UAE Pavilion

Novum Structures www.novumstructures.com

The Freeform Structure of the UAE Pavilion at the Shanghai EXPO 2010

Soeren Stephan Feng Pan Yongqjan Huang

Novum Structures USA, China, France, Germany, India, Singapore , Turkey, UAE, United Kingdom



• Design & Build Specialty Contractor for Architectural Steel, Cable, Glass & Membrane Structures


Grid Shell & Cable Structures Freeform Structures Structures with ETFE Cladding

Seattle Airport, USA

Dali Museum St. Petersburg, USA Tours Shopping Mall, France Wrigley’s R&D Center Chicago, USA

Yueda 889 Shopping Mall Shanghai, China Old Castle Dresden, Germany



Holding Company:

Menomonee Falls, WI

San Francisco, CA

Sarasota, FL

Chicago, IL

Diss, UK

Wurzburg, Germany

Sangerhausen, Germany

Beijing, China

France Istanbul, Turkey

Farnham, UK

Dallas, TX

Bangalore, India

Dubai UAE

Singapore

• Novum Structures International Network


BB-System BK-System FF-System KK-System SSM-System AFP-System CCG-System ECG-System

• Selection of Novum Component Systems for Building Structures & Envelops



1. Introduction

2. Pavilion Structure

3. Grid Shell Geometry

4. Freeform Grid Shell Node Connector 4.1. Node Connection Bending Stiffness and Capacity Tests 4.2. Numerical Calculation of Node Connection Bending Capacity 4.3. Analytical Calculation of Node Connection Stiffness 4.4. Finite Element Analysis of Node Connection

5. Structural Analysis 5.1. Global Stability Analysis

6. Fabrication and Installation

Picture: Foster + Partner


1. Introduction


• Design Architect: Foster + Partner, London, UK • Design Engineer: Halvorson & Partners, Chicago, USA • Architect & Engineer of Record: ECADI East China Architectural Design & Research Institute Co.Ltd. • General Contractor: CSCEC China Construction Industrial Equipment Installation Co. Ltd. • Contractor Freeform Structures: Novum Structures China Co. Ltd. in cooperation with

Novum Structures LLC (USA) & GmbH (Germany)

Pictures: Foster + Partner


1. Introduction


• Pavilion shape is resembling 3 sand dunes as natural formations typical for UAE deserts like the Rub Al Khali (aka “the Empty Quarter”) with distinct dune features – gradually curved windward sides, sharp ridges and almost flat leeward sides

• Height of the southern dune is 20 m, height of northern dunes is about 18 m • Pavilion has almost circular footprint with a diameter of about 65 m • After the EXPO 2010 the pavilion will be disassembled & moved to Saadiyat Island, Abu Dhabi, UAE




1. Introduction










• Southern halves of dune shapes (“windward sides”) are single layer freeform grid shell structures • Northern halves of dune shape (“leeward sides”) are inclined, straight -beams (horizontally braced) • Dune shapes are subdivided and supported by a central spine structure with portal frames every 6 m • Northern dune shape is additionally supported by 2 -beams in inflection zone of grid shell • Crescent shaped canopies with “tension ring belt” edge beams & entrance wall structures are

enclosing the northern and southern buidling entrances • Dune ridges are made of curved, large diameter pipes • Pavilion structure is supported on reinforced concrete

stripe foundation




• Conceptual grid shell design by Halvorson & Partners was calling for SHS profiles 200x200x6 mm • To avoid extremely large node connectors , profiles were changed to RHS 240x80x8 (steel Q345) • Grid shell members are interconnected with concealed bolted Novum FF node connectors in order

to enable the diassembly, shipment and reuse of the complete pavilion structure after the EXPO • Cladding is supported by posts, bolted to the top surface of the node connector



1. Introduction










• 2 basic methods to develop a grid on continuous surfaces:

Surface Grid Development

Planar Projection Method Surface Partitioning Method

• Boundary lines get subdivided into portions of similar length, thus creating “orthogonal” auxiliary grid on surface

• Final grid is tied into this auxiliary grid

• Planar grid is projected on continuous sur-face and manually improved where needed (suitable for surfaces with small curvature)




• Grids created by those 2 methods have different specific properties:

Surface Grid Development

Planar Projection Method Surface Partitioning Method

Grid along boundaries is unproblematic Resulting grid can appear slighly more irregular, although this strongly depends on the current perspective of the viewer

Resulting grid is usually evenly spaced and balanced Planar grid projection is not considering boundary lines, thus creating problematic grid zones along boundaries

Southern dune grid created with planar projection Southern dune grid created with surface partitioning


• Final step of grid development is the identification of local coordinate systems for nodes and members based on the given grid panels: 1. normal vector of a member is the average normal vector of the 2 adjacent grid panels 2. normal vector of a node is the average normal vector of all adjacent grid panels



Normal Vector Node

Normal Vector Panel

Normal Vector Member

Normal Vector Node

Normal Vector Member

Normal Vector Panel



1. Introduction








4. Freeform Grid Shell Node Connector


• Concealed bolted Novum FF node connectors, used for grid shell member connections, consist of: - 2 forged discs 200x85 mm (steel #45) with individually machined faces as required by geometry - each machined face has one threaded hole to receive a M24 or M27 bolt - precision cast steel adapters (steel GS-20Mn5V) with top & bottom hole, welded to member ends - concealed & pretensioned socket head bolts 10.9, fixing the end adapters to the 2 node discs

