The cross-section is a central fundamental concept in structural analysis, materials engineering, and demolition practice. It describes the cut surface of a component or body and decisively determines load-bearing behavior, stress distribution, and separation strategy. Whether in concrete demolition, gutting works, rock excavation, or natural stone extraction: the correct assessment of cross-sectional area, geometry, and wall thickness governs tool selection, procedure, and efficiency—for example when using concrete demolition shears or rock and concrete splitters from Darda GmbH.
Definition: What is meant by cross-section
By cross-section we mean the two-dimensional area and shape that arises when a body is conceptually or actually cut by a plane. In construction this includes the component thickness of walls and slabs, the profile geometry of beams and columns, and the cross-sections of reinforcing bars or pipes. Technically, both the shape (e.g., circular, rectangular, hollow section) and the cross-sectional area are relevant, because from it derive parameters such as load-bearing capacity, stiffness, and the local stress σ, which can be ideally described as force divided by area. In the practice of concrete demolition, gutting works, and rock excavation, cross-sections steer the choice of shears, cutters, hydraulic wedge splitters, and the sizing of the hydraulic power pack.
Technical fundamentals: cross-section, stress, and load transfer
Cross-sectional areas govern loading: with the same force, a smaller area leads to higher stress, which can favor cutting and splitting processes. Conversely, large component cross-sections require higher forces or adapted separation strategies. In hydraulic systems, the piston force results from hydraulic pressure together with the piston area; larger piston cross-sections deliver higher forces but require more flow rate. These relationships determine the selection of appropriate hydraulic power units and tools. For concrete demolition shears, jaw geometry and the contact cross-section influence the notch effect and thus crack initiation in concrete. For rock and concrete splitters, wedge action and cylinder forces act through borehole cross-sections into the component cross-section; the number and grid of boreholes are adapted to thickness, material, and the desired fracture path. In steel separation—e.g., with steel shears or Multi Cutters—the required shear force depends strongly on the bar or pipe cross-section, typically parameterized by diameter, wall thickness, and material.
Cross-section in concrete demolition: components, reinforcement, and material behavior
In concrete demolition and specialized deconstruction one encounters a wide range of cross-sections: thin screed layers, massive foundation bodies, wall and slab cross-sections with variable reinforcement, composite constructions with masonry, as well as composite cross-sections with steel sections. For planning and safe execution, knowledge of component thickness, reinforcement layout, and concrete grade is crucial. Concrete demolition shears can play to their strengths when component thickness and reinforcement cross-section match the jaw opening and geometry. Where cross-sections are particularly heavy or the reinforcement ratio is high, a combination of concrete demolition shears with steel shears or Multi Cutters is often used to cut steel portions in a controlled manner. Rock and concrete splitters are suitable for releasing thick components along defined split lines; for this, borehole diameters and spacings are adapted to the component cross-section so that controlled cracks form along the planned separation cut.
Wall and slab cross-sections
Walls and slabs usually have rectangular cross-sections with one- or two-way reinforcement. Small thicknesses favor biting off with concrete demolition shears; for larger thicknesses a multi-stage approach is sensible—e.g., notches or preliminary separations first, followed by size reduction into manageable sections. Crack propagation can be controlled via contact areas and points of application.
Beams and columns
For beams and columns, bending and compression zones, the reinforcement and confinement concept, and cross-section changes must be observed. Local strengthening, support regions, and head plates alter the effective cross-sectional area and thus the required cutting force. Here coordinated deployments of concrete demolition shears, steel shears and, depending on the construction, also combination shears are advisable.
Reinforcement cross-sections
Reinforcing steel is described by diameter (e.g., round bar), number, and position. The cross-section of the bars determines the cutting forces for steel shears and Multi Cutters. The larger the bar diameter or the bundling, the higher the required shear capacity and the more carefully accessibility must be planned.
Cross-section in rock excavation and tunnel construction
In rock excavation and tunnel construction, rock fabric, bedding, joints, and natural weak planes govern fracture mechanics. For rock and concrete splitters, borehole cross-sections, their spacing, and embedment depth must be chosen in relation to block or bench cross-section thickness. This allows controlled split surfaces to be produced without unnecessarily damaging the surrounding rock. In natural stone quarrying the cross-section geometry is deliberately used to release raw blocks with the desired formats; the orientation of split lines often follows the natural jointing direction.
