Effective use of High Performance Steel Materials Q690 to Q960

Transcription

1 Effective use of High Performance Steel Materials Q690 to Q960 Michael C H Yam 1),2), Xuemei Lin 1),2) 1) Department of Building and Real Estate, The Hong Kong Polytechnic University, HK, China 2) Chinese National Engineering Research Centre for Steel Construction (Hong Kong Branch), The Hong Kong Polytechnic University, HK, China

2 Research objectives to perform experimental and numerical studies of the net-cross section strength of HSS connections to evaluate the applicability of the current net-cross section equation for HSS connections, and to develop new design equations for net section strength of HSS connections if necessary;

3 Research objectives to perform experimental and numerical studies of the effects of the geometry parameters (i.e. connection length, bolt spacing, bolt stagger) on the bearing strength of HSS connections and to propose new design equations for HSS connections if necessary, and

4 Research objectives to perform experimental and numerical studies of the block shear strength of HSS plates, to evaluate the applicability of current block shear design equations for HSS plates, and to develop a new design method for predicting the block shear strength of HSS plates if necessary.

5 Research objectives other related studies such as the use of HSS connections with smart materials and the use of HSS steel members and connections in an energydissipation frame system are also considered in the research programme.

6 Current work The net section strength of HSS bolted connections: finite element (FE) analysis and experiment programme design.

7 1. Background In general, ductility of HSSs is lower than that of normal steels. Limited studies have been conducted to analyse whether the ductility is enough to redistribute the stresses around bolt holes. net section fracture splitting failure [1] [2] transition boundary bearing failure [1] P. Može, Ductility and resistance of bolted connections in structures made of high strength steels, Politehnica University of Timisoara, Romunija, [2] Y.B. Wang, Y.F. Lyu, G.Q. Li, J.Y.R. Liew, Behavior of single bolt bearing on high strength steel plate, Journal of Constructional Steel Research 137 (2017)

8 1. Background However, the connections employed by them were only equipped with single bolt or two bolts positioned perpendicular to the loading direction. Whether these proposed transition boundaries are still applicable for the multi-bolted connections requires further study. Therefore, various configurations of HSS bolted connections will be investigated in this project. The behaviour of the connections will be comprehensively analysed numerically. The design formulas in the current design codes and the proposed modified design formula in the existing literatures will both be re-examined.

9 2.1 Validation of finite element model A series of HSS bolted connections equipped with different numbers of bolts in double shear were selected from the existing papers and the corresponding FE models were developed. The connections selected were designed to fail with net section fracture, bearing failure and splitting failure, respectively.

10 2.1 Validation of FE model SD SD B204 Fig.1 FE models L18

11 2.1 Validation of FE model SD (Tear-out failure) SD (Splitting failure) B204 (Net section fracture) L18 (Net section fracture) Fig.2 The failure modes of the connections

12 2.1 Validation of FE model Fig.3 The load-deformation curves of FE analysis and experiments

13 2.1 Validation of FE model Table1 The ultimate loads and the corresponding deformations of the connections Model Test results FE model results Percentage difference P u,test D u,test P u,fem D u,fem P u D u SD % 8.10% SD % 2.10% B % 6.67% L % 2.40% P u ----the ultimate loads D u ----the corresponding displacement

14 p2 b e2 2.2 Preliminary FE analysis 14 models were developed to study preliminarily the effect of the number of the bolts on the net section strength of HSS bolted connections. The typical configurations are presented in Fig.4 and 5. The dimensions of the models are summarised in Table 2. P P Fig.4 The configuration of a typical double shear butt connection p1 e1 Row 1 Row 2 Row 3 d0 Column 3 Column 2 Column 1 Fig. 5 The configuration of the specimen

15 2.2 Preliminary FE analysis Table 2 The dimensions of the models Model b (mm) t (mm) d 0 (mm) d (mm) e 1 /d 0 e 2 /d 0 p 1 /d 0 p2/d 0 A n (mm 2 ) 1 1R1C R2C R3C R4C R6C R1C R2C R3C R4C R6C R1C R2C R3C R4C The specimens are named as mrnc-b-p2/d0-steel grade-p1/d0. mrnc means the connection is equipped with m rows and n columns of bolts. m ranges from 1 to 3, n ranges from 1 to 6.

16 2.2 Preliminary FE analysis Half model of each connection was developed due to symmetry and to save calculation time, as shown in Fig.6. Applied displacement Applied symmetry constraint Fig.6 FE model of 2R2C

17 2.2 Preliminary FE analysis 1R1C R2C R6C R3C Fig.7 The failure modes of typical models

18 2.2 Preliminary FE analysis 1RnC-series models 2RnC-series models 3RnC-series models Fig.8 The load-displacement curves of the mrnc-series models

19 2.2 Preliminary FE analysis Results:Take 1RnC-series models as an example to illustrate the detail behaviour of the connections. With the increase of the bolt number, the stiffness of the connection increased. However, the deformation capacity decreased. The maximum loads of the 1RnC-series specimens were similar, ranging from to kn. All the design codes (i.e. Eurocode3, AISC-2010, AS 4100 and CSAS16-14) give conservative predictions of the net section capacity regardless of the row and column numbers.

20 2.2 Preliminary FE analysis Among the four design codes, the best prediction was found for the 1RnCseries specimens, followed by the 2RnC- and 3RnC- series. This means that the bolts on the net section may affect each other and influence the net section strength of the connection. Therefore, in the experiment design, extra 4 specimens were added to study the effect of p 2 on the behaviour of the connection based on the 2R1Cseries. The designed dimensions are summarised in Table 3. The p 2 /d 0 ranges from 2, 2.5, 3.0, 3.5, and 4.

21 3. Experiment design 3.1 Experiment design Table 3. The dimensions of the specimens Specimen b (mm) t (mm) d 0 (mm) d (mm) e 1 /d 0 e 2 /d 0 p 1 /d 0 p2/d 0 A n (mm 2 ) 1 1R1C R2C R3C R4C R6C R1C R2C R3C R4C R6C R1C R2C R3C R4C R1C R1C R1C R1C

22 3. Experiment design 3.2 Schedule for experiment The next stage is mainly to focus on the fabrication of the specimens and the setup of test programme for the study of the net section strength of HSS connections. The test is planned to be finished during the summer of A conference paper will be completed before March 2018 based on further FE analysis. The study of the bearing strength and block shear strength of HSS connections will be commenced at the same time.