Transverse anchors are indispensable connecting elements in structural and rock engineering. They secure components transverse to the primary load-bearing direction, transfer tensile forces, and stabilize masonry, concrete elements, and rock. In demolition, special demolition, strip-out, and tunnel construction, transverse anchors often determine the sequence and method of work because they maintain load paths or transfer forces into the ground. For safe exposure and cutting, different hydraulic tools are used depending on material and geometry, such as concrete pulverizers, rock and concrete splitters, combination shears, or steel shears, powered by hydraulic power packs.
Definition: What is a transverse anchor
A transverse anchor is a/an tension-loaded connecting element that connects components or geological structures transverse to the prevailing stress or member axis. Transverse anchors transfer tensile forces, can be prestressed or non-prestressed bars, bolts, or anchoring systems, and act via form-fit, friction, or bond. They are used in masonry (wall and façade anchors), in reinforced concrete (anchor rods, anchor channels, reinforcement penetrations), in rock and tunnel engineering (rock anchors, rock bolts), as well as for temporary stabilizations.
Structure, types, and working principle of transverse anchors
Transverse anchors typically consist of a steel bar or threaded rod with an anchor plate or head, possibly with sleeve, grout, or injection adhesive. Depending on the application, different designs are used:
- Masonry anchors: Visible or concealed anchors that tie back façades, gables, or wall panels transverse to the wall plane. Frequently configured as tie rods with anchor plates.
- Rock anchors and rock bolts: Bars or hollow anchors installed in boreholes that secure bedding planes and excavation zones. They act through bond and, where applicable, prestress.
- Bonded and grouted anchors: Transverse tension anchors embedded with mortar in concrete or masonry to resist tensile forces, also used as micropiles subjected to transverse loads.
- Prestressed transverse anchors: Anchors with defined prestress for crack control, stabilization, or load redistribution.
The working principle is based on reliable force transfer into the base material: steel failure, concrete breakout, bond failure, and uplift of the anchor plate are governing limit states. Edge distances, concrete cover, rock quality, and corrosion protection are critical.
Fields of application in construction and their relevance to demolition and deconstruction
Professionals encounter transverse anchors in many situations. The most important relationships:
- Concrete demolition and special demolition: Transverse anchors hold brackets, column heads, or bridge components transverse to the axis. Before separation, they must be identified, exposed, and relieved of tension. Concrete pulverizers facilitate the selective removal of concrete around anchor heads.
- Strip-out and cutting: When making separation cuts in slabs, downstand beams or walls, undiscovered transverse anchors prevent controlled lowering. Rock and concrete splitters decouple components by controlled crack formation before steel parts are cut with steel shears or combination shears.
- Rock excavation and tunnel construction: Rock anchors and bolts stabilize the crown, sidewalls, and tunnel face. During dismantling, modification, or removal of temporary stabilizations, anchor heads must be exposed, stresses relieved, and bars safely cut.
- Natural stone extraction: Transversely acting restraints hold quarry faces and blocks. When releasing blocks, existing preloads must be accounted for to avoid uncontrolled movements.
- Special applications: In historic buildings, masonry anchors made of wrought steel stabilize gables and slab bearings. Their preservation or removal requires gentle exposure, for example with handheld concrete pulverizers, before bars are mechanically cut.
Exposing, relieving, and removing transverse anchors: practical procedure
An orderly approach minimizes risks. In practice, the following sequence has proven effective:
- Investigation and documentation: Review drawings, perform locating and probing. Identify anchor heads, plates, and nuts. Check the load condition and, if necessary, provide temporary shoring.
- Selective exposure: Use concrete pulverizers to remove concrete around anchor heads, plates, and nuts in a controlled manner. In massive areas, rock and concrete splitters can be used to initiate cracks and reduce tensile stresses in the edge concrete.
- Relieving: Carefully release prestress, loosen nuts step by step. Install additional shoring in areas at risk.
- Cutting: Mechanically cut steel bars, threaded rods, or plates with steel shears, combination shears, or Multi Cutters. In hard-to-reach areas, staged exposure with handheld concrete pulverizers is appropriate.
- Removal and finishing: Pull out anchor remnants or cut them flush; dress edges. Prepare surfaces for subsequent repair.
