Segmental construction describes building with prefabricated, dimensionally accurate individual components made of concrete or reinforced concrete that are assembled on the construction site into an overall load-bearing structure. It is widely used in tunnel construction, bridge construction, and shaft and tank construction. Prefabrication improves quality, construction time, and occupational safety, while assembly in confined or hard-to-access areas proceeds precisely and in a planned manner. For deconstruction, adapting existing structures, or creating openings in segments, hydraulic demolition tools such as concrete demolition shear or hydraulic wedge splitter from Darda GmbH are frequently used—especially when vibrations and emissions need to be minimized.
Definition: What is meant by segmental construction
Segmental construction is a design principle in which a structure is assembled from individual segments, either standardized or project-specific. These prefab segments are geometrically and structurally designed to permanently carry loads after placement, safely transfer forces, and meet the required serviceability criteria (watertightness, dimensional accuracy, durability). Typical examples include segment rings in tunnel construction, match-cast bridge segments in building and civil engineering, and segment rings for shafts and pressure pipelines.
Design principles and segment types
The configuration of segmental construction depends on the application but follows recurring principles: load-bearing action through force-locked joints, reliable shear transfer, defined prestressing or ring action, and durable sealing. In tunnel construction, rings consist of multiple partial segments plus a closure segment; in bridge construction, box-girder or slab cross-sections are assembled from segments with bonded joints and prestressing.
Fields of application for segmental construction
Segments are used where repeatability, precision, and short construction times are decisive. Key fields of application are:
- Rock excavation and tunnel construction: Segment rings in shield-driven tunnelling, segmental lining in compressed-air or hard-rock drives.
- Concrete demolition and special deconstruction: Selective dismantling of segments, creation of cross passages and technical openings in existing structures.
- Building gutting and cutting: Openings in segment walls, adjustments during refurbishments.
- Natural stone extraction: Similar modular principle when constructing shafts and galleries with segmental lining.
- Special use: Temporary construction stages, temporary support structures, tank and shaft systems.
Production and quality assurance of segments
Production usually takes place in industrial circulation plants or project-specific precast facilities. Critical are tight tolerances, reproducible concrete quality, and controlled curing. In match-cast processes, segments are cast sequentially against the previously produced segment to achieve a precise joint (“imprint method”).
Essential steps
- Pre-assemble reinforcement and embedded components (dowels, anchors, inserts).
- Concreting with defined consistencies, compaction, and curing.
- Stripping, finishing of joint faces (e.g., grinding, cleaning).
- Inspection of geometry, surfaces, edges, and embedded components; documentation.
- Intermediate storage, transport logistics, and protection of sealing faces.
Joints, sealing systems, and force transfer
The joint is the heart of segmental construction. It governs force transfer and watertightness. In tunnel construction, radial and circumferential joints are often distinguished; sealing profiles are inserted into grooves, and a joint grout may be used if required. In bridge construction, epoxy joints and shear dowels are used, combined with internal or external prestressing.
Typical elements
- Sealing strips and profiles: Elastomers integrated into the joint, sometimes with double chambers.
- Shear transfer: Dowels, keys, friction via bonded joints.
- Prestressing: Longitudinal and transverse prestressing to close joints and reduce cracking.
- Fit and closure segments: Geometrically adapted for ring completion and tolerance compensation.
Assembly and construction sequence
In tunnel construction, installation is ring by ring, often inside the shield. Segment grabs place the elements, bolts or keys secure position, and then ring closure follows. In bridge construction, segments are lifted in cycle, temporarily shored, bonded, and prestressed.
Practical aspects
- Dimensional accuracy of joint faces is critical for watertightness and load paths.
- Documented assembly sequences and torques prevent misalignment.
- Weather protection for adhesives and seals secures quality.
Structural analysis, design, and durability
Design considers load-bearing action in the final state and during construction stages. Ring and arch effects, contact pressures in the joint, local notch stresses, and shear flow in the adhesive layer must be considered. Durability is improved through concrete cover, low water-cement ratios, and robust detailing; joint sealing must be matched to subsoil and groundwater parameters.
Actions and verifications
- Permanent and variable loads, temperature effects, assembly situations.
- Settlements, TBM-related thrust forces, contact pressures, and ground reactions.
- Minimum compression in joints and limitation of tensile stresses for crack control.
Advantages and limitations of segmental construction
Advantages include short construction times, high manufacturing quality, planned assembly in confined work areas, and limited impact on the surroundings. Limitations arise from complex joint requirements, high planning effort, and the need for precise construction logistics. In existing structures, adaptations via openings or segment replacements may be required; here, a concept-based deconstruction is essential.
