Structure Engineering
101
For Mechanical Engineers
Class outline
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Structural systems
IBC 2006 Seismic provisions
Information your structural engineer needs
Coordination
Building Information Modeling
Structural Systems
• Foundations
– Drilled piers and pier caps
– Driven piles
– Footings
– Mat footings
– Perimeter grade beams
– Basement walls
– Tie beams
– Post-Tensioned slabs on grade
Yes I know the video is side
ways….I am just a structural
engineer…
Drilled pier video
So what does a mechanical
engineer need to know about a
drilled pier?
• Underground coordination
• Top of pier elevation is critical
• Trenches and excavations next to piers undermine piers
capacity
• Pier caps and tie beam coordination
• Electrical grounding
• Piers are bigger then shown on structural
• Piers are not the ideal place to
put the geo-exchange system….
Driven piles
Electrical Grounding Driven Pile
Screw Piles
Mat Foundations
Foundation grade beam
How do foundation problems effect the
mechanical engineer?
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Expansive soils
Soil settlement
Void forms
Crawl spaces and molds
Void form
Foundation heave/ settlements
Structural Systems
• Steel Frame
– Beams and columns
– Gussets
– Acoustical
– Vibration
Slab thickness… see schedules and details
Beam depth… see plan
Camber… not to worry…
Beam reactions… does not effect you
Dimensions… not something a mechanical engineer uses…..
• Steel Beam Sizes
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Link to steel section properties look up table:
http://www.efunda.com/math/areas/RolledSteelBeamsW.cfm
Commonly used steel beam sizes:
Size
Depth (d)
Width (bf)
W10x19
10”
4”
W10x30
10”
6”
W12x22
12”
4”
W12x35
12”
7”
W14x26
14”
5”
W14x38
14”
7”
W14x53
14”
8”
W16x31
16”
6”
W16x57
16.5”
7”
W18x46
18”
6”
W18x70
18.5”
7 1/2”
W21x57
21”
6 1/2”
W21x68
21”
8 1/4”
W24x62
24”
7”
W24x84
24”
9”
W27x94
27”
10”
W30x99
30”
10 1/2”
W33x130
33”
11 ½”
W36x160
36”
12”
Cutting the metal deck……
Floor drains in the metal deck……
Hydronic Heating
Joists and joist Girders
MAXIMUM DUCT OPENING SIZES
LONGSPAN (LH SERIES)
JOIST
DEPTH
(in.)
18
20
24
28
32
36
40
44
48
52
56
60
64
68
72
ROUND
(in.)
12
13
14
17
18
21
25
28
30
33
36
37
40
43
46
SQUARE
(in.)
10x10
11x11
12x12
13.5x13.5
14.5x14.5
17.5x17.5
20x20
22x22
24x24
26x26
28.5x28.5
30x30
32x32
34.5x34.5
37x37
RECTANGLE
(in.)
7x17.5
8x19
9x18
11x18.5
12x19.5
14x23
16x26.5
18x29.5
20x30
22x33
24x36
25x37.5
27x40.5
29x43.5
31x46.5
PANEL
LENGTH
(in.)
45
48
48
48
53
60
67
73
72
78
84
90
96
102
108
MAXIMUM DUCT OPENING SIZES (K SERIES)*
JOIST
DEPTH
ROUND
SQUARE
RECTANGLE
8 inches
inches
12 inches
14 inches
16 inches
18 inches
20 inches
22 inches
24 inches
26 inches
28 inches
30 inches
5 inches
6 inches
7 inches
8 inches
9 inches
11 inches
11 inches
12 inches
13 inches
15 1/2 inches
16 inches
17 inces
4x4 inches
5x5 inches
6x6 inches
6x6 inches
7 1/2x7 1/2 inches
8x8 inches
9x9 inches
9 1/2x9 1/2 inches
10x10 inches
12x12 inches
13x13 inches
14x14 inches
3x8 inches
3x8 inches
4x9 inches
5x9 inches
6x10 inches
7x11 inches
7x12 inches
8x12 inches
8x13 inches
9x18 inches
9x18 inches
10x18 inches
*FOR LH SERIES CONSULT WITH VULCRAFT
Actual size and location of duct must
be indicated on the structural
drawings
Structural Systems
• Cast-in-place concrete frame
– Wide beams center on columns Concrete
slabs that generally can be readily sleeved for
piping
• Mechanical shafts and chases
• Sleeves and floor sinks.. electrical
conduits…
Structural Systems
• Cast-in-place concrete core walls
– Avoid locating telecom and electrical rooms
inside of closed in concrete core walls
– Locate shafts at ends of cores
– Coordination of openings
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Mechanical ducts
Stair pressurization
Piping sleeves
Electrical conduits
Fire house cabinets
Recessed drinking fountains
Do you make site visits during
structural construction?
