Transcript 1426_C_2016-06-21_17-49

SEISMIC RETROFITTING OF AN EXISTING
INDUSTRIAL STRUCTURE FOR CONVERTING
INTO AN EDUCATION BUILDING
Özgür BOZDAĞ
Dokuz Eylül University
Mutlu SEÇER
Katip Çelebi University
Izmir, Turkey
Introduction
 After the destructive earthquakes occurred in last decades,
ensuring the safety of existing buildings has become one of
the most important tasks of architects and engineers.
 It is well known that vast amount of existing buildings in
Turkey and in earthquake prone zones of Europe have poor
seismic performance, since most of them were built before
modern seismic codes.
 Earthquakes may cause heavy damage or collapse a building
before its predicted life time.
 In this case, building waste and other kinds of wastes are
suddenly emerged and removal of these wastes becomes a
great problem.
Introduction
 Under these circumstances, there is a significant need to
perform adequate assessment of existing buildings and to
investigate possible retrofitting schemes prior to future
seismic events.
 Another benefit of seismic retrofit is to prevent the
occurrence of sudden structural failure or damage before
predicted lifetime in the design phase of the building.
Introduction
 Improvement of safety of existing buildings can be ensured
in two ways:
 demolition of existing building and the construction of new
building according to modern codes.
 retrofitting the existing building.
 The first solution is simple and easieri however high impact
on the environment due to demolition wastes.
 The second solution is challenging for architects and
engineers, because of the complexity of ensuring structural
safety and all sustainability requirements at the same time.
However, it seems like a necessity when considering huge
amount of existing building stocks in cities.
 At the present paper seismic retrofitting of an existing
industrial structure for converting into an education building
is presented.
Building Sustainability and Seismic Rehabilitation
 Sustainable building can be referred as a building which has
the least impact on the natural environment, both in terms
of the building itself and its surroundings and global settings.
 For constructing a new building or retrofitting existing
structure to ensure seismic safety in a sustainable way,
minimization of non-renewable resource consumption and
enhancement of the natural environment are basic
requirements to be followed.
Building Sustainability and Seismic Rehabilitation
 Parallel to rapid development in building sector, safe and
sustainable building concept and life cycle analysis methods
become more popular issue in recent years.
 The lifecycle of a building project starts before any physical
construction activates and ends after its useable life.
 In life cycle analysis, a building should be able to fulfill the
estimated service life which includes all these phases.
 However, buildings may reach to the end of its usable life
before the predicted lifetime in the design phase due to
natural disasters like earthquakes.
Building Sustainability and Seismic Rehabilitation
 The concept of service life is a key parameter for the life
cycle consideration and it relates to performance based
design.
 Structural components such as materials, construction
technique, isolation details etc. are selected according to
building facilities and estimated service life.
 Since service life influences initial cost, the building should
be able to sustain the predicted life time.
 All life cycle considerations estimated in the design phase of
a building may become waste with a destructive earthquake.
Building Sustainability and Seismic Rehabilitation
 After catastrophic earthquakes occurred especially in last 20
years, improving the seismic safety of existing buildings against
earthquakes have gained attention.
 In order to assess the structural performance of a building
several methodologies are established and many guidelines are
prepared such as Vision2000, ATC-40, FEMA-356 and FEMA-440.
 Furthermore, some countries like Turkey, these methodologies
have become a part of the seismic design codes for evaluating
the seismic performance of RC buildings.
 In general, retrofitting strategy of building intends to improve
the seismic performance of a building to life safety performance
level.
Building Sustainability and Seismic Rehabilitation
 For evaluating seismic performance of existing buildings,
these modern design codes play a leading role.
 Based on the results, it is possible to decide one of the two
options:
 demolition and reconstruction of existing building
 retrofitting for ensuring adequate seismic safety
 From the economic point of view, retrofitting of existing
building is not the best solution for some cases.
 For this reason, conversion of structural function after
retrofitting may be an alternative solution for reducing
depreciation time.
Rehabilitation of the industrial building
 Investigated building was built as a part of the large
industrial complex around 1970 in Izmir city of Turkey.
 Parallel to economic developments, vicinity of the building
become one of the most rapid growing areas of the city and
it is needed to evaluate existing structures in the region.
 At the present time, investigated building is placed among
the educational buildings and there is no any active
industrial facility.
 There are two options:
 demolition of building
 inversion of building into educational facility after retrofitting.
Building features
 Existing industrial structure is six story
building with a basement.
 Based on the in situ investigations, building
plan dimensions are measured as 12.00 m
and 26.25 m.
 Total building height is 26.00 m from the
ground.
 Existing structural system is an ordinary RC
frame system with some irregularities.
 Since the weak soil conditions under the
foundation, considerable amount of
settlement was observed.
 Tests on the concrete specimens shown that
existing compressional strength of concrete
is about 7.9 MPa which does not satisfy
neither current nor previous code
requirements.
 Based on weak structural system and low
material quality, safety of the structure is
evaluated as insufficient against
earthquakes.
Retrofitting strategy
 Since seismic resistance of the building is not enough to satisfy code
requirements, retrofitting is required.
 However, it is not possible to use the building as industrial facility
because of inversion of area where building is placed. For this reason, it
is decided to convert the structure into an education building.
 For improving structural resistance of the structure, shear walls are
added into the exterior frames. These additional shear walls are planned
from base to top of the building.
 Furthermore, columns are mantled according to specifications in the
Turkish Seismic Code for increasing the lateral stiffness of the building
and for improving shear resistance of the columns.
Evaluation of proposed repairing and retrofitting system
 Structural performance of the
building is evaluated according
to Turkish Earthquake Code.
 In this code, performance
objectives for educational
structures are;
 life safety for earthquakes
probability of exceedance 2%
in 50 years and
 immediate occupancy for
earthquakes probability of
exceedance 10% in 50 years.
Evaluation of proposed repairing and retrofitting system
 Building is analysed by pushover analysis and lateral loads are increased until
top level of the building reach the target displacement at analysis direction.
 Analyses show that seismic performance of the building fulfil the code
requirements with proposed retrofitting technique.
Capacity curves and target displacements for %10 probability of exceedance a) X direction b) Y direction
Capacity curves and target displacements for %2 probability of exceedance a) X direction b) Y direction
Evaluation of proposed interventions from sustainability perspective
 Life cycle analyses of the buildings are performed based on
several stages. During analyses, it is assumed that building
reaches end of life without any sudden interruption.
 For the earthquake prone areas, this assumption is not
satisfied in some circumstances.
 In the preresent study, strengthening elongates the service
life of the existing industrial building and minimizes the risk
of the building to collapse due to earthquakes before
reaching its economic life.
 Durability, maintenance, energy efficiency and structural
safety will be improved accounting the benefits of structural
strengthening.
 Moreover, the strengthening of the building gives
opportunity for maintenance and non-structural renovations
of constructions.
Conclusions
 Earthquakes occurred especially in last decades indicate that
seismic performance of the existing buildings do not meet
the modern design codes requirements.
 According to seismic performance analyses, demolition of
the buildings is generally more suitable solution compared to
retrofitting due to economical perspective. However,
demolition of building may cause great amount of waste and
this is not admissible from environmental point of view.
 In the present paper, performance analysis of an existing
industrial building with insufficient seismic safety is
explained. Retrofitting expenses become acceptable by
converting existing industrial building into educational
building. This study showed that conversion of the building
into another facility can be an alternative solution instead of
demolition.
Thanks for your
attention……