JP2008050788A - Seismic strengthening structure of existing building - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seismic strengthening structure of an existing building with excellent strength, which is based on proper design strength. <P>SOLUTION: In this seismic strengthening structure 10, a reinforcing body 16, which is composed of concrete higher in compressive strength than concrete constituting a columnar body 12 and a beam body 14, is fixed onto the outer surface of the beam body 14 and that of the columnar body 12 positioned on the side of the exterior wall of the existing building. In this case, anchor bolts 22 can also be driven between the outer surface of the columnar body 12 and the reinforcing body 16, and between the outer surface of the beam body 14 and the reinforcing body 16, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a seismic reinforcement structure for an existing building, and more particularly to a seismic reinforcement structure for an existing building that reinforces a column or a beam from the outside of the existing building.

  Conventionally, as a seismic reinforcement structure for existing buildings, it is possible to proceed with construction while using the building, and it is possible to work without dismantling existing walls and sashes, etc. The one to be constructed by this work has been proposed.

  For example, in Patent Document 1, as shown in FIG. 7, a concrete body 68 including a steel plate 66 is formed by anchor bolts 64 placed on the outer surface of a columnar body (beam body) 62 located on the outer wall side of an existing building. A seismic reinforcing structure 60 for an existing building is disclosed in which a reinforcing body 70 is integrated.

  Conventionally, it has been considered that the reinforcing body 70 is integrated with the columnar body (beam body) 62 of the existing building by the anchor bolts 64 that have been placed, so that the dowel resistance of the anchor bolts 64 is reduced. The design yield strength of the joint between the reinforcing body 70 and the column (beam) 62 of the existing building was evaluated by the evaluated shear strength formula.

Japanese Patent No. 3051071

  However, when an earthquake occurs, the anchor bolt exerts its proof strength after the joint between the reinforcing body and the column or beam of the existing building is greatly displaced. On the other hand, as shown in Patent Document 1, in the seismic reinforcement in which a reinforcing body is added to the outside of a column or beam body of an existing building, the inner peripheral side of the existing frame composed of the column body and the beam body Unlike seismic reinforcement that adds additional reinforcement to the existing structure, the reinforcement is not constrained by the existing frame, so if the joint between the reinforcement and the column or beam of the existing building is displaced significantly, the earthquake resistance will deteriorate rapidly. .

  In other words, with seismic reinforcement that adds reinforcements to the outside of the columns and beams of existing buildings, evaluating the design strength due to the dowel resistance of the anchor bolts results in an evaluation in the range where the seismic performance deteriorates rapidly. Design strength of the part is not correctly evaluated. Therefore, in this case, the design strength of the joint should be evaluated in a range where the joint between the reinforcing body and the column or beam of the existing building is not greatly displaced.

  The shear resistance element of the joint at this time is considered to be fixed resistance. However, at present, there has not been proposed a method for evaluating a shear strength formula that can appropriately evaluate the fixed resistance. Therefore, it is desired to perform seismic reinforcement of existing buildings having excellent proof strength based on appropriate design proof strength.

  The problem to be solved by the present invention is to provide a seismic reinforcement structure for an existing building having an excellent strength based on an appropriate design strength.

  Therefore, as a result of intensive studies by the present inventors, it has been found that the bond strength of the joint can be evaluated by the split tensile strength of the concrete constituting the column or beam of the existing building. And this knowledge came to complete the seismic reinforcement structure of the existing building which has the excellent proof strength based on the appropriate design proof strength.

  In order to solve the above-mentioned problems, the seismic reinforcement structure for an existing building according to the present invention comprises the column and / or the beam on the outer surface of the column and / or the outer surface of the beam located on the outer wall side of the existing building. The gist of the invention is that a reinforcing body composed of concrete having a compressive strength higher than that of the concrete to be fixed is fixed.

  In this case, anchor bolts may be provided between the outer surface of the column body and the reinforcing body and / or between the outer surface of the beam body and the reinforcing body.

