JP6539639B2 - Column beam structure using square steel pipe and cross section determination method of column beam - Google Patents

Description

  The present invention relates to a column cross beam structure using a square steel pipe and a method of determining the cross section of the column cross beam, by determining the cross section of the square steel pipe based on a more realistic deformation when an assumed load is applied. To provide a reliable and economical column cut beam structure and a method of determining the cross section of the column cut beam.

  H-shaped steel is generally used as a cutting beam in pile work, but since the bending rigidity in the weak axis direction (usually horizontal direction) decreases as the span becomes longer, an intermediate pile is installed as a buckling stopper. There are many.

  On the other hand, column cut beams using square steel pipe have no difference in bending rigidity in the vertical direction and horizontal direction, so it is possible to reduce or omit intermediate piles for buckling and to improve site construction, so demand is needed. It is expanding.

  In any of the cut beams, safety is examined against the self weight acting as a vertical load and the earth pressure or water pressure acting as an axial compression load at the time of erection, and usually, when these loads act simultaneously In contrast, the limit of usable strength of the cross-section beam, that is, the cross section of the square steel pipe has been conventionally examined by the equation (7).

………(7)式

......... (7)

However, in the equation, σ _c is the axial compression stress degree of the cutting beam, and is the stress degree due to the earth pressure or water pressure acting through the ups and downs. σ _b is the bending compressive stress degree of the cut beam, which is the bending stress degree due to its own weight acting as a vertical load and the load. Further, σ _ca is an allowable axial compressive stress degree of the cutting beam, and σ _ba is an allowable bending compressive stress degree. And, (1−σ _c / σ _ea ) is an expansion coefficient set in consideration of an increase in deflection of the cutting beam due to the axial compression force.

Japanese Patent Laid-Open No. 04-68113 Japanese Patent Application Laid-Open No. 04-68114

However, equation (7) is not derived based on the theory for determining actual deformation, but the effect of buckling or the increase of deflection due to axial force, etc., is permitted for allowable compressive stress σ _ca and allowable bending compressive stress σ _ba It is an equation that is derived by taking into account the factor and is based on the ultimate limit condition that considers the safety of the cutting beam as safety, so it is unreliable and uneconomical design that relies on the safety factor And was not originally suitable for the design of column cross beams.

  The present invention has been made to solve the above problems, and by determining the cross section of a square steel pipe used for column cross section beams based on a more realistic deformation when an assumed load is applied, It is an object of the present invention to provide a reliable and economical column cut beam structure and a method of determining the cross section of a column cut beam.

  According to the present invention, in a column cross beam structure using a square steel pipe which receives vertical load and axial compression load, a cross section of the square steel pipe is formed to satisfy the equation (1) with respect to the vertical load and axial compression load. It is characterized by

………(1)式

………(1 set

However, N is an axial compression load due to earth pressure, water pressure, etc. acting on the column cutting beam through ups and downs. N _y is the yield axial force of the column cutting beam, which is determined based on the yield stress of the steel material of the square steel pipe used for the column cutting beam.

Further, M is a bending moment generated with the vertical load and the axial force action, and is obtained from the equation (6). M _y is a yield bending moment of the column cut beam, which is obtained based on the yield stress of the steel material of the square steel pipe used for the column cut beam. And, φ _c is a safety factor.

The safety factor φ _c may vary in residual stress, yield point, etc. depending on the material steel of column cut beam, manufacturing method, etc., so it is appropriate to set it within the range of 1.2 to 1.6 taking these into consideration Yes, about 1.6 is desirable from experimental results.

Generally, column cut beams using cold roll-formed rectangular steel tubes are susceptible to residual stress due to the manufacturing method etc. Therefore, 1.4 ≦ φ _c ≦ 1.6 or so is appropriate, and safety is enhanced when it exceeds 1.6 It is easy to fall into uneconomical circumstances.

In addition, column cut beams made of rectangular steel pipes formed by forming a plurality of steel plates in the material axis direction and welding the steel plates together in the material axis direction into a rectangular cross-sectional shape are suitably about 1.2 ≦ φ _c ≦ 1.4. is there.

  In addition, since there is no difference in flexural rigidity between the vertical and horizontal directions in the column cross beam, it is possible to reduce or omit the intermediate pile for buckling prevention and improve on-site construction. It is economical to do.

