Transcript Building Planning - mjobrien architect

Building
Planning…
Egress &
Core strategies
Example, multi-tenant office
bulding
 Key issues
 Return on investment
 Clear circulation/wayfinding
 Maximize value of perimeter glass/views
 Allow for street level retail
 High net to gross ratio (what’s that?)
 Net: What you can rent…
 Gross: everything else
 Face of wall to face of wall
 Stairways
 Lobby
 The higher the net
assignable square footage
(NASF) the higher the
income
 Also used to compare
efficiency between
concepts
 Toilets
 Custodial
 Mechanical/electrical
 Wall thicknesses
 Amenity spaces
(workout/atrium…)
Some common net to gross
ratios
 Administrative buildings
67/33
 Auditorium buildings 70/30
 Courthouse 61/39
 Hospital 55/45
 Office buidling 75/25 (80/20
common)
 Science building 60/40
 Warehouse 93/7
 The larger number is usually
the net…those functions
that are the reason to build
the building
 The smaller number is the
net…those functions that
serve the above.
… even star architects watch it very closely between schemes
Public/employee sequence
dominates…
but doesn’t locate
elevators
retail
Lobby/Rec
eption/dire
ctory/secur
ity
retail
Double loaded lobby allows
two retail tenants
Entry/vestib
ule
Single loaded would allow
one larger tenant
Challenge might be identity
Other core responsibilities
 Besides housing egress, access, toilets and
HVAC, cores often act as the primary space
definition elements on a floor.
 They also are often used for lateral bracing of
the structural frame, with walls reinforced to be
shear diaphragms or with “X” bracing or chevron
bracing concealed within their enclosing walls
Core location…always center?
Willis Tower, Chicago
53,000 net rentable s.f.
Empire State
Designed for
Rapid-Building
• … 2,768,591s.f. in 410
days?
6,752 s.f. per day!
• Standard Bay sizes
• Standard Mullion
spacing
• Stone sizes fit to milling
equipment
• Steel sizes fit to
transport/lifting
equipment
Setbacks
change
floor plates
• Meeting zoning
required
stepping back
the building,
reducing the
number of
repeated floors
• Upper floors
consumed by
elevators (73
total)
End Core location responds to local
conditions…view, climate…
What looks problematic?
Lever House, NYC,
Gordon Bunshaft, 1952
Multi Core placement for large
floor dimensions (<300’)
Sendai Mediateque, Ito atomizes
the core
Easy Street
So…if its an office building…
Alley
Highvalue
corner
retail
Lowervalue
streetfront
retail
Main Street
Adjacent
structure
…but the tail can’t wag the dog
 The corner retail will produce higher rental costs,
but will it compromise the 15 floors of building
above it?
 The street-front retail will tolerate more spatial
disruption due to its lower rents, but how much
can we intrude on it?
Time to consider the cores
 coreS?...not just one?
 Every floor will need
 Elevator access
 2 means of egress (elevators won’t count)
 Toilets for each gender
 Some electrical/telecom space
 Some space for ventilation/hvac
 Could be a shaft
 Could be a fan room
A midrise building core
men
elevators
egress
mech
egress
women
Will Paton, final
study F2011
Basic organization forms
You might generate alternatives in
more than one
Or the site, or inner organization of
the clients enterprise might hint at
which is most appropriate
Ultimately these begin to form a
backbone, an armature to hang the
building infrastructure upon.
Deploying infrastructure
 Building planning is a design stage where the
infrastructure elements of the building are
located in ways that meet the appropriate
codes and delineate space for the primary
functions of the building
Put these somewhere…in a way
that makes the primary functions
better
 Elevators
 Stairways
 Entry/Lobby
 Toilets
 Mechanical/Systems spaces
 Circulation elements, corridors, egress paths
Know the land
 From a building planning perspective, this might
mean answering these questions
 Where do we enter?
 Where should trash and deliveries go?
 Does the building have to be phased or planned
for an addition?
 Which orientation or orientations have the highest
value? Which have the lowest?
Know a few things about the
code
 …how to get out in a fire
 …how to arrange exits
 …how big they have to be
 …
Egress
 Promoter P.T. Barnum is said to have charged people 25
cents to enter a darkened room and “See the Egress.”
 Once in the darkened room, the people could only see a
dim light over a door with a sign on it saying “This way to
the Egress.”
