When the number of foot bolts per saddle is 4, what does \"bolt spacing on both sides of the saddle axis\" in the SW6 saddle data refer to?
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As shown in the figure, for a certain horizontal storage tank, an saddle is selected; the number of anchor bolts required for this saddle is 4. In the SW6 saddle design, there is a column indicating the bolt spacing on both sides of the saddle’s axis. The questions now are: 1. When the number of foot bolts on a saddle is 4, what does \"the bolt spacing on both sides of the saddle axis\" in the SW6 saddle data refer to? 2. Does “bolt spacing on both sides of the saddle axis” refer to ① or ② in the diagram? Please ask an expert to help!
In the actual SW6 calculation, I chose 2.
This post was last edited by chifanyelei on 2021-3-10 at 19:57. The spacing between the two outermost bolts is relevant, with a total of 2 bolts. The two middle bolts are considered as a safety backup and are not taken into account in the calculations! The software uses the NBT47042 method for calculations; the specific values shall comply with the standard requirements.
The bolt spacing on both sides of the saddle axis is used to calculate the overturning moment caused by earthquakes; this moment is then used to determine the tensile stress in the foundation bolts, hence data ② is used
Check the stress strength of the foundation bolts as follows: 1) The foundation bolts on the same side of the two saddle axes experience tensile stresses caused by the overturning moment resulting from seismic forces (compressive stresses on the other side). 2) The anchor bolts of the fixed saddle bear the shear stress caused by seismic horizontal forces (sliding saddles do not bear it). Based on the formula for calculating the tensile stress induced by the overturning moment of seismic forces, the bolt spacing is conservatively taken as 1. In both cases, the number of anchor bolts subjected to force is 4.
The standard formatting of these saddles is becoming increasingly poor in quality
Transferred from another website – According to the standards for horizontal containers, it is the lateral loads acting on the container (primarily seismic loads) that generate bending moments, resulting in a lifting force on one side. If this lifting force is less than half of the device’s weight, the device tends to tip over. In such cases, the calculated stress on the bolts should be greater than 0, indicating tensile stress. This tensile stress is borne by the bolts on one side of the saddle; whether there are two supports or multiple supports, only half of the bolts experience tensile stress. If two bolts are symmetrically arranged in a saddle, only the tensile stress on one bolt is considered. For a support with 2 bolts (of different spans) on one side, the support standards do not specify how to account for the distribution of bolt loads in the calculation of tensile stress. I recommend considering only the outermost bolts (the sum of those on the outside of all supports) and performing the verification using the formula standard for horizontal tanks. If the number of bolts on the outermost side does not meet the requirements, it is possible to consider distributing the bolt tensile stress according to the span ratio for verification. However, the shear stress check is performed only based on the total number of bolts at the fixed supports (4).