This is a two stage process. The second stage is necessary to avoid lateral loads on simple beams and distributed loads on simple columns, but is done for all element types.
•
The initial decomposition of wind zone loads to wall members is similar to the roof decomposition. Again all types of elements are considered except bracing and cold rolled members.•
Full/partial UDLs and VDLs on elements (lengths of beams/columns between nodes) are distributed back to nodes as if the elements were simply supported at either end.Wind Modeller Documentation page 154 Chapter 45 : References
Chapter 45
References
1. British Standards Institution (2000). Loading for Buildings – Part 2: Code of practice for wind loads. BS6399-2:1997 Incorporating Amendment No. 1.
2. Cook, N.J. (1999). Wind Loading - a practical guide to BS 6399-2 Wind Loads on buildings. Thomas Telford, London. ISBN: 0 7277 2755 9.
3. Bailey, C.G. (2003). Guide to Evaluating Design Wind Loads to BS6399-2:1997.SCI
Publication P286.
4. BREVe software package version 2.0.4.2. Written by Cook N.J. copyright Building
HANDBOOK
Fastrak
CSC
Structural steelwork
analysis and design
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SIMPLE BEAM
Chapter 1 : Introduction and application Simple Beam Engineer’s Handbook page 157
Simple Beam Engineer’s Handbook
Chapter 1
Introduction and application
This is design software which allows you to analyse and design a structural steel beam or cantilever which may have incoming beams providing restraint, and which may or may not be continuously restrained over any length between restraints
You can use Simple Beam:
•
to determine those sections which can withstand the applied loading,•
to check a beam of known size to determine whether it is able to carry the loading. Unless explicitly stated all calculations in Simple Beam are in accordance with the relevant sections of BS 5950-1:2000. You may find the handbook and commentary to the Code of Practice published by the Steel Construction Institute useful.Practical applications
Simple Beam can be used both to design and check simple beams. You might find the following procedures useful.
Designing a beam
In the typical procedure below items in brackets [] are optional.
Step
Icon
Instructions
1
Launch Simple Beam,2
Create a new project giving the project name [and other project details],3
Choose the type of beam as either a Simple Beam or a Cantilever Beam [and give the beam reference details],4
Set Simple Beam into design beam mode,5
Define the properties for the beam:
•
grade;•
span.Simple Beam Engineer’s Handbook page 158 Chapter 1 : Introduction and application
Checking a beam
In the typical procedure below items in brackets [] are optional.
7
Define the loadcases that apply to the simple beam.8
Incorporate the loadcases into a series of design combinations,9
[Make any Design Wizard settings that you want to use to control the design.]10
Perform the design11
From the list of suitable sections preview the results for the more desirable sections and then choose the one that you would like to use,12
Add in any web openings that you need to allow access for services etc.13
Check the beam with the web openings. [Stiffen the web openings if necessary, or increase the size of the beam until the beam with openings is satisfactory.]
14
Specify the content of the report [and print it].15
Save the project to disk.Step
Icon
Instructions
Step
Icon
Instructions
1
Launch Simple Beam,2
Create a new project giving the project name [and other project details],3
Choose the type of beam as either a Simple Beam or a Cantilever Beam [and give the beam reference details],4
Set Simple Beam into check beam mode,5
Define the properties for the beam:
•
section size,•
grade,•
span,Chapter 1 : Introduction and application Simple Beam Engineer’s Handbook page 159
Worked Example
If you want to work through this example you will find the file Engineer’s Example in the
\documents and settings\All Users\Application
Data\CSC\Fastrak\Examples folder. You can open and use this file, but you can not save it away unless you change its name, this is done to protect the original.
Let’s take a simple example of a 9 m span spine beam with 6 m span secondary beams at third points.
6
Add in any web openings that you need to allow access for services etc.7
Give the details of the beam restraints.8
Define the loadcases that apply to the simple beam.9
Incorporate the loadcases into a series of design combinations,10
[Make any Design Wizard settings that you want to use to control the design.]11
Perform the check, (including any web openings),12
[Stiffen the web openings if necessary, or increase the size of the beam until the beam with openings is satisfactory.]13
Specify the content of the report [and print it].14
Save the project to disk.Simple Beam Engineer’s Handbook page 160 Chapter 1 : Introduction and application
The floor loading is:
Design Pass 1
If you run a design you will find that Simple Beam shows a dialog of acceptable sections. If no one has tailored the sections that Simple Beam investigates, then the list will appear as below.
