2013 Steel Conference Recap

Posted on May 30, 2013 by Dan Popp

Last month I was privileged to attend the 2013 NASCC Steel Conference in St. Louis. This was my first steel conference and I can now agree with the sentiment of a friend: if you’re a structural engineer and can only attend one conference a year, make it this one. I look forward to being able to attend again next year.

AISC routinely shares more free information than you would expect, and the conference presentations are no exception – every session was recorded and is now available, absolutely free, on their website. Here are a few of the sessions I found most useful.

Practical Use of the Direct Analysis Method

You can’t spell his name or sport a better mustache, but you will want to use the Direct Analysis Method after listening to Lou Geschwindner. Key takeaways:

  • Chapter C of the 2010 AISC Specification contains the requirements; alternatives including the K-factor approach are now in an appendix
  • K = 1.0 for all members when using DA (Direct Analysis)
  • “Most of you are not calculating K correctly anyway” – Lou
  • A “rigorous” second-order analysis is required. Lou’s simple definition of rigorous: “superposition does not apply”

50 Tips for Designing Constructible and Economical Steel Buildings

Cliff Schwinger shared a wealth of knowledge that he has accumulated over his decades of experience. Highlights:

  • Use the deepest practical columns (e.g. W14s rather than W12s)
  • Size truss members to have adequate strength on the net section
  • Use R=3 “unless you have the seismic code memorized”
  • Talk with the fabricator and understand their preferences for connections

Load Paths! The Most Common Source of Engineering Errors

Carol Drucker has earned a reputation as one of the leading steel connection designers. She shared wisdom gained from observing the work of many engineers of record on countless projects. One key insight from her talk was: understand diaphragm forces from vertical trusses.

Structural Innovation: Combining Classic Theories with New Technologies

Bill Baker is smarter than you. And smarter than me, and smarter than everyone else who was in the room for the T.R. Higgins Award Lecture on the final day of the conference. Much of what he said went over my head, but the designer best known for the Burj Khalifa was enthusiastic and engaging as he applied Maxwell’s Theorem (which we all know, right?) to structural optimization problems, with fascinating results. It speaks to his charisma that I came away wanting to learn graphic statics, which probably hasn’t been taught at any university in 50 years.

Were you in St. Louis? Leave a comment and share your favorite session or design tip!

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ETABS 2013 Initial Reactions

Posted on May 3, 2013 by Dan Popp

The wait is over: ETABS 2013 was released last Tuesday, April 23rd. CSI was kind enough to upgrade my firm’s licenses that same day, so I’ve spent the better part of two weeks tinkering with the new version. Following more than half a decade after the release of ETABS 9, the new release has gobs of improvements and changes, meaning it will be months before I explore and understand all of the intricacies. What follows is a “first look” at the release along with general impressions.

Improvements

  • Better Graphics – Spinning a model in a 3D view is no longer painful.
  • Improved Solvers – ETABS 2013 implements the SAPfire solver used by SAP, leading to vastly improved run times. Using the advanced solver can reduce run times by 80% or more compared to ETABS 9, while the standard solver is at least twice as fast. One caveat: the “percent force and moment errors” given in the log file by ETABS 9 are apparently no longer available, even with the standard solver.
  • Rigorous P-Delta – The best ETABS 9 could do was an iterative P-Delta performed after the elastic solution. The results from this analysis could only match the AISC benchmarks if columns were split into at least two elements. In ETABS 2013, the P-Delta analysis is performed prior to running the elastic analysis, which more closely approximates a full “rigorous” approach. ETABS 2013 can match the AISC benchmark results without subdividing elements. Note that this is still not true “rigorous” analysis (where superposition does not apply), but is close enough for all but the most extreme theoretical cases.
  • Text File – The $et/e2k files that permit text-based model manipulation are in the same format as version 9. This is not an improvement per se, but the fact that they are still easily readable (unlike SAFE v12 text files) is a win.

