JP4855659B2 - Method for analyzing reinforced concrete columnar member having lateral restraint bars and recording medium on which a program for causing a computer to execute the analysis method is recorded - Google Patents

Description

The present invention records high-strength reinforced concrete columnar members that are applied to parts subjected to large axial forces and bending moments during earthquakes, such as reinforced concrete columns and reinforced concrete piles in buildings, and reinforced concrete piers in bridges, and methods for evaluating the effect of restraining the lateral restraint bars. More specifically, with regard to the recording medium, more specifically, with regard to the lateral restraint bars used to achieve a high strength structure, the confinement effect of the lateral restraint bars, the compressive strength of the concrete used, and the yield of the lateral restraint bars The present invention relates to an evaluation method for determining regardless of the strength and an electronic medium on which the evaluation method is recorded.

Since the Hyogoken-Nanbu Earthquake, high-performance seismic structures have been discussed.
Structural forms such as high toughness and high seismic isolation are attracting attention. Among these, one of the high strength structures is the development of reinforced concrete members (RC members) using high compressive strength concrete and / or high tensile strength reinforcing bars.

In general, RC members are designed with stirrup bars, hoop bars, and spiral bars for the purpose of reinforcing the shear of members and improving toughness, in addition to the axial bars (main bars) that handle compressive loads. Is done. However, RC column members that receive large axial forces and bending moments during earthquakes, such as reinforced concrete columns and reinforced concrete piles in buildings, and reinforced concrete piers in bridges, are designed to have a high strength cross-section with the expectation of a confining effect on these strip reinforcing bars. It is necessary to determine the amount of lateral restraint reinforcement (that is, the volume ratio and area ratio of the band reinforcement and the intermediate band).

The basis for determining the amount of lateral restraint bars is the stress-strain curve of confined concrete. The lateral restraint effect refers to a phenomenon in which the proof stress and the deformability are remarkably increased when a lateral stress is applied to concrete, which is a brittle material, and axial stress is applied. This confined concrete is also used for steel pipe filling columns and reinforcement methods, and is expected as a column member with high strength.

JP 2001-289841 A Japanese Patent Application Laid-Open No. 2002-88977

By the way, in the road bridge specifications (seismic design), the stress-strain curve of confined concrete using ordinary concrete with a compressive strength of 18.5 to 28.8 MPa is obtained, and the horizontal strength and horizontal displacement of single-column RC piers are calculated. Seeking. However, in the same specification, when the concrete design strength exceeds 40 MPa, or when using lateral restraint bars different from the normal strength, the stress-strain relationship of the confined concrete will be examined separately by experiment and analysis. I am going to do that.

In order to design a structure with higher yield strength, it is conceivable to use RC members using high compressive strength concrete and / or high tensile strength reinforcing bars. To evaluate the seismic performance of such RC column members. Currently, the mechanical properties are not well understood.

In the present invention, effective lateral restraint pressure ( _pe ) is introduced to analyze the mechanical properties of reinforced concrete columnar members based on the stress-strain relationship of confined concrete under uniaxial compressive stress. An object of the present invention is to provide a reinforced concrete columnar member capable of reproducing proof stress and deformation performance regardless of strength, and a recording medium on which a method for evaluating the effect of restraining the lateral restraint is described.

In order to achieve the above object, the first invention of the present application is a reinforced concrete columnar member having lateral restraint bars, and effective lateral restraint obtained from the area ratio (ρ _w ) of the lateral restraint bars and the number of cross sections of the lateral restraint bars. coefficient (k _e), unrestrained concrete and Confined muscle mechanical Confined muscle stress acting in compression strength development obtained from various number (f _{s, c)} and based on the formula
p _e = k _e · ρ _w · f _{s, c}
From this, the effective lateral restraint pressure ( _pe ) is obtained and the relation between the compressive strength (σ _c0 ) of unconstrained concrete and the compressive strength (σ _cc ) of laterally constrained concrete using the effective lateral restraint pressure ( _pe ) as a parameter. Maximum axial strain of constrained concrete (ε _c0 ) and maximum axial strain of laterally constrained concrete (ε _cc )
And the relationship between the compressive strength (σ _c0 ) of unconstrained concrete and the descending slope of stress (E _des ), and the behavior of the stress-strain relationship of a reinforced concrete columnar member with laterally constrained bars based on the above relationship This is a method for analyzing a reinforced concrete columnar member having lateral constraining bars.

In order to achieve the above object, a second invention of the present application is a recording medium on which a program for causing a computer to execute the method for analyzing a reinforced concrete columnar member having a transverse constraint bar described in the first invention is recorded.

