STEEL STACK CODE
STEEL STACK MAC

The first Upper Mac Days will be Friday, June 23, through Sunday, June 25, in Grange Park, the township's 165-acre open space. A new ArtsQuest festival in conjunction with Upper Macungie Township will bring three days of family-friendly music, games, food and amusements, it was announced Tuesday. Please contact FE Consultants if you require additional information or assistance with the design of large steel stacks or chimneys.UPPER MACUNGIE TWP., Pa. Hence, using wind loads calculated via AS1170.2 directly with the design codes can prove to be troublesome unless the inputs are carefully selected.

STEEL STACK CODE

In summary, the strength assessment for each design code has been developed specifically for use with the method provided to calculate wind loads.

CICIND is a limit states design code, which is considered more appropriate for large stacks given that second order effects are often significant.

Therefore, the designer can confidently manipulate this factor to account for different ARI’s.

CICIND explicitly explains the derivation of the design factor for stresses generated by wind loads.

CICND uses a common exponent to describe the variation of wind speed with height.

AS1170.2 contains region specific data to characterise wind loads, in particular the terrain height multiplier.

The following issues should be considered with the use of AS1170.2 in combination with CICIND for the following reasons Hence, to directly compare wind loads generated on the stack, the same input velocity must be used so that the same damping is applied. The other point to note is that the wind load predicted by each code is dependent on the inherent damping of the structure, which, in the case of aerodynamic damping, is dependent on the wind velocity. Further, when supplying the expected base over-turning moment due to wind loads for the civil/structural designer it must be clearly communicated on which basis the loads have been calculated. With that said, the allowable stress includes a safety factor of 1.5, which mirrors the CICIND factor for increasing stresses in tropical storm regions so the designer must be careful comparing any wind load generated using AS1170.2 directly with CICIND and ASME STS-1-2011 allowable stresses as neither have been developed using typical Australian Standard ARI’s. In ASME STS-1-2011 there is no explicit mention of the potential for the 50 year ARI wind load to be exceeded.

This should be compared against the desired ARI required based on the structure’s importance level.

For tropical storm regions and non-critical chimneys the ARI is effectively increased to 300 years for wind region C and 225 years for wind region D. This is explicitly outlined in the commentary for the code and effectively increases the ARI. In CICIND the stresses generated by the 50 year ARI wind load are factored up to account for the potential that this wind load will be exceeded. Both CICIND and ASME STS-1-2011 use a 50 year annual recurrence interval as the basis for the calculation. In addition, it is important to recognise at which point in the analysis the stresses generated by these loads are compared against the code allowable stresses.Ī major difference is the selection of the annual recurrence interval (ARI). When making this judgement it is important to recognise the differences in the methods used by all three codes to calculate the loads. In this regard, the engineer must make a judgement on whether these wind loads should be substituted with those calculated by the Australian wind code: AS1170.2. Importantly, both codes present different methods of calculating the wind load on the stack. Both codes present methods to calculate the strength of the stack shell that is unique to other steel structures. The two most commonly used codes are CICIND – Model Code for Steel Chimneys and ASME STS-1-2011 – Steel Stacks.

Steel stack