Indrasurya B. Mochtar
Fakultas Teknik Sipil dan Perencanaan Institut Teknologi Sepuluh Nopember Surabaya

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Usulan Metoda Perhitungan Interaktif Struktur Pondasi di Atas Tanah Lunak dengan Menyertakan Pengaruh Penurunan Konsolidasi Jangka Panjang Lastiasih, Yudhi; Mochtar, Indrasurya B.
MEDIA KOMUNIKASI TEKNIK SIPIL Tahun 16, Nomor 2, JUNI 2008
Publisher : Department of Civil Engineering, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (250.848 KB) | DOI: 10.14710/mkts.v16i2.3691

Abstract

Calculation of shallow foundation, as mat foundation or other types of raft foundation, on soft soil has never included any consideration of soil consolidation. Generally in calculation, the upper structure is considered separate from the lower structure. If long term consolidation is included, the problem will occur when a relatively very rigid structure (on shallow foundation) is assumed to cause relatively uniform settlement, so as to assume no differential settlement. Whereas, uniform consolidation settlement is induced only by non-uniform soil reaction, so that this problem can never be solved with the assumption of separate upper-lower structures. In this paper, a method of structural calculation is suggested so that building may undergo uniform settlement as long as the soil consolidation occurs, without causing any damage to the building. The calculation is performed using special program with assumption that the induced soil reaction is always to cause uniform settlement. From this method, a procedure of soil –structure interaction is proposed that building on soft soil may experience large settlement without damage. Keywords: Method of foundation design, Soil-structure interaction, Consolidation settlement, Shallow foundation, Soft soil problem ABSTRAK Perhitungan pondasi dangkal seperti pondasi pelat penuh ( mat foundation) atau tipe pondasi rakit lainnya di atas tanah lunak belum ada yang memasukkan unsur penurunan konsolidasi tanah dasar dalam perhitungan. Umumnya dalam perhitungan yang ada, struktur atas dan bawah dianggap terpisah. Untuk memasukkan konsolidasi jangka panjang, masalah akan terjadi ketika gedung yang relatif sangat kaku diasumsikan menyebabkan penurunan yang merata,sehingga dianggap tidak ada beda penurunan. Padahal untuk penurunan konsolidasi yang merata dibutuhkan reaksi tanah yang tidak merata, sehingga masalah ini tidak akan pernah dapat diselesaikan dengan sistem perhitungan terpisah. Pada uraian ini diupayakan suatu metoda perhitungan struktur yang dapat mengalami penurunan secara merata selama konsolidasi tanah berlangsung, tanpa menyebabkan terjadinya kerusakan pada strukturnya. Perhitungan dilakukan dengan program khusus dengan asumsi reaksi tanah selalu menghasilkan penurunan yang merata. Dari metode ini diusulkan cara perhitungan interaksi tanah – gedung di tanah lunak yang menyebabkan gedung dapat mengalami settlement tanpa rusak. Kata kunci: Metoda perencanaan pondasi, Interaksi tanah-gedung, Penurunan konsolidasi, Pondasi dangkal, Masalah tanah lunakPermalink: http://ejournal.undip.ac.id/index.php/mkts/article/view/3691[How to cite: Lastiasih, Y. dan Mochtar, I.B. (2008), Usulan Metoda Perhitungan Interaktif Struktur Pondasi di Atas Tanah Lunak dengan Menyertakan Pengaruh Penurunan Konsolidasi Jangka Panjang, Jurnal Media Komunikasi Teknik Sipil, Tahun 16, Nomor 2, pp. 160-170]
Pengembangan Metode Fast-Track untuk Mereduksi Waktu dan Biaya Pelaksanaan Proyek Studi Kasus Rumah Menengah di Malang, Jawa Timur Tjaturono, Tjaturono; Mochtar, Indrasurya B.
MEDIA KOMUNIKASI TEKNIK SIPIL Tahun 17, Nomor 1, PEBRUARI 2009
Publisher : Department of Civil Engineering, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (301.682 KB) | DOI: 10.14710/mkts.v17i1.3775

