1. Introduction
Architectural nonstructural members (other than load-bearing skeletal systems) are fixed components in buildings [1]. Among these, suspended ceilings are an important component. Compared with other nonstructural components, suspended ceilings typically suffer severe damage after low-intensity or medium-intensity earthquakes. In the 2010 earthquake in Chile, some hospitals lost 75% of their capacity to function due to damaged ceilings or other nonstructural components connected to ceilings. The operation of the main terminal of Santiago Airport was interrupted owing to the seismic damage to the ceiling system [2]. In the 2011 Ms 6.3 earthquake in Crested Butte, New Zealand, the seismic damage to nonstructural components was of $ 16 billion; the damage to suspended ceilings accounted for a large proportion of this [3]. In the 2013 Ms 7.0 Lushan earthquake in China, the structures of schools and many other buildings were intact; however, the seismic damage to suspended ceilings was severe (Figure 1 and Figure 2) [4]. In the 2017 Ms 7.0 Jiuzhaigou earthquake in China, ceilings were either severely deformed or damaged [5]. When the structure is slightly damaged or intact, severe seismic damage to ceilings reduces the resilience of urban infrastructure and is detrimental to urban sustainability development.
Today, the seismic performance of ceilings is mainly studied by shaking table tests and numerical simulations. Yao et al. [6] studied typical suspended ceilings in Taiwan through shaking table tests and reported that the addition of diagonal wires had a negligible impact on its seismic response. By contrast, the introduction of connecting perimeter runners with a structure that used pop rivets was able to improve seismic performance. Badillo et al. [7] carried out six sets of shaking table tests on a ceiling and obtained fragility curves. They defined four damage states according to the percentage of fallen ceiling panels and damaged runners: minor damage, moderate damage, major damage, and grid failure. McCormick et al. [8] conducted shaking table tests on ceiling systems with and without seismic design and found that when the displacement angle exceeded 1/100 rad, the acceleration of a seismically designed ceiling plate was approximately 80% greater than that of a ceiling with no seismic design. Waitakere et al. [9] designed a shaking table test for a 2.7 m × 5.0 m suspended ceiling and found that the damage to the runner grid joints was one of the main causes of seismic damage to suspended ceiling systems. Soroushian et al. [10,11,12] obtained joint fragility curves through the monotonic tensile and hysteretic tests of a ceiling system and the perimeter connection joints. They also explored the effects of the ceiling area, support conditions, boundary conditions, joints of main/cross and perimeter runners, and the weight of ceiling panels on seismic capacity by implementing shaking table tests on a full-size ceiling system. Through shaking table tests, Li [13] found that diagonal wires aggravated ceiling damage. Jiang [14,15] performed shaking table tests on a 12.52 m × 5.32 m ceiling while taking into account the influence of boundary conditions and input frequency on the seismic capacity of a ceiling system. The natural frequency of a free-boundary suspended ceiling was greater than that of a fixed-boundary suspended ceiling. Moreover, a seismic clip installed on the boundary was able to effectively reduce seismic damage to the system. Brandolese et al. [16,17] obtained joint hysteretic curves through tests on ceiling runner connection joints in Europe, established a numerical model, and found that the geometry of the connections only had a slight influence on the seismic capacity of the ceiling. Wang et al. [18,19,20] identified the joint failure mechanism and established joint fragility curves through the hysteretic tests of the main runner splice, main cross-runner joint, and perimeter runner joint of light steel runners. The damage assessment of the ceilings was studied carefully [21,22,23].
Mineral wool ceiling systems in China provide excellent sound insulation and absorption. They are widely used in hospitals, office buildings, and public buildings. The material of runners is usually light steel or aluminum alloy; iron sheet-backed painted runners (ISBPRs) are also common. ISBPRs are widely used because of their excellent quality and low cost. However, seismic research on mineral wool ceiling systems with ISBPRs that also sustained damage during earthquakes is insufficient. Moreover, no special seismic standards or relevant reference data are available.
In this study, shaking table tests were conducted on the basic units of a mineral wool panel ceiling with ISBPRs (Figure 3). Nine types of basic ceiling unit specimens were selected based on construction. A total of 90 different test scenarios for the nine groups of specimens are conducted to investigate the influence of construction factors (such as suspension devices, panel specifications, and boundary conditions) on the seismic performance of the basic ceiling units.
