Seismic Behaviour of a Single Span Historical Masonry Bridge Alper ÖZMEN, Erkut SAYIN
A major portion of the cultural heritage consists of old structures that are susceptible to earthquakes. These structures are prone to significant damage from natural disasters, particularly earthquakes. This study's primary goal is to assess the historical masonry bridge's seismic response to strong far-fault ground motions (FFGM) and near-fault ground motions (NFGM). The historical Sultan Suyu Masonry Bridge is used as a case study in this study. It was created with three-dimensional finite element software. The time history response of the bridge model is contrasted with one another in terms of stresses and displacements produced for FFGM and NFGM. The assessments take into account the FFGM and NFGM of the 1999 Düzce, 1999 Kocaeli, and 1992 Erzincan earthquakes, which had nearly equal peak ground accelerations. The results show that FFGM is equally significant as NFGM and that FFGM could be used in conjunction with NFGM to further evaluation of historical masonry arch bridges.
Received : 06 January 2023
Revised : 12 April 2023
Accepted : 29 April 2023 Performance of geopolymer mortars prepared by different alkaline solutions under elevated temperature
Mariam F. Ghazy, Metwally A. Abd Elaty, Mohamed Taman, Alaa M. Mehriz
Fire has severe effects on concrete as it causes a significant deterioration in its properties. Geopolymers (GP) are considered as an emerging alternative binder to Portland-cement OPC). This paper presents an investigation of the performance of fly ash (FA) based GP-mortars made with different alkaline solutions after exposure to elevated temperatures (200, 400, 600, and 800 ℃). The main investigated parameters were the type of hydroxide (NaOH and KOH), type of silicate (Na2SiO3 and K2SiO3), molarity levels of NaOH, Na2SiO3/NaOH ratios, alkaline-solution to FA ratio and sand to FA ratio. Compressive, flexural, and indirect tensile strengths were measured before and after exposure to elevated temperatures. Moreover, SEM analysis was conducted on GP and OPC mortars. The results showed that performance of GP mortars containing Na2SiO3 with KOH was better than GP mixes that contained Na2SiO3 with NaOH or K2SiO3 with KOH after exposure to elevated temperatures. A higher loss rate in mechanical properties after exposure to 800℃ was observed as the NaOH molarity increased. Increasing Na2SiO3/NaOH ratio up to 2.5 caused an increase in the mechanical properties, while increasing that ratio from 2.5 to 3 caused higher loss in the mechanical properties of GP mortars. After exposure to 800 ℃, sand to FA ratio of 2 and alkaline solution to FA ratio of 0.5 gave higher residual strengths than the other ratios. Behavior of GP mortar was found to be better than OPC mortar after exposure to elevated temperatures. SEM images showed that the structure of the GP mortar, after exposure to elevated temperatures, was denser than that of the OPC mortar. Empirical equations capable of predicting the residual mechanical properties of GP-mortars made using different alkaline solutions with good correlation have been proposed.
Received : 08 December 2022
Received : 10 March 2023
Accepted : 15 April 2023 STUDIES ON HARDNESS AND TENSILE TESTING OF AlSi10Mg PRODUCED BY SELECTIVE LASER MELTING
Suresha S, Subramanya Raghavendra
AlSi alloys have a wide range of applications in the Additive Manufacturing area, including automotive, aerospace, and residential industries. Despite their appealing mix of mechanical qualities, high heat conductivity, and low weight, they are more difficult to treat by Selective Laser Melting due to their high reflectivity and heat conductivity. In this work, samples were exposed to heat treatment at temperatures of 4000C, 5000C, and 5500C and an artificial ageing treatment for 180oC for 12h, to control the mechanical behaviour of selective-laser- melting (SLM)-produced AlSi10Mg alloys, after which material properties such as tensile strength and hardness were evaluated. The highest tensile and yield strengths are shown by the as-built SLM specimens, which have values of 432.45 and 322.76 MPa. On the other hand, the lowest tensile and yield strengths are shown by the solution heat-treated specimens, which have values of 168.11 and 90.52 MPa. Similar to as-built SLM specimens, the highest hardness value measured was 132.55Hv1.
Received 25 October 2022
Revised 15 April 2023
Accepted 29 April 2023 Using optimization algorithms to detect damages on free-free beam based on dynamic results Quoc-Bao Nguyen
This article describes a Modal Analysis method for detecting damage in free-free beams using natural frequency data. The method involves updating a numerical model of the beam with experimental or reference natural frequencies to determine the damage location and damage index. The accuracy of the method was verified through simulations and experiments on beams with both single and double damage zones. The results demonstrate that the method is effective in detecting the damage location for single damage zone and double damage zones with the same or different damage index. However, when the two damage zones are close together, the method that updates the model through PSO optimization algorithm using the reference frequency data may produce inaccurate results. Furthermore, when using experimental frequency data for damage beams, the results indicate that the method has a damage location error of approximately 3.5% along the entire beam length, which is considered acceptable in practical applications. The natural frequency-based damage detection method described in this article offers a useful tool for the assessment of damage in free-free beams and can be effectively combined with visual inspection techniques.
