JP7202949B2 - Design method of joint structure - Google Patents

Description

The present invention relates to a method for designing a joint structure.

A through-diaphragm construction method is known as a joint structure between a steel pipe column and an H-shaped steel beam. In the through-diaphragm method, the steel pipe column is cut at the upper and lower flange positions of the H-shaped steel beam, the diaphragm is inserted and welded to the steel pipe column, the upper and lower flanges of the beam bracket are welded to the diaphragm, and the web of the beam bracket is attached to the steel pipe. It is welded to the skin plate of the column, and the beam bracket and the H-beam are high-strength bolted.

On the other hand, Patent Document 1 discloses an outer diaphragm construction method in which a diaphragm is installed on the outside of a steel pipe column without cutting the steel pipe column. A technique is described in which the outer diaphragm to be joined is a divided diaphragm divided in the outer peripheral direction of a steel pipe column, and the divided diaphragms are tightened and fixed to each other so that contact pressure acts on the column surface of the steel pipe column.

In the technique described in Patent Document 1 as described above, the installation of the outer diaphragm eliminates the need to cut the steel pipe column, and in addition, the outer diaphragm is joined to the steel pipe column by surface friction, so welding at this portion is unnecessary. It becomes unnecessary, and the amount of processing is greatly reduced.

WO2017/026113

By the way, in the joint structure described in Patent Document 1, since the outer diaphragm is not welded to the steel pipe column, the tensile couple generated in the flange by the bending moment acting on the H-shaped steel beam is directly transmitted to the column surface of the steel pipe column. Instead, it acts as a compressive force on the opposite column face through an outer diaphragm clamped around the steel column. When the own weight or load is applied, a tension couple is generated in the flange of the H-shaped steel beam joined to the outer diaphragm on the opposite side, so the above compression force is canceled and no problem occurs.

However, for example, when an earthquake load acts and a compression couple is generated in the flange joined to the outer diaphragm on the opposite side, the compressive force acting on the column surface of the steel pipe column becomes excessive, causing local deformation of the steel pipe column. may occur. When such local deformation occurs, a gap is generated between the column surface of the steel pipe column and the outer diaphragm, and the energy absorption capacity of the joint structure is lowered. Therefore, it is necessary to evaluate the effect of local deformation of square steel pipe columns in the design considering earthquakes, but no effective method has been proposed yet.

Therefore, the present invention provides a joint structure design method that makes it possible to evaluate the influence of local deformation of a square steel pipe column in a joint structure of a square steel pipe column having an outer diaphragm joined by surface friction and a beam. intended to

According to one aspect of this embodiment, first and second flat surfaces facing each other, third and fourth flat surfaces orthogonal to the first and second flat surfaces and facing each other, and including a rectangular steel pipe column whose side surfaces include cylindrical surfaces between the four flat surfaces; 4 divided diaphragms are arranged so as to surround the square steel pipe column in plan view and are joined to the outer diaphragm and at least the first divided diaphragm, which are constructed by fastening each other so as to exert contact pressure on the flat surface. A method for designing a joint structure comprising a beam and a beam, comprising a step of evaluating a total plastic strength calculation value _CL P _p0 of a square steel pipe column due to local deformation of a first flat surface, and a total plastic strength calculation value _CL P _p0 At least one of the total plastic strength of the beam, the total plastic strength of the square steel pipe column, or the total plastic strength of the panel zone between the beam and the square steel pipe column based on the nodal moment calculation value _CL M _p0 when A method of designing a junction structure is provided, comprising the step of determining.

In the above joint structure design method, the _{total plastic strength} of the _beam , the total plastic strength of the square steel pipe column, the total plastic strength of the square steel pipe column, or determine at least one of the total plastic strength of the panel zone between the beam and the square steel column.

In the above joint structure design method, the total plastic strength calculated value _CL P _p0 is 1/2 the length b of the area where the first flat surface and the first split diaphragm contact, and the thickness center of the cylindrical surface It may be calculated by the formula (i) using the radius r of the partial cross section and the total plastic moment _mpc per unit length on the cylindrical surface.

