Gilberto Mosqueda

Performance of Nonstructural Components during the 27 February 2010 Chile Earthquake

The 27 February 2010 Chile earthquake caused widespread nonstructural damage in practically all types of buildings. While few commercial, residential, office, and industrial buildings suffered structural damage, the functionality of many more facilities was disrupted, and significant economic losses were reported due mainly to nonstructural damage. Design requirements for nonstructural components in Chilean design codes are rarely enforced, unless explicitly requested by owners. In addition, construction predating modern codes has not been upgraded to current standards, even for such critical facilities as hospitals. This earthquake highlights that more attention should be devoted to enforcing regulations and improving the seismic performance of nonstructural components whose failure can lead to injuries, substantial economic losses, and partial or total loss of functionality. This is especially important for facilities critical to the response and recovery, such as hospitals and airports that should remain operational even after strong earthquakes.

Experimental Seismic Fragility of Cold-Formed Steel Framed Gypsum Partition Walls

AbstractAs part of the Network for Earthquake Engineering Simulation Research (NEESR)-Grand Challenge Project Simulation of the Seismic Performance of Nonstructural Systems, an experimental program was carried out to evaluate the seismic responses, failure mechanisms, and fragilities of cold-formed steel framed gypsum partition walls. Understanding the seismic behavior of building interior partition walls is important because damage to these nonstructural components can initiate at relatively low story drift levels, potentially degrading the overall functionality of the building and contributing toward earthquake economic losses. To this end, in-plane quasi-static and dynamic tests were conducted on 36 partition walls constructed using common construction details. Variables examined on the 16 configurations tested include framing thicknesses, stud connections to top and bottom tracks, wall intersection details, and partial height walls among others. In addition, new details are proposed to increase the dr...

Static and Dynamic Stability of Elastomeric Bearings for Seismic Protection of Structures

AbstractBearings used in the seismic isolation of buildings can be subjected to large horizontal deformations combined with high axial loads from overturning forces during strong shaking. Elastomeric bearing design requires an evaluation of the critical load capacity under this combined loading to ensure stability. To better understand and estimate the capacity of elastomeric bearings, a comprehensive experimental program was carried out to examine bearing stability using two quasi-static and one dynamic loading procedures. The first method to evaluate the bearing critical load follows previous experimental research, where a single elastomeric bearing is held at prespecified horizontal displacements while increasing the axial load until the critical load is achieved. In a second method implemented here, a similar setup is used to apply a constant axial load followed by increased horizontal displacement until the stability limit is observed. This second method is shown to be an accurate and more direct app...

Testing Protocol for Experimental Seismic Qualification of Distributed Nonstructural Systems

Building codes and standards now require seismic qualification of mechanical and electrical equipment and their mounting systems in important buildings to ensure that they remain functional during and after major seismic events. To better understand the seismic behavior of nonstructural building contents and equipment, experimental procedures have been proposed for either displacement or acceleration sensitive nonstructural components, through racking or shake table protocols, respectively. However, certain types of nonstructural systems are sensitive to both accelerations and interstory drifts. An innovative testing protocol is proposed that can subject nonstructural systems to the combined accelerations and interstory drifts expected within multistory buildings during seismic shaking. Moreover, the proposed protocol, when used with equipment such as the University at Buffalo Nonstructural Component Simulator (UB-NCS), allows for the assessment of the seismic performance of distributed nonstructural systems with multiple attachment points, and the evaluation of seismic interactions between components. The versatility and capabilities of the testing protocol are demonstrated through testing of a full-scale hospital emergency room containing typical nonstructural components and life support medical equipment.

