Publications

The Berke Arch Dam is the highest arch dam constructed in Turkey. The dam height is 201 m, and the crest length is 270 m. This paper describes the Berke Arch Dam, its finite-element modeling, ambient vibration testing, finite-element model calibration, and earthquake behavior before and after model calibration. First, three-dimensional (3D) models of dam-reservoir-foundation interaction were developed to obtain analytical dynamic characteristics, such as natural frequencies and mode shapes using the Ansys finite-element program. In the analyses, reservoir water was represented by a Lagrangian approach. Then, ambient vibration tests were conducted on the dam on 4 days in May 2009 to obtain experimental dynamic characteristics. In ambient vibration tests, the sensitive accelerometers were placed on several points on the arch dam, and signals were collected from accelerometers. The enhanced frequency domain decomposition technique was used in the extraction of experimental natural frequencies, mode shapes, and damping ratios. After that, 3D finite-element models of the Berke Arch Dam were calibrated using ambient vibration test results. Finally, earthquake behaviors of initial and calibrated models of the Berke Arch Dam were obtained using the Adana-Ceyhan Earthquake in 1998. It was observed that model calibration affects the results considerably.

Abstract Commercial tools for measurement and analysis of vibration signals have traditionally been very expensive. In the last decade, however, multi-channel measurement systems have become relatively inexpensive. The analysis functionality in most inexpensive instruments is limited. Therefore, many companies are using alternatives for post processing of measurement results. MATLAB is a platform that is popular for this purpose and which offers many advantages over dedicated menu driven systems. The open functions in MATLAB assure flexibility and the possibility to modify functions for specific needs. In this paper, the presentation and numerical applications of an interactive and comparative digital signal processing software developed in MATLAB by writers is described. The software is named as SignalCAD. For developing SignalCAD, about 120 new functions have been created and are used with MATLAB Signal Processing Toolbox functions. The SignalCAD program is a powerful tool that deals with processing raw measured data obtained from forced and ambient vibration testing of engineering structures. SignalCAD offers extensive functionalities for the visualization and processing of the measurement data and the determination and visualization of the spectral analysis results. The program disposes of a graphical user interface, which what makes it very intuitive and easy to handle. The most common spectral analysis techniques have been used in SignalCAD. The possibilities of the program are demonstrated with a three dimensional steel frame model vibration test and some results are compared with commercial PULSE signal analysis software.

This paper describes an arch type steel footbridge, its analytical modeling, modal testing, finite-element model updating, and dynamic analysis. A modern steel footbridge which has an arch type structural system and is located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed three-dimensional finite-element model of footbridge to provide analytical frequencies and mode shapes. Field ambient vibration tests on the footbridge deck under natural excitation such as human walking and traffic loads are conducted. The output-only modal parameter identification is carried out by using peak picking of the average normalized power spectral densities in the frequency domain and stochastic subspace identification in the time domain, and dynamic characteristics such as natural frequencies, mode shapes, and damping ratios are determined. The finite-element model of the footbridge is updated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modeling parameters such as material properties. Dynamic analyses of the footbridge before and after finite-element model updating are performed using the 1992 Erzincan earthquake record. At the end of the study, maximum differences in the natural frequencies are reduced from 22 to only 5% and good agreement is found between analytical and experimental dynamic characteristics such as natural frequencies and mode shapes by model updating. Also, maximum displacements and principal stresses before and after model updating are compared with each other.

Structural parameter identification based on the measured dynamic responses has become very popular recently. This paper presents structural parameter identification of fixed end beams by inverse method using measured natural frequencies. An added mass is used as a modification tool. The measurements of the flexural vibrations of a fixed end beam with and without added mass are performed by using experimental modal testing. The solution of free bending transverse vibration of the beam is obtained by solving the differential equation motion of Bernoulli‐Euler beam. By introducing the natural frequencies from experimental measurements into the solution of differential equation, the structural parameters of the fixed end beam are calculated. It is seen from the results that the values of the mass distribution and elasticity modulus identified using the first natural frequency of the beam nearly close to the real values. Besides, the theoretical frequencies obtained using the identified structural parameters also close to the measured frequencies.

