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CMC INTERNATIONAL
Changzhou Cranes Mechanical Electrical Engineering Co., Ltd. Sandy(Manager) Mobile no. 0086-18001505166 Tel: +86-519-81886887 Fax: +86-519-85163887 Add: No.8-20 Shunyuan road, Xinchen industrial park, Xuejia town, Xinbei district, Changzhou city, Jiangsu province, P.R.China. Postalcode: 213125 Email: kaison1110@qq.com craneschina@gmail.com info@craneschina.cn |
Design Loads Analysis for New Container Cranes Girders
ANALYSIS - GENERAL CONSIDERATIONS CRITERIA The strength of the crane rail girder shall be calculated using the strength design provisions of the Building Code Requirements for Reinforced Concrete ACI 318-89 (Revised 1992) (ACI code). The structural strength of piles shall be calculated using the provisions of Section The applied loadings are multiplied by load factors consistent with the ACI code. Crane dead load is treated as an ACI dead load because the weight of crane is known. LOADINGS The loads on the crane rail girder include the container horizontal and vertical crane wheel loads, loads on crane stowage hardware, the wharf dead load tributary to the girder, and wharf live load tributary to the girder. The components of crane loads shall be applied to cause the maximum load. The load components are shown so the crane wheel loads may be calculated after the crane designer provides the actual crane load data. The design wheel load is shown in the Design Strength section. METHOD OF ANALYSIS The analysis used shall include the effects of the elastic deflection of the piles when determining forces in the crane rail girder structure. The maximum effect of the factored loads shall be determined. The beam-on-elastic-foundation method shall be used to design continuous spread footings that support crane rails supported on continuous spread footings. STIFFNESS The girder may be modeled with cracked section properties. Cracked properties would be used because the girder moments with an uncracked section are high enough to crack the section. In the analysis, the support stiffness for the girder shall be modified to include the effects of soil stiffness. The pile stiffness may be modeled with uncracked section properties since the pile is prestressed and under axial compression. SPAN LENGTH Moments may be calculated at the face of the piles in accordance with ACI. The effective length of the crane girder is greater than the pile spacing, since the piles are modeled as elastic supports. Ordinarily, the crane girder would be designed as a deep beam if the piles didn¡¯t deflect, since the distance between piles is relatively short. However, the girder need not be designed as a deep beam, since the elastic supports cause the girder to spread the load over several piles. Allowance should be made in the girder span length for pile driving tolerance. The usual tolerance is 6 inches. ARRANGEMENT OF LOAD The crane design load shall be moved along the girder to determine the most critical load position. DESIGN STRENGTH The design strength of the girder for moment and shear shall be determined using the provisions of Chapters 10 and 11 of the ACI code. The pile capacity shall be checked for two cases: (1) structural strength of the pile, and (2) the bearing capacity of the soil. The pile strength may be taken from interaction diagrams for the pile that are in conformance with ACI and PCI provisions. The soil strength shall be provided by a geotechnical engineer. DESIGN LOADS The recommended loads are the maximum expected for a dual hoist post-panamax 40 LT container crane with a rail gage of least 90'. The loads include reasonable contingencies. These recommendations apply to typical conditions. The proper loads should be developed for each specific situation. If there are special conditions such as heavy lift or a wheel gage less than 90', these design recommendations should be evaluated for their suitability for the specific situation. The design loads in Table 2 should be considered a minimum. The crane supplier should be required to supply the basic loads so that the factored loads can be calculated using Table 1 and compared to the criteria. MISSING PILE In the design of a new waterside crane girder, there should be an economic analysis made to determine the cost of designing for one and two missing piles. The incremental cost should be determined to: design the wharf for the loads in Table 2 with one pile missing; and design the wharf for the loads in Table 2 with two piles missing. Once the cost is reported to the port, the port will decide if some provision for missing piles should be included in the design. If no provision is made for missing piles, then the following information shall be provided to the port on the wharf design drawings: |