Snow loads in the 1985 National Building Code of Canada: Curved roofs

1985 ◽  
Vol 12 (3) ◽  
pp. 427-438 ◽  
Author(s):  
Timothy H. R. Kennedy ◽  
D. J. Laurie Kennedy ◽  
James G. MacGregor ◽  
Donald A. Taylor
Keyword(s):  
Shear Force ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Building Code ◽  
Bending Moments ◽  
Snow Load ◽  
Wide Range ◽  
Loading Case ◽  
Snow Loads ◽  
Load Intensity

In the 1985 edition of the National Building Code of Canada (NBCC) the intensity of the specified snow load at any location on a roof is obtained by multiplying the ground snow load for the building locale by a series of factors. These factors reflect the overall reduction in average snow loads on roofs as compared with that on the ground, the effect of exposure to wind, the effect of roof slope, and the effect of drifting, sliding, creep, and drainage.The four loading cases for the design of curved roofs suggested in the Commentary on snow loads accompanying the 1980 NBCC were examined by determining, for roofs of circular cross section, the variation across the span of load intensity, shear force, and bending moment for a wide range of spans, ground snow loads, and roof edge slopes. The purpose of the examination was to fully describe known inconsistencies arising from these loading cases.A new case for drift loading was developed (case III) that, when used with "full" or "uniform" loading and with the unbalanced loading developed for the 1977 NBCC (case II), eliminates or at least reduces the inconsistencies. With this new loading case and the derivation of a formula to define when to switch from loading case II to the new case III the designer now has to consider only one unbalanced loading condition rather than three as before.A simplified method for establishing specified load intensities, shear forces, and bending moments, suitable at least for preliminary design, is also presented. Key words: bending moments, curved roofs, drifts, load intensity, shear force, snow load factors, wind.

Investigation of Smooth Pipe Bends Under the Effect of In-Plane Bending

2017 ◽  
Author(s):  
Diana Abdulhameed ◽  
Michael Martens ◽  
J. J. Roger Cheng ◽  
Samer Adeeb
Keyword(s):  
High Stress ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Bend Angle ◽  
Bending Moments ◽  
Bend Radius ◽  
Pipe Bend ◽  
Cross Sectional ◽  
Smooth Pipe ◽  
Plane Bending

Pipe bends are frequently used to change the direction in pipeline systems and they are considered one of the critical components as well. Bending moments acting on the pipe bends result from the surrounding environment, such as thermal expansions, soil deformations, and external loads. As a result of these bending moments, the initially circular cross-section of the pipe bend deforms into an oval shape. This consequently changes the pipe bend’s flexibility leading to higher stresses compared to straight pipes. Past studies considered the case of a closing in-plane bending moment on 90-degree pipe bends and proposed factors that account for the increased flexibility and high-stress levels. These factors are currently presented in the design codes and known as the flexibility and stress intensification factors (SIF). This paper covers the behaviour of an initially circular cross-sectional smooth pipe bend of uniform thickness subjected to in-plane opening/closing bending moment. ABAQUS FEA software is used in this study to model pipe bends with different nominal pipe sizes, bend angles, and various bend radius to cross-sectional pipe radius ratios. A comparison between the CSA-Z662 code and the FEA results is conducted to investigate the applicability of the currently used SIF factor presented in the design code for different loading cases. The study showed that the in-plane bending moment direction acting on the pipe has a significant effect on the stress distribution and the flexibility of the pipe bend. The variation of bend angle and bend radius showed that it affects the maximum stress drastically and should be considered as a parameter in the flexibility and SIF factors. Moreover, the CSA results are found to be un-conservative in some cases depending on the bend angle and direction of the applied bending moment.

Combined Bending and Compression of a Pressurized Circular Cylindrical Membrane Column

1965 ◽  
Vol 87 (3) ◽  
pp. 372-378
Author(s):  
W. E. Jahsman
Keyword(s):  
Compressive Strength ◽  
Cross Section ◽  
Compressive Load ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Maximum Load ◽  
Bending Moments ◽  
Lateral Deflection ◽  
The Cross

Load-lateral deflection curves are developed for a pressurized tube of circular cross section under combined bending and compression. The tube walls are assumed to have negligible compressive strength so that wrinkling develops if the stress tends to become negative. It is found that for a given bending moment, the load increases monotonically with deflection until a maximum is reached beyond which the load decreases with increasing deflection. An interaction curve of the maximum load versus bending moment shows that the presence of only a small amount of bending significantly decreases the maximum compressive load below the classical Euler load. Conversely, for bending moments which produce almost complete wrinkling of the cross section, only very small amounts of compressive load can be supported.

A New Approach to Analyzing Reactions and Deflections of Beams: Formulation and Examples

2006 ◽  
Author(s):  
I. C. Jong ◽  
J. J. Rencis ◽  
H. T. Grandin
Keyword(s):  
Boundary Conditions ◽  
Shear Force ◽  
Flexural Rigidity ◽  
Bending Moment ◽  
Bending Moments ◽  
Shear Forces ◽  
Concentrated Force ◽  
New Approach ◽  
Concentrated Forces ◽  
The Right

This paper is aimed at developing a new approach to analyzing statically indeterminate reactions at supports, as well as the slopes and deflections, of beams. The approach uses a set of four general formulas, derived using singularity functions. These formulas are expressed in terms of shear forces, bending moments, distributed loads, slopes, and deflections of a beam having a constant flexural rigidity and carrying typical loads. These loads include (a) a bending moment and a shear force at the left, as well as at the right, end of the beam; (b) a concentrated force, as well as a concentrated moment, somewhere on the beam; and (c) a uniformly, as well as a linearly varying, distributed force over a portion of the beam. The approach allows one to treat reactions at supports (even supports not at the ends of a beam) as concentrated forces or moments, where corresponding boundary conditions at the points of supports are to be imposed. This feature allows one to readily determine reactions at supports as well as slopes and deflections of beams. A beam needs to be divided into segments for study if it contains discontinuities in slope at hinge connections or different flexural rigidities in different segments. Several examples are included to illustrate the new approach.

