group3 structure report ahmed abbas 4209834

7/31/2019 Group3 Structure Report Ahmed Abbas 4209834

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Table of Contents

Introduction

3.1 Shelter concept

3.1.1 Principle and exploration3.1.2 Design Process

3.2 Load Cases and calculation3.2.1 Form analysis 1

3.2.2 Form analysis 23.2.3 Comparison

3.3 Stress ow analysis

3.3.1 Material selection

3.4 Grand stand structure

3.4.1 Material selection3.4.2 Conclusion

3.5 Construction components

Structure design reportAhmed Abbas


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Introduction

The nal structural design is integrated mainly in two components -the shelter for the

multipurpose stadium and the grand stand integrated with the facade. The structure of the

shelter and the grand stand is dealt independently from each other for the purpose that shelter

being the by-product of new functions added to the building and surrounding context, while

grand stand being a by-product of strict fa regulations and rules.

The shell structure is explored for the design ing the shelter and further analysed and calcul ated

in structural analysing software, GSA by Oasys. Comparing the results and checking the

performance in this software nalized the form. The structure of the sliding pitch beneath the

grand stand is also analysed to obtain the required material and section property.

3.1 Shelter ConceptThe challenge in designing the shelter was to create a continuous homogenous shell structure.

The overall shape and the form were highly inuenced from the discipline of climate (gure

3 &4).

Architectural requirements for the shelter:

- A close shell (xed shelter and no retractable elements)

- As light and transparent possible

- Integration of double skin

A space frame structure was chosen for the further exploration in order to full ll the above-

mentioned architectural requirements.

Figure 1: Options of shell

Figure 2

Figure 3: Drawing by Climate expert discipline, Maysam FooladyFigure 4:


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3.1.1 Principle and exploration

With the help of minimum surface (soap lm) approach and catenary arches initial form ndings

were conducted considering the limitation of the site boundary and the aim of the project.

Minimum surface was explored for a reason that such a surface allows calculating equal

number of u and v direction because of its nature. The soap-lms formation is considered

as ideal lightweight tension structures and have constant surface stress, a minimum surface

area which is in stable equilibrium and zero mean curvature at every point on the surface.

Using the soap lm as a single surface (gure 7) for this large span area of stadium createsa at surface in the central area. This surface may not turnout to be good during the rainfall

and snowfall. The other possibility was to create a soap-lm surface in two parts (gure 8) but

again it creates a peak line in the middle, w hich means extra support requires holding this kind

of structural system. This approach was also discarded from the architectural perspective of

integrating a continuous homogeneous shelter structure.

3.1.2 Design Process

Further to eliminate the peak line created due to use of more then one soap lm surface, a

point cloud (gure 9w) was generated in rhinoceros software from the same surface. Further

few points in this point cloud are eliminated which were creating the peaks on the middle of the

surface. Using rhino-resurf a smooth surface was developed from the left over points of point

cloud. Though the surface created by this process is not purely based on soap lm surface but

it provides the closest surface related to minimum surface.

As described before diagram ( gure 8) shows the entire process for dening the surface

through rhino re-resurf. After calculating the u and v direction using grasshopper plug-in for

rhinoceros, members of space frame are dispatch (gure 9 and 10) according the boundary of

the entire shelter. The members are dispatch in a way that it constitute the complete frames of

quadrangular grid on the boundary condition and further all these frames on the edge condition

were joined manually.

: . .

Figure 5 Figure 6

Figure 8

Figure 8: Process

Figure 9: Dispatching Figure 10: Grasshopper script for dispatching

Figure 7


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3.2.1 Form analysis 1

The quadrangular space frame structure developed out of soap-lms were analysed later in GSA and

results of different quadrangular grid sizes were compared. These results were compared only with

respect to the dead load so to have a basic understanding of performance of these different quadrangular

grids. Figure shows the results of 3mx3m, 4mx4m and 5mx5m quadrangular grid with respect to Axial

force, combined force C1 and displacement occurring in each case. Comparison shows that 5m x 5m

quadrangular performs the best as compares to other others in each analysis shown. The maximum

combined stress in 5mx 5m is found to be 800 N/mm 2 and whereas the maximum displacement

is 450mm but in case of 3mx3m and 4mx4m it seem to have more stress and displacement. It

concluded that as the size of quadrangular grid of space frame is increased it performs the better.

