Alicia Echevarria

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

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.

Experimental Comparison of the Performance and Residual Capacity of CFFT and RC Bridge Columns Subjected to Blasts

AbstractThe blast performance of concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) bridge columns was studied through a two-phase study comprised of blast and residual axial capacity experiments. Two one-fifth-scale CFFT columns and two one-fifth-scale conventional RC columns having comparable flexural capacities were subjected to distinct levels of explosive loading, causing damage but not complete failure. The blast resilience of the damaged columns was quantified by measuring the residual axial capacity of each column. The damaged CFFT columns exhibited superior strength and ductility retention compared with the damaged RC columns. Additionally, the damaged CFFT columns demonstrated a more predictable axial compressive mode of failure because the exterior FRP tube resisted the shear crack initiation observed in the damaged RC columns.

CFFT Bridge Columns for Multihazard Resilience

AbstractBridges play a significant role in postevent recovery and disaster resiliency of communities. Recent megadisasters, such as the 2011 Great East Japan Earthquake, have prompted the technical community to understand the robustness of infrastructure when subjected to extreme events and the shortcomings of conventional structural systems under multiple hazards. Columns are the most critical load-carrying elements of bridge structures. Enhancing the robustness of bridge columns can improve the resiliency of the bridge itself and the surrounding community by reducing repair costs and downtime after an extreme event. In recent years, the concrete-filled fiber reinforced polymer (FRP) tube (CFFT) system has been widely investigated as a durable and cost-effective alternative design for more robust bridge columns. However, the current AASHTO guide specifications are limited to nonductile, unreinforced CFFT elements. This study summarizes the findings of blast, fire, and seismic experiments performed on CFF...

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

AbstractA comprehensive analytical model is developed for a pressurized fire sprinkler piping system of a hospital building. A suite of ninety-six artificial triaxial floor acceleration histories is used to generate seismic fragility parameters of the sprinkler piping system. The analytical model accounts for the inelastic behavior of braces, hangers, and wire restrainers. It incorporates an experimentally validated hysteresis model developed, as part of this study, for the moment-rotation relationship of grooved fitted joints. Component fragility parameters were obtained for lateral restrainers, hangers, and pipe joints. Three system-level damage states were defined based on the level of functionality of fire sprinkler systems and severity of leakage after a seismic event and a joint probabilistic model were utilized to obtain system-level fragility parameters. Finally, the seismic fragility of fire sprinkler systems with grooved fit joints is compared to that of a piping system with threaded joints.

Analytical Simulation of the Performance of Ceiling-Sprinkler Systems in Shake Table Tests Performed on a Full-Scale 5-Story Building

A ceiling system is composed of interlocking grid members including 4-ft.-and 2ft-long cross-tees. These members are held together at each intersection by interlocking clips attached to both ends of the members. A series of component-level experiments was performed on such members. The 4-ft.- and 2-ft.-long cross-tees were subjected to tensile and compressive forces to obtain their axial strength and stiffness characteristics. Tension and compression tests were also performed on the 2-ft. and 4-ft. clips to define their strength. Finally, the behavior of the interlocked cross-tees under cyclic axial load was investigated until failure of the connection. The experimental results were used to calibrate an integrated OpenSees model of a ceiling-sprinkler assembly that was tested at the E-Defense shake table facility in 2011. A full-scale, five-story steel moment frame building was subjected to a number of biaxial and triaxial excitations. In these experiments, more than 900 ft2 of suspended ceiling with lay-in tiles was installed on the 4th and 5th floors of the building, along with 100 ft. of sprinkler piping. The results from the analytical simulation were compared to the experimental results. This research promotes the experimentally validated computer simulation of non-structural systems and establishes a modeling methodology for future studies.

Seismic fragility study of displacement demand on fire sprinkler piping systems

Seismic damage to fire sprinkler piping systems is not only caused by inertial forces or interstory drifts, but also by impact with surrounding objects. The collision of constituents of piping systems with nearby objects increases the chance of damage to the piping itself and to adjacent objects. In this study, the probability of seismic damage to fire sprinkler systems due to impact is quantified by obtaining seismic fragility parameters for large diameter pipes passing through walls and floors, as well as small diameter pipes that typically interact with suspended ceilings. The results of two shaking table experiments conducted at the University of Nevada, Reno and E-Defense test facility, and a high-fidelity numerical model of a hospital piping system are used to evaluate the displacement demands. Piping interaction fragility curves are generated based on clearances between adjacent objects and pipes. The probability of piping interactions and damage to piping systems subjected to different levels of peak floor acceleration is compared for different clearances. It is found that the probability of damage due to impact is comparable with the probability of exceeding other limit states, like the leakage in fittings, when a 1 in or 2 in gap is provided around large and small diameter pipes, respectively.

Seismic Fragility Study of Fire Sprinkler Piping Systems

A numerical modeling method was developed for fire sprinkler piping systems with threaded/grooved joints and used to generate seismic fragility parameters. The model accounts for the inelastic response of grooved/threaded joints, braces, hangers, and wire restrainers. The model incorporates a nonlinear model recently developed for the cyclic moment-rotation relationship of grooved tee joints, as well as a numerical model formerly developed for threaded tee joints. The models are validated using the results of extensive experiments on tee subassemblies performed at University at Buffalo. The model is adaptable to different pipe diameter joints. A real fire sprinkler system of a hospital was simulated and its seismic response was obtained under a suite of ninety-six artificially generated tri-axial floor acceleration records. Three system damage states were defined and a combined probabilistic seismic demand model was utilized to obtain system-level fragility parameters.