Steel plate deck structure design method

Abstract

An object of the present invention is to solve the problems of the related art, that is, to provide a steel plate deck structure design method capable of determining a structure of a steel plate deck having a smaller maximum stress range and a smaller total steel weight than those of a steel plate deck based on standard specifications.SOLUTION: The steel floor slab structure design method is a method for determining the structure of a steel floor slab of a road bridge, and includes a standard model analysis process, a primary design structure model setting process, a rib width determination process, a secondary design structure model setting process, and a vertical rib interval determination process. In the rib width determination step, the "optimum rib width" of the longitudinal rib and the "optimum deck plate thickness" of the steel deck plate are determined. In the longitudinal rib interval determining step, the "optimum longitudinal rib interval" of the longitudinal ribs is determined.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to technology relating to steel decks of road bridges, and more specifically to a steel deck structural design method that can determine the structure of steel decks so as to improve fatigue durability and economic rationality. [Background technology]

[0002] Steel decks are lighter than concrete decks and have shorter construction times, so they are widely used, especially for viaducts on urban expressways, bridges in coastal areas with soft ground, and long-span bridges. These steel decks are made of a steel deck plate and longitudinal and transverse ribs, and are welded together to form a thin plate assembly structure. The longitudinal and transverse ribs are components that stiffen the steel deck plate, with the longitudinal ribs being positioned so that their longitudinal direction is primarily in the bridge axis direction, and the transverse ribs being positioned so that their longitudinal direction is primarily perpendicular to the bridge axis.

[0003] Urban expressways, which are primarily comprised of viaducts, support large volumes of traffic every day. For example, the Hanshin Expressway has a cross-sectional traffic volume of nearly 100,000 vehicles per day, with a very high proportion of large vehicles. This means that road bridges on urban expressways are subjected to numerous wheel loads over many years, and it is easy to imagine that fatigue damage can occur in the steel decks that make up the road bridges.

[0004] There are two types of longitudinal ribs: closed section ribs (U-ribs) and open section ribs (flat plate ribs, valve plate ribs, etc.), and it is known that steel deck plates that use closed section ribs are prone to fatigue cracks. In particular, there have been many reported cases where fatigue cracks have occurred directly below the position where the wheel load of large vehicles is constantly applied, from the weld between the closed section rib and the steel deck plate, penetrating through the steel deck plate.

[0005] On the other hand, the occurrence of fatigue damage in steel decks is greatly influenced by various conditions, such as the rigidity of the pavement against stress caused by vehicle loads, variations in wheel loads, and the distribution of wheel load positions (driving positions), and because it depends on local deformations and local stresses that cannot be obtained by normal design calculations, it is generally difficult to make an appropriate evaluation through stress verification based on the stress range obtained by design calculations.Therefore, Non-Patent Document 1 states that if the design durability period is set at 100 years, the fatigue durability of steel decks that meet predetermined specifications (hereinafter referred to as "standard specifications") is considered to be ensured. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Highway Bridge Specifications and Commentary: Steel Bridges and Steel Members Summary of the Invention [Problem to be solved by the invention]

[0007] The standard specifications set forth in Non-Patent Document 1 include specifications for longitudinal rib spans (pitch of transverse ribs in the bridge axis direction), longitudinal ribs, and steel deck plates. Specifically, the longitudinal rib span must be 2.5 m or less, longitudinal ribs must be flat ribs, bulb plate ribs, or standard closed-section ribs, and the steel deck plate must have a thickness of 16 mm or more at the location where the wheel load of large vehicles is constantly applied. Here, standard closed-section ribs refer to four types of U-ribs: U-320 (top width) x 240 (height) x 6 (plate thickness), U-320 x 260 x 6, U-320 x 240 x 8, and U-320 x 260 x 8. Previously, the plate thickness of steel deck plates was set at 12 mm or more, but due to the frequent occurrence of fatigue cracks as described above, the 2012 revision of the "Highway Bridge Specifications and Commentary (Non-Patent Document 1)" required a thickness of 16 mm or more.

