Publications by Alexander Riley Hartloper

Warping-Inclusive Kinematic Coupling in Mixed-Dimension Macro Models for Steel Wide Flange Beam Columns

Albano António De Abreu E Presa De Castro E Sousa, Dimitrios Lignos, Alexander Riley Hartloper

A warping-inclusive kinematic coupling method to be used in finite-element analysis of members featuring wide-flange cross sections is proposed in this paper. This coupling method is used in mixed-dimension macromodels that combine continuum and beam-colum ...

2022

Best-fit constraint equations for coupling mixed-dimension simulation models with wide flange cross sections

Albano António De Abreu E Presa De Castro E Sousa, Dimitrios Lignos, Alexander Riley Hartloper

A new mixed-dimension coupling method is formulated for members with (bi-symmetric) wide flange cross sections based on the idea of least squares transformations between two sets of point clouds. This coupling method imposes the minimum number of constrain ...

ELSEVIER2022

Closure to "Proposed Updates to the ASCE 41 Nonlinear Modeling Parameters for Wide-Flange Steel Columns in Support of Performance-Based Seismic Engineering" by Dimitrios G. Lignos, Alexander R. Hartloper, Ahmed Elkady, Gregory G. Deierlein, and Ronald Hamburger

Dimitrios Lignos, Alexander Riley Hartloper

ASCE-AMER SOC CIVIL ENGINEERS2021

Reduced-order Models for Simulating Coupled Geometric Instabilities in Steel Beam-columns Under Inelastic Cyclic Straining

Alexander Riley Hartloper

Numerical models that can simulate coupled geometric instabilities in steel beam-columns are required for the seismic assessment of certain steel moment-resisting frames. Reliably simulating coupled instabilities requires that the steel material is precise ...

EPFL2021

Cyclic metal plasticity model parameters with limited information: a constrained optimization approach

Albano António De Abreu E Presa De Castro E Sousa, Dimitrios Lignos, Alexander Riley Hartloper

Tensile test data for structural steels are ubiquitous. Yet, the information monotonic loading provides with respect to the material's characteristics is limited. Notably, features of inelastic response to cyclic loading, such as the Bauschinger eect, can ...

2021

Experimental behavior of iron-based shape memory alloys under cyclic loading histories

Elyas Ghafoori, Albano António De Abreu E Presa De Castro E Sousa, Diego Isidoro Heredia Rosa, Masoud Motavalli, Dimitrios Lignos, Alexander Riley Hartloper

The present paper investigates the behavior of iron-based shape memory alloys (Fe-SMAs) subjected to cyclic inelastic straining by means of uniaxial coupon experiments. The tests feature round bar coupons subjected to a broad range of uniaxial cyclic strai ...

2021

Steel column stability and implications in the seismic assessment of steel structures according to Eurocode 8 Part 3

Dimitrios Lignos, Alexander Riley Hartloper

Seismic performance assessment of new and existing steel structures based on nonlinear static (pushover) analysis necessitates the use of engineering‐oriented models that trace the nonlinear response of structural steel elements under static and cyclic loa ...

2020

Behavior of iron-based Shape Memory Alloys under Cyclic Loading Histories

Albano António De Abreu E Presa De Castro E Sousa, Diego Isidoro Heredia Rosa, Masoud Motavalli, Dimitrios Lignos, Alexander Riley Hartloper

Shape memory alloys (SMAs) have gained considerable attention in a broad range of engineering applications. In particular, iron-based SMAs (Fe-SMAs) have been recently developed and used as a cost-effect method for prestressed-strengthening of civil struct ...

2019

Proposed Updates to the ASCE 41 Nonlinear Modeling Parameters for Wide-Flange Steel Columns in Support of Performance-Based Seismic Engineering

Dimitrios Lignos, Alexander Riley Hartloper, Ahmed Mohamed Ahmed Elkady

Nonlinear static and dynamic analyses are utilized by engineers for performance-based seismic risk evaluation of new and existing structures. In this context, nonlinear component modeling criteria are typically based on ASCE 41 guidelines. Experiments on w ...

2019

Sensitivity of Simulated Steel Column Instabilities to Plasticity Model Assumptions

Albano António De Abreu E Presa De Castro E Sousa, Dimitrios Lignos, Alexander Riley Hartloper

Current experimental studies on the seismic behavior of steel wide-flange columns under multi-axis cyclic loading reveal that these members, depending on their geometric characteristics, may be susceptible to axial shortening, out-of-plane deformations and ...

2019

Revised ASCE-41 modeling recommendations for moment-resisting frame systems

Dimitrios Lignos, Alexander Riley Hartloper, Ahmed Mohamed Ahmed Elkady

Nonlinear static and dynamic analysis is utilized by engineers to evaluate the seismic behavior of new and existing structures in the context of performance-based earthquake engineering. Numerous experiments on steel moment-resisting frames and their compo ...

2018

Updates to the ASCE-41-13 Provisions for the Nonlinear Modeling of Steel Wide-Flange Columns for Performance-based Earthquake Engineering

Dimitrios Lignos, Alexander Riley Hartloper

Performance-based earthquake engineering requires numerical models that are able to reliably predict the expected component behavior of buildings under seismic excitations. The nonlinear modeling guidelines provided in ASCE-41-13 have historically been use ...

2017

Experimental and Numerical Evaluation of Steel Columns for Performance-Based Seismic Assessment of Steel Moment Frames

Dimitrios Lignos, Alexander Riley Hartloper, Ahmed Mohamed Ahmed Elkady

This paper summarizes the findings of a long term experimental program corroborated with detailed finite element simulations that investigated the hysteretic behavior of wide-flange columns in steel moment-resisting frames (MRFs) designed in highly seismic ...

2017