This research presents finite element modelling, vibration-based operational modal analysis, and finite element model updating of a restored historic arch bridge. Mikron historic bridge, constructed on Fırtına River in Rize, Turkey, is the subject of this case study. The General Directorate for Highways of Turkey repaired the bridge's main structural elements, arches, sidewalls, and filler material in 1998. To construct a 3D finite element model of the bridge, ANSYS finite element software estimated the analytical dynamic characteristics. Induced ambient vibrations such as human walking and wind excited the model bridge to allow measurement of the bridge's responses. Enhanced frequency domain decomposition in frequency domain and stochastic subspace identification in time domain methodologies extracted experimental dynamic characteristics. A comparison of the analytical and experimental results showed significant agreement between mode shapes, but some differences in natural frequencies appeared. Consequently, updating the finite element model of the bridge by changing boundary conditions minimised the differences between analytical and experimental natural frequencies. After the finite element model updating process, the differences between natural frequencies declined from 7% to 2%.
Masonry arch bridges, which were generally built using brick and stone materials, still form a significant part of the highway and railway networks in the World. The subsoil deformability may considerably affect seismic damage mechanics of masonry arch bridges. The paper investigates the effects of nonlinear foundation soil behavior on the seismic damage mechanisms of brick and stone semicircular masonry arch bridges. Direct soil-structure interaction (SSI) approach is taken into account in the 3 D finite element models of the masonry arch bridge-foundation-soil interaction systems including contact, finite and infinite elements. Nonlinear behaviors of masonry units and homogenous soil domain are modeled using the Concrete Damage Plasticity (CDP) and Mohr-Coulomb failure criteria. The selected ground motion is matched and deconvoluted for hard and medium soil domains. Seismic damage mechanisms of brick and stone masonry arch bridges subjected to combined longitudinal and vertical deconvolved ground motion components are obtained for hard, medium, and partially hard and medium soil domains and are compared with each other.
In this paper, it is aimed to determine the finite element model updating effects on the structural behavior of long span concrete highway bridges. Birecik Highway Bridge located on the 81stkm of Sanliurfa-Gaziantep state highway over Firat River in Turkey is selected as a case study. The bridge consist of fourteen spans, each of span has a nearly 26m. The total bridge length is 380m and width of bridge is 10m. Firstly, the analytical dynamic characteristics such as natural frequencies and mode shapes are attained from finite element analyses using SAP2000 program. After, experimental dynamic characteristics are specified from field investigations using Operational Modal Analysis method. Enhanced Frequency Domain Decomposition method in the frequency domain is used to extract the dynamic characteristics such as natural frequencies, mode shapes and damping ratios. Analytically and experimentally identified dynamic characteristics are compared with each other and finite element model of the bridge is updated to reduce the differences by changing of some uncertain parameters such as section properties, damages, boundary conditions and material properties. At the end of the study, structural performance of the highway bridge is determined under dead load, live load, and dynamic loads before and after model updating to specify the updating effect. Displacements, internal forces and stresses are used as comparison parameters. From the study, it is seen that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %46.7 to %2.39 by model updating. A good harmony is found between mode shapes after finite element model updating. It is demonstrated that finite element model updating has an important effect on the structural performance of the arch type long span highway bridge. Maximum displacements, shear forces, bending moments and compressive stresses are reduced %28.6, %21.0, %19.22, and %33.3-20.0, respectively.
In the present paper it is aimed to perform the stochastic dynamic analysis of fluid and fluidstructure systems by using the Lagrangian approach. For that reason, variable-number-nodes twodimensional isoparametric fluid finite elements are programmed in Fortran language by the authors and incorporated into a general-purpose computer program for stochastic dynamic analysis of structure systems, STOCAL. Formulation of the fluid elements includes the effects of compressible wave propagation and surface sloshing motion. For numerical example a rigid fluid tank and a dam-reservoir interaction system are selected and modeled by finite element method. Results obtained from the modal analysis are compared with the results of the analytical and numerical solutions. The Pacoima Dam record S16E component recorded during the San Fernando Earthquake in 1971 is used as a ground motion. The mean of maximum values of displacements and hydrodynamic pressures are compared with the deterministic analysis results.
The effect of the non-linear material behavior of a rock-fill dam subjected to random loads is investigated by the equivalent linear method that considers the non-linear variation of soil shear moduli and damping ratios as a function of shear strain. The Keban dam constructed in Elazig, Turkey is chosen as a numerical example. The interaction of the rock-fill dam with the reservoir is neglected, but not the foundation rock. The properties of the dam materials were taken from the dam project and assumed to be isotropic in the analysis. A stationary and ergodicity assumption are made for stochastic dynamic analysis. The E-W component of the Erzincan earthquake recorded on March 13, 1992, Erzincan, Turkey is chosen as a ground motion since it occurred nearby the dam site. The component considered is applied to the dam in the horizontal direction. The non-linear stochastic responses of the Keban dam are compared to its linear stochastic and deterministic response.
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.
To investigate the effect of the presence of surrounding ice sheet on the stochastic response of offshore wind turbines subjected to random seismic excitation, this research uses a three-dimensional, numerical, finite-element model that includes viscous boundaries. The model of the ice–seawater–offshore wind turbine–soil interaction system uses the Lagrangian fluid (displacement-based) and solid-quadrilateral-isoparametric finite elements. Random seismic excitation from a filtered white-noise model and applied to each support point of the three-dimensional finite-element model of the coupled interaction system provides the experimental environment. A parametric study examines the effects of both the presence of and variation in mechanical and geometric properties of the surrounding ice sheet on the stochastic response of offshore wind turbines. The investigation also includes the effect of the wind turbine’s wall thickness in relation to the ice sheet on the stochastic seismic response of the coupled interaction system.
