Design of Residential Buildings Using CSC Orion (Step by Step with Eurocode 2)

Previously, I discussed the Structural Analysis and Design of Residential Buildings Using Manual Calculations , today, I will clearly explain step by step procedures on how to design residential buildings using CSC Orion. You should be able to make use of CSC Orion for Design after reading this Article.

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GENERAL ARRANGEMENT (G.A.)

The architectural drawing enables the engineer to prepare what is normally referred to as the ‘general arrangement’ of the building, popularly called the ‘G.A.’. The G.A. clearly specifies the disposition of the structural elements such as the columns, beams, and the panelling of the floor slabs. The G.A. also contains the labelling of the axes and the members, based on the grid lines. After completing the GA, the engineer makes preliminary sizing of the structural elements which may be governed by past experience or by deflection requirements based on the code of practice. After the sizing, the engineer is faced with the challenge of loading the structure. But let us briefly review how we go about the G.A.

There are no spelt out rules about how to select the appropriate general arrangement of a structure. To me, adequate presentation of the general arrangement has more to with years of design experience.

In this article, a small residential building on a 10m x 15m plot of land has been presented for the purpose of analysis and design. The ground floor plan of the building is shown in the diagram below. From the architectural disposition, the building is a two family occupancy arrangement, with each family occupying a floor level. To minimise interruption, the staircase has been placed at the extreme of the left-hand side of the building. The 1st floor of the building is also shown below. It has a balcony at the kitchen, a cantilever sit-out/verandah, and a little balcony by the staircase area. Apart from that, the general arrangement is fairly the same.

 

My style of General Arrangement (GA)

The architectural drawing of a building can come in many forms. If it comes as a soft copy of a CAD drawing, then the work is made much easier. It is advisable to place the ground floor plan side by side on the graphical user interface window of your CAD program (e.g. AUTOCAD) with the floor plan of the subsequent stories as shown in the diagram below:

Note that architectural drawings come with their own grid lines for different axes. In the current building, we are trying to design here, some details (like gridlines) have been removed from the architectural drawing (Ground & First Floor Plan) for the purpose of clarity of very necessary details like dimension lines. After placing the floor plans side by side on the window, you can start noticing a few different things about the floor plans immediately. For more ideas on how to proceed, copy the floor plans to another location on the window (still leaving the ones you placed side by side). Now, copy the plan of the first floor, and paste it on the ground floor plan, so that the dimensions and axes are matching perfectly.

You can choose a prominent corner of the building as a pick-up point for your copy and paste operation. For more clarity, you can change the colour or thickness (or both) of the ground floor elements and first-floor elements and gridlines, so that you can rightly distinguish between the two.

After you have pasted the first floor on the ground floor, you can now see the interaction of the two floors. All axes that are coincidental will be visible, and all axes that are on the first floor and are not on the ground floor and vice versa will also become visible. At this point, you can also see the outline of block work on the first floor, and this is more critical for the general arrangement of the floor slab. It will properly guide you on the selection of floor beam axis. The block work axis of the ground floor will aid you on the design of the foundation plan. Do not work on the ground floor alone without looking at the first floor – the last thing you will want to happen is to place a column somewhere on the ground floor, and see it popping out through the lobby of the first floor. So carefully make your selections based on matching axes, and fair uniformity. And as I hinted earlier, your arrangement must be consistent with what the architect has in mind. So this is much like art, and you have to use your ingenuity here. (My supervisor during my industrial training once told me that it is one of the hardest things to do in structural design).

As a hint, the next thing to do is to create a rectangular box (say 230 x 230mm) on AUTOCAD and hatch it with any pattern appealing to you (I normally use SOLID). This represents your columns on the floor plan. Now carefully copy this element and start pasting it at the locations where you have decided to place your columns (this usually occurs at intersections between axes). Also, I normally start at the corners of the building; more often than not, columns must be there irrespective of the arrangement. After that, move to the interiors and place your columns as desired. After you are satisfied with what you have done, carefully check the interaction of the arrangement, and make sure that they are reasonable. Areas, where primary and secondary beams will interact, will also become very visible.

To make some points clearer, let us look at a portion of the plan we are considering in this article;

We wish to place columns along axis A. A little consideration will show that we can place columns at points A1, A3, and A5. Also, we can alternatively place columns at points A1, A2, A4, and A5. Without reading further, ponder on that arrangement and see the alternative that you will prefer.

