UK’s longest rail viaduct – HS2 Colne Valley Viaduct – Marwan El Jamous, Frederic Turlier

UK’s longest rail viaduct – HS2 Colne Valley Viaduct
PWI Birmingham Section meeting (Online)
8 February 2024

You for attending tonight’s presentation the presentation is organized in roughly two parts the first part which gives an overview of the project uh and the design aspects uh will be done by myself and after that I will pass to maran’s very capable hands to discuss with you

About to present to you the uh the construction part um I apologize that I’ve got another meeting at the other end of London so I’ll leave around uh 35 P so I won’t be here for the question and answer but Maran is every day on this project so he

Knows it very well so he should be able to answer most of them so the first part is the general presentation um wasn’t sure how many of you know all the details of hs2 so the first slide was really to give a broad overview of hs2 uh phase one here so London to

Birmingham obviously uh cut in broadly three sections the South the center and the north if we look at the South it’s all tunnels coming out of London uh and in the central section section C1 which is the one where Marwan and I are involved is when the trains come out of

The tunnels coming out of London get onto the Valley vict and then go again in a tunnel to go under the M25 under the chill turns coming out around amam then it’s mainly at grade over most of the length and then uh in N1 and N2 the

Northern section you start having a bit of tunnels and um and viaducts again so the section that Maran and I are involved is C1 package Central package number one which broadly starts just before the M25 and goes for about 25 kilm so Maran if you go to the next

One so the uh the contract C1 has been awarded to a joint venture consisting of three Partners I think we have a slide after on that I’ll no if you go back Mar sorry to the to the overall uh view so package C1 it’s uh two main parts to the

Package one is which is the corn Valley vict which is the 3.4 kilomet vict and then the broadly 16 kilm tunnels the contract as all the other civil contracts was awarded in 2017 uh we had a first stage which was quite long of uh design and establishing

Target cost Etc and we’ve been on site now for about uh two a bit years so exact length 21.6 km 3.4 km VCT 2. 2 * 16 kilm twin board tunnel so one tunnel for each uh track progress today is fantastic in our rise 98% of the boring

Of the tunnel is complete all the segments that form the rings of the tunnel uh have been cast and we should be seeing the first TBM coming out of the ground uh any day now in terms of the viu which is really where this presentation focuses uh we’ve got more

Than two3 of the vict uh length has been completed with 80% of the Precast segments already cast so you see on the map broadly we start just inside the M25 and we go for 20 kilomet and we come out uh in the chill turns a bit after amam

If we go to the next next slide so package C1 of hs2 has been awarded to a joint venture so obviously the ultimate client is Department of Transport who have uh entrusted hs2 limited which is a private company wholly owned by the government to U procure and supervise

The execution of all these packages and package C1 has been awarded to a joint venture consisting of bug Trav public so bug Civil Works for whom I work who are the main party in the Align joh Venture at 60% and 20% each to our two other partners fuler Fitzpatrick and Sir

Robert MCC albine the design because this is a designed and build project uh has been uh subcontracted by the joint venture to what is called align D so the Align design joint venture which is formed 20% align itself and um the the rest 48% and

37% to uh Jacobs and 32% sorry to Jacobs and enop Randall in terms of execution of the project uh foundations for the viu have been uh completed by a joint venture of Keller and vssl pierc by kilbridge Mor spherical bearings the deck installation which is where we are

Going to mainly focus in this Pres presentation uh is being carried out by vssl with the precasting of the segments because this is a pre-cast segmental structure we will get to that um being done by the joint venture themselves with uh specialist equipment designed and supplied by vsl um and obviously the

Erection is vsl with the post enging we’ll get to that so the design organization um had a very large scope which included the option earring the consent the preliminary final design and a large architectural package so the design is an integrated Consortium for all the permanent works as I said Jacobs

And jro prandle and align with key subcontractors LDA design for the landscape Grimshaw as The Architects and kathri cheze in fact subcontracted to um a joint venture of arcadis K and setc who are the designers of C2 C3 section for nor which means that it was a very

Efficient way to do it because they already have a very good knowledge of our common client hs2 and the way uh the way uh the systems work and a lot of experience in from their own packages to provide independent checking for our own package so the com valy vict if we look

In the second section at the the context the con Valley is the first open air section out of London where the train emerges out of the tunnels it’s really the first really green area uh outside of London within the M25 and it’s an environmentally sensitive area because we go through woodlands and uh

Lakes so even though the lakes are remnants of uh of old queries which have filled since it teams with a lot of marine life or water life uh so it’s quite an important um uh area that we’re going through so if we go uh in terms of how the vict was

Procured so uh what people don’t necessarily realize is that at the time of tender the the concept for the viu was totally open there was no reference designed to be followed uh from the client which means that um getting the concept for the viu was a really critical part of

The works and we had originally envisage two possible two possible options a steel composite structure and a uh classic concrete box gerder um Vu what happened then is that um hs2 rightly so realized that this was going to be really a a a key a landmark structure uh for the project overall so

They commission a specialist architect Martin Knight to really look at his specimen design whilst the contract had already started so um uh Martin Knight Architects uh shared a vision which was this uh this Arch vuck that you see here on the original concept which was to remind Stone skip

Skimming Stones over the lake so we were given this concept and we were asked to then uh develop a design a structural design that would uh use this concept with uh still being practical and um easier to build on the scale of a 3.4 kilometer vict so the photo above is the

Original concept from the architect and the photo below is what we’re actually uh building today so a structure which has this effect of SCH scheming stones but also takes into consideration um the structural aspects and that whole process took about two years to get to this point so

The other points to note on the um on the architecture for the vict is that the architect had a Clear Vision uh they wanted a curve sofit to give this aspect of of arches or skimming Stones uh incline panels to break uh the the deck the depth of the

