theodore by niusheng11

VIEWS: 29 PAGES: 12

									The Pearl River Tower
On September 8, 2006 ground broke on the Pearl
River Tower project in Guangzhou, China. The
Pearl River Tower will be part of the Zhujiang
New Town development on the banks of the Pearl
River in Guangzhou. This new development is
quickly becoming the cities new center for
business and commerce. Upon completion in 2010,
The Pearl River Tower will be 309.6 m tall with 71
stories. The entire project will have a total of 2.3
million square feet of floor space. Ironically, the
owner of this new skyscraper is the Chinese
National tobacco company which will occupy most
of the building’s office space upon completion.
The engineering work for this The Pearl River
Tower was contracted out to Skidmore, Owings &
Merril (SOM) with Gordon Gills as head architect
and Roger Frechette as lead engineer on the
project. The contruction is being directed by the
Rowan Williams Davies & Irwin company.
         The Pearl River Tower is a modern
skyscraper with some of the most cutting edge
“green” technology. In fact the most interesting
aspect of the Pearl River Tower is that it was
initially designed to be a net-zero energy building.
The building was originally designed to be able to generate its own power and sell the excess
                                                    power back to the local grid. However, due to
                                                    some reservations on the behalf of the owners
                                                    and the sub-par local power grid, SOM was
                                                    forced to modify the design. As it stands, the
                                                    Pearl River Tower is still incredibly “green” and
                                                    is able to produce around 60 percent of its own
                                                    power.
                                                             In order to accomplish the goal of
                                                    designing a “high performance” skyscraper with
                                                    “significantly less power consumption” as were
                                                    the owner’s requirements, SOM used four
                                                    concepts; reduction, absorption, generation and
                                                    reclamation. With the goal to generate 60
                                                    percent of the buildings power demand, SOM
                                                    needed to first significantly reduce the power
                                                    demand.
Reduction Strategy:

        Using double walls with mechanized blinds, they were able to have a well insulated
interior and trap some of the heat in the double walls to be used in their de-humidification
system. Since Guangzhou is a very humid city in the southern Guangdong province, this system
of de-humidification was very necessary. A “chilled radiant” ceiling was used in place of normal
ventilation and air conditioning. This system pumps cold water through copper pipes in the
ceiling which cool plates in the ceiling and consequently, the surrounding air. This chilled air
cools the office space below and above. Also, the building’s façade is made of triple glazed
glass which helps insulate the building’s interior.




Absorption Strategy:

         Some of the most advanced wind and solar
technologies were incorporated into the design of this
skyscraper in order to generate or “absorb” the natural energy
from the building’s surroundings. Photovoltaic cells were
incorporated into the mechanized shade system to capture the
sun’s energy. These solar panels were placed all over on the
building’s façade and were designed to be built into the
design. The blue areas of the picture show the location of the
solar panels. Apparantley it is much cheaper to incorporate
the solar panels into the façade than to add them to the façade
after it has been completed. The automated blinds system is
also very beneficial because the blinds are programmed to
make the most of the natural lighting.
                                 Probably the most innovative aspect of the building’s design
                                 was the use of vertical-axis wind turbines to generate electricity.
                                 As can be seen from the exterior of the building, there are four
                                 large holes, 6 by 6.8 meters wide, on either side of the core at
                                 the mechanical levels. The room for these holes was made
                                 available due to the lack of ventilation shafts and fans in this
                                 building. These holes run through the building and are funnel
                                 shaped to increase the air speed as it rushes through the
                                 building. Unlike most skyscrapers, the Pearl River Tower is
                                 positioned so that the broadest side of the building faces directly
                                 into prevailing winds. This is to the advantage of the wind
                                 turbines though it does greatly increase the building’s wind
                                 load. However, the four holes do serve to reduce the wind load
                                 somewhat. The funnel shaped openings at either end of the
                                 holes, along with the large pressure differential created as the
                                 wind flys around the side of the skyscraper dramatically
                                 increase the wind speeds as they rush through the building.




 For example, it was estimated using wind tunnels and a small scale version of the building, that
a 2 m/s wind velocity could be increased to 8 m/s. This is incredibly important because any gain
in wind velocity gives the building huge gains in power generation. The simplified equation for
power generation is:

Power = Velocity^3

From this equation it is obvious to see that these wind turbines will be able to produce electricity
at an accelerated rate thanks to these augmented wind speeds.
Power Generation:

        In order to achieve it’s goal of becoming a net-zero
building, the Pearl River Tower needed to use a system of linked
microturbines. These small, highly efficient turbines would run
off of anything from biodiesel to natural gas. With these
microturbines in place the excess electricity being generated
would have been sold back to the grid making the Pearl River
Tower a mini power plant. However, as mentioned before
Guangzhou authorities did not warm up to the idea. Their
reluctance coupled with the faulty electrical grid led to these
microturbines being put on hold. There is however room for
these microturbines in the final design should the local grid be
upgraded and everything approved. If these microturbines were
added, the Pearl River Tower would become the net-zero tower
it was designed to be.

Reclamation:

        Much of the energy being used in modern skyscraper’s is wasted or not used as
efficiently as possible. The Pearl River Tower was designed to reuse energy through certain
methods such as recirculating cooled air and reclaiming the heat captured between the double
walls to be used in other areas of the building.