Obviously, A1 and A5 are certain (corner columns). If I should choose to place a column at point A3 (neglecting A2 and A4), these are the implications:

• I will have a larger span for A:1-3 and A:3-5
• I will have a floor beam running along axis 3 (the beam will probably have to run down to axis C before encountering another support, unless I extend any other beam to act as primary beam to it). That’s a complexity on its own.
• The floor slabs on the bedroom and kitchen will be subjected to block work load from the walls on axis 2 and 4, which some part of it will be subsequently transferred to the beams on axis 3. This is based on the assumption that the ground floor block walls do not carry any load (so I have neglected the effect of the ground floor axis 2 and 4 walls on this assumption)

If I choose the second alternative;

• I will have shorter spans, and three spans instead of 2. The bending moment on Span A:2 – 4 will probably be hogging.
• I will have a wall along axis 3, but by proximity and considering load sharing implication, it will not be critical, and will not affect my designs like the previous alternative.
• My floor beam at axis 2 will stop at axis B, and my floor beam at axis 4 will stop at the wall close to axis B. So I will not have a complex arrangement to deal with.

Considering all these consequences, I preferred the second alternative. However, if the building is being located in area where the soil is so bad that constructing a single footing will be very expensive, we can settle for alternative 1. The final GA I adopted for the whole model is shown diagram below;

 

MEMBER DATA

Thickness of slab = 150mm

Dimensions of floor beams = 450mm x 230mm

Dimension of roof beams = 250mm x 230mm

Dimensions of columns = 230 x 230mm

 

All the elevation views of our case study building are as shown below;

Approach View

Rear view

Right Side View

Left Side view

Section through the building (section A – A)

 

 

MODELLING ON CSC ORION

Orion is a structural analysis, design, and drafting program developed for the design of concrete building systems (CSC Orion Reference Manual). The program consists of several modules for performing the following tasks;

[1] 3-D Analysis of the structural model of the building

[2] Column, Shear wall, Slab, and Beam reinforcement design

[3] Column, Shear wall, and Beam detailing

[4] Foundation design and detailing

[5] Analysis and Design of Stairs

[6] Concrete and Steel Quantity extractions

Unlike general purpose structural analysis program, Orion is concentrated on accurate analysis, fast data preparation, automated reinforced concrete design, and automated preparation of engineering drawings and details. In summary, Orion model allows you to;

[1] Create GA drawing

[2] Design the floor slabs, and decompose floor loads onto the beams

[3] Analyse the building frame

[4] Design continuous beams, columns, walls, and foundation

[5] Automatically generate RC detail drawings

Having completed your general arrangement, you have to go into modelling of the structure. GA is the first step, irrespective of whether you are undertaking manual or computer-aided analysis. It is assumed that you have already purchased and installed Orion software package on your computer. There are many approaches of modelling in Orion like importing from other software etc. But in this text, I am concentrating on modelling from scratch.

The structure below is our end target.

Final Target Model on CSC Orion

 

[1] GETTING STARTED

Launch the Orion Software. On launching, this dialogue box below comes up;

Click on New Project.

Enter the Project Code of your choice. In this case, note that no spacing is allowed on the project code. You can use underscore to separate words. Hit the ENTER button

On hitting the ENTER button, the Settings Centre Dialog box comes up as shown below. Select UK(Eurocode), and ensure that that all the parameters on ‘Current Project Settings’ are checked. Then click on IMPORT.

Select your ‘sheet data as you desire, and click OK. Note that various sheet sizes like A2, A3, A4, A5 etc are available from the drawdown menu. Specify as desired and click ok.

At this point, the graphical user interface (GUI) comes up, shown in the diagram below. The green rectangle on the screen represents the sheet size you have selected in the previous dialogue box. Now, we wish to create the GA of the building. By this time, you should have manually prepared your GA (could be a rough sketch), and have accurately placed your beams and column where you desire them to be. In this case, note that the GA we want to prepare has been shown above, you must have carefully specified the preliminary structural dimensions of your elements, and the concrete cover viz;

Dimensions of columns (In this case 230 x 230 mm)

Dimensions of all floor beams (In this case 450 x 230 mm)

Dimensions of roof beams (In this case 250 x 230 mm)

Thickness of slab (h) = 150mm

CSC Orion main GUI page

 

[2] CREATING AXES

Having decided on all these things, go to Axes (circled in red in the diagram above) by the left-hand side of the GUI, and right click on it. At this point, we wish to create all our specified axes. So by right-clicking on it, select the Orthogonal Axis Generator, and click on it. Our cursor at this point changes to a hairpin cross with thin lines. Now move your mouse to the specified sheet on the GUI (the green rectangle box) and click at a good location on it. The following dialogue box comes up;

Dir-1 Axes represent your y-axis (vertical axes on your plan), while Dir-2 Axes represent your x-axis (horizontal axes on the plan). You can interchange your Axis Label as you wish. So to be consistent with our original plan, let us leave it the way it is.