Since the present invention is configured as described above,
(1) RC based on the material properties of the concrete and lateral restraint bars used and the reinforcement arrangement of the lateral restraint bars
The stress-strain behavior of the column member can be easily obtained.
(2) The stress-strain behavior can be formulated regardless of the strength conditions of the concrete and transverse restraint used, the cross-sectional shape of the reinforced concrete columnar member, and the restraint shape.
(3) By using high-strength concrete and high yielding lateral restraint bars, and by setting the lateral restraint bar volume ratio above a certain level, it is possible to provide RC column members with high strength and toughness.
(4) Even when the lateral restraint bar volume ratio is small, it is possible to provide an effective RC column member with high strength and toughness by simply changing the bar arrangement method without changing the volume ratio.
(5) A design method for a high-strength RC member can be provided as an electronic medium from simple parameters and reinforcement arrangements based only on material tests.
It has various effects.

Hereinafter, the present invention will be described in detail. The present invention introduces effective lateral restraint pressure ( _pe ) to analyze the mechanical properties of reinforced concrete columnar members by the stress-strain relationship of confined concrete under uniaxial compressive stress, and the strength of the concrete and transverse restraint used. Regardless of
It is an object of the present invention to provide a reinforced concrete columnar member capable of reproducing proof stress and deformation performance, and a recording medium describing a method for evaluating the effect of restraining the lateral restraint bars.

によって求めるが、これは横拘束筋に拘束されたコンクリートの力学的諸数を、無拘束コ
ンクリートの力学的諸数との関係において一般化するために、実験的に回帰分析して求め
たものである。 The effective lateral restraint pressure ( _pe ) introduced in the present invention is expressed by the following formula 1

This is obtained by experimental regression analysis in order to generalize the mechanical numbers of concrete constrained by lateral restraint bars in relation to the mechanical numbers of unconstrained concrete. is there.

The effective lateral confining pressure (p _e), as shown in Equation 1 above, the effective lateral restraint coefficient (k _e),
It is defined by the three components of the lateral constraint muscle area ratio (ρ _w ) and the lateral constraint muscle acting stress (f _{s, c} ) when the compressive strength is developed. The effective lateral restraint coefficient of the (k _e), as shown in Equation 2 below, obtained from the cross-section various number of lateral restraint muscle.

Further, the laterally constrained muscle acting stress (f _{s, c} ) when the compressive strength is expressed is obtained from mechanical numbers of the unconstrained concrete and the laterally constrained muscle as shown in the following formula 3.

Here, the compressive strength (σ _c0 ) of the unconstrained concrete is experimentally obtained by multiplying the strength obtained from the material test of the cylindrical specimen by 0.85. Further, it has been confirmed that the axial strain (ε _c0 ) at the compressive strength of the unconstrained concrete is expressed by the following formula 4.

In general, the confining effect is evaluated based on the compressive strength of the unconstrained specimen with only the main muscle and no lateral restraint, and the strain at that time, but if the confining effect can be evaluated from an unmuscle cylindrical specimen, Design becomes easier.

Next, using the effective lateral restraint pressure ( _pe ) as a parameter, the relation between the compressive strength (σ _cc ) of the constrained concrete and the compressive strength (σ _c0 ) of the unconstrained concrete, the maximum axial strain of the constrained concrete ( The relationship between ε _cc ) and the maximum axial strain (ε _c0 ) of unconstrained concrete is expressed by various concrete strengths (39.2 MPa to 128 MPa) and various yield strengths (317 MPa to
When the confined concrete specimen shown in FIG. 1 using a lateral restraint bar of 1420 MPa) (not shown, but also having no intermediate strip rebar) was regressed from those experimental values, the following formula 5 and formula 6 was obtained.

Further, it is known that the compression softening behavior depends on the compressive strength of concrete. Therefore, if the slope of the stress after compressive strength (E _des ) cannot be determined centrally so as not to depend on the compressive strength of the concrete, the stress of the confined concrete that can be applied from normal strength RC columns to high strength RC columns. -Strain behavior cannot be formulated.

Therefore, similarly, the maximum stress at compressive strength (σ _c0 ) is considered to be the most average evaluation of all the experimental results for confined concrete specimens using transverse restraint bars of various concrete strengths and various yield strengths. The descending slope (E _des ) was determined from the slope of the straight line connecting the points that reached 50% stress after the maximum stress. The result is shown in FIG.

The relationship between the descending gradient (E _des ) and the effective restraint pressure ( _pe ) is obtained as a regression equation of the experimental result, and the following equation 7 is obtained.

