aristotle university of thessaloniki faculty of engineering school of civil engineering postgraduate

192 Pages·2017·14.98 MB·English

by  Theocharis Kartalis Kaounis

ARISTOTLE UNIVERSITY OF THESSALONIKI
FACULTY OF ENGINEERING
SCHOOL OF CIVIL ENGINEERING
POSTGRADUATE SPECIALIZATION PROGRAMME
«EARTHQUAKE ENGINEERING AND SEISMIC DESIGN OF STRUCTURES»

Master Thesis

«GiD+OpenSees Interface: A major extension to nonlinear finite element analysis»

Theocharis Kartalis Kaounis
Civil Engineer, AUTh

Committee members:
Assistant Prof. Vassilis K. Papanikolaou (Supervisor)
Assistant Prof. Dimitrios Pitilakis
Assistant Prof. George Stefanou

Thessaloniki, November 2017
Acknowledgments

Completing my Master Thesis as part of my Postgraduate Specialization studies, I could not
leave out the paragraph in which I want to express my deep thanks and give the credits to the
people who supported my work and me for finishing my Master Thesis.
I would first like to express deep gratitude to my thesis supervisor Vassilis K. Papanikolaou,
Professor (Assistant) at the Laboratory of Reinforced Concrete and Masonry Structures, School
of Civil Engineering at Aristotle University of Thessaloniki in Greece, for his continuous
guidance and the time he dedicated for the whole project. His frequent counselling and advice,
that have been critical for the outcome of the present thesis, is mostly appreciated.
Moreover, I would like to thank the members of my Dissertation committee, Dimitrios Pitilakis,
Assistant Professor at Laboratory of Soil Mechanics and Geotechnical Earthquake Engineering,
Division of Soil Mechanics at Aristotle University of Thessaloniki and George Stefanou,
Assistant Professor at Laboratory of Structural Analysis and Dynamics of Structures, Division
of Structural Engineering at Aristotle University of Thessaloniki. Each of them has provided
me extensive personal and professional guidance and taught me a great deal about scientific
research.
Last but not least, I am obliged to thank my parents, Maria and Nikolaos, as well as my whole
family and friends for their continuous support all these years, which definitely contributed to
the accomplishment of my studies.
ABSTRACT

The objective of this dissertation is to present a new graphical user interface that has been
recently developed for OpenSees, which seamlessly connects the OpenSees solver with the
general pre/post-processor GiD including its recent extension to nonlinear finite element
analysis. This interface, available as open-source, is easily installed in the GiD graphical
environment and provides an extended set of user dialogs and tools to efficiently create model
geometry, assign materials, elements and boundary conditions, select various analysis options
and finally invoke the OpenSees solver to execute the analysis. The interface automatically
transforms the bulk of numerical results produced by OpenSees to a GiD compatible format,
for the user to take advantage of the versatile GiD graphical postprocessor. This includes a
deformed shape viewer with animation capabilities, force/stress/strain vectors and contours,
line diagrams and x-y graphs. At the present state of development, majority of advanced
modeling capabilities of OpenSees are supported, which renders the interface as a promising
alternative to the cumbersome code-based modeling, considerably shortening the respective
learning curve, especially for new and inexperienced users.
ΠΕΡΙΛΗΨΗ

