Experimental study of earthquake-resilient end-plate type prefabricated steel frame beam-column joint

Journal of Constructional Steel Research 166 (2020) 105927

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Journal of Constructional Steel Research

Experimental study of earthquake-resilient end-plate type prefabricated steel frame beam-column joint Ai-Lin Zhang a,b, Ping Qiu a, Kang Guo a, Zi-Qin Jiang a,⁎, Liang Wu a, Shuang-Cheng Liu a a b

Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China Beijing Advanced Innovation Center for Future Urban Design, Beijing 100044, China

a r t i c l e

i n f o

Article history: Received 30 July 2019 Received in revised form 31 December 2019 Accepted 3 January 2020 Available online xxxx Keywords: End-plate type Prefabricated structure Beam-column joint Seismic performance Earthquake-resilient

a b s t r a c t In order to avoid the complex stress field of traditional beam-column joints caused by arranging end side plate or support plate on beam end, and realize the earthquake-resilient of joints, based on the plastic damage control idea, a kind of end-plate type prefabricated steel frame beam-column joint (EPPSFJ) is put forward in this paper. The new type joint mainly consists of the circular steel tube column with cantilever beam, ordinary beam, and the connecting devices. The EPPSFJ can realize stiffness control of the connection by adjusting the thickness of the flange cover plate (FCP), the distance between the middle bolts and other parameters, and make use of the plastic distortion and friction sliding of the FCP to dissipate the seismic energy, so as to ensure the basic elasticity of the structural member and realize the rapid post-earthquake repair of the joint. In the article, the low cycle load test is carried out on five specimens and one repair specimen to obtain the failure pattern, hysteresis curve and strain curves of joints etc., The impact rule of parameters such as the thickness of cantilever beam flange, the distance between the middle bolts, thickness and weakening form of FCP on the seismic performance is researched. The experimental study shows that: the joints have good seismic performance by reasonably designing parameters of bolts and the FCP, and the plastic distortion is focused on the FCP easily replaced, which make sure that plastic damage does not occur at the structural member. The repaired specimen still has great energy dissipation capacity, ductility and other seismic performance indexes, which indicates that the joint can be quickly repaired post-earthquake through replacing the FCP and other connecting devices. © 2020 Elsevier Ltd. All rights reserved.

1. Introduction In recent years, prefabricated steel structure has become a new direction and trend of the development of architectural steel structure. As a green building structure with a full life cycle, prefabricated steel structure has the characteristics of standardized design, factory production, assembly construction, etc. Compared with other structures, the steel structure has a better ductility, a more excellent plastic energy dissipation capacity in earthquakes and superior seismic performance [1], which have been widely used in building and bridge engineering [2,3]. And the prefabricated steel frame beam-column connection is the key to popularize fabricated steel structure. While the existing prefabricated joints have an installation process that is too complex to meet the needs of rapid construction. And due to its defect in energy dissipation mechanism, it is unable to guarantee that the plastic damage does not occur at the principal member such as beams and columns, which makes it more difficult to repair after earthquakes. In the Northridge earthquake and the Kobe earthquake [4,5], a great deal of brittle failure occurred on the beam-column connection, resulting in a great decline in seismic ⁎ Corresponding author. E-mail address: [email protected] (Z.-Q. Jiang).

https://doi.org/10.1016/j.jcsr.2020.105927 0143-974X/© 2020 Elsevier Ltd. All rights reserved.

performance of the overall structure. Therefore, the research and development of the prefabricated beam-column joints that is suitable for building industrialization and post-earthquake recoverable function can transform the structure from overall damage to partial replaceable component damage, taking advantages of prefabricated steel structure building performance. In order to solve energy dissipation problem of beam-column joints under cyclic load, Latour et al. [6] proposed an innovative beam-column connection method, which can realize the seismic energy dissipation and keep the steel components away from plastic damage. To develop the earthquake-resistant composite steel frame structure with energy dissipation fuse, Castiglioni, Valente et al. [7–9] carried out on an experimental research and evaluated the seismic performance of the new steel frame in terms of overall structural energy consumption and frame stability. Oh et al. [10] proposed a structural system with slit damper. Through conducting the cyclic loading experiment on the designed specimens, it was found that the connection had good hysteretic performance, and the energy dissipation and plastic deformation in the structural system concentrated on the slit damper. Wolsk et al. [11] put forward the earthquake-resistant frame beam-column joint equipped with Bottom Flange Friction Device, which provides a reliable energy dissipation path for the joint. Banisheikholeslami et al. [12] proposed

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A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

an innovative seismic energy dissipation connection, and the study found that this new type of connection has stable hysteretic performance. Chen et al. [13] put forward the connection applied to modular steel structure buildings, which avoids the inconvenience and weld defects caused by field welding and facilitates installation. In order to enhance the rotation capacity and ductility of end-plate bolted connections, D'Aniello M et al [14–16] analyzed the influence of joint design parameters on the joint response under cyclic load through finite element simulation, and proposed the design requirements to improve the ductility of the joints, providing theoretical basis for the design of end plate beam-column joints to improve ductility and energy dissipation capacity. Liu et al. [17–19] developed a modular frame beamcolumn joint, and obtained its energy dissipation capacity, rotation capacity and other mechanical performance curves of the joint through static test and finite element analysis. Mirghaderi et al. [20] proposed a reduced beam section connection, and carried out cyclic load test research to verify the cyclic performance of this connection mode. Maleki et al. [21] put forward the hybrid beam-column joint with reduced flange, and the cyclic load test results show that the seismic performance of this joint is better than that of the previous connection of reduced beam section. Gong et al. [22] developed the assembled bolted beam-column joint, and carried out load test and numerical simulation on the designed joint specimen. The test results showed that the joint has excellent seismic performance. Wang et al. [23,24] put forward an all-steel bamboo-shaped energy dissipater, and it shows in the experiment that the new type of energy dissipaters have a good hysteretic performance when exerted with reciprocating load. To realize the rapid post-earthquake restoration of steel frame beam-column joints and reduce its cost, domestic and foreigner scholars have done a lot of research. Farrokhi et al. [25] realized postearthquake repair of beam-column joint by setting replaceable plates. Lu et al. [26] put forward three kinds of energy consumption fuse in the coupling beam and carried out experimental research on them. Ji et al. [27] set energy-dissipating beam section in the middle of steel beam, and by reasonably controlling the bearing capacity ratio of energy-dissipating beam section and common beam section, the plastic deformation and damage of the steel beam in heavy earthquake are concentrated in the energy-dissipating beam section that can be easily replaced. Mou et al. [28,29] performed an experiment on the effect of composite action between steel beam and concrete slab on the seismic performance of frame beam-column joints. The test results show that the composite action between steel beams and composite plates improves the bearing capacity and deformation of beam-column joints of