If you move down the list of Available files, you will see all the Section Designations that can carry the applied loading. These are only the ones that pass the design, Simple Beam has tried all the sections in each of the Available files, to determine the acceptable ones. You may have noticed the different section designations in the progress bar as the design ran. However checking all these sections comes at a price, the more sections there are to investigate, the longer the design takes.
Simple Beam allows you to choose just the sections you want to include for the design through its Design Wizard.
Condition
Value
giving point load at 3 m and 6 m of
Dry Slab 2.0 kN/m2 36kN Services 1.0 kN/m2 18kN Live load 5.0 kN/m2 90kN
Chapter 1 : Introduction and application Simple Beam Engineer’s Handbook page 161
Design Pass 2
Remove the tick against all the Available files whose section types you don’t want to
investigate, and Simple Beam won’t look at any of these sections during the design process. If you remove the tick against all the Available files other than UBBeamOrder.Eur, and then re-perform the design you will find a significant increase in speed as Simple Beam only investigates the universal beams.
Furthermore Simple Beam investigates the sections in the order that they appear in the Section Designation list. If you scroll down many of the lists, you will find that there is a point at which larger sections give way to smaller ones again.
We have ordered the Section Designation list based on our many years experience of the industry, the sections at the top of the list are the ones we know you prefer to use, whilst those at the bottom are those which you use less frequently if at all. By default all the Section Designations are ticked, but you might want to remove the ticks against some or all of the non-preferred sections. Again this will speed the design process.
You may also have other requirements specific to your own company, for instance you may never want to use sections with flanges less than 150 mm wide for erection purposes. If you remove the tick against these section sizes, then Simple Beam will never include them when it is performing a design. Thus you are controlling the design, making Simple Beam look at just the section designations you are likely to accept, and in the process speeding up the design itself.
Simple Beam Engineer’s Handbook page 162 Chapter 1 : Introduction and application
Design Pass 3
With the tick removed against all the non-preferred sections, and all sections with flanges less than 150 wide, Simple Beam only has to check around 20 sections and the design is
instantaneous.
Simple Beam maintains the Sections for Study settings that you make, until you choose to change them again. It is therefore worthwhile taking the time to tailor the list so that Simple
Chapter 2 : Scope Simple Beam Engineer’s Handbook page 163
Chapter 2
Scope
This section summarises the scope of your Simple Beam application. You will find information on items such as:
•
basic beam details,•
available steel sections,•
web opening checks.•
types of load that may be used,•
Ultimate Limit State design checks,•
Serviceability Limit State checks,Simple Beam has been developed in order to provide you with a comprehensive design tool which can determine the sizes of member which can carry the forces and moments resulting from the applied loading.
Alternatively you may give the size of a beam and Simple Beam will then determine whether it is able to carry the previously mentioned forces and moments and satisfy the deflection requirements.
Additionally you can also use Simple Beam to check any web openings that are necessary, stiffening them where needful to attain an acceptable result.
Scope of simple beam
The following sections cover each of the aspects of simple beam design, and indicate the power of the Simple Beam application.
Beam
You can specify and design any simply supported simple beam with a span up to 100 metres.
Steel sections
Simple Beam can handle design for an international range of steel I-sections for many different countries.
Web openings
If you need to provide access for services, etc., then you can add openings to a designed beam and Simple Beam can then check these for you.
You can define rectangular or circular openings and these can be stiffened on one, or on both sides.
The checks that are performed are in accordance with the guidelines and design process given in the booklet Design for openings in the webs of simple beams.
