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Hiscs - LMK PT System

LMK PT system manufacturer & supplier. Specialized Engineeting Services for Infrastructures

Having experience of more than 30 years in the field of specialized Engineering services, HiSCS can provide services in design, inspection, supervision, maintenance & retrofitting of structural elements requiring sophisticated know‐how such as Bridge Bearings, Expansion Joints, Road Traffic & Highway Safety Systems. Offering a broad range of professional services HiSCS can successfully accomplish

demanding projects meeting all requirements of the modern construction industry and Standards. HiSCS is a supplier of a full range of specialized equipments and machinery such us inspection tools, lifting & stressing jacks, pumps, threading and grouting machines, de-coilers, grout test and hydraulic pressure apparatus, presetting and deforming devices, mixers & tanks, lifting & hoisting devices.

06/06/2024

European Technical Assessment Document (ETA) for LMK External Post Tensioning Kit

We are happy to announce LMK external post tensioning system accreditation with ETA.
We welcome our new ETA member in LMK family.

04/06/2024

Inspection of Athens Int’l Airport, access bridges

HiSCS bridge inspectors accomplished the routine inspection of the access bridges, located in El. Venizelos Int’l Airport (NAIA) in Athens, Greece.
In total, 5 road bridges and 2 aircraft bridges were thoroughly inspected. The inspection did record the overall condition of structural elements, above and on traffic, such as concrete and steel elements, bearings, expansion joints, utilities, pavements, safety features etc.
The inspection lasted more than a month, with day and night shifts, considering the sensitive matter of the minimum annoyance of airport operation, which had to be secured by the inspection teams.
A detailed inspection and evaluation report with classifications, ratings and maintenance proposals was delivered to the NAIA operator.

08/02/2024

Calatrava Stayed Cable Bridge – Special Inspection & Maintenance

HiSCS bridge inspectors and technicians, together with the stayed cable manufacturer’s specialist, accomplished the detailed inspection of the cables and anchorages of the pedestrian stayed cable bridge, located in Athens, Greece commonly known as “HARP BRIDGE” or Calatrava bridge – a name adopted from the Architect Santiago Calatrava who designed this impressive footbridge. The shape of the bridge looks like an harp inspired by the ancient Greek monuments and sculptures of the Classical Era.

What makes this bridge one of its kind is the arrangement of the cable-stay back span. In an asymmetric cable-stay bridge, where the main span is longer than the back-span, the back-span cables are generally anchored to the ground to provide the necessary stability. In most such bridges, the back-span cables are angled so that they provide a horizontal force, helping the bridge’s mast to resist the horizontal pull from the main-span cables. On this specific bridge, the two back-span cables are vertical, resisting none of the sideways pull from the main span. Instead, that pull is absorbed through the curvature of the pylon, as a compressive thrust.

The inspection took place at the anchorages of the two (2) vertical and the fourteen (14) angles high strength steel wire cables by which the steel deck (94m walkway of about 6m width) is suspended from the main curved pillar (50m height).

This type of inspection is considered as a special inspection in line with the remarks and proposals of the overall bridge routine inspection and evaluation.

A telescopic crane was used to access the anchorages located on the vertical pylon.

Anchorage’s body units were partially disassembled and cleaned so as the inspectors are able to collect information regarding their condition and evaluate their structural integrity.

HiSCS adopted a special laser device to remove superficial oxidation, restoring the rusted areas of the anchorages body. New-end cables protective cover has been designed and installed by HiSCS for further evaluation and testing. A detailed inspection and evaluation report with classifications, ratings and maintenance proposals was delivered to the bridge operator.

