Collapse Behavior of Steel Columns as Part of Steel Frame Buildings: Experiments and Numerical Models

Dimitrios Lignos
International Association of Earthquake Engineering, 2017
Article de conférence

Résumé

Earthquake-induced collapse risk assessment of steel frame buildings requires the use of deterioration models that simulate instabilities that cause strength and stiffness deterioration of structural steel components. In the case of steel columns in addition to cyclic deterioration in flexural strength, such models should capture the axial load – bending interaction, the axial contraction as well as the axial strength deterioration after the formation of local buckling within the column cross-section. Based on the available literature, experimental data that characterizes the hysteretic behavior of steel columns at large deformations is scarce. Therefore, the validation and further refinement of new or available steel column deterioration models becomes challenging. This paper discusses the main findings of an extensive experimental program that characterized the hysteretic behavior of wide-flange and hollow structural steel (HSS) columns. The effect of various types of lateral loading protocols on the hysteretic behavior of steel columns was examined with nominally identical specimens. It is shown that a primary failure mode observed in steel columns is the axial shortening. The amount of axial shortening can be considerably different in end columns compared to that observed in interior columns within the same story of a steel moment-resisting frame (MRF). Symmetric loading protocols that are typically used for experimental testing of structural components provide insufficient information for modeling the cyclic deterioration in flexural strength and stiffness of steel columns near collapse. A fiberbased deterioration model is developed for HSS columns that is able to simulate the cyclic hardening prior to the formation of local buckling and the steel column post-buckling behavior including axial shortening. The proposed model is validated with steel column test data that became available from the experimental program.

Official source

https://infoscience.epfl.ch/record/224511?ln=fr

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Concepts associés

Chargement

Publications associées

Chargement

Dimitrios Lignos
International Association of Earthquake Engineering, 2017
Article de conférence

Résumé

Official source

https://infoscience.epfl.ch/record/224511?ln=fr

À propos de ce résultat

Concepts associés (10)

Concepts associés

Chargement

Publications associées (12)

Publications associées

Chargement

Fiber-based hysteretic model for simulating strength and stiffness deterioration of steel hollow structural section columns under cyclic loading

Dimitrios Lignos

An efficient component model has been developed that captures strength and stiffness deterioration of steel hollow structural section (HSS) columns. The proposed model consists of two fiber-based segments at a member's ends along with an elastic segment in between. The fibers exhibit nonlinear uniaxial stress-strain behavior, which is explicitly defined by uniaxial monotonic tensile and cyclic round coupon tests. The postbuckling behavior of an HSS column is traced through a proposed uniaxial effective stress-strain constitutive formulation, which includes a softening branch in compression and an energy-based deterioration rule to trace the influence of cyclic deterioration in the inelastic cyclic straining. These may be inferred by uniaxial stub-column tests. The component model captures the coupling between the column axial force and flexural demands. Consistent model parameters for a number of steel materials used in the steel construction in North America and Japan are proposed along with the associated model calibration process. The efficiency of the proposed model in predicting the hysteretic behavior of HSS columns is demonstrated by comparisons with physical steel column tests subjected to various loading histories, including representative ones of ratcheting prior to earthquake-induced collapse. The proposed model is implemented in an open-source finite element software for nonlinear response history analysis of frame structures. The effectiveness of the proposed model in simulating dynamic instability of steel frame buildings is demonstrated through nonlinear response simulations of a four-story steel frame building, which was tested at full-scale through collapse. Limitations as well as suggestions for future work are discussed.

WILEY2020

Chargement

Recent experiments on steel columns under multi-axis cyclic loading suggest that a steel column may experience appreciable axial shortening due to local buckling. Reconnaissance reports from recent earthquakes indicate that a number of embedded column base (ECB) connections in steel frame buildings were found to be lightly damaged although they are expected to remain elastic. As a result, the amount of inelastic damage concentrated in the respective steel columns was much less than it was expected to be. This paper investigates the influence of the ECB strength on the residual deformations of first story interior steel columns in steel moment resisting frames (MRFs) under multi-axial cyclic loading. The evaluation is conducted with rigorous finite element (FE) simulations. The developed FE model is able to simulate the pinching hysteretic behavior of typical ECBs. The parametric study involves two main cases. In the first one the ECB remains in elastic. In the second case the inelastic behavior is spread to the ECB and the steel column itself. The simulation results suggest that the resultant plastic deformation within the steel column is much smaller in the latter. The onset of column local buckling is delayed; therefore, the residual column axial shortening becomes fairly minimal. In particular, it is reduced by 50% at lateral drift demands associated with low-probability of occurrence earthquakes.

2018

Chargement

Fiber-based model for earthquake-induced collapse simulation of steel frame buildings

Dimitrios Lignos

Earthquake-induced collapse risk assessment of steel frame buildings requires the use of simulation models that can realistically replicate dynamic instability of frame buildings. Such models for steel columns should consider the coupling between the axial force and flexural demands. In end columns, the axial load demand variations due to dynamic overturning effects may be considerable. Other important aspects to be considered are the cyclic hardening prior to the onset of local buckling; the column post-buckling behavior under various axial and lateral loading histories. The potential of utilizing different steel materials should also be considered. This paper proposes a component model that simulates the hysteretic behavior of steel columns utilizing hollow structural sections at large deformations. A fiber-based approach is adopted that combines an equivalent engineering stress-strain constitutive relation assigned to a fiber crosssection within a pre-defined plastic hinge length of a force-based beam-column element formulation. The pre- and post-buckling behavior of the equivalent engineering stress-strain relation is defined based on uniaxial cyclic coupon tests and extensive stub column finite element analyses. The effectiveness of the proposed model in simulating the steel column behavior is demonstrated through comparisons with steel column collapse experiments as well as frame simulation studies validated with shake table collapse tests.

2018

Chargement