  According to the seismic reinforcement structure of an existing building according to the present invention, since the reinforcement is fixed to the outer surface of the column and / or the outer surface of the beam located on the outer wall side of the existing building, The proof stress is exhibited in a micro-deformed region before the joint between the column and / or the beam of the existing building is greatly displaced. Thereby, the reinforcement body and the existing building are integrated, and the shearing force due to the earthquake is transmitted between the two.

  At this time, since the reinforcing body is fixed to the column and / or beam of the existing building, in the evaluation of the design strength of the joint, not the dowel resistance of the anchor bolt but the fixing strength that demonstrates the strength in a minute deformation region Can be evaluated. As a result, the design strength of the joint is correctly evaluated.

  And the fixation strength by adhesion strength can be evaluated by the splitting tensile strength of the concrete which comprises the column and / or beam of an existing building. Since the evaluation of the bond strength with the split tensile strength of the concrete that constitutes the columns and beams of the existing building is not an evaluation based on the shear strength formula of the joint surface, the degree of roughening of the joint surface, the amount of anchor bolts, anchors It is not related to the effective depth of the bolt. Therefore, since the fixing strength can be evaluated without being influenced by these factors, seismic reinforcement based on an appropriate design strength is possible.

  Further, according to this knowledge, the reinforcing body is made of concrete having a compressive strength higher than the compressive strength of the concrete constituting the column and / or the beam of the existing building, so at least the column of the existing building and / or Alternatively, the reinforcement body is not destroyed before the concrete constituting the beam body is destroyed, and the seismic reinforcement structure for an existing building having an excellent strength based on an appropriate design strength is obtained.

  In this case, if an anchor bolt is driven between the outer surface of the column body and the reinforcing body and / or between the outer surface of the beam body and the reinforcing body, the existing portion at the joint surface due to a large earthquake. Even if the concrete is destroyed, the reinforcement is prevented from falling off the existing building.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of the seismic reinforcement structure for an existing building according to the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the seismic reinforcement structure of the existing building shown in FIG.

  As shown in FIG. 1, the seismic reinforcement structure 10 for an existing building according to an embodiment of the present invention includes a column body 12 and a beam body 14 of the existing building, and each of the column body 12 and the beam body 14. This is a structure in which a reinforcing body 16 is added to the outer surface of the. The column 12 and the beam 14 of the existing building are located on the outer wall side of the existing building, and the reinforcing body 16 is added to the outside of the existing building. The column 12 and the beam 14 of the existing building are made of concrete. The concrete which comprises the column 12 and the beam body 14 is not specifically limited, Any of concrete, a reinforced concrete, steel concrete, and reinforced steel concrete may be sufficient.

  The reinforcing body 16 is steel concrete in which a steel frame 18 made of H-shaped steel is included in a concrete 20, and is fixed to the concrete constituting the column body 12 and the beam body 14 by concrete on each outer surface.

  The concrete constituting the reinforcing body 16 is higher in compressive strength than the concrete constituting the column 12 and the beam 14 of the existing building.

  Anchor bolts 22 arranged in parallel in two rows along the H-shaped steel 18 are interposed between the columnar body 12 and the beam body 14 of the existing building and the reinforcing body 16.

  In the seismic reinforcement structure 10 of the existing building, the reinforcement part of the column 12 is enlarged and described. As shown in FIG. 2A, a mounting hole 24 for attaching the anchor bolt 22 is provided on the outer surface 12a side of the column 12 of the existing building, and the anchor bolt 22 is fixed to the mounting hole 24 with an adhesive. Yes. An H-shaped steel 18 is attached to the anchor bolt 22 by being sandwiched between a pair of nuts 28 and a washer 30 through an insertion hole 26. The concrete 20 of the reinforcing body 16 is placed on the outer surface 12a of the column 12 so as to surround the anchor bolt 22 and the H-shaped steel 18.

  Next, an example of a method (seismic reinforcement method) for constructing the earthquake-proof reinforcement structure 10 for an existing building according to the present embodiment will be described.

