In construction field, a time completion and an adherence to budget are two factors that mainly influence the successful of the projects. The adherence to the budget can be achieved when the estimated budget is closed to the actual cost. For the owners, cost estimation is necessary as a guidance in determining the amount of investment. Therefore, it is very important to know the estimation of the project cost by using the limited data before the detailed plans and specifications of the project are identified. However, in the case of bridge substructure preliminary cost estimation, there is a lack information about material quantity estimation models due to the difficulties of soil characteristic and hydrological conditions. Hence, this research aims to develop the estimation of material quantity models of the abutment and caisson of bridge, with the Presetressed Concrete I-Girder (PCI Girder) superstructure located in Sleman district, Yogyakarta province, Indonesia. The database used for developing model was obtained by conducting sub-structure structural analysis of 15 abutments and 45 caissons. The bridges have a various span length, abutment height, and caisson depth. Material quantity estimation models were analysed by the multiple regression analysis methods. The span length and the abutment height are determined as independent variables to predict the concrete volume, the reinforcing steel weight, the caisson concrete volume, the cyclops concrete volume and the caisson reinforcing steel weight. This research proposed 11 equation models to estimate the concrete volume and reinforcing steel weight of abutment and caisson.

The connection system is a critical part of Timber – Concrete Composite (TCC) floor structures. The behaviour of the connection needs to be known to predict the behaviour of composite structure accurately. Screws are one kind of connector that mostly used in the composite structure due to its installation ease and high withdrawal strength. This study carried out a two-dimensional numerical simulation to examine the behaviour of LVL Sengon-concrete joint using OpenSees software. The lag screw used to connect LVL Sengon and concrete. In this simulation, the screw was assumed as a beam with hinges element that supported by a set of springs representing the strength of LVL Sengon and concrete. Some input parameters for this simulation were obtained from the material test and previous research. The effect of secondary axial force was considered into the load-displacement curve resulted from the numerical simulation.  This study performed several simulations towards the variation of the screw diameter, penetration depth, and concrete compressive strength. The capacity of the connections resulted from the numerical simulation were overestimates the manual calculation using EYM theory and NDS 2018 equations. The capacity of the connection increased about 146% to 284% due to the addition of secondary axial forces. In addition, this simulation can adequately predict the shear force, bending moment, and deformation of the screw. There is a plastic hinge formed in the screw after the screw being deformed a quite large.  It shows the same yield mode with the manual calculation using EYM theory and NDS 2018 equations. This simulation also can show the contribution of each spring elements to resist the load until its ultimate strength.

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Penggunaan bambu sebagai material konstruksi meningkat seiring dengan isu lingkungan yang semakin banyak dibahas. Namun demikian, tidak ada regulasi yang secara spesifik mengatur tentang desain konstruksi bambu di Indonesia. Penentuan sifat mekanik bambu di Indonesia kebanyakan masih diambil dari rata-rata hasil pengujian di laboratorium, sementara ISO 22156 mengatur penggunaan nilai persentil kelima dari hasil pengujian. Oleh karena itu, studi komparasi perilaku bambu yang nilai sifat mekanik dihitung menggunakan metode rata-rata dan persentil ke-5 hasil pengujian sangat penting untuk dilakukan karena akan meningkatkan perhatian dan pemahaman para perencana untuk menggunakan sifat mekanik dari persentil ke-5 hasil pengujian dalam perencanaan struktur bambu. Makalah ini menyajikan hasil studi komparasi perilaku lentur balok bambu yang sifat mekanik lentur, modulus elastisitas lentur dan modulus patah, dihitung menggunakan 3 metode yaitu metode rata-rata, metode persentil ke-5 ISO 22156, dan metode persentil ke-5 hubungan antara modulus elastisitas dan modulus lentur. Hasil analisis menunjukkan bahwa penggunaan modulus elastisitas dan modulus patah bambu yang didapatkan dari metode rata-rata hasil pengujian laboratorium tidak disarankan karena memberikan nilai kapasitas beban, baik pada beban maksimum maupun beban pada kondisi lendutan ijin, yang lebih tinggi dibandingkan data beban pada kedua kondisi yang diperoleh dari hasil pengujian lentur statik. Hal ini akan meningkatkan risiko kegagalan pada struktur bambu. Selain itu, hasil analisis menunjukkan bahwa persyaratan kekakuan adalah faktor yang lebih menentukan pada perencanaan struktur balok bambu. Penggunaan  nilai modulus elastisitas dan modulus patah yang diperoleh dari metode ISO 22156 lebih direkomendasikan.