Techno Press
Tp_Editing System.E (TES.E)
Login Search
You logged in as...

acc
 
CONTENTS
Volume 20, Number 1, July 2025
 

Abstract
This study investigates the effectiveness of using ultra-high performance fiber reinforced concrete (UHPFRC) to strengthen RC beams and improve their shear strength. Thirteen RC beams were cast and tested up to failure using a four-point loading test. One beam was kept as a control beam without strengthening, and the other twelve beams were strengthened by various strengthening schemes. The following key parameters were investigated: the number of strengthening sides, the thickness of the UHPFRC layer, the reinforcement of the strengthening layer (type of steel mesh, inclined stirrups, and without any reinforcement), and the volume fraction of steel fibers. The test results demonstrate that using the UHPFRC strengthening technique provides an efficient method for improving R.C. shear performance. In comparison with the un-strengthened beam the shear strength and ductility of the strengthened beams with UHPFRC layers have increased by 91% and 56%, respectively. The behavior of the beams is improved by increasing strengthening sides. The beam with three strengthened sides has demonstrated the highest shear strength. It reached 65% increase in ultimate load, while strengthening on one side and two sides reached 41% and 56%, respectively, compared to control specimens. As expected, the results also revealed that using the strengthening layer with reinforcement provides better shear performance than using UHPFRC layers without reinforcement. It has also been found that inclined stirrups perform more effectively than steel mesh.

Key Words
cast in situ; inclined stirrups; RC beams; shear strengthening; ultra-high performance fiber reinforced concrete; welded and expanded steel mesh

Address
Civil Department, Benha Faculty of Engineering, Benha University, Egypt.


Abstract
The shear lag effect in bridges can cause uneven cross-sectional stress distribution, compromising load-bearing capacity and structural performance, particularly in continuous rigid-frame bridges. This study integrates energy variation method, finite element modeling, and construction monitoring data to analyze shear lag effects in a single-cell continuous rigidframe box girder bridge during construction. The energy variation method was employed to establish fifth-degree polynomial analytical formulas for calculating shear lag coefficients under various loading conditions. Finite element analysis indicates that prestressing load primarily dominates the transverse shear lag distribution, while optimal tendon placement significantly reduces the maximum shear lag coefficient. During cantilever construction with suspended scaffolding, the shear lag coefficients at the top slab-rib junction follow the sequence λ3 > λ2 > λ1 > λ5 > λ4 across five stages: segment n tensioning (λ1), subsequent hanging basket installation (λ2), segment (n+1) concrete pouring (λ3), segment (n+1) tensioning λ4) and hanging basket movement (λ5). Monitoring data indicate that in the early stages of cantilever construction, the shear lag coefficients and average normal stresses are high in the top and bottom slabs, whereas subsequent segments exhibit decreasing shear lag coefficients and increasing average normal stresses. The findings provide essential guidance for improving bridge design and construction.

Key Words
cantilever construction; construction monitoring; energy variation method; shear lag effect; single cell box bridge

Address
(1) Weihao Sun, Shitong Hou:
School of Civil Engineering, Southeast University, Nanjing 210096, China;
(2) Luchang Zhao, Zhihong Ran:
School of Architecture and Planning, Yunnan University, Kunming, 650051, China;
(3) Fengbo Ma:
China Construction Third Engineering Bureau Group Co., LTD, Wu Han 430075, China.

Abstract
The increasing demand for resilient infrastructure in seismically active regions necessitates innovative approaches to enhance the seismic performance of concrete structures. This study investigates the potential of elastic nano-composites as a transformative solution for optimizing the seismic resistance of concrete. By incorporating nano-scale elastic materials into traditional concrete mixes, this research aims to improve the material's ductility, energy absorption capabilities, and overall robustness under dynamic loading conditions. Experimental testing was conducted on specimens reinforced with varying concentrations of nano-silica and nano-clay-based composites subjected to simulated seismic loads. The results demonstrate significant improvements in crack resistance, flexural strength, and energy dissipation compared to conventional concrete. Integrating these advanced materials not only enhances the structural integrity of buildings but also contributes to eco-efficient construction practices by reducing the need for repairs and replacements over time. This study underscores the importance of adopting nano-engineered solutions in concrete technology to achieve safer, more durable, and sustainable infrastructures, thereby addressing key challenges outlined in modern construction practices.

