Yoke beam girder

Yoke beam girders are relevant in construction and deconstruction practice wherever load-bearing members are slid in, retrofitted, or temporarily installed in existing structures. This ranges from installing a steel beam in a masonry or reinforced concrete slab for new openings, to temporary shoring during building gutting, and to load-bearing elements that are integrated into existing structures in tunnel construction or industrial buildings. Because creating the necessary bearing zones and openings must be done with minimal material damage, there are close links to tools for selective concrete and stone removal, such as the concrete pulverizer and the hydraulic wedge splitter. Cutting steel sections with a steel shear or a hydraulic demolition shear and supplying tools via a hydraulic power pack also play a role. This knowledge connects fundamentals, execution, and deconstruction of yoke beam girders with typical tasks in concrete demolition and special deconstruction, building gutting and cutting, as well as work in rock excavation and tunnel construction. In temporary works, the function is comparable to so-called needle beams where loads must be bridged or transferred with precision and low emissions.

Definition: What is meant by a yoke beam girder?

A yoke beam girder is a load-bearing element that is slid or threaded into an existing structure to take up or redirect loads. It is often a steel section (e.g., IPE, HE, or hollow sections), a composite girder made of steel and concrete, or a temporary auxiliary girder that is inserted into prepared bearing pockets (wall recesses) or openings. Typical applications include shoring of slabs when creating new openings, strengthening existing slabs, replacing beam lines, installing underbeams or crane runway girders, and temporary support functions during deconstruction. The term is also used when girders are slid into construction states as part of a sliding or assembly procedure (an insertion method). In essence, the girder acts as a controlled load path that enables safe redistribution while limiting interventions in the existing fabric.

Fields of application and interfaces with demolition, deconstruction, and installation

Yoke beam girders connect structural design with precise interventions in existing buildings. The term is particularly present in the following areas:

• Concrete demolition and special deconstruction: Installing steel beams for shoring before load-bearing components are selectively released with a concrete pulverizer; exposing bearing edges in a deconstruction-friendly manner using a hydraulic wedge splitter to minimize vibrations.
• Building gutting and cutting: Temporary auxiliary girders as yoke beam girders for load redistribution in buildings; cutting reinforcement and steel parts with a hydraulic shear (demolition shear); adjusting beam lengths with a steel shear.
• Rock excavation and tunnel construction: Integration of steel girders into shotcrete linings or into crown/invert as temporary bracing; precise creation of bearing surfaces in rock or shotcrete using controlled splitting.
• Natural stone extraction: Less common, but possible as rails and auxiliary girders in processing and treatment plants; adjustments to steel parts with shears are common there.
• Special use: Installation of yoke beam girders in existing facilities with constrained access, e.g., in industrial or tank areas; cutting torch and steel shear can be used to separate steel shells and girder elements.
• Bridge and building rehabilitation: Temporary underbeams and transverse yokes for staged load transfer during bearing replacement or the creation of new service penetrations.

Configuration, materials, and typical girder forms

Yoke beam girders are selected depending on function, installation space, and construction state. Common types:

• Rolled sections: IPE/HE sections for underbeams and replacements; good availability and ease of installation.
• Composite girders: Steel girders with shear connectors (e.g., studs) and concrete complement; advantageous where construction depth is limited and shear connection is required.
• Hollow sections: Rectangular/square hollow sections for slender cross-sections and torsionally stiff details, for example for crane runways.
• Welded plate girders: For large spans or high actions in special deconstruction.
• Temporary auxiliary girders: Demountable sections for temporary construction states, often reusable.

Detailing typically includes bearing stiffeners, end plates, and corrosion-protected contact faces. Where bolted splices are needed, high-strength preloaded assemblies support slip-resistant connections in dusty or damp environments.

Planning and design: Loads, bearings, and construction states

The load-bearing capacity of a yoke beam girder results from bending, shear, deflection, and interaction with the existing structure. Key factors:

• Load assumptions: Self-weight, imposed loads, construction-state loads, dynamic actions from demolition and cutting works.
• Support: Bearing lengths in wall pockets, line bearings in slabs, intermediate props; elastic bedding layers where appropriate.
• Composite action and connections: Studs or anchors for shear transfer; end plates, angles, or brackets; masonry injections and grout mortar.
• Deformations: Limiting deflections to protect adjacent components; installation camber may be applied.
• Component separation: Targeted decoupling of non-load-bearing layers before sliding-in reduces edge spalling – here the concrete pulverizer and hydraulic wedge splitter are advantageous for controlled separation.

Verification and detailing

Design should cover ultimate and serviceability limit states for both the final condition and intermediate phases, including stability checks for lateral torsional buckling and local bearing. Tolerances for axis, elevation, and bearing flatness must be specified to ensure even contact pressures and predictable load transfer.

Preparing the installation space: Openings, pockets, and edges

The quality of the bearings and installation points determines durability. In existing structures, bearing pockets are usually created with low vibration:

• Selective concrete removal: The concrete pulverizer releases concrete edges in a controlled manner while reinforcement remains visible; cutting sequences are aligned with stress redistribution.
• Controlled splitting: A hydraulic wedge splitter produces defined crack patterns to separate masonry or concrete without impact and vibration peaks – important near sensitive adjacent components.
• Cutting steel inserts: A hydraulic shear (demolition shear) cuts reinforcement and embedded parts; a steel shear adjusts beam lengths on site.
• Clean bearing faces: Flatness and squareness ensure uniform bearing pressures; grouting with shrinkage-compensated grout mortar or high-strength fillers.

