www.seipub.org/ce Construction Engineering Volume 3, 2015 doi: 10.14355/ce.2015.03.005
The Comparative Study on Seismic Behavior of End‐plate Connections Between PEC Column and H‐type Steel Column Zhao Gentian, Gao Chao* School of Architecture and Civil Engineering, Inner Mongolia University of Science & Technology, Baotou, Inner Mongolia, China zhaogentian93110@sina.com; gaochao_opt@163.com Abstract In order to compare the seismic performance of end‐plate connections between PEC column and ordinary H‐beam columns, this paper designed three different specimens to test their performance under low cyclic load. The focuses of the analysis are the influence of some factors like filling with concrete between the flanges, the amount of steel and backing plate on hysteresis, ductility and capacity of energy dissipation. Experiment and comparative results show that the end plate connections of PEC column can not only use fewer amount of steel than the ordinary H‐beam column, but also have a good carrying capacity and hysteretic property. Besides, the back plate has great influence on the stiffness of the combination. Keywords PEC Column; End Plate; Seismic Performance; Comparative Study
Introduction The performance of the node plays a key role on the earthquake resistance for the whole structure. The end plate connection is a form of semi‐rigid connections that has a good ductility and energy dissipation capacity[1]. Partially encased composite column, which is called PEC columns, is a type of H‐beam columns placed concrete between two flanges. Compared with general steel frame structures, frame structures equipped PEC columns can save the problem that the plastic hinge can’t be formed at the end of the beam because of the local buckling when the flakiness ratio of plates is too large or structures bearing large load[2]. In recent years, scholars have done parts of studies on the seismic performance of the partially encased composite structure. However, comparative study between it and the ordinary H‐beam structure is still inadequate. In summary, this paper designed three different specimens to test their performance under low cyclic load to compare with the literature. Test Overview In this paper, parts of specimens in Guo Bing’s test[3] were analyzed as comparison objects. They were all produced by Q235‐B steel. Bolts were M20, friction‐type high‐strength bolts. The detail drawing of the node is shown in Figure 1 (a) as below. The numbers of specimens and specific parameters in the document are shown in Table 1 from SJ‐A to SJ‐C. This paper’s specimens shown in the same Table from SJ‐1 to SJ‐3 were designed to compare with the literature. The specifications of steel and bolts were the same with the document. TABLE 1 NBUMER AND SPECIFIC PARAMETERS OF SPECIMENS IN DOCUMENT
NO.
26
Sectional dimension of columns(mm)
Thickness of end Stiffening ribs of Stiffening ribs of plates (mm) end plates webs
Backing plate
SJ‐A
200×200×8×l2
12
No
Yes
No
SJ‐B
200×200×12×l8
18
No
No
No
SJ‐C
200×200×12×l8
25
No
Yes
No
SJ‐1
200×200×8×12
12
No
No
No
SJ‐2
200×200×8×12
18
No
No
No
SJ‐3
200×200×8×6
24
No
No
Yes
Construction Engineering Volume 3, 2015 www.seipub.org/ce
This article didn’t design stiffening ribs of webs. The transverse tie bars, which were made by HPB235 steel with a diameter of 10mm and the spacing 200mm, were welded along the longitudinal direction through the column between the up and bottom flanges. Then concrete was placed between the two flanges. The size of the end plate was 400×80×24mm. The detail drawing of the node is shown in Figure 1.1 (b). Among them, SJ‐3’s flakiness ratio of the flange went beyond the limit of “Code for Seismic Design of Buildings[4]” and “Code for Design of Steel Structures[5]”. It belonged to the category of thin and soft steel.
(a) The NODE in the DOCUMENT (b) The NODE in THIS PAPER FIGURE 1 THE DETAIL DRAWING OF THE NODES
Test Results and Analysis Final failure modes and analysis of the data of specimens in document and this paper are shown in Table 2 and Table 3. TABLE 2 FINAL FAILURE MODES
NO.
Final failure modes
SJ‐A
Welds between beam flanges and the end plate are break
SJ‐B
The beam basically formed plastic hinge
SJ‐C
The beam formed plastic hinge
SJ‐1
The beam formed plastic hinge and end plate fractured
SJ‐2
The beam formed plastic hinge
SJ‐3
The beam formed plastic hinge TABLE 3 ANALYSIS OF THE DATE
NO.