Issues

  • Lateral Point Loads – After importing existing ETABS 9 models, I am consistently seeing numerical errors at points where lateral loads are applied to diaphragms. These nodes are not directly connected to model elements, but are used by the program to deliver, say, wind loads to the structure. ETABS 9 never batted an eye; ETABS 2013 returns an error message for every wind load at every floor. Even though this may be trivial by itself (no load is lost), it could obscure other ‘true’ errors in the long list.
  • Frame Subdivision – The very first model I ran in 2013 was the single column AISC benchmark (See figure C-C2.2 in the 2010 Specification, page 16.1-276). When I subdivided this column into two elements, it created an overlapping double element for the top half of the column. After I found this problem and deleted the redundant member, it recreated it when the analysis was run. This error is easy to miss and is not found by the “Check Model” command, and is thus very problematic.
  • 64-bit vs. 32-bit – I initially installed the 64-bit version, thinking that bigger is better. Not so. The 64-bit version does not play nicely with Microsoft Office 32-bit, meaning that exporting tables to Excel or Access is not possible. Because Microsoft discourages using 64-bit Office (due to limited compatibility with add-ins), I installed the 32-bit version of ETABS. CSI tells me and I have confirmed that analysis times do not suffer; the sole advantage of 64-bit is that the 2GB memory limitation is removed. Any model larger than this ought to be simplified anyway.

Summary

ETABS 2013 represents a major step forward for design software and will be my default software – in a few months. My initial recommendation is to not use it for production; let the chumps like me sort out the bugs. As they say with Windows: wait for the first service pack.

So, what do you like or dislike in the new version? Leave a comment and let me know!

Posted in ETABS | 35 Comments

Quick tip: when applying temperature loads to a diaphragm (for example, in a parking structure), make sure the diaphragm is set to semirigid, not rigid. I definitely did not just make this mistake in my model and I don’t know why you’re asking. But if I did I fixed it immediately.

Posted on March 25, 2013 by Dan Popp | Leave a comment

ETABS Keyboard Shortcuts

Posted on March 21, 2013 by Dan Popp

My wife and I had a standing disagreement for the first year after moving into our house: she thought it was faster to turn at the stoplight; I thought it was quicker to get there the back way. It turns out we were both wrong – a middle route is nearly always the fastest way to reach our house from the west. Though I was proven wrong, I was still happy to have found a shortcut.

Why Shortcuts?

Shortcuts on the keyboard can dramatically improve your productivity when using software. Knowing the shortcut keys for common commands reduces the ‘friction’ of having to select a certain button among dozens or digging through menus. Saving a few seconds a hundred times a day adds up, both in time saved and frustration avoided.

Shortcuts in ETABS

Out of the box, ETABS does not have many shortcuts, but thankfully it does allow customization. To add your own, click the drop-down arrow at the right-end of any of the toolbars and select “Customize”:

CustomizeShortcutsStep1

Hit “Keyboard” at the bottom. You’re now in the “Customize Keyboard” dialog, where you can specify new shortcuts for any commands (including some that are not active and hint at features that never made it to prime time, e.g. Steel Beam Connection Design). Note that the ‘Shift’ key cannot be used alone nor can the ‘Escape’ key (which should be used for clearing the selection, but isn’t).

CustomizeShortcutsStep2

Shortcut to Shortcuts

You were hoping for this, I know: you don’t have to create your own. At the link below, you can download a .tb2 file containing all of my custom shortcuts. Here’s a partial list:

  • F2 – Rubber Band Zoom (Zoom Window)
  • F3 – Restore Full View (Zoom All)
  • F5 – Run Analysis (default shortcut)
  • Insert – Set Default 3D View
  • Home – Set Plan View
  • End – Set Elevation View
  • Page Up – Move Up in List (moves one story up in plan)
  • Page Down – Move Down in List (moves one story down in plan)
  • Ctrl+E – Set Building View Options
  • Ctrl+Shift+W – Show Selection Only
  • Ctrl+Shift+Q – Show All

All shortcut keys are displayed in the tooltip (displayed when hovering over a button) and on the menus. To install the shortcuts, close ETABS and then paste the .tb2 file here:

C:\Users\%username%\AppData\Local\VirtualStore\Windows

(If UAC is disabled or if you’re still inexplicably using XP, paste it here: C:\Windows)

Download Custom ETABS Shortcuts

Have any favorites I’ve left out? Let me know in the comments.

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ETABS Recovered Loads

Posted on March 19, 2013 by Dan Popp

When designing a structure, you as the structural engineer must keep in view the big picture. What are the ‘vital signs’ of the structure? What do you tell your supervisor when they ask for a quick status?

ETABS, like other analysis programs, doesn’t provide a quick answer to these questions. Enter the “Recovered Loads” spreadsheet, which provides a 30,000-foot view of your building on one printed page.

