Elsevier

Composites Part B: Engineering

Volume 42, Issue 6, September 2011, Pages 1617-1629
Composites Part B: Engineering

Flexural behavior of prestressed composite beams with corrugated web: Part II. Experiment and verification

https://doi.org/10.1016/j.compositesb.2011.04.019Get rights and content

Abstract

This paper presents an experimental study on the flexural behavior of three full scaled non-prestressed and prestressed composite beams with corrugated web, which had been developed by authors in their previous study. Also, the performance of the proposed flexural behavior model considering the accordion effect was examined, comparing to the test results. The test result showed that, due to the accordion effect before composite with the concrete, the introduced prestress in the top and bottom flanges of the steel beam has drastically increased, and that after composite with concrete, the flexural strength and stiffness of the prestressed specimens were superior to those of the non-prestressed specimen. It was verified that the proposed flexural behavior model accurately estimated the flexural behavior, before and after the composite with concrete, of the prestressed composite beams with corrugated web. Also, the horizontal shear strengths of the composite members, summing the average shear bond strength between steel plate and concrete and the direct shear strength of concrete, were evaluated considering the horizontal shear failure observed in the test specimens.

Introduction

The authors, in their previous study, proposed a prestressed composite beam with corrugated web that is advantageous for a long span and saving story height. The corrugated web utilized in the proposed composite beam enhances the efficiency of prestressing by making full use of the stress to the top and bottom flanges utilizing the accordion effect, and additional web stiffener is not required due to its great local and out-of plane buckling strength. The proposed composite beam with corrugated web has excellent performance on the composite action between concrete and steel beam, and provides good flexural rigidity and strength [1].

The authors, in their previous paper [1], proposed the concept of effective sectional area and effective moment of inertia to reflect the accordion effect that occurs on the steel beam with corrugated web before composite with concrete and also developed an analysis method on the behavior of the composite beam. While there have been some experimental researches on the externally prestressed composite beams [2], [3], [4], [5], [6], there has been no such study on the encased prestressed composite beam, which is presented in this study. Therefore, this paper, following the previous paper by the authors, presents experimental results on two encased prestressed composite beams with corrugated web and a non-prestressed composite beam, in which the effect of prestressing is analyzed and the proposed analysis method for the accordion effect and the flexural behavior of the composite beam are verified.

On the other hand, most of the composite beams in previous experimental researches [7], [8], [9] had a narrow flange width of the concrete slab and the top flange of the steel beam extended to the height of the center of the slab, resulting in the neutral axis being located lower than the top flange of the steel beam. However, the effective width of the actual T-shaped concrete section may be larger than that of previously studied specimens. In fact, in the construction site, it is quite common that the neutral axis locates in the slab due to the relatively wide effective width of slab. In such a case, it is possible to have a shear failure between slab and beam, which may occur before the composite beam reaches its ultimate flexural capacity. Therefore, this study also includes the analysis on the horizontal shear strength that reflects the actual failure mode observed in this experiment.

Section snippets

Experimental program

A total of three full-scaled specimens have been fabricated to evaluate the flexural strength and behavior of the prestressed composite beams with corrugated web. As shown in Table 1, two specimens, FPCE1 and FPCE2, were prestressed, whereas the specimen FNC was not. Fig. 1a and b shows the tendon profiles and geometry of the steel beam specimens before composite. The tendon was arranged in a way that a drape point was at the center of FPCE1 and two drape points were near the center of FPCE2.

Accordion effect

As reported in the authors’ previous paper [1] and existing studies [3], [12], [13], [14], [15], it is known that the prestress introduced to the top and bottom flanges increases because there is little stress introduced to corrugated web due to the accordion effect. Fig. 7 shows the strain distribution along the height of the section at midspan when the specimens FPCE1 and FPCE2 were prestressed. It can be observed that there is no or little strain on the corrugated web whereas the top and

Verification of the proposed analysis model

Authors, in their previous research, proposed an approach utilizing the concept of effective section for the analysis of the accordion effect by the corrugated web [1]. As concretized by the effective moment of inertia (Ieff) and the effective area (Aeff), the concept of effective section is expressed by:Ieff=ηfIgAeff=Aflange+ηaAwebwhere Ig is the gross moment of inertia, Aflange is the sum of the sectional areas of the top and bottom flanges, and Aweb is the sectional area of web. ηf and ηa

Conclusion

In this study, a non-prestressed and two prestressed composite beams with corrugated web have been fabricated in full scale and experimental tests were conducted to examine their flexural behavior. In addition, the flexural behavior model, reflecting the accordion effect, proposed for the prestressed composite beam with corrugated web in the previous study, was verified. The study resulted in the following conclusions:

  • 1.

    The steel beam with corrugated web was very efficient to introduce larger

Acknowledgments

This work (Grants No. 00041190) was supported by Business for Cooperative R&D between Industry, Academy and Research Institute funded by the Korea Small and Medium business Administration in 2010.

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