Quality Assurance For Structural Engineering

Quality assurance for structural engineering

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Clifford Schwinger
Clifford Schwinger, P.E. is Vice President and Quality Assurance Manager at The Harman Group. Mr. Schwinger
received his BSCE degree from Lehigh University and has been with The Harman Group for 22 years. He’s on the
AISC Manuals and Textbooks Committee

Changes have occurred in the structural engineering profession over the past twenty years which have created a need
for engineering firms to implement formal in-house quality assurance programs. This paper discusses the
components of a model QA program and reviews procedures, tips, techniques and strategies for conducting in-house
quality assurance reviews on structural drawings with a focus specific to structural steel building structures

The structural engineering profession has undergone dramatic changes over the past twenty years. With fast-track
construction, computerized design, complex building codes and younger engineers taking on more responsibility
earlier in their careers, the need for structural engineering firms to have a comprehensive in-house Quality
Assurance program has never been greater. Adoption of a comprehensive Quality Assurance program will result in
better design, high quality contract documents, fewer RFI’s and change orders during construction, a better product
for clients and increased profitability for engineering firms

A Quality Assurance program is a defined set of procedures and standards used to facilitate design and to facilitate
documentation of that design. Implementation of a QA program results in:
– Better design
– Better drawings
– More efficient design process
– Fewer mistakes
– Fewer RFI’s and Change Orders
– Increase client satisfaction
– Enhanced reputation
– Increased profit
Prior to 1990 the concept of formal QA programs was virtually unheard of within the profession. Quality was
assured by relying on the experience, skill, continual oversight and expertise of trained engineers, structural
designers and drafters. Structural design was a linear process and contract documents were usually not issued for bid
until the design and the drawings were 100% complete. Formal QA programs, where they existed, consisted
primarily of a senior engineer being assigned as the “go to” person for answering technical questions. That engineer
would also review the drawings before the project went out for bid – providing a second set of eyes on the contract
documents in order to catch mistakes. Such a QA program, consisting of a “technical guru” and a single QA review
does not work today

Today a comprehensive QA program requires the following components:
– Training for young engineers
– Design standards
– Drafting and CAD standards
– Project delivery system
– Knowledge base
– Involvement of the QA Manager and QA reviews
Training for Young Engineers
Prior to the use of computers, young engineers working in design offices typically spent the first several years of
their careers doing repetitive manual calculations. Most new engineers also spent “time on the board” learning the
art of structural drafting under the guidance of experienced engineers and senior drafters. The training of a young
engineer was a gradual process. As experience was gained, more responsibility was delegated - reviewing shop
drawings, developing details and eventually coordinating projects with architects and answering questions from
contractors. Computers have eliminated most laborious manual calculations and while they have greatly increased
productivity, computers have also altered the informal training phase that all new engineers go through. Young
engineers today are faced with the challenge of taking on much more responsibility early in their careers. Further
challenging a young engineer’s transition into the profession are complex building codes, the details of which are
usually not learned in school and the lack of any knowledge of structural drafting, a skill which is just as valuable
today as it was years ago. The ability to convey one’s ideas to paper for interpretation by others will always be an
essential skill. For moderate to large-sized engineering firms, the solution to this problem is establishment of a
formal in-house training program

Training for young engineers should consist of in-house lunchtime training seminars covering the full spectrum
structural engineering topics that are pertinent to the type of work performed by the firm. Because the goal of the
training program is to pass on the combined knowledge of the senior staff, the list of topics for these seminars is
long. Passing knowledge includes not just interpretation of codes, standards and design procedures, but also a
discussion of practical applications and lessons learned. A short listing of typical seminars includes:
AISC 360-05 Braced frames
IBC 2006 Moment frames
Dead, Live & Snow load Trusses
Wind loads Joists
Wind Tunnel Studies Metal deck
Seismic loads Slabs on metal deck
Site Specific Seismic Analysis Floor and roof diaphragms
Load Paths 101 Window washing davits
Reviewing shop drawings Elevators and escalators
Connection design Facade systems
Member design Post-installed anchors
Stability Expansion joints
Braced frames Slide bearing connections
Vibration Concrete mix design
Coordination issues with MEP Slabs-on-grade
Stairs and monumental stairs Masonry design
Structural drafting Wood design
Framing plans How to perform a self-QA review
How to draw details Lessons Learned
Foundation design Communication skills
Concrete design Legal and liability issues
These seminars are best conducted once or twice per week. While some topics can be covered in a single session,
others, such as structural steel connection design, can take several sessions to fully cover

