JP2005076339A - Structural analysis method of steel concrete composite structure and composite structure designed by using this method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform rational and highly accurate design on a steel concrete composite structure of forming a steel structure and a reinforced concrete structure into an integral structure, by using a nonslip means such as a stud bolt on a contact plane. <P>SOLUTION: In this structural analysis method of the steel concrete composite structure formed by joining a steel structure part and a reinforced concrete structure part via the dislocation preventive means such as the stud bolt, a rigid beam element 13 is arranged up to a contact plane position from a joining nodal point 19 of respective beam elements, in a nonslip position between a beam element 11A set along the axis of the steel structure part and a beam element 12 set along the axis of the reinforced concrete structure part. An analytical model is set by connecting both nodal points by adding a shearing spring element 20 between the nodal points by setting a tip nodal point 14 of the respective beam elements 13 as a double nodal point in nodal point coordinates of the nonslip means position. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a structural analysis method for a steel-concrete composite structure, and in particular, a steel concrete composite structure in which a steel structure and a reinforced concrete structure are integrated by using a locking means such as a stud bolt on a joint surface. The present invention relates to a structural analysis method for a steel-concrete composite structure set by performing an analysis model that can be designed, and a composite structure designed using the method.

  The underground outer wall structure that uses the core material of the continuous underground wall of the columnar column constructed as a temporary retaining wall for foundation excavation as part of the main body structure built in the interior space reduces construction costs and makes effective use of the site There are cases where it is advantageous in view of the above, and the number of cases adopted for reinforced concrete underground structures is increasing. 5 and 6 are partial cross-sectional views showing an example of a conventional underground outer wall structure 50 of this type. As shown in both figures, the columnar continuous underground wall 51 is formed at a predetermined pitch in the wall body extending direction so that the tip 51a reaches the support layer 52, and has a narrow width H shape as a core material. Steel (steel material) 53 is embedded in each wall (see FIG. 6). On the flange outer surface 53a of the H-shaped steel 53 on the main body structure side, stud bolts (hereinafter simply referred to as studs) 54 are implanted at a predetermined pitch in the depth direction of the core material (H-shaped steel). The stud 54 is embedded in a reinforced concrete housing 55 that is a main body structure, and the steel material 53 and the reinforced concrete housing 55 are integrated.

  By the way, in the design of the composite structure that uses the core material of the continuous underground wall like the above-mentioned underground outer wall structure and integrates steel and reinforced concrete, the composite cross-section considering the rigidity and dimensions of different components The plane frame analysis model having the above is set, and the conversion member characteristics per unit width (e.g., corresponding to the H-section steel placement interval) are set to perform the structural analysis. The obtained cross-sectional force is distributed according to a coefficient determined by the rigidity ratio of each member constituting the composite structure, and the cross-sectional design of walls and beams per unit width is performed. At this time, the steel material and the reinforced concrete show an integral behavior with respect to the external force due to an anti-slip member such as a stud (shear resistance member, shear connector) provided on the joint surface, but mechanical evaluation of this stud is difficult. For this reason, for example, even when studs are arranged at different pitches in the depth direction, modeling of uniform arrangement in the depth direction has been performed.

  Further, there is Non-Patent Document 1 as a design guideline showing a design method of a steel-concrete composite structure using a retaining wall whose main body is an H-shaped steel such as the above-described underground outer wall structure.

Edited by Japan Tunneling Technology Association, “Guide for using retaining wall with H-shaped steel core”, published in July 2002

For example, it is known that the conventional design that is designed by using the above-described analysis method or that conforms to a design guideline (for example, Non-Patent Document 1) has the following problems.
(1) In order to evaluate the distribution of the cross-sectional force for each member of steel and reinforced concrete from the rigidity of the composite structure as a whole, based on the total number of studs and other non-slip members and the joint area, A rational shift preventing member cannot be designed according to the state of occurrence of the cross-sectional force of each part. For this reason, since it is premised on the member arrangement of the safety side design, the design must be uneconomical.
(2) No structural analysis method has been established for specially shaped parts such as joints and corners between different members in a composite structure.
(3) The above design guideline presupposes design in the elastic region. On the other hand, in order to confirm the safety of a structure in consideration of an earthquake (for example, assuming a level 2 earthquake), it is necessary to perform nonlinear analysis for grasping the elastoplastic behavior of the structure. In this case, in steel structures and reinforced concrete structures, design methods applying nonlinear characteristics have been established in each design standard based on past cases, but in structural analysis of steel-concrete composite structures using studs, The stud has not been properly evaluated.

