Tan, MichaelSaktiotoEmrinaldi, Tengku2016-02-012016-02-012016-02-01wahyu sari yenihttp://repository.unri.ac.id/xmlui/handle/123456789/7870Vibration-induced strain and natural frequency of Siak I Bridge were investigated in this research. A Strain was calculated from laser power measured by powermeter. Natural frequency was calculated using manual calculation with single-girder analysis. The research has been done at five measurement points at Siak I Bridge. The five measurement points were 10 m, 87,5 m, 175 m, 265 m, dan 287,5 m from the one point of the bridge in Senapelan Subdistrict. The car used to induce vibration was Xenia and the power measurement was conducted in predawn. The instruments used were laser diode, Fiber Bragg Grating (λB = 1550 nm), and powermeter. The results showed that five measuring points almost experienced strain below 20με. The natural frequency of the five measuring points at Siak I Bridge were 2,68 Hz, 2,68 Hz, 2,48 Hz, 2,99 Hz, and 2,68 HzenFiber Bragg GratingStrainNatural FrequencySiak I Bridgestudent Paper Post Degree