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This paper presents damage identification and localization in laminated composite beams including multiple cracks by automated model updating. For this aim, a cantilever beam made of glass/epoxy composite laminate under six simulated damage scenarios is considered. Experimental frequencies and mode shapes of the beam are validated with those of ANSYS® finite element analyses. For damage detection and localization, FEMtools®, a software for automated model updating, is employed. To simulate damages in FEMtools®, material moduli and mass density of the beam are chosen to be uncertain parameters, and the sensitivity analysis based on the Bayesian parameter estimation is performed. In-plane material moduli are found to be the most sensitive parameters for damage evaluation in composite laminates. The locations of the cracks are determined by evaluating the changes (decrease) in these parameters. According to the results of the study, the proposed method can locate the multiple cracks of different severity for the considered cantilever beam. However, in the case with multiple damages of equal severity, only the crack nearest to the fixed-end can be successfully determined while others cannot because the existence of damage near the support in cantilever beams obscures the effects of other damages and the method fails to identify them.

Damages to structures may occur due to construction defects during various stages such as design, construction, and operation phases, or due to natural disasters during their lifetime. The Operational Modal Analysis (OMA) method enables engineers to experimentally determine the changes in dynamic characteristics of the structures that resulted from these undesirable incidents. This method can also help to estimate the structural damages and determine the usage situations depending on stiffness changes. Fire is one of the most important effects that can cause changes in dynamic behavior of structures. Considering the damages caused by fire disasters in recent years, there is a crucial need to address the effects of high temperature on the relevant field of study. This study experimentally examined the effects of elevated temperature on changes in dynamic characteristics of reinforced concrete (RC) and steel structural members. In this regard, a total of 14 (10 columns and 4 frames) laboratory models are built. These models have been constructed with various cross-sectional dimensions considering furnace dimensions. The models have undergone high temperature tests based on ISO 834 standard fire curve. Ambient vibration measurements are conducted to identify and compare the experimental dynamic characteristics both before and after fire exposure. The results show that the damages caused by high temperature significantly affect the dynamic characteristics. Damping ratios generally show a tendency to increase and some minor alterations have been observed in the mode shapes. After the fire the natural frequencies of the models have decreased. It is also observed that increases in the cross-sectional area of RC elements are an effective parameter on these decreases. The use of steel bars affects the dynamic characteristics and temperature distribution within their sections. Besides, different types of steel profiles have an effect on deformations caused by high temperatures.

This work aims to experimentally show the effectiveness of annular cylindrical tuned liquid dampers (ACTLDs) on the classical tuned liquid column dampers (TLCDs) under the effect of inclined ground motion. For experimental measurements, a single-story model structure constituted by two plates at the top and bottom connected by four columns was constructed. Since the water length within the tuned liquid dampers (TLDs) is a very important parameter that affects the performance of the absorber, ACTLD and TLCD devices were designed such that their total water lengths be equal for comparison purposes. The modal characteristics of the model structure were determined by ambient vibration tests. The resonant frequency, head-loss coefficient, damping ratio, and water height-frequency diagram of ACTLD and TLCD devices were obtained experimentally through the shaking table tests. Then, the shaking table tests on the model structure with and without the absorbers under consideration were performed to obtain the acceleration and displacement time-histories and the damping ratio for the coupled system. In experimental tests, different excitation directions from 0 to 90 deg were considered. Results of the study show that ACTLDs are better than TLCDs at suppressing vibrations caused by ground motions acting on the structure at oblique angles.