 Upon opening the door and walking through they found
themselves on the street!
 Egress is the term applied to the various means (corridors,
stair enclosures, stairs) to be used as a means of escape in
the event of a fire or other disaster in the building.
Some key IBC Definitions
 Area of Refuge: Area where persons unable to use
stairways can remain temporarily to await instructions or
assistance during emergencies
 Corridor: An enclosed exit access component that defines
and provides a path of egress travel to an exit.
 Exit: That portion of a means of egress system which is
separated from other interior spaces of a building by fire
resistance rated construction and opening protectives as
required to provide a protected path of egress travel
between the exit access to the exit discharge including exit
doors, exit enclosures, exit passageways
How Many People?
 The IBC offers the choice of two processes for determining
the number of people (occupants) in the building.
 The first method is to determine the actual number of people in
the space.
 This is easier to do in a building with fixed seating (auditorium)
than in say an open office space where, the density varies over
time.
 The second method is to refer to the Maximum Floor Area per
Occupant table, find your use type, divide the number of gross
square feet per occupant in the table into your project’s gross
square footage to arrive at the number of occupants in the
building, or per floor.
Occupant load table …excerpted
Occupancy
Assembly without fixed
seats
Concentrated (chairs)
Standing space
Unconcentrated
(tables and chairs)
Business Areas
Dormitories
Educational
Classroom Area
Vocational Areas
(shops)
Library
Reading Area
Stack Area
Floor Area in Square Feet
per occupant
7 net
5 net
15 net
100 gross
50 gross
20 net
50 net
50 net
100 gross
So our Business
Occupancy
would take the
program area
(40,000 s.f.) and
divide it by 100
s.f. to determine
we have 400
occupants
Egress convergence
100
 As the occupants from a floor
100
above exit through lower floors,
they don’t impact the exit size for
the floor the pass through, but the
exit size cannot get smaller.
 But when exits converge at a floor,
100
like the ground floor where they
leave the building, the occupant
load for the ground floor must take
into account the occupant load
of the floor immediately above.
 First floor, 10,000 s.f. = 100 occ +
100 + 100
100 from second, 200 occupants
How wide does that make the
exit?
 The IBC reads “The total width of the means of egress in inches
shall not be less than the total occupant load served multiplied
by”
.3 for stairs in unsprinkled buildings
 .2 for corridors, other egress components in unsprinkled buildings

.2 for stairs in sprinkled buildings
 .15 for other components in sprinkled buildings

 So our top floor stair in our unsprinkled example could be no
less than 100 x .3 or 30 inches…not nearly wide enough to meet
minimums of the IBC or ADA
 So the code continues to read “nor less than specified
elsewhere in this code” so it let’s itself out of an apparent
contradiction
Stairways
 Two required
 Fully enclosed with 2
hour fire rated
construction
 Minimum stair width 48”
 Max stair width without
Minimum depth
Of Landing, 48”
Max riser 7”
intermediate railing = 5’
Min tread 11”
Minimum headroom
Within 3/8 of
80” from nosing line
same
dimension for  Max height between
all steps
landings = 12’-0”
Max
intrusion of
door on
landing = 7”
Stairways…cont’d
 Handrail height
34” - 38”
 Handrails
required both
sides. 1-1/4 to 2”
dia, 1-1/2” from
wall (clear)
11”
12”
 Handrails must
extend 12”
beyond top riser,
and one tread
(11”min) beyond
bottom tread
2 exit spacing
 Exits cannot be
Diagonal is
100’ long so
1/2 diagonal is 50 feet
60 feet
80 feet
closer than 1/2
the maximum
diagonal
distance of the
floor plate
2 exit
spacing
• So in this example, the exit
stairs could not be placed
closer than 50 feet apart
So stair entries
must be 50
feet apart,
minimum
• Maximum travel distances
80 feet
would be for this type ‘B’
50 feet
building
– 200 feet without sprinklers
– 250 feet with sprinklers
• What would be the
maximum stair spacing in
a sprinkled type ‘B’
building?
60 feet
Dead End
Corridors
Dead End
20 feet
 A corridor not ending in an
exit is considered a dead
end corridor
 Dead end corridors are
limited to 20 feet in length
in most occupancies.
 In occupancy group B with
Ends in an exit
Not a dead end
a sprinkled building, the
dead end can be
extended to 50 feet long.
On your way to the exit...
