Load factor calibration for the proposed 2005 edition of the National Building Code of Canada: Companion-action load combinations

2003 ◽  
Vol 30 (2) ◽  
pp. 440-448 ◽  
Author(s):  
F M Bartlett ◽  
H P Hong ◽  
W Zhou
Keyword(s):  
Companion Paper ◽  
Building Code ◽  
Wind Loads ◽  
Load Factor ◽  
Live Load ◽  
Dead Load ◽  
Limit States ◽  
Snow Load ◽  
Load Factors ◽  
Snow Loads

The 2005 edition of the National Building Code of Canada (NBCC) will adopt a companion-action format for load combinations and specify wind and snow loads based on their 50 year return period values. This paper presents the calibration of these factors, based on statistics for dead load, live load due to use and occupancy, snow load, and wind load, which are summarized in a companion paper. A target reliability index of approximately 3 for a design life of 50 years was adopted for consistency with the 1995 NBCC. The load combinations and load factors for strength and stability checks recommended for the 2005 NBCC were based on preliminary values from reliability analysis that were subsequently revised slightly to address major inconsistencies with past practice. The recommended load combinations and factors generally give factored load effects similar to those in the 1995 NBCC, but are up to 10% more severe for the combination of dead load plus snow load and are generally less severe for the combination of dead load, snow load, and live load due to use and occupancy. Load factors less than one are recommended for checking serviceability limit states involving specified snow and wind loads. Importance factors for various classifications of structure are also presented. Revisions to the commentaries of the NBCC are recommended that will provide guidance on dead load allowances for architectural and mechanical superimposed dead loads and cast-in-place cover slabs and toppings.Key words: buildings, code calibration, companion action, dead loads, live loads, load combinations, load factors, reliability, safety, snow loads, wind loads.

Load factor calibration for the proposed 2005 edition of the National Building Code of Canada: Statistics of loads and load effects

2003 ◽  
Vol 30 (2) ◽  
pp. 429-439 ◽  
Author(s):  
F M Bartlett ◽  
H P Hong ◽  
W Zhou
Keyword(s):  
Companion Paper ◽  
Reduction Factor ◽  
Building Code ◽  
Wind Loads ◽  
Load Factor ◽  
Live Load ◽  
Dead Load ◽  
Wind Speeds ◽  
Code Calibration ◽  
Snow Loads

The 2005 edition of the National Building Code of Canada (NBCC) will adopt a companion-action format for load combinations and specify wind and snow loads based on their 50 year return period values. This paper summarizes statistics for dead load, live load due to use and occupancy, snow load, and wind load that have been adopted for calibration, and a companion paper presents the calibration itself. A new survey of typical construction tolerances indicates that statistics for dead load widely adopted for building code calibration are adequate unless the dead load is dominated by thin, cast-in-place concrete toppings. Unique statistics for live load due to use and occupancy are derived that pertain specifically to the live load reduction factor equation used in the NBCC. Statistics for snow and wind loads are normalized using the 50 year values that will be specified in the 2005 NBCC. New statistics are determined for the factors that transform wind speeds and ground snow depths into wind and snow loads on structures.Key words: buildings, code calibration, companion action, dead loads, live loads, load combinations, load factors, reliability, safety, snow loads, wind loads.

scholarly journals Snow on two-level flat roofs — measured vs. 1990 NBC loads

1992 ◽  
Vol 19 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Donald A. Taylor
Keyword(s):  
Average Density ◽  
Research Needs ◽  
Snow Density ◽  
Limit States ◽  
Snow Load ◽  
Load Factors ◽  
Multi Level ◽  
Snow Loads ◽  
Upper Level ◽  
Flat Roofs

Between 1967 and 1982, depths and specific gravities of snow were recorded on 44 single- and multi-level flat-roofed buildings between Halifax and Edmonton. The average density of snow in the drifts where the roofs change elevation was about 3.0 kN/m3, the value used consequently in the 1990 National Building Code of Canada (NBC). This is some 25% higher than the value used in the 1985 NBC. Data on drift geometry and maximum loads in the drifts are presented and compared with provisions in the 1990 NBC. As well, the paper presents measured values of average and maximum roof-to-ground load ratios for upper level roofs and for lower roofs away from the drifts. These compare favourably with those recommended in the 1985 and 1990 NBC. The statistical variabilities of snow loads and densities are given, since these are required to establish load factors used for limit states design in the NBC. Further research needs are identified. Key words: snow loads, snow drifts, uniform snow, flat roofs, snow density, snow load variability, snow load survey.

scholarly journals Force reduction factors for the seismic provisions of the National Building Code of Canada

