The aim of this study concerns with the construction stage analysis of highway bridges constructed with balanced cantilever method using time dependent material properties. K<TEX>$\ddot{o}$</TEX>m<TEX>$\ddot{u}$</TEX>rhan Highway Bridge constructed with balanced cantilever method and located on the 51st km of Elazi<TEX>$\check{g}$</TEX>-Malatya, Turkey, highway over Firat River is selected as an application. Finite element models of the bridge are modelled using SAP2000 program. Geometric nonlinearity is taken into consideration in the analysis using P-Delta plus large displacement criterion. The time dependent material strength variations and geometric variations are included in the analysis. Elasticity modulus, creep and shrinkage are computed for different stages of the construction process. The structural behaviour of the bridge at different construction stages has been examined. Two different finite element analyses with and without construction stages are carried out and results are compared with each other. As analyses result, variation of internal forces such as bending moment, axial forces and shear forces for bridge deck and column are given with detail. It is seen that construction stage analysis has remarkable effect on the structural behaviour of the bridge.
Historical masonry domes are an important part of the architectural and engineering heritage in the World. They have been extensively used to cover the spaces of temples, mausoleums, palaces, forts, baths, churches, mosques, etc. Damages and collapses of masonry domes occurred as a result of earthquakes or lack of maintenance. Therefore, many efforts have been devoted to clarifying the theoretical and experimental responses of masonry domes by researchers. In addition to traditional techniques, significant developments have been achieved on the strengthening of masonry domes using innovative techniques. The study firstly presents a complete review on the state of knowledge about theoretical and experimental responses and strengthening of masonry domes under static and dynamic loads. Then crack patterns and failure mechanisms of masonry domes are explained, and traditional and innovative strengthening techniques that can be rehabilitated the masonry dome without any harmful intervention or disagreement with conservation principles are introduced and evaluated in detail.
Historical masonry aqueducts were constructed to convey water over rivers, valleys, etc. Many of them have deteriorated due to different effects and may need to be repaired or strengthened to increase their load carrying capacities. Historical aqueducts are invaluable cultural heritage, and they require particular attention and appropriate seismic strengthening techniques including minimal intervention, better workability and reduced cost. The present study proposes filling the canal with water to improve structural seismic performance of historical masonry aqueducts. The influence of fluid–structure interaction in seismic performance improvement of historical masonry aqueducts is numerically investigated in this study. Three-dimensional (3D) finite element models of an aqueduct including without and with fluid–structure interaction are created using the coupled acoustic fluid–structure (CAS) approach. Concrete Damage Plasticity (CDP) material model adjusted to masonry units and ground motion records matched to site-dependent are utilized in the nonlinear seismic analyses. Seismic performances of the aqueduct models with and without fluid–structure interaction for the only-transverse, combined transverse and longitudinal, and combined transverse and longitudinal and vertical component cases are evaluated and compared with each other.
The present paper investigates the stochastic seismic responses of steel structure systems with Partially Restrained (PR) connections by using Perturbation based Stochastic Finite Element (PSFEM) method. A stiffness matrix formulation of steel systems with PR connections and PSFEM and MCS formulations of structural systems are given. Based on the formulations, a computer program in FORTRAN language has been developed, and stochastic seismic analyses of steel frame and bridge systems have been performed for different types of connections. The connection parameters, material and geometrical properties are assumed to be random variables in the analyses. The Kocaeli earthquake occurred in 1999 is considered as a ground motion. The connection parameters, material and geometrical properties are considered to be random variables. The efficiency and accuracy of the proposed SFEM algorithm are validated by comparison with results of Monte Carlo simulation (MCS) method.
This paper demonstrates an application of the perturbation based stochastic finite element method (SFEM) for predicting the performance of structural systems made of composite sections with random material properties. The composite member consists of materials in contact each of which can surround a finite number of inclusions. The perturbation based stochastic finite element analysis can provide probabilistic behavior of a structure, only the first two moments of random variables need to be known, and should therefore be suitable as an alternative to Monte Carlo simulation (MCS) for realizing structural analysis. A summary of stiffness matrix formulation of composite systems and perturbation based stochastic finite element dynamic analysis formulation of structural systems made of composite sections is given. Two numerical examples are presented to illustrate the method. During stochastic analysis, displacements and sectional forces of composite systems are obtained from perturbation and Monte Carlo methods by changing elastic modulus as random variable. The results imply that perturbation based SFEM method gives close results to MCS method and it can be used instead of MCS method, especially, if computational cost is taken into consideration.
In recent decades there has been a trend towards improved mechanical characteristics of materials used in footbridge construction. It has enabled engineers to design lighter, slender and more aesthetic structures. As a result of these construction trends, many footbridges have become more susceptible to vibrations when subjected to dynamic loads. In addition to this, some inherit modelling uncertainties related to a lack of information on the as-built structure, such as boundary conditions, material properties, and the effects of non-structural elements make difficult to evaluate modal properties of footbridges, analytically. For these purposes, modal testing of footbridges is used to rectify these problems after construction. This paper describes an arch type steel footbridge, its analytical modelling, modal testing and finite element model calibration. A modern steel footbridge which has arch type structural system and located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed 3D finite element model of footbridge to provide the analytical frequencies and mode shapes. The 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 the 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 footbridge is calibrated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modelling parameters such as material properties. 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, mode shapes by model calibration.