 DO NOT plan the egress path to exit through another
tenants space
 DO NOT plan the egress path to exit through storage
spaces, kitchens, mechanical rooms…or other high
hazard occupancies.
 But exiting through a non hazardous accessory space
is acceptable, as long as there is a clear path
discernable to the exit.
Where do we enter?
 Prominence
 Number of entries
 Security
 Types
 Public
 Employee
 Service
 Shipping/receiving
Easy Street
A 150x250 site
Alley
Adjacent
structure
Main Street
Easy Street
Zoning setbacks
Alley
Adjacent
structure
Main Street
Easy Street
Where do we enter?
Possible
employee
entry
Alley
Possible Service
Barrier!
No view!
Best public/ employee entry
Main Street
Adjacent
structure
Now you need the insight
 If the employees have to clock in, change
clothes, and report to the workspace, then the
lockers/lunchroom/timeclock need to be near
their entrypoint
 If they just walk in and go to their workstation,
there’s no need for this
Now you need the insight
 If there is a public/retail first floor, the street-fronts
become high value, so putting employee or
utility functions there would be
counterproductive
 If the business ships and receives high volumes of
product, then the side-street and alley become
high value.
 Regardless, we need to keep in mind, trash
storage, backup generators, and misc. delivery
Example, multi-tenant office
bulding
 Key issues
 Return on investment
 High net to gross ratio (what’s that?)
 Clear circulation/wayfinding
 Maximize value of perimeter glass/views
 Allow for street level retail
Public/employee sequence
dominates…
but doesn’t locate
elevators
retail
Lobby/Rec
eption/dire
ctory/secur
ity
retail
Double loaded lobby allows
two retail tenants
Entry/vestib
ule
Single loaded would allow
one larger tenant
Challenge might be identity
Easy Street
If its an office building…
Alley
Highvalue
corner
retail
Lowervalue
streetfront
retail
Main Street
Adjacent
structure
…but the tail can’t wag the dog
 The corner retail will produce higher rental costs,
but will it compromise the 15 floors of building
above it?
 The street-front retail will tolerate more spatial
disruption due to its lower rents, but how much
can we intrude on it?
Time to consider the cores
 coreS?...not just one?
 Every floor will need
 Elevator access
 2 means of egress (elevators won’t count)
 Toilets for each gender
 Some electrical/telecom space
 Some space for ventilation/hvac
 Could be a shaft
 Could be a fan room
A midrise building core
men
elevators
egress
mech
egress
women
Will Paton, final
study F2011
A minimal stair
• 48 inches between handrails
• 1.5” handrails (each side) that are 1.5” from the walls
• So a single run of stairs is 54” wide
• If the stair runs between 12 foot floors,
• 12x12=144” of rise
• divided by max riser 7.0 = 20.5 risers, say 21 at 6.8” or just over 6
and ¾ inches.
• always one less tread than riser so 20 risers at min dimension of
11 inches so 20x11inches = 220 inches or 18 feet 4 inches of
horizontal run, add 6-5 foot landings at the top and bottom if
doors open into the stairs) (and, not counting the ARA), the
overall inside of the straight run stair is 31’2” x 5’4” wide.
• now work out a dual run stair.
Building
Planning… Part II
Core strategies
Other core responsibilities
 Besides housing egress, access, toilets and
HVAC, cores often act as the primary space
definition elements on a floor.
 They also are often used for lateral bracing of
the structural frame, with walls reinforced to be
shear diaphragms or with “X” bracing or chevron
bracing concealed within their enclosing walls
Core location
Core location
Lever House, NYC,
Gordon Bunshaft, 1952
Core location
Sendai Mediateque, Ito atomizes
the core
Easy Street
Considering cores…
Alley
Highvalue
corner
retail
Lowervalue
streetfront
retail
Main Street
Adjacent
structure
A minimal stair
• 48 inches between handrails
• 1.5” handrails (each side) that are 1.5” from the walls
• So a single run of stairs is 54” wide
• If the stair runs between 12 foot floors,
• 12x12=144” of rise
• divided by max riser 7.0 = 20.5 risers, say 21 at 6.8” or just over 6
and ¾ inches.
• always one less tread than riser so 20 risers at min dimension of
11 inches so 20x11inches = 220 inches or 18 feet 4 inches of
horizontal run, add 6-5 foot landings at the top and bottom if
doors open into the stairs) (and, not counting the ARA), the
overall inside of the straight run stair is
31’2” x 5’4” wide.
