Andre Filiatrault

Performance evaluation of friction damped braced steel frames under simulated earthquake loads

This paper presents the results obtained from tests of a new friction damping system, which has been proposed in order to improve the response of steel Moment Resisting Frames (MRF) and Braced Moment Resisting Frames (BMRF) during severe earthquakes. The system consists of a mechanism containing brake lining pads introduced at the intersection of frame cross-braces. Seismic tests of a three storey Friction Damped Braced Frame (FDBF) model were performed on an earthquake simulator table. The experimental results are compared with the findings of an inelastic time-history dynamic analysis. The results clearly indicate the superior performance of the FDBF compared to conventional building systems.

Experimental Seismic Response of a Full-Scale Light-Frame Wood Building

A full-scale, two-story, light-frame wood townhouse building, designed according to modern U.S. engineered seismic design requirements, was tested on two triaxial shake tables operating in unison. The main objective of this experimental study was to determine the dynamic characteristics and the seismic performance of the test building under various base input intensities, representative of both ordinary and near-field ground motions in southern California. The building was tested with and without interior (gypsum wallboard) and exterior (stucco) wall finishes. The test results revealed that the installation of gypsum wallboard to the interior surfaces of structural wood sheathed walls substantially improved the seismic response of the test building. The application of exterior stucco further improved the seismic response of the test building, particularly in its longitudinal direction, where the shear response of low aspect ratio wall piers dominated. These shake table test results provide the evidence of...

Seismic Behavior of Steel-Fiber Reinforced Concrete Interior Beam-Column Joints

ACI Structural Journal, V. 92, No. 5, September-October 1995. Received April 18, 1994, and reviewed under Institute publication policies. Copyright

Experimental Seismic Fragility of Cold-Formed Steel Framed Gypsum Partition Walls

AbstractAs part of the Network for Earthquake Engineering Simulation Research (NEESR)-Grand Challenge Project Simulation of the Seismic Performance of Nonstructural Systems, an experimental program was carried out to evaluate the seismic responses, failure mechanisms, and fragilities of cold-formed steel framed gypsum partition walls. Understanding the seismic behavior of building interior partition walls is important because damage to these nonstructural components can initiate at relatively low story drift levels, potentially degrading the overall functionality of the building and contributing toward earthquake economic losses. To this end, in-plane quasi-static and dynamic tests were conducted on 36 partition walls constructed using common construction details. Variables examined on the 16 configurations tested include framing thicknesses, stud connections to top and bottom tracks, wall intersection details, and partial height walls among others. In addition, new details are proposed to increase the dr...

Seismic Performance of Code-Designed Fiber Reinforced Concrete Joints

An experimental investigation is presented on the use of steel fiber reinforced concrete to provide ductility in beam-to-column joints during earthquake excitation. Four full-scale exterior beam-column joints, part of a prototype building designed according to the National Building Code of Canada, were tested under cyclic reverse loading. The first specimen was made of normal concrete but ignored all the special seismic recommendations related to the spacing of lateral reinforcement in the beams, columns, and joints. The second specimen was also made of normal concrete and incorporated full seismic details. The third and fourth specimens were similar to the first one but used steel fiber reinforced concrete in the joint region. Experimental results indicated that fiber reinforced concrete is an appealing alternative to conventional confining reinforcement. Steel fibers bridging across cracks in the concrete mix increase the joint shear strength and can diminish requirements for closely spaced ties. The performance of a joint is closely related to the volume content and aspect ratio of the fibers.

Seismic response control of buildings using friction dampers

In the last decade, many energy dissipating systems have been proposed to raise the seismic design of structures beyond the conventional ductility design approach. Among these new systems, friction damping has shown some great potential. In a friction damped system, friction damping devices are inserted in a structure and slip at a predetermined optimum load during severe seismic excitations, before any yielding of the structural members has occurred. Slipping of the devices allows the structure to dissipate the input seismic energy mechanically by friction rather than by inelastic deformation of the structural elements. This paper presents an overview of the recent research and development in Canada on a particular type of friction damped bracing. Analytical and shake table test results are first summarized to illustrate the earthquake performance of friction damped structures compared to the performance of conventional building systems. The development of a design slip load spectrum for the rapid estimation of the optimum slip load distribution is then presented. Finally, two practical examples of the implementation of this system are described: (1) the design of a reinforced concrete library building; and (2) the retrofit of a precast concrete school building.

Three-Dimensional Seismic Response of a Full-Scale Light-Frame Wood Building: Numerical Study

The experimental seismic responses of a full-scale two-story light-frame wood townhouse building, designed to modern U.S. engineered seismic design requirements, were compared against the predictions of a new software package entitled seismic analysis package for woodframe structures (SAPWood) developed recently within the NEESWood Project. The main objective of this paper was to verify the accuracy of the predictions from the SAPWood model, which incorporates shear deformations of shear walls as well as cumulative floor displacements caused by the out-of-plane rotations of the floor and ceiling diaphragms. A comparison was conducted on interstory drifts and shear wall deformations for various structural configurations (construction phases) of the test building and excitation levels. Good agreement was found between the numerical predictions and test results for the four different construction phases. The SAPWood model was shown to be a promising numerical tool for predicting the seismic response of light...

Hysteretic damping of wood framed buildings

Abstract The direct-displacement seismic design of wood buildings requires knowledge of the global load–displacement behavior of the building and the variation of the global equivalent viscous damping with displacement amplitude. This paper proposes a simple numerical model for the determination of these parameters. The proposed model is validated with results of shake table tests of a full-scale two-story wood framed house. The model is then used for the monotonic and cyclic pushover analyses of full-scale woodframe buildings, representing various construction qualities. From these analyses, a simple equation is proposed for the variation of the global equivalent viscous damping with building drift.

Performance evaluation of passive damping systems for the seismic retrofit of steel moment-resisting frames subjected to near-field ground motions

Passive friction and viscous damping systems for retrofitting steel moment-resisting frames located along the west coast of the United States are considered. First, preliminary design procedures are presented for friction as well as linear and nonlinear viscous damping systems. Thereafter, nonlinear dynamic analyses are performed on a six-story moment-resisting frame designed according to seismic provisions for California prior to the 1994 Northridge earthquake. A flexural strength degradation model is considered to account for the brittle behavior of pre-Northridge welded beam-to-column connections. The structure was subjected to three different earthquake ensembles including near-field records developed for major crustal earthquakes in California. The results of a parametric study indicate that, although both friction and viscous damping systems reduce significantly the response of the structure, they are unable by themselves to prevent fracture of welded beam-to-column joints. Connection retrofit measures of the types elaborated after the Northridge earthquake would still be required.

Testing Protocol for Experimental Seismic Qualification of Distributed Nonstructural Systems

Building codes and standards now require seismic qualification of mechanical and electrical equipment and their mounting systems in important buildings to ensure that they remain functional during and after major seismic events. To better understand the seismic behavior of nonstructural building contents and equipment, experimental procedures have been proposed for either displacement or acceleration sensitive nonstructural components, through racking or shake table protocols, respectively. However, certain types of nonstructural systems are sensitive to both accelerations and interstory drifts. An innovative testing protocol is proposed that can subject nonstructural systems to the combined accelerations and interstory drifts expected within multistory buildings during seismic shaking. Moreover, the proposed protocol, when used with equipment such as the University at Buffalo Nonstructural Component Simulator (UB-NCS), allows for the assessment of the seismic performance of distributed nonstructural systems with multiple attachment points, and the evaluation of seismic interactions between components. The versatility and capabilities of the testing protocol are demonstrated through testing of a full-scale hospital emergency room containing typical nonstructural components and life support medical equipment.