• Title, Summary, Keyword: flexural members

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Flexural strength of prestressed concrete members with unbonded tendons

  • Lee, Deuck Hang;Kim, Kang Su
    • Structural Engineering and Mechanics
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    • v.38 no.5
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    • pp.675-696
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    • 2011
  • It is difficult to accurately predict the flexural strength of prestressed members with unbonded tendons, unlike that of prestressed members with bonded tendons, due to the unbonded behavior between concrete and tendon. While there have been many studies on this subject, the flexural strength of prestressed members with unbonded tendons is still not well understood, and different standards in various countries often result in different estimation results for identical members. Therefore, this paper aimed to observe existing approaches and to propose an improved model for the ultimate strength of prestressed members with unbonded tendons. Additionally, a large number of tests results on flexural strength of prestressed members with unbonded tendons were collected from previous studies, which entered into a database to verify the accuracy of the proposed model. The proposed model, compared to existing approaches, well estimated the flexural strength of prestressed members with unbonded tendons, adequately reflecting the effects of influencing factors such as the reinforced steel ratio, the loading patterns, and the concrete strength. The proposed model also provided a reasonably good estimation of the ultimate strength of over-reinforced members and high-strength concrete members.

Local Buckling Behavior of Pultruded Structural Flexural Members (펄트루젼 구조용 휨부재의 국부좌굴 거동)

  • 정재호;윤순종
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.147-151
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    • 2003
  • In this study, we discussed the local buckling behavior of pultruded structural flexural members. Previous works were briefly reviewed and the local buckling behavior of orthotropic box-shape flexural members was discussed. The simplified form of equation for finding the width ratio of plate element of box-shape flexural members in which all plate components buckle simultaneously was proposed and the macro flow-chart for finding local buckling strength of pultruded flexural members was also suggested. To establish the design guide line for the local buckling of pultruded flexural members, further studies need to be performed as follows; the simplified form of solutions for finding the minimum buckling coefficient of orthotropic plate with various loading and boundary conditions including rotationally restrained boundary conditions, the simplified form of equation for calculating the coefficient of restraint provided by the adjacent plate elements.

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Flexural behavior model for post-tensioned concrete members with unbonded tendons

  • Kim, Kang Su;Lee, Deuck Hang
    • Computers and Concrete
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    • v.10 no.3
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    • pp.241-258
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    • 2012
  • The need for long-span members increases gradually in recent years, which makes issues not only on ultimate strength but also on excessive deflection of horizontal members important. In building structures, the post-tension methods with unbonded tendons are often used for long-span members to solve deflection problems. Previous studies on prestressed flexural members with unbonded tendons, however, were mostly focused on the ultimate strength. For this reason, their approaches are either impossible or very difficult to be implemented for serviceability check such as deflection, tendons stress, etc. Therefore, this study proposed a flexural behavior model for post-tensioned members with unbonded tendons that can predict the initial behavior, before and after cracking, service load behavior and ultimate strength. The applicability and accuracy of the proposed model were also verified by comparing with various types of test results including internally and externally post-tensioned members, a wide range of reinforcement ratios and different loading patterns. The comparison showed that the proposed model very accurately estimated both the flexural behavior and strength for these members. Particularly, the proposed model well reflected the effect of various loading patterns, and also provided good estimation on the flexural behavior of excessively reinforced members that could often occur during reinforcing work.

Cracking in reinforced concrete flexural members - A reliability model

  • Rao, K. Balaji;Rao, T.V.S.R. Appa
    • Structural Engineering and Mechanics
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    • v.7 no.3
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    • pp.303-318
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    • 1999
  • Cracking of reinforced concrete flexural members is a highly random phenomenon. In this paper reliability models are presented to determine the probabilities of failure of flexural members against the limit states of first crack and maximum crackwidth. The models proposed take into account the mechanism of cracking. Based on the reliability models discussed, Eqs. (8) and (9) useful in the reliability-based design of flexural members are presented.

A Study on the Moment Capacity of H-Section Flexural Members with Local Buckling (국부좌굴이 발생하는 H-형강 휨부재의 강도에 관한 연구)

  • Seo, Gun-Ho;Seo, Sang-Jung;Kwon, Young-Bong
    • Journal of Korean Society of Steel Construction
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    • v.23 no.6
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    • pp.647-657
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    • 2011
  • This paper describes the moment capacity of flexural members with local buckling based on a series of FE and experiment results. Thin-walled flexural members undergo local, lateral-torsional, or interactive buckling according to the section geometries and lateral boundary conditions. Flexural members with large width-to-thickness ratios in the flanges or the web may undergo local buckling before lateral-torsional buckling. Local buckling has a negative effect on the flexural strength based on the lateral-torsional buckling of flexural members. This phenomenon should be considered in the estimation of the flexural strength of thin-walled sections. Flexural members with various width-to-thickness ratios in their flanges and web were analyzed. Initial imperfections in the local buckling mode, and residual stresses, were included in the FE analyses. Simple bending moment formulae for flexural members were proposed based on the FE and test results to account for local and lateral-torsional buckling. The proposed bending moment formulae for the thin-walled flexural members in the Direct Strength Method use the empirical strength formula and the grosssection modulus. The ultimate flexural strengths predicted by the proposed moment formulae were compared with the AISC (2005), Eurocode3 (2003), and Korean Highway Bridge Design Specifications (2010). The comparison showed that the proposed bending moment formulae can reasonably predict the ultimate moment capacity of thin-walled flexural members.

