Abstract
The construction industry is confronted with substantial challenges due to the ecological consequences of traditional concrete production, a substantial role player in carbon emissions. In light of these issues, there is increasing interest in sustainable alternatives, such as geopolymer concrete, which can be enhanced with steel fibres to improve mechanical properties. This study aims to examine the critical aspect of fracture toughness in steel fibrous one-part alkali-activated concrete (OAAC). The one-part clinker-free binder for geopolymer concrete used in the study has been developed utilizing activators synthesized from agricultural and industrial waste, specifically waste glass powder (WGP) and rice husk ash (RHA). Thirty-nine mixing combinations were prepared using varying WGP/RHA to sodium hydroxide (NaOH) ratios from 1:0.50 to 1:1.75 in 0.25 intervals, alongside 0%, 0.5%, and 1% steel fibre. The parameters investigated in this study included compressive strength and fracture toughness against Mode I, Mode III, and mixed-mode (I/III) loading conditions using edge-notched disc bend specimens. The obtained results indicate that under mode I loading, 1.0% steel fibres yielded a maximum fracture toughness improvement of 18.1% at an RHA-NaOH ratio of 1:1.00. In OAAC mixes with steel fibres, a WGP-NaOH ratio of 1:1.25 resulted in notable improvements in fracture toughness, with increases of 8.1% for 0.5% steel fibres and 16.3% for 1.0% steel fibres. The formation of amorphous aluminosilicate gel and semi-crystalline phases identified in the SEM and XRD analyses show that RHA and WGP-derived activators enhance bonding and reactions with the aluminosilicate precursor in OAAC, resulting in a strong microstructure with reduced porosity and improved compressive strength.
Address
Anoop Kallamalayil Nassar, Parthiban Kathirvel: School of Civil Engineering, SASTRA Deemed University, Thanjavur, 613401, India
G. Murali: Centre for Promotion of Research, Graphic Era (Deemed to be University), Clementtown, Dehradun, India
Abstract
Conventional seismic design, while effective in preventing collapse, often results in high post-earthquake repair costs. This study proposes a novel Dual-Slope (DS) structural fuse to address this issue. The DS fuse utilizes opposing inclineslotted infill plates, ensuring consistent stiffness and superior energy dissipation during earthquakes. This innovative design also offers self-buckling restraint through interaction between the plates, eliminating the need for additional components. This simplification not only reduces construction complexity but also decreases weight and cost compared to traditional metallic yielding fuses. The effectiveness of the DS fuse was confirmed through experimental tests and finite element (FE) analysis, demonstrating stable behavior and efficient energy dissipation. Numerical models validated against experimental data enabled comprehensive parametric studies to explore the effects of key design parameters on performance. Furthermore, FE analysis led to the development of a relationship for estimating the load-bearing capacity of the DS fuse based on key parameters for specific DS structural fuse (240 MPa yield stress, and 3 mm thickness). This research highlights the DS structural fuse as a promising advancement in passive control technologies, paving the way for enhanced seismic resilience and significant reductions in postearthquake damage.
Key Words
dual-slope; energy dissipation; hysteretic behavior; incline-slotted infill plates; structural fuse
Address
Rahim Abdi: Department of Civil Engineering, Khomein Branch, Islamic Azad University, Khomein, Iran
Masoud Ahmadi: Department of Civil Engineering, Faculty of Engineering, Ayatollah Boroujerdi University, Boroujerd, Iran; Department of Civil and Geomechanics Engineering, Faculty of Earth Sciences Engineering, Arak University of Technology, Arak, Iran
Mehdi Ebadi-Jamkhaneh: Department of Civil Engineering, School of Engineering, Damghan University, Damghan, Iran
Hamid Mazaheri, Ali Parvari: Department of Civil Engineering, Khomein Branch, Islamic Azad University, Khomein, Iran
Abstract
In this paper, a new mathematical model of linear dynamic theory of photothermoelastic with diffusion and microtemperature is considered. The governing equations are made dimensionless, which are expressed in terms of elementary functions by assuming time harmonic variation of the field variables (displacement, temperature distribution, chemical potential and carrier density distribution). Fundamental solutions are constructed for the system of equations for steady oscillation. The internal and external boundary value problems (BVPs) of steady vibrations are formulated. The Green's first identity in the assumed model is also obtained. In the second part, the vibration of plane waves is examined by expressing the governing equation for two dimensional case. It is found that for the non-trivial solution of the equation yield that there exist five
longitudinal wave (P-wave), thermal wave(T-wave), mass diffusive wave (MD- wave), plasma wave(N-waves), longitudinal microtemperature wave (MT-wave), which advance with the distinct speeds, and one transverse wave which is free from thermal, mass diffusive, microtemperature and carrier density response. The attributes of waves i.e., phase velocity and attenuation coefficient are plotted in figures for the two models (i) with microtemperature (WMT), (ii) without microtemperature (WOMT). Various particular cases of interest are also deduced from the present investigations. The result obtained in this study should be useful for researchers who are working on thermodynamic energy, material science and hyperbolic thermoelastic models.