Safety aspect: When releasing prestressed transverse anchors, spring-back and sudden load redistributions are possible. A work and safety plan and defined exclusion zones are essential.
Design fundamentals and detailing rules
The design of transverse anchors considers shear and tensile loads, edge distances, concrete breakout cones, bond stresses, and settlements. Practical detailing rules:
- Adequate edge and axial distances to avoid concrete breakout and splitting failure.
- Verification of steel capacity, bond, and bearing of anchor plates.
- Consideration of temperature, creep, shrinkage, and prestress losses.
- For rock anchors: assess rock class, stratification, water ingress, and borehole quality.
For existing structures, a conservative estimate is common when documents are missing. Proof loads and probing provide additional confidence without replacing case-specific assurances.
Materials, corrosion protection, and durability
Transverse anchors are usually made of non-alloyed or stainless steels. Corrosion protection is provided by concrete cover, galvanization, encapsulation, or bonded grout. In chloride-exposed areas or with moisture fluctuations, stainless steels or encapsulated systems are advisable. In rock engineering, grout increases durability and bond area. Regular inspections detect cross-section losses or loosenings at an early stage.
Typical risks during deconstruction of transverse anchors
- Unknown prestress: Sudden release can displace components. Stepwise stress relief and shoring reduce the risk.
- Hidden anchors: Undetected transverse anchors hold components together and prevent controlled lowering. Careful exposure with concrete pulverizers improves visibility.
- Concrete breakout: Insufficient edge distances or brittle old concrete lead to breakout cones. Rock and concrete splitters enable targeted crack guidance.
- Rebound during cutting: When cutting bars with steel shears, snap-back can occur. Plan for shields and holding fixtures.
Transverse anchors in rock and tunnel construction
Rock anchors and bolts stabilize crown, sidewalls, and tunnel face. They often act transverse to the main excavation direction and are combined with shotcrete. For modifications or cross-section enlargements, the following applies:
- Probe anchor layout and lengths; core samples and endoscopy can provide indications.
- Expose anchor heads; prestress or relieve, depending on the construction stage.
- Mechanically cut steel components; minimize vibrations near existing load-bearing structures.
Where vibration and noise control are required, hydraulic concrete pulverizers and rock and concrete splitters enable precise, controlled interventions with low secondary damage to adjacent structures.
Detecting and testing transverse anchors in existing structures
Low-damage methods are suitable for surveying existing conditions. Frequently used:
- Optical probing at anchor heads, plates, and nuts.
- Metal localization with scanners; supplementary assessment of drilling resistance.
- Proof loads or torque checks on accessible anchors, where structurally permissible.
The results are cross-checked with drawings, construction phases, and material samples. Clear documentation facilitates subsequent steps in deconstruction or strengthening.
Relation to tool and process selection in deconstruction
The choice of technique depends on material, cross-section, accessibility, and environmental requirements. In practice, the following combinations are used:
- Concrete pulverizers + steel shears: Remove concrete in a targeted manner, then cut steel. Suitable for anchor plates, parapet brackets, and corbels.
- Rock and concrete splitters + combination shears: Release components with low residual stress and then cut the anchors. Advantageous in thick components or where edge distances are limited.
- Multi Cutters: For confined situations or mixed materials of steel, reinforcement, and thin-walled sections.
- Hydraulic power packs: Supply the tools with the required energy; matching pressure and flow increases efficiency and control.
Repair and strengthening with transverse anchors
For strengthening, new transverse anchors stabilize crack planes, wall panels, or rock zones. Important points:
- Borehole cleaning and suitable bonding grout for a load-bearing bond.
- Corrosion protection and durable covering of anchor heads.
- Apply prestress only with appropriate measuring equipment and controlled boundary conditions.
In existing structures, a solution tailored to the fabric is expedient. Major interventions are avoided by opening only locally and then closing with suitable grouts.
Occupational safety, environment, and permits
Work on transverse anchors requires a structured safety concept. This includes:
- Hazard assessment focusing on prestress, fall hazards, and crushing hazards.
- Protection against falling parts, sparks, and splinters; barriers and personal protective equipment.
- Dust and noise reduction; appropriate protective measures in contaminated environments.
- General compliance with local regulations and permits; special care in heritage-protected areas.
By combining controlled exposure and mechanical cutting, emissions can often be significantly reduced.