Axis spacing(s) refers to the spacing of the various axes (or our gridlines). Even though it is not specified in the GA diagram, the edges of our cantilever slab must have its own axis. This is to facilitate the modelling of our Cantilever slabs.

So from our GA, we can specify the axis spacings (each spacing is separated by a comma, all dimensions in mm)

Dir-1 Axes

Axis Spacing(s): 823,3715,1285,3625 (entering values from bottom to the top)

Dir-2 Axes

Axis Spacing(s): 2000, 3225, 1400, 1960, 3400 (entering values from left to the right)

Now you will discover that there are some gridlines that we have not captured. Do not be bothered. If you wish, you can take your time and specify as accurately as possible, the spacing of the gridlines. This is probably the best way. Otherwise, there is a faster way of doing it, which is to offset the already existing axis by the distance you want. The only difference is that your labels will become alphanumeric. For instance, if you offset axis A, you will probably get axis label A1. I guess this should not be a major concern since it is subsequently editable. Leave the axis extension line the way it is (at 2000mm) and click OK.

On clicking OK, the figure below is obtained on the user interface, showing the grid lines.

On looking at the diagram above, you can verify that Axis E on the interface stands for the Axis A on our GA, and Axis 6 on the GUI stands for the axis 8 on our GA. Now, if you look at our GA, we have axis 7, which we have not yet captured. To create it, we know the distance between axis 7 and 8 to be 2035mm on our manual GA. We wish to create axis 7 on Orion by offsetting axis 8. Through this way also, we create all other axes, including the free edge of our cantilever slabs. So right click on Axis 6 on the Orion GUI, and click on Offset Axis.

Now, the dialogue box by the right above appears, and you have to specify the offset distance by inputting 2035mm on ‘Offset from Previous’. After inputting the value, click on the direction you wish to make the offset. In this case, you have to click towards the left-hand side of axis 6 for the axis to be created. Through this way, we create all other axis remaining on our GA.

The final axes/gridlines that capture the entire model is shown below;

 

[3] CREATING OF COLUMNS

After creating our axes, the next step is to place the columns at their exact locations. We have to be careful to ensure that the columns are where they are supposed to be.

Click on Column icon at the menu bar

Input the cross-section of the column (in mm) at the spaces provided at b1 and b2. b1 and b2 are the depth and width of the column as defined below. e1 and e2 define the eccentricity of the axes with the column. So in the cases where you are modelling a column that will project out of a building, you should have a good idea of how to manipulate your eccentricities. In this case, I want it to pass through the centroid of the column, so I will have to divide the cross-section by two; hence e1 = e2 = 230/2 = 115mm

Now, carefully move your columns to the GUI, and place the columns at the locations they belong by clicking your mouse at the intersections where we have our columns. Your final output should be as shown below- carefully verify its consistency with our GA.

 

[4] CREATION OF FLOOR BEAMS

After creating our columns, the next step is to place the floor beams at the axes where they belong.

Click on beam icon, and the dialogue box below comes up

Input b, which is the width of the beam. In the case we are treating, b = 230mm. b2 is the eccentricity of the axis with the beam, which we desire to pass through the centroidal axis at b/2 = 230/2 = 115mm. hbot is the total depth of the beam, and the value is 450mm for our present case study. Disregard htop by leaving the value as zero.

To add the beams, click at the intersection point of any column you choose as your starting point, and drag it to another column location. Keep clicking and dragging it until you create all the floor beams. Note that a beam that is being dragged can only terminate at a point where two orthogonal axes intersect. Your final arrangement should be as shown below;

To ensure that we are in order, click on 3D icon at the bottom of the GUI to see the 3D view of our creation so far

If your arrangement is as shown above, let us proceed. Click on the plan icon and return to the plan view.

 

[5] DESIGN PARAMETERS SETTINGS

Ideally, we should just go ahead and create our floor slab, but there are some settings that I will like us to do. It will subsequently affect our results.

Take your mouse and click on Building on the menu bar. Select Parameters

On clicking Parameters, the dialog box below comes up;

Ensure once again that the Code for design is at Eurocode 2(UK), and that the Loading Code is Eurocode 1(UK).

