Seismic Performance of Prefabricated Beam-to-column Joint with Replaceable Energy-dissipatingSteel HingeLianqiong Zheng  ( zhenglianqiong@fjut.edu.cn )

Fujian University of Technology https://orcid.org/0000-0002-8996-8151Xiaoyang Chen 

Fujian University of TechnologyChanggui Wei 

Fujian University of TechnologyGuiyun Yan 

Fujian University of Technology

Research Article

Keywords: Prefabricated beam-to-column joint, Replaceable energy-dissipating steel hinge, Prefabricatedsteel tube con�ned joint core, Hysteretic test, Seismic performance

Posted Date: July 24th, 2021

DOI: https://doi.org/10.21203/rs.3.rs-725075/v1

License: This work is licensed under a Creative Commons Attribution 4.0 International License.  Read Full License

1

16 June 2021

Dear Editor:

I wish to submit an original paper for publication in Bulletin of Earthquake Engineering, titled

“Seismic performance of prefabricated beam-to-column joint with replaceable

energy-dissipating steel hinge.” The paper was coauthored by Xiao-Yang Chen, Chang-Gui Wei,

and Gui-Yun Yan.

This study presents a novel prefabricated beam-to-column joint for frame and hysteretic tests was

conduct to evaluates the seismic performance and the restorable functional characteristics of the

proposed joints. We believe that our study makes a significant contribution to the literature because

the proposed prefabricated joint providing advantages for precast concrete reinforced frames, such

as complete assembly, damage control, and maintainability of the structure after an earthquake.

This manuscript has not been published or presented elsewhere in part or in entirety and is not

under consideration by another journal. We have read and understood your journal’s policies, and we believe that neither the manuscript nor the study violates any of these. There are no conflicts of

interest to declare.

Thank you for your consideration. I look forward to hearing from you.

Sincerely,

Lian-Qiong Zheng

School of Civil Engineering, Fujian University of Technology

Fuzhou 350118, Fujian Province, People’s Republic of China

Tel.: (+86) 18950383840

Email address: zhenglianqiong@fjut.edu.cn

2

Seismic performance of prefabricated beam-to-column joint with

replaceable energy-dissipating steel hinge

Lian-Qiong Zheng a,b,*, Xiao-Yang Chen a, Chang-Gui Wei a and Gui-Yun Yan a,b

a School of Civil Engineering, Fujian University of Technology, Fuzhou 350118, P.R. China

(*Corresponding author, E-mail: zhenglianqiong@fjut.edu.cn)

b Fujian Provincial Key Laboratory of Advanced Technology and Informatization in Civil Engineering, Fuzhou

350118, Fujian Province, P.R. China

Abstract: This study presents a novel energy-dissipating prefabricated joint for connecting beam to

column in a precast frame structure. The joints are characterized by a replaceable steel hinge and a

prefabricated steel tube confined joint core, providing advantages for precast concrete reinforced

frames, such as complete assembly, damage control, and maintainability of the structure after an

earthquake. The hysteretic behavior of the proposed prefabricated joint was studied through two tests.

First, a full-scale prefabricated joint was tested under cyclic loading until failure. On the basis of the

initial test, only four weakened dissipaters of the steel hinges in the prefabricated joint were replaced

and the second test was conducted to investigate the restorable functional characteristics of the

proposed prefabricated joints. For comparison, a reference monolithic joint was also tested. The

experimental results demonstrate that the novel prefabricated beam-to-column joint displayed

excellent hysteretic performance, and corresponding to the monolithic joint, the load-bearing, energy

dissipation, and deformation capacity were improved. The damage of the prefabricated joint was

concentrated on the weakened dissipaters of the steel hinges, indicating that the failure mode and

damage degree of the prefabricated joint can be controlled. In the second test, the prefabricated joint

exhibited similar hysteretic behavior to that of the first test; however, the initial stiffness was slightly

lower. Therefore, the prefabricated joint can meet the replaceability requirement and achieve

satisfactory beam-to-column joint function recovery after an earthquake.

Keywords: Prefabricated beam-to-column joint, Replaceable energy-dissipating steel hinge,

Prefabricated steel tube confined joint core, Hysteretic test, Seismic performance

1

1. Introduction 1

Prefabricated buildings have attracted increased attention in research owing to their advantages of 2

high quality, easy in situ operation, short construction period, and cost savings. Moreover, 3

prefabricated buildings meet the growing demand for building industrialization throughout the 4

world and also satisfy the requirements of environmental friendliness and sustainability. 5

Consequently, prefabricated structures have been extensively applied in building construction [1–5]. 6

Precast concrete frames account for a large proportion of prefabricated buildings owing to their 7

flexibility regarding architectural layout and standardization of the modular components. However, 8

in contrast to conventional cast-in-place structures, a prefabricated building structure demonstrates 9

poor integrity and most prefabricated building structures lose their normal functionality with 10

connection failure due to complex stress conditions, which is important in force transfer between 11

components; in particular, the beam and column. Beam-to-column joints are a vulnerable 12

component and thus it is important to develop good mechanical performance for their use in 13

prefabricated building structures. 14

Therefore, substantial research has been devoted to developing new connections; particularly, 15

beam-to-column joints [6–12] with excellent mechanical behavior for application in prefabricated 16

building structures to achieve good structural integrity. Previous studies indicated that connections 17

between precast frame members could be classified into three main classes: dry connection, wet 18

connection, and hybrid connection. The equivalent monolithic reinforced concrete frame system 19

was developed using cast-in-situ joints or fabricated connections [13–18]. In addition, considerable 20

research has been conducted to better understand the mechanical behavior and evaluate the seismic 21

performance of newly developed connections or precast structures with new connections [7]. 22

2

Restrepo et al. [19] conducted experimental research on four mid-span connections and two 23

beam-to-column connections. It was shown that the connection configurations had a slight effect 24

on the mechanical behavior of the structure. All tested connections exhibited good ductility, 25

energy-dissipation capacity, and bearing resistance and such connections could be constructed to 26

emulate monolithic cast-in-place connections. Zhao et al. [20] investigated the behavior of a precast 27

beam-to-column joint with high-strength concrete, using a full-scale test, and the structure with this 28

new connection demonstrated equivalently desirable seismic performance, such as failure mode, 29

hysteresis behavior, and ductility. Parastesh et al. [21] proposed a novel ductile moment-resisting 30

connection for precast RC frames in seismic regions, which could provide excellent structural 31

integrity and rapid construction. The seismic performance was investigated experimentally and the 32

results demonstrated that the proposed connections could develop adequate flexural strength, as 33

well as higher ductility and energy consumption. Moreover, the failure mode could be improved by 34

concentrating damage to the plastic hinge region. 35

Prestressed steel strands can effectively provide a self-centering capacity for beam-column joints 36

and improve the energy dissipation capacity, without serious structural damage [22–31]. Li et al. 37

[27] researched precast beam-to-column joint subjected to bidirectional lateral loading to assess 38

precast RC frames under the action of an earthquake. The results demonstrated that the prestressed 39

connection exhibited similar performance to the cast-in-place connection. This column remained 40

damage-free during the loading period and an equivalent viscous damping pattern was established, 41

considering the effects of prestress loss and energy dissipater yield. Wang et al. [28] proposed a 42

prefabricated prestressed beam-column joint, which uses replaceable mild steel reinforced bars to 43

provide an energy disappearance capacity and steel strands to provide a self-centering capacity. 44

The effectiveness of the proposed joint was experimentally validated. In addition, the configuration 45

3

was improved based on the results and a parametric study using a calibrated FEA model was 46

conducted to determine the essential parameters the effect of the parameters of interest on joint 47

performance [29]. Through experiments and numerical research, the design specifications to 48

ensure full utilization of the joints were determined. Wang et al. [30,31] developed an all-steel 49

bamboo-shaped energy dissipater and applied it to precast concrete beam-column joints, which 50

played an important role in fusing and protecting the main structure. Through experimental 51

research on five precast concrete connections under cyclic loading, it was found that these 52

connections exhibit good hysteretic performance and self-centering action. 53

Using supplemental energy dissipaters in connection is another research topic aimed at enhancing 54

the energy dissipation capacity and concentrating plastic damage to target members rather than 55

beams or columns, such as top-and-seat angles [32,33], reduced flanges [34], and friction devices 56

[35–37]. To improve the failure mode of the frame structure, a beam-column hybrid joint using 57

flange cover connecting plates for energy-consuming and web connection plates for load 58

transferring [15] is proposed. The efficiency of the hybrid joint is investigated based on 59

experimental research on PC joints and monolithic control connections. Song et al. [23] used bolted 60

web friction devices and a self-centering prestressed connection and adopted them in a 61

moment-resisting frame to reduce residual drift under large drifts and improve the energy 62

dissipation ability with friction damping. Experimental and numerical studies were performed to 63

evaluate its effectiveness. The research results demonstrated that this bolted connection has 64

capabilities of energy dissipation and self-centering comparable to welding connections and 65

simultaneously avoids expensive field welding. Li et al. [38] developed an innovative type of 66

prefabricated beam-to-column joint and investigated the influence of the damper’s geometric 67

dimensions on the hysteretic performance of the prefabricated joint. Similarly, another type of 68