Industrial structures built with different materials and methods play an important role in the sector with development of industry and increase in energy need. Many parameters are considered in the design and application phase of industrial structures to provide service for many years. The aim of this study is to examine dynamic behavior of reinforced concrete industrial chimneys depending on soil-structure interaction (SSI). For this reason, a reinforced concrete industrial chimney, which was exposed to the 1999 Kocaeli Earthquake, was chosen as a sample. The effect of soils with different properties (hard, medium and soft) on the dynamic behavior of the selected structure was investigated numerically by linear time history analysis in ANSYS finite element program. The horizontal component of the Kocaeli Earthquake (1999) was used in analyses. As a result of the studies, besides the mode shape and frequency of structure, stress, strain and displacements were also obtained. It has been observed that as the hardness of the soil environment decreases (transition from hard soil to soft soil), chimney apex displacements and stresses on the edge of the voids increase., Farklı malzeme ve yöntemlerle inşa edilen endüstriyel yapılar, sanayinin gelişmesi ve enerji ihtiyacının artması ile sektörde önemli bir rol oynamaktadır. Endüstriyel yapıların uzun yıllar hizmet verebilmesi için tasarım ve uygulama aşamasında birçok parametre dikkate alınmaktadır. Bu çalışmanın amacı, betonarme endüstriyel bacaların zemin-yapı etkileşimine (SSI) bağlı dinamik davranışını incelemektir. Bu nedenle örnek olarak 1999 Kocaeli Depremi'ne maruz kalan betonarme bir endüstriyel baca seçilmiştir. Farklı özelliklere sahip (sert, orta ve yumuşak) zeminlerin seçilen yapının dinamik davranışına etkisi ANSYS sonlu elemanlar programında lineer zaman alanı analizi ile sayısal olarak incelenmiştir. Analizlerde Kocaeli Depremi'nin (1999) yatay bileşeni kullanılmıştır. Çalışmalar sonucunda yapının mod şekli ve frekansının yanı sıra gerilme, gerinim ve yer değiştirmeler de elde edilmiştir. Zemin ortamının sertliği azaldıkça (sert zeminden yumuşak zemine geçiş), baca tepe yer değiştirmelerinin ve boşluk kenarlarındaki gerilmelerin arttığı gözlemlenmiştir.

This paper presents results of an experimental study that focuses on monitoring changes in dynamic characteristics of a damaged and retrofitted two-story reinforced concrete (RC) building model with poor detailing. In the study, ambient vibration tests are performed via four test setup protocols in order to monitor changes in dynamic characteristics before and after such setups. The four main test setups are: (i) undamaged (as-built) case (Setup # 1), (ii) damaged cases with different degrees of damages (Setup # 2), (iii) repaired case with different types of repair methods (Setup # 3), and (iv) strengthened case with externally bonded CFRP composite laminates (Setup # 4). In addition, a total of eight ambient vibration tests are conducted in order to assess the effects of degree of damage and associated retrofit systems on building's dynamic characteristics such as natural frequencies, mode shapes, and damping ratios. The Stochastic Subspace Identification (SSI) Method is used to identify the dynamic characteristics. Experimentally identified dynamic characteristics obtained from all setups are compared with each other in order to detect the effect of damage and repair applications on the structure's dynamic characteristics. Moreover, Modal Assurance Criterion (MAC) and Coordinate Modal Assurance Criterion (COMAC) are determined to examine the changes of stiffness of each RC building model.

Reinforced concrete structures used in many areas of our daily life constitute an important part of the building stock in the construction sector. There are many buildings such as reinforced concrete buildings, bridges, tunnels, mosques and dams, and the construction of new buildings in line with the need continues. Many uncertainty factors play a role in the design phase of these structures from the dimensioning as a result of the analysis performed under the required loadings to the implementation phase in the field. Many unpredictable factors such as errors in the analysis, defects in materials and workmanship affect the success rate of the project of the structure. For this purpose, Experimental Modal Analysis method, which is widely used in the literature, is used to determine the success rate of new structures, to determine the dynamic characteristics and damage conditions of existing structures and structural health monitoring. Natural frequencies, which are the dynamic variables of the structure obtained by experimental modal analysis techniques, and mode shapes and damping ratios corresponding to these frequencies are used in the examination of the current state and structural properties of the structures. However, this experimental data can be obtained by with foreign-source software by allocating large budgets. The results of the native experimental modal analysis and finite element model update software developed within the scope of doctoral thesis are compared with the results of the existing software in the literature. As the application, raw signal data of Gülburnu Bridge and scaled Type-1 Arch Dam constructed in laboratory environment were used. The experimental results of the developed software and the existing software were found to be closely related to each other.

