A Case Study for Seismic Assessment and Restoration of Historic Buildings: The Arditi Residence

Introduction

It is always an important task to assess the present condition of existing historic structures and to develop intervention strategies if required for preservation and sustainability of cultural heritage. This becomes even more crucial in earthquake prone regions. The most challenging part of the problem is that every historic structure is unique and possesses its own structural characteristics. Hence it is not possible to develop and employ a standard procedure for the seismic assessment and rehabilitation of historic structures. There are many studies in the literature regarding the condition and seismic safety assessment of historical masonry structures (Asteris et al. 2005, Asteris 2008, Betti et al. 2010, Betti et al. 2011, Asteris et al. 2014).

There are numerous historic structures and monuments in Turkey in accordance with the cultural wealth and diversity over the centuries. On the other hand, Turkey is a seismically active country, where a major earthquake occurs in every decade. Therefore one of the privileged missions in earthquake mitigation studies in Turkey is to assess the seismic performance of historic structures and develop rehabilitation techniques for their preservation. This study focuses on one of these historical buildings, the Arditi Residence in Urla, Izmir.

The Arditi Residence is a two story building with a partial basement. The building, which is nearly 150 years old, had been constructed for one of the most prominent families of that region in that era. It was used as a residence since 1930s, after which it was used by the local authorities as a public building. From the structural point of view, the building can be regarded as a mixed system since three different techniques had been used during the construction.

The building is located in a seismically active region. In the last decade, the building experienced four earthquakes with moment magnitudes ranging between 5.0 and 6.0. The preliminary assessment of the building reveals that it had been slightly affected by these small-to-moderate magnitude events. Due to the seismotectonic characteristics of the region, it is probable that the building may experience an earthquake with the order of magnitude 6.5-7.0 in the future.

The Arditi Residence has been investigated in three stages: preliminary evaluation, seismic performance assessment and intervention. The preliminary evaluation stage started with a building site visit. The conditions of all structural components were assessed and the damaged components were recorded. The observations indicated that although the building had not been subjected to any severe seismic action, it possessed serious problems due to poor maintenance over the years. Some of the walls were not able to maintain their structural load-carrying capacity due to degraded material properties. Existing crack patterns reveals that wall-to-wall and wall-to-floor connections of the building were poor. The cross sectional sizes and the connection details of the timber floor indicates that it was not able to exhibit the rigid floor diaphragm action. This deficiency endangers the even distribution of shear forces in accordance with the relative rigidities of structural components.

In order to quantify these observations in a detailed manner, seismic performance assessment of the building was carried out in the second stage. To achieve this, the current Turkish seismic code was considered as a reference. At the end of the assessment, it was observed that existing structural walls in the building was insufficient for the seismic hazard level of a design earthquake (with a return period of 475 years). Details are provided in the assessment of the existing condition of the building section.

After preliminary and detailed evaluation, the structural deficiencies of the building were assessed and some unique intervention strategies were developed. Depending on the impact of the deficiency, intervention strategies are grouped into two sets. Deficiencies that are creating local effects such as if it is related to a member or a limited portion of the structure, it is investigated under the member level interventions. On the other hand, if the deficiency is causing a global effect on the structure and its solution needs multi member interventions, it is called structure level interventions. The details of the interventions are explained in detail in last section of this chapter.