Abstract
Seismic isolation systems are essential components in improving the earthquake resistance of structures by reducing the forces transmitted to the building during seismic events. These systems come in various types, such as elastomeric bearings and sliding bearings, each offering unique advantages in terms of energy dissipation and flexibility. While seismic isolators have been widely studied, the determination of damping type and damping ratio in numerical analysis of base-isolated steel structures is a significant phenomenon. In this study, two separate experimental investigation involving steel structures with seismic isolators were selected for numerical analysis. The lead rubber bearing isolators were used in both 1/20 scaled 2-story steel structure and 1/16 scaled 4-story steel structures in the experimental tests and numerical modelling. The nonlinear time history analyses were performed to evaluate how different damping types influence the seismic response of the isolated structures. In the numerical models, mass-proportional, stiffness-proportional, and Rayleigh damping types and different damping ratios ranging from 1% to 8% were used. The numerical analysis results were compared with the experimental results by considering displacement values at different floor levels. The closest approximations to experimental results were achieved with a 6% damping ratio for mass proportional damping type, and a 1% damping ratio for stiffness-proportional and Rayleigh damping types. The findings provide insights into the optimal selection of damping ratios for accurately simulating the behavior of steel structures equipped with Lead rubber-bearing seismic isolators.
Key Words
base-isolated steel structure; damping ratio; damping type; nonlinear time-history analysis; seismic isolation system
Address
Burak Çakil, Ömer Faruk Osmanli and Muhammet Karaton: Department of Civil Engineering, Faculty of Engineering, Firat University, Elazig, Turkey
Abstract
In this study, waste marble powder (WMP) was employed replacing aggregates in certain quantities. To achieve this objective, fine aggregates were substituted with WMP at different percentages of 0%, 10%, 20%, 30%, and 40%. This was done to compare the effects of various tests on the compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS). First, the CS test was performed on the specimens. It was measured that CS of MA10% (10% aggregates were replaced with WMP) was 2.2% larger than that of reference concrete (REF). Furthermore, a noticeable decrease in the strength were observed for 40% of WMP when compared with REF. Then, the STS test was conducted to compare the test results with those of CS. As expected, it was found that the results of STS ordinarily followed the similar trend as CS. For the 10% WMP utilized as stepped replacement for fine aggregates, the significant enhancement in STS of concrete was up to 4.1%. However, while the quantity of WMP was improved to 30% and 40%, it resulted that the values of STS were affected in a downward trend. The FS test was also done. It was revealed that the maximum FS was achieved with 10% adding of WMP, and the minimum FS was obtained with 40% adding of WMP. Additionally, microstructure analysis was performed. It was found that WMP is a good binder with cement and the use of 10% WMP, as replacement of aggregates, is recommended to increase the capacity. Moreover, 20% and 30% of WMP can be utilized without the loss of the strength, however, the use of 40% WMP should be avoided. Moreover, an equation was derived to predict the capacity of concrete with WMP employing the experimental results and findings presented in the literature. Additionally, an estimation method of ARX (autoregressive with external input) models was used to more accurately predict the mechanical behavior of concrete with WMP.
Key Words
aggregate; compressive; flexural; marble; powder; recycled; tensile; waste
Address
Yasin Onuralp Özkiliç: Department of Civil Engineering, Faculty of Engineering, Necmettin Erbakan University, Konya, Turkey
Özer Zeybek: Department of Civil Engineering, Faculty of Engineering, Mugla Sitki Kocman University, Mugla, 48000, Turkey
Memduh Karalar: Department of Civil Engineering, Faculty of Engineering, Zonguldak Bulent Ecevit University, Zonguldak 67100, Turkey
Ali İhsan Çelik: Department of Construction, Tomarza Mustafa Akincioglu Vocational School, Kayseri University, Kayseri, 38940, Turkey
Essam Althaqafi: Civil Engineering Department, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia
Abstract
The novelty of this manuscript is the use of a simple refined higher order shear deformation theory for micromechanical behavior analysis of functionally graded (FGM) plates. To achieve this purpose, a new shear deformation shape function is employed. Furthermore, the present refined theory considers a new displacement field that includes undetermined integral terms and contains fewer unknowns 'variables while considering the effect of transverse shear stresses and strains. The plate's material properties are assumed to be graded in the thickness direction according to various micromechanical models, starting with the Voigt's model, which is commonly used in most functionally graded plates studies, to the Reus's, LRVE's and Mori-Tanaka's models. The principle of virtual displacement is used to determine the equilibrium equations and several numerical results are given to validate the precision of the present method for the bending behavior of FGM plates. Afterwards, a parametric study is conducted to determine the effect of different parameters on the deflection of the FGM plates, where we found out that the mechanical behavior of these FGM plates is significantly influenced by the type of micromechanical model considered to determine the plate's stiffness and the type of boundary conditions. Numerical results are obtained to investigate the effects of power-law index, length-to-thickness ratio and micromechanical models on the displacements and stresses. In the light of the present research, it can be concluded that the present theory is accurate and simple in predicting the deflection behavior of functionally graded plates under mechanical effects and micromechanical models.
