ANALISIS RESPON DINAMIK DAN KINERJA STRUKTUR BAJA KOMPOSIT TERHADAP BEBAN LEDAKAN UDARA (FREE-AIR BURST) - Muhammad Aidhil Dzikri; Nurti Kusuma Anggraini; Endah Kanti Pangestuti (Universitas Perjuangan Tasikmalaya, 2026)
Abstract— The security of strategic infrastructure from the threat of explosive drones is a critical focus of modern engineering. This study aims to elicit the dynamic response of composite steel beams (BA1 and BI1) to exposure to a Free-Air Burst with a load variation of 0.5 to 10 kg TNT equivalent at a perpendicular distance of 3 meters. Numerical simulations based on finite element execution using ETABS v22.0.0 software, supported by Friedlander shock wave calculations and Dynamic Increase Factor (DIF). The analysis results show that at low-scale load exposure (0.5–1 kg TNT), the structure operates intact in the elastic phase with a cross-sectional stress ratio below the safe limit of 1.0. In contrast, extreme loading (5–10 kg TNT) triggers a drastic transition to the elasto-plastic phase. The dynamic deflection in the child beam (BA1) soars to 51.73 mm, exceeding the allowable limit of 30.02 mm. Although statistically considered a failure, the ductility of the composite material is able to efficiently absorb the blast energy without triggering damage. This local sacrifice mechanism successfully kept the support rotation beams BA1 and BI1 below the 3° limit. In conclusion, the composite nonlinear response is proven to prevent progressive collapse of the building while fulfilling the extreme protective philosophy oriented towards the safety of occupants' lives. Keywords — Composite Beams; Blast Load; Free Air Burst; Support Rotation. Abstrak— Keamanan infrastruktur strategis dari ancaman pesawat nirawak berpeledak menjadi fokus kritis rekayasa modern. Penelitian ini bertujuan mengevaluasi respon dinamik balok baja komposit (BA1 dan BI1) terhadap paparan ledakan udara bebas dengan variasi muatan 0,5 hingga 10 kg ekuivalen TNT pada jarak tegak lurus 3 meter. Simulasi numerik berbasis elemen hingga dieksekusi menggunakan perangkat lunak ETABS v22.0.0, didukung perhitungan gelombang kejut Friedlander serta Faktor Peningkatan Dinamis (DIF). Hasil analisis menunjukkan bahwa pada paparan beban skala rendah (0,5–1 kg TNT), struktur beroperasi utuh di fase elastis linier dengan rasio tegangan penampang di bawah batas aman 1,0. Sebaliknya, pembebanan ekstrem (5–10 kg TNT) memicu transisi drastis menuju fase elasto-plastis. Lendutan dinamis pada balok anak (BA1) melonjak mencapai 51,73 mm, melampaui batas izin 30,02 mm. Meskipun secara statis dinilai gagal, daktilitas material komposit secara efisien mampu menyerap energi ledakan tanpa memicu patah getas. Mekanisme pengorbanan lokal ini sukses menjaga rotasi sudut tumpuan balok BA1 dan BI1 tetap di bawah batas 3°. Kesimpulannya, respon nonlinear komposit terbukti mencegah keruntuhan progresif gedung sekaligus memenuhi filosofi pelindung ekstrem berorientasi keselamatan nyawa penghuni. Kata kunci — Balok Komposit; Beban Ledakan; Ledakan Udara; Rotasi Tumpuan.