the frame. Fang et al. [30,31] put forward the idea of using shape memory alloy bolts instead of ordinary high-strength bolts for endplate connection, and conducted experimental research and numerical simulation on it, verifying that the end-plate connection using shape memory alloy bolts has excellent seismic performance and postearthquake recentering abilities. Jia et al. [32] conducted finite element simulation study on the self-centering dual-steel buckling-restrained braces to study its energy dissipation capacity and self-centering capacity, and the results show that the proposed braces can greatly reduce the maximum inter-layer displacement of the frame structure and facilitate post-earthquake repair of the joints. He et al. [33] conducted an experimental study on the moment-resisting connection which can concentrate the damage on the replaceable steel angle, and verified the hysteretic performance of the connection under earthquake actions and the replaceable property of bottom steel angle after earthquakes. Li et al. [34] put forward a beam-column joint with cantilever beam, and proved through experiments that the connection can adjust the position of plastic hinge and improve the connection seismic performance. Shi et al. [35] proposed an enlarged weld access holes connection, in which the plastic failure can be transferred to the beam flange, reducing the possibility of brittle failure at the connection weld and improving the ductility of the connection. Wang et al. [36], with the design concept of controlling the formation of plastic hinge, opened holes in the web of the beam to form a new joint form. Experimental analysis shows that this type of joint can effectively control the location of plastic hinge. Zhang and Jiang et al. [37–43] developed a new type earthquakeresilient prefabricated sinusoidal corrugated web beam-column joint, which realizes the plastic damage control of beam-column joints. The plastic damage is mainly focused on the easily replaced flange cover plate (FCP), so as to ensure the main structure is in the elastic state when the earthquake happens. In order to meet the needs of building industrialization, improve the degree of assembly of building structure, realize post-earthquake repair of beam-column joints, avoid the complex stress field formed by multiple welds and realize the outward displacement of plastic hinge, this paper proposes a new end-plate type prefabricated steel frame beamcolumn joint (EPPSFJ), and its specific structure is shown in Fig. 1. This joint can realize stiffness control of the connection by adjusting the thickness of the FCP, the distance between the middle bolts and other parameters, and make use of the plastic deformation and friction sliding of the FCP to dissipate the seismic energy. This design avoids the single mode of energy consumption, ensuring principal component such as beams and columns to be in the elastic state when earthquake happens,

Connecting devices Upper flange cover plate

Ordinary beam

Upper circular steel tube column

Ordinary beam Ordinary beam endplate

Upper annular baffle

Connecting devices

Lower annular baffle

Circular steel tube column with cantilever beam

(a) Split view

High-strength bolt Lower flange cover plate

Middle circular steel tube column

Lower circular steel tube column

Cantilever beam rib plate

(b) Assembly view

Fig. 1. End-plate type prefabricated steel frame beam-column joint. (a) Split view. (b) Assembly view.

cantilever beam end plate

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

5060 60

Lbolt

60 60 50

tpi 12

tcp

3

267 299

12

12

g

350

200

6

97

276 300

g 1750

16

60 60 50

97

350

Lbolt

12

3000

70 80 80 70

200 50 60 60

1750

16

(a) Vertical view

(b) Top view

Fig. 2. Details of the specimens. (a) Vertical view. (b) Top view.

and realize post-earthquake repair of joints by replacing the FCP and other connecting devices. In this paper, the influence of design parameters such as flange thickness of cantilever beam, distance between the middle bolts, the thickness and weakening form of FCPs on the failure mode and seismic performance of the joints is investigated through the Low cycle reciprocating load test of 6 specimens, finally many beneficial conclusions are obtained. 2. Test overview 2.1. Specimens design The new type EPPSFJ consists of the circular steel tube column with cantilever beam, ordinary beam, and the connecting devices between them. The cantilever beam and ordinary beam were welded by Ishaped beam and end-plate. The connecting devices between the cantilever beam and ordinary beam include the FCP and high-strength bolt group etc. The detailed structure is shown in Fig. 1(a). A total of 5 specimens have been designed in this paper. All the columns were made of circular steel tubes with diameter of 299 mm and wall thickness of 16 mm, with the length of 3000 mm. The cantilever beam was made of 300 × 200 × 12×tcpmm I-steel, and the ordinary beam was made of 300 × 200 × 6 × 12 mm I-steel. The total length of the two beams was 1750 mm, and the detailed dimensions of the joints are shown in Fig. 2. The connection between the two beams adopted the mode of single FCP, which facilitates the lower FCP of the cantilever beam to support the ordinary beam, making high-altitude installation of beamcolumn joints more convenient. The cantilever beam and the ordinary beam were connected through the beam end plate, FCP and highstrength bolt group. At the same time, a certain gap was set between the end plates of the two beams to increase the rotation capacity of the joint. Q235B steel was used for the FCP, other structural member were made of Q345B steel. All connecting bolts were adopted 10.9grade M22 high-strength bolts, and the pretension force of 190 kN was applied to the bolt according to GB50017 [44]. The main design parameters of all specimens are shown in. Table 1. Specimen A-SJ1R is the repair specimen of A-SJ1, which means that the FCP, high-strength bolt and other connecting devices which were identical with those of

