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ISSN : 2093-5145(Print)
ISSN : 2288-0232(Online)
Journal of the Korean Society for Advanced Composite Structures Vol.9 No.4 pp.65-71
DOI : https://doi.org/10.11004/kosacs.2018.9.4.065

# Strength Behavior of High-tension Bolted Connections for I-shaped Plate Girder

Su Thazin1, Won-Sup Hwang2, Jun-Su Ham3
1M.E., Department of Civil Engineering, Inha University, Incheon, Korea
2Professor, Department of Civil Engineering, Inha University, Incheon, Korea
3Ph.D, Department of Civil Engineering, Inha University, Incheon, Korea

본 논문에 대한 토의를 2019년 2월 28일까지 학회로 보내주시면 2019년 3월호에 토론결과를 게재하겠습니다.

Corresponding author: Hwang, Won-Sup Department of Civil Engineering, Inha University, 100 Inha-Ro, Yonghyoung-Dong, Nam-gu, Incheon, Korea Tel: 032-873-2130, E-mail: hws@inha.ac.kr
August 16, 2018 October 30, 2018 October 31, 2018

## Abstract

I-shaped plate girders are frequently used for the construction of the large span structures, especially large span bridges and railway bridges as they can be built up by (riveting or bolted connection) and welding the steel plates to get the desired sizes of the designers. Riveting or bolting type has many advantages such as avoiding both of the strength reducing problem during the construction and high maintenance cost after the construction as it is chosen over the welding type. However, such riveting has the problem of slipping around the bolted connection when the load is applied to the girder, which might cause strength reducing problems. Therefore, in this study, the slip behaviors of the bolted connection of the I-shaped plate girder, beside it’s strength behaviors were investigated through the FEM analysis program. Moreover, various effects of the vertical stiffeners’ interval on the strength of the girders were also examined along with this study.

# I-형 플레이트거더 고장력볼트이음부의 강도특성

수 타진1, 황 원섭2, 함 준수3
1인하대학교 토목공학과 석사
2인하대학교 사회인프라공학과 교수
3인하대학교 토목공학과 박사

## 초록

I형 플레이트 거더는 장경간 구조물, 특히 장경간 교량 및 철도교에 자주 사용되며 리벳 또는 볼트 이음과 같은 방법 으로 조립할 수 있고 강판을 용접하여 설계자가 원하는 크기의 거더를 제작할 수 있다. 리벳 또는 볼트를 이용한 연결방식은 시공 중 구조물의 내하력 저하 문제를 피할 수 있고 용접으로 제작된 거더에 비해 유지관리비용이 적다는 장점이 있다. 하지만, 리벳 또는 볼트연결의 경우 하중이 거더에 전달될 때 연결부 주위에 미끄러짐이 발생 할 수 있어 이로 인한 강도감소가 발생할 우려가 있다. 본 연구에서는 유한요소 해석 프로그램을 통해 I형 플레이트 거더의 볼트 이음부의 거동특성을 검토하였다. 또한 수직보강재의 간격이 거더의 강도에 미치는 영향에 대해 검토하였다.

## 1. INTRODUCTION

This research was initiated by observing the experiment results of the previous study. Strength behaviors of the three specimens were investigated through an experiment implemented by the steel structure lab. All of these specimens are the plate girders with high tension bolted connections. Two of the plate girders have the same specifications,however, one is with the horizontal stiffeners, while the other, horizontal stiffeners are omitted around the bolted connection.

The detailed specifications and shape of the test specimens are shown in Figure 1. Both of the specimens are the plate girder with the separated type of high-tension bolted connection, which is that the moment splice plates and shear splice plates are separated in the web panel. In this case, the shear splice plate with the high-tension bolts become responsibles of horizontal stiffeners and boosted the buckling strength of the web panel, as a result.

Therefore, it is possible to omit the horizontal stiffener around the bolted connection as in the Figure 1(b). The failure shapes of the both specimens after the experiments has been revealed in Figure 2.

Fig. 3 is experimental results of specimen-1 and specimen-2 in the relation of applied load(P) and displacement(δ) at the center of the girders. According to our results, the girder with the horizontal stiffeners doesn’t show the high strength performances while it’s comparing to the one without the horizontal stiffeners. The graph also shows that the specimens have the same strength behaviors in the elastic range, a slight difference behavior appear in the plastic range. Moreover, both test specimens showed the same loading capacity, yielding strength behaviors and finally, the ultimate strength of the girder were also the same.