Pu (kN)
Δu (mm)
θu (rad)
Mc (kNm)
Rin (104kNm/rad)
δd
Ce
SJ‐A
58.6
17.8
0.045
93.76
1.13
5.8
1.4
SJ‐B
77.1
24.0
0.060
123.36
1.51
7.0
2.5
SJ‐C
85.9
16.2
0.040
137.44
1.58
6.4
2.2
SJ‐1
62.5
17.6
0.044
75.04
1.14
6.2
1.7
SJ‐2
64.3
13.2
0.033
77.18
1.08
5.2
2.2
SJ‐3
64.8
14.8
0.037
77.76
1.56
5.7
1.8
Pu is the ultimate load of beam ends; Δu is the ultimate displacement of beams; θu is the ultimate corner, θu =Δu/400mm; Mc is the ultimate moment; Rin is the initial rotational stiffness of nodes; δd is the ductility factor; Ce is the energy dissipation factor. Hysteretic Performance In this paper’s test, the ultimate corner of all the specimens is greater than 0.03rad, meeting requirements for plastic corner of inelastic bending steel frame between the beam and the column in FEMA‐97[6]. All the specimens show good plastic deformability. The hysteresis curve of SJ‐1 is full when the low cyclic load was exerted to it. It is typically fusiform. The hysteresis curve of SJ‐A and SJ‐1 is shown in Figure 2. Due to differences in loading system, two hysteresis curves have some
27
www.seipub.org/ce Construction Engineering Volume 3, 2015
differences in the number of cycles. The buckling of column flanges are effective controlled because of concrete fill. Besides, concrete bears a part of the moment of nodes, so the plastic hinge appears on beams. Although SJ‐1 set no stiffening ribs of webs, but has the similar ultimate corner and initial rotational stiffness. It shows that the role of web stiffeners similar to concrete in this regard. 80
M/kN·m
60 40 20
-0.05 -0.04 -0.03 -0.02 -0.01
0 0.00 -20
0.01
0.02
0.03
0.04
0.05
θ/rad
-40 -60 -80
(a)SJ‐A (b)SJ‐1 FIGURE 2 HYSTERESIS CURVES OF SJ‐A AND SJ‐1
The column’s web and flange of SJ‐2 were thinner than the SJ‐B. The test results of SJ‐2 are all lower than SJ‐B. This suggests that although filled with concrete, the column web and flange are so thin that it has some side effects on the hysteretic behavior. SJ‐3 was equipped with the backing plate and SJ‐C was fitted with stiffening ribs of webs. They showed the same ultimate corner and initial rotational stiffness. The reason is that concrete and the backing plate effectively inhibit the occurrence and development of the local buckling of column flanges, which make up for their weak of deformability after local buckling. Ductility and Energy Dissipation Capacity Filled with concrete, the ductility and energy dissipation factor of SJ‐1 are improved higher than SJ‐A. The reason is that compression concrete in the node effectively suppressed the local buckling of column flanges and replenished the role of the web. However, the ductility and energy dissipation factor of SJ‐2 and SJ‐3 are lower than SJ‐B and SJ‐ C. Thus it can be seen that it can’t simply fill concrete to reduce the amount of steel. But the ductility factors of all these three specimens are between 5.2 and 6.2. It meets the requirement in “Code for Seismic Design of Buildings[4]”, which requires the factor more than 4.0. The energy dissipation factor is between 1.7 and 2.4, higher than the concrete structure and similar with steel reinforced concrete structures. In summary, all the specimens show good ductility and energy dissipation capacity. Conclusions This paper pertinently designed three different PEC column connections to study the failure mode hysteretic behavior, ductility and energy dissipation capacity of the node under low cyclic load. Now conclusions are summarized as follows: 1) PEC column connections have a good combination of hysteretic behavior. The occurrence and development of local buckling are suppressed nearby nodes due to constraints of concrete filled between flanges. In addition, the ultimate corner and the ultimate moment are all increased. 2) Ductility factors of all these three specimens are between 5.2 and 6.2, and the energy dissipation factor are between 1.7 and 2.4. It means that although the column flanges are thin, it still reflects good ductility and energy dissipation capacity. 3) The method of filling concrete and installing backing plate can solve the problem that flakiness ratio of the flange goes beyond the limit. This can not only improve the hysteretic behavior of the structure, but also provide
28
Construction Engineering Volume 3, 2015 www.seipub.org/ce
the possibility to improve the flakiness ratio of the flange in the code and make it possible to use this type of structure in earthquake resistance protection zone. REFERENCES
[1] Guo Bing, Liu Feng. Experimental Study of Beam‐column End Plate Connections on Hysteretic[J]//Journal of Building Structures, 2002, Vol.23(3):8‐13. [2] Zhao Gentian, Cao Fubo, Wang Shan, Wan Xin. Behavior of Partially Encased Composite Columns Subjected to Eccentric Compression[C]//Proceeding of Shanghai International Conference on Technology of Architecture and Structure, ICTAS 2009. Shanghai: Tongji University Press, 2009: 602‐607. [3] Guo Bing. Failure Mechanism and Seismic Design Strategies of Steel Frames Beam‐column End Plates under Cyclic Loading[D]//Xiʹan University of Architecture and Technology, 2002:17‐31. [4] Code for Seismic Design of Buildings GB50011‐2010[S] // Beijing: China Building Industry Press, 2010. [5] Code for Design of Steel Structures GB50017‐2003[S] // Beijing: China Planning Press, 2003. Gentian Zhao, Xinzhou City, Shanxi Province, 1962‐ . D Sc Tech, Shanghai University, Shanghai City, 2007, main research direction is the steel structure and steel‐concrete composite structure. He is Professor of School of Architecture and Civil Engineering, Inner Mongolia University of Science & Technology, Baotou, Inner Mongolia, China. Chao Gao, Zhangjiakou City, Hebei Province, 1989‐ . Master graduate student, main research direction is the steel structure and steel‐concrete composite structure.
29