Click on Foundations, and set the allowable stress of soil to 150 KN/m2 (allowable bearing capacity).

Since we are not bothered about the effect of wind, you can neglect Lateral Loading and Lateral Drift.

You can go to Title, and set project title and other information as you desire.

Close the dialogue box, and go to Building Analysis. We have some important settings to take care of there.

Then click on Edit Materials, and another dialogue box comes up

We can select the concrete grade we are employing in our design by clicking on the ‘concrete grade’ tab of any of the elements. In this case, fck = 25 N/mm2 (cylinder strength) for all elements. The default as you can see above is C35/45. So select C25/30 of which the compressive strength is 25 N/mm2. Now check the box for ‘Apply to All Member Types’ to apply it to all the structural Elements.

In the same vein, we can select the steel grade by clicking on the ‘steel grade’ tab of any of the elements. In this case, we are adopting fyk = 460 N/mm2 for all elements. The default steel grade as you can see above is Grade 500 (Type 2). So select Grade 460(Type 2) of which the yield strength is 460 N/mm2. Now check the box for ‘Apply to All Member Types’ to apply it to all the structural Elements. Click OK

You can verify that the density of concrete is 25 KN/m3 by default. You can leave the weight of block and coefficient of expansion the same way it is.

You can also select your desired bar sizes for various elements by clicking on the ‘Dia’ tab. For instance, if you desire the minimum bar sizes for your columns to be 16mm, you can specify it by checking and un-checking the bar sizes as you desire. Click OK after all your selections.

After editing the materials, you can go the Parameters Tab. A little consideration will show that we have already taken care of that. Now go to the load combinations Tab. On clicking on it, we the following dialogue box below pops up. We can see that the partial factor for dead loads is 1.25, instead of the 1.35 that we know in Eurocode 2. We have to change that. You can start by editing them one after another, or you click on ‘Loading Generator’ Tab.

 

On clicking the Load Generator Tab, the dialogue box below comes up. Now change the Maximum G Factor from 1.25 to 1.35. You can see that the partial factor for variable loads is 1.5. We will leave that the way it is. Then click ok

 

On doing that, the dialogue box below comes up;

 

As you can see, the number of load cases has been reduced to just 8. These 8 load cases are sufficient for our analysis. On going to the next tab, you can neglect, ‘Storey loads and Parameters’ tab.

After we are done with this, we can then start modelling of our floor slabs.

 

[6] MODELLING OF FLOOR SLAB

Click on the ‘Slab’ icon

On clicking the slab icon, the dialog box below comes up.

On the General Tab, Change the thickness of the floor slab (h) to 150mm

Specify the concrete cover (Con. Cov) = 25mm

On the Loads Tab, the self weight of the slab is automatically calculated based on the density of the concrete, and the thickness of the slab. As you can see, it is equal to 3.75 KN/m2

There are additional dead loads to be specified;

Weight of finishes = 1.2 KN/m2

Partition allowance = 1.5 KN/m2

The total dead load is 2.7 KN/m2

The specified imposed load (see chapter 2) is 1.5 KN/m2

After specifying all the data above, now move the cursor to the GA and start clicking on each panel.

Due to the presence of gridlines at the edge of the cantilever panels (panels 10 and 11), the panels are automatically generated. But a little consideration will show that PANEL 5 is very problematic due to the presence of multiple gridlines, and the fact that we have some curved sections. See the sample difficulty below.

You can verify that the arrangement we have at PANEL 5 is very far from the arrangement that we have in mind. Multiple panels have been created based on the areas created from the gridlines. So how are we going to solve this problem? We are going to apply a little trick. Also note that there is need for a new gridline to adequately capture the edges of the slab of PANEL 5 (see the MANUAL GA). We will offset axis B1 by 1200mm below to create the edge (this creates Axis B2). Now, we have to delete the multiple slabs created in the region of interest (simply click on each of them, and hit the delete button). We will now create beams along the exterior edges of PANEL 5, including a curved beam where it is required (follow the procedure described for beam creation). See what was done below.

We have created beams from axis 6:B1- B2, Axis B2: 5 – 6, and Axis 3: B – B2. Now we will create a curved beam along Axis A: 3 – 5. To do this click the beam creation cursor at3B2 axis intersection, hold the ‘shift’ button, and click at the 5B2 intersection. The following dialog box comes up;

Place the Chord Offset (h) as – 450mm

Making it negative implies that you want the chord to curve in the reverse direction. The centre offset (c) and radius (R) are automatically generated based on the value input.

