Yeah, I'd like to go ahead and start our
evening's lecture. My name is Finley Charney. I'm
a professor of the Department of Civil Environmental Engineering
and my specialty in structural engineering. And it's my
pleasure to have hosted these CELES lectures over
the past 10 years ago. CELES stands for the
Center for Extreme Load Effects on Structures. Principally we
look at wind and seismic loads, more seismic in the
past. Recently. I think we're getting back into the
wind area for a variety of reasons. I apologize
at this slide like that. We transferred the slide
of the black text, which used to be like
, you can't read it very well, but this
is just a list of some of the sponsors,
some people who have actually contributed two oh center over
the past several years and who helped fund this lecture
. We've been also very fortunate over the years to
have and including today some of the most distinguished structural
engineers. It's not just in the United States in
the world, lectures present lectures to us here in
this lecture suit and some of these names should be
very recognizable to you. Very riffles. Irwin john
Rose, thank you baker, David. Goodyear.
Asan Corinne has given us fascinating lectures over the years
, mostly about building. Somehow, this has been
a tall, building oriented presentation in the past.
We did go horizontal with David a few years ago
we talked about hoover dam five past. And so
this year we're going to actually go vertical again and
robert sent with thornton thomas city in Chicago Is going
to tell us about this new one km tall kingdom
tower. So if you take Bill baker's burst cloth
e, the empire statement went on top of it
. Then you have this building kilometer tall. It's
pretty amazing. Um, this, let me give
you a little introduction uh, about robert. After
our chatting this afternoon, robert and I realized we've
known each other for about 15 years back when we're
both more active than sc, which has a committee
on paul buildings. We're both a member of that
committee at the same time. Uh Mr Sent is
currently a principal in the Chicago office of thomas city
and as the firm white director of structural engineering for
new buildings, They have 30 years of combined experience
starting out skin borrowings, Amero and for the last
seven years of Thomas A and has been involved in
the structural design. Obviously a very important buildings.
Guggenheim Museum in Spain trump International Hotel and Tower on
Chicago and the people in power will be talking about
here. He is a fellow of the American Society
of Civil Engineers and the International Association of Bridge Construction
. Okay, uh, he received as M.
S. From Northwestern University, mm. MSC E
. At Technology 1934. So with that I'd like
to welcome robert for I'm sure will be a very
interesting presentation. We also have. Okay. Mhm
. Okay. He's like me all metal he gets
credit for. Well, thank you. It's an
honor to be invited to come here today from Chicago
, beautiful weather outside. And I'd like to give
you a few details of a very important project for
our firm that we've been working on for actually over
five years now. A few sort of technical information
in terms of the team thorn thomas said er the
structural engineers for the project. The architect is Adrian
smith and Gordon Gill a couple of Old colleagues of
mine from Skidmore owings and Merrill. They left the
firm in 2006, I left the firm in 2007
. Um The contractor for the project is the Saudi
bin laden group. The we won the competition all
the way back in June of 2009 and we,
after a few stops and starts, we finished the
design drawings just recently about a little over a year
ago in August 2013. Um All the design for
the tower is two american codes and the concrete reinforced
concrete design is to a ci 3 18. Uh
This is the Rogue's gallery of most of the tall
buildings. Most of these have actually been completed at
this time, but this was the council's idea of
what the tall buildings would look like in 2020 which
is not that far away, it's only six years
down the road, They call anything over 600 m
super tall. Uh and of course, the Kingdom
Tower would be the tallest of all uh peeking just
above. Uh one kilometer will be the first man
made structure to reach one kilometer in height. So
it's sort of the uh Alan bannister for those of
you know the four minute mile. It's sort of
the Alan bannister of tall buildings. But the tower
is part of an overall master plan in the city
of Jeddah in Saudi Arabia. So the idea is
you build the tower and then you can have a
lot of other buildings around it, residential buildings,
even office towers. And it becomes part of a
really an entire city in a lot of ways.
Um Just some news, the picture you see there
on the left is Prince uh Al walid. And
if you follow the news, the prince is very
famous actually. He's uh he's the fellow they call
the Saudi Warren Buffett. He's the one that does
buys all the stock in city core and other U
. S. Properties, US companies. And he's
his company is called Kingdom Holdings. He has two
or three partners that are also contributing the funding for
the project. This is a picture on site as
piling was going on and if you look closely in
the foreground you'll notice that this is actually one of
our drawings here. This is a foundation plan from
from thornton thomas et the picture on the right for
those of you uh know your geometry. The project
is in Jeddah in the kingdom of Saudi Arabia.
It's right on the Red Sea. Um The site
itself is just north of the air. This is
the airport. So this is this is the Hajj
terminal. This is where the people come from their
pilgrimage. They go through the Hajj terminal in Jeddah
as a sort of gateway to the holy cities of
Mecca and Medina. And the site for the,
for the tower is just north of the creek,
north of the airport. And right now it's barren
land. I'll show you a few pictures of that
. Um, The tower is a mixed use but
primarily residential. At the base of the tower.
There will be a little bit of office space,
very little actually only 10 floors. Uh and then
there's a four seasons hotel just above that. And
then the rest of it is all residential. It's
basically condominiums from there on Up to about 670 or
80 m. It's habit id and the rest of
it is actually avoid, I'll get to that in
a minute. It's, the tower will be not
only uh the tallest building in the world, but
also the most, one of the most slender.