Deck which is quite significant the deck at its deepest is 9 Metter and uh vary The Depths according to the context uh the sorry vary the spans and the depths according to the context where we are in the 3.4 kilomet because obviously in the 3.4 kilom the landscape changes quite a

Bit and the view was to really adapt the viu as we were going through the landscape so the vict is not repetitive it’s not the same from one end to the other um So that obviously creates challenges and the last point was that a great emphasis on Textures and facets

Etc to catch the Light provide shade was was envisaged by the architect so I have to say uh hand on my heart that in fact when we started the process typical Engineers were like the architect or creating all these complications Etc in fact now that we see the uh the the

Final product and I’m not the only one to say it actually the architect was right to really push push us to do something that is not just practical but also beautiful because at the end of the day this is a landmark structure that’s going to be here for 120 years plus so

For the sake it would have been a shame toh do something that is not as beautiful as what we’re actually building now just for the sake of a little bit of ease of construction so you can see as I was saying various uh different structures depending on the

Context where we’re crossing canals Etc but we’ll get to that point in a in a in a few slides a picture so above the uh the the render of the the design that we carried forward and a couple of pictures but we’ll see better pictures in the next

Few few slides of where we are today so in terms of of the technical design for the corn Valley viu so a lot of you are are involved in Real Construction so you will recognize a lot of this so the con value vict is a single single box

Meaning that it’s one deck which carries uh two tracks plus service walkways on the side anti- derailment uh barriers noise barrier um post for the for the power ceries Etc and in terms of structure it’s what we call a concrete box gerder so it’s a beam which is hollow with uh

Three uh three cents this is just really a terminology of the various elements so if we start so you see when we go into the next slide so if we start from the very bottom we have foundations which are B piles so rotary board piles in a

Chalk uh on top of these piles typically eight piles per column we have a reinforced concrete pile cap or footing which supports in its turn a solid P the column uh on top of the column there is there are elements that we call bearings which are the intermediary between the

The deck and the column and the deck itself is a uh concrete box gerder which is built in a Precast segmental manner with uh post tensioning and then on top you have the transfer slab for the track slab it’s a track slack sorry track slab system so it’s not ballast um which had

Some challenges with anti derailment parapets noise barrier um which are um most of them built or large element built with what we call hpfi which is ultra high performance fiber reinforced concrete so that’s the overview of what the main structural elements are you can see the drawing and more importantly you

See on the picture the actual cross-section what what it looks like yeah on the top hand right corner so the next uh the next slide um I think a lot of you who are involved with ra will will very much understand this we have a bridge which is 3.4 kilom long we have

Of course uh long welded rails because uh on a high-speed train it’s Unthinkable to have joints a large number of joints between rails so these this is a long welded rail system but we do need to have a rail Expansion Joints because otherwise it’s just too much the rail struct the

Rail structure interaction becomes a problematic so the structure is actually the 3.4 kilom is broken down in four sections that we call modules module four from the north which is where we started construction going to module 3 module 2 and module one module 2 3 4 or

About 900 M long and the last module is about half half of that and between these modules is where we have the rail Expansion Joints and these are on a simply supported slab because it’s to accommodate the movement the relative movement between the concrete structure

And the long welded steel rail um so the the deck is interrupted at is continuous for all the for on each module and when you get to the end of the module you we will see you have a single span before we start the next module and on that

Single span is where we accommodate the rail Expansion Joints in the middle of each module of course because we have significant braking and uh and traction loading longitudinal loads we have uh the point of longitudinal fixity which is roughly in the middle of each module and we will see how that is accommodated

By a specific special foundation and substructure slightly different from the typical ones if we go to the next slide Maran so bit more technical details so starting with foundations I won’t necessarily go into all the details I mean this is a presentation that we’ve done with Maran

In the past we can easily spend an hour and a half but we don’t have that time today so I’ll go bit quickly rotary Bo piles 1.5 M diameter so we we we drill hole in the ground that we stabilize with what we call Bentonite which is a

Stabilizing fluid we lower down the rebar cage and with a try we pump concrete which displaces the Bentonite which is re recycled and reused on the next on the next uh foundations the pile caps and PE a classic reinforced Concrete Solutions so uh placing reinforcement placing formwork and ping

Concrete with a small complication that we have quite a few PS which are in the water which obviously required what we call Coffer dams to do construction of the of the footings in the dry The Columns you can see the architectural aspect these various facets so they are

Not just square boxes they have a facet with different structure with different texture which I believe gives a really really nice architectural finish even though it did complicate our life quite a bit but the end result is very pretty the bearings are some of the largest bearings we’ve ever installed on Bridges

Very large spherical bearings uh the photo doesn’t really give it justice but some of these bearings are as big as a dining room table so very very large bearings in terms of the deck this is where we spend a little bit more time uh the deck design it’s a segmental bridge

Meaning that the bridge is not PED in one go not assembled in one go but is formed of what we call segments which are a slice of bridge uh typically three 3.5 M long depending where we are and these elements have to be built Lego style one against the other to be able

To uh Reach the the final length of the viu so this is done with what we called match casting so match casting what does it mean it means that we cast the first segment then we move this first segment slightly by a few meters and the next

Segment that will go in the structure is cast against this first segments we’ve we’ve done which means that the two segments have been cast against one another which means that we have a perfect fit of the surface between the two segments which means that after we’ve stored them and we cured them when

We bring them to assemble them to the side because they’re all numbered and they’re not inter changeable each segment has a specific position within the bridge when we bring the two segments again on the site and we glue them together literally then the the the faces of the segments will match

Perfectly without any hole or hard points Etc so this is what is called match casting if we go to the next one the next important point on the deck construction where we’re spending a bit more time is the fact that what we use here is called a balance con

Um construction and uh it means that we erect the segments which go on on top of the column first and then we add a segment one at a time on each side so the deck grows from the Cent column towards uh towards the middle of the