specimen A-SJ1 were replaced to form the repair specimen A-SJ1R after the loading of specimen A-SJ1. Test mainly examines the effect of the flange thickness of cantilever beam, distance between the middle bolts, the thickness and weakening form of the FCP on failure mode, bearing capacity and energy dissipation capacity of the new joints. Three weakening forms of FCP are respectively straight dog-bone weakening, circular arc dog-bone weakening and no weakening (Fig. 3), and respectively represented as specimen A, B and C. According to the requirements of relevant specifications [45], the material properties of FCPs and other plates are tested. The corresponding material properties of each plate are shown in Table 2, in which fy is steel yield strength, fu is tensile strength of steel. 2.2. Test loading scheme The low frequency cyclic loading test was carried out on five joint specimens and one repair specimen. The test loading device is shown in Fig. 4. The right and left circular steel tube columns were respectively connected with the hinged joint of the reaction frame and hydraulic jack, and the jack maintains the axial pressure with the radio of 0.2 during the whole loading process. The loading point is located at the end of the ordinary beam, and hydraulic jack is used for low frequency cyclic loading test. The ordinary beam end was clamped with two lateral

Table 1 Main parameters of specimens. Specimen Thickness of cantilever beam flange tcp(mm)

Gap between the end plates g(mm)

Distance between the middle bolts Lbolt(mm)

Thickness of FCP tpi(mm)

A-SJ1 A-SJ1R A-SJ2 B-SJ3 C-SJ4 C-SJ5

10 10 10 10 10 10

180 180 180 180 180 100

16 16 16 16 12 12

18 18 12 18 18 18

60 80 60

150 lbo,m

30

140

140

R30

150 lbo,m

60 80 60

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927 60 80 60

4

lbo,m

(a) FCP with straight dog-bone

(b) FCP with circular arc

weakening

dog-bone weakening

(c) FCP without weakening

Fig. 3. Schematic view of the weakening form of the FCP. (a) FCP with straight dog-bone weakening. (b) FCP with circular arc dog-bone weakening. (c) FCP without weakening.

supports fixed on the reaction frame to prevent the beam section from out-of-plane instability during the loading process. At the same time, the lateral support was coated with lubricating oil to reduce the effect of the friction between the support and the beam on the test results. In this paper, the joint loading protocol is formulated by referring to the American seismic code [46]. The displacement amplitude, cycle number and corresponding joint rotation during loading are shown in Table 3. The test loading termination criteria are mainly based on the following two aspects: (1) The specimen fails suddenly and cannot continue to bear the load; (2) The beam end load reaches the ultimate load, and then it drops to below 80% of the ultimate load. 2.3. Test measurement scheme The arrangement scheme of strain measuring points and displacement meter of specimens is shown in Fig. 5. Some strain gauges were set at the column, cantilever beam, ordinary beam as well as FCPs. Among them, the strain gauge on the circular steel tube column was numbered as Z-n. The strain gauge on the cantilever beam was numbered as X-n. The strain gauge on the ordinary beam was numbered as L-n. The strain gauge on the FCP was numbered as P-n. A total of five displacement meters were arranged on each specimen. W-1 was arranged at the beam end loading position to measure the lateral displacement of the ordinary beam end. W-2 was set on the cantilever beam flange to measure the lateral displacement of cantilever beam. W-3 and W-5 were respectively used to measure the relative displacement between the FCP and ordinary beam or cantilever beam. W-4 was arranged between the two end plates to measure the gap variation between the end plates.

flange can be obviously observed. At this time, the gap between the cantilever beam end plate on the tensile side and the ordinary beam end plate increased, and the two end plates of the compression sides are pressed and contacted. As the loading processes, the slip of FCP increased significantly, the gap between two end plates on tensile side increased continuously. While the paint layer on the contact surface of compression side of end plate was squeezed and peeled off. As the loading point returned to the initial position again, the gap between the two end plates became smaller with the bolts at the end plate becoming loosed. As the joint rotation reached 0.04 rad, the slight distortion occurred on the dog-bone weakening region of FCPs. When the joint rotation reached 0.05 rad, the FCP deformation was more obvious, and no obvious plastic distortion was examined in other components of specimens, as shown in Fig. 6.

3.1.2. Specimen A-SJ1R After the loading of A-SJ1, the FCP and bolt group that have undergone plastic deformation were replaced to form specimenA-SJ1R. At this time, the gap between two end plates of the specimen A-SJ1R was

3. Test results and analyses 3.1. Failure mode 3.1.1. Specimen A-SJ1 At the initial period of loading, the load-displacement curve of the specimen changes linearly in both positive and negative directions. Except for the rotating deformation of the ordinary beam, the rest parts of the specimen basically have no deformation. As the joint rotation reached 0.01 rad, the FCP began to yield, and the slope of the specimen load-displacement curve decreased; when the joint rotation reached 0.02 rad, a relative slippage between the FCP and the cantilever beam Table 2 Material properties of the plate. Location of steel plate

Thickness of plates

Yield strength fy (MPa)

Tensile strength fu (MPa)

Strength-yield ratio fu/fy

Flange cover plates Other plates

12 mm 16 mm 12 mm 16 mm 18 mm

289.7 285.3 425.7 409.3 412.4

402.1 397.6 547.6 532.8 539.2

1.39 1.39 1.29 1.30 1.31

Fig. 4. Loading system.

