The research project VisCoDyn was completed – 'Innovative method for continuous monitoring of co
About Project
Creep of reinforced concrete has been attracting a great deal of attention recently due to the long term deflections that largely overcame the design values of several bridges throughout the world, such as the well-known case of the Palau Bridge and others. The resulting serviceability problems cause very expensive repairs to be necessary.
The importance of adequate knowledge of concrete creep behavior is also recognizable in several other situations: (i) disproportionate creep deflections due to premature loading; (ii) need for adequate deflection prediction and prestress compensations during the construction of staged cantilevers; (iii) inaccuracies in the estimation of self-induced stresses in concrete at early ages.
Even though the importance of concrete creep is widely recognized, the design code approaches are relatively simplified, and research efforts still struggle with experimental difficulties both at very early ages of testing (less than 72h of age) and at long term (decades). In fact, it is probably due to current experimental limitations and relatively scarce comprehensive sets of data focused on these two opposing time spans, that the existing models for creep behavior tend to exhibit limitations in such concern.
The intent is to explore the possibility of using dynamic test approaches to continuously assess viscoelastic properties of concrete, with the proposal of a new methodology termed VisCoDyn. Such innovative implementation can be achieved through the submission of a concrete specimen (e.g. a beam) to a known dynamic excitation. According to the theory of viscoelasticity, the deflection response of the beam to the known excitation allows the identification of viscoelastic parameters.
The project's Principal Investigator, Miguel Azenha, is a specialist in the field of concrete's early age behaviour, with several publications, including a patent for an innovative method for assessing concrete's elastic modulus since casting (EMM-ARM).
The project's PhD student, José Granja, is writing his PhD thesis "Continuous characterization of stiffness of cement‐based materials: experimental analysis and micro-mechanics modeling" and has experience with dynamic characterization of mechanical properties since early ages.
VisCoDyn is a project that began in March 2014 and ended in February 2015. During this 12 months, the tasks developed consisted in:
Task 1: Equipment acquisition, training and software development
Task 2: Assembly of the experimental setup and preliminary testing/tuning
Task 3: Experimental program and round-robin testing
Task 4: Analytical and numerical evaluation of creep data
Task 5: Dissemination of results and connection with industry
