Journal of the Civil Engineering Forum
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The Estimation Modeling of Abutment Volume with Variations of Bridge Span, Abutment Height, and Seismic Zone
Full text linkThe initial cost of a bridge project determined using an estimation model depends on the dimensions, types, and materials but only a few studies have included bridge location as a determinant variable. The inclusion of the location is, however, important due to the different seismic accelerations and seismic load analysis attached to it. Therefore, this study aimed to create a model to calculate the quantity of materials needed for the construction of abutment in different locations with a PCI-Girder superstructure. Moreover, the data used for the quantity estimation model was derived from the abutment design results and those associated with concrete and reinforcing steel quantities were based on the variations of the bridge span at 20 m, 25 m, 30 m, 35 m, and 40 m, abutment height at 4 m, 6 m, and 8 m, and seismic zone 1, 2, 3, and 4. Meanwhile, the volume estimation models were obtained through multiple linear regression analysis. The results showed a very strong correlation between the span of the bridge and the height of abutment with the dependent variables while the seismic zone was observed to have a strong correlation with the dependent variables but was unable to meet the linear regression assumptions. Therefore, the statistical analysis was conducted separately for each seismic zone and the data for abutment height was transformed from H into H2. This study developed 8 models with R2 values ranging between 0.983 – 0.997 and this means they were adequately designed to estimate abutment volumes with a PCI-Girder superstructure
Regional Frequency Analysis of Rainfall, using L-Moment Method, as A Design Rainfall Prediction
Full text linkFrequency analysis is a method for predicting the probability of future hydrological events, based on historical data. Generally, frequency analysis of rainfall data and discharge data is performed using the moment method, but this method has a large bias, variant, and slope, thus there is a possibility of producing inaccurate hydrological design magnitudes. Meanwhile, the L-moment method is a linear combination of Probability Weighted Moment, with the ability to process data concisely and linearly. This study was therefore conducted to discover the L-moment method’s capacity to obtain a regional probability distribution and design rainfall, used as a basis for calculating hydrological planning, in anticipation of disasters. The study location, Mount Merapi, was selected to enable a more accurate prediction of maximum rainfall with the capacity to cause cold lava in the area, and consequently, reduce the risk of loss for people living within close proximity. According to the results, the L-moment regional ratio results were τ2R = 0.203, τ3R = 0.166, and τ4R = 0.169. The homogeneity and heterogeneity tests show all rainfall stations are uniform or homogeneous, and no data were released from the discordance test results. Also, the growth factor value increases in each return period design rainfall prediction. In this study, the suitable regional probability distribution for the research area is the Generalized Logistic distribution with formulated design rainfall equation. Regional design rainfall is able to predict possible rainfall within the area. The Test model showed the minimum RBias = 0.45%, maximum RBias = 41.583%, minimum RRSME = 0.45%, and maximum RRSME = 71.01%. Meanwhile, the L-moment method’s stability was shown by the model test minimum error = 1.64% and maximum error = 16.60%. The higher error value in the higher return period shows L-moment is able to reduce bias data, however, this has limitations in the higher return period
Behaviour of Precast Concrete Beam-to-Column Connection with SHS Hidden Corbel Subjected to Monotonic Load
Full text linkBeam-to-column connection is the most critical part of a precast concrete (PC) that governs the integrity of the entire structure, hence its characteristics need to be determined for safe applications in the construction industry. Therefore, this study developed a beam-to-column connection with square hollow section (SHS) hidden corbel. A full-scale test was conducted on eleven T-subframe specimens with various configurations used to investigate the behaviour of the connection under an incremental static load. It was further evaluated using the beam-line method to determine the moment-rotation response and the mechanical properties. Furthermore, this research analyzed the parametric response, the load resisting mechanism, and the feasibility of the connection for PC structures. Due to extensive usage of steel elements, the PC connection gave a higher ultimate strength than the reinforced concrete (RC). Its moment resistance was largely contributed by the hidden corbel embedded in the beam and column, increasing with the column and beam's embedded length. The grout infill prevented the lateral deformation of the hidden corbel and hence strengthened the connection. Due to the low bending resistance of the steel endplate, the PC connection possessed a low stiffness, which led to a larger rotation deformation than the RC connection, and a low design strength. This could be overcome by modifying the shape of the endplate for a higher second moment of inertia in resisting bending. The PC connection was classified as semi-rigid and partial-strength, and only specimen PC-3 was considered feasible for PC structures
Acceptance Analysis of PDAM Sleman’s Water Tariff, Based on Revenue and Willingness to Pay Projection
