JP5149745B2 - Steel and steel shell joint structure - Google Patents

Description

  The present invention relates to a joining structure of a steel frame (H-shaped steel) and a steel shell.

In construction work such as composite ramen bridges, it is basically designed to be a rigid joint at the part where the steel frame and steel shell are joined to join the bridge substructure (bridge pier) and the bridge superstructure. Therefore, when a pulling force acts on the steel frame, it is necessary that the relative extraction amount of the steel frame and the steel shell be kept small.
As a joint structure between a bridge pier and a bridge superstructure to which such a steel frame-steel shell joint structure is applied, for example, concrete is filled so as to project the upper ends of a plurality of steel frames to form a bridge pier. And the cross beam is formed in a frame shape by a plurality of main beams arranged in parallel and a horizontal plate connecting the main beams. In addition, there is a technology that divides the internal space of the cross beam into a plurality of cell chambers by the main beam and the horizontal plate, inserts the steel frame of the pier into the cell chamber, and fills the inside with concrete to join the pier and the cross beam. It is known (see, for example, Patent Document 1).
JP 2007-322232 A

However, the technique described in Patent Document 1 describes the method of filling the constituent material of the joint structure and the concrete, and does not describe the design method and arrangement method of the constituent material. The evaluation method of the bonding performance and the design method and arrangement method for ensuring sufficient bonding performance are not clear.
Therefore, the present invention determines the dimensions and arrangement methods of main constituent materials in consideration of the load transmission mechanism and damage mechanism from the steel frame to the steel shell based on several structural experiments and FEM analysis. And it aims at providing the joining structure of the steel frame and steel shell which has sufficient joining performance by evaluating joining performance of a steel frame and steel shell, and performing appropriate design.

In order to solve the above-mentioned problems, the invention of claim 1 is, for example, as shown in FIG. 1, in which a steel frame 2 made of H-shaped steel 21 is arranged in a steel shell 1 and concrete 3 is placed in the steel shell. In the joint structure of steel frame and steel shell,
When the H-shaped steel is withdrawn from the steel shell, the split crack generation load P _{cr in which the} split crack 4 is generated in the concrete from the flange end of the H-shaped steel generated when the pulling force is resisted is expressed by the following equation (1) and The expression (2) is satisfied.
P _cr = L ′ × 4W _r × f _t Formula (1)
P _cr > P _y Formula (2)
[here,
L ′: fixing length of H-shaped steel to concrete (mm) (including transition zone length),
W _r : Split crack resistance length (mm) {W _r = 0.40B + 40, where 0.84B ≦ W _r },
B: H-shaped steel flange width (mm) {provided that 150 ≦ B}
f _t : Concrete tensile strength (N / mm ² ),
P _y : _Y- shaped steel yield load {P _y = A _s × f _y },
A _s: cross-sectional area of the H-section steel (mm ^2),
f _y : The yield strength (N / mm ² ) of the H-shaped steel. ]

According to the invention of claim 1, since the split crack generation load P _cr generated when the H-shaped steel is pulled out from the steel shell satisfies the above formula (1), the split crack generation load P _cr is the tensile strength and resistance area of the concrete. Determined by Therefore, by calculating the split crack generation load P _cr and making this split crack generation load P _cr larger than the yield load P _y of the H section steel, the fixing length of the H section steel, the flange width of the H section steel, concrete The tensile strength of is appropriately selected. As a result, the design is facilitated, and the steel shell and the steel frame can be reliably joined.

The invention of claim 2 is, for example, as shown in FIG. 1, in the joining structure of the steel frame and the steel shell according to claim 1,
The steel shell is formed by assembling a steel plate (for example, main girder 11 and cross beam 12) in a frame shape,
When pulling out the H-shaped steel from the steel shell, an adhesion damage generation load Pb that causes adhesion damage generated at the interface between the H-shaped steel and the concrete when resisting the pulling force is expressed by the following formulas (3) to (5 ) Is satisfied.
P _b = τ × L × 2B × n × βv (3)
τ = √f ′ _c · (1.28 + 6.60 Kc) (4)
P _b > P _y Formula (5)
[here,
τ: adhesion strength (N / mm ² ),
L: Length of fixing of H-shaped steel to concrete (mm) (excluding transition zone length),
f ′ _c : Concrete strength (N / mm ² ) (f ′ _c ≦ 60 N / mm ² ),
Kc: constraint coefficient (= t / B),
t: half the thickness of the steel sheet (mm)
B: Flange width (mm) of H-shaped steel (width per one),
n: number of H-section steels
βv: coefficient relating to the out-of-plane rigidity of the steel shell (= 0.3 / (v + 0.3) +0.7),
v: Deflection amount of steel shell (mm). ]

