Analysis A
Analysis in Kerillo generally involves determining the design forces acting on an element subjected to loads. These design forces are then used to inform the actual design of the element, verifying whether it meets the requirements of the relevant Eurocodes.
The basic loads that you enter will be factored according to your chosen Limit States. A series of a load combinations (the load and its accompanying factor or factors) will be generated to create a loadcase (a collection of load combinations). The generation of load combinations and hence loadcases are based on the requirements of BS EN 1990, Eurocode 0.
The type of analysis typically carried out is linear elastic - it's based on the linear stress/string and moment curvature laws. More specifically, Kerillo will perform a first-order analysis without redistribution i.e. the analysis is performed on the initial geometry of the element alone.
Elements A1
Kerillo supports the analysis and design of a range of different timber elements. For the analysis, you'll need to provide us with some basic information on the geometry of your element. For a timber beam this will be the height and width of the section, as well as the strength class of the wood.
The basic geometry of your element will not only inform the design, but is also used in the analysis of your elements. For example, in the case of a timber beam, the height, width and strength class are used to determine the deflection of the beam under the applied loads (the strength class informs us of the Young's Modulus, while the cross-section allows us to calculate the Second Moment of Area).
The analysis and design of most elements in Kerillo will start with you supplying the basic geometric and mechanical information.
Loads A2
Kerillo contains three different types of load: point loads, uniformly distributed loads, and uniformly varying loads (sometimes shortened to PTL, UDL and VDL respectively in the application). With these three loads you'll be able to accurately modal almost any scenario you're likely to encounter.
Each load has the ability to function as either a dead or live load (permanent or variable load in Eurocode terminology). When it comes to live loads you'll also have the option to tell Kerillo exactly what type of imposed load it is (this is based on the requirements of Eurocode 0, with the categories based on Table NA.A1 of the UK National Annex).
Types of Load A2.1
For the sake of completeness, we're going to pretend that you don't know what point loads, uniformly distributed loads, and uniformly varying loads are.
- Uniformly distributed loads — these are loads that act over a portion of your element and are uniform in magnitude
- Uniformly varying loads — these are loads that action over a portion of your element, but unlike uniformly distributed loads, the start and end of the load differ uniformly in magnitude
- Point loads — these are loads that act at a discrete point along your element
Creating LoadsA2.2
The process of creating loads is largely the same, regardless of the type of load. When dealing with timber beams, you can add a load by:
- Hovering or tapping the "Add" button found to the right-hand-size of the loads table
- Select the type of load that you wish to add
- In the load modal, fill out all the properties that you wish to apply to the load. At a minimum you'll need to supply a magnitude for the load
The load properties vary according to the type of load. You can find out more about individual loads and their properties in the following section.
Load Properties A2.3
Load properties are simply the name given to the characteristics that define the load, for example, to create a point load you'll want to specify the location and the magnitude of the load. There are other properties that can applied, each of which is discussed in the following sections.
Common Load Properties A2.3.1
Common load properties are properties which all to all types of load. Note that to access some of these properties you might have to click the "Advanced" button in the modal to reveal them.
| Name | Description | Type |
|---|---|---|
| Action Type | Whether the load is a permanent (dead) or variable (live) load | switch |
| Variable Category | If the action is set to a variable load, you will have the option to set the type of variable load | option |
| Description | Text to describe your load, for example a point load might represent a column above | text |
| Favourable | Whether the load is a favourable load (this will affect the load factors applied in accordance with EC0) | switch |
Point Load Properties A2.3.2
Point loads will have access to the following properties in addition to the common properties listed above.
| Name | Description | Type | Units |
|---|---|---|---|
| Value | The magnitude of the load applied | number | kN |
| Position | The location along the element at which the point load is applied | number | m |
| Angle | The angle at which the point load is applied | number | degrees |
Note: if you apply the point load at an angle other than perpendicular to the element, the resulting design force will be split input a horizontal and a vertical component. The horizontal component of the design force will be a compressive axial force when dealing with beams.
Uniformly Distributed Load Properties A2.3.3
Uniformly distributed loads will have access to the following properties in addition to the common properties listed above.
| Name | Description | Type | Units |
|---|---|---|---|
| Value | The magnitude of the load applied | number | kN/m |
| Start Position | The location along the element at which the distributed load starts | number | m |
| End Position | The location along the element at which the distributed load ends | number | m |
Note: if you leave the start and end positions empty the uniformly distributed load will be applied over the length of the entire element.
Uniformly Varying Load Properties A2.3.4
Uniformly varying loads will have access to the following properties in addition to the common properties listed above.
| Name | Description | Type | Units |
|---|---|---|---|
| Start Value | The magnitude at the start of the load | number | kN/m |
| End Value | The magnitude at the end of the load | number | kN/m |
| Start Position | The location along the element at which the distributed load starts | number | m |
| End Position | The location along the element at which the distributed load ends | number | m |
Note: if you leave the start and end positions empty the uniformly distributed load will be applied over the length of the entire element.