Table 3 Load protocol. Load step

Joint rotation (rad)

Number of cycles (cycle)

Displacement amplitude (mm)

1 2 3 4 5 6 7 8 9

0.00375 0.005 0.0075 0.01 0.015 0.02 0.03 0.04 0.05

6 6 6 4 2 2 2 2 2

6.19 8.25 12.37 16.50 24.75 34.00 49.49 65.98 82.47

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

W-3

L-6

L-7

L-1 L-2 L-3 L-12 L-13 L-14

P-7

W-4 W-2 X-1 X-2 X-3

W-5

P-6

P-8

P-5

X-7 X-8 X-9

Z-1 Z-2 Z-3

(a) Front view

(b) Left view

Fig. 5. Arrangement scheme of displacement meters and strain measuring points. (a) Front view. (b) Left view.

almost zero, and there was slight residual deformation at the end plates of the ordinary beam. Similar to specimen A-SJ1, the hysteretic curve of the specimen A-SJ1R at the initial stage of loading basically changed linearly, indicating that the specimen was basically in an elastic state. When the joint rotation reached 0.01 rad, relative slippage between the FCP and the cantilever beam can be obviously observed. The two end plates on the compression side contact with each other, and the gap between two end plates on the tension side increased, but the end plate did not have obvious deformation. When the joint rotation increased to 0.03 rad, the slip of the FCP increased significantly, and slight bending distortion occurred at the FCP. As the joint rotation continued to increase, the deformation of FCPs also gradually increased, slight buckling deformation appeared in the middle of the cantilever beam end plate. Both ends of the ordinary beam end plate were wrapped upward, and no obvious plastic distortion was observed in other parts of the specimen. After the test, the FCP and bolts were removed. Clear slip marks can be observed on the cantilever beam, ordinary beam and the FCP. Besides, white slip marks appeared on the bolts at the end plate, as shown in Fig. 7.

5

3.1.3. Specimen C-SJ4 The hysteretic curve of specimen C-SJ4 at the initial period of loading was similar to that of specimen A-SJ1, and no obvious plastic distortion was observed at all parts of the specimen. As the joint rotation reached 0.01 rad, the FCP yielded, and the slope of the specimen's curve decreased. As the joint rotation reached 0.02 rad, relative slippage between the FCP and the cantilever beam can be obviously observed, and the gap between the end plates on the tensile side increased. As the loading point returned to the initial position, the gap between the two end plates was basically zero. When the joint rotation increased to 0.03 rad, the relative slip of the FCP increased significantly, and the slight deformation of the FCP occurred. As the loading point returned to the initial position, the gap between the two end plates became smaller, and the bolt at the end plate was slightly loose. When the joint rotation reached 0.05 rad, there was about 13 mm transverse buckling deformation on the FCP, the extrusion contact between end plates appeared, and the bearing capacity of the beam end showed a continuous upward trend. Except for the FCPs on both sides, no deformation was observed in other parts of the specimen. After the test, the FCP and bolts were removed. Clear slip marks can be observed on the cantilever beam, ordinary beam and FCP. Besides white slip marks appeared on the bolts at the end plate, as shown in Fig. 8. 3.1.4. Other specimens The rest of the three specimens have undergone a relatively complete test procedure, the test phenomena is basically similar to three previous specimen. And all specimens experienced the elastic period, FCP yield period, and buckling or slippage stage of the FCP. The difference was only the corresponding displacement and load of the beam end when the test phenomenon occurred, which will not be described here. 3.2. Hysteresis curves Fig. 9 shows the load-displacement curves of the ordinary beam end of 6 joint specimens. As can be seen from the figure, the hysteresis curves of all specimens were relatively full, indicating that the new joints have good bearing and energy dissipation capacity. Taking the basic specimen A-SJ1 as an example, the specimen were in an elastic state at the initial period of loading. At this time, the load-displacement curve of the beam end basically changed linearly. As the loading continued, the specimen began to yield, the slope of the load-displacement curve decreased, and the bearing capacity gradually increased. In the

Fig. 6. Test phenomenon of specimen A-SJ1. (a) End plate deformation. (b) End plate warping. (c) Deformation of left FCP. (d) Deformation of right FCP.

6

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

Fig. 7. Test phenomenon of specimen A-SJ1R. (a) Deformation of left FCP. (b) Deformation of right FCP. (c) Slip mark of the FCP. (d) End plate deformation. (e) White slip mark of bolts.

(a) End plate deformation

(d) Deformation of the FCP

(b) Bolt hole wall indentation of end plate

(c) White tensile bands of bolts on end plates

(e) Slip mark of the FCP

Fig. 8. Test phenomenon of specimen C-SJ4. (a) End plate deformation. (b) Bolt hole wall indentation of end plate. (c) White tensile bands of bolts on end plates. (d) Deformation of the FCP. (e) Slip mark of the FCP.

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

the FCP made the platform segment appear in the hysteresis curve, and the curve as a whole shows a Z-shape with obvious “pinch” phenomenon. By comparing specimen A-SJ1 with specimen A-SJ1R, it can be found that the hysteretic curves of the two specimens were basically the same. However, since specimen A-SJ1R is the repaired one of A-SJ1, its hysteretic curves have no obvious elastic stage, and its energy dissipation capacity is slightly better than that of specimen A-SJ1. The cantilever beam flange thickness of the specimen A-SJ2 was relatively thin where the plastic hinge was more likely to appear. The hysteresis curve of the specimen is relatively full, and the energy dissipation performance is good. However, the specimen is not suitable

300

300

200

200

100

100

Load (kN)

Load (kN)

middle of the test loading, the bolts at the FCP began to slip. The slope of the load-displacement curve gradually decreased with the increase of displacement, and the hysteresis curve no longer linearly changed. With the loading continuing, more obvious plastic distortion occurred on the FCP, and the relative slip of the FCP increased continuously. The load-displacement curve showed a clear platform segment. After that, there was the extrusion contact between the bolt rod and the holes wall of FCPs, and the specimen entered the strengthening stage with the bearing capacity increasing again. In the later period of the test, the two beam end plates began to bear pressure, the load-displacement curve curved and had sharp angle, and the buckling distortion appeared on the FCP. The bolt slip and the plastic distortion of

0 -100 -200

0 -100 -200

A-SJ1 A-SJ1R

-300 -100 -80

-60

-40

-20

0

20

40

60

80

-300

100

-100 -80

-60

Displacement (mm)

