Document Type
Dissertation
Date of Award
8-30-2020
Degree Name
Doctor of Philosophy in Civil Engineering - (Ph.D.)
Department
Civil and Environmental Engineering
First Advisor
Matthew J. Bandelt
Second Advisor
Methi Wecharatana
Third Advisor
M. Ala Saadeghvaziri
Fourth Advisor
Bruno M. Goncalves da Silva
Fifth Advisor
Ezra Jampole
Abstract
High-Performance Fiber-Reinforced Cementitious Composites (HPFRCCs) have made striking advances over the last two decades as an alternative material to replace ordinary concrete in regions of high seismic intensities. In contrast to ordinary concrete which has a brittle tensile response, HPFRCCs exhibit tensile strain hardening and multiple crack propagation. The application of HPFRCC in various structural components demonstrate effectiveness by improving damage resistance, deformation capacity, and energy absorption capacity. Despite these benefits, the failure mode of reinforced HPFRCC components is dominated by reinforcement fracture unlike traditional reinforced concrete components which fail in flexure by crushing. The unique behavior of HPFRCC members necessitates the development of efficient numerical models and simulation techniques that can predict the nonlinear response of structures using ductile concrete materials. In this dissertation, modeling tools and methods are developed to simulate the flexural response of HPFRCC members and are applied to evaluate the collapse risk of frame structures using HPFRCCs in potential plastic hinge region of Beams.
First, a fiber-hinge lumped-plasticity model is adopted to simulate the non-linear response of reinforced HPFRCC components and material level modeling parameters are calibrated. A simple expression for plastic-hinge length is developed as a function of cross-section properties to predict the force-deformation response and the deformation associated with reinforcement fracture. Inaccuracies in the initial stiffness and cyclic response are mitigated by calibrating the rotational stiffness of an elastic spring and cyclic degradation parameters of a steel material model. The proposed modeling strategy is evaluated by comparing the strength, energy absorption capacity, drift at onset of reinforcement fracture and intermediate tensile strains.
Second, a spring-hinge model is adopted to simplify the modeling strategy and further improve the numerical stability and predictions of cyclic behavior. A large-scale experimental database of 36 specimens with variability in material properties, geometry, testing configuration, and fiber types is developed. Backbone parameters are selected using a mechanics-based approach combined with calibration of hysteretic parameters to match an energy-based damage index. Forward stepwise regression analysis is conducted to develop an empirical equation for a stiffness reduction factor and a cyclic strength degradation parameter as functions of material properties and cross-section geometry. The spring-hinge models are then applied to a four story archetype reinforced concrete frame structure using incremental dynamic analysis to compare the seismic performance of reinforced concrete structures with and without ductile concrete materials in terms of median collapse capacity, collapse fragility curve, mean annual frequency of collapse, and the sequence of hinge formation in collapse mechanisms.
The final phase of the research study investigates the seismic performance of a group of six special moment resisting frames (SMRF) with HPFRCC material in plastic-hinge regions. This study quantifies the effect of design variants, height and frame configuration on collapse risk. The research program provides a method to simulate the performance of ductile cement-based materials under large deformations, including collapse, and will improve the performance-based earthquake engineering analysis techniques for structures using ductile cementitious materials.
Recommended Citation
Tariq, Hasan, "Modeling strategies for structures using ductile concrete materials in seismic applications" (2020). Dissertations. 1751.
https://digitalcommons.njit.edu/dissertations/1751
