DESIGN DRIFT REQUIREMENTS FOR LONG-PERIOD STRUCTURES
Author: Gary R. Searer and Sigmund A. Freeman | Size: 96 KB | Format:PDF | Quality:Unspecified | Publisher: 3th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 3292 | Year: 2004 | pages: 9
The code provisions for calculating the design seismic drift of buildings have been substantially revised over the past 40 years. While these changes in the code are fairly well documented, the reasons behind these changes and the consequences of the changes are not as well known. This paper presents a brief history of design drift requirements, technical background for the requirements, and the reasoning behind the changes, starting with the 1961 Uniform Building Code (UBC) through present day. Emphasis is given to the discussion of minimum base shears for calculation of drift for long-period structures. Specifically, in Section 1630.10.1 of the 1997 UBC, it is not immediately apparent why Equation 30-6 may be disregarded in the calculation of drift while Equation 30-7 may not, since both equations tend to give very similar minimum base shears for typical buildings. In prior versions of the UBC, the minimum design base shear was determined by only one equation that could be disregarded during determination of drift. This paper discusses the reasoning behind Equation 30-7 in the current UBC and discusses the current controversy and differences of opinion regarding this equation. Also discussed are equivalent requirements in the National Earthquake Hazards Reduction Program (NEHRP) and Minimum Design Loads for Buildings and Other Structures (ASCE 7-02), which require a similar minimum base shear for determining drift of long period structures.
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A simple procedure to estimate the local displacement demands in regular frame-type structures that respond in elastic limits
is described. Given the spectral displacement and beam-to-column stiffness ratio, the procedure estimates the maximum ground story and maximum interstory drifts along the height of the structure. A total of 145 near-fault ground motions recorded on dense-to-firm soil sites are used for the evaluation of the procedure. The approximate drift demands computed from this procedure and the exact results from 27,550 response history analyses are used for calculating the error statistics. The calculations show that the procedure can be used with confidence for frames with fundamental periods between 0.3 and 1.5 s when they are subjected to near-fault records without pulse. The approximations are in good agreement with the exact response history results of near-fault records with pulse when the fundamental period to pulse period ratio is less than 1.5. The performance of the new procedure is also compared with other approximate methods that
are employed for similar purposes. The method can be useful for preliminary design of new structures or rapid assessment of existing buildings.
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Control of Seismic Drift Demand for Reinforced Concrete Buildings with Weak First Stories
Author: Manabu Yoshimura 1) 1) Department of Architecture, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji, Tokyo, | Size: 730 KB | Format:PDF | Quality:Unspecified | Publisher: Earthquake Engineering and Engineering Seismology, Vol. 4, No. 1 | Year: | pages: 9
This paper studies seismic drift demand for RC buildings with weak first stories, the potential seismic vulnerability of which has been revealed in many past earthquakes including the 1995 Kobe and 1999 Chi-Chi earthquakes. In a building that collapsed during the Kobe earthquake the strength balance between the first story and the upper stories is shown to have had a significant effect on the collapse of this building. Nonlinear dynamic analyses are then conducted for a model representing weak-first-story buildings to study the first story drift demand, where the first-story strength and the strength balance along the height are taken as analysis variables. Based on the results,
conditions that the two parameters should satisfy for controlling the first-story drift demand within an allowable level are discussed.
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Seismic Drift Demand and Capacity of Non-seismically Designed Concrete Buildings in Hong Kong
Author: R.K.L. Su;N.T.K. Lam;H.H. Tsang | Size: 262 KB | Format:PDF | Quality:Unspecified | Publisher: EJSE Special Issue: Earthquake Engineering in the low and moderate seismic regions of Southeast Asia and Australia (2008) | Year: 2008 | pages: 12
ABSTRACT: This paper reviews the seismic engineering research conducted in Hong Kong with special
emphasis on the prediction of the seismic drift demand and capacity of existing buildings which have not been
designed and detailed to address potential seismic hazards. The paper begins with a comprehensive summary
of the local construction and detailing practice of concrete structures, followed by a summary of the drift ratio
capacity, ductility capacity, stiffness variation and non-linear damping properties of the non-seismically designed
reinforced concrete components. Seismic design response spectra for rock sites developed from Chinese
Code GB50011-2001 are compared with the uniform hazard response spectra developed at the University
of Hong Kong. The over-conservatism of the Chinese Code particularly in the long period range (T > 2 sec)
is highlighted. A direct displacement based method used for the prediction of the maximum drift demands of
existing buildings in Hong Kong is also introduced. Phenomena such as stiffness degradation, period shifting,
non-linear damping and higher mode effects have been incorporated into the modelling. Lastly, the predicted
maximum inter-storey drift demand of 0.3% is compared with the minimum ultimate drift capacity of approximately
1.5%. The capacity predictions were based on results from experimental cyclic load testings of
concrete sub-assemblages undertaken in Hong Kong in recent times. The potential risk of damage in Hong
Kong buildings under seismic attacks is discussed.
