ACD_SM1/2021_Assignment 2_Guangen Jin

Single story building design

Single storey shell structure This section explores the possibility of self-support shell structure covering an area of 40 by 40 metres. The shell is made of 250mm reinforced concrete Progress 1 - Free form generation

Progress 2 - Live physics simulation

5.45 m

Progress 3 - Finite element analysis

Max.Disp: 11.2 cm Mass weight: 1142 ton

11.7 m

0.5 cm

Sweep NURBS curves to create a free form surface to get orthogonal grids on the plan view.

Evaluate the height variation of the shell and analyse the water flow on the shell surface.

Select one point from each circle and project them to the zero level height.

Fix the perimeter and anchor point in red.

Simulate soap film generation process in Kangaroo to create mean zero curvature mesh.

(Livesoap component applied)

5.0 cm

Gravity and 2kN/m load are applied on the 250mm thick reinforced concrete shell. Anchor points are marked in grey circles.

2

Generation 1 Max. Disp 15.4cm | Mass: 1141ton

Max. Disp 5.3cm | Mass: 1145ton

Max. Disp 11.6cm | Mass: 1142ton

Max. Disp 4.7cm | Mass: 1150ton

Max. Disp 9.8cm | Mass: 1140ton

Max. Disp 4.8cm | Mass: 1150ton

Max. Disp 9.7cm | Mass: 1140ton

Max. Disp 4.6cm | Mass: 1146ton

Max. Disp 9.6cm | Mass: 1140ton

Max. Disp 4.4cm | Mass: 1150ton

Max. Disp 8.6cm | Mass: 1140ton

Max. Disp 4.3cm | Mass: 1149ton

Generation 4

Genetic algorithm optimisation This section explores the possibility of a self-support shell structure covering an area of 40 by 40 metres. The shell is made of 250mm reinforced concrete

Mutation

Generation 7

Generation 11

Rhino/Grasshopper Interface

FEA Interface

Variable: position of anchor points

Load: gravity + 2 kN/m2 live load Output: Max. disp and mass weight

Generation 20

Converge

Input

Goal

Generation 30

Selected

Generation 35 Max. Disp 8.6cm | Mass: 1140ton

Max. Disp 5.1cm | Mass: 1143ton

Max. Disp 4.6cm | Mass: 1145ton

Max. Disp 4.5cm | Mass: 1147ton

Max. Disp 4.3cm | Mass: 1148ton

Max. Disp 4.3cm | Mass: 1149ton

GA interface Objective: minimise Max.disp and mass weight

0.5 cm

5.0 cm

Structure material reduction Based on the selected iteration from GA optimisation, shell structure material utilisation is used to remove the extra material to make the shell more efficient and light-weighted, which will have little impact on the structure performance.

Material Utilisation

0.5%

Material utilisation of selected iteration

20%

0.5%

FEA

20%

Manually put draw circles to remove extra materials

0.5%

Remove the materials in the blue zone. There is little impact on material utilisation.

20%

0.5 cm

Max. Disp: from 4.6 cm to 4.7 cm Mass weight: from 1145 ton to 1066 ton

5 cm

Cross section thickness optimisation This is the last step to reduce shell cross-section profile thickness, which differs from 2cm to 30cm. The shell is made of reinforced concrete and the maximum allowed material utilisation is limited to 50%.

Overall perspective

0.5 cm

5 cm

Max.Disp: from 4.7 cm to 4.8 cm Mass weight: from 1066 ton to 64.2 kg Load and anchor are same as the preliminary stage.

2 cm

30 cm

The shell thickness mapping on the plan view.

Conclusion In the shell optimisation, it begins from a free form shell structure with Max. Displacement at 11.2 cm and mass weight at 1142 ton. However, through the GA optimisation (change anchors’ position), manual material reduction (puncture holes) and cross-section thickness optimisation, the Max. Displacement of the shell structure has been reduced to 4.8 cm, with only 64.2 kg of reinforced concrete covering an area of 40m by 40m. The thinnest part of the shell is only 20mm thick, but it is still able to support the live load at 2kN/m2.

Edge view comparing the thickness of top edge and column edge

Multi stories building design From solid wall to girded tube wall The test aims to replace the solid thick concrete wall with a steel tube which makes the load-bearing structure more efficient and light-weighted.

For facade walls: Max. Displacement: 0.34 cm Material Weight: 1400 ton Concrete slab: Density: 2500 kg/m3 Thickness: 150 mm Gravity: 9.8 N/kg Slab weight is evenly distributed on the facade

First principal stress lines on the facade with source points

Second principal stress lines on the facade with source points

Draw the first line to intersect with the 1st PSL and intent to paralel to the 2nd PSL

Duplicate and evenly rotate the line to intersect with centre line

Catenary lines from anchor to intersection points

Mirror the catenary lines

Horizontal reinforcement as the second layer

Slab weight distributed at intersection points between facade and slab

Steel tube generation procedure - form finding

For grid tube: Max. Displacement: 3.00 cm Material Weight: 139,447 kg (10% of the solid concrete wall) RHS: Width: 100 mm Height: 200 mm Flange and Web: 5 mm

Design interation and optimisation

Variables for optimisation Two variable inputs are used for the facade optimisation: 1. Angle of the first catenary line 2. Steel tube density Rotation angle from 20 - 60 degree.

Rhino/Grasshopper Interface

FEA Interface

Variable: bottom line rotation angle

tube density

Angle = 25 degree

Angle = 37 degree

Angle = 49 degree

Angle = 60 degree

Load: gravity + 3200 kN live load per floor Output: Max. disp and mass weight Steel tube density from 1 to 10 (density is defined by subdivision times of the surplus angle)

Input

Goal

GA interface Objective: minimise Max.disp and mass weight

Density = 2

Density = 3

Density = 5

Density = 10

Evolution and optimisation Two optimisation goals are set: max. displacement and material weight. In the evolution, it attempts to reach the lowest value for both max. displacement and material weight. Nine iterations in the GA mutation stage are compared to each other and case No.3 is selected.

1

2

3

FEA of Case no. 3 The building envelope is 40 x 40 x 42m The facade truss is made of 200 x 100mm RHS steel beam For steel spatial frame, both top and bottom beams are 250 x 150 RHS steel, and middle web is 100 x 70mm steel.

14.929cm, 611.29ton 4

12.465cm, 616.47ton 5

10.281cm, 643.90ton

7

Selected 10.517cm, 639.13ton 6

9.588cm, 684.89ton

8

9.508cm, 692.96ton

9

0.5 cm Max. Displacement: 10.517 cm Material weight: from 639.125 ton (Inc. spatial frames) 9.092cm,713.19ton

8.975cm, 746.23ton

8.794cm, 793.51ton

10 cm

Beam profile optimisation Further optimisation for facade beam element profiles is applied. The profile height varies from 5 to 50 cm, and the width is set as twothirds of the height.

0.5 cm

5.0 cm

Max. Displacement: from 10.517 to 11.128 cm Material weight: from 639.125 ton to 671.645 ton (Inc. spatial frames)

Conclusion Steel truss tube is more efficient and lightweight than the solid reinforced concrete wall. Beam profile optimisation in this case increases the overall mass weight because the thickness of the bottom beam increases 2.5 times to achieve a better visual effect.

The max.displacement point is located on the slab centre, which is a design flaw in this experiment.