Browsing by Author "Nguyen, Quy Thue"
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Publication A health monitoring solution on damage detection of minarets(Pergamon-Elsevier Science Ltd, 2022-02-12) Nguyen, Quy Thue; Livaoğlu, Ramazan; Nguyen, Quy Thue; LİVAOĞLU, RAMAZAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0003-3436-8551; 0000-0001-8484-6027; AAW-6878-2021; M-6474-2014Historical buildings play a monumental role in religious communities around the world. Masonry structures such as minarets built in areas prone to dynamic effects such as earthquakes are vulnerable as a consequence of their brittle materials and slenderness. Structural health monitoring (SHM) has not been carried out in the regular control of minarets' health for early warning of collapse. Meanwhile, the protection and preservation of such a cultural heritage are urgent. Effective techniques to recognize damage occurrence and location in minarets are vital. In this study, a health monitoring solution on damage detection of minarets is presented. In particular, damage detection of the minaret (24.25 m high) of Hacilar mosque that was built using stone and brick in 1467 in Bursa city (Turkey) is aimed. Only four accelerometers are erected along with the height of the minaret to collecte lateral displacements, making an incomplete number of measured degrees of freedom (DOFs). To circumvent the complicated problem, the minaret is transferred into a lumped mass system correspondingly to the erected sensor network considering the similarities in terms of bending behavior at low modes between slender minarets and beamlike structures. Due to the changes in modal data at two bending modes, an eigenvalue problembased inverse solution is employed to localize damage in the minaret based on the reduction in terms of stiffness of the simplified system. As a result, reliable damage detection is achieved as long as the modal data is noise-free or low-level noise-contaminated (about 0.5%-1% random noise level).Publication ANN-based averaging scheme for damage detection of high-rise buildings under noisy conditions(Elsevier, 2023-11-23) Nguyen, Quy Thue; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü; 0000-0001-8484-6027; M-6474-2014Structural health monitoring (SHM) is crucial for assessing the condition of deteriorated high-rise buildings subjected to sudden and hazardous loads. This study proposes a novel averaging scheme to enhance the performance of an existing hybrid damage detection technique based on Artificial Neural Networks (ANNs). The proposed technique is validated numerically on a 30-storey building. The objective is to address the discrepancy between noise levels used during training and those present in generated modal data, thus mitigating the impact of measurement noise on damage predictions. By employing a series of ANNs trained with varying noise levels, a diverse range of predictions is obtained. These predictions are averaged to yield decisive conclusions, even when indecisive predictions outnumber decisive ones. This averaging scheme effectively reduces the influence of random noise, particularly when there is a notable disparity between the actual noise levels in measured data and statistical networks. Moreover, this study investigates the impact of the number of measurements on noise reduction, recommending approximately 100 measurements, in line with other experimental studies. Through the integration of the averaging scheme and increased measurement numbers, the ANN-based damage detection technique achieves remarkable accuracy in damage detection. Storey-level detection can be achieved when the noise levels in mode shapes reach up to 3.5 %. Additionally, the approach exhibits promising results in detecting damaged walls, with a noise threshold of up to 3 %. For damaged columns, a more modest threshold of 0.75 % suffices for light and complex damage scenarios.Publication Damage detection of high-rise buildings using an eigenvalue problem-based inverse solution(Elsevier, 2021-10-08) Nguyen, Quy Thue; Livaoğlu, Ramazan; Nguyen, Quy Thue; LİVAOĞLU, RAMAZAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0003-3436-8551; 0000-0001-8484-6027; AAW-6878-2021; IUQ-1185-2023; M-6474-2014Structural health monitoring (SHM) has been applied in the regular control of high-rise buildings' health that has deteriorated having being subjected to a sudden loading. Storey-level damage detection has been a subject of focus, due to the complexity of high-rise buildings. In this study, that of two-dimensional (2D) high-rise buildings is the objective of this study. The eigenvalue problem-based inverse solution is a promising method to identify the changes in the mechanical matrices of a building, once the issues related to the huge number of degrees of freedom (DOFs) can be dealt with. The Guyan static condensation procedure is applied to reduce the full matrices based on the limited size of eigenvectors measured in field. The modal data is obtained from a simple sensor network in which requires only one uniaxial accelerometer per floor. Two techniques, particularly damage detection and mass recognition, are developed, based on the inverse solution. The proposed approach is validated numerically on 20-storey and 30-storey buildings. Reliable storey-level detection is achieved as long as the modal data is noise-free or low-level noise-contaminated. Furthermore, the mass recognition procedure is successfully verified using an experimental test on a 3-storey frame.Publication Degradation of the first frequency of an rc frame with damage