Dynamic Behavior of Concrete: Constitutive Models - Dynamic Behavior of Concrete and Seismic Engineering - page 56

the response is initially of transient type, then a quasi-stationary vibration regime
develops if the structure stress is exerted for a period of time that is long relative to
its natural frequencies, as is the case during an earthquake . The strain rates reached
are lower than those observed at the location of an impact. The behavior of the
structure can be described by the strength of materials theory, i.e. the structure can
be modeled by means of plates and beams subjected to traction, compression or
bending. However, the strain modes can be completely different to those observed
under static loading.

2.1.1.3. Analyses of the failure elementary phenomena

We consider a reinforced concrete wall receiving a dynamic loading on one side
(Figure 2.1). The observed phenomena are the following:

- concrete compaction near the loaded side;

- scabbing on the non-loaded side;

- failure of the structure under shear or bending.

Here we describe the mechanisms separately; actually, they are linked and
simultaneous.

Shear
Bending

Compression
Compaction

Scabbing

Figure 2.1. Fracture mechanism

2.1.1.4. Compaction of the loaded side
In the first microseconds and in the case of high-intensity loading (impact from a
solid or strong pressure), the loaded side is subjected to high pressure and the
superficial concrete is reduced to powder. A volume reduction caused by the porous
structure of the material collapsing occurs. The stress state is close to that of a uni-
axial strain and to approximately model that behavior, we resort to the so-called