In-use bridge \ gantry crane girder deflection under Investigation and Analysis

According to GB/T14405-1993 "General  overhead bridge crane " and GB/T14406---1993 "universal  gantry crane   requirement, the new factory bridge, gantry crane girder span camber should be (0.9 / 1000 ~ 1.4/1000) S, and the maximum camber should be controlled across the S / IO range. Our company has years of l0, 106 Taiwan major cities to test bridge crane survey found: Average crane factory camber is S/IO00 (where S is the crane span), the use of a 20% reduction after 1 year, the use of 2 ~ 5 years decreased by 30% to 50%, more than 5 years reduction of 60% or more, the use of l0 years camber disappear, and then began to scratch down below the horizon. Deflection of the main beam on the crane and to what extent it is not allowed to use, currently there is no clearly defined national standards, so testing in a bridge girder gantry crane should attract attention.

First, according to GB6067 - 1985 "crane safety regulations" scrap metal structures Standard No. 4 states: "The main force component due to plastic deformation, so that institutions can not properly working safety
Run-time, if not repaired, should be scrapped. For general overhead crane, when the car is in the mid-span and at the rated load, the lower girder span deflection values   under the horizon, to span 1/700, if not repaired, should be scrapped. "And according to GB381l-l983" Crane design specifications "in the electric single, double girder  bridge crane  type (including gantry cranes and crane) static rigidity provides:" When fully loaded car (or electric hoist) located at midspan, main beam (main truss) As rated lifting load and trolley (or hoist) caused weight across the vertical static deflection l, shall meet the following requirements: working-level A5 or A5 below cranes, Y ≤ S/700 ; working-level A6 cranes, Y ≤ S/800; working-level A7, A8 crane Y ≤ S/IO00; (where S is the crane span). "Can be inferred from the above provisions: ignoring the car weight (or hoist) under the premise of the rated load caused by the main beam deflection values   under the metal structure without exceeding its rated load scrapped due under the main beam deflection values that at this time in the main beam under no-load condition scratch in the security area, or that the state of the main beam under load deflection is in an unsafe area, then they should be rated for the load test equipment to verify whether the main beam should fix the standard, that is for working-level in A5 or A5 below crane, when it reaches the main beam deflection under S/700 a Y = 0, that is under the main beam deflection occurs, it the device should be rated load test to verify whether the main beam should fix the standard; For working-level A6 crane, when it reaches the main beam deflection under .S/700 a Y: S/5600 when rated load of the equipment should experiment to verify whether the main beam should fix the standard; For working-level A7, A8 crane, when it reaches the main beam deflection under S/700 a Y: 3S/7000, then deal with the piece of equipment rated load test to verify whether the main beam should fix standards.

Since crane design and material selection of the different methods and other reasons, the main beam crane static rigidity at rated load deflection caused by the actual values   will be different the next, so that the main beam at no load, the actual deflection values   have been exceeded under the above defined values, but during the rated load experiments, the actual values   may not reach down deflection retirement provisions of the standard metal structure, so this value is only when in use as a bridge girder gantry crane for a rated load experiments reference value, and not as a right in with the bridge, the main beam gantry crane scrapped criteria.