[0008] As mentioned above, if a steel deck conforms to the standard specifications specified in Non-Patent Document 1 (however, it must also comply with the provisions of 8.5.2 and 11.8 of the Specifications for Highway Bridges and Commentary), 100 years of fatigue durability is guaranteed. This essentially guarantees compliance with the Specifications for Highway Bridges and Commentary, allowing for reliable and easy steel deck structure determination. On the other hand, it would be impossible to adopt a steel deck that is less costly than a steel deck based on the standard specifications. In other words, depending on the design conditions, a standard steel deck may be overdesigned (i.e., have excess stress), which would result in a missed opportunity to reduce the cost of the steel deck. For example, if a detailed analysis using the finite element method (FEM) reveals that a steel deck does not meet the standard specifications but has sufficient fatigue durability and can be manufactured and installed at a lower cost (especially in terms of steel weight) than a standard steel deck, it would be more reasonable to adopt that steel deck.

[0009] The object of the present invention is to solve the problems associated with the prior art, namely, to provide a steel deck structural design method that can determine the structure of a steel deck that has a smaller stress that causes fatigue (hereinafter referred to as the "maximum stress range") and a smaller total steel weight than steel decks based on standard specifications. [Means for solving the problem]

[0010] The present invention was made by focusing on the point that the maximum stress range and total steel weight for steel decks based on standard specifications are used as standards, and the appropriate steel deck structure is determined on the condition that these are below these, and is an invention based on an unprecedented idea.

[0011] The steel deck structural design method of the present invention is a method for determining the structure of a steel deck for a highway bridge, and includes a standard model analysis process, a primary design structural model establishment process, a rib width determination process, a secondary design structural model establishment process, and a longitudinal rib spacing determination process. In the standard model analysis process, a "standard structural model" is analyzed using a "standard closed section rib" selected from U-320x240x6, U-320x260x6, U-320x240x8, or U-320x260x8, a steel deck plate of a predetermined standard thickness, and transverse ribs. The "standard maximum stress range" and "standard steel weight (total steel weight) for the standard structural model" are calculated based on the standard closed section rib. In the primary design structural model establishment process, the "primary design structural model" is established by changing the standard structural model to longitudinal ribs with a smaller rib width than the standard closed section ribs and changing the steel deck plate to a thinner thickness than the standard thickness. In the rib width determination process, analysis is performed using the primary design structural model to calculate the "intersection maximum stress range" that occurs in the steel deck plate at the rib intersection (where the longitudinal ribs intersect with the transverse ribs). The "optimal rib width" of the longitudinal ribs and the "optimal deck plate thickness" of the steel deck plate are determined, provided that the intersection maximum stress range is below the standard maximum stress range. In the secondary design structural model setting process, a "secondary design structural model" is set by changing the longitudinal rib spacing from the primary design structural model to a smaller spacing than in the primary design structural model. In the longitudinal rib spacing determination process, analysis is performed using the secondary design structural model to calculate the "general section maximum stress range" that occurs in the steel deck plate at the general section (where the longitudinal ribs do not intersect with the transverse ribs). The "design steel weight (sum of steel weights)" for the secondary design structural model is calculated, and the "optimal longitudinal rib spacing" of the longitudinal ribs is determined, provided that the general section maximum stress range is below the standard maximum stress range and the design steel weight is below the standard steel weight. The standard maximum stress range, intersection maximum stress range, and general maximum stress range are the differences between the maximum stress and minimum stress occurring in the steel deck plate in each structural model.Then, the primary design structural model setting process and the rib width determination process are repeated while changing the rib width of the vertical ribs and the plate thickness of the steel deck plate until the optimal rib width and optimal deck plate thickness are determined, and the secondary design structural model setting process and the vertical rib spacing determination process are repeated while changing the vertical rib spacing until the optimal vertical rib spacing is determined.

[0012] The steel deck structural design method of the present invention can also include a tertiary design structural model setting process and a rib height determination process. In this tertiary design structural model setting process, a "tertiary design structural model" is set by changing the spacing of the transverse ribs and the rib height of the longitudinal ribs from the secondary design structural model. In the rib height determination process, an analysis (e.g., a frame analysis) is performed using the tertiary design structural model to calculate design verification stresses. The "optimum transverse rib spacing" for the transverse ribs and the "optimum rib height" for the longitudinal ribs are determined, provided that the design verification stresses satisfy predetermined stress limit values. The design verification stresses are stresses in the bridge axis direction that occur in the steel deck plate and longitudinal ribs in the tertiary design structural model. The tertiary design structural model setting process and the rib height determination process are then repeated while changing the spacing of the transverse ribs and the rib height of the longitudinal ribs until the optimal transverse rib spacing and optimal rib height are determined.

