A new Distinct Element meso‐model for simulating the rocking‐dominated seismic response of RC columns

Abstract

The rocking-dominated seismic response of reinforced concrete (RC) columns is a complex mechanism that entails P-Δ effects, concrete crushing and spalling, rupture and dislocation of steel bars and stirrups, as well as combined localized failures causing splitting and shear-flexure cracking. In this paper, we present a new meso-scale numerical modeling strategy for the detailed simulation of the rocking response of slender RC columns under seismic actions. This work advances the current state-of-the-art by exploring the unprecedented use of the Distinct Element Method (DEM), originally conceived for geotechnical studies and whose applicability in earthquake engineering has been primarily limited to the assessment of unreinforced masonry sub-structures. To decrease analysis time and enable the use of DEM for RC problems, concrete is herein idealized as an assembly of solid macro-block layers of size directly proportional to their distance from expected plastic hinges. These layers are connected by nonlinear interface springs to simulate tensile and shear cracking via a simplified Mohr-Coulomb criterion. Crushing of concrete in deformable blocks is modeled using the Feenstra and De Borst strain-softening linearized compression law, while confinement and combined failures are accounted for numerically through the explicit representation of longitudinal and transversal reinforcement bars, idealized as link elements. Previous experimental static and dynamic tests on full-scale RC column specimens and results from fiber-based Finite Element and sectional analysis models are used to evaluate DEM results and quantify the influence of key modeling parameters, including block number and deformability, as well as the amount of damping. The agreement between simulated failure modes and force and displacement capacities and their experimental counterparts demonstrate the applicability of the proposed approach, while demonstrating the pros and cons of simplified numerical methods.

Intelligent Diagnosis of Concrete Defects Based on Improved Mask R-CNN

“…When the inspectors work, they must take a special detection vehicle to reach the vicinity of the defect, but there are still some defect locations that cannot be reached. At this time, some researchers have used numerical simulation techniques to assess the residual capacity of the concrete elements in question [4], such as the innovative discrete element method [5,6] and the traditional finite element method [7]. However, only the overall bearing capacity of the structure can be assessed and subtle concrete defects cannot be detected.…”

An Intensity Measure for the Rocking Fragility Analysis of Rigid Blocks Subjected to Floor Motions

“…As a very early study in this area, Housner [12] proposed a seminal framework to evaluate the seismic response of a solitary rigid block placed on a rigid base. Following this pioneering work, investigators over the world have endeavored to evaluate the rocking response of freestanding blocks, including experimental [13][14][15][16][17][18][19][20][21][22][23][24] and numerical approaches [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Early researchers have observed that a rocking motion has extremely complex dynamic characteristics and is barely "nonrepeatable" [40][41][42][43].…”

Seismic Overturning Fragility Analysis for Rigid Blocks Subjected to Floor Motions

“…As a pioneering work, the seminal framework proposed by Housner [11] for the seismic response evaluation of freestanding rigid blocks has been followed by many in-vestigators, including experimental [12][13][14][15][16][17][18][19][20] and numerical efforts [21][22][23][24][25][26][27][28][29][30][31][32][33]. To predict the occurrence of overturning, Ishiyama [34] proposed overturning criteria involving the overturning acceleration and velocity, which are the minimum peak acceleration and velocity of the input excitation needed to overturn a rigid block, respectively.…”