And we measure for these tall buildings, the slender
nous as the height divided by the least dimension at
the base. and for this building, that number
is about 12-1. Just to give you a little
bit of perspective on that. The Sears Tower and
the Hancock building in Chicago, where I'm from.
The aspect ratio on those buildings is about six or
7-1 maybe, maybe Sears tower is almost eight.
So you can see that buildings nowadays are getting taller
, but they're also getting more slender than they were
30 or 40 years ago. The tower has two
systems that are linked their, their distinctly different systems
, but they're fundamentally link. There's not a discontinuity
in the systems For the bottom 2/3 of the building
, essentially a bearing wall building. And I'll get
to exactly what that means in a minute. But
and above that is the silo, which is basically
a closed concrete tube without any windows whatsoever in it
. This is what this system looks like in concept
. It's um basically all walls. I tell my
colleagues when they ask about the system, they said
, you know, how big are the columns and
I say we don't have any columns, it's all
walls, there's no uh inside and outside, there's
no perimeter columns and inside core, like most tall
buildings, everything is connected together through coupling beams,
all pieces of wall contribute in the system to resisting
the gravity loads and the lateral loads. There's no
outriggers, lot of the tall buildings and super tall
buildings. In fact, almost all of them,
including Burj Khalifa in Dubai have outriggers that extend from
walls to other columns. There are no outriggers in
Kingdom Tower, there are no column transfers. There
are no wall transfers, walls simply go up and
when they're no longer needed due to the tapering of
the tower, they drop off. The system in
concept is very simple. It's it's a building was
made to be built. There was no uh everything
we did in the planning, architectural and structurally was
to make it simple to build. Now you've seen
the tapering of the tower. What uh just to
be clear about the geometry? There's it's a 33
winged tower. Three wings to it. Each of
the wings tapers. Those three tapers for the three
individual wings are slightly different but but for a single
wing it's a single taper basically one angle from the
top of the foundation all the way to the top
of the building. But because of the three wings
taper at slightly different angles, they reached the top
at different elevations. And that gives you the sort
of the characteristic architectural top of the building. So
it's very simple, very, very easy to build
, simple geometry from that standpoint. That's what the
floor plan looks like. Ah there's no spaniel beams
, All flat plate construction, 250, about a
10 in reinforced concrete flat plate, conventionally reinforced all
walls and coupling beams. The the spacing between the
we call them the thin walls. This this spacing
in between here, that's about nine m and that's
important for the planning. So this is what the
architects, what they ended up with. Again,
this is primarily a residential building. This system would
not work nearly as well for an office use because
what happens, it tends to compartmentalize the floor plate
with these, these transverse walls. But this is
what happens. You basically take your elevator in the
center of the tower. These are all the elevators
. And because it's residential, there's far fewer elevators
that there would be in an office tower. You
come out, you come down the corridor and that
corridor has structural walls on either side of it and
then you call me and then you turn left or
right through a doorway into your into your unit,
All of the fire stairs. And there are three
at the end of each wing are completely encircled by
concrete walls. So that's the fundamentals of how the
by the building is planned structurally and architecturally. This
is what a unit looks like. And you can
see that yes, the thin walls are in some
of the units, but the layout's worked very well
, the corner is open and uh you can see
how the kitchens and the bathrooms layout amongst all the
structure. It's actually works quite well for residential type
of use. Now I mentioned that there's really two
systems that are linked. You have the system of
walls and coupling beams that go up wherever the floors
are inhabited by tenants in the building. And then
they come up to about the 2/3 and then the
rest of the building is a concrete silo, it's
really open void, it's truly, there's very there's
no windows in it all the way to the top
of the building. And those two systems Are actually
linked and they're linked at a four metre thick sky
raft. And that's that's this element here. So
what happens is that the walls of the floors that
the last walls that are tilting, they become closer
and closer and closer to the central triangular core and
then finally they almost touch and there's a transition to
the top uh aspire, what we call, that's
made of just reinforced concrete walls above. So there's
no dis continuity this wall that you see here.
That's the spire. That's a, that's a single
plane, a tilted plane that goes all the way
to the top of the foundation without any kinks or
interruptions whatsoever. For those of you who like your
history of tall buildings and history of structural engineering,
certainly, this tower came on the heels of the
Burj Khalifa and Dubai, we won the competition.
The organizer of the competition wanted to use the Berge
as a way of reducing risk. So a system
that would be similar to the Berge, but maybe
improve upon it a little bit and change a few
things that didn't work quite as well on that tower
when we did this one. But if you look
at this is a picture of three buildings cut at
basically foundation level. So this is at the bottom
of the building, what they look like Kingdom Tower
Burj Khalifa, you see the similarities between our tower
and the bird. You have a central, this
is a hex core. This we have a triangle
, you have the corridor walls, you have the
thin walls. These are columns that we don't have
, we replaced those with the, with the end
walls in the stairs. But I think this,
that there's there's some fundamental differences. This this building
did have outriggers, uh it did have a steel
part of the upper level, whereas we have concrete
and I think if you really wanted to go back
to the bearing wall system for very tall buildings,
you would look at the CN tower in Toronto,
that's this one, that's not a building, it's
an observation tower, but look how similar they are
. Now, this is obviously CN tower isn't one
kilometer tall, but it's got a central, it's
got very thick walls including a very to meter thick
wall at the extremity of the floor plate, just
like Kingdom Tower. It's got basically compartments that are
created by these cross walls. Very, very similar
system. There's no transfers in this building either.
