This paper describes a historical arch bridge; its analytical modelling, modal testing and finite element model (FEM) updating. For this purpose, Senyuva historical arch bridge which is built in 1696 and located in Camlihemsin, Rize, Turkey, is selected as an application. 3D FEM of the bridge is modelled using ANSYS software to obtain analytical dynamic characteristics such as natural frequencies and mode shapes. Then, operational modal analysis using ambient vibrations is performed to attain dynamic characteristics experimentally. Human walking and wind are used as natural excitation. The output-only modal parameter identification is carried out using the Peak Picking method in frequency domain and the Stochastic Subspace Identification method in time domain. After, analytically and experimentally identified dynamic characteristics compared with each other and FEM of the historical bridge is updated to minimize the differences between modal parameters by changing uncertain modelling parameters such as boundary conditions. As a result, differences between the natural frequencies are reduced from 27% to 3% and good agreement is found between analytical and experimental dynamic characteristics after FEM updating.
This paper presents the analytical modeling, modal testing, and finite-element model updating for a two-span masonry arch bridge. An Ottoman masonry arch bridge built in the 19th century and located at Camlihemsin, Rize, Turkey is selected as an example. Analytical modal analysis is performed on the developed 3D finite-element model of the bridge to obtain dynamic characteristics. The ambient vibration tests are conducted under natural excitation such as human walking. The operational modal analysis is carried out using peak picking method in the frequency domain and stochastic subspace identification method in the time domain, and dynamic characteristics (natural frequencies, mode shapes, and damping ratios) are determined experimentally. Finite-element model of the bridge is updated to minimize the differences between analytically and experimentally estimated dynamic characteristics by changing boundary conditions. At the end of the study, maximum differences in the natural frequencies are reduced on average from 18 to 7% and a good agreement is found between analytical and experimental dynamic characteristics after finite-element model updating.
In this study, the earthquake damage response of the concrete arch dams was investigated including dam-reservoir interaction. A continuum damage model which is a second-order tensor and includes the strain softening behavior was selected for the concrete material. Fluid-structure interaction problem was modeled by Lagrangian approach. Sommerfeld radiation condition was applied to the truncated boundary of reservoir. The improved form of the HHT-<TEX>${\alpha}$</TEX> time integration algorithm was used in the solution of the equations of motion. The arch dam Type 5 was selected for numerical application. For the dynamic input, acceleration records of the 10 December 1967 Koyna earthquake were chosen. These records were scaled with earthquake acceleration scale factor (EASF) and then used in the analyses. Solutions were obtained for empty and full reservoir cases. The effects of EASF and damping ratio on the response of the dam were studied.
There are several idealizations in numerical analysis of structures. In the joints and supports, which is usually assumed to be pinned or rigid, semi-rigid connection should be considered to obtain more realistic, reliable and also economical results. In this study, rotational spring stiffness-connection ratio relation is clearly explained and revealed. A finite element program SEMIFEM is developed in FORTRAN language for the numerical analysis. This program provides to define semi-rigid connections in terms of rotational spring stiffness or connection ratio simultaneously. In the numerical applications, rotational spring stiffness - connection percentage relation of the semi-rigid connected structural members is submitted. Semi-rigid connections are considered in column-to-foundation connection of a portal frame, beam-to-column connection of a prefabricated structure, steel brace connection to reinforced concrete (RC) frame of a steel X-braced RC frame and truss member connection to joint of a steel truss system. The variation of moment, shear force, axial force, displacement and stress is investigated in a selected axis of the structures. Numerical examples are performed with respect to connection percentage of the related structural members by using finite element method. According to finite element analysis results, the degree of the semi-rigid connection is important as much as its existence in the design phase. This study reveals that the effect of semi-rigid connections on structural systems shows different variations from structure to structure.
