Improved Model Tests to Investigate the Failure Modes of Pipes Under Beyond Design Basis Earthquakes

2018 ◽  
Author(s):  
Izumi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Piping System ◽  
Input Frequency ◽  
Shaking Table Tests ◽  
Pure Lead ◽  
Design Basis ◽  
Improved Model

In order to investigate the failure modes of piping systems under the beyond design basis seismic loads, the authors proposed an experimental approach to use pipes made of the simulation material instead of steel pipes in the previous study. Though the ratchet-collapse (ratchet and subsequent collapse) was successfully obtained as the failure mode through the shaking table test using the pure lead (Pb) pipes as the simulation material pipe specimens, there was concern that characteristics of pure lead was somewhat extreme considering the analogy with the stress-strain relationship of steel. In order to resolve such concern, a modified experimental procedure has been developed. In the modified procedure, lead-antimony (Pb-Sb) alloy is used as the simulation material. Through the shaking table tests on single elbow pipe specimens made of Pb-Sb alloy, it is found that the typical failure mode is the ratchet and subsequent collapse, as same as the results by the shaking table tests of the Pb pipe specimens. The results indicate that the lower input frequency than the specimen’s natural frequency is prone to cause failure to the specimen, while the higher input frequency hardly causes the failure. The tendency of the global behavior of specimens is similar each other between the Pb pipe specimens and the Pb-Sb alloy specimens, but the strength of self-weight collapse of the Pb-Sb alloy pipe specimen is much higher than that of the Pb pipe specimen. Due to such higher strength of Pb-Sb alloy pipes, a prospect to conduct an excitation test on a more complicated piping system model is obtained.

Discussion On Failure Behavior of Piping Systems Under Extremely Large Seismic Loads in BDBE

2021 ◽  
Author(s):  
Izumi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Static Loading ◽  
Failure Modes ◽  
Shaking Table ◽  
Failure Behavior ◽  
Seismic Loads ◽  
Shaking Table Tests ◽  
Additional Mass ◽  
Pure Lead ◽  
Piping Systems ◽  
Loading Tests

Abstract To investigate the failure behavior of piping systems under severe seismic loads considering beyond design basis event (BDBE), an experimental approach to use pipes made of simulation materials was applied. "Simulation material" means the substitute material for steel to realize the structural experiment by the existing testing facilities. The simulation materials adopted in this study were pure lead (Pb) or lead-antimony (Pb-Sb) alloy. Using pipe elbows made of simulation materials, static loading tests on elbows and shaking table tests on simple piping system models composed of one or two elbows and an additional mass were conducted. From the static loading tests, the load-deflection relationship of an elbow under monotonic loading was obtained as well as the fatigue failure modes under cyclic loading depending on the several cyclic displacement levels. From the shaking table tests, several failure modes were obtained, namely, "Collapse by self-weight", "Collapse by a few cycles of input", "Ratchet and subsequent collapse", "Overall deformation", and "No failure". It was considered that the occurrence of these failure modes was affected by the ratio of the input frequency to the specimen's natural frequency, the ratio of additional mass weight to the limit mass weight, the configuration of the specimen, and the input acceleration level. The experimental results indicated that it was crucial to understand the structure's ultimate behavior when treating BDBE, and that the research approach using simulation material is effective to investigate the ultimate behavior of piping systems.

scholarly journals Shaking Table Tests to Validate Inelastic Seismic Analysis Method Applicable to Nuclear Metal Components

2021 ◽  
Vol 11 (19) ◽  
pp. 9264
Author(s):  
Gyeong-Hoi Koo ◽  
Sang-Won Ahn ◽  
Jong-Keun Hwang ◽  
Jong-Sung Kim
Keyword(s):  
Seismic Analysis ◽  
Kinematic Hardening ◽  
Shaking Table ◽  
Plastic Behavior ◽  
Piping System ◽  
Test Results ◽  
Analysis Method ◽  
Shaking Table Tests ◽  
Hardening Model ◽  
Design Basis

