Structural Analysis for Demolition

Structural analysis for demolition is the engineering discipline that ensures structural stability during deconstruction. It combines structural mechanics, construction stage assessment and a precise sequence of steps when removing structural elements. The goal is to redistribute load paths in a controlled manner, to ensure residual load-bearing capacity in every construction stage, and to secure both local and global stability — while minimizing vibrations, dust and noise emissions. In practice, this concerns concrete demolition and special demolition, gutting works and cutting of openings, rock excavation and tunnel construction, natural stone extraction as well as complex special demolition. Devices such as concrete pulverizers or rock and concrete splitters from Darda GmbH significantly influence the structural analysis assessment, because they enable low-load, low vibration levels and well-dosed interventions.

Definition: What is meant by structural analysis for demolition

Structural analysis for demolition comprises the entirety of analytical, constructive and organizational measures that ensure the load-bearing capacity and serviceability of structures or rock masses during deconstruction in all construction stages. It includes:

determining the as-is structure (geometry, material, damage, reinforcement, connections),
predicting load redistribution and deformations when members are separated, weakened or removed,
verifying residual load-bearing capacity and stability for each deconstruction stage,
specifying the sequence of steps, safeguarding measures and admissible equipment actions.

Structural analysis for demolition is not a copy of new-build structural analysis. It focuses on intermediate states, local weakening, loss of composite action, incomplete cross-sections, temporary supports and uncertain boundary conditions. The choice of methods — for example hydraulic splitting with rock and concrete splitters or crushing with concrete pulverizers — is an integral part of the structural analysis for demolition, because it determines the type and magnitude of loads and the dynamics of the actions.

Fundamentals and terminology of structural analysis for demolition

The structural analysis for demolition is based on understanding load paths, load dispersion and the role of composite action between members. Typical influencing factors are:

Construction stage: Every intermediate state with altered shoring, separation cuts or partial deconstruction.
Residual load-bearing capacity: Load reserves after cross-section reduction, cracking, loss of bond/composite action.
Boundary conditions: Temporary shoring, support redistribution, site installations, crane and equipment reactions.
Dynamics/vibrations: Depending on the method (e.g., splitting, cutting, shearing/crushing).

Structural mechanisms

In deconstruction stages, mechanisms often differ from the final state: arch and membrane actions are lost, substitute systems arise (strut-and-tie models), load participation shifts from plate to beam action. Structural analysis for demolition identifies and controls these transitions.

Planning, construction stages and verifications

Robust planning follows clearly structured steps and documents every construction stage.

Existing structure survey: Recording geometry, material parameters, reinforcement, joints, connectors and pre-damage.
Load assumptions: Self-weight, construction process live loads, equipment reactions, wind, water levels, vibrations.
Deconstruction concept: Sequence of steps, separation cut locations, order of weakening, removal and transport.
Verifications: Load-bearing capacity (bending, shear, punching), stability (overturning, buckling, sliding), serviceability (deflections, crack widths), local contact pressures.
Safeguards: Shoring, bracing, catch and protective measures; release criteria for each step.
Monitoring: Measurands (settlements, cracks, inclinations), limit values, intervention plan.

Cautious legal context

Codes and authority requirements must be considered for each project. Structural analysis for demolition verifications and releases should be provided by qualified specialist engineers; project-specific requirements may vary.

Method selection and structural analysis for demolition: concrete pulverizers, rock and concrete splitters and other tools

The choice of method shapes the actions on the structure. Devices from Darda GmbH enable different action modes relevant to the structural analysis:

Concrete pulverizers: Local crushing without high-frequency vibrations; reaction forces are introduced via gripping arms, cross-sections are reduced progressively. Well controllable for slabs, drop beams, walls and member edges.
Rock and concrete splitters including rock wedge splitters: Introduction of splitting forces along prepared boreholes; generates directed crack formation with low vibration levels. Suitable for separating massive cross-sections and in rock.
Multi Cutters and combination shears: Cutting and crushing in one tool; useful for varying cross-sections and mixed materials.
Steel shears: For sections, reinforcement bundles and decoupling composite connections; reduces joint forces in a controlled manner.
Tank cutters: Precise opening and disassembly of vessels; for structural analysis, slot sequence and residual body stability are decisive.
Hydraulic power pack: Power supply; relevant to the structure due to self-weight, hose routing and bearing areas, not due to impulsive actions.

Static consequences of the methods

Splitting methods shift forces already during crack initiation, shearing/crushing methods reduce cross-sectional areas stepwise, cutting methods decouple composite action abruptly. Structural analysis for demolition specifies which safeguard is required at which time.

Application in concrete demolition and special demolition

In selective concrete demolition and deconstruction, sequence of steps and separation cut locations are decisive. Concrete pulverizers from Darda GmbH allow controlled nibbling of edges and ribs, while rock and concrete splitters divide massive bodies with low vibration levels.

Typical procedure

Create relief cuts (e.g., with Multi Cutters) to constrain load paths.
Targeted weakening (concrete pulverizers) while simultaneously shoring the remaining fields.
Separation of massive regions by splitting; then lifting smaller pieces.
Successive redistribution of support reactions and deconstruction of temporary safeguards.

For drop beams, slabs and wall panels, overturning safety and punching shear reserves are verified at every step. The low vibration intensity of splitting and crushing methods has a positive effect on adjacent sensitive areas, but the reaction forces at the application points must be taken into account.

