14th World Conference on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures

September 9-11 2015 San Diego, Ca USA

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EVALUATION OF SEISMIC ISOLATION APPLICATIONS OF HEALTH

CARE FACILITIES IN TURKEY

Mustafa ERDIK

Kandilli Observatory and Earthquake Research Institute Department of Earthquake Engineering

34684, Cengelkoy, Istanbul, Turkey erdik@boun.edu.tr

Cuneyt TUZUN

Kandilli Observatory and Earthquake Research Institute Department of Earthquake Engineering

34684, Cengelkoy, Istanbul, Turkey cuneyt.tuzun@boun.edu.tr

Omer ULKER

Ulker Consulting Engineers 34738, Erenkoy, Istanbul, Turkey oulker@ulkermuhendislik.com.tr

ABSTRACT - Health care facilities are of great importance among the building stock of a city since they are expected to serve after a major seismic event. In other words based on performance based seismic design approach the expected performance objective for this type of facilities is to be "functional" in design bases earthquake level. In order to achieve this performance level the only design approach is to use seismic base isolation technique.

In recent years number of base isolation applications in health care facilities is increasing rapidly with the regulation that has been released by Turkish Ministry of Health that states "seismic base isolation should be applied in hospitals with more than 100 beds located in seismic zone I and II according to Turkish Seismic Code". The relevant regulation also involves the design criteria of isolation system, superstructure and testing procedure of the isolation units. Within the content of this initiation a health care facilities are planned to be constructed with various capacities almost every city around Turkey in the coming 5 years. Additionally in the content of Istanbul Seismic Risk Mitigation and Emergency Preparedness Project (ISMEP) the existing hospitals are retrofitted with base isolation techniques.

Keywords: functionality performance, lead rubber bearing, friction isolator, health care facility

1 INTRODUCTION

In this paper a brief summary of seismic isolation applications in Turkey have been evaluated through two actual applications one of which is a retrofit design of an existing hospital named as Marmara Basibuyuk Training and Research Hospital located in Istanbul and a new hospital building namely Adana Health Complex that will also be constructed with base isolation located in Adana. The design, testing and application process has been summarized for the relevant health care facilities and problems encountered in the process have been emphasized.

Additionally the authors are also involved in seismic base isolation applications of 8 other health care facilities namely Goztepe, Okmeydanı, Kartal, Elazıg, Isparta, Bursa which are located

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all around Turkey. Important issues revealed throughout base isolation application process have also been indicated based on these case studies.

Since currently there is no official Code for the design of seismically isolated structures in Turkey, the design process is regulated based on US or European Codes. But "seismic isolation" chapter will be included in new Turkish Seismic Code planned to be released in second half of 2015 of which the authors are also involved in the formation process.

The future of base isolation applications in Turkey is promising and the number of base isolated structures will involve not only health care facilities but also the residential buildings. With the introduction of the new Code seismic isolation design in Turkey will be based on more sound rules and problems in the design process would be decreased.

2 INFORMATION ON SEISMIC ISOLATION APPLICATIONS IN TURKEY

The seismic isolation applications in Turkey have been started in last decade. By the introduction of the regulation in 2013 by the Ministry of Health of Turkey, the number of seismic isolation has been rapidly increased in recent years. This regulation states that “health facilities to be constructed in seismic zone 1 and 2 with more than 100 bed capacity should be design with seismic isolation”. This document also involves the analysis, design and testing procedure and criteria to be followed in the design process. Ministry of Health has developed another project namely “Public Private Partnership (PPP)” in which investors are asked to design and construct health facilities with seismic isolation based on the regulation introduced by Ministry of Health.

PPP is being used in the construction of 38 integrated health campuses (so-called “City Hospitals”), that would encompass 26,000 beds, under the “Health Transformation Program”. Under the build-lease-transfer PPP model, healthcare facilities are constructed and leased by the project company to the government for a certain period and price.

This program has resulted as a rapid increase in the seismic isolation applications throughout Turkey.

On the other hand a special project named as İstanbul Seismic Risk Mitigation and Emergency Preparedness (ISMEP) basically focused on seismic retrofit of public buildings in Istanbul. In the content of this project some of the hospitals are retrofitted and reconstructed with seismic isolation. As of March 2015 approximately 25 health facilities are either in design and construction phase.