Estimating Hydrodynamic Sectional Loads for FPSOs Using Artificial Neural Networks

2017 ◽  
Author(s):  
Espen Engebretsen ◽  
Zhi Shu ◽  
Jon Erik Borgen
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Shear Force ◽  
Bending Moment ◽  
Computational Time ◽  
Radius Of Gyration ◽  
Optimal Size ◽  
Diffraction Radiation ◽  
Wide Range ◽  
Artificial Neural

Sizing of a new build FPSO hull is an iterative optimization process, where the main dimensions of the FPSO are varied until the optimal size is found, within a defined input domain. A wide range of criteria should be evaluated per size iteration, and thus the sizing process may be a very time consuming task. In order to speed up this process, it may be beneficial to adopt an automated iterative algorithm for performing the sizing of new build FPSOs for the Concept and Front-End Engineering Design (FEED) phase. The hull steel weight should be calculated for each size iteration, thus the hydrodynamic bending moment and shear force are needed. Obtaining the hydrodynamic sectional loads requires relatively time consuming calculations (compared to e.g. the required hydrostatic calculation), such as linear diffraction/radiation analysis and stochastic postprocessing. The required computational time of the automated sizing algorithm can be significantly reduced by calculating the hydrodynamic sectional loads by a simplified estimator, eliminating the need for e.g. diffraction/radiation analysis. Such an estimator may be obtained by the use of Artificial Neural Networks (ANNs). This paper presents how to estimate the hydrodynamic vertical bending moment and shear force for FPSOs, within acceptable accuracy to be used for initial sizing, using ANNs. The estimators, i.e. the ANNs, take known inputs such as the main dimensions, draft and pitch radius of gyration of the FPSO. The ANNs are trained on a database containing linear diffraction/radiation analyses for a variety of FPSO main dimensions, hull shapes and loading conditions. The database has been established by batch processing of the DNV-GL software HydroD [1], Wadam [2] and Postresp [3] through MATLAB [4]. This paper presents the methods used to obtain the results contained in the database, as well as training and performance of the ANNs.

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.

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.

An experimental investigation of a right-angled single unreinforced mitred-bend subjected to various bending moments

1966 ◽  
Vol 1 (3) ◽  
pp. 248-263 ◽  
Author(s):  
N Jones ◽  
R Kitching
Keyword(s):  
Cross Section ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Straight Tube ◽  
Bending Moments ◽  
Curved Pipe ◽  
Design Procedures ◽  
Out Of Plane ◽  
Plane Bending ◽  
Comprehensive Study

It is well known that, upon the application of an in-plane bending moment, the initially circular cross-section of a curved pipe tends to flatten and become approximately elliptical in shape making it much more flexible than an equivalent straight tube. Mitred-bends exhibit similar properties though the behaviour is far more complex. A comprehensive study of a 90° single unreinforced mitred-bend having a radius/thickness ratio of 19 has been performed by means of a stress-probing method. In order to make the work more complete, results have been obtained for a similar bend when subjected to out-of-plane bending and twisting moments. Experimental measurements of stress and flexibility for each type of loading are discussed and certain modifications suggested to existing design procedures.

scholarly journals Expected Snow Loads on Structures from Incomplete Hydrological Data

1977 ◽  
Vol 19 (81) ◽  
pp. 185-195 ◽  
Author(s):  
J. Martinec
Keyword(s):  
Snow Cover ◽  
Frequency Analysis ◽  
Building Code ◽  
Return Periods ◽  
Snow Load ◽  
Hydrological Data ◽  
Regional Effects ◽  
Direct Measurements ◽  
Snow Loads

Abstract An assessment of snow loads in Switzerland was required for a revision of the building code. Settling curves of snow are used to compute water equivalents of snow if direct measurements are not available. Based on a frequency analysis, relations between the snow load and the altitude are given for various return periods. Problems of regional effects and of converting the snow-cover data to roof loads are outlined.

scholarly journals Expected Snow Loads on Structures from Incomplete Hydrological Data

1977 ◽  
Vol 19 (81) ◽  
pp. 185-195 ◽  
Author(s):  
J. Martinec
Keyword(s):  
Snow Cover ◽  
Frequency Analysis ◽  
Building Code ◽  
Return Periods ◽  
Snow Load ◽  
Hydrological Data ◽  
Regional Effects ◽  
Direct Measurements ◽  
Snow Loads

AbstractAn assessment of snow loads in Switzerland was required for a revision of the building code. Settling curves of snow are used to compute water equivalents of snow if direct measurements are not available. Based on a frequency analysis, relations between the snow load and the altitude are given for various return periods. Problems of regional effects and of converting the snow-cover data to roof loads are outlined.

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