Tesi angela saviotti

a. a. 2011-2012

Faculty of Civil and Industrial Engineering

Department of Structural and Geotechnical Engineering

“FINITE ELEMENT ANALYSIS OF INNOVATIVE SOLUTIONS OF

PRECAST CONCRETE BEAM-COLUMN DUCTILE CONNECTIONS”PRECAST CONCRETE BEAM-COLUMN DUCTILE CONNECTIONS”

Advisor:

Prof. Ing. Franco Bontempi

Co-advisor:

Ing. Pierluigi Olmati

Candidate:

Angela Saviotti

Treated models

2D MODEL:

-Model “A” with mortar stratum for beam-column connection;

-Model “B” without mortar stratum for beam-column connection.

“Finite element analysis of innovative solutions of precast concrete beam-column

ductile connections”

2D “A” 2D “B”

Faculty of Civil and Industrial EngineeringDepartment of Structural and Geotechnical Engineering 2/25

•3D MODEL:

-Model “A” with mortar stratum for beam-column connection;

-Model “B” without mortar stratum for beam-column connection.

3D “A” 3D “B”

“Finite element analysis of innovative solutions of precast concrete beam-column

ductile connections”

•FEM analytical program: DIANA V. 9.3

•Geometry and Mesh of the structure, to assign boundary

conditions and loads: Midas FX+ for DIANA

•Non-linear mechanisms :

-Cracking of the concrete

3/25

-Yielding of the steel.

Faculty of Civil and Industrial EngineeringDepartment of Structural and Geotechnical Engineering

CONCRETE – Total Strain Crack Model

Tensile Behavior Compressive Behavior

STEEL – Von Mises

Angela Saviotti - Finite element analysis of innovative solutions of precast concrete beam-column ductile connections

Beam

L=3770 mm

Column

H=4700 mm

STRUCTURE

4/25Faculty of Civil and Industrial Engineering


BOUNDARY CONDITIONS AND LOADS

FIRST LOAD CONDITION

SEISMIC SITUATION

2D

Beam-Column

joint failure after

earthquake -

http://strutturisti.

wordpress.com/


5/25

SECOND LOAD CONDITION

ACCIDENTAL SITUATION


The Bombing of the Federal

Building in Oklahoma City -

http://911research.wtc7.net/ind

ex.html


MODEL “A” MODEL “B”



MODEL 2DMESH

Four-node quadrilateral plane

Concrete, Mortar, Rubber and Steel Plates


Beam and Column:

Concrete C40/50

Rubber padConnection

Stratum:

Mortar

Steel Plates

MODEL “A”

MODEL “B”

7/25

Four-node quadrilateral plane

stress elements (Q8MEM)

Three-node triangle plane stress

elements (T6MEM)


MODEL “B”

Zoom of Beam-Column jointReinforcing Steel

Two-node straight truss

elements (L2 TRU)

Linear Elasticity Ideal Plasticity Linear Elasticity Ideal Linear Elasticity

Tension Softening

curve based on

fracture energy

A1 X X X

B1 X X X

A2.1 X X X

B2.1 X X X

A3.1 X X X

B3.1 X X X

A4.4 X X X

B4.4 X X X

STEEL CONCRETE

Compressive Behavior Tensile Behavior

NON LINEAR ANALYSIS

FIRST LOAD CONDITION : Applied Horizontal Force at the top of the column 2D




Linear Elasticity Ideal Plasticity Linear Elasticity Ideal Linear Elasticity

Tension Softening

curve based on

fracture energy

STEEL CONCRETE

Compressive Behavior Tensile Behavior

FIRST LOAD CONDITION : Applied Horizontal Force at the top of the column

NON LINEAR ANALYSIS

2D


A1 X X X

B1 X X X

A2.1 X X X

B2.1 X X X

A3.1 X X X

B3.1 X X X

A4.4 X X X

B4.4 X X X



NON LINEAR ANALYSIS – CYCLIC ANALYSIS

MODEL “A”

SECOND LOAD CONDITION : Imposed vertical displacement at the top of the column

Deformed

configuration developed

by the structure at STEP

n. 25 imposed maximum

displacement δ=80 mm.

