The columns of a building must be stronger than the beams. The aim of this study is to obtain the cause of the long-term deformation difference by shrinkage between the beams and columns of high performance concrete with compressive strength of 60 MPa. This research was done experimentally in Indonesia during 410 days. Specimens measuring 150 mm × 150 mm × 600 mm were used, 3 pieces for the beams and 2 pieces for the columns. Deformation was obtained by using an embedded vibrating wire strain gauge for each specimen. The difference of long-term deformation in columns and beams is in their autogenous deformation behavior. This is because during the autogenous phase, swelling abnormally occurs in the column before shrinkage occurs. The abnormal swelling is caused by the press of its own weight. This phenomenon does not occur in beams. In the age range of 1 to 200 days, the behavior of the beam deformation has a similar pattern to the deformation behavior of the column with a high deformation rate. After that, at 200-410 days, column deformation changes to a very slow deformation rate. Long-term deformation in columns is lower (64%) than in the beams at 410 days age.
Abstract. The research is done by observing the growth of real structure cracking in Natar, Lampung, Indonesia compared to C. Niken's et al research and literature study. The rigid pavement was done with open traffic system. There are two main crack types on Natar rigid pavement: cracks cross the road, and cracks spreads on rigid pavement surface. The observation of cracks was analyzed by analyzing material, casting, curing, loading and shrinkage mechanism. The relationship between these analysis and shrinkage mechanism was studied in concrete micro structure. Open traffic make hydration process occur under vibration; therefore, fresh concrete was compressed and tensioned alternately since beginning. High temperature together with compression, cement dissociation, the growth of Ca 2+ at very early age leads abnormal swelling. No prevention from outside water movement leads hydration process occur with limited water which caused spreads fine cracks. Limited water improves shrinkage and plastic phase becomes shorter; therefore, rigid pavement can't accommodate the abnormal swelling and shrinking alternately and creates the spread of cracks. Discontinuing casting the concrete makes both mix under different condition, the first is shrink and the second is swell and creates weak line on the border; so, the cracks appear as cracks across the road.
Misalignment cracks are transverse cracks that occur not in the cutting line but that are shifted within less than 500 mm of the cutting line. This crack does not cross other segments. This paper describes the mechanism of the formation of misalignment cracks and the stresses that occur in concrete pavement under plastic and brittle condition. This paper was written based on observations of misalignment cracks on toll roads in Lampung Province, Indonesia. Bending strength of the concrete pavement is ±4.5 MPa. This crack was found at the concrete age of 18-72 hours. This research is supported by observing deformation and inner temperature in the laboratory on a concrete plate with compressive strength of 60 MPa measuring 300 cm × 160 cm × 15 cm, which is placed on several supports. Observations were made every 15 minutes for 90 days. Misalignment cracks occur because cutting in concrete pavement is done in brittle conditions. Misalignment cracks were also found on one side, which dowel shift. In this phenomenon, misalignment cracks follow dowel shifting.
Pekerjaan pembangunan Rumah Sakit PTN Universitas Lampung dimulai pada tahun 2011, namun terhenti proses pembangunannya serta struktur eksisting tidak mendapat perawatan terhadap kondisi lingkungan. Hal ini mengharuskan dilakukannya evaluasi kekuatan struktur bangunan yang sudah lama terbengkalai. Hasil analisis pengaruh kondisi lingkungan berlumpur, tergenang air, terkena sinar matahari langsung dan terlindung pada material eksisiting beton dan baja tulangan menjadi parameter rencana untuk dibangun kembali RS PTN Universitas Lampung. Metode dalam penelitian ini dilakukan pengamatan secara visual den pemeriksaan secara khusus pada struktur plat bangunan basement gedung 1,2 dan 3. Pemeriksaan khusus yang dilakukan yaitu core drill test, hammer test, SEM-EDX, uji tarik baja tulangan dan uji lengkung statis baja tulangan. Terdapat genangan air dan lumpur pada basement gedung 1,2 dan 3 serta terjadi korosi pada tulangan sambungan kolom, plat, dinding penahan tanah dan dinding geser. Berdasarkan hasil uji tarik baja tulangan kondisi eksisting memenuhi persyaratan Pasal 20.2.2.4a SNI 2847-2019 dan hasil uji lengkung statis masih bersifat elastis. Kuat tekan beton kondisi basah (terendam air) 30 MPa dengan tidak terdapat unsur Ca yang disebakan air yang merendam melarutkan Ca. Kuat tekan disebakan unsur Si yang padat karena perendaman sehingga tumbuh optimal. Hasil kuat tekan kondisi terlindung 25 MPa dengan unsur pemberi kekuatan adalah Ca dan Si tetapi kekuatan terseut diruntuhkan oleh C
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