Wind Effects in Tensile Membrane Structuresconstruct/20160224_CONSTRUCT_PhD... · PhD 2016 | 3 2016 CONSTRUCT PhD Workshop Wind Effects in Tensile Membrane Structures • Objectives

Wind Effects in Tensile

Membrane Structures

Pedro Gil Marques de Queirs Ferreira

Elsa de S Caetano

2016

PhD 2016 | 2

2016 CONSTRUCT PhD Workshop

Wind Effects in Tensile Membrane Structures

Motivation

Growing use of tensile membranes in special

structures has brought increased demand in the

assessment of their structural behavior

Membrane structures are characterized by: high

flexibility, leading to strong geometric nonlinear

behavior; complex shapes; slight prestress;

orthotropic materials; and construction methods

Recent damages due to aerodynamic and

ponding effects of these lightweight structures

and lack of standards motivated this work

PhD 2016 | 3



Objectives & Tasks

The work focused two main aspects

Form-finding

Characterization of the wind effects in membranes

Two types of examples

Roof of a multisport arena

Role of prestress & orthotropy on structural behavior

Wind effects considering generation of stochastic wind

loads and numerical evaluation of membrane response

through a simplified model, characterizing the

aerodynamic mass, stiffness and damping

470 Sailboat

Develop and validate a methodology of form-finding of

a boat sail in real-time based on strain measurements

Case studies

Roof

Sailboat

PhD 2016 | 4



Structural form-finding and optimization methods

Force Density Method (FDM): 1lFDM and 2nlFDM

Independent of the material properties and linearize the

Equilibrium equations using a force density coefficient q

= t/l for the truss elements

Surface Stress Density Method

Analogous to FDM setting a surface stress density

coefficient qs for the constant strain triangle elements

Dynamic Relaxation Method: Viscous & Kinetic model

Explicit direct time-integration of the dynamic

Equilibrium equations using central finite differences.

[Cs Xf q F]1,2 + Qz

2 X t l

Cs Xf Xini qs F Xend t l S = 4qsS

Cs Xf Xini F (E A ti )truss el. Xend t l

kN/m

0 2 4 6 8 100

1

2

3

4

5

6

7

8

9

10

1 2

3

4 5

6

7 8

9

Geometria Inicial - MDFl

x

y

0 2 4 6 8 100

1

2

3

4

5

6

7

8

9

10

1

2

3

4 5

6

7 8

9


x

y

0 2 4 6 8 100

1

2

3

4

5

6

7

8

9

10

1

2

3

4 5

6

7 8

9


x

y

0 2 4 6 8 100

1

2

3

4

5

6

7

8

9

10

1 2

3

4 5

6

7 8

9


x

y

PhD 2016 | 5


Wind Effects in Tensile Membrane Structures Linear Force Density Method (lFDM)

Example of a cooling tower

Solution is obtained iteratively: rinf 9

m, rsup 7 m, Hc 21 m e Hm 25 m

Configurao a) b) c)

qs (N/m) 400 400 400

qcomp (N/m) -2800 -3000 -3000

qc,v (N/m) 100 100 1000

qc,h (N/m) 100 100 100

Configurao a) b) c)

qs (N/m) 400 400 400

qcomp (N/m) -2800 -3000 -3000

qc,v (N/m) 100 100 1000

qc,h (N/m) 100 100 100

Suspension cables

Upper compression ring

Lateral cable net (horizontal

or circumferential and vertical

cables)

Mast

Lower compression ring

PhD 2016 | 6

2016 CONSTRUCT PhD Workshop 2016 CONSTRUCT PhD Workshop

Wind Effects in Tensile Membrane Structures Viscous Dynamic Relaxation Method

1 Evaluation of the critical damping:

2 Evaluation of the static equilibrium response

Kinetic Dynamic Relaxation Method

=1

= 4

=1

2

+

+

0

1

2

3

4

5

0 50 100 150 200

Kin

eti

c e

nerg

y (

J)

