...engineering out of engineering," says Craig Baltimore, associate professor of engineering at California Polytechnic State University, San Luis Obispo, and the current trial design leader.
The argument is not over whether codes are increasingly complex. It is over whether that is good, bad or both.
James R. Harris of the Denver firm that bears his name and chair of the ASCE/SEI 7-05 committee, says increased complexity results from a need to make more economical use of resources, a demand for more complex structures, and an increasing understanding of the magnitude of seismic demands coupled with a need to manage the costs of seismic-resistant construction. But for simple buildings, "in many instances there are simplified alternative provisions," he says.
Ron O. Hamburger, principal of Simpson Gumpertz Heger, San Francisco, adds that some complexity is aimed at reducing the potential for failures. "Buildings constructed in the 1970s and earlier do collapse in earthquakes, do lose cladding in hurricanes and severe windstorms, and do experience roof failures in blizzards," he says.
Competitive pressures are pushing for ever-more-economical structures. That translates to more-exact designs. That means safety factors are substantially reduced from historic levels, says Hamburger. He advocates a tiered set of provisions that permit very simple, though not necessarily economical solutions for simple buildings and progressively more complex requirements for more complex buildings.
For steel frames, simplification is happening. With the 2005 steel spec, AISC is providing two, 5 x 8-in. cards that distill only the typically needed and used information. With these, one can perform simplified analysis and design all typical beams, columns, braces, tension members and connections, says Charles J. Carter, AISCs chief structural engineer. The cards cover W-shapes, channels, hollow structural sections, pipe, bolts, welds and connected parts.
For ASCE 705, due out by September, effort has been devoted to clarifying the main body of seismic requirements and to developing simplified alternatives for simple buildings, says Harris.
Code and standards groups have been striving to reformat the codes so the body of the model code governs scoping, policy, hazard definition and administrative requirements only, says John D. Hooper, director of earthquake engineering for Magnusson Klemencic Associates, Seattle, and chair of ICCs structural code committee. The technical engineering requirements are then referenced.
Hooper admits that the long-term goal of using reference standards has created some short-term confusion. The good news is that "unless future, substantial changes are deemed necessary and successfully undertaken," there will likely be only "maintenance" changes in the standards, says Hooper.
Many engineers support stretching code cycles to five or six years, with critical and unsafe provisions addressed mid-cycle. Local jurisdictions would benefit by reducing the frequency of the effort needed to evaluate new provisions. Engineers would benefit by reducing the frequency of the effort to relearn the code. The public benefit for all proposed changes would be vetted more thoroughly, say sources.
But Claude G. Cooper, chairman of the American Major Building Officials Association and the Richmond, Va., building commissioner, thinks the three-year IBC cycle is "ideal." It provides opportunity to use the code, while enabling "quick" adjustments to provisions not working, he says.
Though IBCs cycle has been driving new editions of the standards, ASCE/SEI does not plan to publish again until 2010. "I am convinced we have been changing structural design standards too rapidly" for people to keep up, says Harris.
The edition will be out early enough for the materials standards targeting the 2012 model code to cite it in 2011 editions, he says. ASCE 7 will then issue a supplement updating its references to the then-current materials standards. If the stretched cycle is successful, others are expected to follow ASCE, says Harris.
The next steel spec is planned for 2010, based upon the planned IBC cycle. "If ICC extends, we will," says Carter.
ACI is eyeing a six-year overall cycle, with minor changes after three years, as not perfect but reasonable for code activities, says Jim Wight, chair of the ACI 318 committee and a professor at the University of Michigan, Ann Arbor.
The trend toward lengthening standards cycles bodes well for the future, but has little impact on daily work. Problems are most pronounced in loading criteria in Chapter 16 of IBC and in ASCE/SEI 7, sources say. "Formulas, tables and charts are confusing and sometimes use inconsistent terminology," says DeStefano. That could be dangerous, he adds.
In 1980, establishing loading criteria was not a big adventure for engineers, says DeStefano. Codes had simple, unambiguous tables that defined snow, wind and live loads. There was a simple formula for determining equivalent static lateral forces for seismic design. "Most of an engineers time was spent designing and analyzing, not trying to figure out what loading criteria to use," he says.
|Conquered. Schwinger finally deciphered "22.214.171.124" on July 9 and sent yet another code explanatory note.|
In 2005, determining a simple roof snow load requires a detailed analysis that considers factors such as how exposed the site is, how much heat is lost through the roof and how slippery are the shingles. "Evaluating wind loads is a bit more involved and evaluating earthquake loading is a real adventure," says DeStefano.
For Schwinger, the most mind-boggling sections in ASCE 7 are 126.96.36.199, 188.8.131.52, 184.108.40.206, which address the gust effect factor. The worst of these, 220.127.116.11, was so daunting that he kept avoiding cracking it. That was until July 9. At 9:15 p.m., he "sent" TEK 595. Click here to view image
Schwinger recently decided to shed his pocket protector, at least occasionally, and become a "poster engineer" for code reform. For starters, he joined AISCs manuals and textbooks committee.
The "fresh blood" is welcomed by veterans for the cause. "If we want to improve the process, we must get out of the office, join the debate and participate in the struggle," says Griffis, who admits he has no patience for "whining from the sidelines."
|Architects Seek Engineers in the Teaming Match-Up Maze||May 9, 2005|
|February 21, 2005|