforcing method will be considered.

[0086] The above has described an embodiment of the joint reinforcement design method for a tensile member according to the present invention. A At present, it is realistic to rely on methods such as FEM analysis to calculate this, but since analyzing all the various combination patterns in advance requires a lot of time and effort, it is thought that in practice it will be possible to do so by limiting it to bolt joints that correspond to the range of tensile member sizes that are commonly used in practice.

[0087] As shown in FIG. 1, the bolt joint is reinforced by bonding the reinforcing plate 4 determined by the joint reinforcement design method for tension members according to the present invention. The reinforcement can be completed simply by applying adhesive to the new reinforcing material 4 and tightening the bolts within the width of the shaft of the existing angle member 1, resulting in a compact fit and easy on-site construction.

[0088] In other words, it is easy to install even in narrow places where it is difficult to reinforce bolted joints, and since no large-scale equipment is required, it is easy to work in high places outdoors such as steel towers. Of course, it can also be used for general purposes on existing steel structures other than steel towers.

[0089] The reinforcing plate may be made of any material that is effective for reinforcement with an adhesive, such as steel or fiber reinforced plastic (FRP). [Industrial Applicability]

[0090] The method of reinforcing bolted joints using adhesive and the adhesive-reinforced joints covered by this invention eliminate the need to replace existing components, leading to reduced reinforcement costs and construction time, and will contribute significantly to earthquake and wind resistance reinforcement measures, particularly for the countless power transmission towers currently in existence throughout the country. Furthermore, the invention, which can significantly improve the efficiency of bolted joint design work, is not limited to steel towers and the like, and 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 : Peel stress (normal stress)

Claims

1. A design method for determining the required cross-sectional dimensions and required length of a reinforcing plate in a bonding method for bonding a reinforcing plate to a bolt joint of a tension member with an adhesive, comprising: (Step 1) The size of the tension member to be reinforced, the bolt shank diameter of the bolted joint of the tension member, and the number of bolts are input via the computer input device. (Step 2) Based on the information of the tension 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 calculates the tensile strength T e and the required strength T of the bolted joint, which is set as a predetermined value exceeding the tensile yield axial force of the shaft of the tension member by a certain percentage. un The ratio T e / T un The strength fulfillment rate S of the tensile member bolt joint defined as (Step 3a) The value of the strength fulfillment rate S calculated in Step 2 is automatically determined by the computer's calculation device, and if S≧1.0, it is determined that the bolted joint of the tensile member does not require reinforcement, and the calculation is terminated. (Step 3b) If the result of the automatic determination 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 tension member to be reinforced, and necessary condition: T B / T S > 1.0 {However, T B : Reinforcement plate yield strength, T S : Insufficient required strength = (1-S) x T un The calculation unit of the computer searches and selects a candidate thickness of the reinforcing plate that satisfies the above condition} from the list in the database stored in the storage device. (Step 5) Of the thickness candidates for the reinforcing plate found in step 4, the one with the smallest thickness is determined. (Step 6) When the reinforcing plate having the minimum plate thickness determined in Step 5 and a predetermined length without a tapered or stepped inclined portion at its tip is glued to the bolt joint with an adhesive, a tensile axial force acts on the bolt joint, and the adhesive in the vicinity of the small end of the tip of the reinforcing plate peels off. A is searched by the arithmetic unit of the computer from the list in the database stored in the storage device. (Step 7a) The retrieved peel strength T A is a sufficient condition: T A / T un If ≧1.0 is satisfied, it is determined that the required length of the reinforcing plate is sufficient, and the calculation is terminated. (Step 7b) T A / T un If it is <1.0, proceed to step 8. (Step 8) T in Step 7b A / T un < 1.0, the necessary condition: T B / T S When the reinforcing plate having a thickness satisfying the condition of 1.0 and a predetermined length with a tapered or stepped inclined portion at its tip is bonded to the bolted joint of the tension member with an adhesive, a tensile axial force acts on the bolted joint, and the adhesive in the vicinity of the small end of the inclined portion of the reinforcing plate peels off. A is searched by the arithmetic unit of the computer from the list in the database stored in the storage device. (Step 9a) The retrieved peel strength T A is a sufficient condition: T A / T un If ≧1.0 is satisfied, it is determined that the required length of 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 the bolted joint of the tension member cannot be adhesively reinforced with a reinforcing plate, and the calculation is terminated. A method for designing joint reinforcement for a tensile member, comprising the above steps.

2. 2. The method for designing joint reinforcement for a tensile member according to claim 1, wherein the database stored in the storage device of the computer is a list of various values ​​required to determine the dimensions and shapes of reinforcing plates for reinforcing bolted joints, corresponding to each of a range of member sizes used for the tensile member, "(DB1) Strength fulfillment rate S of bolted joint of tension member" "(DB2) Plate thickness t of reinforcing plate (when S<1.0)" (DB3) Plate length L and peel strength T of reinforced plate (without inclined portion) A (Required condition: T B / T S >1.0) (DB4) Plate length L and peel strength T of reinforced plate (with inclined portion) A (Required condition: T B / T S >1.0) It consists of the first to fourth databases mentioned above, The first database contains the tensile strength Te at the effective cross section or bolt shank fracture at the bolt hole position of the bolt joint of the tensile member to be reinforced, and the required strength T required for the bolt joint. un Therefore, the strength sufficiency rate S, which indicates the excess or deficiency of the bolt joint strength, is e / T un A list of the indices defined as follows for each member size range used for tension members: The second database stores the necessary strength T required for the bolted joint for all member sizes for which the strength fulfillment rate S is less than 1.

0. un The purpose of this is to select the thickness t of the reinforcing plate necessary to compensate for the insufficient strength of the reinforcing plate. B and the required strength T un The ratio of the required strength deficiency TS to B / T S are listed by member size range used for tension members, The third database includes the ratio T B / T S For a reinforcing plate having a thickness that satisfies the requirement of 1.0 and that does not have a tapered or stepped inclined portion at its tip, the peel strength T of the reinforcing plate is the limit at which peeling occurs at the tip of the reinforcing plate for a predetermined plate length. A is calculated by stress analysis, and the required strength T un For each size of the tensile member to be reinforced, T A / T un The results of whether it is <1.0 are organized and listed, The fourth database is A / T un < 1.0, the peel strength T of the reinforcing plate when a tapered or stepped inclined portion is provided at the tip of the reinforcing plate A is calculated by stress analysis, and the T A / T un The results of determining whether the value is ≧1.0 are organized and listed. A method for designing joint reinforcement for a tensile member, characterized by:

3. A joint of a tensile member, characterized in that a reinforcing plate for reinforcing the bolted joint of the tensile member, determined based on various numerical values ​​for reinforcing plates for each size of tensile member that have been previously compiled into a database using the joint reinforcement design method for a tensile member as described in claim 1 or 2, is adhesively attached to the bolted joint of the tensile member.

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