Seminars focus on actual application of the principles discussed and are interspersed with lessons learned,
discussion of common mistakes, examples of manual calculations and tips and techniques for verifying the accuracy
of computer analysis and design. Software limitations and assumptions are reviewed with continual emphasis that
computers are tools to be properly used by engineers; the creativity and solutions to structural engineering
challenges come from the mind and imagination of the engineer, not the computer

Design Standards
Design standards are comprised of:
– Design Guides
– Formal design procedures
– Checklists
Medium and large-sized engineering firms must have written formal design procedures, standards and
methodologies in order to produce consistently high quality design and to minimize the risk of errors due to

Office standards must be formally established so that there is no confusion regarding design procedures and
methodologies. Is office policy to use ASD design or to use LRFD design? Is the policy to show beam reactions on
framing plans or to require that shear connections be designed for a percentage of the member uniform load
capacity? Are connections designed by the EOR or is connection design delegated to the steel fabricator’s engineer?
Is there a minimum percentage of code wind load below which the wind tunnel wind pressures will not be used?
Serious consequences could result if two engineers are working on a project with one showing service level member
reactions on the framing plans and the other showing factored reactions. The purpose of office design standards is
to keep everyone on the same page and to provide a roadmap to insure uniformity of design

Design guides are one of the ways that design procedures are set forth. Design guides delineate office policy
regarding design procedures and bring together building code and design standards, textbook theory, local
construction practices, practical applications and lessons learned

Checklists are useful tools both for engineers new to the profession as well as for experienced engineers trying to
remember the hundreds of things that go into design and documentation of a building structure. While major items
like reviewing diaphragm strength and stiffness are well ingrained in a seasoned engineer’s mind, little things like
remembering to coordinate locations of fall protection tiebacks on the roof might occasionally slip by but for
reminders provided on checklists

Drafting and CAD Standards
Structural drafting is fast becoming a lost art. Whereas mechanical drawing used to be taught to students in high
school and college, many engineers now arrive in the profession with no training in a skill that is essential for
communication of their design intent to others. Likewise, most structural drafters have now been replaced by CAD
operators who, while proficient in use CAD software, may be lacking in the knowledge and understanding of how to
lay out framing plans, draw weld symbols or dimension details. The solution to this problem is to establish drafting
and CAD standards, the components of which include:
– Standardized drafting procedures
– CAD checklists
– Typical detail library
– “go-by” drawings
– Standard block library
Drafting procedures include information related to rules for laying out framing plans, drawing sections and details,
setting up column schedules, etc. Uniformity and consistency within the office requires that everyone draw objects
consistently on the correct layers and use the same linetypes and linetype scales. While these may seem like trivial
issues having no bearing on structural design, they will improve the quality and legibility of a set of structural

Checklists include the myriad of things needed to produce complete and legible drawings. They cover things as
seemingly minor as making sure north arrows are shown on the framing plans to more important items such as
making sure that beam reactions are indicated

A comprehensive structural engineering typical detail library will contain over hundreds of typical details

“Go-by” drawings are reference drawings that show examples of how to indicate information on framing plans,
schedules, etc. While “go-by” framing plans may have originated from actual projects, they will usually be modified
over time to include everything that can possibly occur on a framing plan. “Go-by” framing plans for various
structural systems provide engineers and drafters a single point of reference to see how to properly draw anything
they will encounter on the plans. The use of “go-by” drawings prevents younger engineers from using previous
projects for learning how to show things on the drawings. While using other projects as a frame of reference is not
necessarily a bad idea, doing so can lead to a gradual divergence of drafting standards in larger firms

