Nonlinear Finite Element Models for Embedded Base Connections

Abstract

Column base connections are one of the most critical components in Steel Moment Frames (SMFs) since these connections transfer the loads (i.e., gravity, seismic, wind) from the entire superstructure into the concrete-foundation, being an interface between them. Typically, exposed base plates are preferred for low-and mid-rise buildings, while embedded base connections are the norm for tall buildings. This latter base configuration response is controlled by complex interactions between the column flange and the bottom base plate with the concrete foundation, where the mechanisms to transfer internal forces are idealized to underpin the current strength design methods. These mechanisms include horizontal bearing stresses between the column flange and the surrounding concrete and vertical bearing stresses of the base plate and the concrete foundation. Current methods to estimate the strength of these connections are validated against a limited number of experimental tests complicating their generalization for the different configurations that have not been tested. Although the results from these methods show good agreement with test data, the assumptions that underpin these methods have not been verified through sophisticated nonlinear finite element models. Motivated by this issue, this paper presents a series of nonlinear finite element models developed to provide insights into the behavior of embedded base connections for SMFs. These models incorporate the essential aspects that control the connection behavior, including constitutive material modeling and contacts among the connection components. Possible design implications are discussed, while the limitations of the current work and future lines of research are outlined.

Reliability Analysis of Embedded Base Connections

“…Specifically, Torres-Rodas [14] recommended design loads for these connections based on nonlinear time history analyses (NTHA) of archetype steel moment frames (SMFs). Other studies investigated their behavior using sophisticated finite element models (e.g., [15][16][17]) determining internal stress distributions and patterns of deformation. Apart from that, the influence of the behavior of EBCs on the seismic performance of SMFs has been studied with the use of NTHA conducted on archetype frames [18][19][20][21].…”