Metallic Structure

ASCE 7-16 Controversy

ASCE 7-16 Controversy

A Long Overdue Wake-up Call

By Jim DeStefano, P.E., AIA


I have been watching, with some interest as the recent drama unfolded, the effort to block the adoption of the American Society of Civil Engineers’ ASCE 7-16 into the 2018 International Building Code (IBC). I was particularly amused to see the way that the structural engineering community has rallied in defense of a standard that they openly despise. If you get more than two structural engineers in a room, it is only a matter of time before they start complaining about the latest edition of ASCE 7 and the misery that it has brought to their practice.


Has ASCE 7 improved the practice of structural engineering or the lives of structural engineers? The answer is easy and not particularly controversial. There have been many editorials written about the misery that ASCE 7 has brought to the practice of structural engineering, yet I do not recall ever seeing an editorial extolling the virtues of the standard.

When I first started practicing forty years ago, the building code section on structural loading was somewhat brief and only filled a few pages. Although the loading provisions were easy to understand and interpret, they were not sufficient. The American National Standards Institute (ANSI) Standard 58.1, first released in 1972, was a huge improvement. It contained all of the important stuff that had been missing from previous building codes, such as snow drift loads and a rational approach to wind pressures, yet it was still easy to understand and use. When ASCE 7-88 replaced ANSI 58.1-82, the loading provisions became more complex and less intuitive. It has been downhill ever since. Today, structural engineers must spend a disproportionate amount of their time determining the loading criteria for their projects rather than designing the structures.


Do we need a cookbook for structural engineering? There seems to be a belief, held by many engineers that serve on standards committees, that building code adopted standards should be written as cookbooks that prescribe each step that an engineer takes in designing a structure. This kind of thinking has had a deleterious effect on the profession and tends to stifle innovation and the application of sound engineering principles. We should not need a cookbook to tell us how to design a structure.


Where do we go from here? Maybe it is time to take back our profession – make structural engineering great again. Despite all the grumbling, the ASCE 7 committee has not gotten the message. We need a reasonable and practical standard for calculating loading criteria that does not keep changing.

I do not mean to belittle or demean the hard work that has gone into writing the ASCE 7 standard. I have served on SEI standards committees, and I know the effort that goes into them. However, the standards committee needs to be sensitive to all of the unnecessary hard work and lost profits they have generated for all of us that are trying to make a living designing structures.

We cannot turn back the clock to 1982 and go back to the ANSI 58.1 standard, but it would not be so bad if we did.

Maybe those guys at NAHB and NRCA have the right idea and are not really anarchists. If we want to take back our profession, a grassroots movement is needed. Not just at the ICC hearings, but at every state level. If we, as structural engineers, start lobbying to delete ASCE 7 from our local state building codes in favor of simple, understandable loading provisions, maybe then our message will be heard.


A Rebuttal

By Ronald O. Hamburger, S.E. SECB


Jim DeStefano raises many good points as to the complexity of the building codes in general and the ASCE 7 standard in particular. I have made these same arguments many times over the years, in this same magazine and other venues. However, the challenges to adoption of ASCE 7-16 had nothing to do with code complexity or changes in design procedures. Rather, these challenges were about two things: 1) significantly increased values of wind pressure coefficients at areas of discontinuities on roofs, the principal concern of the roofing industry; and 2) changes to site class coefficients for long period structures on soft soil sites, causing an increase in seismic design values for some structures.


Countering these increases in design conservatism, the wind speed maps have been revised based on the availability of long-term wind data from hundreds of stations, allowing substantial reductions in design wind speeds and design wind loads across most of the U.S. In fact, except in exposure D, limited to a 600-foot wide strip along the Atlantic and Gulf coasts, these speed reductions mostly counter the change in cladding coefficients and allow substantial reductions in the required strength of the main wind force resisting system. Further reductions in wind load can be obtained by accounting for reduced air density at high elevation sites, allowing substantial reductions in wind pressures in places like Denver and Reno.


What else has changed? Well, the snow loading Chapter has indeed become longer and more complex. How? Instead of the so-called “case study” zones on the maps in mountainous regions, the Standard now provide tables with specific ground snow load values for most major communities in the affected areas. Thicker document? Yes. Easier to use? Yes. Other important changes include addition of a chapter on tsunami-resistant design, an Appendix on performance-based fire-effects design, and a substantial update of the seismic nonlinear response history procedures bringing them in line with procedures commonly used in the Western U.S. The seismic isolation and energy dissipation procedures have been harmonized with those in ASCE 41, which also has been updated to adopt the new response history procedures. The rain load procedures have been made substantially clearer and easy to apply.


This aside, I agree that the Standard is far larger, more complex and challenging to use than the design criteria specified by building codes 40 years ago when Jim and I first entered practice. The complexity has slowly grown for several reasons, including, as Jim suggests, a desire to over-prescribe the design procedures rather than allowing engineers to use basic knowledge and judgment to determine loads and other facets of design. At the start of this cycle, I made a significant effort to reverse this, simplify the procedures, and eliminate prescription. At one point I pushed for a two-volume standard; one containing basic procedures that would apply to the design of most ordinary buildings, and the other containing more complex procedures used only a fraction of the time. The basic procedures would have included criteria for dead and live loads, snow loads for buildings of simple geometry, the simplified wind procedure, and the equivalent lateral force procedure for seismic. All other procedures, used only a fraction of the time, if ever, would have appeared in the second volume. We felt most engineers would use only the first volume, which they would find short and user-friendly. Those engineers who design more complex structures would go to the second volume, where the more elegant procedures would reside. Ultimately this concept was discouraged by ASCE staff as being confusing, since some loads, such as wind and seismic, would have chapters in multiple volumes. Perhaps we will find a way to do this in future editions.


In the end, complex evolving codes and standards do place a burden on engineers. We cannot complacently leave school thinking that we know everything that we will ever have to know. Instead, we have to keep current with developments in our field, learn new procedures, and yes, do more work. Of course, 40 years ago, the electronic slide-rule calculator was just becoming a mainstay. Today we have untold power at our fingertips in the form of personal computers, with far more power than the IBM and Sperry mainframes of 40 years ago, to help us deal with the complexity. Do we really want to go back to the world of the 1970s? I do not think so.