Applications of experimental modal analysis for bridges

Deneysel modal analiz son 30 yıldır çeşitli araştırmacılar tarafından yapısal sistemlerin durum tespiti/izlemesi ve hasar tanılaması amacıyla kullanılmaktadır. Ölçüm ve analizlerin tekniğine uygun olarak tasarlanıp uygulanması durumunda bu teknik ile yapısal bir sistemin dinamik özellikleri (frekanslar, sönüm oranları ve modal şekilleri) kestirilebilmektedir. Sistemde oluşacak herhangi bir hasarın sistemin sıkılığını ve aynı zamanda dinamik özelliklerini değiştireceği gerçeğinden yola çıkılırsa, hasar öncesi ve sonrası dinamik özelliklerin izlenmesi sayesinde yapıda oluşan hasarlar tahribatsız bir biçimde tespit edilebilir. İzmir Yüksek Teknoloji Enstitüsü (İYTE), İnşaat Mühendisliği Bölümü’nde bir TÜBİTAK projesi kapsamında deneysel modal analiz tekniğinin kullanılması yönünde çalışmalar yapılmaktadır. Bu bildiri kapsamında deneysel modal analiz tekniklerinin köprülerin durum tespiti ve hasar tanılamasında ne şekilde uygulanabileceği konusunda kısa bir özet verilecek ve İYTE’de bugüne kadar öğrendiğimiz teknikleri uygulamada gösterebilmek amacı ile laboratuvarda imal, basitleştirilmiş bir köprü maketi üzerinde modal analiz teknikleri kullanılacak ve sonuçlar sergilenecektir. Ayrıca maket köprünün sonlu elemanlar modeli kurularak analiz ve deney sonuçları karşılaştırılacak ve sonuçlar irdelenecektir.Experimental modal analysis is used by researchers for the purpose of condition assessment and damage detection of structural systems. If the experiment and analysis are performed accordingly, it is possible to identify the dynamic parameters of the systems such as natural frequencies, damping ratios and the modal vectors. Since any damage in the system changes the stiffness and at the same time dynamic parameters of the system, it is possible to detect and locate the damage in the system. System parameters should be identified before and after the damage for such an evaluation. Experimental modal analysis technique is under study in IYTE, Civil Engineering Department. Through the paper a limitedliterature survey will be presented in relation with the application of modal analysis techniques for condition assessment and damage detection of bridges. Also a simple bridge model will be tested and analyzed with techniques that we have acquired in IYTE up to now. In order to discuss the results of the modal analysis results, a finite element model of the model bridge will also provided.TUBITAK-MAG 104I10

Seismic performance of wide-beam infill-joist block RC frames in Turkey

Observations after the 2011 Van-Erciş earthquake show that some of the recently constructed reinforced-concrete buildings were either heavily damaged or had collapsed. As a building subtype, wide-beam, infill-joist block reinforced-concrete frames got attention because of their mode of failure. There were several such buildings that failed in strong-column, weak-beam mode. Considering the demand created by the earthquake, structures were not expected to reach their full capacity. The purpose of this study is to review the history and current practice of infill-joist frames in Turkey and to conduct a performance evaluation of infill-joist frames designed per the current earthquake code (2007). Regulations for this building subtype are critically reviewed, and the designer's response to code regulations is discussed. Results indicate that the force-based design approach used in the current code is not always adequate to satisfy the displacement demands. In addition, it is observed that layout, proportioning, and detailing requirements of beam-end regions and beam-column connections do not always warrant ductile behavior as targeted

Applications of experimental modal analysis for bridges

Deneysel modal analiz son 30 yıldır çeşitli araştırmacılar tarafından yapısal sistemlerin durum tespiti/izlemesi ve hasar tanılaması amacıyla kullanılmaktadır. Ölçüm ve analizlerin tekniğine uygun olarak tasarlanıp uygulanması durumunda bu teknik ile yapısal bir sistemin dinamik özellikleri (frekanslar, sönüm oranları ve modal şekilleri) kestirilebilmektedir. Sistemde oluşacak herhangi bir hasarın sistemin sıkılığını ve aynı zamanda dinamik özelliklerini değiştireceği gerçeğinden yola çıkılırsa, hasar öncesi ve sonrası dinamik özelliklerin izlenmesi sayesinde yapıda oluşan hasarlar tahribatsız bir biçimde tespit edilebilir. İzmir Yüksek Teknoloji Enstitüsü (İYTE), İnşaat Mühendisliği Bölümü’nde bir TÜBİTAK projesi kapsamında deneysel modal analiz tekniğinin kullanılması yönünde çalışmalar yapılmaktadır. Bu bildiri kapsamında deneysel modal analiz tekniklerinin köprülerin durum tespiti ve hasar tanılamasında ne şekilde uygulanabileceği konusunda kısa bir özet verilecek ve İYTE’de bugüne kadar öğrendiğimiz teknikleri uygulamada gösterebilmek amacı ile laboratuvarda imal, basitleştirilmiş bir köprü maketi üzerinde modal analiz teknikleri kullanılacak ve sonuçlar sergilenecektir. Ayrıca maket köprünün sonlu elemanlar modeli kurularak analiz ve deney sonuçları karşılaştırılacak ve sonuçlar irdelenecektir.Experimental modal analysis is used by researchers for the purpose of condition assessment and damage detection of structural systems. If the experiment and analysis are performed accordingly, it is possible to identify the dynamic parameters of the systems such as natural frequencies, damping ratios and the modal vectors. Since any damage in the system changes the stiffness and at the same time dynamic parameters of the system, it is possible to detect and locate the damage in the system. System parameters should be identified before and after the damage for such an evaluation. Experimental modal analysis technique is under study in IYTE, Civil Engineering Department. Through the paper a limitedliterature survey will be presented in relation with the application of modal analysis techniques for condition assessment and damage detection of bridges. Also a simple bridge model will be tested and analyzed with techniques that we have acquired in IYTE up to now. In order to discuss the results of the modal analysis results, a finite element model of the model bridge will also provided.TUBITAK-MAG 104I10

