Mix-structured beam
The mixed structure beam addresses the vulnerability to external forces by integrating precast concrete members and a frictional force adjustment mechanism, reducing damage and repair needs during earthquakes through controlled slip and maintained frictional forces.
Patent Information
- Application Number
- JP2023178601
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-10-17
- Publication Date
- 2025-04-30
AI Technical Summary
Mixed structure beams are prone to damage at the root wound and beam-column joints when excessive external forces, such as those from earthquakes, are applied, leading to potential structural failure and prolonged repair periods.
The mixed structure beam incorporates a steel beam with precast concrete members attached along its longitudinal ends and a frictional force adjustment mechanism. This mechanism allows for controlled relative slip between the precast concrete members and the steel beam under excessive seismic forces, thereby reducing stress and potential damage.
The solution effectively reduces damage to the mixed structure beam during earthquakes by allowing controlled slip and stress release, while maintaining frictional forces to ensure vibration-damping effects post-earthquake, thus minimizing repair needs.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a mixed construction beam. [Background technology]
[0002] As a beam to be erected between columns of reinforced concrete construction, a mixed structure beam is known in which a reinforced concrete wrapping section is provided at the end of a steel beam that surrounds the steel beam, and this wrapping section is joined to a column (beam-column joint) of reinforced concrete construction (see, for example, Patent Document 1). Such a mixed structure beam has higher rigidity and smaller deflection than a beam made only of steel beams due to the reinforced concrete wrapping section surrounding the end of the steel beam, so that deformation of the structure during an earthquake can be reduced. In addition, since the steel beam is joined to the column of reinforced concrete construction via the reinforced concrete wrapping section surrounding the steel beam, processing and welding of the steel beam is not required, which reduces costs. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] Patent No. 4029339 Summary of the Invention [Problem to be solved by the invention]
[0004] In the case of the above-mentioned mixed structural beams, when an excessive external force is applied due to an earthquake or the like, the shear force acting on the steel beams may damage the reinforced concrete lining and the beam-column joints. If the lining and the beam-column joints are damaged, repairs are required on a large scale, and the use of the building may be restricted during the repair period.
[0005] Therefore, an object of the present invention is to provide a mixed structural beam that can reduce damage when an excessive external force is applied due to an earthquake or the like. [Means for solving the problem]
[0006] In order to achieve the above-mentioned object, the mixed structural beam of the present invention comprises a steel beam, a precast concrete member arranged along the outer peripheral surface at the longitudinal end of the steel beam, and a fixing member that presses and fixes the precast concrete member against the steel beam, wherein the reinforcing bars of the precast concrete member are fixed to a reinforced concrete column, and the fixing member has a friction adjustment mechanism that can adjust the force pressing the precast concrete member against the steel beam to adjust the friction force between the precast concrete member and the steel beam, and the friction adjustment mechanism sets the friction force between the precast concrete member and the steel beam so that when an earthquake force of a predetermined magnitude or less acts on the steel beam, no relative slip occurs between the precast concrete member and the steel beam, and when an earthquake force exceeding the predetermined magnitude acts on the steel beam, a relative slip occurs between the precast concrete member and the steel beam.
[0007] In this invention, when an excessive earthquake causes a seismic force exceeding a predetermined magnitude to act on the steel beams, relative slip occurs between the precast concrete members and the steel beams, and the stress between the precast concrete members and the steel beams is released, thereby reducing damage to the precast concrete members. Even after the seismic force acts, the friction force between the precast concrete members and the steel beams can be maintained at the initially set value, so the vibration control effect can be maintained even after the earthquake. As a result, repair work after an earthquake can be reduced.
[0008] In the mixed structural beam of the present invention, the precast concrete members are arranged in a pair at opposing positions across the steel beam, the fixing member has a pair of fixing steel members arranged at opposing positions across the pair of precast concrete members, and a bolt and a nut for fixing the pair of fixing steel members together, and the friction force adjustment mechanism may adjust the axial force of the bolt by adjusting the tightening force of the nut, thereby adjusting the force with which the precast concrete member is pressed against the steel beam, and adjust the friction force between the precast concrete member and the steel beam.