Damage to Engineered Buildings and Bridges in the Wake of Hurricane Katrina

Hurricane Katrina made landfall on August 29, 2005 causing significant damage to the built environment including buildings, roads and bridges, utility distribution systems for electric power and water, waste water collection facilities, and vital communication networks. This paper details post-disaster field reconnaissance of the Gulf Coast immediately following Hurricane Katrina organized by MCEER. The objectives of the reconnaissance were to examine and document the impact of Hurricane Katrina from a multi-hazard perspective. More specifically, lessons learned from Hurricane Katrina are being evaluated to mitigate damage not only from future hurricanes, but also from other extreme events such as earthquakes or terrorist attacks. As an example, a multi-hazard objective of this mission was to identify similarities between damage typically observed after earthquakes and damage caused by Hurricane Katrina with the goal of identifying seismic design principles that could mitigate structural damage caused by wind and storm surge forces. Researchers observed extensive losses from nonstructural damage to cladding, windows, and roof-mounted equipment while the structural frame remained undamaged. In storm surge regions such as the Mississippi coast, however, structural damage was observed in buildings and bridges exposed to storm surge and impact from large storm surge debris such as barges, much of which relates to tsunami risk.

Experimental Seismic Fragility of Steel Studded Gypsum Partition Walls and Fire Sprinkler Piping Subsystems

1 Associate Professor, Department of Civil, Structural and Environmental Engineering, University at Buffalo, State University of New York, Buffalo, NY, USA 2 Professor, Department of Civil, Structural and Environmental Engineering, University at Buffalo, State University of New York, Buffalo, NY, USA 3 Consulting Engineer, Ruben Boroschek y Asociados Ltda. 4 Graduate Research Assistant, Department of Civil, Structural and Environmental Engineering, University at Buffalo, State University of New York, Buffalo, NY, USA

Large-Scale Hybrid Simulation of a Steel Moment Frame Building Structure through Collapse

AbstractThe implementation of two series of hybrid simulations that aim to trace the system-level seismic response of a four-story steel moment frame building structure through collapse is presented. In the first series of tests, a half-scale 1½-bay by 1½-story physical substructure of a special steel moment-resisting frame is considered, while in the second series the physical substructure corresponds to the gravity framing system with a similar-sized specimen. An objective of these tests is to demonstrate the potential of hybrid simulation with substructuring as a cost-effective alternative to earthquake simulators for large-scale system-level testing of structural frame subassemblies. The performance of a recently developed substructuring technique and time-stepping integration method for hybrid simulation are evaluated when employed with large and complex numerical substructures exhibiting large levels of nonlinear response. The substructuring technique simplifies the experimental setup by reducing th...

Experimental Seismic Fragility of Pressurized Fire Suppression Sprinkler Piping Joints

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.

Fast Hybrid Simulation with Geographically Distributed Substructures

The hybrid simulation test method is a versatile technique for evaluating the seismic performance of structures by seamlessly integrating both physical and numerical simulations of substructures into a single test model. Using hybrid testing, complex structural systems composed of multiple large-scale experimental and numerical substructures can be evaluated by linking experimental facilities using the internet. In this paper, a distributed control strategy is presented that supports the implementation of hybrid testing with geographically distributed substructures using advanced algorithms that offer improved accuracy. The objectives are to provide a scalable framework for multiple-substructure testing at distributed sites and to improve the reliability of the test results by minimizing strain-rate and force relaxation errors in the remote experimental substructures. The control strategy is based on a multi-threaded simulation coordinator combined with an event-driven controller at the remote experimental sites. The effectiveness of this procedure is demonstrated by computing the earthquake response of a six-span bridge model with five remote experimental and numerical column substructures distributed within laboratories across the U.S. Further, the distributed tests were implemented using a secure network link between the testing sites that was developed for the NEES cyber-infrastructure.

Assessing the Collapse Probability of Base-Isolated Buildings Considering Pounding to Moat Walls Using the FEMA P695 Methodology

The collapse probability of two three story base-isolated buildings considering pounding to moat walls is examined using the methodology in FEMA P695. The superstructure models consist of a steel intermediate moment frame and a steel ordinary braced frame designed for the same seismic hazard. The behavior of these buildings under various ground motions is first examined, and it is found that the more rigid braced frame results in larger displacements demands on the isolation system, increasing the potential for impact. The collapse studies examine the effect of moat wall gap distance on the probability of collapse for these structures. These studies show that the flexibility and ductility of the moment frame model allow the superstructure to better absorb the impact forces. The braced frame superstructure tends to impact at lower shaking intensities and degrades in strength more rapidly due to the limited ductility that increases the risk of collapse.