The Rakanji stone arch bridge has three spans of approximately 26 m, and the total length of the bridge is approximately 89.3 m. The rise:span ratio is approximately 0.19; hence, the arches are very shallow. To clarify the structural characterization of the Rakanji stone arch bridge, a series of dynamic, non-destructive and destructive tests are conducted. From material tests, the Young's modulus and compressive strength of the stone are estimated to be 17.2 kN/mm² and 28.5 N/mm², respectively, whereas those of the mortar are estimated as 5.5–7.8 kN/mm² and 3.9–9.1 N/mm², respectively. From the results of dynamic tests, the fundamental frequencies, modes, and damping factors of the Rakanji stone arch bridge are identified by eigensystem realization algorithm (ERA) model. From the results of numerical model updating based on inverse eigensensitivity method (IEM), the damaged areas including the effect of boundary condition and bridge-soil interaction are identified and these areas correspond well to those through the in situ tests and visual inspection.

The paper presents experimental and numerical works to assess the in-plane shear characteristics of rammed earth (RE) structures in Bhutan. The material characterization works involve compressive and tensile splitting strength tests on extracted cylindrical core samples. The effects of the RE layer thickness and drying period in the strength characteristics of the rammed earth is presented. The main experimental part reports in-plane shear tests on 3 test specimens, 1200 mm long, 1200 mm high, and 600 mm wide. The test matrix has unreinforced and reinforced specimens with variable RE layer thicknesses. For the reinforced RE specimen, the effectiveness of a simple intervention with insertion of reinforced concrete dowel at the RE block interface as a strengthening measure is discussed. Furthermore, corresponding finite element models were developed to verify the test observations. Both the experimental observations and numerical computations showed the effectiveness of proposed intervention technique in enhancing the shear strength and delaying the slip along the RE joint interface. The results showed that the shear strength of the reinforced specimen increased by 12.3% over the benchmark specimen.