Ask to go along with your structural engineer sometime… It is a lot of
fun…check this video out
Structural Systems
• Post-tensioned Cast-in-place concrete
– Most common on Residential and Hotels
– Flat thin slab
– Highly stressed cables embedded in slab
– Sleeves around columns are critical to design
– Drilled in hanger inserts limited to about 1
inch in depth.
– Pipe sleeves by columns
Structural Systems
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Precast concrete
– Tee stems spaced at 4’-0” or 5’-0” and
6-inches wide at the top.
– Field concrete topped and pre-topped
tees (no electrical conduit in pretopped tees)
– Mechanically hang from tee flanges if
hangers are drilled in inserts, do not
drill stems. Pre-stress tendons are
located in stems.
•Light gage cold formed steel (Studs)
Masonry
Structural Systems-Wood
Roof mechanical stacks
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SMACNA provisions.
Guyed stacks
– Performance specifications
» Wind loads
» Anchoring locations and
requirements
» Tensioning load criteria
Roof mechanical stacks
• Large Tall Stacks….design and detail
stacks and connections to structure or
retain a structural engineer.
• Stack design is generally not a part of your
structural engineers scope of service.
IBC 2006
SECTION 1613
EARTHQUAKE LOADS
1613.1 Scope.
Every structure, and portion thereof, including nonstructural
components that are permanently attached to structures and
their supports and attachments, shall be designed and
constructed to resist the effects of earthquake motions in
accordance with ASCE 7, excluding Chapter 14 and
Appendix 11A.
ASCE 7 2005
Chapter 13
SEISMIC DESIGN REQUIREMENTS FOR NONSTRUCTURAL
COMPONENTS
13.1 GENERAL
13.1.1 Scope. This chapter establishes minimum design criteria
for nonstructural components that are permanently attached to
structures and for their supports and attachments.
13.1.2 Seismic Design Category. For the purposes of this chapter,
nonstructural components shall be assigned to the same seismic
design category as the structure that they occupy or to which
they are attached.
ASCE 7 2005
13.1.3 Component Importance Factor. All components shall
be assigned a component importance factor as indicated in this
section. The component importance factor, Ip, shall be taken as
1.5 if any of the following conditions apply:
1.
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3.
The component is required to function for life-safety purposes
after an earthquake, including fire protection sprinkler systems.
The component contains hazardous materials.
The component is in or attached to an Occupancy Category
IV structure and it is needed for continued operation of the
Facility or its failure could impair the continued operation of the
facility.
All other components shall be assigned a component importance
factor, Ip, equal to 1.0.
ASCE 7 2005
13.1.4 Exemptions.
1.
The following nonstructural components are exempt from the requirements of
this section:
Architectural components in Seismic Design Category B other than parapets supported by bearing walls or shear
walls provided that the component importance factor, Ip, is equal to 1.0.
2. Mechanical and electrical components in Seismic Design Category B.
3. Mechanical and electrical components in Seismic Design Category C provided that
the component importance factor, Ip, is equal to 1.0.
4. Mechanical and electrical components in Seismic Design Categories D, E, and F
where the component importance factor, Ip, is equal to 1.0 and either:
a.
Flexible connections between the components and associated ductwork,
piping, and conduit are provided.
b.
Components are mounted at 4 ft (1.22 m) or less above a floor level and weigh
400 lb(1780 N) or less.
5. Mechanical and electrical components in Seismic Design Categories D, E, and F
where the component importance factor, Ip, is equal to 1.0 and
a.
Flexible connections between the components and associated
ductwork, piping, and conduit are provided.
b.
The components weigh 20 lb (89 N) or less or, for distribution
systems, weighing 5 lb/ft (73 N/m) or less.
Information needed
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Schematics
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Conceptual requirements of mechanical
systems, including preliminary location
and equipment weight
Non “Standard” criteria
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Vibration
Acoustical separation
Under floor mechanical systems
Take care of your structural
engineer…spend time coordinating
during DD!