[0009] With this configuration, the friction force between the precast concrete member and the steel beam can be easily adjusted.
[0010] In the mixed structural beam of the present invention, the precast concrete members may be a pair of first precast concrete members arranged along the upper surface of the upper flange and the lower surface of the lower flange of the steel beam, respectively, and the fixing member may be a first fixing member that fixes the pair of first precast concrete members to each other and presses them against the upper surface of the upper flange and the lower surface of the lower flange.
[0011] With this configuration, the mixed structural beam has higher rigidity at the longitudinal end (where the first precast concrete member is provided) than a steel beam alone, resulting in less deflection and reducing structural deformation during an earthquake.
[0012] In addition, in the mixed structural beam of the present invention, the precast concrete members may be the pair of first precast concrete members and a pair of second precast concrete members arranged along each of both sides of the web of the steel beam and each joined to the columns, and the fixing members may be the first fixing members and second fixing members that press and fix the pair of second precast concrete members against the sides of the web.
[0013] A mixed structural beam has a first precast concrete member provided along the upper surface of the upper flange and the lower surface of the lower flange at the longitudinal end of the steel beam, which increases the rigidity of the longitudinal end of the mixed structural beam (where the first precast concrete member is provided) compared to a steel beam alone, thereby reducing deflection and reducing structural deformation during an earthquake. A mixed structural beam has a second precast concrete member provided along both sides of the web of the steel beam, which prevents lateral buckling of the steel beam. The first and second precast concrete members can be used as fire-resistant covering materials for the longitudinal ends of the steel beam. Effect of the Invention
[0014] According to the present invention, damage caused when an excessive external force is applied due to an earthquake or the like can be reduced. [Brief description of the drawings]
[0015] [Figure 1] FIG. 1 is a side view of a mixed construction beam according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a plan view of a mixed construction beam according to an embodiment of the present invention. [Diagram 3] 2 is a cross-sectional view taken along line AA in FIG. 1. [Figure 4] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Diagram 5] FIG. [Figure 6] This is a graph showing the distribution of friction coefficients between concrete and steel beams in the axial direction (length direction) of the root wrapping member, estimated from the test results. [Figure 7] 13 is a graph showing the distribution of friction coefficient between a precast concrete member and a steel beam in the longitudinal direction obtained by the friction adjustment mechanism in the mixed structural beam according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Hereinafter, a mixed structural beam according to an embodiment of the present invention will be described with reference to FIGS. A mixed structural beam 1 according to this embodiment shown in Figures 1 and 2 is erected between reinforced concrete columns 2. The mixed structural beam 1 extends horizontally. Figures 1 and 2 show a state in which a mixed structural beam 1 is joined to each side of one column 2. In explaining the mixed structural beam 1, the direction in which the mixed structural beam 1 extends (the direction of arrow A in the drawings) is referred to as the length direction. The horizontal direction perpendicular to the length direction (the direction of arrow B in the drawings) is referred to as the width direction.
[0017] The mixed structural beam 1 has a steel beam 3, a first precast concrete member 4, a first fixing member 5, a second precast concrete member 6, and a second fixing member 7. The steel beam 3 is, for example, a shaped steel such as an H-shaped steel or an I-shaped steel. The end face in the longitudinal direction of the steel beam 3 faces the side surface 2a of the column 2. The end portion 3a in the longitudinal direction of the steel beam 3 is not inserted inside the column 2 (column-beam joint).
[0018] The first precast concrete member 4 shown in FIG. 1 to FIG. 4 is made of precast concrete. The first precast concrete member 4 is formed in a flat plate shape. The first precast concrete member 4 is provided along the upper surface 31a of the upper flange 31 and the lower surface 32a of the lower flange 32 at the end 3a in the longitudinal direction of the steel beam 3. The two first precast concrete members 4 are arranged in a state in which the steel beam 3 is sandwiched from above and below. The two first precast concrete members 4 have approximately the same shape. The two first precast concrete members 4 are joined to each other by a first fixing member 5. The first precast concrete member 4 on the upper side of the steel beam 3 is pressed against the upper surface 31a of the upper flange 31. The first precast concrete member 4 on the lower side of the steel beam 3 is pressed against the lower surface 32a of the lower flange 32. As shown in FIG. 3 and FIG. 4, the width dimension of the first precast concrete member 4 is the same as the width dimensions of the upper flange 31 and the lower flange 32. A widthwise end face 4a of the first precast concrete member 4 is disposed substantially flush with widthwise end faces 31b, 32b of the flanges 31, 32.