05/01/2024

Bridge Bearing replacement - Single pier jacking & lifting at Athens International Airport El. Venizelos, Greece

HiSCS Engineers & Technicians successfully accomplished another jacking & lifting, at the main terminal bridge of Athens Int’l Airport El. Venizelos in Greece.
The routine inspection of this bearing revealed extreme bulging and broad debonding phenomena in the elastomer, depicting its deficiency to bear loads and movements, thus the need of its replacement.
Six (6) hydraulic jacks, with lifting capacity 250 tons each, connected in parallel with a hydraulic pump, were used to lift the superstructure (max 15mm), remove the existing bearing, and replace it with the new one. Moreover, construction of new plinths took place, as well as repair of contact surfaces between bearing and superstructure.
The rubber bearing that was installed, was a non-anchored elastomer bearing, formed by layers of rubber and steel plates (reinforcement), factory bonded (vulcanized), with a diameter of 800mm, height of 309mm, weighting more than 400 kg.
The effort required to replace a bearing weighting more than 400kg in a very narrow area (max 15mm lifting), with deck opened to traffic, imposed another challenge on our team which successfully completed the task, following all safety precautions and requirements.
HiSCS studied and designed the jacking & lifting methodology, provided the equipment (hydraulic jacks, pumps, hoses, gauges, distribution plates etc.) and coordinated all onsite works.

14/12/2023

Jacking & lifting of Mall for Seismic Isolation Bearings Replacement

The Mall of Cyprus is the first shopping mall of its kind in Cyprus and has become a landmark since its first day of operation, September of 2007.
The building consists of two commercial levels – ground floor and 1st floor – with two extra supportive levels – basement and mezzanine floor.
HiSCS has been involved in the jacking and lifting operations to replace the seismic isolation bearings located on the columns supporting the building.
The existing bearings were elastomeric isolators, made of High Damping Rubber known as HDRB, shielding the superstructure from seismic forces.
Two specially designed steel temporary supports were installed, close to the columns, to place the jacking system (hydraulic jacks) since there was no area close to the bearings.
Five bearings were replaced, in total, by lifting the slab up to 15mm, removing the old bearings and replacing them with the new ones. The new anti-seismic devices are of the same type with the old ones and their isolation characteristics adhere to the relevant design.
MEP networks such as ventilations, electrical and firefighting systems were closely monitored during lifting to avoid any damages/malfunctions.
Hydraulic pressure vs lifting load, lifting elevations and jacks’ piston extraction were constantly monitored during the process, to ensure the proper ex*****on and to observe the structural behaviour of the building.
Works were accomplished in line with the approved methodology, within a very tight schedule. The replacement of the seismic isolators had to be carried out one by one, with jacking system and temporary supports being moved to the next position at the earliest, avoiding any disturbance to the busy operation of the Mall.

13/11/2023

Bridge Bearing replacement at Athens International Airport El. Venizelos, Greece

HiSCS Engineers & Technicians successfully accomplished the Jacking & lifting, of the main terminal bridge of Athens Int’l Airport El. Venizelos in Greece.
The bridge, which was designed and erected between 1999 & 2001, serves as the main access to the departure hall of the airport. It has the form of a prestressed solid slab with voids, and it is composed of a complex of ramps, whose width ranges from 7.7m to 32m.
The routine inspection of the bearing revealed extensive punctures, extreme bulging and debonding phenomena in the elastomer, depicting its deficiency to bear loads and movements, thus the need of its replacement.
Four (4) hydraulic jacks, with a total lifting capacity of 1000 tons, connected in parallel with a hydraulic pump, were used to lift the superstructure (max 15mm), remove the existing bearing and replace it with the new one. Moreover, construction of new plinths took place, as well as repair of contact surfaces between bearing and superstructure.
The rubber bearing that was installed, was a non-anchored elastomer bearing, formed by layers of rubber and steel plates (reinforcement), factory bonded (vulcanized), and it had a diameter of 450mm and height of 189mm.
HiSCS studied and designed the jacking & lifting methodology, provided the equipment (hydraulic jacks, pumps, hoses, gauges, distribution plates etc.) and coordinated the onsite works of the bearing replacement following all safety precautions and requirements.

