Presentazione della validazione di sistemi di continuità per strutture prefabbricate

Università degli Studi di Bergamo – Dipartimento di Ingegneria

ACI Italy Chapter

I Collegamenti nelle Strutture Prefabbricate

Connections in Precast Structures

Validazione di sistemi di continuità per strutture prefabbricateA. Saviotti, P. Olmati, F. Bontempi, S. Zambelli, C. Pagani, L. Sgambi

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Continuity connection is based on a few elements, designed and engineered to get

100% controlled connections, "dry" assembly and offers the chance to meet all the basic

structural design goals:

- coupling tolerance;

- ductility;

- fire resistance;

- vertical and height adjustment;

- foundation anchoring;

- foundation fixing set;

- simplified structural calculations.

Validazione di sistemi di continuità per strutture prefabbricate 2/37

Università degli Studi di Bergamo – 5 ottobre 2012 A. Saviotti, P. Olmati, F. Bontempi, S. Zambelli, C. Pagani, L. Sgambi

The present study represents an intermediate step of a larger study in which the

connecting devices will be analyzed in detail.

Differents failure mechanisms will be investigated for the node column-foundation or

beam-column node.

Last goal of the whole study is the demonstration of the efficiency of the continuity

system in question.



Continuity

sleeve

Continuity sleeve

Side view of the

continuity connection

system

Anchor sleeveAdjustment footFixing ring and

anchoring base

Continuity connections guarantee

direct transfer of the forces

between two rebars, doing away with

the need to overlap the rebars and

eliminating the risk of eccentricity in

the junction components or the bars

inside concrete elements.



Investigation

Local behavior Global behavior

Column type 1

50x50x100

Column type 2

50x50x500

Column type 3

50x50x500

Beam-Column

node

Device

of type A

Numerical

Experimental In progress Tested Tested Tested In program

In program In program In progressIn progress In progress

Experimental

Local behavior

Global behavior

Numerical

Local behavior

Global behavior

Politecnico di Milano


La Sapienza Università di Roma


Eucentre, Pavia



Column type 3



To investigate the bending

mechanism, two full-scale

specimens have been designed

and built. Both specimens are

composed of a column and a

foundation connected with

continuity devices. The column

has a square section of 50 x 50

cm and is 5 m height. The rate

of vertical reinforcement is

different for the two columns,

respectively equal to 1.70% (for

a total of 8Φ26) for the first

column and 2.55% (for a total of

12Φ26) for the second column.

We will examine the

experimental and numerical

behavior of the second

specimen.



The experimental test consists of a series of

horizontal displacements cycles imposed at the

top of the column with growing levels of drift.

The horizontal displacement is imposed in

displacement control. In addition at the

horizontal displacement a constant axial load of

400 kN is imposed to simulate the effect of

vertical load present in an existing building.



P.G. Malerba, E. Garavaglia, L. Sgambi



The device of type A is a transfer device in which the bars are screwed

to its ends. The connection is very hard because the tension present in

the first bar is converted in tension into the device by a shear

mechanism on the thread, and then in tension into the second bar.



The element of type B is a less rigid connection. The steel bars passing in

axis to the device and transmit the axial force to the mortar through

internal mechanisms of adhesion and shear.

The diffusion mechanisms and the formation of

compression struts are emphasized by the

corrugated shape of the lateral walls of the

device.



The numerical analysis shows that the

presence in the model of a discrete crack at

the base of the column (between the column

and the foundation) is required to achieve,

on a structural element, the stiffness

measured experimentally.

Two nonlinearities are presents in the model:

- Material nonlinearity

- Contact nonlinearity



Material Compression strenght [MPa]

Concrete 64.2

High strenght mortar 86.0

Yelding stress [MPa] Ultimate stress [MPa]

Reinforcement bars 450 540

Steel 355 600

The column is composed of three materials: concrete, mortar and steel. The concrete is

modeled using a two different constitutive models. A linear elastic law is used at the top

of the column and in foundation where experimentally there were no cracks. Most of

the column is modeled in non-linear field using damage concrete plasticity.



Università degli Studi di Bergamo – 5 ottobre 2012 21/37

Validazione di sistemi di continuità per strutture prefabbricate A. Saviotti, P. Olmati, F. Bontempi, S. Zambelli, C. Pagani, L. Sgambi

Beam – Column node



Treated models

2D MODEL:

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

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

•3D MODEL:

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

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

3D “A” 3D “B”

2D “A” 2D “B”



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

Beam

L=3770 mm

Column

H=4700 mm

STRUCTURE





BOUNDARY CONDITIONS AND LOADS

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

Total of around 142941 degree of

freedom

Two-node straight truss

elements (L2 TRU)

Two-node, two-

dimensional class-II

beam element (L7BEN)

Longitudinal reinforcement steel

Stirrups



MODEL “A”

Displacements

MODEL “B”

mm mm

LINEAR ANALYSIS

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

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



NON LINEAR ANALYSIS

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



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

NON LINEAR ANALYSIS

MODEL “A”MODEL “B”

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

mmmm

3D



References

A. Saviotti, P. Olmati & F. Bontempi (2012), “Finite element analysis of innovative solutions of precast concrete beam-column

ductile connections”, 6th International Conference on Bridge Maintenance, Safety, Management, Resilience and Sustainability

(IABMAS 2012), Stresa, Italy. Editor: Taylor & Francis Group.

L. Sgambi, P. Olmati, F. Petrini, F. Bontempi (2011), “Seismic performance assessment of precast element connections”, 2011 PCI

Annual Convention and National Bridge Conference, Salt Lake City, USA.

L. Sgambi, S. Zambelli, C. Pagani, F. Bontempi (2011), “Experimental and Numerical Assessment of a Special Joint Connection for

Precast Columns”, 2011 World Congress on Advances in Structural Engineering and Mechanics (ASEM11+), Seoul, Korea. Editor:

Techno-Press.

F. Bontempi P. Olmati F. Petrini A. Saviotti L. Sgambi



Presentazione della validazione di sistemi di continuità per strutture prefabbricate

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