Abstract

Construction cost of the middle-class housing in Indonesia tends to increase especially if a delay occurs at critical-path activities. Up to the moment the solution of this problem is by doing trade-off between the time and the cost. With this procedure, usually the completion time can be accelerated, but the increase in construction cost is unavoidable. It is described in this paper a method to accelerate the completion time of activities in the critical patch, so that the completion time can be kept as planned, but the construction cost does not increase. One of the efforts carried out here is by developing the fast-track method on critical activities with a modification of CPM model scheduling, and it is for case of construction of middle-class housing in Malang, East Java. The methods applied were site observation in the construction time and cost of the critical activities, and interview with the site manager as well as the supervisor. The data was processed non-statistically. The results obtained prove that the developed fast-track method here gives an advantage in time saving of 34% from the completion time in general and cost saving of 2.45%. Keywords: Time saving, cost reduction, CPM model, fast-track, middle-class housing. ABSTRAK Biaya pembangunan rumah menengah di Indonesia cenderung membengkak, terutama jika terjadi keterlambatan waktu penyelesaian aktifitas-aktifitas pada lintasan kritis. Hingga kini cara yang digunakan untuk mengatasi masalah ini adalah dengan melakukan trade-off antara waktu dan biaya. Dengan cara itu, umumnya percepatan waktu penyelesaian dapat dilakukan, tetapi pembengkakan biaya pembangunan tidak terelakkan. Diuraikan dalam tulisan ini cara percepatan waktu pelaksanaan pada aktifitas di lintasan kritis agar waktu penyelesaian dapat dicapai sesuai rencana, tetapi biaya pembangunan tidak membengkak. Salah satu upaya yang dilakukan di sini adalah melakukan pengembangan metode fast-track pada aktifitas di lintasan kritis dengan modifikasi penjadwalan model CPM, dan untuk kasusnya adalah pada pembangunan rumah menengah di Malang, Jawa Timur. Metode yang digunakan adalah observasi lapangan terhadap waktu dan biaya pelaksanaan aktifitas pada lintasan kritis, dan wawancara dengan Site Manager serta Pengawas Lapangan. Data diolah secara non-statistik. Hasil yang diperoleh membuktikan bahwa pengembangan metode fast-track seperti ini memberikan keuntungan berupa penghematan waktu sebesar 34% dari waktu yang umumnya dibutuhkan dan penghematan biaya sebesar 2,45%. Kata kunci: Penghematan waktu, penghematan biaya, model CPM, fast-track, rumah  menengah
A Formula for Predicting Primary Settlement of Tropical Highly Organic Soil and Peat in the Field Prativi, Ayu; Mochtar, Noor Endah; Mochtar, Indrasurya B.
Civil Engineering Journal Vol 10, No 11 (2024): November
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2024-010-11-03

Abstract

Highly organic soil and peat are problematic soils due to their low bearing capacity and high compressibility. In tropical regions, the presence of woody material in these soils often affects the stress-compression and time-compression curves in load-increment consolidation tests, leading to unusual shapes. Consequently, conventional inorganic soil theory and the Cα/Ccconcept are inadequate for analyzing their compression behavior. As an alternative, the Gibson and Lo model can be used to obtain compression parameters from single-load consolidation tests. However, this method introduces considerable discrepancies when predicting the primary settlement. To address this issue, this paper proposes a formula for predicting the primary settlement in highly organic soil and peat in the field, especially in tropical regions. Samples were collected from several locations in Indonesia. The formula was constructed from the stress-strain relationship during the primary compression stage, obtained from numerous single-load consolidation tests. Long-term field settlement is predicted by combining this empirical equation for primary settlement with the Gibson and Lo model for secondary settlement. The proposed formula was verified using field soil monitoring data, demonstrating reasonable accuracy in predicting the primary settlement of highly organic soil and peat. Doi: 10.28991/CEJ-2024-010-11-03 Full Text: PDF