Before the installed Bailey bridge is officially put into use, the Bailey bridge load capacity test must be carried out. Only the Bailey bridge that has passed the test can be put into use. In order to test whether the strength, stiffness, and overall stability of the precast steel Bailey bridge can meet the design load requirements, the main content of the Bailey bridge load test includes static load test and dynamic load test.
Project Overview Waiting for Bailey Bridge Load Capacity Test
The Bailey bridge load capacity test was carried out on a 45.72m single-span single-lane CB200 modular steel bridge. The net width of the bridge deck is 4.2m, and the bridge type adopts a QSR3H structure, namely quadra rows of single-layer reinforced type. The compact 200 Bailey bridge can be divided into single and double layers, depending on the design load requirements. The Bailey panels can be arranged from one row to four rows in parallel and can be selected as reinforced or unreinforced. For the correspondence relationship between Bailey bridge load and bridge structure, please refer to the following Bailey bridge load capacity table.
Technical Standards for the Design of Bailey Bridge Load Capacity Test
- Actual width of bridge deck: 0.73m Bailey beam + 0.17m curb + 4.2m carriageway + 0.17m curb + 0.73m Bailey beam = 6m
- Design load of Bailey Bridge: Chinese Bridge Load Standard Automobile-10 class, trailer-120
- Longitudinal slope: 0%, cross slope: 0%
Preparation before Bailey Bridge Load Capacity Test
The Bailey bridge load test uses a dump truck and a flatbed trailer as the test vehicle.
The test vehicle travels at a constant speed along the bridge deck. In this process, the tester is responsible for collecting the settlement value and deflection of each test section.
- Situation 1: The test vehicle drove over the test Bailey Bridge at a constant speed of 5km/h;
- Situation 2: The test vehicle drove over the test Bailey Bridge at a constant speed of 10km/h;
- Situation 3: The test vehicle drove over the test Bailey Bridge at a constant speed of 15km/h.
Specific Steps of Bailey Bridge Load Capacity Test
- Before starting the test, relevant personnel should measure and record the test point located at the center of the largest span of the Bailey Bridge. The deflection value measured before opening to traffic is the deflection before load. When the deflection before load does not exceed the allowable value, proceed to the next step.
- For safety reasons, a small unloaded vehicle passed the Bailey Bridge several times. Before opening to traffic, relevant personnel set up a measuring point at the center of the maximum span, and when small unloaded vehicles pass several times, measure whether the bridge deflection has excessive changes and whether it exceeds the allowable value. When there is an excessive change or beyond the allowable range, the corresponding treatment should be carried out, otherwise, proceed to the next step.
- 80% standard load test. The vehicle is loaded with 80% of the load of the design standard Bailey bridge, and the vehicle is driven to the center of the maximum span to stop, and the deflection and deformation values of the measuring point are recorded. If the measured deflection does not exceed the maximum allowable range, proceed to the next step.
- Standard load test. Record the corresponding value at the center of the maximum span of the vehicle whose weight is the design-approved load. This value is the deflection under load. If the measured deflection does not exceed the allowable value, proceed to the next step.
- Overload test. Load the vehicle with 120% of the design standard approved load weight, park the vehicle at the center of the largest span of the Bailey Bridge, and record the relevant data.
By comparing and analyzing the recorded test values, it meets the relevant value range in the Chinese bridge standard GJB1162-91. The main components of the CB200 Bailey Bridge have a high degree of standardization, good interchangeability, high rigidity, and convenient assembly and connection. The bridge deck is smooth and the vehicle traffic performance is good. Through the Bailey bridge load capacity test, it can be seen that the strength, rigidity, and overall stability of the 45.72m single-span and single-lane Bailey Bridge meet the design requirements, pass the test, and can be put into use.