Needham & Associates

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25 Νοε 2013 (πριν από 3 χρόνια και 4 μήνες)

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Needham & Associates

Consulting Engineers

Fort Wayne, IN
-

Overland Park, KS

http://www.needhamassoc.com

Serviceability Design of
Metal Buildings


Or….Why is my customer so
unhappy???


What does a contractor need to
know???

Your Speakers


Jeff Needham, Principal


P.E., S.E in 20 states, started firm in 1989 in
Fort Wayne


BS and MS from University of Kansas


Andy Carter, Principal


P.E., S.E in 25 states, started in PEMB in
1968


BS Virginia Military Institute, MS from
Georgia Tech

What Does Needham and
Associates Do?


General Practice Structural/Civil
Engineers


Consultants to PEMB Industry


Heavy Structures ( ex: large clear
-
spans,
steel mills, special structures)


Hardwall Buildings ( ex: site
-
cast, tilt
-
up
concrete)

Introduction


Why consider
serviceability
(source of
many problems and claims)


Owner input (must have active input,
common problem)


Specific to structure’s use


Easy to build in, difficult to repair


Example of Breakdown in
Serviceability Considerations


Probably lack of communication between
owner and contractor


Project in Terra Haute, IN


Flammable Vapor Build
-
up in
Insulation

Types of Serviceability Issues


Deflections and Drift (primary focus of this
talk)


Expansion/Contraction


Camber


Vibration


Corrosion


Connection Slip

Responsibility for Determining
Serviceability Requirements


Generally not code issue


Building manufacturer’s consideration only if
informed by dealer


Entity (Architect or Owner) specifying the
building parameters specifies criteria


Serviceability criteria need owner agreement
of requirements & cost


Basic Deflection and Drift Ratios

Wall Considerations
-

Drift


Metal walls usually have no real limit


Masonry/tilt
-
up/precast wall vs. frame drift


Base condition free to rotate
-

H/100


Base condition fixed to rotate
-

H/200


Do not use unreinforced masonry walls with
PEMB


Typical NEW PEMB Hardwall
Buildings


Designed for strict serviceability issues


Load bearing walls


Wall Considerations
-

Deflection


Wainscot walls & framing above


Total deflection


sum of frame drift & girt deflection


Spandrel Beam (single girt) L/240, but not
more than 1.5 inches


Details to enhance compatibility of
materials, allow for movements


Special Considerations for
Bridge Cranes


Complex topic


Common drift limit H(eave ht)/200 under
crane lateral load


Crane beam deflection L(bay)/600 for vertical
deflection


Crane beam deflection L(bay)/400 for
horizontal deflection


Typical Crane Installation


Serviceability often controls design as
opposed to strength


Steel and weldment fatigue is a major
serviceability issue


Therefore, serviceability dictates cost


Crane Serviceability Controls


References for Bridge Cranes


CMAA Standard 74 (Single Girder TR and UH
Cranes)


CMAA Standard 70 (Double Girder TR Cranes )


Call (704) 552
-
8644 to order


About $40 each


CMAA Standards 70 and 74



Interior Partitions & Ceiling
Considerations


Suspended ceilings will telegraph roof
deflections


Sprinkler Heads Indicate
Deflection


Common winter callback


May or may not indicate a real problem


Interior Partitions & Ceiling
Considerations


Suspended ceilings will telegraph roof
deflections


Noticeable


in large open offices


junctions of ceilings & interior walls


Typical Ceiling Problem

Interior Partitions & Ceiling
Considerations


Suspended ceilings will telegraph roof
deflections


Noticeable


in large open offices


junctions of ceilings & interior walls


Don’t tie interior partitions to main framing


Good and Bad Details

Bad Good

Interior Partitions & Ceiling
Considerations


Suspended ceilings will telegraph roof
deflections


Noticeable


in large open offices


junctions of ceilings & interior walls


Don’t tie interior partitions to main framing


Remember
-

Actual deflections are as much as
25% higher than calculations indicate

Roof Considerations


“L/Span” deflections


Comparison of L/Span
Deflections


L/180 on typical Z
-
purlin


20 foot bay = 1.33 inches, 30 foot bay = 2
inches


L/240 on typical roof bar joist


30 foot bay = 1.5 inches less initial camber of
3/8


Net deflection is 1.125, much less than Z
-
purlin


Z
-
purlin deflection is magnified by “purlin
roll”

Purlin Deflection



Roof Considerations


“L/Span” deflections


Purlin deflection at eaves and rakes


Eave Deflection/Ice Dam

Roof Considerations


“L/Span” deflections


Purlin deflection at eaves and rakes


Ponding, with low slope roofs


Ponding


Common failure type of joist roofs due to
clogged drains, scuppers


Can be caused by snow drifting


Design checks for stability failure are usually
not required for slopes of 1/4/12 or greater


Stability checks may be required for slopes
of 1/4/12 or greater if ice dams/snow drifts
occur…Be Careful with this condition!


Ponding Problem on 1/2 to 12 Slope



Roof Considerations


“L/Span” deflections


Purlin deflection at eaves and rakes


Ponding, with low slope roofs


Panel distress & leakage caused by
excessive purlin or frame deflections…this
may be first “clue” of serviceability issue


Non
-
Deflection/Drift
Serviceability


Expansion/Contraction


Not usually an issue with all steel building


Watch for adjacent structure


Watch for collateral materials..tilt
-
up
concrete especially


Non
-
Deflection/Drift
Serviceability


Camber


Corrosion


Vibration


Connection Slip


Summary


MBMA states that is up to owner (or his
agent) to identify all materials so that the
metal building can be designed to be
compatible


Know your owner/customer


Don’t forget to “program” the job in the rush
to start a design build job


Require that manufacturer meet AISC “Steel
Design Guide 3”



AISC “Steel Design Guide 3”


Call AISC 800
-
644
-
2400


Price $16


Questions????


Thank You!...Needham &
Associates

Consulting Engineers

http://www.needhamassoc.com


233 W. Baker St.

Fort Wayne, IN 46802


(219)420
-
3400


8417 Santa Fe Dr.
Overland Park, KS 66212


(913)385
-
5300