Senin, 11 Juli 2011

distribusi tegangan elastis berbagai tipe pondasi dangkal

(sumber: Esmaili D., etal - 2008)


Pondasi dangkal umumnya berbentuk tapak (footing/pad) dengan tujuan pekerjaan konstruksi menjadi mudah. Beberapa bentuk lain yg lebih effektif dibandingkan jenis tapak adalah jenis pondasi cangkang (shell) berbentuk seperti mangkuk terbalik yg tertanam, dapat berupa bulat atau pesegi.

Gbr.1 Pondasi Cangkang sebelum ditanam


Gbr. 2 Test pembebanan terukur (loading test)


Gbr.3 Grafik hasil pengukuran


(Sumber: Huat B.B.K., etal - 2007)


Pada tulisan ini akan dipelajari distribusi tegangan elastis dibawah pondasi dari beberapa jenis pondasi tersebut diatas. Analisa elemen hingga jenis plane strain menggunakan program bantu SAP. Walaupun jenis analisa masih elastis terlihat cukup dalam memprediksikan, namun akan lebih baik juga jika dilakukan dgn program bantu spesifik interaksi pondasi tanah yg advanced seperti PLAXIS sehingga dapat merepresentasikan interface dan nonlinearitas material tanah serta pola keruntuhan (failure surfaces).

Gbr. 4 Jaring elemen hingga (meshing FE)


Gbr. 5 Distribusi tegangan jenis pondasi tapak


Gbr. 6 Distribusi tegangan jenis pondasi cangkang 1


Gbr. 7 Distribusi tegangan jenis pondasi cangkang 2


Terlihat jenis cangkang menunjukan distribusi tegangan tanah dan penurunan yg lebih rendah dibanding pondasi tapak biasa. Pada tegangan sendiri pelat pondasi juga memperlihatkan bahwa jenis cangkang menjadikan tegangan tekan beton (compression)  lebih merata yg berarti pembesian tarik akan minimum.

Banyak penelitian menunjukkan bahwa defleksi dari hasil analisa linear elastis FE biasanya lebih kecil dari sesungguhnya dgn selisih berkisar separuhnya, seperti diperlihatkan salah satu contoh grafik dibawah ini (Weber J.W., etall - 1984).

Selasa, 05 Juli 2011

struktur atap baja bentang lebar

(source:Nagy Z.,2010)


Biasanya digunakan jenis truss untuk atap dgn spans > 40m karena keterbatasan profil HB/Tee yg tersedia dipasaran,kecuali alat fabrikasi yg sudah capable cut&weld presisi tinggi untuk built-up welded section membentuk haunched beam/column.


(source:Nagy Z.,2010)


Jika diperlukan profil built-up dapat dikombinasikan dgn batang tarik (pipe) untuk melayani atap bentang panjang tsb.



Desain struktur baja yg effisien akan tercapai jika sistem struktur rangka dapat mereduksi gaya tekan dan menjaga dgn sendirinya thd stabilitas pada daerah batang tekan tersebut.


contoh yang mempunyai konsep yang mirip (**updates)



fig.1 model tiga dimensi analisa dgn program bantu SAP



fig.2 Pembesaran gambar daerah pertemuan




fig.3 Gaya aksial akibat beban gravitasi (preliminary design)

Konsep dari struktur diatas cukup sederhana, ditinjau sebagai portal. Pertemuan balok/rafter dgn kolom akan mengalami momen negatif sedangkan daerah lapangan akan mengalami momen positif. Besarnya momen negatif yg terjadi akan lebih besar berkisar 1.5 s/d 2 kalinya momen positif yg terjadi, sehingga tinggi truss daerah tersebut diperbesar agar menjadikan gaya kopel tekan/tarik menjadi kecil. Penentuan perbandingan banyaknya batang chord atas/bawah didasarkan gaya tekan akan mereduksi kapasitas batang karena pengaruh tekuk (buckling) sehingga batang chord bawah akan lebih efisien dipasang dua buah.

(**updates Dec'13)

ternyata konsep struktur diatas juga sudah ada di indonesia hasil karya arsitek dari france dan kebetulan tahun lalu sya ada kesempatan mereview berikut tampilannya

AtapBusurBSH01a

2013-01-15_234035

dibawah juga ditampilkan untuk struktur bentang panjang pada bangunan lain di area yg sama, karena bentang cukup panjang maka diperlukan dua kolom di tengah bentang dan ini sudah dibicarakan dgn pihak arsitek.. syg design tidak berlanjut ada hal non teknis diluar kelihatannya.