4

damper was proposed by Qi et al. [39] for prefabricated beam-to-column joint, and the seismic 69

performance of the joint were studied as well as the design procedure was proposed. 70

Although previous studies have demonstrated that the behavior of prestressed joints or hybrid 71

connections is comparable to that of monolithic connections [40,41], there are still issues, such as 72

the difficulty in constructing connections between framing components, the feasibility of damage 73

or failure mode control, and the potential for replacing the damaged energy dissipaters. Therefore, 74

according to the present research, a new prefabricated beam-to-column joint is developed to 75

mitigate the unsolved issue. Pseudo-static research was conducted on a novel prefabricated joint 76

and the failure mode, load-bearing capacity, stiffness, ductility, energy dissipation, and 77

earthquake-resilience were analyzed. In addition, the dissipaters of the steel hinges in the 78

prefabricated joint were replaced and a second hysteretic test was conducted to study the restorable 79

characteristics of the proposed prefabricated joints. 80

81

2. Mechanism of novel prefabricated joint 82

Based on the combination of load-carrying and energy-dissipation elements, an innovative type of 83

prefabricated beam-to-column joint was developed, according to the schematic illustration in Fig. 1. 84

The new beam-to-column joint is characterized by replaceable steel hinge and prefabricated steel 85

tube confined joint core, providing advantages, such as complete assembly, damage control, and 86

maintainability of the structure after an earthquake. 87

88

2.1 Replaceable energy-dissipating steel hinge

As described in Fig. 1a and b, replaceable steel hinges are set at the ends of the precast beam 89

adjacent to the column. I-shaped steel with an endplate is embedded at the precast beam end. In 90

addition, I-shaped steel is welded at both sides of the joint core steel tube. Therefore, the precast 91

5

beam can be bolted to the column via a steel hinge. The steel hinge is composed of two types of 92

connected components, replaceable upper and lower energy dissipaters and the pin shaft connection, 93

as shown in Fig. 1c. Low-yield point steel (LYP) is cut into a dog-bone shape to reduce geometry as 94

described in steel design codes, such as FEMA 350–351 [42,43] and EC8 [44], and an arc-shaped 95

stiffener is welded under the LYP plate to avoid premature buckling. The LYP plate, arc-shaped 96

stiffener, and end plates formed an energy dissipater, which was used to transfer the bending 97

moment between the beam and column, and also acted as a fuse to dissipate energy and concentrate 98

plasticity under earthquake excitations. Weakened areas are easily formed due to the low yield 99

strength and reduced section of the LYP plate; therefore, the damage position and damage degree 100

can be controlled. Owing to the excellent seismic behavior of LYP steel [45], the LYP plate will 101

concentrate most of the plasticity and damage, maintain the main structural members, such as 102

beams and columns, and remain elastic. The pin shaft connection of the steel hinge contains left and 103

right lugs, a high-strength pin, and end-plates. The pin hinges the lugs and supplies the shear 104

capacity in the steel hinge. The steel hinge adequately rotates around the pin, which can outward the 105

plastic hinge away from the beam-column interface and shift into the weakened region of the steel 106

hinge. This can improve the uncertainty of the location of plastic hinges in traditional reinforcement 107

concrete frames owing to their limited rotation ability. 108

Steel hinges are used to connect the precast beam and column with high-strength bolts, which are 109

easy to manufacture, disassemble, and replace. Moreover, endplates of the energy dissipaters and 110

endplates of lugs are independent, as shown in Fig. 1c, allowing for the replacement of the 111

dissipaters instead of the entire steel hinge after an earthquake. 112

6

113

(a) Precast concrete frame (b) External joint (c) Steel hinge 114

Fig. 1. Description of the prefabricated joint for a precast concrete frame with replaceable 115

energy-dissipating steel hinge 116

117

2.2 Prefabricated steel tube confined joint core

For the newly developed prefabricated beam-to-column joint, a steel tube was employed to confine 118

the core area to realize the seismic design concept commonly referred to as a strong connection, as 119

well as to connect the upper and lower precast column segments. As shown in Fig. 2, the proposed 120

prefabricated steel tube confined joint core is comprises a steel tube, joint core concrete, internal 121

diaphragms, connected components, and ducts for the insertion of reinforcements and grout pouring. 122

The joint core concrete is confined by the steel tube, improving its shear resistance. Thus, shear 123

failure in the joint core area can be avoided. Two internal diaphragms are welded in the steel tube to 124

transfer the horizontal force in the core area, which is equivalent to the continuous longitudinal 125

reinforced steel bar of the beam passing through the core area utilized in the cast-in-place 126

beam-to-column joint. 127

Connected component: Pin Shaft Connection

Lugs

Pin

Endplate Beam

Precast RC column Precast RC beam

Connected component:

Replaceable energy dissipater

(Fuse, yield firstly, energy

dissipation, damage concentration)

Beam end plastic

steel hinge

Co

lum

n

Prefabricated steel tube confined joint core

Steel hinge

Stiffener

Low yield point

steel (LYP) plate

Endplate

Embedded I-shaped steel in the beam

I-shaped steel welded at

joint core steel tube

7

128

Fig.2. Proposed prefabricated steel tube confined joint core 129

The connection system between precast columns in this research is based on the use of precast 130

columns, with sleeves encased on the lower end and longitudinal reinforcements protruding from 131

the upper end. For the column-to-column connection assembly, as displayed in Fig. 3, the lower 132

precast column is placed in position. Then, the prefabricated joint core is lifted, aligned with the 133

lower column, and lowered to insert the protruding reinforcements of 134

the lower column through the corrugated steel ducts of the joint core. High-strength grout is then 135

poured to fill the ducts and create a layer at the interface between the lower column and the joint 136

core. Finally, the upper precast column is lifted and positioned to insert the protruding 137

reinforcements of the lower precast column into the sleeves of the upper precast column. The 138

sleeves were grouted to achieve continuous longitudinal reinforcement of the column and the 139

interface between the upper precast column and prefabricated joint core was simultaneously 140

grouted. Both ends of the precast column are concrete rough surfaces to ensure the transfer of shear 141

force at the interface. 142

143

component: Connect with

steel hinge at beam end

Steel tube

Joint core concrete

Ducts for insertion

of protruding bars

Upper internal diaphragm

Duct for grout

pouring

Lower internal diaphragm

8

144

Fig.3. Connection system between precast columns 145

3. Experimental Program 146

3.1 Test specimens

Two quasi-static tests were conducted to investigate the hysteretic behavior of the novel 147

prefabricated beam-to-column joint. First, a prefabricated joint was tested under cyclic loading until 148

failure. According to this previous test, only four weakened steel hinge dissipaters were replaced 149

and the second test was conducted to investigate the restorable functional characteristics of the 150

proposed prefabricated joints. The specimens of the prefabricated joint under the two loadings were 151

labeled as PJ-1 and PJ-2, respectively. Finally, a cast-in-place monolithic joint specimen (labeled 152

MJ) was also tested to estimate the seismic behavior of the proposed prefabricated joint. 153

This specimen adopts an interior beam-to-column joint idealized from the prototype structure; the 154

beam has a span of 4000 mm, and the length of the column is 3040 mm. This prefabricated joint was 155

composed of precast RC columns, precast RC beams, a steel tube confined joint core, and an 156

energy-dissipating steel hinge with weakened flanges. The detailed configuration of the 157

Protruding

reinforcement

layer filled at the

interface

Lower precast column

Grouted corrugated

steel ducts

Grout inlet

layer filled at the

interface Lower precast column

Grouted corrugated

steel ducts

Upper precast

column

layer filled at

the interface

Grout outlet

Sleeves

Connect with steel

hinge at beam end Pouring grout

9

prefabricated joint and geometrical dimensions of the steel hinge and steel tube confined joint core 158

are presented in Fig. 4. The section of the precast beams was 250 mm × 550 mm (width × height) 159

and the section width of the square precast column was 400 mm. The precast column and beam 160

were reinforced with 12 longitudinal bars 22 mm in diameter and eight bars that were 18 mm in 161

diameter, respectively. In addition, 8 mm diameter hoops were provided and the stirrup spacing was 162

150 mm. For comparison, as shown in Fig. 5, the geometry and reinforcement of the monolithic 163

joint were identical to those of the prefabricated joint. 164

165

166

Section (1-1) 167

Fig. 4. Prefabricated specimen configuration (unit: mm) 168

250

4000

200 125 125 Replaceable energy dissipater (Weakened)

950 150 50

450 50

400 150 50

450 50

150 950 150

75

400

400

1370

1170

500

1800 1800

Welded to flange of steel beam Internal Connected

400

Grouted sleeve

Section (3-3)