[0019] The concrete portion of the first precast concrete member 4 is referred to as the concrete portion 41, and the reinforcing bar embedded in the concrete portion 41 is referred to as the reinforcing bar 42. The concrete portion 41 is flat. The reinforcing bar 42 protrudes from the end surface 41a of the concrete portion 41 on the column 2 side and is inserted into the column beam joint 8. In this embodiment, the reinforcing bars 42 of the first precast concrete members 4 of the mixed structural beams 1 facing each other across the column 2 are connected to each other at the column beam joint 8 by mechanical joints or the like. The reinforcing bars 42 of the first precast concrete members 4 are fixed to the concrete of the column beam joint 8. Note that, when the reinforcing bars 42 of the first precast concrete members 4 of the mixed structural beams 1 facing each other across the column 2 can be secured to a predetermined fixed length within the column 2, these reinforcing bars 42 do not have to be connected to each other within the column 2 by mechanical joints or the like.
[0020] The second precast concrete member 6 is made of precast concrete and formed in a flat plate shape. The second precast concrete member 6 is provided along both side surfaces 33a of the web 33 at the longitudinal end 3a of the steel beam 3. The two second precast concrete members 6 are arranged so as to sandwich the web 33 in the width direction. The two second precast concrete members 6 are fixed by the second fixing members 7 so as to be pressed against the side surfaces 33a of the web 33. The height dimension of the second precast concrete member 6 is the same as the height dimension of the web 33. The thickness dimension (width dimension) of the second precast concrete member 6 is approximately the same as the dimension from the side surface 33a of the web 33 to the widthwise end faces 31b, 32b of the flanges 31, 32. A surface 6a (hereinafter referred to as the outer surface 6a) opposite the side facing the web 33 of the second precast concrete member 6 fixed to the steel beam 3 is disposed approximately flush with the widthwise end faces 31b, 32b of the flanges 31, 32. The longitudinal dimension of the second precast concrete member 6 is the same as the longitudinal dimension of the first precast concrete member 4.
[0021] The second precast concrete member 6 has a flat plate shape.
[0022] As shown in FIG. 3, the first fixing member 5 has a pair of first fixing steel members 51, 51, a bolt 52, and a nut 53. The pair of first fixing steel members 51 is a long steel plate. The pair of first fixing steel members 51 has a plate surface facing the vertical direction and is provided along the upper surface 4b of the upper first precast concrete member 4 and the lower surface 4c of the lower first precast concrete member 4 in a direction extending in the width direction. The dimension in the width direction of the first fixing steel member 51 is larger than the dimension in the width direction of the first precast concrete member 4. The end portion 51a in the width direction of the first fixing steel member 51 is disposed outside the end surface 4a in the width direction of the first precast concrete member 4. At the positions of both ends 51a in the width direction of the first fixing steel member 51 that do not overlap with the first precast concrete member 4 in the vertical direction, a hole portion 511 into which the bolt 52 is inserted is formed.
[0023] The bolt 52 is a rod-shaped long screw such as a PC steel bar. The bolt 52 is inserted into the hole 511 of each of the upper and lower first fixing steel materials 51 in a posture extending in the vertical direction. A nut 53 is fastened to the bolt 52 at a position of an upper surface 51b of the upper first fixing steel material 51, and a nut 53 is fastened to the bolt 52 at a position of a lower surface 51c of the lower first fixing steel material 51. The axial force (tension) of the bolt 52 is adjusted by adjusting the tightening force of the nut 53. By fastening the nut 53 to the bolt 52, the first precast concrete member 4 on the upper side of the steel beam 3 is pressed against the upper flange 31 of the steel beam 3, and the first precast concrete member 4 on the lower side of the steel beam 3 is pressed against the lower flange 32 of the steel beam 3.
