Bracing

Bracing describes all structural and organizational measures used to safeguard buildings, structural components, or geological structures against horizontal actions and loss of stability. The term is relevant to planning, new construction, deconstruction, strip-out, and the separation of components just as much as to rock excavation, tunnel construction, and natural stone extraction. In practice, structural principles, work sequences, and the choice of appropriate tools overlap. In particular, the selective use of concrete pulverizers as well as hydraulic rock and concrete splitters enables controlled modification of load paths without unnecessarily weakening the residual load-bearing capacity.

Across all phases, bracing aims to limit lateral deformations, ensure robustness and redundancy, and prevent progressive collapse under temporary and accidental actions. In sensitive environments, low-vibration and low-noise techniques, controlled sequencing, and dust mitigation form part of an integrated safeguarding concept.

Definition: What is meant by bracing?

Bracing refers to the entirety of systems and measures that stabilize a load-bearing structure against overturning, sliding, twisting, and lateral buckling. This includes moment-resisting frames, bracing systems (diagonals), shear walls and cores, the diaphragm action of slabs, and temporary shoring in construction and deconstruction stages. Bracing ensures that horizontal loads – such as wind, erection forces, vibrations, or earth and water pressure – are transferred in an orderly manner into the foundation or rock, and that no instability arises due to imperfections and second-order effects. In deconstruction, additional temporary bracing is used to safely guide altered load paths during selective removal. In structural terminology, the ensemble of these elements is often referred to as the lateral force-resisting system; collectors and drag struts couple diaphragms to shear walls and frames.

Fundamentals of load transfer and horizontal actions

Horizontal loads and eccentricities activate shear, bending, and torsion in members. Load paths run via shear fields (wall diaphragms), beam-column systems, and bracing members to adequate supports or the ground. The distribution of stiffness determines which part of the system takes how much load. When intervening in the fabric – such as removing wall panels or cutting openings – load paths shift. Therefore, cuts and partial demolitions are combined with temporary bracing and a step-by-step approach.

Key principles include compatibility and redundancy, control of second-order (P-Delta) effects, and allowance for imperfections. Drift limits and serviceability criteria protect non-structural components, while robustness provisions limit disproportionate collapse if an element is removed or fails during the works.

Terms at a glance

• Bracing system: Set of elements that transfer horizontal loads.
• Shear wall/core: Wall or core regions that primarily take shear forces.
• Bracing: Diagonal cross-bracing that stabilizes via tension/compression.
• Construction stage: Temporary condition with its own load paths and safeguards.
• Diaphragm and collectors: In-plane slab or deck action and the members that transmit these forces to the vertical bracing.

Structural bracing systems

Depending on material, geometry, and task, different systems are used. In existing structures, deconstruction, and special foundation engineering they are often combined and supplemented for construction stages.

• Shear walls and cores made of concrete or masonry
• Moment-resisting frames in steel and reinforced concrete construction
• Bracing systems (diagonals, K-braces, V-braces)
• Horizontal diaphragm action of slabs and plates
• Temporary shoring, props, and needling
• Buckling-restrained or energy-dissipative braces in special cases

Concrete and reinforced concrete: shear walls and cores

Shear walls and elevator/stair cores provide the majority of the bracing. In deconstruction, their function may only be removed once an equivalent replacement is in place. Selective removal with concrete pulverizers enables controlled reduction of wall thicknesses, exposure of reinforcement, and staged redirection of forces before entire panels are removed. Precutting and interface preparation reduce unintended stress releases and help maintain diaphragm connectivity via collectors.

Steel construction: bracing and joints

In skeletal structures, diagonals and moment-resisting joints provide bracing. When removing bracing members in a dismantling-oriented manner, steel shears and Multi Cutters help to relieve the tension members first and only separate them after temporary shoring has been installed. This reduces the risk of overturning and buckling. Slip-resistant bolted joints and adequate gusset continuity are essential to safely pass loads into temporary systems.

Temporary bracing in concrete demolition and special deconstruction

During deconstruction, bracing shifts dynamically with each work step. The goal is to utilize reserves of the remaining system while simultaneously establishing new load paths. Low vibration levels and controlled crack propagation are crucial, for example in inner-city settings or near sensitive neighboring structures.

Procedural principles

1. Existing-structure analysis: identification of bracing elements and critical shear forces.
2. Temporary securing: installation of propping, needling, and auxiliary bracing.
3. Selective removal: detach components section by section with concrete pulverizers, cut reinforcement in a controlled manner.
4. Crack control: targeted weakening with rock and concrete splitters to guide fracture lines.
5. Monitoring: deformation and vibration control, continuous adjustment of the safeguarding concept.

Complementary measures include low-vibration cutting methods, staged release of restraints, and defined hold points for structural checks. Exclusion zones and fallback supports are set to address residual risks if measured values approach threshold criteria.

Selective demolition with concrete pulverizers

Concrete pulverizers enable edge-near removal, breaking out individual segments, and gentle exposure of bond zones. This allows residual structures to be maintained while loads are systematically transferred to temporary bracing. This is particularly relevant in the application areas of concrete demolition and special deconstruction as well as in strip-out. Combined with predrilled relief holes and controlled reinforcement cutting, fracture energy is reduced and the residual diaphragm action is preserved for longer.

Crack control with rock and concrete splitters

Rock and concrete splitters generate defined compressive stresses and steer fracture joints. In this way, components can be separated along planned planes without harmful secondary cuts or uncontrolled crack branching. This supports a safe sequence for openings, partial lowering, or the separation of bracing elements. The method helps limit vibration levels and protects adjacent finishes and sensitive equipment.