Full text linkIn Sleman, the Regional Water Company (PDAM) provides clean water to the community and charges a tariff for each cubic meter of water sold to customers. According to the Minister of Home Affairs Regulation No. 71 of 2016 states, PDAM tariffs requiring an annual review in November. The most recent tariff was set by PDAM Sleman in 2016, therefore, a recalculation is required. In addition, there is a need to analyze the tariff acceptance from the service provider, and service recipient’s point of view. In this study, the calculation tariff method utilized a formula based on the Minister of Home Affairs Regulation No. 71 of 2016. Meanwhile, the acceptance analysis from profit point of view conducted by calculating the projection of water sales revenue, profit to earning assets ratio, and customer willingness to pay (WTP). Furthermore, revenue projections were obtained by multiplying tariffs with the water sold volume, while the WTP projection is obtained using the inflation method, based on the PDAM Sleman customers’ wTP, from the 2007’s research. PDAM Sleman tariffs based on calculations resulted in low tariffs of IDR3727.48, basic tariffs of IDR4659.36, and full rate of IDR9460.17. Based on the WTP analysis, the tariffs are feasible from the service recipient’s (PDAM customers) point of view, because this is affordable by customers, for the average water consumption. However, from the service provider’s (PDAM Sleman) point of view, the tariffs are not feasible a 0.31% profit ratio is much lower, compared to the 10% profit ratio. Therefore, tariff adjustments are required to increase profits. These strategies include determining tariffs based on consumption blocks alone, without breaking down based on customer group categories and adjusting the second and third consumption blocks’ rate
The Utilization of Soybean as a Catalyst Material in Enzyme-Mediated Calcite Precipitation (EMCP) for Crack Healing Concrete
Full text linkThe effect of using soybean as a catalyst in the Enzyme-Mediated Calcite Precipitation (EMCP) method of crack healing concrete is discussed in this research. The existence of cracks in concrete reduces its quality, therefore, there is the need for repair efforts and one of these is through injection using the EMCP method. This technique employs the plant-derived urease enzyme to catalyze the reaction between calcium chloride (CaCl2) and urea (CH4N2O) towards precipitating calcium carbonate (CaCO3). Its effectiveness was, however, evaluated using a test tube experiment, and the optimum combination of urease, urea, and calcium chloride was selected and used as the preliminary data for the soybean added as a catalyst. Meanwhile, the concrete samples were prepared in the form of 5 cm x 10 cm cylindrical concrete and the crack was made through Universal Testing Machine (UTM) with a controlled area observed to be in the range of ± 0.2-0.3 mm. The injection solution was added to the concrete using the percolation method up to the period the height of the solution was 5 mm above the concrete surface and this was conducted several times with the effect on the concrete cracks evaluated through permeability tests which were used as one of the concrete quality parameters. Moreover, the permeability coefficient value was found to be inversely proportional to the quality and this means a smaller value of the coefficient produced better concrete quality and vice versa. The results showed the total calcite formed in the sample after the 4th injection was 18.3% of the total surface area of the concrete crack and was able to reduce the concrete permeability value by 95.43%. This, therefore, means the use of soybean in the EMCP method is considered feasible to repair concrete cracks
Analysis of The Impact of Traffic and Pedestrianization Environment in Malioboro
Full text linkThe phenomenon of the increasing number of Malioboro tourists is known to be raising traffic problems in the area, annually. These problems ranges from congestion and increased vehicle exhaust emissions, to increasing side friction. This has placed pressure on the Yogyakarta city government, as they have been tasked to plan and improve traffic management, through the transformation of Malioboro into a pedestrianized area. Moreover, pedestrianization in urban centres has been widely practiced in big cities of various countries. This application also has an impact on the significant changes in traffic flow on roads, around the area. This study simulated a traffic flow scenario on roads around Malioboro, via the use of a VISSIM software, in order to determine the saturation level of the movement, as well as the resulting emissions. The collection of generation and attraction data were carried out through household interview or traffic surveys, around the research area. However, the data used were obtained from the traffic survey results. The VISSIM is known to be a Microscopic flow simulation software, which is often used for traffic models. In this simulation, the existing condition, i.e, the Malioboro road that was still opened for motorized vehicles, was compared with the area's scenario (closed from motorized vehicle), as well as several gyratory alternatives on the surrounding. In order to determine the emission data released due to transportation activities, a node was placed at several simulated intersections. Also, three alternatives were observed to have been compared, with recommendations stating that those having less traffic impacts should be used
The Utilization of Bacillus Subtilis Bacteria to Improve the Mechanical Properties of Concrete
Full text linkThe utilization of concrete as a building material is well-known worldwide and increasing continuously due to its sustainability, low maintenance cost, durability, performance, etc. The ingredients of concrete, its constructional methodology, and exposure conditions have been observed to be moderating and improving daily but the focus of this research is on the laboratory investigation of Bacterial Concrete which is the technology established on the application of the mineral producing microbes like Bacillus subtilis which have the properties of bio-calcification and the ability to precipitate CaCO3 effectively inside concrete structures. This CaCO3 precipitation is able to fill the pores and cracks internally and this subsequently makes the structure to become more compact. Nutrient Broth (NB) media was employed for the growth and spore formation of Bacillus subtilis bacteria in this experimental study and four different bacterial culture densities including 0.107, 0.2, 0.637, and 1.221 were estimated at OD600 and directly added to the concrete matrix using the previously fixed water to culture ratio of 0.5:0.5. Moreover, 100 mm cubical concrete specimens were cast, subjected to compressive and tensile strength tests for different curing ages, and finally compared with Conventional Concrete with OD600=0. A significant increase was observed in the mechanical strengths due to the addition of Bacillus subtilis bacteria in concretes with a culture density of 0.637. Furthermore, cylindrical concrete specimens with 100 mm diameter and 200 mm height were prepared for Ultrasonic Pulse Velocity (UPV) analysis and the results showed specimens prepared with culture density of 0.637 have higher pulse velocity than other microbial groups. A UPV vs. compressive strength relationship curve was, however, later proposed for different strengths of concrete