[0024] The frictional force between the first precast concrete member 4 and the upper flange 31 and the frictional force between the first precast concrete member 4 and the lower flange 32 can be adjusted by adjusting the axial force of the bolt 52 by adjusting the tightening force of the nut 53 and adjusting the force with which the first precast concrete member 4 is pressed against the upper flange 31 and the lower flange 32. In this way, the mechanism for adjusting the frictional force between the first precast concrete member 4 and the upper flange 31 and the frictional force between the first precast concrete member 4 and the lower flange 32 by adjusting the tightening force of the nut 53 and the axial force of the bolt 52 to adjust the force with which the first precast concrete member 4 is pressed against the upper flange 31 and the lower flange 32 corresponds to a frictional force adjustment mechanism.
[0025] A plurality of first fixing members 5 are provided across the entire length of the pair of first precast concrete members 4,4 at intervals in the longitudinal direction of the pair of first precast concrete members 4,4.
[0026] The friction force between the first precast concrete member 4 and the steel beam 3 is set so that when an earthquake force of a predetermined magnitude or less acts on the steel beam 3, no relative slip occurs between the first precast concrete member 4 and the steel beam 3, and when an earthquake force exceeding a predetermined magnitude (for example, an earthquake force due to an excessive earthquake) acts on the steel beam 3, a relative slip occurs between the first precast concrete member 4 and the steel beam 3. The friction force between the first precast concrete member 4 and the steel beam 3 is estimated, for example, by a friction coefficient estimation method between the concrete part in the end RC part and the steel beam part in the mixed structure beam of Patent Application No. 2023-077201 already filed by the applicant.
[0027] As shown in FIG. 4, the second fixing member 7 has a pair of second fixing steel members 71, 71, a bolt 72, and a nut 73. The pair of second fixing steel members 71 is a long steel plate. The pair of second fixing steel members 71 is provided along the outer side surface 6a of each of the second precast concrete members 6 on both sides of the web 33 in a vertical direction. The vertical dimension of the second fixing steel member 71 is larger than the length dimension from the upper surface 4b of the upper first precast concrete member 4 provided above and below the web 33 to the lower surface 4c of the lower first precast concrete member 4. The upper end portion 71a of the second fixing steel member 71 is disposed above the upper surface 4b of the upper first precast concrete member 4. The lower end portion 71b of the second fixing steel member 71 is disposed below the lower surface of the lower first precast concrete member 4. Holes 711 into which bolts 72 are inserted are formed in the upper end 71a and the lower end 71b of the second fixing steel member 71 at positions that do not overlap with the first precast concrete member 4 in the width direction.
[0028] The bolt 72 is a rod-shaped long screw such as a PC steel bar. The bolt 72 is inserted into each hole 711 of a pair of second fixing steel materials 71 in a posture extending in the width direction. A nut 73 is fastened to the bolt 72 at a position of one side surface 71c in the width direction of the second fixing steel material 71 on one side in the width direction, and a nut 73 is fastened to the bolt 72 at a position of the other side surface 71d in the width direction of the second fixing steel material 71 on the other side in the width direction. The axial force (tension) of the bolt 72 is adjusted by adjusting the tightening force of the nut 73. By fastening the nut 73 to the bolt 72, the second precast concrete members 6 on both sides in the width direction of the web 33 of the steel beam 3 are pressed against the web 33.
[0029] The frictional force between the second precast concrete member 6 and the web 33 can be adjusted by adjusting the fastening force of the nut 73 to adjust the axial force of the bolt 72 and thereby adjusting the force with which the pair of second precast concrete members 6 are pressed against the web 33. In this way, the mechanism for adjusting the frictional force between the second precast concrete member 6 and the web 33 by adjusting the fastening force of the nut 73, adjusting the axial force of the bolt 72, and adjusting the force with which the pair of second precast concrete members 6 are pressed against the web 33 corresponds to a frictional force adjustment mechanism.
[0030] A plurality of second fixing members 7 are provided across the entire length of the pair of second precast concrete members 6, 6 at intervals in the longitudinal direction of the pair of second precast concrete members 6, 6. The first fixing members 5 and the second fixing members 7 are arranged alternately in the longitudinal direction.