Bracing in rock excavation and tunnel construction

In rock, load paths follow discontinuities in the massif (bedding, joints). Bracing is created by interlinking rock blocks with shotcrete, rock anchors, and the ring action of tunnel linings. When releasing blocks in a controlled manner, stresses are reduced without compromising the stability of the remaining rock mass. Rock and concrete splitters as well as rock splitting cylinders support precise separation along suitable weakness zones.

Natural stone extraction

When extracting natural stone blocks, the residual stability of the bench is essential. Splitting cylinders make it possible to activate separation joints along bedding and joint directions. This preserves the bracing of the back benches and the stability of slopes, facilitating safe haulage. Sequencing from top to bottom benches and maintaining sufficient web thicknesses further reduces the risk of wedge failures.

Strip-out and cutting: interaction between cuts and bracing

Sawing and core drilling alter the diaphragm action of slabs and walls. Load paths must be secured before cutting larger openings. A proven approach is to combine temporary shoring, the gradual release with concrete pulverizers, and the cutting of reinforcement with Multi Cutters. In this way, residual stiffnesses are maintained until new bracing elements or auxiliary bracing are engaged.

Steel components and tanks

In constructions with shell and frame action – such as steel beams, bracing, or tank structures – every cut influences bracing. Steel shears and tank cutters are used when shell panels, ribs, and rings must be separated in a controlled way. Before each cut, auxiliary tie-backs should be installed to avoid unintended deformations and buckling. The sequence typically proceeds from non-load-bearing attachments to primary stiffeners, then to main bracing elements under protected conditions.

Planning, verification, and monitoring

Bracing is a subject requiring verification. For construction and deconstruction stages, simplified and more detailed models are used depending on complexity. Deformation and vibration measurements support assessment during the process. Interventions are carried out in stages, with each stage documented and released. Provisions in standards, guidelines, and official requirements must be observed; specific evaluations must be performed project-specifically by competent parties.

Verification approaches and modeling

• Stage-by-stage global models with appropriate boundary conditions and stiffness assumptions.
• Consideration of second-order effects, notional horizontal loads, and imperfections.
• Capacity design and robustness checks for element removal and redistribution.
• Serviceability limits for drifts, vibrations, and crack control during interim states.
• Interfaces and collectors verified for force transfer between diaphragms and vertical bracing.

Safety and legal notes

Work on bracing members requires qualified personnel, appropriate protective measures, and continuous monitoring. The notes in this contribution are of a general nature and do not replace structural checking or project design. Measures must always be defined project-specifically. Threshold values, inspection regimes, and hold points are to be agreed and documented before work starts.

Practical references from application areas

• Concrete demolition and special deconstruction: sequential removal, temporary propping, controlled release with concrete pulverizers, guiding fracture lines by rock and concrete splitters.
• Strip-out and cutting: preservation of diaphragm action by pre-shoring, edge-near working-out, targeted separation of reinforcement.
• Rock excavation and tunnel construction: blockwise release along joints, securing by anchors/shotcrete, pressure-controlled splitting.
• Natural stone extraction: splitting along bedding joints, gentle disengagement of blocks, maintaining stability of the remaining benches.
• Special operations: work in sensitive areas with limited vibrations, precise control of load redistribution.

Selection of equipment in the context of bracing

The choice of equipment depends on the material, the interface to the structure, and the desired depth of intervention. Concrete pulverizers are suitable for selective removal of concrete while maintaining residual stiffness. Rock and concrete splitters steer cracks and reduce separation forces. Combination shears and Multi Cutters cut reinforcement and sections; steel shears process bracing bars and stiffeners; tank cutters separate shell panels. Hydraulic power packs supply the tools with the required pressure and flow rate.

• Selection criteria: access and reach, required force and stroke, jaw geometry and cut width, vibration and noise limits, hydraulic compatibility, and debris management.

Hydraulic power packs

Hydraulic power units provide the energy to apply forces in a controlled manner. Appropriate sizing supports finely metered work: enough capacity for cutting or splitting operations, yet adjustable so that the bracing of the residual structure is not impaired abruptly.

• Key parameters: operating pressure and flow, cooling capacity, filtration quality, remote-control capability, and noise emission limits for sensitive sites.

Typical failure patterns and prevention

• Removing bracing walls or bracing members too early without replacement – Prevention: establish temporary securing first.
• Uncontrolled cracking during cuts – Prevention: crack control with rock and concrete splitters, plan the cutting sequence.
• Underestimated construction stages – Prevention: staged verifications, monitoring, and approvals per work step.
• Lateral buckling of slender elements – Prevention: intermediate bracing, reduced cut lengths, intermediate shoring.
• Excessive vibrations – Prevention: selective removal with concrete pulverizers, low-vibration separation techniques.
• Collector or chord discontinuity in diaphragms – Prevention: install temporary collectors and maintain chord continuity until replacements engage.
• Insufficient anchorage or bearing of temporary props – Prevention: verify anchorage lengths, bearing checks, and slip resistance.

Documentation and communication

A clear construction sequence plan, marked cutting and propping points, and continuous documentation of measurements support safe implementation. Short communication channels between design, site, and monitoring teams help to react quickly to deformations or load redistributions and to keep bracing effective at all times.

• Method statements with defined hold points and acceptance criteria.
• Instrumented monitoring with alarm thresholds and escalation paths.
• As-built updates for each stage and release records for the next step.