Design of Ground Beams, Rafts & Pile Caps using MasterSeries 2018

Posted on January 10th, 2019 in Webinars

Summary

This video transcript explores various aspects of concrete foundation design using MasterSeries software, focusing on ground beams, rafts, and pile caps. The presenter demonstrates how to use different modules of the software, such as frame analysis and concrete design, to model and analyse these structural elements. A key emphasis is placed on the importance of load patterning for continuous beams to accurately capture maximum and minimum moments, as well as the consideration of torsional stiffness in grillage frames, with the option to ignore it for simpler, pinned-end designs. The video also details the design of rafts, highlighting the critical role of subgrade modulus and demonstrating how to apply various load types and refine the finite element mesh for accurate results. Finally, it covers the design of pile caps, showcasing the software's ability to handle eccentric columns and moments while offering both strut and tie and beam theories for analysis.

Key Points

• Concrete Design Software
• Load Patterning
• Raft Foundation
• Pile Cap Design
• Spring Supports

Description

The "MasterSeries 2019" video transcript details the use of the MasterSeries modular suite for the design of ground beams, rafts, and pile foundations.

Here's a summary of the key aspects covered:

• MasterSeries Software Suite

    ◦ The MasterSeries is a modular suite that includes tools for frame analysis, finite elements (for rafts), concrete design (for ground beams), and a pile cap designer.

    ◦ Concrete beams can be designed using the dedicated concrete beam designer for simple continuous beams or the MasterFrame with concrete design for two-dimensional grillage beams.

• Concrete Ground Beam Design

    ◦ For continuous beams, load patterning is crucial to determine maximum and minimum sagging and hogging moments. The software allows for alternating loads (e.g., D1 L1, D2 L2) to create various load cases (e.g., all spans loaded, max-min patterns).

    ◦ The design process involves setting parameters like bar sizes (12mm to 32mm), covers (e.g., 30mm top, 50mm bottom), curtailment, and using design codes like Eurocode 2 (EC2).

    ◦ Reinforcement can be modified, and the software will indicate if it's satisfactory. Moment redistribution can be applied to adjust elastic moments by a percentage at specific points to aid design.

    ◦ A two-zone design method is popular for ground beams, simplifying the reinforcement layout by making it similar throughout.

    ◦ For complex grillage frames, the software allows ignoring torsional stiffness during analysis if stability is maintained, simplifying the design by eliminating torsional links and reducing steel requirements. This is only suitable if cantilevers are resisted by a back span.

    ◦ Super members can be created to "glue" multiple beam segments together, treating them as one continuous length for simplified reinforcement design.

    ◦ The software can scan for failures (e.g., transverse reinforcement spacing) and provides options to print out designs, export to DXF for CAD drawings, and generate bar bending schedules.

    ◦ The loading for grillage frames can be applied using alternate loading grips for effective load patterning.

    ◦ The system also supports elastic support reactions, spring supports, and settlements by defining spring stiffnesses or specific nodal displacements.

• Raft Foundation Design

    ◦ Rafts are typically used for smaller domestic structures.

    ◦ The design involves defining the surface boundary with members, specifying openings, and applying edge supports with a spring stiffness, which represents the subgrade modulus of the soil. Typical values for subgrade modulus range from tens of thousands to over 100,000 kN/m³ depending on soil type.

    ◦ Loads can be applied as superimposed dead, live, perimeter, or internal wall loads, including line loads, area loads, and varying area loads.

    ◦ To improve analysis accuracy and reduce errors in finite element models, global and local meshing options can be adjusted, allowing for finer mesh intensity in critical areas.

    ◦ Analysis results focus on moments (MRX, MRY, principle moments) and Wood and Armour moments, which are used for reinforcement design.

    ◦ The software facilitates the design of top and bottom steel reinforcement based on these moments.

    ◦ Serviceability checks include evaluating Y displacement to ensure minimal movement.

    ◦ Users can create sections through diagrams to view moment distributions and apply strip averaging to account for localized high moments.

    ◦ Attached beams can be integrated into raft designs, allowing for deeper sections below the slab to span longer distances or provide additional stiffness.

• Pile Cap Design

    ◦ MasterSeries offers a dedicated, powerful program for designing pile caps.

    ◦ It can handle various configurations, including 2-pile, 3-pile (triangular), or 4-pile pile caps, even with eccentric columns.

    ◦ The software accounts for imposed loads like wind, generating moments in both axes.

    ◦ It calculates design moments by proportioning ultimate loads from pile loads and their distances.

    ◦ Designs can be done according to BS or Eurocode standards and can accommodate square piles by creating a circumscribed circle around the pile for perimeter calculations.

    ◦ The program identifies and warns about shear perimeter overstressing and suggests increasing the foundation depth as a solution, which rapidly improves capacity.

    ◦ It can employ strut and tie or beam theory for design, and intelligently advises the user on the appropriate method for deep beams.

    ◦ Bar bending schedules are also available directly from the pile cap program.