After reviewing the two experimental results, it could be clearly noticed that the horizontal stiffeners around the high-tension bolted connection since it doesn’t conduct the role of increasing the strength of the girder. In order to prove this hypothesis, the FEM analysis for the omission of the horizontal stiffener was proceeded.

## 2. OUTLINE OF ANALYSIS MODEL

### 2.1 Analysis Method

In order to efficiently investigate the behavior of the desired models, the standard FEM analysis program was used. The solid element was especially chosen over the thin shell element in order to support the accuracy of analysis results during the analysis process.

Specifically, the half model was used by considering the central plane of the model as the symmetric boundary plane in order to save the analysis period and reduce the errors during the analysis process. Moreover, the bolted load were considered for the bolted-connection, thus, the design bolt load which mentioned in the "Korean Highway Bridge Design Code (KHBDC, 2012)" was applied along with the axial of the high-tension bolts. The detail boundary conditions and loading conditions of the analysis models are shown in the Figure 4.

The analysis model is considered as the SS400 steel, therefore, the mechanical properties of that is assigned to the model. The stress-strain relationship is calculated by using the steel composite equation in order to obtain the non-linear stress-strain results of the analysis.

### 2.2 Verification of Analysis Method

In Figure 5, the comparison of the experimental results and analytical results can review in order to observe the validity of the analysis method. Here, the standard experimental results are obtained by the test results which is done by the Akiyama(1996) in his thesis named "A Study on the limit States of HSFG Bolted Joints."

According to the graph, experimental and analysis results show the same behavior in elastic and plastic ranges and also under the unloading condition. The slip behavior occurred at around the loading capacity of 610kN which is slightly earlier than the experimental results, that is caused by the difference in the friction resistance of experimental and analytical program. Although there is a slight difference in slip interval, yielding, elastic and plastic behaviors show that this analysis program has high vilidity.

### 2.3 Specifications of Analysis Models

In this study, the strength behavior of the plate girder is investigated by varying the aspect ratio(α ) and the web proportion(h/tw ) independently in order to analyzed the effects of the horizontal stiffeners on the strength of the girder.. In the Table 1, the specifications of the analysis model can be observed.

The research proceeded by analyzing the models with different web proportion(h/tw ), and the aspect ratio(α ) varies as 0.4, 0.7 and 1 for each model. The detail specifications of the analytical models can be observed in the Table 2 and the shape of the model can be seen in the Figure 6.

## 3. ANALYSIS RESULT

### 3.1 Effect of Aspect Ratio(α )

Fig. 7 shows the effect of the aspect ratio on the strength of the girder. The results are in the relationship of the displacement of the loading capacity at the center of I-shaped girder and the ratio of the analytical moment to the theoretical yield moment.

According to the results, the yielding of the girder occurs at the moment ratio (M /My ) of 1.0 while aspect ratio(α ) is 0.4, then, the yielding point occurs at the moment ratio (M /My ) of 0.9 while the aspect ratio(α ) is 1.0. Therefore, results manifest that the aspect ratio is inversely proportional to the strength of the girder. The effect that the larger the aspect ratio, the lower the strength of the girder can obviously be seen through this graph.

### 3.2 Effect of Web Proportion(h/tw)

In the Fig. 8, the effect of the web-thickness ratio (h/tw) on the strength of the girder can be seen in the relationship of the plastic moment ratio(M /My ). Herein, the models with the same aspect ratio while varying the h/tw from 140 to the maximum 260, which is the maximum design limit in the "Korean Highway and Bridge Design Code (KHBDC,2012)" are analyzed through the same program.

According to the Fig. 7, yield point occurs at the plastic moment ratio(M /My ) at 0.9 for the designed (h/tw ) of 140, while it presents at 0.7 when the (h/tw ) designed as 200, while it’s found at 0.55 when the (h/tw ) designed as 260, however, the aspect ratio was kept to be constant at 0.4 in all the aforementioned cases. Here, the effect that the larger (h/tw ), the more reducing the strength of the girder can be clearly reviewed.

### 3.3 Slip Strength Behavior

As it is mentioned before, this analysis method used the solid element for the parts of the model, therefore, the occurrence of slip behavior at the high-tension bolted connection can be investigated. The slip behavior can be reviewed in the Fig 8.