Spans so we are not building a span but we’re building from a column going half a span and half a span and of course on one side you will see on other photos it connects with the other con or half span coming from the previous Pier so this is

What we call the balance con construction and it allows us to um to build spans which are here the longest spans are 80 M so these are very long spans that we wouldn’t be able to construct with other pre-cast segmental methods span by span Etc so the the

Method to build the the the bridge is adapted to to the span two important points on the design um which I think will interest people is that uh one is that this is the first reintroduction of preast segmental Vu with internal Post tensioning in the UK uh as some of you may

Know based on accidents in the 80s there was a first moratorium or ban total ban on use of internal Post tensioning in concrete bridges in the UK the ban then got lifted saying well if it’s internal but these are segments cast in place then it’s okay and there

Was still a moratorium to this day on the use of uh internal post tensioning uh inside concrete segments where we have joints between pre-cast elements and the view was that um because you have a discontinuity of the protection duct around the cable at the Joint the

View is that it’s a it’s a point of entry for chlorides for corrosion it’s a weak point however the moratorium also and the the the the the specifications recognize that technology has evolved quite a lot since the 80s and that if uh we’re able to demonstrate that we are uh

Ensuring a positive connection of the post tensioning across the joints which effectively means that you have the same level of encapsulation whereas you’re inside a segment or at the Joint then um internal post tensioning was then allowed with the other Proviso that you demonstrate that you have a method to measure

Throughout time that the encapsulation or the protection layer around the cable remains effective throughout the life of the structure so um this is what was done and the reason for the internal post tensioning I won’t go into the details because we don’t have time is with this type of

Construction in order to have the spans required to meet the obstacles etc for this 3.4 kilomet we cannot avoid having cables which run inside the concrete we do have also have what we call external which is a bit of a misnomer because they’re not inside the concrete section

Itself but they’re inside the cavity within that box beam so external is a bit of a misnomer but basically it’s post tensioning that only touches the structures at a few points and doesn’t run completely en case in the in the concrete everywhere so there’s advantages to both types of

System and in fact by combining these two system we get an Optimum solution for this for this bridge the um so uh as I said the challenge really was to demonstrate that we have a system that is robust with no weak points at the joint and that is uh monitorable uh

In the long term so this was done with a particular type of post enging which is a vssl system um which is called a P3 so protection level three which is the highest level that the specifications recognized today worldwide um and it’s a system that not only demonstrat a full

Encapsulation protection of the cable everywhere but also is what we called an EIT system so electrically isolated tendons and the idea being that um the structural steel of the cable is completely uh isolated from an electrical point of view from the passive reinforcement the rebar inside

The concrete okay and by uh with that system by measuring the resistance between the the steel of the tendon and the steel of the rebar um the higher this resistance you demonstrate that there are no uh straight currents or leak currents that go from one to another and if you don’t have currents

Passing then it means that you don’t have chloride ions or any contamination ions that can penetrate within the encapsulation and corrode the strands inside okay again a very very uh important topic very dear to my heart so I could spend hours talking about it but unfortunately we don’t but at the end if

You’ve got questions I won’t be here for questions uh we’ll take the questions and we will respond individually to to some of the questions as as required the second important point in terms of the technical aspects of the project was how do you manage to the design of a very

Complex structure where in fact we have 1,000 segments on this structure in terms of what we call the typical segments uh which are not the ones where you are over the pi we have different types which means that we have very few segments that uh look the

Same uh we have different spans because of the architecture we have this Arch effect that needs to be perfect as we’re changing spans so uh quite a lot of complexity and not much repe itiveness on uh on the structure of this of this length uh 57 Spence is what we have and

Typically on a very long structure you would have a few types of con lever a few types of segment and you just repeat but here with the architectural vision and the desire to vary the structure shape according to where we are in the 3.4 kilm length of the bridge uh we ended up

With 9 count types for these 57 spans 111 typical segments geometries and 17 different what we call deviator section so quite a lot of means the impact of such complexity a lot of drawings about 1500 rebar drawings about 3,000 segment catalog drawings so for each segment

Each of the Thousand segments we have a catalog which gives the various drawings the inserts Etc the post tensioning that is required to build this particular slice and 3,000 uh drawings so in average three drawings for each segment which is a lot for a what should be a

Repetitive uh structure so obviously the impact is uh delays complexity possibility of Errors uh quite a bit of resistance to changes when when changes are required um brings complexity to the casting cells so the special formwork that we designed to cast segments you can get errors in the Drone Etc so

Really the solution was to have a lot of digital tools so we did Implement quite a few digital tools I think the next step really we didn’t implement it but that would certainly be the next step on the structure of this complexity is to construct directly from the model so we

Have a bin model obviously for the entire structure but it was felt at the time that in order to build we had to translate the build model into drawings that uh people on site would be more more used to building but definitely the step that the industry is going is

Directly building from from the bin models with augmented reality Etc so that would be an improvement for the next structure and really the final point is that it’s absolutely essential at the start of a project to have a very good understanding of the expectations of the different parties and because of a bit

Of floating at the start that did create some complications but with obviously we got through it because we have more than two3 of the viu built fantastic quality and a great safety record so well it is possible even though you have a bit of difficulty at the start to still achieve

Something very very good in terms of casting cells so what we call casting cell and Maran will will show you a bit more later this is effectively the name of the specialist formwork that is used to cast these segments which are maximum 140 tons so these are not small pieces

They are 11 M wide the tallest are 9 M tall 3 m long so these are Big lumps complicated shape that are C in specialist FW workk which are called casting cells in the uh in the industry so these ones were totally modeled in 3D and in fact the fabrication was done

Directly from the Bim model by the Fabricators which avoided quite a lot of mistake but in the end you always have a few bits and pieces surprises when when everything comes together but on a casting cells of this complexity I think the the 3D modeling and the fabrication