[0013] The steel deck structural design method of the present invention can also be a method that further includes a prototype model creation process, a joint testing process, and a side angle determination process. In this prototype model creation process, a "prototype model" consisting of a steel deck plate and two or more longitudinal ribs arranged in a line in the bridge axis direction is created based on the specifications of the secondary design structural model in which the optimal longitudinal rib spacing has been determined. In the joint testing process, the longitudinal ribs arranged in the bridge axis direction are joined in the prototype model using splice plates and high-strength bolts, utilizing the space formed by the longitudinal ribs arranged perpendicular to the bridge axis. In the side angle determination process, the angle of the side panel of the vertical rib is determined as the "optimal side angle," provided that the longitudinal rib can be joined in the joint testing process. Note that if the longitudinal rib cannot be joined in the joint testing process, the angle of the side panel of the vertical rib is changed and a new prototype model is created. The prototype model creation process, joint testing process, and side angle determination process are repeated while changing the angle of the side panel of the vertical rib until the optimal longitudinal rib spacing is determined.

[0014] The steel deck structural design method of the present invention can also be a method of performing analysis using a standard structural model with a standard plate thickness of 12 mm or 16 mm. [Effects of the Invention]

[0015] The steel deck structural design method of the present invention has the following effects. (1) By designing without being bound by the standard specifications stipulated in the "Highway Bridge Specifications and Commentary," it is possible to determine a steel deck that has sufficient fatigue durability while reducing the total steel weight compared to steel decks based on the standard specifications. (2) By reducing the total weight of steel, the energy and resources required to manufacture steel decks are also reduced, and the impact on the environment can be reduced compared to conventional technologies. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a steel deck of a road bridge. [Figure 2] FIG. 4 is a cross-sectional view schematically showing the structure of a rib intersection portion. [Figure 3] 1 is a flow chart showing the flow of the main steps of the steel deck structural design method of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing a schematic diagram of a prototype model during joining of longitudinal ribs. [Figure 5] Analysis results comparing the maximum stress ranges for each case. [Figure 6] (a) is a graph showing the maximum stress range of the intersection part in each case, and (b) is a graph showing the maximum stress range of the general part in each case. [Figure 7] A steel weight comparison diagram comparing the total steel weight in each case. DETAILED DESCRIPTION OF THE INVENTION

[0017] An example of an embodiment of the steel deck structural design method of the present invention will be described with reference to the drawings.

[0018] The steel deck structural design method of the present invention is a method for determining the structure of a steel deck for a road bridge. As shown in Figure 1, this steel deck 10 is composed of a steel deck plate 20, longitudinal ribs 30, and transverse ribs 40, and is a deck structure supported by main girders 50. In addition, pavement 60 is laid on the top surface of the steel deck plate 20, and road guards 70 may be installed at the edges.

[0019] The vertical ribs 30 that make up the steel deck 10 are arranged in multiple rows with their longitudinal direction (axial direction) aligned with the bridge axis and spaced apart in a direction perpendicular to the bridge axis. Furthermore, since bridges generally have a considerable length, multiple vertical ribs 30 that are short compared to the bridge length are arranged side by side in the bridge axis direction and connected at adjacent positions in the bridge axis direction by splice plates and high-strength bolts.

[0020] On the other hand, the transverse ribs 40 are arranged in multiple rows with their longitudinal direction (axial direction) perpendicular to the bridge axis and at intervals in the bridge axis direction. The longitudinal ribs 30 and transverse ribs 40, which act as stiffeners, are welded to the underside of the steel deck plate 20, respectively, so that there are areas where the longitudinal ribs 30 and transverse ribs 40 intersect so that they overlap on the same plane (hereinafter referred to as "rib intersections"). Therefore, as shown in Figure 2, "notches" are provided in the transverse ribs 40. These notches are, in a sense, openings carved out to match the outer shape of the longitudinal ribs 30, and by inserting the longitudinal ribs 30 into these notches, the overlap between the two is eliminated. The longitudinal ribs 30 inserted into the notches are welded to the transverse ribs 40.

[0021] Longitudinal ribs are broadly divided into closed-section and open-section types, but the steel deck 10 targeted by the steel deck structural design method of the present invention is composed of closed-section vertical ribs 30 (so-called U-ribs). As shown in Figure 2, this vertical rib 30 is formed by left and right side panels 31 and a bottom panel 32, and has a U-shaped cross section with an open top and a wider upper width than lower width. In other words, the side panels 31 are inclined at an acute angle (less than 90°) with respect to the horizontal plane. For convenience, the angle between the side panels 31 and the horizontal plane will be referred to as the "side angle."

