Lookup Tables and a Little Chat - Getting the Type Name into a Text Parameter

I've very recently been looking at using Revit lookup tables for structural families. These are traditionally used in the MEP side of things, but I have been looking for a structural application for a while. In the course of this, one of the things I have been able to achieve is to pass the lookup table's first column 'Type Name' to a text parameter in the family. As my knowledge of lookup tables is relatively new, I assumed this was something widely used and known. At the last London Revit User Group meeting, I was chatting to Jose Fandos of Andekan and we got onto the subject of this. He assures me that it most certainly isn't and people would be interested in this little tip. So here goes:

I created a sample lookup table as follows:

In Revit, the parameters in the test family:

 

 

A text parameter is created in the family called 'Type Name'.  The formula is broken down as follows:

• size_lookup                   

Tells Revit it's a lookup command

• (Lookup Table,              

Refers to the lookup table name in the 'Lookup Table' parameter

• "",                                 

Usually there is a value between the quotation marks. This refers to which column to reference in the lookup table, but in this case  we create a 'null' value. This is what allows this method to work

• "NOT SPECIFIED",

The text value that is used if there is no matching value in the lookup parameter

• Size)

the lookup parameter value for the lookup formula to reference.

 

I'm not sure why this actually works, but I suspect that even though the syntax for the formula is correct for a lookup, the omission of a search column reference means it returns the first value it comes across, which is the 'Type Name' in the first column.

Hope this is useful.

 

Revit 2014 Family Parameters - Sneaky Sneaky

I can't seem to find anything that lists this change, but this is a new one on me and could cause some upset generally, which is why I'm giving a heads up

Up until now, it has always been possible to mix different case parameters of the same name in a family. You could have a parameter called 'T' and one called 't' and it would sit very happily.

It now appears to be a different case in Revit 2014 and this has been swept away. It's not actually apparent with existing families until they are loaded into a project, taking you from this:

 

 



 

 

to this:

 

 

 

 

 

 

In hindsight, it's probably not best practice to have parameters named in this way. I'm guessing we'll just have to take our medicine and get on with it!



Sharp Elbows - New Revit 2013 'Structural Material' Parameter and Model Upgrade Problems

The purpose of this post is to shed a bit of light on a Revit 2013 model upgrade problem. It will also assume a certain level of Revit knowledge

The materials functions have been seriously overhauled for Revit 2013.
On the Structures side, a new built-in parameter 'Structural Material' has been introduced.

This parameter is non-modifiable and non-removable. It can only be altered from 'Instance' to 'Type' and vice-versa. The function is by design and appears to be for the purpose of using extended information for calculation and to provide a more fixed and stable platform in the structural model for third party analysis software linking

When family files are updated in Revit 2013, the upgrade elbows out any existing material parameter and replaces it with this.

However, we have discovered a slight complication with this. Take specifically families which have a nested component, and the material parameter in this nested component is linked to a material parameter in the host.

If you open the family file directly in Revit 2013, the upgrade process will 'sever' this link, but it will upgrade.

If you are upgrading a project that contains such a family, the upgrade will fail for these elements and Revit will require that these are deleted from the model before continuing. This is happening here with our Pile Cap families, which have a Pile family nested inside.

To get around this, you have to open the project model in the previous Revit version and edit the offending families to de-couple the material parameter link. The model will now upgrade in Revit 2013. You can now re-edit these families to re-couple the parameters, then reload back into the model.  You may also want to consider changing the previous material parameter to the new 'Structural Material' to take advantage of the new functionality

I trust this helps and is clear, but please feel free to comment

Profile Families & Reference Lines

When building a complex Profile family, sometimes this can be hampered by the fact that Reference Lines are not available and you are limited to Reference Planes. One thing you can do however, is nest a Detail Item family in a Profile family. Using this fact, you can build a 'rig' of Reference Lines in a Detail Item family. This can then be loaded in and lines can be traced over and locked to this. The Detail Item family is flexed by through-linking its type parameters to identical parameters in the Profile family. The concept is demonstrated in the video below:

I understand that the example can be perfectly achieved directly in a profile family, but I wanted to keep the example simple for the purpose of this post

Steel Weight - A Conversation, Further Thought and Another Method

• A Conversation

Mike: "So, the Revit weight schedule calculates using volume?"