  First, anchor bolts 22 are driven from the outer surfaces of the column 12 and the beam 14 located on the outer wall side of the existing building at a constant pitch. Next, the H-section steel 18 is fixed to the anchor bolt 22 and the H-section steel 18 is arranged on the outer wall side of the existing building. For example, the H-shaped steel 18 is disposed about 10 cm away from the outer surface of the column 12 or the beam 14 and attached to the anchor bolt 22.

  The anchor bolts 22 are placed in one or a plurality of rows along the axial direction of the column body 12 or the beam body 14. When the anchor bolts 22 are driven in a plurality of rows along the axial direction of the column bodies 12 and the beam bodies 14, it is preferable in that the reinforcing bodies 16 are more firmly fixed to the column bodies 12 and the beam bodies 14. The anchor bolt 22 is fixed by an adhesive (not shown) when it is placed on the column body 12 or the beam body 14. The anchor bolt 22 and the H-shaped steel 18 may be placed on both the column body 12 and the beam body 14 or may be placed only on either the column body 12 or the beam body 14.

  Next, a mold (not shown) is assembled so as to surround the anchor bolt 22 and the H-shaped steel 18 fixed to the column body 12 and the beam body 14, and this mold is wrapped so as to wrap the anchor bolt 22 and the H-shaped steel 18. Concrete 20 is placed in the frame. As the concrete 20 to be placed, concrete having a higher compressive strength than the concrete constituting the column body 12 and the beam body 14 is used. When the concrete 20 is placed, the concrete 20 of the reinforcing body 16 is fixed to the outer surface 12a of the concrete constituting the column body 12 and the beam body 14.

  According to the seismic reinforcement structure 10 for an existing building configured as described above, the reinforcement body 16 is fixed to the outer surface of the column body 12 and the outer surface of the beam body 14 located on the outer wall side of the existing building. The proof stress is exhibited in a micro-deformed region before the joint between the column 16 and the beam body 14 of the existing building 16 and the beam body 14 is greatly displaced. Thereby, the reinforcement body 16 and the existing building are integrated, and the shearing force due to the earthquake is transmitted between the two.

  And since the reinforcement body 16 is comprised with the concrete which has a compressive strength higher than the compressive strength of the concrete which comprises the column 12 and the beam 14 of an existing building, at least the column 12 and the beam 14 of an existing building are used. The reinforcing body 16 is not destroyed before the constituting concrete is destroyed, and has excellent proof stress.

  Furthermore, since the anchor bolt 22 is driven between the outer surface of the column 12 and the reinforcing body 16 or between the outer surface of the beam body 14 and the reinforcing body 16, the concrete in the existing portion at the joint surface due to a large earthquake. Even if it is destroyed, the reinforcing body 16 is prevented from falling off the existing building.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment at all, A various change is possible in the range which does not deviate from the summary of this invention.

  For example, the seismic reinforcement structure 10 of the existing building shown in FIG. 1 reinforces both the column body 12 and the beam body 14, but reinforces only one of the column body or the beam body. Of course it is good. Moreover, in the earthquake-proof reinforcement structure formed by concrete placement on site, the anchor bolt 22 may not be used. The shape steel included in the reinforcing body is not limited to the H-shape steel 18, and various shape steels can be used. Moreover, a plate-shaped steel plate may be sufficient. The section steel and the steel plate may be reinforced. The concrete used for the reinforcing body may be reinforced with fiber reinforced concrete.

  Further, the reinforcing body is not limited to concrete placed on site, but may be made of precast concrete 34, such as the seismic reinforcement structure 32 of an existing building shown in FIG. The precast concrete 34 may be unreinforced concrete or reinforced concrete. At this time, the precast concrete 34 is fixed to the column 12 of the existing building through the adhesive 36.

  Furthermore, it is also possible to combine a damping member such as a streak type or a stud type on the inner peripheral part of this reinforcing frame.