Basically the walls just tilt at a constant angle from
top to bottom. Very, very similar system.
This was done in the early 1970s. So the
system has been around a long time. The Burj
Khalifa was a very excellent structure but it wasn't necessarily
new. Okay, so there's a hierarchy in the
walls, the most important of all are the ones
that are furthest from the neutral axis from the center
of the building. And those are the end walls
. These are the these are the only walls that
slope. Everything else is vertical. Okay, at
the base of the tower, those are 1.2 m
thick. So about I guess about 4, 4.5
or five ft thick. No more than that at
the at the base of the tower and they continue
up And they reach about 500. By the time
you get up into the spire, the second most
important walls are the ones along the corridor. Those
are about a meter thick at the base. Those
are attached to the, to the end walls through
the stair towers. Um Sorry, just going back
a minute. Those are the ones that have more
coupling beams. The end walls have no coupling beams
. This is a solid wall, no coupling beams
. The corridor walls are the ones that are uh
you know, punctured with coupling beams at every floor
so people can get into their units. Those coupling
beams are 1.5 m deep in general. The third
is the fin walls. I would call those more
stabilizers. They're stabilizing the corridor and end wall systems
laterally. They are, They reach 8 50 thick
at the base of the tower. They also have
coupling beams so that people can go in between the
compartment als and then finally, is the triangular core
. The triangular core is very critical for the two
orginal stiffness of the building. A lot of the
torso resistance is being generated through the triangular core.
It's a closed shape, it has very few openings
in it. It houses as I mentioned before,
all, all of the elevators for the tower.
Now, one of the things that was very important
in the planning that caused almost World War Three with
the architects was the the the alignment of the walls
through the corridors. We had to really impose some
pretty draconian measures with the architects. They had to
line up and the reason they had to line up
is because the the flow through here is very dependent
on the pattern, not just the gravity load flow
, which is important enough, but also the wind
loads. If you start moving these doors around,
you're gonna be cutting off the flow. So what
we did is working with the architects, we actually
plotted the entire elevation of the building on paper And
it was about 20 ft long and we put it
put it in the office there in Chicago. We
we taped it all together and and told the architects
to come over and we we would stand next to
it and say you can't have that when you can't
have that one. And and by doing that I
think they kind of got the idea of what we
were trying to achieve. Yes, there's a few
few outliers, you know, this is a this
is a special fire exit for that particular floor,
but generally speaking, we were able to line them
up very, very carefully and very, not just
structurally important, but also from a construction standpoint,
the more you start moving things around, the formwork
system has to be adjusted for those as well.
So once again, the design was to be built
in terms of materials. Um the concrete strength is
not as high as you might think. It's about
85 mega pascal uh cylinder strength, which is about
12,500 which is at least in the United States,
is its high strength concrete, no doubt about it
, but we certainly know of higher strengths uh you
know, that have been used, this was set
not so much that they couldn't produce higher strength concrete
. The tower would have benefited greatly from higher strength
concrete. I think if I had my choice,
the strength would have been 15 or 16 K.
C. Concrete. And the reason I say that
is at the bottom of the tower, there's a
lot of reinforcement to make up for the lack of
concrete strength. So if we had higher strength concrete
we could have reduced the rebar which would have helped
the construction quite a bit. But the reason It's
only 12,500 is they could do higher but not in
the volumes that we need. And there's a lot
of concrete in this building and they, from a
quality standpoint and the quantity that's about as high as
they thought they could get rebar, were using some
75 Ks. I bar at the at the bottom
of the tower which is readily available in the Middle
East. But the vast majority of it is just
normal 60 Ks I reinforcement. This is a mixed
design. Just give you an idea for the 85
MPA concrete. It's being adjusted a little bit.
