China Prefabricated Steel Structure for Workshop Office Building

1. Detection of component size and flatness. Each dimension is measured at 3 parts of the component, and the average value of the 3 locations is taken as the representative value of the dimension. The dimensional deviation of steel components should be calculated based on the dimensions specified in the design drawings; the allowable value of the deviation should comply with the requirements of its product standards. The deformation of beams and truss members includes vertical deformation in the plane and lateral deformation out of the plane, so the straightness in both directions must be detected. The deformation of the column mainly includes the tilt and deflection of the column body.

When inspecting, visual inspection can be performed first. If any abnormalities or doubts are found, a wire or thin wire can be tightened between the fulcrums of the beams and trusses, and then the sag and deviation of each point can be measured; the inclination of the column can be measured with a theodolite or lead. vertical measurement. Column deflection can be measured by stretching a wire or thin wire between the fulcrum points of the member.

2. Detection of steel corrosion

Steel structures are prone to rust in humid, water-containing and acid-alkali-salt corrosive environments. Rust causes the steel section to weaken and the bearing capacity to decrease. The degree of corrosion of steel can be reflected by changes in its cross-sectional thickness. Instruments used to detect steel thickness (rust must be removed first) include ultrasonic thickness gauges (sound speed setting, coupling agent) and vernier calipers. The ultrasonic thickness gauge adopts the pulse reflection wave method. When an ultrasonic wave propagates from one uniform medium to another, it will be reflected at the interface. The thickness gauge can measure the time from when the probe emits the ultrasonic wave to when it receives the interface reflection echo. The propagation speed of ultrasonic waves in various steel materials is known, or determined through actual measurements. The thickness of the steel is calculated from the wave speed and propagation time. For digital ultrasonic thickness gauges, the thickness value will be directly displayed on the display.

3. Detection of surface defects of components-magnetic particle inspection

The basic principle of magnetic particle inspection: When there are defects inside the steel structure, such as cracks, inclusions, pores and other non-ferromagnetic substances, the magnetic resistance is very large and the magnetic permeability is low, which will inevitably cause the distribution of magnetic lines of force to change. The magnetic field lines at the defect cannot pass through and will bend to a certain extent. When defects are located on or close to the surface of the steel structure, they will leak through the surface of the steel structure into the air to form a fine leakage magnetic field.

The intensity of the leakage magnetic field mainly depends on the intensity of the magnetizing field and the influence of defects on the vertical cross-section of the magnetizing field. Magnetic powder can be used to display or measure the leakage magnetic field, so as to analyze and determine the existence, location and size of defects.