Iterations

0.01

0.03

0.05

0.07

0.09

0 500 1000 1500 2000

u (

m)

Iterations

= 0

< 1

= 1

> 1

Equilibrium position:

Mx. kinetic energy = 0

Instable position: = 0

Vibration

F

=

= 0 < 1

= 1 > 1

PhD 2016 | 7




Tensile membrane roof structure located in Cartuja Island, Seville

Doubly symmetric tubular metallic structure in plan, nearly rectangular in

plan 24 x 46 m2, including suspended cables and calibrated rods

Tensile membrane made of PES/PVC, comprised by 4-top (hip. parab.)

and 4-lateral modules (flat)

Tubular section F 323x8 (mmxmm)



Cable F 36 mm

Calibrated rod F 25 mm

U warp

T fill

PhD 2016 | 8




Form-finding of the membrane with prestress of 2 kN/m

through all implemented methods and specialized

software, and comparing the same premises of

orthotropic orientations, showed slightly different results

Numerical simulation studies of the influence of the

prestress, orientation of orthotropic directions, and

Poisson coefficient evidenced significant differences on

the static and dynamic responses of the membrane

Nonlinear dynamic analysis in time domain considering

geometric nonlinearity and large displacements showed

dynamic amplification coefficients Rdyn of about 0,8

Identification of wrinkles on the corners of the lateral

modules due to non-economic shapes

0

1

2

3

4

5

6

7

0

20

40

60

80

100

120

140

160

0 10 20 30 40

Fre

qu

n

cia

(H

z)

Fa

tor

de

pa

rtic

ipa

o

Modo

X

Y

Z

Freq.

3.79

5.97

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.E-12

1.E-08

1.E-04

1.E+00

0 5 10 15 20 Fato

r d

e h

ibri

diz

ao

(F

H)

Am

plitu

de

Frequncia (Hz)

Dir. x

FH

Pa

rtic

ipa

tio

n f

ac

tor

Mode

Fre

qu

en

cy (

Hz)

Dis

p.

(m)

Am

plitu

de

Hy

bri

diz

ati

on

facto

r

Frequency (Hz) Time (s)

-0.002

-0.001

0.000

0.001

0.002

0.003

100 150 200 250 300

Deslo

cam

en

to (

m)

Tempo (s)

Rdin = 1.08

Ux, quasi-esttico

Ux, din

quasi-static

0

5

10

15

20

25

30

35

40

45

50

0 100 200 300 400 500 600 700 800

Ve

loc

ida

de

(m

/s)

Tempo (s)

1

534

Velo

cit

y (

m/s

)

Time (s)

PhD 2016 | 9



Form-finding of a boat sail in real-time

This work describes a monitoring system based

on fiber optic strain gauge sensors used to

reconstruct in real time the form of a sail

The installation of FBG sensors on a beam allows

to obtain curvatures in specific cross-sections,

and evaluate, by interpolation, the coordinates of

the deformed beam and consequently the most

significant parameters of the sail shape

Uncertainties related to optical technology,

require the calibration and validation of the results

through an alternative system.

Since large amplitudes of deformations are

measured, the fiber optic monitoring system was

validated based on a imaging based system

Draft position

Chord

Cam

ber

(cm

)

(%)(cm)

Conclusions

Implementation of form-finding routines

Application to a tensile membrane roof

Identification of more relevant aspects of

the behavior through parametric analysis

Wind action and effects assessment

Sail case: development, implementation

and validation of an algorithm already

patented for real-time assessment of sail

shape. This methodology can be used for

SHM of other engineering applications

Documents

Wind Effects in Tensile Membrane Structuresconstruct/20160224_CONSTRUCT_PhD... · PhD 2016 | 3 2016 CONSTRUCT PhD Workshop Wind Effects in Tensile Membrane Structures • Objectives