2. Test Scheme
2.1. Test Specimen and Carrier
Four identical steel frames were built to carry the basic unit of the suspended ceiling. The frame was divided into four layers by height: top layer, ceiling I, ceiling II, and bottom layer. The ceiling layers, which contained layers I and II, were used to adjust the suspension height using preset backing plates, bolts, and detachable ring beams. The bottom plates were used to connect the frame to the shaking table. The columns of the frames were welded to the bottom plates, which were connected to the shaking table using anchor bolts. The steel frame is illustrated in Figure 4a. The specimen of the basic unit is connected to the ring beam by perimeter runners and to the top layer by a suspension device. The ceiling panel floats on the frame. Then, the main runners were connected to beams of the top layer by three types, hanger wire, hanger rod, and hanger rod–diagonal wires, respectively. The perimeter runner was stuck with ring beams every 200 mm. The connection detail pictures are shown in Table 1. Figure 4c,d shows the basic ceiling unit and assembly on the shaking table, respectively. Figure 5 shows the specimens and carriers on the shaking table. During the shaking tests, the load was transferred to the basic ceiling unit through the top layer and ring beams.
The basic unit of the ceiling is composed of main runners, cross runners, perimeter runners, ceiling panels, and a suspension device, as shown in Figure 4c. All runners were ISBPRs. Moreover, the cross-sections of the main and cross runners were T-shaped and that of the perimeter runners was L-shaped. The main runners were then arranged uninterruptedly along the Y direction. The 600 mm-long cross runners were perpendicular to the main runners, and the perimeter runners were fixed to the ring beam. The cross-sections of the runners are shown in Figure 6a–c. The ceiling panel was made of mineral wool and laid on the runner grid. The suspension device included a hanger rod, hanger piece, diagonal wire, and hanger wires. The hanger rod was an 8 mm steel rod, and the hanger and diagonal wires were 2 mm steel wires.
The details of the joints of the ISBPR basic ceiling unit, shown in Figure 7, are considered the standard of interior decoration and interior ceilings (12J502-2) [24], and identifying them is a common engineering practice, as summarized in Table 1. Material parameters and joint performance of ceilings were studied by Lu and Wang [25,26,27]. The failure loads for joints of main runner–cross runners, hanger wires–main runners, and hanger rods–main runners are 27.3 N, 150.9 N, and 116.8 N, respectively.
According to the Technical Regulations for Ceiling Works in Public Buildings (JGJ345-2014), the installation process for the basic ceiling unit is as follows [28].
(a). Set the baseline height and position along the longitudinal and transverse axes.
(b). Install perimeter runners.
(c). Locate the position of the hanging point at the top layer of the steel frame.
(d). Install the hanger rod, hanger piece, and wires.
(e). Install the main and cross runners.
(f). Install ceiling panels.
Nine basic ceiling unit specimens are designed to consider the influence of various constructions according to the standard of interior decoration and interior ceilings (12J502-2); details are listed in Table 2. Specimen A is used for basic construction. Then, based on Specimen A, the suspension device for Specimens B–E is changed; the panel specifications for Specimens F and G are modified; and the M/C–P joints for Specimens H and I are modified. Additionally, all the specimens are prototypes. The details of the nine specimens are shown in Figure 8.
2.2. Loading Regime
The specimens were subjected to three-dimensional shaking on a 5 × 5 m shaking table at the Institute of Engineering Mechanics, China. Then, as shown in Figure 9, acceleration sensors were mounted on the specimens, steel frames, and shaking table to record the motion. The acceleration sensors mounted on the center of the top layers were used to obtain PFA. Then, the acceleration sensor at the center of the shaking table was used to obtain PGA. The acceleration sensors mounted on the specimens and shaking table were used to observe torsion.
For a technical reason, the technical staff in charge of operating the shake table recommended the Wolong seismic waves record, which was also obtained in the western Sichuan province, but during the 2008 Wenchuan earthquake, for the table input. The recorded Wolong seismic waves are in the low PGV to PGA ratios and of short duration, which suggests rich content in a high-frequency domain. Thus, the potential differences in structural load-bearing capacity, deformation, and damage development when using other types of waves were complex and could not be clarified clearly with short lengths here. The history of the earthquake motion is shown in Figure 10a–c, and a comparison of the acceleration spectra between the earthquake motion and the standard is shown in Figure 11.