Environmental processing, such as thermal cycling and ultraviolet (UV) exposure contribute to mechanical properties degradation of polymer composites. This paper focused on assessing the mechanical properties of triaxial carbon/epoxy (CFRP) composite laminates used in fabricating light-weight composite bridges when exposed to both thermal cycling and ultraviolet radiation. In this study, five test series with a total of 39 specimens were performed to evaluate such exposure effects on tensile, compressive, and shear behavior of CFRP laminates. The experimental program was divided into five groups, including (i) Pre-exposure (baseline) test group tests; (ii) Unstressed thermal cyclic aging where unloaded specimens are exposed to fifty thermal cycles from 71 °C to –33 °C; (iii) Tension thermal cyclic test group where specimens are pre-tensioned to 30% of the baseline ultimate tensile strength and are exposed to fifty thermal cycles from 71 °C to –33 °C; (iv) Compression thermal cyclic test group where specimens are subjected to 30% of the baseline ultimate compression strength while exposed to fifty thermal cycles from 71 °C to –33 °C; (v) UV radiation test group where unstressed specimens are continuously exposed to 313 UVB ultraviolet radiation for 750 h. Experimental results indicated that thermal cycling effects on both tensile and compressive moduli are larger than its effect on tensile and compressive strengths of the triaxial composite laminates. In addition, the effect of thermal cyclic exposure on specimens loaded in tension has a larger impact on laminate tensile properties. It was also found that thermal cycling effects on shear strength are larger than its effect on the laminate shear modulus and that the effect of thermal cycling of pre-compressed laminates has a major influence on the CFRP composite laminate shear properties. Results also indicated that exposure to ultraviolet radiation has a large effect on both tensile strength and modulus, as well as the compressive strength of CFRP laminates. However, it has a negligible effect on compressive and shear moduli, as well as laminate shear strength.

Structural damage caused by terrorist attacks or explosions resulting from accidents is an essential crucial issue for civil engineering structures. After the explosion, heavy damage and total collapse occur in the structural carrier system, and these destructions can cause significant loss of life and property. This study aimed to determine the structural behavior of brick walls exposed to blast loading with different explosive weights using analytical, numerical, and experimental methods. The masonry brick walls were selected for the application and constructed in the allowed quarry area for experimental studies. 40g, 150g, and 290g of TNT, which are placed inner base center of brick walls, were used respectively to observe the progressive damage. The analytical blast responses, such as maximum pressure values etc., were calculated and predicted empirical formulas. The numerical blast responses were determined with Ansys Workbench and Autodyn software. At the end of the study, damage situations, pressures, displacement values, and energies are presented comparatively. It is observed from both experimental and numerical methods that 40g and 150g TNT explosives caused several damages on the wall. The wall collapsed on supporting points in 290g TNT explosives. It can be seen that the mean values of pressures and displacements increase respectively by three and six times, with the TNT explosive weight increasing from 40g to 290g. A good agreement is also found between the finite element results and empirical formulas proposed by Henrych and Sadovsky. However, inconsistent blasting responses are obtained with empirical formulas depending on the scaled distance.

On January 24 at 8.55p.m, a major earthquake of moment magnitude Mw = 6.8 struck the Sivrice district of Elazig, located in the southwest of the Eastern Anatolia region of Turkey. A total of 7429 buildings were severely damaged or collapsed. Unreinforced masonry buildings still represent a significant part of the residential building stock in rural surroundings of the Eastern Anatolia region. Unfortunately, most of the masonry buildings near to epicenter were found to have collapsed or suffered severe damage. This study provides an evolution of seismological characteristics of the earthquake, including recorded accelerograms and acceleration response spectra. Case studies of damaged masonry buildings and failure or collapse mechanisms are also examined. It is concluded that almost all the damaged buildings had not been designed or constructed in accordance with contemporary Turkish earthquake codes.

The explosions caused by terrorism and/or accidental lead to serious damage and/or collapse in structures, economic losses, and most importantly endanger public safety. The blasting loads that can be larger than design loads are generally neglected in the design stage of civil engineering structures, despite these catastrophic effects. For these reasons, especially strategically important structures such as hospitals, military buildings, and bridges should be designed considering the blasting effects. To this aim, the effects of design parameters such as concrete strength and openings in infill walls on blasting responses of reinforced concrete (RC) buildings are investigated in this study. In situ experimental tests are firstly conducted on a test specimen constructed with brick elements to verify the finite element (FE) model criteria and assumptions. The blasting experiments are performed using 40, 150, and 290 g trinitrotoluene (TNT) explosives. Then, two RC buildings are selected as application, and blasting analyses are done with numerical and empirical methods. FE models of the buildings including structural and non-structural elements are constituted in ANSYS Workbench software. The blasting analyses are carried out with ANSYS AUTODYN software using 100 kg TNT explosives. In the analyses, two different openings in infill walls and six different concrete classes are considered. The blasting pressures, displacements, absorbed and released total energies, and damage ratios are obtained and presented as comparison parameters. The results obtained from the blasting analyses are presented with graphics and tables, comparatively. The study shows that peak pressures and maximum displacements decrease by 22.50% and 32.16% with the increase in concrete strength. Also, it is observed from numerical analyses that openings in infill walls lead to a change of 8.16% in peak pressures and 13.92% in maximum displacements.