  Next, examples will be described.

(Outline of specimen)
The test body was an element model in which an existing part and a reinforcing part shown below were joined. As for the joining method between the existing part and the reinforcing part, the specimens used in Examples 1 to 3 in Table 3 are joined with concrete and anchor bolts. It is joined with. That is, in the embodiment, all are fixed by concrete. On the other hand, in Comparative Example 1, although it was joined with the anchor bolt, the concrete was not fixed on the joining surface. In addition, the joint surface of the existing part is subjected to roughing processing in a checkered pattern with a bishan finish. Placing the reinforced concrete was carried out with the joint surface vertical, just like the actual reinforcement work.
Existing part: 500 x 1400 x 450 mm rectangular concrete Reinforced part: 300 x 800 x 200 mm rectangular concrete

  Table 1 shows the concrete material characteristics of the existing part and the reinforced part.

(Table 1)

The shear design yield strength Q by the anchor bolt of the test body was calculated using the following (formula 1) to (formula 4). In other words, the proof stress of the steel material constituting the anchor bolt and the bearing strength of the concrete are compared, and the smaller one is set as the shear design proof strength Q _a per anchor bolt.

Q = n × Q _a (Formula 1)
Q _a = min [Q _a1 , Q _a2 ] (Formula 2)
Q _a1 = 0.7 × σ _y × S (Formula 3)
Q _a2 = 0.4 × √ (E _c × σ _B ) × S (Formula 4)
n: Number of anchor bolts (pieces)
Q _a1 : Shear strength per anchor bolt (N) determined by the strength of steel
Q _a2 : Shear strength per anchor bolt (N) determined by concrete bearing strength
σ _y : Yield point strength of anchor bolt (N / mm ² )
S: Cross section of anchor bolt (mm ² )
E _c : Young's modulus (N / mm ² ) of the concrete in the existing part
σ _B : Compressive strength (N / mm ² ) of existing concrete

Here, σ _y = 387 (N / mm ² ), S = 286.5 (mm ² ), E _c = 21106 (N / mm ² ), and σ _B = 16.0 (N / mm ² ). Q _a1 = 78.0 (kN), Q _a2 = 66.6 (kN) According to (Formula 1) to (Formula 4), all of Examples 1 to 4 and Comparative Example 1 were tested. The shear design proof strength Q of is the number of anchor bolts × Q _a2 . Therefore, when there are three anchor bolts, Q = 200 (kN), when there are four anchor bolts, Q = 267 (kN), and when there are five anchor bolts, Q = 333 (kN).

(Outline of test method)
This test assumes reinforcement at the center of the outer surface of the beam located on the outer wall side of the existing building. In such a position, the rigidity of the reinforcing part in the out-of-plane direction is smaller than that of the existing part including the slab. Therefore, the vertical stress acting on the joint surface due to eccentric bending is concentrated on the joint surface at the end of the beam body. This is based on the assumption that the joint surface between the existing part at the center of the body and the reinforcing part is close to a pure shear stress state in which only shear stress is applied. Therefore, loading onto this joint surface was performed by the method described below.

  FIG. 3 is a schematic diagram illustrating a test method in the examples, and is a plan view (a) and a front view (b). As shown in FIG. 3, the existing portion 42 of the test body 38 is fixed to the loading frame 46 with bolts 44 so that the reinforcing portion 40 of the test body 38 faces the front. Next, a pair of hydraulic jacks 48a and 48b disposed on the same plane as the joint surface 38a are brought into contact with both side portions of the reinforcing portion 40 from both sides of the loading frame 46, and the pair of hydraulic jacks 48a and 48b are expanded and contracted left and right. By doing so, only the shearing force is loaded (loaded) on the joint surface 38a.

Table 2 shows the loading program at this time. The loading program loads the shear design proof strength (number of anchor bolts × Q _a2 ) of the anchor bolts evaluated for dowel resistance in cycles 1 to 5 by load control. In cycles 6 to 10, the existing parts and the reinforcing portions are loaded. It was loaded by displacement control based on the amount of displacement in between.