A standard block library is essential for increasing productivity and maintaining drawing uniformity. “Blocks” are
pre-drawn objects such as bolts, angles, W-shapes, weld symbols, headed studs, section cuts, etc

Project Delivery System
The Project Delivery System is a library of forms, checklists, procedures and correspondence templates used for
administratively carrying a project from inception through construction. The PDS is divided into five sections:
– Project startup
– Schematic design
– Design development
– Contract documents
– Construction administration
The Project Startup section contains things required at the beginning of a project such as a design criteria form
listing design information such as the applicable building code, design standards, loads, wind, snow and seismic
design criteria, summary of the structural systems being used and fire ratings required. Correspondence templates
for letters to the client regarding information needed from the geotechnical consultant and wind tunnel consultant as
well as correspondence templates that summarize presumed design criteria and required “due by” dates to meet
schedules, etc. are provided

The Schematic Design, Design Development and Contract Document sections contain checklists and procedures
related to the deliverables in each phase of design

The Construction Administration section contains meeting agenda templates for the pre-steel detailing meeting, the
pre-concrete meeting, meetings with the inspector as well as checklists to be used when reviewing shop drawings

Knowledge Base
The Knowledge Base (KB) is a searchable electronic database of all knowledge related to structural engineering

The KB contains the notes from training seminars, design guides, design standards, drafting and CAD standards, and
information on all other topics that engineers may need to access. The primary feature of the KB is that it’s a single
source for answers to all questions related to structural engineering. When a question or topic comes up for which
there’s no answer on the KB, that information is added. When problems occur or lessons are learned, the solutions to
those problems and lessons learned are added to the KB

Involvement of the QA Manager and QA Reviews
The QA manager is senior level engineer who is responsible for establishing and maintaining engineering standards
and for verifying that all design is done in accordance with those standards. The QA manager has the following
– Establishing and maintaining design and drawing standards
– Answering technical questions and getting the answers to those questions onto the KB as appropriate

– Staff training
– Maintaining familiarity with all projects during design and providing input and suggestions as required

– Signing off on sections and details prior to them going to the CAD department. (A cursory review and
signoff of sections and details by the QA manager is required to catch mistakes before sending sections and
detail to the CAD department. Such a review saves time, is informative for the engineer whose details are
being critiqued.)
– Performing quality assurance reviews on all projects

Quality Assurance reviews are in-house reviews conducted to verify that all design is performed and documented in
conformance with the procedures and standards mandated by the QA program

QA reviews serve two purposes. The primary purpose of QA reviews is to provide redundancy via a second set of
experienced eyes on the drawings to catch mistakes, errors or omissions. The second purpose is to monitor the
effectiveness of the QA program. If the QA program is working properly and engineers are following the procedures
and utilizing the resources provided therein then problems, mistakes, errors and omissions caught during the review
should be minor. While the QA manager is usually the one who performs the reviews, other experienced engineers
can likewise perform the task

Changes in the way contract documents are now issued have altered the way QA reviews are performed. Until ten
years ago a single QA review was performed prior to the contract documents being issued for bid. Fast-track
construction scheduling now requires multiple reviews at stages during design. It’s not uncommon to have eight or
more reviews on large projects. While the number varies from project to project, a typical QA review schedule for a
steel framed structure on pile foundations might be as follows:
– Pile bid
– Steel mill order
– Foundation concrete bid
– Steel Addendum / detailing issue
– 100% concrete
– 100% structural steel
– “Issued for Construction” final review
Multiple reviews are also a good idea for those projects still delivered via the traditional design-bid-build process

Interim reviews will catch mistakes early when corrections can be easily made

There are two primary goals of QA reviews. The first and most important goal is to review the contract documents
to verify that the structure was properly designed, is efficiently framed and is constructible. The second goal is to
verify that the contract documents are complete, well detailed, correct and coordinated. The goal of issuing complete
and well detailed contract documents is not just one founded on a desire to reduce RFI’s and change orders – it is
one that is essential to insuring structural integrity. Finishing the drawings during construction via the RFI process is
a bad idea. Not only do RFI’s frequently lead to change orders, unless senior level experienced engineers are the
ones answering RFI’s, mistakes can slip through. If the drawings are complete and well detailed before construction,
those details will have gone through the scrutiny of the QA review process and the probability of engineering
mistakes being made during the process of answering RFI’s during construction will be greatly reduced

