This current dissertation is focusing in the
comparison of the European Standards Eurocode 8 with
the Greek Code for earthquake resistant structures
E.A.K.2000 that are currently applied, with interest
in the design of reinforced concrete constructions
and the examination of failure criteria of an 8th
floor building .
This diploma thesis is consisted in six chapters.
Chapters 1-5, state both E.A.K 2000 and EC8 and the
main differences of the two provisions. Chapter 6
is focused in the design and analysis of an 8
floor building and its response when specific
columns are removed in the ground floor and
examining its response under static loading. This
comparison concerns the earthquake resistant design
of all structures.
More specifically, Chapter 1 is focused in the
introduction of Greek Code and EC8, and the
performance requirements and compliance criteria are
discussed.
In chapter 2 , the ground conditions and seismic
actions are described emphasizing the differenced of
the two Codes. In addition, Seismic zones and their
effect in the elastic response spectra is presented.
Then , importance classes and importance factors are
shown followed by energy dissipation capacity and
ductility classes.
Chapter 3 focuses on the seismic response of
concrete structures and mentions of the methods of
structural analysis. Comparison between the two
codes is given for the Lateral force method of
analysis, the modal response spectrum analysis,
non-linear methods and the displacement analysis.
Moreover, the safety verifications are stated
concluding with the damage limitations.
Chapter 4 focuses on the characteristics of
earthquake resistant buildings, mentioning the
importance of structural simplicity, uniformity,
symmetry and redundancy, bi-directional resistance
and stiffness, torsional resistance and stiffness
and diaphragmatic behavior. Moreover, the criteria
of structural regularity is stated for both plan and
elevation.
Chapter 5 focuses on the specific rules for concrete
buildings, the design concepts of buildings, how
energy dissipations capacity, ductility classes and
structural type affect the behavior factor q.
Concrete buildings are classified into
structural types according to their behavior under
horizontal seismic actions and each is thoroughly
explained. Local ductility is discussed and the
importance of the formation of plastic hinges at
specific regions is shown .is In this chapter it is
stated how some forms of failure should be avoided
by the capacity design rule. This chapter ends by
stating the rules of concrete foundation elements as
well as for connections between these elements. In
all the above, both EC8 and E.A.K 2000 are compared.
Chapter 6 focuses on the non-linear static analysis
( pushover analysis). The static pushover analysis
procedure is becoming the dominant method to
evaluate the seismic performance of a structure. In
this kind of analysis , the structure is loaded
under permanent vertical loads and gradually
monotonic lateral forces. From this, a graph of
total base shear vs top displacement in the
structure is plotted. On this graph, the position of
the first hinge a1 is noted, together with the
position of au which is the point where the
structure has reached its maximum capacity for
horizontal loading, final hinge formation- mechanism
, therefore , failure. During these steps , the
hinge formation will be displayed for each member
for increasing horizontal loading, until failure is
reached.
Finally, in
the 7th chapter, two 8 floor buildings
are solved with the structural engineering software
FESPA ver 5.6.0 with Eurocode8 . First, a dynamic
analysis of the model is performed, taking into
account the calculation parameters set. The solver
utilizes the complete quadratic combination (CQC)
modal combination method. During dynamic analysis
all calculations are performed and the number of
modes, Eigen values, member loads, load
combinations, member deformations are all
determined. The two buildings differ because in
building B 3 square columns 50/50 are added, and a
shear wall in Z direction is increased from 2m to
3m. From the dynamic analysis and from the results
it is shown that building B has smaller lateral
displacements since its stiffness has increased, and
smaller period. After the dynamic analysis, a
non-linear pushover analysis is performed in order
to extract more results.
The structure
is subjected to the constant gravity loads and
monotonically increasing horizontal loads. Two
vertical distribution of lateral loads are applied,
uniform and modal patterns. From this analysis, the
capacity of the building is plotted, the points a1
and au, from which we get the ration au/a1 which is
used to determine the q factor. Then, the
displacement demand of the structure is plotted.
After plotting the capacity and demand curves, a
performance check is made to verify that structural
components are not damaged beyond the acceptable
limits of the performance levels examined. It is
proven that by inserting three columns will result
in higher redundancy accompanied by higher
redistribution capacity and a more widely spread
energy dissipation. The period of Building B is
reduced, resulting in lower lateral displacements,
higher au/a1 ratios giving higher q value, and
overall higher strength for the structure. It is
shown that failure is caused at much higher lateral
loads, therefore, building B has an overall higher
performance.
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