Endplates and Bolts

400

400

12 22

8@150

Endplate

2

2

3 3

1 1

①Embedded I-shaped steel

550

250 60 60 60 35 35

M20

M30

25

25

85

105

120

105

85

250

550

8 18

Section (2-2)

8@150

Steel hinge

17

5

175

200

550

25

25

85

65

120

65

85

40

40 R9050 R20

225400

50

180

225

R60

60

10

105

②

Steel tube

100 100 100 50 400

100

50

100 5

0

Internal diaphragm

R50

R20

10

0

10

10

250

10

Section of ① and ②

430

550

10

169

Fig. 5. Monolithic specimen configuration (unit: mm) 170

3.2 Specimen construction

The fabrication procedure of this prefabricated joint began with the production of the upper column, 171

lower column, beams, steel tube confined joint core, and energy-dissipating steel hinges, as shown 172

in Fig. 6. The formwork for the precast columns and precast beams was prepared using plywood. 173

Then, the reinforcements and grouted sleeves of the columns were installed, and the upper and 174

lower flanges of an I-shaped steel beam with a length of 300 mm were welded with the 175

corresponding longitudinal reinforcements of beams. Subsequently, concrete with a strength grade 176

of C55 was poured for columns and beams and cured for 14 days. A steel tube was welded using 177

four plates measuring 400 × 500 mm2 for confining the core area. Two internal diaphragms were 178

welded to the steel tube at the position aligned with longitudinal reinforcements of the precast beam 179

400

Section (3-3) Section (4-4) Section (1-1)

250

550

8 18

8@100

250

550

8 18

8@150

12 22

8@100

400

400

Section (2-2)

400

1800 1250 550

1800 1250 550

3

3

550

945

12 22

8@150

400

400

400

745

1 1

2 2

4

4

11

to ensure a reliable bending moment at the beam ends. After two I-shaped connecting beams were 180

welded to the steel tube, concrete was cast into the joint core between two internal diaphragms. 181

182

Fig. 6. View of the prefabricated specimen series for the (a) reinforcement and grouted sleeve of the 183

upper precast column, (b) lower precast column, (c) precast beams, (d) prefabricated steel tube 184

confined joint core, and (e) energy-dissipating steel hinge 185

186

When the concrete strength of the columns, beams, and joint core reached the hoisting allowable 187

strength, the top surfaces of the lower column and bottom surface of the upper column were 188

roughened, as shown in Fig. 6b, to transfer the shear force between the interfaces of the upper 189

column, joint core, and lower column. Then, the prefabricated components were assembled 190

according to the following steps: (1) presented in Fig. 7a, hoist the prefabricated steel tube confined 191

joint core to make the protruding longitudinal reinforcements in the lower precast column through 192

the reserved hole formed by the steel syphon bellows in the joint core. Then, the prefabricated joint 193

core was placed on the top of the lower column. (2) High-performance cement paste was grouted to 194

the duct between the bellows and reinforcements, as shown in Fig. 7b, to ensure the stability of the 195

reinforcements and connect the top surface and joint core. (3) The upper precast column was 196

installed at the top of the joint core (Fig. 7c). (4) The sleeves of the upper precast column were 197

grouted to connect the longitudinal reinforcements of the lower and upper columns and the bottom 198

Grouted sleeve a b Steel tube d

c Roughen surface

I-shape steel beam (150mm embedded

and 150mm for connecting)

e

Internal diaphragm

I-shaped connecting beam

Lugs

Pin

Dissipater Pouring hole

Rebar through hole

12

surface of the upper column and joint core. As shown in Fig. 7d, a high-performance cement paste 199

was grouted from the bottom and flowed out of the top to ensure that the cavity of the sleeve was 200

filled with paste. (5) The steel hinge was connected to the precast beam using high-strength bolts 201

(Fig. 7e). (6) Two precast beams and steel hinges were connected to each side of the joint core (Fig. 7f). 202

203

Fig. 7. Assembly process of the prefabricated joint: (a) assemble the prefabricated steel tube 204

confined joint core and lower precast column, (b) duct grouting of the joint core, (c) install the 205

upper precast column, (d) grout the sleeves of the upper precast column, (e) install the 206

energy-dissipating steel hinge, and (f) connect the precast beams and columns. 207

208

3.3 Material properties

LYP was applied to a replaceable energy dissipater. The other steel components, including the lugs, 209

I-shape steel, steel tube, and internal diaphragms of the beam and column connector, were made of 210

Q355. HRB400 was used as reinforcements in the precast beams and columns. The material 211

properties of the steel plates and bars were obtained by tensile tests that were based on 212

GB/T228.1-2010 [46]. The determined yield strength (fy), yield strain (εy), ultimate strength (fu), 213

elastic modulus (Es), and Poisson’s ratio (μs) values are listed in Table 1. High-strength bolts (Class 214

10.9) were employed for connections between the prefabricated joint core, steel energy-dissipating 215

hinge, and precast beam. 216

a b c

f d e

13

All specimens were cast using concrete with identical mix proportions. The cubic compressive 217

strength (fcu) and elastic modulus (Ec) of the concrete were measured by a cube with dimensions 218

of 150 mm × 150 mm × 150 mm and a prism with dimensions of 150 mm × 150 mm × 300 mm, 219

respectively. At the testing days, fcu and Ec of the concrete were 56 MPa and 35400 MPa, 220

respectively. 221

222

Table 1 Material Properties of the steel plates and bars 223

Type

Thickness

(Rebar diameter)

(mm)

fy (MPa) fu (MPa) y () Es (MPa) s

Low-yield-point steel 10 269.8 373.6 1659 200334 0.284

Steel plate (Q355) 10 374.2 489.7 2322 193229 0.273

Longitudinal reinforcement of the columns 22 414.9 563.7 2527 196966 0.294

Longitudinal reinforcement of the beams 18 419.9 558.5 2446 199576 0.283

Stirrups of the columns and beams 8 432.2 572.5 2612 200566 0.287

224

3.4 Test setup and loading scheme

Hinge support boundary conditions are set for the column bottom and beam ends to simulate 225

infection points in a frame. To reflect the actual working conditions and account for the second-order 226

influence in the frame, a constant axial load was applied to the free top of the column during the 227

lateral cyclic loading for all specimens. First, an axial compression of 1600 kN (an axial load ratio of 228

approximately 0.3) was applied and maintained constant using a jack with a capability of 2000 kN. 229

This jack was connected to a rigid reaction beam by a rolling support to ensure that the compression 230

on the column was concentric. The cyclic load was provided by a hydraulic actuator with an ability of 231

±500 kN. The test setup is shown in Fig. 8. 232

The tests were conducted under force and displacement control following ACT-24 [47]. In the force 233

control phase, load levels of 0.25 Puc, 0.5 Puc, and 0.7 Puc were selected, where Puc denotes the 234

predicted lateral ultimate strength by finite element analysis. When the yield strain was observed, the 235

14

displacement control was then obtained at increments of Δy, 1.5Δy, 2Δy, 3Δy …, where Δy represents 236

the yielding displacement. The cyclic loading scheme of the lateral load is shown in Fig. 9. Two 237

cycles and three cycles at each level were conducted for load and displacement control phase, 238

respectively. 239

240

Fig. 8. Photo of test set-up 241

242

243

Fig. 9. Cyclic loading scheme of the lateral load 244

245

During the test, the lateral load-displacement (P-Δ) hysteretic curves were automatically recorded 246

by the loading system. Four extensometers (Nos. 1 – 4 in Fig. 10a) were set at the upper and lower 247

flanges of the steel hinge to indirectly measure the rotation of the steel hinges. The shear drift of the 248

joint core was measured using two extensometers (No. 5 and 6 in Fig. 10a) installed along the 249

-6-5-4-3-2-10123456

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Load

(P

/Puc)

Cycle number

Rolling support

Hydraulic actuator Hydraulic jack

Hinge Support

Upper precast column

Energy-dissipating steel hinge

Precast beam

Lower precast column

Steel tube confined joint core

Dis

pla

cem

ent（

Δ/Δ y）

Force control Displacement control

0.25Puc 0.5Puc 0.7Puc 1.0y 1.5y

2.0y 3.0y

4.0y

15

diagonal lines. Displacement transducers 1,2, and 3,4 were set at the bottom of the upper precast 250

column and the top of the lower precast column, respectively, to evaluate the rotations of the 251

columns. The ranges were ± 200 mm for the displacement transducers and ± 50 mm for the 252

extensometers. 253

For the prefabricated specimens, as presented in Fig. 10b, a total of 13 strain gauges and two strain 254

rosettes were used to obtain the strains in energy dissipaters and the lugs of the steel hinge, 255

respectively. Strain gauges mounted on the longitudinal reinforcements and the steel tube of the 256

joint core are shown in Fig. 10c. For the monolithic specimen, strain gauges were set at a distance of 257

100 mm from the joint core for the longitudinal reinforcement in the columns and beams. 258