3 DESIGN PHILOSOPHY OF SEISMIC ISOLATED HEALTH FACILITIES

The regulation of Ministry of Health with number of 2013/3 has an annex named as “Minimum Requirements for Design, Testing and Construction of Seismically Isolated Health Care Facilities”. In this document, the performance objectives have been defined as “continuous functionality” at earthquake level of probability of exceedance 10% in 50 years (DBE) and “immediate occupancy” at the earthquake level of probability of exceedance in 2% in 50 years (MCE). The basic design criteria are defined in order to satisfy the performance objectives are given as:

- The structural system should be designed based on earthquake level of probability of exceedance 10% in 50 years. The structural system below isolation layer shall be designed to remain essentially elastic, in other words structural behaviour factor shall be taken as 1.0. The structural system above isolation layer shall be designed by using structural behaviour factor of minimum 1.5.

- The isolation layer displacement shall be determined at earthquake level seismic of 2% probability of exceedance in 50 years. The isolation system displacements shall be increased by 10% in order to talk in to account the torsional affects.

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- The drift values above isolation layer shall be less than 0.50%. - The base shear transmitted to the upper section of the isolation layer shall be less than 20% of the superstructure weight at earthquake level of 10% probability of exceedance in 50 years. - The lateral acceleration at each story above isolation level should be less than 0.20g. - The non-structural element (i.e. HVAC, plumbing, electro-mechanic systems) below

isolation layer should be designed to accommodate the isolation system displacement and continue its function after earthquake.

In addition to the design criteria defined above, procedure of the prototype and production tests are defined. In the same document requirements for the designer and manufacturer are also defined. As the new concept in design and construction process in Turkey, qualifications of the people and institutions to be a member in “peer review board” that will act in analysis, testing and application of isolation system. As the last point minimum requirements for the structural health monitoring system are also defined in the same document.

4 SEISMIC ISOLATION APPLICATION EXAMPLES

In this section brief information on the design, testing and application seismic isolation system of Basibuyuk Training and Research Hospital which is a retrofit project within ISMEP project in Istanbul. The other sample application is a construction of health care complex in Adana as a PPP application in southern Turkey. 4.1 Maltepe Basibuyuk Training and Research Hospital Application

The hospital complex is located in Anatolian side of Istanbul which is retrofitted with seismic isolation within ISMEP project. The complex is composed of 16 blocks with number of storeys 5 to 10 and has an approximately total area of 113.000 m2. The layout plan and 3D view of the complex is given in Figure 1.

Figure 1 – Layout and 3D view of Basibuyuk training and research hospital

The hospital complex has been originally designed according to 1975 Turkish seismic code

and as the result of the seismic assessment calculations seismic performance of the structure has been determined as under code limits. The retrofit strategy has a performance objective of

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“continuous functionality” as such in order to upgrade the seismic performance of the structure seismic isolation methodology is selected. Prota Inc. has conducted the retrofit and renovation design with base isolation system within the scope of the ISMEP-IPCU “Consultancy Services Retrofitting Design of Selected Public Buildings in Istanbul (EIB-CB1.3A)” project. 4.2.1. Seismic Design Approach of Maltepe Basibuyuk Training and Research Hospital

Since currently there is no official code for the design of seismically isolated structures, the design of the relevant complex is performed based on Chapter 17 of ASCE 7-10. As the isolation design approach instead of determining the isolation system type in advance, a generic solution has been proposed by the designer in terms of displacement and damping and the manufacturers are asked to meet these requirements. This approach has an advantage as having a flexibility to compare different type of isolator types but has a disadvantage as having a long period of time in design process.

The seismic isolation system design criteria is to limit the base shear of the superstructure below 12.5% of the superstructure weight at DBE earthquake level and drift values limited by 0.5% and 1.0% for DBE and MCE earthquake level respectively.

Based on the criteria given above, different types of isolation systems have been proposed. Considering the architectural limitations and construction practice the isolation layer has been selected as the top of the second basement floor. The structural members below isolation layer have been retrofitted through RC jacketing of the columns. The isolation layer configuration has been shown in Figure 2 below.

