Punching shear behaviour of interior slab-column connections strengthened by steel angle plates

摘要

The present paper is concerned with a series of tests on reinforced concrete flat slabs to examine the behaviour of interior slab-column connections employing steel angle plates and high strength bolts as strengthening elements. The angle plates were bolted to the column faces and slab at both tension and compression sides. The shorter leg of the angle plate attached to the column face acts as a column capital of an equivalent concrete width whilst the longer leg is treated as a drop panel of an equivalent concrete depth. Four flat slabs of practical size were constructed and tested to failure under shear load applied through the column. The strengthening technique has effectively turned the final mode of failure from punching shear to flexure-induced punching outside the strengthened zone. Such slab system has shown appreciable increases in the deformation capacity, stiffness, energy absorption and particularly load-carrying capacity with 20%, 24%, 209% and 51% in average, respectively over that of the unstrengthened slab. Non-linear finite element models were developed, analysed and validated against the test results, only to find that both findings were found to be in a good agreement. A parametric study was performed to investigate the effects of bolts strength, bolts spacing and dimensions of angle plates on the ultimate load behaviour of the slab. A simple theoretical method based on yield line theory to predict the flexural capacity of the strengthened slab is also outlined. In addition, the tests and numerical results are compared with the values predicted using the ACI design code.