Η παρούσα μεταπτυχιακή εργασία έχει ως κύριο στόχο την παρουσίαση ενός νέου γραφικού
περιβάλλοντος που αναπτύχθηκε πρόσφατα για το πρόγραμμα ανάλυσης OpenSees που
χρησιμοποιεί τη μέθοδο Πεπερασμένων Στοιχείων, καθώς και των εκτεταμένων δυνατοτήτων
που υποστηρίζονται πλέον στο πλαίσιο της μη γραμμικής ανάλυσης. Πρόκειται για τη
συνεργασία του OpenSees με το γενικής χρήσης πρόγραμμα προεπεξεργασίας και
μετεπεξαργασίας GiD μέσω της ανταλλαγής αρχείων. Το γραφικό περιβάλλον, διαθέσιμο
πλέον ως ανοικτού κώδικα πρόγραμμα, αποτελεί μια επέκταση στο γραφικό περιβάλλον του
GiD και παρέχει παράθυρα αλληλεπίδρασης με το χρήστη καθώς και πλήθος εργαλείων που
αφορούν τη σχεδίαση, τον ορισμό υλικών, στοιχείων, συνοριακών συνθηκών κλπ., τη
διακριτοποίηση, καθώς και πληθώρα επιλογών ανάλυσης, για την οποία λαμβάνει χώρα το
πρόγραμμα OpenSees. Το πρόγραμμα αυτόματα μετατρέπει τα ογκώδη αριθμητικά
αποτελέσματα που εξάγει το OpenSees σε ειδικά αρχεία για την εισαγωγή τους στο γραφικό
περιβάλλον μετεπεξαργασίας που παρέχεται από το GiD, μέσα από το οποίο ο χρήστης μπορεί
να παρακολουθήσει τα επιθυμητά αποτελέσματα όπως παραμορφωμένους φορείς, δυνάμεις,
τάσεις, παραμορφώσεις μέσω διανυσμάτων ή με κλίμακα χρωμάτων, διαγράμματα
εφαρμοσμένα πάνω στον φορέα καθώς και διαγράμματα μορφής x-y. Με αυτόν τον τρόπο το
παρόν πρόγραμμα αποτελεί ένα εναλλακτικό και πολλά υποσχόμενο εργαλείο προσομοίωσης,
ανάλυσης και μετεπεξαργασίας μοντέλων, έχοντας ως παράλληλο στόχο την εύκολη και
γρήγορη ανάλογη εκπαίδευση, ειδικά για νέους και άπειρους χρήστες του OpenSees.
Table of Contents
Introduction ............................................................................................................... 1
General ................................................................................................................... 1
Objectives ............................................................................................................... 2
Overview ................................................................................................................. 3
User Manual .............................................................................................................. 4
Introduction ............................................................................................................. 4
General ................................................................................................................... 5
Installing/Uninstalling the Interface ...................................................................... 5
Loading the OpenSees problem type .................................................................. 6
Pre-Processor ......................................................................................................... 9
General ................................................................................................................ 9
Theme ................................................................................................................. 9
Units .................................................................................................................... 9
Problem Type Transformation ........................................................................... 10
Reset to new Problem Type .............................................................................. 10
Geometry Modeling ........................................................................................... 11
Materials/Sections F-D Types ........................................................................... 16
Section F-D models ........................................................................................... 18
Steel Uniaxial Materials ..................................................................................... 27
Concrete Uniaxial Materials ............................................................................... 36
Other Uniaxial Materials .................................................................................... 43
Combined Materials........................................................................................... 53
nD Materials ...................................................................................................... 55
Element Types .................................................................................................. 67
Beam Column Elements .................................................................................... 69
Beam-Column Local Axes ................................................................................. 72
Truss Elements ................................................................................................. 73
Surface Elements .............................................................................................. 74
Volume Elements .............................................................................................. 76
Conditions ......................................................................................................... 77
Zero Length Elements ....................................................................................... 78
Records ............................................................................................................. 79
Restraints .......................................................................................................... 82
Constraints ........................................................................................................ 83
Loading Parameters .......................................................................................... 85
Masses .............................................................................................................. 89
Rayleigh Damping ............................................................................................. 90
Dead Loads ....................................................................................................... 92
General Data ..................................................................................................... 94
Intervals Data .................................................................................................... 96
Output Options ................................................................................................ 100
Meshing Options ............................................................................................. 101
Analysis Options .............................................................................................. 104
GiD+OpenSees menu ..................................................................................... 107
Processor ............................................................................................................ 112
OpenSees to GiD converter ............................................................................ 112
Post Processor .................................................................................................... 113
View Results and Deformation ........................................................................ 115
Plot Graphs ..................................................................................................... 119
Animation ........................................................................................................ 121
Quick Start .......................................................................................................... 124
Tutorial 1 – Static and Modal Analysis of a Three-Story Building .................... 124
Tutorial 2 – Pushover Analysis of a Three-Story Building................................ 138
Tutorial 3 – Dynamic Analysis of a Three-Story Building ................................. 149
Tutorial 4 – Nonlinear Reversed Cyclic Static Analysis on Beam-Column Joint
........................................................................................................................ 154
Tutorial 5 – Site Response Analysis of a Layered Soil Column ....................... 161
Tutorial 6 – Pushover Analysis on 2D Frame considering Soil sustainability .. 174
REFERENCES ....................................................................................................... 183

