Egress amp Core strategies Example multitenant office bulding Key issues Return on investment Clear circulation wayfinding Maximize value of perimeter glassviews Allow for street level ID: 272881
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Slide1
Building Planning…
Egress &
Core
strategiesSlide2
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?)Slide3
Net: What you can rent…
Face of wall to face of wall
The higher the net assignable square footage (NASF) the higher the income
Also used to compare efficiency between concepts
Gross: everything else
Stairways
Lobby
Toilets
Custodial
Mechanical/electrical
Wall thicknesses
Amenity spaces (workout/atrium…)Slide4
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.Slide5
… even star architects watch it very closely between schemesSlide6
Public/employee sequence dominates…but doesn’t locate
elevators
Lobby/Reception/directory/security
Entry/vestibule
retail
retail
Double loaded lobby allows two retail tenants
Single loaded would allow one larger tenant
Challenge might be identitySlide7
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 wallsSlide8
Core location…always center?Slide9
Willis Tower, Chicago
53,000 net rentable
s.f
.Slide10
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 equipmentSlide11
Setbacks change floor plates
Meeting zoning required stepping back the building, reducing the number of repeated floors
Upper floors consumed by elevators (73 total)Slide12
End Core location responds to local conditions…view, climate…
What looks problematic?Slide13
Lever House, NYC,
Gordon
Bunshaft
, 1952Slide14
Multi Core placement for large floor dimensions (<300’)Slide15
Sendai
Mediateque
, Ito atomizes the coreSlide16Slide17
So…if its an office building…
Alley
Main Street
Easy Street
Adjacent
structure
High-value corner retail
Lower-value
streetfront
retailSlide18
…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?Slide19
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 roomSlide20
A midrise building core
Will Paton, final study F2011
men
women
egress
egress
mech
elevatorsSlide21
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.Slide22
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 buildingSlide23
Put these somewhere…in a way that makes the primary functions better
Elevators
Stairways
Entry/Lobby
Toilets
Mechanical/Systems spaces
Circulation elements, corridors, egress pathsSlide24
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?Slide25
Know a few things about the code
…how to get out in a fire
…how to arrange exits
…how big they have to be
…Slide26
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
.Slide27
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 Slide28
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.Slide29
Occupant load table
…excerpted
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
occupantsSlide30
Egress convergence
As the occupants from a floor 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, 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 from second, 200 occupants
100
100 + 100
100
100Slide31
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 ADASo the code continues to read “nor less than specified elsewhere in this code”
so it let’s itself out of an apparent contradictionSlide32
Stairways
Two required
Fully enclosed with 2 hour fire rated construction
Minimum stair width 48”
Max stair width without intermediate railing = 5’ Minimum headroom 80” from nosing line
Max height between landings = 12’-0”
Minimum depth
Of Landing, 48”
Max riser 7”
Min tread 11”
Within 3/8 of
same dimension for all steps
Max intrusion of door on landing = 7”Slide33
Stairways
…cont’d
Handrail height 34” - 38”
Handrails required both sides. 1-1/4 to 2” dia, 1-1/2” from wall (clear)
Handrails must extend 12” beyond top riser, and one tread (11”min) beyond bottom tread
11”
12”Slide34
2 exit spacing
Exits cannot be closer than 1/2 the maximum diagonal distance of the floor plate
80 feet
60 feet
Diagonal is
100’ long so
1/2 diagonal is
50 feetSlide35
2 exit spacing
So in this example, the exit stairs could not be placed closer than 50 feet apart
Maximum travel distances would be for this type ‘B’ building
200 feet without sprinklers
250 feet with sprinklers
What would be the maximum stair spacing in a sprinkled type ‘B’ building?
80 feet
60 feet
So stair entries must be 50 feet apart, minimum
50 feetSlide36
Dead End Corridors
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 a sprinkled building, the dead end can be extended to 50 feet long.
20 feet
Dead End
Ends in an exit
Not a dead endSlide37
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.Slide38
Where do we enter?
Prominence
Number of entries
Security
Types
PublicEmployeeService
Shipping/receivingSlide39
A 150x250 site
Alley
Main Street
Easy Street
Adjacent
structureSlide40
Zoning setbacks
Alley
Main Street
Easy Street
Adjacent
structureSlide41
Where do we enter?
Alley
Main Street
Easy Street
Adjacent
structure
Possible Service
Barrier!
No view!
