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- ArticleYalnız künye2026Damage simulations of the historic masonry aqueduct at Sümela monastery under rockfall and post-disaster landscape management
Genç, Ali Fuat; Nasery, Mohammad Manzoor; Cosgun, Suleyman Istemihan; Yalçınyavuz, Azapay Ümmühan
This study presents a numerical damage simulation of a historical masonry aqueduct at the Sümela Monastery (Virgin Mary) under rockfall. This monastery site has a sharp topography and is exposed to significant rockfall risk. In recent years, local authorities have implemented safety applications, including controlled blasting, anchoring, and cleaning to identify the risky blocks and eliminate rockfall risks. Rockfall risk analyses were conducted considering the topographic features of the site to simulate damage caused by natural rockfalls and those induced by the safety measures employed at the site. Numerical impact analyses were conducted to investigate the resulting damage on the historical aqueduct after determining rockfall risks. In these analyses, four different rock volumes were dropped at the midpoint of each arch. The results of the impact analyses indicated that low-volume rocks (e.g., 0.06–0.09 m3) induced localized surface damage, whereas rocks with larger volumes (2.5–5.0 m3) caused more extensive global failure patterns. The results clearly demonstrate the destructive effects of rockfall on the structure. Finally, this study discusses post-disaster landscape planning for a site that receives thousands of visitors annually.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2024Performance of steel protective structure for historical masonry aqueducts against rockfall: Numerical and field studies
Cosgun, Suleyman Istemihan; Nasery, Mohammad Manzoor
This study investigates the design and impact performance of novel steel protection system intended to safeguard historical masonry aqueducts from damage caused by hazardous rocks. The historical aqueduct under consideration is located on the Sumela Monastery campus. To achieve this, we developed a three-dimensional (3D) photogrammetric model of the study area and identified all risky blocks along with their real positions. Subsequently, we conducted 3200 probabilistic rockfall analyses in eight critical trajectories with four different rock sizes to calculate the velocity, kinetic energy, and run-out distance of fallen blocks. In the second part of the study, finite element models of the steel protective structure were created using Abaqus software. A nonlinear dynamic impact analysis method was applied to analyze nine rockfall scenarios with two different geometries and four different sizes. Based on the rockfall and impact analyses, sections of the protection structure were designed using plastic design criteria. The steel protection structure for aqueducts demonstrated high effectiveness against rockfall, with a risk index (Ir) ranging from 0.93 to 1.00 (except for the upper end of the column–beam connection impacts). Even in these scenarios, the structure provided protection by reducing rock energy and altering its trajectory. In the third part, a steel structure was constructed in the field, and a rock cleaning process was carried out. During rock cleaning, punctures occurred while breaking sharp rocks. To mitigate this risk, a parametric study was conducted using a steel angle stopper. The proposed simple steel angle stopper effectively reduced rockfall damage to historical structures by blocking rock passages and rapidly reducing kinetic energy. Ultimately, during the removal of 5000 m³ of hazardous rocks, no damage was inflicted on the historical structure. The protection system showed a near 100 % success rate in safeguarding the aqueduct. This temporary structure can be employed to protect historical structures from rockfall hazards.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Experimental Study on the Pull-Out Capacity of Blind Rivet Nuts (BRNs) Mounted on Cold-Formed Square Hollow Section Members with Different Wall Thickness
Cosgun, Suleyman Istemihan
In this study, pull-out tests of blind rivet nuts (BRNs) mounted on cold-formed square hollow section (SHS) webs with 100×100 mm nominal cross-section dimensions and different wall thicknesses (2.0 to 5.0 mm) were performed, and the effect of different wall thicknesses and BRN thread sizes on the test results was experimentally investigated. M10 and M12 stainless steel BRNs were mounted on SHSs using a standard riveter tool, and the test elements were prepared for the experiment. Load–displacement curves and the final damage modes were obtained for each test specimen. The results show that the pull-out capacity depends on both the SHS wall thickness and rivet nut thread size. Although the pull-out capacity increased in both thread sizes with the increase in wall thickness parameters, the effect of thread size is negligible in the case of 2.5, 3.0, and 4.0 wall thickness. In addition, when a connection is created using a BRN, the design should consider the stripped thread strength in addition to the pull-out capacity.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2023Seismic evaluation of historical Pertev Pasha Mansion under February 6 Kahramanmaraş (Pazarcık) Earthquake (Mw 7.7)