06/09/2023

Lifting & Jacking of Oil Terminal Jetty – Bearings Replacement

The jacking and lifting works to replace the structural bearings supporting the steel pipe racks of an oil terminal jetty located in Cyprus have been accomplished by HiSCS.
Marine oil terminals jetties are storage depots for oil, fuels, and petrochemical products providing a deep water mooring for tankers. Jetties have loading/unloading arms and pipe racks for transferring petrochemicals to/from ships to shore storage tanks.
The jetties are designed to withstand the petrochemical cargo loads, wind, seismic and vessel accidental collisions.
The multi-span steel trestle is located on pile caps and is supported on bearings of several types including viscous dampers.
An accidental detachment of two existing bearings from the steel superstructure has been revealed during the routine inspection.
More precisely, the upper anchoring steel plates of bearings had been shifted (failure of mechanical anchoring with the steel superstructure) jeopardizing the proper transfer of service and seismic loads.
Two (2) hydraulic jacks of lifting capacity 390tons each, connected in parallel with a hydraulic pump were used to lift the superstructure in order to remove the existing bearings and replace them with new.
HiSCS studied and designed the lifting methodology by providing the hydraulic equipment (jacks, pumps, hoses, gauges, distribution plates etc.) coordinating the site as well works of the lifting, jacking and bearings replacement.
HiSCS Engineers & Technicians successfully accomplished the works in a very demanding environment following all safety precautions and requirements of the petrochemical facility.

03/08/2023

We are happy to inform you that from now on you can also Follow us on Instgram: https://www.instagram.com/hiscslmk/

02/08/2023

Jacking & Lifting of Silo Roof for Bearings Replacement

HiSCS has commenced the jacking and lifting works to replace the bearings supporting the steel roof of a silo clinker located in Vassilikos area in Cyprus.
The initial installation of bearings took place circa 2007. The existing bearings are steel spherical fixed type with anti-lifting capacity.
The bearings support the circular roof consists of central beams in the radial direction (34 pcs) connected with IPE beams in the circumferential direction of concentric circles. All 38 bearings are installed on the silo’s perimeter wall made of reinforced concrete.
Following the routine inspection, the bearings have been found with defects such as anchoring failures and excessive misalignment – speculations – due to accidental silo overfilling and loads transferred to the roof from the stored material.
The new lifting design foresees the replacement of all 38 bearings by jacking and lifting of silo roof using hydraulic jacks.
The jacking and lifting are performed partially in groups of 2-3 consecutive bearings, using 2 jacks of 300tons capacity each, connected in parallel with a hydraulic pump.
Lifting of no more than 10mm was sufficient to remove the existing bearings and replace them with the new ones.
The new bearings are of the same type but with improved characteristics (higher vertical-horizontal and uplift load capacity). In addition, they allow small movements in both horizontal directions prior of their locking up to bear the horizontal loads and have higher rotational capacity.
HiSCS designed the lifting methodology and provided the hydraulic equipment (jacks, pumps, hoses, gauges, distribution plates etc.) coordinating the works of the liftings, jackings and bearings replacement.
HiSCS Engineers & Technicians share their experience by training and supervising the executed works in such demanding project (silo under operation with clinker powder covering the area of works). We highlight the importance of routine inspections revealing any defects in structural elements ensuring the Safe for Use and FIt for Purpose (SUFIP) mentality.