They don't have slag in the kingdom but they do
have fly ash. So fa is fly ash,
It's got a fairly high content of micro silica silica
fume and ordinary Portland cement. And you can see
the other characteristics. I would say that this mix
design because it has the polycom box lit uh It's
essentially near self consolidating concrete and that's because there's a
lot of rebar congestion near the bottom. It's also
because it has to be pumped. So they're using
basically 10 3/8 aggregate because it has to be pumped
. The one thing about the concrete, these high
strength concrete that a lot of people don't realize is
they're, they're denser. Most of your calculations,
I'm sure using 100 and£45 per cubic foot for
your concrete density. This one is 1 49 not
including any rebar. So most of our calculations were
using 150 to£253 per cubic foot for the self
weight of the concrete elements. In terms of foundations
and geo technics. The uh, it's, it's
basically uh very competent rock, but not what I
would call bedrock. There's no layer that you want
to take a foundation down and sit it on bedrock
. It's basically starting with Coraline limestone. It's basically
the coral from the Red Sea that's been disintegrated over
the years and with basically cemented together with the moisture
in the ground. And then there's a couple of
very annoying layers of silt, stone and gravel,
which caused problem with piling and then actually weaker ground
below that than up above the strongest Materials are actually
near the surface, the top 50 m, but
basically types of limestone and sandstone is what you have
there for for this particular site. Now the foundation
system is, It's a matrix of bored piles,
basically the piles, there's 270 piles, they're all
in, they've all been constructed, they go to
various depths, the ones in the center of the
tower Go to a depth of 100 105 m,
so about 350 ft deep, The shorter ones go
to 45 m. The diameter is about 1.5 m
, a few 1.8 m diameter piles. So this
is a very common type of foundation in the Middle
East, which is basically an augured pile. It's
a friction pile, there's very little end bearing,
it's usually constructed under bentonite or polymer slurry, but
it's done over and over and over again in the
Middle East on top of the piles is up uh
five metre thick raft foundation, tying them all together
. So that rap is also completed. Now,
the one thing you'll probably say is I get it
, you know, that the towers tolerant in the
center of the building, so therefore the in the
center of the building uh wrong. Uh Here's what
happened. There's um there's a good deal of soil
structure interaction going between the tower and the foundations.
And the best way to think of it is is
if if the foundation itself without the stiffening effect of
the walls of the tower, if it's not stiff
enough because it's a continuous bearing wall. Though bearing
walls themselves will try to limit the differential settlement so
they'll actually be stressed. The superstructure will be stressed
, not the piles And what we found if you
look on the left, if we use all short
piles, 45 m piles were getting. This is
just with the loads. This isn't with the tower
on top of the model. This is just with
the loads from the tower, 170 of settlement with
a differential between the middle and the outside of 85
mm. With the same loads from the tower again
, just putting the loads on a foundation settlement analysis
, if we do the longer piles in the center
And the shorter piles on the wing, the total
is reduced 115 mm in. The differential is 25
mm. So what you're seeing there is you're seeing
a system, a foundation system with the longer piles
that's set up for the tower to be resting on
it properly. And that's that, that took a
fair amount of work to get to that point.
And the thing that we did is we looked at
the base of the tower in these two situations.
The situation on the left, what happens is you
get very high stresses in the bottom few stories of
the tower, if you have only short piles,
because the tower itself is trying to there can't really
be differential settlement when you have walls are kilometer tall
, it's impossible. So what what happens is the
tower tries to restrain that differential settlement itself and actually
get stressed on the right side is where we have
the piles that we ended up with. Those stresses
were reduced dramatically In that case. So I'll let
you ponder that a little bit. It's not not
obvious, but it's one of the interesting things in
designing these tall towers, you get into things that
for a 40 or 50 story building, it would
be almost irrelevant. You'll never get into something like
this we're expecting uh at the end of construction,
about what about four inches of settlement for the tower
. The interesting thing is the tower has several buildings
around it. I showed you the master plan,
but there's podiums that house all the parking and and
some of the amenities for the hotel like that,
there's a, a conference center and so forth.
What happens is we told them they could they shouldn't
build the buildings around the tower, because what will
happen is the tower as it gets built, it
will draw down the buildings around it. There's a
zone of influence for the tower as it gets built
, it will the dish everything around it. Obviously
the further you get away from the tower the less
that influences. But the longer you can wait the
less problems you'll have with this sort of dishing and
the influence of the tower drawing down the buildings around
it. In terms of seismicity, I would characterize
it as moderate to low if there's a fault in
the middle of the Red Sea. Um But the
the Arabian peninsula is basically stable. There's very very
little activity within the peninsula itself. It's you can
see obviously in Iran there's a lot of activity but
they're basically the Arabian plate is moving slowly but surely
towards Iran. Are kept telling that to our client
Saudi client. I said you know the Arabian peninsula
is moving toward Iran and he'd always smile and say
very funny mr since if you know if you know
mhm mm. But you can see some of the
activity obviously in Iran, there's a lot of activity
, there's a little there's uh influence at the Sinai
, there was some activity for far field effects and
so forth. But by and large the tower is
controlled by wind. I think you probably guess that
already. And what we do at the beginning of
the project is we always try to mark where are
we at in terms of the basic wind speed,
that's the best way of figuring out what kind of
effect you're going to have for wind. So we
look at what we're used to were used to Chicago
, were used to new york were now we're even
used to Dubai, here's Jeddah. The code wind
is 42.2 m/s, that's a three second gust.
Basic wind speed. The climate, the actual climate
that's brought from the wind tunnel is quite a bit
lower, but this is what we have to design
for for strength. But compared to places like Miami
and Hong kong where you get into hurricanes were nothing
like that. So it's a fairly moderate wind climate
. So between foundation conditions, those are critical.
If you're going to do a tall building low to
moderate seismicity, reasonable wind speeds, all in all
high strength concrete availability. Not a bad place for
a tall building actually. You know, sometimes one
of those four things is one you can't overcome actually
to build something quite this tall In terms of the
dynamics of the building, the first period, first
fundamental period is about 12 seconds. We think for
such a tall building and such a massive building that's
really quite stiff. When you think about the old
world trade centers, the twin towers had fundamental periods
approaching 10 seconds. So this is much taller.
