Abstract
The self-weight of a structure has a significant influence on both cost and structural performance; therefore, its reduction remains a key design objective. Since concrete slabs are among the heaviest structural elements, the adoption of hollow-core systems provides an efficient solution for reducing self-weight without a significant loss in load-carrying capacity. When combined with geopolymer concrete, these systems further reduce self-weight and material consumption while enhancing sustainability through lower energy demand and reduced environmental impact. In the present study, a finite element investigation was conducted using ANSYS to evaluate the influence of key parameters on the load-carrying behavior of geopolymer concrete hollow-core slabs. These parameters include the shear span-to-effective depth ratio (a/d), core size, core shape, and reinforcement ratio. Experimental results were used to calibrate the adopted geopolymer concrete material model. The calibrated Menétrey-Willam constitutive model showed strong agreement with the experimental compressive and flexural responses, confirming its suitability for simulating the nonlinear behavior of geopolymer concrete structural elements. The results indicate that geopolymer hollow-core slabs can effectively reduce self-weight without a significant reduction in load-carrying capacity. The solid slab exhibited the highest stiffness and ultimate load, whereas the circular-void configuration achieved the most efficient balance between structural strength and self-weight reduction.
Address
Yasmin Hefni Abdel Aziz: Civil Engineering Department, Faculty of Engineering, Modern University for Technology & Information (MTI), Cairo, 11571, Egypt
Taha A. El-Sayed: Department of Civil Engineering, Shoubra Faculty of Engineering, Benha University, Cairo, 11625, Egypt
Abstract
This study analyzes the vibrational characteristics of functionally graded piezoelectric-elastic (FGPE) annular nanoplates under rotational and thermal loads. The material system consists of piezoelectric (BaTiO3) and non-piezoelectric elastic (CoFe2O4) phases. The thermo-electro-elastic properties of the nanoplate vary continuously along its thickness according to a power-law distribution. The analysis employs the nonlocal strain gradient theory (NSGT), the governing equations are derived using Hamilton's principle and solved via the Runge-Kutta method. Results demonstrate that: The natural frequency exhibits complex behavior influenced by rotational speed, initially decreasing, then increasing, and subsequently fluctuating. Increasing the functionally graded index or porosity volume fraction reduces the natural frequency by softening material stiffness and weakening piezoelectric coupling efficiency. The electric potential enhances frequency at low rotational speeds but induces complex fluctuations beyond a critical speed. Temperature changes cause a non-monotonic frequency response, initially decreasing, then increasing, and finally decreasing again. Clearly, initial geometric imperfection significantly alter the vibration characteristics, with frequency decreasing at low speeds, increasing beyond a critical rotational speed, and decreasing again at higher speeds, highlighting the importance of accounting for geometric imperfections in nanoscale structural design.
Address
Xiao-Qiang Sun: Chongqing Industry Polytechnic University, Chongqing, 401120, P.R. China
Gui-Lin She: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing, 400044, China
Abstract
In this study, a simplified design method for shear wall-frame systems based on the Direct Displacement-
Based Design (DDBD) approach is proposed. The method is developed using a continuous-system analytical model. For this purpose, an equivalent flexural-shear beam model is formulated based on the assumption that the frame shear force remains constant over the height of the building. By solving the differential equation governing the equivalent flexural-shear beam and applying equilibrium conditions, analytical relationships are derived for the effective mass, effective height, wall base moment ratio, and the location of the wall moment inflection point. Based on these relationships, practical design tables and charts are developed to illustrate the variation of the effective mass,
effective height, wall base moment ratio, and wall moment inflection point with the frame shear ratio (defined as the
ratio of the frame base shear to the total base shear). These design aids allow rapid estimation of the key design
parameters required for DDBD applications. The proposed flexural-shear beam model extends the application of
DDBD and enables the design of wall-frame systems to be carried out more efficiently and in a shorter time than
conventional DDBD procedures. To evaluate the applicability of the proposed approach, a series of design examples was examined. The first example was presented in detail to facilitate a clearer understanding of the design procedure.
The results indicate that the proposed method yields sufficiently accurate and reliable results for preliminary design applications. Consequently, the proposed approach provides a practical and efficient framework for the
Displacement-Based Design (DBD) of wall-frame systems.
