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Semesta Teknika
Published by Universitas Muhammadiyah Yogyakarta
ISSN : 1411061X     EISSN : 25025481     DOI : https://doi.org/10.18196/st
Core Subject : Engineering,
Engineering
SEMESTA TEKNIKA is a reputable refereed journal devoted to the publication and dissemination of basic and applied research in engineering. SEMESTA TEKNIKA is a forum for publishing high quality papers and references in engineering science and technology. The Journal is published by the Faculty of Engineering, Universitas Muhammadiyah Yogyakarta, INDONESIA. Copyright is by the publisher and the authors. The Journal is issued in electronic form and also issued in printed form as annual volume for the contributors only. The journal contains original research papers, review articles, short notes and letters to the editors. The topics of interest include modeling, experimental, analytical and numerical investigations on the mechanical, physical, chemical and mineralogical properties of material, developing the prototype/instrument, technology and construction process. Topic of management in industry and civil construction is also considered. SEMESTA TEKNIKA receives manuscripts from the contributor written in the Indonesian and English. Manuscripts submitted to the journal for publication must not have been previously published or is under consideration simultaneously by any other publication. Manuscripts submitted to SEMESTA TEKNIKA will be reviewed Peer Reviewers local and foreign.
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Articles 715 Documents
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Aplikasi Value Engineering dengan Metode“Paired Comparison” pada Struktur Pelat Beton Budi Sutrisno; Mandiyo Priyo
Semesta Teknika Vol 16, No 2 (2013): NOVEMBER 2013
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v16i2.4910

Abstract

This research studied the application of value engineering with a paired comparison method with the case study in Tourism Building of Sleman Regency, Special Region of Yogyakarta. Several steps need to be carried out which consisted of information, creativity, a paired comparison method analysis, development and recommendation for the new design of a concrete plate. The concrete plate was redesigned using 2 alternatives. The first alternative was reducing the thickness of the plate from 12 cm to 10 cm without changing the concrete quality. The second alternative was using precast concrete. The result shows that the first alternative will save project budget to Rp. 10,569,562.-. Moreover, by using precast, the budget for the project will be increased by Rp.4,208,058.-. According to the paired comparison method and alternative comparison evaluation matrix, the second alternative has the highest percentage (59%), while first alternative and current condition only have 25% and 16% respectively. The second alternative was chosen to be applied to replace the existing design since it will gain more profit than any other which were included concrete quality, time, controlling, weather and human resources.
Pengaruh Fraksi Volume Serat terhadap Peningkatan Kekuatan Impak Komposit Berpenguat Serat Nanas-Nanasan (Bromeliaceae) Kontinyu Searah dengan Matrik Unsaturated Polyester Nur Rahman, Muhammad Budi; Suwanda, Totok
Semesta Teknika Vol 13, No 2 (2010): NOVEMBER 2010
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/jst.v13i2.714

Abstract

The objective of this research is to determine the effect of fiber volume fraction and alcali (5% NaOH solution) treatment on the impact strength and failure mode of continuous bromeliaceae fiber/BQTN 157 polyester composites. Specimens being tested were produced using press mold technique. Fiber volume fraction was varied from 20% to 40%, while the the soaking time of the alcali treatment was between 2 and 8 hours. Whilst the impact test was carried out in accordance with the ASTM D5941 standard, the micro-structures of the broken specimens were presented as photo macrographs. The result showed that failure energy was sharply increase, 0.22 J (69.23%), upto fiber volume fraction of 34,44%. Further increase of fiber content resulted in decreasing slope of the failure energy increase. The corresponding impact strength was found being 0,0046 J/mm2. The effect of soaking time of the alcali treatment on the failure energy and impact strength showed similar trend. Optimum result was obtained at 6 hours of soaking time, i.e. 0,27 J of failure energy and 0,0055 J/mm2 of impact strength. Eight hours of soaking time resulted in the damage of fiber surface leading to decrease of failure energy and impact srength of the resulted composites. Hinge break showing fiber pull out was observed in the failure surfaces of various fiber contents, with the increase of soaking time resulted in decrease of the amount of pulled-out fibers.
Analisis Percepatan Waktu Dan Biaya Proyek Konstruksi Dengan Penambahan Jam Kerja (Lembur) Menggunakan Metode Time Cost Trade Off : Studi Kasus Proyek Pembangunan Prasarana Pengendali Banjir Mandiyo Priyo; Adi Sumanto
Semesta Teknika Vol 19, No 1 (2016): MEI 2016
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v19i1.2233