24/07/2023

Inspection of Steel Arch Bridge

The Inspection and evaluation of the bearings, stoppers, shear-keys, and viscous dampers of Tsakona arch steel bridge in Korinthos-Tripoli-Kalamata Highway (Southern Greece) has been accomplished by HiSCS Inspectors.
The Tsakona arch bridge is one of the world's longest multi-span arch bridges. It crosses the Tsakona valley bridging a dangerous location with landslides phenomena often occurred the last decades.
It has a total length of 390m, consists of three (3) spans of length 75m - 55m and 260m respectively. The first and second spans form a prestressed reinforced concrete box section, while the third span of 260m long is a steel composite deck suspended by two steel arches trough wire ropes.
The prestressed deck of the bridge rests on the abutment on two (2) free-sliding elastomeric bearings (800x800mm plan area). The shear forces are transmitted through a shear-key device (of 6000KN/±160mm capacity) movable along the longitudinal axis. The deck is monolithically connected on the V shaped pier.
The steel arches are seated on four (4) elastomeric bearings (900x900mm plan area) capable to bear an uplift load of 250KN. In addition, the deck is connected through eight (8) hydraulic viscous dampers with capacity 500KN/±200mm, oriented in the longitudinal and transverse direction of the bridge.
The combination of elastomeric bearings and viscous dampers is one of the best design approaches to secure the seismic protection of a structure.
All inspected elements have been checked about functionality (residual sliding/deformation capacity, rotations/inclination, defects etc.) and a relevant evaluation report has been issued. A special inspection software has been used so as to speed-up the site works.
The inspected elements were manufactured and installed in 2009-2010.
Supporters of a robust inspection and maintenance regime in all structures we are pleased to see that this mentality spreads among the Engineers and Authorities. Inspection and maintenance is considered as a necessity in nowadays.

07/07/2023

Inspection & Evaluation of Dampers in Athens Metro Station

The Inspection and evaluation of one hundred twenty-eight (128) viscous dampers located in the Athens Metro – Line 1, in Marousi station bridge has been accomplished by HiSCS Inspectors.
Viscous dampers are considered anti-seismic hydraulic devices which through hydraulic operation (network of special oil inside internal chambers and orifices in the body of the device) can absorb (consume) kinetic energy, which is produced during the movement of the structure under dynamic actions (earthquake).
The service movements of the structure (temperature effects-contractions/expansions etc.) are taking place with zero reaction of the damper (very low velocity of damper’s piston movement).
The constitutive law of hydraulic damper is exponential, following the formula:

FD = C · Vα (MN)
Where:
C = unit constant [MN x (s/m)α],
V= the velocity of the superstructure (m/s) and
α = an appropriate exponent usually between 0.10 and 0.50.

The exponent α, if it is not specifically defined in the design stage, can be chosen by the manufacturer considering the following criteria:

- the device will not develop resistance to very slow movements of the superstructure (e.g. thermal contractions etc.)
- the device will be activated very quickly in dynamic movements.

The composition of the viscous liquid (oil) and the design details of the device are the know-how of the manufacturer.

The dampers were manufactured in 2004 having the following characteristics:

- Maximum design axial load: 75 KN
- Maximum piston movement speed: 400mm/sec
- Maximum piston extension/compression capability: ±55mm
- Exponent α ~ 0.15 KN/[m/sec] with damping constant C = 30.53
- Nominal axial length (neutral position) from pin to pin: 570mm

The Marousi Metro station is a concrete bridge constructed in 1955-1957 consists of 16 spans with monolithic pier-frames. The bridge serves the metro line needs as a train platform station for the passengers.
Following a regime of structurally upgrading of this old bridge, new concrete columns have been erected along its length connecting the superstructure with steel beams through the dampers, thus implementing the concept of isolating the bridge deck from ground accelerations during earthquake.

The inspection works have been accomplished by a team of 2 inspectors and 2 technicians avoiding any disturbance to the passengers and operation of the station/urban area. A movable working platform has been used to reach the dampers and perform all needed measurements and inspections.

All dampers have been checked and measurements about their function (residual movement capacity, leakage phenomena, rotation, piston condition etc.) have been recorded.
A special inspection software has been used so as to speed-up the site works to a minimum possible (5 days in total, average 25-26 dampers/day).