[0022] The steel deck structural design method of the present invention will be described with reference to Figure 3. Figure 3 is a flow chart showing the flow of the main steps of the steel deck structural design method of the present invention. When determining the structure of a steel deck 10 using the steel deck structural design method, a standard steel deck 10 structure is first set. To do this, a standard structural model (hereinafter simply referred to as the "standard structural model") consisting of a steel deck plate 20 and closed cross-section longitudinal ribs 30 and transverse ribs 40 is set in accordance with the "Highway Bridge Specifications and Commentary, Steel Bridges and Steel Members Edition (hereinafter simply referred to as the "Highway Bridge Specifications")" (Step 101 in Figure 3). Specifically, a standard closed section rib is selected from U-320×240×6, U-320×260×6, U-320×240×8, and U-320×260×8, which are standard closed section ribs (hereinafter simply referred to as "standard closed section ribs") according to the Highway Bridge Specifications, and the thickness of the steel deck plate 20 is set to the standard thickness (16 mm) specified by the Highway Bridge Specifications.Furthermore, the span of the vertical ribs 30 is set to 2.5 m or less, and the spacing of the vertical ribs 30 perpendicular to the bridge axis (hereinafter referred to as "longitudinal rib spacing") is appropriately set, thereby setting a standard structural model.

[0023] Once the standard structural model is established, an analysis is performed using that standard structural model (Step 101 in Figure 3). At this time, it is recommended to perform the analysis using FEM or similar. The standard structural model is then evaluated, for example, using the allowable stress method. If it satisfies various design conditions, the standard structural model is confirmed. If it does not, the standard structural model is modified and then analyzed again to evaluate the standard structural model. Once the standard structural model is established, the "maximum stress range" occurring in the steel deck plate 20 is recorded, and the sum of the steel weights for the standard structural model (hereinafter referred to as the "standard steel weight") is calculated. Here, the "maximum stress range" refers to the difference between the maximum stress (tensile side) and the minimum stress (compression side) occurring in the steel deck plate 20 of the standard structural model. For convenience, the maximum stress range will be simply referred to as the "maximum stress range," and the maximum stress range obtained as a result of analyzing the standard structural model will be referred to as the "standard maximum stress range."

[0024] Once the standard structural model has been determined and the standard maximum stress range and standard steel weight have been obtained, a design structural model is set (Step 103 in Figure 3). Note that in the steel deck structural design method of the present invention, a design structural model is set in each of three stages, so for convenience, the design structural model in the first stage will be referred to as the "primary design structural model," the design structural model in the second stage as the "secondary design structural model," and the design structural model in the third stage as the "tertiary design structural model."

[0025] The primary design structural model is established by changing some of the specifications of the structural model. Specifically, the primary design structural model is established by changing the specifications of the longitudinal ribs 30 (i.e., standard closed section ribs) of the standard structural model and by changing the plate thickness of the steel deck plate 20. In other words, all specifications except for the longitudinal ribs 30 and the steel deck plate 20 are the same as the standard structural model. In other words, at this stage, the "appropriate rib width (hereinafter referred to as the "optimum rib width")" of the longitudinal ribs 30 and the "appropriate plate thickness (hereinafter referred to as the "optimum deck plate thickness")" of the steel deck plate 20 are determined. However, the longitudinal ribs 30 of the primary design structural model are adopted to have a rib width smaller than the rib width (particularly the upper width) of the standard closed section ribs, and the plate thickness of the steel deck plate 20 of the primary design structural model is set to be thinner than the standard plate thickness (16 mm).

[0026] Once the primary design structural model is set, an analysis is performed using that primary design structural model (Step 104 in Figure 3). At this time, it is recommended to perform the analysis using FEM or similar. Then, the maximum stress range that occurs in the steel deck plate 20 at the rib intersection (hereinafter referred to as the "intersection maximum stress range") is calculated. Since the influence of the longitudinal rib spacing at the rib intersection is considered to be limited, the optimal rib width and optimal deck plate thickness are first determined based on the maximum stress range at the rib intersection, and then the longitudinal rib spacing is determined (in the secondary design structural model).