  According to the present invention, the cross section of the square steel pipe used for the column cutting beam is determined on the basis of a more realistic deformation when the assumed load is applied, which is highly reliable and economical. Column cut beam structure can be provided.

It is a top view which shows the outline | summary of column cross beam structure. The structure of a column cutting beam and the outline of a loading method are shown, FIG. 2 (a) is a top view, FIG.2 (b) is a side view. It is a figure showing the result of the tension test of the square steel pipe used for column cross beam. Across the pin support as a load of the column Setsuhari central receiving a beam center vertical load P _v (load due to vertical jack) P _v - is a diagram showing a relation of vertical displacement u _v. Figure 5 (a-1), ( a-2), (a-3) , in the column Setsuhari undergoing vertical load P _v and axial compression load N as across the pin _{support, P v = 25kN, P v} = 50kN , P _v = represents a moment distribution bending at each vertical load of 70 kN, FIG. 5 (b-1), ( b-2), (b-3) _{is, P v = 25kN, P v} = 50kN, P v = It is a figure showing distribution of value (phi) calculated by (1) Formula in each vertical load of 70 kN.

  FIG. 1 shows the outline of the column cutting beam structure dealt with in the present invention, which comprises the column cutting beam 1 and the preload jack 2, the hammering piece 3 and the adjusting member 4, and the respective members are bolted to each other There is.

  Further, a cold-rolled rectangular steel pipe (STKR 490) is used as the column cutting beam 1, and an adjusting material 4 obtained by processing an H-shaped steel having the same outer diameter as the column cutting beam 1 is used.

  Also, pin supports are provided at both ends of the column cutting beam 1, the rotation direction is the vertical direction in FIG. 2 (a), and the supporting span (length between pin centers) of the column cutting beam 1 is 13393 mm. There is.

  In such a configuration, when the vertical load (uniform distribution load) and the axial compression load act on the column cutting beam 1, a theoretical formula for determining the bending moment M generated in the column cutting beam 1 is derived.

  However, in consideration of the fact that the adjustment members 4 and the preload jacks 2 at both ends have a short material length and that the bending rigidity is not extremely low, and the compression load always acts in the material axial direction, column cutting is uniform over the entire length Treated as a single member of a beam, that is, a square steel pipe.

Considering the balance of microelements with EI for bending rigidity of column cutting beam 1, u for deflection, u _{0 for} initial deflection, N for axial compressive force acting on column cutting beam 1 and w for equally distributed load (2 The relationship of the equation is established.

The initial deflection u ₀ is the deflection before loading and is given by a half-wave sin wave having an amplitude k ₁ (however, the member length (the length between pins) is l), and the relationship of the equation (3) Is established. Further, since both ends of the column cutting beam 1 are pin-supported, the equation (4) is established at z = 0 and z = 1.

………(2)式

......... (2)

………(3)式

......... (3)

………(4)式

......... (4)

  Then, according to the equations (2) to (4), the deflection curve u when the axial compressive force N and the equally distributed load w act on the column cutting beam 1 is determined by the equation (5), and the bending moment M is (6) It is obtained by the formula.

………(5)式

......... (5)

………(6)式

......... (6)

Further, in order to take account of the single point concentrated load P _v in the vertical direction shown in FIG. Axial force N is not applied, only the P _v is defined as a new initial deflection values plus the initial deflection u ₀ in deflection occurs when applied, (2), the curve u deflection from (4) It can be asked.

The bending moment distribution can be obtained by superposing the bending moment distribution when only P _v acts on the left side of the equation (6).

  FIGS. 2 (a) and 2 (b) illustrate the outline of the test loading method of the column cross beam which receives vertical load and axial compression load as both-ends pin support. Moreover, FIG. 3 represents the result of the tension test of the square steel pipe used for column cross beam.

  As the column cutting beam, STKR 490 having a sectional size of -350 × 16 was used. In addition, ignoring the blowout pieces, pin supporting members were provided at both ends of the column cutting beam, and a support (not shown) was provided to support the entire column cutting beam horizontally. The rotation direction of the pin is the vertical direction in FIG. 2A, and the pin center distance is 13393 mm.

  In such a configuration, the support for horizontally supporting the column cutting beam is removed, and then an axial force of 1950 kN is applied by the horizontal hydraulic jack, and incrementally loaded by the vertical hydraulic jack at the center of the column cutting beam while holding this. Continued loading until the load resistance decreased.