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1 BUILDING PERFORMANCE IN THE BOUMERDES, ALGERIA, EARTHQUAKE OF MAY 21, 2003
Author: Svetlana Brzev British Columbia Institute of Technology, Burnaby, | Size: 1.1 MB | Format:PDF | Quality:Unspecified | Year: 2003 | pages: 13
Algeria, a gateway between Europe and Africa, is located in Northern Africa. The Sahara desert covers over 80% of the country’s territory. A narrow northern zone is dominated by the Atlas mountain chain. The population of Algeria is over 30 million – most of the population lives in the northern part of the country. The capital city Algiers (including the suburbs) has the population of around 3.5 million. Algeria was under the French rule from 1830 to 1962, and prior to that under the Turkish rule for 300 years. With regards to the seismotectonic setting, the northern part of Algeria is located at the margin
between the north moving African plate and the Eurasian plate, creating a zone of compression,
which manifests itself by a series of thrust and normal faults that have been mapped in the area.
This region has a rich history of seismicity and had experienced many destructive earthquakes in the past (see Fig.1). According to the historic records, the capital Algiers was completely destroyed by a major earthquake in 1365; there are also reports of earthquakes that struck Northern Algeria in 1887, 1910, 1922, and 1934. On October 10, 1980, the city of El Asnam (formerly Orleansville and today Ech-Cheliff) was severely damaged by a magnitude 7.1 earthquake that killed at least 3000 people (El Asnam is situated approximately 220 km to the west of the May 21, 2003 earthquake). The same city, as Orleansville, had been heavily damaged on September 9, 1954, by a magnitude 6.7 earthquake that killed over 1000 people. Five other damaging earthquakes (of magnitude 5.4 or higher) were reported in the country in the period
from 1989 to 2000.
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INFLUENCE OF MASONRY INFILL WALLS AND OTHER B UILDING CHARACTERISTICS ON SEIS MIC COLLAPSE OF CONCRETE FRAME BUILDINGS
Author: SIAMAK SATTAR B.S ., Azad University of Najafa bad, Iran, 2004 M.S ., Mazandaran University of Science and Technology, Iran , 2007 M. S ., University of Colorado Boulder | Size: 5.2 MB | Format:PDF | Quality:Unspecified | Year: 2013 | pages: 225
Reinforced concrete frame buildings with masonry infill walls have been built all around the world, specifically in the high seismic regions in US. Observations from past earthquakes
show that these buildings can endanger the life of their occupants and lead to significant damage and loss. Masonry infilled frames built before the development of new seismic regulations are more susceptible to collapse given an earthquake event. These vulnerable buildings are known as non-ductile concrete frames. Therefore, there is a need for a comprehensive collapse assessment of these buildings in order to limit the loss in regions with masonry infilled frame buildings.
The main component of this research involves assessing the collapse performance of masonry infilled, non-ductile, reinforced concrete frames in the Performance Based Earthquake
Engineering (PBEE) framework. To pursue this goal, this study first develops a new multi-scale modeling approach to simulate the response of masonry infilled frames up to the point of
collapse. In this approach, a macro (strut) model of the structure is developed from the response extracted from a micro (finite element) model specific to the infill and frame configuration of interest. The macro model takes advantage of the accuracy of the micro model, yet is computationally efficient for use in seismic performance assessments requiring repeated nonlinear dynamic analyses. The robustness of the proposed multi-scale modeling approach is examined through comparison with selected experimental results.
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A welded steel moment-frame building is used to assess performancebased engineering guidelines. The full-scale four-story building was shaken to collapse on the E-Defense shake table in Japan. The collapse mode was a side-sway mechanism in the first story, which occurred in spite of a strongcolumn and weak-beam design. Computer analyses were conducted to simulate the building response during the experiment. The building was then evaluated using the Seismic Rehabilitation of Existing Buildings (ASCE-41) and Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings (FEMA-351) for the collapse prevention performance level via linear and nonlinear procedures. The guidelines had mixed results regarding the characterization of collapse, and no single approach was superior. They mostly erred on the safe side by predicting collapse at shaking intensities less than that in the experiment. Recommendations are made for guideline improvements.
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Seismic collapse analysis on core-outrigger structures
Author: F.F. Sun, R.X. Ge & J.M. Xu | Size: 1.1 MB | Format:PDF | Quality:Unspecified | Publisher: Dept. Of Building Engineering, College of Civil Engineering Tongji University, Shanghai, China | pages: 18
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