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Prof Rombach Presentation

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  • TUHH - Prof. Rombach

    Introduction

    Beam and truss structures

    Spatial structures- shear walls- slabs- shells

    Material nonlinear analysis

    3-d models

    Design of real concrete structures with finite element software- model problems and errors Prof. Dr.- Ing. Gnter A. Rombach

    Hamburg University of TechnologyE-mail: [email protected]

  • TUHH - Prof. Rombach

    Special problems of concrete structures

    complex material behaviour (cracks, time dependant)

    detailing arrangement of rebars significant

    construction process significant

    complex loading exact value not known

    no mass product fast design

    massive members (Bernoulli hypothesis not valid)

  • TUHH - Prof. Rombach 3

    Zuse Z1 1936-38

    Built the first programmable computer in the world

    Argyris: Civil Engineer

    Clough: Civil Engineer

    Zienkiewicz: mathematician;lecturer in faculty of civil eng.

  • TUHH - Prof. Rombach

    The Sleipner platform

    accident

    Collapse: August 1991

    Financial loss: 250 Mio US$

  • TUHH - Prof. Rombach

    The Sleipner platform accident

  • TUHH - Prof. Rombach

    The Sleipner platform accident tricells

  • TUHH - Prof. Rombach

    The Sleipner platform accident tricells

    7

    3.453.413.252.32Tension force T1 [MN/m]

    1.661.671.350.95Tension force T1-D1 [MN/m]

    N4N3N2N1Elementmesh

  • TUHH - Prof. Rombach

    The Sleipner platform accident tricells

    8

  • TUHH - Prof. Rombach

    Sleipner platform accident

    9

    Consequences:

    distorted 8-noded volume elementsshould not be used

    qualified staff

    indenpendant checks

    Sea Troll Plattform, Bj. 1995, h=472 m (330m)

    better hard- and software more elements

    substructure techniques

    adaptive mesh refinement

    nonlinear material models

    independant checks engineering knowledge required

    Seite:

  • TUHH - Prof. Rombach

    Software faults loadcase G had not been considered since version 10.0-96

    minimum reinforcement had been estimated with fyk instead of fyd

    Errors

    10

    Numerical errors 245 - 0,8 - 245 = 0,8008

    250 - 0,8 - 250 = 0,00

  • TUHH - Prof. Rombach

    Program errors

    Software faults

    Model errorsmaterial model reinforced concrete behaves nonlinear

    loading FE-Model considers only nodal loads

    design slab, shear wall, column, tension member, shear reinforcement

    modelling size of elementstype of elementsupport conditionssingularities

    ErrorsReales Bauwerk

    Numerisches Modell

  • TUHH - Prof. Rombach

    Modelling

    12

    u2v2

    2u1

    1

    v1 MV

    N

    MBemessung

    FsdFcdV

    N

    Spannung

    Knotenlasten

    reale Einwirkung Beam element

    Beam element

    stresses

    design

    loading

    real structure

    real loading

    Numerical model

    beam -, plate-, shell-,volume elements

  • TUHH - Prof. Rombach 13

    Prof. Dr.-Ing. G. A. RombachHamburg University of Technology

    E-mail: [email protected]

    Design of real concrete structures with finite element software

    Introduction

    Beam and truss structures Spatial structures- shear walls- slabs- shells

    Material nonlinear analysis

  • TUHH - Prof. Rombach 14

    Beam or truss element

    Beam element

    Strains stresses

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    -190.

    187.

    -176.

    124.

    8.

    -137.

    138.

    -178.

    176.

    -193.

    259.

    -139.

    122.

    -141.