The third mode is tours in a 5.8 seconds and
we think that's actually reasonable and quite low period for
a building of this height as well. Very pure
modes. You can see there now as you can
imagine, there's been all kinds of wind tunnel testing
. I think we've done no fewer than eight tests
. We started as soon as we won the competition
, we started with the most basic test of all
, which is a very 1 to 8 hundreds of
small model, fixed based model. All everything is
measured at the base. The so called high frequency
force balance test. We just wanted to get some
results so that we start to get an idea of
how we're doing in terms of design forces and the
performance. We moved into pressure integration models. These
models have pressure taps over the entire surface. So
they're measuring even though the bases rigid, they're actually
measuring not at the base but all over the surface
. So they take all these instantaneous pressures are able
to integrate those to give us the design forces and
responses. So that's the so called high frequency pressure
integration model we went into because The spire was so
slender, they couldn't get enough taps in the tower
in the top of the spire. So we actually
did a model at 1-400 scale, just the top
half of the building. And so they were able
to at a larger scale and they were able to
get enough taps in there and then analytically they can
stitch that together with the results from the larger scale
model. So that was a refinement. And then
finally, the most sophisticated models that were able to
do uh these days are the air elastic models and
the air elastic models are again measured at the base
. But it's the only type of model that isn't
rigid. All other models are rigid. This one
actually has the feedback effects of the tower moving in
the wind in the wind tunnel and you don't want
to do those. Those are very expensive models.
You want to wait on those until everything is settled
with the architects and even the structural engineering. On
top of that, I'll get into the upper level
wind climate event. But we also did an independent
wind tunnel tests in a second wind tunnel. Most
most of the testing was done at R. W
. D. Laboratories at Wealth in Ontario Canada.
We did a separate companion model in the University of
Western Ontario at the boundary layer wind tunnel laboratory there
we gave them the same geometry as we gave our
W. D. I. We gave them the
same structural properties and we told the boundary layer,
don't talk to our W. D. I.
Just give us your results and we compared the two
and after I would say a little bit of discussion
, uh quite a bit of discussion actually, the
results were pretty close and people say well how can
it be different? Wind tunnel testing is wind tunnel
testing? The models are very similar. There's no
difference in the models, There's really, in my
opinion, very little difference in the wind tunnels themselves
. What is different is how they treat the climate
, The basic climate model that they use to get
the results from the testing itself. Now, one
thing that came up in the in the wind engineering
is that The wind speeds above 600 m, you're
basically getting away from the atmospheric boundary layer, which
is the influence of the earth on the wind speeds
. So there was some uncertainty about the wind speeds
above that height. And this came up on the
Burj khalifa as well. It obviously doesn't come up
very often, but there was some idea of what
happens to the normal power law is basically the wind
speeds just continue to go up basically. Just goes
up as symptomatically or, you know, power law
, basically. Um, But the question is what
really does happen above 600 m. So they did
use several techniques that are new, balloon launches were
used from the airport that the most airports actually do
have balloon launches. They can get some data from
very high altitudes on wind speeds, but they did
something very different. They actually looked at the much
more detailed analysis of the wind speeds that were measured
at the airport. I'm talking about surface wind speeds
. They actually modeled the airport to see the shielding
of those and tried to correct for that. But
the one thing they did that was probably the most
important is they did something called a weather resource forecasting
model. So basically all of the, the weather
in the world is in this database that they can
use going backwards. They can actually predict what's going
forward and what they came with all these techniques and
they're all, they all have their merits and demerits
. I suppose this is the weather forecasting model is
we think that the wind speeds that we're using and
the profiles that were using the basic power law that
you see in all the textbooks on wind speeds with
height, probably our our conservative we certainly didn't design
to uh, you know, a profile that looks
almost vertical here where there's almost no increase of wind
speed. We used we used the normal but this
whole effort of verifying the wind speeds at high elevations
was to make sure that we were being conservative with
what we're doing with our engineering. That was a
very important part of the project. We determined from
the uh, we call it the upper level wind
climate assessment. It's a long term of saying the
wind speeds at height That the 42.2 m/s, which
is specified in the Saudi building code at 50 years
three second gust really from the climate data is equivalent
to about 870 year return period. So we think
it's very conservative and the Saudis are very conservative.
So they made us designed for it anyway. And
we did. But uh, you know, that's
something that makes you at least have something in your
backpack and feel a little bit better about your design
. In terms of software that we use, we
use practically every program you've probably heard of. We
do use obviously e tabs and SAP quite a bit
. That's the sort of the bare, bare bones
of what we do. We use a program called
Midas gen. I'll give you some details on that
. We use Strand and we use advocates for some
of the buckling studies that we did, sort of
global global studies on the tower itself. The other
thing that we do that I like to do is
as we move from the various design phases of the
project, from schematic design, for example, early
on to design development into final design. We tend
to uh take a start a new model. So
we will not only start a new model, we
will start in a new program in in a new
engineer. This is a quality control maneuver because um
if you don't, if you just have one model
, what are you checking against? You're not checking
against anything. So by having several models being done
by different engineers, you can check the results to
see if there's consistency, uh and different programs as
well. So we do do that quite a bit
for these major projects. I think it's very important
. We had a we had a model during the
competition and as soon as we started the actual schematic
design, we started a whole new model from scratch
even though nothing really changed from the competition. And
yes, it's time consuming. But honestly, these
models don't take that long to build. I would
say that building this model in Need tabs is a
matter of maybe 2, 34 weeks, it's not
234 months and most of the effort is getting the
uh, gravity loads in. The geometry is very
simple. We usually take autocad or another three dimensional
program and import it into the program first. So
they don't take that long to build these days.