200

200

100

100

Load (kN)

300

0 -100

-300

-300 -20

0

20

20

40

60

80

100

60

80

100

-100 -200

-40

0

0

-200

-60

-20

(b) Specimen A-SJ2

300

-100 -80

-40

Displacement (mm)

(a) Specimen A-SJ1 and A-SJ1R

Load (kN)

7

40

60

80

100

Displacement (mm)

-100 -80

-60

-40

-20

0

20

40

Displacement (mm)

(c) Specimen B-SJ3

(d) Specimen C-SJ4

300

Load (kN)

200 100 0 -100 -200 -300 -100 -80

-60

-40

-20

0

20

40

60

80

100

Displacement (mm)

(e) Specimen C-SJ5 Fig. 9. Hysteretic curves of the ordinary beam. (a) Specimen A-SJ1 and A-SJ1R. (b) Specimen A-SJ2. (c) Specimen B-SJ3. (d) Specimen C-SJ4. (e) Specimen C-SJ5.

8

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

gradually increasing, the bearing capacity of specimen rises again after the end plates of two beams are squeezed. Compared with the specimen C-SJ4, the distance between the middle bolts of the specimen C-SJ5 decreased, which made the FCP less prone to instability. And the C-SJ5 can make full use of plastic deformation of FCP to consume energy. The cantilever beam hysteretic curve of the specimen is shown in Fig. 10. According to the Fig. 10, the load-displacement curves of the

300

300

200

200

100

100

Load (kN)

Load (kN)

for post-earthquake repair because the cantilever beam flange easily enters into the plasticity. The specimen B-SJ3 changed the form of the dog bone weakening, leading to the result that its yield load was greatly improved and the hysteresis curve was also fuller. The thickness of the FCP of C-SJ4 was thinner than A-SJ1, FCP is more prone to buckling deformation, which can realize plastic deformation energy consumption of FCP. But thinner FCP is prone to instability, which makes bearing capacity of C-SJ4 relatively lower. With the joint rotation

0 -100 -200

-100 -200

A-SJ1 A-SJ1R

-300 -6

0

-5

-4

-3

-2

-1

0

1

2

3

4

5

-300 6

-6

-5

-4

-3

Displacement (mm)

300

300

200

200

100

100

0 -100

-300

-300 -3

-2

-1

0

1

2

1

2

3

4

5

6

3

4

5

6

-100 -200

-4

0

0

-200

-5

-1

(b) Specimen A-SJ2

Load (kN)

Load (kN)

(a) Specimen A-SJ1 and A-SJ1R

-6

-2

Displacement (mm)

3

4

5

6

Displacement (mm)

-6

-5

-4

-3

-2

-1

0

1

2

Displacement (mm)

(c) Specimen B-SJ3

(d) Specimen C-SJ4

300

Load (kN)

200 100 0 -100 -200 -300 -6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

Displacement (mm)

(e) Specimen C-SJ5 Fig. 10. Hysteresis curves of the cantilever beam. (a) Specimen A-SJ1 and A-SJ1R. (b) Specimen A-SJ2. (c) Specimen B-SJ3. (d) Specimen C-SJ4. (e) Specimen C-SJ5.

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

cantilever beam of joints were basically center-symmetrical. Among them, the displacement meter at the cantilever beam of the A-SJ1R failed, and the incomplete data led to some deviation of the curve. According to the load-displacement curve of all specimens, it can be seen that the cantilever beam of the other specimens were basically in an elastic state except for the A-SJ2. Since the cantilever beam flange of the A-SJ2 was relatively thinner, the cantilever beam entered the plasticity earlier, so the corresponding curve was spindle-shaped.

3.3. Strain analysis Fig. 11 shows the strain change curves of specimens at the key test points of the cantilever beam and the ordinary beam flange. According to the measured results, the yield strength of the cantilever beam and the ordinary beam was about 410 MPa, indicating that the specimen was considered to be plastic when the strain reaches 1990 με. As can be seen from the figure, the stress development rule of each specimen was basically the same. Before the joint rotation reached 0.04 rad, the

6000

6000 0.01rad 0.015rad 0.02rad 0.03rad 0.04rad 0.05rad

Strain ( )

4800 4200 3600

4800

3000 2400

4200 3600 3000 2400

1800

1800

1200

1200

600

600 L-7

L-6

0.01rad 0.015rad 0.02rad 0.03rad 0.04rad 0.05rad

5400

Strain ( )

5400

0

X-7

X-8

Strain gauge

0

X-9

X-7

X-8

Strain gauge

X-9

(b) Specimen A-SJ2

6000

6000 0.01rad 0.015rad 0.02rad 0.03rad 0.04rad 0.05rad

4800 4200 3600

5400 4800

Strain ( )

5400

Strain ( )

L-7

L-6

(a) Specimen A-SJ1

3000 2400

4200 3600

2400 1800

1200

1200

600

600 L-7

L-6

X-7

X-8

Strain gauge

X-9

(c) Specimen B-SJ3

0.01rad 0.015rad 0.02rad 0.03rad 0.04rad 0.05rad

3000

1800

0

9

0

L-6

L-7

X-7

X-8

Strain gauge

X-9

(d) Specimen C-SJ4

6000 5400

Strain ( )

4800 4200 3600

0.01rad 0.015rad 0.02rad 0.03rad 0.04rad 0.05rad

3000 2400 1800 1200 600 0

L-6

L-7

X-7

X-8

Strain gauge

X-9

(e) Specimen C-SJ5 Fig. 11. Strain analysis of the beam. (a) Specimen A-SJ1 and A-SJ1R. (b) Specimen A-SJ2. (c) Specimen B-SJ3. (d) Specimen C-SJ4. (e) Specimen C-SJ5.

10

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

200

Load (kN)

Table 5 Equivalent viscous damping coefficient of the specimens.

