Seismic response control of rigid block systems by using Tendon System: the case of Greek column

1 
 
1
1
.
.
 
 
I
I
N
N
T
T
R
R
O
O
D
D
U
U
C
C
T
T
I
I
O
O
N
N
 
 
1.1. SEISMIC ENGINEERING EXPERIMENTATION 
The paramount objective of Seismic Engineering is to contribute in deep for the 
policies of prevention, formation or development leading to the mitigation of the seismic 
risk concerning the structural damage or collapse. The safety verification of a  seismic 
action involves several concepts: necessary conditions, performance criteria, 
probabilistic reliability, hazard scenarios and quality guarantee. In spite of several 
scientific areas being under constant development, it is still nowadays very common to 
get important knowledge following the occurrence of each new catastrophic earthquake
2 
Seismic response control of rigid block systems by using Tendon System:
The case of Greek column 
 
 
 
in a developed zone of the globe. In fact, there is no better seismic testing “laboratory” 
than the real place where an earthquake takes place, because it is absolutely impossible 
to reproduce artificially, and simultaneously, all the concerned phenomena. Anyway, 
and despite the wide numerical methods and computer capability developments, the 
tests will be always indispensable because they are the only way to reproduce seismic 
actions allowing its systematic repetition and the necessary scientific observation of 
their effects. Consequently, the main objective of the Seismic Engineering 
experimentation is, basically, to allow the observation and analysis of the damage and 
behaviour of different types of structures, under different conditions, while submitted to 
a seismic action. In fact, the response of a structure to a seismic action is influenced by 
innumerable parameters whose implications must be widely analyzed. For instance, not 
only the characteristics of the seismic action itself, but also the foundation and 
bordering structures interaction, the structural and material characteristics or the 
already existent damage induced by previous events. 
Seismic Engineering experimentation is also indispensable for the validation of 
analytical models and for the verification of new design methodologies or new 
strengthening or reinforcement structural techniques. The study of new materials 
behaviour and the analysis of the new methodologies still in a pre-normative phase 
need also the use of experimental tests. It should be noticed too that, apart the multiple 
aspects already referred, experimentation with earthquake simulators provides the 
certification of several types of equipment in order to ensure their proper way of 
functioning during the occurrence of a major earthquake. In fact, shaking table tests of 
important equipment are quite common; mechanical, electrical and electronic 
equipment of various types are main-stations and sub-stations material, nuclear power 
plants control units or hospital vital devices, just to quote a few of the more relevant
Chapter One
Introduction 
3 
 
 
 
examples. Moreover the already referred activities, of seismic engineering itself or 
equipment certification, civil protection authorities can also use earthquake simulators 
for didactic campaigns. This utility is a role very disseminated in countries, like Japan, 
where the occurrence of earthquakes felt by all the population is part of their common 
life. Without the purpose of exhausting, there is however another aspect of the seismic 
engineering experimentation that should be mentioned; that is its use in order to 
evaluate the seismic vulnerability of different types of the building stock, with obvious 
applications in the aim of the insurance companies activities. Consequently, it is of 
paramount importance the improvement of the seismic engineering experimental 
conditions in order to raise new techniques to pay a better and clearly more important 
role in the seismic risk mitigation.[1] 
Testing of complete structures is normally used to enable the understanding of 
the global behaviour of a construction and to capture the interplay of the response of its 
different components. It corresponds to quite expensive tests but, in principle, provides 
quite realistic information on the expected response of the specific structure under 
testing. By the nature of these tests and the usually high degree of redundancy of 
complete structures, the comparison of the experimental results with analytical 
simulations can only be made in terms of global variables as for instance storey 
displacements or accelerations and external forces or base reactions. Measurements of 
internal forces are normally quite difficult, among other reasons, because normally the 
corresponding load cells would disrupt or significantly modify the structural behaviour 
and also due to the large number of those load cells that would be required to enable the 
complete identification of the internal action effects pattern. 
On the contrary, tests on single structural elements or sub-assemblages are 
much less expensive but can only provide information of what could be called local
4 
Seismic response control of rigid block systems by using Tendon System:
The case of Greek column 
 