Key Words
continuum model; flexural-shear beam; shear wall-frame; simplified method
Address
Ahmet Eyol, Kanat Burak Bozdogan: Faculty of Engineering, Canakkale Onsekiz Mart University, Canakkale, Turkey
Abstract
Stay cables in cable-stayed bridges often experience high-nonlinear vibrations under complex end excitations during strong earthquakes, resulting in severe damage to their seismic safety. Conventional discretized truss element models for simulating large-deformation cable vibrations frequently suffer from reduced accuracy, decreased computational efficiency, and numerical divergence. This study proposes an improved multi-element model (MT-EBCE) in OpenSees, which combines a truss element and an elastic beam-to-column element between multiple sharing nodes to compute coupled cable responses. Its superior computational accuracy and efficiency are validated against mainstream multi-element models. Subsequently, based on the improved MT-EBCE cable model, a numerical analysis is conducted to investigate the nonlinear vibration characteristics of stay cables under multidirectional and multi-frequency coupled complex end excitations. The results demonstrate that the improved MTEBCE model can effectively simulate loosening and fracture phenomena of the cable. The response characteristics of cables subjected to multi-directional and multi-frequency coupled excitations cannot be obtained through superposition from individual inputs. In some cases, calculations based on simple superposition may underestimate the cable displacement response by up to 50% compared to the true value under complex end excitation. Therefore, it is necessary to utilize the improved MT-EBCE model to conduct nonlinear vibration characteristic analysis for cables under complex end excitations.
Key Words
cable nonlinear vibration; complex seismic input; finite element analysis; multi-element model; spatial effect of excitation
Address
Jiang Yi: Guangzhou University, Guangzhou, China
Ruicheng Liu: Guangzhou University, Guangzhou, China
Huaisheng Ruan: State Key Laboratory of Bridge Intelligent and Green Construction, China Railway Major Bridge Reconnaissance & Design Institute Co., Ltd., Wuhan, China
Wei Wang: State Key Laboratory of Bridge Intelligent and Green Construction, China Railway Major Bridge Reconnaissance & Design Institute Co., Ltd., Wuhan, China; Tongji University, Shanghai, China
Yingqi Liu: Wuhan University of Technology, Wuhan, China
Abstract
This study presents a combined finite element and component mode synthesis (FEM-CMS) approach for the vibration and stability analysis of a cracked tapered Euler-Bernoulli beam with linearly varying thickness, constant width, and a single open edge crack subjected to axial compressive loading. The crack is modeled as a massless rotational spring through a local flexibility matrix derived from fracture mechanics principles, and the cracked beam is treated as an assembly of subcomponents coupled by the crack stiffness matrix. Both clamped-free and pinned-pinned boundary conditions are considered, and parametric investigations are conducted over crack depth ratios (a/b=0.2-0.8), crack locations (Lc/L=0.1-0.9), thickness ratios (t2/t1=0.5-0.9), and normalized axial load levels (P/Pcr=0-0.9). The results demonstrate that crack-induced reductions in both buckling capacity and natural frequencies are strongly governed by the spatial correspondence between the crack location and the region of maximum bending moment of the associated mode shape, and that the boundary condition fundamentally alters the spatial distribution of crack sensitivity. For the clamped-free beam, a deep crack (a/b=0.8) near the fixed end reduces the critical buckling load by approximately 66%; for the pinned-pinned beam, the most critical position shifts to midspan, where a similar crack produces a 70% reduction. The applied axial load amplifies crack-induced frequency reductions in a strongly nonlinear manner at high load ratios, particularly in the fundamental vibration mode. The present findings provide a systematic quantitative framework for vibration-based damage assessment in non-uniform beam structures subjected to compressive loading.
Key Words
axial load; buckling analysis; component mode synthesis; cracked tapered beam; finite element method; free vibration; structural health monitoring; varying thickness
Address
Mehmet Haskul: Department of Mechanical Engineering, Faculty of Engineering, Sirnak University, Sirnak, Turkey
Huseyin Aggumus: Mechanical and Metal Technology Department, Sirnak Vocational School, Sirnak University, Sirnak, Turkey
Murat Kisa: Department of Mechanical Engineering, Faculty of Engineering, Harran University, Sanliurfa, Turkey
Abstract
This study presents a practical multi-objective optimization framework for 3D reinforced concrete (RC) moment-resisting frames using NSGA-II. Its main novelty is a decoupled genetic encoding of column rotation angles (0o/90o), combined with a section database that embeds ACI 318-19 reinforcement detailing—crossties, skin reinforcement, and seismic hooks—directly as discrete design variables. Two objectives are minimized: a normalized sum of total construction cost and embodied CO2, and the maximum inter-story drift ratio. On 4-, 6-, and 8-story irregular benchmark frames, the decoupled approach (Scenario A) attains a 4.5% higher Hypervolume and up to 22% lower cost at equal drift than the conventional coupled approach (Scenario B), and ten independent runs confirm convergence robustness. Construction cost and embodied CO
Address
Jaemin So, Seungjae Lee, Donwoo Lee: Future Convergence Engineering, Department of Architectural Engineering, KOREATECH, Cheonan, 31253, Chungcheongnam-do, Republic of Korea
Koichi Kusunoki: Earthquake Research Institute, The University of Tokyo, Tokyo, 113-0032, Japan
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