Abstract

Time and cost have significanteffect on the success and failure of the projects.Thebenchmark for the success project is usually seen by short finishing time with theminimum cost without leaving the quality.Project management systematically isrequired to ensure the project implementation time in accordance with the contractor even faster so the cost can provide benefits, and also avoid the penalty due todelay in the completion of project. The aim of this research is to calculate thechanges of the cost and (overtime) and to compare the results between the cost ofpenalty cost with the changes after adding the overtime.The secondary dataobtained from the contractor.Data analysis in this research is using MicrosoftProject 2007 program and methods of time cost trade off. The results of theprogram Microsoft Project 2007 is the critical path and the results of the method oftime cost trade off is duration acceleration and cost increases due to the accelerationof the duration in any activities that increased.The results of this study indicate that:(1) From the time cost trade off with the addition of 1 hours of work per dayconducted on first day on critical jobs during the project, obtained the reduction inthe duration of 57 days, from the normal duration of 196 days to 139 days with atotal project cost changes from the normal cost of Rp 16,371,654,833.56 to Rp 16133 .588.292,57 (the difference between the cost of Rp. 238,096,540.99) as well ascausing an increase in the direct cost of Rp 15,469,452,846.76 to Rp15,493,731,373.36 (the difference between the cost of Rp. 24,278,526.60) andindirect costs experienced a decrease of US $ 902,201,986.80 to Rp 639,826,919.21(the difference between the cost of Rp. 262,375,067.59), (2) cost of accelerating theduration of the project with overtime is cheaper than the cost to be incurred ifprojects experienced delays and penalty.
Perilaku Lentur Panel Beton Semi-Precast pada Daerah Lapangan Tanpa Metode Perkuatan Elemen Pracetak: Tinjauan pada 1, 2 dan 3 Panel Umi Khoiroh; Suprapto Siswosukarto; Bambang Supriyadi
Semesta Teknika Vol 12, No 2 (2009): NOVEMBER 2009
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/jst.v12i2.730

Abstract

A slab where only the lower portion of the floor slab is prefabricated and receives the top layer of floor slab which is cast in situ, in the context of this research is called semi-precast. For small projects, the transportation, storage, and installation of precast units can be a problem. There will be more problem if it is located in congested urban area. For this reason, precast slab panel system in smaller size and weight was introduced. The precast concrete element which is has a rough surface was predicted capable to act as composite, although no shear reinforcement method was used. The objective of this research is to study the characteristic behavior of semi-precast panel without shear reinforcement method on its interface. The characteristic investigated includes flexural capacity, stiffness, ductility, and failure mode of the slab. In this study, the specimens were divided into two groups. The first group is monolith slab that consists of one, two, and three panel(s). Each panel has 120 mm thickness, 3000 mm span length, and 200 mm width of concrete slab. The second group is semi-precast slab that consists of one, two, and three panel(s). Each panel has 70 mm thick precast slab that serves as formwork for 50 mm in situ concrete layer, to form a 120 mm thick of concrete slab. Dimension and shape between semi-precast and monolith slabs are identical. All specimens were tested under static load and failure load. Experimental results revealed that the stiffness of semi-precast slabs is lower than the monolith slab. More number of panels reduced stiffness differences between semi-precast and monolith slab. It also increases the value of stiffness and flexural capacity of the slabs. The failure mode and crack pattern is classified as flexure. Existence of interface plane which is using no shear reinforcement method can decrease the value of stiffness and flexural capacity of the slab. From the results, it is shown that the slip occurred on the semi-precast slab’s interface. It is predicted that the slip was due to the influence of no shear reinforcement on the interface.
Analysis of Cellular Traffic Homogeneity in A Specific Area using Statistical Test Surahmat, Indar
Semesta Teknika Vol 19, No 2 (2016): NOVEMBER 2016
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v19i2.2184

