Push-out tests on J-hook connectors in steel-concrete-steel sandwich structure

New form of J-hook connectors and ultra-lightweight cementitious material have been developed by the authors in the previous research to produce steel-concrete-steel sandwich slim decks which have superior performance to resist blast and impact loads. This paper investigates the shear strength behavior of the J-hook connectors embedded in ultra-lightweight cement composite core and compares the behavioral differences with those in normal strength concrete. A total of 102 push-out tests were carried out on standard test specimens with varying parameters including concrete types (normal weight, lightweight and ultra-lightweight), concrete strengths, and types of J-hook connectors. Design guides are proposed to predict the shear strength and load-slip behavior of the J-hook connectors embedded in ultra-lightweight cement composite. The predicted results are compared with the test results together with those predicted by modern codes which were primarily developed for headed shear studs. Through the comparisons and verifications, it is observed that the proposed formulae offers better and more reliable predictions on shear strength as well as load-slip behaviors compared with the available methods in the literature.