Deflection measurement of masonry arch bridges with tall piers: A case study of Shahbazan bridge

A common practice for detailed assessment of masonry bridges is to use recorded deflection signature of mid-span of such structures due to predefined loading schemes. However, measuring the deflection of bridges with tall piers or those situated over deep valleys introduces certain difficulties, since common deflection-meters require a reference point relative to which the measurement is carried out. Common approaches currently proposed by researchers include indirect measurement of deflection based on acceleration or tilt measurements; but due to small values of deflection in masonry arch bridges, such approaches may not produce the expected results. Moreover, optical methods are also difficult and rather expensive to implement due to small deflection values and far reaching points. This paper proposes the application of piers as the reference point of common deflection meter, which is also compared to conventional approaches. To demonstrate the applicability of the proposed approach, a case study is carried out in which a 70 years old railway masonry arch bridge is instrumented for structural health monitoring. The studied bridge is a seven span railway masonry arch bridge with tall piers of almost 40 meters and span lengths of 21.5m. The method proves to work efficiently and the results could be used for calibration of numerical model of the bridge

Keywords:

Health monitoring , Masonry arch bridge , Dynamic load tests , Deflection-meters