Review of design parameters for FRP-RC members detailed according to ACI 440.1R-06

  • Jnaid, Fares;Aboutaha, Riyad
    • Computers and Concrete
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    • v.11 no.2
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    • pp.105-121
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    • 2013
  • This paper investigates the parameters that control the design of Fiber Reinforced Polymer (FRP) reinforced concrete flexural members proportioned following the ACI 440.1R-06. It investigates the critical parameters that control the flexural design, such as the deflection limits, crack limits, flexural capacity, concrete compressive strength, beam span and cross section, and bar diameter, at various Mean-Ambient Temperatures (MAT). The results of this research suggest that the deflection and cracking requirements are the two most controlling limits for FRP reinforced concrete flexural members.

Effective flexural rigidities for RC beams and columns with steel fiber

  • Bengar, Habib Akbarzadeh;Kiadehi, Mohammad Asadi;Shayanfar, Javad;Nazari, Maryam
    • Steel and Composite Structures
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    • v.34 no.3
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    • pp.453-465
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    • 2020
  • Influences of different variables that affect the effective flexural rigidity of reinforced concrete (RC) members are not considered in the most seismic codes. Furthermore, in the last decades, the application of steel fibers in concrete matrix designs has been increased, requiring development of an accurate analytical procedure to calculate the effective flexural rigidity of steel fiber reinforced concrete (SFRC) members. In this paper, first, a nonlinear analytical procedure is proposed to calculate the SFRC members' effective flexural rigidity. The proposed model's accuracy is confirmed by comparing the results obtained from nonlinear analysis with those recorded from the experimental testing. Then a parametric study is conducted to investigate the effects of different parameters such as varying axial load and steel fiber are then investigated through moment-curvature analysis of various SFRC (normal-strength concrete) sections. The obtained results show that increasing the steel fiber volume percentage increases the effective flexural rigidity. Also it's been indicated that the varying axial load affects the effective flexural rigidity. Lastly, proper equations are developed to estimate the effective flexural rigidity of SFRC members.

Flexural-torsional buckling tests of cold-formed steel compression members at elevated temperatures

  • Heva, Yasintha Bandula;Mahendran, Mahen
    • Steel and Composite Structures
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    • v.14 no.3
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    • pp.205-227
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    • 2013
  • Current design standards do not provide adequate guidelines for the fire design of cold-formed steel compression members subject to flexural-torsional buckling. Eurocode 3 Part 1.2 (2005) recommends the same fire design guidelines for both hot-rolled and cold-formed steel compression members subject to flexural-torsional buckling although considerable behavioural differences exist between cold-formed and hot-rolled steel members. Past research has recommended the use of ambient temperature cold-formed steel design rules for the fire design of cold-formed steel compression members provided appropriately reduced mechanical properties are used at elevated temperatures. To assess the accuracy of flexural-torsional buckling design rules in both ambient temperature cold-formed steel design and fire design standards, an experimental study of slender cold-formed steel compression members was undertaken at both ambient and elevated temperatures. This paper presents the details of this experimental study, its results, and their comparison with the predictions from the current design rules. It was found that the current ambient temperature design rules are conservative while the fire design rules are overly conservative. Suitable recommendations have been made in relation to the currently available design rules for flexural-torsional buckling including methods of improvement. Most importantly, this paper has addressed the lack of experimental results for slender cold-formed steel columns at elevated temperatures.

Deformation-based Strut-and-Tie Model for flexural members subject to transverse loading

  • Hong, Sung-Gul;Lee, Soo-Gon;Hong, Seongwon;Kang, Thomas H.K.
    • Computers and Concrete
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    • v.18 no.6
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    • pp.1213-1234
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    • 2016
  • This paper describes a deformation-based strut-and-tie model for the flexural members at post-yield state. Boundary deformation conditions by flexural post-yield response are chosen in terms of the flexural bar strains as the main factor influenced on the shear strength. The main purpose of the proposed model is to predict the shear capacities of the flexural members associated with the given flexural deformation conditions. To verify the proposed strut-and-tie model, the estimated shear strengths depending on the flexural deformation are compared with the experimental results. The experimental data are in good agreement with the values obtained by the proposed model.

An Experimental Study on the Strengh and Ductility of High-Strength Flexural Members (고강도 휨재의 강도와 연성에 관한 실험적 연구)

  • Lee, Seung-Joon
    • Journal of Korean Society of Steel Construction
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    • v.13 no.1
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    • pp.19-28
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    • 2001
  • The strength and ductility of steel flexural members are investigated experimentally in this study. As for the performance evaluation of flexural members. experimental studies on the 9 test specimens were carried out. Four specimens were fabricated from SM490 and five specimens were fabricated from SM570. The experimental results of the specimens were analyzed with focus on the flexural strength and ductility. The experimental results exhibited that all the specimens provided sufficient flexural strengthes which exceeded the nominal flexural strengthes specified in the current Limit State Design Specification by average ratio of 1.22. However. the experimental results showed that the compact-section specimens fabricated from SM570 did not provide the required rotational ductility. The yield-to-tensile strength ratio(YR) of SM570 of about 0.9 might be the causes of such insufficient capacities.

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