PSI - Issue 52

Govardhan Polepally et al. / Procedia Structural Integrity 52 (2024) 487–505 Govardhan Polepally/ Structural Integrity Procedia 00 (2019) 000 – 000

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3.5. Modal identification technique The Operational Modal Analysis (OMA) approach utilizes various techniques in both the time and frequency domains in the Stochastic Subspace Identification technique (SSI) in the TD, and Frequency Domain Decomposition (FDD) in the FD are largely applied methods due to its simplicity and accuracy (Vinay shimpi et al 2019). 3.5.1. Stochastic Subspace Identification (SSI) SSI is a technique used for identifying operational modal parameters, which operates directly on time-domain data, eliminating the need for converting them to correlations or spectra. This approach is particularly well-suited for output only analysis (Peeters, B., et al 2000, Londono, N. A 2004). ȗ ̈ ሺ–ሻ൅ ȗ ̇ ሺ–ሻ൅ȗ—ሺ–ሻ ൌ ˆሺ–ሻ ൌ ”ȗ’ሺ–ሻ (1) The system comprises mass, damping, and stiffness matrices denoted by M, C, and K, respectively. Additionally, the excitation force is represented by f(t), while the displacement vector at continuous time t is denoted by u(t). To factorize the force vector f(t), it is split into a matrix r that describes the inputs in space and a vector u(t). 4. Results and discussions 4.1. NDT results

Table 5. Bridge 1 NDT test results. Location Average Strength RH (Mpa)

Average UPV (m/s)

Average Half Cell value (mV)

Profometer Results (Cover in mm)

52 47 48 51 45 44 48 51 52 51 45 48 51 49 50

3904 4022 3970 4014 4095 4115 4059 4079 4117 4116 3998 4146 4016 4056 4208

-160 -168 -195

40 to 51.8 41.3 to 52.4 44.4 to 53.5

Abutment wall (A1)

-190 -173 -218

35.5 to 45.3 38.0 to 47.5 38.5 to 44.5

Pier wall (P1)

Abutment wall (A2)

Results of the NDT tests performed on Bridge 1 as shown in table 5, are based on the concrete RH tests conducted at the tested regions of the RCC structure ranging from 44 to 52 MPa. The concrete quality in the aforementioned places is rated as being between good and very good. The UPV results show that the concrete at the RCC Structure's at the tested site location, on average, grades as being of good quality. According to the Half Cell Potential test findings, there is a 90% chance that the concrete at the maximum tested site of the RCC structure will not corrode or be doubtful. From the concrete core test results, the RCC Pier wall of the Bridge construction has an average compressive strength of 39.90 MPa.