Transition structures are key components in bridge and civil engineering. They connect movable superstructures to the adjoining roadway and bridge expansion and movement joints. In doing so, they ensure serviceability, ride comfort, and watertightness against water ingress. As soon as these components are renewed or repaired, in addition to planning and site supervision, precise deconstruction and cutting operations are required. Depending on the boundary conditions, tools such as concrete pulverizers, hydraulic rock and concrete splitters, steel shears, as well as mobile hydraulic power units come into play, for example in the fields of concrete demolition and special demolition or during special operations under live traffic.
Definition: What is meant by transition structure
A transition structure is understood to be the roadway transition structure at bridges, valley crossings, or frame structures. It compensates for movements of the superstructure (thermal expansion, creep, shrinkage, settlements, braking and starting forces) and transfers traffic loads safely. Technically, it is a system consisting of reinforced anchorage concrete, load-bearing and anchoring steel components, seals, channels, and running-surface profiles. In rail and industrial construction, the term also refers to constructive solutions that bridge stiffness jumps or joints between components. The aim is always to accommodate movements, ensure tightness, and avoid edge impacts.
Structure and operating principle of transition structures
Transition structures are modular in design. They connect the bridge curb or anchorage zone with the adjacent roadway and drain surface and splash water in a controlled manner. The essential components are:
- Running-surface profiles (e.g., lamella or finger profiles) for load-bearing bridging of the joint
- Anchorage elements in concrete (anchors, ribs, beams) for reliable load transfer
- Seals and drainage channel systems to ensure tightness and controlled drainage
- Backfill and protective layers (asphalt/surfacing) for levelness, skid resistance, and noise mitigation
- Lateral curb and edge zones with reinforcement that integrate the transition structure
The operating principle is based on freedom of movement with simultaneous load transfer: The roadway is guided without a noticeable bump, while the structure accommodates horizontal and vertical relative movements and seals the joint against water ingress.
Types and construction methods of transition structures
The construction method depends on movement range, traffic load, and environmental conditions. Common systems are:
- Elastomer and profile transitions with small movement ranges and smooth rolling behavior
- Lamella transitions for medium movements and high traffic loads
- Finger transitions for large movements, often on long spans and with high temperature differences
- Special systems (e.g., sinusoidal profiles) for noise reduction and optimized drainage
Movement ranges and design parameters
Key parameters include temperature range, loads from braking and lateral forces, settlements at abutments, fatigue, and requirements for tightness and skid resistance. In cold regions and on long bridge spans, larger movement reserves must be provided; in urban settings, low noise and splash protection are the focus.
Common damage patterns and causes
Damage affects both steel and sealing elements as well as anchorage zones in concrete. Typical findings include:
- Breakouts and spalling in anchorage concrete due to fatigue, impact loading, and freeze–thaw/de-icing salt exposure
- Corrosion of reinforcement and steel elements as a result of insufficient watertightness
- Wear of running-surface profiles, uneven joints, and noise generation
- Clogged channels, washouts, and moisture damage at edge sealing
Causes often lie in inadequate drainage, insufficient movement reserve, incorrect bearing conditions, or in structural movements exceeding the design scope.
Repair and replacement: planning and sequence
The decision between repair and replacement is made based on condition assessment, remaining service life, and the traffic concept. During ongoing operations, phased construction sequences, temporary drive-overs, and compact removal methods are needed to minimize closures. Deconstruction regularly affects asphalt/surfacing, curb zones, the anchorage concrete, as well as steel and sealing components.
Selection of removal and cutting method
The choice of method depends on component thickness, reinforcement ratio, vibration limits, and accessibility:
- Concrete pulverizers: segmental removal of reinforced concrete at curbs and abutment heads; good control, reduced vibrations, suitable near sensitive existing components.
- Stone and concrete splitters: low-vibration, controlled splitting demolition, advantageous for special operations, in densely built-up areas, or where strict vibration limits apply.
- Wire saws and core drilling: precise separation cuts to create lift-out segments and installation spaces.
- Steel shears or combination shears and Multi Cutters: cutting lamellas, fingers, anchor profiles, and reinforcement; clean material separation.
- Hydraulic power packs: power supply for mobile pulverizers, shears, and split cylinders, especially where access is restricted.
Deconstruction sequence in the bridge area
A sequential approach has proven effective: mark and saw the separation cuts, lift off surfacing packages, remove the anchorage concrete piece by piece with concrete pulverizers, split massive zones with stone split cylinders, expose anchors, and perform orderly dismantling of steel components using steel shears or combination shears. This is followed by cleaning, concrete repair of the bearing joint, installation of the new transition structure, connection to the sealing, and restoration of the wearing course.
Interfaces and detail points
The transitions to the bridge waterproofing, the connections to curbs and handrail posts, and the drainage are particularly sensitive. Levelness and skid resistance of the tie-in ramps influence ride comfort and noise emissions. In edge zones under traffic, low-vibration removal is crucial; here, concrete pulverizers and stone and concrete splitters have established themselves as precise methods.
Operation, quality, and monitoring
Correct position and anchorage, tight connections, functional drainage, and uniform rolling behavior are decisive for durability. Regular visual inspections, cleaning of channels, and checking fasteners support serviceability. Requirements for levelness, low noise, and tightness are usually defined within recognized standards; specific scopes of testing and acceptance must be defined project-specifically.
Special aspects in rail, tunnel, and industrial construction
In railway construction, transition structures often denote solutions for grading stiffness between the earthwork and the engineering structure. Settlement behavior, ballast retention, and dynamic loading are the focus here. In tunnel and frame construction, transition structures occur at portals, cross passages, or between roadway slabs. Deconstruction and adjustment work often take place in confined spaces; low-vibration methods with stone and concrete splitters and precise cutting are advantageous there. In industrial facilities (e.g., at foundation joints and hall transitions), similar principles for movement accommodation and sealing apply.
Occupational safety, environment, and resource efficiency
During deconstruction, strip-out, and cutting, dust protection and noise control, secure load handling, and fall protection must be planned. Water-bearing areas require particular care when handling fines and operating fluids. Clean separation of concrete and steel facilitates recycling. Methods with low vibration and few secondary damages—such as the controlled use of concrete pulverizers or splitting of massive zones—support the preservation of adjacent components.
Practice-oriented steps for planning and execution
- Condition survey and determination of movement demand, including temperature and load spectra
- Concept selection for the transition structure considering tightness, noise, maintenance, and construction phases
- Deconstruction concept with separation cuts, segment sizes, lifting points, and vibration limits
- Method selection: concrete pulverizers for reinforced curb removal, stone and concrete splitters for massive zones, shears for steel components
- Construction phase planning under traffic, including temporary drive-overs and drainage
- Quality assurance: levelness, skid resistance, tightness, anchorage, drainage function
- Documentation and maintenance concept for operation
Darda GmbH offers a broad range of tool types such as concrete pulverizers, stone split cylinders, steel shears, combination shears, Multi Cutters, and the necessary hydraulic power packs which—depending on structure details and boundary conditions—can be deployed for the repair and replacement of transition structures. Selection must always be project-specific, with a focus on safety, structural compatibility, and resource conservation.