Simple Beam Engineer’s Handbook page 164 Chapter 2 : Scope
We advise you to comply with the following positional recommendations for web openings:
•
Web openings are designed using the bending moment and vertical shear values at the sideof the opening where the moment is lower,
•
Openings should preferably be positioned at the mid-height of the section. If not, the depth of the upper and lower sections of web should differ by not more than a factor of two,•
Openings should not be located closer to the support than two times the beam depth or 10% of the span whichever is the greater,•
The best location for any opening is between 1/5 and 1/3 of the span from a support in uniformly loaded beams, or in lower shear zone of beams subject to point loads,•
Openings should be not less than the beam depth, D, apart,•
Unstiffened openings should not generally be deeper than 0.6D or longer than 1.5D,•
Stiffened openings should not generally be deeper than 0.7D or longer than 2D,•
Point loads should not be applied at less than D from the side of the adjacent opening. You cannot currently automatically design sections with web openings, you must perform the design first to get a section size, and then add and check the openings. This gives you complete control of the design process, since you can add appropriate and cost effective levels of stiffening if required, or can choose a different beam with a stronger web in order to reduce or remove any stiffening requirement.Note Adjustment to deflections. The calculated deflection at both construction stage and simple stage are adjusted to allow for shear deformation in the web openings. This is carried our following the principles in Ref. 2 and AD 068.
Note Dimensional checks. The program does not check that openings are positioned in the best position (between 1/5 and 1/3 length for udl’s and in a low shear zone for point loads). This is because for anything other than simple loading the best position becomes a question of engineering judgment.
Restraint conditions
If you need to check the lateral torsional buckling of the beam you can:
•
define the degree of fixity that the end connections are able to provide and hence an effective length associated with the support,•
position additional restraints at any point along the beam (Simple Beam automatically uses 1.0L and 1.2L as the factors for Normal and Destabilizing loads),Help For a definition of Destabilizing Loads see BS 5950-1:2000 clause 4.3.4.
•
Simple Beam automatically takes the average of the effective length factors for differingsupports, or between those for the support and the adjacent sub-beam.
•
alternatively you can specify the factors that you want to use for the lengths between restraints, or you can enter the effective length of the sub-beam directly by entering a value (in m).Chapter 2 : Scope Simple Beam Engineer’s Handbook page 165
Applied loading
You can specify a wide range of applied loading for the simple condition:
•
uniform distributed loads (over the whole or part of the beam),•
point loads,•
varying distributed loads (over the whole or part of the beam),•
trapezoidal loads.Design checks
When you use Simple Beam to design or check a beam the following conditions are examined in accordance with BS 5950-1:2000:
•
section classification (Clause 3.5.2),•
shear capacity (Clause 4.2.3),•
moment capacity:•
(Clause 4.2.5.2 for the low shear condition•
Clause 4.2.5.3 for the high shear condition),•
lateral torsional buckling resistance (Clause 4.3.6)Note This condition is only checked in those cases where the profile decking does not provide adequate restraint to the beam,
•
total load deflection check.Error messages and limitations
As you are defining the data for your beam Simple Beam continually checks to ensure that the data is valid. If a particular value is not valid, then it will be shown using a colour of your choice in the dialog. If a value causes a potential problem, then a different colour will be used in the dialog. If you allow the cursor to rest over the error or warning field you will see a tip telling you the acceptable range of input. Until all the information within the dialog is valid (but not free of warnings) you will not be able to save the dialog since OK will be dimmed. Although checking in this way prevents you from defining an invalid beam there are some cases where particular errors occur that cannot be trapped in this way (for instance where an error occurs due to inconsistencies that have arisen between information covered on different dialogs). In these cases when you attempt to perform a design you will see an error message indicating that data is not suitable for the design to proceed. Each message is self-explanatory. You should take a careful note of the error message and then change the beam data to correct the problem.
If there are other problems with the design, then you will see a series of warning messages in the results viewer. You should take note of any such warnings and take the action that you deem appropriate. Engineering tips are also available in the results viewer which may give you useful information about the steps required to overcome a particular problem.
Simple Beam Engineer’s Handbook page 166 Chapter 2 : Scope
Note Adjustment to deflections. The calculated deflections are adjusted to allow for shear deformation in the web openings. This is carried our following the principles in Ref. 5 and AD 068.
Note Dimensional checks. The program does not check that openings are positioned in the best position (between 1/5 and 1/3 length for udl’s and in a low shear zone for point loads). This is because for anything other than simple loading the best position becomes a question of engineering judgment.
Note Asymmetric Slimflor beams (ASB) For all section types flange classification is only performed for the top flange, because for a simple beam this will be the flange in compression. However, in the case of a cantilever beam the bottom flange goes into compression. Hence for a cantilever beam, for the flange
classification to be valid the section must be symmetric about the major axis. As a consequence ASB sections must NOT be specified for cantilever beams.