Modern Construction Materials Prof. Ravindra Gettu Department of Civil Engineering Indian Institute of Technology Madras

Transcription

1 Modern Construction Materials Prof. Ravindra Gettu Department of Civil Engineering Indian Institute of Technology Madras Lecture 42 Anchors - Guest Lecture (Refer Slide Time: 00:10) Good Afternoon ladies and gentleman, I am Vinoth Kumar from technical team of HILTI; HILTI is into fastening and demolition segment and here we go; we welcome you all for the session. (Refer Slide Time: 00:15)

2 The agenda goes like this; introduction to HILTI group and HILTI solution that we would offer in India namely measuring and positioning systems, drilling and demolition and cutting systems, fastening systems, post installation of rebarring, installation system and firestop. So, out of these we are going to discuss only on fastening system and post installation of the rebar connection and of course we are going to speak about technical support that we can offer you. (Refer Slide Time: 00:38) To speak about the profile of a company, HILTI is a global organization, we have a plant across the globe and it has founded in the year 1941 in the place called Schaan. Schaan is in between Switzerland, Germany and Austria. It is the small town comprising of more than a less somewhere around 50,000 employees and we have more than 20,000 employees across the globe. Our CEO is Mr. Bo Risberg and Chairman is Mr. Baschera and our brand promises is outperform, outlast. (Refer Slide Time: 01:13)

3 And this is our generation thing; it started in the year 1941 until We have different; we have launched a different products and we have stepped into different platforms and we are keep on growing as such and HILTI India is started in (Refer Slide Time: 01:33) This shows the production network what we have a across the globe. For India, the nearest godown would be from Singapore. Singapore is a nearest manufacturing unit for India and from there, we import the material and from there we supply from a Bombay and Delhi and HILTI solution that we could offer in India. (Refer Slide Time: 01:57)

4 HILTI India is headquartered at a New Delhi and we have 275 employees in India and more than that 25 service centres available and we have a network across the; completely across the globe, across the country. (Refer Slide Time: 02:15) And this is the HILTI team taken in team conference (Refer Slide Time: 02:21)

5 And we have separate technical team in PAN India basis serving all technical queries on our anchor fasteners and rebarring. (Refer Slide Time: 02:30) And our system solutions is; will go like this. Laser technologies; lase power tools in form of measuring and measuring aligning equipments and drilling machines in the form of drilling and demolition tools and again for cutting; concrete cutting and other thing. Fasting technologies of course we have mechanical and chemical anchors and of course, plastic anchors. In modular channel supports for insulation systems which will be replacement of building. (Refer Slide Time: 03:06)

6 And fire stop system to avoid a; to stop the fire spread from the; spread inside the building. Let us go for the fatening system. First; for fastening system we have this tool called the Profis software which will design the anchor fastness and which will indicate the minimum edge distance and minimum spacing between the anchors and all which is safe installation and we also have a FTM that is fastening technology manual, where in structural consultant can refer the manual and recommend the anchor directly for his requirement. (Refer Slide Time: 03:31) So, the design concept goes like this. Normally, anchor will have to take tension and shear. Tension will be component of steel and concrete; steel may fail and concrete may fail, whereas shear again, it is in terms of a steel it may fail due to steel or it may fail due to concrete. Again in

7 case of concrete, tensions there are 3 failures; concrete cone, pull out and splitting and whichever is smaller will be recommended. Again in case of steel, that are 2 failures; one is bending, and other is pure shear. In case of concrete, the shear edge failure and pry out and among all these 4 failures which will be the smallest will be taken into the design consideration and that will taken as a load combination and also combined loading also will be checked under by this software. Everything will be done by the software and the manual design also. This is how our design practice goes. (Refer Slide Time: 04:22) And before going further, this is a basic principle for our anchors that is friction; friction principle works on friction between the anchors and the base material and keying principle works on the keying principle that is concrete will be cut as a key upon expansion and combined friction and keying will be combination of other 2 principles and other last but not least is resin principle which works on bonding mechanism. (Refer Slide Time: 04:54)

8 There are some different failure modes as long as anchors are concerned. Failure modes are; first one is pull out that is, the anchor is coming out of the base material, second one is pullover, that is the fastening material is coming out of the anchor fastens. Pull over is basically due to a larger hole or a higher clearance gap between the anchor and the fastening material and third failure is concrete break through breakage where in a concrete cone is completely sheared off. (Refer Slide Time: 05:28) This might happen because of poor grade of concrete or a higher load which concrete cannot withstand. The other failure modes are steel breakage. Here the steel is getting cut on shear; due to shear, this is some typical picture and other is concrete splitting, here the crack is formed in

