the experiment on earthquake-proof performance … experiment on earthquake-proof performance of...

The experiment on earthquake-proof performance of stainless steel piping with pipe fitting of the mechanical type for water supply Kazuharu Tsuneto(1), Kyosuke Sakaue(2), Tetsuhiko Aoki(3), Hiroshi Iizuka(4), Yukinobu Yokote(5), and Tsutomu Nakamura(6)

1. [email protected] 2. [email protected] 3. [email protected] 4. [email protected] 5. [email protected] 6. [email protected] 1. Engineering Department, O.N.INDUSTRIES LTD , Japan 2. Dept. of Architecture, School of Science and Technology, Meiji University, Japan 3. Dept. of Civil and Environmental Engineering, Aichi Institute of Technology, Japan 4.M&E Engineering Department, NIKKEN SEKKEI LTD , Japan 5.Mechanical & Electrical Engineering Department,SHIMIZU CORPORATION,Japan 6. Technical Headquarters, SUGA CO., LTD. , Japan Abstract In Japan stainless steel piping system has been widely used in hospitals, hotels and other public buildings from a standpoint of safety and durability. Two types of pipe fitting −mechanical type and housing type −are mainly used in the system. On the other hand, The Great Hanshin Earthquake in 1995 and The off the Pacific Coast of Tohoku Earthquake in 2011 prompted the necessity for further improvement in earthquake-proof performance of water supply piping in buildings. In view of this trend, the authors conducted a series of experiments on stainless water supply piping with the mechanical type fitting applying various excitation waves by using a shaking table. The tested water supply piping was 2.8 m long vertical pipes with diameters of 50 Su and 100 Su having horizontal branch. As a result of shaking test, sufficient seismic resistance performance was confirmed for all pipes.

CIBW062 Symposium 2013

473

Keywords stainless steel piping system, earthquake, earthquake-proof performance, pipe fitting of the mechanical type, shaking test 1 Introduction The water supply systems in Japan are built on the premise that supplied water is safe to drink. Therefore the following factors must be taken into account in terms of safety, hygiene and durability of the system: a) Water supplied by the system should be free of any toxic substances. b) The system should be reasonably durable against corrosion, earthquake, etc. c) The materials used to build the system should be 100% recyclable. To meet these requirements, stainless steel piping system has been widely used in building equipment plumbing including both public water supply and interior piping systems particularly in buildings such as hospitals, hotels and other pubic buildings where safety, hygiene and durability play an important role. Because of its good manipulability, thin-walled stainless steel pipe with thickness of 1 mm to 2.0 mm as prescribed in JIS G3448 have been widely used in these plumbing systems. Although two types of pipe fitting of mechanical and housing are available, the mechanical type pipe fitting exclusively designed for thin-walled stainless steel pipe tends to be preferred as it is easily handled and connected on construction sites. Meanwhile, some secondary disasters due to the breakdown of building equipment plumbing such as indoor water supply piping are known to have occurred during the Great Hanshin Earthquake in 1995 and the off the Pacific Coast of Tohoku Earthquake in 2011. [1,2] Since then improvements, in particular, of earthquake-proof performance in water supply piping have been particularly promoted from the viewpoint of BCP (Business Continuity Plan) [3] that seeks functional maintenance. In view of this, we conducted a series of seismic experiments for the earthquake-proof performance of the stainless steel piping system with pipe fitting of mechanical type. This piping system has been widely used in buildings such as hospitals, hotels, and other pubic buildings where safety, hygiene, and durability play an important role. One horizontal branch pipe was connected to vertical pipes by the real scale in the test and dynamic shaking experiments were carried out by various seismic waves. 2 Shaking equipment, test piping, and details of experiments 2.1 Shaking equipment and test piping Figure 1 shows the outline of the experimental facility where shaking equipment was installed. The detail of shaking equipment is shown in Figure 2. The equipment, consisting of a shaking table and a shaking machine, was placed on the seismic isolation


474

floor so that vibrations from the machine should not have any influence on other measuring instruments.