259

(a) Transducer location 260

261

(b) Strain gauge layout of the energy-dissipating steel hinge 262

263

Strain gauge

1# 2# 3#

4# 5#

175 175 50 50

450

500

25

25

8# 9# 10#

11# 12# 13#

250

450 125 125 200

50

50

50

50

50

50 50 50 50 50 50

1#

75

3# 5# 6# 7# 4#

75

2#

B

A 45

45

45

45

Extensometers 5, 6 Extensometer 3 Extensometer 1

Extensometer 2 Extensometer 4

Displacement transducer 4 Displacement transducer 3

Displacement transducer 1 Displacement transducer 2

16

(c) Strain gauge layout of the longitudinal reinforcement and confined steel tube of the prefabricated 264

specimens 265

Fig.10. Arrangement of the instrumentation 266

267

4. Test results and analysis 268

4.1 Test observations

4.1.1 Initial loading test for the prefabricated specimen (PJ-1) 269

During the first load step of the prefabricated specimen, specimen PJ-1 experienced an approximate 270

elastic deformation at the force control stage. Yielding occurred on the flange near the maximum 271

weakened position of the replaceable energy dissipaters in steel hinge, at a load of 100 kN 272

(approximately 0.5Puc), and the corresponding displacement of column top was 9.6 mm. After that, 273

displacement control loading was applied based on Δy = 10 mm. 274

When the displacement reached 1.5Δy, four longitudinal shear sliding cracks appeared in the precast 275

beam along the interface between the flanges of the embedded steel and the nearby concrete. The 276

length of the cracks was similar to that of the embedded part of the I-shaped steel. A flexural crack 277

through the bottom of the left beam was observed at the same time, which was approximately 150 278

mm away from the concrete edge of the precast beam. Under reversed loading and the second cycle 279

of 1.5Δy, symmetric flexural cracks at the top and bottom of the beams adjacent to the column were 280

observed. 281

New flexural cracks were observed approximately 150 mm from the initial flexural crack as the 282

displacement increased to 2Δy and further outward flexural cracks developed at 3Δy. In addition, the 283

cracks developed from the bottom and top to the sides of the beam and inclined cracks subsequently 284

formed. Slight cracks appeared in the lower precast column near the joint core at a displacement of 285

4Δy; however, no cracks appeared in the upper precast column owing to the reinforcement of the 286

grouted sleeve during the entire loading process. 287

17

288

Slight local buckling on the energy dissipation hinge in the compression flange was observed at an 289

incremental displacement of 5Δy. Subsequently, the precast beam and column developed no further 290

cracks and the plastic deformations were mainly concentrated in the energy dissipaters of the steel 291

hinge. As the displacement increased, local buckling of the steel hinge became apparent. Specimen 292

PJ-1 attained forward and reversed peak loads at 7Δy and -8Δy, with values of 230.08 kN and -229.02 293

kN, respectively. Then, the load-bearing capacity of the specimen deteriorated owing to further 294

loading. A slight crack was observed in the upper tension flange of the right beam in the first cycle of 295

10Δy, and the fracture developed at the second cycle of 10Δy. Then, the specimen failed. The final 296

failure appearance of specimen PJ-1 is shown in Fig. 11. During the loading process, the strains for 297

the longitudinal reinforcements in the precast beam and column were in the elastic range. 298

299

(a) Finial failure appearance 300

Fracture

Flexural

crack

Local buckling

Local buckling Local buckling

18

301

(b) Crack development of the left precast beam (c) Crack development of the right precast beam 302

Fig.11. Crack development and failure mode of specimen PJ-1 303

304

4.1.2 Second loading test for the prefabricated specimen (PJ-2) 305

Based on the previous test, four damaged dissipaters of the steel hinges were replaced, forming 306

specimen PJ-2 and the second loading test for the prefabricated specimen was conducted under the 307

same scheme as the first loading test. The replacement process is shown in Fig. 12. During the 308

initial stage of loading, there was no new crack development and specimen PJ-2 was in the elastic 309

stage. New cracks at the end of the shear cracks on the beam sides were first observed at 2Δy, 310

following which new crack propagation was rare. The crack development in the precast beams of 311

specimen PJ-2 is marked by the red line, as shown in Fig. 13a. 312

Similar to the first test, slight local buckling on the compression dissipaters of the steel hinge was 313

observed at 5Δy. Subsequently, the precast beam and column developed no further cracks when the 314

plastic deformations were centralized in the dissipaters. In addition, the local buckling of the steel 315

hinge became more obvious upon further loading. Specimen PJ-2 reached its peak load at 7Δy. The 316

values were 225.70 kN and -233.41 kN for the push and pull directions, respectively, which is 317

similar to the load-bearing capacity of specimen PJ-1. The failure area of specimen PJ-2 was in the 318

energy dissipaters of the steel hinge as well as that of specimen PJ-1. At the third cycle of 10Δy, the 319

lower tension dissipater of the right steel hinge fractured and the test was terminated. The 320

deformation development of the steel hinges is shown in Fig. 13b and c. 321

Shear sliding crack

Initial flexural crack Flexural cracks

Shear sliding

cracks

Inclined cracks

19

322

Fig.12. Process of replacing the left energy-dissipating steel hinge 323

324

(a) Crack development of the precast beams 325

326

(b) Failure development characteristic of the left energy-dissipating steel hinge 327

328

(c) Failure development characteristic of the right energy-dissipating steel hinge 329

Fig.13. Crack development and failure mode of specimen PJ-2 330

331

During the two tests for the prefabricated specimens, no other visible buckling or changing 332

phenomenon was observed. The confined steel tube was removed after testing specimen PJ-2 for 333

direct observation of the core concrete. As shown in Fig. 14, only a slight crack was found in the 334

core area, indicating that the novel prefabricated joint met the seismic design concept commonly 335

referred to as “strong connection”. 336

New cracks New cracks

5y 7y 10y

Fracture Severe buckling

Slight buckling

5y 7y 10y

Severe buckling Slight buckling

20

337

Fig.14. Concrete in the core area of the joint 338

4.1.3 Monolithic specimen (MJ) 339

In the monolithic specimen, the first cracks occurred near the beam and column interface at a load 340

of 80 kN (0.5Puc) and some flexural cracks were located at the bottom and top of the beams. The 341

corresponding displacement was 7.6 mm. Then, displacement control loading was applied based on 342

Δy = 7 mm. 343

During the displacement control phase, the flexural cracks in the beams developed from the 344

position close to the core area to the end; then, the inclined crack developed into a through-crack at 345

a displacement of 1.5Δy. When the displacement attained 2Δy, a horizontal flexural crack was found 346

in the column at a position close to the joint core. Upon further loading, no cracks developed in the 347

beam. The occurrence and development of cracks were concentrated in the joint core area. 348

Furthermore, oblique shear cracks were formed at an angle of approximately 38 – 45 ° in the 349

horizontal direction in the joint core area at 3Δy and specimen MJ attained maximum strength. 350

Some concrete gradually began to crush and fall off within the four joint core area corners at 5Δy 351

and this became more serious and extended to the upper column at incremental displacements of 352

5Δy – 7Δy, which caused exposure of the reinforcements. After the peak load, as shown in Fig. 15, at 353

10Δy, the lateral load reduced to 85 % of the peak load, the monolithic joint failed by shearing at the 354

joint core, and the test was terminated. 355

A slight crack

21

356

Fig.15. Failure mode of specimen MJ 357

During testing, the relationship between the precast columns and precast beams was reliable and the 358

prefabricated specimens and monolithic specimen exhibited good overall mechanical performance. 359

Compared with the monolithic joint, the plastic hinge was forced outward from the column face, 360

and damage was controllable in the prefabricated joint owing to the steel hinge. The replaceable 361

energy dissipater made of low-yield-point steel entered the plastic stage first and dissipated the 362

energy. Therefore, the crack development and damage of the precast RC beams, precast RC 363

columns, and joint core area were efficiently controlled. There were no significant differences in the 364

failure mode and load-bearing capacity of the prefabricated specimens under the first and second 365

loading times (specimens PJ-1 and PJ-2). Thus, the hysteretic performance of the proposed novel 366

prefabricated joint can be restored by replacing only the energy dissipater. 367

4.2 Lateral load-displacement (P-Δ) hysteretic curves

The P-Δ hysteretic curves of all specimens are shown in Fig. 16. The hysteretic curves of all 368

specimens approached straight lines and the specimens experienced elastic deformation during the 369

initial loading stage. For prefabricated specimens PJ-1 and PJ-2, the slope of the hysteretic curves 370

decreased slightly as energy dissipater in the steel hinge yielded while the strength increased 371

22

consistently owing to the stress strengthening of the dissipater, and residual displacement was 372

observed when unloading. The P-Δ hysteretic curves of the prefabricated joints are plump in shape 373

and have no obvious pinching effect, as shown in Fig. 16a, indicating excellent energy dissipation 374

capacity. When the lateral displacement reached 80 mm — i.e., that the drift ratio reached 2.5% — 375

the load capacity decreased owing to the local buckling of the dissipaters. When the prefabricated 376

specimens failed, the drift ratio reached 3.33 %. Moreover, the P-Δ hysteretic curves of PJ-1 and 377