Nine sets of runs are conducted for the nine groups of specimens. Consider specimen A as an example. The peak ground acceleration (PGA) of each run is listed in Table 3.
3. Test Results
The following measures are adopted to avoid the effect of cumulative damage on the test results.
White noise is used to sweep the frequency before each set of run. The tested frequencies of the four frames approximate the natural frequencies before the tests, and the deviation does not exceed 5%. The frames must be in excellent condition to ensure that the previous condition is satisfied.
After each set of runs, the group of specimens of the completed run are removed and then the next group of specimens is set up. This is implemented to ensure that the tested specimens are new.
After each run, the tested specimens are carefully observed, and impaired components are replaced. The tested specimen must be in excellent condition to ensure that the previous condition is satisfied.
3.1. Damage Phenomena and Repair Measures
The details of six damage phenomena are as follows.
Slight drift of cross runner at the M–C joint. As shown in Figure 12a, a distinct displacement is observed between the cross and main runners in the direction of the cross runner length; however, they are not separated. No evident damage is observed at the end of the cross runners. Moreover, their use can continue after implementing a simple repair.
Severe damage of cross runner at the M–C joint. The damage to the M–C joint cannot be repaired (e.g., buckling and dropping in Figure 12b,c, respectively). Moreover, the damaged components must be replaced.
Severe damage or dropping of main runner. The main runner cannot recover from considerable deformation. Although the main runner does not fall, the runner grid loses its integrity, as shown in Figure 12d,e; hence, these components must be replaced.
Tilting or damage to corner or side of panel. As shown in Figure 12e,f, the corner or side of the panel is tilted or damaged. Hence, the tilted panel must be reset. The use of the panel may continue unless the damage affects the support or its appearance. In the case of the latter, the panel must be replaced.
Fallen panel. As shown in Figure 12h, the panel loses sufficient support and falls after the runner grid sustains considerable deformation. The panel that falls may be severely damaged upon hitting the floor and must be replaced.
Large deformation of suspension joint at main runner. As shown in Figure 12i,j, the main runner loses support when the joint between the main runner and hanger piece sustains considerable deformation. Consequently, the main runner may be severely damaged. These components may be replaced.
The damage classifications and repair measures are listed in Table 4.
3.2. Failure of Basic Ceiling Units
Basic ceiling units have two possible types of failure.
Failure initiated by falling ceiling panel. A gap is retained between the grid and panel. The square runner grid is unstable and deforms easily. The panel is supported by the flanges of the runners; the average overlapping length does not exceed 3 mm. Thus, provided that the deformation is insignificant, the panel simply tilts. Subsequently, the panel falls off the supports. Consequently, the integrity of the basic ceiling unit is reduced, and the M–C joint is gradually damaged. Finally, all the panels fall. The failure process is shown in Figure 13.
Failure initiated by damage to the M–C joint. The M–C may be severely damaged. Subsequently, the runner grid undergoes significant deformation, and the panels fall. The failure process is shown in Figure 14.
The two possible failure types of basic ceiling units were consistent with numerical simulation results [27].
4. Characteristic Seismic Response of Basic Ceiling Units
Soroushian et al. [10] defined four damage states: (I) undamaged, (II) slightly damaged, (III) repaired, and (IV) collapsed. Damage is defined in terms of the percentage of fallen panels, as listed in Table 5.
4.1. Hanger Wire
To investigate the influence of the arrangement of the hanger wire, the test results of Specimen B are compared with those of Specimen A. Two more hanger wires are used in Specimen B than in Specimen A, as shown in Figure 8. The relationship between PFA and basic ceiling unit damage, which is adopted for data analysis, is usually used to assess seismic capacity.
The following was observed:
Specimens A and B are intact when the PFA ∈ [0.00 g, 1.70 g] (PGA ∈ [0.10 g, 0.60 g]).
The percentage of fallen ceiling panels was 37.5% for Specimen A. When PFA ∈ [1.70 g, 2.00 g] (PGA ∈ [0.60 g, 0.80 g]), Specimen B had no fallen panels.
Specimens A and B have fallen ceiling panels when PFA ∈ [2.00 g, 3.50 g] (PGA ∈ [0.80 g, 1.80 g]).