 
 
nature. They are mostly suitable for the calibration and validation of analytical models 
of the elements that can be incorporated into a computer code with which the 
simulation of the response of a complete structure may be achieved. Hence, tests on 
elements or sub-assemblages are normally conducted on a large series of specimens so 
that the effect of different variables (for instance, geometrical proportions, mechanical 
properties or sequence of loading) can be checked and considered in the above referred 
validation of analytical models.[2] 
1.2. ARCHITECTURAL HERITAGE PRESERVATION 
Protection from the inclemency of the seasons was the mother of architecture. In 
fact, the necessity for obtaining frequent shelter from the great heat, or from the 
inclemency of the climate, no doubt first suggested the piling up materials in some form 
to effect this purpose. Shelter was perhaps readily found in some wood, and in rocky 
countries in some cavern; but as it was necessary, particularly for pastoral tribes, to 
inhabit plains where there were neither groves nor caves, that which at first was a 
protection afforded by nature was imitated by a sort of rude art. Branches of trees were 
no doubt carried into the open country, and were piled up, so that the people might 
creep under and find shelter from the sun’s heat or the chilling storm. On the wild 
moors, where there are no trees, and where the ground is covered with scattered 
fragments of rock, the remembrance of the natural caverns no doubt suggested the 
piling up stones in such form as to be a protection against the outer elements. Where 
trees abounded, stone probably was the last material used, as it would entail so much 
more labour than timber; but of course it was soon found stone had two great 
advantages – it would neither burn or rot; so that it soon had the preference for all
Chapter One
Introduction 
5 
 
 
 
durable purposes. Where there were many trees, as in Greece, the stone architecture 
exhibits traces of the original timber construction. 
Architecture, of little account at its birth, it rose into light and life with the 
civilization of mankind; and, proportionately as security, peace, and good order were 
established, it became, not less than its sisters, painting and sculpture, one method of 
transmitting to posterity the degree of importance to which a nation had attained, and 
the moral value of that nation amongst the kingdoms of the earth. Monumental 
architecture must have originated in a desire to commemorate important events, such as 
the death of great men; hence it is supposed that the first consideration would be to 
make such memorial as durable as possible, and this circumstance would lead to the use 
of stone instead of wood. 
The testimonies of the past stone architecture got to the present, are represented 
by some Greek, Roman, Byzantine, Romanesque and Gothic buildings; the fact that these 
ancient works still exist, prove an extreme stability of their structure. On the other hand, 
these constructions are only a few examples of the wide activity conducted by the 
ancient populations, since in the history urban settlements have been mainly located in 
seismic zones. This is a consequence of the fact that most convenient geographical 
locations for building a city are valleys and cross-roads, which frequently follow the 
locations and intersections of active seismic faults. Thus, the most historical monuments 
ever lived have been destroyed principally by earthquakes. 
Consequently, the possible occurrence of seismic events has been bringing to 
spend an increasing interest in the conservation of vulnerable historical buildings 
located in seismic areas. These pieces of cultural heritage, thus, need to be seismically 
evaluated and strengthened by appropriate methods. Upgrading historical buildings in 
order to survive strong ground motions is a challenging task: their historical value must
6 
Seismic response control of rigid block systems by using Tendon System:
The case of Greek column 
 
 
 
be protected and this means that the originality of the structure must remain intact, 
together with providing improved seismic performance. The more difficult question 
with respect to the maintenance problem and the restoring technique is to have a 
correct measure of the stability degree, by means of a model able to simulate the 
mechanical behaviour as close as possible. Hence, the seismic response of the historic 
construction is a subject in continual elaboration. 
1.3. OBJECT OF THE THESIS 
Besides the Egyptian one, the architecture nowadays most known by means of its 
sacred monuments is that of Greece, from whose monuments – namely the temples – is 
deduced all the knowledge of its principles. Grecian Architecture is very much common 
not only in Greece, but also in its colonies, like those of Magna Graecia formed in the 
southern Italian peninsula by Greek colonization starting from eighth century B.C.. One 
of these is Paestum, where there is a still existing proof of Greek settlement, constituted 
by three temples, whose oldest one is dated at 540 B.C. Despite the fact that these 
temples do still exist, it has to be pointed out that they are exposed to a high seismic risk, 
in fact Paestum arises in Campania, a region characterized by such a risk. For instance 
the recent Irpinia earthquake, happened in 1980 and gifted of a moment magnitude 
6.89, hit Campania and the surrounding areas, causing almost three thousands death. 
It has been said, seismic updating of historical buildings should be obtained 
without affecting their original character. Advanced structural engineering technologies 
are capable of achieving this by means of structural control concepts, one of which is 
the Tendon System. This system introduces a rigid body mechanism into the structure 
which is controlled through tendons with very little pre-stressing. In an effective
Chapter One
Introduction 
7 
 
 
 
Tendon System, the forces in the structure remain limited and are controlled at low 
levels by the tendons, not the earthquake. The very simple and effective idea is to tie 
loose building blocks with tendons that run through their centres reducing 
displacement and dissipating energy at the joints. Practical applications of this strategy 
are already available, nevertheless to fully understand its potentiality and to provide 
general design rules, an analytical model for the controlled system, with emphasize on 
non-linear joint dynamic behaviour should be validated by means of experimental tests. 
According to this purpose, the present thesis is aimed to prove the efficiency of 
the above mentioned Tendon System, by performing an experimental campaign 
focusing on the dynamic response of small scale specimens representing Greek columns 
of Paestum, retrofitted by Tendon System. The experimental campaign is being executed 
at the laboratories of Steel & Composite Structures Department of Kassel University, 
Germany, under the supervision of Prof. Uwe Dorka. The testing facilities, among which 
the shaking table for the application of input excitations and the basic components of 
the specimens are provided by the same University.
9 
 
2
2
.
.
 
