Description
The following specification particularly describes the invention and the manner in which it is to be performed.
Title Precast Track Plinth
Field of the Invention
Structural engineering and precast construction techniques of precast concrete track plinth for railway and mass transit systems.
Backgroud of the Invention
There are several kinds of ballastless track formation which have been designed and constructed on elevated, at-grade or underground railway/mass transit systems around the world such as Direct Fixation Track, Low-Vibration Track, Shinkansen Slab Track, Rheda 2000 Slab Track, etc. Some track systems are fully cast in-situ and some are partially designed in precast elements before embedding by cast-in-situ concrete at site.
Track plinth is one of the track formations which have been designed and constructed as a cast in-situ system where the quality of the works is hardly controlled at site depending on site accessibility, workmanship, formwork and falsework system, etc. Time for casting of cast-in-situ track plinth is also quite long because of a lot of sequences to fix the rebar cage with fastening systems, rails and all embedded elements, set up the formworks and adjust final elevation before casting concrete.
Therefore, the inventor has developed the precast concrete track plinth system to solve such problems by designing and adjusting its dimension, reinforcement and all embedded elements with appropriate fastening systems according to international recognized standards. The quality of works and construction time cycle will be improved by this precast concrete track plinth.
Summary and Purpose of the Invention
The upper part of track plinth will be pre-cast in L-shape from factory, where the quality could be better controlled, with rectangular openings between fastenings. Some reinforcement will be extruded through these openings for further bonding with sub-structures or concrete slab below through cast-in-situ concrete and shear connectors.
As a precast system, plastic inserts for fastenings will be cast at the same time with precast plinth. The spacing of inserts/fastenings could be varied according to the client's specification and requirement. Steel reinforcement of precast track plinth is comprised of longitudinal rebars and stirrups. Their positions and spacing are designed and adjusted to retain the stress during transportation and handling also.
The preparation of concrete sub-structures or slab below is similar to the conventional cast-in-situ system. Their concrete surface shall be roughen for proper bonding. The shear connectors could be pre-embedded in sub-structures or installed later to plastic dowels which previously cast with the sub-structure.
After delivery of precast track plinth to construction site, these precast elements will be put in place, fastened to rails and fastenings. The alignment and level of the whole track will be adjusted according to the design. Then the concrete will be poured through the openings to bond the precast elements to sub-structures below by embedding the extruded reinforcement of the precast track plinth and shear connectors of sub-structures.
The Purpose of the Invention is to develop a conventional cast-in-situ concrete track plinth to be a precast track plinth system in order to improve the quality of works and construction time cycle. The construction cost could also be reduced from these improvements.
Brief Description of the drawings
Drawing 1 is the top view of the precast track plinth according to this invention. Drawing 2 is the cross-section of the precast track plinth after being installed
according to this invention.
Drawing 3 is 3-dimension view of a precast track plinth element according to this
invention.
Detailed Description of the Invention
Drawings 1, 2 and 3 show the features of a Precast Track Plinth element to be installed on a concrete sub-structures or slab according to this invention and all embedding elements to be installed with the precast plinth. Track plinth cross-section is in L-shape where its 1st longitudinal structure (11), namely the up-stand, is in parallel with 2nd longitudinal structure (14). The height of 1st longitudinal structure is higher than the 2nd one for damage protection after train derailment.
The length of the 1st longitudinal (11) and of the 2nd longitudinal structures (14) are varied from 2.4 to 5.7 metres which are the proper sizes for handling, construction and drainage between each track plinth.
The top ridges of the 1st longitudinal structure (11) and the 2nd longitudinal structure (14) are higher than the top ridge of the transverse structure (13) which links between two longitudinal structures at equal spacing. The spacing of transverse structures is in accordance with the spacing of fastenings as specified in the design. Plastic Inserts are embedded in each transverse structure (13) for further installation of the fastenings at construction site.
There are three sets of steel reinforcement in precast track plinth i.e. longitudinal reinforcement (7) and transverse stirrups (8, 9). First stirrups (8) are reinforced vertically along 1st longitudinal structure (11). The second stirrups (9) are reinforced horizontally linking between the 1st longitudinal structure (11) and the 2nd longitudinal structure (14).
The openings or blockouts (2) are located in the middle between the two longitudinal structures (11, 14) and the transverse structure (13). Therefore, steel reinforcements (7, 9), at opening position, are extruded through the openings and they will be fully embedded and bonded by cast-in-situ concrete at construction site.