[0027] Once the intersection maximum stress range is obtained, it is compared with the standard maximum stress range. If the intersection maximum stress range is below the standard maximum stress range (or equal to or less than the standard maximum stress range) (Yes in Step 105 of Figure 3), the primary design structural model is finalized, and the rib width of the longitudinal ribs 30 constituting the primary design structural model is determined as the "optimum rib width," and the thickness of the steel deck plate 20 is determined as the "optimum deck plate thickness." On the other hand, if the intersection maximum stress range is above the standard maximum stress range (or exceeds the standard maximum stress range) (No in Step 105 of Figure 3), the primary design structural model is modified and the analysis is performed again to evaluate the primary design structural model. Then, the setting of the primary design structural model (Step 103 of Figure 3) and the analysis of the primary design structural model (Step 104 of Figure 3) are repeated until the optimal rib width and optimal deck plate thickness are determined.

[0028] Once the primary design structural model has been finalized and the optimum rib width and optimum deck plate thickness have been determined, the next step is to set up a secondary design structural model (Step 106 in Figure 3). The secondary design structural model is set up by changing some of the specifications of the primary design structural model. Specifically, the secondary design structural model is set up by changing the longitudinal rib spacing of the primary design structural model. In other words, all other specifications except for the longitudinal rib spacing are the same as the primary design structural model; in other words, at this stage, the "appropriate longitudinal rib spacing (hereinafter referred to as "optimum longitudinal rib spacing")" is determined. However, the longitudinal rib spacing of the secondary design structural model is set to a value smaller than the longitudinal rib spacing of the primary design structural model.

[0029] Once the secondary design structural model is set, an analysis is performed using that secondary design structural model (Step 107 in Figure 3). At this time, it is recommended to perform the analysis using FEM or the like. Then, the maximum stress range (hereinafter specifically referred to as the "general part maximum stress range") that occurs in the steel deck plate 20 in the part where the longitudinal ribs 30 and the transverse ribs 40 do not intersect (hereinafter referred to as the "general part") is calculated, and the total steel weight related to the secondary design structural model (hereinafter referred to as the "design steel weight") is calculated.

[0030] Once the general maximum stress range is obtained, the general maximum stress range is compared with the standard maximum stress range, and the design steel weight is compared with the standard steel weight. If the general maximum stress range is below the standard maximum stress range (or below the standard maximum stress range) and the design steel weight is below the standard steel weight (or below the standard steel weight) (Yes in Step 108 of Figure 3), the secondary design structural model is finalized, and the longitudinal rib spacing that constitutes the secondary design structural model is determined as the "optimal longitudinal rib spacing." On the other hand, if the general maximum stress range is above the standard maximum stress range (or above the standard maximum stress range) or the design steel weight is above the standard steel weight (or above the standard steel weight) (No in Step 108 of Figure 3), the secondary design structural model is modified and analyzed again to evaluate the secondary design structural model. The secondary design structural model is then repeatedly set up (Step 106 of Figure 3) and analyzed (Step 107 of Figure 3) until the optimal longitudinal rib spacing is determined. In determining the optimum rib width, optimum deck plate thickness, and optimum vertical rib spacing, they may be changed appropriately within the cross section depending on the vehicle running position, etc.

[0031] The secondary model (i.e., steel deck) obtained through the process up to this point has a smaller total steel weight than the standard structural model, and the maximum stress range of the steel deck plate 20 is the same as or less than that of the standard structural model. Therefore, the steel deck determined by the steel deck structural design method of the present invention has reduced manufacturing and construction costs and is comparable in fatigue durability to so-called standard steel decks designed in accordance with the Highway Bridge Specifications (designed in accordance with deemed regulations).

[0032] While the secondary design structural model can be used as the final structure, a more economically rational steel deck structure can be determined by determining the appropriate transverse rib spacing (hereinafter referred to as the "optimal transverse rib spacing") and the appropriate rib height of the longitudinal ribs 30 (hereinafter referred to as the "optimal rib height"). Note that the "transverse rib spacing" here refers to the spacing between the transverse ribs 40 in the bridge axis direction, i.e., the longitudinal rib spans. In this case, a tertiary design structural model is first established (Step 109 in Figure 3). The tertiary design structural model is established by changing some of the specifications of the secondary design structural model. Specifically, the tertiary design structural model is established by changing the transverse rib spacing and the rib height of the longitudinal ribs 30 in the secondary design structural model. In other words, all specifications except for the transverse rib spacing and the rib height of the longitudinal ribs 30 are the same as those of the secondary design structural model. Note that the transverse rib spacing of the tertiary design structural model can be set to a value larger or smaller than that of the secondary design structural model, and the rib height of the longitudinal ribs 30 of the tertiary design structural model can be set to a value larger or smaller than that of the secondary design structural model.

