This study investigated the utilization of plastic-waste concrete as an effort to reduce urban waste problems. The waste plastic bottles were utilized to form the hollows of the hollow-core slabs (HCSs). The bottles were made of polyethylene terephthalate (PET). As a part of green research to reuse waste material, shredded PET was also added to the concrete mixture to improve the HCS strength. The cast-in-site HCS could be constructed without any difficulties. Three parameters were investigated: the effects of void content, shredded PET content, and steel-fiber (SF) content on the HCS ultimate bending capacity (Mu). Fifteen specimens were tested under static loads until failure, and the results were compared with those of the solid slab. Two different void contents 19% and 24% were studied. The other parameters were the shredded PET content (0.5% and 0.7%) and the SF content (0.19% and 0.32%). The Mu values of the HCS specimens were 12% to 16% less than that of the solid slab. However, the strengths were still within the theoretical capacity of the slab. The addition of the shredded PET could improve the HCS bending capacity by 18% to 38% compared with that of the solid slab. Similar results were also found for the specimens with SFs, whose Mu values were 11% to 46% greater than that of the solid slab. AbstrakKajian Eksperimen Lempengan Inti Berongga yang Berisi Botol-botol PET Limbah. Kajian ini menginvestigasi pemanfaatan beton limbah plastik sebagai suatu upaya untuk mengurangi masalah limbah perkotaan. Botol-botol plastik limbah dimanfaatkan untuk membentuk rongga-rongga dari lempengan inti berongga (the hollow-core slabs (HCS)). Botol-botol tersebut dibuat dari polietilena tereftalat (PET). Sebagai suatu bagian dari riset awal (green research) untuk menggunakan ulang bahan limbah, PET yang sudah dicacah juga ditambahkan ke campuran beton untuk meningkatkan kekuatan HCS. HCS yang dicor di tempat dapat dikonstruksi tanpa ada kesulitas apapun. Tiga parameter diinvestigasi: efek-efek dari konten kosong, konten PET cacahan, dan konten serat baja (steel-fiber (SF)) pada kapasitas pembengkokan akhir HCS (Mu). Lima belas spesimen diuji dengan beban statis sampai kegagalan, dan hasil-hasilnya dibandingkan dengan hasil uji lempengan padat. Dua konten kosong yang berbeda 19% dan 24% dikaji. Parameter-parameter lainnya adalah konten PET cacahan (0,5% dan 0,7%) serta konten SF (0,19% dan 0,32%). Nilai-nilai Mu spesimen-spesimen HCS adalah 12% sampai 16% lebih kecil dibandingkan dengan nilai-nilai MU lempengan padat. Namun demikian, kekuatannya masih berada di dalam kapasitas teoritis lempengan. Penambahan PET cacahan dapat meningkatkan kapasitas pembengkokan HCS sebesar 18% sampai 38% dibandingkan dengan kapasitas pembengkokan lempengan padat. Hasilhasil serupa juga diperoleh untuk spesimen-spesimen dengan SFs, dengan nilai-nilai Mu sebesar 11% sampai 46% lebih besar dibandingkan dengan nilai-nilai MU lempengan padat.

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Damage index is a define scale to describe damage of the structure due to earthquake. Several studies of damage index have been carried out on reinforced structures, but not many studies performed on steel structures. Numerical research about damage index on moment resisting frame of steel structure has been conducted. Monotonic and semi-cyclic pushover analyses using OpenSEES software was carried out to obtain the index. Two paramaters that affect the damage index value are the displacement ratio and energy absorbsion. Damage index value of MRF obtained in this research is governed by the displacement ratio. The main objective of this study is to correlate damage index and the natural frequency. SAP2000 is used to get the natural frequency through modal analysis. The results show that natural frequency can be used to assess structural damage. Hence, structural health monitoring can be simplied by assesing the natural frequency.

Recovery by Equilibrium in Patches (REP) is a recovery method introduced by B. Boroomand. This method is using patch as recovery media as is used by Superconvergent Patch Recovery (SPR) which is well known as a good recovery method. In this research, a numerical study of REP implementation is held to estimate error in finite element analysis using DKMQ element. The numerical study is performed with both uniform and adaptive h-type mesh refinement. The result is compared with three other recovery method, i.e. SPR method, averaging method, and projection method

The dynamic test of an elevated freeway bridge in Surabaya has been conducted. Eccentric mass shaker succeeded to apply an excitement to the bridge and hence the dynamic parameters such as the mode shape, the natural frequency and the damping ratio were obtained. The two main mode shapes from the test were the first vertical mode and the first longitudinal mode. The average damping ratio attained is within the range of damping ratio of prestresses concrete where the average is 2.12% whereas the range is between 2-3%. The test results are closely represented by a 3D FE model using SAP2000 without modelling the whole foundation. The deviation of the natural frequency compared to the test results is 8.50%. The elastomeric bearing effectively reduces the acceleration from upper to the bottom structure by 54.62% and 60.22% obtained from two measurements.