Figure 2 – Isolation layer location

4.2.2. Structural Analysis of the Isolation System

A 3D mathematical model of the building is constructed considering the nonlinear behaviour of the isolation system with the force-displacement relationship provided by the manufacturer. Response spectrum analysis has been performed at DBE earthquake level and nonlinear time history analysis has been performed using the ground motion set for MCE earthquake level. Acceleration response spectra and ground motion set have been determined based on site specific hazard analysis. The mathematical model of the system, acceleration and displacement response spectra have been shown in Figure 3 and Figure 4 respectively.

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Figure 3- 3D mathematical model of the structural system

Figure 3- Acceleration (left) and displacement (right) response spectra for DBE and MCE level

As the result of the nonlinear time history analysis properties of the isolation system for DBE

and MCE level are given in Table 1 below.

Table 1 – Isolation system results at DBE and MCE level

DBE Level MCE Level

T (s) 3.2 Kmin (kN/m) 534,467 T (s) 3.7 Kmin (kN/m) 399,777 ξ 30% kmin (kN/m) 635 ξ 25% kmin (kN/m) 475

B 1.7 Δ (m) 0.215 B 1.6 Δ (m) 0.454

In Table-1, T is the isolation system period, Kmin is the minimum isolation system stiffness, kmin is the minimum isolation unit stiffness, ξ is the isolation system damping, B is the spectrum reduction factor and ∆ is the isolation system displacement. As the other important design parameter, drift values for DBE and MCE level is given in Figure 4 below.

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Figure 4- Drift profile for DBE (red) and MCE (blue) level

4.2.3. Determination of Isolator Types

Based on the analysis results and architectural limitations of the building, isolation system has been determined as a combination of LRB (lead rubber bearing, 688 units) and NTM (sliding bearing, 154 units) which are shown in Figure 5. Both the LRB and NTM type bearings are manufactured by Freyssinet Inc. The distribution of totally 688 unit of LRB type isolators with the displacement capacity of 500mm is determined to minimize the torsional response of the isolation system.

Figure 6. LRB 650 type isolator section and plan view (Supplied by Freyssinet Inc.) 4.2.4. Isolator Unit Prototype Tests

Prototype test of LRB bearings have been performed based on the testing criteria defined in EN 1529 document. The prototype tests have been performed in order to control the LRB bearing unit parameters in terms of stiffness, damping ratio, stability and displacement capacity and compared with the criteria defined in EN15129. As the results of the tests all the bearing types satisfied the criteria so production and application of the isolator unit started as the next phase. A force-displacement relationship is given in Figure 7 as a sample of test result.

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Figure 7- Force –displacement relationship result of an LRB unit (EU Centre )

4.2.5. Installation of the Isolator Units

As it has been indicated in the previous sections the isolation layer is located at the top of second basement. Once the structural members are retrofitted below isolation layer, an installation process by supporting the columns by using a post tension mechanism in order to cut the column and install the LRB unit. Before the installation process the designer has provided an installation sequence in order to avoid any vertical deflection that may cause damage in the structural members above isolation layer.

In the proposed installation process, a mechanism with a post tensioning mechanism is located above and below the isolation layer. Once the adequate vertical load is satisfied, the column is cut and LRB unit is installed. During cutting and installation process vertical deflection is monitor in order to avoid any loss of post tension force. The installation process is shown in Figure 8. The isolator unit installation process is being carried out by Freysaş Inc, under the retrofit contractor Tima Engineering Inc. and Khatib Alami Inc.

Figure 8- Installation of the isolation unit at the top of first basement columns (Freysaş Inc.)

4.2 Adana Heath Complex Application

The hospital complex is located in Adana southern part of Turkey with 1500 bed capacity and approximately 450000m2 total area. The isolation layer is located at the base of the structure and the isolation system is composed of 1552 triple pendulum isolators. The complex is located on a

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octagonal base and 4 towers with 11 storey stand at each corner in a symmetric fashion. The 3D view is shown in Figure 9.

