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Beton Mutu Tinggi dengan Bahan Tambah Superplastisizer dan Fly Ash As’at Pujianto
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.v13i2.718

Increasing concrete strength is one of the main necessities of concrete technology. For more than the last 20 years, high strength concretes with compressive strength ranging from 50 MPa up to 140 MPa have been used worldwide in high rise buildings and bridges with long spans, or buildings in aggressive environments. But in Indonesia high strength concretes possesses maximum compressive strength of 60 MPa. The properties of concrete are affected by cementitious matrix, aggregate, and the transition zone between these two phases. Reducing the water-cement ratio and the addition of pozzolanic admixtures like fly-ash are often used to modify the microstructure of the matrix and to optimise the transition zone. The reduction of the water-cement ratio results in a decrease in porosity and refinement of capillary pores in matrix, but flowing ability of the concrete will also decrease so that it can’t be workable. Then it workablity can be improve by the use of a superplastisizer. The method used refers to the planning of normal concrete, which is contained in the SKSNI 03-2834-1992. The results showed that superplastisizer with doses of more than 2% of the cement paste does not increase the strength of concrete. For all the rest of the experiments, the superplastisizer dosage was determined about 2 % of the powder mass. The first tests showed a good workability of the fresh concrete and a good self compacting ability with the fly-ash dosage of 12 % of the powder mass. The interest in reducing costs for increasing the concrete strength, can be successfully achieved in this research.

Pengaruh Beban Pada Permukaan Tanah Dan Frekuensi Gempa Terhadap Respon Seismik Linier Elastis Lapisan Tanah As’at Pujianto
Semesta Teknika Vol 8, No 1 (2005): MEI 2005
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v8i1.909

Respon seismik lapisan tanah akibat gempa merupakan suatu parameter gerakan tanah akibat gempa. Selama getaran merambat dari pusat gempa sampai ke permukaan tanah, maka faktor tanah sebagai penghantar getaran mempunyai peran yang sangat penting. Berbagai parameter penting mengenai jenis tanah tersebut meliputi keadaan geologi secara lokal dan kondisi tanah itu sendiri. Di samping itu juga ada beberapa faktor yang berpengaruh terhadap respon tanah, di antaranya adalah indeks plastisitas (PI), kandungan frekwensi gempa serta keadaan beban diatas permukaan lapisan tanah. Beban pada permukaan lapisan tanah akan berpengaruh terhadap kekakuannya. Kekakuan tanah yang mempunyai beban lebih kecil akan berbeda dengan tanah yang mempunyai beban lebih besar. Dengan keadaan seperti itu maka tanah yang mempunyai berat beban bangunan berbeda akan menghasilkan respon yang berbeda juga. Penelitian dengan menggunakan satu data profil tanah tanpa beban dan lima variasi pembebanan telah dilakukan, akibat gempa Koyna dan Bucharets yang telah dinormalisai, sehingga hanya mempunyai perbedaan frekuensi. Analisis hitungan menggunakan program sederhana dengan dasar metode analisis dinamika struktur “Multi Degree of Freedom” dan pemodelan matematis lapisan tanah berupa model “Shear Building” serta penyelesaian problema dinamik dengan metode numerik “Central Difference”. Hasil analisis menunjukan bahwa Semakin besar beban mengakibatkan simpangan semakin kecil. Dengan percepatan maksimum sama akibat gempa Koyna dan Bucharest, namun mempunyai frekuensi yang berbeda, mengakibatkan respon yang tidak sama besar. Parameter percepatan tanah bukan satu-satunya parameter yang dapat dipakai untuk mengetahui damage potential suatu gempa tetapi terdapat parameter lain yang harus diperhatikan. Kandungan frekuensi gempa Koyna maupun Bucharest terhadap frekuensi struktur masih cukup jauh (tidak berimpit), sehingga jika terjadi gempa dengan frekuensi tersebut struktur tanah tidak akan mengalami resonansi.

Pengaruh Penggunaan Bambu Sebagai Pengganti Agregat Split terhadap Kuat Tekan Beton Ringan As’at Pujianto; M. Tajuddin
Semesta Teknika Vol 15, No 2 (2012): NOVEMBER 2012
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v15i2.1357

The use of bamboo as an aggregate replacement is one of the efforts to reduce the density and static load of structural elements, sincethe structural strength of bamboo is high. This study focus on the issue of the using bamboo as aggregate concrete with flowing method on a review of specific gravity and compressive strength of the concrete. This study uses bamboo as a percentage of the aggregate at 0% (normal), 20%, 40%, 60%, 80% and 100% of the conventional split and using additional silicafume aggregates. Specimens used in this study is the concrete cylinder (diameter 15 cm and height 30 cm). The identification and testing of tap density after 14 days of treatment.Results show that using more bamboo aggregate will result lower slump value, higher water absorption, decreasing in both specific gravity and compressive strength.

