Reinforcement system

Reinforcement systems are a central topic in structural repair, strengthening, and the safe remodelling of existing load-bearing structures. They are used when the load-bearing capacity, serviceability, or durability of components must be specifically increased—for example in cases of change of use, damage, seismic requirements, or during partial deconstruction and the creation of new openings. In practice, they directly influence the selection of work methods and tools in concrete demolition and special demolition. Where concrete members are strengthened or subsequently braced, mechanical cutting and splitting methods behave differently: concrete pulverizers must expose and sever reinforcement and bond layers, while hydraulic rock and concrete splitters exploit defined split lines to open components with low vibration. Proper preparation determines safety, emissions, and efficiency.

Definition: What is meant by reinforcement system

A reinforcement system is the entirety of structural measures and components that increase the load-bearing capacity and stiffness of existing components or improve their ductility. These include bonded steel or fiber‑reinforced polymer laminates (e.g., CFRP/GFRP), section enlargement by concrete jacketing, sprayed mortar/shotcrete, external or internal prestressing, additional reinforcement with bonded anchors, steel sections and frames, temporary shoring, and local detail strengthening at supports and connection zones. The goal is reliable load transfer with a sound bond to the existing structure, controlled crack width limitation, and sufficient durability with minimal impact on the structure. Design is based on recognized engineering standards; execution and supervision account for substrate preparation, bonding and anchorage techniques, anchor spacing, corrosion protection, and quality assurance testing.

Configuration, materials, and working principles of reinforcement systems

Reinforcement systems combine materials and joining techniques to increase flexural, shear, or torsional resistance in a targeted way. In reinforced concrete construction, three principles dominate:

• Section enlargement: Concrete jacketing or shotcrete with additional embedded reinforcement improves flexural and shear capacity and protects against environmental influences.
• Externally bonded elements: CFRP laminates, CFRP fabrics, or steel plates provide additional capacity with minimal added depth; performance depends strongly on substrate preparation and bond quality.
• External prestressing/tensioning: Tendons or bar anchors carry forces outside the original section, reducing cracking and deflection; prestressing requires particular attention during deconstruction works.

In masonry, injection, flat steel anchors, strapping, and fabric-reinforced render systems are used. In steel construction, strengthening of girders is implemented by plating, coupling plates, and stiffeners. In tunnelling and rock engineering, shotcrete, anchors (rock bolts), spiles, lattice girders, and steel rings act together as a composite system to stabilize the ground.

Relevance in concrete demolition and special demolition

Reinforcement systems alter fracture patterns, bond behaviour, and load redistribution—and thus the approach to dismantling, gutting works, and cutting operations. Members with CFRP laminates or steel plates show higher tensile and shear capacity in the strengthened zone; members with external prestressing store energy that can be released suddenly if severed uncontrollably. In special demolition, careful identification and sequencing are therefore crucial:

• Expose the system: Using concrete pulverizers to remove cover concrete in a controlled manner makes reinforcement, laminates, or plates visible.
• Targeted separation: steel shears, multi cutters, or combination shears cut reinforcing bars, sections, or strapping, while concrete splitters open components along defined lines with low vibration.
• Stepwise stress relief: For prestressed or tied systems, perform controlled stress relief and sequential removal, supported by temporary shoring.

The choice of tool and sequence reduces vibration, noise, and dust and increases construction site safety.

Work preparation: investigation, design, and documentation

Preliminary investigations clarify structural behaviour, bond quality, and the location of critical elements. A combination of document review and low‑impact testing has proven effective:

• Component diagnostics: locating reinforcement, laminates, and anchors; cover depth measurement; assessment of crack patterns, concrete carbonation, and chloride content.
• Structural assessment: reserve capacities, load redistribution, demolition and assembly states; verification of intermediate conditions.
• Work and safety concept: sequence plans, exclusion zones, shoring concept, emissions protection (dust suppression, noise reduction measures, low vibration levels), emergency procedures.
• Documentation: photo records, approvals, test certificates, and inspections—careful, traceable, and continuous.

These steps are generally carried out in accordance with recognized engineering standards and with reference to the relevant codes and guidelines. The statements are general and do not replace a project‑specific assessment.

