Özet: Tarihi yÕğma kargir yapÕlarÕn onarÕm ve güçlendirilmesi, ülkemizin tarihsel ve kültürel mir... more Özet: Tarihi yÕğma kargir yapÕlarÕn onarÕm ve güçlendirilmesi, ülkemizin tarihsel ve kültürel mirasÕnÕn sonraki nesillere aktarÕlmasÕ bakÕmÕndan üzerinde önemle durulmasÕ gereken bir konudur. Bu tür yapÕlarÕn restorasyon, onarÕm ve güçlendirme ...
During the last eight years, Turkey has experienced many severe earthquakes: Erzincan earthquake ... more During the last eight years, Turkey has experienced many severe earthquakes: Erzincan earthquake (Ms = 6.8) of March 13, 1992, Dinar earthquake (Ms = 6.0) of October 1, 1995, Adana-Ceyhan earthquake (Ms = 6.2) of June 27, 1998, Kocaeli earthquake (Ms = 7.4) of August 17, 1999 and Duzce earthquake (Ms = 7.2) of November 12, 1999. Most of them affected heavily populated city centers leading to huge loss of human life and economical crisis in the country. The last two earthquakes were rather catastrophic and affected a wide area in the Marmara region. This study mainly aims to evaluate the effect of structural irregularities and short columns on the seismic response of buildings during the last Turkey earthquakes, based on the site investigations of the authors. In this respect, buildings having regular and irregular structural systems are discussed as reference to the old and new Turkish Earthquake Code. Common types of irregular buildings in the big cities of Turkey are typically summarized. Many outstanding photographs of damaged and undamaged buildings taken from the earthquake areas are given, In addition to their irregular structural systems, many buildings were heavily damaged or collapsed due to short column failures during the earthquakes. Since this kind of damage to reinforced concrete (RC) framed buildings is frequently encountered, short column incidents are separately investigated. Further, architectural based damage to buildings are discussed and possible solutions are proposed to minimize collapses due to structural irregularity and short columns.
Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rul... more Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rules to obtain the maximum structural response under multi-directional earthquake effects. An unfavorable internal force usually develops under the combined effects of an earthquake motion. The spectrum intensity concept can be used to investigate the bi-directional effects of earthquakes on structures. For this purpose, a set of recent and past thirteen earthquakes (M>6) are selected to predict bi-directional effects. Elastic velocity response spectra of these earthquakes are numerically obtained and plotted for damping ratios of ξ=0.00, 0.05, 0.20, and 0.50, representing a wide range of undamped and heavily damped structures. Spectrum intensities for both orthogonal directions and for the resultant direction are calculated using a computer program developed for this purpose. Unfavorable response is then calculated by equating the resultant spectrum intensity to principle direction’s intensity plus the other direction’s contribution as a percentage of the principle component, or equating the resultant spectrum intensity to principle direction’s intensity plus a percentage of the other direction’s contribution, or vice versa. Although the results obtained are strongly earthquake-dependent, sensitivity to damping ratio seems relatively less. Based on this analysis, well-known building regulations are reviewed and evaluated by emphasizing the prescribed combination rules. These numerical results support the combination rules given in the current codes. A safe value of 0.20 ~ 0.25 seems reasonable for regular structures.
In recent years, significant developments have been achieved on repair, strengthening and seismic ... more In recent years, significant developments have been achieved on repair, strengthening and seismic retrofit of ancient cultural heritage structures. There are also some traditional retrofitting techniques that could be carried out to improve the seismic behaviour of historic buildings. As many unreinforced masonry domed structures have damages on their domes (even under gravity loads), this study mainly focuses on an investigation of effectiveness of placing a steel ring at the dome’s support level to improve the structural behaviour. In the present study, the problem is considered through an example of a real conservation case study of the Ahi Celebi Mosque in Istanbul. The structure is subjected to gravity and seismically originated forces and FEM analysis is conducted using SAP2000. The behaviour of the system before and after retrofitting process is compared. Also, the site observations are explained in detail. Numerical results showed that external confinement or tightening using steel rings reduced the principal stresses and displacements of the structure significantly and a more distributed stress condition was obtained.
Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rul... more Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rules to obtain the maximum structural response under multi-directional earthquake effects. An unfavorable internal force usually develops under the combined effects of an earthquake motion. In this study, the spectrum intensity concept is used to investigate the tri-directional effects of earthquakes on structures. For this purpose, a set of recent and past fifteen earthquakes (M>6) are selected to predict tri-directional effects. Elastic velocity response spectra of these earthquakes are numerically obtained and plotted for damping ratios of =0.00, 0.05, 0.20, and 0.50, representing a wide range of undamped and heavily damped structures. Spectrum intensities for both orthogonal directions and for the resultant direction are calculated using a computer program developed for this purpose. Unfavorable response is then calculated by equating the resultant spectrum intensity to principle direction’s intensity plus the other direction’s contribution as a percentage of the principle component, or equating the resultant spectrum intensity to principle direction’s intensity plus a percentage of the other direction’s contribution, or vice versa. Although the results obtained are strongly earthquake-dependent, sensitivity to damping ratio seems relatively less. Based on this analysis, well-known building regulations are reviewed and evaluated by emphasizing the prescribed combination rules. Numerical results show that coefficient for the vertical component as a value of 0.30 seems conservative for regular structures.
In the present study a heavily damaged 17th century library structure which is located in the hea... more In the present study a heavily damaged 17th century library structure which is located in the hearth of historical area in Istanbul is investigated. The structure has a cross shaped plan and made of masonry. In order to evaluate the seismic capacity of the structure and to select the appropriate retrofitting technique, the structure is analyzed by means of limit analysis and finite element method. For this purpose the structure subjected to gravity and seismically originated forces and nonlinear analysis with FEM is conducted using DIANA code. Moreover kinematic limit analysis approach applied to the structure to evaluate the seismic individual response of the considered mechanisms. Several numerical simulations are performed starting with linear elastic model comprehending the global structure. Results of the limit analysis approach, allowing the definition of rigid plastic capacity curves for the considered mechanisms are finally compared with the results of the non linear numerical models.
Wood and/or iron tension members in the form of either tie bars (both wood and iron) in historic ... more Wood and/or iron tension members in the form of either tie bars (both wood and iron) in historic masonry arches or externally applied tension rings (iron) of masonry domes have been used in historic buildings especially in the areas that are vulnerable to severe earthquake excitations. Earthquake reconnaissance investigations revealed that masonry arches and domes with tension members showed satisfactory behavior under earthquake loading. To investigate their effectiveness on behavior, three case studies are analyzed from Turkey. The first one is a 16th century mosque having major structural cracks on its 25m-diameter brick masonry dome. Combined steel and CFRP sheets as tension members at several dome levels are proposed as a seismic retrofit measure. Significant improvement is obtained in response, leading to maximum 60% reduction in stresses. The second case study is a stone masonry vault having damaged wooden tie bars. Similarly, numerical results show that stresses as well as deformations can be reduced up to 50% by replacing the old ties with the new wooden tie bars. The third one is a 508-year-old tomb having a nearly collapsed brick masonry dome. At the support level of the dome, externally applied steel rings were used as tension members to limit stresses and deformations. Similar amounts of reductions in stresses are obtained. This study also shows that both traditional and contemporary retrofit strategies can be used in the same project when required.
This study mainly focuses on the effectiveness of using wooden ties on the behavior of historic s... more This study mainly focuses on the effectiveness of using wooden ties on the behavior of historic stone masonry vaults. The problem is considered through an example of a real conservation case study of the Firdevs Bey Antique Bazaar in Isparta. Both gravity and seismic effects are numerically taken into account using FEM analysis with SAP2000. After detailed architectural and structural site investigations, structural weaknesses of the building like cracking, material flaws, and inappropriate interventions over the course of time were determined. It was concluded that the major structural problems were the missing wooden ties of the vault and the excessive roof load resulting from irregular infills. Two retrofit strategies were developed, namely replacing the missing wooden ties with new ties and removing excessive roof load from the building. The whole building was then modeled for the present case (i.e. without ties and with heavy roof load) and the retrofitted case (i.e. with wooden ties and with light roof load). The principle normal stresses before and after retrofitting process is compared. Numerical results show that these stresses after retrofit are significantly reduced up to 57% of the non-retrofitted case for gravity loads and 60% of the non-retrofitted case for earthquake loads. The selected retrofit strategy was approved by architectural historians and restorators with pleasure since the structural intervention was less and the building was near its original form and factor of safety.