According to the invention of claim 2, since the deposited damage generated load P _b occurring H-section steel and the interface of the concrete that occurs when pulling out the H-shaped steel from the steel shell satisfies the above formula (2), adhesion damage generated load P _b is It is determined by factors relating to adhesion strength, fixing length of H-shaped steel, flange width and number of H-shaped steel, and out-of-plane rigidity of the steel shell. Therefore, to calculate the adhesion damage generated load P _b, the adhesion damage generated load P _b to be larger than the yield load P _y of steel, adhesive strength, fixing the length of the H-shaped steel, the flange width of the H-shaped steel and By appropriately selecting the number and the coefficient relating to the out-of-plane rigidity of the steel shell, the design is facilitated and the steel shell and the steel frame can be reliably joined.

  According to the present invention, an appropriate design can be performed, and sufficient joining performance can be ensured in a joining structure of a steel frame and a steel shell.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 (a) is an external perspective view showing a joining structure of a steel frame and a steel shell according to the present invention, FIG. 1 (b) is a front sectional view of FIG. 1 (a), and FIG. 1 (c) is FIG. FIG. 1 (d) is a top sectional view of FIG. 1 (a).
The steel shell 1 includes a main girder 11 provided opposite to each other, and cross beams 12 and 12 arranged between the main girds 11 and 11. The steel shell 1 has a space formed therein by assembling the main beam 11 and the cross beam 12 into a rectangular frame shape. And the steel frames 2, 2, ... are arrange | positioned in the internal space of the steel shell 1, and also the concrete 3 is laid.
The steel frame 2 is an H-shaped steel 21, and a large number of striped transverse nodes 212 are formed on the outer surface of the flange 211. The H-shaped steel 21 is rigidly connected to the concrete 3 placed in the steel shell 1 by the horizontal nodes 212. In the present embodiment, three H-shaped steels 21 are arranged in the steel shell 1 at equal intervals.

In the joint structure of the H-shaped steel 21 and the steel shell 1, when the H-shaped steel 21 is pulled out from the steel shell 1, split cracks are generated in the concrete 3 from the tip of the flange 211 of the H-shaped steel 21 that is generated when the pulling force is resisted. The split crack generation load P _{cr at} this time satisfies the following expressions (1) and (2).
P _cr = L ′ × 4W _r × f _t Formula (1)
P _cr > P _y Formula (2)
[here,
L ′: fixing length of H-shaped steel to concrete (mm) (including transition zone length),
W _r : Split crack resistance length (mm) {W _r = 0.40B + 40, where 0.84B ≦ W _r },
B: H-shaped steel flange width (mm) {provided that 150 ≦ B}
f _t : Concrete tensile strength (N / mm ² ),
P _y : _Y- shaped steel yield load {P _y = A _s × f _y },
A _s: cross-sectional area of the H-section steel (mm ²⁾
f _y : The yield strength (N / mm ² ) of the H-shaped steel. ]
In addition, the code | symbol 4 has shown the crack crack generation | occurrence | production area | region in FIG. The transition zone length refers to the length of L2 in FIG. 1 (b) and is the length of the non-fixed section of the H-shaped steel. Therefore, L ′ = L (designed fixing length: for example, the length of the portion where the horizontal node 212 of the H-shaped steel 21 in FIG. 1 is formed) + L2 (transition zone length).

