Abstract
The assessment of seismic behavior and seismic performance of ageing Sariyar concrete gravity dam constructed on Sakarya River in Türkiye is the main focus of this paper. For this purpose, the impact of sediment domain, ageing of concrete material under the impact of chemical and mechanical actions, and dam-water-sediment interaction are included in the twodimensional (2D) finite element (FE) model developed in FORTRAN 90 environment. In the FE model, the dam and age dependent sediment domains are modeled by solid elements, while reservoir domain is modeled by Lagrangian fluid elements. The radiation of reflected waves to the unbounded water domain is modeled by infinite Lagrangian fluid elements, while unbounded sediment domain is modeled by infinite solid elements. The coupled system was assumed to be under the simultaneous impact of Vertical (V) and Horizontal (H) ingredients of 1976 Koyna earthquake and the coupled system was analyzed in Laplace domain by direct method. Due to the deterioration of the concrete, the H and V displacement responses together with the fundamental period of the body, elongate throughout the lifetime and this reduce the seismic safety of the dam. It was deduced that the ageing dam body will not experience major damages under the Koyna earthquake both at the earlier and later ages. Furthermore, at the heel of the dam, the hydrodynamic pressure responses are decreased by rising the sediment domain depth.
Abstract
The objective of this study is to analyze, using the finite element method, the durability of damaged and repaired structures under the effect of mechanical loading coupled with environmental conditions (water absorption and/or temperature). The study is based on the hybrid patch repair technique, considering several parameters based on the J integral to observe the behavior of the adhesive in transferring load from a damaged plate to the repair patch. The results clearly show that water absorption and increased temperature cause degradation of the mechanical properties of the adhesive, leading to an increase in its plasticization, which is beneficial for the assembly's strength. However, the degradation of the adhesive's properties due to aging in the repair results in poor load transfer from the damaged area to the patch. The findings of this study allowed the authors to conclude that the [0o]8 sequence consistently offers the best performance, with the lowest J integral values and superior crack resistance. The lowest the J integral for the [0o]8 stacking sequence is typically 3-7% lower than that of the [0/-45/45/90]S and [0/-45/90/45]S sequences at elevated temperatures. At 60oC, the J integral increases by approximately 3-6% compared to 40oC and 20, depending on the aging duration and stacking sequences.
Key Words
damage plate; hybrid; J integral; patch; repair; temperature; water absorption
Address
Habib Achache: University of Oran 2 Mohamed Ben Ahmed, B.P 1015 El M
Abstract
In the world, the construction science and technology industry has developed strongly thanks to the application of
Ultra-High Performance Concrete (UHPC) technology, with a strength greater than 150 Mpa and unprecedented durability.
compared to previous materials. However, this technology can build special structures but has limited use in construction
because it is not commercially feasible to replace regular concrete in most structural types due to material costs. high, lack of availability, limited design standards, complex manufacturing and maintenance techniques. This article examines the composition of UHPC materials and their performance in composite structures with conventional concrete, a promising choice for promoting the development of UHPC technology in construction. It is based on the combined use of UHPC as a covering layer around normal concrete or as an inner core to increase the strength of normal concrete, create a slender structure and reduce the cost and repair of construction works. Construction and transport infrastructure are degraded. Manufacturing costs are expected to be reduced with composite construction due to the advantages of combined materials.
Address
Thanh Vy Nguyen: Faculty of Engineering and Technology, Tra Vinh University, No.126 Nguyen Thien Thanh, Hamlet 4, Ward 5, Tra Vinh City, Vietnam; Ho Chi Minh City University of Transport, No.2, Vo Oanh Street, Ward 25, Binh Thanh District, Ho Chi Minh City, Vietnam
Tuan Anh Nguyen, An Hoang Le: Ho Chi Minh City University of Transport, No.2, Vo Oanh Street, Ward 25, Binh Thanh District, Ho Chi Minh City, Vietnam
Abstract
The objective of this research is to improve public safety in civil engineering by recognizing fractures in concrete structures quickly and correctly. The study offers a new crack detection method based on advanced image processing and machine learning techniques, specifically transfer learning with convolutional neural networks (CNNs). Four pre-trained models (VGG16, AlexNet, ResNet18, and DenseNet161) were fine-tuned to detect fractures in concrete surfaces. These models constantly produced accuracy rates greater than 80%, showing their ability to automate fracture identification and potentially reduce structural failure costs. Furthermore, the study expands its scope beyond crack detection to identify concrete health, using a dataset with a wide range of surface defects and anomalies including cracks. Notably, using VGG16, which was chosen as the most effective network architecture from the first phase, the study achieves excellent accuracy in classifying concrete health, demonstrating the model's satisfactorily performance even in more complex scenarios.
Key Words
concrete structures; convolutional neural networks; crack detection; structural health monitoring; transfer learning
Address
Ali Bagheri, Mohammadreza Mosalmanyazdi and Hasanali Mosalmanyazdi: Department of Civil Engineering, Maybod Branch, Islamic Azad University, Maybod, Iran
Abstract
This research plans to investigate the simultaneous impact of bamboo fibers (BF) and steel fibers (SF) on the mechanical and spalling characteristics of ultra-high-performance concrete (UHPC) exposed to high temperatures (HT). To this aim, 25 mixtures were made and assessed. BF was added at five contents of 0, 2.5, 5, 7.5 and 10 kg/m3. Additionally, SF was used at five weight contents: 0%, 1%, 2%, 3% and 4%. Specimens were exposed to temperatures ranging between 25oC and 800oC. Thus, com-pressive, tensile, and flexural strengths, elastic moduli, mass loss, and permeability were measured. Experiments revealed that the simultaneous use of low BF and SF contents could totally prevent spalling of UHPC, but the use of either SF or BF alone could not prevent spalling at high levels of fibers. Besides, the synergetic positive impact of BF and SF on the spalling resistance of UHPC was by reason of the rise of BF' permeability and the bridging role of SF at HT. Moreover, it was concluded that the use of SF could moderate the adverse influence of BF on the compressive resistance of UHPC.