The result of this activity is shown below;

The beam outlining the exterior of the slab has been created as shown above.

Now, create a slab on the area by clicking on the slab icon as described above, and clicking on the panel area. Now DELETE the exterior periphery beams that we created for it. By implication, we have created the slab.

 

Setting Slab Types Automatically

Now clear all selection by clicking on ‘clear selection’ icon

Now, go to the slab icon by the left-hand side of the screen, and right-click on it. On the options, click on ‘Set Slab Types Automatically’. When the ‘Slab Type Determination’ dialog box comes up, click OK

Now a message pop up comes up (shown below) to show that the slab type has been set (based on edge conditions, and direction of spanning).

As you can see, 1S11 type (PANEL 9 of our GA) cannot be automatically determined (the curved slab we created). The implication of this is that we will use Finite Element Analysis for our floor slab load transfer, instead of Yield Line method. Click OK.

Kindly refer to Orion Engineer’s handbook for more information on Finite Element Analysis and Yield Line Methods of slab load transfer.

 

[7] COMPLETING THE MODEL

We wish to specify the number of storeys on our structure. Go to Storey by the left-hand side of the GUI, right click on it, and click on Insert Storey. On the Add Storeys dialogue box that pops up, enter the number of storeys as 2. Click ok.

Generating Storey

We wish to generate some of the elements on the ground floor to the 1st floor. We will generate only the columns and the floor beams. However, we know that roof beams are of different cross-section with the floor beams. So all we have to do is to change their properties.

Go to Storey again, and right click on it. Select generate storey. When the ‘Generate Storey’ dialogue box pops up, click on St01 (Storey 1) as the Source Storey, and St02(Storey 2) as the Target Storey (see the plates below). That is to say, we are moving some elements from the ground floor to the 1st floor. As I hinted earlier, we are generating only columns and beams. So you will have to uncheck Slabs and its associated elements. Click OK

Click on 3D view icon, our output should be like this;

Specifying Storey Height

Got to Storey again and right click on it. Select ‘Edit Storey’, and the following dialogue box comes up.

The height of each storey is 3000mm which is desirable, and we are extending the foundation depth to 1500mm. 1000mm is actually the real depth of the foundation, while 500mm is the height of the Damp Proof Course (DPC) above the ground level. We should account for this for the purpose of ground floor column design. Click OK. You can view the effect of this on 3D view if you wish.

Arranging the roof beam

Go back to the plan view;

Click on St02 twice, to switch your plan to the roof beam removing some unnecessary beams, adding some important beams, and editing the depth from 450mm to 250mm. I am removing beams I marked X, and drawing some green lines in the areas that I am adding new beams.

We need to add the roof beams to the front area to adequately brace the front columns. The roof beams will aid in resisting possible wind loads, even though we are not explicitly accounting for it in this design. Also edit the depth of the beam to 250mm, by right-clicking on it, and changing hbot to 250mm. For aesthetics and to represent the architectural disposition, leave the beams at the front column as 450mm. The final 3D disposition should be as shown below.

 

[8] LOADING ON CSC ORION

This where we specify the loads acting on the floor beams and roof beams.

Loading the floor beams with wall load

Click on St01 twice, to return to the first-floor plan. Right-click on any beam that will carry any block workload. Click on ‘Edit Beam Wall Load’. On Clicking on it, the Load Profile Editor (Wall Load) dialogue box comes up. The unit weight of block work and finishes in Nigeria averages 3.47 KN/m2 (Oyenuga, 2009), and the height of the wall is 2.75m. As you know, the height of the storey is 3.0m and the roof beam is dropping by 250mm (0.25m), so the height of the wall is 3.0m – 0.25m = 2.75m. The thickness of our wall is 230mm. Note that we are neglecting the effects of opening on the wall load, so as to easily relate with our manual analysis results. On the other hand, it is more conservative. With the data generated, the dead load is automatically generated. Click OK

Note: You can specify the wall opening dimensions (doors and windows) at the locations specified.

The colour of the beam carrying the wall load now changes to purple (see the pictures above). We can copy the beam wall load to the other beams where it applies. Right click on the beam and click on ‘Copy Beam Wall Load’. Hold the control button and click on all the beams where you want the load to be applied. Then right click your mouse, and click on ‘Paste Copied Beam Loads’. To verify that you are successful, all the beams affected will change to purple. You can verify that I did not load the beams crossing the lobby area with wall load.

