4 Romanian Earthquake Engineering Code

8/7/2019 4 Romanian Earthquake Engineering Code

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CHAPTER 4

Romanian Earthquake Engineering Code, P100

Romania experienced strong earthquakes during the 20th

Century. In 1940, many

buildings collapsed in Bucharest, capital of Romania, after a strong earthquake.

There were many victims and huge damages. After 1940, civil engineers had applied

German regulations in building design. In 60s, the national P100 code for anti-

seismic buildings' design had been issued.

A M=7.2 degree on Richter scale earthquake occurred in 1977, March 4, at

21h 21m 56.2 sec. The epicenter was located in Vrancea area at a depth of 90 to 100

km. The earthquake was composed from one pre-shock (M=5.0) and three main

shocks (M=6.5, 6.5, and 7.2).There were more than 2000 deaths most of them from Bucharest and

Zimnicea. The last is a small town in south of Romania, with around 40000 people,

which was practically destroyed. In Bucharest, a city with more than 2.5 million

people, mainly the old buildings, risen before 1940, had been broken down. More

than 11000 people were injured, 35000 families lost their homes.

In 1978 and then in 1981 the P100 Code was modified taking into account a

periodicity of 35 to 40 years for a strong earthquake to occur in Romania. That theory

was invalidated by the earthquake from 1987, August 29. It was a 7.6 degree

earthquake on Richter intensity scale. No victims were registered but many buildings

experienced smaller or medium damages that made them vulnerable to a future

earthquake. However, the building anti-seismic design had been proven to be veryeffective.

P100 Code was reviewed in 1991 and slightly modified in 1992. A new

Appendix, G, was added in 1996.

In what follows, a short description of the P100 Code is done. The structure of

this code is kept. It refers to the 13 subchapters and seven Appendices. Some parts,

thought to be more important, are treated in more details than others, considered less

important for this work. However, a civil engineer interested in using this regulation

should carefully read and observe the original document.


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4.1 GENERALITIES

P100-92 Code is referring to the anti-seismic protection of the next type of buildings:

apartment buildings, social and cultural buildings, agricultural and industrial

buildings. For other types of buildings and constructions specific regulations shall beapplied. Research programs for setting similar codes for other types of constructions

are underway.

The aim of the anti-seismic design is to limit the damages and the collapse of

structural, non-structural elements, and equipment. At the same time, the next shall be

avoided:

- loss of human life and human injuries

- break off of essential activities

- damages of cultural or artistically high valued goods

- spill of dangerous substances.

The anti-seismic protection is realized in all stages of a building:

a)During building design stage by:- taking a favorable site

- choosing a good general shape

- assuring proper structural qualities as: strength, stability, stiffness, and ductility.

b)During building construction stage by:- using designed quality materials

- using proper technologies

- observing all the design details.

c)During building maintenance stage by:- keeping unchanged the strength of the structure

- watching the structure's state for repairing damages and removing the sources of

damages.

For a proper anti-seismic protection design, the next criteria must be followed:

- natural seismicity of the area (maximum peaks of ground acceleration, frequency

content of the seismic motion)

- local conditions for the site (geological, geotechnical, hydrological)

- the importance of the building

- the density of people inside the building

- type and characteristics of the structure.

In the case of construction's design which involves special technical and/or

economical problems (as for very important building, frequently repeated

constructions, constructions with unusual dimensions and characteristics) it shall beissued theoretical and experimental studies for:

- the influence of local condition to the seismic action and structural response

- the behavior of the structure and structural components by using experimental

researches

- development and application of high level methods that would improve the

knowledge about the behavior of the structure under seismic action.

As it is stipulated in the Romanian P100-92 Anti-seismic Code, the anti-seismic

design accepts that, under designed actions, a building may suffer:

- local, slight, controllable, and repairable damages in conjunction with post-elastic

predicted strain, at structural elements

- more extended damages that could not jeopardize the people's life or importantmaterial goods, at non-structural elements.


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The responsibility for the seismic behavior of the constructions is evaluated on the

observation of the P100 Code. However, the content of the code is minimal and not

limited when refers to anti-seismic protection measures.

4.2 ANTI-SEISMIC DESIGN PRINCIPLES

Anti-seismic design involves, in P100 Code's philosophy, a structural response with

post-elastic crosses and specific damages. It targets to realize next three principles.

