TKOF ROLL; 100 KTS; ACFT RECEIVED SEVERE JOLT ATTRIBUTED TO PREVIOUSLY LNDG B757 WAKE. AURAL WARNING AND WARNING LIGHT ILLUMINATED; 'ELEVATOR DISCONNECT.' TKOF WAS ABORTED AND ACFT RETURNED TO RAMP FOR REPAIR.

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WE WERE CLRED INTO POS AND HOLD ON RWY 30 AWAITING LNDG TFC ON RWY 1L. SAW TFC PASS OVER OUR DEP RWY; SEVERAL SECONDS LATER WE RECEIVED OUR TKOF CLRNC. WX WAS VMC WITH WINDS AT 300 DEGS 12 KTS. BECAUSE OF THE LOW LEVEL OF THE LNDG TFC; WE DIDN'T THINK WAKE TURB WOULD BE A FACTOR. WE COMPLETED BEFORE TKOF CHKLIST AND INITIATED OUR TKOF ROLL. AT APPROX 90-100 KTS WE RECEIVED A SEVERE JOLT TO THE ACFT; A CAS MESSAGE THAT SAID ELEVATOR DISCONNECT WITH AURAL WARNING; I THEN RECEIVED AN 'ABORT-ABORT' CALL FROM MY FO AND INITIATED A NORMAL ABORT TKOF PROC. WE THEN INFORMED TWR OF THE ABORTED TKOF AND PROCEEDED BACK TO THE GATE. ESTIMATED TIME FROM LNDG TFC/TKOF CLRNC TO TIME OF ENCOUNTER 30-40 SECONDS. BECAUSE OF PROX OF LNDG TFC TO THE GND; WE SURMISED THAT WAKE TURB SHOULDN'T BE A FACTOR. RECOMMEND THAT TIME SEPARATION BE ENFORCED FOR TKOF PROC ON RWY 30 WITH LNDG TFC ON RWY 1L AT IAD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AFTER RECEIVING THE SEVERE JOLT DURING TKOF; THE CAS (CAUTION ADVISORY SVC) LIGHT ON THE MFDU (MULTI- FUNCTION DISPLAY UNIT) ILLUMINATED ACCOMPANIED BY AN AURAL WARNING. THE WARNING LIGHT INDICATED 'ELEVATOR DISCONNECT.' TKOF WAS ABORTED. CAPT RPTR SAYS THE JOLT FELT LIKE A LARGE HAMMER HITTING THE ACFT. RPTR SAYS THAT THE ONLY POSSIBLE CAUSE OF THE ELEVATOR DISCONNECT WAS THE WAKE OF THE LNDG B757 DRIFTING INTO THEIR FLT PATH. WHEN THE ELEVATOR DISCONNECTED; THE ONLY WAY TO RECONNECT IT WAS BY MECHS. RPTR'S COMPANY CONTACTED DORNIER WHOSE ENGINEERS SAID IT WAS IMPOSSIBLE FOR A WAKE TO CAUSE THE DISCONNECT. RPTR CONTACTED IAD TWR CHIEF WHO SAID THEY WILL CHANGE THEIR PROCS FOR TKOFS BEHIND B757'S.