# Dissertations, MSc, Diplomas, Technical Reports

Copyright of the papers below rests with a variety of different parties.

They are made available solely on the same basis that I would supply a single copy of a paper to an individual. It is up to you to ensure that your use of a paper does not infringe copyright law.

** DISSERTATIONS: **

**Spyros Giannakos, Ph.D. Thesis :**

“Contribution to the Static and Dynamic Lateral Response of Piles”, NTUA, 2013. (Full Text)**Marios Apostolou, Ph.D. Thesis :**

“Soil–structure interaction under strong seismic moment : Material and geometric nonlinearity”, NTUA, 2011. (Full Text)**Fani Gelagoti, Ph.D. Thesis :**

“Metaplastic Response and Collapse of Frame-Foundations Systems, and the Concept of Rocking Isolation”, NTUA, 2010. (Full Text)

** DIPLOMAS, MSc:**

- PARASKEVOULAKOS CHARIS , Diploma Thesis (2012) :

“SOIL – CAISSON – BRIDGE PIER INTERACTION TO LATERAL LOADING”, National Technical University of Athens (ΝΤUA), supervised by Assistant Professor N. Gerolymos. (Full Text) - SOULIOTIS Christos, Diploma Thesis (2012) :

“DEVELOPMENT of MACROELEMENT for LATERAL RESPONSE of CAISSON FOUNDATION to STATIC and CYCLIC LOADING” National Technical University of Athens (ΝΤUA), supervised by Assistant Professor N. Gerolymos. (Full Text) - LIMNIATI Ypatia , Diploma Thesis (2012) :

“UNCONNECTED PILE FOUNDATION SYSTEM : MONOTONIC and SEISMIC RESPONSE”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas& Assistant Professor I. Anastasopoulos. . (Full Text) - TSIRANTONAKI Danai, Diploma Thesis (2012) :

“SEISMIC RESPONSE of a BRIDGE on a SEDIMENTARY VALLEY” National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Dr. F. Gelagoti. . (Full Text) - PANAGOULIAS Stavros, Diploma Thesis (2012) :

“CANTERBURY EARTHQUAKES : RESPONSE and FOURIER AMPLITUDE SPECTRA DYNAMIC SOIL AMPLIFICATION by LINEAR METHODS”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Dr. E.Garini. (Full Text) - HASHEMI Kiana, Master Thesis (ΜSc) (2012) :

“3D EXPERIMENTAL and NUMERICAL ANALYSIS of FAULT RUPTURE – SOIL – FOUNDATION – STRUCTURE INTERACTION” National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas. (Full Text) - KARAPIPERIS Constantinos , Diploma Thesis (2012) :

“INSIGHT to the NUMERICAL MODELING of the LATERAL RESPONSE of CAISSON FOUNDATIONS to STATIC and CYCLIC LOADING”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor N. Gerolymos. (Full Text) - DRITSOS Nikos, Diploma Thesis (2012) :

“INELASTIC RESPONSE of EMBEDDED FOUNDATIONS”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - KONTOROUPI Thaleia, Master Thesis (ΜSc) (2012) :

“1-Dof SYSTEM ROCKING on INELASTIC SOIL : DEVELOPMENT of SIMPLIFIED NON-LINEAR METHODOLOGY”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - SPARI Markella, Diploma Thesis (2012) :

“METAPLASTIC ROCKING RESPONSE of SDOF OSCILLATOR under BI-DIRECTIONAL SEISMIC EXCITATION”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - VASILEIADIS Michalis, Diploma Thesis (2012) :

“BURIED PIPELINE SUBJECTED to NORMAL AND REVERSE TECTONIC FAULT RUPTURE”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - SIDERI Evgenia & SPYRIDAKI Athina, Diploma Thesis (2011) :

“INELASTIC ROCKING OF ASYMMETRIC FRAME”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - PAPADOPOULOS Eythimios, Diploma Thesis (2011) :

“ΜETAPLASTIC ROCKING RESPONSE of 1-DOF SYSTEM: EXPERIMENTAL INVESTIGATION”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - KOUTRAS Andreas, Diploma Thesis (2011) :

“SEISMIC RESPONSE of an EXISTING RC BUILDING with CORE WALL CONSIDERING SOIL-STRUCTURE INTERACTION”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - ADAMIDIS Orestis, Diploma Thesis (2011) :

“STATIC and DYNAMIC ROTATION of CYLINDER on RIGID, ELASTIC and INELASTIC SOIL”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - ARGYROU , Christina Diploma Thesis (2011) :

