Seismic Analysis of Fire ySprinkler Systems

P t d bPresented by:Arash E. Zaghi, Ph.D., P.E.

Research ScientistResearch Scientist University of Nevada, Reno

R h t t UNRResearch team at UNR:Manos Maragakis, PI of NEES-GC

Arash E. Zaghi, Research Associate

Quake Summit 2011, June 9-11, Buffalo, New York

Siavash Soroushian, PhD Student

Research Plan

• Making use of experimental data to develop and validate an analytical model for the suspended piping systemssuspended piping systems.

• Developing a full system model of a hospital sprinkle pipingsprinkle piping.

• Subjecting the piping model to the obtained floor motions to investigate the effects of thefloor motions to investigate the effects of the dynamic response of the building on piping system.y

• Development of fragility curves for the piping system. 2y 2

Experimental Model• System modeled after University of California, Davis

hospital piping system– Modified to accommodate dimensions and geometry restrictionsModified to accommodate dimensions and geometry restrictions

of testing facility• Subassembly included

100 ft of 3 in and 4 in diameter schedule 40 ASTM grade A 53– 100 ft. of 3 in. and 4 in. diameter schedule 40 ASTM grade A-53 black steel pipe

– Four typical valvesT t h t– Two water heaters

– One simulated heat exchanger• Heat exchanger and water heaters were anchored to g

the shake table• Pipes were braced and hung from a stationary frame

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Experimental Model (Cont.)

Seismic Braces

Four systems were tested:1. Welded braced2. Welded unbraced3. Threaded braced4. Threaded unbraced

Bracing and Hanging Points

Bracing Detail

11 Hanging points 5 Unidirectional Braces 2 Bidirectional Braces

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2 Bidirectional Braces

S b t bj t d t th ti ti th t

Shaking Table ExperimentSubsystem was subjected to a synthetic motion that was generated according to AC156 uni- and bi-directional.

6Threaded Braced Subassembly E-W Shake 6Threaded Braced Subassembly E W Shake

Analytical Model of the Test Assembly

Eff i S iff f BEffective Stiffness of Braces

Braced Unbraced

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Effect of Multiple Floor Excitation

Braced Unbraced8

Seismic Simulation of a Hospital Sprinkler PipingHospital Sprinkler Piping

System

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G l D l t f fl ti f lti t b ildi

Analytical Model of Hospital BuildingGoal: Development of floor motions of a multistory building

3D Model

A three-story Special Moment Resisting Frame (SMRF) was designed

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y p g ( ) g OpenSees was used for the analyses Model was subjected to all three components of the ground motion

Input MotionsTh i t ti d f th l f th b ildi

Seismic Design Number of

The input motions used for the analyses of the building are adopted from the SAC project.

GroupSeismic Design 

CategorySuite of motions

Number of Motions

1 A, BBoston 2% in 50 yearsBoston 10% in 50 years

20Boston 10% in 50 years

2 CSeattle  10% in 50 years

Los Angeles  50% in 50 years20

Seattle 2% in 50 years3 D, E

Seattle  2% in 50 yearsLos Angeles  2% in 50 yearsLos Angeles  10% in 50 years

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4 F Near Field motions 20

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4 F Near‐Field motions 20

Goal: Introduce different levels of nonlinearity in the building 11

Analytical Model of the Sprinkler Piping Sprinkler piping plan was adopted from USF medical center modified sprinkler piping system

Piping System

12Sprinkler Piping Model

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Analytical Model of the Sprinkler Piping

SSolid Braces

Wire Restraints

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Wire Restraints

Modeling Assumptions

• Model was subjected to floor acceleration responses (multiple support excitation)responses (multiple support excitation)

• Piping system was modeled using elastic• Piping system was modeled using elastic members.

• The displacements of sprinkler heads and the forces in the brace members were recorded

NEES - UNR Test-bed14

forces in the brace members were recorded.

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Fragility Analysis

• The maximum relative displacement of each 489 heads were obtained.

• The maximum displacements were sorted and the 85-percentile values were found. p

• The 85-percentile displacements were plotted vs PGA or the associated PFAvs. PGA or the associated PFA.

• Log-normal distribution was used to plot the fragility curves

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fragility curves.

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Sample Fragility Curves

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Conclusions

– Effective stiffness of the cable bracing system may be as low as 10% of the gross stiffnessmay be as low as 10% of the gross stiffness.

– In a heavily braced piping system, the dynamic i ll th ki tiresponse is smaller than kinematic response.

– Yielding of the parent structure significantly changes the demands on the piping system.

– Forces and displacement are lower in a yielding

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p y gstructure due to smaller floor accelerations.

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Acknowledgement

– The experiment was supported by MCEER through a grant from the Earthquakethrough a grant from the Earthquake Engineering Research Centers Program of the NSF under award number EEC-9701471.

– The analytical efforts were supported by the NEES-GR Nonstructural project under GrantNEES GR Nonstructural project under Grant No. 0721399.

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Thank You