This paper reports on a study to determine the structural dynamic characteristics, such as natural frequencies, mode shapes and damping ratios, of timber mosques using ambient vibration tests after restoration. Kuşluca historical timber mosque in the Sürmene district of Trabzon, Turkey is selected as a case study. The mosque was built in the early twentieth century with two floors. Restoration projects were prepared in 2008 and the mosque was re-opened in 2011. A finite-element model of the mosque was constituted based on restoration drawings, and modal analysis was performed using orthotropic material properties. A literature review was used to determine the initial dynamic characteristics, such as natural frequencies, mode shapes and damping ratios. Non-destructive experimental measurements were conducted after construction to validate the numerical results using in situ tests. The first three natural frequencies were obtained numerically and experimentally. There was a close agreement between mode shapes, but 30% difference in natural frequencies. To minimise the differences, the finite-element model was updated using manual and automated updating procedures, changing uncertain parameters such as material properties, semi-rigid element connections, boundary conditions and section properties.

This paper presents a numerical and experimental investigation regarding changes in dynamic characteristics (natural frequencies, mode shapes, and damping ratios) of encased steel profile of concrete-encased composite column-steel beam connections prior to and following lateral cyclic loading tests. To do so, four specimens with different column-beam connection details were considered. Pre-ambient vibration measurements were first conducted to extract experimental dynamic characteristics of encased steel profile in column-beam connections using enhanced frequency domain decomposition (EFDD) method in frequency domain and stochastic subspace identification (SSI) method in time-domain. Next, encased steel columns were enforced with longitudinal rebar, stirrups, and concrete to turn them into concrete-encased composite column. Lateral cyclic loading tests were performed on composite column-beam connections until failure. Concrete, stirrups, and rebar were removed and cleaned from the encased steel column after the cyclic loading tests. Post-ambient vibration measurements were repeated on the damaged models for further evaluation and comparisons. Additionally, 3D finite-element models of the samples were constituted using Abaqus program, and modal analyses were performed for each specimen to obtain the numerical dynamic characteristics and compare them with experimental results. The results show that natural frequencies distinctly decrease due to damages in the column-beam connection zones. The maximum decreases were calculated as 8.53% and 16.01% in EPCSB-I; 6.92% and 16.44% in EPCSB-II; 17.38% and 12.20% in EPCSB-III; as well as 23.10% and 22.85% in EPCSB-IV for EFDD and SSI methods, respectively. Also, after the cyclic loading tests, increasing of flexibility and rotational movements due to the decrease in joint stiffness has affected the mode shapes. When the initial finite-element analyses and experimental results were compared with each other, the maximum differences were obtained between 0.18% and 8.99% for EPCSB-I, 2.62% and 25.27% for EPCSB-II, 0.84% and 28.60% for EPCSB-III, and 0.19% and 29.87% for EPCSB-IV, respectively.

The dynamic parameters obtained depending on the existing structural properties, material properties, boundary and damage condition are quite effective on the behavior of the structures under the effect of dynamic loads. These dynamic parameters have characteristic features for each structure. In this study, the effect of damping ratio, which is one of the dynamic characteristics, on the seismic behavior of historical structures was studied. For this aim, historical masonry Guesthouse Building belong to the Church of Santa Maria was selected to examined. Linear time history analyses were performed for three different damping ratios as 2%, 5%, and 10%. The horizontal component of Erzincan Earthquake (1992) was used in linear time history analyses. The maximum displacement, principal stress and strain values obtained from performed linear time history analyses for different damping ratios were compared. It is observed that, displacement, stress and strain values increase as the damping ratio decrease when the results are examined. It is concluded that, damping ratio is the important parameter for the evaluation of seismic response of historical masonry structures which are weak to external effect especially earthquake. Therefore, the damping ratios should be obtained with experimental tests before the numerical evaluation of seismic behavior.

