Time filter

Source Type

San Francisco, CA, United States

Okazaki T.,Hokkaido University | Lignos D.G.,McGill University | Midorikawa M.,Hokkaido University | Ricles J.M.,Lehigh University | Love J.,Degenkolb Engineers
Earthquake Spectra | Year: 2013

A joint U.S.-Japan reconnaissance team examined the damage to steel building structures caused by the 2011 Tohoku-oki earthquake. In the city of Sendai, where the peak horizontal ground acceleration exceeded 1 g, the majority of steel buildings performed well. Buildings that used older cladding systems for external finish sustained damage to their claddings even if their structural performance was excellent. Damage to a few braced frames offer insight into the seismic design of bracing connections. In areas attacked by the violent tsunami, many steel buildings stood upright after the tsunami subsided, although these buildings lost much of their external and internal finishes along with their contents. These steel buildings did not provide safe shelter for tsunami evacuation when the building submerged under the tsunami wave. A number of buildings suffered foundation failure, which was likely caused by scouring or liquefaction or a combination of multiple effects. © 2013, Earthquake Engineering Research Institute. Source

Miller D.J.,Degenkolb Engineers | Fahnestock L.A.,University of Illinois at Urbana - Champaign | Eatherton M.R.,Virginia Polytechnic Institute and State University
Engineering Structures | Year: 2012

Buildings designed with conventional ductile earthquake-resisting structural systems are expected to provide life safety performance, but they rely on significant structural damage to dissipate the seismic energy. This structural damage and the residual drift that may result from the inelastic response can make a building difficult, if not financially unreasonable, to repair after an earthquake. As a result, development of systems that dissipate energy, minimize structural damage, and return to their initial position (" self-center" ) following an earthquake is needed. This paper presents a viable solution including experimental investigation of the cyclic behavior and performance of a self-centering buckling-restrained brace (SC-BRB). A SC-BRB consists of a typical BRB component, which provides energy dissipation, and pre-tensioned superelastic nickel-titanium (NiTi) shape memory alloy (SMA) rods, which provide self-centering and additional energy dissipation. The SMA rods are attached to the BRB portion of the brace using a set of concentric tubes and free-floating end plates that cause the SMA rods to elongate when the brace is in both tension and compression. Large-scale SC-BRBs were designed, fabricated and tested using a cyclic protocol to validate the brace concept. The experimental program demonstrated that NiTi SMA SC-BRBs provide stable hysteretic response with appreciable energy dissipation, self-centering ability, and large maximum and cumulative deformation capacities. © 2012 Elsevier Ltd. Source

Naito C.,Lehigh University | Cox D.,Oregon State University | Kent Yu Q.-S.,Degenkolb Engineers | Brooker H.,Lehigh University
Journal of Performance of Constructed Facilities | Year: 2013

Field investigation of infrastructure damage following the March 2011, Tohoku, Japan, Tsunami uncovered failure of numerous fuel storage containers as a result of the high inundation depths and velocities associated with the event. Observations focused on two areas, Ishinomaki, Japan and Onagawa, Japan, where inundation depths of up to 6 and 17 m, respectively, were measured. The failure modes observed include: crushing of containers as a result of inward hydrostatic forces or debris impact, tie down failures as a result of elevated buoyancy forces, and sliding failures as a result of the hydrodynamic forces imparted during the event. The loss of restraint resulted in movement of the containers outside of their containment walls, fuel spillage, and ground contamination. Sample calculations based on observed container failure, water levels, and estimated flow velocities illustrate the demands and failure patterns observed. A retrofitting mechanism is proposed to minimize loss of fuel storage containers during tsunami events. © 2013 American Society of Civil Engineers. Source

Kim I.S.,Degenkolb Engineers | Jirsa J.O.,University of Texas at Austin | Bayrak O.,University of Texas at Austin
ACI Structural Journal | Year: 2015

In many reinforced concrete frame structures designed before issues related to progressive collapse became important, it was common to have discontinuous positive reinforcement through a column. To provide toughness to such frames under dynamic loading, which may be generated due to sudden loss of a gravity support, carbon fiberreinforced polymer (CFRP) materials can be installed on the bottom face or side faces of a reinforced concrete (RC) beam parallel to discontinuous longitudinal reinforcement. Behavior of rehabilitated RC beams was studied experimentally under dynamic loading, in which CFRP materials were used to provide continuity to the discontinuous reinforcement. Different levels of dynamic performance were observed depending on the details of application of CFRP materials. The test results indicated that anchored CFRP sheets successfully provided continuity to the positive reinforcement under dynamic loading so that plastic rotation capacity of the beams was realized. In addition, it was possible to develop fracture of the CFRP sheets after delamination using CFRP anchors and/or CFRP U-wraps. Copyright © 2015, American Concrete Institute. All rights reserved. Source

Restrepo J.I.,University of California at San Diego | Bersofsky A.M.,Degenkolb Engineers
Thin-Walled Structures | Year: 2011

This paper presents results from quasi-static racking tests on gypsum wallboard sheathed light gage metal stud partition walls used in buildings. Eight nearly identical pairs of specimens were constructed following common United States practice. Each specimen consisted of a 4.88 m long and 2.44 m tall web wall and two return walls each 1.2 m long and 2.44 m tall. The main variables were (i) the configuration of the specimen, (ii) the spacing of wallboard-light gage stud self-tapping screws, (iii) the stud thickness and spacing, (iv) the presence of a vertically slotted track at the top of the partition wall, and (v) the wallboard thickness. © 2010 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations