Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 1 -
Structural Concepts/Structural Existing Conditions Report Resubmitted November 5, 2004
Executive Summary
The Arlington Gateway Hotel is a 15 story cast-in-place reinforced concrete
structure totaling 240,000 square feet. The hotel also includes three levels of
below grade parking under the structure. The flooring system is a mix of two
way flat plate and flat slab design depending on floor loading conditions.
The exterior precast cladding is non load bearing and supported by each
floor. The structure uses moment frames to resist lateral forces due to wind.
The loading on the structure was calculated using BOCA 96 and ASCE 7-95.
The calculated loadings used throughout this report are current codes of
ASCE 7-02 and IBC 2003. Calculations are limited do to the nature of the
building being a two way slab and not having an in depth study of this
subject in classes at this time. Through simplified calculations, no significant
differences in member sizes have been found. It will take much
understanding of the structure to accurately define the lateral systems of the
building and this calculation has been omitted from this assignment to be
completed at a later date.
Through this analysis, wind and seismic forces were calculated. A maximum
base shear of 710 kips was found for combined wind forces. Maximum base
shear of 895 was found due to seismic forces. These forces were not used in
checking members in this report, but will need to be checked as part of
future investigations.
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 2 -
Building Description
The Arlington Gateway Hotel is a 240,000 square
foot structure located in Arlington, Virginia. The
hotel is part of Arlington Gateway, a mixed use
development. The height of the building is 170’
from ground level to the top of the mechanical
penthouse. There are 336 units in the 15 story
building. The break down
of each floor total area is
shown in the figures on the left. There is also an
additional 3 levels below grade that is the parking
garage. The lowest level of the parking garage is 30’
below ground level. The exterior of the building is
composed of non load bearing precast concrete
panels. Structural steel is used on the north east face
and for the roofing system of the ballroom and pool
areas.
Summary of the Overall Structural System
The overall structural system of the building is a two
way flat plate. The slabs are generally 8” thick with
#4@12” on center, each way. 4000 psi concrete is
used in all floor slabs. The building bears on spread footings and continuous
wall footings. Column dimensions are generally 32”x32” in the lower levels
and require 6000 psi concrete. On the second through eighth floor, columns
require 5000 psi concrete and 4000 psi concrete is used on the rest of the
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 3 -
building. Reinforcing steel is to be grade 60, except for column ties and
beam stirrups which are to be grade 40, minimum.
Foundation
The foundation of the building bears on decomposed rock. The structure
uses spread footings that were designed for two different bearing
conditions, 40ksf and 80ksf. The soil bearing conditions needs to be checked
by a geotechnical engineer for each footing, to determine what design to
use. The footings are to use 4000 psi normal weight concrete. For design of
foundation walls, an equivalent fluid pressure of 60 pcf should be used
above the water table and an additional 62.5 pcf below the water table.
Codes
The hotel’s structural members were designed using ACI 318-97 and AISC –
8th Edition. ACI 318-97 was used to design minimum requirements of
concrete members along with calculating loading using the equation of
1.4D + 1.7L for factored loads. AISC – 8th Edition is the manual for Allowable
Stress Design (ASD), this was used for the steel members in the pool and
ballroom areas. Through my analysis I will use ACI 318-02 and AISC – 3rd
Edition (LRFD). ACI 318-02 uses a loading equation of 1.2D + 1.6D for
factored loads.
Loading on the building was determined using BOCA 96 and ASCE 7-95.
These codes were used to define the loading on the lateral systems due to
wind and seismic forces. Also they define the minimum required gravity
loads, such as live loads. The live loads include snow loading and loading
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 4 -
due to objects that can be moved such as people and furniture. To
determine design loads for this assignment I used ASCE 7-02.
Lateral Systems
The lateral load resisting system uses moment frames to resist the forces of
wind. The whole structure acts as a moment frame. There were only
calculations of forces in the lateral system at this time. No lateral load
resisting members were checked due to the complexity of the structure and
the use of a two way flooring system. This will be accomplished in a later
report.
Wind
Wind loads for the structure were calculated by the engineer using BOCA 96
and ASCE 7-95. I calculated wind loads using ASCE 7-02. For simplicity of
calculations, I based my buildings shape on a rectangle equal to that of the
floor area of the upper floors.
The dimensions of the
rectangle are 73’ x 217’. On
the left are the Wind Pressure
Diagrams for the hotel. The
red area is the windward
pressure (+) and the blue
represents leeward pressure
(-). The max pressure in the N-
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 5 -
S direction is 15.9 psf at the top on the windward side with 9.8 psf acting on
the whole face of the leeward side. In the E-W direction the max wind
pressure is 17.04 psf at the top on the
windward side and 5.25 psf on the
leeward side. The tables provided on this
page show the exact breakdown of wind
pressure per height of building. In
Appendix E there is a diagram of the wind
pressure broken down into story forces
acting on each floor. I found the total
base shear in the N-S direction to be 710
kips. The N-S direction diagram reflects the
load at each floor for the 27’ bay believed
to be part of the lateral system. This was
done to aid in the 2-D calculation of the
lateral system in this direction that I will
compute at a later date. The E-W wind
loading diagram in Appendix E has the total
forces acting on each floor and a total base
shear of 195 kips.
Seismic
ASCE 7-02 was the code I used for my seismic
analysis. I first found the snow load for the
building to be 19.25 psf which is less than 30 psf; therefore, it was not
required to be used in the accumulation of loads on the structure. I used
N-S Direction
Height (ft)
Windward
(psf) Leeward
(psf)
Total MWFRS
(psf) 0-15 8.04 -9.82 17.86
15-20 8.75 -9.82 18.57 20-25 9.31 -9.82 19.13 25-30 9.88 -9.82 19.70 30-40 10.72 -9.82 20.54 40-50 11.43 -9.82 21.25 50-60 11.99 -9.82 21.81 60-70 12.56 -9.82 22.38 70-80 13.12 -9.82 22.94 80-90 13.55 -9.82 23.37
90-100 13.97 -9.82 23.79 100-120 14.67 -9.82 24.49 120-140 15.38 -9.82 25.20 140-160 15.94 -9.82 25.76
E-W Direction
Height (ft)
Windward (psf)
Leeward (psf)
Total MWFRS
(psf) 0-15 8.60 -5.25 13.85
15-20 9.35 -5.25 14.60 20-25 9.95 -5.25 15.20 25-30 10.56 -5.25 15.81 30-40 11.46 -5.25 16.71 40-50 12.21 -5.25 17.46 50-60 12.82 -5.25 18.07 60-70 13.42 -5.25 18.67 70-80 14.02 -5.25 19.27 80-90 14.48 -5.25 19.73
90-100 14.93 -5.25 20.18 100-120 15.68 -5.25 20.93 120-140 16.44 -5.25 21.69 140-160 17.04 -5.25 22.29
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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the values from seismic use group III and site
classification C. Through my calculations of seismic
shear I found the base shear to be 895 kips, which is
actually greater than my calculated base shear for
wind. There is no significant fault line in the area; the
large value for seismic base shear could be a result of
a very conservative approach I took in calculating
seismic story forces. The diagram on the left displays
the magnitude of seismic forces at each floor.
Loads
The building’s roof was designed using a live load of 16 psf. This varies a little
with my calculated snow load of 19 psf. The slight difference could be
because of a change in code or because some of the load goes to the
penthouse floor that was designed for 150 psf. The building’s roof was
designed using a live load of 16 psf. This varies a little with my calculated
snow load of 19 psf for this area. The slight difference could be because of
a change in code or because some of the load goes to the penthouse floor
that was designed for 150 psf. Typical floors were designed using 40 psf + 15
psf for partitions. 40 psf is the value I found in ASCE 7-02 for live floor loads for
a hotel. Corridors were designed using a live load of 70 psf, which is the
same value as found in ASCE 7-02. The 15 psf load for partitions is usually
taken as dead load, but in this case the engineer may have thought about
future remodeling of the floors. This would change locations of walls and a
new distribution of loads. Other live loads include 150 psf for mechanical
penthouse floor, 100 psf first floor and stairs, and 250 psf for the loading
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 7 -
dock. Wind and seismic loading on the structure is stated in the analysis of
the lateral system.
The accumulation of dead loads includes the weight of the building
materials and miscellaneous mechanical, electrical, and plumbing fixtures.
The 8” flat slab has a dead load of 100 psf. I have assigned 10 psf to MEP
and other miscellaneous being applied to each floor. The total loading on
each floor is shown in the diagram on the next page. For quick analysis a
live load of only 40 psf
was used in the table,
corridors make up a
small percentage of
floor area so it was not
included at this time.
Spot Checking
Through my
calculations, I
checked the design of
the two way slab
between columns. I had to simplify the design and treat this section as a
thin beam. My results were similar to the design; calculations can be seen in
Appendix A. For the one foot wide and 8” deep beam I found that
minimum steel requirements governed. To meet minimum steel
requirements I needed to use a #5@12”. The slab called for #4@10”. The
difference is due to the wider spacing of my design. Using the minimum
Level Total Live Load (psf)
Total Dead Load (psf)
Dead Weight
Live Weight
Factored Total
Weight 15(roof) 170 110.0 1742510 2692970 6399764
14 40 125.0 1980125 633640 3389974 13 40 125.0 1980125 633640 3389974 12 40 125.0 1980125 633640 3389974 11 40 125.0 1980125 633640 3389974 10 40 125.0 1980125 633640 3389974 9 40 125.0 1980125 633640 3389974 8 40 125.0 1980125 633640 3389974 7 40 125.0 1980125 633640 3389974 6 40 125.0 1980125 633640 3389974 5 40 125.0 1980125 633640 3389974 4 40 125.0 1980125 633640 3389974 3 40 125.0 1980125 633640 3389974 2 40 125.0 1980125 633640 3389974 1 40 125.0 1980125 633640 3389974
Sum 29464260 11563930 53859400
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 8 -
reinforcing provides a member to have a capacity of 88 foot kips. Using ACI
moment coefficients I found a maximum moment of 5.8’k (negative
moment). The extra capacity of the slab would take moments from lateral
forces, which will be calculated later. This will have to be checked to see if
82.8’k is more than the moments caused by the lateral forces.
Columns are now to be checked for capacity of gravity loads. There are 30
columns in the area of the above loading table. Through quick analysis
total building weight was divided between the 30 columns, each column
roughly supports 1795 kips. At this time only gravity loads have been found,
later lateral forces will need to be checked with the chosen column to see if
it will still be adequate. Columns under the first floor use 6,000 psi concrete
and 60,000 ksi steel and have a common dimension of 24” x 36”. Using CRSI
Handbook 2002, the maximum capacity for this column is 11079”k of
moment and a vertical load of 3043 kips. Due to the nature of the moment
frame design, I believe moments acting on each column will have a major
impact on the final design and sizing of the column. Checks on lateral
system are not yet complete
Miscellaneous Loading and Conditions
Through inspection and the building having cast-in-place concrete roof
slab, uplift due to wind does not need to be checked on the slab due to the
weight of the slab. Extra load due to the precast façade needs to be
checked on exterior members. The slabs of the below grade parking area
aid in retaining the lateral earth pressure applied to the basement walls.
Also loading due to mechanical units will need checked.
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Arlington Gateway Hotel - Technical Assignment 1 - 9 -
Appendix Title Pages
A. Member Check - Slab 10-11
B. Snow Load Calc. 12
C. Seismic Design 13-14
D. Wind Design 15-17
E. Wind Loading Diagram 18
Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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Michael Gray Structural Option Faculty Consultant – Dr. Linda Hanagan Arlington Gateway Hotel Arlington, VA
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