Transient dynamic response of brick masonry walls under low velocity repeated impact load

Abstract

An experimental and numerical investigation have been carried out on the clay brick masonry walls against repeated impact load in order to estimate the transient dynamic response. The experiments were carried out on 110 mm thick masonry walls against 60 kg mass impactor with hemisphere nose shape with the velocity of 1.98 m/s. In the first phase, the experiment on the wall of 1.2 × 1.2 m (height (h) x breadth (b)) was conducted considering the bed (W1) and head (W2) joint of walls parallel to the boundary in order to verify the conservative design of the joint interface. It was observed that the W2 found resistance up to 3 hits whereas W1 offered resistance up to 11 hits and it was concluded that the W2 found to be sensitive. In the second phase, the aspect ratio of sensitive wall W2 was varied by reducing the breadth from 1.2 to 0.25 m, corresponding aspect ratio (h/b), 1.33 – 4.8 (W3-W6) whereas, the height of the wall remains constant, i.e. 1.2 m. It was observed that the aspect ratio was found to have marginal effect on the peak force however it changes the failure pattern significantly. In the third phase, the influence of mortar strength has been studied and it was observed that the mortar strength does not impart any stiffness into the wall. As a fourth phase, the response of W2, W3 and W4 walls was studied under repeated loading and the resistance offered up to 2, 3 and 2 hits by W2, W3 and W4 walls, respectively. Further, numerical simulations on W1, W2, W3 and W4 walls were carried out using ABAQUS and the Drucker Prager model and traction separation law were used to simulate the brick and interface joints, respectively. The results thus predicted were compared with the experimental results and found in good agreement however, a maximum deviation of 14% on the prediction of peak force. Further, the sensitive parameters were identified which are sensitive to the qualitative numerical results. It was concluded that the parameters such as cohesion, fracture energy, friction and penalty stiffness found to affect the numerical results significantly. Further, wall W2 with externally bonded engineered cementitious composite (ECC) layers has been studied in order to estimate the resistance of wall with backing plate. It was concluded that the ECC backing plate was found to enhance the response of masonry wall in terms of contact force, damage and failure pattern, significantly.