Practical benefits in deconstruction
For selective deconstruction of individual segments or for creating penetrations, controlled, low-vibration methods are helpful. Concrete demolition shear crush components in a targeted manner, while hydraulic wedge splitter initiate cracks via defined splitting forces and separate components—advantageous in sensitive environments or where minimization of impacts is required.
Deconstruction and processing of segments: methods and tools
Deconstruction in segmental construction requires methods adapted to the material and the joint. The goals are to preserve adjacent components, control load redistributions, and minimize dust, noise, and vibrations.
Tool selection by task
- Concrete demolition shear: For biting off and downsizing reinforced segments, suitable for openings, recesses, or removal of local component areas.
- Hydraulic wedge splitter: For controlled splitting of massive concrete sections, e.g., at segment thicknesses or in areas with reduced reinforcement density.
- Hydraulic power pack: Supplies the tools with the required power, mobile and suitable for confined construction sites via mobile hydraulic power units.
- Combination shears, multi cutters, steel shears: For steel cutting of reinforcement, anchors, or embedded components in conjunction with concrete removal.
Process steps in selective segment deconstruction
- Structural assessment and temporary shoring of construction stages.
- Mark separation lines, considering joint and sealing profile locations.
- Prepare separation joints, if necessary predrill for hydraulic wedge splitter.
- Material removal with concrete demolition shear in a stepwise sequence; separate reinforcement as required.
- Controlled splitting of massive areas with hydraulic wedge splitter to reduce vibrations.
- Rework edges and joint faces; protect intact sealing profiles.
Segmental construction in tunnel construction
In shield tunnelling, segment rings are assembled ring by ring. Segment geometry, the position of sealing profiles, and joint contact pressures are matched to TBM parameters. For subsequent modifications—such as cross passages, equipment recesses, or utility channels—the effects on ring continuity and watertightness must be carefully evaluated. Low-vibration methods, such as splitting, help avoid affecting adjacent rings.
Typical interventions in existing structures
- Creating openings in segment rings with concrete demolition shear followed by steel cutting.
- Segment replacement under temporary shoring and defined load redistribution.
- Local repairs with concrete patching and joint sealing.
Segmental construction in bridge and building construction
Bridge segments are often produced using the match-cast method and are bonded with epoxy and prestressed on site. Segment sequences are planned so that deformations and construction-stage stresses remain under control. During conversions or repairs, segment-oriented separation and dismantling steps enable precise interventions.
Deconstruction and adaptation works
- Removal of edge beams or web areas with concrete demolition shear, controlled extraction of segment parts.
- Splitting of massive node areas with hydraulic wedge splitter, then cutting of prestressing duct grouts only after structural assessment.
Planning, logistics, and occupational safety
Segmental construction requires a well-thought-out chain of planning, production, transport, and assembly. For interventions in existing structures, increased requirements apply to safeguarding, dust and noise protection, as well as emergency plans. Procedures should be coordinated with the responsible authorities; specific permit issues are project-dependent and must be clarified on a case-by-case basis.
Safety aspects during processing and deconstruction
- Calculate load redistributions before starting and provide temporary shoring.
- Operate hydraulic tools only with appropriate hydraulic power pack; regularly inspect lines and couplings.
- Avoid fall and crushing hazards; ensure safe work platforms and communication.
- Consider dust suppression and noise reduction measures through suitable methods and extraction.
Sustainability and resource efficiency
Prefabrication enables resource-saving production with reduced waste and planned maintenance. In deconstruction, segments can be selectively dismantled and materials sorted for recycling. Methods with low vibration levels—e.g., splitting instead of impact—protect the existing structure and surroundings and can reduce emissions.
Quality control and documentation
Seamless documentation of production, transport, assembly, and interventions in existing structures is central. Test plans for joint contact pressures, watertightness verifications, geometry records, and assembly reports create transparency and traceability. For works in existing structures, photo documentation, measurement records, and approvals ensure quality.
Typical damage and repair
Frequent issues include leaky joints, edge spalling, local cracks, and damage to sealing profiles. Repairs include joint cleaning, seal replacement, grouting, and local concrete repair. For larger interventions, segment-by-segment replacements are possible; deconstruction benefits from controlled separation with concrete demolition shear and splitting of massive areas.
Guide for tool selection in existing segment structures
The method depends on member thickness, reinforcement ratio, environmental constraints, and desired reusability. As a rule: as little vibration as possible, as much control as necessary. Hydraulic wedge splitter are suitable for quiet, controlled separations; concrete demolition shear for precise, sectional removal. Additionally, hydraulic wedge splitter, multi cutters, and steel shears are used for metal cutting.
Practical notes
- Survey the member (locate embedded components, reinforcement), define the cut line.
- Size predrilled holes for splitting wedges; consider pressing pressure on adjacent components.
- Select shears with suitable jaw opening and blade geometry; plan the sequence.
- Monitor hydraulic pressure, feed, and retract; secure removed pieces.