Abstract
This study investigated the effect of Ultra-High-Performance Concrete (UHPC) on the beam-column joint in precast structures subjected to reverse cyclic loading. The major setback faced in reinforced concrete (RC) construction following the current seismic codes like IS 13920:2016 [20] is that it results in joint reinforcement congestion which leads to honeycombing and poor compaction. The primary objective of this research is to develop a UHPC mix that could alleviate the reinforcement congestion by optimizing the reinforcement requirements at joint. The experimental testing consisted of 7 specimens mainly- one monolithic specimens (ML), One precast specimen with M30 joint (PSM30) and five precast specimens with UHPC joint and varying anchorage length and stirrups ratio at joint (100%, 75% and 50%). The UHPC jointed precast specimens outperformed the ML and PSM30 specimens. There was 50% increase in peak load capacity compared to PSM30 specimen and 32% increase compared to ML specimen for the precast UHPC specimen (PS100AS) with 100% anchorage and stirrups. The specimens with 50% reduction in stirrup ratio (PS50SR) and 50% reduction in anchorage length (PS50AR) also showed 24% increase in peak load capacity with respect to ML specimen indicating the high bond strength and confinement efficiency due to fibre-bridging action of the dense UHPC matrix. There was an increase of nearly 27% in the ductility of the joint. This study contributes significantly to the development of design guidelines for precast joints with optimized reinforcements serving as viable solution in high seismic regions.
Key Words
beam-column joint; cyclic loading; Stirrup ratio; UHPC; UHPFRC
Address
R. Anandlal, K.P. Jaya: Department of Civil Engineering, Anna University, Chennai, 600025, India
Abstract
This study investigates the aftershock fragility of buried gas pipelines, focusing on an API X65 steel pipeline that is widely applied in Korea. Pipelines that experience structural deformation during a mainshock are expected to exhibit greater fragility under subsequent seismic loading; thus, the compounded effects of mainshockaftershock sequences are explicitly considered. To capture these effects, ten sets of recorded mainshock-aftershock ground motion sequences are employed, providing a realistic representation of seismic demand. A total of forty-one analytical pipeline models are developed by systematically varying key parameters, including soil type, burial depth, bend angle, and boundary conditions, in order to evaluate their relative contributions to seismic performance. Strainbased damage states are defined to represent minor, moderate, and major damage, and aftershock fragility functions are derived using the maximum likelihood method. The results indicate that mainshock-induced plastic deformations significantly increase aftershock fragility, with pipelines in soft clay and deeper burial conditions exhibiting the highest fragility, while fixed-end and straight pipelines show superior seismic resistance. The findings highlight the necessity of integrating key design parameters to enhance the seismic resilience of buried pipelines in aftershockprone regions.
Key Words
buried gas pipeline; mainshock-aftershock sequence; maximum likelihood method; seismic fragility; soil-pipeline interaction
Address
Sangmok Lee: Dam Safety Management Center, Korea Water Resources Corporation (K-water), Daedeok-gu, Daejeon 34350, Republic of Korea
Do Hyung Lee: Department of Civil, Environmental and Railroad Engineering, Paichai University, Seo-gu, Daejeon 35345, Republic of Korea
Hyung-Jo Jung: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon 34141, Republic of Korea
Sungsik Yoon: Department of Artificial Intelligence, Hannam University, Daedeok-gu, Daejeon 34430, Republic of Korea
Abstract
Excessive vertical floor acceleration (VFA) induced by seismic and ambient excitations presents a significant risk to human comfort and the functionality of vibration-sensitive equipment. To overcome this, a scheme utilizing laterally restrained column-embedded dampers (CEDs) has been proposed in recent years as a promising solution for enhancing vertical structural damping. This study introduces a rational CED configuration incorporating viscoelastic rubber to elevate structural damping while maintaining adequate lateral shear stiffness and strength. Dynamic compressive loading tests of laminated rubber specimens were conducted to generate an appropriate mechanical model for the CED. The model is integrated into a substitute dynamic model of frame structures subjected to vertical ground excitations. In the integrated model, the axial flexibility of columns and the out-of-plane flexibility of the beam-slab system are properly accounted for. Numerical analyses of some 3-story, 6-story, and 9-story frames under seismic and ambient excitations demonstrate the effectiveness of CEDs in mitigating vertical accelerations, whereas a more pronounced benefit is observed at higher stories, given the significant reduction in the acceleration transfer function. Parametric studies further indicate that optimising the stiffness ratio between the CEDs and the column, or placing the CEDs in the lower stories, could better reduce the structural acceleration response. When the stiffness ratio between the CED and the conventional column is 0.05, the peak vertical acceleration at the centre of the top floor slab in a 6-story vertically damped frame can be reduced by 85% on average compared with the conventional structure under 20 seismic excitations.
