Detail of GB/T 25851.2-2023

Introduction of GB/T 25851.2-2023

Mobile cranes - Experimental determination of crane performance - Part 2: Structural competence under static loading 1 Scope This document applies to mobile construction-type lifting cranes utilizing a) rope supported, lattice boom attachment or lattice boom, and fly jib attachment (see Annex E, Figure E.3), b) rope supported, mast attachment and mast mounted boom, and fly jib attachment (see Figures E.1 and E.2), or c) telescoping boom attachment or telescopic boom and fly jib attachment (see Figure E.4). Mobile crane manufacturers can use this part of ISO 11662 to verify their design for the mobile crane types illustrated in Figures E.1 through E.4. This test method is to provide a systematic, non-destructive procedure for determining the stresses induced in crane structures under specified conditions of static loading through the use of resistance-type electric strain gauges, and to specify appropriate acceptance criteria for specified loading conditions. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 9373:1989, Cranes and related equipment - Accuracy requirements for measuring parameters during testing 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 Strain relative elongation or compression of material at any given point with respect to a specific plane passing through that point, expressed as change in length per unit length (m/m) 3.2 stress S internal force per unit area resulting from strain Note 1: The unit expressed in pascals (Pa) or newtons/square meter Note 2: For this document, megapascals (Mpa) will be used for brevity. 3.3 Stress at the yield point Sy stress at which a disproportionate increase in strain occurs without a corresponding increase in stress Note: For purposes of this code, yield point is to be considered as the minimum 0.2 % offset tensile yield point or yield strength specified by the appropriate standard for the material used. 3.4 critical buckling stress Scr average stress which produces an incipient buckling condition in column-type members (See Annex C) 3.5 initial reference test condition defined no-stress or zero-stress condition of the crane structure after the “break-in” as established by a) supporting the structure on blocking to minimize the effects of gravity, or b) the crane structure components in an unassembled state or any alternate method that will establish the zero-stress condition. Under this condition, the initial reference reading for each gauge is obtained, N1. 3.6 dead load stress condition completely assembled crane structure on the test site and in the position or attitude, ready to apply the specified live load at the specified radius Note 1: Under this condition, the second reading for each gauge is obtained, N2. Note 2: The hook, hook block, slings, etc. are considered part of the suspended load but may be supported by the crane when this reading is taken. For dead load purposes, the hook in the “home” position - suspended from the crane without lifting the test load. This position has to be repeated after placing the load back on the ground (see 9.4.4). 3.7 dead load stress S1 stress computed as defined in Clause 10 by using the difference in the readings obtained in 3.6 and 3.5 for each gauge (N2 - N1) 3.8 working load stress condition completely assembled crane structure on the test site and in the specified position, supporting the specified rated load Note: Under this condition, the third reading for each gauge is obtained, N3. 3.9 working load stress S2 stress computed as defined in Clause 10 by using the difference in the readings obtained in 3.8 and 3.5 for each gauge (N3 - N1) 3.10 resultant stress Sr stress induced in the structure as a result of dead load stress (S1) or the working load stress (S2), whichever is greater in absolute magnitude 3.11 column average stress Sra direct compression stress in a column or the average stress computed from several gauges located at the section (see Annex B) 3.12 column maximum stress Srm maximum compression stress in a column computed from the plane of buckling as established from several gauges located at the section (see Annex B) 3.13 loadings application of weights and/or forces of the magnitude specified under the condition specified 3.14 load radius horizontal distance between the axis of rotation of the turntable of the crane and the vertical axis of the hoist line or load block when the crane is erected on a level site 4 Symbols and abbreviated terms E modulus of elasticity K effective length factor for a column L un-braced length of column Lb length of boom Lj length of fly jib L1 small arbitrary projected length of fly jib along x-axis L2 projected length of fly jib strut along y-axis n strength margin n1 strength margin, Class I area, ratio of yield strength to resultant or equivalent stress n2 strength margin, Class II area, ratio of yield strength to resultant or equivalent stress n3 strength margin, Class III area, derived from an interaction relationship N1 strain reading at initial reference test condition N2 strain reading at dead load stress condition N3 strain reading at working load stress condition r radius of gyration RL rated load as specified by manufacturer “R” plane (Figure 1) perpendicular to boom foot pin centreline (CL) RR rated radius as specified by manufacturer S stress

Contents of GB/T 25851.2-2023