çeşme, köprü gibi tarihi eserler zaman içinde doğal afetler veya canlıların tahribatları neticesinde çeşitli hasarlara maruz kalmaktadırlar.Genellikle en sık rastlanılan bilinçsiz müdahale şekillerinden biri, ahşap çatılı tarihi yığma camilerin ahşap çatısının yerine betonarme kubbe yapılmasıdır.Bu çalışmada, bu tip müdahalelerin tarihi taş duvarlı camilerin dinamik özelliklerini nasıl etkidiğinin belirlenmesini

Abstract In this study, dynamic characteristics of a prototype arch dam-reservoir-foundation model are determined by operational modal analysis method using frequency and time domain techniques. For this purpose, a prototype arch am-reservoir-foundation model is constructed in laboratory conditions. Ambient vibration tests were conducted to the arch dam to identify its natural frequencies, mode shapes, and damping ratios. Natural excitations such as small impact effects were used to vibrate the arch dam. Sensitivity accelerometers were used to collect signals from the measurements. Measurements were recorded for empty and full reservoirs. The signals collected from the tests were processed by operational modal analysis software, and the dynamic characteristics of the dam were estimated using enhanced frequency domain decomposition and stochastic subspace identification techniques. The dynamic characteristics obtained from both techniques are close to each other. It can be stated that the both enhanced frequency domain decomposition and stochastic subspace identification techniques are very useful to identify the modal parameter of the prototype arch dam. In addition, it is observed that there is 20–25 % difference between natural frequencies for empty and full reservoirs.

The aim of this article is to clearly show linear and non-linear earthquake behaviour of a concrete-faced rockfill (CFR) dam. For this purpose, a typical CFR dam model is considered with its reservoir water. Reservoir water is modelled by using fluid finite elements based on the Lagrangian approach. Free-field surface motions recorded during earthquakes are deconvolved to the base of the foundation from the soil layers for earthquake analysis. Geometrically and materially non-linear behaviours of the dam are considered in the finite element analysis. The Drucker–Prager model is used for concrete slab, and the multi-linear kinematic hardening model is used for rockfill and foundation rock in the materially non-linear analysis. Non-linear behaviour of the rockfill is obtained by the uniaxial stress–strain relation. Stress–strain curve of the rockfill is obtained using the shear modulus–shear strain relation produced for the gravels. Various joints in the CFR dam are modelled considering welded and friction contacts. In this study, one-dimensional surface-to-surface contact–target element pair based on the Coulomb's friction law provides friction. According to this study, maximum displacements appear when the friction is considered in the joints. In addition, hydrodynamic pressure increases the horizontal displacements of the dam. The horizontal displacements also increase by the effect of the non-linear behaviour of the rockfill and concrete slab.

Historical masonry structures have an important value for cultures and it is essential for every society to strengthen them and confidently transfer to the future. For this reason, determination of the seismic earthquake response, which is the most affecting factor to cause the damage at these structures, gain more importance. In this paper, the seismic earthquake behaviour of Kaya Çelebi Mosque, which is located in Turkey and the restoration process has still continued after 2011 Van earthquake, is determined. Firstly the dynamic modal analysis and subsequently the seismic spectral analysis are performed using the finite element model of the mosque constructed with restoration drawings in SAP2000 program. Maximum displacements, tensile, compressive and shear stresses are obtained and presented with contours diagrams. Turkish Earthquake Code and its general technical specifications are considered to evaluate the structural responses. After the analyses, it is seen that the displacements and compressive/shear stresses within the code limits. However, tension stresses exceeded the maximum values at some local regions. For this mosque, this is in tolerance limits considering the whole structure. But, it can be said that the tension stresses is very important for this type of the structures, especially between the stone and mortar. So, some additional strengthening solutions considering the originality of historical structures may be applicable on maximum tensile regions.