A variety of tactics are employed when performing QA reviews. Those tactics are as follows:
– Look at the big picture
– Verify load paths
– Review framing sizes
– Look at connection details (constructability)
– Look for mistakes
– Look for subtleties
– Look at the drawings for constructability
– Review for clarity
– Look for omissions
– Look for “little” little things
– Look for the ”big” little things
– Verify that the structural drawings match the architectural & MEP drawings
Looking at the Big Picture
Engineers immersed in large projects can lose sight of the big picture and miss things that are often immediately
obvious to someone who was not working on the project. Some common mistakes in this category include:
a. Missing or improperly located expansion joints
b. Improperly detailed connections at expansion joints (example: uni-directional slide bearing connections
locking up the expansion joint at corners. See figure 1.)
c. Load path problems (example: braced frames cut off from floor diaphragms; failure to design diaphragms
at vertical irregularities in the lateral load force resisting system.)
d. Equilibrium of forces not investigated (example: horizontal kick at base and top of sloping columns not
considered and connections not detailed. See figure 2.)
e. Constructability issues (example: moment connections in both directions at a column where beams are
different depths and stiffener plates are specified in both directions)
f. Inefficient connections (example: severely skewed joists framing to W shape girders.)
g. Connection problems (example: column base plate anchor rods that don’t fit in the piers or are too deep
for the footings.)
h. Inefficient framing configurations (example: too many pieces; beams framed in wrong direction)
i. Inefficient spandrel details (example: too much “gingerbread” framing.)
j. Wrong design loads used
k. Problems with computer model (examples: problems related to “infinitely rigid” diaphragms; double
counting structure self-weight or ignoring self-weight; pushing “reduce live loads” button on computer
where live load reductions are not permitted.)
l. Using wrong “R” factor (Use R=3 for steel buildings in areas of low seismicity.)
m. Failure to consider snow drift
n. Failure to consider loads such as folding partition storage pockets, heavy runs of piping, window washing
davits, etc

o. Excessive deflections on spandrels or ends of cantilevered beams
Figure 1: Example of improperly detailed
slide bearing connections locking up the
expansion joint because they are detailed to
permit movement in one direction only

Figure 2: Forces must resolve

Verify Load Paths
There must be continuous and realistic load paths from the point at which loads are applied to the structure down to
the foundation. While this may seem so basic as to not warrant discussion, it is a common problem

The most common load path problems are with floor diaphragms - usually because when engineers define floor
diaphragms as rigid, computer programs give those diaphragms infinite strength and stiffness, both assumptions
often being unrealistic

Some examples of problems associated with assumptions of rigid diaphragm:
– Lateral loads in braced frames increase from the top to the bottom of the braced frame. When braced frame
member forces get smaller on the lower levels (see Figure 3), that’s usually a sign that an “infinitely rigid”
floor diaphragm diverted lateral load out of the braced frame and sent the load elsewhere. Relying on a
slab-on-metal-deck diaphragm to drag loads out of one braced frame and into another is usually not a good

– Figure 4 shows a rectangular building with a shear wall at one end and a moment frame at the other. The
computer results indicated that 95% of the north-south lateral load was resisted by the shear wall and only
5% was resisted by the moment frame. This result was due to the combined effects of the floor diaphragms
having infinite rigidity and the two east-west shear walls preventing the floor from twisting. The problem
with this analysis was that while the floor was probably closer to the building code definition of a rigid
diaphragm than it was to a flexible one, it did not have sufficient strength to work as a rigid diaphragm

The lateral loads were manually adjusted and conservatively enveloped to account for a more reasonable
lateral load distribution between the shear wall and moment frame

– Figure 5 shows a portion of a floor where the slab-on-metal-deck was input as a rigid diaphragm and the
computer then modeled the exterior columns as braced at each floor. In reality, the floor slab did not have
sufficient strength to provide P-δ buckling restraint to the columns in the strong axis direction at each floor