2D




MODEL “A”

Step 25, imposed

displacement δ=80

mm

Step 50, imposed

displacement δ=0

mm

Step 80, imposed

displacement δ= - 80 mm

Step 110, imposed

displacement δ=0 mm

Step 25

Step 50Step 80

Step 110

2D



NON LINEAR ANALYSIS – CYCLIC ANALYSIS



Step 25 σmax=450 .0 N/mmq Step 50 σmin = - 450 .0 N/mmq

Step 80 σmin= - 450 .0 N/mmq Step 110 σmin= - 203.25 N/mmq

STRESS on reinforcing steelCRACKING STATUS

Step 25

Step 50 Step 80

Step 1


12/25Faculty of Civil and Industrial EngineeringDepartment of Structural and Geotechnical Engineering

MODEL 3DMESH

Four-node, three-side iso-

parametric solid pyramid

elements (TE12L)

Concrete, Mortar, Rubber and Steel Plates

158634 solid elements

9106 bar elements

31639 nodes Two-node straight truss




31639 nodes

Total of around 142941 degree of

freedom

Two-node straight truss

elements (L2 TRU)

Two-node, two-

dimensional class-II

beam element (L7BEN)

MODEL “A”

Displacements

MODEL “B”

mm mm

LINEAR ANALYSIS

FIRST LOAD CONDITION: Applied Horizontal Force of 600 kN at the top of the column

3D




MODEL “A”

Stress on reinforcing steel

MODEL “B”

LINEAR ANALYSIS

FIRST LOAD CONDITION: Applied Horizontal Force at the top of the column


c



NON LINEAR ANALYSIS

FIRST LOAD CONDITION : Applied Horizontal Force at the top of the column 3D





NON LINEAR ANALYSIS

MODEL “A”MODEL “B”

mmmm

3D


17/25

Deformed configuration developed by the structure at

STEP 20 – Fmax= 390.2 kN, δmax=88.6 mm.

Deformed configuration developed by the structure at

STEP 15 - Fmax= 269.83 kN, δmax=87.27 mm


NON LINEAR ANALYSIS: Stress on Reinforcing Steel


STEP 5 Fmax= 128 kN,

δmax=5.17 mm

σmax=108.21 N/mmq


STEP 5 Fmax= 128.7 kN,

δmax=6.97 mm

σmax=233.0 N/mmq


3D




δmax=12.75 mm –

σmax= 206.66 N/mmq


δmax=88.56 mm

σmax=450.0 N/mmq

STEP 15 Fmax=270 kN,

δmax=87.27 mm

σmax=450.0 N/mmq


δmax=16.9 mm

σmax=365.0 N/mmq




δmax=5.17 mm

σmax=108.21 N/mmq



δmax=6.97 mm

σmax=233.0 N/mmq

3D





δmax=12.75 mm –

σmax= 206.66 N/mmq


δmax=88.56 mm

σmax=450.0 N/mmq


δmax=87.27 mm

σmax=450.0 N/mmq


δmax=16.9 mm

σmax=365.0 N/mmq

FIRST LOAD CONDITION: Applied Horizontal Force at the top of the column

NON LINEAR ANALYSIS: Cracking Status



δmax=5.17 mm


δmax=6.97 mm

3D





δmax=12.75 mm


δmax=88.56 mm


δmax=16.9 mm


δmax=87.27 mm

NON LINEAR ANALYSISMODEL “A” MODEL “B”

Deformed

configuration developed

by the structure at LAST

STEP imposed

displacement δ=120 mm.

Deformed

configuration developed by

the structure at LAST STEP

imposed displacement

δmax=150 mm

SECOND LOAD CONDITION : Imposed vertical displacement at the top of the column 3D




Force-Displacement graph: Model “A” Vs. Model “B” Stress–Strain graph of beam-column ductile connection Model “A” Vs

Model “B”





δmax=10 mm

σmax=268.1 N/mmq


δmax=10 mm

σmax=196.41 N/mmq

STEP 5 Fmax= 232.5kN,

δmax=50 mm

σmax=450.0 N/mmq


δmax=50 mm

σmax=348.3N/mmq

3D




STEP 12 Fmax= 223.13

kN, δmax= 120 mm

σmax=450.0 N/mmq

σmax=348.3N/mmq


kN, δmax=120 mm

σmin=-450.0 N/mmq

NON LINEAR ANALYSIS: Crack Strain




δmax=10 mm

εknn=0.00242 %


δmax=10 mm

εknn=0.00703 %

3D




STEP 5 Fmax= 232.5kN,

δmax=50 mm

εknn=0.0359 %


kN, δmax= 120 mm

εknn=0.224%


δmax=50 mm

εknn=0.0548 %


kN, δmax=120 mm

εknn=0.132 %

• Structural continuity is an important problem.

•DIANA software, modeling the nonlinear behavior of concrete and mortar using total

strain crack model. The reinforcing steel is modeled by a bilinear plasticity model

• The full load capacity of the bars is developed without the failure of the concrete and

the mortar


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• The progress of the cracking of the concrete is well reproduced.

• The similarity between the results obtained with two different finite

element programs, the previously mentioned DIANA and ASTER.

• The role of the mortar stratum is weighted

• The introduction of the connectors inside the mass of concrete.


2D


25/25Faculty of Civil and Industrial EngineeringDepartment of Structural and Geotechnical Engineering

3D

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