1987 ◽  
Vol 14 (4) ◽  
pp. 447-454 ◽  
Author(s):  
J. H. Rainer
Keyword(s):  
Building Code ◽  
Load Factor ◽  
Limit States ◽  
Load Factors ◽  
Earthquake Resistant Structures ◽  
Structural Configurations ◽  
Force Reduction ◽  
Factor Α ◽  
Reduction Factors

A derivation of force reduction factors for the seismic provisions of the National Building Code of Canada (NBCC), 1985, is presented. This includes the following: classification of seismic actions, applicable limit states, change in load factor, derivation of force reduction factors, and classification of structural configurations. Quantitative comparisons are made between the derived force reduction factors and the response modification factors of the Applied Technology Council and good agreement was found. It is suggested that seismic requirements should be considered as accidental actions with a load factor αQ = 1.0. These results can form the basis for possible modifications to the 1985 NBCC seismic provisions. Key words: earthquake resistant structures, building code, loads, load factors.

Development of loading-truck model and live-load factor for the Canadian Standards Association CSA-S6 code

1987 ◽  
Vol 14 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Akhilesh C. Agarwal ◽  
Moe S. Cheung
Keyword(s):  
Highway Bridges ◽  
Load Level ◽  
Load Factor ◽  
Live Load ◽  
Limit States ◽  
Load Factors ◽  
Loading System ◽  
Using Data ◽  
Council Of Ministers ◽  
Level Loading

Studies have shown that the MS-200 loading model in the Canadian Standards Association standard CAN3-S6-M78 for design of highway bridges no longer represents modern-day heavy trucks in Canada. For the new edition of the CSA-S6 code, based on the limit states philosophy, a new loading-truck model was developed based on the Council of Ministers' loading, which is the legal load limit for interprovincial transportation in Canada. The loading model, designated as the "CS-W loading truck," provides the flexibility to adopt a multiple-level loading system appropriate to various jurisdictions.The live-load factor was determined from a statistical approach using data from a truck survey conducted across Canada in seven provinces. Responses in simple-span bridges were determined by running one or more trucks from the survey across the bridge. Based on this study, a live-load factor of 1.60 was determined and CS-600, with a gross weight of 600 kN, was selected as the standard load level. As well, the validity of the truck model and the live-load factors were checked for continuous-span bridges. Key words: highway bridges, design loads, codes and standards, live-load models, load factors, load surveys, vehicle weight regulations.

scholarly journals Study on Dynamic analysis of Diagrid and Outrigger Structures Subjected to Seismic and Wind Load

2021 ◽  
Vol 9 (VII) ◽  
pp. 2813-2828
Author(s):  
Sharath Kumar N
Keyword(s):  
Wind Loads ◽  
Seismic Loads ◽  
Live Load ◽  
Structural Members ◽  
Floor Plan ◽  
Base Shear ◽  
Dead Load ◽  
Modeling And Analysis ◽  
Analysis And Design ◽  
Story Drift

A Comparative study of G+30 story regular, diagrid, outrigger structure is presented. A square shaped floor plan of 18 m × 18m size was considered. ETABS 2016 was used in modeling and analysis of structural members. All structural members were designed as per IS 456:2000, load combinations such as dead load, live load, earthquake and wind loads were considered for analysis and design of the structure. Later Regular, Diagrid and outrigger structural systems were compared; the key results like Base shear, story displacement and story drift are obtained. It is found that diagrid system is efficient in resisting seismic loads and outrigger system is found efficient in resisting wind loads.

Probabilistic assessment of a design truck model and live load factor from weigh-in-motion data for Mexican Highway bridge design

2015 ◽  
Vol 42 (11) ◽  
pp. 970-974 ◽  
Author(s):  
A.D. García-Soto ◽  
A. Hernández-Martínez ◽  
J.G. Valdés-Vázquez
Keyword(s):  
Bridge Engineering ◽  
Load Factor ◽  
Engineering Practice ◽  
Live Load ◽  
Bridge Design ◽  
Statistical Characterization ◽  
Motion Data ◽  
Weigh In Motion ◽  
Load Factors ◽  
Truck Load

This study is focused on the statistical characterization of live load effects on bridges using weigh-in-motion data from a Mexican highway. A truck load model that is simpler than the design truck model implemented in the current Mexican requirements is suggested for design. The statistics are employed in target-reliability based calibration and verification of load factors in Mexican bridge design. Suggestions that could be useful for the Canadian bridge engineering practice are included.