1)A general favorable conformation for the building through:- a favorable horizontal and vertical shape for the structure

- a correct location of structural and non-structural elements and equipment

- avoiding the uncontrolled interaction between buildings or parts of buildings,

between structural and non-structural elements and between building and stored

materials (as liquids and other).

2)Assurance of a sufficient stiffness that can limit the lateral absolute and relative

displacements to acceptable values.3)To obtain a favorable energy dissipation mechanism under strong seismic actionsthrough:

- driving the post elastic areas to those elements that has an increased capacity of

post-elastic deformability, that could not jeopardize the structural stability and that

can be repaired with minimum of technical and economical effort

- post-elastic behavior of the elements non-mentioned above must be reduced to a

level that the risk of collapse or high damages shall be avoided. In any cases the

vertical columns must be able to support their correspondent gravitational loads

- plastic hinges have to be distributed such a way that the post-elastic structural

strain capacity to be as higher as possible. The concentration of plastic hinges

shall be avoided

- to avoid the premature brittle failure, by proper dimensioning and drawing up the

elements

- the potential plastic areas to have sufficient post elastic strain capacity and a stable

hysteretic behavior.

P100 establishes that for anti-seismic design the next methods can be applied:

a)The common method. For this method, the main steps are:- evaluation of the statically equivalent seismic force

- structural analysis in linear domain under seismic and under other loads from the

special group of loads. Establishment of the envelope values of the stresses at the

extremities of structural elements- improvement of the bending moments, at the ends of structural elements, to obtain

a favorable energy dissipation mechanism

- establishment of the envelope of stresses in structural elements associated with

potential plastic hinges

- dimensioning the significant sections and reinforcement of structural elements

- verification of the lateral displacements, ductility, and improvement of

dimensioning and reinforcement.

b)The nonlinear method. It is based on step-by-step iterations. A biographical waycan be also used. The method is recommended for special buildings.


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4.3 PLAN AND LOCATION OF BUILDINGS

Planning of buildings' location has to follow the next principles:

i) Location of new buildings in the natural and built environment have to be donesuch a way that to avoid the increase of direct and indirect potential risks of future

strong earthquakes.ii) To limit the time of provisional stages of building in which the anti-seismic

protection degree is lowered.

iii) Correlation of new building erection with replacement and repairing of notsufficient anti-seismic protected old buildings.

Locations of buildings need to be done so that:

- the anti-seismic measures' cost to be minimum

- to avoid the location on slide land, sand, etc. When this is not possible, the soil of

foundation shall be improved

- for important and special buildings, the location will be specified by special

regulations.

4.4 GENERAL DRAW UP OF BUILDINGS

4.4.aThe plan view and elevation view shape

When drawing up the shape of one building, it is preferable to choose regular,

compact and symmetrical in plan view shape.

In Figure 4.1 some favorable, recommendable, in plan view shapes are shown.

Figure 4.1 Favorable shapes for buildings

Some unfavorable shapes and the way of solving them, dividing the structure are

presented in Figure 4.2.

Figure 4.2Some unfavorable shapes and the way of solving them


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When the plan view shape of the structure has irregularities, it is advisable that the

length of them to be no more than the forth of the total length on that direction, Figure

4.3.

Figure 4.3 Conditions for plan view shape non-regularities

L1x

L1y

LxL

L2Ly

L1

25.021

L

LL25.025.0

11

y

y

x

x

L

L

L

L

In the cases in which the above condition cannot be kept, it is better to divide the

structure as it was already mentioned. When neither of both conditions can be

observed, then simplified methods for computing the structure are forbidden.

For tall buildings located in A, B, and C seismic areas, it is advisable to limit

the plan dimensions to 40m, in order to prevent the asynchronous seismic excitations.

The height of buildings is not limited but it is preferable to be small for high

permanent and utilities' masses.

4.4.b General directions for structural drawing up

The structural elements shall assure a short and direct transmission of gravitational

loads to foundations, as it is possible. It will be avoided to bear a column on a beam,

with some exceptions (buildings with small size, at the last two floors).

Figure 4.4 Hole creating weak sections

Also, it shall be avoided to transmit high forces by bearing a girder on another one.

The same situation shall be avoided for long and/or very loaded cantilevers.

Vertical structural elements will work together through rigid horizontal platesat each floor. The holes will be located avoiding very weak sections (see Figure 4.4).


