Multiscale and Multiphysics Simulation of Reinforced Concrete Structures

Sustainability – the ability of being durable, reliable, and economically affordable during the entire lifecycle – and Resiliency – the capacity of withstanding exceptional loads such as unintentional overloading, high winds, earthquakes, and man-made hazards – are the two key characteristics of modern structural systems. Scientists, engineers, educators and policy makers have the responsibility to ensure that our structures are both sustainable and resilient. The overarching goal of this project is to improve the capability of the civil engineering community to analyze and design sustainable and resilient structures. Towards this goal, the specific research objective of this proposal is to formulate and validate a multiscale and multiphysics computational framework for reinforced concrete structures based on a three-scale description: plain concrete scale, structural element scale, and full-structure scale. Intellectual Merit. The objective stated above will be accomplished by carrying out three main research tasks in which a mesoscale model, the so-called Lattice Discrete Particle Model (LDPM), will be used as foundation for the multiscale models formulated at the various scales. The first task deals with the multiscale modeling of plain concrete. LDPM will be first formulated to account for aging and deterioration effects induced by freeze-thaw cycles and, in addition, it will be equipped with the ability to simulate shrinkage and creep. Next, an incremental macroscopic homogenized continuum model will be obtained by exploiting a homogenization technique that can handle non-periodicity and nonlinear behavior. The second task focuses on the multiscale modeling of reinforced concrete structural elements. Rebars will be modeled as cylindrical solids and their mechanical behavior simulated by threedimensional finite elements featuring elastic-plastic constitutive behavior. They will be then coupled with LDPM and an appropriate bond law will be formulated to simulate slippage and concrete crushing occurring in the vicinity of the reinforcement ribs. At this scale, rebar deterioration due to corrosion as well as the expansive character of corrosion products will be considered. Evolution laws for rebar corrosion will be formulated on the basis of availability at the rebar surface of corrosive agents as predicted by the simulation of water and ion transport through uncracked and cracked concrete. Finally, the multiscale technique used in the first task, will be exploited to obtain a macroscopic continuum model embedding the effect of intact and deteriorating reinforcement. The third task deals with the multiscale modeling of reinforced concrete frames. The basic idea is to model frames by systems of beam-like elements whose incremental nonlinear behavior stems from the solution of separate structural element scale problems where the driving boundary conditions are given by the nodal degrees of freedom at the full-structural scale. The complete multiscale framework will be employed only in critical regions, as identified by preliminary elastic analyses, and elastic beam elements will be used elsewhere. Broader Impact. The PI plans to undertake a wide range of activities aimed at broadening the impact on education, promotion of diversity, and enhancing society benefits. The research team will foster and develop further existing relationships with K-12 schools in the Chicagoland area especially in underprivileged neighborhoods from the southern portion of the city of Chicago. The PI and his RAs will work wit