scholarly journals Calibration of the Live Load Factor for Highway Bridges with Different Requirements of Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Lang Liu ◽  
Qingyang Ren ◽  
Xu Wang
Keyword(s):  
Structural Reliability ◽  
Highway Bridges ◽  
Calibration Method ◽  
Mean Value ◽  
Load Factor ◽  
Live Load ◽  
Load Effect ◽  
Load Factors ◽  
Short Period ◽  
Traffic Volumes

Highway bridge load rating has been moving toward structural reliability since the issuance of AASHTO LRFR specifications; however, the recommended load factors were carried out by a few reliable truck data. The objective of this study is to calibrate the live load factor in AASHTO LRFR Rating Specification by using huge amount of WIM data collected in California for more than ten years between 2001 and 2013. Since traffic volumes, vehicular overloads, and traffic components are highly related to the load effect induced, a set of calibration equations is proposed here, in which the nominal standard load effect models are used and different requirements of loading are taken into account. By the analytical model of platoons of trucks and the extrapolation of the gathered WIM data over a short period of time to remote future over a longer time period, the expected maximum live load effects over the rating period of 5 years are also obtained. Then, the live load factor is calibrated as the product of the codified value multiplied by the ratio between the nominal standard load effect and the expected mean value. The results show that the products of the two ratios present rather constant, implying the proposed method and load configurations selected are effective. In the end, the live load factors of 1.0 and 0.7 along with load configurations are recommended for a simple span length less than 300 ft. The recommended calibration method and live load factors will eliminate the unnecessary overconservatism in rating specifications.

scholarly journals Design loadings

1976 ◽  
Vol 9 (1) ◽  
pp. 56-62
Author(s):  
G. W. Butcher
Keyword(s):  
Wind Loads ◽  
Design Load ◽  
Load Factors ◽  
Snow Loads

This paper covers those parts of the loadings code NZS 4203 which relate to dead, live and snow loads. Seismic and wind
loads are dealt with in other papers. The parts of the code discussed are Part 2 and that section of Part 1 dealing with design load equations and load factors.

Revised ground snow loads for the 1990 National Building Code of Canada

1989 ◽  
Vol 16 (3) ◽  
pp. 267-278 ◽  
Author(s):  
M. J. Newark ◽  
L. E. Welsh ◽  
R. J. Morris ◽  
W. V. Dnes
Keyword(s):  
Method Of Moments ◽  
Snow Depth ◽  
Extreme Value Distribution ◽  
Building Code ◽  
Snow Pack ◽  
Snow Density ◽  
Snow Load ◽  
The Mean ◽  
Snow Loads ◽  
Made In

The last systematic recalculation of ground snow loads in the Supplement to the National Building Code of Canada was made in 1977 and used data up to 1975. Data from three times as many stations are now available and there is also an additional 10 years of record. Using this expanded data base, ground snow loads have been recalculated for the 1990 Supplement.Several changes in methods have been utilized, the most significant of which is the use of an objective technique to estimate ground snow loads at Code (or other) locations. It explicitly incorporates an assumed dependence of the snow load on topographical elevation, and accounts for the magnitude of errors at snow depth observation sites. Other differences include (a) the use of the method of moments to fit the Gumbel extreme value distribution for the purpose of estimating the 30-year return period snow depth; (b) the use of geographically varying snow pack densities; and (c) using probabilistic rain components of the total snow load and estimating this component by use of a snow pack model.Results show an average national decrease of 6.6% in the 1990 loads compared with those in the 1985 Supplement. A regional exception is in the Northwest Territories where the use of a greater snow density has led to an average increase of about 16% in the loads. A reduction in the standard deviation about the mean load suggests a more spatially consistent set of values for the 1990 Supplement. Key words: snow, loads, building, code.

Safety and limit states design for reinforced concrete

1976 ◽  
Vol 3 (4) ◽  
pp. 484-513 ◽  
Author(s):  
J. G. MacGregor
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
American Concrete Institute ◽  
Building Code ◽  
Structural Safety ◽  
Reinforced Concrete Structures ◽  
Limit States ◽  
Load Factors ◽  
New Formula ◽  
State Of Art

This state-of-art paper reviews the concept of limit states design. Following a brief review of statistical definitions the sources of variability in reinforced concrete structures are reviewed. Methods of defining structural safety are reviewed. Following a derivation of the procedures used to compute load and [Formula: see text] factors, a series of [Formula: see text] factors compatible with the 1975 National Building Code of Canada load factors are computed. With the exception of the value for shear the new [Formula: see text] factors are lower than the current American Concrete Institute and Canadian Standards Association values by about the amount of the ratio of load factors in National Building Code of Canada and American Concrete Institute. The computed [Formula: see text] for shear is considerably lower than the corresponding value from the American Concrete Institute Code. An Appendix traces the development of the American Concrete Institute load and [Formula: see text] factors.

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