Pengaruh perkuatan Carbon Wrap pada pelat lantai beton bertulang pada saat dan setelah temperatur tinggi

YENINAR, Alfred Kristian, Ir. HRC. Priyosulistyo, M.Sc.,Ph.D

2005 | Tesis | S2 Teknik Sipil

Perilaku beton pasca kebakaran dipengaruhi oleh beban api (load fire). Load fire ini dipengaruhi oleh besar suhu dan lama pembakaran. Struktur pelat beton bertulang mengalami penurunan kekuatan pada beton maupun baja tulangan sejalan dengan kenaikan temperatur. Struktur pelat beton bertulang dengan carbon wrap yang terbakar, dapat tidak mampu mendukung beban rencana yang disebabkan luasnya bidang kontak api. Antisipasi yang dapat dilakukan antara lain dengan penggunaan lapisan carbon wrap untuk mengurangi rambatan panas. Pemahaman yang baik tentang distribusi temperatur, kekuatan, perilaku, respon dan pola keruntuhan struktur serta efektifitas penggunaan carbon wrap sangat diperlukan untuk memperoleh desain yang aman. Dalam penelitian ini digunakan enam benda uji pelat beton masing-masing berukuran 120 cm x 60 cm x 6 cm (panjang x lebar x tinggi) dengan beton mutu normal yang mempunyai kuat tekan 40 MPa dan tulangan baja dengan diameter 6 mm yang memiliki kuat leleh 450 MPa. Variasi jenis perkuatan yaitu: pertebalan fire proofing, pertebalan selimut beton dan perkuatan hanya dengan carbon wrap. Pembakaran disesuaikan dengan kurva standar ASTM E-119 untuk ketahanan 2 jam dan dibebani beban rencana yang tereduksi sesuai kondisi kebakaran. Hasil penelitian menunjukkan bahwa distribusi temperatur dari exposed surface ke bagian dalam pelat membentuk garis lengkung exponential sejalan dengan kedalaman beton. Lendutan pelat beton bertambah seiring dengan durasi pembakaran dan peningkatan temperatur, serta semakin bertambah besar di atas suhu 300 0C. Pelat beton normal yang terbakar selama 30 menit mengalami lendutan sebesar 119% dari lendutan batas aman L/360 dan sisa kuat lentur turun menjadi 93%, sisa keruntuhan lentur pelat meneruskan retak rambut akibat kebakaran. Pertebalan selimut beton (concrete cover) dengan carbon wrap mereduksi temperatur pada 15 menit awal. Suhu pada kedalaman 1 cm dibanding suhu permukaan beton tinggal 61,43%, sisa kekakuan 45,49% serta mereduksi lendutan saat dibakar sebesar 40,2% terhadap lendutan batas aman. Carbon wrap dilapisi fire proofing mereduksi temperatur pada 15 menit awal. Suhu pada kedalaman 1 cm dibanding suhu permukaan beton tinggal 35,73%, sisa kekakuan 8,07% terhadap benda uji kontrol serta mereduksi lendutan saat dibakar sebesar 70% terhadap lendutan batas aman. Bentuk carbon wrap yang paling efektif adalah carbon wrap pertebalan selimut beton (concrete cover).

The behaviour of concrete after fire was influenced by load fire. This load fire was affected by the degree of the temperature and length of exposure. Strength of reinforced concrete slab, either concrete or steel structure, decreases exponentially with the increase of temperature. Reinforced concrete slab with carbon wrap, cannot be able to support the design load due to the large surface are of fire contact. Anticipation can be conducted by applying carbon wrap layer to reduce to flow of head. Good understanding about distribution of temperature, strength behaviour, response of structural failure pattern and effectiveness of use on carbon wrap was greatly needed to get safe design. In this research, it was used six testing objects of concrete slab sized 120 cm x 60 cm x 6 cm (in length x with x height) with normal quality concrete having compression strength of 40 MPa, 6 mm diameter of reinforcing steel having tensile strength of 450 MPa. Variation of kind of carbon wrap included: thickening fire proofing, thickening concrete cover and the strengthening with carbon wrap. Burning pattern was in accordance with standard curve of ASTM E-119 to resist 2 hour of fir load and the design load was scaled down in relation to the scale of fire load. Result of research show that distribution of temperature from exposed surface to the part inside slab formed exponential curve line, in line with the depth of concrete. Sagging of concrete slab increases with the increase of duration of burning and of temperature, and raised higher over 300 0 C. Slab that burned for 30 minutes without strengthening of carbon wrap experienced sagging of 119% of the limit L/360 and the rest of bending moment decreased by 93%, the rest of stiffness of concrete slab decreased by 52,64% toward control testing object and the bending failure of slab continued the hair crack caused by burning. Thickening of concrete cover reduced temperature at the first 15 minutes. Temperature on 1 cm in depth remain 61,43% in comparison to the temperature of the surface, the rest of the stiffness was 45,49% and to reduce the displacement as much as 40,20% toward allowable bending limit. Combining carbon wrap and fire proofing it also in reduced temperature at first 15 minutes. Temperature at 1 cm in depth was of 35,73% in comparison to the surface temperature, the rest of stiffness was 8,07% toward control testing object and also reduce the displacement as much as 70% toward allowable bending limit. More effective form of carbon wrap was carbon wrap with thickened concrete cover.

Kata Kunci : Beton Bertulang,Carbon Wrap,Rambatan Panas, carbon wrap, concrete cover, exposed surface, hot flow