Testing of bridge structures
In accordance with SNiP 3.06.07-86 tests for acceptance into operation should be run on bridges with large spans, as well as with the experimental and first time used designs. Tests are held with facilities used when decisions relating to the operation of the installations, cannot be obtained only by calculation according to the surveys.
Test facilities are carried out in several stages:
- Selection of the test load. The value of the test load in static tests is chosen so that in accordance with SNiP 3.06.07-86 efforts that occur at the ends of the test design, at least 70% (para. 3.8) and not more than 100% (para. 3.7) efforts from normative live loads with full dynamic coefficient.
- Development of the program of testing
- Calculation in the case of test load. Calculation of theoretical values of stress-strain state for each loading is done in preparation for the tests using software packages that implement the finite element method.
- Static tests. In accordance with the programme of tests in specific sections of the span (usually in the middle of the span, and for bearing structures over the supports) tensile sensors are installed.
- Dynamic tests. Deformations of structures that occur during the load passes with different speeds detect in real time during the dynamic tests. To simulate the roughness of pavement small step through which dump truck moves with different speeds is used.
- Processing of the results. Conformity assessment of the work under the influence of temporary construction loads of theoretical assumption`s behind the calculation is carried out. Rate of construction in static tests is a constructive factor K, i.e. the ratio of experimental value of the parameter to its theoretical value. Operational reliability is considered as secured if it’s relation to stress and strain does not exceed 1. During dynamic testing records are processed in the program "Spectrum", developed at the Institute IMIDIS.
- Conclusion. Decision is drawing about the possibility of acceptance of construction into operation under design load.
- Scientific and technical report. The report provides detailed data on the technical state of buildings, formulated conclusions on basic consumer properties of constructions (load capacity, traffic safety and comfort, durability). In addition the Passport of structure compiled.
For each section, a group of four or six sensors connected to the radio module by the wires
Uploading designs in accordance with the schemes developed in the test program. Laden trucks (from 20 to 40 tons each) used as the load.
Radio signals from sensors on the server radio module are received by your computer.
KIS-IMIDIS system developed at our Institute, records the stresses and deflections for each of the sensors.
Beside this in some cases according to the results of test load moving on lanes it is possible to draw experimental lines of influence in those sections where sensors installed. The measurement results are compared with settlement values received under test load.
At the same time deflection measurements are made on bridges with large spans using KIS-IMIDIS and transit.
As a result of the dynamic tests the experimental values of the dynamic factor, periods of natural oscillations of structures and, if necessary, the logarithmic decrement of the oscillations are taken.