Program Eksperimental Perilaku Siklik Pilar Persegi Berongga Jembatan dengan Beton Berkekuatan Ultra Tinggi
DOI:
https://doi.org/10.5614/jts.2015.22.2.4Keywords:
HRSP-UHSC, Perilaku histeretik, Daktilitas perpindahan, Degradasi kekuatan, dan Disipasi energiAbstract
Abstrak. Makalah ini membahas perilaku histeretik pilar beton bertulang berpenampang bujursangkar berongga (Hollow Rectangular Section Pier, HRSP) dengan mengaplikasikan material beton berkekuatan ultra tinggi (Ultra High Strength Concrete, UHSC). Program eksperimental dilaksanakan pada dua model spesimen HRSP-UHSC yang dibebani kombinasi gaya aksial tekan yang konstan dan perpindahan lateral siklik quasi static melalui aktuator pada loading frame. Pembebanan lateral berbasis pada control perpindahan sesuai ACI-374.1-05 (2005). Gaya aksial tekan diaplikasikan pada HRSP-70 dan HRSP-60 dengan rasio masing-masing sebesar 0.075fc'Ag. dan 0.15fc'Ag. Hasil ekeperimental menunjukkan bahwa peningkatan rasio gaya aksial tekan berpengaruh signifikan terhadap peningkatan kekuatan geser pilar, namun selanjutnya pilar mengalami degradasi kekuatan lebih cepat dengan pencapaian drift ratio dan faktor daktilitas perpindahan yang menurun. HRSP-70 mampu mencapai drift ratio 5.80% dengan faktor daktilitas perpindahan 5.35, sedangkan faktor daktilitas perpindahan HRSP-60 menurun menjadi 4.58 pada drift ratio 3.50%. Kecenderungan ini mengakibatkan HRSP-70 mampu mengakomodir degradasi kekakuan dari keadaan leleh pertama sampai pada kondisi batas hingga 82.99%, sedangkan pada HRSP-60 hanya sekitar 77.86%. Begitu pula pendisipasian energi pada HRSP-60 menurun 39.46% setelah gaya aksial tekan dinaikkan sebesar 50%.Abstract. This paper discusses the hysteretic behavior of Hollow Rectangular Section Piers (HRSP) by applying Ultra High Strength Concrete (UHSC) material. The experimental program conducted in two models of HRSP-UHSC specimens were loaded by combination of a constant axial compression force and quasi static lateral cyclic loads through actuators on the loading frame. The lateral loads were based on displacement controls in ACI 374.1-05 (2005). The constant axial compression forces were applied into the HRSP-70 and HRSP-60 of 0.075fc'Ag and 0.15fc'Ag, respectively. The experimental results indicate that the increasing of the axial compression force ratio enhances the shear strength significantly, but then it experiences higher strength degradations with lower attainment
of drift ratio and displacement ductility factor. The HRSP-70 achieved a displacement ductility factor of 5.35 at drift ratio of 5.80%, while HRSP-60 achieved a displacement ductility factor of 4.58 at drift ratio of 3.50%. This trend resulted that HRSP-70 was able to accommodate the stiffness degradation of the first yield state to the ultimate conditions up to 82.99%, while the HRSP-60 was only about 77.86%. Similarly, the energy dissipation of HRSP-60 decreased by 39.46% after the constant axial compression force had been increased 50% from previous specimen.
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