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Country. Norm. Grade. Re (MPa). Rm (MPa). Rm/Re. Agt (%). Elongation (%). BRAZIL. ABNT NBR CA Min Min Min 1, Min 5. A10d - 8. bestthing.info - Free download as PDF File .pdf) , Text File .txt) or read online for free. standardized in Brazil by ABNT NBR [1] requires appro-. cifications of ABNT NBR [8].5 For quality control of.


Nbr 7480 Pdf

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This website uses cookies to ensure you get the best experience on our website. Our partners will collect data and use cookies for ad personalization and. (η), which is specified by ABNT-NBR (). The minimum surface conformation values (η) obtained in bond tests are prescribed by this. NBR CA CA CA CANADA. CAN/CSA G M Gr Gr Gr W. Gr W. CHILE. NCh AH. AH. CHINA .

The correlations between numerical-experimentals results and several parameters validate the proposed combination of resources and identiies the signiicance of various efects on the response. Introduction Among these tools, the FEM analysis presented in this paper uses an appropriate combination of resources.

The material behavior of Reinforced concrete is the most important building material and concrete is described by the Microplane Constitutive Model, briely it is widely used in modern structures. So, theoretical and experi- described in section 2. An embedded reinforcement model is used mental researches become more and more necessary in order to to represent steel inside a concrete element and take into account develop advanced analysis methods.

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The experimental program is Experimental research provides the basis for the theoretical detailed in section 4. In section 5, both pullout tests and inite ele- models and also supplies the basic information for the analysis ment simulations are presented and the results from the two are methods, such as material properties.

In addition, the results of compared. Microplane model Theoretical research can reduce the number of required test speci- mens for the solution of a given problem. The development of ana- The application of Microplane Theory Mohr [2], Taylor [3] to lytical models for reinforced concrete structures is complicated be- modeling concrete structures is quite pertinent because the as- cause of its complex behavior that includes: The model prescribes constitutive behavior numerical and computational resources.

Carol [7], Leukart [8], Leukart and Ramm [9]. All of them follow the This paper deals with the Finite Element Analysis of the bond-slip schema showed in Figure 2. Given the macro- The FEM models were created using the INSANE Interactive scopic strain tensor at a material point, kinematic constraints are Structural Analysis Environment computational system, open imposed in order to calculate the strains on the microplanes.

The source software available at www. The cur- direction of each microplane is deined to be normal to the surface rent version of INSANE has a set of FEM tools for nonlinear analy- of a sphere centered at the material point Figure 3.

After imposing sis of reinforced concrete structures, such as: In the inal stage, macroscopic stresses constitutive models; and 3 FEM models for reinforcement and as well as the global constitutive tensor are evaluated after using bond-slip. BARBOSA Figure 2 — Synthesis of the Microplane Models formulation The model proposed by Leukart and Ramm [8] adopts step 1 a The numerical simulations presented in this paper use one decomposition of the macroscopic strain tensor into its volumet- of the options of the unified environment for microplane mod- ric and deviatoric components V-D split ; step 2 that the dam- els of the INSANE system.

Specifically, the simulations uses age process is the main dissipation mechanism which describes volumetric-deviatoric strain split proposed by Leukart and the degradation on the material and that degradation is evaluated Ramm [8] and the equivalent strain defined by de Vree [12], through a single equivalent strain combined with a single damage according to: The stifness matrix of the composed element is given by: Reinforcement and bond-slip model The sub matrix kcc is due the constitutive model chosen for representing concrete and the matrices k ss , kbb and kbs Reinforcement and bond-slip can be represented into reinforced represent the contributions of steel and bond on the stifness of the concrete FEM models according to three diferent approaches: The numerical simulations presented in this paper adopt the em- s 5 bedded reinforcement model proposed by Elwi and Hrudey [16], combining with the bond stress-slip laws proposed by Eligehausen [18] and Hawkins [19].

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In this model, the normal strain in the tangent direction to the re- slip interpolation functions; Eb is the tangent module of the bond inforcement segment is provided by the sum of two components.

Experimental program functions relative to the tangent direction of the reinforcement lay- er; Es is the tangent module of the stress-strain relation for the The experimental program, presented here, has been performed by steel; As is the reinforcement area per unit of thickness; t is the Silva [1] and is also described in Silva [20]. The steel-concrete bond element thickness; Bs contains the derivatives of the interpolation was evaluated on two concrete mixtures corresponding to strength functions of the parent element relative to the tangent direction of classes 25 MPa and 45 MPa C25 and C45 and three diameters the reinforcement layer.