Address
Xi-Ling Yang, Shi-Li Guo, Yu-Kun Liu: Department of Structural Engineering, Tongji University, Shanghai 200092, China
Yang Xiang: Department of Structural Engineering, Tongji University, Shanghai 200092, China; State Key Laboratory of Disaster Reduction in Civil Engineering, Shanghai 200092, China; Qinghai College of Architectural Technology, Xining 810012, China
Guo-Qiang Li: Department of Structural Engineering, Tongji University, Shanghai 200092, China; State Key Laboratory of Disaster Reduction in Civil Engineering, Shanghai 200092, China
Abstract
Due to the unique specifications of metal foams, scientists have long been interested to broaden the respective knowledge. Metal foams are porous materials with metal-made stiff skeletons, making them useful in many fields, including medical engineering. However, the porous nature of these materials makes them susceptible to undesirable stiffness loss upon pore expansion. To overcome this shortcoming, these structures can be integrated in different ways. One of these ways that helps to reach more stiffness, is to coat the metal foam structures with composite layers which are reinforced by nano-fillers. So, for the first time, the current work provided an analysis on natural frequencies of a metal foam structure which is skinned by two nanocomposite patches in which the agglomeration effect of carbon nanotubes is regarded. Also, to consider more parameters effects, it is assumed that the structure is affected by hygro-thermal environment and an external magnetic load is applied to it. To bring up the results' accuracy, shear deformation effect is taken into account via different higher-order theories. The governing differential equations are solved analytically for three types of boundary conditions and different examples are presented numerically to evaluate the structure's natural frequencies.
Key Words
higher-order shear deformation theory; hygro-thermal environment; magnetic load; metal foams; vibration analysis
Address
Andre Yvaz: World-Class Research Center "Advanced Digital Technologies", State Marine Technical University,
Saint Petersburg, 190121, Russia
Hala Mostafa: Department of Information Technology, College of Computer and Information Sciences, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh, 11671, Saudi Arabia
Alireza Yarmohammadi: National Polytechnic University of Armenia (NPUA), Yerevan, Armenia
Arameh Eyvazian: National Polytechnic University of Armenia (NPUA), Yerevan, Armenia; Department of Mechanical Engineering, Politecnico di Milano (Technical University), Milan, Italy
Hovhannes Chibukhchyan: National Polytechnic University of Armenia (NPUA), Yerevan, Armenia
Abstract
In this study, the structural integrity of a 65-kW horizontal-axis wind turbine blade subjected to delamination in its root region is investigated. The analysis specifically focuses on varying spatial parameters of the defect, comprising its radial position and longitudinal propagation length. Additionally, to rigorously evaluate the impact of aerodynamic loads on the aeroelastic behavior of the blade, a one-way fluid-structure interaction (FSI) coupling scheme is employed. The aerodynamic flow is solved with a turbulence model suitable for boundary layer separation, and the structural response is evaluated through prestressed modal analysis. Simulations are performed at a wind speed of 15 m/s and an angle of attack of 20o, resulting in a predicted power output of 63 kW with a deviation of less than 6% from the reference data. Delamination lengths ranging from 30o to 180o and varying thicknesses, as well as different environmental positions, are investigated. Results show that delamination reduced the natural frequency ratio (damaged to undamaged blade) by 18% in the first case and by 15% in the second case. The largest reduction occurred when the center of delamination coincided with the flow-induced vortices, resulting in increased local stiffness loss. Furthermore, the prestressing effects caused by FSI shifted the natural frequencies by 2.3% at a wind speed of 15 m/s. Moreover, the results demonstrated the important role of delamination-flow interaction in reducing blade stiffness and vibrational stability. The developed numerical approach provided a powerful tool for predicting damage effects in composite blades and guiding the design of more fatigue-resistant and reliable wind turbine systems.