20/06/2023

PT Application in Existing Building for Upgrading Purposes

The implementation of post tensioning in an existing building to improve its structural strength has been accomplished by HiSCS.
The building consists of 2 basements, ground floor, a mezzanine floor and 5 typical floors. All roofs (from first basement till the upper elevations) were designed using the concept of PT slabs and beams.
The initial design was dated in 1969. The slabs have a span to the order of 16m and a thickness ranging from 26 to 34cm.
A recently performed structural evaluation followed by inspection and Non-Destructive Testing (NDT), revealed a questionable structural capacity (PT reduction by at least 20% from the initially specified). Furthermore, the additional permanent loads on the slabs increased by 2.25 times compared to the initial design.
A policy of upgrading structurally the existing PT slabs & beams was adopted by implementing the external PT technique.
External post-tensioning is one of the latest developments in prestressed concrete technology. It refers to a prestressing technique where the prestressing tendons are placed outside the structural element section (outside beam/slab) and the prestressing force is transferred to the concrete by means of anchorages and deviators.
Customized steel anchoring plates and deviators (special design) using stressing steel bars (PT bars) were utilized to accommodate the anchorages and implement the necessary mechanism to transfer the PT forces to the structure.
PT bars are placed through holes on the existing beams. Prior of core drilling a Ground Pe*******on Radar (GPR) investigation took place in all existing PT beams to verify the PT tendons trajectories avoiding any damage of the existing tendons during core drilling.
There is always a distance from theory to practise and this rule has been confirmed once more in this project by recording discrepancies in the as-built drawings of PT tendons elevations/geometry with the actual recorded with GPR up to 35cm.
Eight (8) PT bars with nominal tensile strength 1050 N/mm2 of 18mm diameter per anchorage, were stressed up to a force of 177KN applying a friction enough to accommodate the stressing force of external cables. Additionally, a strong epoxy resin has been injected filling the gap between the holes and the PT bars.
Four (4) 7-wire strands (greased and plastic coated) of section 140mm2 (dia 15.3 mm) gripped at both ends with barrels & wedges have been utilized for each beam and stressed with a force of 200KN/strand.
The installation works have been accomplished from drilling to stressing of PT bars & strands within a period of about 7 days per beam considering the need for concrete contact surfaces grinding/smoothing and the curing of epoxy materials.
All exposed steel elements were painted for anti-corrosion protection and plastic heat shrink sleeves have been utilized covering the barrels and strands ends.
In addition to the external PT, a new cast-in-situ beams (about 28m in length) have been casted beneath the existing slabs, utilizing the technique of unbonded post-tensioning.
The casting has been achieved by openings on the roof at specific intervals. Customized steel cages have been used.
Seven (7) 7-wire strands (greased and plastic coated) of section 100mm2 (dia 12.9 mm) have been utilized per beam and stressed with a stressing force of about 140KN/strand.
Unbonded PT technique consists of single (mono) strands which remain unbonded to the surrounding concrete giving them the freedom to move locally relative to the structural member. The strands are coated with grease having an outer layer of seamless plastic sheath to protect them against corrosion.
The unbonded tendons technique has been preferred over the conventional bonded PT method considering on the one hand the structure’s economy (absence of pt duct and grouting need) and on the other the easy and rapidly installation in narrow and spaceless areas with lack of conventional lifting apparatus.
Light and flexible tendons without the need of ducts and grouting, having less losses of effective stress due to minor friction compared with the bonded PT, were placed within a period of about 3 days per beam.
In less than 4 months all PT works have been accomplished successfully.
HiSCS has been appointed as a specialized PT designer and installer.
It is the first time where unbonded and external PT design has been adopted in an existing building project in Greece for rehabilitation/upgrading purposes.

