According to the nature of test load, bridge load test can be divided into static load test and dynamic load test.

Although the test on the purpose and content are different,for bridge structure that give priority to bear vehicle load ,the two kinds of the nature load test are the same important for comprehensive analysis and understanding the working state of bridge structure.Static load test can arrange more points to facilitate a more comprehensive analysis of the structure of the force.Dynamic load test is necessary for researching bridge structure under vehicle load or other power load vibration characteristics .

In the bridge dynamic load test, according to the mode of action, the dynamic load can be divided into impact load , vibration load and braking load.We can choose the way of loading according to the specific requirements.

At present, in the practice of bridge design, for the effects of dynamic action that caused by vehicle load,we consider that by adopting load impact factor.The impact factor that take span or load as parameter is a comprehensive technical indicator which includes various influencing factors.The range of impact factor usually confirmed by bridge dynamic load test and comprehensive analysis.

1 The main content of load test

Bridge load test is a complicated and meticulous work with high technical content, which should carefully analysis and survey based on the purpose of load test, if necessary conduct relevant theory analysis .The main content of load test are:

(1) the load test plan (including the static and dynamic load test program);

(2) the load test station setup and equipping test instruments and equipment;

(3) the load test load level control and safety test process control;

(4) test data analysis and the structure performance evaluation;

(5) test report writing.

2 The basis of load test

Highway bridge load test should based on the regulations, technical standards and design specifications about highway bridge that issued by the country and ministry of communications.For some bridges that adopt new structure,new material and new technology,if there are no relevant provisions, we can borrow abroad or domestic relevant provisions of the relevant specifications and codes in other industries.Our country's construction engineering standards and specifications can be divided as follows:

(1) Comprehensive basic standards, such as “the engineering structure reliability design standard "(GB 50153-92), is a professional guide to establish basic standards of national standard.

(2)Professional basic standards, such as "the technical standards of highway engineering" (JTJ 001-97), "the highway engineering reliability design standard "(GB/T 50283-1999), is to guide the professional general standard and special standard of industry standard.

(3)Professional common standards:

Highway bridge design general specification (JTJ 021-89)

Highway brick and concrete bridge design code (JTJ 022-85)

Highway reinforced concrete and prestressed concrete bridge design code (JTJ 023-85)

Highway bridge ground and foundation design code (JTJ 024-85)

Highway bridge steel structure and wood structure design code (JTJ 025-86)

Highway engineering specification earthquake resistant design code (JTJ 004-89)

Highway engineering quality inspection evaluation standard (JTJ 071-98)

Highway old bridge carrying capacity appraisal methods (trial) (1988).

(4)Special professional standards:

Highway cable-stayed bridge design specifications (trial) (JTJ 027-96)

Highway suspension bridge design code (making)

Long-span highway Bridges wind-resistant design code (making)

Long-span highway bridge seismic design code (making)

We should point out that, some of the professional general standard and special standard above are under revision, during the load test we should carried out according to the new standard.