Abstract

Capacity and coverage are the most important issues on providing services by cellular operator companies. The companies measure the condition of their network and services continuously including data collection, monitoring, evaluation and future prediction.  These are part of activities to maintain grade of service. In this paper, homogeneity analysis in cellular traffic data is analysed. This step is a part of evaluation of current situation which it will be used for planning purposes. It is done by processing data provided by network statistic monitoring tool. This paper limits on analysis in a particular area. The area is served by some cell surrounding the area.  The result shows a good homogeneity amongst the cell covered a certain area during low traffic (1 am to 1 pm). Otherwise, in high traffic, the serving cells are relatively different in terms of traffic variation and homogeneity test using Fligner-Killeen is more suitable
Model Cabut-Serat Nylon 600 Tertanam Dalam Matriks Sementitis Berbasis Fraktur Retno Susilorini
Semesta Teknika Vol 11, No 1 (2008): MEI 2008
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v11i1.774

Abstract

The fracture mechanics is known as a fracture based approach to prohibit a catastrophic failure of structure. In micro scale field, the fracture mechanics is implemented especially to determine the performance of interface between fiber and cementitious matrix in ‘fiber-reinforced cementitious composite’. The studies and applications of nylon clearly define the advance characteristic of nylon may influence the overall performance of composites and become a crucial issue to be learned, therefore, this paper forwards a fractured based pull-out model of short nylon 600 embedded in cementitious matrix with main concern on fracture phenomenon. The research applies experiment that applies pull-out test with embedded nylon 600 in cementitious matrixand the analytical method that constructs the fractured based pull-out model. The experiment results show the specimens with pull-out fibers have embedded length lf = 30-60 mm and the broken fibers lf = 70-100 mm. The pull-out test also shows several stages: (a) Pre-slip stage, (b) Slip stage, and (c) Strain-hardening stage. The model fits to experimental results. Several theories meet conclusions: (a) Whenever fracture takes place, it is always an unstable crack, (b) Stable cracks are established by the presence of crack arrester, (c) There is no way directly to determine the length of stable crack, but it still can be determined by fractured based approach, (d) The length of stable crack is determined by the position of crack arrester, (e) There is an equation derived for pull-out model (f) There is an equation to determine the stable crack length, (g) Stable cracks may be used to determined the bond capacity, (h) After the establishment of stable cracks, increasing strain beyond  strain e1 will not increase stress s1, hence do not induce additional fracture, (i) Increasing of strain e after the establishment of stable cracks will increase stress s, then the second slip will not take place, (j) Broken nylon fibers have a longer embedded length because of the possibility of crack arrester presence is bigger than the shorter ones.
Metode Ekstraksi Ciri untuk Membedakan Citra Wajah Asli dan Foto Berbasis Perceptron Afri Yudamson , Indah Soesanti, Warsun Najib
Semesta Teknika Vol 16, No 1 (2013): MEI 2013
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v16i1.431

Abstract

Face is one of media for human identification. Previous studies aimed at identifying human face were for a two-dimensional images. Thus, fraud may occur when providing input in two-dimensional face images (photos). This study aims to distinguish the original three-dimensional face image with two-dimensional face image. Feature extraction based on facial geometry principles (Incomplete sentence, subject only, do not know what the authors mean). Face images (both the original and the photos) were captured at deviated angle, to the left and to the right. Each image is then sliced for each face components (eyes and nose) and sought the position of the center point of each component. Comparison between the value of the right eye-nose projection vector to the left-right eye vector and the value of the left-right eye vector become the characteristics of each image. The perceptron method was used for the classifiers. The result, the software can distinguish the original three-dimensional and two-dimensional face image with an error of 8.33% of the 24 tested images. Error occurred for some samples that show big round nose.
Deteksi Cacat Bantalan Bola Pada Pompa Sentrifugal Menggunakan Spektrum Getaran Berli P Kamiel; Mulyani Mulyani; Sunardi Sunardi
Semesta Teknika Vol 20, No 2 (2017): NOVEMBER 2017
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v20i2.3543