1

Introduction
General
Nowadays, Engineering students and researchers as well use almost exclusively computer
programs for the modeling and analysis of structural and geotechnical problems. The vast
majority of these programs are based on the Finite Element Method with which, complicated
geometrical problems can be solved easily enough where analytical solutions cannot be
obtained. Furthermore, nonlinear dynamic and static analysis is used more and more in the
assessment of existing structures in regions of high seismic risk and in the development of
retrofit strategies. The Open System for Earthquake Engineering Simulation (OpenSees) is one
of most powerful Finite Element Analysis programs which is deeply established in the student
and research community despite the fact that it is a text-based solver which makes it hard to be
used from inexperienced users without programming skills. More specifically, the OpenSees
was developed as open-source at the PEER Center [1] and is increasingly popular analysis
software framework in earthquake engineering research, since it provided a robust solver with
numerous standard and advanced constitutive laws, finite element types, boundary conditions
and analysis capabilities. However, both the analysis solver and the produced result files are
text-based, which requires a prior knowledge of TCL coding, even for building simple models.
More importantly, the bulk of numeric results, especially when large in size, require the
development of ad-hoc postprocessing tools (e.g. MATLAB) for easier interpretation via
plotting or visualization. The above disadvantage is often a deterring factor for new users to
adopt OpenSees in their research, usually resorting to other software packages with graphical
capabilities. Consequently, there is a great need for a graphical user interface allowing users to
deeply learn and understand OpenSees modelling as well as allowing them to model difficult
geometrical problems in greatly reduced time.
GiD+OpenSees Interface was first developed in the context of the writer’s diploma thesis in
cooperation with Evangelos Protopapadakis and Theocharis Papadopoulos under the
supervising and contribution of Assistant Prof. Vassilis K. Papanikolaou. At that point, the
interface was limited to elastic linear analysis only but including all the geometry capabilities
and functions that GiD provides and extending mainly the OpenSees geometry modelling
capabilities. It was very soon incorporated into the academic community, being a software
package analysis tool of a few diploma theses, which formed a key role to further development
and validation of the GiD+OpenSees Interface. The writer, continuing his studies on
2

postgraduate level, was extending and upgrading the Interface functionalities by placing
emphasis on the non-linear (static and dynamic) finite element analysis.
Objectives
The main goal of this dissertation was to extend the standard capabilities of the GiD+OpenSees
Interface to few advanced ones supported by OpenSees, so that it will be a remarkable free open
source tool which will be helpful to the Engineering research society. Furthermore, in a
comparison between the use of OpenSees alone and using the present Interface, inexperienced
users can learn faster with less experience required. This advantage is depicted in Fig. 1
comparing the two learning curves.

Figure 1: Comparison between OpenSees and GiD+OpenSees learning curves
At the current state of development there exists a balance point above which the OpenSees user
(experienced enough) will no longer be benefited from the Interface, due to the current
limitations in terms of supported materials and elements. However, since the Interface is
provided as open-source, it is believed that future versions will contain the complete OpenSees
functionality, shifting this balance point to infinity.
More specifically, the addition of advanced modeling as well as analysis features was attempted
and achieved. Consequently, this thesis aims to present the GiD+OpenSees Interface
functionalities in detail, as well as to provide to users the necessary knowledge and tools for
using this Interface efficiently through a detailed Interface user manual. [2]