Furthermore, based on the nodal moment calculated value _CL M _p0 , the nodal moment calculated value _CL M _p corresponding to the total plastic strength calculated value of the square steel pipe column due to local deformation considering the combined stress of the bending moment and the axial force is Calculated by formula (ii) using the nodal moment _CC M _p corresponding to the total plastic bending yield strength calculation value of the steel pipe column, and based on the nodal moment calculated value _CL M _p , the total plastic yield strength of the beam and the total plastic yield strength of the square steel pipe column The yield strength and/or the total plastic yield strength of the panel zone between the beam and the square steel column may be determined. Here, it is sorted by the nodal moment, but it may be sorted by the moment of another position, the shear force of the beam or the column, and the like.

In the joint structure design method described above, the joint structure may further comprise a beam joined to at least one of the second, third or fourth split diaphragm.

According to the above configuration, it is possible to evaluate the influence of local deformation of the square steel pipe column in the joint structure between the beam and the square steel pipe column having the outer diaphragm joined by surface friction.

1 is a perspective view of a joint structure according to one embodiment of the present invention; FIG. 1. It is a figure which shows the outline|summary of the cross test implemented about the joint structure shown in FIG. 3 is a graph showing the results of the cross test shown in FIG. 2; It is a graph which shows the result of the cross test of a through-diaphragm construction method. 1. It is a figure which shows the example of the generation|occurrence|production state of the tension couple and compression couple in the joining structure shown in FIG. It is a figure which models and shows the local deformation of a square steel pipe column. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. 4 is a graph showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

FIG. 1 is a perspective view of a joint structure according to one embodiment of the present invention. A joint structure 1 shown in FIG.

The square steel pipe column 2 is a steel pipe having a rectangular cross section as a whole and rounded corners, specifically, for example, a cold roll formed square steel pipe. The side surfaces of the square steel pipe column 2 are flat surfaces 21A and 21B facing each other, flat surfaces 21C and 21D perpendicular to the flat surfaces 21A and 21B and facing each other, and a cylindrical surface 22 between the flat surfaces 21A to 21D. including.

The outer diaphragm 3 includes split diaphragms 31A to 31D that are brought into contact with the flat surfaces 21A to 21D of the square steel pipe column 2, respectively. The split diaphragms 31A-31D are arranged to surround the square steel pipe column 2 in plan view, and are fastened together so as to apply contact pressure to the flat surfaces 21A-21D. In this embodiment, as will be described later, the H-shaped steel beam 4 has an upper flange 41, a web 42 and a lower flange 43, and the outer diaphragm 3 is joined to the upper outer diaphragm 3A joined to the upper flange 41 and the lower flange 43. and the lower outer diaphragm 3B.

Each of the divided diaphragms 31A to 31D includes a beam plate 311 joined to the upper flange 41 or the lower flange 43 of the H-shaped steel beam 4, and a column plate 312 abutting on the flat surfaces 21A to 21D of the square steel pipe column 2, respectively. including. The beam plate 311 is spliced to the upper flange 41 or the lower flange 43 as in the illustrated example, and is joined to the upper flange 41 or the lower flange 43 by bolt joint such as high-strength bolt joint or fillet welding. be. Alternatively, beam plate 311 may be joined to upper flange 41 or lower flange 43 by butt welding.

Further, in the illustrated example, each segmented diaphragm 31A-31D includes a fastening plate 313 extending on either side of the post plate 312. As shown in FIG. By overlapping the fastening plates 313 between the split diaphragms 31A to 31D adjacent to each other and fastening them using bolts 314 and nuts 315, the column plates 312 of the split diaphragms 31A to 31D are attached to the flat surface of the square steel pipe column 2. 21A to 21D are pressed against each other to apply contact pressure, and the outer diaphragm 3 can be joined to the square steel pipe column 2 by surface friction.

