Structural steel is the backbone of load-bearing construction—from reinforcement in reinforced concrete to profile members in steel construction. In practice, its importance becomes evident not only during construction but also in deconstruction: In concrete demolition and special deconstruction and in selective cutting, the properties and arrangement of structural steel are decisive for methods, tools, and occupational safety. Where reinforced concrete is deconstructed, concrete pulverizers are frequently used to expose and separate reinforcement, and hydraulic wedge splitters are deployed for controlled, low-vibration releasing. Understanding structural steel supports designers, contractors, and deconstruction teams in all phases—from design and construction execution to special demolition.
Definition: What is meant by structural steel
Structural steel refers to steels intended for load-bearing structures and construction applications. These include, above all, reinforcing steels (reinforcement in bars and meshes) for reinforced concrete as well as unalloyed and low-alloy structural steels for welded and bolted constructions (e.g., profiles, plates, hollow sections). Central mechanical properties include yield strength, tensile strength, and ductility, as well as weldability and bendability. In reinforced concrete, structural steel takes tensile forces while the concrete carries compressive forces—the bond action arises through ribs, surface profiling, and adequate concrete cover. In steel construction, defined grades enable reproducible load-bearing capacity and safe connection technology.
Properties, grades, and standard terminology
Structural steel is produced in grades with defined mechanical and technological properties. Typical reinforcing steels have ribbed surfaces, characteristic yield strengths (e.g., about 500 MPa), and specified ductility classes. Profile and plate steels are characterized by their minimum yield strength (e.g., 235–460 MPa) and toughness properties. Weldability depends, among other factors, on the carbon equivalent; low values favor safe welding and cold cutting.
Key material parameters
- Yield strength/Re: decisive for plastic load behavior and deformability
- Tensile strength/Rm and elongation at break: relevant for reserve capacity and ductility
- Bond behavior for reinforcing steel: rib geometry and concrete cover ensure force transfer
- Weldability and cold formability: important for connections and processing
Formats and delivery forms
- Reinforcing bars, coils, meshes, and prefabricated cages
- Rolled profiles (e.g., I-, U-, H-sections), plates, sheets, and hollow sections
- Wire and strand products for prestressing (special safety and separation concept required)
Structural steel in concrete construction and deconstruction
In reinforced concrete members, the diameter, position, and anchorage of reinforcing steel determine structural behavior—and, in deconstruction, the choice of methods. During removal of components, the combination of concrete size reduction and selective separation of structural steel has proven effective.
Exposing and cutting reinforcement
- Concrete pulverizers break up concrete in a targeted manner, expose reinforcement, and cut small to medium diameters. This allows concrete and steel to be separated into clean fractions right at the source.
- Hydraulic wedge splitters generate controlled crack formation without sparks and with reduced vibrations—advantageous in sensitive environments, during strip-out, and in special demolition.
- For larger bar diameters and structural steel sections, additional cold-cutting tools such as steel shears or multi cutters are used.
Particularities of prestressed concrete
Prestressing steel is under high tensile stress. Before interventions, location and stress state must be determined by experts; cuts are made with suitable, controlled methods. Controlled cracking of the concrete with low vibrations can help to make tendons accessible. Information in structural documentation and test reports is decisive for this.
Separation and processing methods in demolition
Structural steel can be separated thermally or mechanically. In many applications, low-spark hydraulic methods offer advantages—for example, in buildings that remain in operation, in areas with fire or explosion hazards, and in tunnel construction.
Cold cutting with hydraulic tools
- Concrete pulverizers: crush concrete, expose reinforcement, and—depending on the model—cut reinforcement bars.
- Steel shears/multi cutters: cut structural steel sections, meshes, and pipes; suitable for deconstruction of steel structures and reinforcement bundles.
- Hydraulic wedge splitters: split components, guide crack propagation, and make steel selectively accessible.
Thermal and abrasive methods
- Oxy-fuel cutting/plasma cutting: powerful on thick plates and sections, but associated with sparks, heat, and emissions.
- Abrasive cutting/waterjet: flexible, but usable only to a limited extent depending on the environment.
Corrosion, durability, and condition assessment
Corrosion of reinforcing steel is often triggered by concrete carbonation or chloride contamination. It affects cross-section, bond, and load-bearing capacity and can be recognized during deconstruction by typical damage patterns. For planning and execution, non-destructive testing, probing, and recording of reinforcement layouts are helpful.