Pengaruh Lapisan Pasir di Bawah Fondasi terhadap Redaman dan Frekuensi Natural Akibat Beban Gempa As’at Pujianto
Semesta Teknika Vol 12, No 1 (2009): MEI 2009
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v12i1.746

Sand layer under foundation has been widely used for vibration damping by an earthquake since centuries ago. Due to being located in earthquake-zone and sand as natural material is widely distributed over regions, research on the use of sand for earthquake vibration damping is becoming important in Indonesia. The aim of this work is to study sand layer behavior in reducing earthquake vibration. Parameters of soil structure, i.e. damping ratio, displacement, soil pressure, and the change of natural frequencydue to the existence of sand layer under foundation were observed. In this study, soil structure was modeled as layered soil profile where top layer is a clay soil layer. Foundation base is located at a depth of 300 cm underlying varied thicknesses of course sand layer, i.e. 0, 50, 100, 150 and 200 cm under foundation. In order to produce various soil pressures, load magnitudes of 0, 10,000, 20,000, 30,000 and 40,000 tons were selected. Therefore, earthquake loadings with high and low frequency from Koyna and Bucharest earthquake record were implemented to soil structure models. Results showed that the increase of sand layer thickness does not essentially affect to the decrease of displacement. It is depending on the frequency of an earthquake. However, a thickness of 50 cm shows decrease of displacement due to high and low frequency earthwuake loading with the average deviation of 3.67 %. The displacement due to Bucharest earthquake loading is greater than that of Koyna earthquake, with the average ratio of 9.38 times. If ground frequency is higher than earthquake frequency, ground displacement is becoming smaller.

Beton Mutu Tinggi dengan Admixture Superplastisizer dan Aditif Silicafume As’at Pujianto
Semesta Teknika Vol 14, No 2 (2011): NOVEMBER 2011
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.v14i2.550

Increasing concrete strength is one of the main necessities of concrete technology. For more than the last 20 years, high strength concretes with compressive strength ranging from 50 MPa up to 140 MPa have been used worldwide in high rise buildings and bridges with long spans, or buildings in aggressive environments. But in Indonesia high strength concretes possesses maximum compressive strength of 60 MPa. The properties of concrete are affected by cementitious matrix, aggregate, and the transition zone between these two phases. Reducing the water-cement ratio and the addition of pozzolanic admixtures like fly-ash are often used to modify the microstructure of the matrix and to optimise the transition zone. The reduction of the water-cement ratio results in a decrease in porosity and refinement of capillary pores in matrix, but flowing ability of the concrete will also decrease so that it can’t be workable. Then it workablity can be improve by the use of a superplastisizer. The method used refers to the planning of normal concrete, which is contained in the SK-SNI 03-2834-1992. The results showed that superplastisizer with doses of more than 2% of the cement paste does not increase the flowing ability of the paste anymore. For all the rest of the experiments, the superplastisizer dosage was determined about 2 % of the powder mass. The first tests showed a good workability of the fresh concrete and a good self compacting ability with the silicafume dosage of 10 % of the powder mass. The interest in reducing costs for increasing the concrete strength, can be successfully achieved in this research.

Design and Implementation of Muhammadiyah Green School (MGS) Yogyakarta Classroom As’at Pujianto; Mandiyo Priyo; Aditya Kurniawan
Prosiding Seminar Nasional Program Pengabdian Masyarakat 2022: 7. Sarana dan Prasarana Publik dan Mitigasi Bencana
Publisher : Universitas Muhammadiyah Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/ppm.57.1146

Muhammadiyah Green School disingkat MGS adalah Lembaga Pendidikan milik Muhammadiyah yang berupa pesantren, yang memiliki 4 (empat) karakteristik sekaligus sebagai keunggulan, yaitu karakter Al-Qur’an, pengembangan diri berbasis multiple intelligences (kecerdasan majemuk), berwawasan lingkungan alam, dan akrab dengan Teknologi Informasi. MGS Yogyakarta dikelola oleh Pimpinan Cabang Muhammadiyah Gamping yang berlokasi di Mancasan Ambarketawang Gamping Sleman, terdiri dari SD Muhamadiyah Ambarketawang 2, SMP Muhammadiyah 1 Gamping, SMK Muhammadiyah Gamping. MGS Yogyakarta digagas sejak 19 Agustus 2018 dan mulai beroperasi sejak 2019. Hingga saat ini, MGS Yogyakarta belum memiliki Gedung Kelas Permanen, tetapi sudah memiliki tanah seluas 780 m2 yang sudah siap didirikan Gedung Kelas Permanen dan sudah difondasi, ditambah tanah wakaf seluas 3.590 m2 yang sudah diberi fondasi pagar keliling untuk Asrama Siswa. Kondisi tanah yang akan dipergunakan untuk Ruang Kelas sudah siap bangun, tetapi belum ada desainnya. Dalam mendesain dibutuhkan Tenaga Ahli Struktur, Rencana Anggaran Biaya dan Drafter. Solusi yang dapat dilaksanakan dalam mengatasi masalah mitra tersebut, yaitu membantu mendesainnya, baik dari segi struktur maupun arsitekturnya, termasuk merencanakan anggaran biayanya, membantu dalam pelaksanaannya. Dari Hasil perencanaan secara keseluruhan didapat rencana anggaran sebesar Rp3.500.000.000,00 (tiga miliar lima ratus juta rupiah), dan kedalaman fondasi terletak pada kedalaman 3,0 m. PCM Gamping bersama Mitra Pengabdian berusaha untuk menyediakan anggaran sehingga kegiatan ini bisa terlaksana

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