Strip-out and cutting: openings, separation cuts and boundary conditions

During strip-out and the creation of openings, local effects dominate: loss of cross-section, interruption of reinforcement, edge breakout at opening corners.

Guidelines for structural analysis for demolition

Prior redistribution: install temporary underpinning before cutting.
Crack control: opening radii and cutting sequence against notch stresses; concrete pulverizers minimize spontaneous spalling.
Composite control: deliberately separate steel beam connections and shear connectors (steel shears) to avoid unintended restraint forces.
Transport concept: select piece weights such that lifting and support reactions remain manageable.

Rock excavation, tunnel construction and natural stone extraction: structural considerations

In rock, the geometry of joints and bedding planes dominates. Rock and concrete splitters and rock wedge splitters from Darda GmbH use directed splitting forces to activate existing weakness zones and detach controlled blocks.

Essential aspects

Block and wedge stability: analysis of potential sliding and overturning bodies along discontinuities.
Sequence: from exposed, small blocks to larger ones — reducing restraints.
Stabilization: rock bolting, bracing or anchoring as temporary measures on exposed slopes or at the tunnel face.
Tunnel construction: interactive influence of lining, tunnel face and loose rock; low vibration reduces the impact on the lining.

In natural stone extraction, directed splitting allows predictable block geometries; for structural analysis during demolition, stability of the remaining wall and the controlled sequence of block release are decisive.

Loads from equipment and auxiliary structures

Equipment-induced actions result from self-weight, reaction forces and supports. Structural analysis for demolition accounts for:

Contact and reaction forces of concrete pulverizers at member edges and bearing points.
Splitting forces along borehole axes, transverse tension and splitting tension; minimum edge distances.
Cutting forces with Multi Cutters, combination shears, steel shears; immediate cross-section reduction.
Auxiliary structures: Loads from shoring, needle beams, brackets, shoring scaffolds; load redistribution during assembly and dismantling.

Dynamics and vibrations

Hydraulically operated devices from Darda GmbH are characterized by well-controllable, relatively low-frequency actions. Nevertheless, dynamic amplification factors, loosening and impact effects should be applied conservatively in the verification.

Temporary safeguards and monitoring

Temporary safeguards are an integral part of structural analysis for demolition and are linked to release criteria.

Shoring: preliminary design to construction stage loads; consider misalignment and buckling.
Bracing: diagonal bracing against overturning/sliding; anchoring in load-bearing areas.
Catching/protection: protective roofs, nets, catch scaffolds.
Monitoring: cracks, settlements, inclinations; define stop criteria for interventions.

Stepwise releases

Each deconstruction step receives defined measurement and visual inspections. Only after compliance with limit values and visual release does the next measure proceed. Changes in the construction process require a new structural analysis for demolition.

Deconstruction of steel, tank and composite components

In steel and composite structures, shear connectors, welds and connections govern load transfer. Steel shears cut sections and reinforcement in a targeted manner, tank cutters enable the planned opening of shells and lids.

Notes for structural analysis for demolition

Loss of composite action: cutting stud bolts creates new load paths; provide temporary supports before cutting.
Tanks: geometry changes influence stability; plan cutting sequence to prevent buckling and overturning.
Mixed structures: consider differing stiffnesses of steel and concrete; controlled reduction of composite action.

Calculation approaches and practical simplifications

Structural analysis for demolition uses a combination of detailed and simplified models:

Beam and plate models with modified supports for intermediate states.
Strut-and-tie models to describe local load paths after loss of cross-section.
Plastic limit capacity approaches for conservative reserves in bending and shear.
Discontinuity analyses in rock (wedge and block models).

Simplifications are permissible if they are on the safe side and are supported by measurements/observations.

Risk management, documentation and occupational safety

Deconstruction projects benefit from systematic risk analysis. A method statement consolidates concept, verifications, sequence of steps, safeguards, equipment deployment (e.g., concrete pulverizers, rock and concrete splitters, Multi Cutters, combination shears, steel shears, tank cutters) and monitoring. Occupational safety is an integral part of planning; specific measures depend on project, equipment and environment.

Communication in the project

Defined reporting paths, releases and stop rules create clarity. Changes in equipment configurations (e.g., different jaw geometry, splitting wedges) are assessed and documented within the structural analysis for demolition.

Frequent failure patterns and prevention

Underestimating the construction stage effects: missing shoring before separating a load-bearing element.
Unclear separation cut location: unwanted crack propagation and unexpected load paths.
Local over-pressures: edge distances too small for splitters; edge breakouts.
Neglected composite action: unseparated steel parts continue to transmit forces.
Missing monitoring concepts: response too late to deformations/crack growth.

Preventive measures

Adequate preliminary investigation, conservative assumptions, stepwise approach, monitoring and an adapted tool selection are the most effective means against typical errors.

Resource efficiency and environmental aspects

Structural analysis for demolition enables selective, low-emission deconstruction. Splitting and crushing methods reduce vibrations and help protect adjacent structures. Targeted separation improves material purity and supports reuse and recycling. A planned use of concrete pulverizers as well as rock and concrete splitters from Darda GmbH helps to convert members into manageable segments and to ensure statically safe transport and interim storage.