This study presents the experimental and numerical assessment of natural frequencies and corresponding mode shapes of cross-laminated timber (CLT) beams subjected to a series of damage cases. To this aim, two different cantilever CLT beams consisting of three layers are considered. Damages on the beam are represented by transversal notches (cracks) through the thickness. Six damage scenarios on the beam models are considered. Experimental measurements via the operational modal analysis are performed to extract the natural frequencies and corresponding modes shapes of the beams under the considered damage cases. To verify the experimental results, the finite element modal analysis is also performed by ANSYS® finite element software. The material moduli necessary for the numerical analyses are determined from a single-layer cantilevered timber beam by applying the finite element model updating procedure. The effect of damages (cracks) on the modal characteristics of CLT beams is investigated. Experimental and numerical results show that especially the cracks near the fixed-end are highly effective on the natural frequencies, corresponding mode shapes, and damping ratios of the beams considered. In cases of multiple damages, the serious damage severity causes a change in the order of mode shapes. There is not found a direct relationship between the gluing applied to the piecewise material in the core layer and the modal characteristics. The results from this study can highly benefit the emerging research field of structural health monitoring on timber structures.

The strong shallow earthquake with a moment magnitude (Mw) range between 6.6 and 7.0 according to different sources (AFAD, KOERI and USGS) took place at local time 14:51 on 30th October 2020, in Aegean Sea near Samos Island. According to the data given from Earthquake Department of the Disaster and Emergency Management Presidency (AFAD), the epicenter of the earthquake is 27.17[Formula: see text]km far away from the İzmir coast and the duration of the earthquake that occurred in 14.9[Formula: see text]km deep of the ground is 15.68[Formula: see text]s. The main shock of the earthquake brought about a small local tsunami that struck especially Seferihisar district in Izmir and Vathi in Samos. The main shock was followed by more than 5799 aftershocks with magnitudes varying between 0.7 and 5.1 in 62 days. Turkey, Greece and the islands in Aegean Sea felt the earthquake but it caused heavy damage and casualties at Bayraklı location in the city center of Izmir due to ground effects and structural problems. According to the data released after the field investigations made by the Turkish Ministry of Environment and Urbanization in the regions affected by the earthquake, 103 buildings collapsed and urgently demolished, 700 were severely damaged, 814 were moderately damaged, 7889 were slightly damaged and 159,000 were undamaged. The earthquake and tsunami resulted in 117 deaths and 1632 injured in Turkey, whereas two deaths and several injured in Samos, despite the distance between the epicenter and Turkey coast being more than Samos Island. One of these deaths occurred as a result of the tsunami and according to official sources; it was recorded as the first person to die from a tsunami in Turkey. This study aims to examine the damage and collapses that occurred on the structures due to the earthquake and the tsunami. The types and causes of damage that occurred on both reinforced concrete (RC) and masonry structures were evaluated in detail with taking into account the conditions of the existing Turkish Building Earthquake Design Code, [TBEC, [2018] Turkish Building Earthquake Design Code. Specifications for Structures to be Built in Disaster Areas (Earthquake Department of the Disaster and Emergency Management Presidency, Ankara, Turkey).] and previous Turkish Earthquake Codes (TECs).

After destructive events such as earthquakes, attempts have generally been made to repair and strengthen structures using such methods as filling cracks by injection, wrapping structural elements with fiber-reinforced polymer (FRP). These applications can allow the recovery of lost structural performance. In this paper, the aim was to investigate the structural performance of an RC frame under different conditions—undamaged, damaged, repaired, and strengthened—by comparing results of nonlinear dynamic analyses. In addition, finite-element (FE) model updating effects were investigated in the case of the undamaged condition. To this end, an RC frame model was first constructed in the laboratory, and then, the model was damaged by lateral forces, repaired with epoxy injection, and lastly strengthened by wrapping with FRP. To obtain the dynamic characteristics of the RC frame under the different conditions, ambient vibration tests were performed for each condition. The FE model of the RC frame, obtained through global and local model updating using the ambient vibration test results, was modeled to achieve the nonlinear dynamic analyses. The results of the analyses were presented in the form of maximum displacements, principal stresses, and strains with contours diagrams. The maximum displacement increased significantly (133%) with the degree of damage, sharply decreased with the repaired (32%), and strengthened (36%) applications. The maximum and minimum principal stresses decreased by 24% and 35%, respectively, with the damaged condition. In addition, maximum differences between the undamaged and strengthened conditions were calculated as 17% for the maximum principal stress and 38% for the minimum principal stress. Findings indicated that the epoxy injection with FRP wrapping eliminates effect of the damage and recovers the model’s performance to its initial state. In addition, it is demonstrated in this paper that the updating procedure considerably changes the dynamic analysis results.