But for the sake of production it not advisable to have more long members and also the long

members requires more thickness or diameter which makes overall structure to rigid and heavy

from the aesthetic point of view.

Figure 11: Stress ow diagram


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To optimize the overall surface area of the structure, the top edge

boundary of the grand stand was given as an input in order to

have the structure not far from the grand stand. The major issue

in this case was that it was providing a very limited space for

the architectural requirements at the corner (gure 12), where

structure comes down. In order to solve this issue another surface

with more relaxed on the corners were developed, to compare the

results of structural performance in GSA.

3.2.2 Form analysis 2

Diagrams in gure13 shows the comparison between different

ranges of quadrangular grid of the space frame in form nding

2 which is not related to soap-lm surface. Again even in this

case the form with highest range of quadrangular grid 5mx5m to

9mx9m performance the best in terms of combined stress and

displacement because of dead load. But as mentioned before the

grid of 9mx9m becomes too huge and requi res much more thicker

or diameter of material. For this purpose the form with range of

quadrangular grid 4mx4m to 7mx7m was chosen to compare

its result with 5m x 5m quadrangular grid of minimum surface.

Following shows the result of both form nding 1 and 2.

Figure 12:


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Results from both the form nding shows that form nding 2 seems better in terms of combined stress

but the displacement due to dead load is 1250 mm and which is very high compared to the form nding

1 which has a maximum displacement of only 450mm. From the architectural terms the form 2 full lls

the requirements needed for the functions but at the same time it has a high displacement on central

region of the surface. Although the form 1 has very less displacement, decision for improving the form

2 was further carried in order to have architectural advantages.

Further the form 2 was modify in order to remove the atness causing the displacement of

1250mm in the central region of the surface. Also the input of sectional property of space frame

member on the four base corner was assigned with bigger diameter and thickness of hollow pipe

as compared to rest of other member of space frame structure. The result due to these changes

can be prominently seen in the following analysis diagrams.

Figure 13: Comparison of stress ow diagram between form analysis 1 and form analysis 2.

3.2.3 Comparison


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LC1: Dead load (gravity load included) LC1: Displacement

LC2: Dead load L1 + Wind Load L2 LC2: L1 + L2, Displacement

LC3: Dead Load L1 + Snow load L3

3.3 Stress ow analysis for nal form

The modied form was further analysed with re-

spect to different combination of load cases. Figure

13a is with dead load, gure 13c is combination of

dead load and wind load, and gure 13e is with com-

bination of dead load and snow load. From all the

outputs seen in the diagrams it seems that this new

form with minor changes in surface and sectionalproperties of material performs far better than form

1 and form 2. During the dead load LC1 (gure 13a)

it has a maximum combined stress of 250 N/mm 2

and a maximum displacement of 0,70m , which is

not much for such a huge large span structure. When

combining the dead load with the extreme wind

load LC2 (gure 13c) it has a maximum combined

stress of 300 N/mm2 and maximum displacement of

0,80m. On the basis of analysis the performance of

the structure during the dead load combined with

the snow load LC3 ( gure 13e) seems to be not

at all affected in terms of stress and displacement.

It concludes that this particular form can withstand

rmly in all the combined situations of loads acting

on it.

LC3: L1 + L3, Displacement

Support Reactions

Figure 13: Stress ow diagrams for nal form

ab

c d

e

f


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Sectional properties for the members of space frame

To nd out the suitable material for the space frame structure in such a context and weather condition analyses was

done in CES software in conjoint with material science assignments.

Following important properties was used as input in the CES.

-Corrosion Resistant: The stadium is located near the sea in Rotterdam and therefore it

requires very good resistance against moistures climate, the salt

water and fresh water.

- Light weight and stiff: Space frame structure itself occupies the large span with lots of members. It requires light

weight in nature and at the same time stiff and strong.

- Non ammable: For the sake of safety for the people in a stadium the material should consist of non ammable

property.

Different graphs were made during the analysis stage to limit the material form the aspect of

price, tensile - compressive strength, density and higher fracture toughness. Finally from CES

analysis, a stainless steel ferritic, austenitic, AISI 201, wrought, 1/2 hard was chosen because

of its low density, hence light weight compares to other and at the same it posses high tensile

and compressive strength. Also this material allows the excellent weldability options which very

important property required for the space frame.