This paper examines the ice cover effects on the seismic response of concrete gravity dam-reservoir-foundation interaction systems subjected to a horizontal earthquake ground motion. ANSYS program is used for finite element modeling and analyzing the ice-dam-reservoir-foundation interaction system. The ice-dam-reservoir interaction system is considered by using the Lagrangian (displacementbased) fluid and solid-quadrilateral-isoparametric finite elements. The Sariyar concrete gravity dam in Turkey is selected as a numerical application. The east-west component of Erzincan earthquake, which occurred on 13 March 1992 in Erzincan, Turkey, is selected for the earthquake analysis of the dam. Dynamic analyses of the dam-reservoir-foundation interaction system are performed with and without ice cover separately. Parametric studies are done to show the effects of the variation of the length, thickness, elasticity modulus and density of the ice-cover on the seismic response of the dam. It is observed that the variations of the length, thickness, and elasticity modulus of the ice-cover influence the displacements and stresses of the coupled system considerably. Also, the variation of the density of the ice-cover cannot produce important effects on the seismic response of the dam.
This paper investigates environmental effects on dynamic characteristics of isolated highway bridges constructed with the balanced cantilever method using ambient vibration test. The Gülburnu Highway Bridge located on the Giresun-Espiye state highway is selected as an application. Measurement time, frequency span and effective mode number are selected by considering similar studies found in the literature. The first measurement tests are conducted in June 2009 and traffic over the bridge is used as a source of ambient vibrations to obtain the dynamic characteristics such as natural frequencies, mode shapes and damping ratios. The second measurement tests are conducted in November 2011 using ambient vibrations and the dynamic characteristics are obtained, experimentally. The output-only modal identification of the bridge is effectively carried out using the enhanced frequency domain decomposition method in the frequency domain and stochastic subspace identification method in the time domain. At the end of the study, experimentally identified dynamic characteristics are compared with each other and environmental effects are investigated in detail. The analysis results reveal that the identified natural frequencies provide an effective indication for changes of dynamic characteristics of the bridge due to environmental effects. Significant variability in the identified natural frequencies is changing by up to maximum 14%.
The investigation of dynamic response for civil engineering structures largely depends on a detailed understanding of their dynamic characteristics, such as the natural frequencies, mode shapes, and modal damping ratios. Dynamic characteristics of structures may be obtained numerically and experimentally. The finite-element method is widely used to model structural systems numerically. However, there are some uncertainties in numerical models. Material properties and boundary conditions may not be modeled correctly. There may be some microcracks in the structures, and these cracks may directly affect the modeling parameters. Modal testing gives correct uncertain modeling parameters that lead to better predictions of the dynamic behavior of a target structure. Therefore, dynamic behavior of special structures, such as minarets, should be determined with ambient vibration tests. The vibration test results may be used to update numerical models and to detect microcracks distributed along the structure. The operational modal analysis procedure consists of several phases. First, vibration tests are carried out, spectral functions are produced from raw measured acceleration records, dynamic characteristics are determined by analyzing processed spectral functions, and finally analytical models are calibrated or updated depending on experimental analysis results. In this study, an ambient vibration test is conducted on the minaret under natural excitations, such as wind effects and human movement. The dynamic response of the minaret is measured through an array of four trixial force-balanced accelerometers deployed along the whole length of the minaret. The raw measured data obtained from ambient vibration testing are analyzed with the SignalCAD program, which was developed in MATLAB. The employed system identification procedures are based on output-only measurements because the forcing functions are not available during ambient vibration tests. The ModalCAD program developed in MATLAB is used for dynamic characteristic identification. A three-dimensional model of the minaret is constructed, and its modal analysis is performed to obtain analytical frequencies and mode shapes by using the ANSYS finite-element program. The obtained system identification results have very good agreement, thus providing a reliable set of identified modal properties (natural frequencies, damping ratios, and mode shapes) of the structure, which can be used to calibrate finite-element models and as a baseline in health monitoring studies.
Abstract The aim of this paper is to determine the earthquake behaviour of the Kömürhan Highway Bridge, located at the 51st kilometre of the Elazığ-Malatya highway over the Fırat River, after finite element model updating using operational modal analyses. Finite element models of the bridge are built with the SAP2000 program to obtain analytical dynamic characteristics such as natural frequencies and mode shapes. The ambient vibration tests are performed using operational modal analysis under traffic loads to attain experimental dynamic characteristics. Vibration data is gathered from both the box girder and bridge deck to compare the results. Measurement time, frequency span, and effective mode number are determined following similar studies and literature. The peak picking method in the frequency domain is used for output-only modal identification. The finite element model of the bridge is updated by changing some uncertainties in the parameters such as material properties and boundary conditions to eliminate the differences between analytical and experimental dynamic characteristics. An analytical model of the bridge after finite element model updating is analyzed using the 1992 Erzincan, Turkey earthquake record, which occurred near the region, to determine the earthquake behaviour of the bridge. At the end of the study, the maximum differences in the natural frequencies are reduced on average from 10 % to 2 %, and a good agreement is found between analytical and experimental natural frequencies and mode shapes by model updating. Also, the variation of internal forces such as bending moment, axial forces, and shear forces for the bridge deck and columns are presented in detail.
