Cantilever: Jurnal Penelitian dan Kajian Bidang Teknik Sipil

Flexural and Shear Strength of RC Beam with Embedded Polystyrenes

2026-06-27T23:59:45+07:00

This study examines the structural performance and material efficiency of reinforced concrete (RC) beams embedded with trapezoidal polystyrene, tested under flexural and shear loadings. The integration of polystyrene aims to reduce concrete volume while maintaining structural integrity. Twelve specimens were tested under four-point static loading, including five different polystyrene configurations and one control specimen for each loading type. Performance was evaluated based on load-displacement behavior, structural capacity, and material efficiency (i.e., strength gain vs concrete volume reduction). Results indicate that beams incorporating polystyrene remain functional. However, not all configurations increased load-bearing capacity; for example, PB5 showed decreased capacity. Performance is significantly influenced by the geometry of the embedded polystyrene, with increasing width having a more detrimental effect than depth. Among the specimens, PB2 exhibited the best overall performance, achieving 10% higher flexural capacity and 18% greater shear capacity despite a 10% reduction in concrete volume, resulting in 22% and 31% higher material efficiency under flexural and shear loadings, respectively. Some specimens, such as PB5, showed decreased capacity. These gains, however, were offset by lower cracking resistance and reduced ductility, which could limit the beam’s serviceability and affect its suitability for structural applications requiring high deformation capacity or crack control. Despite its potential, the use of polystyrene in RC beams presents practical challenges, including the study’s limited replication, construction complexity, and fire safety concerns, which must be addressed before broader implementation in structural applications.

Faktor Penyebab Gerakan Tanah di Desa Noelmina Kecamatan Takari, Kabupaten Kupang, Provinsi Nusa Tenggara Timur

2026-06-27T23:59:43+07:00

A landslide is a process where the mass of rock or soil that forms a slope moves due to the force of gravity in a weak area. Landslides that occurred in Noelmina Village, Takari District, Kupang Regency on February 17, 2023, resulted in the main road, which connects the provincial capital of East Nusa Tenggara and several districts on Timor Island, being completely damaged. This research aims to identify the factors that contribute to landslides in Noelmina Village. This research began with collecting regional geological data, a regional geological structure, then continued with primary data collection in the field for geological mapping, geomorphological, and land use data, while rainfall data was taken from the CHIRPS satellite data. Results indicated that the landslide occurred within the Bobonaro carbonate mudstone unit, characterized by a rather steep slope where the geological structure consisted of joints in the rock mass. Additionally, the landslide was situated in an area influenced by the regional geological structure, specifically the left-hand horizontal fault. The land use conditions of the research area are quite varied, but the areas that experienced landslides were located in forest land uses that directly border residential areas and roads. The rainfall conditions during the landslide in February 2023 had a high intensity of 431mm - 463mm. An XRD analysis was conducted on rock or soil samples from the landslide area, and it was found that expansive minerals, namely montmorillonite, illite, and kaolinite, were present. The results of this research indicate that landslide events in the research area were significantly influenced by factors such as rock/soil conditions, geomorphology, geological structure, land use conditions, and the presence of expansive clay minerals. Furthermore, the dominant factor triggering the landslide was the high-intensity rainfall that took place in the study area of less than one month.

Faktor Risiko Penyelenggaraan Infrastruktur Daerah dengan Skema KPBU Availability Payment

2026-06-27T23:59:41+07:00

Regional infrastructure is the backbone of the economy and public services, but local governments often face fiscal capacity constraints. Public-Private Partnership (PPP) with the Availability Payment (AP) scheme emerges as a solution to overcome the funding gap. However, its implementation at the regional level still faces a high rate of project failures. This study aims to develop a framework of critical risk factors in the implementation of regional PPP AP to improve risk management effectiveness. Using a systematic literature review approach on 38 scientific articles and operational reference documents, the study identifies 35 risk factors categorized into 10 main groups. The analysis results show that the risk landscape of regional PPP AP is dominated by governance and institutional challenges, with three main vulnerable areas: (1) AP Payment Risk (uncertainty of government commitment and fiscal capacity), (2) Political Risk (policy instability due to local political dynamics), and (3) Interface Risk (limitations in government coordination capacity and human resources). The framework provides a foundational tool for stakeholders to develop risk mitigation strategies and practical guidelines, supporting more effective and sustainable regional infrastructure development.

