Cyclic Behavior of Large Beam-Column Assemblies

1985 ◽  
Vol 1 (2) ◽  
pp. 203-238 ◽  
Author(s):  
Egor P. Popov ◽  
Navin R. Amin ◽  
Jason J. C. Louie ◽  
Roy M. Stephen
Keyword(s):  
San Francisco ◽  
Seismic Design ◽  
Cyclic Behavior ◽  
Steel Buildings ◽  
Cross Sectional ◽  
Moment Resisting ◽  
Series Of Experiments ◽  
Story Building ◽  
The U.S ◽  
Large Moment

A series of experiments were conducted in order to verify the design criteria for beam-column joints under extreme seismic conditions for a 47-story building in San Francisco. The half-scale cruciform specimens were exceptionally large requiring 18 in. deep sections. The overall size of the specimens was the largest ever tested in the U.S. for this kind of application. The data on the behavior of such large moment-resisting joints under severe cyclic loading are very limited. The experimental evidence clearly supports the use of stiffeners and doubler plates at the joints for the cross-sectional geometries tested. The results are of direct relevance to seismic design of many steel buildings.

Code-Oriented Methodology for the Seismic Design of Regular Steel Moment-Resisting Braced Frames

2014 ◽  
Vol 30 (4) ◽  
pp. 1683-1709 ◽  
Author(s):  
Edgar Tapia-Hernández ◽  
Arturo Tena-Colunga
Keyword(s):  
Seismic Design ◽  
Time History ◽  
Federal District ◽  
Design Parameters ◽  
Braced Frames ◽  
Steel Buildings ◽  
Moment Frames ◽  
Concentrically Braced Frames ◽  
Design Spectrum ◽  
Moment Resisting

In order to help improve the seismic design of regular steel buildings structured with ductile moment-resisting concentrically braced frames (MRCBFs) using the general design methodology of Mexico's Federal District Code (MFDC-04), suitable design parameters were first assessed using the results of pushover analyses of 13 regular MRCBFs. In order to insure collapse mechanisms consistent with the assumptions implicit in a code-based design (strong-column/weak-beam/weaker-brace), it is proposed to relate the minimum strength ratio for the resisting columns of the moment frames and the bracing system. Improved equations are proposed for a more realistic assessment of ductility and overstrength factors. In a second stage, the effectiveness of the improved methodology was assessed with the design of six regular steel buildings with MRCBFs. Buildings were evaluated by performing both pushover and nonlinear time-history analyses under ten selected artificial ground motions related to the corresponding design spectrum.

Seismic design of steel buildings: lessons from the 1995 Hyogo-ken Nanbu earthquake

1996 ◽  
Vol 23 (3) ◽  
pp. 727-756 ◽  
Author(s):  
Robert Tremblay ◽  
Andre Filiatrault ◽  
Michel Bruneau ◽  
Masayoshi Nakashima ◽  
Helmut G. L. Prion ◽  
...  
Keyword(s):  
Seismic Design ◽  
Steel Structures ◽  
Structural Systems ◽  
Braced Frames ◽  
Steel Buildings ◽  
Concentrically Braced Frames ◽  
Framed Structures ◽  
Concentrically Braced ◽  
Moment Resisting ◽  
Column Bases

Past and current seismic design provisions for steel structures in Japan are presented and compared with Canadian requirements. The performance of steel framed structures during the January 17, 1995, Hyogo-ken Nanbu earthquake is described. Numerous failures and examples of inadequate behaviour could be observed in buildings of various ages, sizes, and heights, and braced with different structural systems. In moment resisting frames, the damage included failures of beams, columns, beam-to-column connections, and column bases. Fracture of bracing members or their connections was found in concentrically braced frames. The adequacy of the current Canadian seismic design provisions is examined in view of the observations made. Key words: earthquake, seismic design, steel structures.

scholarly journals Strength resistance factors for seismic design of exposed based plate connections in special steel moment resisting frames