  In addition, in the design of the cut beam, in general, the vertical load assumes an equally distributed load of about 5 kN / m assuming its own weight and loading load, but it is not easy to reproduce this by an experiment and substitute it with one point concentrated load. did.

FIG. 4 shows the relationship between the load P _v -vertical displacement u _v by the vertical jack in the center of the column cutting beam in FIGS. 2 (a) and 2 (b).

Further, FIG. 5 (a-1), ( a-2), (a-3) is vertical load _{P v = 25kN, P v =} 50kN, P v = 70kN each load P _v of (in FIG. 4 ▼) Bending moment distribution of the column cutting beam in. However, the bending moment M was calculated using the curvature calculated | required from the strain gauge measurement value stuck on the upper and lower surface of the column cutting beam.

Moreover, FIG. 5 (b-1), (b-2), (b-3) is calculated from (1) Formula in each load of vertical load _Pv = 25kN, _Pv = 50kN, _Pv = 70kN. It represents the distribution of the value φ. φ _c = 1 represents a yield condition.

………(1)式

………(1 set

In FIG. 5, the solid line is an experimental value, and the broken line is a calculated value calculated by the theoretical formula (1). However, as shown in FIG. 3, the column shear beam material has an early decrease in tangential stiffness, and here N _y is the axial force (yield stress is 0.2 when the tangential stiffness is half of the initial stiffness). Approximately 70% of the% offset resistance = 324 N / mm ² ).

5 from P _v = 25 kN, values calculated using the theoretical expression of the P _v = 50kN (1) can be said to capture generally the experimental results. The difference between the calculated result and the experimental result is considered to be due to the difference between the initial deflection assumed in the calculation and the experimental result, and the difference in the generated deformation mode (the calculation assumes a symmetric first-order mode) Be

Moreover, at P _v = 70 kN, φ _c = 1 is exceeded, and the bending rigidity of the column cutting beam 1 starts to decrease, so the experimental value slightly exceeds the calculated deflection value assuming elastic retention There is.

  From the above, it has been proved that the cross section of the square steel pipe used for the column cutting beam 1 can be determined easily and appropriately using the equation (1) within the elastic range.

  In addition, in the verification by FEM, it has been proved that it is possible to appropriately determine the cross section of the square steel pipe by the equation (1).

  The present invention determines the cross section of the square steel pipe used for the column cut beam based on the more realistic deformation when the assumed load is applied, thereby providing a highly reliable and economical column cut beam structure. Can be provided.

1 Column cut beam 2 Preload jack 3 Burned piece 4 Adjustment material

Claims (5)

In the column cutting beam structure using a square steel pipe receiving a vertical load and an axial compression load, the square steel pipe satisfies the equation (1) for the vertical load and the axial compression load and within the range of 1.2 ≦ φ _c ≦ 1.6. Column cross beam structure characterized in that a cross section of the cross section is formed.

………(1 set

EQUATION 6 EQUATION 6 EQUATION 6 (6) Formula However, N is axial compression force, N _y is yield axial force, M is a bending moment produced with a vertical load and axial force action, M _y is yield bending moment, (phi) _c is a safety factor . The column cut beam structure according to claim 1, wherein the square steel pipe is a cold roll formed square steel pipe, and a cross section of the square steel pipe is formed in a range of 1.4 ≦ φ _c ≦ 1.6. Cross beam structure. In the column cut beam structure according to claim 1, the square steel pipe is a square steel pipe including a plurality of steel plates and a welded portion connecting the steel plates, and a cross section of the square steel pipe is in a range of 1.2 ≦ φ _c ≦ 1.4. Column cutting beam structure characterized by being formed of   The column cutting beam structure according to any one of claims 1 to 3, wherein a support span of the column cutting beam is 10 m or more. In the method of determining the cross section of a column cut beam using a square steel pipe subjected to vertical load and axial compression load, the above equation (1) is satisfied for the vertical load and axial compression load , and within the range of 1.2 ≦ φ _c ≦ 1.6. section determining method of a column switching beams and determining the cross-section of the square tube.

………(1 set

Where N is axial compression force, N _y is yield axial force, M is bending moment generated with vertical load and axial force, M _y is yield bending moment, and φ _c is safety factor .

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