Structural System:

        The Structural system for the Pearl River Tower is similar to many modern skyscrapers.
The design takes advantage of a system of outriggers and megacolumns connected to a large
central core. There are also a series of mega braces on the narrow sides of the building. There
are four composite mega columns made of built up I shapes encased in concrete. These columns
are approximately 3 meters by 2.7 meters at the base and 2.5 meters by 2.5 meters at the top.
There are 13 steel perimeter columns that are approximately 0.6 meters by 0.6 meters. The
outriggers and belt trusses are two stories deep and are found at the mechanical levels of the
building. There are a number of stories below grade which serve as a foundation for the building
as well as a 3.5 meter thick concrete matte below the core. Also, the foundation consists of 4
meter thick spread footings below the main columns which extend 28 meters below ground and
bear on rock.
Minpu Bridge
The Minpu Bridge which is under construction in
Shanghai, China will be one of the longest cable
stayed bridges in the world and will be the longest
double decker cable stayed bridge in the world.
The bridge is being designed and built by the
Shanghai Municipal Engineering Design General
Institute, SMEDI. The bridge is currently under
construction and will be completed by the 2010
World Expo which is going to be held in Shanghai.
        The bridge is a massive structure that spans
the Huangpu river. The upper and lower decks will
both be used for automobile traffic. No pedestrian
walkways can be found on this bridge. The upper
deck will have 8 lanes of traffic while the lower
deck will have 6 lanes. The bridge is made up of
two pylons each over 200 feet tall with 44 stay
cables running along the front and back of each
tower. Altogether there are 176 stay cables.
Each of these cables is anchored into the deck and
top of the tower and then tightened at the top of the
tower to the correct tension.
        The two pylons are made of reinforced
concrete while the sections of the deck between the
two pylons is made of structural steel. The sections
of the deck behind both pylons is made structural
steel members filled with concrete. This is done in
order to give these sections weight and counter the
compressive force of the larger steel deck sections
of the main span. Since the right and left sides of
each tower are unsymettrical it was necessary to
make the deck on the pier side heavier to balance
the other side.
Construction Sequence:

The construction sequence of the Minpu bridge was similar to that of most cable stayed bridges.
The deck on the pier side of the bridge was built first using standard construction methods. One
interesting thing to note was that the deck was so heavy that temporary columns had to be built
in order for it to be able to hold its own weight until the cables were attatched. The smaller
columns in the picture are
entirely temporary and will be
removed before the bridge is
opened to the public.

        The construction of the
main span was accomplished by
floating sections of the deck on
barges to the appropriate
location beneath the bridge. The
sections of deck were then raised
into place using a winch set up
on the main bridge deck. This
process is very common for cable stayed bridge construction and can be seen in the picture
below. It takes the workers hours to raise a section of the deck into place. Also, the workers are
able add a new section of the deck every 7 days.
Honk Kong Convention and Exhibition Center




The Hong Kong Convention and Exhibition Center was opened in 1988 and since that time has
helped make Hong Kong the Asian trade fair capital. The exhibition center has used heavily
since it opened which led to the it’s expansion in 1997. The expansion of the exhibition center
cost $620 million USD and more than doubled the floor space. The center now has almost 2.4
million square feet of floor space. The break down of the floor space is as follows:

Six (6) Exhibition Halls - 573,630 sq ft
Two (2) Convention Halls - 61,344 sq ft
Three (3) Foyers - 46,188 sq ft
Two (2) Theatres - Seating for 1,000 - 8,611 sq ft
Fifty-two (52) Meeting Rooms - 64,627 sq ft
Loading/Marshalling Areas - 129,167 sq ft
Four (4) Restaurants Total seating for 930
Two (2) Underground Car Parks Over 1, 000
In 2007 alone, over 1000 events were held at the Hong Kong Convention and Exhibition center.
Forty five of these events were world trade fairs. The convention center boasts a very large
grand foyer with a hanging glass curtain that was the largest at the time it was built.
Results from Analyses:


MinPu Bridge Results

      The 22 stay cables on each side of the towers range in diameter from 11.9 cm to 7.5 cm.

      The deck compressive force(F) ranges from 14945 kN to 1459 kN.

      The deck area ranges from 0.52 m2 to 0.69 m2.

      Out of plane buckling will not occur, there is a safety factor of 22.

                          2 (200GPa)4(0.693m 2 )(20.25m) 2
                                                               22
                                  (708m) 2 203.1MN

   (See calculations in appendix for more information on uniform load, bending moment etc)


Pearl River Tower Results

In order to analyze the Pearl River Tower I needed to make a few assumptions since I had no
floor plan or any information other than the size of the core and columns. I assumed the
following using my engineering judgment, some architectural renderings and a scale:

   •   Width of tower at base: 30 m
   •   Length of tower at base: 65.5m
   •   Width of core: 13 m
   •   Length of core: 35 m
   •   Width of tower at mechanical levels: 20 m
   •   The width of the tower at the top two floors tapered off to 24 m and 20.5 m.
   •   The cross sectional area of a rectangle with the same length and width was used for each
       floor area to simplify the calculations.
   •   The vertical area was calculated at the top and bottom and varies linearly in between.
   •   The four holes in the building’s exterior were not part of the analysis
   •   The location of the core was assumed by looking at pictures of construction
   •   The centroid of the buildings cross section was assumed to be slightly to the right of the
       center of the core. In the picture below it is depicted by the black dot.
   •   Allowable wind drift: h/400
   •   Allowable seismic drift: h/200

SAFETY FACTORS
  •   Wind displace  1.838 at level 49
  •   Seismic displacement  2.54 at level 52
  •   Wind stress  4.32 at level 1
  •   Seismic stress  3.94 at level 1
  •   Buckling  2.04 at level 1

CALCULATED WIND DISPLACEMENTS

  •   Flexure w/o columns  1.24ft
  •   Flexure with columns  0.784ft
  •   Shear  0.331ft

								
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