[0031] The friction force between the second precast concrete member 6 and the steel beam 3 is set so that when an earthquake force of a predetermined magnitude or less acts on the steel beam 3, no relative slip occurs in the longitudinal direction between the second precast concrete member 6 and the steel beam 3, and when an earthquake force exceeding a predetermined magnitude (e.g., earthquake force due to an excessively large earthquake) acts on the steel beam 3, relative slip occurs in the longitudinal direction between the second precast concrete member 6 and the steel beam 3.
[0032] Next, the action and effect of the mixed structural beam 1 according to this embodiment will be described. In the mixed structural beam 1 according to this embodiment, when an excessive earthquake causes a seismic force exceeding a predetermined magnitude to act on the steel beam 3, relative slip occurs between the precast concrete members 4, 6 and the steel beam 3, and the stress between the precast concrete members 4, 6 and the steel beam 3 is released, thereby reducing damage to the precast concrete members 4, 6. Even after the seismic force acts, the friction force between the precast concrete members 4, 6 and the steel beam 3 can be maintained at the initially set value, so the vibration control effect can be maintained even after the earthquake. As a result, the amount of repair work after an earthquake can be reduced.
[0033] In the mixed structural beam 1 according to the present embodiment, the first precast concrete member 4 and the second precast concrete member 6 are provided in pairs at positions facing each other with the steel beam 3 in between. The first fixing member 5 and the second fixing member 7 have a pair of fixing steel members 51, 71 provided at positions facing each other with the pair of first precast concrete members 4 or the pair of second precast concrete members 6 in between, and bolts 52, 72 and nuts 53, 73 for fixing the pair of fixing steel members 51, 71 to each other. The first fixing member 5 and the second fixing member 7 are configured such that the axial force of the bolts 52, 72 is adjusted by adjusting the tightening force of the nuts 53, 73, thereby adjusting the force with which the precast concrete members 4, 6 are pressed against the steel beam 3, and the frictional force between the precast concrete members 4, 6 and the steel beam 3 is adjusted. With this configuration, the frictional force between the precast concrete members 4, 6 and the steel beam 3 can be easily adjusted.
[0034] In the mixed structural beam 1 according to this embodiment, the first precast concrete members 4 are provided above and below the longitudinal ends 3a of the steel beam 3. This increases the rigidity of the longitudinal ends of the mixed structural beam 1 (the portions where the first precast concrete members 4 are provided) compared to the case of only the steel beam, reducing deflection and reducing deformation of the frame during an earthquake.
[0035] In the mixed structural beam 1 according to this embodiment, the second precast concrete members 6 are provided on both sides of the web 33 of the steel beam 3. This makes it possible for the mixed structural beam 1 to prevent the steel beam 3 from lateral buckling. In the mixed structural beam 1 according to this embodiment, the first precast concrete member 4 and the second precast concrete member 6 can be used as a fire-resistant covering material for the end portion 3a of the steel beam 3 in the longitudinal direction.
[0036] This section explains an example of estimating the coefficient of friction between the concrete and steel beam in a wrapped section of a mixed structural beam that has a reinforced concrete wrapped section surrounding the steel beam at the end of a conventional steel beam. Figure 5 shows a diagram of the test specimen, and Figure 6 shows the distribution of the coefficient of friction between the concrete and steel beam in the axial direction (length direction) of the wrapped section, estimated from the test results. Figure 6 shows the distribution of the coefficient of friction between the concrete and steel beam for part A shown in Figure 5. The method for estimating the friction coefficient is the method described in Japanese Patent Application No. 2023-077201. The mixed structural beam 101 joined to the left side of the column 102 shown in Fig. 6 corresponds to the test specimen. In Fig. 6, it is indicated as "No. 1-1".