[0033] Once the tertiary design structural model is set, an analysis is performed using the tertiary design structural model (Step 110 in Figure 3). At this time, it is advisable to perform the analysis using a framework analysis or the like. Then, the stress in the bridge axis direction that occurs in the steel deck plate 20 and the longitudinal rib 30 in the general section (hereinafter referred to as "design verification stress") is calculated.

[0034] Once the design verification stress is obtained, it is compared with the predetermined stress limit values ​​(stress range, or upper and lower limits). If the design verification stress meets the stress limit values ​​(Yes in Step 111 of Figure 3), the tertiary design structural model is finalized, and the horizontal rib spacing that makes up the tertiary design structural model is determined as the "optimum horizontal rib spacing," and the rib height of the vertical ribs 30 is determined as the "optimum rib height." On the other hand, if the design verification stress does not meet the stress limit values ​​(No in Step 111 of Figure 3), the tertiary design structural model is modified and the analysis is performed again to evaluate the tertiary design structural model. Then, the setting of the tertiary design structural model (Step 109 of Figure 3) and the analysis of the tertiary design structural model (Step 110 of Figure 3) are repeated until the optimal horizontal rib spacing and optimal rib height are determined.

[0035] It is possible to set a tertiary design structure model by appropriately changing both the horizontal rib spacing and the rib height of the vertical ribs 30, or to set a tertiary design structure model by determining the horizontal rib spacing and then appropriately changing the rib height of the vertical ribs 30, or to set a tertiary design structure model by determining the rib height of the vertical ribs 30 and then appropriately changing the horizontal rib spacing. For example, if the horizontal rib spacing needs to be reduced due to structural constraints, it is advisable to determine the horizontal rib spacing and then set the rib height of the vertical ribs 30 (which will be a small value).

[0036] By determining the optimum horizontal rib spacing and optimum rib height in this manner, it is possible to reduce the number of horizontal ribs 40 while suppressing the design verification stresses that occur in the steel deck plate 20 and vertical ribs 30, thereby achieving reductions in costs and steel weight.

[0037] As mentioned above, in an actual steel deck 10, multiple longitudinal ribs 30 are arranged in the bridge axis direction and are connected at adjacent positions in the bridge axis direction with splice plates and high-strength bolts. Therefore, even if the optimal rib width, optimal longitudinal rib spacing, and optimal rib height have been determined in the process up to this point, it is possible that the structure is such that splicing work using splice plates and high-strength bolts is not possible. If there are concerns about this splicing work, it is a good idea to actually create a test model based on the secondary design structural model (or tertiary design structural model) and perform trial splicing work.

[0038] In this case, a prototype model is first created (Step 112 in Figure 3). While the standard structural model and the design structural model (primary to tertiary design structural models) are merely models for analysis and are, in a sense, fictitious models, this prototype model is a real model created using actual steel deck plates 20 and longitudinal ribs 30. The prototype model is then created to realize the secondary design structural model (or tertiary design structural model). In other words, the prototype model is created based on the optimal rib width and optimal deck plate thickness determined based on the primary design structural model, the optimal longitudinal rib spacing determined based on the secondary design structural model, and the optimal rib height determined based on the tertiary design structural model. However, the longitudinal ribs 30 are arranged in two or more rows spaced apart in the direction perpendicular to the bridge axis, and in each row, two or more longitudinal ribs 30 are arranged in the bridge axis direction. Note that the transverse ribs 40 can be omitted from the prototype model.

