Authors:
David Fletcher (dfletcher@vms1.uop.edu)
Suggested Courses:
Reinforced Concrete Design
Level:
Senior
I. Narrative
Mary Johnson has recently passed the PE exam. She works for Spire
Engineering as a structural design engineer. For her first project
as lead engineer, she designs a parking structure in an area where
the soil is poor. She requests a detailed soils report, and the
geotechnical engineer recommends continuous footings. Mary designs
a reinforced concrete section according to the prevailing ACI
standards. The design is reviewed by another of Spire's PE's
and Mary proudly stamps and signs her first set of plans.
The owner of the structure engages Spire to monitor and inspect
the construction process, take concrete samples, etc. Since Mary
is the engineer of record, she visits the construction site during
the site preparation phase. Although she has heard about the
way in which women are sometimes treated by construction workers,
she was unprepared for what she encountered. The whistling, taunting
and general crudeness made her very uncomfortable, but she was
determined to follow through.
Mary is relatively inexperienced in dealing with contractors.
Thus, in the eyes of the superintendent and construction workers,
her credibility is suspect. On the first day of pouring concrete,
Mary is on site, taking cylinder samples, inspecting the placing
of reinforcement, and generally getting a feel for the construction
process. She notices a few problems and brings them to the superintendent's
attention. He accommodates some of her concerns, but also dismisses
others as unnecessary, commenting on her lack of familiarity with
day-to-day construction practices. Mary protests and makes additional
suggestions. The superintendent takes advantage of her inexperience
and ignores her concerns. When she gets back to the office, she
talks to some of her more experienced colleagues and they give
her some additional advice about construction and contractors.
The following day is a warm one, and after about half the concrete
pour is completed, the batch plant breaks down and the trucks
stop coming. Mary knows from school and the previous evening's
discussion that if more than an hour or two passes, the poured
concrete will begin to set up and will not bond well with newly
poured concrete, forming a "cold joint." She discusses
the problem with the superintendent who assures her that the plant
will be up soon and tells her not to worry. After an hour and
a half has passed, the batch plant is not yet on line. Mary tells
the superintendent that the already placed concrete will have
to be removed. A protracted discussion ensues in which the superintendent
says such a drastic action is unnecessary and that if Mary knew
anything about construction, she would understand. He also makes
several other derogatory comments about her level of knowledge
and competence. He says that he can simply agitate the already
poured concrete and produce a structurally sound joint. At that
instant, the first concrete truck arrives, and Mary must decide
right away.
Mary is not sure about the nuances of placing concrete and does
not want to risk further abuse from the superintendent and construction
workers. Thus she decides to trust the experience of the superintendent
and continue the pour. The finished product looks OK, and the
rest of the construction is completed without incident.
After about two years of service, the parking garage is severely
damaged in an earthquake. In the failure some cars are crushed
and, unfortunately, three people are permanently crippled. The
injured parties and the car owners sue the owner of the parking
structure who in turn sues the contractor and Spire Engineering.
An evaluation by a forensic engineering firm shows that the proximate
cause of the failure was a break that occurred in the footing
at the point where the cold joint was. (See Figure 1) At the trial
several people who rent space in the garage testify that a large
crack had developed in the foundation about six months after the
garage was opened. The owner admits he had an employee fill the
crack with driveway patching compound; saying he thought it was
just a minor settlement crack, typical of concrete slabs. The
owner did not inform anyone else of the patch.
The contractor claimed that Spire Engineering, through its agent,
Mary, had approved the construction process and that since the
superintendent was not a professional engineer, his recommendations
should not have legal weight in determining liability. Spire
Engineering claimed that the superintendent had engaged in deliberate
deception and that the contractor should share liability.
II. Numerical and Design Problems
1. Determine the factored pressure diagram on the bottom of the
footing using the unfactored loads (Assume 60% DL and 40% LL.)
shown in Figure 1. Also draw the factored moment and shear diagrams
for the continuous footing.
2. Select the reinforcement for a 24" square tied column
to carry the loadings shown on the center column. Assume a short
column and single axis bending.
3. Given the two footing cross-sections shown, determine the moment
and shear capacities of the footing at the following points: a)
immediately beneath the center column; b) at the point of the
alleged cold joint. Use fy = 40 ksi and f'c
= 3.5 ksi.
4. If a "cold joint"actually existed at the point shown
in Figure 1, assume the footing will behave as if a hinge were
there. Write a brief qualitative description of the likely result
of such a hinge if an earthquake produces the lateral loads shown
in Figure 1.
5. Compute the size of the bars and give the location of the dowels
needed to transfer the moment and shear from the center column
to the footing. Provide a detailed scale drawing.
III. Questions about Ethics and Professionalism
1. Consider Mary's preparation before visiting the site. Did
Mary fulfill her professional obligation to her employer? Give
an argument for your answer with reference to the ASCE code of
Ethics.
2. What about Mary's actions on the site the second day? Did
she behave in a professional, ethical manner? Cite the relevant
ethical references in formulating your answer. If you think her
actions should have been different, describe what you would do
in similar circumstances.
3. Should Mary's boss have let her inspect the construction job
without supervision? Be sure to substantiate your answer with
reference to the ASCE Code of Ethics.
4. Suppose that Mary's boss, after hearing of her experiences
on the first day, assigns Alex, a more experienced engineer, to
accompany her to the site. Rather than simply advising and supporting
her, Alex takes over the inspection process, ignoring Mary but
also preventing the cold joint problem. Analyze the ethical positions
of Mary, Alex and their boss.