A-SJ1 A-SJ1R A-SJ2 B-SJ3 C-SJ4 C-SJ5

300

100

Specimen

A-SJ1 A-SJ1R A-SJ2 B-SJ3 C-SJ4 C-SJ5

0 -100 -200

Equivalent viscous damping coefficient of the specimens under each rotation 0.01 rad

0.015 rad

0.02 rad

0.03 rad

0.04 rad

0.05 rad

0.187 0.321 0.170 0.167 0.160 0.190

0.275 0.355 0.217 0.249 0.164 0.251

0.261 0.314 0.235 0.261 0.248 0.256

0.246 0.279 0.228 0.253 0.278 0.251

0.199 0.197 0.214 0.220 0.237 0.199

0.191 0.187 0.207 0.200 0.207 0.186

-300 -100

-80

-60

-40

-20

0

20

40

60

80

100

Displacement (mm) Fig. 12. Skeleton curves.

specimen was in the elastic stage as a whole, and after the joint rotation reached 0.04 rad, some part of the specimen were in the plastic stage. The ordinary beam of each specimen were mostly in the elastic range during the whole loading process. However, as the joint rotation of each specimen reached 0.04 rad, except for the A-SJ1 and the C-SJ4, some partial regions on the cantilever beam of other specimens entered into plasticity, but the cantilever beam as a whole was basically in an elastic state. Among them, the smaller thickness of the cantilever beam flange of the A-SJ2 resulted in the cantilever beam entering the plasticity when the joint rotation reacheed 0.03 rad. The C-SJ4 had a lower overall strain value due to the lower load value at the beam end. According to the analysis of strain, by reasonably designing the cantilever beam flange thickness, distance between the middle bolts, thickness and weakening form of FCP, the plastic hinge can be transferred to the FCP, which makes the main component of specimens within elastic state and realize the post-earthquake repair of the joint. 3.4. Skeleton curves Fig. 12 shows the skeleton curves of 6 specimens. It can be seen from the figure that the development trend of skeleton curves of all specimens was basically the same. In the elastic stage, the curves were basically identical and straight lines. The rotational stiffness of joints varied little, but the beam end load was different when bolts slip. Compared with specimen A-SJ1, the repair specimen A-SJ1R had a lower sliding load due to the reduced friction coefficient between the plate interface and the slight plastic deformation of bolt holes. All specimens can achieve large displacement in both positive and negative directions, and the bearing capacity was still in the strengthening stage at this time, indicating that the specimens still have certain plastic development after sliding and the joints have excellent bearing capacity and seismic performance. The forward and reverse skeleton curves of specimens were not completely symmetric, which was related to the machining errors and the damage accumulation of joints under reciprocating load.

3.5. Performance indexes By processing the test data of each specimen, the load Ps and displacement Δ s of the specimen entering the obvious sliding stage, the maximum load Pu in the loading progress, the displacement Δu, and the displacement ductility coefficient μ = Δu/Δs are obtained. The displacement Δ u is the maximum horizontal displacement when the bearing capacity of the specimen does not degrade significantly. Δs is the corresponding displacement when the significant slip appear on the contact surface of specimens. The main performance indexes of all specimens are shown in Table 4. It can be seen from Table 4 that the ductility coefficients of the six specimens in this test were basically the same. The ductility coefficients of the positive and negative directions had little difference, which were all greater than 3.0, indicating that the ductility of the joint was satisfactory and met the requirements of seismic performance [47]. As the repair specimen of the A-SJ1, friction and slip of FCP have occurred on the A-SJ1R in the first loading, and sand blasting treatment on the contact surface has been damaged to some extent. Therefore, the bolt slip of A-SJ1R appeared earlier, leading to slightly higher ductility coefficient of the specimen. The specimen C-SJ4 bolt slid relatively late, which led to the low ductility coefficient of the specimen. The equivalent viscous damping coefficient of specimens are shown in Table 5. By comparing and analyzing the equivalent viscous damping coefficient of the A-SJ1 and the repair specimen A-SJ1R, it can be seen that the energy consumption performance of the A-SJ1R was still stable at the end of the test loading, which was not much different from that of the A-SJ1. It shows that the repair specimens still meets the seismic performance requirements of the joint. Fig. 13 shows the cumulative energy dissipation curve of each specimen. According to the Fig. 13, each specimen consumed little energy at the initial stage of loading. As the loading continued, each specimen showed excellent energy consumption performance, and the final total energy consumption was different. The slope of cumulative energy dissipation curve gradually increased with the increase of load, and the energy dissipation of specimens mainly concentrated in the later stage of loading. During the test loading process, specimen A-SJ1 mainly relied on friction slip and buckling deformation of FCPs to dissipate energy. The end plates of the two beam participated in energy dissipation at the later stage of the test loading, so the total energy dissipation

Table 4 Main performance indexes. Specimen

A-SJ1 A-SJ1R A-SJ2 B-SJ3 C-SJ4 C-SJ5

Δs/mm

Ps/kN

Δu/mm

μ

Pu/kN

PLD

NLD

PLD

NLD

PLD

NLD

PLD

NLD

PLD

NLD

112.1 93.4 94.4 146.6 148.8 106.6

−124.7 −111.8 −135.0 −110.8 −165.6 −126.3

17.0 13.1 16.8 17.1 24.6 16.8

−16.5 −12.4 −16.7 −16.8 −25.1 −16.5

82.3 80.0 82.2 81.8 82.5 82.6

−82.3 −81.2 −84.6 −84.0 −83.1 −82.6

286.4 271.3 214.9 266.4 221.3 266.1

−275.4 −290.9 −254.8 −269.0 −260.3 −250.9

4.83 6.11 4.89 4.79 3.36 4.91

4.99 6.57 5.01 5.01 3.31 5.00

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

Cumulative energy dissipation (kJ)

200

References

A-SJ1 A-SJ1R A-SJ2 B-SJ3 C-SJ4 C-SJ5

160 120 80 40 0 0

10

20

11

30

40

50

60

70

80

90

Displacement (mm) Fig. 13. Cumulative energy dissipation curves.