Loadcases A3
Loadcases are a series of load combinations (a load value with it's corresponding factor[s] that are derived from your chosen limit states equations).
Kerillo includes analysis for both Ultimate Limit State (ULS) and Serviceability Limit State (SLS). The specifics of each are discussed below.
Ultimate Limit State A3.1
Kerillo includes the option to analyse your elements with each of the Ultimate Limit State conditions in mentioned in Eurocode 0.
| Condition | Shortcode | Use |
|---|---|---|
| Equilibrium | EQU | To confirm that the structure of element is not unstable |
| Strength | STR | To confirm that the structure and its elements will not fail due to stress, by element instability or at connections |
| Geotechnical | GEO | To confirm that the foundations will provide the required strength and stiffness to support the structure |
An additional limit state condition - Fatigue (FAT) - is listed in Eurocode 0. However, for the design of timber based elements and structures, Fatigue is already account for through the Strength limit state.
Serviceability Limit State A3.2
For Serviceability Limit State there are two requirements to satisfy:
- Vibration
- Deformation
Vibration is accounted for through the design checks where applicable. For deformation, there are three SLS conditions that you can check your element against.
| Condition | Shortcode | Use |
|---|---|---|
| Charactistic | Chr | For irreversable limit states, where the deformation persists after the removal of the load |
| Frequent | Freq | For reversible limit states, where the deformation receeds after the removal of the load |
| Quasi-Permanent | Qui | For the assessment of long-term effects, such as creep |
Results A4
The results of your analysis are lumped together with the design results when you check your element. You'll be presented with a series of utility values that represent the capacity of the element under the corresponding design force.
For example, you might have a result for moment capacity with a value of 86%. This tells you that the element is at 86% of it's maximum allowable capacity for moment. If the value had been 120%, the element would be stressed 20% beyond it's allowable capacity, and therefore would not be suitable for use.
Typically, for a timber beam you'll have a result for moment, shear, bearing (if a bearing length is supplied), and deflection (if a deflection limit is supplied). If your timber beam is also subjected to a compressive axial force, you'll have a result for a combined moment and axial condition, as well as a separate axial result.
If you decide to produce a report of your element, you'll be able to view the force diagrams, and the loadcases and load combinations responsible for producing the design forces. The design forces are always taken from the loadcase which produces the highest value.
Note: Kerillo assumes that the peak force for shear and moment are coincident.
Design B
All design calculations are carried out in accordance with Eurocode 5.
Design Variables B1
The majority of the items which can affect your design are usually contained within a Design Variables block. In this block you'll typically have the option to select or adjust:
- Select the service class that the timber is exposed to
- Select the load duration to be applied
- Set the bearing length at the ends of the beam
- The allowable deflection limit
- The effective length in the Y and Z directions
- If the element is part of a load sharing system
- If the compressive edge is fully restrained
Some elements may have a few more or less inputs, but that's more or less it. All the hard work is done under the bonnet, freeing you up to stick on a brew and settle in to the latest copy of The Structural Engineer.
Design Results B2
A brief overview of the elements design results will be presenting after clicking the "Calculate" button. See the Analysis — Results section above for some pretty pictures and more detail.
If you decide to proceed with your design and produce a report, you'll have the option to include all the design checks in detail, or reduce it to a short and sweet summary.
Output C
Engineering software is pointless if it doesn't include reporting facilities, which is why we've not only included it, but allowed you to tailor your output to your needs and wants.
Reports C1
Element design reports are generally composed of five sections. They are:
- Title block
- Analysis results
- Design checks
- Summary of results
- Notes
You can include or exclude each of these items as you see fit.
Title Block C1.1
This contains all your company, contact, project and user information.
Analysis Results C1.2
This section is dedicated to displaying the results of the analysis. It will usually contain information regarding the design forces, which loadcases they were generated from and their force diagrams, if applicable.
Design Checks C1.3
This section of the report contains detailed design checks. For example, in the in case of a timber beam report, it would contain all the calculations for bending, shear, bearing and deflection checks. It may also contain checks for compression and bi-axial bending if your beam is subject to an axial force.
Summary of Results C1.4
The results summary is a table that contains an overview of your elements performance with regard to the allowable and actual stresses or limits. If you want to save on paper (or the readers time) you might opt for a short summary of the design results as opposed to including the calculations in full.
Notes C1.5
Notes allows you to include an other relevant information that might be pertinent to your report. It accepts text input only.
Printing Reports C1.6
When printing it's recommended you do so by clicking the "Print" button, as opposed to using your browsers print facility. This will allow us to tidy up the display for printing, if you option to use the browser print facility directly, you'll end up printing the entire webpage instead of the report pages.