PREPER: Looking for the lost prestress. Multi-level strategy and non-destructive method for diagnosis of existing concrete structures
Principal researchers:
JOSÉ ROCÍO MARTÍ VARGAS
JUAN NAVARRO GREGORI
Team members:
- PEDRO SERNA ROS
- ESTER GIMÉNEZ CARBÓ
- CARMEN CASTRO BUGALLO
- TÉCNICO: F.J. MARTORELL ROMERO
Funding Agency:
Duration: 01/09/2021 – 31/08/2024
Reference: PID2020-118495RB-I00
Abstract:
The accurate determination of the residual prestressing force is essential within the context of the assessment of existing prestressed concrete structures (EPCSs), since the effect of prestressing has a major impact on the stress-deformation responses and capacities of such structures. In the prestressing design, the designer must set the prestressing force and estimate the prestressing losses, so that the structure meets its requirements over its service life. Since construction practice has not considered the incorporation of measurement devices in the EPCSs for monitoring over time, prestressing losses are usually not known, and therefore the residual prestressing force. There is great uncertainty when addressing the assessment of the extensive park of EPCSs, which has used up most of its service life. Hence, the need to move forward the scientific method and cuttingedge knowledge in this topic.
Despite these uncertainties, there are few empirical methods available, either destructive or non-destructive. The most recent is the Isolated Concrete Block Method (ICBM), based on the local decompression of concrete by introducing surface cuts. Only two pioneering applications, without direct control of the prestressing force, are known so far. Therefore, it is of great interest to investigate its application along with the prestressing force monitoring to know the sensitivity to parameters such as separation between saw-cuts, depth of cut and level of released compressive stress.
This proposal is motivated by the need to formulate reliable assessment in the field of EPCSs, within a context of a lack of regulation that forces to advance at the frontier of knowledge. The Project aims the implementation of a specific methodology for the diagnosis of residual stress-deformation state of EPCSs, and is based on the potential synergy of ICBM as an empirical basis and a multi-level structural modelling strategy following the latest trends. After the development of ICBM, it will be applied to beams from a set of designs including different combinations of variables such as concrete strength, prestressing force and eccentricity, cross-sectional depth and distribution of transverse reinforcement. With a plan developed through ten tasks, it is intended to follow a working methodology that integrates the design/modelling and experimental aspects, so that there is an almost continuous feedback between both.
ICBM, which has a clear potential to become a reference non-destructive, practical, economical and reliable method, will promote an active approach to EPCSs maintenance. In turn it will be specified how to perform structural analysis with different degrees of modelling refinement, which will most probably avoid over conservative assessments and unnecessary costs arising from decisions taken after the assessment. The development of predictive models and modelling tools for structural evaluation from their residual stress-deformation state, and the development of ICBM application guidelines, will be key aspects when reviewing design methods for estimating prestressing losses.
