R = rain loads
For temporary conditions that persist for one month or less, rain loads need not be considered for construction during months with historical rainfall averages of less than 1 in. (25 mm) per month. Otherwise, rain loads must be considered. Care must be taken to keep drains clear and to provide unobstructed paths for rainwater to flow from structures. Water that accumulates in unfinished structures should be removed.
I = ice loads
For construction during seasons when structures are not susceptible to ice accumulation, ice loads need not be considered. Structures that will be enclosed when construction is complete and are designed for live loads of 1.0 kPa or more need not be considered as ice-sensitive structures while open during construction. Otherwise, ice loads must be considered.
However, should ice accumulate on these structures, it should be removed. Or, the construction and live loads applied to the structure should be reduced by an amount corresponding to the weight of the accumulated ice.
E = earthquake effects
It is not reasonable to require seismic resistance for temporary works where major earthquakes are infrequent or unlikely. This means that earthquake loads need not be considered, unless required by the competent authority and the mapped Risk-Targeted MCER, 5% damped, spectral response acceleration parameter equals or exceeds 0.40 at a period of 1 s, S1, as defined in Section 11.4.1 of the ASCE/SEI 7-10 code. It has to be considered that the seismic data is not equivalent between the ASCE and NBCC codes because of different damping criteria used.
In short, the loads on structures during construction may be considered practically in such a way:
- Loads due to construction activities must be aligned with the construction strategy and evaluated with the construction team in accordance with the ASCE 37 standard or at least as a guideline.
- Environmental loads do not need to be considered if they definitely will not happen during construction, otherwise
- Environmental loads must apply with certain reduction factors based on the construction schedule.
For more information about this topic, please contact us. The BBA team has a solid background in structural engineering, as well as constructability analysis and technical assistance during construction.
NBC 2015 – National Building Code of Canada
ASCE 37-14 – Design loads on Structures during Construction
EN 1991-1-6 – General actions – Actions during execution