Reinforcement strut

The reinforcement strut is a central element of bracing in buildings and technical structures. It secures load paths, limits deformations, and stabilizes components in new construction, existing structures, and deconstruction. In practice, one encounters permanently installed struts as well as temporary shoring and diagonal bracing. Especially in concrete demolition and special deconstruction projects, in strip-out and cutting, as well as in rock excavation, tunnel construction, and natural stone extraction, reinforcement struts influence the choice of work sequence and the tools used. Relevant interrelations exist in particular when using concrete demolition shears and rock and concrete splitters from Darda GmbH.

Definition: What is meant by a reinforcement strut

A reinforcement strut is a predominantly compression-loaded member that is arranged between load-bearing elements for bracing and load transfer. It forms part of a system of frames, beams, posts/columns, and diagonals that safely transfers horizontal and vertical actions into the ground. Reinforcement struts can be permanent (structural struts, e.g., in steel and timber frames, in trusses, or in tunnel heading) or temporary (emergency shoring, erection and deconstruction shoring, formwork and scaffold bracing). In solid construction, they often act as external diagonals or compression struts; they are to be distinguished from the internal reinforcement of reinforced concrete.

Construction, materials, and anchorage

Reinforcement struts are made of steel, aluminum, or wood; in special foundation engineering, composite and hollow-section struts are also used. Common cross-sections are tubular, angle, U-, I-, or box sections, as well as heavy round or square timber. Force transfer occurs via pinned or moment-resisting connections with lugs and gusset plates, via fork heads, spindles, anchor plates, or bearing points with load distributors. Anchorage in concrete or masonry members is often provided by heavy-duty anchors, through-bolts, embedded parts, or clamping consoles; for temporary solutions, shoring against abutments, support trestles, and counter-bracing is typical.

Geometry, arrangement, and load paths

The arrangement of the reinforcement strut largely determines the stiffness of the system and the force flow. Diagonal struts reduce deflections; K- and X-bracing distributes wind and seismic loads; horizontal or inclined struts stabilize cantilevers, column heads, and crane foundations. Slender struts require anti-buckling measures and sufficiently stiff connection points to limit secondary stresses and twisting.

Typical arrangements

• Single diagonal between column and beam for lateral bracing
• X- or K-bracing in frame bays to increase shear stiffness
• Coupled compression struts at openings in load-bearing walls
• Temporary shoring of slab edges and façades in existing structures

Constructive aspects

• Stability verification against buckling and overturning; support conditions influence the effective buckling length
• Sufficient bearing area with distribution plates to limit local concrete bearing pressures
• Dimension eccentricities and connection welds/bolts to carry forces appropriately
• Consider pre-load or settlement in timber and screw-jack struts

Fields of application in construction and deconstruction

Reinforcement struts are found in building and structural engineering, in bridge, industrial, and plant construction, in scaffolding and formwork, in tunnel and gallery construction, as well as in provisional safety measures during conversions and strip-out. In deconstruction, they serve to temporarily secure components before load-bearing elements are separated, split, or fragmented. In voids, shafts, or poorly accessible zones, struts often enable controlled load redirection for subsequent work steps in the first place.

Relation to applications of Darda GmbH

• Concrete demolition and special deconstruction: Reinforcement struts stabilize wall and slab panels before sections are separated with concrete demolition shears or loosened with rock and concrete splitters.
• Strip-out and cutting: When creating openings or removing edge strips, struts prevent impermissible deformations until the residual load-bearing capacity is reorganized.
• Rock excavation and tunnel construction: Steel frames with diagonals secure the working face, crown, and walls; struts work together with props and walers while the rock is pre-fractured using splitting technology.
• Natural stone extraction: Temporary struts stabilize equipment, saw gantries, or block yards; vibrations and separation joints must be coordinated with the shoring.
• Special applications: In complex inner-city deconstruction or in plant demolition, special struts ensure the safety of partial structures during sequential cutting operations.

Reinforcement struts in concrete demolition and special deconstruction

In the deconstruction of existing reinforced concrete members, reinforcement struts are an integral part of the safety planning. Before compression struts, corbels, wall panels, or column sections are worked with concrete demolition shears or prepared with splitting wedges, temporary load transfer via struts must be ensured. This reduces uncontrolled crack formation, prevents load redistributions into unintended areas, and increases the precision of cut lines.