Stairways
 Two required
 Fully enclosed with 2
hour fire rated
construction
 Minimum stair width 48”
 Max stair width without
Minimum depth
Of Landing, 48”
Max riser 7”
intermediate railing = 5’
Min tread 11”
Minimum headroom
Within 3/8 of
80” from nosing line
same
dimension for  Max height between
all steps
landings = 12’-0”
Max
intrusion of
door on
landing = 7”
Stairways…cont’d
 Handrail height
34” - 38”
 Handrails
required both
sides. 1-1/4 to 2”
dia, 1-1/2” from
wall (clear)
11”
12”
 Handrails must
extend 12”
beyond top riser,
and one tread
(11”min) beyond
bottom tread
Other core responsibilities
 Besides housing egress, access, toilets and
HVAC, cores often act as the primary space
definition elements on a floor.
 They also are often used for lateral bracing of
the structural frame, with walls reinforced to be
shear diaphragms or with “X” bracing or chevron
bracing concealed within their enclosing walls
Easy Street
Considering cores…
Alley
Highvalue
corner
retail
Lowervalue
streetfront
retail
Main Street
Adjacent
structure
Chicken or the egg?
What sets the core-to-skin distance?
How far is it from the core to the
skin?
Know your typology
…what’s that mean?
typology meets client
culture…meets market…
Client Culture, Organization, and
Form
Market needs
inform
Modularity…common
denominators…
• Planning grids
• Structural
grids
• Lighting grids
• Power grids
• Mechanical
grids
Built from the most
common…and smallest
acceptable unit of space
10’
14’
6’
10’
Minimum
skin to
core?
10’
10’
10’
Minimum
structural?
14’
6’
10’
Check structural capability
Steel Frame
Cast-in-Place Concrete Frame
Precast Frame
Steel R.O.T.
p.356
Depth of Girders = 1/15 span
(width=1/3 to 1/2 depth)
Depth of Beams 1/20 span
(depth of slab included in composite
structures)
Depth of bar joists 1/20 span
(spacing 2 to 10 feet depending on
decking / concrete thickness)
Depth of decking and concrete for
floors 1/24th of span (2 1/2 to 7 inches
typical)
Depth of decking for roof 1/40 th of
span (1 to 4 inch decking available)
Bay proportions…are long girders
better?
20’
Here the girders are spanning 40’ and
are framing into the columns and carry
the secondary floor beams.
This requires
W30x108 girders
And
40’ W16x26 beams
With a 5 1/4” slab over the beams
that’s 6,400 pounds of steel in this bay
16”
30”
14” for ductwork, lights...
Site-Cast-Concrete
Systems…Basic flavors
All diagrams from Allen “Architects Studio Companion”

Basically, there are 4 types
of slabs an architect
chooses from when
considering a system for a
project.

Slabs are usually flat, can
be reinforced to span one
way or two ways. Their span
usually depends on their
depth, but there is a point
where the extra concrete in
the depth works against the
slab due to its weight.

Joist slabs usually can span
farther and carry heavier
loads because they
eliminate concrete not
contributing to the slabs
strength. (hence the joists)
One way flat slabs…will it work?
 The one way slab spans between beams
or columns. It requires a structural bay
(spacing between columns in both
directions) that is within 20% of being
square.
 It is usually used for light loading
applications where it’s thin structural
depth gives a low floor to floor height.
Span min6’
Span max 18’
 When heavily loaded it requires the
R.O.T. Slab depth
beams below the slab, It is more desirable
to NOT have these beams as they take
1/22th of span
additional labor to form and pour.
Postten rot Slab depth
1/40th of span
Min thick for 2hr = 5”
Min thick for 3hr = 6
1/2”
 Costs
 25x25 6” 40psf load about $13.80 per sq.ft.
 25x25 6” 125psf load about $17.20 per sq.ft.
One way joist slabs
Joist
Slab
Joist band (beam)
void
•
•
•
Span min12’
Span max 45’
R.O.T. Slab depth
•
1/18th of span
Postten rot Slab depth
1/36th of span
Min thick for 2hr = 5”
Min thick for 3hr = 6
1/2”
To address heavier loading conditions, its necessary to
remove the concrete that’s acting as dead weight working against the slab that comes along with an
increase in the uniform thickness of a slab.
