Seismic Performance of Prefabricated Beam-to- column Joint with Replaceable Energy-dissipating Steel Hinge Lianqiong Zheng ( [email protected]) Fujian University of Technology https://orcid.org/0000-0002-8996-8151 Xiaoyang Chen Fujian University of Technology Changgui Wei Fujian University of Technology Guiyun Yan Fujian University of Technology Research Article Keywords: Prefabricated beam-to-column joint, Replaceable energy-dissipating steel hinge, Prefabricated steel tube conヲ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
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Seismic Performance of Prefabricated Beam-to-column Joint with Replaceable Energy-dissipatingSteel HingeLianqiong Zheng ( [email protected] )
Fujian University of Technology https://orcid.org/0000-0002-8996-8151Xiaoyang Chen
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
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)
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