Historical structures are important cultural relics which illustrate the progress of engineering development. They are a valuable source of information on construction techniques and materials selection over the centuries. However, many factors, including environmental conditions and natural disasters, contribute to damage and destruction of historical structures. Today, the aim of restoration is to carry out necessary works with care and sensitivity while ensuring historical buildings are restored as near as possible to their original structural strength. However, the extent of the contribution of the restoration to the structure and the determination of the restoration success is carried out by various non-destructive experimental studies. This aim of this paper was to obtain structural modal parameters for the historical timber Buzlupinar Bridge using non-destructive ambient vibration tests after restoration. From calculations of natural frequencies and mode shapes, it can be seen that the six natural frequencies obtained are between 2.0 and 20.0 Hz. To minimize the 34.55% differences in experimental and numerical natural frequencies, a FE model of the timber bridge was updated using manual model updating procedures. The maximum differences were reduced to below 1% except for the fourth mode.

Free vibration analysis of laminated composite beams including open transverse cracks is presented by using a shear-deformable thirteen degrees-of-freedom finite element model, which considers extension-twist, bending-twist and bending-extension couplings, and the Poisson's effect. Lagrange's equation is employed to derive the equations of motion. Trial functions are selected as cubic Lagrange polynomials for deflections while quadratic for the others in derivation of element mass and stiffness matrices. Damage is introduced into the beam by reducing stiffness of elements within damaged zone. Comparisons are made with the available literature to show the present element's accuracy. Experimental validation is also performed with through ambient vibration tests on a cantilever laminated composite beam under six damage scenarios. According to the results, the methodology presented in this study provides a simple and quick way in a sufficient accuracy to determine the natural frequencies and mode shapes of laminated composite beams with open transverse non-propagating edge cracks.

This paper presents an experimental study about the effects of damage on modal parameters of haunch strengthened composite column–steel beam connections. Five specimens having various composite column and steel beam connection details were constructed in order to be examined in laboratory condition. Non-destructive experimental measurements were conducted to extract the modal parameters using frequency and time domain methods before and after damage conditions. Quasi-static cyclic tests were performed to assess the damaged conditions in connection zones of the test specimens. At the end of the study, it is observed distinctly that there is a decreasing trend in natural frequencies with damages. Also, no compliance is observed between mode shapes pre- and post-cycling loading tests. The biggest dissimilarities concerning natural frequencies were determined among 26.57% and 36.54%. The value for modal assurance criterion was 1.0 for undamaged condition. However, in post-damaged situation, the mode shapes have changed and modal assurance criterion values nearly approached zero. Finally, experimentally obtained damping ratios have been analyzed. The outcome of the study has shown some dissimilarity and that the values are not being correlated constructively. Despite the fact that the results are consistent with the available literature, it is assumed that these dissimilarities point to the fact that higher levels of excitation might be need to precisely record the damping ratios.

This study investigates the performance of annular cylindrical liquid column dampers (ACTLDs) for vibration suppression of structures with experimental tests. To this aim, a shear-type frame consisting of a top and bottom plate with four columns is constructed in laboratory and is exposed to ground motion with different directions. Dynamic characteristics of the shear frame are first extracted by the finite element analyses, ambient vibration tests and shaking table tests. Then, with employing the resonant frequency of the shear frame, resonant frequency, head-loss coefficient, damping ratio and water height–frequency diagram of the designed ACTLD are determined experimentally by the shaking table tests. Finally, ACTLD-shear frame coupled system is considered to extract the first natural frequencies and related mode shapes to evaluate the performance of ACTLD in suppressing vibrations of the model structure under different excitation angles of motion between 0° and 90° with increment of 15°. The acceleration and displacement time histories are examined to obtain damping of the structure. Results show that proposed ACTLD is good enough to suppress vibrations due to the ground motion with inclined exposing direction to the structure.

The objective of this paper is to evaluate the acceptable differences limit between analytically and experimentally identified modal parameters and to assess its contribution to the success of finite element model updating. To achieve this aim, three one-story reinforced concrete buildings consisting of raft foundation, columns and beams were simultaneously constructed under laboratory conditions. Experimental measurements were taken for each building to determine the modal parameters using ambient vibration tests. All parameters, which could be expected to affect structural behavior, such as structural dimensions, concrete properties, reinforcement detailing, construction joints, concreting days, workmanship, temperature and humidity, were made the same, as far as possible, for each building to eliminate the influence of environmental effects on experimental measurements. At the end of the study, the differences in the experimentally identified natural frequencies were obtained between 3.14% and ...