Further, when pulling out the H-shaped steel 21 from the steel shell 1, is adhered damage generated load P _b which adhere damage is generated at the interface of the H-shaped steel 21 and concrete 3 caused when the resist pullout force, the following equation (3) -Formula (5) is satisfy | filled.
P _b = τ × L × 2B × n × βv (3)
τ = √f ′ _c · (1.28 + 6.60 Kc) (4)
P _b > P _y Formula (5)
[here,
τ: Adhesion strength (N / mm ² )
L: Length of fixing of H-shaped steel to concrete (mm) (not including transition zone length)
f ′ _c : Concrete strength (N / mm ² ) (f ′ _c ≦ 60 N / mm ² )
Kc: Restraint coefficient (= t / B)
t: half the thickness of the steel sheet (mm)
B: H-shaped steel flange width (mm) (width per one)
n: number of H-section steels βv: coefficient relating to out-of-plane rigidity of steel shell (= 0.3 / (v + 0.3) +0.7),
v: Deflection amount of steel shell (mm). ]

FIG. 2 shows a design flow when designing a joint structure of a steel frame and a steel shell according to the present invention using the above formulas (1) to (5).
As shown in FIG. 2, first, in designing the structure, P _cr is calculated using the above equation (1). Moreover, to calculate the yield load P _y of H-section steel from the yield strength of the cross-sectional area A _s and H-type steel H-section steel fy. On the other hand, _Pb is calculated using the above equation (3) (step S1). Then, it is determined whether or not the above formula (2) P _cr > P _y and the above formula (5) P _b > P _y are satisfied (step S2). If the above equation (2) P _cr > P _y and the above equation (5) P _b > P _y are satisfied, the design is finished. If the above formula (2) P _cr > P _y and the above formula (5) P _b > P _y are not satisfied, P _cr, P _b , P _y are set so as to satisfy the above formula (2) and formula (5). Adjustment is performed by appropriately changing each parameter value (step S3), and steps S1 and S2 are performed again. In step S2, the above equation (2) P _cr > P _y and the above equation (5) P _b > P _y are set. Steps S1 to S3 are repeated until they are satisfied.

FIG. 3 is an external perspective view showing a joining structure of a steel frame and a plurality of steel shells.
In the joining structure shown in FIG. 3, three main beams 11, 11,... Are arranged at a predetermined interval, and the two cross beams 12, 12 are arranged to face each other so as to be perpendicular to the main beam 11. . As a result, three steel shell blocks 1, 1,... Are formed. In each steel shell block 1, three steel frames (H-shaped steels 21, 21,...) 2, 2,.

Next, a concrete girder and steel girder joint structure will be described as an example in which the above-described steel frame and steel shell joint structure is applied.
FIG. 4 (a) is a perspective view showing a joint structure of one concrete girder and a steel girder.
The concrete girder 4 is formed by placing and hardening the concrete with the upper end of the H-shaped steel 21 protruding from the steel shell 1 as in the joining structure shown in FIG.
On the other hand, an insertion port 51 into which one end of the H-shaped steel 21 of the concrete girder 4 is inserted is formed on one end surface of the steel girder 5 joined to the concrete girder 4. And the concrete girder 4 and the steel girder 5 are rigidly connected by inserting one end part of the H-shaped steel 21 in the insertion slot 51 of this steel girder 5, and placing concrete in the insertion slot 51. .
FIG. 4B is a perspective view showing a joint structure of two concrete columns and a steel girder.
In FIG. 4 (b), two insertion openings (not shown) into which one end of the H-shaped steel 21 of each concrete column 41 is inserted are formed on the side surface of the steel beam 5. Then, one end portion of the H-shaped steel 21 of each concrete column 41 is inserted into each insertion port of the steel girder 5, and concrete is placed in the insertion port, whereby the concrete columns 41 and 41 and the steel girder 5 are inserted. Are firmly connected.

