【正文】 strength bolts for us. High strength bolt mainly control the quality of the project including the minimum load detection, pretension the reinspection, torque, the reinspection torque coefficient and coefficient of slip resistance test. Steel material mechanical test and chemical analysis results, should ply with the provisions of the corresponding procedures. B, steel structure detection (a) steel structure thickness of section is measured by thickness gauge Steel structure because of the influence of the processing accuracy and section of corrosion, the steel structure of the section thickness is often some changes. Especially corrosion section thinning, bearing capacity decreased, the structure safety degree of influence is very big. Therefore, thickness of section steel structure determination is an important task. At present, the thickness measurement is a kind of caliper, one is thickness is measured by thickness gauge. Described below using ultrasonic thickness gauge Numbers of cross section thickness measuring method. The ultrasonic pulse reflection method. Ultrasonic spread from a homogeneous medium to another kind of homogeneous medium, boundary will occur on the surface of acoustic reflection, from the launch of the ultrasonic probe, after a delay block into the piece under test, ultrasonic wave arrived at interface, and be reflected back, be received through delay block and probe receives, measured between the transmitted pulse to the received pulse time, deduct the delay time, according to the relationship between sound velocity, time, distance, and the thickness of the piece being tested. That is, the thickness of the instrument display values. Such as ~ 100 instrument shows a value of mm, mm, the accuracy is mm. (2) the steel structure coating thickness measurement And in identification of steel structure coating quality and coating thickness is an important parameter, therefore determination of coating thickness is an important project. Coating thickness measurement generally magic thickness tester is used to test, have the product at home and abroad. Domestic magic coating thickness gauge material testing in tianjin factory of the product, name is QCC type A magic thickness gauge. With magic thickness gauge, adjusted the instruments, make it has normal work performance. Must first determine the measurement range, the first leg of 0 ~ 50 microns, the second leg of 0 ~ 500 microns. When measured in the probe contact coating to be tested. Determination of first to remove the coating surface dirt and oil, in case influence precision. When testing coating according to the specific circumstances to determine, first, through the instrument to determine presence of coating, because coating under the action of a longterm environmental damage until disappear coating, coating or not is an important parameter of coating. Because the presence of residual coating is an important structure corrosion level line, is also a permanent evaluation of important boundaries. (3) the steel structure roof deflection measurement General span steel roof truss is larger, such as 21, 24, 30 m), measuring the deflection of more difficult, have to use a lot of force to