Cultural heritage buildings are valued in contemporary societies as they reflect the lifestyles and creative achievements our predecessors. For this reason, many countries have introduced regulations to ensure conservation of their historic buildings for the future, permitting minimal changes only to their original structure and characteristics. The key question addressed in this study is: how best can we assess the current structural behavior of a historical building, in particular wooden structures which may have survived for several centuries despite the deleterious consequences of decay, ageing and earthquakes? This paper focuses on a structural behavior assessment under current conditions (i.e. before restoration) of the Velipasa Han Building, an impressive "caravanserai" or han (inn) building dating from the 19th century, in the central Anatolian region of Turkey. This assessment includes non-destructive tests to obtain the resistance of the timber structural elements and to determine the modal response of the building. In addition, a finite element model was developed, based on an on-site investigation and the proposed restoration project, and validated by consideration of in situ experimental measurements. The model also used a condition assessment of the building after proposed restoration. Through in situ inspection, experimental measurement and numerical investigation, the current structural behavior of the building was evaluated and, based on this, recommendations for intervention are presented in the study.

Arch dams have delicate sections thanks to their curvature. The fact that these dams are large, costly and construction takes many years increases the importance of the structure. Mistakes and / or accidents that may occur during the construction of such structures may occur major loss of life and property. Considering the volumes, masses and slenderness of arch dams, they can be significantly affected by dynamic forces such as changing water pressure, temperature, wind and earthquakes. The level of these effects and to what extent they affect the dam can be determined by the analysis to be made to finite element model created by computer. Since Finite Element Analysis is based on certain assumptions, the results obtained should be compared and / or verified with the results obtained by experimental methods. One of the most suitable methods preferred in many engineering structures is the experimental modal analysis method. Within the scope of the study, experimental vibration tests were carried out in order to evaluate and determine the structural behavior of the double curvature Deriner Arch Dam, which has a body height of 249m and a crest length of 720m. Experimental measurements were carried out with accelerometers placed in appropriate places in order to obtain the mode shapes of the dam. The dynamic characteristics of the dam were determined using OMA software. The first seven natural frequencies of the Deriner arch dam were obtained in the range 1.60-4.10Hz. As a result of the negotiations with the DSI 26th Regional Directorate, the acceleration data obtained from the existing accelerometer system of the dam was instantly taken and a continuous monitoring process was initiated. This data was transferred to the web-based monitoring site and a structural condition monitoring platform was created.

Fire performance of load bearing elements in steel buildings such as columns and frames has major importance for structural designers. This study aims to assess the elevated temperature effect on dynamic characteristics of steel columns and frames by conducting sequential heat transfer and modal analyses. A series of finite element analyses including heat transfer analysis aere performed on 62 different steel columns and frames. Three-hour part of ISO 834 fire curve is taken into consideration in the analysis. Modal analyses are conducted for the purpose of providing a more comprehensive image of dynamic characteristics in specific duration of elevated temperature. The presented study accommodates the effect of various steel profile types, cross-sectional dimensions and exposure durations on changes in dynamic characteristics. The outcomes of the performed parametric study revealed the decrease in natural frequencies with the temperature growth. The research has also shown the existence of a correlation between temperature variations and changes in mode shapes. The change in mode shapes depends on the profile type. Mode shapes do not change depending on the temperature in some profile types, while in some profile types they change after a certain temperature. The obtained results of the performed sequential analyses are presented in forms of tabulated data and approximate formulas. They can facilitate the damage detection process and contribute in required structural health monitoring measurements while enhance the accuracy of damage assessment for fire exposed steel structures.

In modal testing, the quality of vibration signals and clarity of peak points to extract the natural frequencies, corresponding mode shapes and damping ratio depend on the number and location of the sensors. High measurement costs are required for structural identification and long-term structural health monitoring in large structures, which require a high number of sensors. Therefore, the minimum number of sensors should be placed at appropriate locations on the system during experimental measurements to ensure both information of sufficient quality and cost reductions. The aim of this study is to perform cost-efficient non-destructive modal tests for a laminated composite and steel cantilever beams using an optimal sensor placement approach. Finite element models of the sample beams are constituted in ANSYS® software to determine the initial candidate set of sensor locations. Then, ambient vibration tests are conducted. Based on the experimental modal amplitudes and mode shapes, optimal sensor locations are determined using the effective independence method, and measurements are repeated. The study shows that there is good agreement between the natural frequencies and mode shapes obtained from the initial measurements and those obtained using the limited number of sensors.