[0039] To connect the vertical ribs 30, as shown in Figure 4, they are connected using splice plates PL and high-strength bolts BL (Step 113 in Figure 3). Specifically, the splice plates PL are first attached to the side panels 31 of the vertical ribs 30. Then, high-strength bolts BL are inserted from the inside of the vertical ribs 30 using handholes provided on the undersides of the vertical ribs 30. The high-strength bolts BL are then tightened using a specified tightening machine MC. This series of connecting operations is possible if the space formed between adjacent vertical ribs 30 in the direction perpendicular to the bridge axis (hereinafter referred to as "adjacent spaces") and the space inside the vertical ribs 30 (hereinafter referred to as "internal rib spaces") are wide. However, if the adjacent spaces or the internal rib spaces are narrow, this series of connecting operations cannot be performed. The size of the adjacent spaces and the internal rib spaces is highly dependent on the "side angle (Figure 2)" of the side panels 31. Therefore, if the entire jointing process can be performed (Yes in Step 114 of FIG. 3), the side angle of the longitudinal rib 30 is determined as the "optimal side angle." On the other hand, if the entire jointing process cannot be performed (No in Step 114 of FIG. 3), for example, because a tightening machine MC, welding machine, or welding deformation correction machine cannot be inserted into the adjacent space, or because a handheld high-strength bolt BL cannot be inserted into the bolt hole, a prototype model using a longitudinal rib 30 with a different (e.g., larger) side angle is fabricated, and the jointing process is performed again. Then, the fabrication of the prototype model (Step 112 of FIG. 3) and the jointing process (Step 113 of FIG. 3) are repeated until the optimal side angle is determined. This type of constructability check can be performed only on the final design structural model (secondary design structural model or tertiary design structural model), or on all design structural models (primary design structural model to tertiary design structural model). Furthermore, the load-bearing capacity of the compression stiffening plate, as conventionally performed, can also be checked.

[0040] (Example) The inventors of the present invention have actually carried out the structural design of a steel deck 10 using the steel deck structural design method of the present invention. However, structural analysis was carried out using FEM analysis. Below, we will explain two cases of steel decks 10 out of several cases obtained using the steel deck structural design method, by comparing them with a standard steel deck 10 designed in accordance with the Highway Bridge Specifications (in other words, designed in accordance with the deemed provisions of the Highway Bridge Specifications). Each case is as follows: CASE0-1: According to the old road bridge specifications, the standard thickness of the steel deck plate 20 is 12 mm. CASE0-2: According to the current road bridge specifications, the standard thickness of the steel deck plate 20 is 16 mm. CASE3-d2: A steel deck plate according to the present invention, in which the thickness of the steel deck plate 20 is 14 mm, the rib width of the vertical rib 30 is 220 mm, and the vertical rib spacing is 480 mm. CASE4-a: A steel deck plate according to the present invention, in which the thickness of the steel deck plate 20 is 12 mm, the rib width of the vertical rib 30 is 180 mm, and the vertical rib spacing is 400 mm.

[0041] Figure 5 shows the analysis results comparing the maximum stress ranges for each case. The maximum stress ranges analyzed under double and single tire conditions are shown for the rib intersections and general sections. For CASE3-d2 and CASE4-a, cross-sectional diagrams with various dimensions are also shown. Figure 6 is a graph showing the maximum stress ranges for each case, with (a) showing the rib intersections and (b) showing the general sections. In Figure 6, the results for the double tire condition are shown on the left, and the results for the single tire condition are shown on the right. As shown in these figures, the maximum stress ranges for the intersections and general sections for CASE3-d2 and CASE4-a according to the present invention are both below the standard maximum stress ranges for CASE0-1 and CASE0-2 according to the Highway Bridge Specifications. In other words, the steel decks designed using the steel deck structural design method of the present invention have comparable structural stability to standard steel decks designed according to the Highway Bridge Specifications.

[0042] Figure 7 is a steel weight comparison diagram comparing the total steel weight (shown as "steel material cost" in the diagram) for each case. As shown in this diagram, the total steel weight of CASE3-d2 and CASE4-a according to the present invention is at least lower than the total steel weight of CASE0-2 according to the current Highway Bridge Specifications. In other words, the steel decks determined by the steel deck structural design method of the present invention are more economically rational than standard steel decks designed according to the Highway Bridge Specifications. [Industrial Applicability]

[0043] The steel deck structural design method of the present invention can be used for various bridges, including viaducts on urban expressways, bridges over rivers or oceans, overpasses over roads, and overpasses over railway tracks. It can be used not only for new bridges, but also when replacing existing decks. Considering that the present invention can provide safer traffic and extend the service life of bridges, it can be said to be an invention that can be expected to not only be used industrially but also to make a significant contribution to society. [Explanation of symbols]

[0044] 10 Steel deck slab 20 Steel deck plate (for steel deck) 30 (Steel deck) vertical rib 31 (Vertical rib) side panel 32 (vertical rib) bottom plate 40 (Steel deck) horizontal rib 50 Main digit 60 Pavement 70 Earth Cover BL high strength bolt MC tightening machine MD prototype model PL attachment plate