In recent years, significant developments have been achieved on repair, strengthening and seismic... more In recent years, significant developments have been achieved on repair, strengthening and seismic retrofit of ancient cultural heritage structures. There are also some traditional retrofitting techniques that could be carried out to improve the seismic behaviour of historic buildings. This study deals with the seismic evaluation and retrofit of a 16th century single domed mosque, which was built between 1562 and 1565 by the architect Sinan by the order of Mihrimah Sultan, daughter of Suleiman the Magnificent. According to records, this monumental structure has been severely damaged by a series of earthquakes in 1719, 1814, and 1894. Recently during the 1999 Marmara earthquake further damages occurred at one of the stone arches supporting the dome of the mosque. The main reasons for the damages at the arch are supposed to be the bad ground conditions supporting the mosque and probable damages at the iron tension bars. For the retrofitting of the damaged arch post-tension steel bars are intended to be used subsequent to an improvement of the ground conditions. Within the scope of this study a three-dimensional model is built up to simulate the static and the seismic behaviour of the structure before and after the retrofitting and then the structure is analyzed under gravity and seismically originated forces using FEM.
Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rul... more Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rules to obtain the maximum structural response under multi-directional earthquake effects. An unfavorable internal force usually develops under the combined effects of an earthquake motion. This study uses the spectrum intensity concept to investigate the tri-directional effects of earthquakes on structures. For this purpose, a set of recent and past thirteen earthquakes (M>6) are selected to predict tri-directional effects. Inelastic velocity response spectra for these earthquakes are numerically obtained and plotted for damping ratios of =0.05 and 0.20, representing a wide range of damped and heavily damped (e.g. base isolated) structures. Spectrum intensities for both orthogonal and vertical directions and for the resultant direction are calculated using a computer program developed for this purpose. Unfavorable response is then calculated by equating the resultant spectrum intensity to principle direction’s intensity plus the other direction’s contribution as a percentage of the principle component, or equating the resultant spectrum intensity to principle direction’s intensity plus a percentage of the other direction’s contribution, or vice versa. The results obtained are strongly earthquake-dependent. Based on the proposed analysis way, well-known building regulations are reviewed and evaluated by emphasizing the prescribed combination rules. Numerical results show that coefficients for the tri-directional contribution varies largely in the range between 0.01~0.68 for the selected force reduction factors of =2 and 8, revealing that in some cases the code defined combination values may yield unconservative seismic designs.
Özet: Tarihi yÕğma kargir yapÕlarÕn onarÕm ve güçlendirilmesi, ülkemizin tarihsel ve kültürel mir... more Özet: Tarihi yÕğma kargir yapÕlarÕn onarÕm ve güçlendirilmesi, ülkemizin tarihsel ve kültürel mirasÕnÕn sonraki nesillere aktarÕlmasÕ bakÕmÕndan üzerinde önemle durulmasÕ gereken bir konudur. Bu tür yapÕlarÕn restorasyon, onarÕm ve güçlendirme ...
During the last eight years, Turkey has experienced many severe earthquakes: Erzincan earthquake ... more During the last eight years, Turkey has experienced many severe earthquakes: Erzincan earthquake (Ms = 6.8) of March 13, 1992, Dinar earthquake (Ms = 6.0) of October 1, 1995, Adana-Ceyhan earthquake (Ms = 6.2) of June 27, 1998, Kocaeli earthquake (Ms = 7.4) of August 17, 1999 and Duzce earthquake (Ms = 7.2) of November 12, 1999. Most of them affected heavily populated city centers leading to huge loss of human life and economical crisis in the country. The last two earthquakes were rather catastrophic and affected a wide area in the Marmara region. This study mainly aims to evaluate the effect of structural irregularities and short columns on the seismic response of buildings during the last Turkey earthquakes, based on the site investigations of the authors. In this respect, buildings having regular and irregular structural systems are discussed as reference to the old and new Turkish Earthquake Code. Common types of irregular buildings in the big cities of Turkey are typically summarized. Many outstanding photographs of damaged and undamaged buildings taken from the earthquake areas are given, In addition to their irregular structural systems, many buildings were heavily damaged or collapsed due to short column failures during the earthquakes. Since this kind of damage to reinforced concrete (RC) framed buildings is frequently encountered, short column incidents are separately investigated. Further, architectural based damage to buildings are discussed and possible solutions are proposed to minimize collapses due to structural irregularity and short columns.
Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rul... more Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rules to obtain the maximum structural response under multi-directional earthquake effects. An unfavorable internal force usually develops under the combined effects of an earthquake motion. The spectrum intensity concept can be used to investigate the bi-directional effects of earthquakes on structures. For this purpose, a set of recent and past thirteen earthquakes (M>6) are selected to predict bi-directional effects. Elastic velocity response spectra of these earthquakes are numerically obtained and plotted for damping ratios of ξ=0.00, 0.05, 0.20, and 0.50, representing a wide range of undamped and heavily damped structures. Spectrum intensities for both orthogonal directions and for the resultant direction are calculated using a computer program developed for this purpose. Unfavorable response is then calculated by equating the resultant spectrum intensity to principle direction’s intensity plus the other direction’s contribution as a percentage of the principle component, or equating the resultant spectrum intensity to principle direction’s intensity plus a percentage of the other direction’s contribution, or vice versa. Although the results obtained are strongly earthquake-dependent, sensitivity to damping ratio seems relatively less. Based on this analysis, well-known building regulations are reviewed and evaluated by emphasizing the prescribed combination rules. These numerical results support the combination rules given in the current codes. A safe value of 0.20 ~ 0.25 seems reasonable for regular structures.
In recent years, significant developments have been achieved on repair, strengthening and seismic ... more In recent years, significant developments have been achieved on repair, strengthening and seismic retrofit of ancient cultural heritage structures. There are also some traditional retrofitting techniques that could be carried out to improve the seismic behaviour of historic buildings. As many unreinforced masonry domed structures have damages on their domes (even under gravity loads), this study mainly focuses on an investigation of effectiveness of placing a steel ring at the dome’s support level to improve the structural behaviour. In the present study, the problem is considered through an example of a real conservation case study of the Ahi Celebi Mosque in Istanbul. The structure is subjected to gravity and seismically originated forces and FEM analysis is conducted using SAP2000. The behaviour of the system before and after retrofitting process is compared. Also, the site observations are explained in detail. Numerical results showed that external confinement or tightening using steel rings reduced the principal stresses and displacements of the structure significantly and a more distributed stress condition was obtained.
Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rul... more Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rules to obtain the maximum structural response under multi-directional earthquake effects. An unfavorable internal force usually develops under the combined effects of an earthquake motion. In this study, the spectrum intensity concept is used to investigate the tri-directional effects of earthquakes on structures. For this purpose, a set of recent and past fifteen earthquakes (M>6) are selected to predict tri-directional effects. Elastic velocity response spectra of these earthquakes are numerically obtained and plotted for damping ratios of =0.00, 0.05, 0.20, and 0.50, representing a wide range of undamped and heavily damped structures. Spectrum intensities for both orthogonal directions and for the resultant direction are calculated using a computer program developed for this purpose. Unfavorable response is then calculated by equating the resultant spectrum intensity to principle direction’s intensity plus the other direction’s contribution as a percentage of the principle component, or equating the resultant spectrum intensity to principle direction’s intensity plus a percentage of the other direction’s contribution, or vice versa. Although the results obtained are strongly earthquake-dependent, sensitivity to damping ratio seems relatively less. Based on this analysis, well-known building regulations are reviewed and evaluated by emphasizing the prescribed combination rules. Numerical results show that coefficient for the vertical component as a value of 0.30 seems conservative for regular structures.
In the present study a heavily damaged 17th century library structure which is located in the hea... more In the present study a heavily damaged 17th century library structure which is located in the hearth of historical area in Istanbul is investigated. The structure has a cross shaped plan and made of masonry. In order to evaluate the seismic capacity of the structure and to select the appropriate retrofitting technique, the structure is analyzed by means of limit analysis and finite element method. For this purpose the structure subjected to gravity and seismically originated forces and nonlinear analysis with FEM is conducted using DIANA code. Moreover kinematic limit analysis approach applied to the structure to evaluate the seismic individual response of the considered mechanisms. Several numerical simulations are performed starting with linear elastic model comprehending the global structure. Results of the limit analysis approach, allowing the definition of rigid plastic capacity curves for the considered mechanisms are finally compared with the results of the non linear numerical models.
