Tie beam yang menghubungkan dua kolom selama ini diperhitungkan sebagai balok ikat (tie beam) agar kolom tidak bergeser. Tie beam diasumsikan menggantung atau tidak bertumpu di atas tanah sehingga tie beam murni sebagai pengikat antar dua kolom. Sebaliknya, kenyataan di lapangan tie beam bertumpu di atas tanah atau di atas pasangan batu. Oleh karena itu, tie beam akan menerima beban vertikal dari bangunan. Dengan demikian, desain tie beam perlu diubah karena kondisi ini. Tujuan utama dari penelitian ini adalah untuk membandingkan pengaruh tie beam pada kondisi menggantung dan pada kondisi bertumpu terhadap penurunan fondasi, beda penurunan dan angular distortion antar fondasi. Selain itu, juga untuk membandingkan momen pada tie beam dari dua kondisi tersebut. Analisis dilakukan dengan menggunakan program SAP2000. Tanah dan pasangan batu dimodelkan sebagai spring dengan input parameter modulus reaksi tanah dasar (ks). Pemodelan gedung dilakukan atas dua kondisi. Kondisi pertama dilakukan pemodelan gedung dengan kondisi tie beam menggantung. Kondisi ke-dua dilakukan pemodelan gedung dengan kondisi tie beam bertumpu di atas pasangan batu atau di atas tanah. Selain itu, pemodelan juga dilakukan pada variasi jenis tanah dan variasi kekakuan tie beam. Analisis dilakukan terhadap dua keadaan yakni keadaan beban permanen dan keadaan beban gempa. Dari hasil analisis diperoleh penurunan fondasi telapak pada kondisi tie beam bertumpu di atas tanah atau di atas pasangan batu lebih kecil dibandingkan kondisi tie beam menggantung. Selisih penurunan rata-rata sekitar 26%. Beda penurunan dan angular distortion antara dua kolom menjadi lebih kecil ketika tie beam bertumpu di atas tanah atau di atas pasangan batu dibandingkan kondisi tie beam menggantung. Momen lapangan yang bekerja pada tie beam menggantung adalah positif sedangkan momen tumpuan adalah negatif. Sebaliknya, momen lapangan yang bekerja pada tie beam bertumpu di atas tanah maupun di atas pasangan batu adalah negatif, sedangkan momen tumpuan adalah positif. Dengan demikian, desain tulangan tie beam harus disesuaikan dengan kondisi tersebut.

Tie beam connecting two columns has been calculated as a tie beam to keep them from moving apart. It was assumed as the hanging tie beam or not rested on the ground. Hence it was purely as a tie between two columns. However, in the field, tie beam is rested on the ground or the stone foundation. Therefore the tie beam will receive the vertical load of the building. The tie beam design need to be changed due to this condition. The main aim of this research is to compare the effect of tie beam on the hanging condition and rested condition toward the settlement of the foundation, the differential settlement and the angular distortion between two column footings. Also, to compare the moment on tie beam on both conditions. An analysis was conducted using SAP2000. The ground and the stone foundation were modeled as springs at which the modulus subgrade reaction (ks) was the input parameters. The building model was calculated in two conditions. The first model was runned with hanging tie beam condition. The second model was runned with the rested tie beam condition on the stone foundation and on the ground. Also, The model was runned based on the type of ground and the stiffnes of tie beam. The analysis was conducted toward two conditions, which are permanent load condition and earthquake load condition. The results showed that the settlement of footing when the tie beam resting on the ground or the stone foundation was smaller than the hanging tie beam. The difference of the settlement was about 26% on average. Differential settlement and angular distortion between two column footings became smaller when the tie beam was rested on the ground or the stone foundation compared to the hanging tie beam. The field bending moment that occurred on the hanging tie beam was positive, while the restraint moment was negative. In contrary, the field bending moment that occurred on the tie beam rested on the ground or the stone foundation was negative, while the restraint moment was positive. Hence, the reinforcement design of tie beam should be based on the condition above.

Kata Kunci : Tie beam bertumpu, penurunan, angular distortion, momen / Resting tie beam, settlement, angular distortion, moment