Figure 1- Building for experiments Figure 2- Shaking equipment The shaking machine used is 250kN hydraulic shaking machine Model/Type 244.31 SLVDT (Stroke: 800mm) made by MTS Systems Corporation shown circled in Figure 2. The photograph of the seismic isolation floor is shown in Figure 3. The test piping is shown in Figure 4, and the layout of test piping in Figure 5.

Figure 3- Seismic isolation floor Figure 4- Drawing of piping Figure 5- piping Two types of stainless steel pipes, 50Su and 100Su specified in JIS G3448 were used for vertical pipes, and the upper and lower sections were connected with U-bolts. Stainless steel mechanical fittings were attached at 1200 mm from the lower secured section. The upper and lower sections were connected in such a way that the upper and lower secured sections were 2800 mm apart. The fittings were secured with reducing tees and horizontal branch pipes were connected. The horizontal branch pipes were secured with a table attached to the shaking table. Branch pipes of 20Su and 50Su were used for the 50Su vertical pipe and 100Su vertical pipe respectively.

Seismic isolation floor

Shaking to-and-fro

Cei

ling

Floo

r

U-bolt

U-bolt


475

Water pressure of 2.0MPa was applied to a sealed test piping and water leakage was checked with a Bourdon pressure gauge. The structures of the pipe fittings used in the experiments are shown in Figure 6. The reflecting plate of a laser displacement meter and an accelerometer shown in Figure 7 were attached to the reducing tees of 50Su and 100Su vertical pipes. The reflecting plate of a laser displacement meter and an accelerometer were also attached to the shaking table to measure acceleration and displacement. 60Su or less 75Su,80Su,100Su

Figure 6- Structure of pipe fitting of the mechanical type The measuring instrument of all kinds in this experiments are as given below. Accelerometer : Tokyo Sokki Kenkyujo Co.,Ltd. ARF-50A 2 units

ARF-100A-T 1 unit Laser displacement meter : OPTEX FA CO., LTD.

Controller CD5A-N Sensor heads CD5-W2000 2 units

CD5-W500 1 unit Instrument : Tokyo Sokki Kenkyujo Co.,Ltd. Strain measurement DRA-30A Measurement Software: Tokyo Sokki Kenkyujo Co.,Ltd. Visual LOG DRA-7630 Reflecting plate Accelerometer

Figure 7- Reflecting plate for laser displacement meter and accelerometer 2.2 Details of experiments Four experiments showed below were carried out. 1. Sweep test Seismic waves of 1.0 ~ 10.0 Hz were administered in increments of 0.1 Hz to measure the response magnification factor of response acceleration at the reducing tees of the vertical pipes to determine the resonance frequency of the piping. The frequency with the largest response magnification factor was taken as the resonance frequency.

Stainless steel pipe

Stainless steel pipe


476

2. Resonance test Based on the resonance frequency obtained in the sweep test, input acceleration of 800 gal was applied for 30 seconds to measure the response acceleration at the reducing tees of the vertical pipes, and leakage from and deformation of the test piping were checked. 3. Relative-story displacement test Relative-story displacement 1/50 with input acceleration of 800 gal was applied to the test piping for 30 seconds, and the response acceleration and displacement were measured at the reducing tees of the vertical pipes to check leakage from and deformation of the test piping. 4. Earthquake wave test Seismic waves with maximum acceleration of 818 gal were recorded at Kobe JMA observatory during The Great Hanshin Earthquake in 1999. We simulated seismic waves that could have reached height of the tenth floor if an earthquake of the same magnitude had occurred and applied them to the test piping, and checked the piping for leakage and deformation. 3 Results and considerations 3.1 Sweep test The results of the sweep test are shown in Figure 8 and Table 1.

Figure 8- Seismic frequency and acceleration response magnification factor

Table 1 Resonance frequency, resonance period and acceleration response magnification factor

Size Frequency Period Magnification factor 50Su 6.8Hz 0.15sec. 5.6 100Su 9.2Hz 0.11sec. 1.5

As a result, an extremely large response magnification factor for small diameter pipes was created, which indicated that the influence of seismic waves on thin pipes could not be ignored.


