Block shear strength of coped beams with single-sided bolted connection

Highlights

• Seven coped beam specimens with single-sided bolted connection were tested.

• Test parameters included the out-of-plane eccentricity and web block aspect ratio.

• The block shear capacity of the specimens was not affected by the eccentricity.

• Finite element analyses of the specimens were conducted.

• Various design codes were used to predict the capacity of the specimens.

Abstract

Block shear is one of the major failure modes for coped steel I-beams. While focus of previous studies on the block shear capacity of coped steel I-beam was mainly given to the connections with double clip angles, single-sided connections, which induce out-of-plane loading eccentricity, have not been adequately considered. Ten full-scale coped steel I-beam tests were conducted to examine the effects of two main test parameters, namely, out-of-plane loading eccentricity and web block aspect ratio (ratio of shear area to tension area). It was found that nine test specimens failed with tension fracture along the bottom bolt row of the web, and the remaining one failed in a whole block tear-out manner. Twisting of the web near the cope was observed for specimens with single-sided connection. More importantly, the test results showed that the out-of-plane loading eccentricity due to the single-sided connection did not have a detrimental effect on the block shear capacity of the specimens. Moreover, increasing the connection rotational stiffness could increase the block shear capacity. These effects are further discussed via a finite element analysis and a preliminary parametric study. Finally, the test results are compared with four major design standards. It is found that the Canadian Standards CAN/CSA-S16-09, which gives a test-to-predicted ratio ranged from 0.93 to 1.17, provided relatively good predictions for the specimens with single bolt line layout, while the predictions by other codes are too conservative. For those specimens with double bolt line layout, the capacities are underestimated by all the considered standards.

Introduction

In steel construction, secondary beams are often connected to the main girder at the same elevation in order to support the slabs. To allow enough clearance for the intersection of the beams, the flanges of the secondary beams are usually coped, as illustrated in Fig. 1(a). The cope can be located at the top flange, bottom flange, or both flanges of the beam ends, depending on different construction requirements. To connect the coped beam end to the main girder, various connection types can be used, including double clip angles, single angles, welded plates (fin plates) or tees.

Because of the removal of the flange(s), the strength of coped beams is reduced. The potential local failure modes of the coped beam ends include flexural yielding, shear yielding, local web buckling and block shear. For the block shear failure, which is considered in this study, the web block (which forms part of the connection) can be torn out from the beam web, as shown in Fig. 1(b). This block shear failure of coped beams was first observed by Birkemoe and Gilmor [1]. Subsequently, Yura et al. [2] and Ricles and Yura [3] performed a series of full-scale experiments and proposed a block shear capacity model which considered one-half of the tensile strength on net tension area plus the shear yield strength on gross shear area. The coped beam test results from Aalberg and Larsen [4] showed that the web block was partially torn-out with tension fracture of the web in the vicinity of the bottom bolt hole. Kulak and Grondin [5] examined the block shear capacity equations used by various design standards and discovered that the predictions of the block shear capacity of coped beams based on major standards were generally inconsistent. Subsequently, Franchuk et al. [6], [7] conducted seventeen full-scale tests to examine the effect of different geometric parameters and different bolt layouts on the block shear behaviour of coped beams. Finite element analysis based on the test results of Ricles and Yura [3] and Franchuk et al. [7] was further conducted by Topkaya [8].

While most of the previous studies focused on coped beams with bolted double clip angle connections, the block shear response of coped beams with single-sided connections using tees or single angles has not been adequately examined. Compared with double clip angle connections, the use of single-sided connections can simplify the procedure of shop fabrication and reduce the cost of manufacturing. However, an out-of-plane loading eccentricity is induced between the centreline of the beam web and the centroid of the connection when single-sided connections are used, as shown in Fig. 1(c). The secondary bending caused by the out-of-plane loading eccentricity may influence the block shear capacity of the coped beam web, but test evidence is not available regarding this concern. In addition, other factors such as bolt arrangements and connection rotational restraints have not been sufficiently studied in previous studies. To address these issues, ten full-scale tests were conducted to examine the block shear behaviour and strength of coped beams with single-sided bolted connections, where different bolt layouts and connection sizes were employed. Finite element (FE) models of the test specimens were subsequently established and a preliminary parametric study was conducted to further discuss these effects. Finally, the test results were compared with the predicted block shear capacities according to various current standards, including AIJ [9], AISC-LRFD [10], EN 1993-1-8:2005 [11] and CAN/CSA-S16-09 [12], and the test-to-predict ratios were presented and discussed.