(Table 2)

  The maximum proof stress was the maximum load when loaded based on the above loading program, and the fixed proof stress was the load at which the displacement increased when the load was applied. Therefore, the adhering strength is a load when the rigidity is lowered before the target displacement (0.4 mm) of cycle 6 is reached by the load controlled by the displacement control of the load program described above.

(Example)
Based on the loading program described above, the load is applied to the reinforcing part of each specimen using a hydraulic jack, and the shear force is applied to the joint surface between the existing part of the specimen and the reinforcing part (loading), and the maximum proof stress and adhesion are achieved. Yield strength was measured. The results are shown in Table 3. Moreover, the relationship between the load measured by Example 1 and a displacement is shown in FIG. FIG. 4A shows the relationship between the load and displacement in cycles 1 to 6 in an enlarged manner, and FIG. 4B shows the relationship between the load and displacement in cycles 1 to 10. It is a thing.

(Comparative example)
The maximum proof stress and the sticking strength were measured under the same conditions as in Example 1 except that the concrete was not stuck to the existing portion of the reinforcing portion. The results are shown in Table 3. Moreover, the relationship between the load measured by the comparative example 1 and the displacement is shown in FIG. FIG. 5A is an enlarged view of the relationship between the load and the displacement in cycle 1, and FIG. 5B shows the relationship between the load and the displacement in cycles 1 to 10 and the presser. It is a thing.

(Table 3)

  In Example 1, as shown in FIG. 4 (a), there is no progress of displacement in cycles 1 to 5 by load control with the shear design proof stress of the anchor bolt (267 kN, indicated by a broken line in the figure) as a loading target, and elastic. The rigidity is lowered before the target displacement (0.4 mm) is reached in cycle 6 by displacement control. As a result, the sticking strength was 391 kN. The yield strength at the target displacement (0.4 mm) was 513 kN. Then, since the load has reached the fixing strength in cycle 6, as shown in FIG. 4B, in the subsequent cycles 7 to 10, the proof stress at each target displacement gradually decreases. Therefore, the proof stress 513 kN at the target displacement (0.4 mm) of cycle 6 was the maximum proof stress.

  On the other hand, in Comparative Example 1, as shown in FIG. 5 (a), the displacement progressed from cycle 1 by the load control with the loading design target of the shear design strength of the anchor bolt (267 kN, indicated by the broken line in the figure). . Moreover, as shown in FIG.5 (b), in cycles 6-10 by displacement control, the yield strength in each target displacement is falling gradually with the progress of displacement. Then, when the displacement was set to the push-off, the proof stress exceeding the shear design proof strength (267 kN) of the anchor bolt was exhibited for the first time when the displacement exceeded 10 mm, and the maximum proof stress was 301 kN when the displacement was about 25 mm.

  Based on this result, looking at the influence of the concrete of the reinforcing part to adhere to the concrete of the existing part, when there was no adhesion as in Comparative Example 1, the shear design strength (267 kN) of the anchor bolt was experienced five times. In the subsequent 6th cycle and after, the same proof stress as the anchor bolt's shear design proof strength (267 kN) was finally exhibited when it was greatly displaced (displacement exceeded 10 mm). Further, it was confirmed that a larger deformation (displacement of about 25 mm) is required to reach the maximum yield strength. On the other hand, when there is sticking as in Example 1, even in the 6th cycle after experiencing the shear design strength (267 kN) of the anchor bolt 5 times, the displacement of the anchor is less than 0.1 mm in the small deformation region. It was confirmed that the sticking strength significantly exceeding the shear design strength (267 kN) was exhibited.

  In external seismic reinforcement that adds reinforcements to the outside of an existing building, the seismic performance deteriorates drastically when the joint between the reinforcement and the pillars and beams of the existing building is displaced greatly. It should be designed, and in the seismic reinforcement according to the present embodiment, it is better to design the proof strength not by the shear design proof strength of the anchor bolt but by the fixing proof strength of the joint surface.