Next, as a damage process at the interface between the H-shaped steel and the concrete, the reproducibility of the point where split cracks are first generated and then adhesion damage proceeds with an increase in load will be described with reference to experimental examples.
FIG. 5 is a perspective view of a test body used for an experiment of extracting H-shaped steel from a steel shell.
As shown in FIG. 5, two main beams 11, 11 arranged opposite to each other, and two horizontal beams 12 sandwiched between these main beams 11, 11 so as to be perpendicular to the main beam 11. , 12 form a steel shell 1. Further, horizontal stiffeners 13 and 13 that are long in the lateral direction are fixed to the outer surfaces of the main girders 11 and 11, respectively. The longitudinal length of the main girder 11 is longer than the longitudinal length of the cross beam 12. A steel shell base plate 14 is attached to the upper end of the main girder 11 so as to close the upper end opening.
On the other hand, three H-shaped steels 21, 21,... Are erected on the H-shaped steel base plate 22, and a part of the upper side of the H-shaped steel 21 is disposed in the steel shell 1, and the concrete 3 is cast into the steel shell 1. The test body 100 is formed.
The fixing length L ′ of the H-shaped steel used here is 190 mm, the concrete nominal strength is 30 N / mm ² , the number of horizontal stiffeners is one, the main girder web interval is 200 mm, the main girder web thickness is 9 mm, and the horizontal beam The web interval is 600 mm and the cross beam thickness is 9 mm.

In such a test body 100, the H-shaped steel base plate 22 was loaded downward. At this time, the relationship between the pulling load (kN) of the H-shaped steel 21 per piece and the extraction displacement (mm) of the H-shaped steel 21 is shown in FIG.
As is apparent from the results of FIG. 6, first, split cracks occurred, and then adhesion damage progressed with increasing load. Specifically, when there are three H-shaped steels 21 as in Test Pair 100, split cracks occurred in the filled concrete with a pulling load of about 200 kN and an extraction displacement of about 0.1 mm. After that, further load was applied. Adhesion damage occurred at the interface between the filled concrete and the H-shaped steel when the extraction load was about 250 kN and the extraction displacement amount was about 0.4 mm.
Although not shown here, when the number of H-shaped steels is one, the increase in displacement associated with split cracking is small, and when the number is three, the increase in displacement is large. Further, in the case of one H-shaped steel, cracks generated from the flange tip progressed toward the steel shell, whereas in the case of three H-shaped steels, the flange tips of adjacent H-shaped steels are connected. It was confirmed that the split cracks had progressed.

Next, the calculation formula (1) of the split crack generation load is derived from the above experimental results, and the load P _cr calculated by the calculation formula (1) is lower than the initial split crack generation load by experiment and analysis. By confirming the above, it is confirmed that the calculation formula (1) has sufficient safety in the set scope. Here, the split crack generation load is a load at the time when the amount of the H-shaped steel starts to increase rapidly.
Hereinafter, a method for deriving the calculation formula (1) based on the split crack generation load will be described.
Splitting cracks occur when the tensile stress of concrete reaches the tensile strength. It was assumed that the tensile load at that time can be calculated by multiplying the area of the region where split cracks are generated by the tensile strength of the concrete.
P _cr = A _cr × f _t
[A _cr : split crack generation area (mm ² ), f _t : tensile strength (N / mm ² )]
Tensile strength _{f t} of the concrete is obtained from design strength (compressive strength) f _'c. Moreover, the split crack generation region was set based on the following assumptions.
(1) It is assumed that there is a dominant area for generating split cracks.
(2) It was assumed that the cracks were uniformly distributed along the flange surface of the H-shaped steel.
(3) One side of the dominant area is assumed to be the fixing length L ′ of the H-shaped steel (however, in the case of the experiment, the length of the non-fixing section (transition zone length) is included).
(4) the other side is referred to as the splitting crack resistance length W _r.
The load P at which the split crack is generated can be expressed as follows using the tensile strength f _t , the fixing length L ′, and the split crack resistance length Wr. “4” in the equation represents that there are four H-shaped steel flange tips for one H-shaped steel.
P = A _cr × f _t = L ′ × 4 W _r × f _t
W _r = P / ( _ft × L ′ × 4)

FIG. 7 is a diagram showing the relationship between the half value W _F of the flange tip distance of the H-shaped steel and the split crack resistance length W _r, and the basis of the crack crack generation load (crack resistance length W _r (mm ) Plot). From the results of FIG. 7, it can be confirmed that _Wr shows a constant value even when the flange tip distance of the H-shaped steel is increased. In addition, with the size of the H-shaped steel 75H, 200H, to increase the 300H, _{W r} is it can be confirmed large. Here, “75H”, “200H”, and “300H” described in FIG. 7 mean that the flange width B of the H-shaped steel is “75 mm”, “200 mm”, and “300 mm”. Further, “2.67B” means that the center interval L1 of the H-shaped steels adjacent to each other is “2.67 times the flange width B”.