From the model avoided a lot of u a lot of errors that we would have seen traditionally a few years ago before before 3D modeling became so prevalent okay if we go to the next uh so Maran will will take you through a lot of more details on the construction

He’s the one with all the pretty pictures so he’s got’s he’s got the best part of of the presentation and I think he’ll be very very uh uh interested with what he’s got to show to you as I said at the very start I’m really sorry but

I’ve got another meeting I’ve got to go to um which means that Maran may not have all the answers for some of the technical or design aspects but Maran is the Project Director in charge of building the the Vu superstructure so on any construction questions he’ll be a

Lot more familiar and a lot better to answer than than uh than I would be um I think there’s a few questions that have come to the onto the chat I guess Kate do we wait until the very end for the questions is that uh is that the plan or

Do you want to address one or two of the if there are design design questions that I’m the best person to address quickly before we move on as you wish I mean yeah usually I do them at the end but as you’re going to be go in yeah if

You want to answer one of those two questions that that’ be great thank you yeah so the questions sorry I didn’t see the chat but uh I did see questions arriving but I didn’t have time to read them uh how are the incline panels made non-structural with a box so the incline

Panels are cast at the same time as the rest of the Box the only thing is that uh the face of the panel is recessed by a couple of centimet on each side which means that when we glue the segments the the incline panels do not touch so they

Are not part the incline parts are not part of the uh the longitudinal structural section the section that gets compressed by the post tensioning and experiences the shear and and the bending the incline panels have a function which is purely in terms of transverse resistance to hold to help to

Hold the wings of the Box in place plus the architectural effects of course but from a longitudinal glob behavior of the deck the incline panels are not structural they’re only structural in the transverse there’s a gap have a gap of 10 mm between each of the segments on the inclin panel

Entrance yeah so even though they are cast at the same time of the Box by putting these low recess we make sure that they don’t touch from one from one segment to another so they don’t participate to the resistance of the longitudinal beam yeah uh the second

Question could you please share the name of the vsl system for tendons coupling of the joint yes so um it’s a what we call a P3 system for vsl so the couplers are called remind me the name vsl segmental coupler we call them I mean very original name not but it

Does what it says on the tin it’s a coupler for the duct so the protection of the cables through uh through a segment joint and that’s that couplers that have undergone a lot of testing which are certified Etc and today with two3 of the vict um constructed the results that we

Are picking uh every time in terms of measuring the resistance which you doing on on a regular basis at various stages uh all the results so far are showing that the segmental couplers in the case of the hs2 C1 con Val vict are working extremely well and are doing exactly

What they’re supposed to do so we are achieving the high resistance that we are um we are contracted to achieve with the PT system more question for you I might have I might have time for one more question and then I’ll have to go this end plate or isolation plate it appears

So small um yes so what happens is that traditionally in post tensioning you have what we call the Anchorage block which is the the um the the big circular piece of Steel that bears against the cast iron Trump which we call the the casting which is cast into the concrete

So typically these two steel elements are in contact which means that there is no electrical isolation so what happens here is that first of all inside this casting you we have a plastic trumpet which means that the strands the post tensioning strands cannot touch the side of the casting uh in the concrete

Because you have this this second plastic sleeve around and between the casting and the uh the Anchorage block you have a uh a non-conductive material but with very very hard compressive U uh strength which is between the two meaning that the The Strand touches the anchor block

Because this is where you have the wedges that anchor it but the anchor block doesn’t touch the casting which is in the concrete because you have this isolation plate and the isolation plate in fact is just slightly bigger than uh than the Anchorage block and that is enough to break the electrical contact

Between the two elements and then after we have another plastic cap going around to protect this which also Bears onto the onto the uh the isolator plate so in fact the whole system you have no electrical contact between what we call the structural part which is the Strand

And the Anchorage block and the wedges and the non-structural the casting and uh because the casting is in contact with the rebar which are inside the concrete so you have a perfect electrical isolation between the tendon element and the passive steel that is on the outside I hope that the question I

Think Frederick the question ifs the the one with the photo I think the gentleman saying the casting when what we see the hand plate in reality this is the casting of the external posttensioning looks very small compared to the loads so this is not only a plate to answer

It’s not only a plate this is a casting so a cast iron element that is cast inside the concrete and behind this there is a lot of bursting reinforcement and the reinforcement of the segment so this is part of the uh post tensioning catalog and the the the casting and the

Anchorage has been designed for a certain strength of concrete and calculated and tested fatigue tested etc for this so yeah the the casting also has a series of rings behind it and all the series of rings this is all uh designed and certified per European technical agreement of course yeah and

This whole system of casting is capable of your right these are very large forces because if you take one strand okay and here in this case these external tendons go up to 37 strands each strand is 20 tons right so 37 strands that’s a cable that cable is

Putting a force of 740 tons in that location and whilst it looks maybe a bit small it is perfectly designed and um perfectly designed to transfer that force and it’s a system it’s a product in fact it’s an industrial product for vssl that is a placed all over the world

And which comes with all the technical agreements that that you would expect um so sorry so I misunderstood the questions but in fact on that picture first the external tendons are not electrically isolated they’re not because they are external but um that low isolation plate in fact is even

Smaller than this uh this Square plate that you’ve highlighted in red it’s between the size is between the Anchorage block the circular part and the square which is the casting sorry so I hope hope that answers the questions and I really apologize but I’m going to have to uh to

Go but I leave you in the extremely capable hands of Maran so do enjoy the rest of the presentation and if you have further questions send some uh questions through through email and we’ll uh we’ll try to address them uh as quickly as we can thank you very much everyone than

Youi thank you byebye for tomorrow then yes good afternoon everyone yeah so we’ll go now through a section that is maybe more down to earth if I might say so the construction methods and quite few techniques that were used to construct the the okay so uh yeah the conine main