“ΤΗΕ EFFECT of ΝΟΝ‐LINEARITIES in the ROTATIONAL STIFFNESS of SHALLOW FOUNDATIONS”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - FOUNTA Vasiliki, Diploma Thesis (2011) :

“ROCKING of FRAME on TWO–LAYERED INELASTIC SOIL” , National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - TSATSIS Angelos, Diploma Thesis (2010) :

“PILEGROUP SUBJECTED to FAULT RUPTURE: DUCTILITY DEMAND” National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - BOUZIOU Dimitra Diploma Thesis (2010) :

“3-D SEISMIC RESPONSE of PIER FOUNDANION PILES : TOWARDS A NEW DESIGN CONSEPT”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - KOTTAKI Nomiki, Diploma Thesis (2010) :

“AMELIORATION DES SOLS PAR INCLUSIONS RIGIDES PROJECT NATIONAL ASIRI”, Ecole National des Ponts et Chaussees es (ENPC) joint programme between ENPC-NTUA. (Full Text) - ΚΟΚΚΑLΗ Panagiota , Diploma Thesis (2010) :

“METAPLASTIC ROCKING RESPONSE of 1-DOF SYSTEMS: DIMENSIONAL ANALYSIS”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - GAVRAS Andreas, Diploma Thesis (2010) :

“METAPLASTIC ANALYSIS of ROCKING 1–DOF SYSTEMS on TWO–LAYERED SOIL”, National Technical University of Athens (ΝΤUA), supervised by Professor G. Gazetas & Assistant Professor I. Anastasopoulos. (Full Text) - PANAGIOTIDOU Andriani-Ioanna, Diploma Thesis (2009) :

“2D and 3D INELASTIC SEISMIC RESPONSE of FOUNDATION with UPLIFTING and P-Δ EFFECTS”, National Technical University of Athens, supervised by Professor G. Gazetas & Assistant Professor N. Gerolymos.

(Full Text) - ΣΤΑΥΡΟΠΟΥΛΟΥ Ελένη, Diploma Thesis (2009) :

“DYNAMIC RESPONSE of PIER FOUNDATION of the MESSINA BRIDGE”, National Technical University of Athens, supervised by Professor G. Gazetas. (Full Text) - ΠΑΛΑΙΟΛΟΓΟΥ Μαργαρίτα, Diploma Thesis (2009) :

“FAULT RUPTURE–SOIL–FOUNDATION INTERACTION: EXPERIMENT and ANALYSIS”, National Technical University of Athens, supervised by Professor G. Gazetas. (Full Text)

** TECHNICAL REPORTS : **

**Tasiopoulou P., Smyrou E., Bal I.E., Gazetas G., Vintzileou El.,(2011) :**

“Geotechnical and Structural Field Observations from Christchurch, February 2011 Earthquake, in New Zealand”, Research Report, NTUA, website : http://geoengineer.org/files/Tasiopoulou_et_al_2011.pdf , October 2011.**Zιotopoulou A., Gazetas G. (2009) :**

Non-Linear Seismic Response Analysis of Soil Deposits and Piles; Proposed Unique Bi-Normalized Design Spectrum, Research Report LSM.NTUA-09-01.

[ABSTARCT]

Seismic codes have largely adopted smooth design acceleration spectra, on the basis of statistical processing of a large number of elastic response spectra of actual recordings. Such spectra have, for each soil category, an essentially constant acceleration branch and a declining acceleration branch. The period range of the constant-acceleration plateau is larger for softer soils. However, the flat shape of the spectra has no resemblance to an actual soil-amplified spectrum. This unrealistic shape stems from the fact that the spectra of motions recorded on soft soil attain their maxima at different well separated periods, and thereby, averaging them eliminates their peaks and leads to a flat spectrum. Through an extensive parametric study we attempt to investigate the shape of normalized spectra and we proceed with the normalization of the period-axis of a spectrum by dividing all periods with the predominant one. This results in a bi-normalized spectrum having a peak acceleration at T/Tp = 1. We use 2 values of soil thickness, 3 values of Vs,30 (representative of soil category D according to NEHRP), 3 distributions with depth (homogeneous, linear, and with crust) and 2 values for the impedance contrast ratio. Our profiles are subjected to 7 near-field recordings from earthquakes (M=6-8) each one scaled to PGA=0.2, 0.4 and 0.6g. We perform 1008 equivalent linear and 1008 inelastic analyses in total. The resulting bi-normalized spectra are averaged. The average bi-normalized spectrum is almost the same for the equivalent linear and inelastic analyses. This bi-normalized spectrum is tested against extreme soil stiffnesses, and extreme values of soil plasticity index (from PI=0 to PI=100). It is found out that this spectrum remains unchanged having a peak of Sa/A≈3.75 for a very narrow range of normalized periods. Finally, we analyze an interesting case history referring to ground motions recorded on the ground surface and at 153m depth (in the bedrock) during the Tokachi-Oki earthquake (M=8, 26/9/2003, Hokkaido-island, Japan). This case also involved the presence of nearby piles which failed due to kinematic effects. Our analysis of both soil response and kinematic pile distress proves very satisfactory.