Cosgun, Suleyman Istemihan
Historical masonry structures with aesthetic aspects play an important role in cultural heritage. However, such structures are vulnerable to seismic effects. Therefore, periodic maintenance and structural evaluations are required for these structures. In this study, a historical masonry building called the Pertev Pasha Mansion, located in Trabzon, Turkey, was selected for the evaluation. The building was demolished in the last few years and has been planned to be rebuilt in its original form. In the study, the finite element model of the building was created based on reconstruction drawings. Modal analysis was performed to obtain the frequencies and mode shapes of the building. Finally, seismic analyses were conducted based on the February 6 Kahramanmaraş earthquakes for two different acceleration records that were collected from different stations, one near the epicenter (Pazarcık station) of the earthquake and the other near the building (Ortahisar station). From the results of the modal analysis, the frequency and mode shapes of the structure were obtained. The displacement and stress results were obtained from the seismic analysis and presented with contour diagrams. At the end of the study, a general evaluation considering the novel Turkish guidelines for historic structures was conducted. According to the results of the seismic analysis performed using the Pazarcık station data, the drift ratio values of the structure exceeded 0.7%, which corresponds to the Collapse Prevention (CP) performance level. However, according to the seismic analysis results obtained using Ortahisar station data, the maximum drift ratio of the structure was 0.001%, corresponding to the Limited Damage (LD) performance level. Consequently, if the building had been built close to the center of the earthquake, it was likely to collapse, but it was estimated that it would have received limited damage because its current location was far from the center of the earthquake.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Multi-Scenario Analysis of Rockfall Hazard for a Historical Vaulted Masonry Building in Sumela Monastery
Nasery, Mohammad Manzoor; Cosgun, Suleyman Istemihan; Temel, Bayram Ali
Sumela Monastery located in the northeast city of Trabzon is one of the most-visited touristic places in Turkey. As it is located in a mountainous area, rockfall hazards have become a crucial problem that the Monastery complex faces, especially in the last decade. Due to several rockfall cases, the monastery was closed for visitors in 2015 to take preventative measures. The current study examines the whole stages assessing and eliminating rockfall hazards that a historical Vaulted masonry building in the Sumela Monastery is exposed to. First of all, field studies were conducted to determine the kind and type of rockfall hazard. For this purpose, the regional geology of the area was evaluated and due to the inaccessibility of the region, industrial climbers were recruited to climb the slope above the Historical Vaulted building to determine the locations, dimensions, and risk level of the risky blocks that threatened the building. After that, the terrain of the risky area was modeled with Unmanned Aerial Vehicle (UAV) using the digital photogrammetry method. In the last step of the field studies, samples were taken to determine the mechanical and physical properties of the rocks and several laboratory tests were conducted. In the second part of the study, probabilistic analyses of 2400 rockfall simulations with eight different trajectories were conducted to calculate the maximum run-out distance, velocity, kinetic energy, and bounce heights of falling blocks. In the third part, to evaluate the damage status on the vaulted building, six different possible rockfall scenarios determined by the rockfall analysis were simulated using the Finite Element Method. After determining the rock block size that would not cause significant damage to the building, the cleaning and controlled removal method of the risky blocks was determined. In the last stage, controlled crushing and removing practices for risky rock blocks were carried out and the building was restored. Consequently, the rockfall hazard for the historical Vaulted building was eliminated and the monastery complex opened for visitors in 2021.
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