Where necessary, diamond drilling of access holes and saw cuts around openings can supplement splitting to create stress-relieved edges and minimize microcracking at the bearing zone.

Installation sequence: Sliding in, aligning, grouting

Installation follows a structured sequence that considers the safety of the construction state:

1. Existing-condition survey: Document materials, reinforcement layers, and utilities; define routes for bringing components in.
2. Exposure: Create openings with minimal vibration; removal sequences starting along load-bearing axes.
3. Lifting and sliding-in: Use rollers, lifting devices, or a chain hoist; protect bearing surfaces.
4. Alignment: Check axis, elevation, and slope; temporarily fix with wedges, tensioning devices, or a screw clamp.
5. Grouting/connection: Backfill bearing pockets; install composite connectors; complete connection details.
6. Release of shoring: Transfer loads to the yoke beam girder; remove temporary props.
7. Inspection and monitoring: Verify grout fill, bearing contact, and bolt pretension; initiate crack and settlement monitoring where sensitive structures are affected.

Deconstruction of yoke beam girders in existing structures

In selective deconstruction, yoke beam girders are unloaded in a controlled manner and then dismantled. Practical steps:

• Unloading: Install temporary props, redistribute load paths step by step.
• Separating composite action: Release concrete layers with a concrete pulverizer; controlled splitting minimizes collateral damage to adjacent components.
• Metal cutting: A steel shear or hydraulic demolition shear makes clean cuts in flange and web; short cutting paths through prepared openings.
• Sectional dismantling: Divide the girder into transportable lengths, secure edges, coordinate lifting operations.
• Recovery and segregation: Remove grout and anchors cleanly; sort steel, concrete, and masonry for reuse or recycling.

Quality, safety, and standards

The applicable technical rules and the principles of occupational safety apply to planning and execution. Generally recommended:

• Structural verification: Verification of load-bearing capacity for final and construction states; consideration of stability and connection details.
• Construction site safety: Protection against fall protection issues and crushing hazard, verification of lifting gear load capacities, restricted areas during cutting and splitting.
• Emissions: Minimize dust, noise emission, and vibrations; use hydraulic tools with a suitable hydraulic power pack to provide controlled process forces.
• Documentation: Test records, grouting certificates, tightening torques, welding/bolting documents, approvals before unloading shoring.

Monitoring and acceptance

For critical interventions, implement surveying control points, crack gauges, and settlement readings. Define acceptance criteria for bearing flatness, grout quality, and residual deflection to ensure the design intent is achieved before removing temporary supports.

Typical mistakes and how to avoid them

• Insufficient bearing surfaces: The result is local overpressure; create plane bearing faces and fully grout.
• Lack of construction-state planning: Define demolition sequences precisely before sliding-in; plan temporary shoring early.
• Unclear composite load paths: Explicitly verify shear connection in composite girders; do not cut reinforcement indiscriminately.
• Excessive vibrations: Prefer the concrete pulverizer and hydraulic wedge splitter over impact tools to limit crack propagation.
• Poor-quality cuts: Cut steel sections with appropriate shears; poor cut quality complicates installation and leads to notch effects.
• Inadequate tolerances: Missing control of axis and elevation increases secondary stresses; specify and check tolerances during alignment.

Practice in tunnel and industrial environments

In tunnel construction, yoke beam girders often serve as temporary bracing or as support girders for a work platform. Bearing edges in shotcrete or rock are preferably created with low vibration. In industrial and plant construction, yoke beam girders are used for crane runway girders, pipe bridges, or as replacements in steel platforms. Clean steel separation is decisive here; a steel shear and hydraulic demolition shear make it possible to adapt girder geometry in tight spaces. Where vessels or hollow bodies block access, a cutting torch may be considered for preparatory separation work depending on boundary conditions, including in tank demolition or tank dismantling contexts. Aggressive atmospheres and confined spaces call for corrosion-aware detailing, low-emission tools, and robust logistics for component handling.

Material selection, corrosion, and fire protection

The durability of a yoke beam girder is determined by material, environment, and protection systems:

• Steel grade: Suitable for load-bearing capacity and welding/bolting; consider toughness at lower temperatures.
• Corrosion protection: Coating systems or hot-dip galvanizing; ensure protection also within bearing pockets.
• Fire protection: Claddings, coatings, or composite construction to meet required fire resistance ratings.

In addition, seal interfaces at grout transitions and wall pockets to prevent moisture ingress. Where future inspection is required, prefer removable claddings and accessible bolted joints.

Coordination of tools and energy supply

The choice of hand-held or carrier-mounted tools influences construction time, quality, and emissions. The concrete pulverizer and the hydraulic wedge splitter are suitable for low-vibration exposure of bearings. A hydraulic demolition shear and steel shear cover cutting of reinforcement and structural steel. Hydraulic power pack provides the required pressures and flow rates and enables finely metered work in confined existing environments.

Proper hose management, leak prevention, and pressure monitoring are essential in sensitive interiors. Tool selection should reflect access routes, required cutting forces, and the desired surface quality at the bearing interface.

Economy and sustainability

Precise preparation and material-conserving methods reduce rework and the risk of damage. Selective deconstruction promotes the reuse of steel components and the sorted separation of construction waste. Low vibrations and reduced dust improve working conditions – a plus in sensitive environments such as hospitals, laboratories, or heritage buildings. Considering reuse scenarios during planning, including demountable connections and reversible grout solutions where feasible, supports circular construction goals and lowers whole-life carbon.