Perancangan Pemanenan Hujan untuk Penyediaan Air Bersih dan Pengurangan Aliran Permukaan di Pasar Datah Manuah

2026-06-27T23:59:39+07:00

Pasar Datah Manuah is one of the largest traditional markets in Palangka Raya. During heavy rainfall with a long duration, the water level in the drainage channels outside the market area rises quickly, while the drainage channels inside the market building often experience flooding. This situation leads to ponding in several areas of the market courtyard. One alternative solution to this problem is the implementation of a rainwater harvesting system. This study aims to design rainwater storage components for three large buildings in Pasar Datah Manuah. The rainwater storage is designed to serve as an alternative source of clean water while also reducing peak surface runoff. The storage volume is designed by comparing the cumulative rainwater supply with the cumulative clean water demand. Peak surface runoff analysis uses the Rational Method. The study results show that to meet the daily clean water needs for the three buildings with a floor area of 4,806 m², a rainwater storage volume of 74.87 m³ is required. The study also indicates that the average peak surface runoff, calculated at two drainage outlets in the market courtyard, reaches 0.36 m³/s without the rainwater harvesting scenario. With the rainwater harvesting scenario, the average peak runoff decreases to 0.27 m³/s. In other words, under the rainwater harvesting scenario, the average peak surface runoff at the market courtyard outlets decreases by 25.95%.

Reliability Assessment of Bored Pile Foundations using a Probabilistic Approach based on SPT Data

2026-06-27T23:59:37+07:00

Deep foundations perform an important role in supporting structural loads and transferring them to deeper and stronger soil layers. The soil parameters used in geotechnical design practice are commonly obtained from field tests, such as the Standard Penetration Test (SPT), which exhibit a high degree of uncertainty due to variations in soil conditions, testing procedures, and data interpretation. These uncertainties significantly influence the reliability of deep foundation design. Such study aims to evaluate the reliability of bored pile foundations and determine their safety level based on SPT data from five boreholes at various depths using a probabilistic approach. The Monte Carlo simulation method was employed to model the variability of soil strength, determine the reliability index (β), and estimate the probability of failure (Pf). The analysis results show that although the deterministic safety factor (SF ≥ 1) indicates a safe condition, the probabilistic analysis reveals that the system still has a failure probability of approximately 48% and a reliability level of only about 52%, indicating a marginal state. The reliability index limit (β = 0.05) serves as a minimum threshold separating safe and unsafe conditions. Increasing the pile diameter significantly improves the reliability index and reduces the failure probability, demonstrating a strong correlation between design parameters and reliability performance. Overall, the findings highlight that the deterministic approach alone cannot adequately capture soil parameter uncertainty, and reliability-based design (RBD) provides a more realistic and quantitative framework for assessing foundation safety in geotechnical engineering.

Evaluation of Roundabout Performance in the Sudirman Central Business District (SCBD), Jakarta