Key Words
bamboo fibers; high temperature; spalling resistance; steel fibers; ultra-high-performance concrete
Address
Arash K. Pour: Innovative Structural Engineering and Mechanics Group, USA
Amir Shirkhani: Department of Structural Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
Ehsan Noroozinejad Farsangi: Urban Transformations Research Centre (UTRC), Western Sydney University, NSW, Australia
Abstract
The vibration of elastically supported bidirectional functionally graded (BDFG) sandwich beams on an elastic
foundation is investigated. The sandwich structure is composed of upper and lower layers of BDFG material and the core layer of isotropic material. Material properties of upper and lower layers are assumed to vary continuously along the length and thickness of the beam with a power-law function. Hamilton's principle is used to deduce the vibration equations of motion of the sandwich Timoshenko beam. Then, the partial differential equation of motion is spatially discretized into a time-varying ordinary differential equation in terms of Chebyshev differential matrices. The eigenvalue equation associated with the free
vibration is formulated to study the influence of various slenderness ratios, material gradient indexes, thickness ratios, foundation and support spring constants on the vibration frequency of BDFG sandwich beams. The present method can provide researchers with deep insight into the impact of various geometric, material, foundation and support parameters on the vibration behavior of BDFG sandwich beam structures.
Key Words
BDFG sandwich beams; Chebyshev collocation method; foundation; gradient index; natural frequency; support spring; thickness ratio
Address
Wei-Ren Chen: Department of Mechanical Engineering, Chinese Culture University, Taipei 11114, Taiwan
Liu-Ho Chiu: Department of Mechanical and Materials Engineering, Tatung University, Taipei 104, Taiwan
Chien-Hung Lin: Department of Mechanical Engineering, Chinese Culture University, Taipei 11114, Taiwan
Abstract
Soft bending actuators have gained significant interest in robotic applications due to their compliance and lightweight nature. Their compliance allows for safer and more natural interactions with humans or other objects, reducing the risk of injury or damage. However, the nonlinear behaviour of soft actuators presents challenges in accurately predicting their bending motion and force exertion. In this research, a new comprehensive study has been conducted by employing a developed 3D finite element model (FEM) to investigate the effect of geometrical and material parameters on the bending behaviour of a soft pneumatic actuator reinforced with Kevlar fibres. A series of experiments are designed to validate the FE model, and the FE model investigates the improvement of actuator performance. The material used for fabricating the actuator is RTV-2 silicone rubber. In this study, the Cauchy stress was expanded for hyperelastic models and the best model to express the stress-strain behaviour based on ASTM D412 Type C tensile test for this material has been obtained. The results show that the greatest bending angle was achieved for the semi-elliptical actuator made of RTV2 material with a pitch of 1.5 mm and second layer thickness of 1 mm. In comparison, the maximum response force was obtained for the semi-elliptical actuator made of RTV2 material with a pitch of 6 mm and a second layer thickness of 2 mm. Additionally, this research opens up new possibilities for development of safer and more efficient robotic systems that can interact seamlessly with humans and their environment.
Key Words
bending behaviour; casting method; finite element model; hyperelastic model; pneumatic actuation; soft actuator
Address
Sina Esmalipour, Masoud Ajri and Mehrdad Ekhtiari: Department of Mechanical Engineering, University of Mohaghegh Ardabili, Ardabil 56199-13131, Iran
Abstract
Sparse regularization methods have proven effective in addressing the ill-posed equations encountered in moving force identification (MFI). However, the complexity of vehicle loads is often ignored in existing studies aiming at enhancing MFI accuracy. To tackle this issue, a double l1 regularization method is proposed for MFI based on a response spectrum-based weighted dictionary in this study. Firstly, the relationship between vehicle-induced responses and moving vehicle loads (MVL) is established. The structural responses are then expanded in the frequency domain to obtain the prior knowledge related to MVL and to further construct a response spectrum-based weighted dictionary for MFI with a higher accuracy. Secondly, with the utilization of this weighted dictionary, a double l1 regularization framework is presented for identifying the static and dynamic components of MVL by the alternating direction method of multipliers (ADMM) method successively. To assess the performance of the proposed method, two different types of MVL, such as composed of trigonometric functions and driven from a 1/4 bridge-vehicle model, are adopted to conduct numerical simulations. Furthermore, a series of MFI experimental verifications are carried out in laboratory. The results shows that the proposed method's higher accuracy and strong robustness to noises compared with other traditional regularization methods.
Key Words
inverse analysis; moving force identification; response spectrum; sparse regularization; vehicle-bridge interaction; weighted dictionary
Address
Yuandong Lei, Bohao Xu and Ling Yu: MOE Key laboratory of Disaster Forecast and Control in Engineering, School of Mechanics and Construction Engineering, Jinan University, Guangzhou 510632, P.R. China
