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To investigate the multi-hazard resilience of cold-formed steel (CFS) construction, a full-scale ten-story CFS building was subjected to two post-earthquake compartment fire tests on the NHERI shake table in San Diego in July 2025. The objective was to evaluate the fire performance of a beyond-code CFS-framed building, including the influence of prior seismic damage. The tests were conducted in identical 30.8 m2 compartments (opening factor 0.017 m1/2) at the 6th and 9th stories, with fuel load densities of 391 MJ/m2 and 334 MJ/m2, respectively. The two fires exhibited heating phase durations of 35 to 41 min and burned uncontrolled for 90 min including the cooling phase, reaching gas temperatures above 900 °C. The structural system maintained global stability under the tests. Stud wall temperatures remained below 550 °C, attesting to the integrity of single-layer (15.9 mm) Type X gypsum during the fully developed phase, despite visible post-test detachment. Ceiling gypsum loss in the 6th story test caused a sudden rise in joist temperatures, leading to development of permanent deflection of joists. Comparisons with fire zone and finite element heat transfer models showed conservative agreement with average temperatures but highlighted limitations in predicting spatial variability and gypsum fall-off. 

This paper is the second of a set presented within the session: Findings from the CFS10 MultiHazard Test Program. The emphasis within this article is to highlight correlations between physical damage to nonstructural components and systems with measured response during a suite of 18 earthquake tests and two subsequent fire tests. This damage was documented within a 10story cold-formed steel-framed building test specimen outfitted with various nonstructural components, including suspended ceilings, architectural finishes, a resilient stair system, windows and doors, pressurized fire sprinkler and gas piping systems, and roof-mounted mechanical equipment. The test building and multi-hazard protocol are described in the session companion paper. This paper provides test observations correlated with measured engineering demand parameters such as floor acceleration, building inter-story drift or peak local temperature responses and offers related literature emerging from the project. Damage data and functionality checks will support development of fragility functions for these nonstructural systems for use in recoverybased frameworks. 

This paper is the first in a pair presented within the session: Findings from the CFS10 Multi-Hazard Test Program. The emphasis within this article is to, in brevity, describe the scope of a landmark full-scale 10-story cold-formed steel (CFS) framed building tested under multi-hazard (earthquake and fire) scenarios at the UC San Diego 6-DOF Large High-Performance Outdoor Shake Table (LHPOST6). Coined CFS10, this unique building specimen is designed beyond current code height limits, adopting advances in cold-formed steel shear wall detailing, varied construction modalities, and enriched with nonstructural components and systems. The landmark CFS10 building specimen was subjected to extreme multi-hazard (earthquake and fire) loading conditions. This paper sets the framework for presentations to be shared at the Congress, while also aiding in ongoing documentation of findings from the program. 

A 10-story cold-formed steel (CFS) building, referred to as CFS10, was constructed and tested at the 6-DOF Large High Performance Outdoor Shake Table (LHPOST6) at UC San Diego (NHERI@UC San Diego). This unique building specimen was designed beyond current seismic provisions, notably exceeding the height limit as prescribed in ASCE 7-22 and employing shear wall detailing that is currently not available in the most recent AISI S400-20 design standard. The test specimen was additionally outfitted with a wide range of nonstructural components and systems, designed and installed at various levels of the building, to understand the evolution of damage in a real building system under multi-directional seismic excitation. Limiting damage to nonstructural components plays a key role in maintaining or regaining post- earthquake building functionality. To this end, an essential aspect of the test program is to improve upon the key gaps in the state of knowledge of nonstructural seismic performance and functional recovery of buildings, especially in CFS-framed buildings. This paper presents preliminary observations of damage and functionality correlated with the measured seismic response of select nonstructural systems, namely suspended ceilings, and pressurized fire sprinkler and gas piping systems, focusing on their performance and interactions at the ceiling of Story 10 in the building. Observations related to damage and functionality can inform the development of fragility functions for these nonstructural systems and support improved functional recovery design provisions. 

The seismic performance of acceleration-sensitive mechanical equipment is a major area of interest within the field of nonstructural components and systems (NCSs). To save indoor space, conserve energy, or meet functional requirements, such equipment is often installed on building rooftops, where higher acceleration demands during earthquakes make rooftop-mounted units more susceptible to damage. Floor-mounted mechanical equipment is typically supported by vibration and noise isolation devices to reduce the transmission of unwanted motion to the supporting structure. However, limited attention has been given to understanding under what conditions, and to what extent, vibration and acoustical design strategies may enhance, or potentially compromise, the seismic performance of lightweight NCSs. To investigate this issue, five lightweight air-conditioning condenser units, each weighing no more than 1,500 N, including three with a slender aspect ratio of 3.7 and two with a squat aspect ratio of 1.1, were installed on the rooftop of a full-scale, ten-story cold-formed steel (CFS) building tested on a six-degree-of-freedom outdoor shake table. Different base attachment strategies were employed. All three slender units were screwmounted at four manufacturer-provided feet to the CFS studs. Two of the units had a modified base boundary condition, with neoprene pads and spring isolators respectively added under the base feet. Both squat units were screw-mounted using four steel angles connected to the CFS studs, with one additionally supported by neoprene pads placed beneath the equipment. This paper presents the first release of preliminary results from the recently completed experimental program, focusing on rooftop mechanical equipment responses under service-level, design-level, and maximum-considered earthquake motions. Results presented include measured floor acceleration amplification factors, peak component accelerations, and component amplification factors. These findings are compared with code-based provisions to evaluate the adequacy of current design coefficients in capturing the acceleration demands on lightweight components. 