5. Imagine yourself as an expert witness for Spire Engineering. How would you assess the actions of Mary and her boss with respect to the firm's liability.
IV. Answers to Ethical Questions:
1. Consider Mary's preparation before visiting the site. Did
Mary fulfill her professional obligation to her employer? Give
an argument for your answer with reference to the ASCE code of
Ethics.
There are several items noted in the ASCE code of ethics that
are relevant to this case:
1. "Engineers shall hold paramount the safety, health and
welfare of the public in the performance of their professional
duties."
2. "Engineers shall perform services only in areas of their
competence."
3. "Engineers whose professional judgment is overruled under
circumstances where the safety, health, and welfare of the public
are endangered, shall inform their clients of the possible consequences."
4. "Engineers who have knowledge or reason to believe that
another person or firm may be in violation of any of the provisions
of Cannon 1 (to hold paramount the safety, health, and welfare
of the public) shall present such information to the proper authority
in writing and shall cooperate with the proper authority in furnishing
such further information or assistance as may be required."
Mary's preparation before the visit is suspect. Mary seems to
have the technical knowledge to handle this case. However, Mary's
knowledge about practical construction techniques and ability
to deal with the contractor are in question. Mary has probably
not been trained to deal with contractors. However, she was aware
of the way women were sometimes treated at construction sites.
She was not prepared for the abuse she received at the sight.
Is she expected to prepare herself for this abuse? Mary should
not have been subjected to the 'whistling, taunting, and general
crudeness'. However, Mary shouldn't allow that to affect the
way that she performs her job. Is Mary's preparation at fault?
If it is, is this a case of Mary acting outside of her expertise.
2. What about Mary's actions on the site the second day. Did
she behave in a professional , ethical manner? Cite the relevant
ethical references in formulating your answer. If you think her
actions should have been different, describe what you would do
in similar circumstances.
The same codes that applied to question 1 apply to question 2.
Mary's foremost obligation is to the public. It is questionable
whether Mary was competent in this situation. She did not know
the 'nuances of placing concrete.' One might ask if she is acting
out of her area of expertise, which would be a direct violation
of the ASCE codes. Also, she allows herself to be overruled in
this situation which involves the safety of the public. Is Mary
only responsible for technical expertise, suggestions, and consultation,
or is Mary on sight to police the contractor and make sure he
doesn't cut corners? Mary has voiced her concerns about the 'cold
joint', however she is badgered into backing down from that recommendation.
In this situation Mary has some different options. She could
refuse to back down from her recommendation. Mary could notify
her employer of the contractor's actions. If it is determined
that there is a problem with the 'cold joint', Mary could notify
the owner of the structure. If there was any criminal action
by the contracting firm then the appropriate government officials
could be notified.
3. Should Mary's boss have let her inspect the construction job
without supervision? Be sure to substantiate your answer with
reference to the ASCE Code of Ethics.
In hindsight, it appears that Mary was not quite ready to deal
with the contractor. If Mary's boss foresaw problems in the relation
between Mary and the contractor, he might have chosen to ease
her transition by allowing her to go with a supervisor. On the
other hand, it seems that Spire Engineering had confidence in
Mary's abilities. Perhaps they thought that Mary was qualified
to go into the field, and that this would be the best way to give
her experience. If Spire sent Mary into a situation that they
knew she would not be able to handle, then that might be considered
equivalent to practicing outside of your area of expertise, which
the ASCE code explicitly forbid.
4. Suppose that Mary's boss, after hearing of her experiences
on the first day, assigns Alex, a more experienced engineer, to
accompany her to the site. Rather than simply advising and supporting
her, Alex takes over the inspection process, ignoring Mary but
properly handling the cold joint problem. Analyze the ethical
positions of Mary, Alex, and their boss.
The ASCE Code of Ethics also states:
"Engineers shall give proper credit for engineering work
to those to whom credit is due, and shall recognize the proprietary
interests of others. Whenever possible they shall name the person
or persons who may be responsible for designs, inventions, writings
or other accomplishments."
By ignoring Mary's recommendations on a project Mary designed,
Alex might be trying to take credit for Mary's work. This is
a violation of the ASCE code. However, Alex's primary obligation
is to the public's safety, and he has apparently lived up to that
obligation. Mary has an obligation to herself to get credit for
her work. If she feels that she is not given credit for her work,
she might voice that opinion to her employer. The boss in this
situation has an obligation to his client and to the public.
By sending Alex with Mary he has prevented possible problems resulting
from Mary's inexperience. The boss also has an obligation to
maintain a good working environment for his employees. In this
situation Mary's opinions were valuable, and she should have been
able to voice them. The boss might make the working environment
more open, to allow Mary room to express her views.
5. Imagine yourself as an expert witness for Spire Engineering.
How would you assess the actions of Mary and her boss with respect
to the firm's liability.
Mary has put her company in a very precarious position. By allowing
the contractors to go against her better judgment, she may have
incurred liability for the company. She was on sight to make
sure that construction would go as expected and she failed to
do so. So, she has put her company in a position where they are
liable. The question is raised again: is Mary only responsible
for technical expertise, suggestions, and consultation, or is
Mary on sight to police the contractor and make sure he doesn't
cut corners?
V. Answers to Numerical Problems