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Figure 4.6 Calculation of the anti-seismic joint

1 2

20 mm

(1) (2)

4.5 STRUCTURAL COMPUTATION UNDER SEISMIC ACTION

4.5.1 Ways to take into consideration the seismic action

The seismic action operates as:

a)Inertia forces generated by construction - soil accelerations interface.

b)Stresses generated by different displacements of building's parts located under theground level.c)Additional pressure generated by inertia forces in liquids, powder masses, etc.,which are stored in buildings.

d)Forces transmitted by bearing and coupling systems for equipment andinstallations.

In what follows, the common way of setting the inertia forces generated by seismic

action is presented. These forces are statically applied. For a linear or non-linear

dynamic computation, the seismic action is input as a registered or artificial

accelerogram. In this case, particular regulations shall be used.

4.5.2 Analytical structural models

The model will reflect the general shape of the structure, mass distribution, stiffness

distribution, and links with the environment. For non-linear analytical models, the

strength and strain capacity will also be specified.

The next approximations are allowed for a structural model:

Real mass distribution can be changed with a distribution that leads to a less effort

in computing but, at the same time, not modifying in a sensible manner the result. For

seismic loads, application points are the points of location for lumped masses.

In the case of reinforced concrete floors, when the hypothesis of infinite rigid floor

in its plan view can be adopted, the displacements of vertical elements shall be

computed taking into consideration this hypothesis.


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For very large structures' computation, which could lead to a too long computation

time or to errors in computation, it is allowed to adopt condensed structural models.

The values for equivalent masses, stiffness, and strength capacities will be established

through validated techniques.

Spatial character of seismic loads is reflecting as it follows:

The coordination axes are one vertical and the other two in a horizontal plan along

the structural elements (for an orthogonal distribution) or along the main axes.

Seismic design forces are independently applied along the two horizontal axes. For

flexible structures, the hypothesis of seismic action acting at 45 will be studied.

General torsion effect is computed using the simplified method described later.

The foundation soil (active area) effect will be also taken into consideration in

structural modeling.

4.5.3 Equations used for horizontal seismic load computation

For the common structural design, next equations give the static equivalent loads.They consider, in a simplified manner, the influence of dynamic behavior and post

elastic strains.

Horizontal seismic loads are computed for each vibration mode.

When seismic vibration is taken place in a plane, the sum of horizontal seismic

loads (base shear force), corresponding to earth shaking direction for the rvibration

mode, is (the indirect method):

GcS rr (4.2)

where

rrsr kc (4.3)

and

cr is the seismic coefficient corresponding to the rmode of vibration

G is the total gravitational load

is the building importance coefficient

ks is a coefficient dependent on building's location

r is the dynamic gain coefficient for the rvibration mode. It depends on spectral

seismic movement composition for building's location

is a coefficient for seismic effect reduction taking into account the ductility of

the structure, the re-distribution of stresses, the weight of strength capacity

reserves not taken into computation, the non-structural damping, etc.r is the coefficient of equivalence between the real system and a system with one

degree of freedom.

Calculation of the coefficients used in horizontal seismic load:

i) The coefficient makes the difference of anti-seismic protection level by takinginto account the importance class of the building. There are four importance classes:

I vital buildings, = 1.4

II very important buildings, = 1.2

III normal buildings, = 1.0

IV buildings with reduced importance, = 0.8

ii) ks is the ratio between the peak ground acceleration (with a return period of 50years corresponding to the building's location) and the gravity acceleration (see the

attached map at the end of this part of work, Figure 4.13).


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A area - ks = 0.32

B area - ks = 0.25

C area - ks = 0.20

D area - ks = 0.16

E area - ks = 0.12

F area - ks = 0.08iii) ris a function of the natural periods, Tr, and the cornerperiods, Tc:

r=2.5 for Tr Tc

r=2.5-( Tr-Tc) for Tr> Tc

r 1

A diagram relating r and Tr is presented in Figure 4.7 and a map for T c in Figure

4.14.

