Analytical Seismic Fragility Analyses of Fire Sprinkler Piping Systems with Threaded Joints

2015 ◽  
Vol 31 (2) ◽  
pp. 1125-1155 ◽  
Author(s):  
Siavash Soroushian ◽  
Arash E. Zaghi ◽  
Manos Maragakis ◽  
Alicia Echevarria ◽  
Yuan Tian ◽  
...  
Keyword(s):  
San Francisco ◽  
Experimental Results ◽  
System Level ◽  
Seismic Fragility ◽  
Piping System ◽  
Inelastic Behavior ◽  
Demand Model ◽  
Piping Systems ◽  
Threaded Joints ◽  
Fire Sprinkler

For the first time, an analytical modeling methodology is developed for fire sprinkler piping systems and used to generate seismic fragility parameters of these systems. The analytical model accounts for inelastic behavior constituents of the system, including: threaded joints, solid braces, hangers, and restrainers. The model incorporates a newly developed hysteresis model for threaded tee joints that is validated by the experimental results of several tee subassemblies. The modeling technique at the subsystem level is validated by using the experimental results of a sprinkler piping system. The methodology is used to obtain the seismic response of the fire sprinkler piping system of University of California, San Francisco Hospital under a suite of 96 artificially generated triaxial floor acceleration histories. After the component fragility parameters are obtained for the components of the system, three system-level damage states are defined, and a joint probabilistic seismic demand model is utilized to develop system fragility parameters.

Fragility Analysis of Threaded T-Joint Connections in Hospital Piping Systems

2011 ◽  
Author(s):  
Bu Seog Ju ◽  
Sashi Kath Tadinada ◽  
Abhinav Gupta
Keyword(s):  
Cyclic Loading ◽  
Time History ◽  
System Level ◽  
Seismic Fragility ◽  
Piping System ◽  
Multiple Time ◽  
Damage State ◽  
Non Linear ◽  
Piping Systems ◽  
Joint Section

The cost of damage to the non-structural systems in critical facilities like nuclear power plants and hospitals can exceed 80% of the total cost of damage during an earthquake. Studies assessing damage from the 1974 San Fernando and 1994 Northridge earthquakes reported a widespread failure of non-structural components like sprinkler piping systems (Ayer and Phillips, 1998). The failure of piping systems led to leakage of water and subsequent shut-down of hospitals immediately after the event. Consequently, probabilistic seismic fragility studies for these types of structural configurations have become necessary to mitigate the risk and to achieve reliable designs. This paper proposes a methodology to evaluate seismic fragility of threaded T-joint connections found in typical hospital floor piping systems. Numerous experiments on threaded T-joints of various sizes subjected to monotonic and cyclic loading conducted at University of Buffalo indicate that the “First Leak” damage state is observed predominantly due to excessive flexural deformations at the T-joint section. The results of the monotonic and cyclic loading tests help us evaluate the following characteristics for a given pipe size and material: (i) Maximum allowable value of rotational deformation at the T-joint section to prevent “First Leak” damage state; (ii) The force-displacement and moment-rotation relationships at the T-joint section. A non-linear finite element model for the T-joint system is formulated and validated with the experimental results. It is shown that the T-joint section can be satisfactorily modeled using non-linear rotational springs. The system-level fragility of the complete piping system corresponding to the “First Leak” damage state is determined from multiple time-history analyses using a Monte-Carlo simulation accounting for uncertainties in demand.

Seismic Fragility Study of Displacement Demand on Fire Sprinkler Piping Systems

2014 ◽  
Vol 18 (7) ◽  
pp. 1129-1150 ◽  
Author(s):  
Siavash Soroushian ◽  
Arash E. Zaghi ◽  
E. “Manos” Maragakis ◽  
Alicia Echevarria
Keyword(s):  
Seismic Fragility ◽  
Piping Systems ◽  
Displacement Demand ◽  
Fire Sprinkler

Inelastic Behavior of Threaded Piping Connections: Reconciliation of Experimental and Analytic Results

2011 ◽  
Author(s):  
Yonghee Ryu ◽  
Anahid Behrouzi ◽  
Tsega Melesse ◽  
Vernon C. Matzen
Keyword(s):  
Inelastic Behavior ◽  
Test Results ◽  
Element Analysis ◽  
Shell Elements ◽  
Rotational Spring ◽  
Beam Elements ◽  
Piping Systems ◽  
Threaded Joints ◽  
Rigid Connection ◽  
Euler Bernoulli Beam

Modeling the behavior of piping systems with threaded joints is difficult because the joints do not act as rigid connections. At one level of approximation the connection can be modeled as a semi-rigid connection using a rotational spring. This study modeled a straight pipe using either Euler-Bernoulli beam elements [4] or Finite Element Analysis (FEA) shell elements and a support condition using the rotational spring. Laboratory tests were conducted on 1 in. diameter specimens of black iron Schedule 40 pipe in a cantilever configuration. The specimen was loaded monotonically into the inelastic region. A Ramberg-Osgood model [5] was used to represent the rotational spring and the correlation between test results and analytical predictions was quite good.