ETABS Recovered Loads.xlsxETABS Recovered Loads

At a glance, this tool tells you what you need to know about the building:

  • Area
  • Mass and Weight
  • Dead, Superimposed Dead, and Live Loads (total and per area)
  • Steel and concrete weight per area
  • Base Shears for all loads
  • First three building periods

Instructions are found on the first tab of the spreadsheet. Questions? Let me know via the comments.

Posted in ETABS, software, tools | 5 Comments

ETABS 2013

Posted on February 26, 2013 by Dan Popp

The eternally-pending release of ETABS 2013 is a recurring topic of conversation in my office these days. As a major factor in my productivity and thus my bringing home the necessary bacon, I have a great deal of interest in the new release myself.

etabs_2013_4

Timing

Overheard in my office: “2013? We said 2030.” It was late 2005 when ETABS 9.0.0 was released; more than seven years later, CSI has been promising ETABS 2013 in “the next few weeks” for some time. Recent support inquiries have been answered with “wait for the next version, coming soon.” CSI has told me that for the last few years, other sectors (bridges, oil and gas) have been hot while buildings have decidedly not been, which has certainly slowed the development. I expect that the new version will actually and finally be released this spring.

What to Expect

  • “SAPification” – If you use SAP v15 or SAFE v12, you should not be surprised by anything in the new interface. Improved graphics will be appreciated so long as they don’t make the program seem less snappy.
  • “Web-activated licensing schema” – This info comes from a recent support response. ETABS 2013 will apparently be the first CSI product licensed via the web, a la Bentley. If done well, this will be helpful, particularly if it allows occasional over-usage for deadline days (as RAM products do).
  • Advanced shear wall design tools – This was in the works all the way back in 2009. I expect better visualization of bars and the ability to more easily check boundary zones.
  • Improved composite beam design – Check this under-construction page on CSI’s website for more info.
  • Goodbye to keyboard shortcuts – I use custom keyboard shortcuts in ETABS incessantly and will be chagrined to see ETABS 2013 follow the “what we give you is all you get” path of SAP and SAFE.
  • A few problems – Past experience with major upgrades says that one might do well to wait a few months to make the jump, unless you want to be the one wrestling with the bugs. At the very least, test ETABS 2013 against the current release as much as necessary to develop trust.

What are you looking forward to in ETABS 2013?

 

 

Posted in ETABS, software | 6 Comments

Hard Lessons

Posted on February 23, 2013 by Dan Popp

Dear Young Engineer,

A friend and I were talking not long ago and I mentioned my “I’ll never do that again” list. He asked if he could see it for his own benefit and I told him that it wasn’t written down, although my boss seemed to enjoy quoting from it. Even though these have been hard lessons and are not flattering, I trust that publishing some of them here can help you avoid the same problems.

erase

  • Remember the Live Load – I performed a preliminary design of a two-story structure using RAM Structural System, dutifully adding 20psf of roof live load. After returning from a week away, I learned that my boss had found a small problem: the general criteria in the program were set such that roof snow load was considered rather than roof live load. Fortunately, this was early in design and did not cause any more problems beyond my embarrassment. Ironically, it was yours truly that had warned the entire office of this possibility some months prior to this incident.
  • Watch the Hatch – Strictly speaking, this was not my error, but I was responsible for catching it and did not. A metal deck roof diaphragm was properly designed with tighter weld patterns at the perimeter, which were shown with a hatch pattern on the drawing. However, the legend was switched such that the tighter spacing was shown in the field. This wasn’t noticed by anyone until a site observation during construction. We were able to show that the existing pattern did work at the perimeter, thankfully. Lesson: just because it looks right doesn’t mean it is.
  • Dicey Splice – I designed a moment frame lateral system for a small parking structure. I failed to notice that the typical detail shown for the column-to-footing detail specified a compression lap splice. The saving grace here was the ample conservatism in the generic code splice lengths, allowing a much shorter length to suffice in a particular situation such as this one.

Note that none of these errors has led to dramatic consequences, let alone danger to the public. They have, however, increased my humility and my near-paranoia about checking my work in every way possible. They’ve also brought home the absolute necessity of another set of eyes on a set of drawings. As project engineer, you are incapable of seeing your own design clearly, making even basic errors more likely to be missed.