The main purpose of this study is to perform shaking table tests to validate the inelastic seismic analysis method applicable to pressure-retaining metal components in nuclear power plants (NPPs). To do this, the test mockup was designed and fabricated to be able to describe the hot leg surge line nozzle with a piping system, which is known to be one of the seismically fragile components in nuclear steam supply systems (NSSS). The used input motions are the displacement time histories corresponding to the design floor response spectrum at an elevation of 136 ft in the in-structure building in NPPs. Two earthquake levels are used in this study. One is the design-basis safe shutdown earthquake level (SSE, PGA = 0.3 g) and the other is the beyond-design-basis earthquake level (BDBE, PGA = 0.6 g), which is linearly scaled from the SSE level. To measure the inelastic strain responses, five strain gauges were attached at the expected critical locations in the target nozzle, and three accelerometers were installed at the shaking table and piping system to measure the dynamic responses. From the results of the shaking table tests, it was found that the plastic strain response at the target nozzle and the acceleration response at the piping system were not amplified by as much as two times the input earthquake level because the plastic behavior in the piping system significantly contributed to energy dissipation during the seismic events. To simulate the test results, elastoplastic seismic analyses with the well-known Chaboche kinematic hardening model and the Voce isotropic hardening model for Type 316 stainless steel were carried out, and the results of the principal strain and the acceleration responses were compared with the test results. From the comparison, it was found that the inelastic seismic analysis method can give very reasonable results when the earthquake level is large enough to invoke plastic behavior in nuclear metal components.

Computer Simulation of the Shaking Table Tests on Harder Soil-Structure Interaction System

2011 ◽  
Vol 261-263 ◽  
pp. 1619-1624
Author(s):  
Pei Zhen Li ◽  
Jing Meng ◽  
Peng Zhao ◽  
Xi Lin Lu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Soil Structure ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Soil Structure Interaction ◽  
Shaking Table Tests ◽  
Site Condition ◽  
Element Analysis ◽  
Structure Interaction

Shaking table test on soil-structure interaction system in harder site condition is presented briefly in this paper. Three-dimensional finite element analysis on shaking table test is carried out using ANSYS program. The surface-to-surface contact element is taken into consideration for the nonlinearity of the state of the interface of the soil-pile and an equivalent linear model is used for soil behavior. By comparing the results of the finite element analysis with the data from shaking table tests, the computational model is validated. Based on the calculation results, the paper gives the seismic responses under the consideration of soil-structure interaction in harder site condition, including acceleration response, contact analysis on soil pile interface and so on.

Experimental studies of a typical sprinkler piping system in hospitals

2016 ◽  
Vol 49 (1) ◽  
pp. 1-12
Author(s):  
Zhen-Yu Lin ◽  
Fan-Ru Lin ◽  
Juin-Fu Chai ◽  
Kuo-Chun Chang
Keyword(s):  
Failure Modes ◽  
Experimental Studies ◽  
Hysteresis Loops ◽  
Research Programme ◽  
Shaking Table ◽  
Piping System ◽  
Improvement Strategy ◽  
Flexible Pipes ◽  
Piping Systems ◽  
Cyclic Loading Tests

Based on the issue of life safety and immediate needs of emergency medical services provided by hospitals after strong earthquakes, this paper aims to introduce a research programme on assessment and improvement strategies for a typical configuration of sprinkler piping systems in hospitals. The study involved component tests and subsystem tests. Cyclic loading tests were conducted to investigate the inelastic behaviour of components including concrete anchorages, screwed fittings of small-bore pipes and couplings. Parts of a horizontal piping system of a seismic damaged sprinkler piping system were tested using shaking table tests. Furthermore, horizontal piping subsystems with seismic resistant devices such as braces, flexible pipes and couplings were also tested. The test results showed that the main cause of damage was the poor capacity of a screwed fitting of the small-bore tee branch. The optimum improvement strategy to achieve a higher nonstructural performance level for the horizontal piping subsystem is to strengthen the main pipe with braces and decrease moment demands on the tee branch by the use of flexible pipes. The hysteresis loops and failure modes of components were further discussed and will be used to conduct numerical analysis of sprinkler piping systems in future studies.

