Analytical Assumptions: Wind Posts and Lintels

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Under Construction

MasterSeries software makes several critical assumptions regarding wind posts and lintels (above openings) when designing wall panels. These assumptions relate to load transfer, structural behavior, stiffness, and analysis methodology.

Wind Posts

Main article 📑 Wind Posts

1. Vertical Load Transfer

No Vertical Load Support: The software assumes wind posts are "bending only or non-axial" elements. They do not transfer any vertical loads from the top of the wall to the base.

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Any vertical point loads or line loads applied to the wall at the location of a wind post are assumed to be carried entirely by the masonry panel itself, not the steel post. You must detail the connection to ensure the load goes where the software assumes it goes.

2. Composite Action vs. Acting in Unison

Not Composite: Unlike a masonry pier, a wind post is not assumed to act compositely with the wall panel (i.e. it does not form a T-section with the masonry).
Acting in Unison: The post is assumed to act in unison with the wall, adding its flexural capacity and stiffness to the overall system without being an integral material part of the leaf.

3. Yield Line Analysis and Capacity

Implicit Design: The wind post is not designed as a separate isolated member. Instead, its properties (moment capacity) are incorporated into the wall's Yield Line Analysis. The software checks if the failure mechanism involves the wind post yielding (a yield line passing through the post) or if the post is strong enough to force the yield lines to form around it (acting as a support),.
Plastic Capacity: You can choose to use the plastic moment capacity of the section. However, sources note that if the post is acting elastically (not yielding), changing this setting may not affect the result, as the post is simply providing stiffness rather than failing.

4. Stiffness and Effective Height (hef)

Assumed Stiffness Compliance: For the calculation of the wall's effective height (hef), the software assumes that any wind post you input provides the "appropriate stiffness" required by BS EN 1996-1-1 Cl. 5.5.1.2 to count as a stiffener.

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The software does not check if the post actually meets the code-required stiffness relative to the wall. It is the engineer's responsibility to verify that the post is stiff enough to reduce the panel length (L) for slenderness calculations,.

5. Continuity and Support Conditions

Support Defaults: By default, wind posts are assumed to be simply supported at the top and bottom. However, you can modify this to assume fixity at the base or a free top (cantilever).
Wall Continuity: You can specify if the wind post "breaks the continuity" of the inner or outer leaf.
- Unbroken: The software assumes the masonry is continuous over the post.
- Broken: The software assumes the masonry is simply supported on either side of the post (e.g., if movement joints are present). If you do not specify this, the analysis may assume continuity that does not exist in practice,.

6. Shear Limitations

No Out-of-Plane Shear Check: The software does not check the out-of-plane shear forces in the wind post or the wall panel. Even when wind posts are present, the software does not run an algorithm to determine the shear distribution. The user must check shear by other means.

Lintels (above openings)

Main article 📑 Openings

MasterSeries Masonry software makes several specific assumptions and uses distinct methodologies regarding lintels and the transfer of loads around openings in wall panel designs.

1. Vertical Load Distribution (Load Takedown)

The software assumes that vertical loads do not simply vanish at an opening but are redistributed through the lintel to the surrounding masonry.

Load Path: The software calculates the load coming from the masonry and floors above an opening. It assumes this load is distributed along the lintel, which then transfers the load to the masonry bearings on either side.
Point Load Behavior: Loads distributed from the lintels of openings are treated similarly to point loads acting on the wall. They are assumed to produce a concentrated area of axial force pressure near the mid-height of the wall, rather than a uniform distribution.
Buckling Force Averaging: Because lintels concentrate the vertical load at their bearings, the software allows for "Buckling Force Strip Averaging." It assumes that this concentrated axial force varies horizontally and allows the user to spread this variable load over a sensible design strip (a factor of the leaf thickness) to avoid unrealistically failing the wall due to a peak stress occurring over a very small section.

2. Compressive Stress Checks

While the software does not strictly "design" the steel or concrete lintel beam itself (in terms of checking the bending capacity of a proprietary steel box lintel), it rigorously checks the masonry directly under the lintel.

Local Stress: In the Advanced Yield Line Analysis (AYLA) method, localized additional compressive stresses are explicitly calculated and taken into account where lintels bear on the wall.

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Between 2 wall opening, stresses can vary between Yield Line Analysis and Standard Panel Methods. This is because the Yield Line Analysis considers the maximum stress from the distributed loads, whereas the standard panel method distributes these loads uniformly across the panel.

Bearing Enhancement: The software checks if the masonry can withstand the concentrated bearing stress from the lintel. If a failure occurs here, the software assumes the user might need to introduce a padstone or engineering bricks to distribute the stress, similar to how it handles beam point loads.

3. Lateral Load Transfer (Wind)

Regarding wind loads applied to the opening area (windows/doors):

Distribution to Panel: The software assumes that wind load hitting the opening is transferred back to the surrounding masonry panel. The default assumption is that the opening acts as two-way spanning, distributing the load to all adjacent masonry edges (including the head/lintel area).
Span Adjustments: The user can alter this assumption to make the opening span vertically or horizontally. For example, for a roller shutter door, the user might specify "bottom free," implying the load goes to the lintel and the sides, but not the floor.

4. Geometry and Interaction

Geometric Validity: The software can handle complex geometries, including openings that touch or overlap (which it merges into complex shapes), and it assumes the load transfer logic (lintel action) updates automatically to reflect these combined shapes.
Supports: If a wind post or lateral support passes through an opening, the software logically assumes there is no support through the opening void itself.