This is a share and overturning moment cumulative plot,
basically saying that the wind loads govern over seismic.
That's what you should basically glean from this by by
a wide margin. Obviously, I would say that
the tipping point is much lower. Buildings in this
, in this kind of seismic zone, probably 400
m and below. Might be controlled by seismic.
But anything of this height, there's no question will
be governed by wind. This is a drift pot
. You can see it's non linear. The spire
at the top does get quite non linear, but
you know, but the building is quite stiff in
terms of the motions, I'll get to that here
. So this is what we do for the for
the motions. This is the perception of the motion
of the building by the occupants. And what we
use is the I. S. O 10137 is
the standard criteria we use nowadays. And this this
we usually use a one year criteria. So you're
looking at a storm that on average is going to
be on a yearly event. And the so would
tell you that for the top occupied floor, which
is at 654 m in the air, well over
2000 ft. Um The criteria would be about 12
million, Jeez is what is acceptable for the motion
on a one year storm based on the fundamental period
of our building and the esso criteria and the predictions
from the wind tunnel testing uh Pegged the motion at
about five or six million, jeez so this is
going to be, in my opinion, a very
comfortable building for the occupants. And why is that
? Why? Why is it so well behaved in
terms of the motion? Most important is that it's
tapered. So the aerodynamics are really quite good.
The vortexes, the vortex shedding phenomenon that you see
, particularly for prismatic buildings that don't change and profile
along the height, this one changes constantly. So
the tapering is very helpful. The other thing that's
extremely helpful is it's very massive, very, very
heavy building and the masses, basically the accelerations uh
go with the inverse of the generalized mass of the
building. So the heavier ever it is, it's
almost a linear distribution. It's also fairly heavy at
the top of the building. Now, I showed
you the deflection plot that gets quite non linear up
in the spire. The building for the occupants itself
requires no damper whatsoever. It's going to be very
very comfortable. But the motions in the spire starting
to concern me a bit. There will be people
in the spire, there will be maintenance workers.
Uh They have to go up and change light bulbs
every once in a while. So there'll be a
small lift that goes up into the spire and the
motions up there, we're going to be quite quite
high. So we are putting a damper for the
spire alone. It's being designed right now by our
W. D. I. So that's the plan
to reduce the motions up in the spire by about
30 or 40 by using an auxiliary damping device in
the spire itself. Now there's a lot of coupling
beams in the building and this is something that's sort
of been developing for several years now. Uh there
there's about 6000 of them. Um so we wanted
a consistent way of designing all these coupling beams.
Some of our multi span coupling being, some are
single span, um We're using strut and tie modeling
for all the coupling beams and this has gone gone
around around. It's not that common even today that
engineers are using strut and tie analogy, but for
this one we have 100 and we use uh you
know, uh to be models and one day models
. And we we basically have a menu, so
we basically have a series of designs and then we
fit the coupling beams into those menu of designs.
So we don't take every single coupling beam and have
a separate design for it. We basically group them
to make a little bit easier to build. These
coupling beams get to be very heavily reinforced, as
you might imagine. This is one of the drawbacks
of the bearing wall system. The coupling beams are
tough to build. There's a lot of reinforcement in
them and there's a lot of congestion as well.
And in some places the amount of reinforcement gets to
be so much, you actually have to go to
a steel I shaped beam embedded in the coupling beam
because the shear stresses are higher, much higher than
allowed by code. So there are several places in
the tower where we have to put steel reinforced coupling
beams uh, in the design. So in that
we use some finite element analysis, obviously there's a
, there's a location at the front of the steel
beam that's going to have a very high bearing stresses
. So we look into things like that with separate
sub models for the finite element analysis. Now,
in terms of the construction, what we're anticipating in
and what this contractor has told us is the walls
will go up first. There will be uh probably
5 to 10 stories in front of the slabs,
all of them, not just the central triangular core
. Every single wall will be sticking up Five or
six by maybe 10 at the most floors above any
floor construction. And the floor slabs will be connected
to the, to the walls through these types of
details where you have couplers that are cast in the
wall and then you have basically threaded bars that are
connected and key ways at the face of all the
walls. So the slabs will slowly follow the walls
After 5, 5 to 10 stories to embrace the
walls during the construction. And what we do is
we use a program that the Midas gen program is
a korean program. It's uh it's actually very powerful
in terms of its ability to do stage construction modeling
. Um this is something that's uh been a big
development for tall buildings analytically for structural engineers. 10
or 15 years ago, maybe not even 10 years
ago, we were resorted to spreadsheets. Basically,
you would take up a big core and idealize it
as a big column and you would do a spreadsheet
calculation for the creep and shrinkage calculations of vertical shortening
calculations for that. Then you would take a column
, for example, you do the same thing for
that and you try to link them to, but
that's very difficult to do through spreadsheets. It's idealized
this. You're actually building the building in the computer
in a sequential way and you're building it in the
entire three dimensional domain. It's not a spreadsheet,
it's an analytical model that keeps getting updated. So
what we do is we use the minus programme.