PJ-2 coincided, indicating that the seismic behavior of the novel prefabricated joint can be restored 378

by replacing only the energy dissipater. 379

380

The P-Δ hysteretic curves of the monolithic joint exhibited significant pinching in the middle, as 381

shown in Fig. 16b, because specimen MJ failed in a shear-dominant mode in the joint core area. 382

After the peak load, the strength decreased gradually owing to the concrete crushing and spalling. A 383

comparison of all the P-Δ hysteretic curves revealed that the seismic performance, such as the 384

load-bearing capacity, energy consumption, and ductility, of the designed novel prefabricated joint 385

was better than that of the monolithic joint. 386

387

(a) Prefabricated joints (b) Monolithic joint 388

Fig.16. P－ hysteretic curves of all specimens 389

4.3 P-Δ envelope curves

-300

-200

-100

0

100

200

300

-150 -100 -50 0 50 100 150

P(k

N)

Δ (mm)

PJ-1

PJ-2

-300

-200

-100

0

100

200

300

-150 -100 -50 0 50 100 150

P(k

N)

Δ (mm)

MJ

23

Fig. 17 shows the P–Δ envelope curves of all specimens. The yield load (Py) and yield displacement 390

(Δy) were determined by the geometrography method, as presented in Fig. 18 in [48]. The load and 391

displacement at the peak point of the P-Δ envelope curve were labeled as Pmax and Δmax, 392

respectively, and the failure load (Pu) and corresponding displacement (Δu) were determined when 393

the load decreased to 85 % of Pmax. The displacement and load at the points of yield, peak, and 394

failure are listed in Table 2 for all specimens. 395

In Fig. 17, the initial stiffness of specimen PJ-2 was slightly lower than that of PJ-1; this is because 396

of the existence of cracks in the PJ-2 specimen precast beams and columns from the beginning, as 397

only the dissipaters were replaced after the first load. Thus, Δy of specimen PJ-2 was slightly higher 398

than that of specimen PJ-1. After the yield point, the difference between the P and Δ envelope 399

curves of specimens PJ-1 and PJ-2 can be considered negligible. The load-bearing, energy 400

dissipation, and deformation capacities can be fully restored by replacing the dissipaters of the steel 401

hinges. 402

As can be seen from Table 2, the load-bearing capacities of prefabricated specimens PJ-1 and PJ-2 403

were 48 % and 49 % higher than that of the monolithic specimen MJ, respectively. This is because 404

specimen MJ failed in a shear-dominant pattern in the joint core area while the core area was 405

enhanced by a steel tube for the prefabricated specimens. Moreover, plastic hinges were bound to 406

occur at the beam ends, which protected the precast beam and column from damage. 407

24

408

Fig.17. Skeleton curves of all specimens 409

410

Fig.18. Determination of the yield point, peak point, and ultimate state of the specimens 411

412

Table 2 Characteristic values of P-Δ envelope curves and ductility coefficients for all specimens 413

Specimen Yield point Peak point Failure point Ductility

coefficient μ

Average

of μ Δy (mm) Py (kN) Δmax (mm) Pmax (kN) Δu (mm) Pu (kN)

PJ-1 17.21 161.54 67.18 230.08 92.21 195.50 5.35

5.79 -16.21 -154.65 -78.48 -229.02 -100.81 -197.56 6.22

PJ-2 26.18 152.91 78.56 225.70 100.83 205.10 3.85

3.99 -24.39 -166.85 -66.88 -233.40 -100.81 -201.80 4.13

MJ 13.42 99.96 22.41 149.20 72.32 126.82 5.38

5.67 -14.27 -102.23 -22.41 -162.40 -85.11 -138.04 5.96

414

4.4 Stiffness degradation

-300

-200

-100

0

100

200

300

-120 -80 -40 0 40 80 120P

(kN

)

(mm)

PJ-1

PJ-2

MJ

Py

Pmax

Pu (0.85Pmax)

y

u

max

P

Yield point

Peak point Failure point

O

25

The average secant stiffness is used as the stiffness of the specimens under different loading levels, 415

and the relative stiffness of the i-th average secant stiffness Ki is defined as [49]: 416 𝐾𝑖 = |+𝑃𝑖|+|−𝑃𝑖||+𝛥𝑖|+|−𝛥𝑖| , (1) 417

where Pi and i are the peak load and lateral displacement, respectively, under the i-th /y and ‘+’ 418

and ‘－’ represent the positive and negative directions, respectively. 419

Fig. 19 compares the Ki – Δ/Δy curves of all specimens. For all specimens, the stiffness decreases as 420

the lateral displacement increases. The stiffness under the first loading cycle for the cast-in-place 421

monolithic joint is approximately 23.1% higher than that of prefabricated specimen PJ-1, 422

demonstrating that the steel hinge connection results in a slight deterioration of the integrity of the 423

beam. However, specimen MJ showed a more severe rate of stiffness degradation. Therefore, the 424

stiffnesses of specimens MJ and PJ-1 were similar at 1.5 Δy. Subsequently, the stiffness of specimen 425

PJ-1 was higher. This is because the cracks occurred and extended continuously during the entire 426

loading process for specimen MJ. In the prefabricated joint, after a certain displacement increment, 427

the damage was concentrated in the steel hinge dispersers, which led to no further cracks in the 428

precast column and beam. 429

From Fig. 19, the initial stiffness of the restored prefabricated specimen PJ-2 is 30 % lower than that 430

of PJ-1, as mentioned in Section 4.3; this is due to the existence of cracks in the precast beams 431

before loading. The two prefabricated specimens, PJ-1 and PJ-2, experienced similar stiffness 432

degradations because the degradation was approximately due to the yield of the dissipaters. 433

26

434

Fig.19. Stiffness reduction curves of the specimens 435

4.5 Strength degradation

Fig. 20 shows the strength degradation of λ2 and λ3 of the specimens as a function of the lateral 436

displacement, where λ2 and λ3 are the strength degradation coefficients of the second and third 437

cycles, respectively, at the same loading level. For prefabricated specimens PJ-1 and PJ-2, λ2 and λ3 438

were stable at approximately 1.0, with a small jitter before fracturing of the dissipater, indicating 439

that the novel prefabricated joint had an excellent load-bearing capacity under cyclic loading. The 440

strength degradation of the monolithic joint occurred earlier than that of the prefabricated joint and 441

the rate of strength degradation was faster; λ2 and λ3 were approximately 0.85 and 0.90, respectively, 442

for specimen MJ. In summary, the strength degradation of MJ is significant. 443

444

(a) 2 (b) 3 445

Fig.20. Strength degradation of the specimens 446

447

4.6 Ductility and energy dissipation

0

2

4

6

8

10

12

0 2 4 6 8K

i(1

03kN

/m)

/y

PJ-1

PJ-2

MJ

0.4

0.6

0.8

1

1.2

-120 -90 -60 -30 0 30 60 90 120

2

(mm)

PJ-1

PJ-2

MJ

0.4

0.6

0.8

1

1.2

-120 -90 -60 -30 0 30 60 90 120

3

(mm)

PJ-1

PJ-2

MJ

27

Following the definition by Han et al. [48], the displacement ductility coefficient (μ) of all 448

specimens is determined by μ = Δu/Δy and listed in Table 2. From Table 2, the average of the active 449

and passive failure displacements for specimens PJ-1 and PJ-2 are 96.51 mm and 100.82 mm, 450

respectively, and the corresponding drift ratios are 3.22 % and 3.36 %, respectively, indicating the 451

excellent deformation ability of the prefabricated joint. The displacement ductility coefficient of 452

PJ-2 decreased by approximately 31 % compared to that of specimen PJ-1, as previously mentioned. 453

This is because the Δy of PJ-2 was slightly higher than that of PJ-1. For specimen MJ, which is 454

cast-in-place, Δy and Δu are 13.85 mm and 78.72 mm, respectively; i.e., significantly lower than 455

those of specimen PJ-1 and PJ-2. In addition, the μ value of specimen PJ-1 was higher than that of 456

specimen MJ. Thus, the deformation capacity of the prefabricated joint was improved. 457

458

The cumulative hysteretic energy (Ep), calculated based on the area enclosed by the hysteretic 459

hoops from the P﹣ hysteretic curves, and the equivalent hysteretic damping coefficient (ζeq), 460

determined according to Fig. 21 shown in [49], was employed to estimate the energy consumption 461

capacity of the joints. The equivalent hysteretic damping coefficient can be expressed as: 462

ζeq= 12π· S(ABC+CDA)

S(OBE+ODF), (2) 463

where SABC+CDA is the hysteresis loop area, and SOBE+ODF is the area of triangle OBE and ODF. 464

