博 士 論 文 概 要

Graduate School of Creative Science and Engineering, Waseda University

博 士 論 文 概 要

Doctor Thesis Synopsis

論 文 題 目

Thesis Theme

Experimental and Numerical Study on Mechanical Behavior of Steel-Concrete Composite Bridges

Subjected to Hogging Moment

負曲げモーメントを受ける鋼とコンクリートの合成橋 梁の力学挙動に関する実験的および数値解析的研究

申 請 者 (Applicant Name)

Weiwei LIN

林 偉偉

(Major in Civil and Environmental Engineering, Research on Structural Mechanics

March, 2012

Composite steel and concrete structures have been extensively used in civil engineering structures, such as buildings and bridge structures due to the benefits of combining the two constructions materials. The continuity of steel-concrete composite bridges has many advantages comparing with simply supported, such as: higher span-to-depth ratio, less deflection, and higher stiffness, so the continuous steel-concrete girders are believed to have the wide application prospects. However, there are also some problems. In the negative moment regions of continuous steel-concrete composite bridges, tensile forces are induced in the concrete slab, and development of cracks in the slab is expected. Much research was carried out to determine positive moment carrying capacity of the composite beams. For simply supported composite beams, the ultimate loading capacity is usually governed by either positive bending moment or shear force bearing capacity, which will be predominated by the compressive strength of the concrete and tensile strength of the joist steel. However, for composite beams in the negative moment regions, this condition may not be fully satisfied. The concrete slab is usually in tension and the lower flange of the steel girder is in compression, which generally has shortcomings in view of the durability, loading capacity and service life of the structures. The present investigation forms a part of a continuing study of continuous composite beams being carried out in the Yoda laboratory in the Department of Civil and Environmental Engineering at WASEDA University in Japan. The primary aims of this dissertation are to provide an comprehensive understanding of the static and fatigue behavior of steel-concrete composite girders subjected to hogging moment through experimental study and numerical investigation, and make an extension study on mechanical behavior of the curved steel-concrete composite girders under negative bending, and finally produce the design equations for predicting the ultimate strength of such girders.

The whole content area is divided into two main parts—the mechanical behavior including the static loading behavior and fatigue behavior of straight steel-concrete composite girders under hogging moment, and the extension study about curved steel-concrete composite girders. According to the different emphasis, the dissertation is organized into seven Chapters.

The first Chapter is an introduction to the topic at hand providing the reader with the background of the topic and the motivation behind the research. One of the first important studies on continuous composite steel and concrete bridges with monolithic decks was published by Sherman in 1954 (Sherman, 1954). Thereafter, some detailed studies were performed to investigate the performance of the composite girder in the support region, which has been a hot research topic in recent years. However, the actual performance of composite beam with different types of shear connectors, new materials such as rubber-latex and the fatigue behavior under different load levels of repeated load and so on are still unknown and need to be defined. In Japan, the first composite two I girder continuous composite bridges with a prestress concrete (PC) slab can be traced back to Chidorinosawagawa Bridge constructed in 1998. Therefore, the mechanical behavior, especially the inelastic behavior of composite girders in support region needs to be studied in order to provide necessary guidelines for design and construction of such structures. Motivation, research objectives, approach and organization of the present thesis were described in details in this Chapter.

In Chapter 2, an experimental investigation on mechanical behavior of steel-concrete composite beams subjected to hogging moment is presented. A total of four specimens were tested under point load in the mid-span. Two of the composite beams with headed studs as the shear connectors, while the other two specimens are using Perfo-Bond Strips (PBLs) as the connection devices between the steel girder and the concrete slab. Ultimate load bearing capacity of composite sections in negative moment region was calculated and compared with experimental values. Crack formation, crack widths development process and strain distribution of the composite section before and after cracking were observed in the experiment and presented in this Chapter. Interface slip distribution was also given. Research results indicate that: (1) the current specifications such as AASHTO, JSCE, and EUROCODE-4 can provide appropriate values for ultimate strength of a composite girder under negative bending moment; (2) both PBLs and Stud connectors are effective as shear connective devices. The PBL connectors can slightly improve the rigidity of the composite girder under both the serviceability limit state and the ultimate limit state in comparison with stud connectors. Stud specimens have relatively better mechanical behaviour in regarding to initial cracking and crack closure loads of test specimens; (3) the location of composite neutral axis is affected by the rubber-latex and it moves between the cross-sectional elastic neutral axis and the plastics neutral axis. The location of the composite neutral axis was found to be the same as un-cracked section before cracking. After cracking, tension stiffening of the concrete is suggested to be considered when

