JP2008031818A - Method for evaluating strength of steel pipe concrete column/beam joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine evaluated strength with a high degree of accuracy even if an Lp value in a column/beam joint is changed. <P>SOLUTION: Among joints between a steel pipe concrete column 4 and a steel-frame beam 3, a joint between a tension-side flange 3F of the steel-frame beam 3 and the steel pipe concrete column 4 is split into an end area e and a central area m. The resultant force of the end yield strength of the end area e and the central yield strength of the central area m is set as the evaluated strength. In this case, when a length Lp to the flange 3F from a boundary between stiffened and unstiffened portions of the steel pipe is set at 0, the evaluated strength is determined by distribution obtained by multiplying a predetermined weighting factor, so as to be set at a value between yield strength in the case where the thickness dimension of the stiffened portion is decreased up to that of the unstiffened portion, and yield strength in the case where the thickness dimension of the unstiffened portion is increased up to that of the stiffened portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, the steel pipe is filled with concrete, and the steel beam is welded to the steel pipe concrete column having a structure in which the joint is stiffened by increasing the thickness of the joint to be joined to the steel beam. The present invention relates to a method for evaluating the strength of steel pipe concrete column / beam joints.

Conventionally, as a method of evaluating the proof stress of this kind of steel pipe concrete column / beam joint, the maximum pull-out of the steel beam is caused by the pull-out flange breaking out from the joint of the steel pipe concrete column. A method is known in which the load is calculated and the maximum load that is pulled out is used as the evaluation strength (see, for example, Patent Document 1). Specifically, the maximum load Pmax is calculated from the shear yield strength Fs of the steel pipe, the pipe thickness tp of the joint, and the peripheral length φf of the flange on the pulling side of the steel beam based on the formula Pmax = Fs × tp × φf Was.
However, with this technique, it has been confirmed by experiments that there is a tendency to overestimate the yield strength of the joint, and there is room for improvement.
In addition, the tendency of such overestimation has been improved as follows. Of the joints between steel pipe concrete columns and steel beams, the joints between the steel beam concrete side flange and steel pipe concrete columns are It is divided into an end region near both ends and a central region between them, and the yield strength of the steel pipe and the yield strength of the flange are determined for each of the end region and the central region. The lower one of the yield strengths of the steel is the end yield strength, and the central region is the yield strength obtained by multiplying the smaller one of the yield strength of the steel pipe and the yield strength of the flange by the stress block factor. A technique has been proposed in which the resultant strength of the yield strength and the central yield strength is the evaluation strength (P (ζ)) (see, for example, Patent Document 2).
In this technique, when the length (Lp) from the boundary between the stiffened portion and the non-stiffened portion of the steel pipe to the flange is 0, the evaluation yield strength (P (0)) is The number 2 was obtained.

JP-A-7-324382 JP 2001-98642 A

As shown in Fig. 1, the range of the stiffening part of the steel pipe at the joint between the steel pipe concrete column and the beam is usually set to a size larger than that of the beam, and the yield strength under such conditions Evaluation was no problem even with the conventional method. However, due to the need to meet various building needs, it is considered that the Lp (the length from the boundary between the stiffening part and the non-stiffening part of the steel pipe to the beam flange) becomes 0 as the joint structure. However, when such a joint structure is assumed, the conventional method for evaluating the proof stress of a steel pipe concrete column / beam joint has a problem in that the accuracy of the proof stress tends to be low.
That is, the proof stress at the joint is generally evaluated to decrease as Lp decreases, but according to the conventional method, when Lp = 0, a tendency to increase is seen, Improvement in accuracy was desired.

  Accordingly, an object of the present invention is to evaluate the proof stress of a steel pipe concrete column / beam joint which can solve the above-mentioned problems and can obtain the evaluation proof strength with high accuracy even if the Lp value in the column / beam joint changes. Is to provide a method.

  A first characteristic configuration of the present invention is a steel pipe concrete column having a structure in which a steel pipe is filled with concrete and the joint portion is stiffened by increasing the thickness over the entire length of the joint portion to be joined to a steel beam. In the method for evaluating the proof stress of steel pipe concrete columns / beam joints where steel beams are joined to each other by welding, the joint between the steel beam concrete column and the steel pipe concrete column is connected in the flange width direction. It is divided into an end region near both ends and a central region between them, and the yield strength of the steel pipe and the yield strength of the flange are determined for each of the end region and the central region. For the end region, the yield strength of the steel pipe and the flange strength of the flange are obtained. The smaller of the yield strength is the end yield strength, and for the central region, the smaller of the steel pipe yield strength and the flange yield strength is multiplied by the stress block factor. The center yield strength, and the resultant strength of the end yield strength and the central yield strength as the evaluation strength (P (ζ)), the length from the boundary between the stiffened portion and the non-stiffened portion of the steel pipe to the flange When the thickness (Lp) is 0, the evaluation yield strength (P (0)) is the yield strength (P *) when the thickness of the stiffened portion is reduced to the thickness of the non-stiffened portion. Allocation multiplied by a predetermined weighting factor (w) so as to be a value between the yield strength (P (∞)) when the thickness dimension of the non-stiffening part is increased to the thickness dimension of the stiffening part Is where you want.

According to the first characteristic configuration of the present invention, the evaluation strength P (0) when Lp = 0 is equal to the yield strength P (∞) of the straight pipe having the full length as the stiffening portion, and the non-stiffening portion having the full length. It is considered to exist between the yield strengths P * of straight pipes, and it can be obtained by multiplying the weighted distribution value of these two, that is, the weighting coefficient, so that it is possible to prevent the occurrence of contradictions as in the past. As shown in FIG. 7, when Lp is close to 0, the evaluation proof strength is also small, and it is possible to evaluate the joint strength with higher accuracy.
Therefore, even if the Lp value at the column / beam joint changes, the evaluation strength can be obtained with high accuracy in any case.

  The second characteristic configuration of the present invention is that a design formula (F) is set as shown in Equation 3 and an evaluation proof stress (P (ζ)) is calculated based on the design formula (F).

  According to the second characteristic configuration of the present invention, in addition to being able to achieve the above-described operation and effect of the first characteristic configuration of the present invention, the evaluation proof stress is calculated based on the set design formula. While it is easy to calculate the proof stress, the accuracy of the evaluation proof strength can be improved, and the proof stress evaluation of the joint can be performed more promptly and appropriately.

  A third characteristic configuration of the present invention is that the weight coefficient (W) is 0.740.

According to the third characteristic configuration of the present invention, in addition to being able to achieve the above-described operational effects according to the first or second characteristic configuration of the present invention, a weighted average of the proof stress P * and P (∞) A weight coefficient W of 0.740 (specifically, 0.74042) is obtained using the least square method so that the difference between the proof stress P (0) and the FEM analysis result of Lp = 0 is minimized. Therefore, the evaluation strength obtained using the weight coefficient W can be obtained as a very close value without performing FEM analysis each time, and can be obtained with high accuracy.
As an example, as shown in FIG. 6, the FEM analysis value on the horizontal axis and the calculated value on the vertical axis show extremely close values.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1, 2, and 3, the steel pipe 1 is filled with the concrete 2, and the steel pipe 1 is thickened over the entire length of the joint portion 1 </ b> A that joins the steel beam 3 using H-shaped steel. A method for evaluating the strength of a steel pipe concrete column / beam joint where a steel beam 3 is welded to a steel pipe concrete column 4 having a stiffened joint 1A. The joint between the flange 3F on the pulling side and the steel pipe concrete column 4 is divided into an end region e near both ends in the flange width direction and a central region m between them, and each of the end region e and the central region m is a steel pipe. The yield strength of 1 and the yield strength of the flange 3F are obtained. For the end region e, the smaller one of the yield strength of the steel pipe 1 and the yield strength of the flange 3F is defined as the end yield strength. Yield resistance And a yield strength multiplied by the stress block coefficient smaller of the yield strength of the flange 3F and central yield strength, is the resultant force of these end yield strength and the central yield strength method to evaluate strength.