  In addition, in the case of a steel-concrete composite structure with a complex shape, it is important to set the working load appropriately and to select the structural analysis method and analysis model in order to accurately obtain the generated sectional force at the time of loading. is there. Hereinafter, an example of setting an analysis model will be described, and problems in each modeling will be shown. FIG. 7 is a cross-sectional view of the tunnel widening portion 60 showing a cross section of a section where the shield tunnels 70 and 71 merge with the side surface of the RC two-story reinforced concrete frame 65. As shown in the figure, the tunnel widening portion 60 is formed by removing a part of the steel shells (steel segments) 72 of the two shield tunnels 70 and 71 excavated at a predetermined distance in the vertical direction. A shear resistance member such as a joint rebar or a reinforcing plate and a tensile resistance member (not shown) joined to the outer surface 72a of the double flange constituting the 72 using a mechanical joint are provided on each slab (top) of the reinforced concrete frame 65. Plate, bottom plate, and intermediate floor) and are joined together.

  As an analysis model for designing the tunnel widening portion, a plane frame beam element set along the axis of the target structure is generally used (see FIG. 8A). Since this analysis model is easy to model and calculate, it can be used for schematic design. However, the behavior of the joint 61 between the steel shell 72 and the concrete frame 65 as shown in FIG. Therefore, it is impossible to design the cross section of the joint 61 in detail.

  On the other hand, as an analysis that reflects the properties of an actual structure and obtains a highly accurate analysis result, a finite element using a solid element considering the thickness and shape of each member as shown in FIG. There is an element method analysis. According to this analysis model, it is possible to properly grasp the stress state of the entire target structure, but it is necessary to create detailed and enormous element data because the joint reinforcement used in the joint is also made into an element. In some cases, analysis calculation takes a long time. To simplify the analysis model, it is possible to set an analysis model in which the steel shell part is a beam element and the concrete frame part is a solid element. However, because the double flange flange height of the steel shell cannot be taken into account at the joint, Therefore, there is a problem that accurate modeling considering various shear resistance members cannot be performed. Therefore, the object of the present invention is to solve the problems of the prior art described above, and a steel-concrete composite structure that has been modeled so that the behavior of the shear resistance member at the joint between the steel structure and the reinforced concrete structure can be accurately reproduced. And a synthetic structure designed by using this structural analysis method.

  In order to achieve the above object, the present invention relates to a structural analysis method for a steel-concrete composite structure in which a steel structure portion and a reinforced concrete structure portion are joined via a shear resistance member, along the axis of the steel structure portion. In the installation position of the shear resistance member between the set beam element and the beam element set along the axis of the reinforced concrete structure portion, a rigid beam element is provided from the joint node of each beam element to the joint surface position, Set the analysis model that connects the two joints by adding a shear spring element between the joints as the joints of the joints of the tip of each rigid beam element as separate joints at the joint coordinates of the installation position of the shear resistance member. Analytical calculation from the elastic region to the elastoplastic region is performed.

  The steel structure part is a core material of a columnar continuous underground wall, the reinforced concrete structural part is a concrete frame constructed in a retaining space of the columnar continuous underground wall, and as the shear resistance member, It is preferable that a stud bolt is melt-planted on the mountain retaining space side of the core material.

  The steel structure part is a steel shell of a shield tunnel, and the reinforced concrete structure part is a reinforced concrete frame constructed at a position where a part of the steel shell merges with a part of the frame according to the excavation of the shield tunnel. In addition, as the shear resistance member, it is preferable that a joining reinforcing bar is arranged on the reinforced concrete frame side of the flange of the steel shell.

  It is preferable that the rigid beam element is a rigid member having a remarkably large bending rigidity including the joint node, and is a member that is arranged perpendicular to each beam element and in which axial expansion and contraction is restricted.

  It is preferable that the shearing spring element has an analytical value by obtaining member characteristics in an elastic region and an elastic-plastic region by a shear experiment.