Best public/ employee entry
Possible employee entrySlide42
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 thisSlide43
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. deliverySlide44
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 retailSlide45
Public/employee sequence dominates…but doesn’t locate
elevators
Lobby/Reception/directory/security
Entry/vestibule
retail
retail
Double loaded lobby allows two retail tenants
Single loaded would allow one larger tenant
Challenge might be identitySlide46
If its an office building…
Alley
Main Street
Easy Street
Adjacent
structure
High-value corner retail
Lower-value
streetfront
retailSlide47
…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?Slide48
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 roomSlide49
A midrise building core
Will Paton, final study F2011
men
women
egress
egress
mech
elevatorsSlide50
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.Slide51
Building Planning… Part II
Core strategiesSlide52
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 wallsSlide53
Core locationSlide54
Core locationSlide55
Lever House, NYC,
Gordon
Bunshaft
, 1952Slide56
Core locationSlide57
Sendai
Mediateque
, Ito atomizes the coreSlide58Slide59
Considering cores…
Alley
Main Street
Easy Street
Adjacent
structure
High-value corner retail
Lower-value
streetfront
retailSlide60
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.Slide61
Stairways
Two required
Fully enclosed with 2 hour fire rated construction
Minimum stair width 48”
Max stair width without intermediate railing = 5’ Minimum headroom 80” from nosing line
Max height between landings = 12’-0”
Minimum depth
Of Landing, 48”
Max riser 7”
Min tread 11”
Within 3/8 of
same dimension for all steps
Max intrusion of door on landing = 7”Slide62
Stairways
…cont’d
Handrail height 34” - 38”
Handrails required both sides. 1-1/4 to 2” dia, 1-1/2” from wall (clear)
Handrails must extend 12” beyond top riser, and one tread (11”min) beyond bottom tread
11”
12”Slide63
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 wallsSlide64
Considering cores…
Alley
Main Street
Easy Street
Adjacent
structure
High-value corner retail
Lower-value
streetfront
retailSlide65
Chicken or the egg?
What sets the core-to-skin distance?Slide66
How far is it from the core to the skin?Slide67
Know your typology…what’s that mean?Slide68
typology meets client culture…meets market…Slide69
Client Culture, Organization, and FormSlide70
Market needs informSlide71Slide72Slide73
Modularity…common denominators…
Planning grids
Structural grids
Lighting grids
Power grids
Mechanical gridsSlide74
Built from the most common…and smallest acceptable unit of spaceSlide75Slide76Slide77
Minimum skin to core?
14’
6’
10’
10’Slide78
Minimum structural?
14’
6’
10’
10’
10’
10’Slide79
Check structural capability
Steel Frame
Cast-in-Place Concrete Frame
Precast FrameSlide80
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)Slide81
Bay proportions…
are long girders better?
20’
40’
Here the girders are spanning 40’ and are framing into the columns and carry the secondary floor beams.
This requires
W30x108 girders
And
W16x26 beams
With a 5 1/4” slab over the beams
that’s 6,400 pounds of steel in this bay
30”
14” for ductwork, lights...
16”Slide82
Site-Cast-Concrete Systems…Basic
flavors
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)
All diagrams from Allen “Architects Studio Companion”Slide83
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.
When heavily loaded it requires the beams below the slab, It is more desirable to NOT have these beams as they take additional labor to form and pour.
Costs
25x25 6” 40psf load about $13.80 per sq.ft.
25x25 6” 125psf load about $17.20 per sq.ft.
Span min
6’
Span max
18’
R.O.T. Slab depth 1/22th of span
Postten rot Slab depth 1/40th of span
Min thick for 2hr = 5”
Min thick for 3hr = 6 1/2”Slide84
One way joist slabs
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
.
Span min
12’
Span max
45’R.O.T. Slab depth 1/18th of span
Postten rot Slab depth 1/36th of spanMin thick for 2hr = 5”Min thick for 3hr = 6 1/2”
JoistSlabJoist band (beam)
voidSlide85
Standard Spanning elements
Solid slabs
Hollow core slabs
Double tees
Rectangular beam
“L” beams
“T” beamsSlide86
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 jointSlide87
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.Slide88
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 $10.50Slide89
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.Slide90
Long beams, short planks or long planks short beams?
One way
20’
40’
2’-8”
8”
3’-4”Slide91
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’Slide92
40’
20’
1’-4”
12”
2’-4”
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!Slide93
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
Space!
DuctSlide94
Mechanical Planning
Is mostly about providing ventilation
…and cooling
…with big…noisy…machines
You can choose to Centralize or Decentralize the air handling machinery in the building
Centralized:
Big
vert
shafts
Decentralized:
Mech
rooms each floor
HybridSlide95
If Shafts…plan for trunks
Don’t trap shafts behind elevators and stairs
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 ductsSlide96
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 interiorSlide97
Structure & trunk
ducts
Plan a short structural span next to the core if possible, it makes for a thinner structural section to allow trunk ducts to pass
Short span
long spanSlide98
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.