Support frames form the load-bearing skeleton of many structures. As a system of columns and beams, they transfer self-weight, imposed loads and, where applicable, wind and seismic actions to foundations. In concrete demolition, special demolition and building gutting, a precise understanding of the structural action is crucial to safely control construction stages. Tools from Darda GmbH such as concrete pulverizers or hydraulic rock and concrete splitters enable controlled interventions in members of frame constructions – with low vibration and along defined load paths.
Definition: What is meant by support frames
A support frame is a column-beam system whose members are connected via pinned or moment-resisting joints. Frames primarily resist bending and shear actions; they provide bracing in one or more directions and, together with floor diaphragms, form a three-dimensional structural system. Support frames occur in reinforced concrete, steel and composite construction, with or without infill walls. Their structural effectiveness depends on joint stiffness, connection details, cross-sectional geometry and interaction with adjacent components.
Configuration and structural behavior of support frames
A frame system consists of vertical columns and horizontal beams. At their joints, moments and shear forces arise that define the load paths. Decisive factors are joint behavior (pinned vs. moment-resisting), flexural capacity of the sections, shear verification and coupling with slabs that distribute loads as diaphragms. Under actions, characteristic bending-moment distributions develop; local interventions — such as opening, cutting or splitting — alter these distributions and require propping or load redistribution.
Reinforced concrete frames
Reinforced concrete frames combine the compressive capacity of concrete with the tensile capacity of reinforcement. Crack formation, shear keys, anchorage lengths and joint reinforcement govern robustness. During deconstruction, brittle fractures must be avoided. Selective biting with concrete pulverizers or controlled introduction of crack joints using hydraulic splitters reduces vibrations and maintains residual load-bearing capacity in construction stages.
Steel frames
Steel frames utilize rolled sections and bolted or welded joints. Copings, web openings and joint stiffness influence structural behavior. During deconstruction, steel shears or multi cutters are used to separate sections in stages. The cutting sequence must be selected to minimize tipping and buckling hazards and to keep temporary shoring functional.
Masonry and mixed systems
In mixed systems, ring beams, downstand beams or retrofitted steel sections assume frame-like tasks. Infills change stiffness. Openings in load-bearing walls are often only safe to produce with support beams. Low-vibration methods prove effective here, such as splitting followed by controlled removal with concrete pulverizers.
The role of support frames in concrete demolition and special demolition
When deconstructing frame structures, the sequence of interventions has a direct impact on stability. First, non-load-bearing components are stripped out; then beams, columns and joint areas follow — always with an eye on the remaining load paths. Temporary support frames bridge situations when joints are opened or beams are separated.
- As-built survey: drawings, site inspections, probes, determination of reinforcement and joint details.
- Structural assessment: model of load redistribution, construction stages, ultimate limit states.
- Demolition sequence: from released bays to edge bays, maintain bracing until substitute measures are in place.
- Methods: concrete pulverizers for selective removal, hydraulic splitters for controlled separation joints, combination shears and multi cutters for reinforcement and embedded parts.
- Monitoring: settlement and crack monitoring, barriers, emergency plans.
Tool selection in the frame context
Concrete pulverizers enable stepwise reduction of cross-sections on beams and columns without percussive loads. Hydraulic splitters create defined crack joints along which members break in a controlled manner — helpful at joints with high reinforcement density. Hydraulic power units provide the required power supply. For steel portions in mixed constructions, steel shears and multi cutters are used; for tank frameworks and frames from tank installations, cutting torches are relevant. The cutting pattern always follows the structurally planned load redistribution.
Openings, strip-out and cutting in frame constructions
Openings in beams, columns or slab-level frames require propping and an exact cutting sequence. The goal is to secure residual capacity at every phase and to limit notch effects.
- Propping and relieving: auxiliary frames provide alternative load paths.
- Pre-cutting and splitting: drilling of relief boreholes; setting splitting wedges; controlled splitting of the concrete.
- Selective removal: biting off with concrete pulverizers to the final opening geometry; reinforcement separated with combination shears.
- Finishing works: edge treatment, corrosion protection on exposed reinforcement, temporary safeguards.
Protecting residual load-bearing capacity
A sufficient distance to joints and supports prevents unintended notch stresses. Cuts must be arranged so that no shear caps or essential reinforcement are separated uncontrollably. Monitoring accompanies every construction stage.
Temporary support frames and propping
In addition to the existing frame, temporary frames (support frames, needling, portal frames) play a key role. They take over loads during deconstruction or conversions. Their design considers concentrated loads, eccentricities and possible impacts from separation works. The combination of hydraulic power packs, hydraulic splitters and concrete pulverizers allows the cutting sequence to be adapted to temporary states.
Support frames in rock demolition and tunnel construction
In tunnel construction, frames serve as preliminary or final lining, often in conjunction with shotcrete and anchors. When breaking through frame foundations or deconstructing installations, low-vibration methods are essential. Hydraulic splitters produce defined separation joints in rock or at foundation beams, while concrete pulverizers continue material removal in a controlled manner. The bracing of the cavity must not be compromised; temporary steel frames secure the cross-section.
Natural stone extraction and frame-like structures
Frame-like structures are also found in natural stone extraction: cut boundaries delimit blocks and create “frames” that stably guide the block. Hydraulic splitters utilize natural joints and separation planes to free blocks with low vibration. The selection of the cutting sequence prevents uncontrolled fractures, especially at edge areas that will later take machining loads.
Concrete demolition at joints and supports
Joints are the most sensitive areas of a support frame. Bending, shear and axial forces superimpose here. Stepwise removal with concrete pulverizers reduces cross-section and stresses in a controlled way; for massive joints, pre-splitting improves separability and reduces loads on the pulverizer. At supports on walls or columns, propping must be maintained until substitute load paths are activated.
Typical damage patterns and prevention
Characteristic damage patterns on frames include joint tears, shear cracks at beam end regions, compressive spalling at column heads and local reinforcement fractures. Causes often lie in unplanned load redistribution, missing shoring or unfavorable cutting sequences. The combination of planning, auxiliary frames and suitable methods — such as splitting before biting — significantly reduces these risks.
Work organization, safety and general notes
Careful organization increases safety and efficiency. In addition to technical planning, work spaces, logistics and communication are important. Legal requirements and professional association rules must be observed; specific requirements can vary by project and must be checked on a project-specific basis.
Practical recommendations
- Position hydraulic power packs securely, protect hose routing and avoid tripping hazards.
- Ensure load relief at the separation line; secure components against tipping and swinging.
- Limit emissions: prefer low-vibration methods (splitters, concrete pulverizers).
- Plan measurements: monitor and document crack widths, settlements and vibrations.
Term delineation and practical classification
The support frame is part of the overarching structural system. Slab and wall components act as diaphragms or infills. For interventions — whether deconstruction, conversion or selective opening — the principles of load redistribution, temporary shoring and controlled separation apply. Tools from Darda GmbH such as concrete pulverizers, hydraulic splitters, combination shears, multi cutters, steel shears and cutting torches can be combined according to material and joint conditions so that construction stages remain under control and load paths are secured.