Scenarios as partial behavior descriptions, are used more and more to represent users requirements, and to conduct software engineering. This paper examines automatic generation of specifications from requirements. This is a crucial step when accuracy is desired in the requirement engineering process. Automatic construction of specifications from scenarios reduces to the merging of partial behaviors into global specifications, such that these specifications can reproduce them. This paper presents an incremental algorithm that synthesizes timed automata from scenarios with timing constraints. The algorithm is based on a formalism developed for scenarios. Its uses operations semantics, and a mapping between concepts of scenarios, and those of the theory of timed automata.