And yes, you know, there's the number of
steps usually are limited. You can do maybe five
story increments, but you build the entire building in
the computer so that when you get done, you
can basically take any member or any location in the
tower and track the forces over time. So you
take the gravity forces at Timex. Are they increasing
or decreasing due to the effects of creep and shrinkage
and elastic shortening of the tower I mentioned before this
tower is very linked. That's a great thing for
the system. But what have what happens is due
to the effects of creep and shrinkage and even elastic
shortening loads get redistributed through those coupling beams long term
and continue to do so over time. And you
can track and predict those those forces. Using the
Midas model, we use it as an engine.
The material curves for the concrete, we develop ourselves
and those are based on the mixed design and some
of the other models we basically use minus only only
to do the the construction. Uh you know,
the stage modeling, this is for example the stresses
in the end walls at overtime, basically they'll build
up until the tower is finished and then they'll slightly
reduce over time. Which is a good thing for
the end walls of course, where does that load
go? It doesn't disappear into the ether, It
has to go somewhere else. So it goes through
the coupling beams to the corridor walls, into the
thin walls. The other thing obviously probably equally if
not more important in terms of the redistribution forces are
the movements of the tower. So we can predict
the vertical movement and then, as you know,
any structure that's asymmetric is going to move horizontally under
its own weight. And Kingdom tower is no different
. Kingdom Tower is asymmetric. I told you that
the three wings reached the top at different locations.
So it is slightly asymmetric. So it will actually
move horizontally under the weight of the tower itself.
So we can actually predict what that will be and
give some instructions to the contractor. So he's aware
of it first of all. So he doesn't freak
out when the building starts moving horizontally on him and
do some compensation for that as well. These are
some of the guidelines we have on our drawing.
This is actually one of our design drawings. So
we give them pictures of the model, some of
the predictions. Um some of the requirements for the
surveying and monitoring of the tower during construction. These
are some of the most important discussions and some of
the most difficult discussions to get right because you can
get something very complicated that the contractor won't be able
to build in a million years needed, sort of
boil it down to something that he can swallow in
terms of his construction. Now, all these creep
and shrinkage calculations are based on testing material testing at
this scale. They're six by 12 cylinders and creep
frames were actually doing testing on the mixed designs for
Kingdom Tower in elaborate Cts laboratory outside Chicago. They
shipped all the constituent materials for the mix, the
aggregates, uh and all of the other cement materials
. They shipped it to Chicago and they're doing the
creep testing. But again this is a picture of
birds actually. But we're taking that data and we're
trying to predict something of a scale, you know
, of these and obviously there is an effect on
that. So we try to do the best we
can. But the research on how these very large
elements behave over time really isn't there yet, There
isn't enough data to do that. So we do
the best we can. All of the drawings these
days. We do in a rabbit program, three
dimensional drawings. So the coordination is actually done in
rabbit And in this case one of the big issues
is penetrations through the walls. All of them have
to be designed. There's no way that you could
build the walls and then try to take a scoring
machine and go through 1.2 m of concrete with a
six diameter hole. So all of them have to
be on the drawings, 15,000 openings through this year
. Walls for for mechanical services, small ones mostly
. So all that's done in the rev IT program
, we can find uh areas that there's a clash
or a problem with the coordination between the structure and
, and the NDP systems. This is some of
the reinforcement of the walls. It gets quite heavy
and the end walls, this is near the bottom
of the tower gets less. After about 20 or
30 stories, it gets quite a bit less.
But you can see the end walls are more heavily
reinforced and more heavily stressed actually. Then, as
you get closer and closer to the central core,
we can do three dimensional rebar drawings and we do
some of those in a program called Tekla, which
is mostly used for steel detailing. But we can
do detailing. This is a picture of the end
walls and that some of the transverse thin walls show
some of the steel coupling beams. So we can
kind of get an idea of the amount of congestion
that might be in some of these walls so that
the contractor knows what he's going to get into when
he builds it okay. A few last things because
I'm running out of time here. But the,
I mentioned, I think I mentioned before that,
you know, tall buildings are one of the few
man made products that really haven't been fully verified at
full scale. You know, we, we do
these final element models, we put a lot of
faith in them. I put faith in him myself
actually. Um, We do wind tunnel testing and
those, those models are at the most 1-500 and
maybe even 1-800. They're pretty small scale models and
they're done in a sort of simulated environment in the
wind tunnel. But there's very, very little Information
of how these buildings are behaving in real scale 1-1
scale compared to when you think about it, automobiles
or airplanes, which you have all kinds of data
on how they behave at full scale. So,
um, there's a huge need, uh, there's
a lot of drawbacks and how that can be accomplished
owners don't really want to know. They don't want
to know bad news, that's for sure. Um
, but what we need to do and it will
happen probably well after I'm finished with my career,
but we need to have a program and I wrote
this program for Kingdom Tower where we have a long
term structural health monitoring program in place. So all
the way from the bottom of the piles to the
top of the spire. We've put a program together
of instrumentation and monitoring program of other buildings behaving all
the way from wind speeds and monitors at the top
of the building, to strain gauges in the walls
, to load cells underneath the raft foundation. And
of course I can't insist upon the client can put
it or not. It's not a code issue.