All opening positions are designed and interfaced to comply with the position of plastic inserts (5) which pre-embedded in the sub-structure or slab underneath for further installation of shear connectors or anchor bolts (6). Shear connectors could be designed as steel rebars in L-shape or U-shape extruding from sub-structures or slab so the opening size, shape and position shall be determined to comply with types of shear connectors.
Plastic clips (10) are fixed between each steel reinforcement, where it crosses and contacts to each other, in order to prevent the flow of electric stray current between each rebar. At each end of precast plinth, a steel flat bar (12) is fixed to lower level of longitudinal steel reinforcement (7) to release electric stray current from track plinth structures for the purpose of steel corrosion protection. After installation of track plinth in place, all steel flat bars will be welded to the main earthing system
A number of plastic inserts (4) for installation of conductor rail system are embedded to the outer side of 1st longitudinal structure (11) at designated positions as required manufacturer specification.
For installation of the precast track plinth, a set of track plinths shall be fastened to rails by all fastenings then the track alignment and level shall be adjusted according to the design. Appropriate gaps between precast track plinth and sub-structure below shall be determined in advance during the design phase for construction flexibility and quality control. Shear connectors (anchor bolts) shall be installed and all formworks shall be assembled to close all gaps between precast track plinth and sub-structure/slab below. Then concrete will be poured into the openings/blockouts to fill all gaps and complete the construction of track plinth.
The Best Means of the Invention
It is the same as described in the Detailed Description of the Invention.

Claims ;
1. One unit of the precast track plinth has a specific feature such that the cross-section is in an L-shape, and the 1st longitudinal structure (11) is in parallel with its 2nd longitudinal structure (14), and both have a different height of ridges. The top ridges of the 1st longitudinal structure (11) and the 2nd longitudinal structure (14) are higher than the top level of the transverse structure (13) which links between the 1st longitudinal structure (11) and the 2nd longitudinal structure (14) at equal spacing. Plastic inserts (3), for fastening installation, are embedded on the top of the transverse structure (13). Openings or blockouts (2) are located between both longitudinal structures (11, 14) and the transverse structure (13). Inside each opening (2), there are reinforced steel bars (7) in longitudinal direction and transverse stirrups (9) linking between longitudinal structures (11, 14). There are two sets of transverse reinforced stirrups (8, 9). The first stirrups (8) are vertically reinforced inside the 1st longitudinal structure (11) and the second stirrups (9) are horizontally linked between the 1st longitudinal structure (11) and the 2nd longitudinal structure (14) as aforementioned. Plastic clips (10) are fixed between each steel reinforcement where it crosses and contacts to each other in order to prevent the flow of electric stray current between each rebar. At each end of precast plinth, a steel flat bar (12) is fixed to lower level of longitudinal steel reinforcement (7) to release electric stray current from track plinth structures for the purpose of steel corrosion protection.
2. The spacing of transverse structures (13), of the precast track plinth in Claim 1, is in accordance with the spacing of sleepers and rail fastenings.
3. For the precast track plinth under Claim 1, the ridge of 1st longitudinal structure (11) is higher than the ridge of 2nd longitudinal structure (14).
4. The precast track plinth under Claim 1 and its components i.e. the 1st and 2nd longitudinal structures (11, 14) are at least 2.40 metres long.
5. The precast track plinth under Claim 1 and its components i.e. the 1st and 2nd
longitudinal structures (11,14) are at least or equal to 5.70 metres long.
6. The precast track plinth under Claim 1 has a number of plastic inserts (4), for
installation of conductor rail system, embedded in the outer side of the 1st
longitudinal structure (11).
7. The precast track plinth under Claim 1 has openings (2) which designed and
interfaced to comply with the positions of plastic inserts (5) pre-embedded in
sub-structure or slab underneath where the shear connectors or anchor bolts (6)
will be installed before pouring cast-in-situ concrete.
8. The precast track plinth under Claim 7, which has the feature of anchor bolts for
shear connectors (6), is applicable with another types of shear connectors i.e.
L-shape or U-shape steel rebars pre-embeded sub-structures or slab underneath
in accordance with the position of the openings (2).
9. For the precast track plinth under any of the Claims 1-8, appropriate gaps between
precast track plinth and sub-structure below are determined in advance for
construction flexibility and quality control. After precast track plinth installation, the
alignment and level of the track could still be adjusted according to these provided
gaps. Concrete then will be placed into the openings to fill all gaps and complete
the construction of track plinth according to the designed alignment and level.