Three-Dimensional Dynamic Nonlocal Beam Formulation for Simulation of Damage and Failure in Reinforced Concrete Structural Elements
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Reinforced concrete (RC) structures account for the largest portion of the nation?s infrastructure. RC structures are typically subjected to complex dynamic loading conditions from natural hazards, such as earthquakes, hurricanes and tsunamis, which result in simultaneous loads in three dimensions. Accurate prediction of damage and failure of RC structures under such complex loading conditions is essential to developing new designs and quantifying the vulnerability of existing structures, and has been identified as a key need in the ?NHERI Five-Year Science Plan: Multi-Hazard Research to Make a More Resilient World?. By providing such a capability, this research will support performance-based design and risk assessment methodologies, considered in various steps of decision-making by stakeholders, including Federal and State agencies and local communities. This research will improve structure and community resilience in accurately assessing the performance of new and existing structures against natural hazards, identifying key vulnerabilities, prioritizing and guiding retrofitting/upgrading efforts, and developing and refining new designs in order to protect people and property from natural disasters. This research will train graduate and undergraduate students primarily from underrepresented minorities, will include outreach to minority-majority schools, and will allow the development of a new graduate course that will be shared with the broad engineering community. The goal of this research is to advance computational simulation and fundamental understanding of damage and failure of RC members. In doing so, this research will establish a computational element formulation capable of holistically simulating (and predicting) flexural, shear and torsional failures of RC members subjected to triaxial dynamic loading conditions generating combined axial, flexural, shear and torsional member loads. This formulation marks a paradigm shift from conventional beam-column modeling approaches by: (i) accurately describing the triaxial stress/strain state within members through higher order cross-section kinematics determined via cross-section sub-domain modeling that enforces the local equilibrium over the cross-section; (ii) naturally reproducing strength and ductility size effects by introducing both material- and member-level characteristic lengths to describe damage initiation and propagation from the material level to the member scale, and (iii) consistently simulating loading rate effects through rate-dependent material laws together with member dynamics. Because member dynamics together with rate-dependent constitutive laws eliminate the solution multiplicity of quasi-statics and reduce the problem nonlinearity, this formulation attains improved computational convergence properties, which makes it particularly efficient for highly nonlinear problems, such as those of structural damage and failure. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.