    142.

    horizontal membrane force

    System

    Width of beam b = 0,22 cm

    see detail

    Loading q = 1 kN/m

    2,5m

    60 80

    9,5m

    Discontinuity regions

  • TUHH - Prof. Rombach 16

    D-regions in beam or truss structures

  • TUHH - Prof. Rombach 17

    Beam with opening

    2max

    2

    810 12,5 195

    8

    q lM

    kNm

    = == =

    max / 195 / 0,6325

    N M zkN

    = = ==

  • TUHH - Prof. Rombach

    5,0m 5,0m

    50

    20

    10kN/m

    Opening 20/50cm 5050

    Model 1 Model 2 Model 3

    Beam with opening

  • TUHH - Prof. Rombach

    50.0

    -50.0

    50.0

    -50.0-49.8

    49.7

    50.4

    -50.3

    85.0

    -15.0

    29.1

    -70.9

    20.8

    -41.7-41.7 -41.7

    33.0

    -76.5

    20.7

    -42.1-40.8

    -42.8

    Bending Moment

    Shear Forces

    5,0m 5,0m

    50

    20

    10kN/m

    Opening 20/50cm

    Model 3Model 2Model 1

    Beam with opening

  • TUHH - Prof. Rombach

    Stress/Strainsection 1-1left

    Stress/Strain section 1-1right

    Model 1 Model 21

    1

    Beam with opening

    Stressessection 1-1 right

    Stressessection 1-1 left

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    compression forces tension forces

    Beam with opening - Strut-and-Tie model

    Tension tieCompression strut

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Summary 1: Beam and truss structures (D-regions)

    The Bernoulli-Hypothesis (linear strain distribution) is not valid in so-calleddiscontinuity regions. Thus beam elements, which are mostly based on a linear strain distribution, can not estimate the forces in discontinuity regions.

    It is important to model the stiffness in the discontinuity regions.

    D-regions can be designed by means of strut-and-tie models whereas themember forces of the truss systems at the boundaries can be used to estimate the forces in the struts.

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Modelling of support - single span girder

    rigid

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Modelling of support

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Modelling of support - single span truss

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Schornbachtalbridge

    Bridge column with pile foundation

    11m

    15m

    1,8m

    Ortbetonramm-pfhle d=61cm

    3m

    3,6m

    6:1

    5:1

    50:1

    2,6m

    3,04m

    1,5m

    7,22m

    1,6m

    5,72m

    1,665m

    1,225m

    50:1

    16:1

    BoredPiles

    D=0.61 m

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Bending stiffness of piles is neglected

    Estimation of pile forces

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Bridge column with pile foundation

    Numericalmodel

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    HVM

    beam

    horizontalspring

    Vertikal-feder

    n=0

    n=0,5

    n=1n=2

    ks

    k (z)=k (d).(z/d)s sn

    n= 0 bindiger Boden

    n =1 nichtbindiger Boden

    Elastic support of piles

    Beam

    Horizontal springs

    Verticalsprings

    Distribution of soilstiffness

    n = 0 cohesive soiln = 1 non-cohesive soil

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Bending moments in the piles

    H = 870 kN

    Base of pile fixed vertically

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    195.

    C=400MN/m

    pile cap cant move horizontally

    Pile cap can move

    +8

    68

    -22

    H = 870 kN

    Bending moments in the piles

  • TUHH - Prof. Rombach

    Hauptm omenteLastfall g=10 kN /m2 -146. 5-125. 0-100. 0-75 .0

    -50 .0-25 .00 .0

    25 .050 .075 .0100. 0

    Summary 02: Beam and truss models

    32

    Beam elements are based on a linear strain distribution member forces in discontinuity region can not be calculated but stiffness of the D-regions has to be considered

    Nonlinear material behaviour of concrete should be considered (e.g. torsion stiffness)

    A realistic model for the support condition has a significant influence on the memberforce of the system. Restraints, which may lead to high forces, should be omitted.

    The basic parameters of an elastic support on ground should be checked. The stiffnessmodulus of the soil is estimated by an Oedometer test, where the soil is fixed by a horizontal stiff ring. Therefore the real soil stiffness can be significant smaller.

    An inclined axis of gravity (haunches) should be modelled with regard to the shear design of a beam. System und Belastung

    Querkraft

    -747

    kN

    607k

    N -375kN

    -375kN

    Normalkraft

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