Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Fw: Shear Walls

[Subject Prev][Subject Next][Thread Prev][Thread Next]


I would say that keeping the shaft R/C AND keeping it connected is the way
to go.  Dual systems, IMO, are the best R/C configurations for seismic
resistance.  The SMRF, if properly detailed, provides an excellent energy
absorbing system, and it can accomodate some pretty high drift levels.  The
shear walls, depending on the configuration and sizes, provides some measure
of deformation control.  Given that the frames are taking most of the
vertical loading, axial load on the walls is usually pretty low, allowing
them to exhibit good hysteretic behavior.

On the other hand, if the walls are in such a configuration that they bring
about a lot of torsional response, you might look at using soft walls, but
for a 7 storey structure I would think it wouldn't be too much of a problem.

Besides, I think the PI is similar to Guam in that R/C is the prevelant
material.  Best to keep things simple (read: leave it R/C), rather than
introduce some separation detail or switch to another material which may
result in construction headaches.

My .02 pesos.

T. Eric Gillham PE
GK2 Inc.
PO Box 3207  Agana, Guam  96932
Email - gk2(--nospam--at)
Ph:  (671) 477-9224
Fax: (671) 477-3456
-----Original Message-----
From: Francis.Ang(--nospam--at) <Francis.Ang(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Friday, March 26, 1999 11:52 AM
Subject: Shear Walls

>I am designing a building that is seven story high. And here in the
>Philippines, we are required to use elevators for 5-storey high structures.
>Can anybody out there offer me suggestions? I intend to use the elevator
>housing as a shear wall. That is based on my experience.  For a change, I
>was thinking of providing an elevator housing but is not connected to the
>Lateral Force Resisiting Element.
>The structure would act as a special space moment resisting frame rather
>than a dual structure.
>Suggestions are most welcome.
>I know that by using a shear wall, there is a need to consider many things
>in the seismic analysis.
>Thanks in advance guys !!!!!
>Allan Yango
>Structural Engineer
>> ----------
>> From: Charles Greenlaw[SMTP:cgreenlaw(--nospam--at)]
>> Reply To: seaint(--nospam--at)
>> Sent: Thursday, March 25, 1999 6:17 PM
>> To: seaint(--nospam--at)
>> Subject: Re: Residential Flexible/Rigid Diaphragm Analysis
>> Responding to Dennis Wish's recent solicitations:
>> Dennis, if you are gleaning prior postings for an Online article, I
>> submitted quite a bit on the diaphragm rigidity issue in 1998 on Aug 29
>> and
>> Nov 18 and 21.
>> I still think the code's demand that we regard diaphragms as conforming
>> reality to the extremes that human-invented figures of speech suggest
>> ("rigid" and "flexible") is the dumbest thing since when young ladies
>> similarly divided into two distinct categories. You remember, there were
>> "good girls" and "bad girls". And nothing else. The first kind were good
>> for
>> marrying and bearing your children. The second kind were good for other
>> purposes we need not specify here.
>> Like with this spurious code expectation that we can tell the difference
>> in
>> diaphragms and rely on the result, telling the difference between good
>> bad girls hasn't been all that certain. My great-grandfather F.B.Ogden in
>> Oakland wouldn't let his daughters wear any red clothing, because it was
>> "the sign of the fallen woman". His judgment seems quaint now, but the
>> voters back then kept re-electing him as a superior court judge.
>> In my own youth, the girls themselves, when it came to being good or bad,
>> seemed to sort out behaviorally as "rigid" or "flexible", so to speak.
>> Performance-based evaluation, we might proudly call it now.
>> But back then, the girl classifications were just for guideline purposes.
>> You didn't get sued or lose your license and retirement savings if you
>> mistook one kind of girl for the other and made a poor choice. But with
>> the
>> building code, mistaking rigid for flexible is disastrous as soon as an
>> adversary's expert opines you got it wrong. The fact that the building
>> itself didn't care is only a curiosity. You are into an expensive defense
>> for violating a regulation intended to protect people from injury.
>> business.
>> So how did this pitfall come to be inflicted on us? I suggest looking to
>> Mark Gilligan's posting on 2-27-99, the pertinent part of which is:
>> >I have observed that a number of code provisions have been adopted with
>> >little technical data backing them up.  The SEAOC Seismology committee
>> has
>> >generally done a good job but ultimately the individuals find themselves
>> >having to make decisions on subjects that they have not seriously
>> >researched.  In this context people use their  best judgement.  I
>> >that the provisions on redundancy probably fell in this catagory. The
>> >problem is that what may seem rational occasionally isn't.
>> I discussed Mark's implication in early March at a SEAOC dinner meeting
>> with
>> another regular code formulation participant, who is with a state agency
>> keenly concerned with seismic codes. He confirmed that code language very
>> often comes from one person on a committee, usually an energetic and
>> forceful advocate, and gets approved with little or no validation in
>> depth.
>> Usually voting committee members shoot from the hip on little
>> knowledgeable
>> debate, because the agenda is too full, and was distributed too close to
>> the
>> meeting date to absorb and find flaws in. And the plane home leaves too
>> soon. This is what my own experiences confirm. On the few issues I can
>> up to speed on and find big defects in, it is still hard at the meeting
>> get an edge in wordwise. I have in past writings referred to these
>> committees as "empires" and been told that is an understatement.
>> I do better at Board of Registration meetings. I have spoken on
>> enforcement
>> issues and pointed out an anomaly:   The Board disciplines individual
>> engineers for failure to fulfill the duty of due care, such as mistakenly
>> making a code violation, on a single element of a single building. But
>> code provision itself was originated with less care than taken by the
>> offending engineer in its use. And the code doesn't just affect that one
>> building, it affects all buidings. With less care taken. How do you Board
>> of
>> Registration members want to discipline that??  Blank stares follow; no
>> complaints were received so they have no idea. But why should the
>> struggling
>> code users suffer the burdens? Why not the code originators? The stories
>> of
>> code formulation proceedings are plainly stories of failure to render due
>> care.
>> Questioning "authority" itself, not the orders disseminated by authority,
>> is
>> where this subject's inquiry should head.
>> Charles O. Greenlaw, SE    Sacramento CA
>> Vietnam Vet who hasn't forgotten what can happen