2013-01-16_002356

 

Minggu, 13 Maret 2011

perangkat utilitas berguna bagi debian linux user

di netbook sya pake winOS udah bawaan, applikasi untuk modem 3g diperlukan saat ingin register unlimited melalui sms. cukup tancapkan lalu auto install. Berbeda saat menggunakan debian based linux (ubuntu) cukup mudah sih saat instalasi dan mau konek, namun saat ingin menggunakan sms dan mengecek quota jadinya gak bisa. coba cari aplikasi, dapet bernama Betavine Connection Manager, sebenarnya ini awalnya untuk modem Vodafone namun kelanjutannya juga bisa buat general usb modem GSM/3G.

.

.
instalasi cukup sederhana (from::Nicholas Herriot,2010), copast text berikut aja di console

sh -c 'wget http://www.betavine.net/repository/bcm_lucid_install.sh -O /tmp/bcm.sh && /usr/bin/xterm -e sudo sh /tmp/bcm.sh'

Rabu, 09 Maret 2011

personal CAD (editor/viewer) di Linux

saat ini sudah ada program CAD cukup close dgn aCAD/iCAD bernama DraftSight keluaran dari Dassault Systemes yg sudah lebih dulu dikenal dgn CATIA dan SolidWorks nya. Walu masih Beta version namun dapat berjalan cukup stabil di Linux Ubuntu 10 sya, karena menurut sebuah sumber menggunakan C++/QT yg dapat native berjalan disemua sistem operasi Win/Ux/Mac. Penginstallan nya juga cukup mudah karena sudah berbentuk paket deb/rpm. Terlihat sedikit berbeda saat setting gambar dan file keseluruhan, mengunakan tree browser yg tersedia dalam satu main menu OPTIONS - Drawing Styles.



berikut beberapa snapshotnya pda saat pertama kali sya install dan gunakan,

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Paket software installasi debian berkisar ~70mb, dapt didownload lewat website sumbernya langsung, DraftSight. perlu koneksi internet untuk aktivasi gratis sebelum 30hri.



skrg sketch gmbar teknik jadi bisa dilakukan di linux dgn akurasi dan kemudahan bagi yg sdh familiar dg aCAD/iCAD waktu jman skul dlu.

Kamis, 20 Januari 2011

bahan rujukan

ACI Structural Journal


1.


[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.civ.utoronto.ca%2Fvector%2Fjournal_publications%2Fjp66.pdf&embedded=true" width="600" height="500" /]


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2.


[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Ffaculty.washington.edu%2Fnemati%2Faci_str1.pdf&embedded=true" width="600" height="500" /]


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3.


[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww2.ceegs.ohio-state.edu%2F~sezen%2FPublication_docs%2FACI_Sezen_Setzler_2008.pdf&embedded=true" width="600" height="500" /]


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4.


[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.civil.northwestern.edu%2Fpeople%2Fbazant%2FPDFs%2FPapers%2F364.pdf&embedded=true" width="600" height="780" /]


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5.


[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.facweb.iitkgp.ernet.in%2F~nilanjan%2FACI_Struc_2009.pdf&embedded=true" width="600" height="500" /]


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6.


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9.


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10.


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12.


[googleapps domain="docs" dir="viewer" query="url=https%3A%2F%2Fengineering.purdue.edu%2F~frosch%2FCE576%2FReferences%2FSlender%2520Columns%2F10.32.pdf&embedded=true" width="600" height="500" /]


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[googleapps domain="docs" dir="viewer" query="url=https%3A%2F%2Fengineering.purdue.edu%2F~frosch%2FCE576%2FReferences%2FSlender%2520Columns%2FMirza%2520-%2520Flexural%2520Stiffness.pdf&embedded=true" width="600" height="500" /]


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14.

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15.

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16.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww-personal.umich.edu%2F~gjpm%2FJournals%2FACI%2520paper%2520HPFRCC%2520joints.pdf&embedded=true" width="600" height="500" /]

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17.

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18.

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19.

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21.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww-civ.eng.cam.ac.uk%2Fcjb%2Fpapers%2Fp55readonly.pdf&embedded=true" width="600" height="500" /]

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22.

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23.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fjaguar.ucsd.edu%2Fpublications%2Frefereed_journals%2FOrakcal_Wallace_Conte_ACI_2004.pdf&embedded=true" width="600" height="500" /]

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23.

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24.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww-personal.umich.edu%2F~gjpm%2FJournals%2FPaper%2520Parra-Wight%2520ACI%2520RCS%2520Repair.pdf&embedded=true" width="600" height="500" /]

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25.