Loading the staircase floor beam

The staircase loading being transferred to the floor beam has been manually defined. A uniformly distributed load dead load of 10.837 KN/m, and a live load of 4.9595 KN/m has been manually applied to Beam D:1-2.

Loading the roof beam

Knowing full well that the beam self-weight is calculated automatically. Let us specify the roof dead load as 2 KN/m, and the weight of parapet (concrete fascia) as 2.0 KN/m for the external beams.

Imposed load on the roof, let us take 0.85 KN/m.

Therefore total dead load for external roof beams (Gk) = 4 KN/m

Therefore total dead load for internal roof beams (Gk) = 2 KN/m

Switch to the St02 (roof beam) and right-click on any external beam of your choice. From the drawdown list, select Edit Member loads, and the dialogue box below comes up.

Click on ‘New Load’ Tab

When the ‘Load Profile Editor’ Dialog box comes up, change the load to uniformly distributed load. Enter the Dead Load and Imposed Load as specified. Click OK

Now, right click on the beam and click on Copy Beam Manual Load. Paste on all external roof beams. Repeat the process for internal beams (remember the dead load is reduced to 2 KN/m).

 

 

[9] SPECIFIC MEMBER DESIGN SETTINGS

Before we go into analysis, there are some further specific settings that I will like us to look at.

Go to Settings, and select Beam Design Settings, and Select Storey beam Settings

When the ‘Settings and Parameters (Storey Beams)’ dialogue box comes up, you can make the adjustments as you wish;

For instance, the option of checking shear at the column face, or at ‘d’ from the column face is available. It is better to leave other options the way they are. For more information on this, you can read the Orion Engineer’s Handbook. Also, all other settings regarding detailing, bar curtailment, etc can be adjusted here. Note that leaving some values as zero means that code requirements should be used. Otherwise, you can specify yours. The only adjustment I did was to specify my minimum steel for beams as Y16mm and Hanger bars as Y12mm.

Also, go to slab design settings and set the minimum concrete cover to 25mm.

I recommend that you leave column design settings the way it is. You can make adjustments on the steel bar sizes if you wish though. Note that the values we input while editing materials influences the number of options we have for steel bar sizes in specific member design settings.

Column spanning more than one storey (Axis G columns)

If you look at the previous 3D views, you will verify that the front columns at axis G of our GA should be single without being broken at the 1st-floor level. We can take care of this and change it to a single column length. This is necessary so that in the design of the columns, the appropriate length of the column will be used for the calculation of slenderness effects.

To do this, return to St02 (Storey 2) plan view

Right-click the column, and go to Properties

Change the Len(Storey) to 2, so that the column will span for 2 storeys. Update this for the three columns concerned.

Now, go back to St01, and delete the columns at that level. The 3D view should be as shown above.

 

[10] SLAB LOAD DECOMPOSITION

Now that the model has been satisfactorily completed, it is time to start the analysis.

Somehow, I normally like to start with the decomposition of the slab load using Finite Element Analysis.

Click on Load Decomposition by FE (pointed with red arrow above).

The dialog box above comes up. Check that you are currently on Storey 1. Click on ‘Determine Loads Transferred from Slab’. Immediately, you are taken to the finite element analysis page (see the picture below). On the FE analysis page, click on ‘Generate Model’ to mesh the floor plate. Once the meshing is complete, close the page to run the analysis. Click Close, and ‘Apply to all beams in the current storey’.

Note that you can adjust the mesh sizes to suit the accuracy level that you are looking for at this page.

Now, all the loads from the floor slab have been transferred to the floor beams

 

[11] FINITE ELEMENT FLOOR ANALYSIS

Click on ‘Finite Element Floor Analysis’. The dialog box below comes up.

On the Column/Wall Model Type, select Short Frame Model, where the structure is represented as a sub frame with the upper and lower columns fully taken into consideration. For other model types, refer to Orion technical manuals.

Another point of interest is the stiffness factors. Orion carries out Finite element analysis based on the input rectangular sections. Therefore, when you are analysing your floor beams, you may want to increase the stiffness to account for the flanges, which are typical for reinforced concrete buildings.

For instance, consider beam A: 1 – 3 on our GA. The effective flange width according to Eurocode 2 is 895mm. We will do a little comparison to show the modification of stiffness that we are talking about.

The moment of Inertia (Ixx) of Figure (a) according to the theorem of the parallel axis is 0.003 m4

The moment of Inertia (Ixx) of Figure (b) is 0.001746 m4

The ratio of the stiffnesses is about 1.76. Therefore, I normally take an approximate beam stiffness factor of 1.5 as adequate. However, this actually calls for more review.