**Tasiopoulou P., Gerolymos N., Gazetas G. (2009) :**

Soil-Pile Interaction due to Liquefaction-Induced Soil Flow, after Large Dispacement of Quay-Wall, Research Report LSM.NTUA-09-03.

[ABSTRACT]

In this technical report, a methodology is proposed to predict pile group displacements under conditions of lateral flow. To overcome the 3‐D geometry, the problem was approached by subdividing it into : (i) a vertical section of the soil–quay‐wall system with no pile in it, and (ii) a horizontal slice of soil–pile–quay‐wall system in the middle of the liquefiable layer. The methodology then, consists of three steps :

- 1. A plane‐strain dynamic effective‐stress analysis of the vertical section. The response of the system in terms of quay‐wall displacements, soil‐movement behind the quay‐wall and depth of the liquefied zone is obtained.
- 2. A static plane‐strain analysis of the horizontal slice, triggered by a unit displacement at the edge of the quay wall. Horizontal out of plane springs are attached to the pile sections. These springs represent the stiffness of the whole pile, controlled largely by its boundary conditions at the top reflecting the stiffness of the pile cap and the kinematic constraints of the superstructure. The ratio of the pile displacement to “free‐field” soil displacement (far from the piles) is defined.
- 3. The final pile group displacement in the liquefied zone is computed as the product of the ratio of step 2 and the (depth‐dependent) soil displacement in the liquefied zone of step 1. The shape of the pile‐deflection line is adequately defined by its boundary conditions. The “undetermined” load‐distribution along the pile has a minor effect on this shape. The function of the pile deflection with depth is calibrated using the aforementioned computed final pile displacement at the depth of the liquefied zone. Thus, the displacements along the pile are determined. The proposed methodology is successfully applied in reproducing analytically the centrifuge tests conducted at the Institute of Technology, Shimizu Corporation, Japan, and presented by Tazoh et al. during the 1st and the 2nd Japan‐Greece Workshops.

**Panagiotidou A.I., Gerolymos N., Gazetas G. (2010) :**

**2D and 3D Inelastic Seismic Response of Foundation with Uplifting and P‐Δ Effects.**

[ABSTRACT]

A numerical study is presented for the response of shallow rigid foundations carrying a tall 1-dof structure and resting on inelastic clayey soil through a tensionless but rough interface. The system is modeled with finite elements, using the ABAQUS code. Three types of lateral loading are applied: static displacement–controlled loading at the mass center, monotonically increasing up to overturning; cyclic displacement–controlled loading at the mass center; and horizontal seismic base excitation in the form of three recorded accelerograms. The analysis accounts for uplifting of the footing from the base and generation of bearing–capacity failure mechanisms in the soil, during large amplitude rotations. The detrimental effect of the slenderness of the structure to increase the overturning moment on the foundation due to the large displacement of its mass (phenomenon P–δ) is also accounted for. The results for the foundation response are presented mainly in the form of moment–rotation and settlement–rotation curves. A number of key problem parameters are identified and their role is explored. Prominent among these parameters are the static vertical bearing–capacity factor of safety, FSv, the slenderness (aspect ratio), H/b, the flexibility of the superstructure, the absolute size of the structure, and the intensity and frequency content of the shaking. The results reveal a remarkable sensitivity of the system response to the above parameters and especially to the static factor of safety. For large static factors of safety (FSv > 2) the dominant nonlinearity in the response is in the form of foundation uplifting, whereas for small static factors of safety (FSv ≤ 2) the bearing capacity mechanisms are fully developed leading to additional settlement of the foundation with permanent rotation. Another surprising conclusion is the non–symmetric overcapacity of the ultimate moment of the footing, observed only in the cases of heavily loaded systems for the cyclic and seismic analysis. This is due to the development of uni–directional bearing capacity type of failure in the preceding steps. Finally, a comparison between 2D and 3D analyses allows the definition of a proper equivalence between a strip and a square foundations.

