Modelling and Assessment of Deficient and Repaired Structures

Modelling and Assessment of Deficient and Repaired StructuresSafe & Sustainable Infrastructure

ABOUT THE PROJECT

This project presents a new focus for develop state-of-the-art analysis tools for concrete structures so that an assessment can be undertaken to determine if a structure is deteriorating to the point where rehabilitation or strengthening is required.

NOTABLE ACHIEVEMENTS (October 2016)

• Researchers have developed two state of the art software packages for the use of accurate modeling and assessing vulnerable reinforced concrete structures: VecTor2 (analysis of 2D reinforced concrete panels and corrosion-damaged reinforced concrete structures) and Cyrus (hybrid simulation modelling). Cyrus, which enables use of the VecTor NLFEA programs in hybrid simulation applications has been successfully applied to the assessment of deteriorated structural elements repaired with FRP materials, previously tested by others
• A pilot test program exploring full hybrid simulation capability is well underway
• Hardware and software for the test facility have been developed

PROJECT UPDATE (April 2016)

On developing improved material models, activity thus far has focused on implementing stochastic analysis capabilities into our nonlinear finite element analysis (NLFEA) programs. Stochastic analyses, using Monte Carlo simulations or Latin Hypercube Sampling, can now be performed with regards to variation in concrete and reinforcement material properties. Work has begun on stochastic modelling of rebar corrosion, with emphasis on pitting corrosion.

An experimental investigation of rebar corrosion is planned to be conducted in collaboration with the Indian research team. Work has also progressed on modelling externally applied FRP materials and modelling internally embedded FRP rebar, both done primarily by the Canadian Research team.

Cyrus, which enables use of the VecTor NLFEA programs in hybrid simulation applications has been successfully applied to the assessment of deteriorated structural elements repaired with FRP materials, previously tested by others. A pilot test program exploring full hybrid simulation capability is well underway; hardware and software for the test facility have been developed and a pilot test will take place shortly.

PROJECT UPDATE (October 2015)

Assessing the structural safety of deteriorating infrastructure remains an ongoing challenge in both India and Canada. The strength of materials and the process of deterioration are inherently random. In order to assess structural safety, a tool that captures this randomness is required. In previous work, the VecTor analysis software was developed to provide advanced modelling and analysis capabilities in predicting the behavior of reinforced concrete structures. This software has now been modified to simulate randomness. The random simulations use statistical knowledge about simple model inputs (concrete strength, steel strength, etc.) to generate statistical knowledge about structural behavior (structure strength, ductility, etc.). This statistical inference can be used to assess the safety of existing infrastructure. Models that predict the behavior of corroded reinforced concrete will next be implemented.

In related work, a multi-scale framework for mixed-type analysis of reinforced concrete structural systems, program Cyrus, has been developed. Cyrus enables combining different analysis tools, which can be based on diverse modelling approaches, while fully considering the interaction between substructures. The framework can greatly extend the application of conventional stand-alone nonlinear analysis specially in assessing the behaviour of repaired structures, beam-column joints in frame structures, and soil-structure interaction. The adequacy of the framework has been verified through mixed-type analysis of a wide range of test specimens presented in the literature. Recently, Cyrus was further extended to combine numerical models with experimental components to accommodate hybrid testing. Currently, a small-scale hybrid simulation experimental program is underway which aims to investigate the behaviour of shear-critical RC frame structures.

RESEARCH ABSTRACT

Reinforced concrete structures, if properly designed and maintained, will typically meet strength and serviceability criteria in a safe and efficient manner over the intended life of the structure. Situations often arise, however, where design codes or constructions standards were not properly followed or where insufficient attention was given to maintaining the structure. In such cases, the safety and serviceability of the structure are at risk. This is particularly true if the structure is subjected to uncommon or extreme loads, if the codes used for the design have been improperly applied or circumvented, or if the structure is deteriorating, for example due to corrosion of steel, and in need of rehabilitation. Today, with our aging infrastructure, the need exists for analytical tools providing advanced assessment capabilities so that safe and economical remedial actions can be taken if necessary. Common commercial software packages are typically of little use in this regard.

This research project presents a new focus in continuing efforts towards developing state-of-the-art analysis tools for concrete structures. Achievements to-date include well-recognized behaviour models for reinforced concrete (e.g., Modified Compression Field Theory) and a suite of advanced nonlinear finite element analysis (NLFEA) programs (i.e., VecTor). Building on this foundation, the proposed research is aimed at formulating improved modelling software for accurately assessing the performance of deficient concrete structures, particularly those that are showing distress due to corrosion of the reinforcement or deterioration of the concrete. The emphasis will be on development of practical tools applicable to the challenges faced by engineers in Canada and India today.