📺5 Examples of Structural Retaining Wall Designs to Eurocode [Webinar Recording]

Posted on September 9th, 2024 in Webinars

Summary

This transcript introduces MasterSeries, a software suite designed for structural analysis and design, specifically highlighting its retaining wall design module. The webinar demonstrates how engineers can utilise the software to model, analyse, and design various retaining wall types, including reinforced concrete, unreinforced masonry, reinforced hollow block, gabion, and grouted cavity walls. It covers essential design considerations such as soil properties, loading conditions, reinforcement, and compliance with British Standards and Eurocodes, emphasising the software's user-friendly interface and its ability to handle both permanent and temporary design scenarios. The presentation also touches upon crucial geotechnical and structural checks to ensure the overall stability and integrity of the designs.

Key Topics

• Retaining Wall Design
• Software Features
• Design Standards
• Wall Types
• Soil Properties

Description

The MasterSeries webinar introduces the MasterSeries Retaining Wall Design Module, a standalone software that can also be part of the Power Pad Suite, designed for structural analysis and design of various retaining wall types. Both new and existing users can access a free trial, and demos are available.

Key Features and Interface of the Module:

• The software interface includes a menu bar, toolbar, dynamic graphics display, design outputs and results, a results summary, and an editing area with various tabs.

• Editing Area Tabs:

    ◦ Design Brief: Allows setting up individual briefs for new walls, with options to add from default data, copy, or select from a database of 29 standard templates. Multiple briefs can be applied within one file.

    ◦ Wall Data: Defines wall geometry, including dimensions for the wall stem, heel, toe, nibs, front and back soil dimensions, slopes, and water table level.

    ◦ Soil Data: Specifies properties for front, back, and base soil, allows soil layering, and includes options for over-consolidation ratios, tension cracks, frictionless virtual backs, and at-rest Earth pressures.

    ◦ Props and Ties: Used to specify ground anchors (ties) or base props.

    ◦ Loads: Defines line loads, full and partial surcharge loads, additional surcharge loads, horizontal surge forces, and wall upstand wind loads.

    ◦ Reinforcement: Allows specification of concrete and reinforcement details for wall main and distribution steel on both faces and the base.

    ◦ Masonry: Configures masonry-only walls, reinforced masonry walls, cavity-filled masonry walls, or reinforced hollow block walls, including specifying piers.

    ◦ Drawing Options and Defaults: Offers controls for turning on/off graphic settings and adjusting default values for surcharge, load factors, and reinforcement bars, with options for exporting reinforcement drawings and bar schedules.

Design Standards and Support:

• The software supports Eurocode and British Standards (BS 8002 for Earth Retainer Structures, BS 8110 for concrete wall elements), along with South African, older, Highway, and Irish codes.

• A comprehensive manual and remote support sessions are accessible via the Help menu.

Examples of Retaining Wall Designs Covered:

1. Standard Reinforced Concrete Wall (British Standards):

    ◦ A 3-meter high wall retaining full soil height, 200mm front face, long toe and heel, no nib.

    ◦ Soil properties are assumed as gravel throughout (front, rear, base), with a density of 18 kN/m², 30° soil friction, and zero cohesion.

    ◦ Frictionless cohesion at concrete-soil interfaces (e.g., via damp-proof membrane or drainage layer) is assumed to prevent interaction.

    ◦ A surcharge load of 10 kN/m² (recommended by BS 8002 for vehicular traffic) is applied.

    ◦ Design checks include geotechnical stability (overturning, sliding, bearing) and structural integrity (wall stem bending, shear, and deflection).

2. Domestic Garden Wall (Unreinforced Masonry, Eurocodes):

    ◦ A simple stepped, unreinforced masonry wall retaining about 1.5 meters of soil.

    ◦ Relies on its compressive strength and self-weight for stability, designed to be thicker at the base.

    ◦ Features reduced default surcharge load as it's not for vehicular traffic.

    ◦ The software allows for soil cohesion (e.g., for clay soils), which significantly benefits wall capacity, though the long-term effects of diminishing cohesion must be considered.

    ◦ Designed to Eurocodes, which use ultimate load cases. An ultimate bearing resistance (e.g., 300 kN/m²) is used, with an option to include a serviceability bearing pressure case with a factor of safety (default of 3).

    ◦ Includes an option for tension cracks in clay soils, allowing for water pressure within the crack to be accounted for in the design.

3. Stepped Hollow Block Wall (Reinforced Masonry):

    ◦ Designed as a reinforced masonry wall using hollow blocks filled with concrete, with vertical and horizontal reinforcement (e.g., Steo system).

    ◦ The software has default templates for these walls, pre-configured with block strength, width, reinforcement details, and cover.

    ◦ Reinforcement allows the wall to take tension forces and bending, increasing capacity and allowing for higher walls compared to gravity walls.

    ◦ Features a "virtual back" option in soil data, which makes the back frictionless and applies lateral loads from the soil body behind the heel, creating a more conservative design.

4. Gabion Walls:

    ◦ Can be modelled in MasterSeries to both Eurocodes and British Standards.

    ◦ Eurocodes: Modelled as a masonry wall using dimensioned natural stone with a flexural value of zero, and the wall density can be adjusted.

    ◦ British Standards: Modelled as a concrete wall with tensile strength set to zero and concrete density adjusted.

    ◦ A geotextile membrane is typically used between backfill stone and retained soil, often resulting in zero interface friction.

5. Domestic Basement (Reinforced Grouted Cavity Wall):

    ◦ Consists of two parallel leaves of masonry units (e.g., 100mm inner, 100mm cavity, 100mm outer) with a cavity of at least 50mm, tied together with wall ties, and the cavity filled with high-slump concrete with reinforcing steel.

    ◦ Outer leaf material and waterproofing (e.g., waterproof coating, drainage layer) are crucial, especially for underground conditions.

    ◦ For permanent cases, the wall experiences no lateral movement due to props (e.g., ground floor, basement slab), making the structure rigid. It's recommended to check the "at-rest Earth pressure" box, which significantly increases bending moment.

    ◦ Reinforcement (vertical bars) is placed within the cavity.

    ◦ Design methodology treats it similarly to a reinforced concrete wall, with reinforcement taking tension and the masonry outer leaf taking compression.

    ◦ The software can be used for temporary works scenarios by creating additional briefs, removing props, and adjusting Earth pressure assumptions to check different construction sequences (e.g., backfill before slab installation)