15/05/2023

Inspection of Viscous Dampers

The Inspection of fifty (50) viscous dampers located in the steel roof of main terminal building of Athens Int’l Airport has been accomplished by HiSCS Inspectors.
Viscous dampers are considered anti-seismic hydraulic devices which through hydraulic operation (network of special oil inside internal chambers and orifices in the body of the device) can absorb (consume) kinetic energy, which is produced during the movement of the structure under dynamic actions (earthquake).
The service movements of the structure (temperature effects-contractions/expansions etc.) are taking place with zero reaction of the damper (very low velocity of damper’s piston movement).
The constitutive law of hydraulic damper is exponential, following the formula:
FD = C · Vα (MN)
Where:
C = unit constant [MN x (s/m)α],
V= the velocity of the superstructure (m/s) and
α = an appropriate exponent usually between 0.10 and 0.50.
The exponent α, if it is not specifically defined in the design stage, can be chosen by the manufacturer considering the following criteria:

- the device will not develop resistance to very slow movements of the superstructure (e.g. thermal contractions etc.)
- the device will be activated very quickly in dynamic movements.
The composition of the viscous liquid (oil) and the design details of the device are the know-how of the manufacturer.
The dampers were manufactured in 1998 having the following characteristics:
- Maximum design axial load: 50 KN
- Maximum axial load capacity: 1.5 X 50 KN = 75 KN
- Maximum piston movement speed: 0.6m/sec
- Maximum piston extension/compression capability: ±125mm
- Exponent α ~ 0.5 KN/[m/sec] with damping constant C = 64.5
- Nominal axial length (neutral position) from stud to stud: 1230mm
In total 50 devices are placed in several locations of the steel roof of MTB.
Considering their age, i.e., 25 years old, a regime of routine inspection has been established to verify serviceability and proper function.

The inspection works took place during midnight hours to keep the least annoyance to the passengers. An electrical driven basket lift has been used to reach the roof where dampers were installed.

All dampers have been checked and measurements about their function (residual movement capacity, leakage phenomena, rotation etc.) have been recorded.

A special inspection software has been used so as to speed-up the site works to a minimum possible.

Dampers are designed and inspected following EN-15129-7 (Anti-seismic devices-velocity dependent devices).

12/03/2023

The inspection and evaluation of the bearings supporting the roof of the Main and Velodrome Stadiums in Olympic Athletic Center of Athens-Greece “Spiros Louis” has been successfully accomplished by HiSCS inspectors.

The iconic Olympic facilities are part of Athens Olympic Sports Complex, named after the first modern Olympic marathon gold medalist in 1896, Spyros Louis.

The main stadium was originally built in the early ‘80s. Since then has hosted many athletic events and has been extensively renovated for the summer Olympics – Athens 2004.

Its roof is suspended by cables through a double steel arch system designed by Architect Santiago Calatrava.

The two gigantic arches have a total span of 304m and a maximum height of 72m. The roof weighs 18,700 tons and is made of 5,000 polycarbonate panels covering an area of 25,000 sqm. Both arches were assembled away from their final position (60-70m) and were slide-moved into place. The roof is designed to withstand winds up to 120 Km/h and earthquakes up to magnitude 8 R.

In total 24 pot free sliding bearings have been installed beneath the South arch ends, having a vertical capacity ranging from 9,000 KN up to 39,500 KN, allowing their slide ± 400mm away from the fixed North side. The pot bearings of 3,950 tons vertical capacity are massive having an overall dimension of upper sliding plate 1.9 x 1.2m and a base diameter of 1.34m.

A similar roof concept has been adopted in Olympic Velodrome stadium which was originally built in 90’s as an outdoor venue. It was extensively refurbished in order to host the 2004 Olympics. Its track is 250 m long and 7.5 m wide.

Velodrome arches are supported by pot bearings, fixed in one end, and sliding guided in the other. The vertical capacity of bearings is to the order of 19,000 KN and can absorb horizontal loads of 13,650 KN allowing a longitudinal slide of ±180mm.

The inspection and evaluation of bearings is part of an ambitious renovation project with energy upgrading of the Country’s infrastructure known as “Green Transition” in line with the National recovery and resilience plan.

HiSCS is proud of being selected as the inspection specialist for these iconic structures/massive bearings.

A site inspection and evaluation with ratings, classifications, health conditions and proposals have been established using special inspection software properly adapted to the needs of this prestigious project. Rotations, remaining sliding capacity, overall condition of bearings and their parts followed by NDT have been recorded verifying the Safe for Use and Fit for Purpose policy for sustainability.

