Journal of Civil Engineering Beyond Limits (CEBEL)

Barış BAYRAK Kaan KOÇ Muhammed Himmet Sami ÖZDEMİR Abdulkadir Cüneyt AYDIN

Ordinary Portland cement is currently generally used cementitious material in the construction industry. However, it has significant drawbacks as it not only depletes natural resources but also releases a substantial amount of carbon dioxide during its production process. On the other hand, alkali-activated cement is an alternative option that is derived from raw materials like slag, fly ash, and metakaolin, which contain silicon dioxide (SiO2) and aluminum oxide (Al2O3). This study investigates the shear capacity of fibre-reinforced geopolymer concrete (GPC) beams under shear loads. In the study, the shear behavior of beams produced from fly ash-based geopolymer of three different fiber types was determined by applying a three-point shear test. Four beams of 100x100x400 mm dimensions were produced: reference, steel fiber, basalt fiber and glass fiber. The results showed that using steel fiber has the greatest impact on shear capacity. In addition, the shear capacity of fibrous samples is greater than the shear capacity of the reference sample.

https://doi.org/10.36937/cebel.2024.1931

Oğuzhan ÇELEBİ Mahmut Kılıç Abdulkadir Cüneyt Aydın

Today, there are many methods for detecting damages in reinforced concrete structures, such as pushover analysis, energy-based analysis and nonlinear analysis in the time domain. These methods are used to determine the dynamic properties of the structure by using accelerometers and a number of measuring devices that determine the mechanical and physical properties of the structure. In this study, it is aimed to diagnose damage with a set of frequencies and corresponding amplitude values obtained from accelerometers that determine the dynamic properties of the structure, instead of these methods that create calculation complexity. In this study, firstly, the damaged elements and joint points of the 1-storey RC frame with a single opening in both directions were determined by pushover analysis, for which the finite element model was built in the SAP2000 program. Later, time history analyzes were carried out under the influence of acceleration data of the Pazarcık earthquake (Mw 7.7) that occurred on February 6. The results obtained in the time domain were converted into the frequency domain and some inferences were made regarding the damaged areas. The study results showed that if the amplitude drop decreases in the same frequency range at a node, damage occurs at that node. It has been determined that the damages occurring in the RC frame increase due to the decrease in amplitude.

https://doi.org/10.36937/cebel.2024.1927

Elif Yazıksız Emre Alpaslan

Determining the modal parameters of historical buildings is crucial for understanding their dynamic behavior, which is essential for preserving them and ensuring their safety for future generations. Both experimental and numerical studies are frequently carried out to characterize certain modal properties, such as natural frequencies and natural mode shapes. Experimental studies typically use the operational modal analysis method, while numerical studies employ the finite element method. Vibration measurements of the structure under various environmental conditions, including wind and traffic, were used to determine the modal parameters. Nevertheless, disparities frequently occur between the modal parameters obtained from experimental research and those assessed by the finite element model. Usually, these discrepancies result from unknown characteristics like boundary conditions and material properties. The purpose of this study was to measure the vibrations of a historic elevated water tank with a history of 150 years in ambient conditions in order to determine its modal characteristics. It became clear from comparing the modal parameters found in the numerical and experimental investigations that the water tank's finite element model needed to be updated in order to match the findings of the experimental modal study. Future structural evaluations will be able to better understand the behavior of the structure with the generate of an updated finite element model.

https://doi.org/10.36937/cebel.2024.1922

Saad Issa Sarsam

The kinetic energy created in the asphalt concrete due to practicing dynamic loading is absorbed and consumed to retain the properties of the asphalt mixture through its flexibility; however, part of the energy is dissipated in the initiation of microcracking and other types of distresses. In this work, the influence of additives (fly ash and silica fumes) on controlling the energy dissipation of asphalt concrete mixtures was assessed. Beam specimens of asphalt mixture were obtained from the roller compacted slab samples and tested for fatigue under three constant strain levels by implementation of the four points bending beam. It was noticed that for fly ash treated mixture, the consumed time for energy dissipation decline by (75, and 97.5) % while the dissipated energy declines by (84.8, and 99.5) % when the constant strain level increases from (250 to 400 and 750) micro strain respectively. However, for silica fumes treated mixture, the energy dissipation declines by (3.3, and 95) % when the constant strain level rises from (250 to 400, and 750) micro strain respectively. It was noticed that the damage resistance as indicated by the increment in dissipated energy increases by (60, and 140) % when fly ash and silica fumes were implicated respectively. However, the silica fumes additive consumes the energy at lower time of 60 seconds than the case of control mixture. The fly ash additive exhibits no significant variation in consuming the energy when compared with the control mixture.

https://doi.org/10.36937/cebel.2024.1898

MELEK AKGÜL

In this experimental study, the effect of wood ash (WA) substituted into Portland cement (PC) at variable proportions by volume on the fresh state, hardened state, and microstructure of self-compacting mortars (SCMs) was investigated. In the designed SCMs, WA was substituted into PC at 5% increasing ratios in the 0%-30% band. A total of 84 40*40*160 mm prism specimens and 42 50*50*50 mm cube specimens were produced for 7 different SCM designs. V-funnel and slup flow test were done according to EFNARC kriteria. Hardened state tests were carried out at 7, 28, 56 and 90 days with oven dry unit volume weight, porosity, capillary water absorption, flexural tensile, compression and splitting tensile tests. In addition, WA used in the mixture and after 28 days of water curing, samples containing WA 0%, 15%, 30% were evaluated after microstructure analysis. According to the results of the study, increasing WA substitution rate has a determining effect on the fresh state properties. Increasing WA substitution has a negative effect on flexural tensile strength and compressive strength and a variable effect on splitting tensile strength. Increasing the amount of WA increases the unit volume weight and decreases the porosity at 5% substitution. For the other substitution cases, the unit volume weight decreases and porosity increases. Except for the control mixture, Magnesium calcite and Aluminum-based compounds were detected in microstructure examinations of SCMs.

https://doi.org/10.36937/cebel.2024.1945