I can't I can't make them do it. But
so far they've said they're very interested in doing the
program. It's going to be extensive. One of
the question is will the information from it ever make
it into the public domain? I hope it does
so that we can learn a little bit about how
the buildings are behaving. Be wonderful to know if
the periods that we predict from those finite element models
and E. Tabs and SAP are close to what's
measured out there in the site. Most of the
stuff needs the anti monitor data. You can't really
getting data that's just data without any correlation to wind
speed is really almost worthless. But that alone just
to figure out if the building is behaving as predicted
or close to what's predicted would be very interesting.
I've been part of a National Science Foundation program with
the University of Notre Dame instrumented. Uh several buildings
were three buildings actually in Chicago. Tell you it's
very difficult to get meaningful information out of that out
of that because basically when you think about it,
when you put the instruments and you're kind of waiting
for the storm to head, it's kind of like
watching paint dry most days there's not there's not enough
wind for there to be any register in terms of
the data. So it's one of the things that's
one of the things that as we build taller and
taller, we really need to look at and it's
going to be your generation. I think that will
push this kind of thing forward in the future.
I hope here I am at groundbreaking. That steak
, you see there is the geometric center of the
tower. We're out, we're out in the middle
of nowhere. As you can see Uh three gentlemen
to my right there. They're the architects. They
all dressed the same. Yeah, they look like
they work for the CIA, The two gentlemen to
my left or the client. So this is the
piling. This was january Earlier this year. All
the piling was completed. The contractors, Saudi Bauer
, basically a consortium that's a joint venture between a
Saudi piling contractor and a German one did a wonderful
job. Very few problems with the pilot. Even
the 105 m long piles are all in place.
uh in terms of the uh corrosion protection, we
actually have a a system in place with the cathartic
protection for the piling and the raft foundation. So
in addition to having a waterproofing membrane underneath the raft
foundation or the mat foundation, we have cathartic protection
system throughout. You can see the tops of the
piles, they're getting trimmed off and cleaned, getting
ready for the, the matte foundation. And this
is actually fairly, fairly, fairly recent. So
this is the this is five m thick. So
this is the the raft, the tying all the
piles together, five metre thick matte foundation over all
of the 270 piles. It turns out that the
water level is quite close to the surface at our
site. So the rat foundation will actually be in
the bottom story of the, of the garage level
of the tower. You can actually be looking right
at the raft foundation is not buried in the ground
as most projects are. And then you can begin
to see some of the walls going up there,
that's the end wall, lot of reinforcement, corridor
walls and the thin walls and coupling beams going up
. And so they've got two or three stories of
walls going up I believe. Uh the latest is
that will be finished in 2018, the end of
2018. It is a real project from if you
think about it, I think that to one of
the two most difficult things. Two of the three
difficult construction challenges on the tower are the pile foundations
, you can't see them, they're they're drilled into
the ground, the raft foundation, you can imagine
the amount of reinforcement and issues with heat of hydration
and everything else with that. Those are done from
here on out. It's just walls and slabs and
I can tell you, Saudi Binladin group knows how
to do walls and slabs. I wouldn't say it's
going to be trivial, but I think the third
thing that's going to be interesting is when they get
up to around 700 m. that's when the wind
speeds up there do get quite high and it gets
difficult, very difficult to build the tower tapers.
So the cranes are going to have less and less
structure to be able to Latch onto to stabilize themselves
. So I'm expecting a call two or three years
saying, Okay, we're up to 700 m now
, what do you want me to do? Uh
, I get this question, I'm going to answer
the question before it's even asked so how how tall
can we go? Kingdom Tower? The building in
the center is frank Lloyd Wright's proposal for Mile high
skyscraper in Chicago, uh, called the Illinois,
actually. Um, anyway, there's been a lot
of conversation in some of the council on tall building
sessions about it and I was a bit taken back
. That's mostly engineers, structural engineers saying it's,
it's uh, there's no problem with the structural engineering
that anything can be done. There's no limit.
The limit is going to be because of the elevators
. It's going to be because of some construction or
pumping concrete or this or that. I'm not so
sure. I think that as you get taller and
taller And if you really want to occupy the buildings
taller and taller and not just to 600 or 700
m. the motions up there will get extreme and
the ability of the contractors to deliver structural materials to
that height are going to be more and more difficult
. So I guess I'm a bit of a nay
Sayer, I'm not saying you couldn't go to 1.1
kilometer or even 1.4 or 1.5, but a mile
high skyscraper when you think about it, That's almost
another 50 or 60 taller than this building. And
I can tell you if anybody's been to Dubai and
seeing the Burj Khalifa, that is one unbelievable building
and this is going to be taller. It really
is a shocking thing to look at. And if
you really in your mind's eye say, what does
a mile high skyscraper look like? I think it
really, in a way, it's a dream.
I think it's maybe it'll curb but certainly not in
my lifetime. No way. And, and I
think there's a lot of, lot of issues that
are gonna have to be solved to build to that
height. So that's my opinion. So hopefully in
three years, view from Jeddah Harbor will look something
like that. Thank you. Okay. Yeah.