19/02/2023

The inspection and evaluation of ten steel bridges in the city of Riyadh – Kingdom of Saudi Arabia has been commenced by HiSCS bridge inspectors.

The multi span bridges serving as major intersections in the city of Riyadh, have a total length ranging from 250m up to 1000m, consisting of two traffic branches with simply supported steel beams and steel pier columns.

Apart from the visual investigation, the inspection will include comprehensive evaluation based on non-destructive testing (NDT), lab and load rating tests. condition ratings, construction performance and health indicators established in line with AASHTO standards.

HiSCS Inspectors use special software to facilitate and unify all site activities for a quick and prompt record & data analysis.
The project is expected to be accomplished by late summer of 2023.

16/12/2022

A demanding simultaneous jacking and lifting of a bridge erected in mid ’90 has been performed by HiSCS for rehabilitation purposes, among them the replacement of the existing bearings.

The superstructure is an overpass crossing a major highway in Greece connecting the cities of Athens and Korinthos, with prestressed concrete voided slab. The bridge consists of 3 spans with total length 77m (21m+41m+15m), skew angle of 77⁰ and a deck width 11.5m, accommodating two traffic lanes. At both abutments superstructure cantilevers are projected increasing the deck width by 2.5m and 7.5m respectively at both abutments.

The initial design specified elastomeric non-anchored bearing with dimensions 900x900x125mm – 3 pcs in each pier and 600x700x110mm - 2 and 3 pieces in each abutment, while the new design foresees their replacement with new bearings type C (EN-1337-3) with dimensions 350x350x166mm at abutments and 600x700x135mm at piers, anchored with external checkered plates.

The type of superstructure (prestressed) in conjunction with the increased height of new bearings following the new anti-seismic demands, defined the need for a simultaneous jacking & lifting allowing a max differential elevation lifting of 20mm per pier/abutment.

Four (4) jacks of lifting capacity 100 tons/each and 5 jacks of lifting capacity 300 tons/each have been placed in abutments and piers respectively, in total 18 jacks were used. Jacks have been connected through a network of high-pressure hoses and distribution valves in parallel per lifting location.

Prior of lifting all elements obstructing the lifting were disassembled or removed (steel guard rails, expansion joints, abutments sidewalls embedded with the deck, public networks etc.). The existing clearance (gap between the lower part of superstructure and the upper part of pier cap), has been recorded to the order of 100mm, defining the size of the jacks and consequently their stroke capacity, i.e., max 20mm.

The lifting took places in phases of 20mm up to a final elevation of about +80mm from the initial recorded elevation. The final elevation of 80mm was necessary for installing the new bearings being thicker in comparison with the old ones.

The whole process took about 3,5 weeks and the superstructure resettled at an elevation of about +60 mm from its initial recorded considering the thicker new bearings, the need of the construction of new bearing plinths as well as the significant lack of horizontality and levelling of contact surfaces in superstructure.

The lifting team had to deal with the fact that the progressed cantilever in abutment lead to an inclined differential lifting by about 4mm due to extra cantilever weight by adjusting the pressure/force in the jacking system for a uniform lifting.

Additionally, the new design requested the orientation of the new bearings to follow the longitudinal axis of superstructure and not the axis of the pier caps. That was another problem for the lifting team trying to relocate the new bearings inside the found recess formed by the embedded to the superstructure of the old bearings due to construction errors.

High strength cementitious mortars have been used for the er****on of the new plinths as well as high strength epoxy resins were applied on upper and lower external checkered plates of the new bearings for bonding and friction purposes.

The use of bearings anchored with external checkered plates is a common practice in cases of replacement of old non-mechanically anchored bearings, since the clearance between the superstructure and pier caps/abutments is limited not allowing any installation of anchoring bars/dowels system (old designs without contractual requirement for bearings replacement).

Address

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Athens
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