Me: "Yes"


Mike: "So when you put a service hole in a beam, it subtracts it from the volume?"


Me: "Yes"


Mike: "But when you buy steel, it doesn't come with holes in. Shouldn't the weight takeoff reflect this?"


Me: "Ahh... Good point"

• Further Thought

In order to overcome this, the weight can be calculated using kg/m multiplied by length. In my mind, this presents a couple of issues:

1. How to get a steel length from a column
2. How to make it multi-category, so it all appears on one schedule

Fortunately, our families all contain cross-sectional area figures 'A', calculated automatically by formula based on the parametrics of the profile. The kg/m value 'M' is calculated from this:

• Another Method

The solution to both problems is to introduce a new shared parameter, 'Section Length' to all the steelwork families. This is set to 'instance' and set as a reporting parameter. A dimension is then run from one end of the beam/column to the other and is set to this parameter. Because it is a reporting parameter, whatever length the beam/column is, its value is fed back to 'Section Length'. This can then be used to calculate the weight. The following video demonstrates this concept

Steel Weight - A Method and Some Thoughts

There are a lot of bit and pieces online regarding steel weights in Revit Structure. The aim of this post is to pull some of it together and to add my own thoughts. The video goes through the procedure for creating the schedule and the information below discusses the finer points

• Before You Start, Content is Critical

We abandoned the OOTB steel families early on and generated our own family content. This allowed us to take a much more holistic approach to the content. In the video example, there are 'Universal Beam' members of both 'Structural Column' and 'Structural Framing' Categories. These families are driven by identical parameters, profiles and most importantly, Type Catalogues. All our steelwork families contain two parameters, 'Section Type' and 'Section Name'. These are only ever used in Steel Families and they allow us to isolate steelwork in schedules. In the case of the example, the values of these two parameters are consistent in both 'Universal Beam' of 'Structural Column' and 'Structural Framing' categories. This allows us to consolidate all 'Universal Beam', regardless of family category, together in a multi-category schedule

• Some Points on Volume
  
  In the 'Material Take-Off' schedule, the parameter 'Material : Volume' is used to calculate the weight. The material parameters in Revit Structure are only available for the following family categories:
  

• Revit will calculate volume based on the medium level of visibility. Another reason we abandoned the OOTB families is that for all rolled sections, the root radii are omitted in the medium level of detail, so the weights were coming out incorrect. Hence our content shows a full profile for both medium and fine detail to get the correct volume.


• The calculated value in full is Volume multiplied by Density. The syntax is:
  (Material : Volume/1)*7.85
  
• The parameter 'Material : Volume' must be divided by 1 to neutralise m³ to a number to avoid an 'Inconsistent Units' error.
  
• 7.85g/cm³ is the metric density value of mild steel (in old money, this is 0.284 lb/in³).
  
• Elements must have physical material applied to them in order to appear in the schedule. I'd recommend that a generic steel material is applied in the family by default so they will show up regardless
  

So that pretty much sums it up. Hopefully this will be of some help

When Shared Parameters Lose their Way

On occasion, a shared parameter that is under one group in a family will mysteriously end up in the 'Other' group, when loaded into a project. In this case,the parameter 'Section Name'

In order to fix this, do the following:

• On the 'Manage' tab, click 'Project Parameters' on the 'Settings' panel
  
  
• Now select the shared parameter from the shared parameter file and set the 'group under' to the match the correct group in the family. Click 'Ok'

• Now go back into the Project Parameter dialogue, select the parameter and hit 'remove'
  

• Now you'll be left with the shared parameter in the family under the correct group
  

I've no idea why Revit does this, but its clearly a bug. It will do it with the same shared parameter used in multiple families, but once you apply this fix, all the families that contain the offending parameter will then be correct.

Starter for 10 - Radius v Diameter

This is my first contribution to the Waterman Revit Blog, which will form the basis of a dialogue of our experience with Revit, particularly in implementation and family creation. This will specifically cover Revit Structure and UK based content, but we hope that all flavours will gain something.

So, introduction over and onto business

Radius v Diameter

If you've ever done anything in a family involving a circular object; pipes, tubular columns etc and wished you didn't have to put in Diameter/2 to drive a radius parameter, then the following video is for you

This outlines a method for creating the parametrics for a tube, using only Diameter and Thickness to drive it, taking your family from this (OOTB example):

To this:

A much neater solution