scholarly journals Engineering applications of new probabilistic seismic ground-motion maps of Canada

1983 ◽  
Vol 10 (4) ◽  
pp. 670-680 ◽  
Author(s):  
A. C. Heidebrecht ◽  
P. W. Basham ◽  
J. H. Rainer ◽  
M. J. Berry
Keyword(s):  
Ground Motion ◽  
Seismic Risk ◽  
Velocity Ratio ◽  
Large Population ◽  
Building Code ◽  
Base Shear ◽  
Probability Of Exceedance ◽  
Seismic Ground Motion ◽  
Short Period ◽  
Current Code

New peak horizontal acceleration and velocity zoning maps with a probability of exceedance of 10% in 50 years and seven seismic zones are developed from new probabilistic strong seismic ground-motion estimates for replacement of the 1970 seismic zoning map in the National Building Code of Canada. The adoption of a probability of exceedance of 10% in 50 years produces reference seismic ground motion appropriate to the level of protection afforded by provisions of the current code; the use of two ground-motion parameters, the relative levels of which vary considerably throughout the country, provides independent reference levels for structures having short and long fundamental periods.For calculating seismic base shear, a new seismic response factor is derived in which seismic forces for long-period structures are directly proportional to zonal velocities, and for short-period structures proportional to zonal accelerations, with an upper limit on the acceleration/velocity ratio applicable for any location. To maintain the same design standard as provided by the current code, the base shear is calibrated to remain the same, on average, in large population centres in regions of moderate to high seismic risk. The resulting changes in the base shear applicable at various locations reflect the improved estimates of seismic risk, in particular the introduction of additional zones in the higher risk regions of the country and the higher levels of short-period ground motion estimated for some regions of eastern Canada.These and associated changes in seismic design provisions have been recommended for adoption in the 1985 edition of the National Building Code of Canada.

Combined seismic base shear and torsional loading provisions in the 1990 edition of the National Building Code of Canada

1991 ◽  
Vol 18 (6) ◽  
pp. 945-953
Author(s):  
A. M. Chandler
Keyword(s):  
Ground Motions ◽  
Building Code ◽  
Soil Conditions ◽  
Building Structures ◽  
Base Shear ◽  
Ground Acceleration ◽  
Period Range ◽  
Natural Period ◽  
Short Period ◽  
Edge Response

This paper evaluates the earthquake-resistant design provisions of the 1990 edition of the National Building Code of Canada (NBCC 1990) for asymmetric building structures subjected to combined lateral shear and torsional dynamic loadings arising from earthquake base excitation. A detailed parametric study is presented, evaluating the dynamic edge displacement response in the elastic range, for the side of the building which is adversely affected by lateral–torsional coupling. A series of buildings is studied, with realistic ranges of the fundamental natural period, structural eccentricity, and uncoupled frequency ratio. These buildings are evaluated under base loadings arising from a total of 45 strong motion records taken from earthquakes in North America, Mexico, Europe, the Middle East, and Southern Pacific, categorized according to site soil conditions and the ratio a/v of peak ground acceleration to velocity. The latter parameter together with the uncoupled lateral period are found to influence strongly the combined dynamic edge response, with the greatest forces on edge members arising from earthquakes with high a/v ratio in structures with natural periods below 0.8 s. In this case the NBCC 1990 loading provisions significantly underestimate the elastic dynamic response. For buildings with periods longer than 0.8 s, the conservatism of the base shear provisions leads to overestimation of combined dynamic edge response in asymmetric systems, and this is also true in the short-period range for buildings subjected to ground motions with low a/v ratio. The NBCC 1990 provisions are reasonably conservative for short-period systems subjected to ground motions with intermediate a/v ratio. Key words: earthquakes, seismic, design, response, spectra, base, shear, torsional, provisions.

Seismic loading provision changes in National Building Code of Canada 1985

1985 ◽  
Vol 12 (3) ◽  
pp. 653-660 ◽  
Author(s):  
A. C. Heidebrecht ◽  
W. K. Tso
Keyword(s):  
Seismic Response ◽  
Seismic Risk ◽  
Seismic Loading ◽  
Building Code ◽  
Seismic Zoning ◽  
Probability Level ◽  
Base Shear ◽  
Response Parameter ◽  
Most Significant Change ◽  
Risk Methodology

This paper describes the process by which Canadian seismic loading provisions are developed and then details the primary changes being introduced in the 1985 edition of the National Building Code of Canada. The most significant change is the inclusion of new seismic zoning maps, based on a new seismic risk methodology, a new probability level, and additional seismic zones, and incorporating both horizontal ground velocity and acceleration as zoning parameters. The format of base shear calculation is revised to incorporate these changes, including the specification of a new seismic response parameter. The base shear formula is calibrated to ensure that, on a cumulative basis throughout the country, the level of seismic loading remains unchanged. Additional changes discussed in the paper include the removal of dynamic analysis as a specific option in the base shear calculation and some significant changes in the calculation of torsional effects.

scholarly journals Evaluation of site amplification factors for shallow rock sites of Islamabad, Pakistan.

