An　adaptive　metamaterial　beam　with　a　couple　of　electromechanical　resonators　in　each　unit　cell　is　proposed　in　this　study　to　open　Bragg　bandgap　or　locally　resonant　bandgap　for　flexural　wave　attenuation　in　Euler-Bernoulli　beams.　The　electromechanical　resonator　is　composed　of　a　piezoelectric　layer　with　segmented　electrodes　and　shunt　circuits,　which　affect　the　dynamic　equivalent　stiffness.　It　is　illustrated　that　there　is　only　a　Bragg　bandgap　when　the　circuits　of　the　two　adjacent　resonators　are　approximate　to　a　short　circuit　or　open　circuit,　and　the　locally　resonant　bandgap　will　be　generated　in　the　pure　inductance　circuits　when　the　resonant　frequencies　are　different　in　general.　The　locally　resonant　bandgap　can　be　broadened　by　adding　more　resonators　into　the　unit　cell　with　the　resonant　frequencies　of　the　shunting　circuits　satisfying　a　proper　ratio.