Pengaruh fire proofing pada perilaku lentur plat beton mutu tinggi dengan tulangan mutu tinggi

MUSTIKANINGTYAS, Reni Sulistyawati Agung, Ir. HRC. Priyosulistyo, MSc.,PhD

2003 | Tesis | S2 Teknik Sipil

Beton mutu tinggi dengan tulangan mutu tinggi banyak digunakan pada bangunan modem disebabkan kebutuhan kinerja strukural yang tinggi baik pada keadaan service, ultimite maupun durability secara jangka panjang. Namun seiring meningkatnya mutu beton resiko dari permukaannya akibat temperatur tinggi juga meningkat, khususnya plat beton dengan permukaan exposure yang luas. Upaya peningkatan ketahanan terhadap kebakaran menjadi hal yang cukup serius, antara lain dengan memberi lapisan fire proofing pada permukaan plat beton exposure. Untuk mengetahui perilaku struktur tersebut akibat temperatur yang tinggi perlu dilakukan penelitian. Penelitian telah dilakukan pada sembilan buah spesimen plat beton dengan kuat tekan 52,68 MPa dan baja tulangan dengan kuat leleh 600 MPa. Spesimen berukuran panjang, lebar, dan tebal masing-masing 1500 mm, 600 mm dan 60 mm dengan selimut beton 10 mm. Delapan dari sembilan spesimen masing-masing dua buah dalam empat variasi. Masingmasing plat referensi (tipe I), plat dipertebal selimut beton (tipe 11), plat dilapis plesteran (tipe HI), dan plat dilapisfireproofing (tipe IV), yang diuji bakar dan pascabakar. Satu spesimen sebagai pembanding diuji prabakar. Pengujian prabakar dan pascabakar sesuai standar ASTM C78-84, sedangkan pengujian bakar sesuai standar pemanasan ASTM E 119 - 88 selama 30 menit sambil memberikan beban terbagi rata sebesar 345 kdm2. Untuk mengamati rambatan panas pada plat beton, digunakan tiga buah thermocouple yang dipasang pada kedalaman yang berbeda dan sebuah thermocouple digunakan untuk mengamati temperatur dalam tungku. Hasil penelitian menunjukkan panas konduksi satu arah pada plat beton dari permukaan terbakar sampai ke bagian lebih dalam menurun secara eksponensial. Pemberian lapisanfire proofing cukup efektif dalam mereduksi panas pa& posisi tulangan. Reduksi panas yang dihasilkan berturut-turut untuk plat tipe I, 11, 111 dan IV sebesar 56,4 YO, 75,3 YO, 86,l %, dan 93,5 %. Berdasarkan prediksi temperatur pada kedalaman tulangan saat terbakar diperoleh perkiraan degradasi tegangan leleh tulangan baja berturut-turut sebesar 11 %, 8 YO, 6 'YO, dan 1 %. Kekakuan plat pasca bakar menurun masing-masing 74 %, 74 YO, 59 %, dan 40 %. Defleksi saat kebakaran masing-masing plat tipe 11, tipe I11 dan IV sebesar 101,l %, 76,2 %, 23,4 % dari plat tipe I. Pola retak pasca bakar pada plat tipe I dan I1 menyebar rata. Spalling lebih banyak terjadi pada plat referensi disbanding plat yang dipertebal selimut beton. Lendutan plat secara eksperimen lebih bersesuaian dengan teori lendutan balok bila dikalikan dengan faktor 1/( 1-3). Pemberian lapisan fireproofing sangat efektif dan efisien dalam mengisolasi panas, keuntungan dalam nilai structural, maupun ekonomis untuk jangka panjang.

High-strength concrete with high strength steel reinforcement has been used in many modern buildings due to the good structural performance during service Ife, ultimate condition and durability in the long run. The risk of the high-strength concrete is in line with the increase of temperature, especially for concrete slab where the surface exposure is relatively wider than beams or columns. The efsort to overcome the problem has been carried out, amongst other is to cover with blanket namely fire proofing. This research is to conduct the characteristics of concrete slabs under fire exposure. Nine samples were cast with concrete having compressive strength of 52,68 MPa and were reinforced with high-strength steel having yield stress of 600 MPa. The samples which were of 60 mm thick, 600 mm wide and 1200 mm long, were equipped with reinforcement at 10 mm deep. Eight of nine samples were grouped into 2 samples each to represent 4 group. Each group represents the reference (type 0, the ones with thicker concrete cover (type II), the ones with additional mortar cover (type 111), and the ones with fire proofingproduct (type Iv). The pre and post fire tests were conducted through all groups. The test procedure follows the ASTM C78-84 and ASTM El 19-88 for pre and post fire tests. The fire exposure was done in 30 minutes and the equivalent live load of 345 kg/m2 was provided during the @re tests. Three thermocouples were also employed at difserent levels of depth of concrete to monitor the heat transfer in the high strength concrete and one thermocouple was used for monitoring firnace temperature. The experiment shows that the temperature decreases exponentially with the depth of concrete. The application offire proofing product is much more eficient in reducing heat of reinforcing bars. The reductions of temperature for slab type I, II, III, and IV are of 56,4%, 75,3%, 86, 1 % and 933% respectively. Theoretical prediction of the yield stress degradation of the reinforcing bars of those slabs at the temperature of experiment was 11%, 8%, 6% and 1 % respectively. The stiffizess of slab after fire exposure decreases by 74%, 74%, 59% and 40% respectively. The deflections of slab of type II, III, and IV aper fire exposure are of 101, 1 %, 762% and 23,4% in comparison to the type I. Crack spreads more evenly in the slab of type I and II. Spalling happens more at the reference slab in comparison to the slab with thicker concrete cover. The experimental deflection matched the theoretical calculation If apply a factor of 1/(1-v? on the beam deflection formula. The application ofjre proojng product is very efective and eflcient to provide heat isolation, and to achieve advantage of structural value and economic in the long run.

Kata Kunci : Ketahanan kebakaran, eksposure, fireproofing, spalling, panas konduksi, fire resistance, exposure, $re proofing, spalling, thermal conduction