Figure 9- 3D view of Adana health complex

4.2.1. Performance Objective of Adana Hospital Complex

The performance objectives of the building are as follows:

a. Minimum Damage / Operational Structural Status for DBE level b. Operational Non Structural Status for DBE level

i. Maximum 0.2g floor acceleration

ii. Maximum 0.005 inter-story drift ratio

c. Minimum Damage Structural Status for MCE level d. Operational Structural Status for the isolation and below isolation level for MCE

level A base shear of 0.10W at the isolation level is targeted for DBE level using upper bound

isolator properties to ensure the operational status. A maximum displacement of 50 cm is targeted for MCE event using lower bound isolator properties. Finally a maximum inter-story drift ratio of 0.01 is targeted for MCE level. Regardless of the earthquake level, a maximum of 30% damping shall be allowed at the isolation level. The site specific acceleration response spectra for Adana Health Complex at DBE and MCE level are given in Figure 10.

Figure 10- Site specific acceleration spectra for DBE and MCE level

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4.2.2. Design Procedure of Adana Hospital Complex

A 3 tier analysis – design methodology has been used for the Adana Hospital Main Building.

• Preliminary Design

Detailed linear model of the structure has been developed for the superstructure. The member dimensions have been determined based on the 0.10W isolation level shear force as the seismic force. ACI 318 reinforced concrete design and AISC 341 steel design codes has been adopted for the preliminary design. The design has targeted for ordinary moment frame and shear wall system based on the ACI 318 code and Turkish Seismic Code 2007 compliance has been ensured.

The mathematical model of the complex has been prepared based on the structural member dimensions obtained as the result of preliminary design process. The 3D mathematical model of the system is shown in Figure 11 below.

Figure 11- 3D view of Adana health complex structural model

• Verification Analysis

The model has been further developed to include the isolator nonlinearity and the sub structure. Based on the data obtained from the manufacturer related to the isolator properties, 7 nonlinear direct integration time histories has been performed in two orthogonal directions for two different hazard levels. A total of 28 nonlinear time history analyses have been performed. The super structure has been modelled as linear. For the DBE analysis upper bound isolator properties have been used to capture the maximum shear force, for MCE analysis lower bound isolator properties has been used to capture the maximum isolation system displacement and deflections.

Capacity of the isolators and the adequacy of the structure have been verified, approval for the prototype testing of the isolators and the testing criteria has been determined at this stage.

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• Detailed Design

Based on the results of the verification analysis, detailed design of the structure shall be realized. ACI 209 has been used to determine in plane behaviour of the podium diaphragm above the isolation level. P-Δ effects have been considered for the design of the sub structure.

4.2.3. Isolation Unit Properties of Adana Hospital Complex

Based on the analysis results the isolation unit has been selected as triple pendulum (FPT) units. Three types of FTP isolator are proposed by the manufacturer, EPS Inc.. The cross section and force- displacement relationship for one of the isolator types FPT 8827/14-12/10-6 is shown in Figure 12 and Figure 13 respectively.

Figure 12 - FPT 8827/14-12/10-6 type isolator section (EPS Inc.)

Figure 13 - FPT 8827/14-12/10-6 type isolator force displacement relationship (EPS Inc.)

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4.2.4. Analysis Results of Adana Hospital Complex

Based on the analysis results based of nonlinear time history analysis, the response quantities in terms of effective stiffness, effective damping and effective period is determined for lower bound, upper bound and nominal values of the isolator units. The above mentioned parameters for DBE and MCE level have been listed in Table 2 below.

Table 2 – Isolation system properties at UB, LB and nominal values

Upper Bound

(DBE)

Lower Bound

(MCE) Nominal

keff (kN/mm/kN) 0.000453 0.000322 0.000380

βeff 28.6% 16.4% 22.8%

Teff (s) 2.98 3.53 3.25

4.2.5. Prototype Tests of Adana Hospital Complex

The isolator units have been tested in EPS Inc. facilities, based on the procedure defined in Chapter 17 of ASCE 7-10 document. The tests have been performed with the actual velocity, in other words dynamically. The results of the prototype tests have been evaluated and parameters in terms of friction coefficient, effective stiffness and effective damping have been checked with the acceptance criteria defined in ASCE 7-10. As the result of evaluation process all the isolator types have satisfied the criteria. A sample test result graph that involves all the measured parameters is given in Figure 14 below.