Abstract

One of the common fault in the centrifugal pump is faulty bearing. Bearings play a very important role for smooth rotation of a shaft. A bearing condition must be constantly monitored to ensure top performance of a pump. Therefore, a method is needed to detect an early defect in the bearings. One of the most widely used methods for bearing faults detection is based on the vibration analysis. Vibration analysis can detect a defect in a bearing without having to disassemble the machine. Furthermore, and it is fast and easy to be implemented. This study aims to develop a fault detection method on the ball bearing using spectrum analysis by applying envelope analysis. This research uses experimental method with three bearings conditions i.e. normal (no fault), outer race fault, and inner race fault. The type of ball bearings used are self aligning double row bearings. The vibration signal from each of bearing condition is taken from the centrifugal pump vibration test rig and measured using accelerometer sensor which is acquired directly with DAQ and then processed into Matlab. The analysis gives the result of frequency spectrum and envelope spectrum. This study concludes that the high amplitude on the frequency that coincide with the frequency of Ball Pass Frequency Outer Race (BPFO) and Ball Pass Frequency Inner Race (BPFI) make an indication of damage to the bearing on the outer and inner race respectively. The envelope spectrum gives better results as compared to the result of the frequency spectrum. This is because the high amplitude of low frequency generated from other components is blocked and removed using a high-pass filter. Consequently, it becomes easier to detect a low amplitude of high frequency vibration signal from a faulty bearing.
Karakteristik Pembakaran Briket Kokas Lokal Pada Beberapa Temperatur Karbonasi Dedet Hermawan Setiabudi; Dwi Aries Himawanto; Sukamta Sukamta
Semesta Teknika Vol 9, No 2 (2006): NOVEMBER 2006
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v9i2.866

Abstract

In order to investigate the better carbonization process that used in foundry application, this research was performed the materials of this research are the local coke that usually used in Ceper Klaten. This local coke was pressed into cylindrical shape and then carbonize in the three variation  carbonized temperature i.e. 100 0C, 200 0C  and 300 0C as long as one hour then taken into furnace to find the combustion characteristics.The result shows that carbonization process has the optimal temperature.
Pengaruh Jumlah Lapisan dan Spasi Perkuatan Geosintetik terhadap Kuat Dukung dan Penurunan Tanah Lempung Lunak Anita Widianti
Semesta Teknika Vol 15, No 1 (2012): MEI 2012
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v15i1.447

Abstract

One of the ways to improve the mechanical characteristics of soft soil is to provide soil reinforcement which is a geosynthetic sheet overlaid on the soft soil. Previous studies show that the installation of geosynthetic layers in soft soil proved to increase the bearing capacity and reduce the settlement. Theoretically, if more layers of reinforcement are given, the support will be stronger, while the soil of settlement will be reduced even greater. In this study, the influence of the number of layers and vertical distance between geosynthetic layers on the magnitude of bearing capacity, and the settlement in base soil will be assessed. The primary research is a load test on each clay included in model boxes of 120 cm x 120 cm x 100 cm size. Water was added to the soil to achieve the liquid limit conditions, then the soil was strengthened by inserting 60 x 60cm2 HRX200 woven geotextile layers whose tensile strength is 20 kN/m2 with various distances and number of layers among different boxes. The bottom of loading foundation on the top side of the samples is square whose side (B) is of 10 cm. The loading process were done until the soil collapse indicated by visual observation or by the condition of no increase of the load magnitude causing settlement. The results showed that 1 layer, 2 layers and 3 layers geosynthetic correspond to the bearing capacity increase of 60.57%, 213.00% and 402.64%, respectively, and experienced a reduction in soil settlement by 40%, 60% and 70%, respectively, compared to that without any reinforcement. Geosynthetic being placed at a distance of 0.4 B and 0.6 B gives the greatest bearing capacity increase, in the amount of 402.64%. Geosynthetic mounted on distance more than 0.6 B resulted in bearing capacity increase of diminishing percentages.

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