Abstract Our research aims to compare the existing damage standard for structures subjected to near-field blast-induced ground motions. Sixty-four different blasting records were collected from the selected quarry during 20 months in Trabzon, Turkey. Blasting characteristics such as peak particle velocities, dominant frequencies, air pressures, maximum accelerations, and maximum displacements were measured during the blasting on hard soil. Longitudinal, transverse and vertical peak particle velocities were evaluated using existing vibration standards or damage criteria such as United States (USBM 8507), Germany (DIN 4150), Sweden (SS 25210), India (IS 6922), England (BS 7385), Australia (CA 23), and Turkey. According to the U.S., English and Turkish vibration standards, the measured blast-induced ground motions did not cause the significant damage on the structures as compared with the other standards. It was observed that U.S., English, and Turkish standards are very suitable to evaluate the structural damage level of structures to near-field blast-induced ground motions. In addition, nonlinear dynamic analyses of reinforced concrete (RC) highway bridge were performed. The analytical model was constituted by ANSYS. From the analysis, displacements are increased along to the middle of the bridge deck. The maximum and minimum principal stresses are obtained at the top of the bridge column and at the middle of the bridge spans.

Final-state field load testing is an effective method for understanding the real behavior of a bridge before it opens to traffic. The paper presents the procedure and the results of final-state static field tests on the new long span Kömürhan cable-stayed bridge with a single pylon and back span anchorage block under torsional and bending loadings. A total of six static loading cases were conducted to investigate real structural behavior of the bridge having a back span anchorage block and main span deck connected to the pylon with 42 tensioned cables in the deck center. Measured results have been obtained from the surveys and sensors while theoretical results have been calculated from the three-dimensional finite element model of the bridge final-state geometry. The results of final-state static load tests include the main span deck deflections, pylon horizontal displacements, the strains of the main span deck and the pylon, and the cable forces. A good agreement has been achieved between the experimental and theoretical results. Both experimental and theoretical results have shown that the real bridge behavior is in the elastic state under the planned test loads and supplies the design requirements. It is also observed that the results from the torsional and bending load cases positioned in the same sections are close to each other.

This paper presents the earthquake response of a historical masonry minaret after a finite element model updating was undertaken using the information from full scale ambient vibration testing. The Iskenderpaşa historical masonry minaret dating back to the 16th century with a height of 21m located in the city center of Trabzon, Turkey is selected as an application. Analytical modal analysis is performed on the 3D finite element model of the minaret considering field survey and engineering judgments to obtain the analytical frequencies and mode shapes. The field ambient vibration tests on the minaret under natural excitations such as wind loading and human movement are conducted. The Peak Picking and the Stochastic Subspace Identification techniques are used to extract the modal parameters from the ambient vibration test. A good correlation was found among the modal parameters identified from the two techniques. The finite element model of the minaret is updated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modeling parameters such as material properties and boundary conditions. The analytical model of the minaret after finite element model updating is analyzed using the 1992 Erzincan earthquake record, which occurred near the area, to determine the earthquake behavior of the minaret. At the end of the study, maximum differences in the natural frequencies are reduced on average from 27% to 5% and a good agreement is found between analytical and experimental natural frequencies and mode shapes by model updating. Also, it is seen from the earthquake analysis that the displacements increase along the height of the minaret and the maximum and minimum principal stresses occur at the region of the transition segment and the cylindrical body.

Abstract General stability and failure behaviours of masonry domes under static loads have been detailly searched in literature. However, researchers have devoted little attention to their seismic failure behaviours under strong ground motions. This study aims a better understanding of seismic failure behaviours of masonry domes with support system including drum and buttresses using advanced 3D nonlinear numerical simulations under strong ground motions. Four types of masonry domes built on historical structures are selected such as a dome with circle drum, a dome with circle drum and buttress, a dome with octagonal drum, a dome with octagonal drum and buttress. The three-dimensional solid and finite element models of the selected masonry domes are created using isotropic continuum macro modelling technique with homogenized properties. Concrete Damage Plasticity (CDP) model is chosen for masonry material behaviour. Three different strong ground motion acceleration records of 1999 Düzce (M = 7.14), 1992 Erzincan (M = 6.69) and 1999 Kocaeli (M = 7.51) earthquakes are selected and matched to the target response spectrum with return period of 475 years in TBEC (2019) using the wavelet algorithm. Static and seismic failure behaviours of the four masonry spherical dome models subjected to the matched strong ground motion records are compared and evaluated using maximum principal stresses, damage propagation patterns and failure angles. Failure behaviour angles under strong ground motions are proposed for spherical masonry domes with support systems and thickness-to-span ratios t/R = 0.092.