The percentage of fallen ceiling in Specimen B was lower than that in Specimen A. Both fallen panel percentage and damage rate to the main runners decrease when more hanger wires are used in the main runners. However, the increase in the number of hanger wires only has a slight effect on the percentage of damage to the cross runner. In other words, the increase in number of hanger wires reduces the damage to the basic ceiling unit and enhances the seismic capacity, as shown in Figure 15.
4.2. Hanger Rod and Hanger Rod–Diagonal Wires
To investigate the influence of the arrangement of hanger rods and hanger rod–diagonal wires, the test results of Specimens A, C, and D were compared. The three specimens were fixed to hanger wires at joints 1, 4, and 6. Unlike the hanger wire at joint 3 of Specimen A, the hanger rod was fixed at joint 3 of Specimen C, and the hanger rod–diagonal wire was fixed at joint 3 of specimen D, as shown in Figure 8.
The following was observed:
Two types of damage to the hanger rod–main runner joint were observed, as shown in Figure 12i,j: (a) the considerable deformation of the hanger piece and (b) the separation between the hanger piece and main runner.
Both constructions were able to reduce the percentage of fallen ceiling panels and enhance the seismic capacity when PFA ∈ [1.70 g, 2.40 g].
The hanger rod–diagonal wire aggravated the damage to the basic ceiling unit when the PFA exceeded the above range, as shown in Figure 16.
The construction connected directly with the main runner, so the performance of the main runner was improved and the damage percentage was reduced. Then, the vibration energy transferred to the cross runner increased. Thus, the three types of construction (hanger wire, hanger rod, and hanger rod–diagonal wires) were not effective in protecting the cross runner. However, the strengthened main runner reduced the fallen panel percentage, and the seismic capacity of the basic ceiling unit improved.
4.3. Suspension Height
To investigate the influence of suspension height, the test results of Specimen E are compared with those of Specimen A. Because Specimen A is 600 mm, its suspension height is 1200 mm, as shown in Figure 8.
The following are observed.
Specimens A and E were intact when the PFA ∈ [0.00 g, 1.70 g] (PGA ∈ [0.10 g, 0.60 g]).
The seismic damage was more severe with the increase in PFA (PFA ∈ [1.70 g, 2.80 g]) for the two specimens.
The percentages of fallen panels and damaged cross runners in Specimen E compared with those in Specimen A increased. Subsequently, the percentage of damaged main runners increased.
Therefore, the increase in suspension height reduces the damage to the basic ceiling units and enhances seismic capacity, as shown in Figure 17. The partial vibration load was delivered to the basic ceiling unit via ring beams. With the same PGA, the higher the suspension height, the lower the ring beam acceleration. Thus, the higher suspension height is good for the seismic capacity of the basic ceiling unit.
4.4. Size of Ceiling Panels
To investigate the influence of panel size, the test results of Specimens A, F, and G are compared; their sizes are 594 mm × 594 mm × 14 mm, 599 mm × 599 mm × 14 mm, and 594 mm × 594 mm × 28 mm, respectively. In comparing the test results between Specimens F and A, the larger panel was found to reduce the seismic damage when PFA ∈ [1.70 g, 3.00 g]. However, no distinct difference was observed when the PFA was outside the aforementioned range, as shown in Figure 18. In comparing the test results between Specimens G and A, the lighter panel is observed to reduce the seismic damage when PFA ∈ [0.80 g, 2.80 g], as shown in Figure 18. The larger ceiling panel corresponds to the smaller gap. Then, the runner grid was strengthened, and the internal deformation of the runner grid was reduced. Thus, the larger panel improves the seismic capacity of the basic ceiling unit.
4.5. Boundary Conditions
To investigate the influence of the boundary, the test results of specimens A, H, and I are compared. One end of the main runner was fixed to the perimeter runners; the other ends of the main or cross runners floated on the perimeter runners in Specimen H. One end of both the main and cross runners were fixed on the perimeter runners, and the other ends floated on the perimeter runner in Specimen I. Moreover, all the ends of the main or cross runners floated on the perimeter runners in Specimen A, as shown in Figure 8.
The fixed end is found to improve the damage to the basic ceiling unit. In Specimen H, the percentage of damaged cross runners increased. In other words, a fixed boundary was able to increase the seismic capacity, as shown in Figure 19. The stronger constraints strengthen the grid and improve the seismic capacity of the basic ceiling unit.