2021 ◽  
Vol 48 (2) ◽  
Author(s):  
Shamsher Sadiq ◽  
◽  
Muhammad Aaqib ◽  
Saeed-ullah J. Mandokhail ◽  
Maqsood-Ur Rehman ◽  
...  
Keyword(s):  
Extended Period ◽  
Site Amplification ◽  
Building Code ◽  
Response Analysis ◽  
Specific Response ◽  
Amplification Factors ◽  
Local Site ◽  
Impedance Contrast ◽  
Short Period ◽  
Current Code

Current seismic provisions in Building Code of Pakistan (BCP-2007), seismic site classifications, and corresponding site amplification factors were determined similar to Uniform Building Code (UBC-1997), which were based on the local site conditions of Western United States with low impedance contrast, deep sites, and high seismicity conditions. The use of these deep sites based amplification factors to the shallow sites may not be appropriate to capture shallow sites' response. In this study, we performed a non-linear site-specific response analysis suite to compute the amplification factors for the six (06) representative shallow bedrock sites of Islamabad, Pakistan. The computed amplification factors are compared with BCP-2007 code-based design estimates; it is found that BCP-2007 code-based guidelines underestimate amplification factors at a short period whereas overestimating at an extended period. The study's findings highlight the potential implications of current code-based amplification factors for Islamabad's shallow sites and suggest improving the current seismic guidelines.

Evaluation of base shear provisions in the 1985 edition of the National Building Code of Canada

1989 ◽  
Vol 16 (1) ◽  
pp. 22-35 ◽  
Author(s):  
T. J. Zhu ◽  
W. K. Tso ◽  
A. C. Heidebrecht
Keyword(s):  
Yield Strength ◽  
Seismic Response ◽  
Structural Damage ◽  
Ground Motions ◽  
Response Spectra ◽  
Building Code ◽  
Base Shear ◽  
Response Factors ◽  
Period Range ◽  
Short Period

A statistical analysis is performed to evaluate the base shear provisions in the 1985 edition of the National Building Code of Canada (NBCC 1985). Three sets of real earthquake records are selected to represent seismic ground motions with low, normal, and high peak acceleration to velocity (a/v) ratios. Single degree of freedom stiffness degrading systems are used as structural models; three damage indicators are employed to measure structural damage. The yield strength of the systems is specified in two different ways: (a) a single seismic response factor is used, irrespective of the a/v ratios of the input ground motions; (b) three different seismic response factors are used in the short-period range, depending upon the a/v ratios of the input ground motions, as suggested in NBCC 1985. A comparison of the statistical results of the three damage parameters for the systems designed with these two methods of strength specification indicates that the NBCC 1985 base shear provisions provide consistent control over structural damage when the structural systems are subjected to ground motions with different a/v ratios. Key words: earthquakes, ground motions, response spectra, stiffness degrading systems, seismic design, base shear, yield strength, inelastic response, damage parameters.

Towards a new base shear format in future NBCC seismic provisions

1994 ◽  
Vol 21 (4) ◽  
pp. 682-695 ◽  
Author(s):  
A. C. Heidebrecht ◽  
N. Naumoski ◽  
A. Rutenberg
Keyword(s):  
Ground Motion ◽  
Earthquake Engineering ◽  
Velocity Ratio ◽  
Degree Of Freedom ◽  
Peak Ground Velocity ◽  
Base Shear ◽  
Ground Acceleration ◽  
Direct Evaluation ◽  
Design Spectra ◽  
Time Histories

Recent trends in the specifications of earthquake design forces are moving away from spectral amplification of ground motion towards direct evaluation of spectral values. Also, the 1988 Saguenay earthquake produced strong evidence for the need to modify the present provisions for low period structures in eastern North America. A new database consisting of 75 time histories was assembled and an extensive parametric study was undertaken to prepare new seismic response factors (S curves) for the National Building Code of Canada (NBCC). These time histories were divided into five categories (15 time histories each) on the basis of their frequency content as measured by their peak ground acceleration to peak ground velocity ratios, ranging from very high (≈3) to very low (≈0.5). Mean and mean + one standard deviation response spectra for one-degree-of-freedom and multi-degree-of-freedom systems were computed for the five categories using several normalizing (scaling) rules for the time histories. The results were compared and spectral amplification factors are presented. Spectra based on peak spectral velocity scaling were compared with spectra based on the present peak ground velocity scaling approach, and some differences are noted. Also, comparisons with the design spectra given in the 1991 edition of the National Earthquake Hazard Reduction Program provisions are presented. On the basis of this study, new S curves are proposed for consideration in the development of future editions of the NBCC. Key words: earthquake engineering, design spectra, building codes, amplification, ground motion, acceleration, velocity, ratio.

Dynamic Characteristics of Base-Isolated Steel Frame under Seismic Ground Motion

2011 ◽  
Vol 255-260 ◽  
pp. 2341-2344
Author(s):  
Mohammad Saeed Masoomi ◽  
Siti Aminah Osman ◽  
Ali Jahanshahi
Keyword(s):  
Ground Motion ◽  
Base Isolation ◽  
Time History ◽  
Steel Structure ◽  
Steel Structures ◽  
Steel Frame ◽  
Nonlinear Time History Analysis ◽  
Seismic Load ◽  
Vector Method ◽  
Seismic Ground Motion

This paper presents the performance of base-isolated steel structures under the seismic load. The main goals of this study are to evaluate the effectiveness of base isolation systems for steel structures against earthquake loads; to verify the modal analysis of steel frame compared with the hand calculation results; and development of a simulating method for base-isolated structure’s responses. Two models were considered in this study, one a steel structure with base-isolated and the other without base-isolated system. The nonlinear time-history analysis of both structures under El Centro 1940 seismic ground motion was used based on finite element method through SAP2000. The mentioned frames were analyzed by Eigenvalue method for linear analysis and Ritz-vector method for nonlinear analysis. Simulation results were presented as time-acceleration graphs for each story, period and frequency of both structures for the first three modes.

Sign in / Sign up

Export Citation Format

Share Document