Sentence:  The research reinforces previous conclusions that most breakage occurs due to impacts between moving units and that the central sections of dolosse and <WSD>tribar</WSD> are too slender to resist these impact loads. 
Meaning of the word marked with <WSD> tags:  A concrete structure made up of three lengths, or bars, separated by air pockets, which is used to construct revetments such as breakwaters.