05-11-2016, 11:52 AM
1465201357-LOADTESTINGOFABRIDGESUPERSTRUCTURE.docx (Size: 14.83 KB / Downloads: 5)
The load test shall be carried out to atleast one full superstructure check and establish the serviceability and working strength of the superstructure.
1. Test Load: The “Test Load” is the equivalent static load equal to the impacted working design Live Load (applied in addition to all dead loads) placed for maximum effect (bending moment, shear, deflection, etc. as the case may be) and applied either through an appropriate test loading truck or through loading platforms resting on tyre contact area plates simulating and actual areas of wheels.
2. Load Application and Testing Procedure
a. Fix deflection gauges (supported on unyielding supports) under the superstructure, just touching its soffit, at the pre-marked critical ‘Points’.
b. Apply the test load in five equal increments (including the weight of platforms of trucks in the first increment), allowing about two hours in between completion of one load increment and commencement of the next. About an hour after completing a load increment, note the deflections and any crack patterns together with maximum crack widths.
c. After measuring the deflections, etc. one hour after applying the fifth increment, i.e. the final load increment, keep the test load maintained for about 24 hours and again measure the deflections and crack widths (if any)
d. Remove the test load in five equal decrements, allowing about two hours in between completion of one load decrement and commencement of the next. Note the deflections and crack widths (if any) at the end of each load decrement.
e. Note the deflection and crack widths (if any – 24 hours after removal of the test load in order to see whether the recovery is completed or there is any residual deflection, etc.
3. Acceptance Criteria
a. Increase and decrease in deflections at a point shall follow a linear relations, with actual deflection not exceeding the theoretically estimated ones by more than 10%.
b. The maximum crack width in reinforced concrete shall not exceed 0.25 mm to 0.30 mm (but no cracks in case of prestressed concrete).
c. The deflection at the end of the 24 hours of maintaining the test load shall not exceed the corresponding values at the start of this 24 hours period by 5% and
d. The residual deflection at any point 24 hours after compete unloading shall not exceed 10% of the maximum observed deflection at the point (i.e. recovery: 90% or more);
e. The cracks in reinforced concrete shall close upon removal of test load but may not completely disappear.