# Modeling of a reinforced concrete beam under a rolling load.

Hi, we're trying to model with ABAQUS a reinforced concrete beam under a rolling load. We want to investigate the compressive low cycle fatigue of reinforced concrete elements under a variable bending moment. We are using a Static Step (total step time: 18000 sec) and a concentrated force applied on the middle cross section with the following load history*:

0    0
1    0.048715313
2    0.115621788
3    0.19938335
4    0.299177801
5    0.413874615
6    0.542343268
7    0.683556012
8    0.836485098
9    1
10    0.864850976
11    0.738129496
12    0.618910586
13    0.505960946
14    0.398355601
15    0.295066804
16    0.194964029
17    0.096916752
18    0

*obviously, in order to represent a loading time of at least 10^3 cycles, this load history is repeated several times.

We modeled the concrete (class C20/25) with the "Concrete Damaged Plasticity" behaviour, using the following parameters:

Dilation angle: 36.31°

Eccentricity: 0.01

fb0/fc0: 1.16

K: 0.66667

Viscosity parameter: 0.002

CONCRETE COMPRESSION DAMAGE

STRESS   INEL. STRAIN   DAMAGE PARAMETER

8.4               0                      0
11.311    7.5E-005                 0
16.801    9.9E-005                 0
22.87      0.000154                0
28.004    0.000761                0
22.532    0.002558            0.193
11.332    0.005675            0.596
2.9442    0.0117331           0.897

CONCRETE TENSION DAMAGE

STRESS   CRACK. STRAIN   DAMAGE PARAMETER

1.864               0                         0
2.65            3.3E-005                   0
1.744           0.00016               0.406
0.805           0.00028               0.696
0.211           0.000665               0.92
0.053           0.001087               0.98

The beam was modeled with a 2D shell having 2 rebar layers representing the steel reinforcement (we think that's a good approximation, since this is a two-dimensional problem).

The reinforcements were modeled with an elasto - plastic behaviour, also including a kinematic hardening.

Our questions are:

1)  Is better to create a Static Step (with a cyclic load history) or a Dyrect Cyclic Step to represent the variable load?

2) Are the parameters used to model the concrete behaviour good?

3) In case that the answer to the second question is "NO", do you have any suggestions?

THANKS

### they are also my

they are also my question.

I modeled two shear wall with a steel beam coupled them under cyclic loading.

but i have a problem.i am going to verify my model with a test program. i must fit beam force - displacment curve (that is a hystersis curve)but my curve (with abaqus) haven't any degradation at consecutive cycles.what reasons are for this problem? why i have'nt any stiffness degradation in my model. i define damage parameter :dt=1 - ft/ft0 and dc=1 - fc/fc0.

what i should devote to stiffness recovery ( compression and tension recovery).