Stair systems, which provide the primary means of egress in and out of a building during and after an earthquake, play a critical role in seismic resiliency. Often, these systems are detailed with fixed flight-tolanding connections. However, previous experimental studies and field reconnaissance have shown that such configurations are prone to severe damage. To mitigate this damage to both the stair systems and the supporting structural members, as well as to avoid the ensuing potential to stiffen the lateral force resisting system of the building, stair connections are often detailed to release drift demands. Referred to as driftrelease, these approaches generally focus on releasing inter-story drift at the flight-to-landing connections. Findings from a recent shake table test of a 10-story prefabricated stair system within a mass timber building showed that stair systems with drift-release connections result in a seismically resilient egress solution. However, due to the free movement of stair flights, handrail connections received damage at multiple levels. In a complementary follow-on study, a 9-story stair system with refined connection details was integrated into a 10-story cold-formed steel (CFS10) building recently tested at NHERI@UC San Diego. Numerical analyses have indicated that stair systems with fixed flight-to-landing connections can influence the dynamic characteristics of the supporting structure due to strut action. As such, stairs in the CFS10 building system were designed to allow for easy modification between fixed and drift-release connections by installing or removing locking bolts at the flight to mid-landing interfaces. In the CFS10 building, white noise tests were conducted in each orthogonal direction under two configurations: first, with the stair connections fixed, and then with the locking bolts removed. This study aims to determine the impact of stair connection detailing on the modal characteristics of the building. In addition, complementary numerical simulations were carried out for both fixed and drift-release stair configurations. Based on both experimental and numerical studies, it is found that, under low-amplitude excitation, the impact of stair flexibility on the building vibration period is not significant because the drift-release connection is not appreciably engaged under small lateral loading. However, the impact of stair strut action under large-amplitude excitation still needs to be investigated. 

As a capstone to the multi-university-industry collaborative CFS-NHERI project, a full-scale 10-story building is constructed and tested under earthquake and live-fire scenarios at the NHERI 6-DOF Large High Performance Outdoor Shake Table (LHPOST6) facility. Coined CFS10, the building specimen is designed with a height of 31.6 m (103 ft 9 in), exceeding the height limitation of 19.8 m (65 ft) set by the current ASCE 7-22 design standard. The design also advances lateral force resisting system (LFRS) details to provide for the increases in seismic shear and overturning moment demands associated with increases in building height. Data generated from this unique experimental program will shed light on the impact of architectural exterior and interior finishes, non-designated systems, such as gravity walls or window/door framing, that are along the same architectural line of the CFS-framed shear wall system. Another key factor, higher mode effects, which can significantly influence the structural and nonstructural seismic response of tall buildings, is studied for the first time for such repetitively framed structures. Finally, the test building integrates conventional stick-framing, panelized (2D), and volumetric (3D) modular construction within one building specimen, allowing a unique opportunity to document and compare the efficiency of each construction method, and any differences in structural performance. The floor and roof diaphragm are also designed to embrace a modular stair system within the floor plan of the building. The seismically resilient stairs will provide safe egress/ingress to the building through the use of a variety of drift-compatible details, including following design and MCE level earthquake tests. This experimental program will provide vital full-scale system-level benchmark test data for a state-of-the-art CFS building under multidirectional seismic input. Furthermore, it will advance knowledge of the post-earthquake fire performance of mid-rise CFS construction, by incorporating a live fire test sequence following seismic test phase completion. 

This project aimed to quantify the heat flux of compartment fires in a cold-formed steel building. The data gathered can be compared to future tests and further analyzed to further current modeling systems. Few studies look at the heat flux of compartment fires, and this is one of the first conducted on an outside building that has been seismically tested. This study is intended both for future researches looking at heat flux and current and future professionals who wish to understand fire hazards more. 

This project investigates the temperature differences of cold-formed steel members in a post-earthquake compartment fire. This data could be used to provide better estimates of damage to CFS residential compartments. This project is unique because it is the first post-earthquake live-fire test of a full-scale 10-story CFS building. The audience is structural or fire protection engineers. 

This project focused on the structural analyzation of a full-scale 10-story building using unmanned aerial vehicles (UAVs) at the Large High Performance Outdoor Shake Table (LHPOST6) at the University of California, San Diego. The goal was to evaluate how the 10-story cold formed steel (CFS) building responded under seismic simulations using UAV-based imagery and other data-acquisition devices. This data can serve to inform researchers on the convenience and reliability of using UAVs for post-disaster damage assessments and the steps to accurately achieve structural displacement results applying UAV-data, the Global Navigation Satellite System (GNSS) and accelerometers. Unlike other projects, the CFS10 LHPOST6 experiment was a large-scaled structure that combined real-world hazards and laboratory research. Natural hazard researchers, structural engineers, civil engineers, and other industry professionals interested in structural or infrastructure safety can use this to learn and enhance their understanding of UAVs and their capabilities to assist in post-disaster assessments and multi-hazard scenarios.