Figure 4.7Relation between rand Tr

Tc=0.7 sec

Tc=1.5 sec

Tc=1.0 sec

r min=1.0

r

2.5

1.0

0.7 1.0 1.5 2.2 2.5 3.0 T (sec)

iv) The reduction coefficient is taken as it follows (some common values):

A. Frame reinforced concrete structures:

1 - multistory buildings

with structural walls - = 0.25

with non-structural walls - = 0.202 - industrial halls and other one floor buildings

with rigid girder-column connections - = 0.15

with hinge joints - = 0.20

3 - structures with structural walls - = 0.254 - structures with walls, columns and slabs (without girders) - = 0.30

5 - tall buildings, as chimneys - = conforming specific regulations

6 - water towers - = 0.35

7 - silo towers - = 0.25

B. Masonry structures:

1 - structures with masonry walls and reinforced concrete girdles and piers - = 0.25

2 - structures with masonry only - = 0.30C. Steel structures:

1 - industrial halls and other structures with one levela. along the vertically non-braced direction

- with one span - = 0.20

- with more than one span - = 0.17

b. along the vertically braced direction- porches with centered joints and V diagonals - = 0.40


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- porches with centered joints and tensed diagonals - = 0.20

- porches with non-centered diagonals - = 0.20

2. - multistory buildings - = 0.173. - structures with rigid trusses as vertical elements, with centered joints

- with tensed diagonals - = 0.25

- with V shape compressed trusses - = 0.50

4. - structures with rigid trusses as vertical elements and non-centered joints - = 0.205. - vertical cantilever structures:

- full section - = 0.50

- truss - = 0.656. - structures with frames and vertical rigid elements which work together by bracing, stiff

plates, stiff slabs and so on:

- vertical elements with tensed diagonals - = 0.20 0.25

- vertical elements with V shape diagonals - = 0.40 0.45.

v) r is determined from the next equation:

n

k

krk

n

k

krk

r

uGG

uG

1

2

2

1

(4.4)

where

ukris the displacement along the k-th degree of freedom, in the rmode of vibration

Gkis the sum of gravitational loads ofk-th level

G is the total weight of the building

n

k

kGG1

(4.5)

For multistory buildings the next condition must be satisfied: r 0.65.Then, the seismic force that actions over the k-th degree of freedom in the r

mode of vibration, is

n

i

iri

krkrkr

uG

uGSS

1

(4.6)

Another way to compute the seismic forces is the next (the direct method):

kkrkr GcS (4.7)

where

krrskr kc (4.8)

and kr is a distribution coefficient of the seismic force for the k-th degree of freedom

and in the r-th vibration mode. It is computed as it follows:

n

i

iri

n

i

iri

krkr

um

um

u

1

2

1 (4.9)

Then, the base share force corresponding to earth shaking direction and for the rvibration mode is


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n

k

krr SS1

(4.10)

Stresses, displacements, etc. are computed separately for each vibration mode.

Usually, only the first modes are taken into consideration. Then the stress for a

specified section will be

r

rNN2 (4.11)

When differences between vibration periods are less than 10%, more general lows of

composition shall be adopted.

4.5.4 Equations used for vertical seismic loads computation

Verifications for vertical seismic action must be performed for:

- elements that are mainly axial stressed (columns, masonry piers, tie rods,

suspended structures, etc.)- girders and cantilevers with high share forces generated by high concentrated

forces and/or large spans

- slab plates, directly supported by columns (without girders).

Vertical seismic loads are computed by multiplying the gravitational loads with a

coefficient cv. After this, the loads, or stresses in that elements must be changed as

follows (Table 4.1).

Table 4.1 Coefficients for computation of vertical seismic loadsElement type The load or stress to be modified Coefficient cv

Elements mainly axial stressed The axial force ks

Frame girders with high share

forces

The share forces from gravitational loads

in the neighborhood of column sections1.5k

s

Girders with high concentrated

vertical loadsThe concentrated loads 1.5ks

Slab plates directly supported by

columns, without girders

The share forces acting directly on

column2.0ks

Long span cantilevers Total gravitational load 1.5ks

4.5.5 Computation of seismic loads for non-structural elements

It is necessary for assurance of anchorage. The seismic total force is determined from:

www GcS (4.12)

where

cw is a global seismic coefficient

Gw is the gravitational load of the element.

For the coefficient cw, the values are listed in the next table.

