An official website of the United States government
A vast amount of experimental and analytical research has been conducted related to the seismic behavior and performance of concrete filled steel tubular (CFT) columns. This research has resulted in a wealth of information on the component behavior. However, analytical and experimental data for structural systems with CFT columns is limited, and the well known behavior of steel or concrete structures is assumed valid for designing these systems. This paper presents the development of an analytical model for nonlinear analysis of composite moment resisting frame (CFT MRF) systems with CFT columns and steel wide flange (WF) beams under seismic loading. The model integrates component models for steel WF beams, CFT columns, connections between CFT columns and WF beams, and CFT panel zones. These component models account for nonlinear behavior due to steel yielding and local buckling in the beams and columns, concrete cracking and crushing in the columns, and yielding of panel zones and connections. Component tests were used to validate the component models. The model for a CFT MRF considers second order geometric effects from the gravity load bearing system using a lean on column. The experimental results from the testing of a four story CFT MRF test structure are used as a benchmark to validate the modeling procedure. An analytical model of the test structure was created using the modeling procedure and imposed displacement analyses were used to reproduce the tests with the analytical model of the test structure. Good agreement was found at the global and local level. The model reproduced reasonably well the story shear story drift response as well as the column, beam and connection moment rotation response, but overpredicted the inelastic deformation of the panel zone.
more »
« less
Numerical Response Estimations of a Frame-Spine-FLC System Prior to Experimental Dynamic Testing
Numerical modeling is widely used in structural engineering to represent buildings response under seismic loading conditions. However, even though numerical modeling is a common tool to characterize the behavior of structures, modeling uncertainties can lead to a broad range of expected response, particularly when representing the behavior of novel systems or components. Addressing different modeling choices can provide more informed insights into the response of structures, especially prior to conducting experimental tests or participating in blind prediction contests. Herein, blind response prediction of a novel steel system was conducted before testing at the E-Defense facility in Japan. The full-scale specimen consisted of a weak Moment-Resisting Frame (MRF) retrofitted with steel spines and force-limiting connections (FLC). The set of pre-test predictions involved addressing of different modeling choices to overcome the many sources of epistemic uncertainties and to provide greater confidence in the design and experimental testing program. Several models were subjected to the records specific to the testing program (Northridge Sepulveda and JMA Kobe) to estimate drift and acceleration responses. Numerical results were compared to the experimental data from the shake-table tests. Although all the models were able to represent general trends in drifts and accelerations and enabled proper development of the testing plan, peak response varied significantly depending on the modeling choices, especially those altering the system’s natural periods or those leading to different yielding patterns.
more »
« less
- Award ID(s):
- 2309829
- PAR ID:
- 10631686
- Publisher / Repository:
- Springer International Publishing
- Date Published:
- Page Range / eLocation ID:
- 370 to 378
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The objective of this paper is to investigate the post-earthquake thermal-mechanical response of cold-formed steel (CFS) members. A 10-story cold-formed steel building (CFS-NHERI) will undergo seismic tests, followed by post-earthquake live fire tests. To support the fire test setup, computational models are developed to simulate the impact of varying post-earthquake damage levels on the fire response of the structure. As a panelized system, damage to different finish and nonstructural systems significantly affects the thermal behavior and load-bearing capacity of the CFS components. The computational models integrate the modeling capability in CUFSM and SAFIR for the elastic buckling, heat transfer, and transient structural analysis under fire. A parametric analysis considering different seismic damage levels is conducted to study the buckling and strength behavior of the CFS members under fire-induced nonuniform temperature fields. These pre-test models inform the duration and severity of the fire tests to maintain structural stability while achieving substantial thermal loading on the CFS load-bearing system. They also provide guidance for the sensor layout plan for the fire tests. This study advances methods for fire resilience of thin-walled CFS structures under multi-hazard scenarios.more » « less
-
This research investigated experimentally the seismic performance of steel gravity framing with a concrete slab at the system level. Two half-story, two-by-three bay steel gravity frame specimens were tested under cyclic loading. Bolted-bolted double-angle connections were used for a beam-to-column gravity connection. Primary design variables and construction details include the orientation of the metal deck to the loading direction, the presence or absence of metal deck seams on secondary beams, and the contribution of additional reinforcement bars in the concrete slab. Concrete blocks were positioned at the midpoint of each bay to simulate gravity loads, and a quasi-static displacement-controlled cyclic loading protocol was applied to the specimen using three hydraulic actuators. These investigations confirmed general observations from previous subassembly testing programs that the composite steel gravity framing system can provide substantial flexural stiffness, strength, and ductility under cyclic loading. Further, the test findings showed that the primary design variables and construction details significantly affected the cyclic behavior of composite gravity connections. Comparing the test results from a multi-bay setup and a subassembly testing setup, the cyclic behavior showed remarkable differences, especially for cases with weak axis decking or strong axis decking with a seam. These large differences are attributed to a significant separation of the girder from the column in the subassembly testing setup, which may not be present in a real building. Virtually all previous cyclic loading tests on gravity connections have been conducted in subassembly test setups. These subassembly tests are therefore the basis for the models that are currently used to include gravity frame connections in the seismic performance assessment of buildings, and these models may be quite inaccurate in some cases. The data generated in this system-level testing program is intended to support efforts to develop improved models of gravity connections subject to seismic loading.more » « less
-
The use of photovoltaic (PV) arrays as a source of renewable energy has become increasingly popular in the USA. Despite their wide usage, rooftop PV arrays are vulnerable to damage under strong winds. This can be attributed to the underestimation of peak wind loads on these systems where dynamic effects are unaccounted for. This study consists of investigating the wind-induced dynamic effects on rooftop PV arrays based on an experimental-numerical program and field calibration. Field measurements were conducted on a rooftop PV array at Central Washington University. Finite Element Modeling was performed to design the PV array model for experimental testing such that its dynamic properties are comparable to the in-situ array. Impact hammer and wind loading tests were carried out at the NHERI Wall of Wind Experimental Facility at Florida International University. The experimental tests were calibrated and validated based on the field measurements. Significant wind-induced vibrations were observed and their effect on the structure’s response was shown to increase with increasing wind speed.more » « less
-
PROGRESSIVE DAMAGE ANALYSIS OF STEEL-REINFORCED CONCRETE BEAMS USING HIGHER-ORDER 1D FINITE ELEMENTSThe present work investigates progressive damage in steel-reinforced concrete structures. An elastic-perfectly plastic material response is considered for the reinforcing steel constituent, while the smeared-crack approach is applied to model the nonlinear behavior of concrete. The analysis employs one-dimensional numerical models based on higher-order finite elements derived using the Carrera unified formulation (CUF). A set of numerical assessments is presented to study the mechanical response of a steel-reinforced notched concrete beam loaded in tension. The predictions are found to be in very good agreement with reference experimental observations, thereby validating the numerical approach. It is shown that CUF allows for the explicit representation of the constituents within the composite beam, resulting in accurate solutions in a computationally efficient manner.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Book Chapter:
- https://doi.org/10.1007/978-3-031-03811-2_37
