20.1 Need for Testing
Testing of structures, members or components of structures is not required when designed in accordance with this standard. Testing may be accepted as an alternative to calculations or may become necessary in special circumstances.
Testing of a structural system, member or component may be required to assist the design in the following cases:
a) When the calculation methods available are not adequate for the design of a particular structure, member or component, testing shall be undertaken in place of design by calculation or to supplement the design by calculation;
b) Where rules or methods for design by calculation would lead to uneconomical design, experimental verification may be undertaken to avoid conservative design;
c) When the design or construction is not entirely in accordance with sections of this standard, experimental verification is recommended;
d) When confirmation is required on the consistency of production of material, components, members or structures originally designed by calculations or testing;
e) When the actual performance of an existing structure capacity is in question, testing shall be used to confirm it.
20.1.1 Testing of structural system, member or component shall be of the following categories:
a) Proof testing — The application of test loads to a structure, sub-structure, member or connection to ascertain the structural characteristics of only that specific unit.
b) Prototype testing—Testing of structures, sub-structures, members or connections is done to ascertain the structural characteristics of a class of such structures, sub-structures members or connection, which are nominally identical to the units tested.
20.2 Types of Test
20.2.1 Acceptance Test
This is intended as a non-destructive test for confirming structural performance. It should be recognized that
the loading applied to certain structures might cause permanent distortions. Such effects do not necessarily indicate structural failure in acceptance test. However, the possibility of their occurrence should be agreed to before testing.
The load for acceptance test, shall be determined from:
(Self weight) + (1.15 Remainder of the permanent load) + (1.25 Variable load)
20.3 Test Conditions
a) Loading and measuring devices shall be calibrated in advance.
b) The design of the test rig shall be such that:
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Loading system adequately simulates the magnitude and distribution of the loading,
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It allows the specimen to perform in a manner representative of service conditions,
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Lateral and torsional restraint, if any, should be representative of those in service,
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Specimen should be free to deflect under load according to service condition,
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Loading system shall be able to follow the movements of the specimen without interruption or abnormal restraints,
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Inadvertent eccentricities at the point of application of the test loads and at the supports are avoided.
c) Test load shall be applied to the unit at a rate as uniform as practicable.
d) Deflections should be measured at sufficient points of high movements to ensure that the maximum value is determined.
e) If the magnitude of stresses in a specimen is to be determined, the strain at the desired
location may be measured and the corresponding stress calculated.
f) Prior to any test, preliminary loading (not exceeding the characteristic values of the relevant loads) may be applied and then removed, in order to set the test specimen on to the test rig.
20.4 Test Loading
20.4.1 Where the self-weight of the specimen is not representative of the actual permanent load in service, allowance for the difference shall be made in the calculation of test loads to be applied.
20.4.2 On the attainment of maximum load for either acceptance or strength tests, this load shall be maintained for at least 1 h. Reading of load and deflection shall be taken at intervals of 15 min and the loading shall be maintained constant until there is no significant increase in deflection during a 15 min period or until at least 1 h has elapsed.
20.4.3 The test load shall be equal to the design load for the relevant limit state in proof testing.
20.4.4 The test load in prototype testing shall be equal to the design load for the relevant limit state as multiplied by the appropriate factor given in Table 27.
20.5 Criteria for Acceptance
20.5.1 Acceptance for Strength
The test structure, sub-structure, member or connection shall be deemed to comply with the requirements for strength if it is able to sustain the strength test load for at least 15 min.
It shall then be inspected to determine the nature and extent of any damage incurred during the test. The effects of the damage shall be considered and if necessary appropriate repairs to the damaged parts carried out.
20.5.2 Acceptance for Serviceability
The maximum deformation of the structure or member under the serviceability limit state test load shall be within the serviceability limit values appropriate to the structure.
| Sl No. | No. of Similar Units to be Tested | For Strength Limit State | For Serviceability Limit State |
|---|---|---|---|
| (1) | (2) | (3) | (4) |
| i) | 1 | 1.5 | 1.2 |
| ii) | 2 | 1.4 | 1.2 |
| iii) | 3 | 1.3 | 1.2 |
| iv) | 4 | 1.3 | 1.1 |
| v) | 5 | 1.3 | 1.1 |
| vi) | 10 | 1.2 | 1.1 |