Wood and/or iron tension members in the form of either tie bars (both wood and iron) in historic ... more Wood and/or iron tension members in the form of either tie bars (both wood and iron) in historic masonry arches or externally applied tension rings (iron) of masonry domes have been used in historic buildings especially in the areas that are vulnerable to severe earthquake excitations. Earthquake reconnaissance investigations revealed that masonry arches and domes with tension members showed satisfactory behavior under earthquake loading. To investigate their effectiveness on behavior, three case studies are analyzed from Turkey. The first one is a 16th century mosque having major structural cracks on its 25m-diameter brick masonry dome. Combined steel and CFRP sheets as tension members at several dome levels are proposed as a seismic retrofit measure. Significant improvement is obtained in response, leading to maximum 60% reduction in stresses. The second case study is a stone masonry vault having damaged wooden tie bars. Similarly, numerical results show that stresses as well as deformations can be reduced up to 50% by replacing the old ties with the new wooden tie bars. The third one is a 508-year-old tomb having a nearly collapsed brick masonry dome. At the support level of the dome, externally applied steel rings were used as tension members to limit stresses and deformations. Similar amounts of reductions in stresses are obtained. This study also shows that both traditional and contemporary retrofit strategies can be used in the same project when required.
This study mainly focuses on the effectiveness of using wooden ties on the behavior of historic s... more This study mainly focuses on the effectiveness of using wooden ties on the behavior of historic stone masonry vaults. The problem is considered through an example of a real conservation case study of the Firdevs Bey Antique Bazaar in Isparta. Both gravity and seismic effects are numerically taken into account using FEM analysis with SAP2000. After detailed architectural and structural site investigations, structural weaknesses of the building like cracking, material flaws, and inappropriate interventions over the course of time were determined. It was concluded that the major structural problems were the missing wooden ties of the vault and the excessive roof load resulting from irregular infills. Two retrofit strategies were developed, namely replacing the missing wooden ties with new ties and removing excessive roof load from the building. The whole building was then modeled for the present case (i.e. without ties and with heavy roof load) and the retrofitted case (i.e. with wooden ties and with light roof load). The principle normal stresses before and after retrofitting process is compared. Numerical results show that these stresses after retrofit are significantly reduced up to 57% of the non-retrofitted case for gravity loads and 60% of the non-retrofitted case for earthquake loads. The selected retrofit strategy was approved by architectural historians and restorators with pleasure since the structural intervention was less and the building was near its original form and factor of safety.
In recent years, significant developments have been achieved on repair, strengthening and seismic... more In recent years, significant developments have been achieved on repair, strengthening and seismic retrofit of ancient cultural heritage structures. There are also some traditional retrofitting techniques that could be carried out to improve the seismic behaviour of historic buildings. This study deals with the seismic evaluation and retrofit of a 16th century single domed mosque, which was built between 1562 and 1565 by the architect Sinan by the order of Mihrimah Sultan, daughter of Suleiman the Magnificent. According to records, this monumental structure has been severely damaged by a series of earthquakes in 1719, 1814, and 1894. Recently during the 1999 Marmara earthquake further damages occurred at one of the stone arches supporting the dome of the mosque. The main reasons for the damages at the arch are supposed to be the bad ground conditions supporting the mosque and probable damages at the iron tension bars. For the retrofitting of the damaged arch post-tension steel bars are intended to be used subsequent to an improvement of the ground conditions. Within the scope of this study a three-dimensional model is built up to simulate the static and the seismic behaviour of the structure before and after the retrofitting and then the structure is analyzed under gravity and seismically originated forces using FEM.
Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rul... more Seismic regulations and guidelines for buildings and bridges prescribe simplified combination rules to obtain the maximum structural response under multi-directional earthquake effects. An unfavorable internal force usually develops under the combined effects of an earthquake motion. This study uses the spectrum intensity concept to investigate the tri-directional effects of earthquakes on structures. For this purpose, a set of recent and past thirteen earthquakes (M>6) are selected to predict tri-directional effects. Inelastic velocity response spectra for these earthquakes are numerically obtained and plotted for damping ratios of =0.05 and 0.20, representing a wide range of damped and heavily damped (e.g. base isolated) structures. Spectrum intensities for both orthogonal and vertical directions and for the resultant direction are calculated using a computer program developed for this purpose. Unfavorable response is then calculated by equating the resultant spectrum intensity to principle direction’s intensity plus the other direction’s contribution as a percentage of the principle component, or equating the resultant spectrum intensity to principle direction’s intensity plus a percentage of the other direction’s contribution, or vice versa. The results obtained are strongly earthquake-dependent. Based on the proposed analysis way, well-known building regulations are reviewed and evaluated by emphasizing the prescribed combination rules. Numerical results show that coefficients for the tri-directional contribution varies largely in the range between 0.01~0.68 for the selected force reduction factors of =2 and 8, revealing that in some cases the code defined combination values may yield unconservative seismic designs.
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