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26.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.civ.utoronto.ca%2Fvector%2Fjournal_publications%2Fjp67.pdf&embedded=true" width="600" height="500" /]

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27.

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28.

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29.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.bechtel.com%2Fassets%2Ffiles%2FTechPapers%2Fexperimental-verification.pdf&embedded=true" width="600" height="500" /]

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30.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.eis.hu.edu.jo%2FDeanshipfiles%2Fpub10541977.pdf&embedded=true" width="600" height="500" /]

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31.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fblogs.uprm.edu%2Fmontejo%2Ffiles%2F2009%2F11%2FACI-Seismic-Behavior-of-Shear-Dominated.pdf&embedded=true" width="600" height="500" /]

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32.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fxa.yimg.com%2Fkq%2Fgroups%2F21948400%2F1733343089%2Fname%2FReinforced_High-Strength_Concrete_Beams_in_Flexure.pdf&embedded=true" width="600" height="500" /]

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33.

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34.

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35.

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[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.library.ltu.edu%2Fcm%2Fattach%2FB6FC1930-05B0-447D-98A2-05ACB25736D1%2FDesignApproach.pdf&embedded=true" width="600" height="500" /]

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37.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Ftestit4free.info%2Fjimoel%2Fdocs%2Fplacibe%2520%2528prelim%2520article%2529.pdf&embedded=true" width="600" height="500" /]

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38.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.reaveley.com%2Fnews%2Fpublications%2Fdamage-based_stress-strain_model_frp_moran_pantelides_aci_102-s06.pdf%3FPHPSESSID%3D53505d43fd211b3ba10f720d6636817b&embedded=true" width="600" height="500" /]

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39.

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40.

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41.

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42.

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[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.bfrl.nist.gov%2F861%2FCMAG%2Fpublications%2Fb98022.pdf&embedded=true" width="600" height="780" /]

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44.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Finfoscience.epfl.ch%2Frecord%2F111715%2Ffiles%2FFernandezRuiz06.pdf&embedded=true" width="600" height="500" /]

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45.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwpage.unina.it%2Fd.asprone%2F8.pdf&embedded=true" width="600" height="500" /]

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47.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.ce.ncsu.edu%2Fsrizkal%2Flinked_files%2FBond_Characteristics_of_ASTM_A1035_Steel_Reinforcing_Bars.pdf&embedded=true" width="600" height="500" /]

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48.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fengineering.tufts.edu%2Fcee%2Fpeople%2Fhines%2FHinesDazioSeible2006.pdf&embedded=true" width="600" height="500" /]

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49.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fcivil.colorado.edu%2F~saouma%2FAAR%2FSaouma-AAR-2.pdf&embedded=true" width="600" height="500" /]

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50.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fcivil.eng.buffalo.edu%2F~reinhorn%2FPUBLICATIONS%2F1996%2C%2520Bracci%2C%2520J....Seismic%2520Retrofit%2520Reinforced%2520Concrete%2520Model.pdf&embedded=true" width="600" height="500" /]

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51.

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52.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fconf.ncree.org.tw%2Fdownload%255C0-A1000705-107-s12.pdf&embedded=true" width="600" height="500" /]

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53.

[googleapps domain="docs" dir="viewer" query="url=http%3A%2F%2Fwww.balvac.com%2Fpdf%2F99-M28.pdf&embedded=true" width="600" height="500" /]

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Kamis, 23 Desember 2010

balok baja dgn btg tarik

balok baja dgn batang tarik dapat berupa rod+turn buckle dan/atau strand prategang.

ditinjau yg paling sederhana yaitu tanpa prategangan





terlihat tidak berbeda signifikan pada distribusi tegangan, yg sedikit berbeda terlihat pada Mcr tinjauan tekuk torsi lateral.







perlu menggunakan strand dan pemberian prategang agar batang tarik bekerja secara optimal, menuntut teknologi dan alat yg lebih dibandingkan batang tarik biasa.





required hi-tech prestressed equipment, out of my interested areas.

 

 

 

 

Jumat, 17 Desember 2010

quad mesh yg auto pd SAP2000

SAP2000 versi terbaru mempunyai fasilitas auto meshing jenis linear unstructured quadrilateral mesh. element ini lebih baik dari linear triangular, terutama pada permasalahan lentur.



.



namun terlihat kurang stabil, seringkali gagal pada jenis object berlubang linkaran lainnya.


example on cellular beams


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