Note that the _{W F} of the horizontal axis in FIG. 7, as shown in FIG. 8, a 1/2 of the tip distance of the flange 211, 211 of the H-section steel 21, 21 adjacent to each other.
Figure 9 is a diagram showing the relationship between the flange width B and Wari裂crack resistance length W _r of the H-shaped steel, the relationship between the flange width B, and sets the splitting crack resistance length W _{r =} 0.40B + 40 .

Next, by comparing the split crack generation load calculated by calculation formula (1) with the load of experiment and analysis, it is explained that calculation formula (1) has sufficient safety in the set application range. To do.
The split crack generation load (calculation load) calculated using the calculation formula (1) was compared with the load (experiment / analysis load) obtained from the experiment and analysis. FIG. 10 is a diagram showing the relationship between the calculated load applying the calculation formula (1) and the experimental / analytical load, and is a plot of the crack resistance length W _r (mm) that is a parameter of the split crack generation load. . From the results of FIG. 10, it is recognized that the calculated load and the experimental / analyzed load are generally located on a one-to-one straight line, and can be evaluated with high accuracy.

  FIG. 11 is a diagram showing the relationship between the deflection v (mm) of the steel shell and the load ratio (maximum load of experiment and analysis / calculated load based on calculation formula (3)). The plot of coefficient βv for the out-of-plane stiffness of the shell). From the result of FIG. 11, the deflection amount v of the case without the stiffener and the cases of 75H-5B, 200H-5B, and 300H-5B in which the center distance of the H-shaped steel is relatively large increased. That is, it can be confirmed that the load ratio decreases as the deflection amount v indicating the out-of-plane rigidity increases. Then, βv was determined so as to correct this load ratio to 1.0.

  FIG. 12 is a diagram showing the relationship between the calculated load to which the calculation formula (3) of the adhesion damage load is applied and the experimental / analytical load. As is apparent from FIG. 12, the calculated load and the experiment / analysis load are generally located on a straight line corresponding to one-to-one, and it is recognized that a highly accurate evaluation is possible.

FIG. 13 shows constituent parts of the joint structure of the H-shaped steel and the steel shell, constituent elements of the constituent parts, and parameters P _y , P _cr , and P _b that are affected by these constituent elements. Constituent parts include steel shells (main girders, cross beams), H-shaped steel and filled concrete. Each component L ′, L, L2, W1, t1, W2, t2, B, L1, etc. shown in FIG. 13 is shown in FIG. 1 and FIG.

As described above, since the split crack generation load P _cr generated when the H-shaped steel is pulled out from the steel shell satisfies the above formula (1), the split crack generation load P _cr is determined by the tensile strength and resistance area of the concrete. . Therefore, the split crack generation load P _cr is calculated, and the fixing length of the H section steel, the flange width of the H section steel, the concrete width of the H section steel so that the split crack generation load P _cr is larger than the yield load P _y of the H section steel. Select the tensile strength as appropriate. As a result, the design is easy and the steel shell and the steel frame can be reliably joined.
Further, since the adhesion damage generated load P _b occurring H-type steel and concrete interface which occurs when removing the H-shaped steel from the steel shell satisfies the above formula (2), adhesion damage generated load P _b is the adhesive strength, the fixing of the H-section steel It is determined by factors relating to the length, the flange width and number of H-shaped steels, and the out-of-plane rigidity of the steel shell. Therefore, to calculate the adhesion damage generated load P _b, the adhesion damage generated load P _b to be larger than the yield load P _y of steel, adhesive strength, fixing the length of the H-shaped steel, the flange width and the number of H-section steel By appropriately selecting a coefficient related to the out-of-plane rigidity of the steel shell, the design is easy and the steel shell and the steel frame can be reliably joined.
Further, since the parameters P _y , P _cr , and P _b are affected by the components shown in FIG. 13, the components can be appropriately selected by applying the above formulas (1) to (5). it can.

