Title: Closed loop control in crushing test for fibre reinforced concrete pipes
Author(s): Monte, R.; de la Fuente Antequera, A.; Dominigues de Figueiredo, A.
Publication: Symposium Paper
Appears on pages(s): 282-291
Keywords: Fibre reinforced concrete. Concrete pipes. Crushing test. Closed-loop control.
The mechanical behaviour of fibre reinforced concrete pipes (FRCP) is usually verified
through three-edge bearing test (TEBT). More recent studies propose a design approach
according to the fib Model Code 2010, involving the evaluation of mechanical behaviour in
both service (SLS) and ultimate (ULS) limit states. The challenge consists in assessing with the
proper accuracy and reliability the mechanical parameters by means of the TEBT method. This
is generally performed using a hydraulic equipment with load control and without using devices
to measure the diametric displacement. In this research program, TEBT was carried out using
three different control systems. Two closed-loop controls, using pipe diametric displacement
or actuator displacement, and an open-loop control by loading rate. The crack width
development was also measured simultaneously with the diametric displacement, only for
closed-loop control. An increase in the post-crack strength of the FRCP were observed when
the closed-loop system was used. The results show significant differences between the
mechanical performances of pipes tested in open or closed-loop control. Conversely, closedloop
tests performed with actuator displacement control or pipe diametric displacement control
show no significant differences. Crack opening measurement allows establishing a linear
correlation with diametric displacement, this permitting to establish the values corresponding
to the SLS and ULS deformation and respective loads. Consequently, the connection with the
Model Code approach becomes possible as well as the design optimization of the FRCP.