The H-beam 4 has an upper flange 41 , a web 42 and a lower flange 43 . In this embodiment, the joint structure 1 includes two H-shaped steel beams 4 that are joined to the split diaphragms 31A and 31B of the outer diaphragm 3 . Here, the split diaphragms 31A and 31B are brought into contact with the mutually opposing flat surfaces 21A and 21B of the square steel pipe column 2 . The joint structure 1 may further include an H-beam 4 joined to either or both of the split diaphragms 31C, 31D. Specifically, for example, the joint structure 1 may include only one H-shaped steel beam 4 joined to the split diaphragm 31A, or two L-shaped steel beams joined to the split diaphragms 31A and 31C, respectively. , or three H-shaped steel beams 4 joined to the split diaphragms 31A to 31C to form a T shape, or joined to the split diaphragms 31A to 31D. It may include four H-shaped steel beams 4 forming a cross. In the illustrated example, the H-shaped steel beam 4 is arranged so as to be orthogonal to the flat surfaces 21A to 21D of the square steel pipe column 2, but in other examples, the H-shaped steel beam 4 is arranged to be perpendicular to the flat surfaces 21A to 21D. may be arranged obliquely to the

It should be noted that detailed configurations and modifications of the joint structure as described above can be appropriately implemented with reference to, for example, International Publication No. 2017/026113.

FIG. 2 shows an outline of a cross test performed on the joint structure shown in FIG. In the cross test, the lower end of the square steel pipe column 2 was fixed, and the vertical displacement of the H-shaped steel beams 4 joined to both sides of the square steel pipe column 2 was fixed at the end opposite to the square steel pipe column 2. In this state, a horizontal load (which simulates the load during an earthquake) was applied to the upper end of the square steel pipe column 2 . As a result, as shown in the graph of FIG. 3, there was a section where the deformation increased without increasing the load from the vicinity of the inter-story deformation angle of 0.02 rad. When a slip-type behavior involving such a section occurs in a joint structure, the joint is less likely to behave as compared to a spindle-type behavior such as similar test results in a through-diaphragm joint structure shown in the graph of FIG. The energy absorption capacity of the structure (represented on the graph by the area of the area enclosed by the loops) is reduced.

Observation of the joint structure 1 after the cross test revealed that the flat surface 21A of the square steel pipe column 2 was deformed, resulting in a gap between the split diaphragm 31A and the column plate 312, which abuts on the flat surface 21A. was This is because, in a cross test, when a tensile couple F1 due to a moment due to a load is generated in the upper flange 41 of the H-shaped steel beam 4 joined to the split diaphragm 31B as shown in FIG. A compression couple F2 is generated in the upper flange 41 joined to the opposing split diaphragm 31A at , and a tensile couple transmitted from the split diaphragm 31B via the split diaphragms 31C and 31D acts on the split diaphragm 31A. As a result of combining in the same direction as the compression couple, the compressive load P acting on the flat surface 21A of the square steel pipe column 2 from the column plate 312 of the split diaphragm 31A became excessive, and local deformation occurred in the flat surface 21A. Conceivable.

Therefore, the present inventors studied a technique for evaluating the total plastic strength of the rectangular steel pipe column 2 in consideration of the local deformation as described above. For example, when a large seismic load acts, the H-shaped steel beam 4 yields and plasticizes before the square steel pipe column 2, thereby preventing or reducing the plasticization of the square steel pipe column 2. However, by evaluating the total plastic yield strength of the square steel pipe column 2 in consideration of local deformation in such a design, the square steel pipe before yielding the H-shaped steel beam 4 The absence of local deformation of the column 2 and therefore of the slip-type behavior shown in the graph of FIG.