5. Conclusions
For the mineral wool panel ceiling supported by ISBPRs, nine types of basic ceiling units were investigated based on construction. A total of 90 different test scenarios were designed and implemented for the nine groups of specimens.
Six types of damage phenomena and corresponding repair measures were analyzed for the basic ceiling units, and two types of failure processes were considered.
In a certain PFA range, the hanger rod and hanger rod–diagonal wires were able to effectively reduce the percentage of fallen panels. However, when the PFA was large, the hanger rod–diagonal wires aggravated the damage.
The measures used for improving the seismic bearing capacity were as follows: large panel, lightweight panel, high suspension height, and fixed boundary. Additionally, the large panel effectively reduces the percentage of fallen panels by increasing the amount of material by 1.7%. Moreover, fixing the boundary joint with adhesive is a convenient method for improving the seismic capacity at a low cost.
The results contribute to the enhancement of the seismic performance, the resilience of urban infrastructure, and the promotion of urban sustainability.
Conceptualization, D.W. and T.W.; methodology, D.W.; validation, D.W.; formal analysis, D.W., Y.W., W.L. and L.X.; investigation, Y.W., W.L. and L.X.; resources, D.W.; data curation, Y.W., W.L. and L.X.; writing—original draft preparation, D.W. and Y.W.; writing—review and editing, D.W. and T.W.; visualization, Y.W., W.L. and L.X.; supervision, D.W.; project administration, D.W.; funding acquisition, D.W. All authors have read and agreed to the published version of the manuscript.
Not applicable.
Not applicable.
Further data that support the findings of this study are available from the corresponding author upon reasonable request.
The authors declare that they have no conflict of interest.
Footnotes
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Enlarge this image.Figure 1. Seismic damage to ceilings of the Radio and Television Center (Lushan earthquake, China).
Enlarge this image.Figure 2. Seismic damage to ceilings of the Qionglai High River Middle School (Lushan earthquake, China).
Enlarge this image.Figure 3. Diagram of mineral wool panel ceiling.
Enlarge this image.Figure 4. Layout of specimen and carrier (unit: mm).
Enlarge this image.Figure 5. Specimens and carriers on shaking table.
Enlarge this image.Figure 6. Geometry of ceiling elements (unit: mm).
Enlarge this image.Figure 7. Layout and numbering of basic units.
Enlarge this image.Figure 8. Nine basic ceiling unit specimens.
Enlarge this image.Figure 8. Nine basic ceiling unit specimens.
Enlarge this image.Figure 8. Nine basic ceiling unit specimens.
Enlarge this image.Figure 9. Arrangement of sensors.
Enlarge this image.Figure 10. History of the earthquake motion.
![View Image - Figure 11. Acceleration spectra of the Wolong earthquake motion compared with the standard spectrum [1].](https://media.proquest.com/media/hms/THUM/8/FwR1W?_a=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%2BgIBWYIDA1dlYooDHENJRDoyMDI2MDUxNzAwNTMwNDg5NTo1NzE1ODQ%3D&_s=KmokTLRg0zE%2B7nzpFcoHSToiYbU%3D "View Image - Figure 11. Acceleration spectra of the Wolong earthquake motion compared with the standard spectrum [1].")
Enlarge this image.Figure 11. Acceleration spectra of the Wolong earthquake motion compared with the standard spectrum [1].
Enlarge this image.Figure 12. Damage phenomena.
Enlarge this image.Figure 12. Damage phenomena.
Enlarge this image.Figure 13. Failure process initiated by falling ceiling panel.
Enlarge this image.Figure 14. Failure process initiated by damage to the M–C joint.
Enlarge this image.Figure 15. Effect of hanger wire arrangement.
Enlarge this image.Figure 16. Effect of hanger rods and hanger rod–diagonal wires.
Enlarge this image.Figure 16. Effect of hanger rods and hanger rod–diagonal wires.
Enlarge this image.Figure 17. Effect of suspension height.
Enlarge this image.Figure 17. Effect of suspension height.
Enlarge this image.Figure 18. Effect of ceiling panel size.
Enlarge this image.Figure 19. Effect of boundary conditions.
