The downward adjustment of hogging moments above is limited to prevent any increase in the maximum span moments of end spans. The corresponding span moments are adjusted downward to maintain static equilibrium.
The maximum hogging moment at each column or internal support is adjusted downward by the specified maximum percentage. The redistribution of moments and shear forces procedure is performed as follows: 1. The downward distribution method aims to reduce the hogging moments at the columns without increasing the sagging moments at midspan. The moment envelopes are calculated for pattern loading and then redistributed using the procedures explained in the following text. Note: No moment redistribution is done for serviceability limit state calculations.
If the method of moment redistribution is set to 'optimised', the design moments are further minimised by redistributing span moments upward as we ll. Moment redistribution Ultimate limit state bending moments are redistributed for each s pan by adjusting the support moments downward with the specified percentage. This adjustment applies to cases where 1.5×DL > 1.2×DL + 1.6×LL or, in other words, LL 1.4×DL + 1.6×LL or, in other words, LL < 6%×DL. lightly loaded roof slabs, this load case can be incorporated by increasing the entered dead load or increasing the ULS dead load factor. In cases where the dead load is large in comparison with the live load, e.g. This load case is not considered during the analysis – if required, you should adjustment the applied loads manually. The South African loading code, SABS 0162 - 1989, prescribes an additional load case of 1.5×DL. a ULS load factor of 1.0 for minimum dead load and the maximum load factor specified for maximum dead load. The program uses the more approach given by the BS 8110 codes at all times, i.e. In contrast, the BS 8110 codes suggest a minimum ULS dead load factor of 1.0 for calculating the minimum ultimate dead load. SABS 0100 - 1992 suggests a constant ULS dead load factor of 1.2 for all pattern load cases. The following are special considerations with pertaining to design using SABS 0100 - 1992: Note: The case where any two adjacent spans are loaded with maximum load and all other spans with minimum load, as was the case with CP 110 - 1972Īnd SABS 0100 - 1980, is not considered. Unequal spans are loaded with the maximum design load and equal spans loaded with the minimum design dead load. The following load cases are considered (the sketch uses the load factors applicable to BS8110):Īll spans are loaded with the maximum design load.Įqual spans are loaded with the maximum design ultimate load and unequal spans with the minimum design dead load. Unity load factors are used at serviceability limit state. Pattern loading At ultimate limit state, the dead and live loads are multiplied by the specified ULS load factors (see page 14). Note: No checks are made for the slenderness limits of columns or beam Columns can optionally be specified below and above the beam/slab and can be made pinned or fixed at their remote ends. Section properties are based on the gross uncracked concrete sections. Sub-frame analysis A two-dimensional frame model is constructed from the input data. Guidelines for detailing: 'Standard Method of Detailing Structural Concrete' published by the British Institute of Structural analysis General principles: BS 4466 and SABS 082. Reinforcement bending schedules are generated in acc ordance to the guidelines given by the following publications: Reinforcement Reinforcement can be generated for various types of beams and slabs, edited and saved as Padds compatible bending ĭesign codes The following codes are supported: At ultimate limit state, moments and shears are redistributed to a specified percentage. Entered dead and live loads are automatically applied as pattern loads during the analysis. Spans can have constant or tapered sections. Cross-sections can include a mixture rectangular, I, T and L-sections. You can design structures ranging from simply supported single span to twenty-span continuous beams and slabs. Theory and application The following text gives an overview of the theory and application of the design ĭesign scope The program designs and details continuous concrete beams and slabs. Complete bending schedules schedules can be generated for editing and printing using Padds. The design incorporates automated pattern loading and moment redistribution. The Continuous Beam and Slab Design module is used to design and detail reinforced concrete beams and slabs as encountered encountered in typical building projects.
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