Rainfall Trend and Variability Over Opak River Basin, Yogyakarta, Indonesia
Full text linkRainfall intensity seems to be increasing nowadays due to climate change as presented in many studies of both global and regional scale. Consequently, cities worldwide are now more vulnerable to flooding. In Indonesia, increasing frequency of floods was reported for the past decades by The National Agency for Disaster Countermeasure (BNPB). To understand the rainfall changes, long-term trend evaluation over a specific area is then crucial due to the large variability of spatial and temporal rainfall distribution. This study investigates the homogeneity and trend of rainfall data from 20 stations over the Opak River basin, Yogyakarta, Indonesia. A long-term ground observation rainfall data whose period varies from 1979 to 2019 were analyzed. Non-parametric Mann – Kendall test was applied to assess the trend, while the magnitude was calculated using the Sen’s slope estimator. An increasing annual maximum of daily rainfall intensity was observed at four stations on a 0.95 confidence level based on the Mann – Kendall test, while the Sen’s slope estimator shows a positive trend at almost all stations. The trend of heavy rainfall frequency was also found to be significantly increased, with only one station showed a decreasing trend. Furthermore, this paper also described the spatial rainfall variability. Positive trend was mostly found during the rainy season, while the negative trend occurred during the dry season. This could pose a challenge for water resource management engineering and design, such as water supply systems or reservoir management. Understanding this phenomenon will benefit hydrologists in preparing future water resource engineering and management
The Effect of Slope on the Infiltration Capacity and Erosion of Mount Merapi Slope Materials
Full text linkThe infiltration on slopes has a specific behavior capable of being parameterized and one of the reasons is due to the ability of the slope to generate less ponding on the sloping soil surface. This, therefore, affects infiltration rate and surface runoff proportion of water from any kind of rainfall distribution and the tendency of the surface runoff to be higher usually leads to a higher erosion rate on the slope. Moreover, slope steepness is the most important parameter of a slope, and its effect at 36%, 47%, and 58% was tested on the infiltration capacity and erosion rate of Mt. Merapi bare slope material in a laboratory using a rainfall simulator. The rainfall intensity was set constant at a rate of 116.31 mm/hour while the infiltration rate was measured by the volumetric balance principle and the erosion rates by collecting the eroded grains at the downstream end flume. Furthermore, the infiltration capacity was evaluated using the Horton method by fitting the equation to the recorded infiltration rate data while the average erosion was through the eroded grain data for each test. The results obtained represent the relationship between slope steepness, the affected infiltration capacity, and erosion for each test, and the infiltration capacity was found to be decreasing in lower slope < 47% and increasing in a higher slope while the erosion rate was increasing between 7% and 15% for each 1% increase in the slope steepness. In addition, polynomial and linear equations were developed to express the relationship between these three indicates at the Mt. Merapi bare slope material
Analysis of the Carrying Capacity and the Total Maximum Daily Loads of the Karang Mumus Sub-watershed in Samarinda City Using the WASP Method
Full text linkWatershed is a multi-aspect ecological system, which functions as a source of water resources, in order to meet daily needs. It also motivates both economical and life matters, as well as serve as a sanitary channel for the surrounding community. Watershed also generates pollutants, which are known to potentially cause a decrease in river water quality. The degradation of river habitats that are caused by high pollutants penetration into the water body, decreases the capacity to carry out self-purification of toxic loads. The water pollutant load-carrying capacity is then calculated through various methods, one of which is the use of a computerized numerical modeling simulation called WASP (Water Quality Analysis Simulation Program). This method was developed by the ES-EPA, in order to process TMDLs (Total Maximum Daily Loads) data on river bodies, as well as examine each part of the water quality, based on spatial and temporal inputs. This study was conducted at the Karang Mumus Sub-watershed flowing through the centre of Samarinda City, with aims to determine the pollutants' carrying capacity, existing load, and toxic waste allocation, via the use of the BOD (Biological Oxygen Demand) technique as a parameter of water quality. The calculation was carried out by segmenting the river into five parts, based on the number of districts it passes through, during pollutant loads inventory. The WASP modeling simulation showed that the total pollutant load-carrying capacity of the whole segments was 5,670 kg/day. It also showed the existing loads of about 3,605 kg/day, with the margin having the ability to receive pollutants at 2,065 kg/day. Moreover, the allocation of pollutant loads varies for each segment, with 2, 3, and 4 observed to reduce the pollutant by 390, 220, and 10 kg/day, respectively. However, segments 1 and 5 were still allowed to receive pollutant loads up to 1,740 and 945 kg/day, respectively