  A steel-concrete composite structure formed by joining a steel structure part and a reinforced concrete structure part via a shear resistance member, wherein the beam element set along the axis of the steel structure part and the reinforced concrete structure part A rigid beam element is provided from the joint node of each beam element to the joint surface position at the installation position of the shear resistance member between the beam element set along the axis and the tip node of each rigid beam element is sheared. Set up an analysis model that connects both nodes by adding a shear spring element between the nodes as separate nodes in the node coordinates of the installation position of the resistance member, and analyze from the elastic region to the elasto-plastic region when a predetermined load is applied It features a composite structure designed by calculation.

  The steel structure part is a core material of a columnar continuous underground wall, the reinforced concrete structural part is a concrete frame constructed in a retaining space of the columnar continuous underground wall, and as the shear resistance member, It is preferable that the core material has a steel-concrete composite structure in which stud bolts are fused on the mountain retaining space side.

  Further, the steel structure part is a steel shell of a shield tunnel, and the reinforced concrete structure part is a reinforced concrete constructed at a position where a part of the steel shell joins a part of the housing in accordance with the excavation of the shield tunnel. It is a frame, and it is preferable that the shear resistance member has a steel-concrete composite structure in which joining reinforcing bars are arranged on the reinforced concrete frame side of the flange of the steel shell.

  According to the above-described invention, by setting a comparatively simple analysis model, it is possible to appropriately evaluate the shear resistance member used in the joint portion of the steel-concrete composite structure to be analyzed, and the actual properties of the structure. It is possible to obtain a highly accurate analysis result reflecting the above, and to perform an appropriate design of the steel-concrete composite structure to be designed.

  Hereinafter, the present invention will be described based on examples with reference to the drawings.

[Structure of analysis model]
As Example 1, the underground outer wall structure 50 described above is modeled with reference to FIG. 5 and the characteristics of the analysis model will be described. The analysis model 10 is a full-section model in order to apply a horizontal load at the time of an earthquake. However, since the structure is symmetrical, only the right half section is shown in FIG. As shown in the figure, the analysis model 10 basically includes beam elements 11A and 11B set along the axis of a concrete frame made of a reinforced concrete structure, and the axis of an H-shaped steel as a core material. The beam element 12 is set. The beam element 11B corresponding to the bottom plate of the concrete frame and the beam element 12 of the shaped steel corresponding to the outer wall are ground spring elements having spring constants (K _hi , K _v ) set based on the ground characteristics of the surrounding ground. It is supported by.

  Further, a shear spring element 20 (indicated by a circle in FIG. 1) is added to the installation position (depth) of the shear resistance member as a detent that is fixed to the H-shaped steel flange. As shown in FIG. 2, the shear spring element 20 has a reinforced concrete beam element 11 </ b> A and a joint surface position (a surface position where the reinforced concrete and the H section steel are in contact with each other). Is provided between the distal end nodes 14 and 14 of each rigid beam element 13 extended to the surface of the H-shaped steel to be implanted. In other words, the distal end portion (the distal end node 14) of the rigid beam element 13 joined to the reinforced concrete side and the H-shaped steel side at the joining node 19 of each beam element is set as a double node having the same coordinates. A spring element 20 having a shear rigidity of a stud planted at a node position as a member characteristic is arranged.

  The rigid beam element 13 is set as a rigid member in which expansion and contraction in the member direction is restricted when a load is applied, and the bending rigidity including the joint node 19 with the beam elements 11A and 12 is extremely large. The tip nodes 14 and 14 are behaviors of the joint surface position where the reinforced concrete side stud targeted for the beam element 11A is implanted and the joint surface position where the stud H side steel targeted for the beam element 12 is implanted. Is accurately reflected.

  In the present embodiment, the analysis value of the shear spring element is obtained by conducting a shear test on the assumed load direction of the stud (φ16, L = 120 mm) which has been welded to the flange of the steel material at a predetermined pitch, and the elastic-plastic property as the shear resistance member. The member characteristic value (trilinear type) that grasped the above was used. The nonlinear characteristics of reinforced concrete and H-shaped steel (material characteristics in the elasto-plastic region) both take into account the axial compression state due to their own weight, and the reinforced concrete part conforms to the road bridge specifications (concrete bridge edition). Given in relation to -φ. The H-shaped steel part was given by a bilinear M-φ relationship with the flange yield point as the break point.