Received : 3 mars 2023
Revised : 24 avril 2023
Accepted : 24 may 2023 Study of the performance of passive cooling strategies in buildings under arid weather conditions
Habiba Kazeoui, Abdelkader Tahakourt, Sofiane Bourbia
In Algeria, the building sector accounts for approximately 43% of total primary consumption and accounts for more than one-third of energy-related greenhouse gas emissions. It should be a primary focus for reducing energy consumption and greenhouse gases (GHG) emissions. The new buildings, particularly in the hot and arid southern regions, are completely unsuitable for the climate. The use of inefficient building materials results in high energy consumption. The goal of this project is to investigate passive cooling solutions in order to reduce discomfort and the use of air conditioning systems inside buildings. A two-pronged approach combined chart-based bioclimatic analysis with building performance simulation. The impact of some passive cooling strategies on typical buildings constructed with conventional and local materials was investigated. The study found that when a building uses passive cooling strategies, total cooling needs can be reduced by up to 27% with conventional materials and up to 40% with local materials. In addition, average daily operating temperatures in local buildings can be reduced by up to 2.5 °C and about 1.5 °C in conventional buildings.
Received 29 sptember 2022
Revised 17 July 2023
Accepted 22 july 2023 Evolution of the forbidden bands of structures based on concrete and steel after substitution steel by molybdenum. Comparison between structures with square periodicity and structures with hexagonal periodicity
Amine Amrane, Abdelkader Hassein-Bey
In this article, a study of the frequency dispersion curves of a periodic structure was made. The cell units of the base model are made of steel cylinders coated with a polymer (rubber) layer embedded in a concrete thin mat.The results show the existence of three band gaps at medium frequencies ranging from 52 - 67 m/s, 101 - 224 m/s and 260 - 323 m/s, which means that we have no propagation of any wave in these frequency ranges. In second step, the steel core has been substituted with molybdenum which is heavier and stiffer than steel. A noticeable shift towards the low frequencies has been achieved together with an improvement in the relative widths of the band gap which pass from 25 to 30.2% and from 75.7 to 86.2% for the first and the second band gap respectively. In order to get closer to the experimental concept, a harmonic study was also made, and the layout of the transmission curves showed a good correlation with the results obtained through the frequency dispersion curves, in particular concerning the position and the width of the band gap. In addition, a comparison of band gaps was also made between a finite two-dimensional structure with square periodicity and a finite two-dimensional structure with hexagonal periodicity for the couple of "molybdenum-rubber" materials. This comparison showed a clear decrease in the band gap width, in particular the second band and the total disappearance of the third band gap, and this, passing from a square periodicity to a hexagonal periodicity. In addition, a shift of the band gap towards high frequencies was observed. This result is also in o good correlation with those given by the transmission curves. Through this result, we can deduce that a square periodicity of a two-dimensional structure is more favourable for the field of civil engineering wich is necessary to be in a low frequencies.
Received
Revised
Accepted Assessment of Influence of Reinforcement Detailing on Blast Resistance of Reinforced Concrete Beam-column Connections
Hafiz Ahmed Waqas, Ali Husnain, Hassan Ubaid, Adil Poshad Khan, Mati Ullah Shah , Muhammad Ilyas, Muhammad Waseem
This study investigates the influence of blast loading on Reinforced Concrete (RC) beam-column connections, which are critical components for maintaining the structural integrity of buildings during extreme events like explosions. The impact of varying blast loads, detonation distance, and reinforcement detailing on the extent of damage in the RC frame and connections is analyzed using ABAQUS/CAE Finite Element Method (FEM) software. Joint rotation is used as a damage indicator to assess the damage level in the structure. The study evaluates the effect of reinforcement detailing on the blast damage resistance of the RC frame and connections and proposes recommendations for reducing damage in the connections through the effective placement of steel reinforcement. The effectiveness of different configurations of reinforcing steel bars is also analyzed, and the presence of shear and diagonal reinforcements is found to reduce joint damage by 3-4 times. This study highlights the significance of reinforcement detailing and recommends its careful consideration in the design of blast-resistant structures.
Received
Revised
Accepted Free Vibration of Statically Deformed Bi-directionally Graded Timoshenko Beam on Elastic Foundation
Hareram Lohar, Anirban Mitra, Sarmila Sahoo
In the present work, geometric nonlinearity is taken into consideration to study the free vibration response of nonlinearly deflected Timoshenko beam with bi-directional gradation, resting on an elastic foundation of Winkler type. Exponential variation of material properties is considered along the thickness and length direction. In order to carry out the present numerical study, the entire physical domain of analysis is converted into a normalized domain and suitable number of computational points are created on it to conduct a whole domain analysis. The adopted mathematical formulation is displacement based and semi-analytical. A unique methodology is used for the formulation, in which the static analysis is taken first under large amplitude static force, then a subsequent eigenvalue analysis is performed on the known statically deformed beam profile. Appropriate energy principles are utilized for both analyses to derive the equation of motion in matrix form, which are solved with the help of the algorithm of direct substitution method. Generated results are validated with the results of previously published paper. New sets of result are also presented as benchmark results to represent the impact of bi-directional gradation and elastic foundation on nonlinear vibration response.
Received 02 Marh 2023
Revised 26 June2023
Accepted 02 july 2023 |