The aim of this paper is to present the field investigation and performance assessment of the mosques and minarets constructed around the cities of Elazig and Malatya and their surrounding ...

Historical timber bridges are significant cultural structures and have a long tradition. There are many pre-1950s bridges still in use today. In recent years, great resources have been devo...

This study presents damage localisation in steel cantilever beams including multiple cracks based on changes in the modal curvature and flexibility. Natural frequencies and corresponding mode shapes of circular-hollow-sectional and box-sectional steel cantilever beams are obtained by analytical and experimental models under six damage scenarios. Based on these data, the modal curvature and modal flexibility methods are employed to localise the cracks within the beams. Comparisons are made to show effectiveness of the methods in determination of crack locations.

Finite element models supply the simulation of the problems to obtain the structural behaviors under different loading conditions. The updating processes based on changing the uncertain parameters such as material properties, boundary conditions, meshing size etc. are made to create actual finite element models in order to represent the real conditions of the problems. This procedure can be made using two methods, namely manual model updating and global/local automatic model updating. The global/local automatic model updating procedures are very popular owing to the applicability to all kind of engineering structures, minimizing the differences nearly to zero, availability of damage localization and structural health monitoring. In this paper a historical masonry armory building selected as an application and its finite element analyses, experimental measurements and automated model updating processes are carried out. The finite element model of the structures was developed with ANSYS software and first three natural frequencies are attained. The experimental dynamic characteristics such as natural frequencies, damping ratios and mode shapes are obtained using ambient vibration method. The differences between experimental and numerical frequencies are minimized up to the range of 0–1%, by using local updating procedure. The linear and nonlinear seismic analyses of the building are conducted on initial and updated models. At the end of the analyses, maximum displacements, principal stresses and strains are given with detail. In addition, crack distributions diagrams are attained to validate the stresses accumulation points. It can be seen that there is an increasing trend in the displacement, stress and strain values after finite element model updating both linear and nonlinear analysis. In addition, linear and nonlinear analysis results are compared with each other to evaluate the nonlinear analysis effect. It is concluded that the displacement and strain values are increased after nonlinear analysis. But, there is not any agreement in stress values.

A major defect in determining the structural response for concrete encased composite columns using finite element is due to the uncertainties and assumption associated with the modeling process. Therefore, experimental measurements should be performed in order to validate the numerical results as well as obtain the real structural response. This paper seeks to address an experimental study about the evaluation of damage effect on the dynamic vibration characteristics of concrete encased composite columns (CECC) considering different column-beam connection types using ambient vibration tests. In an attempt to do so, four half scale concrete encased composite column-steel beam were built and tested in the laboratory with different column-beam connection types abbreviated as CECC-A, CECC-B, CECC-C and CECC-D without any changes in geometrical configuration of specimens and test setup. Cyclic loading tests were conducted in order to assess the post damage condition, while ambient vibration test were performed to extract the experimental dynamic characteristics such as natural frequencies, mode shapes and damping ratios using Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods for both undamaged (intact) and damaged conditions. The natural frequencies have decreased distinctly and mode shapes were broken with damages. These tests revealed that ambient vibration tests are enough to identify the dynamic characteristics of engineering structures for different conditions. The maximum differences in natural frequencies were calculated between 21.72% and 39.96%. A good agreement was noted for undamaged condition, the mode shapes were identical and the Modal Assurance Criterion (MAC) had value of 1.0. In contrast, there was not a good agreement for post damage condition. The mode shapes were different and MAC values were close to zero. Lastly, as the experimental damping ratios were examined, the results supported the idea that there were some differences and the values did not correlate favorably. These results are the compatible with the literature, but it is thought that the differences typically indicate that higher excitation levels are required to accurately capture the damping ratios.

This paper considers a Timoshenko cantilever beam with box cross-section including multiple cracks. Under six damage scenarios, the problem is solved analytically by the transfer matrix method, and numerically by the finite element method. Results are validated by the experimental measurements with the aid of ambient vibration tests, that use Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods. Measured and calculated natural frequencies and mode shapes for undamaged and damaged beams are compared with each other. Modal assurance criterion and coordinated modal assurance criterion values are obtained from two set of measurements to establish the correlation between the measured and calculated mode shapes for the damage location identification.