Work sequence and tool selection

1. As-built assessment: structural analysis, identification of existing bracing and struts
2. Expose: reveal node points, connection details, and bearings
3. Relieving: install additional temporary struts; check bearing pressures
4. Preloading/settling: tighten spindles moderately, check pressure if applicable
5. Separating the concrete: use concrete demolition shears for controlled separation; alternative pre-separation with rock and concrete splitters
6. Separating steel components: use combination shears, multi cutters, or steel shears for lugs, sections, and gusset plates; for large tank components, tank cutters
7. Deconstruction in sections: continuously verify load paths, relocate struts step by step
8. Documentation and monitoring: observe deformations and bearing pressures

Particularities when using concrete demolition shears

• Do not damage strut nodes; maintain sufficient distance between the cut line and the nodes
• Limit rebound and vibrations of the component by bracing
• Consider reinforcement content in the cut zone; selectively trim remaining steel

Particularities when using rock and concrete splitters

• Position splitting wedges so that the pressure cones do not undermine strut bearings
• Use pre-splitting to guide cracks, then remove step by step
• A low-vibration, low-noise workflow benefits work on sensitive bracing

Relevance in rock excavation and tunnel construction

In tunnel and gallery construction, steel frames, lattice arches, and lining rings are combined with diagonal struts. They stabilize crown and sidewall areas until a final lining or a shotcrete vault takes over the loads. When pre-fracturing rock using splitting cylinders, struts must be positioned so that load redistributions remain defined and no impermissible pressure peaks occur at connection points. In shafts and caverns, temporary struts increase safety during sequential removal.

Strip-out and cutting: struts in existing structures

When creating new openings in load-bearing walls, removing slab edges, or modifying crane runways, reinforcement struts are used to minimize deformations and cracking. Steel struts with screw-jack heads and lugs are common; when releasing steel nodes, steel shears, combination shears, or multi cutters are used. For large-format steel plate components, e.g., in plants or tanks, tank cutters can be used as part of a coordinated cutting concept. Concrete sections are removed with concrete demolition shears depending on accessibility or prepared using splitting technology.

Inspection, identification, and exposing of reinforcement struts

Before starting cutting and splitting work, clarify where reinforcement struts are located, what connections exist, and how loads are carried. Visual inspections, review of drawings, exploratory openings, and exposing node points are proven in practice. In concealed areas, low-damage openings, endoscopy, or measurements of support reactions can provide indications.

Typical indications of struts and nodes

• Profiles running diagonally between columns and beams
• Gusset plates at nodes with bolt arrays or weld seams
• Bearing reinforcements, load distribution plates, and screw-jack heads
• Counter-bracing or parallel struts in wall and slab panels

Design and normative classification (general)

The design of reinforcement struts requires verification of load-bearing capacity and serviceability, in particular stability, connection forces, bearing pressures, and deformations. For temporary shoring, the principles of the applicable codes and standards for scaffolding, formwork, and auxiliary structures generally apply. For steel, timber, and concrete members, the respective valid technical standards must be used. The information provided here is always general in nature and does not replace project-specific planning or structural verification.

Safety, risks, and protective measures

The unintentional release or partial cutting of a load-bearing reinforcement strut can lead to abrupt redistributions. Safety concepts therefore consider controlled relieving and relocating of struts, secured work areas, defined cutting sequences, and the monitoring of deformations. Hydraulic shoring and screw-jack struts should be operated with measuring or indication devices; the operation of hydraulic tools requires clearly defined communication and approval processes.

Monitoring and control

• Regular checks of bearing points, bolts, and weld seams
• Observation of crack patterns and deformations in the vicinity of the cut zone
• Documentation of load redistributions when relocating struts

Practical details: connection details and deconstruction of steel struts

Steel struts are often bolted or welded to gusset plates via lugs. In deconstruction, a sequential approach has proven its worth: first create relieving, then loosen fasteners or cut steel sections, and subsequently check the bearing surfaces. Depending on cross-section and accessibility, steel shears, combination shears, or multi cutters can be used for cutting. Anchors that are clamped or cast-in can, after relieving, be exposed and cut off with concrete demolition shears or released by splitting technology.

Typical sources of error and how to avoid them

• Insufficient consideration of buckling length due to unfavorable support conditions
• Bearing areas too small, causing local concrete damage at supports
• Eccentric connections without compensation by lug or gusset plate detailing
• Lack of redundancy in temporary shoring; no secondary load path
• Cutting sequence without prior relieving and without deformation monitoring

Distinction from related elements

The reinforcement strut is to be distinguished from the internal reinforcement in reinforced concrete (bars, meshes), as it is an independent, usually visible component that supplements the bracing. Compared to tension ties, it predominantly carries compression; compared with beams and purlins, it primarily provides bracing rather than load distribution. Temporary shoring in scaffolds and formwork uses the same operating principles but differs in terms of durability and connection details.