of the A-SJ1 was relatively high. The energy dissipation mode of the repair specimen A-SJ1R was similar to that of the basic specimen A-SJ1, so the energy dissipation capacity was not much different from that of the specimen A-SJ1. A weakening form of FCPs different from the A-SJ1 was applied to the B-SJ3. The energy dissipation mechanism of B-SJ3 was the same as that of the A-SJ1 as well as the total energy dissipation curve. The FCP of C-SJ4 was relatively thin, its buckling deformation occurred early, and the bearing capacity was relatively low, so the total energy consumption was relatively low. Compared with the specimen C-SJ4, the bolt spacing of C-SJ5 was relatively small, and the buckling and instability of FCP was difficult to occur. Therefore, the specimen can make full use of the yield of FCPs to consume energy, so the total energy consumption was relatively higher than that of the specimen C-SJ4. 4. Conclusion In this paper, the failure mode and seismic behavior of new EPPSFJ were studied by low cycle reciprocating load test, and the hysteretic curve, slip curve, skeleton curve, strain curve, ductility and energy dissipation capacity and other seismic behavior indexes of the joints were obtained. The following conclusions can be drawn: • The new type EPPSFJ have excellent bearing and energy dissipation capacity, ductility and other seismic behavior, which can be quickly repaired by replacing connecting devices. The repaired joints still have excellent seismic performance. • The new type EPPSFJ can realize joint energy consumption of bolt slip and FCP buckling, and the relative slip between FCP and beams is beneficial to improve joint ductility and rotation capacity. • The distance between the middle bolts of FCP can adjust the joint stiffness, and a reasonable distance can realize the relocation of plastic hinge of the joint, which can realize energy consumption of bolt slip and FCP buckling. • Reasonable flange thickness can ensure the stiffness level of the cantilever beam to realize relocation of plastic hinge of the beam. Declaration of Competing Interest Ai-Lin Zhang, Ping Qiu, Kang Guo, Zi-Qin Jiang, Liang Wu and Shuang-Cheng Liu declare that they have no conflict of interest. Acknowledgements The authors appreciated the funding supported by National Natural Science Foundation of China (Grant No. 51608014 and 51808032), and China Postdoctoral Science Foundation (Grant No. 2017 T100020).

[1] A.L. Zhang, The key issues of system innovation drawing up standard and industrialization for modularized prefabricated high-rise steel, Ind. Constr. 44 (2014) 1–6(in Chinese). [2] Q. Han, Z.L. Jia, K. Xu, et al., Hysteretic behavior investigation of self-centering double-column rocking piers for seismic resilience, Eng. Struct. 188 (2019) 218–232. [3] H.F. Li, X.N. Gao, Y. Liu, et al., Seismic performance of new-type box steel bridge piers with embedded energy-dissipating shell plates under tri-directional seismic coupling action, Int. J. Steel Struct. 17 (2017) 105–125. [4] S.A. Mahin, Lessons from damage to steel buildings during the Northridge earthquake, Eng. Struct. 20 (1998) 261–270. [5] D.K. Miller, Lessons learned from the Northridge earthquake, Eng. Struct. 20 (1998) 249–260. [6] M. Latour, V. Piluso, G. Rizzano, Experimental analysis of beam-to-column joints equipped with sprayed aluminium friction dampers, J. Constr. Steel Res. 146 (2018) 33–48. [7] C.A. Castiglioni, A. Kanyilmaz, L. Calado, Experimental analysis of seismic resistant composite steel frames with dissipative devices, J. Constr. Steel Res. 76 (2012) 1–12. [8] M. Valente, C.A. Castiglioni, A. Kanyilmaz, Numerical investigations of repairable dissipative bolted fuses for earthquake resistant composite steel frames, Eng. Struct. 131 (2017) 275–292. [9] M. Valente, C.A. Castiglioni, A. Kanyilmaz, Welded fuses for dissipative beam-tocolumn connections of composite steel frames: numerical analyses, J. Constr. Steel Res. 128 (2017) 498–511. [10] S. Oh, Y. Kim, H. Ryu, Seismic performance of steel structures with slit dampers, Eng. Struct. 31 (2009) 1997–2008. [11] J.M. Ricles, R. Sause, M. Wolski, Experimental study of a self-centering beam–column connection with bottom flange friction device, J. Struct. Eng. 135 (2009) 479–488. [12] A. Banisheikholeslami, F. Behnamfar, M. Ghandil, A beam-to-column connection with visco-elastic and hysteretic dampers for seismic damage control, J. Constr. Steel Res. 117 (2016) 185–195. [13] Z.H. Chen, J.D. Liu, Y.J. Yu, et al., Experimental study of an innovative modular steel building connection, J. Constr. Steel Res. 139 (2017) 69–82. [14] D. Cassiano, M. D'Aniello, C. Rebelo, Seismic behaviour of gravity load designed flush end-plate joints, Steel.Compos, Struct. 26 (5) (2018) 621–634. [15] D. Cassiano, M. D'Aniello, C. Rebelo, Parametric finite element analyses on flush endplate joints under column removal, J. Constr. Steel Res. 137 (2017) 77–92. [16] R. Tartaglia, M. D'Aniello, G.A. Rassati, Proposal of AISC-compliant seismic design criteria for ductile partially-restrained end-plate bolted joints, J. Constr. Steel Res. 159 (2019) 364–383. [17] X.C. Liu, S.H. Pu, A.L. Zhang, et al., Performance analysis and design of bolted connections in modularized prefabricated steel structures, J. Constr. Steel Res. 133 (2017) 360–373. [18] X.C. Liu, Z.W. Yang, H.X. Wang, et al., Seismic performance of H-section beam to HSS column connection in prefabricated structures, J. Constr. Steel Res. 138 (2017) 1–16. [19] X.C. Liu, X.X. Zhan, S.H. Pu, et al., Seismic performance study on slipping bolted truss-to-column connections in modularized prefabricated steel structures, Eng. Struct. 163 (2018) 241–254. [20] S.R. Mirghaderi, S. Torabian, A. Imanpour, Seismic performance of the accordionweb RBS connection, J. Constr. Steel Res. 66 (2010) 277–288. [21] S. Maleki, M. Tabbakhha, Numerical study of slotted-web-reduced-flange moment connection, J. Constr. Steel Res. 69 (2012) 1–7. [22] W.J. Gong, D.H. Hu, W.H. Zhu, Seismic performance study of new type assembled bolted beam-column joints, Build. Struct. 47 (2017) 899–901(in Chinese). [23] C.L. Wang, Y. Liu, X.L. Zheng, et al., Experimental investigation of a precast concrete connection with all-steel bamboo-shaped energy dissipaters, Eng. Struct. 178 (2019) 298–308. [24] C.L. Wang, Y. Liu, L. Zhou, Experimental and numerical studies on hysteretic behavior of all-steel bamboo-shaped energy dissipaters, Eng. Struct. 165 (2018) 38–49. [25] H. Farrokhi, F. Danesh, S. Eshghi, A modified moment resisting connection for ductile steel frames (numerical and experimental investigation), J. Constr. Steel Res. 65 (2009) 2040–2049. [26] X.L. Lu, Y. Chen, H.J. Jiang, Experimental study seismic behavior of “fuse” of replaceable coupling beam, J. Tongji Univ (natural science) 41 (2013) 1318–1325(in Chinese). [27] X.D. Ji, Y.D. Wang, Q.F. Ma, et al., Experimental study on seismic behavior of replaceable steel coupling beams, J. Build. Struct. 36 (2015) 1–10in Chinese. [28] B. Mou, F. Zhao, Q. Qiao, et al., Flexural behavior of beam to column joints with or without an overlying Concrete Slab, Eng. Struct. 199 (11) (2019) 109616. [29] B. Mou, X. Li, Q. Qiao, et al., Seismic behaviour of the corner joints of a frame under biaxial cyclic loading, Eng. Struct. 196 (10) (2019) 109316. [30] C. Fang, M.C.H. Yam, A.C.C. Lam, et al., Cyclic performance of extended end-plate connections equipped with shape memory alloy bolts, J. Constr. Steel Res. 94 (2014) 122–136. [31] C. Fang, W. Wang, C. He, et al., Self-centring behaviour of steel and steel-concrete composite connections equipped with NiTi SMA bolts, Eng. Struct. 150 (2017) 390–408. [32] L.J. Jia, R.W. Li, P. Xiang, et al., Resilient steel frames installed with self-centering dual-steel buckling-restrained brace, J. Constr. Steel Res. 149 (2018) 95–104. [33] X.Z. He, Y.Y. Chen, R. Matthew, M.A. Eatherton, et al., Experimental evaluation of replaceable energy dissipation connection for moment-resisting composite steel frames, J. Struct. Eng. 144 (2018) 1–14.