Constraints that we had were uh basically few Crossings so we had two roads to cross uh which is done we have two rivers a canal and high voltage power lines and the basically the construction is there are two types of construction on the V on 3.4 kilometer

We have two3 of it which is over land uh and one3 which is really over the water and that has been done with temporary Jetty platforms so Land Based construction what you see here is the first section of the bridge that is already completed structurally with the deck the solid barriers and the

Parapets the only thing missing to have the final view of it or aesthetically would be the sound barriers that will be coming above the the parabit here this has been constructed so there mainly in the valley uh we had an access road at the ground so that’s a whole road that

Running all along the the construction site B and when reaching into the water we had CER Dums to limit the ground water which is very close to the ground a now uh in terms of methods of construction so the idea of constructing that balance G was to do with the

Launching entry in order to uh reduce the impact of uh carbon and instead of refabricating a new machine the the pro project or the the idea of of align was to reuse launching entry that was previously used in Asia so used initially in a project in Hong Kong

Which is it s vict and then this uh launching entry as it was already existing and already designed had limitations in terms of the weight of the segment it can lift so the two Ines on the machine can lift up to 140 tons or 150 ton if we don’t consider lifting

Beams so basically the segmentation of the Bridge of the vict was readjusted in order to match the maximum capacity of the launching G so that was one of the constraints that were defined when defining the geometry of the uh in order to do that so as the LG

Was already already existing and have already been used for for a few years on different projects it had to be rechecked against the Euro code it had to be checked for the wind load so it went through different tests of uh tunnel testing wind tunnel testing in

3D tunnel testing and physical one so model was fabricated of launching G and it was checked into the T analysis were compiled to check everything was okay and fatig was checked as well as it was being used for the first time in terms of assembly of the launching entry um

One of the changes that were done from initial assembly so the basically launching entry we’re speaking of we have two trust we see here two trusts each one of them uh has is 150 M long the overall assembly the full assembly of the EDG is around 700 tons in order

To assemble this while preparing the platform on which it was assembled as the platform was let’s say running late due to weather constraints the the Assembly of the trust was started on the side so not in the final position but next to it so while the TR were being

Assembled on on the platform here the first words and the foundations for the first launching were being done next to it by the time the platform was ready the slabs or the the pads were ready the temporary supports we see here those are red beams here were installed in their

Final position then the truss that was erected on the ground was jacked up on those hydraulic jacks here on the slack of ships here so it was jacked up to the final level and then moved with the spms into position and then lower onto onto the supports before the first launch so

We’ll go now into the first uh uh small video to show how the launching entry works so the machine itself is composed of two long Trust of 150 met as we said it has two main supports which we call the TBS or transversal beams we see here

Here the two double double beams here and it has two lighter legs so the front and rear legs you see one just here behind the TV and the front one is just here that are hanging up in the air these allow the let’s say the launching entry

To land on the Pierce during the the process of launching now a small video that shows how the launching entry move so basically we are crawling the machine forward moving the thrust on the supports and then Landing onto the pier so here the launching entry lands on the

First Pier we bring in the first pair of segments so the what we call the segments on peers or Sops they are placed on the pier then we do Post tensioning those two segments we launch the main TR the main support onto the LG prepare the

Pair of segments that will come from the back and bring them into position now once we are here basically once we have the two segments that are in position time sorry once the two segments are are in position on both sides of the pi once we

Have a pair of segments on both sides of the PE in position we have one pair of tendons that run through those two segments that are stressed this will create a balance C deler or CER that is self supported and able to take the load

Of the next pair of segments so here we have the first two segments here once these are in position we launch the machine to be centered over the the pier so this is one then we get the first two caner segment one will be placed on each

Side of the P assembly so these are first two segments here there is a layer of post tensioning and then one another pair of segments another pair of cables another pair of segments another pair of games until we go to the end so the launching Gentry has been upgraded quite

A lot since it was used on this first project lot of sensor were added on the machine which allow basically to follow remotely the loads on the machine at any moment in time and this was coupled with a few algorithm and sensors that allow to analyze the movements of the

Different parts of the launching G the loads on Ines and this allows to do a a very precise followup of the Cycles we see here the cycles of the different caters in number of days and the algorithm will on its own calculate the number of segment erected and the

Progress of another change that was done to the launching Gentry from its initial setup was the use of lifting beams with what we call the Adel system this basically allows to lift a segment without the need to go on top of the segments I said the segments are up to 7

M high in order to pick them up if we have to go on the top to hook the segment to the beam this is additional risks that means people working at height and the use of this system allows basically to pick up the segment from the top slab by inserting those fingers

Into the segment so we have four recess in the segment we insert those Adel fingers in then by remote control from the ground level or from the deck level the operator will engage those red locks which will basically rotate so from from the vertical position they will rotate

Into horizontal he will lift up they come in contact with the segment and then can lift it up without the need to go on top now going more into the general construction or the can construction as we are con we are constructing C lver so basically we have

Loads coming on both sides uh this means that the structure during its temporary stage is not specifically stable or not necessarily stable and the overturning moment when we put the segment on one side is quite big that means that the uh above the pier we have very little space

To take those out of balance movement as the pier are just a few meter few meter wide top view of the pier here we have when we erect the first pair of segments it’s quite congested we have segments under the first pair of segments the bearings that are already in position

And that doesn’t give much space once we we put the first pair of segments when we start going out of that area it is uh quite High loads coming down in order to take that out of balance movement basically we use a set of crops temporary crops which we see here in

Gray that are uh assembled and fixed outside of the pier or around the pier under the first pair of segments that are in C liver with big jacks on top and we use two levels of nailing which allows basically to clamp down the structure that is supporting as well the

Launching gy on top to clamp it down to the ground to take those out of balance movements in order to do those props and to be efficient the props had to be modular so they allowed to be adjusted so we have most of the modules are 2.5

