Analisa Modifikasi Bentuk Penampang Half Through Truss Bridge Untuk Meningkatkan Stabilitas Lateral Dan Aksesibilitas Jembatan

Rosyidi, Moh. Fadhlan (2022) Analisa Modifikasi Bentuk Penampang Half Through Truss Bridge Untuk Meningkatkan Stabilitas Lateral Dan Aksesibilitas Jembatan. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Jembatan rangka dengan penampang melintang terbuka dapat dijumpai pada jembatan pejalan kaki, jembatan kereta api dan jembatan jalan raya. Biasanya dipakai untuk bentang-bentang jembatan yang kecil, sehingga tidak diperlukan ikatan angin atas atau bisa disebut half through truss bridge. Komponen terlemah dari half through truss bridge adalah batang tekan atas dari salah satu rangkanya. Namun, kurangnya sambungan transversal atas sangat mengurangi stabilitas transversal dari half through truss bridge, dan akibatnya batang tekan atas rentan terhadap tekuk lateral. Tekuk lateral yang tidak terduga dari batang tekan atas akan menyebabkan kerusakan jembatan. Oleh karena itu, stabilitas batang tekan atas sangat penting untuk half through truss bridge dan perhitungan kekakuan elastik lateral untuk pengekangan batang tekan atas berpengaruh terhadap nilai beban tekuk kritisnya. Elemen badan vertikal dan diagonal pada half-through truss bridge yang ditopang secara sederhana bertindak sebagai penahan lateral dari batang tekan atas sampai batas tertentu. Batang tekan atas selalu dianggap sebagai balok kontinu dengan tumpuan lateral elastis pada setiap sambungan. Ketika beban aksial P pada batang tekan atas mencapai nilai kritis, rangka batang menekuk secara lateral. Dalam menangani masalah ini, stabilitas batang tekan atas diselidiki dengan mengasumsikan bahwa kekangan dari anggota badan dapat diwakili oleh aksi pegas yang terletak pada bidang horizontal.
Kajian analitik dasar sudah dirintis oleh Engesser’s pada abad 19 Dengan mengasumsikan jepit pada tengah gelagar melintang. Dari asumsi tersebut diperoleh kekakuan elastik lateral penampang jembatan, yang merupakan kontribusi dari kekakuan lentur gelagar melintang dan batang vertikal. Studi terdahulu yang dilakukan oleh Matthies (2012) memodelkan secara numerik untuk mencari nilai C, kekakuan elastik lateral menggunakan program metoda elemen hingga yaitu Ansys dengan memodelkan penampang elemen jembatan secara sederhana dan nilainya dibandingkan dengan analitikal Engesser.
Untuk meningkatan kekakuan lentur lateral dari batang vertikal, biasanya dipasang pelat segitiga didalam ruang bebas jembatan, sehingga keberadaannya sering mengganggu aksesibilitas. Dalam tesis ini dikembangkan bentuk penampang jembatan terbuka yang memudahkan pengguna melewati jembatan dan tetap mempertahankan lebar ruang bebas. Modifikasi pertama dengan cara menambahkan pelat segitiga setinggi pelat lantai kendaraan dari potongan batang balok lantai. Modifikasi kedua dengan cara menambahkan potongan dari batang vertikal sehingga terbentuk batang vertikal non prismatik. Modifikasi yang ketiga dimana batang vertikal non prismatik pada modifikasi kedua tetap dipertahankan tetapi dikombinasikan ditambahkan juga pelat segitiga setinggi pelat lantai kendaraan.
Hasil penelitian secara numerik dengan menggunakan program bantu Abaqus menunjukkan adanya kenaikan nilai kekauan elastik lateral, C sebesar 36.631% dari modifikasi pertama, sebesar 16.450% dari modifikasi kedua dan 47.988% dari modifikasi ketiga. Seiring juga dengan kenaikan beban tekuk kritis lateral batang tekan atas.
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Truss bridges with open cross sections can be found on pedestrian bridges, railway bridges and highway bridges. Usually used for small spans of bridges, so that no top wind bracing is needed or it can be called a half through truss bridge. The weakest component of the half through truss bridge is the upper compression member of one of the frames. However, the lack of an upper transverse joint greatly reduces the transverse stability of the half through truss bridge, and as a result the upper compression member is susceptible to buckling. Unexpected buckling of the upper compression member will cause bridge damage. Therefore, the stability of the upper compression member is very important for the half through truss bridge and the calculation of the lateral elastic stiffness for the restraint of the upper compression member has an effect on the value of the critical buckling load. The vertical and diagonal web elements in the simply supported half-through truss bridge act as lateral supports to the upper compression member to some extent. The upper compression member is always considered to be a continuous beam with elastic lateral supports at each joint. When the axial load P on the upper compression member reaches a critical value, the truss bends laterally. In dealing with this problem, the stability of the upper compression member is investigated by assuming that the restraint of the web member can be represented by the action of a spring located in the horizontal plane.

The basic analytic study was pioneered by Engesser's in the 19th century by assuming a fixed in the middle of a cross girder. From this assumption, the lateral elastic stiffness of the bridge section is obtained, which is the contribution of the flexural stiffness of the cross girder and the vertical beam. A previous study conducted by Matthies (2012) modeled numerically to find the value of C, lateral elastic stiffness using the finite element method program, namely Ansys, by modeling a simple cross-section of the bridge element and its value compared to the analytical Engesser.
To increase the lateral flexural stiffness of the vertical beams, triangular slabs are usually installed in the free space of the bridge, so that their presence often interferes with accessibility. In this thesis, the cross-sectional form of an open bridge is developed which makes it easier for users to pass through the bridge and still maintain the width of the free space. The first modification is by adding a triangular plate as high as the vehicle's floor plate from pieces of floor beams. The second modification is by adding pieces of vertical beams to form non-prismatic vertical beams. The third modification where the non-prismatic vertical beams in the second modification are maintained but combined are also added a triangular plate as high as the vehicle floor plate.
The results of numerical research using the Abaqus aid program showed an increase in the value of lateral elastic stiffness, C of 36.631% from the first modification, 16.450% from the second modification and 47.988% from the third modification. Along with the increase in the critical buckling load of the upper compression member.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	half thorugh truss bridge, buckling, non-prismatic vertical beam, Engesser, lateral elastic stiffness, Abaqus,jembatan rangka terbuka, tekuk, batang vertikal non prismatik, Engesser, kekakuan elastik lateral, Abaqus
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) > TA347 Finite Element Method T Technology > TA Engineering (General). Civil engineering (General) > TA645 Structural analysis (Engineering) T Technology > TA Engineering (General). Civil engineering (General) > TA656.2 Buckling
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis
Depositing User:	Moh. Fadhlan Rosyidi
Date Deposited:	06 Feb 2022 09:54
Last Modified:	02 Nov 2022 01:26
URI:	http://repository.its.ac.id/id/eprint/92859

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