12

A.-L. Zhang et al. / Journal of Constructional Steel Research 166 (2020) 105927

[34] S.J. Li, S. Wang, Y.X. Bai, et al., Experimental research on aseismic behavior of new beam –column connections of highrise steel frames, Ind. Constr. 40 (2010) 524–529in Chinese. [35] Y.J. Shi, Z.F. Li, H. Chen, et al., Experimental research on cyclic behavior of new types of beam-column connections in highrise steel frames, J. Build. Struct. 23 (2002) 2–7in Chinese. [36] X.L. Wang, Z.Z. Yin, Q.F. Li, D.J. Li, et al., Anti-seismic performance testing study on new type beam-to-column connection in steel frames, Pro. Steel. Build. Struct. 7 (2005) 42–46in Chinese. [37] A.L. Zhang, S.H. Li, Z.Q. Jiang, et al., Design theory of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint, Eng. Struct. 150 (2017) 665–673. [38] A.L. Zhang, Q. Wang, Z.Q. Jiang, et al., Experimental study of earthquake-resilient prefabricated steel beam-column joints with different connection forms, Eng. Struct. 187 (2019) 299–313. [39] A.L. Zhang, H. Zhang, Z.Q. Jiang, et al., Low cycle reciprocating tests of earthquakeresilient prefabricated column-flange beam-column joints with different connection forms, J. Constr. Steel Res. 164 (2020), 105771.

[40] Z.Q. Jiang, X.F. Yang, C. Dou, et al., Cyclic testing of replaceable damper: earthquakeresilient prefabricated column-flange beam-column joint, Eng. Struct. 183 (2019) 922–936. [41] Z.Q. Jiang, C. Dou, A.L. Zhang, et al., Experimental study on earthquake-resilient prefabricated cross joints with L-shaped plates, Eng. Struct. 184 (2019) 74–84. [42] Z.Q. Jiang, X.F. Yang, C. Dou, et al., Design theory of earthquake-resilient prefabricated beam-column steel joint with double flange cover plates, Eng. Struct. (2019) https://doi.org/10.1016/j.engstruct.2019.110005. [43] Z.Q. Jiang, T. Lan, C. Dou, et al., Cyclic loading tests of earthquake-resilient prefabricated cross joint with single FCP, J. Constr. Steel Res. 164 (2020) 105752. [44] GB50017, Code for Design of Steel Structures, China Planning Press, Beijing, China, 2003 in Chinese. [45] GB/T 288.1–-2010, Metallic Materials: Tensile Testing at Ambient Temperature, China Standards Press, Beijing, China, 2010 in Chinese. [46] ANSI/AISC 341-05, Seismic Provisions for Structural Steel Buildings, American Institute of Steel Construction, Inc., 2005 [47] FEMA350, Recommended Seismic Design Criteria For New Steel Moment-Frame Buildings, Federal Emergency Management Agency, Washington, DC, 2000.