Key Words
concrete structures; elastic nano-composite; flexural strength; nano-clay-based; nano-silica

Address
(1) Shuo Dong, Wen Pan:
Faculty of Civil Engineering and Mechanics, Kunming University of Science and Technology, Kunming, 650500, Yunnan, China;
(2) Shuo Dong, Wen Pan:
Yunnan Seismic Engineering Technology Research Center, Kunming, 650500, Yunnan, China;
(3) Jingwei Wang:
HCCI Engineering Technology Group Co., Ltd., Yunnan Branch, Kunming, 650000, Yunnan, China;
(4) Mostafa Habibi:
Universidad UTE, Facultad de Arquitectura y Urbanismo, Calle Rumipamba S/N y Bourgeois, Quito 170147, Ecuador;
(5) Mostafa Habibi:
Department of Biomaterials, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Chennai 600 077, India;
(6) Mostafa Habibi:
Department of Mechanical Engineering, Faculty of Engineering, Haliç University, 34060, Istanbul, Turkey;
(7) Changeh Li:
Institute Sciences and Design of AL-Kharj, Dubai, United Arab Emirates.

Abstract
Functionally Graded Materials (FGMs) are advanced materials characterized by a continuous variation in properties due to a gradual change in composition or structure, enabling them to meet specific functional requirements. FGMs find applications in diverse fields such as aerospace, automotive, energy systems, and biomedical devices, where materials must withstand complex mechanical or thermal environments. Researchers employ various analysis methods to study FGMs, including theoretical modeling, numerical simulations like finite element analysis, and experimental validation, to understand their behavior and optimize their design for enhanced performance and durability. This paper investigates the static behavior of a functionally graded cantilever beam under a second-order polynomial load, unlike traditional studies that typically focus on uniform or linearly varying loads. The elasticity modulus is modeled as an exponential function through the thickness of the beam to represent the material gradation. The analysis employs the Airy stress function, expressed as a fourth-order polynomial along the longitudinal axis for a two-dimensional elasticity problem, to derive the stress and displacement fields. By solving the governing differential equations, integrating the resulting expressions, and applying the appropriate boundary conditions for the cantilever configuration, the tangential and normal stress components, as well as the transverse deflection of the beam, are obtained. The results demonstrate the efficiency of this approach in accurately capturing both the stress distribution and the deflection of the FG beam. Furthermore, the method's adaptability suggests its potential for analyzing other FG beams with varied boundary conditions and higher-order polynomial loads, offering a versatile tool for advanced structural analysis.

Key Words
airy stress function; boundary conditions; FG cantilever beam; polynomial load; static analysis

Address
(1) Mohamed Nassah:
Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria;
(2) Hadj Henni Abdelaziz, Lazreg Hadji:
Department of Civil Engineering, University of Tiaret, Algeria;
(3) Hassen Ait Atmane:
Laboratory of Structures, Geotechnics and Risks, Department of Civil Engineering, Hassiba Benbouali University of Chlef, Chlef, Algeria.

Abstract
In this paper, the vibrational frequencies with different values of height-to-diameter ratios are investigated using modified orthotropic shell model to note the small scale effects. The generality of orthotropic shell model has proven to give better results of single walled carbon nanotubes. The closed form solution gives better accuracy, even for higher frequencies but arriving at the closed form solution might prove to be a challenge. For higher frequencies, the analysis of structure is implemented with well-known approach. The chiral structure is complex structure and frequencies are extracted with to clamped-clamped (C-C) and clamped-free (C-F) boundary conditions. The frequencies (THz) are investigated against the height-to-diameter ratios. The frequencies increase on increasing the height-to-diameter ratios. The behavior of the frequencies is occurring as sag in its nature. The results are validated and excellent similarity is observed.

Key Words
boundary condition; chiral tube; diameter ratio; numerical results; parameters; validation

Address
(1) Mohamed Amine Khadimallah, Abdullah Alnutayfat:
Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia;
(2) Muzamal Hussain:
Department of Mathematics, University of Sahiwal, 57000, Sahiwal, Pakistan;
(3) Sofiene Helaili:
LASMAP (LR03ES06), Polytechnic School, Carthage University, BP 743, La Marsa, 2078, Tunisia;
(4) Sofiene Helaili:
ISTEUB, Carthage University, Rue de L'Artisanat Charguia 2, 2035, Tunis, Tunisia.

Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2025 Techno-Press ALL RIGHTS RESERVED.
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Email: admin@techno-press.com