• The semi-rigid behaviour of these bolted node connections has to be adequately considered in the structural model - typically as a rotational spring stiffness at the end of each grid shell member


4.1. Node Connection Bending Stiffness and Capacity Tests


• 4-point bending test (stiffness & capacity)

（）

（）

Test

#

Failure

Mode

Ram Load,

at Failure

Bending Moment,

at Failure

1 Bolt 127 kN 76.8 kNm



(M24 bolts)


4.2. Numerical Calculation of Node Connection Bending Capacity


• Bending moment capacity of the node connection as a function of the axial connection force was determined using an iterative numerical calculation method assuming planarity of member end section [Space Structures 5, Telford Publ. 2002, p. 759-773]

• Calculations were performed for 3 limit state conditions: elastic, plastic capacity and failure limit

• Test results are conservatively close to the failure limit bending moment

Initial parameters: orig

it

orig

it

orig

itMzmz,Mymy,Nn,0it

Strain parameters: AE

no,

JyE

my,

JzE

mzit

itit

ity

itit

z

itit1ititit1ititit1itMzmzmz,Mymymy,Nnn

> Compression stress in the connection profile / Element force & moments

> Tensile stress in the bolts / Bolt force & moments

> Internal connection force & moments : N<it>, My<it>, Mz<it>

> Deviations from given force & moments: N<it>, My<it>, Mz<it>

All deviations 0 ? it = it + 1 Stress distribution

determined !

N

O

YE

S

(M24 bolts)


• The node connection stiffness can be determined using the measured load-displacement curves • The measured total mid span deflection is obviously a combination of flexural deformation of

the specimen and rotational deformation of the node connection:

• The flexural mid span deformation of the specimen can be calculated as follows:

• The rotational connection stiffness can be determined using a combination of the above formulas:

• The average total mid span deflection in the tests with M24 bolts was 18.5 mm at 100 kN ram load (equivalent to 60.5 kNm connection bending moment)

• The corresponding node connection stiffness is 16110 kNm/rad.

4.3. Analytical Calculation of Node Connection Stiffness


Rot

FlexTotalRotK

lM

2

22 4324

alEI

MFlex

22 4324

2 alEI

M

lMK

Total

Rot

- total measured mid span deflection, m - flexural mid span deformation of the specimen, m - bending moment at node connection, Nm - span, distance from support to support - rotational node connection stiffness of (Nm/rad)

Total

Flex

Ml

RotK

- modulus of elasticity of steel, N/m2 - moment of inertia of tube section, m4 - distance of load introduction point from support, m

E

I

a


4.4. Finite Element Analysis of Node Connection


• As an additional verification of the numerical and analytical node connection parameter calculations, a finite element analysis of the test specimen was performed

• The observed mid span deflection of the FE model is only 80% of the average measured value, due to little initial settlements of the real specimen

• This ratio was then used to calibrate the FE model of the node connection used in the structural analysis



1. Introduction








5. Structural Analysis


• The conceptual structural analysis by Halvorson & Partners had to be adopted by ECADI considering local regulations and all modifications made during the construction phase

• A major update of the structural analysis was required du to the following: - member profiles changed from SHS 200x200x6 to RHS 240x80x8 in order to minimise node size - Halvorson assumed fully rigid node connections – changed to real semi-rigid connection stiffness

• A meaningful structural model of the grid shell portions has to include all other parts of the pavilion structure as well – therefore ECADI and Novum closely coordinated their structural models and performed the analysis simultaneously (ECADI used SAP2000, Novum used Dlubal RStab)


5.1. Global Stability Analysis


• The Chinese guideline JGJ 61-2003 “Technical Specification for Lattice Shells” requires that the ratio of the critical global buckling load to the governing service load combination is at least 4.2 (determined in a linear-elastic buckling analysis of the structure considering global imperfections)

• ECADI established in their structural analysis the governing load cases for the different grid shell portions – for the southern dune this combination was DL + WL45˚ + 0.7 LLroof + 0.7 Tincr (see below)

• The global grid shell imperfections were generated by scaling the first buckling mode to a maximum imperfection value of L/300 = 66 mm (L: span)

• The ratio of the critical buckling load to the governing service load combination was finally 4.6 for the southern dune grid shell



1. Introduction










• Freeform grid shell structures in general (except of small ones) cannot be drawn and fabricated using conventional methods due to time, cost, manpower and reliability constraints

• Instead, interconnected parametric component models for all parts of the members and node connections have to be developed – both in CAD and CAM software programs used

• Then instead of conventional drawings only relevant data and very few parametric drawings are needed to design and fabricate all grid shell components




Node component fabrication: • CNC model data

transfer & check • CNC machining

and marking • Quality control • Crating and shipment




Member fabrication: • Parametric drawing data

transfer & check • Length and hole cutting • Adapter welding • Painting • Crating and shipment







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Thank you !

Documents

UAE Pavilion