RESEARCH ON SHEAR DAMAGE EVOLUTION AND SERVICEABILITY PERFORMANCE OF DEEP FLEXURAL MEMBERS WITH HIGH-STRENGTH LIGHTWEIGHT AGGREGATE CONCRETE

Accidental overload, prolonged environmental erosion and the deformation caused by temperature change, etc., easily lead to strength reduction and cracking of deep flexural members, eventually affecting their serviceability. A total of 15 high-strength lightweight aggregate concrete (HSLWAC) deep flexural members are tested to systematically study their damage evolution laws under shear load. The influencing factors for the shear service ability including shear span-depth ratio (a/h₀), bearing plate width (l_b) and beam sectional height are considered. The relationship between diagonal crack width and load level is established based on the trend of crack propagation, and the application of diagonal crack width limiting value in current codes to such members is discussed. Test results show that the maximum diagonal crack widths of specimens exhibit an increasing trend with the increase of a/h₀ and l_b, and a sufficient amount of horizontal and vertical web reinforcement can effectively inhibit the diagonal cracking of such members. Both the normalized diagonal cracking strength and the maximum diagonal crack width are less affected by the size effect. During the entire shear failure process, the diagonal crack width shows a significant correlation with the applied load, and the serviceability performance index on the basis of normal weight concrete specimens is able to predict the serviceability behavior of HSLWAC specimens. However, it is difficult to satisfy the diagonal crack width limiting value for HSLWAC members designed according to the minimum stirrup ratio in Chinese code, so the minimum stirrup ratio should be appropriately increased.