Or this could happen on your next job…lets watch
Information needed
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Design Development
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Establish Story height……Ceiling height, structural
depth and mechanical space requirements
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Equipment size and weight
Identify heavy hanging loads due to piping
mechanical, boiler rooms, mechanical corridor arenas and stadiums
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Vibration / acoustical isolation of equipment
Structural supports for Mechanical
equipment cooling towers, generators, chillers, boilers,
roof top ducts, stacks
Information needed
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Design Development
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Major shaft openings in floors and roof
Major wall penetrations – shear walls and
structural exterior walls
Roof top mechanical penthouses, platforms,
mezzanines and catwalks
Information needed
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Construction Documents ..getting down to the Nitty
Gritty dimensions and details
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Confirmation of mechanical equipment weights from DD
House keeping pad locations and thickness
Openings in floors and roof – ducts, roof drains, water lines, conduit,
bus ducts, grease traps, floor sinks, etc
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Openings in exterior foundation walls and grade beams
Beam web penetrations/notches
Ducts running through bar joists
Buried tanks
Plumbing inverts /elevations coordinated with footings
Sump pits
Trench drains
Information needed
• Roof top mechanical equipment screen
wall coordination…Bracing of screen walls to equipment
and equipment that has an architectural screen attached.
• Louver back up structure requirements
Information needed
• Early Structural construction
packages…..
….Project specific……
..But in simple terms we need
everything that effects structural by the
end of DD….
Construction Administration
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Dimensions not set during design….Contractor and
MEP supplier to coordinate equipment specific
opening dimension….Always an issue…How can you
help?
Lets structural engineer know if contractor proposes
to switch equipment before the Owner accepts the
change…weight, size and opening requirements may
change and require re-design…be conservative during
design…no savings in structure for equipment
weights.
Coordination
• “…….I do not believe it is possible for a
mechanical or electrical engineer to fully
meet the expectations of the contractor (and
structural engineer) when it comes to coordination
……but we would appreciate your effort….”
Ralph Rempel
Coordination List
Structural depth and MEP systems
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Construction tolerances, structure deflection, fire proofing and the wrap
on the Mechanical ducts and pipes
Floor and roof openings
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Dimensioned opening size and dimensioned to grids
Beam flange widths for telecom and electrical risers and pipes and wall
locations.
Concrete wall openings
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For concrete shear walls structural engineer needs to show everything
that penetrates the wall.
Foundation walls not as critical structural engineer generally has typical
details
Roof slopes
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Locate drains near columns
Floor drains
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Coordinate with beam locations
Coordination List
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House keeping pads
Fire protection beam penetrations
Louver back up frame dimensions
Perimeter drains
Pipes through perimeter grade beams
Floor drains
Embedded pipes and electrical conduits
Coordination List
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Slabs…embedded electrical conduits
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Slabs on metal deck; space 1 ½” OD conduits at 18” for slabs
on metal deck unless Structural designs and details the slab
for the conduit.
Spacing can be reduced to 12 inches with minimal design
effort.
Spacing tighter than 12 inches will require additional
engineering and may cause the slab thickness to increase.
Coordination List
Embedded electrical boxes in concrete
columns (power and fire alarm) …….try to avoid
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Avoid electrical conduits and boxes embedded in cast
in place concrete columns… Why?
Coordination intensive..
Difficult to build at construction joint interfaces.
Electrical boxes need to be on structural column
details
Rebar fire-protection cover to be maintained.
Coordination List
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Specifications
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Embedded electrical conduit
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In general prohibit embedded conduit “unless as
shown on the drawings”.
For embedded conduit specify under the
submittals section that the contractor shall
prepare shop drawing showing the location of
the conduit.
You may want to also specify that if the conduits
are moved in the field that the record drawings
show the changes.
Coordination List
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Specifications cont.
– Hung piping
» Hang heavy pipes with a trapeze from
structural members
» Hanging smaller pipes from the slab
generally ok
» Drilled in inserts
» Cast in hangers
» Supporting piping from the floor below
Architects and BIM
SEAC 3/2010 survey
64% of architects use BIM
71% 3 years or more
Building Information Modeling
Interoperable software
Shared coordinates
Coordination
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First do it the standard old fashion way
Second fly through techniques (navisworks)
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Last Clash detection.