**Loli M., Anastasopoulos I., Gazetas G. (2009) :**

Bridge Pier–Foundation : Beyond Capacity Design, Research Report LSM.NTUA-09-02.

[ABSTRACT]

The conventional approach to foundation design adopts factors of safety which limit the uplifting of footings and prevent the capacity failure of bearing soil to occur. Current seismic code provisions explicitly state that the development of plastic hinging is allowed only in the super–structural elements. Hence, overstrength factors are introduced to assure that the capacity of the foundation will “sufficiently” exceed the ultimate capacity of the superstructure. This conservative treatment of the foundation, which is designed to retain “elastic” behavior even for extreme loading, leads to dramatically increased ductility demands at the over–ground allocated plastic hinges causing structural failure in cases of severe seismic excitation. Through an extensive dynamic analysis we attempt to expand the concept of “capacity design” to the foundation level (new design concept) and we comparatively evaluate the effect of foundation inelastic behavior and bearing capacity “failure”. To this end, we study the response of a bridge pier supported on shallow foundation, resting on a homogenous stiff clay stratum. Two different foundation widths are used representing the two design approaches. The first–conventional approach ensures that plastic hinge formation develops in the column whereas the second–new approach assumes lower safety factors implying that the failure mechanism is restricted to the foundation level. We perform a suite of 2D finite element analysis to investigate the response of the two systems to static and dynamic loading in the light of nonlinear behavior of both soil and superstructure. The nonlinear dynamic time history analysis is conducted, using as excitation: (a) idealized pulses, and (b) a variety of actual records to represent a wide range of earthquake characteristics. It is found out that allowing inelastic foundation behaviour and mobilization of bearing capacity failure mechanisms in the soil, a major change in conventional foundation design, results in a determinative increase in the ductility capacity of the system. Hence, the behaviour of the superstructure remains elastic even under deleterious seismic loading and the system survives failure even when subjected to ground motions of much larger magnitude than designed for. The relatively increased values of cyclic settlement are the penalty to pay and the problem reduces to defining the acceptable displacements of the structure in relation to required performance.

**Gelagoti F., Kourkoulis R., Anastasopoulos I., Gazetas G., (2010):**

Influence of a valley-affected ground motion on the seismic response of moment-resisting frame structures.**Chatzigogos Ch., Pecker A. (2010):**

Seismic response of typical bridge pier with consideration of foundation and superstructure nolinearities through Macro-element modeling.

[ABSTRACT]

The dynamic response of a typical highway bridge pier under seismic excitation is studied through macro-element modeling. The pier is founded on a relatively stiff homogeneous clay stratum by means of a shallow square foundation of width B. Analyses are performed for two values of footing width, namely B = 11 m and 7 m. The first case corresponds to a conventional design of the foundation in which it is envisaged that the soil remains in the elastic regime, i.e. no non-linearity (failure mechanism within the soil or uplifting of the foundation) develops during the seismic excitation. The second case (small footing dimension) corresponds to the newly proposed design philosophy in which development of nonlinear behavior is acceptable in the soil as well. The soil-footing interface is considered to be infinitely resistant in sliding and to possess no resistance in tension, allowing consequently uplift of the footing. The bridge pier consists of a reinforced concrete circular column. The soil being purely cohesive, its resistance is described by the von Mises failure criterion. The soil non-linear behavior up to failure is expressed in terms of a typical G / Gmax versus distortion curve. A detailed 2D model of the presented soil-foundation-column configuration was developed in Anastasopoulos et al. [2010]. The purpose of the present study is the development of a much simpler model making use of the concept of macroelement modeling of shallow foundations. The bridge pier is modeled with non-linear beam elements as in the case of the detailed 2D finite element model. However, the foundation and the soil are replaced by one unique 2-node link element, which is the non-linear dynamic macroelement for shallow foundations. The first node of the macroelement is attached to the superstructure. The mass of the foundation is lumped to this node. The second node of the macroelement is fixed. This establishes the boundary conditions of the model and allows retrieving the reaction forces that act upon the foundation. The macroelement is formulated with a non-linear constitutive law that is reproducing the non-linear phenomena arising at the soil-footing interface; these include: a) the elastoplastic soil behavior leading to irreversible foundation displacements and b) the possibility of the footing to get detached from the soil (foundation uplift). Additionally, the macroelement is coupled with a viscous damping element. This element is used to reproduce the effects of radiation damping as waves will emanate from the foundation towards the infinite extremities of the soil medium.