levels(Gruppo Italiano Frattura, 2023-04-01) Nguyen, Quy Thue; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; 0000-0003-3436-8551; 0000-0001-8484-6027; M-6474-2014; AAW-6878-2021Damage in RC structures causes the degradation of stiffness and frequency. In this study, the relationship between the two coefficients and damage severities is numerically investigated considering a three-dimensional (3D) RC frame in which the concrete damage plasticity model (CDPM) and the elastoplastic model are selected for concrete and reinforcements, respectively. Crack propagation is obtained utilizing a nonlinear static pushover analysis (NSPA). After pushing, according to the base shear force versus top displacement curve, the bending stiffness of the structure is determined rapidly based on the first derivative of the relationship. Thereafter, the degradation of the first frequency is obtained based on the derivative of the nonlinear curve of stiffness, the second derivative of the force -displacement curve viz. As a result, it is observed that the degradation of the first frequency of the RC frame is proportional to the severity of damage but not linearly. More significant damage, a more profound decrease in the frequency. Particularly, the frequency of the frame reduces gradually until the base shear force reaches 70% of the ultimate value at which the parameter is 60% of the healthy counterpart. After that, the reduction gets more significant when the bending capacity approaches the ultimate value.Item The experimental and numerical investigation of the structural performance of a 3d rc frame built using a rc formwork system(Uludağ Üniversitesi, 2018-09-28) Nguyen, Quy Thue; Sağıroğlu, Serkan; Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/İnşaat Mühendisliği Anabilim Dalı/Yapı Bilim Dalı.The effect of using reinforced concrete (RC) formwork system on the static and dynamic structural performance of a three dimensional RC frame is evaluated experimentally and numerically. A single story RC frame that is symmetric in both directions poured using RC formworks, called New Frame (NF) is compared to a reference frame built traditionally, namely Classical Frame (CF). Firstly, the dynamic characteristics of NF is compared with those of CF based on results obtained by shaker test and by modal analysis using finite element method (FEM) in Abaqus CAE. There is no significant deviation between two frames in terms of natural vibration frequencies as well as mode shapes. Secondly, static nonlinear pushover analysis (SNPA), particularly monotonic pushing, is carried out in order to determine the performance point of RC frames. Under a considered seismic condition, NF performs a lower value of spectral acceleration, about 86% of that of CF. Besides that the maximum displacement of NF exceeds the collapsed point of CF approximately 27%. Thirdly, two surface treatment methods consisting of steel shear connectors and rectangular shaped asperities are applied in order to enhance the shear capacity of inter-concrete substrates. The flexural strength of NF is improved about 12% applying a suitable ratio of shear links, about 0,48%. On the other hand, the bending capacity of NF using rectangular irregularities (5mm high 37,5mm wide and 37,5mm apart) is equal to 1,206 times the capacity of NF with smooth surfaces. Finally, the influence of normal load in columns on the inelastic behavior of studied structures is also examined in the present thesis. It is observed that larger normal force in columns upgrades the flexural behavior of structures but results in a performance point with a lower spectral acceleration value.Publication Fundamental mode shape-based normalization scheme for damage detection of minarets: A non-model-based approach(Pergamon-Elsevier Science Ltd, 2023-02-26) Nguyen, Quy Thue; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0001-8484-6027; M-6474-2014Historical, cultural, and artistic masonry structures like minarets constructed in regions prone to dynamic effects such as strong winds and earthquakes are vulnerable as a consequence of their slenderness and brittle materials. Structural health monitoring (SHM) has not been employed adequately in the regular control of minarets' integrity for early warning of disaster. Meanwhile, the protection and preservation of such a cultural inheritance are acute. A non-model-based normalization scheme is proposed to detect damage in minarets based only on the changes in terms of the fundamental mode shape generated by a modest quantity of accelerometers. The backbone idea lies in the similarities in terms of the fundamental mode shape between slender minarets and beam-like structures. Particularly, the modal amplitudes below a specific normal-izing node change significantly if damage occurs below this point. Thereby, moving upward the location of this point straightforwardly leads to damage detection of minarets. The proposed technique is implemented on Hacilar mosque's minaret (24.25 m high) built in 1467 in Bursa city, Turkiye. Reliable damage prediction is attained as long as the modal information is noise-free or reasonable-level noise-polluted.Publication Modal strain energy based enhanced approaches for damage detection and severity estimation(Pergamon-elsevier Science Ltd, 2023-03-03) Nguyen, Quy Thue; Livaog, Ramazan; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0003-3436-8551; 0000-0001-8484-6027; M-6474-2014; AAW-6878-2021Structural health monitoring (SHM) has been utilized to assess structural deficiency for preventing the invisible failure turning into