Cross-section and tool geometry
Tool geometry influences how forces are introduced into a cross-section. Concrete demolition shears use concentrated contact cross-sections to create notch stresses and initiate fractures. Steel shears work with cutting edges whose radius and angle are matched to the material and cross-section; edges that are too blunt increase force demand and cause unwanted burr formation. For splitting cylinders, matching wedge shape, spread, and cylinder piston area to borehole diameter and component thickness is essential. Tank cutters as well as combination shears consider, for hollow sections and vessels, wall thickness in addition to stabilization by curvature; for pipes, elliptical ovalization can increase the effective shear cross-section.
Planning: From the cross-section to practical procedure
Solid planning takes the cross-section as the starting point and translates it into a safe, efficient approach. A structured sequence with clear steps has proven itself:
- Capture the component geometry: thickness, height, width, profile shape, voids.
- Determine reinforcement or inserts: diameter, position, spacing, bundling.
- Assess the material: concrete compressive strength class, aggregates, rock type, moisture, aging.
- Select the tools: concrete demolition shears, rock and concrete splitters, steel shears, Multi Cutters, tank cutters—matched to cross-section and accessibility.
- Set the parameters: hydraulic pressure, piston cross-section, jaw opening, borehole diameter and pattern.
- Trial cut or trial splitting at a representative location to validate assumptions.
- Execution with continuous observation of crack and cut development and adjustment of the sequence.
Hydraulics and cross-section: influence of piston diameter
Hydraulic power packs provide pressure and flow. The achievable tool force results from pressure in conjunction with effective piston area. Larger piston cross-sections deliver higher forces but require sufficient flow rate and influence working speed. Hose and valve cross-sections determine the flow and thus the system’s dynamics. Balanced matching is important to mobilize enough force for massive cross-sections while staying productive.
Gutting works and cutting: cross-section-appropriate separation
For gutting works and when cutting openings, wall thickness, lintels, skins, and embedded items must be considered. Concrete demolition shears can work out openings in masonry or concrete section by section, while steel shears and Multi Cutters cut reinforcement and embedded components with defined bar or profile cross-sections. Where wall thicknesses or claddings vary, work proceeds layer by layer to avoid unwanted load redistribution.
Practical examples by cross-section
For a massive reinforced-concrete wall of large thickness, a combined approach is often recommended: first drill splitting holes and use rock and concrete splitters to create a defined crack line; then concrete demolition shears break down the released segments, while steel shears cut the exposed reinforcement cross-sections. For thin-walled members or infill masonry, direct use of the concrete demolition shear may suffice. In natural stone extraction, the block cross-section is planned so that a dimensionally accurate raw block results with as few splitting passes as possible.
Risks and limits with large cross-sections
Underestimated cross-sectional areas lead to insufficient separation force, excessive tool wear, or uncontrolled fracture patterns. Oversized interventions, in contrast, can cause unnecessary cracks and spalling. An appropriate assessment of the cross-section, conservative assumptions, and, where appropriate, a trial area are sensible to reduce risks. Always maintain safe working distances, controlled force introduction, and an adapted sequence of steps.
Measurement and documentation methods for cross-sections
Cross-sections are derived from drawings, soundings, and measurements. Where information is missing or uncertain, low-destructive methods and spot checks help. The goal is to base tool sizing and demolition sequence on reliable data.
- Visual survey and manual measurements of component thicknesses and profiles.
- Probing and spot openings to determine reinforcement.
- Material samples or core drilling to verify build-up and density.
- Continuous documentation of the cross-sections found and adjustment of planning.
Special deployment: Safely processing unusual cross-sections
In special deployments—such as in confined areas, on tanks, in industrial buildings, or with complex composite cross-sections—special measures are required. Tank cutters must consider wall thicknesses, curvatures, and any coatings. Combination shears help when switching between steel and concrete cross-sections. The strategy always follows the cross-section: create accessibility, identify supports and embedded items, define a suitable cutting or splitting sequence.
Relevant material and cross-section parameters at a glance
In practice, a few but meaningful details are often sufficient: component thickness, cross-section shape, rebar diameter, number of layers, concrete grade or rock type. From this information it can be derived whether direct processing with concrete demolition shears is sensible, whether hydraulic wedge splitters are needed for pre-separation, or whether steel shears or Multi Cutters are governing for the steel portions. The more clearly the cross-section is described, the more precisely tools and hydraulic parameters can be chosen.
Good practice for efficiency and quality
Those who systematically capture the cross-section and translate it into force and tool categories minimize downtime and increase precision. This holds in concrete demolition and specialized deconstruction just as in gutting works, rock excavation, and natural stone extraction. A clean interface between planning and execution—with unambiguous information on cross-sections and material—facilitates alignment between concrete demolition shears, rock and concrete splitters, hydraulic power packs, and complementary tools.