 
C
C
U
U
L
L
T
T
U
U
R
R
A
A
L
L
 
 
H
H
E
E
R
R
I
I
T
T
A
A
G
G
E
E
 
 
Besides wood, masonry is the most important construction material in the history 
of mankind. Masonry has been used, in a wide variety of forms, as a basic construction 
material for public and residential buildings in the past several thousand years: from the 
tower of Babylon, which should have reached the sky if it had been completed, to the 
Great wall of China, which is the only man-made structure visible from the Moon. A 
great number of well preserved old masonry buildings still exist, providing that 
masonry can successfully resist loads and environmental impacts, therefore providing 
shelter for people and their goods for a long period of time, if adequately conceived and 
constructed. In recognition of their importance and value, many of those buildings have
10 
Seismic response control of rigid block systems by using Tendon System:
The case of Greek column 
 
 
 
been ranked among the assets of the highest category of mankind’s historical and 
cultural heritage.[3] 
2.1. ARCHITECTURAL HERITAGE 
Cultural heritage ("national heritage" or just "heritage") is the legacy of physical 
artefacts and intangible attributes of a group or society that are inherited from past 
generations, maintained in the present and bestowed for the benefit of future 
generations. Often though, what is considered cultural heritage by one generation may 
be rejected by the next generation, only to be revived by a succeeding generation. 
Physical or "tangible cultural heritage" includes buildings and historic places, 
monuments, artefacts, etc., that are considered worthy of preservation for the future. 
These include objects significant to the archaeology, architecture, science or technology 
of a specific culture. Heritage can also include cultural landscapes (natural features that 
may have cultural attributes) Recently heritage practitioners have moved from 
classifying heritage as natural as man has intervened in the shaping of nature in the 
past four million years. 
"Natural heritage" is also an important part of a culture, encompassing the 
countryside and natural environment, including flora and fauna, scientifically known as 
biodiversity. These kind of heritage sites often serve as an important component in a 
country's tourist industry, attracting many visitors from abroad as well as locally. 
The heritage that survives from the past is often unique and irreplaceable, which 
places the responsibility of preservation on the current generation. Smaller objects such 
as artworks and other cultural masterpieces are collected in museums and art galleries.
Chapter Two
Cultural Heritage 
11 
 
 
 
Grass roots organizations and political groups have been successful at gaining the 
necessary support to preserve the heritage of many nations for the future. 
Significant was the Convention Concerning the Protection of World Cultural and 
Natural Heritage that was adopted by the General Conference of UNESCO in 1972. As of 
2008, there are 878 World Heritage Sites: 678 cultural, 174 natural, and 26 mixed 
properties, in 145 countries. Each of these sites is considered important to the 
international community. 
A broader definition includes intangible aspects of a particular culture, often 
maintained by social customs during a specific period in history. The ways and means of 
behaviour in a society, and the often formal rules for operating in a particular cultural 
climate. These include social values and traditions, customs and practices, aesthetic and 
spiritual beliefs, artistic expression, language and other aspects of human activity. The 
significance of physical artefacts can be interpreted against the backdrop of 
socioeconomic, political, ethnic, religious and philosophical values of a particular group 
of people. Naturally, intangible cultural heritage is more difficult to preserve than 
physical objects.[4] 
In this work the heritage is meant as architectural heritage. Architecture (Latin 
architectura, from the Greek ἀρχιτ έ κτων – arkhitekton, from ἀρχι- "chief" and τέκτων 
"builder, carpenter") means the art and science – sometimes only a single style - of 
designing and erecting buildings and other physical structures. 
A wider definition may comprise all design activity, from the macro-level (urban 
design, landscape architecture) to the micro-level (construction details and furniture). 
Architecture is both the process and product of planning, designing and constructing 
form, space and ambience that reflect functional, technical, social, and aesthetic 
considerations. It requires the creative manipulation and coordination of material,
12 
Seismic response control of rigid block systems by using Tendon System:
The case of Greek column 
 