2020 ◽  
Vol 36 (2) ◽  
pp. 537-553 ◽  
Author(s):  
Pablo Torres-Rodas ◽  
Jawad Fayaz ◽  
Farzin Zareian
Keyword(s):  
Seismic Design ◽  
Base Plate ◽  
Limit States ◽  
Reliability Factor ◽  
Resistance Factors ◽  
Moment Resisting Frames ◽  
Modes Of Failure ◽  
Moment Resisting ◽  
Plate Connections ◽  
Story Building

This study presents a critical assessment of the reliability of current base plate connections in steel special moment resisting frames (SMRFs). Using a probabilistic outlook, this research evaluates the reliability of exposed column base (ECB) connections in SMRFs designed based on the current seismic design provisions; it suggests (and implements) a statistical approach to compute resistance factors for three modes of failure (concrete bearing, base plate yielding at tensile interface, and anchor bolt fracture) of ECB connections to achieve a target reliability index, β, of 4.5. Since ECB connections are limited to short buildings, therefore, this study is conducted on two-story and four-story SMRFs which are analyzed using a suite of 120 ground motions originating from strike-slip and reverse faults. ECB connections for the two-story building are designed to simulate pinned connection, while the bases of the four-story building represent moment connections. Detailed methodology for calculating the β of ECB connections is presented considering the three limit states in a moment–axial load interaction curve. Results indicate that the implementation of current seismic provisions results in β ~ 3.3 for non-moment resisting ECB connections for all tried combinations of resistance factors. For moment resisting ECB connections, however, only the designs based on a resistance factor for concrete bearing failure mode less than the current 0.65 result in an acceptable reliability factor of β > 4.5.

scholarly journals Implications of the COVID-19 San Francisco Bay Area Shelter-in-Place Announcement: A Cross-Sectional Social Media Survey

2020 ◽  
Author(s):  
Holly Elser ◽  
Mathew V. Kiang ◽  
Esther M. John ◽  
Julia F. Simard ◽  
Melissa Bondy ◽  
...  
Keyword(s):  
Social Media ◽  
San Francisco ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Daily Activities ◽  
Cross Sectional ◽  
Social Distancing ◽  
Bay Area ◽  
Level Of Concern ◽  
The U.S

ABSTRACTBackgroundThe U.S. has experienced an unprecedented number of shelter-in-place orders throughout the COVID-19 pandemic. There is limited empirical research that examines the impact of these orders. We aimed to rapidly ascertain whether social distancing; difficulty with daily activities (obtaining food, essential medications and childcare); and levels of concern regarding COVID-19 changed after the March 16, 2020 announcement of shelter-in-place orders for seven counties in the San Francisco Bay Area.MethodsWe conducted an online, cross-sectional social media survey from March 14 – April 1, 2020. We measured changes in social distancing behavior; experienced difficulties with daily activities (i.e., access to healthcare, childcare, obtaining essential food and medications); and level of concern regarding COVID-19 after the March 16 shelter-in-place announcement in the San Francisco Bay Area and elsewhere in the U.S.ResultsThe percentage of respondents social distancing all of the time increased following the shelter-in-place announcement in the Bay Area (9.2%, 95% CI: 6.6, 11.9) and elsewhere in the U.S. (3.4%, 95% CI: 2.0, 5.0). Respondents also reported increased difficulty with obtaining food, hand sanitizer, and medications, particularly with obtaining food for both respondents from the Bay Area (13.3%, 95% CI: 10.4, 16.3) and elsewhere (8.2%, 95% CI: 6.6, 9.7). We found limited evidence that level of concern regarding the COVID-19 crisis changed following the shelter-in-place announcement.ConclusionThese results capture early changes in attitudes, behaviors, and difficulties. Further research that specifically examines social, economic, and health impacts of COVID-19, especially among vulnerable populations, is urgently needed.

scholarly journals The Impact of the first COVID-19 shelter-in-place announcement on social distancing, difficulty in daily activities, and levels of concern in the San Francisco Bay Area: A cross-sectional social media survey