Mters and then we had smaller modules that were used to get to the proper height depending on the height of the of the pier all the pier are different TI one of the main point that was considered as well by the technical center of VL when this

Designing stary props was the ease of dismantling it and making sure that we are able to dismantle them within the cycle of of operation so they were designed with those lever arms and they can be picked up from the LG after the loads are released they can be picked up

With the launching gy from the top and moved out in order to be transported after to the next location so the same props that we can see here which are taken that out of balance are used as well with an extension in order for to receive the launching entry during the launching

Phase so once we are launching the the LG to the following Pier the front leg will come at the same level than the deck so we used an extension here which will take that load during the launching of the machine and the Machine basically will come sit on that prop which is out

Of the P itself which will allow as well enough space here to position the first two segment uh the pier segments before we transfer the main supports to proceed further so on top of those props in order to take all those loads and to take the naving forces we have on top of

Each of the props Two Jacks of 1,000 tons with a top plate is an inclined plate which which is machined in fact in order to resist any sliding so that’s giving additional friction to resist any sliding due to the clim pH that we have all the loads go back down through

The webs you see here those webs that are transferring all the loes down to the to the promps themselves uh just one more Point compared to the we were discussing earlier about the C post tensioning we see here the castings on top of the segment which will take

Basically the can post tensioning from one segment to the symmetrical segment on the other side of the BL and finally in order to give that all stability we have two level of ning one which is on the pier segments directly into the pier just the loops and the other one which

Comes down from the beam on the top through the segments all the way to the to the ground to the pipe C here we see the Ning inside the P segments so those are the cables that we see here at the lower level and on top we have beams

That are transferring this load from the position where the cable can run down onto the the webs na all the way down into the back we see the cables here they are coming down from the top SL all the way through the the props all the way down into the

Pile C which is somewhere at this level and that Cur with in the ground some in order to do the post tensioning during the the erection of the c l we always need to access the edge uh as we are using pl3 system and we want to

Ensure that all the ducts and the joints are fully sealed after the gluing of the segment we have a platform that allows access in the same time to the top slab uh to do the threading and the stressing of the top tendons and to the bottom

Slab to do the trial or the test of each seals during the construction so we needed a platform that allows to cover that whole height as we were limited with the witches of the machine we had to go with the design of platform that was in aluminium otherwise the auxiliary

Witches of the launching Gantry would not be able to take that again during the construction in order to keep the C stable and the last pair of segments stable before we do the post tensioning the segments are glued together and they are compressed the joints are compressed

So sheet keys that we see here are compressed together by use of temporary PT at two levels so we have one level of temporary PT on the top slab that we see here using brackets that are self loocking into the top slab stress bars across the joint so we see here the

Joints of the segment we see the segment lifting beams here these are segments that are erected epoxy joint and we stress bars across the joint to lock the segments together to compress The Joint squeeze the epox into out and the same is is done as well at the bottom level

With PT bars or poic bars that are going through concrete blisters that case with different shapes depending on the type of span it can be either horizontal as we see in on the bars or it can be inclined when we are on inclined solid now one of the special

Special techniques of construction or one of let’s say of the areas that is slightly different than the standard C Li is the VP this is what being explained earlier by by Frederick so the architectural feature of the project that V shape that’s giving that scheming effect

Here we are not on a standard C Li where the segments are here we have shape that slightly different so in order to do that basically two stages of construction were done so what we see here in dark gray was the VP itself with two uh cast in place segments which was

Done in C2 on top of the jetti and then all the lighter gray ones were cast again preting in the preast yard and transported to site and erected with LA to give you a bit more of an idea of the scale or the size of those VP uh

There is roughly 500 cubic met of the overall weight is around 2,000 tons you see the density of Steel that we have here in size of one it’s a it’s a really massive structure that was built on the jetti so see here the formwork everything here was was ped let’s say in

Two stages so the first stage is this one here and then on top there is only the segment comes second stage so quite massive concretes it had to be done over the temporary J so a lot of subject of differential settlement and self support of that structure which require as well

To have internal post tensioning inside the VP to keep that shape basically together when to De propop the shutter so basically after casting that VP we stress six cables of censing that are going through the VP here before the prop shutter can be St off basically again the

Uh the VPS during the construction were supported in Four Points so under the sofit and under the for we had four columns uh on top of which we had a stack of ships that basically will take the the load once we strike off the formwork that will take the load of the

VP itself and keep it in position until we we are able to adjust it during the construction so here we will see the sequence of construction of the VP itself with the launching gy you will notice inside the VP there is a an infill structure that is used to support

The first pair of segment and to receive the front leg of the launching G so the launching G is launched into the VP we support the front leg we put the first pair of segments then again we will transfer the front main support on top of those two segments release the front

Leg clear the area and then from here we are able to ECT the remaining three segments uh inside once the infield is done there is one uh first line of cting C2 stitches that are cast here so we adjust those segments we cast those stitches and we do a first level of

Permanent post tensioning through that VP then to make it all monolitic let’s say once this is done the rest of the construction is constructed in a normal CER so we put the first segments outside we see here the first five segment infi segment that are Ed over that temporary

Structure or the infi structure that is itself nailed down into the VP which is itself nailed down into the p cup so we have two layers of two levels of nailing in order to stabilize the whole SE now before we do that the stacks of shims that we have seen earlier have been

Removed replaced with four jacks of 2,000 tons at the Four Corners which will allow the adjustment of the C lver once completed to match the previous canver terms of geometry control so a few photos during the the assembly so the one reaches put that this one again completed once the first five segments

Are completed and the post tensioning we see here the post tensioning cables going from one phase to the other are stressed then we go into the next segment so we have another two segments outside of that VP with again two stitches that are to be cast so these

Segments are adjusted on top of towers to match the geometry we cast those stitches again one level of post tensioning and then we go into the real C so one of the challenges there as well was to remove that big frame from inside the VP after the construction segments

