Marmara Hospital Base Isolation for Seismic Protection

Freyssinet retrofitted the Marmara University Basibuyuk Training & Research Hospital with an advanced seismic isolation system, helping bring the long-vacant facility into compliance with modern earthquake protection standards. By installing 687 isolation devices across 16 interconnected buildings, our team enhanced the complex’s seismic resilience while minimizing disruption through an innovative installation methodology.

Despite being completed in the early 1990s, the Marmara University Basibuyuk Training & Research Hospital in Istanbul remained unused for more than two decades. When plans were developed to occupy the facility, retrofitting was required to meet the latest earthquake protection standards for this highly active seismic region.

Owner

Marmara University Basibuyuk Training & Research Hospital
Client

Zeksan
Delivery Date

June 2014
Contractor

Freysas / Freyssinet Product Company
Engineer

Prota

Multiple Blocks

This process was made even more challenging by the fact that the hospital is a large complex consisting of 16 different buildings that vary in height, size, and stiffness. In fact, the facility had already been retrofitted once after its original construction, but standards had subsequently changed, and base isolation had become mandatory. The new codes also specified performance requirements that the seismic protection system had to satisfy to ensure the buildings could remain operational after an earthquake.

Distribution Challenge

Analysis of the structure to determine how and where the base isolators should be distributed beneath the buildings was carried out by the consulting engineer in collaboration with Freyssinet experts. However, the system’s requirements for low stiffness, high damping, and significant horizontal displacement created competing design demands.

It would have been impossible to achieve the desired performance using only lead rubber bearings for seismic protection. These devices are generally designed either with high stiffness to provide high levels of damping or with low stiffness and lower damping. A single unit cannot simultaneously provide both extremes.

Key Figures

Combined Forces

For this project, the solution was to adjust the number and type of seismic protection devices, rather than their individual characteristics, to achieve the required overall stiffness of the interconnected buildings. The proposed system consisted of an equal combination of high-stiffness lead rubber bearings, which dissipate significant seismic energy, and sliding elastomeric bearings, which support vertical loads while reducing the overall stiffness of the complex.

The variation in building heights and basement levels across the 16-building complex also posed a challenge for the design team, which had to identify a suitable elevation for installing the devices. All isolation units had to be installed at the same level to function effectively. Any column sections below this elevation also had to be strengthened with concrete jackets, as they remain directly exposed to full seismic forces.

16

Buildings in the complex
687

Devices installed

Avoiding Torsion

The distribution and use of the protective devices varied according to the characteristics of each building. The primary objective was to ensure that the center of mass of each structure aligned with its center of stiffness, minimizing the risk of seismic damage caused by torsional movement.

Installation Goal

One of the key factors that gave Freysas an advantage in securing the project was its innovative installation approach, which eliminated the need for the intrusive steel support frames originally proposed.

Instead, Freysas developed a custom-designed clamping system that was attached to individual columns above and below the location where the isolation unit was to be installed. The clamps were connected using high-strength prestressing bars, while hydraulic jacks transferred the structural loads during the column-cutting process and installation of the isolator.

This significantly less disruptive procedure reduced both the cost and physical impact of the retrofit while enabling work on each column to be completed in just a few days. Multiple sets of clamps were deployed, allowing crews to work on up to five columns simultaneously across the complex as part of a carefully planned construction sequence.

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