collapses. Damage localization and severity assessment based on vibration-based characteristics have received considerable attention in civil and engineering fields during recent decades. This study presents a modal strain energy (MSE) based damage detection of a beam-like system. Particularly, based on the performances of existing MSE based damage indices (DIs), a robust and fast technique, called averaging scheme is developed. Observing from the two original DIs that one of them leads to underestimations while overestimations are witnessed using the other one when estimating damage severity, the average of their severity estimations absolutely is supposed to result in better anticipations. Furthermore, another MSE-based updating procedure that was also established based on the original method to reach more accurate predictions is also improved in this study. However, the updating technique considers only the fundamental mode while higher modes are ignored. It is assumed that damage can be caused by higher modes and therefore accounting for more modes possibly lead to better failure identification. Hence, in this study, a numerical investigation is carried out to examine the feasibility of the averaging scheme's deployment on a cantilever beam. The contribution of higher modes to the performance of the proposed technique as well as the updating procedure is also evaluated. The numerical validation shows that the proposed averaging scheme is outstanding since it results in damage identification results comparable to that of the updating procedure but more promptly. Furthermore, compared to using only the fundamental mode, the cumulative contribution of higher modes, particularly, the lowest four modes, tremendously leads to more accurate damage identification, especially under noisy conditions.Publication Structural damage identification of high-rise buildings: An artificial neural network based hybrid procedure(Pergamon-elsevier Science Ltd, 2023-06-06) Nguyen, Quy Thue; Livaoğlu, Ramazan; LİVAOĞLU, RAMAZAN; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0001-8484-6027; M-6474-2014Structural damage detection of high-rise buildings is by far not reached because of their complexity. In this study, an artificial neural network (ANN) method-based two-step approach is suggested to detect damage at element levels of a 3D 30-storey 90 m high RC building containing 2880 degrees of freedom (DOFs). One biaxial accelerometer per floor is erected, making the number of measured DOFs equal to about 2% of the full system. Only the first three bending modes in the orthogonal axes are accounted for. A network is constructed in Step 1 to detect damaged storeys based on the similarities between tall buildings and beam-like systems. All components' stiffness parameters of each storey are assigned to one variable. In Step 2, another network is built focusing only on the detected storeys to localize ruined elements. Furthermore, aiming at detecting damage considering modal data generated under ambient conditions, inevitable measurement noise effects are also considered to challenge the proposed ANN technique. As a result, the light and robust networks lead to precise storey- and element-level detection promptly as long as the desired vibration-based properties are free of noise as well as noise-corrupted.Item Yüksek yapılar için modal analiz tabanlı hasar tespiti ve yapı sağlığı izleme yaklaşımı(Bursa Uludağ Üniversitesi, 2022-06-23) Nguyen, Quy Thue; Livaoğlu, Ramazan; Bursa Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/İnşaat Mühendisliği Anabilim Dalı.; 0000-0003-3436-8551Yapı sağlığı izleme (SHM), herhangi bir yüklemeye bağlı olarak hasar gören yüksek katlı yapıların sağlığını kontrol etmek için şu anda az sayıda da olsa uygulanmaktadır. Burada hedeflenen yapıda muhtemel hasar mekanizmasının başlangıç düzeyinde tespit edebilmek ve karar destek sistemlerine bilgi üretebilmektedir. Ancak uygulamada, birçok farklı nedenle bu düzeyde izlemeden ziyade genel maksatlı izlemeler tercih edildiği, çok az sayıda örnekte ise önemli sayıda ve nitelikte sensör ile izlemelerin yapıldığı da aşikardır. Bu maksatla çalışmada, hasarlı katları tespit etmek ve ardından hasarlı elemanların yerini belirleyebilmek için hibrit bir prosedür(ler) önerilmiştir. İlk adım için modal şekildeğiştirme enerjisi (MSE) yaklaşımı, ters çözüm, ve Yapay Sinir Ağı (ANN) yöntemi olmak üzere üç yöntem kullanılmaktadır. Başlangıçta ötelenme serbestlikleri üzerine kurulan yaklaşımlar bir yapının gerçek davranışını daha iyi modelleyebilmek maksadıyla dönme serbestliklerini de içerecek şekilde Guyan statik yoğuşma prosedürü kullanılarak yaklaşık olarak basitleştirilmiş, daha sonra, sadece ilk iki en düşük eğilme modunu kullanarak ters çözüm uygulanarak gerçekleştirilen modeller sayısal ve deneysel olarak doğrulanmıştır. ANN tabanlı teknik, gerek diğer yaklaşılmalarda kat düzeyinde hasarı tahmin etmek için gerekse kat ve eleman düzeyi tespitleri için ayrı ayrı kullanılmıştır. Ağlar, en düşük eğilme modları kullanılarak eğitilmiştir. İkinci adımda, yalnızca belirlenen katlara odaklanarak hasarlı elemanları tahmin edebilmek için ANN yöntemi yardımıyla değişken sayısı etkin bir şekilde azaltılabilmektedir. Çalışmada, farklı yöntemler ve hibrit yaklaşımlar sırasıyla iki boyutlu (2D) problemden başlayarak, yüksek binayı temsilen (3D) 30 katlı bir binanın hasar tespitine kadar farklı senaryolar için adım adım geliştirilerek verilemektedir. Bu veriler ışığında düşük gürültü düzeyleri için tüm seviyelerde hasar tahminlerinin doğru bir şekilde elde edilebildiği gösterilmiştir.