The effects of restoration on the experimental dynamic characteristics of historical masonry Molla Siyah Mosque in Trabzon, Turkey, are investigated in this paper. Firstly, the initial situation and the implemented restoration works of the mosque are mentioned in detail. Then, the experimental dynamic behaviors of the mosque before and after the restoration are obtained by using the Ambient Vibration Tests. High sensitivity seismic accelerometers with cables are used during the tests. The collected signals are evaluated by Enhanced Frequency Domain Decomposition Technique, and experimental natural frequencies, mode shapes and damping ratios of the mosque are determined for the initial and restoration cases. The obtained results are compared with each other and restoration effects on the dynamic behavior of the mosque are discussed in detail
Abstract The effects of the sediment on the earthquake response of concrete gravity dams subjected to horizontal and vertical asynchronous ground motion are investigated including dam-reservoir-sediment-foundation interaction in this paper. Dam-reservoir-sediment-foundation interaction is modeled by the finite element method. The equations of motion of the dam-reservoir-sediment-foundation system are determined using the Lagrangian approach. Solutions are obtained for dam-reservoir-foundation and dam-reservoir-sediment-foundation systems separately. Parametric studies were conducted in order to investigate the effects of the variation of Young's modulus and thickness of the sediment on the dam response. Seismic wave velocities of 250, 3000 m/s and infinite are used in calculations. It is observed that stresses near the dam crest decrease considerably when the sediment is included in the analyses. The variation of the values of Young's modulus and thickness of the sediment influences the stress component slightly. Keywords: Concrete gravity damsedimentfluid-structure interactionearthquakesasynchronous ground motionseismic wave velocityfinite element methodLagrangian approach
With the recent advances in computer technology and digital simulation software, it is now possible to rapidly and accurately build computer models for complex linear and nonlinear dynamic systems. MATLAB is a unique system that can be used for structural and earthquake engineering problems. This study presents MATLAB tools developed for numerical process of all steps of dynamic vibration test of structures. The functions of the tools are processing the signals obtained from forced and ambient vibration tests of structures, determining the dynamic characteristics of structural systems, and automatically updating the analytical finite element (FE) models. The software group is composed of three programs named as SignalCAD, ModalCAD, and FemUP. The SignalCAD program is developed for processing raw measured data obtained from forced and ambient vibration tests of engineering structures. The ModalCAD program is developed for dynamic characteristic identification and validation procedure. The peak picking method, complex exponential method, and polyreference time domain method are used for modal identification process. The FemUP program is developed for automatically updating the numerical models of structures compared to modal testing results. Each program has a unique graphical user interface and is designed as user friendly. The possibilities of the programs are demonstrated with the model vibration test of a steel cantilever beam. The obtained results are compared to the analytical model, and the FE model is automatically updated, whereas the experimental model is considered as the reference model. Finally, it is seen that MATLAB can be used as a scientific programming platform in all vibration test and modal analysis applications.
The aim of this study is to determine the dynamic characteristics of long reinforced concrete highway bridges with post-tension tendons using analytical and experimental methods. It is known that the deck length and height of bridges are affected the dynamic characteristics considerably. For this purpose, Berta Bridge constructed in deep valley, in Artvin, Turkey, is selected as an application. The Bridge has two piers with height of 109.245 m and 85.193 m, and the total length of deck is 340.0 m. Analytical and experimental studies are carried out on Berta Bridge which was built in accordance with the balanced cantilever method. Finite Element Method (FEM) and Operational Modal Analysis (OMA) which considers ambient vibration data were used in analytical and experimental studies, respectively. Finite element model of the bridge is created by using SAP2000 program to obtain analytical dynamic characteristics such as the natural frequencies and mode shapes. The ambient vibration tests are performed using Operational Modal Analysis under wind and human loads. Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods are used to obtain experimental dynamic characteristics like natural frequencies, mode shapes and damping ratios. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge was updated considering the material properties and boundary conditions. It is emphasized that Operational Modal Analysis method based on the ambient vibrations can be used safely to determine the dynamic characteristics, to update the finite element models, and to monitor the structural health of long reinforced concrete highway bridges constructed with the balanced cantilever method.
The focus of the present paper is to determine the effect of compressibility of the fluid on the stochastic dynamic response of fluidstructure systems by using Lagrangian approach. Variable-numbernodes two-dimensional fluid finite elements were programmed in Fortran language by the authors and incorporated into a generalpurpose computer program for stochastic dynamic analysis of solid systems, STOCAL. A two dimensional fluid-structure interaction problem is selected for numerical example. The influence of the compressibility of the fluid is investigated by increasing the value of the bulk modulus of the fluid. Results obtained from Lagrangian approach are compared with each other and those of the Westergaard approach.
An accurate numerical analysis of the behavior of long-span cable-stayed bridges under environmental effects is a challenge because of complex, uncertain and varying environmental meteorology. This study aims to investigate in-situ experimental structural behavior of long-span steel cable-stayed bridges under environmental effects such as air temperature and wind using the monitoring data. Nissibi cable-stayed bridge with total length of 610m constructed in the city of Adıyaman, Turkey, in 2015 is chosen for this purpose. Structural behaviors of the main structural elements including deck, towers (pylons) and cables of the selected long span cable-stayed bridge under environmental effects such as air temperature and wind are investigated by using daily monitoring data. The daily variations of cable forces, cable accelerations, pylon accelerations and deck accelerations with air temperature and wind speed are compared using the hottest summer (July 31, 2015) and the coldest winter (January 1, 2016) days data.