Yield strength (MPa)Compressive strength (MPa)

3.3.1 Material selection

Graph 1

Graph 3

Graph 2

Gaphs of price*density against tensile, compressive

and yield strength was plotted at different stages of

analysis in CES.


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A truss beams made up of I section and L sections as a crossmember is used beneath the grand stand structure for the

sliding pitch mechanism that allows eld to be moved out

during the other activities organised in the stadium ( gure 14).

This truss system including the beams and columns of grand

structure was analysed with different inputs of material and

sectional properties of the entire structure (gure 15, 16&17).

The structure of the shelter and grand stand were analysed

separately since they works independently from each other

in terms of load transfer. The input in GSA for this analysis

was the dead load mainly by the load of people. Considering

that it the smallest part of grandstand which accommodates

around 10000 people, it comes out to be approximately

7000kN load on entire structure and on each beam 5.6kN.

But again considering the factors where people will jump and

will make lot of sound during the matches, a safety factor of1,5 was multiplied to 5,6kN for the input in GSA. After several

experiment with different input of sectional property, a improved

option (gure 19) having maximum combined stress of 400 N/

mm2 and maximum displacement of 0,2m was obtain as an

output. But this stress can be still decrease by using Cobiax

concrete slab (discussed in next page).

Figure 18: Sectional properties of following improved output of GSA

3.4 Grand Stand structure for sliding pitch

Figure 14:

Figure 15: Figure 16: Figure 17:

Figure 19: Stress ow diagrams for the grand stand Figure 20: Displacement diagram

Figure 21: Support Reaction


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3.4.1 Material selection for grand stand structure

As described before the maximum combined stress on the overall structure was 400

N/mm2, which is little more than it should be. But it can be resolved by reducing the

overall weight of concrete grand stand structure so that the truss system beneath it

will undergo with less overall stress. This weight can be resolved by using cobiax,

semi- precast slabs (gure 22).

Combination with semi-precast elements

The Cobiax cage modules are either di rectly built into the semi-precast slab elements

in the precast factory and delivered to site as a whole (gure 22) or only placed on

the semi-precast slab elements on the construction site (gure 23). In both cases

the top reinforcement can be directly laid on the Cobiax cage modules which act as

wire chairs.

Cobiax has been designed to remove the non-working, dead load in concrete slabs

whilst maintaining biaxial strength. This is achieved by placing hollow plastic spheres

between the upper and lower static reinforcement of the concrete slab, displacing

concrete where it has no structural benet. The effect is to decrease the overall

weight by up to 35% when compared to a solid slab of the same bearing capacity.

The reduced weight allows the quantity and dimensio ns of vertical bearing elements,

such as columns, to be reduced. Reduced dead weight means a smaller deection

of the slab, and also provides scope for savings in foundation design, including

fewer piles and/or reduced length of piles. While the design reduces overall weight,the Cobiax slabs offer very high load carrying capacity and exibility. However, in

contrast to more conventional hollowcore slabs which have load transfer in only one

direction, the Cobiax slabs allow load transfer in any direction. Because the Cobiax

at slab does not require beams, at unobstructed softs are produced and the

costs of installing services in a building are also substantially reduced.

3.4.2 Conclusion (shelter)

It seems that the space frame structure of quadrangular grid ranging from 4mx4m

to 7mx7m performs better than other smaller and larger size. A smaller sizes of

quadrangular grid accumulates more stress due to the large number of memberand nodes in the large span structure. Also while exceeding the member length

of quadrangular grid more than 7m was undergoing high deection because of

its long length with small diameter of stainless steel pipe. Presently in the space

frame structure of the shelter, two varied diameters of stainless steel pipes is used

and due to which there was a major change in positive direction. It can even be

improved much using varied diameters of hollow stainless steel pipes at different

region of the shelter knowing the appropriate stress ow.

Figure 21: Figure 22:

Figure 23:

Figure 24:


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160mm

3.5 Construction components

Figure 26: Truss structure for supporting the facade Figure 27: North facade

Figure 29: Detail A at the junction where space frame sits on concrete base

Figure 28: Concrete base

Figure 27: Layers of component

Columns, slabs and beam

Grand stand seats

Space frame structure

Enclosed boundary andconcrete base

A

Stainless steel

hollow pipe

group3 structure report ahmed abbas 4209834

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