Vibration based damage detection is very popular in the civil engineering area. Especially, special structures like dams, long-span bridges and high-rise buildings, need continues monitoring in terms of mechanical properties of material, static and dynamic behavior. It has been stated in the International Commission on Large Dams that more than half of the large concrete dams were constructed more than 50 years ago and the old dams have subjected to repeating loads such as earthquake, overflow, blast, etc.,. So, some unexpected failures may occur and catastrophic damages may be taken place because of theloss of strength, stiffness and other physical properties of concrete. Therefore, these dams need repairs provided with global damage evaluation in order to preserve structural integrity. The paper aims to show the effectiveness of the model updating method for global damage detection on a laboratory arch dam model. Ambient vibration test is used in order to determine the experimental dynamic characteristics. The initial finite element model is updated according to the experimentally determined natural frequencies and mode shapes. The web thickness is selected as updating parameter in the damage evaluation. It is observed from the study that the damage case is revealed with high accuracy and a good match is attained between the estimated and the real damage cases by model updating method.
Historical masonry stone mosques with timber truss roofs were widely constructed all over the world. Due to the complex structural behaviors of this type of building, it is difficult to determine natural frequencies during the seismic safety evaluations numerically. The article aims to develop simplified natural frequency formulas based on ambient vibrations for the historical masonry stone mosques with timber truss roofs. Fourteen masonry stone mosques with timber truss roofs built in the Eastern Black Sea Region of Turkey are selected for the study. Experimental natural frequencies, mode shapes and damping ratios of the selected mosques under ambient vibrations are determined using the Operational Modal Analyses. Ambient vibration-based simplified natural frequency formulas based on the geometrical dimensions for the masonry stone mosques with timber truss roofs are obtained by using the statistical regression analysis. The proposed formulas for the first three frequencies are verified with the control data.
Abstract Natural stone masonry mosques with wooden roof are the most widespread historical building of Eastern Black Sea Region in Turkey. The main walls of buildings are made with the combination of natural stone, lime, soil or horosan mortar and their roofs are constituted with wooden elements. Within the scope of this study, it is aimed to determine the dynamic characteristics of masonry stone mosques with wooden roof in the Eastern Black Sea Region in Turkey with nondestructive experimental methods. For the purpose of practice, Rize Gulbahar Mahallesi Buyuk Mosque, Artvin Hopa Sundura Mahallesi Mosque and Trabzon Merkez Tavanli Mosque are selected. Selected mosques have recently been restored and their geometries and properties are similar. The dynamic characteristics such as natural frequency, modal damping ratios and mode shape of the mosques are determined with the Ambient Vibration Test by using the seismic accelerometer. The results of nondestructive experiments obtained from the mosques are compared with each other and the frequency interval for the control of the analytic models of masonry stone mosques with wooden roof is given. Key Words: Mosques with wooden roof, masonry stone mosques, the Ambient Vibration Test,nondestructive test method, Eastern Black Sea Region. Oz Ahsap catili dogal tas yigma camiler, Turkiye’nin Dogu Karadeniz Bolgesinde siklikla rastlanan tarihi eserlerdendir. Camilerin beden duvarlari dogal tas, kirec, toprak veya horosan harci birlesimi ile yapilmis ve catilari ahsap elemanlarla teskil edilmistir. Bu calisma kapsaminda, Dogu Karadeniz Bolgesinde bulunan ahsap catili yigma tas camilerin dinamik karakteristiklerinin hasarsiz deneysel yontemlerle tespit edilmesi amaclanmistir. Uygulama amaciyla, Rize Gulbahar Mahallesi Buyuk Camii, Artvin-Hopa Sundura Mahallesi Camii ve Trabzon Merkez Tavanli Camii secilmistir. Secilen camiler, yakin zamanda restorasyonu yapilmis eserler olup, geometrileri ve ozelikleri benzerdir. Camilerin frekans, sonum orani ve mod seklinden olusan dinamik karakteristikleri sismik ivme olcerler kullanilarak Cevresel Titresim Testi yontemiyle belirlenmistir. Soz konusu camilerden elde edilen hasarsiz deneysel sonuclar birbirleriyle karsilastirilmis ve ahsap catili yigma camilerin analitik modellerinin kontrolu icin frekans araligi verilmistir. Anahtar Kelimeler: Ahsap Catili Camiler, Yigma Tas Camiler, Cevresel Titresim Testi, Hasarsiz Deneysel Yontemler, Dogu Karadeniz Bolgesi.
