Jarak Optimum Tie Constraint at Screws pada Cold-Formed Steel Built-Up Box Beams dengan Four-Point Flexural Loading

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ABSTRAK

Cold-formed steel (CFS) memiliki sejumlah keunggulan: antara lain kekuatan tinggi, ringan, pemasangan cepat dan praktis, tahan terhadap kebakaran, daya tahan yang baik, serta dapat didaur ulang. Namun, balok dengan penampang terbuka yang umum digunakan pada konstruksi rentan terhadap ketidakstabilan akibat ketidaksamaan letak titik geser dan titik berat. Untuk mengatasi permasalahan tersebut, salah satu solusi yang banyak digunakan adalah penggunaan balok dengan built-up section. Penelitian ini menyajikan studi eksperimental mengenai pengaruh variasi jarak tie constraint at screws pada CFS built-up box beams terhadap pembebanan lentur empat titik. Enam spesimen balok dengan bentang 1.300 mm diproduksi dari profil C75×35 dengan tebal 0,75 mm; kemudian dirakit secara berhadapan menjadi penampang kotak dengan menggunakan self-drilling screw yang dipasang sepanjang sayap untuk berfungsi sebagai tie constraint at screws. Tiga konfigurasi jarak sekrup digunakan, yaitu H; 2H; dan 5,5H; dengan H adalah tinggi penampang. Semua pengujian dilakukan pada kondisi tumpuan sederhana. Hasil pengujian menunjukkan bahwa variasi jarak tie constraint at screws berpengaruh signifikan terhadap perilaku lentur CFS built-up box beams. Berdasarkan hasil yang diperoleh, jarak sekrup 5,5H direkomendasikan untuk aplikasi desain pada kondisi pembebanan lentur empat titik.

Kata kunci: cold-formed steel, built-up box beams, jarak tie constraint at screws, eksperimental

ABSTRACK

Cold-formed steel (CFS) has many advantages, including high strength, lightweight, fast and practical installation, durability, recyclable, non-combustibility, and simple manufacturing procedures. However, since the shear center and the centroid of the cross-section do not coincide, open-section beams are prone to instability modes. To address this issue, researchers have used doubly symmetric built-up sections or built-up closed sections beams. This study presents an experimental investigation on CFS built-up box beams with varying screw spacing arrangements. Six beam specimens; each with a span of 1,300 mm; were subjected to four-point bending tests. The beams were fabricated from C75×35 profiles with a thickness of 0.75 mm, assembled face-to-face into built-up box sections using self-drilling screws positioned along the flanges to act as tie constraint at screws. Three screw spacing configurations were considered—H, 2H, and 5.5H—where H denotes the section depth. All tests were conducted under simple support conditions. Findings indicate that screw spacing significantly influences the flexural behavior of CFS built-up box beams. Based on the outcomes, a screw spacing of 5.5H is recommended for design applications under four-point bending conditions.

Keywords: cold-formed steel, built-up box beams, tie constraint at screws spacing, experiment