Load-bearing system

The load-bearing system is the backbone of a structure. Anyone who modifies structures, performs selective deconstruction, or separates partial areas must understand and deliberately influence the load paths. Especially in concrete demolition, special demolition, natural stone extraction, and tunnel construction, the choice of methods and tools – such as the use of concrete pulverizers or hydraulic rock and concrete splitters – has a direct effect on the load-bearing system, vibrations, noise emissions, and safety. Sequence planning, temporary supports, and method selection determine whether loads are redirected in a controlled manner or trigger unintended redistributions. Where neighboring structures or sensitive installations are present, low-vibration, low-impact approaches are essential to preserve structural integrity.

Definition: What is meant by a load-bearing system?

A load-bearing system (also supporting structure) is the entirety of all load-bearing components and their connections that safely transfer actions such as self-weight, imposed loads, wind, earthquakes, or earth pressure into the ground. It comprises components such as slabs, beams, columns, walls, shafts, cores, frames, trusses, shells, or anchors as well as the joints and supports through which loads are transferred. Characteristic is the continuous load path: loads flow from the point of action through load-bearing elements to foundations and into the subsoil. A load-bearing system is defined by geometry, material, support conditions, and joints and is decisive for structural stability, serviceability, and robustness. In practice, redundancy and toughness counteract progressive collapse; conversely, weak joints or brittle members can interrupt the load path and must be treated with particular caution.

Configuration and load paths of a load-bearing system

Load-bearing systems can be described by how loads are taken up, redirected, and carried away. Vertical loads (self-weight, imposed loads) are often introduced via slabs and beams into columns and walls, horizontal loads (wind, earthquakes) via diaphragms, cores, and frames into foundations. Functionality depends on load reserve, the ductility of connections, and the quality of bond (e.g., concrete-reinforcement). Interventions such as sawing, splitting, breaking, or cutting change stiffness, interrupt load paths, and cause redistributions. These redistributions are plannable if sequence, shoring, and separation cuts are chosen to suit the load-bearing system.

Good practice distinguishes between local and global system effects: local weakening must not undermine global bracing or overall stability. Second-order effects (P-Delta), dynamic amplification due to vibrations, and shear lag can become decisive in temporary states and should be included in the planning of construction stages.

Types of load-bearing systems in construction

Solid construction (reinforced concrete and prestressed concrete)

Typical elements are slabs, drop beams, shear walls, columns, and cores. Load transfer occurs via bending, shear, and punching resistance. Cores and shear walls provide bracing. During deconstruction, punching zones (e.g., at column heads) and bearing areas are particularly sensitive – interventions with concrete pulverizers or splitting near the core require controlled relief. Indicators of risk include crack fans near supports, spalling at edges, and abrupt load redistributions at openings; pre-weakening with saw cuts and staged removal reduces these risks.

Steel construction

Frames, trusses, and bracing transfer forces via pinned or rigid joints. Stability (buckling, lateral-torsional buckling, local buckling) is often decisive. Separation cuts in chord and diagonal members must be placed to avoid destabilizing the system; steel shears and multi cutters are suitable for stepwise, controlled cutting. Residual stresses in members and connections can release suddenly – temporary suspensions and cut sequences that maintain triangulation preserve the system effect.

Masonry

Masonry primarily works in compression. Bracing is provided by cross walls, slabs acting as diaphragms, and the ring beam. Ill-considered openings, cuts, or removals can disturb arch or vault action; localized splitting or small bites with hydraulic demolition shears reduce vibrations and cracks. The thrust line must remain within the middle third of the section; lintels and temporary needles are arranged such that compression paths remain continuous during every stage.

Rock and tunnel construction

In the ground, rock, the rock mass, and the lining (shotcrete, segment rings, rock bolts) form a composite load-bearing structure. In rock excavation and natural stone extraction, targeted separation joints are crucial: rock wedge splitters and hydraulic splitters generate controlled tensile stresses along existing joints without unduly disturbing the surrounding load-bearing system. Ground-structure interaction and convergence control determine whether the composite action between rock mass and lining remains intact in intermediate states.