determining the location of the neutral axis; (4) Strain hardening effect of reinforcements was suggested to be ignored. The phenomenon of “crack closure” was observed for all test specimens, and thereafter the crack width was found keep as a constant. Additionally, average crack spacing on concrete slab was found mainly dependent on the transverse reinforcement spacing, and the maximum crack spacing specified by current specifications was proved to be appropriate values when compared to the test results; (5) Slip distribution along the steel-concrete interface was given in this study, and the interface slip distribution was found closely related to crack pattern of the concrete slab for composite beam under hogging bending moment. Support conditions were considered to be another influencing factor; (6) the application of rubber-latex can be beneficial to reducing the noise pressure levels (about 10 dB in the present test). Flexural stiffness of the shear connectors was also found to be enhanced by using rubber-latex mortar. Besides, adhesion bonding effects of rubber-latex on interface were confirmed in the test by comparing with the specimen without using rubber latex mortar. Moreover, interface slip measurement in the test was considered to be affected by the crack pattern of the concrete slab for composite beam under hogging bending moment.

In Chapter 3, the study on fatigue behavior of composite girders subjected to hogging moment was conducted.

This Chapter deals with the results of a series of experimental work with two test steel-concrete composite specimens. This Chapter keeps a watchful eye on the problems involving on different repeated load levels on the girder stiffness, residual displacement, initial crack formation and crack propagation on the surface of the concrete slab, strain development process of reinforcing bars, shear studs and concrete interaction and flexural strain change process of studs and fatigue behavior of the concrete slab. Besides, a brief description about the final static tests followed by the fatigue tests will also be made. From the results, the following conclusions and recommendations deserving priority are made: (1) When the repeated load is equivalent to the initial cracking load of composite girder under hogging moment, limited number of unrecoverable cracks might occur with the increase of the number of load cycles; simultaneously, the cracking stiffness was found decrease and crack width at the same load level was found increase. Flexural strain of the studs is very small, and the necessary bond forces on the interface are mainly from the friction forces, but not shear forces of studs; (2) When the repeated load is equivalent to the stationary cracking load of composite girder under hogging moment, unrecoverable cracks and residual crack width mainly occurs in the initial static test, but with the load cycles increase, some new unrecoverable cracks also may occur at the beginning of the fatigue test. However, when the number of load cycles increase to certain extent (such as 100000 in the present test), most of cracks are recoverable cracks if the initial residual crack width was not considered. In addition, failure of the bond stress between studs and surrounding concrete was observed in the initial static test and the subsequent static tests, flexural stiffness of studs would become smaller with the increase of the load cycles; (3) No practical change was found on girder stiffness or residual displacement when the repeated cyclic load was limited to initial cracking or stationary cracking loads. Besides, the changes of the rebar strains are found directly correspond to the crack pattern of concrete slab, and the strain jump of the rebar is caused by the crack of the concrete slab; (4) When the repeated load is smaller than the initial cracking load, it seems the fatigue test with 2 millions cycles repeated load does not show obvious effects on the ultimate loading behavior of composite girder under negative bending moment;

however, when the repeated load is larger than the initial cracking load, the fatigue test with larger repeated load will reduce the girder stiffness in the inelastic stage and the ultimate load carrying capacities of such girders.