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0244819
Author(s):  
Holly Elser ◽  
Mathew V. Kiang ◽  
Esther M. John ◽  
Julia F. Simard ◽  
Melissa Bondy ◽  
...  
Keyword(s):  
Social Media ◽  
San Francisco ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Daily Activities ◽  
Cross Sectional ◽  
Social Distancing ◽  
Bay Area ◽  
Level Of Concern ◽  
The U.S

Background The U.S. has experienced an unprecedented number of orders to shelter in place throughout the ongoing COVID-19 pandemic. We aimed to ascertain whether social distancing; difficulty with daily activities; and levels of concern regarding COVID-19 changed after the March 16, 2020 announcement of the nation’s first shelter-in-place orders (SIPO) among individuals living in the seven affected counties in the San Francisco Bay Area. Methods We conducted an online, cross-sectional social media survey from March 14 –April 1, 2020. We measured changes in social distancing behavior; experienced difficulties with daily activities (i.e., access to healthcare, childcare, obtaining essential food and medications); and level of concern regarding COVID-19 after the March 16 shelter-in-place announcement in the San Francisco Bay Area versus elsewhere in the U.S. Results In this non-representative sample, the percentage of respondents social distancing all of the time increased following the shelter-in-place announcement in the Bay Area (9.2%, 95% CI: 6.6, 11.9) and elsewhere in the U.S. (3.4%, 95% CI: 2.0, 5.0). Respondents also reported increased difficulty obtaining hand sanitizer, medications, and in particular respondents reported increased difficulty obtaining food in the Bay Area (13.3%, 95% CI: 10.4, 16.3) and elsewhere (8.2%, 95% CI: 6.6, 9.7). We found limited evidence that level of concern regarding the COVID-19 crisis changed following the announcement. Conclusion This study characterizes early changes in attitudes, behaviors, and difficulties. As states and localities implement, rollback, and reinstate shelter-in-place orders, ongoing efforts to more fully examine the social, economic, and health impacts of COVID-19, especially among vulnerable populations, are urgently needed.

scholarly journals Public Health Workforce Burnout in the COVID-19 Response in the U.S.

2021 ◽  
Vol 18 (8) ◽  
pp. 4369
Author(s):  
Kahler W. Stone ◽  
Kristina W. Kintziger ◽  
Meredith A. Jagger ◽  
Jennifer A. Horney
Keyword(s):  
Public Health ◽  
Health Workforce ◽  
Work Experience ◽  
Large Scale ◽  
Health Workers ◽  
Public Health Workforce ◽  
Cross Sectional Survey ◽  
Public Health Response ◽  
Cross Sectional ◽  
The U.S

While the health impacts of the COVID-19 pandemic on frontline health care workers have been well described, the effects of the COVID-19 response on the U.S. public health workforce, which has been impacted by the prolonged public health response to the pandemic, has not been adequately characterized. A cross-sectional survey of public health professionals was conducted to assess mental and physical health, risk and protective factors for burnout, and short- and long-term career decisions during the pandemic response. The survey was completed online using the Qualtrics survey platform. Descriptive statistics and prevalence ratios (95% confidence intervals) were calculated. Among responses received from 23 August and 11 September 2020, 66.2% of public health workers reported burnout. Those with more work experience (1–4 vs. <1 years: prevalence ratio (PR) = 1.90, 95% confidence interval (CI) = 1.08−3.36; 5–9 vs. <1 years: PR = 1.89, CI = 1.07−3.34) or working in academic settings (vs. practice: PR = 1.31, CI = 1.08–1.58) were most likely to report burnout. As of September 2020, 23.6% fewer respondents planned to remain in the U.S. public health workforce for three or more years compared to their retrospectively reported January 2020 plans. A large-scale public health emergency response places unsustainable burdens on an already underfunded and understaffed public health workforce. Pandemic-related burnout threatens the U.S. public health workforce’s future when many challenges related to the ongoing COVID-19 response remain unaddressed.

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