[0037] Details of the test specimen No. 1-1 shown in FIG. 5 are as follows. Cross-sectional dimensions of RC section (root wrapping section 104): b×D=400×580mm Length of RC section (root wrapping section 104): 800mm Beam main bar: 7-D19 (SD390) at both top and bottom ends Shear reinforcement: D6@90 (SD295) Concentrated reinforcement: D10@10 (SD295) Concrete design strength: Fc30 Steel frame (steel beam 103): H-400 x 150 x 8 x 13 (SN490B)
[0038] Fig. 7 shows the distribution of the friction coefficient between the precast concrete member and the steel beam in the longitudinal direction obtained by the friction adjustment mechanism in the mixed structural beam 1 according to this embodiment. By adjusting the axial force in the part enclosed by the square frame B in the figure, it is possible to set a friction coefficient different from the friction coefficient between the concrete of the base wrapping part and the steel beam in the conventional mixed structural beam shown in Fig. 6.
[0039] Although the embodiment of the mixed structural beam according to the present invention has been described above, the present invention is not limited to the above embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, the mixed structural beam 1 may have a configuration in which a pair of first precast concrete members 4 are provided above and below a steel beam 3, and no second precast concrete members 6 are provided on either side of the web 33 of the steel beam 3. The first fixing member 5 and the second fixing member 7 may have a shape other than that described above. The first precast concrete member 4 and the second precast concrete member 6 may have a shape different from that described above as long as they are pressed and fixed to the steel beam 3 by the first fixing member 5 and the second fixing member 7.
[0040] The Sustainable Development Goals (SDGs) are among the 17 international goals adopted at the United Nations Summit in September 2015. The composite structural beam of this embodiment can contribute to achieving the 17 goals of the SDGs, such as goal 11, "Sustainable cities and communities." [Explanation of symbols]
[0041] 1 Mixed structural beam 2 Pillars 3 Steel beams 3a End in the longitudinal direction 4. First precast concrete member (precast concrete member) 5 First fixing member (fixing member) 6 Second precast concrete member (precast concrete member) 7 Second fixing member (fixing member) 31 Upper flange 32 Lower flange 33 Web 42 Reinforcement 51 1st fixing steel material (fixing steel material) 71 2nd fixing steel material (fixing steel material) 52,72 Volts 53,73 Nut
Claims
1. Steel beams and A precast concrete member provided along an outer peripheral surface at an end portion in the longitudinal direction of the steel beam; and a fixing member for pressing and fixing the precast concrete member to the steel beam, The reinforcing bars of the precast concrete members are fixed to reinforced concrete columns; the fixing member has a friction adjustment mechanism capable of adjusting a friction force between the precast concrete member and the steel beam by adjusting a force pressing the precast concrete member against the steel beam, The friction adjustment mechanism is a mixed structure beam that sets the friction force between the precast concrete member and the steel beam so that when an earthquake force of a predetermined magnitude or less acts on the steel beam, no relative slip occurs between the precast concrete member and the steel beam, and when an earthquake force exceeding the predetermined magnitude acts on the steel beam, relative slip occurs between the precast concrete member and the steel beam.
2. The precast concrete members are provided in pairs at positions facing each other across the steel beam, The fixing members include a pair of fixing steel members provided at positions facing each other across the pair of precast concrete members; A bolt and a nut for fixing the pair of fixing steel materials to each other, The mixed structural beam described in claim 1, wherein the friction force adjustment mechanism adjusts the axial force of the bolt by adjusting the tightening force of the nut, thereby adjusting the force with which the precast concrete member is pressed against the steel beam, and adjusting the friction force between the precast concrete member and the steel beam.
3. The precast concrete members are a pair of first precast concrete members provided along an upper surface of an upper flange of the steel beam and a lower surface of a lower flange of the steel beam, 3. A mixed structural beam according to claim 1 or 2, wherein the fixing member is a first fixing member that fixes the pair of first precast concrete members to each other and presses them against the upper surface of the upper flange and the lower surface of the lower flange.
4. The precast concrete member comprises: the pair of first precast concrete members; a pair of second precast concrete members provided along both sides of the web of the steel beam and joined to the columns, The fixing member is The first fixing member; 4. The mixed structural beam according to claim 3, further comprising a second fixing member for pressing and fixing the pair of second precast concrete members against the side surfaces of the web.
Citation Information
Patent Citations
Construction method of composite structure building
JP4029339B2