Key Words
BVPs; diffusion; fundamental solution; Green's formula; microtemperature; Photothermoelastic isotropic; plane waves; steady oscillations
Address
Rajneesh Kumar: Department of Mathematics, Kurukshetra University, Kurukshetra, Haryana, India
Nidhi Sharma, Supriya Chopra: Department of Mathematics, Maharishi Markandeshwar University Mullana, Ambala, Haryana, India; 3Department of Mathematics, Government College for Women, Ambala City, Haryana, India
Abstract
The quest for industrial and medical structures that combine lightweight with maximum resistance to applied forces
has led to the emergence of Functionally Graded Porous (FGP) panels as a novel solution. These panels, capable of tailoring their mechanical properties along a gradient, offer the potential for optimized mechanical performance. This optimization is particularly crucial in applications such as aerospace thermal protection systems, biomedical implants, and automotive structural components where precise control of material properties is essential. However, accurately analyzing their post-buckling behavior, due to the complexities of geometry and material heterogeneity, remains a challenge. The IGA framework advances existing methods through exact geometric representation capabilities, superior handling of material heterogeneity, enhanced thermal-mechanical coupling analysis, and improved solution stability for nonlinear responses. Isogeometric Analysis (IGA), with its unparalleled capabilities in precise geometry representation and mechanical behavior analysis, has been posited as a powerful computational approach in this domain. In this paper, an IGA framework utilizing Kirchhoff-Love theory and NURBS splines is presented for the precise analysis of FGP panels. The NURBS-based approach eliminates geometric approximation errors inherent in traditional polynomial-based elements, while providing C1-continuous representation across element boundaries-crucial for accurate strain field modeling in FGP materials. Special attention is given to porosity models Poro-I and Poro-II (where Poro-I features uniform distribution throughout thickness for conventional manufacturing processes, while Poro-II implements quadratic variation maximized at mid-surface for optimal weight-to-strength ratios) to examine the influence of porosity distribution on post-buckling behavior. The arc-length method, a robust numerical technique that controls both load and displacement increment simultaneously, is employed to trace the equilibrium path and identify snap-through and snap-back phenomena. This research, through a computational process, aims not only to enhance the precision of engineering analyses but also to improve the understanding of the impact of porosity and other design factors on post-buckling behavior. The framework's performance has been validated against established benchmark solutions, demonstrating superior accuracy in both displacement and stress predictions, despite requiring higher computational resources. This enables engineers to propose more optimized designs for engineering applications that are stronger and lighter, yet more resistant to heavy loads.
Abstract
This paper summarizes the long-period characteristics of earthquake ground motions and provides conceptual guidance for the seismic analysis or seismic mitigation of long-period structures. To this end, 1500 real earthquake ground
motions were selected from the PEER database and their response spectra were calculated by performing dynamic analyses of single-degree-of-freedom (SDF) systems at different structural periods. The results show that ground motions exhibit significantly different characteristics in the long structural periods compared to the short periods, namely, the impulse feature of ground motions at long-periods, smaller pseudo acceleration spectra than absolute acceleration ones, the "crossover" phenomenon of damping effects, developing the maximum seismic response at the same excitation time and the possible development of the maximum response after the end of shaking. Therefore, the following aspects should be carefully considered in the seismic design of long-period structures: (1) The error in the response spectrum analysis method might be significant, and thus it is recommended to employ the time history analysis method, where the dynamic analysis should be extended by half of the structural fundamental period, (2) The damping devices and design parameters should be well selected by taking into full consideration of the "crossover" phenomenon of damping effects.
Key Words
civil engineering; earthquake ground motion characteristics; impulse excitation; long periods; response spectrum method; seismic reduction
Address
Zijie Huang, Junyu Xiao, Jiang Yi: School of Civil Engineering and Transportation, Guangzhou University, Guangzhou 510000, China
De'en Yu: China Highway Engineering Consultants Corporation, Haikou, China
Abstract
The present paper investigates the dynamic thermal stability of a sandwich beam featuring a honeycomb core, intermediate piezoelectric layers, and outer porous viscoelastic graphene layers, resting on a visco-Pasternak foundation using the zigzag theory. Heat transfer within the micro honeycomb-piezoelectric sandwich porous viscoelastic graphene (H-PSPVG) beam is assumed to be transient and along its length. The properties of the viscoelastic graphene layer are determined using the Kelvin-Voigt model, while the strain gradient theory is applied to adapt relationships at the microscale. Considering the visco-Pasternak elastic medium, motion equations within the structure are derived using the energy method and zigzag theory. The Galerkin and Bolotin numerical methods are employed to solve the resulting equations for the micro H-PSPVG beam under simply supported double-ended and clamped supported boundary conditions. This research investigates the impact of small-scale parameters, temperature fluctuations, aspect ratio of length to core thickness, electrical potential, and elastic medium on the dynamic thermal stability of the micro H-PSPVG beam. Results show that increased temperature, porosity coefficient, viscosity, and a decrease in static coefficient and foundation lead to expanded stabilized regions and movement of unstable regions towards lower frequencies. These findings hold potential applications in microsensor and microgenerator fabrication.
Key Words
dynamic thermal stability; honeycomb core; Kelvin-Voigt model; piezoelectric; strain gradient theory
Address
Pooya Pourmousa, Ali Ghorbanpour Arani, Iman Ahghari, Ahmad Reza Ghasemi: Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran
Zahra Khoddami Maraghi: Faculty of Engineering, Mahallat Institute of Higher Education, Mahallat, Iran
