DOWELLED ANCHORS IN BRIDGES: EFFECT ON IMPERVIOUSNESS OF THE INSULATION, CREEP AND LOSS OF PRESTRESSING

DUEBELANKER BEI BRUECKEN: EINFLUSS AUF DIE DICHTIGKEIT DER ISOLIERUNG, KRIECHVERHALTEN, VORSPANNUNGSMINDERUNG

EXPANSION AND ADHESION DOWELS ARE ANCHORS WHICH CAN BE INCORPORATED AFTER THE LAYING OF THE INSULATION; THEY ARE BORED INTO THE STRUCTURAL CONCRETE. THEIR BEARING CAPACITY IS GUARANTEED, BUT THE BEHAVIOUR OF THE SEAL IN THE REGION OF THE BOREHOLE IS NOT CLEAR. IT IS INTENDED TO EFFECT THE SEAL BY PLACING A NEOPRENE PLATE ON THE INSULATION AND SCREWING IT DOWN OVER A STEEL PLATE. BECAUSE OF THE CREEP OF THE BITUMEN IN THE INSULATION THE PRESSURE IS DECREASED WITH TIME. PRELIMINARY TESTS HAVE SHOWN THAT THE PRESSURE STRIVES TOWARDS A BOUNDARY VALUE. SINCE THE MAGNITUDE OF THE REMAINING PRESSURE DETERMINES THE IMPERVIOUSNESS, THIS BOUNDARY VALUE IS TO BE DETERMINED EMPIRICALLY.