In order to find a reliable modeling method for such girders, the numerical results are given and compared with the experimental values in Chapter 4. Two overturned simply supported steel-concrete composite girders with different shear connectors such as Studs and Perfo-Bond Strips (PBLs) were tested under concentrated load in the mid-span. Based on the experimental observations, a three-dimensional FE model capable of analyzing the composite beams subjected to negative bending moment was built. Strength and load bearing capacity, sectional strain distribution and movement of composite neutral axis before and after cracking were observed in the test and compared with the numerical results, and the results predicted by this modeling method are in good agreement with those obtained from the tests. Research results indicate that the proposed numerical models can simulate the test specimens well in regard to load-deformation response, sectional strain distribution, Re-bar yielding and crack developing process on the concrete slab, and it follows that proposed numerical method can be served as a basis for the design of composite bridges under negative bending moment. Besides, perfect bond assumption for concrete-reinforcement interface was proved suitable before re-bar yielding, but relatively large difference was produced after re-bar yielding. Also, the proposed modeling method is going to be used to

conduct an extension study on mechanical behavior of curved steel-concrete composite girders subjected to hogging bending in the following Chapters.

In Chapter 5, the state-of-the-art about analysis, design and construction of curved composite girder was presented. The horizontally curved steel-concrete composite girder bridges have excellent properties, such as quick construction, good seismic performance, saving construction formwork and convenience in spatial arrangement.etc, which have greatly promoted the application of such bridges. The objective of this Chapter is to provide and summarize important references related to the analysis, design and construction of curved composite girder bridges. Subjects discussed in this Chapter include (1) different curved girder bridge configurations and their applied range; (2) current specifications; (3) construction issues; (4) design methods; (5) analytical methods;

(6) load distribution; (7) torsion behavior; (8) warping stresses; (9) stability; (10) ultimate load-carrying capacity;

(11) dynamic and seismic response; (12) loading test; (13) long-term behavior; and (14) design details. The literature survey presented in this Chapter mainly focuses on papers written in English, Japanese and Chinese in relation to curved steel-concrete composite girders. This Chapter discussed the latest research achievements on the analysis, design and construction behaviors of curved composite steel and concrete bridges, which can be served as a basis for the further study. From the literature review we know that there are still numerous of problems need to be served, one of which is about the inelastic behavior of continuous steel-concrete composite girders in support regions. The ultimate strength needs to be defined, and mechanical behaviors of such girders need to be investigated.

In Chapter 6, an extension study was conducted on the mechanical behavior of curved steel-concrete composite girders under negative moment by using the proposed numerical models in Chapter 4. Totally 6 curved steel-concrete composite I-girder numerical models with different curvatures are analyzed. The load-displacement relations, loading capacities, strain distribution and movement of the sectional neutral axis as well as the interaction between ultimate bending and torsion moment were presented in this Chapter. The results indicate that the initial cracking load, girder yielding load and the ultimate load of curved composite girder under negative moment were decreasing as the curvature increase; and the reduction equation for predicting the load carrying capacity of the curved composite girder with different curvatures were proposed on the basis of the numerical results. Rebar strain distribution in the present curved composite girder numerical models was compared in different load levels, and it was found that the strains were different for rebar in different locations, and significant strain difference can be obtained in rebar of curved girder with larger curvatures. Besides, ultimate bending and torsion moment of present numerical models in curved composite girders were calculated and compared with results in typical straight steel-concrete composite girders, and the failure pattern of curved composite girders was found to be changed from bending failure to torsional failure with the increase of the curvatures. Finally, simplified bending–torsion interaction equation was proposed to illustrate the bending-torsion interaction for steel-concrete composite beams under hogging moment.

Finally, summary and conclusions are made in Chapter 7. The present study may give some useful suggestions on mechanical behavior of both straight and curved steel-concrete composite girders subjected to hogging moment, and the present numerical modeling methods can be used to make a further parametric study on interesting parameters. However, it is worth noting that in conjunction with the static and fatigue experimental testing of single overturned composite I-girders under negative bending, the FE model should be extended to model the behavior of actual continuous girders. Furthermore, various parameters affecting the composite girders with double or triple I-girders and box-girder in different cross profiles in negative bending should be investigated. Further research on interface property is also suggested to be conducted.