[Evaluation of analysis results]
The set analysis value was evaluated by comparing the load-displacement (P-δ) relationship between the one-point loading bending test using a composite beam test specimen simulating an actual structure and the analysis result. In the elastic region, the elastic stiffness according to the analysis value of the composite beam is slightly larger than the experimental value (secant stiffness in the long-term allowable stress), and the result almost coincides with the theoretical formula described in Non-Patent Document 1. Moreover, according to the elasto-plastic analysis result (P-δ relation), it was confirmed that the behavior at the time of the experiment could be well reproduced for the non-linear region up to the vicinity of the yield point.

  As Example 2, the steel-concrete composite structure (FIG. 7) in the tunnel widening portion 60 described above is modeled, and the characteristics of the analysis model will be described. In this analysis model, as shown in the figure, the side wall of the reinforced concrete housing 65 has an underground outer wall structure. Therefore, similarly to the case shown in the first embodiment, the reinforced concrete housing 65 and the H-shaped steel 62 are composed of two parallel linear beam elements 15 and 16 each having a continuous beam element, a steel shell 72 and each slab. Two curved beam elements 17 and 18 simulating a joint with (top plate, bottom plate, intermediate floor) are set, and each two beam elements (15, 16), (17, 18) The rigid beam elements 13 are joined to the respective beam elements at positions corresponding to the installation positions of the joint members, the joint reinforcing bars as the shear resistance members, and the reinforcing plates (not shown), and the distal end nodes of the rigid beam elements 13 14 and 14 are the double nodes having the same coordinates, and the shear spring element 20 is disposed between them (see FIG. 3). In the drawing, the arrangement position of the shear spring element 20 is indicated by a circle. As shown in FIG. 4, each rigid beam element 13 is arranged between two bent beams, restrains expansion and contraction in the member direction when a load is applied, and remarkably has bending rigidity including a joint node 19 with the beam element. It is set as a large rigid member. The tip nodes 14 and 14 accurately reflect the behavior of the joint surface position between the reinforced concrete and the H-shaped steel or the reinforced concrete and the steel shell as the target of each beam element 1.

  In this embodiment, the elasto-plastic properties of the joint rebar (D51, @ 250 mm), which are arranged through a mechanical joint at a predetermined pitch in the double flange of the steel shell 65, are grasped and the analysis input value is obtained. Used as (trilinear type). In addition, as in Example 1 above, the nonlinear properties of reinforced concrete and steel shells (material properties in the elasto-plastic zone) both take into account the axial compression state due to their own weight, and the reinforced concrete part is in the road bridge specifications (concrete bridge edition). Based on the trilinear M-φ relationship. The H-shaped steel part was given by a bilinear M-φ relationship with the flange yield point as the break point.

[Evaluation of analysis results]
The evaluation of the set analysis value of the shear spring element at the joint is performed by analyzing the analysis result of the analysis model using the solid element shown in FIG. 8B and the beam element, shear spring element, and rigid beam element shown in FIG. The comparison was made with a synthetic element model. As a result of comparing the cross-sectional force in the cross-section change part (bb) of the reinforced concrete part (aa) and the steel shell and the reinforced concrete at both ends of the joint part, in the (aa) part, the steel shell continuous to the joint part is As a result of acting as a thick-walled shell, it was confirmed that the end moment on the steel shell side of the joint was reduced by about 20% compared to the case where it was replaced with a solid element. Therefore, in the case of the analysis model using the above-described composite element, the steel shell side joint is designed on the safe side, and can be designed in consideration of an appropriate reduction coefficient. In the (bb) part, equivalent results were obtained in both analyses.

  In setting the analysis model, a steel shell and reinforced concrete as shown in FIG. 8B constitute a whole analysis model by solid elements, the installation position of the shear resistance member is a double node, and the corresponding 2 It is also possible to set an analysis model in which the above-described shear spring element is added to the double node.

  Moreover, as a shear resistance member (slipping prevention member) provided on the joint surface between the steel material and the concrete in the steel-concrete composite structure, in addition to the above-described stud, a rebar-processed product, a shaped steel plate-processed product, various shape divels, and the like are used. be able to. Therefore, it is important to grasp the member characteristics of each member used at the time of analysis based on various shear tests, past data, and the like that reproduce an actual joint.