(a) is an external perspective view showing a joint structure of a steel frame and a steel shell in the present invention, (b) is a front sectional view of (a), (c) is a side sectional view of (a), (d) is ( It is a top view of a). It is a design flow at the time of designing the joining structure of the steel frame and steel shell which concerns on this invention using said Formula (1)-(5). It is the external appearance perspective view which showed the joining structure of the steel frame and several steel shells. (a) is the perspective view which showed the joining structure of one concrete girder and steel girders, (b) is the perspective view which showed the joining structure of two concrete pillars and steel girders. It is a perspective view of the test body used for the experiment which pulls out H-shaped steel from a steel shell. In the experiment in FIG. 5, it is the figure which showed the relationship between the extraction load of the H-shaped steel per one, and the extraction displacement of H-shaped steel. Is a diagram showing the relationship between the half value W _F and Wari裂crack resistance length W _r of the flange tip distance H-section steel, it shows evidence of splitting cracks generated load (a plot of W _r). It is a diagram showing a positional relationship such as W _r and W _F. Is a diagram showing the relationship between the flange width B and Wari裂crack resistance length W _r of the H-section steel. It is the figure which showed the relationship between the calculation load which applied the calculation formula (1) of split crack generation load, and an experiment and analysis load. It is the figure which showed the relationship between the deflection amount v of steel shell and load ratio (maximum load of experiment and analysis / calculated load by calculation formula (3)) (plot of βv). It is the figure which showed the relationship between the calculation load which applied the calculation formula (3) of an adhesion damage load, and an experiment and analysis load. The components in the joint structure of the H-shaped steel and the steel shell, and parameters P _y , P _cr , and P _b that are affected by each component are shown.

Explanation of symbols

1 Steel Shell 2 Steel 3 Concrete 4 Split Crack 11 Main Girder 12 Cross Beam 21 H-Shaped Steel

Claims (2)

In a steel-shell joint structure in which a steel frame made of H-shaped steel is placed in the steel shell and concrete is cast in the steel shell,
When the H-shaped steel is pulled out from the steel shell, the split crack generation load P _cr that generates a split crack in the concrete from the flange tip of the H-shaped steel generated when the pulling force is resisted is expressed by the following formula (1) and the following formula: (2) A structure for joining a steel frame and a steel shell characterized by satisfying the above.
P _cr = L ′ × 4W _r × f _t Formula (1)
P _cr > P _y Formula (2)
[here,
L ′: fixing length of H-shaped steel to concrete (mm) (including transition zone length),
W _r : Split crack resistance length (mm) {W _r = 0.40B + 40, where 0.84B ≦ W _r },
B: H-shaped steel flange width (mm) {provided that 150 ≦ B}
f _t : Concrete tensile strength (N / mm ² ),
P _y : _Y- shaped steel yield load {P _y = A _s × f _y },
A _s: cross-sectional area of the H-section steel (mm ^2),
f _y : The yield strength (N / mm ² ) of the H-shaped steel. ] The steel shell is formed by assembling a steel plate into a frame shape,
When withdrawing the H-shaped steel from the steel shell, the attachment damage generated load P _b which adhere damage is generated at the interface of the H-shaped steel and concrete that occurs when the resistance to pull-out forces, the following equation (3) to ( The steel frame and steel shell joint structure according to claim 1, wherein 5) is satisfied.
P _b = τ × L × 2B × n × βv (3)
τ = √f ′ _c · (1.28 + 6.60 Kc) (4)
P _b > P _y Formula (5)
[here,
τ: adhesion strength (N / mm ² ),
L: Length of fixing of H-shaped steel to concrete (mm) (excluding transition zone length),
f ′ _c : Concrete strength (N / mm ² ) (f ′ _c ≦ 60 N / mm ² ),
Kc: constraint coefficient (= t / B),
t: half the thickness of the steel sheet (mm)
B: Flange width (mm) of H-shaped steel (width per one),
n: number of H-section steels
βv: coefficient relating to the out-of-plane rigidity of the steel shell (= 0.3 / (v + 0.3) +0.7),
v: Deflection amount of steel shell (mm). ]

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