Relevance for deconstruction
- Corroded bars may be easier to release from concrete but can cause unpredictable fracture patterns.
- Intact, high-strength reinforcement requires powerful cutting methods and clear accessibility.
- The separability of concrete and steel determines recycling routes and disposal costs.
Overview of structural steel types
Different structural steels are used depending on the construction task. Knowing them facilitates selection, processing, and deconstruction planning.
Reinforcing steel
Ribbed bars and meshes with high yield strength and defined ductility. Bendable and weldable depending on grade and carbon equivalent. In demolition they are often exposed with concrete pulverizers and, if necessary, re-cut with steel shears.
Steels for steel structures
Rolled sections, plates, and hollow sections, usually unalloyed or low-alloy. Processing in deconstruction includes cutting, lowering, and sectioning. Cold-cutting shears and multi cutters enable low-spark operation, for example during strip-out and cutting in existing structures.
Special steels
Prestressing steels, weathering steels, or higher-strength grades require adapted cutting strategies. Early identification of the grade facilitates the selection of tools and cut sequences.
Structural steel in rock and tunnel construction
In tunnel construction and rock engineering, structural steels are used as anchors, lattice girders, and support elements. When deconstructing temporary supports or widening the profile, the steel–rock bond must be released in a controlled manner. Hydraulic wedge splitters are helpful here to partially loosen rock and make embedded steels accessible; steel shears take over the subsequent cutting of support elements.
Special boundary conditions
- Confined spaces and high requirements for vibration and emission control
- Increased safety requirements for tensioned anchors
- Documentation of the cut sequence for controlled load release
Strip-out and selective deconstruction in existing structures
During strip-out, non-load-bearing components are removed, load-bearing components are selectively weakened, and dismantled in a defined sequence. Structural steel serves as a guide material: It indicates load paths and connection details. Exposing with concrete pulverizers and subsequent cutting enables clean separation of materials—the basis for efficient recycling.
Typical work steps
- Existing conditions survey: reinforcement layout, section profiles, connections
- Expose: break concrete in a targeted way, work out the steel
- Cut: low-spark cutting, secure sections, and lower them
- Separate: process steel and concrete, organize haulage logistics
Hydraulic power packs as the energy source
Hydraulically powered tools for concrete demolition, cutting, and splitting require a stable oil supply. Hydraulic power packs (hydraulic power units) provide the necessary flow rate and pressure, enable mobile operation, and precise control. Together with concrete pulverizers, hydraulic wedge splitters, and shears, this creates a low-noise, low-emission, and controlled work chain—particularly advantageous indoors, in tunnel construction, and for special operations.
Structural steel, special operations, and low-spark cutting
In areas with increased fire or explosion hazards and where sensitive building services are present, low-spark methods are required. Cold-cutting hydraulic tools reduce sparks, heat, and emissions compared to thermal methods. For massive steel plates, such as on tanks or thick plates, specially designed cutting tools must be selected; deployment planning considers material grade, plate thickness, and accessibility.
Safety aspects
- Assess the component condition (prestressing, residual stresses, corrosion)
- Define load transfer and cut sequence
- Define clearance and cordoned-off areas, minimize emissions
Sustainability and recycling
Structural steel is almost completely recyclable and retains its material properties in the loop. For high-quality recovery, clean separation of concrete and steel is decisive. Controlled size reduction with concrete pulverizers and targeted splitting with hydraulic wedge splitters facilitate separation already on the construction site. This optimizes transport, processing, and the deconstruction balance.
Quality factors for the material flow
- Low concrete adherence on scrap through clean exposure
- Orderly bundling and sizing of steel sections
- Documented material flows for verification and billing
Planning, execution, and documentation
Whether new construction or deconstruction: The proper handling of structural steel begins with careful planning. In concrete construction, reinforcement layout, concrete cover, and connection details are central. In deconstruction, existing documentation, locating, and probing determine the sequence. Clean documentation of the methods used—from splitting to breaking to cutting—supports quality, safety, and verification.
Practice-oriented guidance
- Early clarification of steel grades facilitates the choice of separation methods
- Plan the combination of tools: expose, split, cut, separate
- Consider the work environment: noise, vibrations, sparks, exhaust gases