The whole analysis model figure showing one example of the analysis model used for the design method by the present invention. Fig. 3 is an enlarged view of an analysis model at a joint between a core shape steel and a reinforced concrete portion. The whole analysis model figure showing other examples of the analysis model used for the design method by the present invention. An enlarged view of the analysis model at the joint between the steel shell and the reinforced concrete part. Structural sectional drawing which showed an example of the underground outer wall structure. The fragmentary sectional view shown along the VI-VI sectional line of the underground outer wall structure shown in FIG. The structure sectional view showing an example of the tunnel widening part constituted by the shield tunnel joining the reinforced concrete frame. FIG. 8 is an overall view of an analysis model of the tunnel widening portion shown in FIG. 7 (by (a) beam element, (b) solid element).

Explanation of symbols

10 Analysis models 11A, 11B, 12, 15, 16, 17, 18 Beam element 13 Rigid beam element 14 Tip node (double node)
19 joint node 20 shear spring element 50 underground outer wall structure 60 tunnel widening part

Claims (8)

In the structural analysis method of a steel-concrete composite structure in which a steel structure part and a reinforced concrete structure part are joined via a shear resistance member,
Joined from the joint node of each beam element to the installation position of the shear resistance member between the beam element set along the axis of the steel structure portion and the beam element set along the axis of the reinforced concrete structure portion A rigid beam element is provided up to the surface position, and the tip node of each rigid beam element is connected as a separate node in the node coordinates of the installation position of the shear resistance member, and a shear spring element is added between the nodes to connect both nodes. A structural analysis method for a steel-concrete composite structure characterized in that an analytical model is set and analytical calculation is performed from an elastic region to an elasto-plastic region when a predetermined load is applied.   The steel structure part is a core material of a columnar continuous underground wall, the reinforced concrete structural part is a concrete frame constructed in a retaining space of the columnar continuous underground wall, and as the shear resistance member, The structural analysis method for a steel-concrete composite structure according to claim 1, wherein stud bolts are fused on the side of the retaining space of the core material.   The steel structure part is a steel shell of a shield tunnel, and the reinforced concrete structure part is a reinforced concrete frame constructed at a position where a part of the steel shell merges with a part of the frame according to the excavation of the shield tunnel. 2. The structural analysis method for a steel-concrete composite structure according to claim 1, wherein as the shear resistance member, joint reinforcing bars are arranged on the reinforced concrete frame side of the flange of the steel shell.   The structural analysis method for a steel-concrete composite structure according to claim 1, wherein the rigid beam element is a member that is set as a rigid member including the joint node and in which expansion and contraction in the axial direction is constrained.   2. The structural analysis method for a steel-concrete composite structure according to claim 1, wherein the shear spring element is obtained by obtaining a member characteristic in an elastic region and an elasto-plastic region by a shear experiment and using it as an analysis input value. It is a steel concrete composite structure formed by joining a steel structure part and a reinforced concrete structure part via a shear resistance member,
Joined from the joint node of each beam element to the installation position of the shear resistance member between the beam element set along the axis of the steel structure portion and the beam element set along the axis of the reinforced concrete structure portion A rigid beam element is provided up to the surface position, and the tip node of each rigid beam element is connected as a separate node in the node coordinates of the installation position of the shear resistance member, and a shear spring element is added between the nodes to connect both nodes. A steel-concrete composite structure characterized by setting an analytical model and designing by analytical calculation from the elastic region to the elasto-plastic region when a predetermined load is applied.   The steel structure part is a core material of a columnar continuous underground wall, the reinforced concrete structural part is a concrete frame constructed in a retaining space of the columnar continuous underground wall, and as the shear resistance member, The steel-concrete composite structure according to claim 6, wherein stud bolts are fused on the side of the mountain retaining space of the core material.   The steel structure part is a steel shell of a shield tunnel, and the reinforced concrete structure part is a reinforced concrete frame constructed at a position where a part of the steel shell merges with a part of the frame according to the excavation of the shield tunnel. 7. The steel-concrete composite structure according to claim 6, wherein as the shear resistance member, a joining reinforcing bar is arranged on the side of the reinforced concrete frame of the flange of the steel shell.

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