Inertial Force-Limiting Anchorage System for Seismic Resistant Building Structures

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Summary This paper presents experimental and numerical studies of a full‐scale deformable connection used to connect the floor system of the flexible gravity load resisting system to the stiff lateral force resisting system (LFRS) of an earthquake‐resistant building. The purpose of the deformable connection is to limit the earthquake‐induced horizontal inertia force transferred from the floor system to the LFRS and thereby to reduce the horizontal floor accelerations and the forces in the LFRS. The deformable connection that was studied consists of a friction device (FD) and carbon fiber‐reinforced laminated low‐damping rubber bearings (RB), denoted as the FD + RB connection. The test results show that the force‐deformation responses of the FD + RB connection are stable under quasi‐static sinusoidal and earthquake loading histories and dynamic sinusoidal loading histories. The FD + RB connection force‐deformation response is approximated with a bilinear elastic‐plastic force‐deformation response with kinematic hardening. The FD is axially stiff, compact, easy‐to‐assemble, and able to accommodate the FD + RB connection kinematic requirements. The FD elastic stiffness controls the FD + RB connection elastic stiffness. The FD friction force controls the force when the FD + RB connection force‐deformation response transitions from elastic to post elastic. The RB provide predictable and reliable post‐elastic stiffness to the FD + RB connection. The machining tolerances for the FD components, the “break‐in” effect, the sliding history, and the dwell time affect the FD friction force. Numerical simulation results for a 12‐story reinforced concrete wall building with FD + RB connections under seismic loading show that a reduction of the FD friction force increases the FD + RB connection deformation demand.

“…A description of the test setup details is presented in Tsampras and Sause . Shake table tests show that the FD + RB connection meets all kinematic requirements shown in Figure .…”

Section: Methodsmentioning

confidence: 99%

Section: Preliminary Studiesmentioning

confidence: 99%

Experimental study of deformable connection consisting of friction device and rubber bearings to connect floor system to lateral force resisting system

Tsampras¹,

Sause

Fleischman

et al. 2017

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“…The studies examined structural performance versus IFAS strength via 2D nonlinear time‐history analyses using a suite of design spectrum compatible earthquakes for 4‐, 8‐, and 12‐story buildings. The building models possessed idealized models for the IFAS devices with similar hysteretic characteristics to the eventual IFAS prototype . Figure 4 shows representative analytical results for the 4‐story evaluation structure: (A) LFRS and GLRS inter‐story drift ratio; (B) relative displacement between the LFRS and floor; and (C) floor acceleration.…”

Section: Inertial Force‐limiting Anchorage System (Ifas)mentioning

confidence: 99%

“…An innovative floor connecting system, termed the Inertial Force‐Limiting Floor Anchorage System (IFAS), is described in this paper. The IFAS is intended to reduce horizontal inertial forces in building structures during major earthquakes . This goal is accomplished by providing an engineered deformable connection as the primary connection between the floor diaphragm and the vertical elements of the Lateral Force‐Resisting System (LFRS).…”

Section: Introductionmentioning

confidence: 99%

“…This relative displacement also allows the IFAS to dissipate part of the earthquake energy in the building structure. The IFAS has the potential to limit the horizontal floor accelerations and to also reduce the seismic demands on the LFRS, actions that could potentially result in less damage to the structural and non‐structural elements …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Shake‐table test performance of an inertial force‐limiting floor anchorage system

Zhang

Fleischman

Restrepo

et al. 2018

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Summary A new floor connecting system developed for low‐damage seismic‐resistant building structures is described herein. The system, termed Inertial Force‐Limiting Floor Anchorage System (IFAS), is intended to limit the lateral forces in buildings during an earthquake. This objective is accomplished by providing limited‐strength deformable connections between the floor system and the primary elements of the lateral force‐resisting system. The connections transform the seismic demands from inertial forces into relative displacements between the floors and lateral force‐resisting system. This paper presents the IFAS performance in a shake‐table testing program that provides a direct comparison with an equivalent conventional rigidly anchored‐floor structure. The test structure is a half‐scale, 4‐story reinforced concrete flat‐plate shear wall structure. Precast hybrid rocking walls and special precast columns were used for test repeatability in a 22‐input strong ground‐motion sequence. The structure was purposely designed with an eccentric wall layout to examine the performance of the system in coupled translational‐torsional response. The test results indicated a seismic demand reduction in the lateral force‐resisting system of the IFAS structure relative to the conventional structure, including reduced shear wall base rotation, shear wall and column inter‐story drift, and, in some cases, floor accelerations. These results indicate the potential for the IFAS to minimize damage to the primary structural and non‐structural components during earthquakes.

Development of deformable connection for earthquake‐resistant buildings to reduce floor accelerations and force responses

Tsampras

Sause

Zhang

et al. 2016

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Summary: This paper presents the development of a deformable connection that is used to connect each floor system of the flexible gravity load resisting system (GLRS) with the stiff lateral force resisting system (LFRS) of an earthquake-resistant building. It is shown that the deformable connection acts as a seismic response modification device, which limits the lateral forces transferred from each floor to the LFRS and allows relative motion between the GLRS and LFRS. In addition, the floor accelerations and the LFRS story shears related to the highermode responses are reduced. The dispersion of peak responses is also significantly reduced. Numerical simulations of the earthquake response of a 12-story reinforced concrete shear wall example building with deformable connections are used to define an approximate feasible design space for the deformable connection. The responses of the example building model with deformable connections and the example building model with rigid-elastic connections are compared. Two configurations of the deformable connection are studied. In one configuration, a buckling restrained brace is used as the limited-strength load-carrying hysteretic component of the deformable connection, and in the other configuration, a friction device is used. Low damping laminated rubber bearings are used in both configurations to ensure the out-of-plane stability of the LFRS and to provide post-elastic stiffness to the deformable connection. Important experimental results from full-scale tests of the deformable connections are presented and used to calibrate numerical models of the connections.Original language English