For slabs, Orion advises that a reduction be made in the value of E to account for creep and cracking on the long term since the cross section is used for the calculation of Ixx. For flat slabs, a range of 0.16 to 0.25 has been recommended. 0.16 is ideal for offices and heavily loaded buildings, while 0.25 is ok for residential buildings. For more information on stiffness factors, kindly read the Orion Engineers Handbook (Page 132). So for this particular work, we are increasing beam stiffness by 1.5, and reducing slab stiffness by about 75%.

Now, for this example, check all options except for including ‘Column Section in FE Model’. It is more ideal for flat slabs. Now click on Floor Mesh and Analysis. It is however advisable to do for the 2nd storey first (a kind of chase down)

Generate the model, and close to run the analysis.

After the analysis, check the AXIAL LOAD COMPARISON REPORT by clicking on it.

The axial load comparison report is satisfactory.

 

[12] FLOOR SLAB POST PROCESSING

Click on ‘Analysis Post-processing’

The post-processing page comes up.

Change it to plan view at the second icon at the top left corner of the screen. Click on ‘standard Contours’. Now, you can view the stress contour for different planes, such as Mx, My, Mxy, deflection (displacement) etc by clicking the options by the right hand side of the screen etc. I will give a brief description of the results to enhance your understanding.

Mx plot – This contour is displayed relative to a single global coordinate system in the horizontal direction

My plot – This contour is displayed relative to a single global coordinate system in the vertical direction

Mxy plot – This contour displays the torsion (twisting) of the slab panels

M1 plot – This is an Mx plot where the contours are displayed relative to a local coordinate system for each slab panel

M1 plot – This is an Mx plot where the contours are displayed relative to a local coordinate system for each slab panel

M2 plot – This is an My plot where the contours are displayed relative to a local coordinate system for each slab panel

Md1-bot plot – This is the M1 sagging moments adjusted to account for plate torsion using the Wood and Armer adjustments.

Md1-top plot – This is the M1 hogging moments adjusted to account for plate torsion using the Wood and Armer adjustments.

As1-bot, As2-bot, As1-top, As2-top are the steel areas that are based on the M1 and M2 moments (not including Wood and Armer Adjustments)

As(d)1-bot, As(d)2-bot, As(d)1-top, As(d)2-top are the steel areas that are based on the Md1 and Md2 moments (moments including Wood and Armer Adjustments)

Orion recommends that you work with As(d) contour results

The displacement contour is shown below. Feel free to check all the other contours.

Now close the Post Processing Page.

Now, if you click the Batch FE Chasedown Tab, you will see it has been carried out for all the storeys. This is indicated by the green tick that shows that it has been successfully carried out for each storey. Just in case anything suggests that it has not been carried out. Click ok to run the analysis.

 

[13] FULL BUILDING ANALYSIS

Click on Building Analysis, and then, go to Analysis Tab.

Make sure that you check by clicking on the tiny boxes provided;

Column/Wall Reinforcement Design

Beam Reinforcement Design

Then click on Start to run the analysis.

When the Building Analysis is completed successfully, click OK.

 

[14] SLAB DESIGN

Click on Slab strips. By default, just leave it at General Strip. The first direction is the X direction. Now, I wish to draw the slab strip across Panels 1, 2, and 3. To start with, I have to select the start and end conditions of the slab. Now, at the start, the slab is simply supported or discontinuous, so I have to select the symbol (bob) in the middle. The end of the slab is a cantilever panel, so I have to select that accordingly by checking the option at the right (just follow the images). To make your strip line straight, hold the Ctrl Key. Click somewhere outside Panel 1 by the left, drag the strip line till somewhere outside the cantilever area at Panel 10 and click there. Automatically, the reinforcements and their spacing are displayed. Repeat the process for all the other panels, bearing in mind to respect all the end conditions. Remember that for vertical directions, you have to use the Y strip direction. Remember that you can also use the Finite Element Strip, but you will have to go to FE Post processing for your design results. To do that, you have to change from Analytical Strip to FE Strip. However, the differences in the results for our case will not be pronounced. (See Orion Engineer’s Handbook).

The expected final output is shown below.

Go to Run, and Select Slab Analysis and Design

Verify the Load Factors and click Design

The results of the floor slab are displayed immediately. To export the floor detailing sheet, click on ‘Export DXF’ on Orion’s main GUI page

 

[15] BEAM DESIGN

Go back to Run, and Select Beam Section Design and Detailing, and select Storey Beams

The beam design page comes up. Green ticks show beams where all major requirements are satisfied.

To view more details, let’s say for Axis 1 beams (Orion’s gridlines), click on it twice, and the dialogue box below comes up.

You can view the bending moment diagram, and the detailing of the member at the top left corner by clicking on ‘diagrams’. The typical bending moment and shear force diagram (design envelope) for Axis A beams on our GA is shown below;

If the member is not failing, and you are satisfied with the reinforcements provided, Click on Detail Drawing to see the reinforcement sketches.

For the entire floor beam or for the entire structure, go back to the main project design and detailed sketches, by closing the Axis 1 Reinforcement Dialog box. Now go to Detail Drawings, and Select Automatic Detail Drawing All Axis. Select the storey beams you want to be detailed. The reinforcement details are automatically detailed. For a very large building, and when a large number of beams are having a problem, you may go to the Batch Design Mode, to automatically re-select the bars provided to take care of the requirements. To view the calculation sheet, click on Design Report.

 

[16] COLUMN DESIGN

Go back to Run, and Select Column Reinforcement Design.

The Column Reinforcement Design page comes up. Green ticks show beams where all major requirements are satisfied.

To view a specific member design detail, double click on the member, Say 1C1, and the dialog box below comes up.

When the section size is not adequate, you can increase it and so on by the bottom left hand side. By the bottom right corner, the Load Combination highlighted in red is the critical one, while at the top right corner, you can reselect the reinforcement and so on. If a column is failing, by clicking the Interactive Design Tab, Orion Automatically selects the appropriate reinforcement. In a case where you will need to increase the section size, you will be warned also.

The Column Analysis Tab enables you to see the Moment and Axial Force Interaction Diagram. You can also print these details if you so desire.

When you click on Save and Print, the following Calculation Sheet is generated. To print the full Analysis Report page for all the columns, return to the main Column Section Reinforcement Page.

 

[17] FOUNDATION DESIGN

To design the foundations, go to St00 on the plan view

To design the footing for Column 1C1, click on the column, and right click on it.

Select Insert Pad Base

The dialog box below comes up;

Set the footing depth to a trial depth of 300mm

Select the surcharge height as suitable. In this case, we are taking 700mm

Now, let us try and use Y12mm bars

Click on Calculate after adjusting the settings to see the design calculation.

With a bearing capacity of 150 KN/m2, a square footing of 1000 x 1000mm has been provided.

The resultant soil pressure has also been shown with a minimum of 109.989 KN/m2 and a maximum of 180.377 KN/m2. With a footing depth of 300mm, all shear requirements at the column face and at d from the column face were all satisfactory. The provided reinforcement was Y12@225mm c/c in both directions. Since this is satisfactory, you click OK. Note that you can adjust footing dimensions as you wish, but you cannot go below the minimum required.

Using this procedure you can design all the footings one after another.

Combined Footings

Where two columns overlap each other, a combined footing may be the best solution. To do this, click on the two columns involved, and group their foundations together. Then insert Pad Bas as usual. This has been done on columns 1C15 and 2C17. Where the columns are spaced too wide from each other, you can consider designing the base as a strip footing.

Foundation Detailing

For detailing purposes, it is good adopt a group design. For instance, instead of having footings of variable dimensions all through, you can group the designs for ease in construction, and possible reuse of materials where applicable. For example, the calculation gave the dimension of column base 1C2 as 1200mm x 1200mm, and base 1C6 gave dimensions 1100mm x 1100mm. Instead of having footings of different variable dimensions, I will simply take footing 1C6 to 1200mm x 1200mm. So each group is now assigned a type – Say footing Type 1, Footing Type 2, etc.

To view the detailing sheet, you can export the plan view just as you export slab details (DXF Export). To view the reinforcement details, click on Foundation details at the bottom left corner of the screen GUI. The Detail Sheets Dialog box comes up. Click on New Detail Sheet, specify the paper size, and click on the GUI for the sheet size to be displayed. Now, if you want the reinforcement details of F1, click on F1, and click on the GUI for the details to be displayed.

The reinforcement detail of F1 is shown below;

The final MODEL of the building in 3D is shown below.

This is the end of our modelling on CSC Orion. I strongly believe that you can now play with it and manipulate it appropriately from now on. Individual results of the structural members will now be displayed as we progress. I strongly recommend that you go through the necessary technical manuals to be more acquainted with Orion modelling and design guides.