(Total plastic yield strength evaluation of square steel pipe by local deformation)
In the study, first, the total plastic yield strength of the rectangular steel pipe column 2 due to local deformation is evaluated by considering only the out-of-plane compressive force. FIG. 6 shows a model of a locally deformed portion of the square steel pipe column 2 . In the model shown in FIG. 6, taking symmetry into account, the area R is half the width of the flat surface 21A and half the length of the contact area between the flat surface 21A and the split diaphragm 31A. and a flat surface 21A and a cylindrical surface 22 adjacent thereto. Here, in the example shown in FIG. 1, the outer diaphragm 3 includes the upper outer diaphragm 3A and the lower outer diaphragm 3B. It is half the length of the area of contact. In the situation shown in FIG. 5, for example, a compressive load P acts on the region R in the direction indicated by the arrow in FIG.

In the model shown in FIG. 6, the yield line passes through the plate thickness center of the square steel pipe column 2 and is set at the boundary between the flat surface 21A and the cylindrical surface 22 and the midpoint of the cylindrical surface 22. Assuming that the plate thickness of the square steel pipe column 2 is t, the outer radius of the cylindrical surface 22 is 2.5t, and the radius of the yield line passing through the cylindrical surface 22 (the radius of the cross section at the center of the plate thickness of the cylindrical surface 22) r is 2.0t. is. FIG. 6 shows a solid line indicating the yield line, a broken line indicating the positions of other members, and nodes A to K of these lines.

In the above model, consider a case where the region R (region ABFE) is displaced by −δ in the Y direction. Considering the restraint by the column plate 312 of the divided diaphragm 31C (or the divided diaphragm 31D) adjacent to the divided diaphragm 31A, the yield line DH is not displaced in the X direction. In this case, assuming that the length of each yield line does not change and rotation at the node occurs, the unit moment, length, and rotation angle increments of each yield line are obtained as shown in Table 1. be done. In Table 1, _mpf is the total plastic moment per unit length on the flat surface 21A of the square steel pipe column 2, and _mpc is the total plastic moment per unit length on the cylindrical surface 22 of the square steel pipe column 2. is calculated by the formulas (1) and (2) of _σyf is the yield point or proof stress of the flat surface 21A (replaced with reference strength in design), and _σyc is the yield point or proof stress of the cylindrical surface 22 (replaced with reference strength in design). Further, as shown in FIG. 6, the length d is 1/2 the width of the flat surface 21A, the length b is 1/2 the length of the region R where the flat surface 21A and the split diaphragm 31A contact, and the length The length c is the length of the shape-changed portion due to the local deformation of the square steel pipe column 2 , and the r is the cross-sectional radius of the cylindrical surface 22 .

Here, from the results of the FEM analysis of the joint structure, when local deformation occurs in the square steel pipe column 2, the yield mainly occurs at the boundary between the flat surface 21A and the cylindrical surface 22 and at the intermediate point of the cylindrical surface 22. Yield lines (yield lines BF, CG, DH indicated by thick lines in FIG. 6). Therefore, if we simplify the model by assuming that plastic deformation does not occur outside of these three yield lines, and consider only the out-of-plane compressive force rather than the balance between the internal and external work using the values in Table 1, local The total plastic yield strength calculation value _CL P _p0 of the square steel pipe column 2 due to deformation is calculated as in the following equation (3).

(Evaluation of total plastic yield strength of square steel pipe considering combined stress)
Next, the total plastic strength of the rectangular steel pipe column 2 is evaluated in consideration of the combined stress of bending moment and axial force. From the results of the FEM analysis of the joint structure, the total plastic yield strength calculation value _CL P _p of the square steel pipe column 2 is the shear span SR (where L is the length of the square steel pipe column 2 and D is the outer diameter, SR = L / 2D ) is large, it converges to the total plastic bending yield strength calculation value _CC P _p of the square steel pipe column 2, and converges to a different value in the range where SR is small. Here, when the SR is small, bending hardly occurs in the square steel pipe column 2. Therefore, the above convergence value is the total plastic yield strength calculated value _CL P _p0 of the square steel pipe column 2 due to local deformation calculated by the formula (3). is considered to correspond to Therefore, the total plastic strength calculated value _CL P _p of the square steel pipe column 2 due to local deformation in consideration of the combined stress is expressed by a correlation equation with _CL P _p0 and _CC P _p as shown in Equation (4) _. Rewriting the equation of P _p results in equation (5). In formulas (4) and (5), since the shear stress is borne by the side surfaces (flat surfaces 21C and 21D) of the square steel pipe column 2, it is considered that the effect on local deformation is small. Only _CC P _p was considered.