 
 
technology, light and shadow. Architecture also encompasses the pragmatic aspects of 
realising buildings and structures, including scheduling, cost estimating and 
construction administration. As documentation produced by architects, typically 
drawings, plans and technical specifications, architecture defines the structure and/or 
behaviour of a building or any other kind of system that is to be or has been constructed. 
[4] 
Architectural works are often perceived as cultural and political symbols and as 
works of art. Historical civilizations are often identified with their surviving 
architectural achievements. 
In many ancient civilizations, like the Egyptians' and Mesopotamians', 
architecture and urbanism reflected the constant engagement with the divine and the 
supernatural, while in other ancient cultures such as Persia architecture and urban 
planning was used to exemplify the power of the state. 
The architecture and urbanism of the Classical civilizations such as the Greeks 
and the Romans evolved from civic ideals rather than religious or empirical ones and 
new building types emerged. Architectural styles developed – the classical orders will be 
seen in the next paragraph. 
In Europe, in both the Classical and Medieval periods, buildings were not 
attributed to specific individuals and the names of the architects frequently unknown, 
despite the vast scale of the many religious buildings extant from this period. 
There was still no dividing line between artist, architect and engineer, or any of 
the related vocations, and the appellation was often one of regional preference. At this 
stage, it was still possible for an artist to design a bridge as the level of structural 
calculations involved was within the scope of the generalist. [4]
Chapter Two
Cultural Heritage 
13 
 
 
 
2.2. CLASSICAL ORDERS 
A classical order is one of the ancient styles of classical architecture, each 
distinguished by its proportions and characteristic profiles and details, and most readily 
recognizable by the type of column employed. From the sixteenth century onwards, 
architectural theorists recognized five orders. Each style has its proper entablature, 
consisting of architrave, frieze and cornice. 
Ranged in the engraving (Figure 2.1), from the stockiest and most primitive to 
the richest and most slender, they are: Tuscan (Roman) and Doric (Greek and Roman, 
illustrated here in its Roman version); Ionic (Greek version) and Ionic (Roman version); 
Corinthian (Greek and Roman) and Composite (Roman). There are just three ancient 
and original orders of architecture, the Doric, Ionic and Corinthian, which were 
invented by the Greeks. To these the Romans added the two lesser ones: the stocky 
Tuscan, which they made simpler than the Doric and the Composite, which was more 
ornamental than the Corinthian, since it’s known as its rich variant, added by 16th 
century Italian architectural theory and practice.  
The order of a classical building is like the mode or key of classical music, or the 
grammar and rhetoric of a written composition. It is established by certain modules like 
the intervals of music, and it raises certain expectations in an audience attuned to its 
language. 
The classical orders belong to the columnar architecture, since they consist in 
several lines of columns. There are three parts of a column. A column is divided into a 
shaft, its base and its capital. In classical buildings the horizontal structure that is 
supported on the columns like a beam is called entablature. The entablature is 
commonly divided into the architrave, the frieze and the cornice. To distinguish
14 
Seismic response control of rigid block systems by using Tendon System:
The case of Greek column 
 
 
 
between the different Classical orders, the capital is used, having the most distinct 
characteristics. 
 
Figure 2.1: Classical orders
Chapter Two
Cultural Heritage 
15 
 
 
 
A complete column and entablature consist of a number of distinct parts. The 
stylobate is the flat pavement on which the columns are placed. Standing upon the 
stylobate is the plinth, a square block – sometimes circular – which forms the lowest 
part of the base. The remainder of the base may be given one or many mouldings with 
profiles. Common examples are the convex torus and the concave scotia, separated by 
fillets or bands. On top of the base, the shaft is placed vertically. The shaft is cylindrical 
in shape and both long and narrow. The shaft is sometimes articulated with vertical 
hollow grooves or fluting. The shaft is wider at the bottom than at the top. The capital 
rests on the shaft. It has a load-bearing function, which concentrates the weight of the 
entablature on the supportive column, but it primarily serves an aesthetic purpose. The 
simplest form of the capital is the Doric, consisting of three parts. The entablature 
consists of three horizontal layers, all of which are visually separated from each other 
using mouldings or bands. The three layers of the entablature have distinct names: the 
architrave comes at the bottom, the frieze is in the middle and the moulded cornice lies 
on the top. In Roman and post-Renaissance work, the entablature may be carried from 
column to column in the form of an arch that springs from the column that bears its 
weight, retaining its divisions and sculptural enrichment, if any. [2] 
2.2.1. MATERIALS AND PROPORTIONS 
Rock is the basic building material of the earth’s crust and the original building 
material used by man to serve as protection from the severe ice age and post-ice age 
raw climate; shelters were made of assembled field stones to form a basic house. Stone 
was later elaborately shaped to satisfy man’s artistic expression. The natural rock 
material is called “stone” when shaped to man’s needs. It is used to speak of building