Compounding the problem, the computer did not consider bending and shear in the diaphragm from wind
loads on the exterior wall because the diaphragm was infinitely stiff and infinitely strong. This framing was
repeated for several floors. The computer sized the columns as W14x90’s. Manual calculations showed that
the columns had to be W14x211’s

– Figure 6 shows a brace frame adjacent to an exterior stair that’s substantially cut off from the floor
diaphragm. While the computer model sees a connection to the floor diaphragm, the slab engagement to the
diaphragm is not sufficient to get the diaphragm load into the braced frame. A drag strut is required

– Figure 7 shows an in-plane vertical discontinuity in a braced frame. A drag strut is needed to transfer the
horizontal load from the base of one braced frame to the top of the adjacent braced frame. The computer
will not design the connecting drag strut member for the horizontal load because the rigid diaphragm is
assumed by the computer to transfer the load from one braced frame to the other

– Figure 8 shows an out-of-plane offset irregularity in a braced frame. The floor diaphragm must be
manually designed to transfer the lateral loads from the braced frame BF2 to the two adjacent braced
frames, BF1 and BF3. Diaphragms, even if they are rigid, must be manually designed and detailed to resist
the applied shears and moments

Figure 3: Load path problem resulting from infinitely
rigid floor diaphragm in computer model diverting
load out of brace frame
Figure 4: Problem related to infinitely
rigid floor diaphragm directing too much
load to shear wall and not enough to the
braced frame

Figure 5: Example of floor problem related to
floor diaphragm not being strong or stiff enough to
brace the columns. Computer model sized columns
as W14x90’s. Actual required size =W14x211

Figure 6: Illustration of floor diaphragm cut off
from braced frame

Solution: Provide drag strut with appropriate
connections to brace frame

Figure 7: Example of shortcoming of computer
model in computing drag strut axial load

Figure 8: :Level 1 floor diaphragm must be designed
to transfer BF2 lateral loads to BF1 and BF3

Review Framing Sizes
Review of member framing sizes is the most basic aspect of a QA review. This task can be daunting on large
projects with thousands of framing members. Fortunately, there are several tricks that can make review of framing
sizes easier

Since most framing is designed by computer, member sizes will usually (but not always) be correct as long as the
input is correct. A global review of floor framing can therefore be performed by verifying that all of the computer
inputs (loads, slab thickness, concrete strength, headed stud sizes, etc.) are correct. This is accomplished by
reviewing several typical beams, girders and columns. If the beam size, number of studs, camber and reactions on
the typical beam and girder are checked and verified to be correct, a review of those two members alone provides a
high level of confidence that the other framing on the floor is correct. If several different design loads are used on
different areas of the floor, then checks of typical beams and girders in each area should be performed

Showing beam reactions on the framing plans is an invaluable aid when performing a QA review. Seeing reactions
allows the reviewer to quickly compute the total load used for design of the member and verify whether or not that
design load is correct. The effort required to show reactions on framing plans is minor. A push of a button in the
analysis/design program will transfer the reactions to the CAD drawings. Showing beam reactions also reduces the
cost of the structural framing by allowing steel fabricators to detail connections for the actual reactions versus
having to detail connections based on arbitrary and usually overly conservative percentages of non-composite
uniform load capacity

The combined use of strength design and 50 ksi steel can result in beams that sometimes have excessively high span
to depth (L/d) ratios. Beams with high L/d ratios are susceptible to problems related to deflection and vibration. A
rule of thumb for the maximum recommended span of composite beams is to limit beam span (in feet) to 2 x depth
of the next larger nominal beam depth (in inches). (Example: Maximum span of a W12 beam = 2 x 14” = 28 feet.)
For non-composite beams the maximum span (in feet) should not exceed 2 x beam depth (in inches). (Example:
Maximum recommended span of a W12 beam = 2 x 12” = 24 feet). This is a general rule and these maximum
recommended spans can be exceeded if justified by analysis

Quality assurance reviews on structural drawings with a focus specific to structural steel building structures. 2 The Project Delivery System is a library of forms, checklists, procedures and …

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