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 Seismic Behavior of a Typical Sprinkler Piping System in Hospitals

2014 ◽  
Author(s):  
Fan-Ru Lin ◽  
Kuo-Chun Chang ◽  
Juin-Fu Chai ◽  
Zhen-Yu Lin ◽  
Wen-I Liao ◽  
...  
Keyword(s):  
Failure Modes ◽  
Hysteresis Loops ◽  
Shear Capacity ◽  
Shaking Table ◽  
Piping System ◽  
Inelastic Behavior ◽  
Improvement Strategy ◽  
Flexible Pipes ◽  
Piping Systems ◽  
Cyclic Loading Tests

Based on the immediate needs of emergency medical services provided by hospitals after strong earthquakes, this paper is to introduce a research program on assessment and improvement strategies for typical configuration of sprinkler piping systems in hospitals. The study involved component tests and subsystem tests. Cyclic loading tests were conducted to investigate inelastic behavior of components including concrete anchorage, screwed fittings of small bore piping and mechanical couplings. Parts of horizontal piping systems of the aforementioned seismic damaged sprinkler piping system were tested using shaking table tests. Furthermore, the horizontal piping subsystems with seismic resistant devices such as braces, flexible pipes and mechanical couplings were tested. The test results show that the main cause of the damaged case is the poor shear capacity of the screwed fitting of the small-bore tee branch. The optimum improvement strategy to achieve higher nonstructural performance level for the horizontal piping subsystem is to strengthen the main pipe with braces and to decrease shear demands on the tee branch by 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.

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.

Trial Model Tests With Simulation Material to Obtain Failure Modes of Pipes Under Excessive Seismic Loads

2016 ◽  
Author(s):  
Izumi Nakamura ◽  
Naoto Kasahara
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Experimental Studies ◽  
Shaking Table ◽  
Seismic Load ◽  
Seismic Loads ◽  
Steel Pipes ◽  
Piping Systems ◽  
Collapse Failure ◽  
Input Motion

Piping systems are one of the central components of NPP; It is well known that the major failure mode under seismic loads is likely to be fatigue failure. Other failure modes, however, such as ratchet-buckling failure, have been reported to occur under particular conditions. It is necessary to clarify the conditions that cause different failure modes of piping systems under very high seismic motion, but experimental studies with steel pipes are difficult to achieve, mainly due to the limitations of testing facilities and safety concerns. In order to overcome such difficulties, we propose a new experimental approach that uses pipes made of a simulation material instead of steel. Lead (Pb) pipes were used for the simulation material, and shaking table tests were conducted on lead elbow pipe specimens. Results showed that ratchet-collapse and overall deformation of pipe specimens were possible failure modes. The ratchet-collapse failure mode appeared to be affected not only by input acceleration level but also by the direction of gravity, the primary constant stress level of its own weight, and the frequencies of the input motion. The dynamic behaviors of pipes in the high inelastic region where a nearly fully plastic section was assumed were quite different from those in the elastic region, and those of the steel pipes in previous studies. We demonstrate that the proposed test approach is effective for qualitatively clarifying various kinds of failure behaviors with large plasticity under excessive seismic load.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

Recent Experiences With Cracking of Load Bearing Dissimilar Metal Welds on Subsea Production Systems

2017 ◽  
Author(s):  
Lars M. Haldorsen ◽  
Gisle Rørvik ◽  
Michael Dodge ◽  
Kasra Sotoudeh
Keyword(s):  
Nickel Alloy ◽  
Production Systems ◽  
Research Programme ◽  
Testing Temperature ◽  
Welding Parameters ◽  
Piping System ◽  
Dissimilar Metal ◽  
Dissimilar Welds ◽  
Piping Systems ◽  
In The Beginning

The process piping on subsea production systems (SPS) is normally made of solid corrosion resistant alloys (CRAs). However, some process components are made of low alloyed steels (LASs) which are internally cladded with a CRA. These components require post weld heat treatment (PWHT) to improve the properties in the LAS heat affected zone (HAZ). In order to avoid PWHT during on-site welding to adjoining piping systems, it has been common to weld a buttering layer (e.g. 15 – 20mm long) on to the connecting end of the LAS. The buttering layer consumable has traditionally been an austenitic nickel alloy, Alloy 625/725. The LAS HAZ and the buttering layer are thereafter PWHT’d and machined prior to on-site welding to the adjoining piping system. By this, it is not necessary to perform PWHT on the on-site (e.g. tie-in or closure) dissimilar welds. In the beginning of the century, some operators experienced cracking along the fusion line interface between the nickel alloy buttering and the LAS. These problems were typically experienced during start-up or prior to first production. An extensive research programme was established in order to determine the causes and remedial actions. A group sponsored project led by TWI was performed to understand the failure mechanisms and essential parameters leading to hydrogen assisted cracking, (HAC) of dissimilar metal welds (DMWs). Recommendations were made related to LASs chemistry, welding parameters, bevel geometry and especially PWHT time and temperature. Based on these recommendations there have been only a few incidents with cracking of such welded combinations before 2013 and onwards. Since then Statoil has experienced four off incidents with cracking of dissimilar welds on subsea LAS components. Common for these incidents are that they have been in operation for about 15 years and the cracking happened during cold shut-down periods. This paper presents key observations made and lessons learnt from the incidents summarized above. The main focus has been on environmental fracture mechanics-based testing of samples charged with hydrogen by cathodic protection (CP). Variables have been pre-charging temperature and time, as well as testing temperature. The testing has revealed strong dependency between the operating temperature (i.e. shutdown versus operation) and the sensitivity to HAC. Further, the investigations have shown that the integrity of the coating, as an effective barrier to hydrogen ingress, is the main feature to prevent HAC on this kind of DMWs. The investigation of the four off cracked welds showed clearly that the insulating polyurethane (PU) coating was heavily degraded by hydrolysis at higher temperatures. This exposed the dissimilar weldments to CP which contributed to the hydrogen charging of the weldments. The paper gives also result that show that it is not only PWHT’d LAS (e.g. type 8630M, 4130 and F22M) with dissimilar welds that may suffer from this failure mechanism. Testing has shown that as-welded F65 steel /Alloy 59 combinations may also suffer when charged with hydrogen and tested at low temperatures (e.g. shut down temperature).

