Hamid Nikraz

Shear Behaviour of Ligthweight Sandwich Reinforced Concrete Slabs

A new lightweight sandwich reinforced concrete (LSRC) section has been developed using prefabricated autoclaved aerated concrete (AAC) blocks as infill in the section where concrete is considered ineffective under bending. This paper presents an investigation into the strength and behaviour of LSRC slabs subjected to shear. Eight tests were conducted on four slabs, one solid and three different types of LSRC slabs. Based on the test results, all LSRC slabs exhibited similar behaviour to the equivalent solid slab and had varying shear capacities depending on the profile of AAC blocks infill. The obtained shear capacities were compared with the design values based on several major design codes and found to be within the safety predictions of the codes. ANSYS was employed to develop nonlinear finite element models of LSRC slabs. The numerical results agree well with the experimental one.

Ultimate Design of Unbound Granular Base Courses for Flexible Pavements

This study aims to introduce alternative design procedures for a flexible pavement base course by utilizing ultimate strength criteria with the sophisticated laboratory results of base course materials. Based on the design protocol, only the design criteria of the horizontal tension and the vertical compression occurring at the bottom of the asphalt layer and at the top of the subgrade, respectively are employed. The real behavior of a base course under traffic loads has been rarely accounted for in the pavement design protocol. Nowadays, traffic is growing in terms of magnitude and frequency far beyond the past causing premature deterioration in base course layers leading to major damage in pavements. The study presents theoretically a more suitable approach of stress and strain distributions in a flexible pavement using the finite element method. The effects of uniform design pressure and material attributes generated when a vehicle travels, namely the stress and strain contributions between tires and pavement layers, were investigated. Moreover, new design criteria for an unbound granular layer were defined as the ultimate strength design and the bearing capacity factor resulting from the application of the shallow foundation bearing capacity concept within the California Bearing Ratio (CBR) results.