Computational Research On The Damage Of Impacted Reinforced Concrete Bridges Based On Modal Testing Technology

This paper focuses on the damage assessment of bridges impacted by ultra-high vehicle with calculation analysis.Based on the modal test technology,the existing methods for structural damage identification are introduced and summarized,and the method of modal flexibility moment is used to study the damage assessment of the damaged beam.On the basis of modal flexibility injury indexes former scholars proposed,a new damage index is proposed.The new index only needs the first order modal parameter,and uses the modal flexibility matrix before and after the structure damage to calculate the modal flexibility change rate,and carries on the center difference,obtains the modal flexibility change rate curvature.New indicator is more precise,simple and practical.The simply supported beam and four-span continuous beam are taken as the numerical simulation examples.For the damage of the simply supported beam,all indicatores identify the damage position in the way of the maximum index value,but the other modal flexibility index has the obvious change of the index value of the non-damage unit,which is easy to cause misjudgment.For the continuous beam,whether it is a single point of damage or more damage,the new indicator is able to accurately identify the location of injury,and superior to other modal indexes.Finally,taking a simple T-beam bridge as an example,the validity of the new indicator in the damage identification of simply supported girder bridge is verified with considering the various damage conditions.At present,most scholars study the the damage index of modal flexibility,which is more concentrated in the numerical simulation calculation.A small number of experimental studies have only been carried out on the experimental components.It is rare to report that the full-scale modal test of the damaged bridge structure was carried out.In view of this,taking a city cross-bridge impacted by ultra-high vehicle as the engineering background,two pieces reinforced concrete beams of the bridge is taken as the research object,and full-scale modal test and a static destructive test were carried out.Damage identification of the damaged beam is carried out by using the new index,and the results were compared with the actual damage.The relationship between the results of static test and the results of new indexes was studied.