This one way joist slab does just that, using prefab
formwork set on a plywood deck voids are formed
between the joists which make the slab lighter, and
stiffer.
The joists bear into beams (called bands) spanning
from column to column. These bands give this system
the ability to move columns off the grid, (as long as
they still fall under the bands) allowing for more plan
flexibility.
Costs
– 25x25 12” 40psf load about $14.10 per sq.ft.
– 25x25 12” 125psf load about $16.50 per sq.ft.
Standard Spanning elements
 Solid slabs
 Hollow core slabs
 Double tees
 Rectangular beam
 “L” beams
 “T” beams
 Each piece is numbered for location according to the shop
drawings.
 This producer also dates each piece to be certain only fully cured
components are installed
Castellated joint
Hollow Core slabs
 Like sitecast slabs, when the depth of a solid slab increases
past a certain point, the extra weight of the concrete works
against the spanning member.
 In precast, the hollow core slab, removes unemployed
concrete increasing the structural efficiency of the slab.
Unlike the solid slab, the hollow core slab is reinforced with
prestressing strands in the top and bottom of the slab.
Spanning
 The hollows are made in different ways by different
companies. Some have expanding air cylinders, some use
pea gravel laid in the bottom half of the pour.
Span max 45’
Widths 2’-0”, 3’-4”, 4’-0”, 8’-0”
Span / Depth ratio 1/40
Min produced depth 6” (2” increments)
Max produced depth 12”
Cost per s.f. topped $12.50
Cost per s.f. untopped $10.50
aka the plank
 Like the solid slab, the hollow core slab (also known as the hollow core
plank) has castellated joints to form shear keys when filled with grout.
 This helps the planks work together and increases structural efficiency.
 Like other precast systems when used as floors, the hollow core plank
needs a topping slab (2” or so) to level out the camber differences, make
a diaphragm for lateral resistance, and make a place for electrical and
hot water heating utilities.
Long beams, short
planks or long
planks short
beams?
20’
One way
8”
2’-8”
40’
3’-4”
40’
20’
• The longer a beam spans, the deeper it must be. While the plank
stays pretty much the same. (the number of prestensioned strands
increases)
• In this example, say the beam span is 20 feet, the rule of thumb of
d=1/15 s gives 20/15=1’-4” deep. The plank spans 40 feet here
and which gives an 12” plank. This makes a 2’-4” deep structural
sandwich
40’
20’
That’s a FOOT thinner! In a 8 story building
it gives the owner an extra floor for FREE!
So bay size has a LOT to do with structural
depth, which has a significant impact on
the projects economics!
12”
2’-4”
1’-4”
Beams & floor to floor
heights…look familiar?
• Supporting the spanning member on top of the beam adds to
the floor to floor height, but, if the spanning member on top of
the beam is a single or double tee, the space between the top
flange and bottom of the stem is available for ductwork to pass
over
the beam with no conflict!
Duct
Duct
Space!
Is mostly about providing ventilation
…and cooling
…with big…noisy…machines
Mechanical
Planning
You can choose to Centralize or Decentralize the
air handling machinery in the building
Centralized:
Big vert shafts
Decentralized:
Mech rooms
each floor
Hybrid
If Shafts…plan for trunks
Trunk ducts are the main ducts that
emerge from the shafts
Since they serve large areas of
floorspace, they contain lots of air
and are bigger than distribution
ducts
Don’t trap shafts behind elevators
and stairs
If Shafts…plan for trunks
Plan return ducts to run inboard of
supply…supply has to be delivered
to the building skin, returns can be
interior
Structure &
trunk
ducts
Short span
Plan a short structural span next to
the core if possible, it makes for a
thinner structural section to allow
trunk ducts to pass
long span
Put it all together…
Seeking modularity
You’re looking for the common denominators
• Is the smallest space an increment of the largest?
• Will the smallest plus a circulation path be modular with the
most frequently found space increment?
• Is the structure an increment of the smallest and largest
spaces?
Remember..
• Grids don’t need to be uniform
• Core functions can be environmental buffers
• Smaller grids spacing makes for shallower structure, very
helpful if coordinated with maximum ductwork depth
• Mechanical zones are usually functional, environmental or
some combination of the two.
• Ductwork is best run over circulation spaces, it gives better
acoustic isolation.