Specifically, when the calculation condition of the evaluation strength (P (ζ)) under the design conditions implemented with the slope factor 1/3 is ζ = ∞, the evaluation strength (P (∞)) expressed by Equation 3 is used. When ζ = 0, the evaluation yield strength (P (0)) expressed by Equation 3 is calculated, and when 0 <ζ <∞, (P (ζ)) expressed by Equation 3 is calculated. As shown in FIG. 4, the slope factor 1/3 is defined as an inclination angle that is 1/3 of the first inclination angle θ ₁ of the elastic region in the load deformation curve of the steel pipe concrete column / beam joint. A load corresponding to a point on the load deformation curve having a tangent angle of 2 inclination angle θ ₂ is a yield load. In the present embodiment, a slope factor of 1/3 is used as a yield load. Then, instead of the slope factor 1/3, for example, numerical values such as a slope factor 1/2, a slope factor 1/4, and a slope factor 1/5 may be adopted. Furthermore, the method for determining the yield load is not limited to the slope factor method, and other methods (general yield method, 0.2% offset method, etc.) may be used.

Here, in order to facilitate the following description, a joint model showing a stress examination section will be described with reference to FIG.
Lp is the length from the boundary between the stiffening portion (joint portion 1A) and the non-stiffening portion to the flange 3F, Dp is the outer diameter of the stiffening portion, and hpi is the non-stiffening portion of the stiffening portion. , Hpo is the protruding length of the stiffened portion from the non-stiffened portion to the outside, Tp is the thickness of the stiffened portion, and Tc is the length of the non-stiffened portion. Thickness, Tf is the thickness of the flange 3F, and Bf is the width of the flange 3F. S ₁ is the surplus amount of welding to the joint portion 1A on the side of the flange 3F, S ₂ is the surplus amount of welding to the joint portion 1A on the lower side of the flange 3F, and S ₃ is the flange 3F. It is the amount of surplus welding of the upper side joint portion 1A. θs is a joint angle formed by a straight line connecting the joint center (left and right center) and the column center, and a straight line connecting the left and right extra-ends of the joint and the column center, and mθ is the joint center (left and right center). The central area angle formed by a straight line connecting the column center and a straight line connecting the region boundary and the column center, and eθ is a straight line connecting the region boundary and the column center, the left and right extra-ends of the joint, and the column center. It is an end region angle formed by a connecting straight line. In the present embodiment, the region boundary is set to a position at a distance of ½ of the thickness Tf of the flange 3F from the side of the flange 3F, but the position setting can be changed as appropriate.

Here, ζ is defined as in Equation 3, where _p σ _y is the material yield stress degree of the stiffened steel pipe.

  Then, the stress acting on the joint when a tensile force acts on the flange 3F is calculated based on the equation shown in Equation 4.

The yield strength eQ ₁ cross-section portion of the excess heap is applied steel tube portion along the flange thickness direction of the end region e (I), excess prime is facilities along the flange width direction of the end region e The yield strength eQ ₂ of one cross-sectional portion (II) of the upper and lower steel pipe portions, the yield strength eT of the cross-sectional portion of the flange portion of the end region e, and one region portion of the central region m divided into two in the flange width direction Yield strength mQ ₂ of one cross-sectional portion (II) of the upper and lower steel pipe portions that are overfilled, yield strength mT of the cross-sectional portion of the flange portion of one region portion that bisects the central region m in the flange width direction , Yield strength eQ ₃ of the cross-sectional portion (III) at the boundary between the stiffened portion and the non-stiffened portion in the end region e when Lp = 0, and the central region m when Lp = 0 in the flange width direction Between the stiffened part and the non-stiffened part The yield strength mQ ₃ of the cross-sectional portion (III) of the boundary portion is expressed by the equation shown in Equation 6.

