Cable tension measurement for cable-stayed bridge considering on the effect of damper

Analysis method for modal frequency of stay cable-damper system considering cable sag is put forward in order to reduce even eliminate the influence of additional damper on the measure precision of cable when frequency method is used. Several factors on modal frequency of cable are studied, including relative height of damper location, damp coefficient, the calculation length of cable, and so on. The method is studied to eliminate the influence of additional dampers on the measure precision of cable. The work shows that there is great influence of additional dampers on modal frequency of cable. With the increase of relative height and damp coefficient, the effect of dampers on modal frequency of cable also increases greatly. When damp coefficient increases to some degree, modal frequency of cable is close to that when damp coefficient is infinite. The proportion factor of equivalent length, ¿, is introduced. For long cable, the calculation length can be simplified simply. While for medium or short cable, the value of ¿ should be determined appropriately by the length of cable and damp coefficient of dampers. This method is validated reasonably by three representative cables in practical.