Table 4.2 Coefficients for computation of seismic loads for non-structural elementsElement type Coefficient cv The direction for seismic action

Non structural walls ks Normal on the surface

Cantilever walls 3ks Normal on the surface

Suspended ceilings ks Normal on the surface

Internal and external ornaments, statues,small towers, small chimneys 4ks Any direction

Cornices and other non-important 2.5ks Any direction


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cantilevers, tanks located on buildings

4.5.6 Computation of seismic loads for industrial equipment and installation

For self-supported industrial equipment and installation the seismic loads are

computed as it was shown in section 4.5.3 and 4.5.4.In the case of supported industrial equipment and installation the seismic force

is computed the same way described at the paragraph 4.5.5. However, in this case

s2kcw (4.13)

4.5.7 General torsion effect

The general torsion effect will be computed using a three-dimensional analytical

model. When the building is a regular one, and:

- the stiffness centers at different levels are located, with approximation, on the

same vertical line

- the mass centers at different levels are located, with approximation, on the samevertical line

then it is possible to use the next simplified procedure.

At each level, the application point of the resultant horizontal seismic force is

considered to be located from the stiffness center at a distance equal to

21 eee (4.14)

where

e1 is the eccentricity between the mass center and the rigidity center

e2 is an additional conventional eccentricity. It considers the asynchronous seismic

movement along the building.The coefficient e2 has the values:

0.050 B - for common regular buildings

0.075 B - for unfavorable to general torsion element distribution and B is the longest

dimension of the building, in plan view.

The seismic resultant force is applied as is shown in the next figures:

Figure 4.8a Application of the unidirectional seismic force

e2 e1

e=e1+e2

B

stiffnessmass

Sk centercenter

e2 e=e1-e2

e1

B

stiffnessmass

Sk centercenter


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Figure 4.8b Application of the bidirectional seismic forces

0.7e2 e1x

ex=e1x+0.7e2

B

stiffnes

mass

Skx=0.7Skcentercenter

Sky=0.7Sk

0.7e2e1y

ey=e1y+0.7e2

4.5.8 Higher complexity computing methods

When the designer estimates to be necessary, higher complexity computing methods

shall be applied. Three of these methods are shortly described in what follows:

a)Dynamic linear approachThe method is based on numerical integration of differential equations that

reveals the dynamic balance at each time step.

The seismic excitation is represented using accelerograms characterizing the

location area.

b)Dynamic non-linear approachIt assumes constant values for stiffness characteristics during each time

interval. These values are different from one time interval to another, corresponding

to plastic strains and structural damages.c)Static non-linear approach

A biographic computation method is applied. It considers the gravitational

loads to be constant. The horizontal seismic loads are statically applied, distributed

after lows that consider different importance weight for vibration modes.

The method highlights the sequence of appearance of plastic hinges, capable

displacements, and the associated horizontal forces.

4.6 SPECIFIC ASPECTS IN STRUCTURAL DESIGN UNDER SEISMIC

ACTIONS

4.6.1 Groups of loads and loading schemes

Seismic loads are exceptional loads and for this reason they must occur in special

groups of loads as is stipulated by the Romanian Code STAS 10101/1.

Gravitational and other static loads with a quasi-permanent character intervene

in special groups of loading. These static loads come from technological processes as:

pressure in pipes and tanks, horizontal forces from conveyer bands, etc.There are not included actions as wind action, roller bridge action (breaks,

impacts, breaks of carriages, etc.), loads from held strains or imposed displacements

(as from variations in temperature and concrete contractions).


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4.6.2 Computing conditions

Using the limit states design method the computation of structures under seismic

actions is performed. For all types of structures, a computation to the limit states of

strength and stability is performed. All the structural elements and important non-

structural elements must be verified.In the cases of elements to which occur unfavorable concentrations of stresses,

the stresses will be amplified by

- 1.5, for joints between precast concrete elements, reinforced concrete or brick

structural walls, plates over the first floor in rigid structures with flexible first

floor

- 2.0, for anchors and bolts for fixing bearings, pre-stressed joints between

reinforced concrete elements

- 3.0, for columns of rigid structures with flexible first floor.

The design at the limit state of strain is highlighted by the next conditions:

a)for structures with non-structural walls made by ceramic blocks, light aggregate

concrete or cellular expended concrete

0035.0e

r

H(4.15)

where

ris the relative horizontal displacement between two floors

He is the height of that level.

b)for structures to which the non-structural walls do not work together with thestructural elements or to which horizontal strains are not restrained, the above

equation becomes

007.0e

r

H(4.16)

c) for structures with just one level with the same characteristics as those presented inthe above paragraph, the equation is

01.0e

r

H(4.17)

For some specified cases, the computation can be performed for other verifications (as

for crack limit state).