  And the stress block coefficient in Formula 3 is defined by the formula shown in Table 1 and Formula 7.

  Next, the calculation by Formula 3 and the FEM analysis were performed on the 139 model whose conditions were changed in order to confirm that the proof stress of the steel pipe concrete column / beam joint can be appropriately evaluated by the evaluation method of the present embodiment.

  The dimensions (shapes) of the models 20 to 158 are shown in Tables 2 to 4, and the physical properties are shown in Tables 5 to 7, respectively.

<result>
Tables 8 to 10 show a list of the FEM analysis value cPy and the calculated evaluation yield strength (P (ζ)).

  Further, FIG. 8 shows the relationship between the FEM analysis value and the evaluation strength calculated by the evaluation method of the present embodiment.

From the above results, it can be seen that when the evaluation method according to the present embodiment is used, it is possible to appropriately evaluate the yield strength with less overestimation and less variation compared to the conventional evaluation method.

  Furthermore, this invention is applicable to the proof stress evaluation of the junction part provided with the steel pipe concrete pillar 4 of various cross-sectional shapes other than circular.

  In addition, as mentioned above, although the code | symbol was written in order to make contrast with drawing convenient, this invention is not limited to the structure of an accompanying drawing by this entry. In addition, it goes without saying that the present invention can be carried out in various modes without departing from the gist of the present invention.

Notched front view of steel pipe concrete column / beam joint Cross section plan of steel pipe concrete column / beam joint Notched side view of steel pipe concrete column / beam joint Graph showing the relationship between load and deformation Schematic diagram of steel pipe concrete column / beam joint Graph showing the relationship between the FEM analysis value and the calculated evaluation strength Relationship diagram between Lp and local yield strength Graph showing the relationship between the FEM analysis value and the calculated evaluation strength

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel pipe 1A Joint part 2 Concrete 3 Steel beam 3F Pull side flange 4 Steel pipe concrete pillar e End area Lp Length from boundary of stiffened part and non-stiffened part of steel pipe to flange m Central area P (ζ ) Evaluation strength P (0) Evaluation strength P * Yield strength when the thickness of the stiffening part is reduced to the thickness of the non-stiffening part P (∞) The thickness of the non-stiffening part Yield strength when weight is increased to w

Claims (3)

The steel pipe is filled with concrete, and the steel beam is welded to the steel pipe concrete column with a stiffening of the joint part by thickening the joint part of the steel pipe over the entire length. A method for evaluating the strength of steel pipe concrete columns and beam joints,
Of the joints, the joint between the flange on the pulling side of the steel beam and the steel pipe concrete column is divided into an end region near both ends in the flange width direction and a center region between them, and each of these end regions and the center region, The yield strength of the steel pipe and the yield strength of the flange are obtained. For the end region, the smaller one of the yield strength of the steel pipe and the yield strength of the flange is the end yield strength, and for the central region, the yield strength of the steel pipe and the flange strength of the flange are obtained. The yield strength obtained by multiplying the smaller of the yield strength by the stress block coefficient is the central yield strength, and the resultant strength of these end yield strength and central yield strength is the evaluation strength (P (ζ)). When the length (Lp) from the boundary between the part and the non-stiffened part to the flange is 0, the evaluation yield strength (P (0)) is set, and the thickness of the stiffened part is set to the thickness of the non-stiffened part. Reduced to wall thickness Predetermined yield strength (P *) and the yield strength (P (∞)) when the thickness of the non-stiffened part is increased to the thickness of the stiffened part. Strength evaluation method for steel pipe concrete column / beam joint obtained by distribution multiplied by weight coefficient (w). The method of evaluating the strength of a steel pipe concrete column / beam joint according to claim 1, wherein the following design formula (F) is set and the evaluation strength (P (ζ)) is calculated based on the design formula (F).

  The method for evaluating the strength of a steel pipe concrete column / beam joint according to claim 1 or 2, wherein the weight coefficient (W) is 0.740.

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