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Volcanic Ash Fall Hazard of Mount Merapi on Yogyakarta Nuclear Area Setiaji, Abimanyu Bondan Wicaksono; Satyarno, Iman; Harijoko, Agung
EKSPLORIUM Vol. 43 No. 2 (2022): NOVEMBER 2022
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2022.43.2.6708

Abstract

The existence of nuclear installations in the Yogyakarta Nuclear Area is vulnerable to the eruption of Mount Merapi, the most active volcano in Indonesia. Tephra hazard has the potential to threaten the operational activities of nuclear installations in the Yogyakarta Nuclear Area; thus, it is necessary to analyze the distribution and potential hazard of volcanic ash from Mount Merapi for future eruptions. Numerical modelling is used in analyzing tephra distribution using TEPHRA2 software with parameters of the 2010 Mount Merapi eruption, which is then visualized to isomass and isopach maps of tephra distribution. The analysis resulted in the ash dispersion leading to the Yogyakarta Nuclear Area in April, May, June, and August with an accumulated mass of 20-50 kg/m3 with a thickness of 0.2-12 cm. It is necessary to deal with volcanic ash hazards such as roof strength, secondary cooling system, filtering system, and electrical system for several installations in the Yogyakarta Nuclear Area.
The Application of Alkali Activator and Admixture for High Early Concrete Compressive Strength with GGBFS Substitution Juesmin, Elvina; Satyarno, Iman; Siswosukarto, Suprapto; Nawangsasi, Ratna Dwiyani; Taufiq, Muhammad Hasan
INERSIA lnformasi dan Ekspose Hasil Riset Teknik Sipil dan Arsitektur Vol. 21 No. 2 (2025): December
Publisher : Universitas Negeri Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21831/inersia.v21i2.87887

Abstract

Concrete with high early compressive strength is designed to reach at least 20 MPa within the first 24 hours after casting. However, achieving this generally requires increased cement content, which unfortunately leads to higher carbon emissions and production costs. To reduce this impact, cement can be partially substituted with pozzolans such as ground granulated blast furnace slag (GGBFS), which has a chemical composition similar to cement. Nevertheless, GGBFS exhibits a slow hydration process; therefore, an alkali activator is required to accelerate the reaction. On the other hand, alkali activation can reduce concrete workability, making the addition of admixtures such as superplasticizers necessary to maintain adequate workability. This study investigates the effect of adding alkali activators and admixtures on concrete's early compressive strength and workability of concrete incorporating GGBFS as a cement substitute. Ordinary Portland cement and GGBFS were used at a ratio of 70:30. The alkali activator consisted of NaOH and Na₂SiO₃, with a Na₂SiO₃/NaOH ratio (R) of 1.5 and a total alkali-to-GGBFS ratio (A) of 0.45. The superplasticizer was Sika® ViscoCrete®-1050 HE at at dosages of 0.5% and 1%. The alkali activator contents tested were 0%, 2.5%, 5%, 7.5%, and 10%. The paste-to-fine aggregate void ratio (Rm) and the mortar-to-coarse aggregate void ratio (Rb) were both set at 1.4. Workability was evaluated using the slump test, while compressive strength was measured at 24 hours. The results showed that the addition of an alkali activator led to a substantial improvement in the compressive strength of the concrete, reaching up to 114.8% of the minimum required early compressive strength. The compressive strength peaked at 43 MPa when 10% alkali activator was added to the mixture. However, increasing the alkali activator content significantly reduced workability, with the slump value reaching zero at the 10% dosage. The addition of a superplasticizer was proven to be necessary to maintain a balance between early strength and concrete workability.
Structural Performance of Circular Hollow Steel Damper with Fins and Gaps Aritonang, Tobok S. M.; Satyarno, Iman; Awaludin, Ali; Setiawan, Angga F.
Civil Engineering Journal Vol. 12 No. 2 (2026): February
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2026-012-02-03

Abstract

Prior studies have shown that fin reinforcement on a circular hollow steel damper (CHSD) could mitigate buckling and enhance shear strength. However, in bridge applications, repeated vibrations from lateral traffic loads and low-frequency cyclic actions may cause premature energy dissipation and fatigue damage, thus reducing the seismic performance of CHSD during design-level earthquakes. To address this issue, this study integrates fins and gaps into CHSD to enhance stability against buckling and to mitigate fatigue-induced damage. The CHSD specimens were fabricated in three variations: without fins, with fins, and with fins and gaps. Cyclic loading tests and nonlinear finite element analyses were conducted to evaluate their effects on mechanical properties and seismic performance. Cyclic loading was performed in accordance with the AISC 341-22 protocol and applied at 0° and 30° to simulate multidirectional lateral forces. The cyclic test results reveal that the addition of fins exhibits both beneficial and adverse effects on the mechanical properties and seismic performance of CHSD, while the gap reduces the equivalent viscous damping ratio. The backbone curves derived from the numerical analyses agree well with experimental results. Furthermore, the damper shear resistance and deformation capacity are delayed by the presence of gaps, mitigating fatigue-related damage.