Selecting suitable methods: cutting, splitting, separating

Strengthened members respond heterogeneously. Methods are therefore combined to selectively release material bonds:

• Concrete pulverizers: For removing cover concrete, controlled breaking of edges, and exposing reinforcement and bonded elements.
• Steel shears: For cutting reinforcing bars, steel sections, strapping, and plate strengthening.
• Combination shears and multi cutters: When concrete and steel must be processed immediately one after the other or in a single pass.
• Concrete splitters: For low‑vibration split openings, targeted crack initiation, and detaching partial areas in dense urban settings or near sensitive neighbouring structures.
• Hydraulic power packs: Reliably supply the tools; power reserves and hose routing influence cycle time and reach on site.
• Cutting torch: In special application on strengthened tanks, steel shells, or complex internals, when stiffeners or strengthening shells must be severed.

The combination of methods depends on member thickness, reinforcement ratio, type of strengthening, space constraints, emission requirements, and the planned reuse or disposal of materials.

Step-by-step procedure for openings in strengthened members

1. Investigation: drawings, locating reinforcement and strengthening elements, marking cut and split lines.
2. Temporary stabilization: shoring of the affected zone, establishing exclusion areas.
3. Removal of cover layers: selective removal with concrete pulverizers, exposing laminates/plates and anchors.
4. Cutting the strengthening: cutting CFRP/steel strengthening, rebar, and connections with steel shears and/or combination shears.
5. Splitting and releasing: creating the opening with concrete splitters along prepared lines; lifting out the segments.
6. Finishing: edge treatment, corrosion protection on remaining steel, check of residual load‑bearing capacity.
7. Final inspection: visual checks, measurements, documentation.

Special systems: CFRP laminates, steel plates, and external prestressing

CFRP laminates and fabrics provide high tensile strength at low weight. During deconstruction, the bond is critical: before cutting, expose adhesive joints and mechanically release laminates to avoid uncontrolled spalling. Steel plate strengthening is more ductile and can be cut well with steel shears and multi cutters; consider contact corrosion and residual bonding mortar. External prestressing systems require special care: reduce prestress forces in a controlled manner, secure anchorage points, and relieve the tendon stretch step by step. The sequence is defined and supervised on a project‑specific basis.

Reinforcement systems in rock and tunnel construction

In underground construction, shotcrete, rock bolts, lattice girders, and steel rings stabilize the ground. For modifications or deconstruction, these systems act like a composite body of rock, shotcrete, and steel. Concrete splitters are suitable for controlled openings in rock or shotcrete linings, while steel shears and combination shears cut reinforcement, stirrups, and lattice girders. The sequence minimizes vibration and maintains the stability of the excavation profile.

Impact on gutting works and cutting

In gutting works, strengthening often meets building services, fire protection claddings, and built‑ins. Removing jacketing and exposing the load‑bearing structure with concrete pulverizers provides visibility of relevant details. Under tight space constraints and in sensitive surroundings, concrete splitters are advantageous due to low vibration. Multi cutters help separate mixed layers of concrete, mortar, metal sections, or strapping before components are segmented for manageable logistics.

Safety, emissions, and environmental protection

Safety takes priority. Regulated procedures, certified tools, and clear responsibilities are essential. Particular risks include stored energy in prestressed systems, spring‑back of laminates, swinging segments, and concealed anchors. Emission control includes dust suppression, noise reduction measures, and limiting vibration. Material‑separated dismantling facilitates recycling: concrete pulverizers and steel shears support clean separation of concrete and steel, improving recovery as recycled concrete and scrap.

Quality assurance and performance control

Work quality is ensured through visual and dimensional checks, substrate strength tests, pull‑off tests for bonded systems, and monitoring of shoring in intermediate states. For remaining strengthening measures, follow‑up inspections for cracking, bond, and corrosion protection are advisable. All findings are continuously documented; deviations lead to adjusted measures.

Common mistakes and how to avoid them

• Incomplete investigation: concealed strengthening elements remain undetected; countermeasure: systematic locating and exposure.
• Incorrect sequence: premature cutting of load‑bearing elements; countermeasure: structurally verified sequences, temporary shoring.
• Insufficient substrate preparation when releasing bonded systems: spalling; countermeasure: defined cut and release lines, stepwise removal with concrete pulverizers.
• Unplanned release of prestress forces: countermeasure: controlled stress relief, securing of anchorage points.
• Poor separation of material streams: countermeasure: early segregation with steel shears and concrete splitters.

Sustainability and resource efficiency

Reinforcement systems can extend service lives and conserve resources. During deconstruction, selective dismantling enables reuse of components, high‑quality recovery of concrete and steel, and minimization of transports. Low‑vibration methods and precise sequencing reduce impacts on neighbouring structures and increase acceptance in urban environments.