Experimental Study on the Seismic Response of Subway Station in Soft Ground

2017 ◽  
Vol 11 (05) ◽  
pp. 1750020 ◽  
Author(s):  
Ma Xianfeng ◽  
Wang Guobo ◽  
Wu Jun ◽  
Ji Qianqian
Keyword(s):  
Seismic Response ◽  
Seismic Design ◽  
Shaking Table Test ◽  
Design Method ◽  
Underground Structure ◽  
Response Characteristic ◽  
Shaking Table ◽  
Subway Station ◽  
Soft Ground ◽  
Shaking Table Tests

Shaking table tests were conducted on typical models of subway structures subjected to several seismic shaking time histories to study seismic response of subway structures in soft ground as well as to provide data for validation of seismic design methods for underground structure. Three types of tests were presented herein, namely green field test, subway station test, and test for joint structure between subway station and tunnel. The similitude and modeling aspects of the 1g shaking table test are discussed. The seismic response of Shanghai clay in different depths was examined under different input waves to understand the acceleration amplification feature in both green field and in the presence of underground structure. Damage situation was checked on internal sections of both subway station and tunnels by halving the model structure. Structure deformation was investigated in terms of element strain under different earthquake loadings. The findings from this study provides useful pointers for future shaking table tests on underground structures/facilities, and the seismic response characteristic of underground structure derived from the shaking table test could be helpful for validating seismic design method for subway station.

Shaking Table Tests With Large Test Specimens of Seismically Isolated FBR Plants: Part 2—Damage Test of Reinforced Concrete Wall Structure

2009 ◽  
Author(s):  
Satoru Inaba ◽  
Takuya Anabuki ◽  
Kazutaka Shirai ◽  
Shuichi Yabana ◽  
Seiji Kitamura
Keyword(s):  
Reinforced Concrete ◽  
Seismic Isolation ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Wall Structure ◽  
Shaking Table Tests ◽  
Concrete Wall ◽  
Restoring Force ◽  
Seismically Isolated ◽  
Rubber Bearings

This paper describes the dynamic damage test of a reinforced concrete (RC) wall structure with seismic isolation sysytem. It has been expected that seismically isolated structures are damaged in sudden when the accelerations of the structures exceed a certain level by hardening of the rubber bearings. However, the response behavior and the damage mode have not been observed by experimental test yet. So, shaking table tests were carried out at “E-Defense”, equipping the world’s largest shaking table, located at Miki City, Hyogo prefecture, Japan. The specimen was composed of an upper structure of 600 ton by weight and six lead-rubber bearings (LRBs) of 505 mm in diameter which provide both stiffness and hysteretic damping. The upper structure consisted of a RC mass and four RC walls with counter weight. The RC wall structure was designed so that the damage of the RC wall occurred between the shear force at the hardening of the rubber bearings and that at their breaking. The dimensions of the RC wall were 1600 × 800 × 100 mm (B × H × t). The reinforcement ratios were 2.46% in vertical by D13 (deformed reinforcing bar, 13 mm in diameter) and 1.0% in horizontal by D10. The shaking table test was conducted consecutively by increasing the levels up to 225% of tentative design earthquake motion. Consequently, because of the increase of the structural response by the hardening of the rubber bearings, the damage of the wall structure with seismic isolation system suddenly happened. In addition, the preliminary finite element analysis simulated the test results fairly well, which were the restoring force characteristics, the crack patterns of the RC wall structure and such.

scholarly journals Shaking Table Tests for Seismic Response of Orthogonal Overlapped Tunnel under Horizontal Seismic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Honggang Wu ◽  
Hao Lei ◽  
Tianwen Lai
Keyword(s):  
Dynamic Response ◽  
Seismic Response ◽  
Seismic Wave ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Acceleration Response ◽  
Test Device ◽  
Deformation Stages ◽  
Superposition Effect