  In addition, when the influence of the number of anchor bolts on the proof stress according to Examples 1 to 4 is shown in Table 3, from the experimental results of changing the number of anchor bolts in the range of 0 to 5, There was no relationship in which the bond strength increased as the number of bolts increased. As shown in the example of FIG. 4A, the displacement when exhibiting the anchoring strength is 0.1 mm or less in any case, and the dowel resistance due to the anchor bolt is reduced to the anchoring strength in the minute deformation region. It was confirmed that there was almost no effect.

  Therefore, in the evaluation of the design strength of the joint, it is considered that the design strength of the joint is correctly evaluated by evaluating the fixing strength that exhibits the strength in the minute deformation region, not the dowel resistance of the anchor bolt.

  Next, the relationship between the bond strength and the split tensile strength of the existing concrete will be described.

  Based on the assumption that pure shear stress is acting uniformly on the joint surface, (Equation 5) is established based on the relationship with the Mohr fracture envelope of the existing part concrete shown in FIG.

τ _k = σ _t (Formula 5)
τ _k : Bond strength of existing concrete (N / mm ² )
σ _t : Split tensile strength of existing concrete (N / mm ² )
However, an adhesion strength (N / ^mm 2) = sticking strength / junction area (mm ^2), the junction area is the junction area between the existing part and the reinforcing part (= 240000mm ^2).

Here, the split tensile strength of the existing part concrete is obtained from the age of the existing part concrete. Table 1 shows the relationship between the age of the material and the split tensile strength of the existing part concrete. Table 3 shows the split tensile strength of the existing part concrete for the specimen used in Example 1-4. Thus, it exists in the range of 1.87-1.90 (N / mm < ² >).

On the other hand, as shown in Table 3, the fixing strength by the fixing strength measured by each test body according to Examples 1 to 4 is in the range of 1.57 to 2.04 (N / mm ² ). That is, it can be seen that the split tensile strength of the existing part concrete agrees well with the fixing strength by the fixing strength measured in Examples 1 to 4.

  As described above, from the relationship between (Equation 5) and the split tensile strength and fixing strength of the existing concrete shown in Table 3 shown from the experimental results, the fixing strength is that of the concrete constituting the column and beam of the existing building. It was confirmed that it can be evaluated by splitting tensile strength.

  And by this knowledge, the reinforcement body is comprised with the concrete which has a compressive strength higher than the compressive strength of the concrete which comprises the pillar and / or beam of an existing building.

  The seismic reinforcement structure of an existing building according to the present invention can be used for seismic reinforcement of various building structures such as steel reinforced concrete construction, reinforced concrete construction, steel construction, etc. Can be used.

It is the schematic showing one Embodiment of the earthquake-proof reinforcement structure of the existing building which concerns on this invention. It is a principal part expanded sectional view of the earthquake-proof reinforcement structure of the existing building shown by FIG. It is the schematic showing the test method of an Example. 3 is a graph showing the relationship between load and displacement in Example 1. 10 is a graph showing the relationship between load and displacement in Comparative Example 1. It is a graph which shows the destruction envelope of Mohr of existing part concrete. It is sectional drawing showing the seismic reinforcement structure of the conventional existing building.

Explanation of symbols

10 Seismic reinforcement structure for existing building 12 Column 14 Beam 16 Reinforcement 22 Anchor bolt

Claims (2)

  Reinforcing body made of concrete having a compressive strength higher than the compressive strength of the concrete constituting the column and / or beam on the outer surface of the column and / or the outer surface of the beam located on the outer wall side of the existing building Seismic reinforcement structure for existing buildings, characterized in that is fixed.   The existing bolt according to claim 1, wherein an anchor bolt is provided between the outer surface of the column body and the reinforcing body and / or between the outer surface of the beam body and the reinforcing body. Seismic reinforcement structure for buildings.

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