Blast-resistant analysis and design of CFRP sheet strengthened masonry infilled walls

Aiming to investigate the performance and design approach of the carbon fiber reinforced polymer (CFRP) sheet strengthened masonry infilled walls subjected to blast loads, the commercial finite element program LS-DYNA is firstly used to develop the simplified micro-finite element model of masonry infilled walls and the corresponding blast-resistant analysis model of the CFRP sheet strengthened walls. By comparing the numerical simulation results with the nine groups field explosion test results of the unstrengthening and CFRP sheet strengthened masonry infilled walls, the applicability of the present simplified micro-modeling approach, as well as the material models and parameters of masonry and CFRP sheet and the corresponding contact algorithm, is thoroughly verified. Furthermore, referring to the CFRP sheet seismic strengthening methods recommended by China standard GB 50608—2020, the dynamic behaviors of the prototype masonry infilled walls strengthened with CFRP sheets under blast loads are analyzed and compared. It is recommended that the diagonal two-way strengthening method be advocated, followed by the vertical two-way and horizontal full-cover strengthening methods. In contrast, the vertical full-cover and mixed three-way strengthening methods are not recommended. Finally, to simultaneously satisfy the conditions of intact CFRP, no scattering debris and the peak central deflection than wall thickness to meet the blast-resistant design goal, the ranges of the scaled distance of the prototype masonry infilled walls with different arrangements of tie bar (non-/cut-off/full-length tie bar) that need to be strengthened under typical sedan (227 kg equivalent TNT) and briefcase bombs (23 kg equivalent TNT) specified by Federal Emergency Management Agency explode at different scaled distances are determined to be 0.8–2.0 m/kg^1/3 and 0.2–1.2 m/kg^1/3, respectively. The suggestions for the optimal number of CFRP sheet layers for effective blast-resistant design are further provided. The arrangement of the tie bar has little effect on the optimal number of strengthening layers, only affecting the critical scaled distance at which the wall needs to be strengthened.