Bridge load test shall be conducted in three stages, namely planning and preparation stage, load and test stage, analyzed and summarized stage.
Planning and preparation stage is a necessary condition for the smooth conduct of bridge load testing.Bridge load test and bridge design have a very close relationship with engineering construction, modern bridge engineering technology put forward higher requirements on test techniques, test plans and organization,therefore, this stage's work is extensive and detailed.Practice has proved that the success of the entire test depends to a large extent on the preparation work before the test.
The main work of planning and preparation stage are: collect and research relevant technical documents on bridge test,inspect the current situation of the test bridge and environmental conditions,develop test programs and test procedures,determine the test organization and staff,constitutes of the test system, equipping and calibration of instruments and the necessary equipment preparation work.
Before formal load test,we should make preparations as followings:
1 The choice of test hole(or pier, tower)
For the same span (or pier, tower) porous Bridges,we can chose optional typical span (or pier, tower) for loading tests.When chose,we should consider the following factors:
(1) the hole (or pier, tower) has the worst calculate stress;
(2) the hole(or pier, tower)has poorer construction quality and serious flaw or disease;
(3) the hole (or pier, tower) is convenient for setting up scaffold and measuring point or loading.
The work of chosing test hole should be combined with the survey work before planning.
2 Set up scaffold and test stand
Scaffold and test support shall be separate erection of each other,they should have enough strength, stiffness and stability.Scaffold should guarantee the safety of the staff and convenient to operate.Test support should meet the needs of instrument installating, not affecting the precision of the test because of its deformation,at the same time it should guarantee the trial is not affected by the interference of vehicles and pedestrians.Scaffold and test stand need adjusting measures to local conditions, local materials, easy to set up and disassemble, such as timber or building steel pipe support.When there is large clearance under the bridge or inconvenient to set-up fixed scaffolding for deep rivers,we can consider using portable crane, with nylon cord or steel cord on both ends fixed to the railings or sidewalks on the kerb.The whole equipment should be tested before use to ensure safe, if need repeatly use,mobile crane can made into assembled type for better transport and store.
At present, parts of the domestic have bridge special check-out car,its outstanding characteristic is fast, flexible, convenient, safe and can be used as a bridge load test mobile scaffold.
When having load test on sunny or cloudy weather,we should set facilities of keeping out sunshine at those measuring points where are direct under sunlight,in order to reduce the test error caused by the temperature change.When having load test on rainy season,in case of necessary,we should prepare rainproof facilities for instruments and equipments.
Set up temporary lab under the bridge with a trailer or tent to place data acquisition instruments and for testers as temporary office.
3 The lofting and unloading location arrangement for the static load test loading location
Before static load test,we should lofting for the loading position on the deck, so that the load test can run smoothly.If there are less loading conditions, time allows, we can temporary lofting before each loading.If there are more loading conditions,we should preloading and use different color marks the differences between different load positions.If chose truck as test load,we usually control the load position by car rear axle or axis.
The placement of static load test load unload should be arranged in advance.Unloading location selection should not only consider the convenience of add unloading , near the loading position, but also to put the load does not affect the stress of the test hole (or pier, tower), the general load can be placed within a certain distance from the abutment.For porous bridge, the load will also be parked on the bridge opening, but generally should be parked in the far distance test hole, for the degree of not affect the test.
4 Test personnel organization and the division of labor
Bridge load test is a strong technical work, we'd better find professional bridge test technical person to undertake the work,or take technical person who is familiar with the task as the backbone to test the work.The division of labor shall consider each one's specialty,the number of instrument that who are in charge of should not only convenient for observation,but also make the time needed for an observation about the same.
All person who participate in the test should be able to skillfully use the equipment that was in charged of, otherwise should exercise before the official starting.In order to make test smoothly, we shall have one test commander in chief, the other people should according to the specific situation into account.
5 Other preparations
The work of load test of safety, power supply, lighting, communication facilities, bridge traffic control etc should be according to the need of the load test to prepare in advance.
If take motor vehicles as the test load,we should book the rent car and confirm the load,test and record the parameters like vehicle type,wheelbase,axle load force as prescribed.