4.7 SPECIFIC REGULATIONS FOR REINFORCED CONCRETE

STRUCTURES

This part develops some specific aspects of principles from part 2, as

- the strength criteria is satisfied if the estimated strength capacity conform to STAS

10107/0-90 code is greater than or equal to the maximum computed stress value in

a specified section

- potential plastic hinges are relative uniform distributed over the building

- for multistory structures, the plastic hinges have to appear firstly to the ends of the

girders and finally, with small values, in columns (better not to appear)


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- the design of the elements must lead to a good local ductility in potential plastic

hinges

- to avoid the brittle breaks

- to observe the concrete quality (minimal class is Bcl5 or Bc20, depending on

some conditions) and steel quality (minimal breaking deformation - 12%, ratio

between breaking stress and flow stress to be less than 1.45).

4.8 SPECIFIC REGULATIONS FOR STEEL STRUCTURES

Steel structures are classified as follows (see also the next figures)

1)Frame structures with one or more levels to which the seismic forces are supportedthrough the elements' bending. The plastic hinges are located near girder-column

joints and the seismic energy is absorbed by post-elastic strains.

2)Structures with rigid trusses as vertical elements, with centered connections for

bars, with- tensed bracing. The seismic action is taken over by stretching

- V connections for bars. The seismic action is taken over by stretching and

compression.

Figure 4.9 Industrial halls and other structures with one storya) rigid connections, b) hinge connections

a) b)

3)Structures with rigid trusses as vertical elements, with non-centered connectionsfor bars. To these structures, the seismic action energy is absorbed by post-elastic

bending and/or post-elastic shear girder's strains.

Figure 4.10 Multistory frame structures

4)Vertical cantilever structures stressed by bending and compression.


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5)Structures with frames and vertical rigid elements that work together by bracing,plates, and other elements. Horizontal forces are taken over by both frames and

vertical rigid elements.

Figure 4.11 Structures with rigid vertical elements and centered bars:a) stretched bracing, b) V connections

b)

a)

The quality of steel must follow the standards specified by the P100 Code. The steel

has to be characterized by a minimal breaking stretch equal to 15%, ratio between

breaking stress and flow stress to be less than 1.25. Then, the P100 Code refers to

welds, screws, screw connections, and anchor screws. In this case it also mentions the

standards to be observed.

Another problem that is stipulated by P100 Code is the slenderness conditions

for steel structural elements located in potential plastic areas. There are three classes:

I for 0.17 < 0.25

II for 0.25 < 0.5

III for 0.5

and for each class type the maximum allowed values of ratios between the height andthickness of the steel in a section is given.

The Code continues with specification on connections: for welded connections

and connections with screws in potential plastic areas, the stress for dimensioning is

the maximum stress capacity of the connected elements multiplied by 1.25. Steel rigid

horizontal structures are loaded with the seismic forces multiplied by 1.5.

Steel flexible structures have to be designed such a way that, under seismic

strong actions, the plastic hinges to appear first in girders and then in the vertical

supports.

If plastic hinges appear in columns then they must appear only in columns and

never in anchorages.


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For beams, the code presents some measures to be taken for avoiding the loose

of stability after a plastic hinge occurs. The same problem is treated regarding the

columns and connections between columns and beams.

Figure 4.12 a) Structures with rigid vertical elements and non-centered bars

b) Vertical cantilever structures

a)

b)

4.9 SPECIFIC REGULATIONS FOR MASONRY STRUCTURES

For this kind of structures the prescriptions from parts 2, 3 and 4, and specific codes

for masonry shall be followed.

4.10 ANTI-SEISMIC DESIGN OF EQUIPMENT AND INSTALLATIONS

Because it is not so important for our purpose, the regulation about equipment and

installations is not presented here.

4.11 ESTIMATION OF THE ANTI-SEISMIC PROTECTION LEVEL OF

EXISTENT BUILDINGS

After an earthquake, existent buildings must be submitted to an expertise or not as it is

shown in the next table.

Table 4.3 Types of estimation for the anti-seismic protection level

Importance of the building Seismic areaA, B, C (ks 0.20) D, E, F (ks < 0.20)

I U U

II U C

III C C

where

U means unconditioned estimation

C means conditioned estimation (on damages, changes in functionality, etc.).

The owner of the building must take the measures to intervene if it is necessary.

For estimation of damages, the next criteria are used:

period of time when the building was risennumber of levels or the height


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structural system

importance

location.