Based on the three parameters σ _cc , ε _cc, and E _des obtained in Equations 5 to 7 above,
The stress-strain relationship of the confined concrete was formulated as shown in the following formulas 8.1 to 8.2.

When the above (Formula 8.1, Formula 8.2) was used as a proposed formula and compared with the experimental behavior of the specimens using the above-mentioned various strength concrete or lateral restraint bars, they showed very similar behavior. A part of the result is shown in FIG.

As described above, by introducing the effective lateral restraint pressure ( _pe ) determined from the strength and strain of the concrete and lateral restraint bars used and the reinforcement structure of the lateral restraint bars, the stress-strain relationship of the RC column can be reduced. It was found that it can be formulated regardless of the strength of concrete and lateral restraint bars. In other words, if the effective lateral restraint pressure ( _pe ) defined in the present invention is introduced, the stress-strain behavior of the confined concrete can be grasped by simply calculating Equations 1 to 8 without repeated calculations and proper use. it can.

By the way, when designing a RC column member having a high yield strength, it is conceivable to use high-strength concrete, but it is known that the confining effect is relatively reduced as the concrete strength increases. On the other hand, even if the strength of the lateral restraint bars is increased, the compressive strength of the confined concrete hardly increases.

However, the descending gradient after the maximum compressive stress becomes milder by increasing the strength of the lateral restraint muscle, and particularly when the lateral restraint muscle volume ratio (ρ _s ) is 2.0% or more, as shown in FIG. , Compression toughness is greatly improved. Therefore, in the high yield strength RC columnar member in the present invention, the compressive strength of the concrete is high strength concrete of 39 MPa or more, and the high strength steel having the tensile strength of the lateral restraint bar of 317 MPa or more is 2.0% or more by volume ratio. It was. In addition, the influence of the presence or absence of the covering of the lateral restraint bars on the outer periphery is small.

On the other hand, it is also effective to change the arrangement method of the lateral constraint muscles (see FIG. 5). In this case, even when the volume ratio of the lateral restraint bars is as small as 0.9%, the test piece with the intermediate band reinforcing bar in the center of the cross section and the pad-shaped test piece is more compressive strength and compressive than the test piece with only the outer peripheral bars. Lateral restraint effects such as strain and descending slope are greatly manifested. As described above, in the present invention, from the material characteristics of the materials used and the bar arrangement structure,
An RC pillar member having a high yield strength can be easily provided.

FIG. 6 is a flow chart of an evaluation method for RC column design based on the stress-strain relationship of the compression bending member according to the present invention. Each formula corresponds to the formula number described so far. FIG. 7 is a configuration diagram of a structural analysis system for a building or the like according to the evaluation method of the present invention. Since no special repetitive calculation is required, an electronic medium can be provided by general general-purpose calculation software.

Diagram showing iron distribution status of confined concrete specimen Diagram showing the descending slope (E _des ) after compressive strength Stress-strain curve of confined concrete specimen Compressive toughness curve by strengthening lateral restraint muscle Lateral restraint effect curve by using a part of the lateral restraint bar as an intermediate zone rebar Process flow diagram of high strength RC column according to the present invention Analysis system configuration diagram

_pe effective lateral restraint pressure k _e effective lateral restraint coefficient ρ _w lateral restraint bar area ratio f _{s, c} lateral restraint muscle acting stress when compressive strength is expressed σ _ck concrete strength ρ _s lateral restraint bar volume ratio σ _sy lateral restraint _bar Yield strength of

Claims (2)

In the reinforced concrete columnar member with lateral restraint bars, the area ratio (ρ _w ) of the lateral restraint bars,
The effective lateral restraint coefficient (k _e ) obtained from the number of cross-sections of the lateral restraint bars and the stress acting on the lateral restraint muscles (f _{s, c} ) And formula based on
p _e = k _e · ρ _w · f _{s, c}
From this, the effective lateral restraint pressure ( _pe ) is obtained and the relation between the compressive strength (σ _c0 ) of unconstrained concrete and the compressive strength (σ _cc ) of laterally constrained concrete using the effective lateral restraint pressure ( _pe ) as a parameter. Maximum axial strain of constrained concrete (ε _c0 ) and maximum axial strain of laterally constrained concrete (ε _cc )
And the relationship between the compressive strength (σ _c0 ) of unconstrained concrete and the descending slope of stress (E _des ), and the behavior of the stress-strain relationship of a reinforced concrete columnar member with laterally constrained bars based on the above relationship A method for analyzing a reinforced concrete columnar member having lateral constraining bars. The recording medium which recorded the program for making the computer execute the analysis method of the reinforced concrete columnar member which has a lateral constrained reinforcement of Claim 1.

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