Post-Earthquake Damage Inspection of Wood-Frame Buildings by a Polarimetric GB-SAR System

Abstract

Structural damage inspection after an earthquake is essential for safety assessment of the affected wood-frame buildings and for making knowledgeable decision regarding their repair, renovation, or replacement. We present a polarimetric radar system for sensing the concealed wood-frames damaged by earthquakes. This system employs an antenna array consisting of four linearly polarized Vivaldi antennas recording full-polarimetric radar echoes in an ultra-wideband ranging from 1 to 20 GHz. The detailed design of the system and the signal processing algorithms for high-resolution 3D imaging are introduced. We conducted a number of surveys on damaged wooden wall specimens in laboratory. The experiment results indicate that the high-frequency radar waves can penetrate the wooden walls. Deformations of wooden structures (about 2 cm displacement) inside the wall, as well as the concealed small metal nails (about 3 mm in diameter and less than 2 cm in length) and bolts can be clearly imaged. The shape and orientation of the wooden members have shown a great sensitivity to the radar polarization. It is concluded that radar polarimetry can provide much richer information on the condition of concealed building structures than the conventional single-polarization subsurface penetrating radar.

An approach to wide-field imaging of linear rail ground-based SAR in high squint multi-angle mode

“…Equation 14is the wave number in the squint direction that contains the coupling term of the range frequency and the azimuth frequency as well as the squint modulation term. It determines the first term in (10).…”

“…Therefore, the accuracy of deformation monitoring is much higher, which is generally considered to be millimeter-level. Moreover, it can be used for long-term monitoring of local areas, such as bridge monitoring [7], discontinuous monitoring of slow deformation [8], iron open pit monitoring [9], post-earthquake damage inspection [10], evaluation of snow-mass characteris-tic [11], post-landslide monitoring [12], subsidence phenomenon in urban environment [13], atmospheric correction [14], height-dependent atmospheric artifacts compensation [15], soil surface roughness characterization [16], and castle cliff monitoring [17].…”

Ultra-wideband elliptical patch antenna for microwave imaging of wood

“…Another paper worked on the MWT to inspect the wood [18]. In addition to that, the imaging of wood not only used for MW region but also for a higher range like THz in [19] and even MWI of wood materials helped to inspect the damage caused by earthquake presented in [20]. The antennas presented in [21, 22] obtained a narrow BW, and their antenna dimensions were larger in comparison with the antenna presented in this paper.…”

The Integrated Simulation and Processing Tool for Ground Based Synthetic Aperture Radar (GBSAR)

“…Exploiting the SAR images will extract various useful information of the targeted area. The cost of developing a GBSAR system relatively lower than that of airborne or space-borne SAR system, this has led to an increase in interest from various agencies to implement GBSAR technique in numerous applications such as human-made structure (bridge [1], dam [2], building [3], etc.) observation, terrain mapping [4], landslide monitoring [5] system and many more.…”