Figure 14 – Sample prototype test result (EPS Inc.)

5 EVALUATION OF PROBLEMS IN SEISMIC ISOLATION APPLICATION PROCESS

As it has been mentioned in the above sections, seismic isolation application is a new type of design and construction methodology in engineering society of Turkey. As such it is inevitable that some problems occur during each phase of the process. These problems can mainly divided into two groups as “technical” and “logistics”.

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The technical problems can be listed as; - Number of experienced engineers for the analysis and design of the seismically isolated

structures is quite limited in Turkey - Similarly, number of architects who has experience in providing solutions in seismically

isolated buildings is also quite limited in Turkey - Currently there is no official code is available in Turkey that regulates the analysis and

design of seismically isolated structures - In the application process, the number of contractors who has the experience of constructing

seismically isolated structures are quite limited in Turkey The logistics problems can be listed as;

- The isolator manufacturers are located outside Turkey - The number of testing facilities are in few in number and located outside Turkey - Lack of knowledge, in investors, contractors and engineers, about the duration of the each

stage of the seismic isolation process which results in delays in construction schedule.

6 CONCLUSIONS

It is a well-known fact that analysis, design and construction of seismically structures involve quite complicated procedure that requires advanced engineering input. Considering the high value of the investments and high seismic risk in Turkey, seismic isolation is one of the most rational solution that could be applied for the seismic safety of these type of health facilities. As such for the sake of quality of future seismic isolation applications in Turkey a series of regulations and improvements should be introduced.

As the first step an official code should be prepared that regulates the analysis, design of seismically isolated structures. Currently a group academicians and practicing engineers, authors of this paper are also a member of these committees, are working on the new version of Turkish Seismic Code that will include a chapter on “Seismic Design of Active and Passive Systems”. The relevant document is planned to be released by the end of 2015 so many problems in analysis, design and testing phase will be solved.

The other vital issue is the testing process of the isolation units. As in the case of other countries an official regulation should be prepared concerning the “third party” testing facility in Turkey. Once this issue has been solved, a great saving could be achieved in terms of time and money that is spent during testing process.

In order to increase the experienced human resource in terms of engineer and architect some initiatives should be started in terms of training. The first address should be the civil and earthquake engineering departments of universities that will provide lectures, research and thesis on this issue. The second can be the Chamber of Civil Engineers that could serve as platform to provide training to the actively practicing engineers.

As the last point it should be emphasized that considering the amount of investment in health sector and high level of seismicity in Turkey, in the framework of performance based design approach, seismic isolation is the only solution to achieve the performance objective of being “operational / functional”. As such seismic safety level of both the structural and non-structural content of the hospitals could be upgraded so that they could serve after a big earthquake. Acknowledgements

Authors would like to thank Ali Atac, MSc, from TIMA Consulting Engineers for his support and providing documents related to Marmara Basibuyuk Training and Research Hospital.

We are grateful the IPCU staff and Director Gökhan Elgin for trust and support of our services. Authors also would like to thank Serdar Binzet, MSc, from Renaissance Construction Comp. for his support and providing documents related to Adana Health Complex.

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References

EN15129, 2009, European Norm Anti Seismic Devices ASCE/SEI 7-10, 2010, “Minimum Design Loads for Buildings and Other Structures” “Marmara Ünüversitesi başıbüyük Hastanesi Deprem Yalıtımı ile Güçlendirilmesi Analiz ve

Tasarım Raporu”, Prota Mühendislik, 2013 (in Turkish) ASCE/SEI 7-10, 2010, Minimum Design Load for Buildings and Other Structures Official Test Report of LRB650, LRB850x297, LRB1000 of Marmara Basibuyuk Hospital by EU

Center, November 2014 Seismic Isolation Desing Report of Başıbüyük Hospital,2013, ISMEP “Adana Sağlık Kampüsü Deprem Yalıtımı Analiz ve Tasarım Raporu”, Ülker Mühendislik ve

Müşavirlik A.Ş., 2014, (in Turkish) Triple Pendulum Bearing Engineering Report for Adana Hospital, Turkey, EPS, January 2015 Prototype Test Report for Adana Hospital, Turkey, EPS, March 2015