Berbagai tipe balok castellated (bukaan lingkaran, heksagonal, dan persegi) telah dikembangkan untuk mengoptimalkan pemanfaatan profil baja. Mengingat tinggi efektif balok castellated yang dihasilkan terbatas, maka kapasitasnya juga akhirnya tidak dapat ditingkatkan lagi. Penelitian ini mengembangkan tipe balok castellated modifikasi, yang dibentuk dari potongan lurus profil IWF di tengah badan, yang dikedua bagian tersebut disambung menggunakan baja profil siku dengan kemiringan 45áµ’, agar tinggi efektif balok dapat diperbesar. Perilaku struktural, yang meliputi respons lendutan, tegangan, regangan, sejak beban kecil sampai mencapai kapasitas balok, beserta mekanisme keruntuhan yang terjadi dikaji secara eksperimental dalam penelitian ini. yang diuji ter Balok Castellated Modifikasi (BCM) buat dari baja profil IWF 150x75x7x5 mm yang dibagi dua secara horisontal kemudian dihubungkan dengan profil baja siku 30x30x3 mm, sehingga menjadi balok dengan tinggi 275 mm dan bentang 920 mm, mengacu dimensi penelitian sebelumnya. Setting up pengujian menggunakan pembebanan statis 2 titik. Pengujian dihentikan ketika beban sudah mengalami penurunan 30% dari Pmaks. : p Berdasarkan hasil penelitian dapat disimpulkan hal-hal berikut ini erilaku geser BCM ditentukan oleh mekanisme batang tekan pada profil siku penyambung; pada beban yang berangsur-angsur meningkat sampai mencapai Pyield, respon lendutan masih proporsional dengan beban; awal terjadinya buckling dimulai pada beban Pyield (111 kN); kapasitas benda uji BCM (Pmaks) ditentukan oleh kapasitas inelastic buckling pada profil siku penyambung yang tercapai pada beban Pmaks = 142,5 kN; kekakuan benda uji BCM lebih besar dibanding dengan kekakuan balok castellated penelitian terdahulu dengan bukaan heksagonal/BCH maupun bukaan Segi-Empat/BCS; pada saat beban Pmaks, lendutan yang terjadi pada benda uji BCM adalah 0,99 mm; berdasarkan hasil back analysis menggunakan model frame 2D pada beban P=0 sampai dengan Pyield diperoleh gaya pada batang profil siku tekan yang nilainya hampir sama dengan gaya batang eksperimen; berdasarkan hasil back analysis menggunakan 3D shell element dan kriteria kegagalan Von Mises diperoleh kesesuaian lokasi titik-titik leleh (pada profil siku penyambung) dengan hasil eksperimen; dan kapasitas benda uji BCM masih dapat ditingkatkan dengan mudah melalui pembesaran luas tampang profil siku penyambung, sementara untuk balok castellated tipe lain kapasitasnya sudah maksimal.

Various kinds of castellated beams (with circular, hexagonal, and rectangular openings) have been developed in order to optimize the use of structural steel profiles. In view of the limitations in the current production of high-effectivity castellated beams, their capacity has for a while undergone a stagnation as to the increase thereof. This thesis develops a type of modified castellated beam, formed from a straight-profile cut in the mid-section whereby the two resulting half-parts are connected by an angle shape steel member inclined at 45ᵒ, in such a way that the effective height of the beam can be readily increased. The structural behavior of the beam construct including displacement, stress, and strain responses along with the associated failure mechanism, is experimentally studied in the present thesis. modified castellated beam is composed of IWF structural steel with dimensions The 150x75x7x5 mm 3 horizontally divided into two parts, which, in turn, are connected by an angle shape steel member with dimensions 30x30x3 mm 2 , in such a way that the beam’s overall height is 275 mm with a span of 920 mm, referring to the beam dimensions found in previous. The set-up behind our experimentation utilizes two-point loading. The experiment ceases when the load has suffered 30% decrease with respect to Pmax. Based on this experiment and analysis, we conclude the followings: The shear behavior of the modified castellated beam is determined by the mechanism of compression of the angle shape connecting member; as the applied loading increasingly approaches Pyield, the displacement response remains proportional to loading; initiation of inelastic buckling occurs at Pyield (111 kN); the capacity of the beam specimen (Pmax) is determined by the inelastic buckling of the angle shape compressional connecting member at Pmax = 142.5 kN; the stiffness of the beam specimen is greater than that of a typical castellated beam with hexagonal opening as well as that of a typical castellated beam with rectangular opening, in comparison with respective stiffnesses found in previous theses; at critical loading value Pmax, the recorded displacement of the beam specimen is 0.99 mm; according to the result of back analysis using a 2D frame model from P = 0 up to Pyield, we obtain the calculated force on the angle shape compressional connecting member is close to that of the measured force in experiment; similarly, via back analysis modelled on 3D shell element and Von Mises failure criteria, we obtain the locations of the yield parts in connecting member agree with that of experiemental results; we find that the beam specimen’s capacity can still be increased rather easily by enlarging the surface area of the angle shape compressional connecting member, while for other types of castellated beams the capacity has rather reached a definite maximum.

Kata Kunci : balok castellated modifikasi, kapasitas, inelastic buckling