28

465

Fig.21. Definition of the equivalent hysteretic damping coefficient 466

Fig. 22 and 23 show the Ep﹣curves and ζeq﹣curves for each specimen. The calculated 467

values of the cumulative hysteretic energy and equivalent hysteretic damping coefficient once the 468

lateral load reduced to 85 % of the ultimate strength — i.e., Ep,u and ζeq,u, respectively — are 469

listed in Table 3. Evidently, Ep increases with increasing displacement. In contrast to monolithic 470

joint MJ, energy dissipation capacity of prefabricated joints PJ-1 and PJ-2 clearly increased owing 471

to the superior plastic energy dissipation capacity of the steel hinge. Here, Ep,u of joints PJ-1 and 472

PJ-2 were higher than that of joint MJ by a factor of approximately 2 and 1.8, respectively. The 473

equivalent hysteretic damping coefficient of the joint MJ developed rapidly during the initial 474

loading stage owing to the serious cracking of the joint core area. However, after the displacement 475

reached 30 mm, the ζeq of the prefabricated joints were higher than that of monolithic joint. The 476

values of ζeq,u for joint PJ-1 and PJ-2 increased by 138 % and 100 %, respectively, compared to 477

joint MJ. From the above, it can be seen that the prefabricated joint provides excellent energy 478

consumption ability through the use of steel hinges. In addition, as shown in Fig. 22 and Fig. 23, 479

the agreement between the cumulative hysteretic energy curves of joint PJ-1 and PJ-2, as well as 480

the similar equivalent hysteretic damping coefficient curves between joint PJ-1 and PJ-2, reveals 481

E A

B

C F

D

O

P

29

that the energy dissipation capacity can be recovered for the prefabricated joint by replacing the 482

dissipater. 483

484

Fig.22. Cumulative hysteretic energy Fig.23. Equivalent viscous damping 485

coefficient 486

487

Table 3 Energy dissipation for all specimens 488

Specimen Ep,u (kN·m) ζeq,u

PJ-1 342.9 0.557

PJ-2 320.8 0.468

MJ 156.3 0.234

489

4.7 Shear deformation of joint core

As mentioned in Section 3.4, the shear drift of the joint core was gauged by extensometers set along 490

the diagonals. As shown in Fig. 24, the shear drift angle () of the joint core can be calculated as: 491 𝛾 = 𝛼1 + 𝛼2 = √𝐷2+ℎ2𝐷∙ℎ ∙ 𝛿1+𝛿22 , (3) 492

where 1 and 2 are the shear drift angles along the height and width direction of the joint core, 493

respectively; h and D are the height and width of the joint core, respectively; 1 and 2 are the 494

deformations along the diagonals. 495

0

50

100

150

200

250

300

350

400

0 30 60 90 120

Ep

(kN

•m)

(mm)

PJ-1

PJ-2

MJ

0

0.1

0.2

0.3

0.4

0.5

0.6

0 30 60 90 120

ζ ep

(mm)

PJ-1

PJ-2

MJ

30

496

Fig.24. Idealized shear deformation of the joint core 497

As shown in Fig. 25, the lateral load-shear drift angle (P-) hysteretic curves of all specimens 498

almost linearly cycled and no obvious residual deformation was observed during the initial loading 499

period. For the prefabricated joints, the development of the shear drift angle under varied loading 500

was between -0.0005 rad and 0.0005 rad, indicating that the joint core area was in the stage of 501

elastic deformation during the entire process, which will also be verified by the measured main 502

strain of the confined steel tube at the joint core in Section 4.8. Moreover, the shapes of the P- 503

curves for joints PJ-1 and PJ-2 are similar, demonstrating that the damage was controlled to take 504

place at the dissipaters of the steel hinges, which could protect the joint core. For the cast-in-place 505

monolithic joint MJ, the cracks at the joint core developed rapidly, leading to a rapid increase in 506

residual shear deformation. After the main diagonal cracks were formed, the shear drift angle 507

reached 0.006 rad. When the concrete was spalled and crushed, the joint failed due to the joint core 508

damage. 509

510

-250

-200

-150

-100

-50

0

50

100

150

200

250

-0.001-0.0005 0 0.0005 0.001

P(k

N)

(rad)

-250

-200

-150

-100

-50

0

50

100

150

200

250

-0.001-0.0005 0 0.0005 0.001

P(k

N)

(rad)

-200

-150

-100

-50

0

50

100

150

200

-0.008 -0.004 0 0.004 0.008

P(k

N)

(rad)

h

D

1

2

1

2

1

2

31

(a) PJ-1 (b) PJ-2 (c) MJ 511

Fig.25. P- hysteresis curves of all specimens 512

4.8 Strain distribution and developement

The lateral load-strain (P-ε) envelope curves for specimens were obtained by sequentially 513

connecting the extreme point of each loading level on the corresponding P-ε hysteretic curves. The 514

longitudinal strains of the longitudinal reinforcements in the beam and column (εbar), the 515

longitudinal strains of dissipaters in the steel hinge (εhinge), and the main strains of the confined tube 516

in the joint core (εtube) are presented in Figs. 26, 27, and 28, respectively. 517

As shown in Fig. 26, the longitudinal reinforcement experienced uniform strain development for 518

the prefabricated joints PJ-1 and PJ-2. The longitudinal strains did not exceed 2000 με during the 519

entire testing, that were less than the yield strains, as listed in Table 1, were 2446 με and 2527 με for 520

the beam and column reinforcements, respectively. In contrast, as shown in Fig. 27, the strains of 521

the dissipaters (εhinge) developed rapidly. After the peak, the strains of the dissipater increased 522

remarkably, the maximum value exceeding 0.02, leading to the fracture of the dissipater. These 523

results illustrate that the damage was controlled to occur at the dissipaters of the steel hinges, which 524

protected the precast beam and column from damage. Fig. 26c shows that the longitudinal strains of 525

reinforcement in the cast-in-place joint MJ were less than their yield strain; however, the 526

longitudinal reinforcements of the beam yielded before the peak point. With crack development, the 527

strain developed rapidly. 528

529

(a) PJ-1 (b) PJ-2 (c) MJ 530

0

63

125

188

250

0 1000 2000 3000 4000 5000

P (

kN

)

bar ()

Upper column

Lower column

Left beam

Right beam0

63

125

188

250

0 1000 2000 3000 4000 5000

P(k

N)

bar ()

Upper column

Lower column

Left beam

Right beam

εy

0

63

125

188

250

0 1000 2000 3000 4000 5000

P(k

N)

bar ()

Upper column

Lower column

Left beam

Right beam

εyεy

32

Fig.26. Longitudinal strain development of the longitudinal reinforcements in the beam and 531

column for all specimens 532

533

It can be seen from Fig. 27 that the strain distribution and development on the dissipater of the 534

steel hinge for prefabricated joints PJ-1 and PJ-2 were similar. For each specimen, only the strains 535

of the upper dissipater of the right beam were presented owing to symmetry. The strain gauges were 536

numbered 1 to 7 from the end connected to the joint core to the end connected to the precast beam, 537

as shown in Fig. 10b. Strain gauge No. 4 yielded first and the strain was maximum during the entire 538

process as it was installed on the weakest section. With the increase in lateral displacement, the 539

plasticity extended from the center to the ends of the dissipater, which led to excellent energy 540

dissipation. Stress strengthening allowed the joint to maintain load-bearing. In addition, strain 541

gauges No. 1 and No. 7 did not yield, limiting stress in the less ductile region near the face of the 542

column and the plastic development was concentrated in the weakened area of the dissipater. 543

Consequently, with the concept of the reduced section of the dissipater, the failure mode and 544

damage position of the proposed prefabricated joint can be controlled and the plastic hinge can be 545

outward from the beam-to-column interface. Although the energy dissipating elements are 546

symmetrically weakened, the strain measured by strain gauges No. 2 and No. 3 are larger than those 547

of strain gauges No. 5 and No. 6, as the bending moment close to the joint core is higher. 548

549

(a) PJ-1 (b) PJ-2 550

Fig.27. Longitudinal strain development of the steel hinge for prefabricated joints 551

0

63

125

188

250

0 5000 10000 15000 20000

P (

kN

)

hinge ()

1#2#3#4#5#6#7#

εy

0

63

125

188

250

0 5000 10000 15000 20000

P (

kN

)

hinge ()

1#2#3#4#5#6#7#

εy

33

Fig. 28 shows the principal stress and direction of a typical measuring point in the steel tube at the 552

joint core area for the prefabricated joints. The principal stresses calculated by the measuring stains 553

are less than the yield stress of the steel tube, indicating that the core area of the prefabricated joint 554

is confined and effectively protected by the steel tube. Thus, the seismic design concept is 555

commonly referred to as a strong connection. The direction of the principal stress in the steel tube, 556

as shown in Fig. 28 b and d, demonstrates that the steel tube was mainly subjected to a shear force. 557

558

(a) Principal stress of specimen PJ-1 (b) Principal stress direction of specimen PJ-1 559