Claims

1. A method for determining the structure of a steel deck of a road bridge, comprising: The steel deck plate is configured to include a steel deck plate, a vertical rib having a closed cross section, and a horizontal rib, a standard model analysis process for calculating the standard maximum stress range generated in the steel deck plate and the standard steel weight, which is the sum of the steel weights related to the standard structural model, by performing an analysis using a standard structural model including a standard closed cross-section rib selected from U-320x240x6, U-320x260x6, U-320x240x8, or U-320x260x8, the steel deck plate having a predetermined standard plate thickness, and the transverse rib; a primary design structural model setting process for setting a primary design structural model by changing the standard structural model to the vertical rib having a rib width smaller than that of the standard closed cross-section rib and changing the steel deck plate to a thinner plate thickness than that of the standard plate; a rib width determination process for performing an analysis using the primary design structural model, calculating a maximum stress range at an intersection where the longitudinal rib and the transverse rib intersect in the steel deck plate, and determining an optimum rib width of the longitudinal rib and an optimum deck plate thickness of the steel deck plate, on the condition that the maximum stress range at the intersection is below the standard maximum stress range; a secondary design structural model setting process for setting a secondary design structural model by changing the spacing of the longitudinal ribs from the primary design structural model to a spacing that is smaller than the spacing of the longitudinal ribs in the primary design structural model; a longitudinal rib spacing determination process for performing an analysis using the secondary design structural model, calculating a general portion maximum stress range that occurs in the steel deck plate in a general portion where the longitudinal ribs and the transverse ribs do not intersect, and calculating a design steel weight that is the sum of steel weights related to the secondary design structural model, and determining an optimum longitudinal rib spacing for the longitudinal ribs under the conditions that the general portion maximum stress range is below the standard maximum stress range and the design steel weight is below the standard steel weight, The standard maximum stress range, the intersection maximum stress range, and the general maximum stress range are the differences between the maximum stress and the minimum stress generated in the steel deck plate, The primary design structural model setting step and the rib width determination step are repeated while changing the rib width of the vertical rib and the plate thickness of the steel deck plate until the optimal rib width and the optimal deck plate thickness are determined; repeating the secondary design structural model setting step and the longitudinal rib spacing determination step while changing the longitudinal rib spacing until the optimum longitudinal rib spacing is determined; A steel deck structural design method characterized by the above.

2. a third-order design structural model setting process for setting a third-order design structural model by changing the spacing between the horizontal ribs and changing the rib height of the vertical ribs from the second-order design structural model; and a rib height determination step of performing an analysis using the tertiary design structural model, calculating design verification stresses occurring in the steel deck plate and the longitudinal ribs in the general section, and determining the optimum transverse rib spacing of the transverse ribs and the optimum rib height of the longitudinal ribs on the condition that the design verification stresses satisfy a predetermined stress limit value. The design verification stress is the stress in the bridge axis direction generated in the steel deck plate or the longitudinal rib, repeating the third design structural model setting step and the rib height determination step while changing the interval between the horizontal ribs and the rib height of the vertical ribs until the optimum horizontal rib interval and the optimum rib height are determined; 2. The steel deck structural design method according to claim 1.

3. a prototype model fabrication process for fabricating a prototype model comprising the steel deck plate and two or more of the longitudinal ribs arranged side by side in the bridge axis direction, based on the specifications of the secondary design structural model in which the optimal longitudinal rib spacing has been determined; A joint test process in which the vertical ribs arranged in the bridge axis direction are joined using splice plates and high-strength bolts, utilizing the spaces formed by the vertical ribs arranged in the direction perpendicular to the bridge axis in the prototype model; and a side angle determination step of determining an angle of a side plate of the longitudinal rib as an optimal side angle, provided that the longitudinal rib can be joined in the joint test step. When the longitudinal rib cannot be joined in the joint test step, the angle of the side plate of the longitudinal rib is changed and the prototype model is newly produced, The prototype model fabrication step, the joint test step, and the side angle determination step are repeated while changing the angle of the side plate of the vertical rib until the optimal vertical rib spacing is determined.

2. The steel deck structural design method according to claim 1.

4. In the standard model analysis step, the standard plate thickness is set to 12 mm or 16 mm, and analysis is performed using the standard structural model.

2. The steel deck structural design method according to claim 1.

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