For this we use a sliding system basically that is going under that frame Jack it up with small hydraulic jack slide it out and once it is out in position like here it’s picked with the crane removed and sent to the next location to be to directed fin or in the following

V the segment transport on the project was the hydraulic trailers nnts so from the pre-cast yard which is 1 and a half kilometer away from the start of the V on the Hall Road it was use of selfpropelled trailers connected with spts connected with the trailer and on the deck itself

It’s self-propelled machine with the power pack at the back to transport them on the deck marh Gast this is what was explained earlier by Frederick so we just have a small video that will show basically this process of the March cast in the casting yard basically the

Segment that is already cast is brought into position and it’s sitting here next to the casting sand we will insert the cage rebar cage into the formwork and uh fill cast that segment the segment that was previously cast is moved out the segment that was recently cast is moving

To mat C position we reinstall again the formwork adjust the height of the formwork put the new cage inside and thenat so again as the segments are variable height because of that can deliv our shape the height of the segment is changing every time so every

Time we cast one segment we remove the bottom part of of the form which is the the bottom form here which is adjustable sort of stack of different shaps to get the proper height so this one is reused every time we move the segment together with the bottom four from its current

Position after casting so when it’s still wet we strike the form mainly only on the side and on the inside but the segment is still supported from the bottom because it’s sitting on the table that table is reloca into the masch position so we don’t lift

The segment we take it from the bottom so basically it can be done at very early stage or very early age when the concrete is still not very hard it’s moved into the new position we install the following table so the next one in it’s adjusted to match the height of the

One already cast and the final geometry the forwork is closed again on the sides all the ducts that are installed in the cage are connected to the ones that are previously cast with a specific set of tools to make sure all the ducts are continuous and are properly fixed then

We P the next segment and again by the time the segment here is pulled this one is already hard enough so it has already passed 48 Hours roughly it is moved out of the way and then the Gantry TR that is on the outside will pick it up from

The the holes don’t see here system and moved into location now here we will see a time lapse of uh exactly the same works but so here you see the cast uh segment that is already in position this one is the new one that was cast the

Other one out it go very fast but segment is cast and then it’s moved out with with the card so there is a card that will come from below the table and we pick up you can see it coming in and out here at the bottom it will come

Under that table uh again hydraulic JS that will allow to it one more time you can if you look at the bottom you will see that there is a card coming in and out under the under the table you see it here is position and then this will be used to

Move the segment out and bring the other one in so the card is used to move the segment and in the same time to adjust the Match cast segment before casting the following one so the the principle of Match cast basically as you have a geometry uh to control very precisely to

Get the final shape of you of the bridge that you want the in the in in principle we have a casting curve that is defined by the designer at the ear stage and every time we cast one segment we will do a survey of the pair of segments so

The newly cast segment and previously cast segment they are surveyed together and we check that the geometry is matching with the theory any modification so let’s say we have tance of 5m any modification that’s outside of the tolerance is adjusted by readjusting the position of the match cast before

Cast the following segment so basically we will always readjust the new segment to correct the curve when casting the next one so if let’s say you go up 5 mm well you correct on the next one to bring it back down 5m and as you go you

Never add up errors you always keep that tolerance within the same liit this is done by surveyor that will be uh using the towers here and now the latest development that is implemented on the project and has been running now for a couple of months is to have have an

Automatic adjustment of the match cast with let’s say laptop and smart system that will measure basically the survey of the points and will automatically give the movement on onto that card to adjust the segment hydraulically without human intervention or without having to go doing the reading again again the time I surveyor

Would read tell the guys okay Jack up 5 mm in this corner 2 mm in this one that the guys adjust the hydraulic jack okay now you went too far Etc repats now all those Cycles are done by laptop so the surveyor himself will do the survey which is done automatically but the

Feedback goes back into the computer the computer will increment the hydraulic jacks by the necessary movement to get to the final geometry and a final final small video this is a time lapse that will show the construction that was done over the a412 that was the first Crossing of roads that was done

Last October sorry October 2022 uh so here we were limited because that’s a road that is used as alternate route for the M25 in case of accident on M25 the a412 is one of the Escape Routes basically so we were not allowed to close it more than 5

Hours six hours per night so all the erection was to be done during the night between between 10 p.m. and 5:00 a.m. and we had to be able to reopen it within a couple of hours in case of major issue on on M25 so this was done

Quite successfully see one more time so we see on this one during the day the back segment of the C was being erected and during the night the segment that is over the road so the road is closed the segment is put in position clean everything uh and get ready to open it

In the morning once the this C was completed which is basically arriving up to halfway above the road here the following c l that we see on this side was elected in the same manner but going backwards until we connect to the same point so that’s a bit uh everything for for

Now thank you for listening and if you have any questions I’m happy to answer thank you Mara I think that was a great overview of the design and the constru tion of the how the vict was done it’s very very very impressive um and I think also it’s quite evident that there’s a

Lot of e effort has been made into reduce the visual impact on the surrounding so you know as as it was mentioned at the beginning with with all the architecture structure looks absolutely beautiful so I think it’s a very very good job that the team has

Done um so we’ve got a couple of questions firstly does anybody want to ask their question or if not I’ll go to the chat and I’ll just read out we’ve got two questions that have been added okay I’ll read the first one so the first one’s from Claudio so basically

Said very interesting presentation so well done to you both um how many and what size were the tie down tendons utilized at the peer segments to cope with the loss of segment scenario the the biggest uh the biggest nailing cables we have are 622 we have 22 two strands of

15.7 one but again the as we said we had four cables uh nailing so we have the four cables on the segment one and we have two cables or two U tendons in the P segment but depending on the type of cver it we could have smaller cables or

Bigger CA the biggest one are 22 strands times four um I think there was a question uh yeah another one another question of bash so what’s what are the key factors to consider when determin the required preber adjustment if any for viod upct beams subjected to the railway loads and then