Key Words
delamination; fluid-solid interaction; vibration; vortex; wind turbine blade
Address
Mojtaba Baghban Noghondari, Ali Amin Yazdi, Erfan Salimipour: Department of Mechanical Engineering, Faculty of Advanced Technologies, Quchan University of Technology, P. O. Box: 94717-84686, Quchan, Iran
Abstract
Columns are critical structural elements and must be assessed against various hazards. Among these, blast loading represents a significant threat to both civil and military structures, arising from either accidental explosions or deliberate attacks. This paper presents a numerical investigation of the response of circular concrete filled steel tube (CFST) columns subjected to contact underwater explosions. An explicit finite element (FE) model is developed in ANSYS Autodyn by coupling an Eulerian formulation for the surrounding media (air, water, and explosive charge) with a Lagrangian representation of the CFST column. The FE model is verified and validated through comparison of some results benchmarks such as pressure in water, damage and displacement with recently published experimental data on blast-loaded targets, the verification demonstrated good agreement. No new experiments presented in the research. A parametric study is then conducted to examine the effects of steel tube thickness, steel tube yield strength, and concrete compressive strength on the structural response of CFST columns, including global deformation, concrete damage, and concrete erosion. The results indicate that the steel tube properties govern the overall structural response, while the influence of concrete strength is comparatively limited within the investigated range. Among the considered parameters, steel tube thickness is the most influential, followed by steel tube yield strength then concrete strength. The findings provide useful insights for the design of CFST columns subjected to contact underwater blast loads, particularly for marine and offshore structures.
Address
Osman M.O. Ramadan, Mohammed H. Serror, Ahmed M. Khalil: Faculty of Engineering, Cairo University, Cairo 12411, Egypt
M. Galal El Sherbiny: Faculty of Engineering and Technology, Future University in Egypt, Cairo 16383, Egypt
Abstract
In recent years, the spread of waste, including industrial waste, has been harmful to the environment. Recycling this waste in mortar is a solution because of its economic and environmental benefits. This study investigated the effects of waste bricks and pomace on the physical and mechanical properties of mortar. Brick waste was used as a partial replacement for cement after grinding. Pomace was incorporated as a partial substitute for sand. Both wastes were used at the same percentages of 10% and 20% by the weight of the cement and sand. Physical and mechanical tests were performed on the variants studied. These parameters included density, compressive strength, flexural strength, water absorption, ultrasonic pulse velocity, and the effect of elevated temperature on mortar properties. In addition, in-depth analyses were conducted on the samples of each variant, including X-ray diffraction (XRD) and thermogravimetric analysis (DSC-TGA). The results showed that the mixture containing 10% brick waste exhibited better compressive and flexural strengths at 600oC.The addition of brick waste to mortar reduced the water absorption by capillarity. This study presents a promising approach to sustainable waste management and the creation of more environmentally friendly mortars by reducing the amount of brick and pomace waste.
Key Words
brick waste; mortar; performance; pomace; waste management
Address
Houssam Eddine Abdelli: Department of Civil Engineering, Faculty of Technology, University Ferhat Abbas Setif 1, 19000 Setif, Algeria
Salim Kennouche: Department of Civil Engineering, Faculty of Sciences and Applied Sciences, University of Bouira, 10000 Bouira, Algeria
Fatma Elif Genceli Güner: Chemical Engineering Department, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
Abstract
In nonlinear analyses under cyclic loading, the behavior of reinforced concrete (RC) columns is often represented using hysteretic models. While ideal elastoplastic or bilinear models are common, real behavior includes strength and stiffness degradation under cyclic loading. Current codes recommend models such as the peak-oriented model, but they lack detailed provisions regarding section dimensions, reinforcement properties, and axial load conditions. Using the Abaqus Finite Element Analysis software, this study investigates RC column behavior under horizontal cyclic loading. Six-column models are created with cross-section length-to-thickness (l/t) ratios of 1.0, 2.0, and 3.0, each modelled with both closely spaced and widely spaced confinement reinforcement to assess confinement effects. The Concrete Damage Plasticity (CDP) model is used, and the effects of its complementary parameters and varying axial load levels are explored through a parametric study. Results showed that columns with l/t equal to 1.0 behaved similarly to ideal elastoplastic models under low axial loads. However, column models with l/t=2.0 and l/t=3.0, especially those with widely spaced confinement, exhibited significant deviation due to shear effects. The study highlights the importance of confinement and geometry in modelling RC column behavior and provides insights into the influence of CDP parameters on simulation accuracy.
Key Words
CDP model; cyclic load; finite element analysis; hysteretic behaviour; RC column
Address
Ramazan Özmen: Department of Mechatronics Engineering, Karabük University, 78050 Karabük, Türkiye
İsmail Tozlu: Department of Civil Engineering, Karabük University, 78050 Karabük, Türkiye