560

(c) Principal stress of specimen PJ-2 (d) Principal stress direction of specimen PJ-2 561 Fig.28 Main stress and direction of measuring point A in the pin of prefabricated specimens 562

5. Behavior of energy-dissipating steel hinge 563

5.1 Moment and rotation curves and deformation capacity

As shown in Fig. 29, the moment-resistant (M) and the rotation () of the energy-dissipation steel 564

hinge can be calculated as: 565 𝑀 = 𝑃 ∙ 𝐻 ∙ 𝑙𝐿 (4) 566 𝜑 = 𝛥c+𝛥tℎ (5) 567

-120

-80

-40

0

40

80

120

0 5000 10000 15000 20000

s i(M

Pa)

Data acquiring times

-60

-40

-20

0

20

40

60

0 5000 10000 15000 20000

(°)

Data acquiring times

-120

-80

-40

0

40

80

120

0 5000 10000 15000

s i(M

Pa)

Data acquiring times

-60

-40

-20

0

20

40

60

0 5000 10000 15000

(°)

Data acquiring times

34

where P is the lateral load applied at the column top, H is the distance from the loading point to 568

the center of the joint core, l is the distance between the steel hinge and the center of the joint core, 569

and L is the distance between the pin support of the beam end and the center of the joint core; c 570

and t are the axial deformations of the compressed and tensioned energy dissipaters, respectively; 571

h is the height of the steel hinge section, which is defined as the distance between the centroids of 572

two energy dissipaters. 573

574

(a) Idealized internal beam-to-column joi (b) Simplified mechanical model for steel hinge 575

Fig.29 Schematic diagram of the bending moment and rotation calculation for the steel hinge 576

577

The -curves are listed in Fig. 30 for all of the specimens. As shown in Figs. 30 a and b, the 578

hysteretic curves of the energy-dissipating steel hinge of the prefabricated joint are plump in 579

shape and show sufficient flexibility. Moreover, the- curves of the left and right steel hinge 580

were almost the same for the prefabricated joint (PJ-1), as well as for PJ-2. This demonstrates that 581

the steel hinge can rotate around the pin axis. The bending moment and rotation at the points of 582

yield, limit, and failure for the steel hinge of the prefabricated joint and plastic hinge for the 583

monolithic joint are listed in Table 4. The average values were calculated as the -curves were 584

similar for the left and right hinge. Again, the characteristic values for the steel hinge in the 585

prefabricated joint under the two tests are close to each other, indicating that the function of the 586

steel hinge can be restored. Furthermore, the failure rotations were 0.048 and -0.055 for 587

t

c

Centroid

h

Section A-A

A

A

P

H

L

l

Energy-dissipating steel hinge

35

prefabricated specimen PJ-1 and 0.051 and -0.052 for PJ-2; the average value reached 0.0515, 588

which is much higher than that of the monolithic specimen MJ (the average failure rotation was 589

0.26) and demonstrated excellent rotation capacity for the steel hinge in the prefabricated joint. 590

591

(a) Specimen PJ-1 (b) Specimen PJ-2 592

593

(c) Specimen MJ 594

Fig.30 Moment-rotation hysteretic curves of replaceable energy-dissipating steel hinges 595

596

Table 4 Characteristic values of M- curves and ductility coefficients for hinges of all specimens 597

Specimen Yield point Peak point Failure point Ductility

coefficient μ

Average of μ

y (rad) My (kN·m) max (rad) Mmax (kN·m) u (rad) Mu (kN·m)

PJ-1 0.0031 176.3 0.021 253.8 0.048 215.73 15.48

16.33 -0.0032 -169.7 -0.036 -255.1 -0.055 -216.8 17.18

PJ-2 0.0033 162.1 0.031 240.9 0.051 220.1 15.45

15.37 -0.0034 -160.2 -0.033 -252.1 -0.052 -218.2 15.29

MJ 0.0028 114.6 0.0085 162.4 0.029 133.2 10.35

10.4 -0.0022 109.8 -0.0065 -187.8 -0.023 -156.6 10.45

5.2 Energy consumption ration

-300

-200

-100

0

100

200

300

-0.08 -0.04 0 0.04 0.08

M (

kN

·m)

(rad)

Left steel hinge Righe steel hinge

-300

-200

-100

0

100

200

300

-0.08 -0.04 0 0.04 0.08M

(kN

·m)

(rad)

Left steel hinge Righe steel hinge

-200

-150

-100

-50

0

50

100

150

200

-0.06 -0.04 -0.02 0 0.02 0.04 0.06

M (

kN

·m)

(rad)

Left plastic hinge Righe plastic hinge

36

The calculated values of the cumulative hysteretic energy (Ep,u) were calculated for the hinges of 598

the beam-to-column joint once the lateral load was reduced to 85% of the ultimate strength and 599

listed in Table 5. For the prefabricated beam-to-column joint, the energy dissipated by the 600

replaceable steel hinges accounted for 67.8 % during the first loading test, indicating that the 601

energy absorption was concentrated on the steel hinges. In addition, for the second loading test, 602

there was no obvious development of cracks, which led to slightly lower energy dissipation and 603

the energy consumption ratio increased to 77.0 %. The energy consumption ratio of plastic hinges 604

for a monolithic joint is 45.8 %. 605

Table 5 Energy consumption ratio for hinges of all specimens 606

Specimen Ep,u of beam-to-column joint

(kN·m)

Ep,u of hinges in joint

(kN·m)

Energy consumption ratio

PJ-1 342.9 232.4 67.8%

PJ-2 320.8 247.08 77.0%

MJ 156.3 71.56 45.8%

6. Conclusions 607

This experimental study investigated the mechanical behavior of an innovative type of 608

prefabricated beam-to-column joint subjected to cyclic loading. Based on this study, the 609

conclusions are drawn as follows: 610

(1) The connection between the precast columns and precast beams was reliable and the new 611

prefabricated beam-to-column joint exhibited good overall mechanical performance. 612

Controllable plastic hinges were formed at the ends of the precast beams because of the 613

prefabricated steel tube confined joint core and energy-dissipating steel hinge, which meet the 614

seismic design concept commonly referred to as a strong connection. The failure of the 615

specimens was concentrated on the flange of the steel hinge, primarily from the buckling of the 616

compressed flange or from fractures forming on the tensioned flange. Only minor flexural 617

37

cracks occurred near the beam and no other visible damage was observed in the prefabricated 618

beam-to-column joints. Even under repeated tests, the failure mode and damage degree of the 619

prefabricated joint can be controllable. 620

(2) The novel prefabricated beam-to-column joints exhibited excellent hysteretic behavior with 621

generally plump lateral load-displacement hysteretic curves; in contrast, the hysteretic curve of 622

the cast-in-place joint has an obvious pinching effect. Compared with the monolithic joint, the 623

load-bearing capacities of the prefabricated joint are approximately 50 % higher and the 624

deformation capacity and ductility are improved. The energy absorption capacity, in terms of 625

the equivalent hysteretic damping coefficient, was approximately two times higher than that of 626

the monolithic joint when the lateral load decreased to 85 % of the peak load. 627

(3) The initial stiffness of the monolithic joint (MJ) was slightly higher than that of the 628

prefabricated specimens; however, the stiffness degradation of specimen MJ was significant. 629

Thus, the stiffness of the monolithic and prefabricated joints was similar at 1.5 Δy. The 630

prefabricated joints exhibited no obvious strength degradation. The strength degradation 631

coefficients of the monolithic joint were approximately 0.85 to 0.90. 632

(4) In prefabricated specimen PJ-2, which only replaced the damaged dissipaters in the steel hinges 633

and was tested under repeated loading, the failure mode and P- hysteretic curve were similar to 634

those of the basic test, specimen PJ-1. However, the initial stiffness was slightly lower, 635

demonstrating that the prefabricated joint sustained a similar hysteretic performance after 636

restoration and the function of the prefabricated joints can be restored after earthquake damage. 637

(5) The - curves of the steel hinge in prefabricated joint are also in pump shape and exhibited 638

sufficient flexibility. The steel hinge can rotate around the pin axis, and the rotation at the 639

failure point reached 0.0515 rad. In the prefabricated beam-to-column joints, the energy 640

38

dissipated by the replaceable steel hinges accounted for 67.8 % and 77.0 %, respectively, 641

indicating that the energy absorption was concentrated on the steel hinges. 642

1

Acknowledgements

This study was supported by the National Natural Science Foundation of China (Grant No.

51578152, 51878174) and the Natural Science Foundation of Fujian Province (2020J01887). The

financial support is highly appreciated.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships

that could have appeared to influence the work reported in this paper.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon

reasonable request.

References

[1] ElliottKim S. Precast concrete structures. first ed. Butterworth-Heinemann; 2002.

[2] VanGeem, M. Achieving sustainability with precast concrete. PCI J 2006; 51(1):42-61.

[3] Jaillon L, Poon C S. Life cycle design and prefabrication in buildings: A review and case studies in

Hong Kong. Automat Constr 2014; 39:195-202.