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: Computational Approach

2007 ◽  
Author(s):  
Satoshi Tsunoi ◽  
Akira Mikami ◽  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Analytical Model ◽  
Failure Modes ◽  
Experimental Investigations ◽  
Seismic Load ◽  
Piping System ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Seismic Loadings ◽  
Local Wall Thinning

The authors have proposed an analytical model by which they can simulate the dynamic and failure behaviors of piping systems with local wall thinning against seismic loadings. In the previous paper [13], the authors have carried out a series of experimental investigations about dynamic and failure behaviors of the piping system with fully circumferential 50% wall thinning at an elbow or two elbows. In this paper these experiments have been simulated by using the above proposed analytical model and investigated to what extent they can catch the experimental behaviors by simulations.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2007 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending ◽  
The Difference

In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3-D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned wall elbow, because the life of piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

scholarly journals Nonlinear Seismic Correlation Analysis of the JNES/NUPEC Large-Scale Piping System Tests

2008 ◽  
Author(s):  
Jinsuo Nie ◽  
Giuliano DeGrassi ◽  
Charles H. Hofmayer ◽  
Syed A. Ali
Keyword(s):  
Correlation Analysis ◽  
Test Data ◽  
Nuclear Power ◽  
Large Scale ◽  
Failure Modes ◽  
Plastic Behavior ◽  
Piping System ◽  
Highly Nonlinear ◽  
Piping Systems ◽  
The U.S

The Japan Nuclear Energy Safety Organization/Nuclear Power Engineering Corporation (JNES/NUPEC) large-scale piping test program has provided valuable new test data on high level seismic elasto-plastic behavior and failure modes for typical nuclear power plant piping systems. The component and piping system tests demonstrated the strain ratcheting behavior that is expected to occur when a pressurized pipe is subjected to cyclic seismic loading. Under a collaboration agreement between the U.S. and Japan on seismic issues, the U.S. Nuclear Regulatory Commission (NRC)/ Brookhaven National Laboratory (BNL) performed a correlation analysis of the large-scale piping system tests using detailed state-of-the-art nonlinear finite element models. Techniques are introduced to develop material models that can closely match the test data. The shaking table motions are examined. The analytical results are assessed in terms of the overall system responses and the strain ratcheting behavior at an elbow. The paper concludes with the insights about the accuracy of the analytical methods for use in performance assessments of highly nonlinear piping systems under large seismic motions.

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.

Seismic behavior of steel-reinforced recycled concrete inner-beam–column connection under low cyclic loads

2017 ◽  
Vol 21 (5) ◽  
pp. 631-642 ◽  
Author(s):  
Jianyang Xue ◽  
Lei Zhai ◽  
Yuze Bao ◽  
Rui Ren ◽  
Xicheng Zhang
Keyword(s):  
Seismic Behavior ◽  
Concrete Beam ◽  
Failure Modes ◽  
Hysteresis Loops ◽  
Reinforced Concrete Beam ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Cyclic Loads ◽  
Cyclic Loading Tests ◽  
Seismic Tests

This article presents the results of low cyclic loading tests on steel-reinforced recycled concrete inner-beam–column connections, including four 1:2.5 scaled specimens with different replacement rates of recycled coarse aggregates. The main objective of this study is to evaluate the seismic behavior of steel-reinforced recycled concrete inner-beam–column connection based on the seismic tests of the four specimens under low cyclic loads with vertical axial force. The main design parameter of the beam–column connections in this research is the recycled coarse aggregate replacement percentage. The crack status, failure modes, hysteresis loops, skeleton curves, energy dissipation, capacity stiffness of degradation, and ductility of steel-reinforced recycled concrete inner-beam–column connections are presented and analyzed. The results indicate that the main failure pattern of the steel-reinforced recycled concrete inner-beam–column connection is the shearing diagonal compression in the beam–column connection zone. As the recycled aggregate replacement percentage increases, both the bearing capacity and ductility of the steel-reinforced recycled concrete beam–column connections decrease to some extent. However, the seismic behavior of the steel-reinforced recycled concrete inner-beam–column connection does not degrade significantly compared with the ordinary steel-reinforced concrete beam–column connection.

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