How do these factors influence the adjustments of the final loads process H this might be more of a question for Frederick I was say however no I can I can I can speak a bit more about the preber and the way it is done for the balance C Construction

Which I know quite well the final interface with the final final loads from the trends are not 100% sure because this really is the designer but but in in principle in terms of of uh of preber this what we say what what has to be considered in the type

Specifically the balance C Li construction is that as you construct the canver geometry or the the shape of the bridge is changing all the time so every time we put a pair of segments we have a deflection that is due to the sufate of the segment there is

Deflections that are due to the working loads and then you will stress the post tensioning cable that will bring back up the the C into a different shape so that’s during the construction of the C itself then there is uh at a later stage once you connect the two c Li together

We have the continuity switch back on some of the photos that on some of the slides that might explain we have the continuity post tensioning that is coming between the two cers this has as well an effect on the overall geometry of the deck and uh the last level which

Is basically the external post tensioning that is coming as well across two or three spans depending on the L of spans will have one more effect on the geometry so basically the the design is done backwards from the final geometry that we are expecting once we have all

The superimposed load uh we remove the superimposed load to know what it should look like basically before these loads come in uh then this would be so the final stage is when you have the external post tensioning so before the superimposed load come on the deck which is basically the parapets the

Barriers the transfer slab the ra everything the the geometry is defined or is finally adjusted by that external PT these are stress the V takes its final shape and then at that stage we can start putting the the permanent loads or the dead loads on top the

Barriers the parit ETC uh so once this is done the gas can start storing the parit before that the previous stage that will affect the geometry as well is the stressing of the midspan uh uh Stitch continue TPT so this is the poing that goes between two c liver when this

Is stressed it will affect as well that geometry and before that during the construction of single C Li so basically we’re looking only at that c Li itself every time we put a pair of segments the gy LI has a tendency to deflect we

Stress the gy LI it goes up so all this information is included in the model and uh basically we know or we have a geometry system that will Define at every stage of construction where the tip of the c l should be and what the level of each of the segments

Should be so during the construction uh this is monitored every time we put a pair of segments the surveyor will survey the can itself check what is the position of the tip of the C on each side after stressing the post tensioning and check that this is in line with the

Model if it is not then we we will adjust as we go and we keep adjusting this until we get to the end of the c l once the whole c l is completed it is adjusted with the use of the Jacks that are on top of the prop to match the

Previous C before pulling the Stitch so we have to make sure that the C is exact position to have a matching with the previous one so we have a tolerance of 20 mm 25 mm at at the tip the Stitch is pulled we stress and then again we

Survey where we are after that there is one more layer of poing as we said which is the external post acing which will give the final shape before we start putting the Deads I’m not sure if that really answers the question but that’s the process as it is going now yeah he

Said thank you very much for the clear explanation so I think yep that did answer the question okay um just one last question then for me so how did you guys or the hs2 project how did you engage with the the local community and stakeholders in sort of planning the planning and

Construction of the viaduct yeah so uh in fact Aline uh I have to say have a very good uh communication team and they have done a lot a lot and they still do quite a lot of work Upstream with all the communities they were engaged at all the stages basically even of of

Designing the the project different different phases to give you an example the tunnel or the tunnel of the VCT not V sorry the tunnel of the project have uh four shafts along the the tunnels that that are either emergency Shaft or Iration shafts so these will fin will be at the top of

This of the shaft you have a technical building that will be visible let say1 in order to integrate those ones into the the environment there was sort of workshops that were done with the L communities in order to look into the design of those building to see how to

Best integrate them and finally the the the four different buildings have different shapes or different looks that are looking slightly like Old Farm and basically the the whole technical technical building is hidden in the in the let’s say the that landscape by looking exactly like Old Farm Etc so

It’s really now in terms of noise and and other constraints for the for the population there is hotlines that are that are open by AGS too uh and complaints are recorded on system and there is a again before any new activity is undertaken consents are being being

Cleared by the consent team with the local council with the the people Etc and uh basically everything is is prepared ahead with the with the local communities in order to avoid as much as possible the disturbance obviously there is always uh things that some some uh comments that would

Come in but they are treated with by hs2 and align on day today and we we connect as me um there is as well a very interesting Visitor Center that has been set up by by a line on the on the Southport layout which explains everything that is being done to protect

The environment to integrate the local communities Etc so to give an example on the launching G for example we have all the lights that are on the launching Gantry all the lights in general that are over Jetty had to be changed to a specific type of lights that do not uh

Uh let’s say endanger the local fona so there is a type of bats that is very sensitive to lights that is uh living in the in the area here so we had to change all the lights to have lights that do not bother the the bats

So a lot of control on the noise so everything is very very say the square door in Case okay thank you I mean once again Mar thank you I think that was a fascinating presentation and thank you for um finding the time to come and speak to the pwi I think there was one question I may from before when Mr R CH I think uh who was asking

How many days are needed to erect and stress a segment uh yeah so days we can’t say this that’s too much on average or on Cycles the best Cycles we have done is around four hours to erect a pair of segments erect them and stress them on average we we are erecting

Between three and three and a half pairs of segment per day which gives a c one C the the shortest we have done but now is four and a half days for a span of 60 M for a full Cycle okay thank you um okay just for everyone who’s left in the pwi um our next technical talk this will take place face to face at our new venue at cisterra so that’ll be in Alpha Tower uh the next talk will basically be uh in Johnson from d gaau and they’ll be discussing

The transitional methodology and clearances so that will be uh March the 21st at 5:00 pm. um this will be an person one so there is limited spaces so please do get yourself booked on as soon as possible if you would like to attend that but yeah once again Mar thank you

Again for your time um I will end the meeting there as no one else has any more questions and thank you everyone take care have a good evening bye bye thank you guys for watching us bye bye thank you