A case study for seismic assessment and restoration of historic buildings: The Arditi residence

This chapter focuses on seismic assessment and restoration of one of the numerous historical buildings in Turkey; the Arditi Residence in Urla, Izmir. It is a 150 years old two story masonry building located in a seismically active region. From the structural point of view, the building can be regarded as a mixed system since three different techniques had been used during the construction. The Arditi Residence has been investigated in three stages: preliminary evaluation, seismic performance assessment and intervention. The building has been observed to possess serious deficiencies, which are not easy to handle due to the complexity of the construction system. On the other hand, the proposed intervention strategies should have the minimal impact on the historic information building carrying and provide a certain level of safety against the seismic demands. Overall, the chapter presents a contribution to seismic assessment and restoration of historical structures on the basis of Arditi Residence, a unique historical building with serious problems in an earthquake-prone region

Effect of infill walls on the drift behavior of reinforced concrete frames subjected to lateral-load reversals

Four-story, single-bay, 1/5 scaled reinforced concrete frames were tested with and without infill walls. Frames were subjected to pseudo-static cyclic loading. In addition, impact hammer measurements were made to obtain the natural frequencies and modal shapes at certain drift levels. It was observed that infill walls cause major changes on both the stiffness and the drift behavior of the frames. Effect of observed changes can be either advantageous or disadvantageous depending on failure mode. Results showed that the distribution of drift that is based on the mode shapes has higher local concentrations than the distribution observed under forced static conditions.Scientific and Technological Research Council of Turkey (MAG-104I107

Numerical model for biaxial earthquake response of reinforced concrete

A numerical constitutive model is developed to simulate the biaxial nonlinear flexural response of slender reinforced concrete members subjected to earthquake excitation. The model is tested using data from two types of experiments with reinforced concrete elements: (1) elements subjected to varying pseudo-static biaxial lateral loads and (2) elements that responded biaxially to simulated earthquake motions. The goal for the model was not only to help determine the absolute maxima for earthquake response but also to enable calculation of the entire waveform, including the ranges of low- and moderate-amplitude response. The comparisons of measured and calculated results and sensitivity of the proposed model to variations in the input parameters are discussed. The output was found to be insensitive to the changes in input parameters related to concrete and sensitive to input parameters related to reinforcing steel. The results of the calculations were tested using experimental data

Seismic Fragility of Wide-Beam Infill-Joist Block Reinforced Concrete Frame Buildings

Wide-beam infill-joist block (WBIJB) reinforced concrete (RC) frame is a popular construction technique in Turkey and the Mediterranean basin. Even though there were previous observations and considerations about the problematic seismic behavior of the WBIJB frames, the behavior was concealed behind the general weaknesses of the RC frames. Currently WBIJB RC frames are not considered as a separate sub-class of RC frame systems during regional damage and loss estimation studies. However, the recent earthquakes shed a light on the possible inferior behavior of this class of building structures. The main difference of the WBIJB frames from conventional moment resisting frames is the presence of wideshallow beams as an architectural preference. Due to shallow beams, the lateral stiffness of these systems decrease which resulted an increase in the period of the buildings. Hence, increased earthquake drift demands resulted. The main goal of the presented study is to develop the fragility curves for this specific class of RC frame buildings, which constitute a significant portion of the existing building stock in Turkey. The resulting fragility information could be employed in future regional loss estimation studies. For this purpose, a generic two dimensional frame is designed and modeled by considering the properties of the existing WBIJB frame buildings, the current seismic regulations and the construction practice in Turkey. Pushover and nonlinear time history analyses are conducted in order to quantify seismic demand and capacity. Then this information is used to calculate the probabilities of exceeding the predefined limit states as a function of seismic ground motion intensity parameters. In the last part of the study, the estimated fragility curves are compared with the available fragility curves of similar construction types

Mechanical behavior of polypropylene-based honeycomb-core composite sandwich structures

This article presents results from an experimental study, investigating the effects of core thickness on the mechanical properties of composite sandwich structures with polypropylene(PP)-based honeycomb core and glass fiber-reinforced polymer (GFRP) face-sheets fabricated by hand lay-up technique. Epoxy matrix and non-crimp glass fibers were used for the production of GFRP laminates. Flatwise compression (FC), edgewise compression (EC), three-point bending (3PB) and double cantilever beam (DCB) tests were performed to evaluate the mechanical behavior of the composite sandwich structures (CSSs). Based on the FC tests, an increase in the compressive modulus and strength was observed with an increase in the core thickness. For EC tests, peak loads up to crush of the sandwich panel is discussed using core thickness. According to the 3PB tests, a decrease in core shear stress and facesheet bending stress was observed as the core thickness increases. © SAGE Publications 2010