Concrete structures decommissioning by blasting: FEM simulation.

 

Courtesy of Innocente Porrone and Alberto Goio

 

 

 

ABSTRACT

 

Studies and methods are described to set up FEM models describing the decommissioning by blasting of concrete structures.

 

Interventions are designed so as to minimize the impact on neighbouring areas and to avoid services hold up.

 

Both static and transient dymanics, linear and non-linear analyses were carried out on Straus 7 overall or simplified models, to investigate the spreading of plastic zones, the plasticity margin, and the evolution of shapes during demolition.

The non-linear static analysis allows to investigate the structural behaviour far above the elastic treshold, taking into account geometric non-linearities, second order effects, and the typical softening of concrete.

The effect of explosions was simulated by progressively eliminating the undermined elements, so as to guess the deformed shapes, and the cinematic sequence which should likely happen

 

In addition, a variety of linear and non-linear static analyses were performer, to operate under safe condition throughout the preparatory phases of the structure.

1.       Introduction

The works described below were designed by IPE Progetti, an engineering company based in Turin. Applied regulations and standards include: D.M. 14 Gennaio 2008 Eurocodes 2,3, 7 and 8, as well as the legislative decrees on the topic. Past experiences of IPE progetti with Italian dismantling companies contributed an important know-how.

 

The approach was employed to dismantle the following structures:

 

-         Punta Perotti-Bari

-         Eur-Roma Towers

-         Commercial Building - San Giuliano Milanese

-         Vinavil Tower - Villadossola

2.       Punta Perotti-Bari

These buildings are by far one of the most famous eco-monster on our territory. A symbol of arbitrary wild building. The work is two 14-storey buildings, orthogonal to the shore. The massive concrete structure is based on the heavy plate and walls systems of the stairswells. A non-linear transient dynamics FEM simulation was used to drive the collocation of the explosive charges and their time sequence, so as to control the collapse and the collapse directions. In fact the main coastal road of the city on the one side of the building, and the railway track just 10 m far on the other side limit significantly the semi-overturning of the structure. The simulation of the collapse was extremely important to meet these requirements. Moreover, before the blasting, the building was weakened in certain key points, so as to help controlling the collapse. These aspects were designed by IPE progetti as well.

 

Work status: dismantled.

 

Pictures of the collapse

 

Modelling the collapse

 

3.       Eur-Roma Towers

The work was awarded by the Comune di Roma, who launched a tender for the dismantling of some buildings at the EUR. The simulation which is shown here is about the ENI building, and was based on a non-linear transient analysis carried out on a fully 3/D model. The explosion was designed to generate a semi-implosion mechanism combined with a partial overturning towards one of the fronts of the building. The analysis covers the initial phases of the collapse, through 15 short-time sequence of explosions. The building is a 17-storey concrete frame, with a regular prismatic shape and a central skylight shaft.

 

Work status: dismantled

 

 

Explosion 0.32 sec.	Explosion 0.50 sec.
Explosion 0.54 sec.	Explosion 1.0 sec.
Explosion 1.58 sec.

 

4.       Commercial building – San Giuliano Milanese

Quite alike the former examples, these buildings have a heavy concrete structure, with side concrete slabs, and rigid stairswells. The y-shaped plan geometry requires positioning the explosive charges in such a way to cause a combined semi-implosion and a building-centric overturning. The transient dynamics study allowed to forecast the behaviour accurately.

 

Sequence of collapse

 

Modelling of collapse

 

5.       Vinavil Tower- Villadossola

The structure is a carbide storage facility, and is presently abandoned. It was build in the mid twentieth century, and is 7 m far from the railway track.

The plan dimensions are 32.30 by 15.20, with the main edge parallel to the railway track. The height is 43 m. The facility is eight silos, by two rows of four, with an off-the-center elevator in a stairswell and a technical volume on the top. The facility is entirely a steel structure.

The transient phase of the collapse was studied, by simulating the behaviour with non linear transient dynamics models.

Since the explosive charges cannot be placed on steel elements, they were placed on new concrete colums supporting the downstream silos. The model was used to check that, during all the collapse sequence, the upstream colums would not plasticize. In fact a collapse of the upstream silos would damaged the railway track. To prevent this risk, a diagonal bootstrap was inserted between the top of the upstream colums, and the base of the front column.

 

 

Work status: dismantled

 

 

Dismantling sequence

IL FILE AVI

 

6.       References

NAD  (2010). DEMOLIZIONI CIVILI ED INDUSTRIALI, linee guida.Vol I e Vol II

HEOPLI (2008). INGEGNERIA DELLE DEMOLIZIONI Principali tecniche di demolizioni civili