Load-bearing system analysis in deconstruction and demolition

Before intervening, an assessment of the existing structure is required: load paths, material qualities, reinforcement layout, connections, construction stages. In deconstruction, temporary states count as independent load-bearing systems. Shoring, suspensions, and relief cuts must be planned to preserve residual load-bearing capacity. Tools influence boundary conditions: low-vibration methods (e.g., splitting) reduce redistribution shocks; mechanical crushing (e.g., with concrete pulverizers) allows controlled removal in small steps.

• Define critical components and interfaces: bearings, bracing, joints, and construction joints.
• Document dependencies between stages with method statements and trigger levels for monitoring.
• Coordinate logistics and access so that system-relevant supports remain available when needed.

Tools and their influence on the load-bearing system

Concrete pulverizers

Concrete pulverizers crush reinforced concrete locally through compressive and tensile fracture. They are suitable for wall and slab edges, beams, corbels, and openings when load redistributions are to be kept small and reinforcement is to be exposed. By biting off material sequentially, load paths remain intact longer; exposing reinforcement facilitates the targeted separation of tension members. In practice, concrete crushers for selective removal support this approach. Attention should be paid to punching-sensitive zones and anchorage lengths; staged relief and short bite lengths improve predictability.

Hydraulic splitters

Hydraulic splitting generates separating tensile stresses along defined rows of drill holes. The intervention is low vibration and has a small effect on far-reaching parts of the system. The method is particularly suitable near load-bearing elements, with sensitive neighboring structures, and in tunnel or rock areas. Crack propagation can be guided by hole spacing and alignment; sequencing from free faces toward supports limits unintended interaction with bracing elements.

Combination shears and multi cutters

These tools combine cutting and crushing for heterogeneous components. In mixed load-bearing systems (steel-concrete-timber), materials can be separated appropriately and in the correct sequence to avoid unwanted redistributions. Interfaces such as composite joints, shear connectors, and headed studs are addressed last to maintain composite action as long as needed.

Steel shears

For steel frames, trusses, girders, and cladding, steel shears enable precise cuts. Node regions and stability elements (bracing) are critical. Cuts are preferably made in unloaded areas while temporary shoring or suspensions ensure the system effect. Where unavoidable, cuts in loaded members are preceded by force re-routing via clamps, chains, or auxiliary frames.

Tank cutters

In shell and tank load-bearing structures (cylindrical or spherical tanks), separation cuts can trigger local buckles and global tilting. Circular segments are kept small, openings are distributed symmetrically, and the shell is shored if necessary before larger segments are released. Cutting sequences that preserve meridional and circumferential stiffness reduce the risk of snap-through.

Hydraulic power packs

Hydraulic power packs ensure the energy supply and, together with appropriate hydraulic power units, influence tool characteristics via pressure and flow rate. A constant, appropriate pressure promotes reproducible fracture patterns and minimizes uncontrolled brittle fractures, increasing the predictability of the load-bearing system response. Flow control, pressure relief, and synchronized actuation of multiple tools enhance process stability and repeatability.

Application areas and load-bearing-system-oriented approach

Concrete demolition and special demolition

• Identify load paths early: bearings, punching shear zones, cores, and bracing elements.
• Work sequentially: edges and non-load-bearing zones first, load-bearing elements last.
• Concrete pulverizers for selective removal; hydraulic splitters for low-vibration separation cuts near sensitive components.
• Define release criteria per stage (deformation limits, vibration thresholds) before advancing.

Building gutting and cutting

• Decouple non-load-bearing layers before intervening in load-bearing elements.
• Saw openings, expose reinforcement, then crush or split in a controlled manner.
• Install temporary shoring before and during cuts.
• Protect remaining supports and bearings from overload by staging and local relief.

Rock excavation and tunnel construction

• Consider rock mechanics: joint orientation, stratification, and the support effect of the lining.
• Rock wedge splitters for defined separation planes; keep vibrations low to avoid compromising rock bolts and linings.
• Stepwise advance with short cantilevering and immediate lining installation.
• Monitor convergence and adjust excavation class and support density to maintain the composite action.

Natural stone extraction

• Separation joints along natural joints or rows of drill holes; release large-format blocks by splitting.
• A gentle approach preserves material quality and reduces microcracks.
• Include transport loads and lifting points in the load-bearing behavior of the blocks.
• Secure neighboring blocks and benches to prevent unintended wedging or toppling during extraction.

