Rapid Application of Wind Loading on Structures 2018-08

Posted on August 9th, 2018 in Wind

Summary

This presentation by "MasterSeries Software" demonstrates their software's capabilities for calculating wind loading on building structures, focusing on the Eurocode standard. The software streamlines a complex process by allowing users to define building geometry, automatically identify wind panels (including canopies, balconies, and parapets), and calculate external and internal wind pressures and suctions. Key features highlighted include site data input using grid references for accurate wind speed determination, the ability to account for dominant openings and building permeability, and the automatic generation of numerous loading cases for comprehensive structural analysis. The tutorial also addresses common modelling issues, such as defining dummy members for load transfer in areas without physical columns and combining wind panels for correct classification, ensuring accurate load application even for complex geometries like curved roofs and open-sided structures.

Key Points

• Wind Analysis
• Structural Loading
• Building Types
• Wind Panels
• Loading Cases

Description

The video details the process of applying wind loading to building structures using MasterSeries software, specifically MasterFrame and MasterPort. The process involves several key steps and considerations:

• Software and Initial Setup

    ◦ The demonstration uses MasterSeries 2018.

    ◦ The first step is to activate the automatic wind loading directions and set up the wind analysis, typically working to the Eurocode.

    ◦ Users can adjust the CSC D factor (design factor), for example, from a conservative default to 0.95 for a 20-meter high building.

    ◦ It's important to consider four wind directions and account for internal pressure and internal suction. The system allows for increasing pressure or suction in specific directions if dominant openings are present.

    ◦ For the Eurocode, worrying about global load reduction is less necessary.

• Site Data and Location

    ◦ The software allows for defining the site location, including regions in the UK. For more accuracy, a grid reference finder website (like "grid reference finder") can be used to pinpoint an exact location, such as Birkenhead, by copying a short six-number and two-letter version into MasterSeries.

    ◦ For Irish sites, a dedicated "Irish grid reference finder" website is used, providing a single letter, five-number, five-number format.

    ◦ The structure's rotation can be set; for example, a frame can be 12.5 degrees off North, with North being anti-clockwise on the Z-axis in plan view.

    ◦ Users can choose wind load return periods, such as 1 in 50 years (standard Eurocode), 1 in 120 years for monumental buildings, 1 in 10,000 for nuclear buildings, or a user-defined value like 1 in 25 years for agricultural structures.

    ◦ Obstructions and fetches (upward and downward wind effects) are derived from the location and topography.

    ◦ For overseas structures (e.g., Timbuktu in Malawi), users can define custom Q values (wind pressure in kN/m²) for different heights, while coefficients remain universal.

• Wind Panels and Load Application

    ◦ The program can automatically find and generate all wind panels for a structure, including canopies, overhangs, balconies, and parapet walls.

    ◦ The system intelligently knows when a surface is not on a specific panel.

    ◦ After auto-generation, users can visualise wind loading; different colours indicate pressure (yellow) and suction (green), with darker shades representing higher intensity.

    ◦ The software displays coefficients (e.g., 0.6, 1.3, 0.86 for roofs), which are then multiplied by wind pressures. It shows how loads change with different wind directions, internal pressure (P1), and internal suction (S1).

    ◦ For cladding design, the software can show maximum positive pressures and minimum (negative) suctions on each surface.

• Loading Cases

    ◦ The software can quickly generate a comprehensive set of standard loading cases, potentially resulting in 89 cases that include external, internal, sway stability, serviceability, and various wind load scenarios (W1, P1, S1, W2, etc.).

• Specialised Structural Elements and Considerations

    ◦ Permeability and Dominant Openings: In MasterPort, the software automatically calculates internal pressure (CPI) and suction (CSI) coefficients based on height, span, and dominant openings, which is a feature hoped to be included in MasterFrame later.

    ◦ Canopies and Parapets: These are automatically detected and receive higher pressures, leading to uplift. For canopies, the local combined coefficients are used rather than CPI.

    ◦ Open-Sided Structures (e.g., Grandstands): For roof members, the system needs to be told that there is wind on both sides. It then automatically calculates separate values for external wind and underside wind (e.g., 0.3 and 0.98 respectively), which are then combined for the total pressure.

    ◦ Curved Beams/Roofs: MasterFrame can perform full curved wind analysis on physically curved members, accounting for different slopes.

• Troubleshooting and Advanced Features

    ◦ Missing Panel Edges: A common problem where physical members don't define a panel edge (e.g., a beam running into another beam). This is solved by adding "dummy members", which are non-physical members used only for framing up loads, ensuring loads are transmitted to nodes.

    ◦ Panel Spanning: Users can define panels as one-way spanning (horizontally or vertically) or two-way spanning.

    ◦ Combining Panels for Classification: If multiple panels are part of one larger surface (e.g., a column of panels), they need to be combined for classification purposes to get correct wind zones (A, B, C) rather than individual "A" classifications for each small panel.

    ◦ Bracing Members: To prevent bracing members from taking wind loads, they must be designated as "bracing" in the software.

    ◦ Tall Buildings: For tall structures where height exceeds width in the wind direction, wind pressure is not constant vertically. The system calculates a uniform wind load portion at the top and bottom (up to the structure's width 'B') and a tapered portion in the middle. This requires defining levels in the structure.

    ◦ Overriding Values: Users can override default panel values and input their own external pressure (CPE) values or dead/live loads for specific panels.

    ◦ Funneling: The software allows for considering funneling effects from nearby buildings by inputting a ratio that overwrites default values, leading to higher wind loads in constricted areas.

• Availability

    ◦ Wind analysis is a purchasable add-on for MasterFrame, MasterPort, or MasterPowerPod.

    ◦ As of 2018, PowerPod includes wind analysis for frames up to 100 members. For structures exceeding 100 members (e.g., PowerPod 500), the full wind analysis add-on is required.

Questions and Answers