Evaluation of Inelastic Seismic Response of a Piping System Using a Modified Iterative Response Spectrum Method

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
A. Ravikiran ◽  
P. N. Dubey ◽  
M. K. Agrawal ◽  
G. R. Reddy ◽  
K. K. Vaze
Keyword(s):  
Failure Mode ◽  
Seismic Event ◽  
Response Spectrum ◽  
Experimental Results ◽  
Piping System ◽  
Strain Accumulation ◽  
Shake Table Tests ◽  
Accumulated Strain ◽  
Piping Systems ◽  
Inelastic Seismic Response

In pressurized piping systems, strain accumulation may take place due to cyclic loading during a seismic event. This incremental plastic deformation called ratcheting may lead to failure of the piping systems. There is no numerical method available to evaluate this accumulated strain in the piping system using response spectrum as input. In the literature, incremental hinge technique is available to predict the failure level conservatively by considering static collapse as the failure mode. However, it is observed from shake table tests that failure in the piping components, especially in elbows, is due to ratcheting. Considering this failure mode and design input as a response spectrum, a modified incremental hinge technique is developed and validated with experimental results. The strain predicted by this analysis closely matches with that of experimental results which are available up to an excitation of 0.75 g ZPA (zero period acceleration). In the experiment, the pressure boundary rupture occurred at 2 g ZPA, while the analysis predicts the failure of the piping system at 2.37 g ZPA. Details of these investigations are presented in the paper.

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.

Seismic Fragility Study of Fire Sprinkler Piping Systems

2013 ◽  
Author(s):  
Siavash Soroushian ◽  
Arash E. Zaghi ◽  
Manos Maragakis ◽  
Alicia Echevarria ◽  
Yuan Tian ◽  
...  
Keyword(s):  
Seismic Fragility ◽  
Piping Systems ◽  
Fire Sprinkler

Experimental Seismic Fragility of Pressurized Fire Suppression Sprinkler Piping Joints

2014 ◽  
Vol 30 (4) ◽  
pp. 1733-1748 ◽  
Author(s):  
Yuan Tian ◽  
Andre Filiatrault ◽  
Gilberto Mosqueda
Keyword(s):  
Fire Suppression ◽  
Seismic Fragility ◽  
Experimental Program ◽  
Joint Rotation ◽  
Global Demand ◽  
Piping Systems ◽  
Critical Facilities ◽  
Threaded Joints ◽  
Using Data ◽  
Analysis Models

Pressurized fire suppression sprinkler piping is a critical nonstructural system that must remain operational after an earthquake, particularly in critical facilities. Observations from past earthquakes have demonstrated that the locations most susceptible to damage in sprinkler piping systems are the joints, sprinkler heads, support hangers, and bracing systems. However, field observations and previous experimentations are insufficient to fully characterize the response of sprinkler piping systems under seismic actions and to develop effective solutions to improve their performance. This paper presents the results of an experimental program designed to evaluate the seismic behavior of sprinkler piping joints. Forty-eight tee joints made of various materials (black iron with threaded joints, thermoplastic (CPVC) with cement joints, and steel with groove-fit connections) and nominal diameters (¾ in. to 6 in.) were tested under reverse cyclic loading to determine their rotational capacities at which leakage and/or fracture occur. The ATC-58 framework is applied to develop a seismic fragility database for pressurized fire suppression sprinkler joints considering joint rotation as the demand parameter. Fragility functions in terms of more global demand parameters, such as floor accelerations, can be developed using data presented here combined with structural analysis models of sprinkler piping systems.

Seismic Fragility Study of Fire Sprinkler Piping Systems with Grooved Fit Joints

2015 ◽  
Vol 141 (6) ◽  
pp. 04014157 ◽  
Author(s):  
Siavash Soroushian ◽  
Arash E. Zaghi ◽  
E. “Manos” Maragakis ◽  
Alicia Echevarria ◽  
Yuan Tian ◽  
...  
Keyword(s):  
Seismic Fragility ◽  
Piping Systems ◽  
Fire Sprinkler

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

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.

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