ASSESSMENT OF BRIDGE LOAD CARRYING CAPACITY UNDER STATIC AND DYNAMIC LOAD TESTING

Abstract

Bridges are important structures in the field of civil engineering, failure of which can result the massive loss of life and the economy of the nation. With proper Structural Health Monitoring (SHM) and timely assessment of the bridges, failure of bridges can be reduced. The assessment of bridge load carrying capacity can be done using Static Load Testing (SLT) and Dynamic Load Testing (DLT). The primary purpose of this study is to explore the feasibility of DLT for the assessment of load carrying capacity of the bridge. The SLT entails the gradual application of load to a bridge, in contrast to DLT where moving load is applied on the bridge. This approach is not only expensive and time-intensive but also causes traffic disruptions during testing. The logistics of managing instruments and heavy equipment for SLT, particularly, in remote areas, present considerable challenges. However, dynamic load testing load overcomes the drawbacks of static load testing providing quick assessment of load carrying capacity of the bridge. To relate the static and dynamic parameters of the bridge, a numerical study has been conducted in MIDAS Civil 2024 V 1.1. With the help of the numerical model and the experimental static load testing data, the static parameter and the dynamic parameter of the bridge are used for the calculation of the Dynamic Load Carrying Capacity (DLCC) of the bridge. The dynamic load carrying capacity (DLCC1) has been calculated using a deflection value (de) of 23.06 mm from the experimental load testing and frequency value ( fn ) of 4.145 Hz from the numerical model and found as 170.49 tons, which was not similar to the static load carrying capacity (SLCC) equivalent to the 70R wheeled vehicle including the impact factor (113.15 tons corresponding to bending moment of 4232 KNm) as reported by the CRRI. This is because the numerical model was not in onsite condition but in ideal condition. With the period of time and usage, the structural integrity of the bridge changes as parameters namely, material property (E), boundary condition (B) and moment of inertial (I) affecting the structural properties of the bridge changes. Then, to tune the numerical model with the onsite condition of the bridge, a parametric study has been carried out based on the iv parameters: material property (E), boundary condition (B) and moment of inertia (I) and an updated model which resembles with the bridge onsite condition was generated. The target frequency ( fn ' ) of 3.376 Hz has been observed for the numerical model with modulus of elasticity (E) of M30, moment of inertia (I) of 65.1% and boundary condition as simply supported. Then, the dynamic load carrying capacity (DLCC1) was again calculated using a deflection value (de) of 23.06 mm and frequency value ( fn ' ) of 3.376 Hz and found as 113.05 tons, which is now similar to the static load carrying capacity (SLCC) equivalent to the 70R wheeled vehicle including the impact factor (113.15 tons ) as reported by the CRRI. Therefore, it can be concluded that the flexural load carrying capacity of the bridge determined using dynamic parameter is 4232 KNm which is similar to the flexural load carrying capacity of 4232 KNm determined experimentally. The study shows static and dynamic parameters bridge can be used to find the dynamic load carrying capacity; which is proposed be equal to static load carrying capacity. In this study, static parameter from the experimental static load testing have been used to calculate the Dynamic Load Carrying Capacity (DLCC1) of the bridge. In future, the dynamic load parameters from the experimental dynamic load test is proposed to be used to calculate the Dynamic Load Carrying Capacity (DLCC2) of the bridge.