No.1

早稲田大学 博士（工学） 学位申請 研究業績書

(List of research achievements for application of doctorate (Dr. of Engineering), Waseda University)

氏 名(Full Name) 林偉偉 印(seal or signature )

（As of March, 2012） 種 類 別

(By Type)

題名、 発表・発行掲載誌名、 発表・発行年月、 連名者（申請者含む）(theme, journal name, date & year of publication, name of authors inc. yourself)

Paper

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Numerical Study on Hybrid Structures Renovated from the Old Railway Steel Bridges, Journal of Structural Engineering, JSCE, Vol. 58A, pp. 925-934. Apr. 2012. Weiwei Lin, Teruhiko Yoda, Nozomu Taniguchi, Norio Koide.

Mechanical Behaviour of Composite Girders Subjected to Hogging Moment: Experimental Study, Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE)) JSCE, Vol.67, No.3. pp. 583-596. Nov. 2011. Weiwei Lin and Teruhiko Yoda.

Inelastic Behavior of Continuous Steel-Concrete Composite Beams with Gum-Latex Mortar Coating, Proceedings of the 2011 World Congress on Advances in Structural Engineering and Mechnaics (ASEM+), Seoul, Korea. pp. 5451-5459, Sep.2011.Weiwei Lin and Teruhiko Yoda.

Ultimate Strength Behaviour of Continuous Composite Girders with Different Shear Connectors, Proceedings of Thirteenth International Summer Symposium, Kyoto, Japan. pp. 23-26.

Aug.2011. Weiwei Lin and Teruhiko Yoda.

Analysis, Design and Construction of Curved Composite Girder Bridges: State-of-the-Art, International Journal of Steel Structures (SCI), 10(3), pp. 207-220. Sep.2010. Weiwei Lin and Teruhiko Yoda.

Current Status of Curved Composite Bridge Research, Proceedings of the Twelfth International Summer Symposium. Chiba, Japan. pp. 33-36. Sep.2010. Weiwei Lin and Teruhiko Yoda.

Research on Sequence Of Prestressing On Cross-Section of Curved Box Girder Bridge, China Civil Engineering Journal (EI). Vol. 42, No. 6. pp. 80-85. Jun.2009. Weiwei Lin, Wu Zhiqin, Ding Hanshan, Ou Qingbao, Wang Lihai. (2009). (in Chinese)

Design of wedge-type anchors for CFRP tendons, Journal of Special Structures. Vol. 26, No.1. pp.

30-34. 2009. Weiwei Lin, Dalong Ren, Fanbo Guo, Chao He, Hanshan Ding. (in Chinese) The Analysis of gate posture pier, Journal of Modern Transportation Technology. Vol. 6, No. 2.

pp. 51-54. 2009. Ting Wu, Weiwei Lin, Hanshan Ding, YanNing Teng, Chao Li. (in Chinese) Experimental investigation of wedge-type anchors for CFRP tendons, Journal of Special

Structures, Vol. 26, No. 2, pp. 83-87. 2009. Hanshan Ding, Weiwei Lin, Yigui Zhang, Rui Zhang and Wenjun Xia. (in Chinese)

No.2

早稲田大学 博士（工学） 学位申請 研究業績書

(List of research achievements for application of doctorate (Dr. of Engineering), Waseda University)

種 類 別 By Type

題名、 発表・発行掲載誌名、 発表・発行年月、 連名者（申請者含む）(theme, journal name, date & year of publication, name of authors inc. yourself)

Others

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Nonlinear Analysis of Composite Beams under Negative Bending Moment, Proceedings of Japan Society of Civil Engineers 2011 Annual Meeting, Ehime, Japan. pp. 181-182.Sep.2011. Weiwei Lin and Teruhiko Yoda. (in CD Rom)

Nonlinear Analysis of a Horizontally Curved Composite Box-Girder Model, Proceedings of Japan Society of Civil Engineers 2010 Annual Meeting. Hokkaido, Japan. Sep. 2010. Weiwei Lin and Teruhiko Yoda. (2010). (in CD Rom)

The Calculation for Reduction Coefficient of Solid Skew Slab Bridges, Proceedings of Seminar for School Anniversary. Southeast University. 2008. Weiwei Lin, Hanshan Ding. (Best Paper Awards, in Chinese)