Here, the total plastic bending strength calculated value _CC P _p of the square steel pipe column 2 can be calculated using the following equation (6), for example. In Equation (6), _Zp is the plastic section modulus of the square steel pipe column 2, L is the length of the square steel pipe column 2, B is the width of the square steel pipe column 2, and n is the axial force ratio. Here, the axial force is taken into account as reducing the total plastic bending strength.

7A to 7I are graphs showing calculated values and analytical values of the total plastic yield strength of square steel pipe columns. As a result of comparing a total of nine cases of three cases of diameter-thickness ratio D/t of 33, 25, and 19, and three cases of axial force ratio n of 0, 0.3, and 0.5, in all cases, the above In the range where the _shear span _SR is small, the calculated total plastic yield strength of the square steel pipe column 2 calculated by the formula (5) is equal to the total plastic yield strength of the square steel pipe column 2 due to the local deformation calculated by the formula (3). The tendency of the total plastic strength analysis value _L P _p of the square steel pipe column 2, which is asymptotic to the calculated value _CL P _p0 and, in the range where SR is large, to the total plastic bending strength calculation value _CC P _p of the square steel pipe column 2, is well understood. catch. The _L P _p / _CL P _p in each example shown in the graph is between 0.96 and 1.22.

In principle, the results of the total plastic yield strength evaluation of square steel pipes as described above are obtained by arranging the load P as the central load of the three-point bending test. In addition, the total plastic bending yield strength calculation value _CC P _p of the square steel pipe column 2 is calculated assuming that the total plastic moment calculation value is uniformly distributed within the range of the material axial length B of the loading jig. . When applying this to the actual design, it is necessary to consider the behavior of the square steel pipe column 2 and the H-shaped steel beam 4, so the joint structure (column-beam frame) is arranged as the nodal moment as follows. First, the nodal moment calculated value _CL M _p0 when the total plastic strength calculated value _CL P _p0 of the square steel pipe column 2 due to local deformation occurs is defined. The nodal moment calculated value _CL M _p0 is _{generated when} the sum of the force couple F1 and _{F2 shown} in FIG. In another example, when the H-section steel beam 4 is joined only to one side of the square steel pipe column 2, the nodal moment calculated value _CL M _p0 is the total compression force F1 received from the H-section steel beam 4 due to local deformation. Occurs when the plastic strength is equal to the calculated value _CL P _p0 (F1= _CL P _p0 ).

Furthermore, as explained in the evaluation of the total plastic yield strength of the square steel pipe considering the combined stress, the total plastic yield strength analysis value _{L Pp} of the square steel pipe column 2 is the total plastic bending yield strength of the square steel pipe column 2 when the shear span SR is large It converges to the calculated value _CC P _p , and in the range where SR is small, converges to the total plastic strength calculated value _CL P _p0 of the rectangular steel pipe column 2 due to local deformation. Similarly, for the nodal moment calculation value _CL M _p corresponding to the total plastic strength of the square steel pipe column 2 due to local deformation in consideration of the combined stress with the bending moment and the axial force, if the shear span SR is large, the total stress of the square steel pipe column 2 It converges to the nodal moment _CC M _p corresponding to the plastic moment, and converges to the calculated nodal moment _CL M _p0 corresponding to _CL P _p0 in the range where SR is small. Therefore, the nodal moment calculation value _CL M _p that considers the combined stress is represented by a _correlation formula with _CL M _p0 and _CC M _p as shown in the following formula (7) _. Equation (8) is obtained.