Special applications

• Confined spaces, heightened requirements for vibration and noise control, vibration-sensitive environments.
• Prioritize splitting or very fine-step pulverizer work to avoid disturbing surrounding load-bearing systems.
• Provide redundant safety and monitoring measures.
• Plan dust control and cutting fluids to protect sensors and monitoring equipment in close proximity.

Planning, structural analysis, and monitoring

The assessment and modification of load-bearing systems belong in expert hands. Before interventions, construction stages, load redistributions, stability, and deformations must be considered. Temporary safeguards (shoring, suspensions, underpinning) are part of the system. Measurement and monitoring measures – e.g., crack monitoring, strain measurements, settlement points, or ground vibration monitoring – help detect the structure’s responses early. Normative requirements and authority stipulations must generally be observed; specific measures depend on the project, component, and boundary conditions. Clearly defined trigger values and action plans ensure timely intervention when measured responses approach limits.

Low-vibration and controlled methods

Low-vibration methods reduce risks to adjacent components and installations. Hydraulic splitters produce defined, calm separation processes that keep load redistributions plannable. Concrete pulverizers allow small, sequential material removal with good visibility of reinforcement and cracks. Both approaches minimize secondary damage compared to percussive methods and are advantageous in sensitive environments. Additional benefits include reduced noise and dust generation, which further protects operations in neighboring areas.

Sequential approach: Example steps

1. Survey the existing structure: drawings, site inspection, probes, investigations.
2. Analyze the load-bearing system: load paths, bracing, critical zones.
3. Plan construction stages: shoring, suspensions, temporary supports.
4. Strip out: separate non-load-bearing components and reduce loads.
5. Prepare separation cuts: drilling, saw cuts, create access.
6. Targeted separation: split in rows, use concrete pulverizers for controlled bites, cut metal parts with shears.
7. Continuous monitoring: deformations, cracks, vibrations.
8. Complete deconstruction: remove remaining load-bearing members, relieve bearings, remove material.
9. Backwork: remove temporary supports in reverse sequence and restore or cap interfaces.
10. Documentation: record stages, measurements, and deviations as part of quality assurance.

Risks, damage patterns, and avoidance

• Unexpected redistribution: avoid through staging and temporary safeguards.
• Punching and shear failure: relieve critical zones in advance.
• Loss of stability in steel: do not cut load-bearing chords without suspensions.
• Crack propagation in masonry: keep vibrations low, dose splitting forces.
• Buckling in shells: choose small segment sizes, distribute cuts symmetrically.
• Release of residual stresses: anticipate with pre-fixation and balanced cut sequences.

Terms and parameters in the context of the load-bearing system

Key quantities are load-bearing capacity, deformation, ductility, stiffness, robustness, stability (buckling, overturning, local buckling), flexural and shear resistance, punching resistance, and support reactions. For practice, residual load-bearing capacity in intermediate states, bond behavior (concrete-reinforcement), joint stiffnesses, and the quality of joints and separation cuts are also important. Tools influence these quantities via the type and intensity of intervention. In temporary conditions, dynamic amplification and second-order effects can govern; redundancy and defined system separation joints improve fault tolerance.

Practice-oriented scenarios

Creating an opening in a reinforced concrete wall

After relief and shoring, edge cuts are sawed, the reinforcement is exposed, and locally broken with concrete pulverizers. Remaining bars are separated in a controlled manner. In this way, diaphragm action remains in place until the last step. Where required, lintels or frames are pre-installed so that horizontal loads continue to be transferred without interruption during and after the intervention.

Selective removal of a cantilevered balcony slab

The cantilever slab is shored from below. Then edge material is removed with concrete pulverizers before core areas are separated in small segments. This sequence avoids a sudden change in load transfer. Particular attention is paid to negative bending zones near the support and to waterproofing layers, which are cut back only after structural separation is complete.

Block extraction in the quarry

Drill holes define the subsequent separation joint; rock wedge splitters release the block along the desired plane. The surrounding rock mass remains largely unaffected, and the load-bearing systems of adjacent areas remain stable. Lifting points are dimensioned for the expected block mass, and the sequence ensures that wedges and chocks do not introduce unfavorable stress peaks during release.