Details of joints.
| Joint | Standard or Common Engineering Practices | Construction |
|---|---|---|
| Joint of main runner–cross runners (M–C) | [Image omitted. Please see PDF.] | [Image omitted. Please see PDF.] |
| Joint of main/cross runner–perimeter runners (M/C–P) | [Image omitted. Please see PDF.] | [Image omitted. Please see PDF.] |
| Joint of hanger wires–main runners | [Image omitted. Please see PDF.] | [Image omitted. Please see PDF.] |
| Joint of hanger rods–main runners | [Image omitted. Please see PDF.] | [Image omitted. Please see PDF.] |
Description of basic ceiling unit specimens.
| Specimen | Constructions | |||||
|---|---|---|---|---|---|---|
| Hanger Joint | Hanger Rod | Diagonal Wire | Suspension Height (mm) | Size of Panel |
Boundary | |
| A | 1, 3, 4, 6 | No | No | 600 | 594 × 594 × 14 | Floating on four sides |
| B | 1–6 | No | No | 600 | 594 × 594 × 14 | Floating on four sides |
| C | 1, 4, 6 | Joint 3 | No | 600 | 594 × 594 × 14 | Floating on four sides |
| D | 1, 4, 6 | Joint 3 | Yes | 600 | 594 × 594 × 14 | Floating on four sides |
| E | 1, 3, 4, 6 | No | No | 1200 | 594 × 594 × 14 | Floating on four sides |
| F | 1, 3, 4, 6 | No | No | 600 | 599 × 599 × 14 | Floating on four sides |
| G | 1, 3, 4, 6 | No | No | 600 | 594 × 594 × 28 | Floating on four sides |
| H | 1, 3, 4, 6 | No | No | 600 | 594 × 594 × 14 | One end of main runner fixed |
| I | 1, 3, 4, 6 | No | No | 600 | 594 × 594 × 14 | Adjacent sides fixed |
PGA of each run.
| Specimen | Serial Number of the Run | PGA (g) | ||
|---|---|---|---|---|
| x | y | z | ||
| A | A-1 | 0.10 | 0.085 | 0.065 |
| A-2 | 0.20 | 0.170 | 0.130 | |
| A-3 | 0.30 | 0.255 | 0.195 | |
| A-4 | 0.40 | 0.340 | 0.260 | |
| A-5 | 0.50 | 0.425 | 0.325 | |
| A-6 | 0.60 | 0.510 | 0.390 | |
| A-7 | 0.75 | 0.638 | 0.487 | |
| A-8 | 1.00 | 0.850 | 0.650 | |
| A-9 | 1.20 | 1.020 | 0.780 | |
| A-10 | 1.50 | 1.275 | 0.975 | |
Damage degree and repair measures for basic ceiling units.
| Component | Degree of Damage | Damage Characteristics | Repair Measure |
|---|---|---|---|
| Cross runner | Minor | Slight drift of cross runner at the M–C joint; not separated | Simple repair |
| Major | Large deformation of cross runner at the M–C joint | Replacement | |
| Fallen cross runner | Replacement | ||
| Main runner | Major | Large deformation of main runner | Replacement |
| Fallen main runner | Replacement | ||
| Ceiling panel | Minor | Tilting at corner or side of panel | Simple repair |
| Slight damage to corner or side of panel | Simple repair | ||
| Major | Severe damage or fallen panel | Replacement | |
| Joint of |
Minor | Slight deformation of hanger piece | Replacement |
| Major | Severe deformation of suspension joint at main runner | Replacement |
Classification of damage states.
| Damage State | Damage Description | Repair Measures | Fallen Panel Percentage |
|---|---|---|---|
| I | - | - | <5% |
| II | Few ceiling panels fall, and some slip | Replace fallen ceiling panels | 5–30% |
| III | Part of ceiling panel falls or part of runner is damaged | Replace fallen damaged runner and fallen part of ceiling panel | 30–50% |
| IV | Numerous ceiling panels fall, and a large area of runner grid is damaged | Replace fallen ceiling panels, and reinstall runner grid | >50% |
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; Wang, Yixing 1 ; Lu, Weikang 2 ; Xie, Li 1 ; Wang, Tao 1 1 Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China;
2 The Second Monitoring and Application Center, China Earthquake Administration, Xi’an 710054, China;