For each combination described, six 3. As said before, the laws proposed by Eligehausen [18] and 4. The additive used was a poly- 7 carboxylate-based third-generation superplasticizer, which accord- ing to the manufacturer has a density of 1. Table 1 shows the mixture proportions of concrete C25 and C For each rupture age three specimens were molded, according to ABNT lated to the maximum bond stress; wb 3 is the slip at the moment NBR [23].

They were compacted using a vibrating table com- when the bond stress reaches its end point.

Table 2 shows the results, indicat- Table 2 — Mechanical properties ing the average and the standard deviation of the sample consist- of concrete ing of three specimens for each age and type of test. This standard speciies that the yield stress of the Compressive strength - fcm MPa For each diameter 8mm , 10mm and The results are shown compression - fctm MPa Std.

Elastic modulus - Ec GPa This test has aimed to study the relationship between matic with the method POT. The pullout force was measured by the bond stress and bond loss of the steel bar.

Both ends of the bar load cell and the linear displacement by LVDT. With this system it was possible to ob- The bond strength t is calculated according to Equation 8 , The specimen is cubic with dimension ten times the diameter of tain the force versus displacement curves. Figure 8 shows concreting in the metal mold on a vibrating table and the pull-out steel bar. The system pull-out to method POT was mounted on a movable F support properly leveled.

The microplane model proposed by Leukart and Ramm [8] combined with the equivalent strain deined by de Vree [12] was used for representing The steel was represented by an elastoplastic stress- By itting the unidimensional behavior observed from the ex- strain law inside the embedded reinforcement model proposed by perimental data, it was possible to obtain the numerical param- Elwi and Hrudey [16], combined with the bond stress-slip laws pro- eters to the exponential damage law based on the equivalent see equation 1 and 2: For consideration of bond loss, according to laws proposed by eters have been adopted: The observations also allow con- Figure 10 shows good agreement between the experimental and cluding that, despite the sophistication of the constitutive model numerical results for the six combinations of two concretes and used for concrete, it was not so important for this FEM analysis.

Both, the Eligehausen and Hawkins laws In spite of good agreement between experimental and FEM anal- represented well the experimental range. This were obtained using a lower limit of bond stress 29 MPa. Figure By comparing Figures 11 and 10, it can be observed Figure 12 — Experimental and FEM results for concrete C45 and reinforcing bars of Nomenclature As can be seen in Figure 13, the maximum values for reinforcement force, bond stress and reinforcement slip are: Also, it is observed that the reinforcement force for point fctm - Tensile strength of concrete by diametral compression aver- A Although, it was noted the occurrence, for all experimental tests for this case C References numerical simulations presented.

The development of ana- The application of Microplane Theory Mohr [2], Taylor [3] to lytical models for reinforced concrete structures is complicated be- modeling concrete structures is quite pertinent because the as- cause of its complex behavior that includes: cracking and crushing, sociation between solid structure of the heterogeneous material creep, reinforcement yielding, steel-concrete bond failure, among cementitious matrix with aggregates of diferent particle sizes and others phenomena.

The model prescribes constitutive behavior numerical and computational resources. Carol [7], Leukart [8], Leukart and Ramm [9]. All of them follow the This paper deals with the Finite Element Analysis of the bond-slip schema showed in Figure 2.

NBR 14859-1 - Laje Pré-Moldada - Requisitos - Lajes Unidirecionais

Given the macro- The FEM models were created using the INSANE Interactive scopic strain tensor at a material point, kinematic constraints are Structural Analysis Environment computational system, open imposed in order to calculate the strains on the microplanes. The source software available at www. The cur- direction of each microplane is deined to be normal to the surface rent version of INSANE has a set of FEM tools for nonlinear analy- of a sphere centered at the material point Figure 3.

After imposing sis of reinforced concrete structures, such as: 1 extensive library such constraints, a local constitutive behavior is assumed in order of analysis models and incremental-iterative methods for solving to evaluate the local stresses as well as a microplane measure of nonlinear equations; 2 an uniied computational environment for the material degradation.