Abstract
This paper investigates the plane stress problem of a cantilever beam subjected to variable loading in bending. The material properties of the beam vary continuously through thickness, according to an exponential distribution. The study proposes a high-order Airy function related to parabolic loading boundary conditions, based on compatibility equations. A mathematical formulation with parameters based on parabolic loading is developed, and a numerical application presented to evaluate the influence of different parameters on the objectives. The solution obtained satisfactory results, indicating its potential for structural calculations.
Key Words
cantilever beams; exponentially graded materials; parabolic distribution loads; static analysis
Address
Abdelaziz Hadj Henni: Civil Engineering Department, University of Tiaret, Algeria
Tahar Hassaine Daouadji: Civil Engineering Department, University of Tiaret, Algeria; Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria
Abstract
In this study, a numerical model was developed which can predict the performance of masonry structures in a hierarchical framework. The proposed model assessed the shear behavior of masonry across different scales and was solved in Abaqus. A concrete damage plasticity (CDP) constitutive model for brick and mortar units was used. The numerical results were in good agreement with experiments with a 3% deviation from the peak shear load, and the computational time was reduced by 50% in comparison to existing approaches. Sensitivity studies were performed to optimize the CDP parameters. The optimum value of CDP parameters such as dilation angle of 11o, eccentricity of 0.1, stress ratio of 1.16, shape factor of 2/3 and a viscosity parameter of 0.001 reported closer match with the experimental findings. In addition, the robustness of the model is checked for a full-scale 3D model of a room and compared in terms of relative rigidity.
Key Words
concrete damage plasticity; continuous microscopic modelling; finite element method; masonry
Address
Bibarg Khan: NUST Balochistan Campus, National University of Sciences and Technology, Quetta 87800, Pakistan
Ather Ali: NUST Institute of Civil Engineering, National University of Sciences and Technology, Islamabad 44000, Pakistan
N.D. Chakladar: Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, West Bengal 721302, India
Abstract
The rising demolition rate of old infrastructure has led to a substantial increase in the accumulation of recycled aggregate, posing a significant threat to environmental sustainability. To mitigate this, it is crucial to incorporate recycled aggregate into construction practices. However, recycled aggregate generally exhibits lower strength compared to conventional natural aggregate, making it necessary to enhance its mechanical properties for practical application. This study investigates the effectiveness of incorporating plastic (PF) and polypropylene (PP) fibers in hybrid configurations to enhance the mechanical and microstructural behaviour of hybrid fiber-reinforced recycled aggregate concrete (HFRAC). The influence of recycled aggregate replacement, hybrid fiber combination and fiber dosage on the mechanical properties, failure mechanism and stress-strain behaviour were studied. Three plastic fibers dosages (i.e., 0.5%, 1% and 2%), and three hybrid fibers combination was (0.5% PF+0.5% PP; 0.75% PF+0.25% PP; 1.5% PF+0.5% PP) tested. Totally 10 different cases of recycled aggregate concrete without fiber, with single fibers and with hybrid fibers were tested. The RAC25-PF0.75-PP0.25 mix achieved a maximum compressive strength of 43.56 MPa, marking a 7% increase over plain RAC. Flexural strength improved by approximately 4%, and splitting tensile strength by 5.5%. Stress-strain behaviour showed a transition from brittle to ductile failure with hybrid fiber addition. SEM and digital image processing confirmed enhanced ITZ density, reduced porosity, and effective crack-bridging. These results validate HFRAC as a sustainable and high-performance alternative for structural applications.
Key Words
digital image processing; hybrid fiber; micro fiber; micro structural analysis; plastic fiber; recycled aggregate
Address
Ramalingam Vijayalakshmi: Department of Civil Engineering, Sri Sivasubramaniya Nadar College of Engineering, Chennai, India
Aswin G. Sriram: Department of Civil Engineering, Sri Sivasubramaniya Nadar College of Engineering, Chennai, India
Ramaiah Prakash: Department of Civil Engineering, Alagappa Chettiar Government College of Engineering and Technology, Karaikudi, India
Nagarajan Divyah: Department of Civil Engineering, PSG Institute of Technology and Applied Research, Coimbatore, India
Ramalingam Geetha: Department of Biomedical Engineering, Saveetha School of Engineering, SIMATS, Chennai, India