[4] Chang Y, Li X, Masanet E, Zhang L, Huang Z, Riese R. Unlocking the green opportunity for

prefabricated buildings and construction in China. Resour Conserv Recy 2018; 139:259–261.

[5] Wang M, Bi P. Study on seismic behavior and design method of dissipative bolted joint for steel frame

with replaceable low yield point steel connected components. Constr Build Mater 2019; 198:677-695.

[6] Engström B. Structural connections for precast concrete buildings. The International Federation for

Structural Concrete (FIB): Commission 6; 2008.

[7] Ghayeb H H, Razak H A, Sulong N H R. Performance of dowel beam-to-column connections for

precast concrete systems under seismic loads: A review. Constr Build Mater 2020; 237:117582.

[8] Breccolotti M, Gentile S, Tommasini M, Materazzi A L, Bonfigli M F, Pasqualini B, Colone V,

Gianesini, M. Beam-column joints in continuous RC frames: Comparison between cast-in-situ and

precast solutions. Eng Struct 2016; 127:129-144.

2

[9] Bahrami S, Madhkhan M, Shirmohammadi F, Nazemi N. Behavior of two new moment resisting precast

beam to column connections subjected to lateral loading. Eng Struct 2017; 132:808-821.

[10] Guan D, Guo Z, Xiao Q, Zheng Y. Experimental study of a new beam-to-column connection for precast

concrete frames under reversal cyclic loading. Adv Struct Eng 2016; 19(3): 529-545.

[11] Nzabonimpa J D, Hong W K, Kim J. Experimental and non-linear numerical investigation of the novel

detachable mechanical joints with laminated plates for composite precast beam-column joint. Compos

Struct 2018; 185:286-303.

[12] Fan J J, Wu G, Feng D C, Zeng Y H, Lu Y. Seismic performance of a novel self-sustaining

beam-column connection for precast concrete moment-resisting frames. Eng Struct 2020; 222:111096.

[13] Vidjeapriya R, Jaya K P. Experimental study on two simple mechanical precast beam-column

connections under reverse cyclic loading. J Perform Constr Facil 2013; 27(4):402–414.

[14] Choi H K, Choi Y C, Choi C S. Development and testing of precast concrete beam-to-column

connections. Eng Struct 2013; 56:1820–1835.

[15] Zhang J, Ding C, Rong X, Yang H, Li Y. Development and experimental investigation of hybrid precast

concrete beam–column joints. Eng Struct 2020; 219:110922.

[16] Ryu H K, Kim Y J, Chang S P. Experimental study on static and fatigue strength of loop joints. Eng

Struct 2007; 29(2):145–162.

[17] Joergensen H B, Hoang L C. Tests and limit analysis of loop connections between precast concrete

elements loaded in tension. Eng Struct 2013; 52:558–569.

[18] Zhang J, Ding C, Rong X, Yang H, Zhang B. Experimental seismic study of precast hybrid SFC/RC

beam-column connections with different connection details. Eng Struct 2020; 208:110295.

[19] Restrepo J I, Park R, Buchanan A H. Tests on connections of earthquake resisting precast reinforced

concrete perimeter frames of buildings. PCI J 1995; 40(4), 44-61.

[20] Zhao B, Lv X L, Liu H F. Experimental study on seismic behavior of precast concrete beam-column

subassemblage with case-in-situ monolithic joint. Journal of Building Structures 2004; 25(6):22-28 [in

chinese]

[21] Parastesh H, Hajirasouliha I, Ramezani R. A new ductile moment-resisting connection for precast

concrete frames in seismic regions: an experimental investigation. Eng Struct 2014; 70: 144-157.

[22] Deng K, Pan P, Lam A, Pan Z, Ye L. Test and simulation of full-scale self-centering beam-to-column

connection. Earthq Eng Eng Vib 2013; 12(4):599-607.

[23] Song L L, Guo T, Chen C. Experimental and numerical study of a self‐centering prestressed concrete moment resisting frame connection with bolted web friction devices. Earthq Eng Struct D 2014; 43(4):

529-545.

[24] Koshikawa T. Moment and energy dissipation capacities of post-tensioned precast concrete connections

employing a friction device. Eng Struct 2017; 138:170–180.

[25] Yan X, Wang S, Huang C, Qi A, Hong C. Experimental study of a new precast prestressed concrete

joint. Appl Sci-basel 2018; 8(10):1871.

[26] Yang J, Guo T, Chai S. Experimental and numerical investigation on seismic behaviours of

beam-column joints of precast prestressed concrete frame under given corrosion levels. Structures

2020; 27:1209-1221.

[27] Li L, Mander J B, Dhakal R P. Bidirectional Cyclic Loading Experiment on a 3D Beam-Column Joint

Designed for Damage Avoidance. J Struct Eng-ASCE 2008;134(11):1733-1742.

[28] Wang H, Marino E M, Pan P, Liu H, Nie X. Experimental study of a novel precast prestressed

reinforced concrete beam-to-column joint. Eng Struct 2018; 156:68-81.

[29] Wang H, Marino E M, Pan P. Design, testing and finite element analysis of an improved precast

prestressed beam-to-column joint. Eng Struct 2019; 199:109661.

3

[30] Wang C L, Liu Y, Zhou L. Experimental and numerical studies on hysteretic behavior of all-steel

bamboo-shaped energy dissipaters. Eng Struct 2018;165:38–49.

[31] Wang C L, Liu Y, Zheng X L. Experimental investigation of a precast concrete connection with all-steel

bamboo-shaped energy dissipaters. Eng Struct 2019; 178:298-308.

[32] Garlock M M, Ricles J M, Sause R. Experimental studies of full-scale post-tensioned steel connections.

J Struct Eng-ASCE 2005; 131(3):438–448.

[33] Christopoulos C, Filiatrault A, Uang C M, Folz B. Posttensioned energy dissipating connections for

moment-resisting steel frames. J Struct Eng-ASCE 2002; 128(9):1111–1120.

[34] Chou C C, Chen J H, Chen Y C, Tsai K C. Evaluating performance of post-tensioned steel connections

with strands and reduced flange plates. Earthq Eng Struct D 2006; 35(9):1167–1185.

[35] Rojas P, Ricles J M, Sause R. Seismic performance of post-tensioned steel moment resisting frames

with friction devices. J Struct Eng-ASCE 2005; 131(4):529–540.

[36] Kim HJ, Christopoulos C. Friction damped post-tensioned self-centering steel moment-resisting frames.

J Struct Eng-ASCE 2008; 134(11):1768–1779.

[37] Chou C C, Lai YJ. Post-tensioned self-centering moment connections with beam bottom flange energy

dissipators. J Constr Steel Res 2009; 65(10-11):1931–1941.

[38] Li Z, Qi Y, Teng J. Experimental investigation of prefabricated beam-to-column steel joints for precast

concrete structures under cyclic loading. Eng Struct 2020; 209:110217.

[39] Qi Y, Teng J, Shan Q, Ding J, Li Z, Huang C, Xing H, Yi W. Seismic performance of a novel

prefabricated beam-to-column steel joint considering buckling behaviour of dampers. Eng Struct 2021;

229:111591.

[40] Eom T S, Park H G, Hwang H J, Kang S M. Plastic hinge relocation methods for emulative PC

beam-column connections. J Struct Eng- ASCE 2016;142(2):04015111.

[41] Mou B, Li X, Qiao Q, He B, Wu M. Seismic behaviour of the corner joints of a frame under biaxial

cyclic loading. Eng Struct 2019;196:109316.

[42] FEMA 350. Recommended seismic design criteria for new steel moment-frame buildings. Washington

(DC), 2000.

[43] FEMA 351. Recommended seismic evaluation and upgrade criteria for existing welded steel moment

frame buildings. Washington (DC), 2000.

[44] Eurocode 8. Design of structures for earthquake resistance-Part 3, Assessment and retrofitting of

buildings [EN 1998-3], 2005.

[45] He Q, Chen Y, Ke K, Michael C H, Wang W. Experiment and constitutive modeling on cyclic plasticity

behavior of LYP100 under large strain range. Constr Build Mater 2019; 202:507-521.

[46] General administration of quality supervision, inspection and quarantine of the people’s republic of

China. Standardization Administration of the People’s Republic of China. Metallic materials-tensile

testing at ambient temperature (GB/T 228-2010). Beijing: China Architecture & Building Press; 2010

[in Chinese].

[47] ATC-24, Guidelines for Cyclic Seismic Testing of Components of Steel Structures, ATC, 1992.

[48] Han L H, Tao Z, Wang W D. Advanced composite and hybrid structures-testing, theory and design

approach. Beijing (China): China Science Press; 2009. [in Chinese].

[49] Ministry of housing and urban-rural development of the people’s republic of China. Specification for seismic test of building (JGJ/T101-2015). Beijing: China Architecture & Building Press; 2015 [in

Chinese].

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Declaration of interests

☒ The authors declare that they have no known competing financial interests or personal relationships

that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may be considered as

potential competing interests: