After analysis you can select the Analysis Post Processing option and begin to review the results. You can select from a number of contour displays and we will look at each of them now.
Deflection Plots
In any analysis package it is always good practice to look at the deflections – if the deflections do not make sense the results will not either. In this case the contours look very reasonable.
The model has an obvious angled line of symmetry, and the deflection contours are also symmetrical. The only point that might draw some attention is the deflections of the primary edge beams. They are not big deflections, but they are more significant than the slab
deflections.
Mx and My Plots
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An Mx plot is shown above. Mx and My contours are displayed relative to a single global coordinate system. Since this model has an angled line of symmetry the contour pattern is not symmetrical.
If you imagine X direction bars running from left to right (horizontally) in the above view then Mx moments are the moments that these bars will need to be designed to resist (but see also the later notes on design moments including Wood and Armer adjustments).
Since it is unlikely that reinforcing bars will be positioned horizontally in the angled wing, these contours are of little value for that region.
M1 and M2 Plots
In the introduction to this example it was noted that a slab angle (the reinforcing angle) has been defined for each slab panel.
An M1 plot is essentially an Mx plot where the contours are displayed relative to a local coordinate system for each slab panel. The local system is defined by the angle of rotation applied to each slab panel. For this model this means that we can now see a symmetrical contour plot where the contours in each wing are relevant to the orthogonal reinforcing system that will be used in each wing.
Notice that in any contour plot you can use the mouse pointer to highlight any node (as shown above) and the precise information about that node is displayed at the foot of the window.
Plots Including Wood and Armer adjustments
Wood and Armer adjustments take plate torsional moments into account to generate adjusted design moments. It is beyond the scope of this manual to present the derivation of the equations for these adjustments. If detailed background on this is required you should refer to slab/bridge design texts, or to the original papers:
• Wood, R.H. “The reinforcement of slabs in accordance with a pre-determined field of moments” as published in Concrete, 2. February 1968, pp69-76,
• Armer, G.S.T. “Correspondence” as published in Concrete, 2. August 1968, pp319-320.
It is noted that the implementation of the adjustments within Orion is limited to orthogonal reinforcing systems.
The adjustments apply differently to hogging and sagging moments, so there are 4 possible contour diagrams that can be displayed.
An Md1-bot plot is shown above. This is essentially the M1 sagging (bottom) moments adjusted to account for plate torsion. The blue zones on the plot are hogging areas, the maximum sagging moment is 5.4, which is almost identical to the M1 sagging moment (5.3) shown previously.
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An Md1-top plot is shown below. This is the adjusted M1 hogging (top) moments. The red zones on the plot are sagging areas, the maximum hogging moment is 8.2, which is a little higher than the M1 hogging moment shown above.
Since they are based on the M1 and M2 moments these design moment plots are also symmetrical for this floor system.
The degree to which Wood and Armer adjustments affect the design moments is entirely dependent on the levels of Mxy (or M12) moments – these can be regarded as twisting moments.
Regular beam and slab systems do not tend to have high twisting moments coincident with peak hogging/sagging moments and Wood and Armer effects are often of little significance.
In this model you can find places where the effect I more significant.
You can review the Mxy or M12 moment contours as shown below.
Corners are always areas where twisting is high. In this model there is also quite a high twist developing over the beams along the angled line of symmetry. We will see how this affects the strip design moments later in this example.
Steel Reinforcing Requirement Contours
2 sets of steel area requirement contours are provided:
• As contours – 4 options
As1-bot, As2-bot, As1-top, As2-top
These steel areas are based on the M1 and M2 moments (i.e. moments that do not include the Wood and Armer adjustments).
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• As(d) contours – 4 options
As(d)1-bot, As(d)2-bot, As(d)1-top, As(d)2-top
These steel areas are based on the Md1 and Md2 moments (i.e. moments that include the Wood and Armer adjustments).
It is recommended that unless you have some specific reason for ignoring the Wood and Armer adjustments you should always work with the As(d) contour results.
Other Contouring Adjustment Options
Before accessing the postprocessor you will have noted the option to apply global adjustment factors to all Positive (Sagging) or Negative (Hogging) moments. This is not the same as moment redistribution, but it would potentially allow for redistribution style effects to be introduced.
It should be noted that FE floor models do not include any pattern loading, it is not feasible/
logical to automate pattern loading to generate every possible worst case scenario for every conceivable irregular arrangement and any size of model. A more realistic use of these adjustments may be to amplify the sagging moments (perhaps 10 to 20%) if you are concerned about allowing for load patterning. This will be discussed further later in this example.
Once you are in the post processor viewing moment contours you will also have noticed a drop down option relating to Col/Wall Node Interpretation. This has little effect on beam and slab systems and is a little more relevant to flat slab design. This option is discussed in more detail in the chapter on Flat Slab Models.