According to the Fig.9, the slip strength of the high-tension bolted connection does not effect by the aspect ratio and it is only effected by the h/tw . Thus, the interval between the splice plates and the vertical stiffener does not related to the slip strength of the bolted connection. Therefore, the slip strength can be controlled by designing the h/tw .

### 3.4 Omission of Horizontal Stiffener

In the Fig. 10, the FEM analytical results in the relationship of aspect ratio (α ) and the ratio of the ultimate moment of the analytical to the theoretical yielding moment(Mu/My) are provided.

Based on results, when the aspect ratio is design as 0.4∼0.7, and the h/tw designed as equal or lower than 180, then, the Mu/My is above 1. This means that the buckling moment at the web panel is effectively secured in that range. And also the Mu/My is above 1 when the aspect ratio is at 1 and h/tw is equal or lower than 140. Consequently the web moment can secure the yield moment within that range.

The relationship of h/tw and the Mu/My can be reviewed in the Fig. 10. When the aspect ratio is 0.4∼ 0.7 and web proportion is equal or lower than 160, the ultimate moment in the web exceeded the yielding moment, thus, it is possible to omit the horizontal stiffener within that range. Similarly, the ultimate moment of the web panel exceeded the yield moment when the aspect ratio is 1 and h/tw is equal or lower than 140, and the omission of the horizontal stiffener is possible.eqs. 1

$h t w = ( − 180 × α ) + 250 ( 0.4 ≤ α ≤ 0.6 ) = 140 ( 0.6 ≤ α ≤ 1.0 )$
eqs. 1

Equation 1 is the suggested design equation for the omission of the horizontal stiffener which is configured by reviewing the omission range in Fig.10 and Fig.11. Fig. 12 is the graph of the analytical results and the results calculated by eqs.1.

## 4. CONCLUSION

In this study, the strength behavior of the I-shaped plate girder was investigated through FEM analysis. The range to omit the horizontal stiffener safely around the high-tension bolted connection is also investigated and the suggested equation is configurated. The slip strength behavior of the high-tension bolted connection also explored in this study.

The following statements are organized by reviewing through this study.

• (1) The aspect ratio(α) and the web slenderness ratio (h/tw ) are reversely proportional to the strength of the girder. The larger the aspect ratio(α) and h/tw , the lower the strength of the girder.

• (2) The more substantial web proportion, the lower rigidity of the girder and thus, the aspect ratio effect more on the girder with more substantial web proportion. Therefore, the web must be thoroughly designed to have the strongest or more rigid girder.

• (3) The slip at the bolted connection is only affected by the slenderness of the web (h/tw ). However, it is not affected by the aspect ratio(α ). If h/tw is designed as the maximum and the aspect ratio is at 1, the yielding of the girder occurs before the slip behavior at the bolted connection appear.

• (4) The horizontal stiffener can be omitted when the h/tw is lower or equal to 180 and the aspect ratio is 0.4. If the aspect ratio is larger than 0.4 and lower than 0.7 and h/tw is equal or lower than 160, then, the horizontal stiffener can also be omitted. Finally, the horizontal stiffener can omit when the aspect ratio is design between 0.8 to 1.0 and the h/tw is 140 or lower.

If the plate girder is designed by the eqs.1, the horizontal stiffener around the bolted connection can be omitted in the ranged which mentioned above. As a result, more economical and feasible girder can be obtained. This study can be referenced for designing the more portable plate girder which can give easy and advanced workability in the construction sites.

## ACKNOWLEDGMENT

This experiment study had been conducted under the financial support provided by a grant(18RTRP-B137 949-02) from Railway Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government.The support is apperitiated.

## Figure

Detail of Test Specimens
Failure Modes of Specimens
Test Results
Boundary Conditions and Mesh Divisions
Comparison of Test and Analysis Results
Detail Specifications of the Analysis Models
Analytical Results
Analytical Results of the Effect of h/tw
Effect of h/tw on the Slip Strength
Relation of Aspect Ratio(α ) and Moment Ratio(Mu/My)
Relation of h/tw to the Mu/My
Omission Range of the Horizontal Stiffener

## Table

Details of Analysis Models
Dimensions of Analysis Models(mm)

## Reference

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