Concatenation Statement throwing shot dump.

Hi

I am facing a problem , I am using a Concatenate statement inside loop and i am using feild symbol instead of work area but while exceuting it's throwing dump . I am also sending the code here , Can you plzz guide me how can i solve this .

TYPES: BEGIN OF GS_EKBE,

EBELN TYPE EKBE-EBELN,

EBELP TYPE EKBE-EBELP,

GJAHR TYPE EKBE-GJAHR,

BELNR TYPE EKBE-BELNR,

BUZEI TYPE EKBE-BUZEI,

DMBTR TYPE EKBE-DMBTR,

LFBNR TYPE EKBE-LFBNR,

AWKEY TYPE BKPF-AWKEY,

END OF GS_EKBE.

data : GT_EKBE1 TYPE TABLE OF GS_EKBE.

FIELD-SYMBOLS : <FS_EKBE1> TYPE GS_EKBE.

LOOP AT GT_EKBE1 ASSIGNING <FS_EKBE1>.

CONCATENATE <FS_EKBE1>-BELNR <FS_EKBE1>-GJAHR INTO <FS_EKBE>-AWKEY.

ENDLOOP.

Thanks

Girdhari