Finally, after the above procedures were done, the expertise report must contain:

a)a technical note with:- the reason of the expertise- type of the expertised structure (group, category)

- a description of the building (structure, function, architecture, location conditions)

- a description of damages and the probable causes of them

- results of quality evaluation

- a proposal for intervention

b)a brief calculations report (technical, economical, technological and functional)c) reasons for interventiond)main drawings of the building designe)architectural and structural drawings for the situations in which there are

differences from the initial designf) drawings of damagesg)laboratory results for testsh)a copy after the expert's license

P100 Code deals with the methods used for investigation. They are named:

- El quality evaluation

- E2 non destructive tests

- E3 simplified computing methods for strength capacity evaluation

- E4 medium complexity type methods for strength capacity evaluation

- E5 dynamic non-linear methods for strength capacity evaluation.

The methods adopted are one or more from them shown above depending on the type

of the building, structure, location and if the expertise is conditioned (C type) orunconditioned(Utype).

One of the goals of these methods is to determine the degree of assurance to

seismic action. An equation describing it is shown below:

nec

cap

S

SR (4.18)

where

Scap is the seismic force able to be supported by the building

Snec is the seismic force estimated as if the building would be new.

4.12 DIRECTIONS FOR MEASURES TO BE TAKEN ON EXISTING

BUILDINGS

The measures that must be taken refer to buildings that

- suffered damages during earthquakes

- have an insufficient degree of assurance against the seismic actions.

It is possible to adopt one of the next types of measures:

a)Measures that keep unchanged the shape and functionality of the building as- Repairing on structural elements in order to bring them to the initial stage. It is

necessary to repair non-structural exterior elements. It is recommendable to repair

the interior non-structural elements, too;


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- Strengthening by introducing new structural elements.

b)Measures that will change the shape and functionality of the building- Reductions of loads on floors and/or modifications of functionality that will

change the building type to a lower importance class

- Partial demolition (of some stories or parts of building)

- Total demolition of the building.

Next tables show how the intervention shall be performed.

Table 4.4 Priorities for interventions

Importance class I II III

Level of

assurance, R < 0.70 0.30 0.30 0.60 0.15 0.15 0.25 0.25 0.35

Emergency

category U1 U1 U2 U1 U2 U3

Table 4.5 Duration of application for the intervention measures

DurationEmergency category

U1 U2 U3

Total duration 2 years 5 years 10 years

Expertise time and decision

for intervention time 1 year 2 years 5 years

4.13 CONDITIONS DURING CONSTRUCTION

Many conditions must be respected during the rising of a building. Between them

there are the next.It is forbidden to make modifications to technical solutions without the written

designer's agreement.

All the materials used for building will be at the quality level stipulated by

designer.

Foundations will be started after the check of the soil and excavations.

The concrete work will be performed under supervision, without joints for one

story (if possible).

The concrete form panels will be removed only after the designed strength is

reached. After the filling in of precast concrete connections, measures for

preventing the drying, freeze, rain washing, etc will be taken.For masonry, a special attention will be given to the filling in of spaces between

bricks and to the links at corners.

4.14 APPENDIXES OF THE P100 CODE

Seven appendixes are closing the P100 Code. They are in connection with the main

chapters of the Code.

Appendix A refers to the seismic zonation of Romania (see the two attached

maps, Figs. 4.13 and 4.14).

Some simplified methods for computing the periods and modes of vibration

are presented in the Appendix B.


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Appendix C shows the modal analysis by taking into account the spatial

deformations.

Other problems about the design of reinforced concrete elements are also

presented in the Appendix D. The same about steel structures is presented in the

Appendix E.

Appendix F refers to some examples of seismic categories of systems,installation, and equipment.

The last one, Appendix G, issued in 1996, is dealing with the non-linear

dynamic methods for anti-seismic design.


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Figure 4.13 P100. Zonation for ks

Figure 4.14 P100. Zonation for Tc

48

47

46

45

44

21 22 23 24 25 26 27 28 29

0 25 50 75 100km

ROMANIA - P100

Zonation for ks

AREA ksA 0.32

B 0.25C 0.20

D 0.16

E 0.12

F 0.08

48

47

46

45

44

21 22 23 24 25 26 27 28 29

0 25 50 75 100km

ROMANIA - P100

Zonation for Tc

Documents

4 Romanian Earthquake Engineering Code