Direct load transmission in hybrid FRP and lightweight concrete sandwich bridge deck

Direct load transmission experiments on hybrid short-span beam specimens for a novel bridge deck were performed. The sandwich construction consists of three layers: a fiber-reinforced polymer composite (FRP) sheet with T-upstands for the bottom skin, lightweight concrete (LC) for the core and a thin layer of ultra high performance reinforced concrete as a top skin. Specimens with adhesively bonded FRP–LC interfaces showed significantly higher ultimate loads than corresponding unbonded specimens with composite action due to pure mechanical interlocking. The degree of composite action between FRP and LC in the unbonded interfaces depended on the LC compressive strength. A correlation of the specimen ultimate loads and the LC splitting tensile strengths was found. Combining the LC splitting tensile strength and the LC characteristic length led to a good correlation with the specimen cracking loads.