In the inal stage, macroscopic stresses constitutive models; and 3 FEM models for reinforcement and as well as the global constitutive tensor are evaluated after using bond-slip. BARBOSA Figure 2 — Synthesis of the Microplane Models formulation The model proposed by Leukart and Ramm [8] adopts step 1 a The numerical simulations presented in this paper use one decomposition of the macroscopic strain tensor into its volumet- of the options of the unified environment for microplane mod- ric and deviatoric components V-D split ; step 2 that the dam- els of the INSANE system.

Reinforcement and bond-slip model The sub matrix kcc is due the constitutive model chosen for representing concrete and the matrices k ss , kbb and kbs Reinforcement and bond-slip can be represented into reinforced represent the contributions of steel and bond on the stifness of the concrete FEM models according to three diferent approaches: composite element, where: Smeared Reinforcement Models, Discrete Reinforcement Models Ngo and Scordelis [13] and Embedded Reinforcement Models Balakrishna and Murray [14], Allwood and Bajarwan [15] and Elwi and Hrudey [16].

The numerical simulations presented in this paper adopt the em- s 5 bedded reinforcement model proposed by Elwi and Hrudey [16], combining with the bond stress-slip laws proposed by Eligehausen [18] and Hawkins [19].

In this model, the normal strain in the tangent direction to the re- slip interpolation functions; Eb is the tangent module of the bond inforcement segment is provided by the sum of two components. Experimental program functions relative to the tangent direction of the reinforcement lay- er; Es is the tangent module of the stress-strain relation for the The experimental program, presented here, has been performed by steel; As is the reinforcement area per unit of thickness; t is the Silva [1] and is also described in Silva [20].

The steel-concrete bond element thickness; Bs contains the derivatives of the interpolation was evaluated on two concrete mixtures corresponding to strength functions of the parent element relative to the tangent direction of classes 25 MPa and 45 MPa C25 and C45 and three diameters the reinforcement layer.

For each combination described, six 3. As said before, the laws proposed by Eligehausen [18] and 4.

The additive used was a poly- 7 carboxylate-based third-generation superplasticizer, which accord- ing to the manufacturer has a density of 1. Table 1 shows the mixture proportions of concrete C25 and C For each rupture age three specimens were molded, according to ABNT lated to the maximum bond stress; wb 3 is the slip at the moment NBR [23]. They were compacted using a vibrating table com- when the bond stress reaches its end point.

Table 2 shows the results, indicat- Table 2 — Mechanical properties ing the average and the standard deviation of the sample consist- of concrete ing of three specimens for each age and type of test.

This standard speciies that the yield stress of the Compressive strength - fcm MPa For each diameter 8mm , 10mm and The results are shown compression - fctm MPa Std. Elastic modulus - Ec GPa This test has aimed to study the relationship between matic with the method POT.

The pullout force was measured by the bond stress and bond loss of the steel bar. Both ends of the bar load cell and the linear displacement by LVDT.

With this system it was possible to ob- The bond strength t is calculated according to Equation 8 , The specimen is cubic with dimension ten times the diameter of tain the force versus displacement curves. Figure 8 shows concreting in the metal mold on a vibrating table and the pull-out steel bar.

The system pull-out to method POT was mounted on a movable F support properly leveled. The microplane model proposed by Leukart and Ramm [8] combined with the equivalent strain deined by de Vree [12] was used for representing The observations also allow con- Figure 10 shows good agreement between the experimental and cluding that, despite the sophistication of the constitutive model numerical results for the six combinations of two concretes and used for concrete, it was not so important for this FEM analysis.

Both, the Eligehausen and Hawkins laws In spite of good agreement between experimental and FEM anal- represented well the experimental range.

FIERRO-CORRUGADO-NBR-7480-BACO.pdf

This were obtained using a lower limit of bond stress 29 MPa. Figure By comparing Figures 11 and 10, it can be observed Figure 12 — Experimental and FEM results for concrete C45 and reinforcing bars of Nomenclature As can be seen in Figure 13, the maximum values for reinforcement force, bond stress and reinforcement slip are: Also, it is observed that the reinforcement force for point fctm - Tensile strength of concrete by diametral compression aver- A Although, it was noted the occurrence, for all experimental tests for this case C This situation is favorable, tribution of moments from positive to negative igure 9.

Seu nome. In Portuguese Google Scholar 9. The source software available at www. The model prescribes constitutive behavior numerical and computational resources.

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