2026-06-27T23:59:35+07:00

The Sudirman Central Business District (SCBD) in Jakarta is characterized by high-intensity, mixed-use activities that generate substantial traffic demand throughout the day. This study evaluates the operational performance of the Lot 13 roundabout, one of the district’s critical internal nodes, using a combination of field observations, analytical assessment, and a microscopic simulation model developed in PTV Vissim. The simulation approach was selected because similar roundabout studies in Indonesia remain largely dominated by analytical capacity assessment, with fewer calibrated microsimulation-based evaluations in dense CBD environments characterized by mixed traffic and high roadside friction.. Traffic data were collected at 15-minute intervals during peak periods and used to construct a detailed behavioural model calibrated to local driving characteristics, including short headways and aggressive merging behaviour typical of mixed traffic in Indonesia. The results reveal severe oversaturation on the Sudirman–Grand Lucky and Sudirman–BEI legs, where maximum queue lengths exceed 550 meters, delays surpassing 70–100 seconds per vehicle, and circulating speeds reduced to 12–18 km/hour, placing the roundabout at Level of Service F. Geometric constraints, high roadside friction, and unbalanced approach volumes further degrade operational capacity, demonstrating that the current unsignalized configuration is insufficient to accommodate prevailing demand. The findings suggest that adaptive signal control or metering signals may represent promising options for further operational performance by creating controlled entry gaps and reducing conflict intensity. The study provides a site-specific operational diagnosis of the Lot 13 roundabout and highlights the combined role of unbalanced approach demand, limited effective entry capacity, and roadside friction in shaping queue formation, delay, and flow breakdown in a dense CBD setting. Recommendations for future research include the evaluation of multi-scenario design alternatives and the assessment of broader network-level impacts to support long-term mobility planning in SCBD.

Performance of Concrete Sheet Piles with Stranded Steel Waste Using Finite Element Method

2026-06-27T23:59:33+07:00

The innovation in precast industrial metal waste-based concrete materials aims to improve the mechanical properties of concrete while reducing its environmental impact. This study examined the performance of 62.25 MPa plain concrete sheet piles with the addition of steel fiber waste through finite element method (FEM)-based numerical modelling with a cantilever configuration that represents actual field conditions used linear modelling. The variations in the steel fiber waste content analyzed were 0%, 1%, 2%, 3%, and 4%. The test specimens were modelled with modified dimensions (50 × 20 × 10 cm) to accommodate the computational limitations. The material parameters refer to the SNI standard, where the elastic modulus of concrete is calculated using an empirical approach, and the steel fiber is modelled as an isotropic elastic material with mechanical properties according to the standard. The analysis focused on the deflection behavior, moment capacity, and deformation response to a design load of 41.5 kN. The simulation results showed that additional 1% strand content produced deflections that were within safe limits (≤ 2.8 mm). The lowest deflection value occurred in the 1% variation, with a decrease of 7.89% compared with normal concrete. Increasing the strand content above 1% did not provide significant additional benefits; in fact, at a content of 4%, the deflection increased by 5.57%. This indicates that an increase in fiber distribution density can reduce the homogeneity of concrete that potentially create weak zones in concrete. Thus, this study confirmed that adding 1% steel fiber waste is optimal for improving the flexural deformation performance of concrete sheet piles.

Analisis Kestabilan dan Rekomendasi Perbaikan Desain Lereng pada Tambang Terbuka

2026-07-01T19:44:36+07:00

This study evaluates the stability of an open-pit mine slope and proposes an optimized slope geometry based on limit equilibrium analysis. Geotechnical parameters were derived from field investigations using the Rock Mass Rating (RMR) and Geological Strength Index (GSI) classification systems, then incorporated into Slide 6.0 for slope stability analysis. The Janbu and Morgenstern–Price limit equilibrium methods were employed to determine the factor of safety (FoS). Initial simulations indicated that the analyzed slope was stable; however, the observed field failure prompted a back analysis, which identified a weak layer with reduced shear strength as the primary cause of instability. The back analysis produced FoS values of 0.774 and 1.154 using the Janbu and Morgenstern–Price methods, respectively. Based on these findings, the slope geometry was redesigned with a slope angle of 45°, a bench width of 13 m, and a bench height of 8 m. The redesigned slope increased the FoS to 1.314 (Janbu) and 1.590 (Morgenstern–Price), satisfying the recommended stability criterion. A comparison of the two methods further showed that the Janbu method consistently yielded FoS values approximately 15% lower than those obtained using the Morgenstern–Price method, indicating its more conservative predictions. The proposed design provides an effective approach for improving slope stability while highlighting the importance of incorporating back analysis to capture actual field conditions that are not represented in initial geotechnical models.