Remember that you are not perfect. Be humble enough to seek out feedback and correction, and not just of your drawings. Over time, you will become a far better engineer with this attitude than one of overconfidence.

So, do you have any ‘lessons learned’ you can share?

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A Structural Engineer’s Toolbox

Posted on June 7, 2012 by Dan Popp

How does a structural engineer work well? The same way as any other professional: by using the right tools. Here are the basics in my toolbox:

  • Pencil and paper – start here, always. You should be able to explain a design via a hand sketch and brief calculations before running to the computer. For a recent long-span truss installed in an existing building, the proof of concept filled just one sheet of paper. I’ve found that having a really good pencil and crisp paper makes it much more satisfying to put graphite on wood pulp.
  • Calculator – I take for granted how easy it is to outsource the grunt work of basic math. I highly recommend using one that is allowed on the SE exam. I switched from a graphing calculator to the TI-30X IIS a year before I took the SE, fully expecting to switch back. I never did and am still happily using this simple but powerful model every day.
  • Triangle and scale – these simple drafting tools allow you to create much better hand sketches and also give you credibility with the older engineers. You can’t draw pretty lines – you’re not an architect – so use the triangle.
  • Codes – these seem to be behaving in the manner of rabbits, with new editions coming out before you’ve even seen the previous one. But they are indispensable to our work, as they both provide the minimum requirements and in many cases explain how to do the design. The steel manual is the clearest of all the codes and contains excellent design aids and examples. For concrete, I use the PCA Notes on ACI 318 alongside the code.
  • Excel – the Swiss Army knife of calculations. I use Excel 2010 for any number-crunching that involves using the same equation more than once. Tables changed my life; I can work only in the first row of a table without a thought of the thousands of rows below.
  • MathCAD – Excel may be powerful, but it has two very significant drawbacks: it is hard to back-check (impossible when printed to paper) and it is not savvy with units. Most of my linear calculations are done in MathCAD 15, which does both the math and the unit conversion while displaying everything in the same form as a hand calc. The unit awareness is particularly useful when working on international projects, as results can be shown both in the native units (say kN-m) and more familiar units (kip-feet).
  • AutoCAD – although my office is using Revit Structure to produce drawings, I use AutoCAD 2012 every day for many tasks: sketching details, measuring dimensions in an architectural drawing, overlaying two drawings for coordination, or building a file to import to the analysis model. It will serve you well to develop skill in a 2D drafting program, at least for the foreseeable future.
  • 3D analysis program – every engineer should have a go-to analysis software. Mine is ETABS, which I’ve used in the design of everything from high-rise buildings to aluminum trusses. I know the program inside and out, including what it should not be asked to do. Pick a program and become expert at using it.
  • Special-purpose software – need to design an anchor? Hilti Profis will help you immensely. Have a single composite steel beam to size? RAM SBeam can’t be beat. There are many trustworthy, simple tools to help with routine design chores. Never let them replace engineering judgment; always find ways to check the results by hand or against a table in the manual.
  • Dropbox – all of the project files in my office are stored and shared with two other offices effortlessly via Dropbox. The best feature: unlimited version history. Saved over that important file? No worries – a few clicks and the previous version is back.
  • Workflowy – the newest addition to my toolbox. This online list tool stores my notes and to-do lists for most of my active projects and allows me to easily share them with coworkers.

Those are a few of my favorite tools. How about you? What do you find useful and why?

Posted in musings, software, tools | 2 Comments

The Missing Manual

Posted on May 11, 2012 by Dan Popp

No career comes with a manual. There is truly no substitute for experience in any field, most especially structural engineering. As I near the end of my first decade as an engineer, I have learned a few things that I wish I knew before I began. I would still have chosen to do this – I consider structural engineering my vocation – but I would have been far more effective. I plan to share those things here, using the following broad categories:

  • Practical Tips – how to ‘hack’ your work, leverage software, become more productive, and get more done.
  • Letters to a Young Engineer – encouragement for those considering or just joining the profession.
  • Musings – thoughts on how things are and how they could be better.

A note to the esteemed engineer with more experience: you’re welcome to read along with us. The more I learn, the smaller my knowledge seems and the more eager I am to listen to those older and wiser than me. Please, join the conversation. Tell us what you wish you had known when you began.

Together, with experience and fresh ideas, we can build the “missing manual” for our profession.

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