In the joint structure 1 according to the present embodiment, the square steel pipes are arranged such that the nodal moment corresponding to the total plastic strength of the H-shaped steel beam 4 is smaller than the nodal moment calculated value _CL M _p calculated using the formula (8). By designing the column 2 and the H-shaped steel beam 4, for example, when a large seismic load acts as described above, the H-shaped steel beam 4 yields earlier than the square steel pipe column 2, and the H-shaped steel beam 4 It is possible to prevent local deformation from occurring in the square steel pipe column 2 before yielding. In addition, in the range where the shear span SR is small, _CL M _{p asymptotically approaches} the nodal moment calculation value _CL M _p0 of the square steel pipe column 2 due to local _{deformation .} A nodal moment corresponding to the plastic strength may be calculated. In the above description, an example of determining the total plastic yield strength of the H-beam 4 based on the total plastic yield strength calculated value _CL P _p0 and the nodal moment calculated value _CL M _p0 of the square steel pipe column 2 due to the local deformation of the flat surface 21A will be described. However, similarly, based on the total plastic strength calculation value _CL P _p0 and the nodal moment calculation value _CL M _p0 , the total plastic strength of the square steel pipe column 2 or the panel zone between the H-beam 4 and the square steel pipe column 2 may determine the total plastic yield strength of

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Joining structure 2... Square steel pipe column 21A to 21D... Flat surface 22... Cylindrical surface 3... Outer diaphragm 3A... Upper outer diaphragm 3B... Lower outer diaphragm 31A to 31D... Divided diaphragm 311... Beam plate, 312... Column plate, 313... Fastening plate, 314... Bolt, 315... Nut, 4... H-shaped steel beam, 41... Upper flange, 42... Web, 43... Lower flange.

Claims (5)

first and second flat surfaces facing each other, third and fourth flat surfaces perpendicular to the first and second flat surfaces and facing each other, and between each of the first to fourth flat surfaces A rectangular steel pipe column including a cylindrical surface on the side at
It includes first to fourth divided diaphragms that abut on the first to fourth flat surfaces, respectively, and the first to fourth divided diaphragms are arranged so as to surround the square steel pipe column in plan view. an outer diaphragm configured by being fastened together to exert contact pressure on the flat surface with
A beam joined to at least the first split diaphragm, and a joint structure designing method comprising:
Evaluating the calculated total plastic yield strength _CL P _p0 of the square steel pipe column due to the local deformation of the first flat surface;
Based on the nodal moment calculated value _CL M _p0 when the total plastic strength calculated value _CL P _p0 occurs, the total plastic strength of the beam, the total plastic strength of the square steel pipe column, or the relationship between the beam and the square steel pipe column and determining at least one of the total plastic strength of inter-panel zones. The total plastic yield strength of the beam, the total plastic yield strength of the square steel pipe column, or the beam and the square shape so as to be smaller than the nodal moment calculation value _CL M _p0 when the total plastic yield strength calculated value _CL P _p0 occurs. 2. The method of designing a joint structure according to claim 1, wherein at least one of the total plastic strength of the panel zone between the steel pipe column is determined. The total plastic strength calculated value _CL P _p0 is the half length b of the region where the first flat surface and the first split diaphragm contact, the radius r of the thickness center section of the cylindrical surface , and a total plastic moment _mpc per unit length on the cylindrical surface, which is calculated by formula (i).

Based on the nodal moment calculated value _CL M _p0 , the nodal moment calculated value _CL M _p corresponding to the total plastic strength of the square steel pipe column due to local deformation considering the combined stress of the bending moment and the axial force is calculated as the square steel pipe. Calculated by formula (ii) using the nodal moment _CC M _p corresponding to the total plastic bending strength calculation value of the column, and based on the nodal moment calculated value _CL M _p , the total plastic strength of the beam, the square steel pipe column 4. The method of designing a joint structure according to claim 3, wherein determining at least one of a total plastic strength or a total plastic strength of a panel zone between the beam and the square steel column.

The joint structure design method according to any one of claims 1 to 4, wherein the joint structure further comprises a beam joined to at least one of the second, third, or fourth split diaphragms. .

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