This paper presents the seismic dynamic response and spectrum characteristics of an orthogonal overlapped tunnel by shaking table tests. First, a prototype of the engineering and shaking table test device, which was used to design details of the experiment, was developed. Then, the sensors used in the test were selected, and the measurement points were arranged. Subsequently, the Wenchuan seismic wave with horizontal direction in different peak ground accelerations was inputted into the model, followed by a short analysis of the seismic response of the overlapped tunnel in the shaking table test as well as the distribution of the peak acceleration. Throughout the studies, the model exhibited obvious deformation stages during the seismic wave loading process, which can be divided into elastic, plastic, plastic enhancement, and failure stage. In particular, the time- and frequency-domain characteristics of the key parts of the tunnel were discussed in detail by using the continuous wavelet transform (CWT) based on the Morlet wavelet as the basis function. We found that the acceleration response was more intense within 25–60 s after the seismic wave was inputted. Furthermore, owing to “the superposition effect,” the seismic response at the crown of the under-crossing tunnel was stronger than that at the invert of the upper-span tunnel. The low and medium frequencies in the transformation of small scales (5–20) significantly affected the overlapped tunnel. These results elucidate the seismic dynamic response of the overlapped tunnel and provide guidance for the design of stabilizing structures for reinforcing tunnels against earthquakes.

Investigation on Failure Behavior of Two-Elbow Piping System Models Made of the Simulation Material Under Excessive Seismic Loads

2020 ◽  
Author(s):  
Izumi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Failure Modes ◽  
Shaking Table ◽  
System Model ◽  
Failure Behavior ◽  
Piping System ◽  
Seismic Loads ◽  
Sinusoidal Wave ◽  
Additional Mass ◽  
System Models ◽  
Piping Systems

Abstract To investigate the failure behavior of piping systems under excessive seismic loads, shaking table tests on piping system models made of a simulation material have been executed. The simulation material adopted in the experiment was lead-antimony (Pb-Sb) alloy. The piping system model was composed of two elbows made of Pb-Sb alloy, one additional mass, and two fixed anchors. Input motions were sinusoidal wave. The failure modes of the piping system were examined by varying the additional mass and frequency of the input sinusoidal wave. Through the excitation tests, the failure mode which was named as “ratchet and subsequent collapse” was obtained successfully. The result which was classified as “no failure after 500 cycles” was also obtained. It was found that the occurrence of the failure depended on the ratio of the input frequency to the specimen’s natural frequency, and the ratio of additional mass weight to the limit mass weight. Though the effect of higher modes on the failure behavior was necessary to be more investigated, it seemed that the tendency of dominant failure behavior was similar to that of the single-elbow specimen investigated in the previous study. Moreover, it was confirmed that the experimental approach to use a simulation material was applicable for piping system model with multiple elbows.

BEHAVIOR OF NONSTRUCTURAL COMPONENT SUPPORTED BY HANGER BOLTS UNDER SEISMIC EXCITATIONS BY SHAKING TABLE TEST

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Haeyoung Kim ◽  
Kunio Mizutani ◽  
Syojiro Motoyui
Keyword(s):  
Shaking Table Test ◽  
Great East Japan Earthquake ◽  
Shaking Table ◽  
Structural Members ◽  
Shaking Table Tests ◽  
Seismic Excitations ◽  
Nonstructural Components ◽  
Pipe System ◽  
Long Period ◽  
Steel Building

During the Great East Japan Earthquake of March 2011, nonstructural components, such as pipe systems, ducts, cable racks and ceilings were severely damaged while main structural members in the building were not damaged seriously. Pipes, cable racks, apparatus and ducts’ hanger bolts were ruptured causing the equipment to fall down. Because of these damages, buildings cannot be used for a long period of time and one person was killed by pipe’s falling in Japan. In this study, the behaviors of nonstructural components are investigated by conducting shaking table tests to verify the cause of damage. More specifically, damage to hanger bolts is investigated by simulating its rupturing mechanism through shaking table test. To simulate the real installation condition of nonstructural components, apparatus-duct-pipe system supported by hanger bolts is selected as specimen. Roof floor response wave at the actual 5-story steel building under the Great East Japan Earthquake and sweep wave are used for the input waves. The maximum response acceleration was about 4 G in X direction under response wave 75% and the damage occurred at the metal fitting which is the connection part between braces and hanger bolt. And without installing braces, the upper hanger bolts at the fixed supporting part were ruptured easily since the natural frequency of the specimen closed to those of target building during excitations and the response became huge.

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