477

3.2 Resonance test From the results of the sweet test, resonance frequencies of 6.8 Hz and 9.2 Hz were obtained for 50Su and 100Su respectively. These frequencies were applied for 30 seconds under the input acceleration of 800 gal from the shaking equipment. The results are shown in Figures 9, 10 and Table 2.

Figure 9- 50Su,response acceleration Figure 10- 100Su, response acceleration

Table 2 Resonance test results

Magnification factors of maximum response acceleration in response to input acceleration were 3.0 times for 50Su and 1.2 times for 100 Su. As there was no leakage or deformation seen in the test piping, its continued use was ensured. There was a tendency for response magnification factor to become large in thin pipes with smaller diameters. The currently published earthquake-proof design and construction guidelines do not give much consideration to thin pipes [4]. During the off the Pacific Coast of Tohoku Earthquake seismic waves with acceleration of over 1,300 gal were recorded at 10 locations. The period derived from the velocity response spectrum and the acceleration response spectrum were found out to be relatively short (0.2 sec. to 0.6 sec.) indicating the necessity of measures against resonance. 3.3 Relative-story displacement test In order to make relative-story displacement 1/50 (story drift angle 0.02 rad.) for the piping height of 2,800 mm, we loaded seismic table displacement of 56 mm with input acceleration of 800 gal on the test piping. The results of the test are shown in Figures 11, 12 and Table 3.

Size

Resonance

frequency

Resonanceperiod

Input acceleration

Input displacement

The max. acceleration

50Su 6.8Hz 0.15sec. 800gal 5.7mm 2,426gal100Su 9.2Hz 0.11sec. 800gal 2.0mm 963gal


478

Figure 11- 50Su,response acceleration Figure 12- 100Su, response acceleration

Table 3 Relative-story displacement test results

JMA intensity obtained from input acceleration and input period recorded the maximum 7. From the results the actual relative-story displacement was found to be 1/50.5 (with the story drift angle of 0.020 rad.). No leakage or deformation that may adversely affect the extended use was seen in the test piping. The movements of the test piping measured by the displacement meter are shown in Figure 13.

Figure 13- Shaking motion of the test piping If the test pipe is fixed at upper and lower ends without fittings (Figure 14), structural mechanics predicts that the following stress would be produced in the pipe (relative-story displacement δ/L=1/50.5). [5]

Input Input Input The max. The max. Size acceleration displacement period acceleration displacement 50Su 800gal 55.5mm 1.7Hz 845gal 32.3mm 100Su 800gal 55.5mm 1.7Hz 880gal 33.7mm

33.7mm 32.3mm

55.5mm

55.5mm

Displacement mm Displacement mm

2800


479

Bending moment generated in the fixed both ends M= ±6EIδ/L2 Max. stress σmax.= MD/2I = ±3EDδ/L2 δ/L= Relative-story displacement, D= pipe outside diameter E= young's modulus =193kN/mm2

Outside diameter of 50Su 48.6mm, Outside diameter of 100Su 114.3mm, Therefore, Max. stress σ max. : σ max. (50Su)= 199.2 N/mm2

σ max. (100Su)= 468.5 N/mm2 Figure 14- Piping fixed both ends

The strength of SUS304 pipes is defined in JIS G 4305 as having tensile strength of 520 N/mm2 or more and yield strength of 205 N/mm2 or more. There are several types of stress that are exerted on pipes: stress due to their own weight, stress due to water pressure, bending stress caused by seismic acceleration and stress caused by relative-story displacement. [6] When other stresses were added to the relative-story displacement described above, there would be a possibility of plastic deformation and breakage. However, the results of the experiments clearly indicate that the earthquake-proof performance of pipes could be improved with the adoption of a sufficient supporting method and the use of earthquake-proof fittings. 3.4 Earthquake wave test Resonance frequencies are likely to occur at the height equivalent of the tenth floor in the RC structure. We simulated the condition and applied response seismic waves. The maximum relative-story displacement was 1/19.6. The displacements of seismic waves used are shown Figure 15, and accelerations in Figure 16. The test results including the response accelerations of fittings are shown in Table 4.

Figure 15- Displacement of earthquake wave

Dis

plac

emen

t m

m

P


480

Figure 16- Acceleration of earthquake wave

Table 4 Earthquake wave test results (The maximum value)

No leakage or deformation that may adversely affect the extended use of the piping was seen. The results here also suggest the occurrence of resonance in thin pipes requiring the implement of some measures against resonance in thin pipes. 3.5 Test piping after experiments The test piping with fittings were checked for leakage and loosening after all the tests had been completed, and none was found. We also took the fittings apart and checked for deformation and breakage. A deformation caused by the U-bolt was found in the upper secured section that supported the test piping. However, it was not serious enough to lead to leakage or to adversely affect its continued use.

Figure 17- Test piping Figure 18- Pipe at the upper supporting part The condition of the connection of the fitting with the vertical pipe 100 Su is shown in Figure 19. There were some scratches due to vibrations inside the fitting and at the connection, but they were not serious enough to damage the pipes or to adversely affect

Input Relative-

story Story drift Input Response

Size displacement displacement angle acceleration acceleration50Su 142.6mm 1/19.6 0.051rad. 1,079gal 1,524gal 100Su 142.6mm 1/19.6 0.051rad. 1,079gal 1,029gal

50Su 100Su

Acc

eler

atio

n ×

100g

al


481

their continued use. No loosening was seen in the nuts and bolts that connected the pipe and the fitting.

Figure 19- Abrasion of pipe and fitting in the joint 1 As is the case with the vertical pipe 100 Su, there were also some scratches due to vibrations inside fitting and at the connection of the vertical pipe 50 Su and the branch pipes 20Su. The damage was not serious enough to adversely affect the continued use of the parts. Nor was there any loosening of the nuts that connected the pipe and the fitting.

Figure 20- Abrasion of pipe in the joint 2 and 3 4 Conclusions 1. In the resonance test, there was a tendency of the acceleration response magnification factor to become larger in thin pipes. Therefore some measures against resonance with short period are thought to be necessary. 2. From the results of the relative-story displacement test, it is conceivable that the adoption of a sufficient supporting method and the use of earthquake-proof fittings play an important role in improving the earthquake-proof performance of pipes. 3. The results of the earthquake wave test, along with those of the resonance test, indicate that there is a possibility of resonance in thin pipes. 4. The conditions of pipes and fittings after the tests indicated that there was some deformation in pipes caused by U-bolts that supported the vertical pipe. However, the

③20Su ②50Su

1

2 3


482

Kazuharu Tsuneto is Engineering Department deputy manager in O.N. INDUSTRIES LTD and a member of The Society of Heating,Air-Conditioning and Sanitary Engineers of Japan. His research interests include the safety, durability, and economy of the stainless steel plumbing systems.

extent of deformation was minimal so that it did not have any adverse effects on the continued use of the pipes. It is indicated that the earthquake-proof performance of pipes improved with the use of the supporting method and fittings.

5 References 1.Editorial Committee for the Report on the Hanshin-Awaji Earthquake Disaster,

‘Report on the Hanshin-Awaji Earthquake Disaster ,Building Series Volume-7, Building Equipments and Environment’, Architectural Institute of Japan , pp.61-67,1999.

2.The tohoku earthquake investigation committee,’ March.11th.2011,The off the Pacific Coast of Tohoku Earthquake, The report about building equipments damage ‘, The Society of Heating, Air-Conditioning and Sanitary Engineers of Japan, pp.80-81, 2013.

3. Takehiro Tanaka ,’ The report on BCP, BCM for construction and preservation’, Heating, air-conditioning and sanitary engineering, Volume 87, no.48, pp.15-26,2013.

4. 2005 edition editorial committee,’ Earthquake-proof design and construction guideline for building equipment’, The Building Center of Japan, pp.41-69,2005.

5. Tetsuhiko Aoki,’Structural Mechanics’,CORONA PUBLISHING CO., LTD. pp.247- 248,1986.

6. Society of Heating, Air-Conditioning and Sanitary Engineers of Japan ,’ Earthquake-proof design and construction method for building equipment’, pp.117-120,2012.

6 Presentation of Author


483

the experiment on earthquake-proof performance … experiment on earthquake-proof performance of...

Documents