9 between the 2 anchors because anchors are installed very close to each other. This is called; this is we called as concrete splitting. (Refer Slide Time: 05:47) And other influencing factors, till now we have seen the failures of anchors and there are other influencing factors from which anchor has to be decided, they are load direction and base material, anchors spacing and edge distance, embedment, tightening torque, reinforcement in the base material and the temperature and corrosion. These are all the factors what we feel is will influence the anchor performance and while designing, all these factors has to be considered. (Refer Slide Time: 06:16) (Refer Slide Time: 06:19)

10 Anchor categories, we have 3 different anchor categories; I can show you the sample at the end of this presentation. Mechanical anchor; in mechanical anchor, we have a medium duty, heavy duty and light duty anchors and we have some anchors especially made for some special duty anchors. Heavy duty anchors are applicated in boilers, in nuclear plants; power plants and medium duty anchors are general construction for utilities, service, fixings and all. (Refer Slide Time: 06:54) Light duty anchors for architectural application or light supports or taking support from gypsum wall, a small kind of loads and all and special duty for special purpose applications. Coming to plastic anchors, it works on completely friction principle, it has a; this red colour sleeve what you

11 are seeing is a plastic sleeve and the friction between the plastic sleeve and the base material will be acting as a resisting force for tension or shear. (Refer Slide Time: 07:18) And lot of other anchors listed down for; mainly for gypsum board; gypsum partition fixing. If you want to take support from gypsum partition, we have some anchors for them and the next is resin anchors which completely work on bonding principle. We have capsule system, we have injection system and we have separate again; here again we have a heavy duty, medium duty and light duty. (Refer Slide Time: 07:50)

12 Heavy duty for like boiler fixing, like machine fixing, I can insert plate fixings and all. Medium duty again comes under utility fixing, pipe gypsum wall fixings and all and light duty again for masonry fixing. We can also take a support from masonry wall, here this is chemical; HY70 is a chemical for masonry supports. These are some of the applications where in; first one you are seeing is door frame fixing application and the next is door frame fixing in hollow block. (Refer Slide Time: 08:09) The same anchor will be applicable for both concrete and hollow block. This is because of the expansion media, here is; here where it is expanded and that is how the resistance acting actually and some applications like bridge fixing, bridge rehabilitation like crash barrier fixing and insert plate fixings. (Refer Slide Time: 08:17)

13 Cross country pipe lines, ladder fixing and the truss fixing, these all some of the application where we can influence. (Refer Slide Time: 08:23) And there is one more different application called stone cladding, dry cladding. Basically, cladding is basically for covering an entire building by using a granite slab or ACP panel, for that also we have support, we have anchor fasteners and also we have this clamps, this clamps is also from HILTI only; SS clamps. These 2 anchors are used for this applications. (Refer Slide Time: 08:44)

14 And some other application like handrail; these are all light duty application as I said, door frame fixing, handrails and cable trays, raised floors, these are all some applications and this is all about anchors what I can talk. (Refer Slide Time: 09:03) And let me go ahead with post installed rebar connection, where this post installed rebar connection with be of use? Basically, when you missed a dowel to take from a beam or column or if you want to raise a column from a beam; from a raft, there where you want to fix some dowels, here that is where a chemical grouting are useful. In this picture, you can see this. This is the post installed bar and this is casting bar. (Refer Slide Time: 09:31)

15 So, here these 2 concretes are getting connected by using this rebars, that is post installed rebars, that is what you are seeing in the picture and rebar grouting; some of the application is like adding a new concrete member like a; like if you want to introduce a beam in between 2 columns or if you want to introduce a column on top of a raft or if you want to extend a column that kind of new; adding new member we have there is a rebar grouting. And strengthening of existing member like jacketing of the concrete or beams; columns or beams and widening or thickening of raft footing pile cap found increase the thickness of slab or if you want to increase the thickness of this wall or pile cap needs to be strengthened or dimension of the concretes needs to be increase, there we can use a jacketing system and providing shear connectors like shear keys are basically to transfer the shear loads from one concrete to the other. (Refer Slide Time: 10:32)

16 I mean the old concrete to new or basically concrete stitching; shear connectors and starter bars from rock. If you want raise a foundation from a rock is something called rock anchoring that is passive rock anchoring, we can support a; support to take a dowels from a rock, directly we can take a foundation instead of excavating the rock and rebar theory basically goes with; with splice and without splice. With splice is basically when a rebar; when the new rebars inserted in parallel to the existing rebar, that we call it as splice, modes of failure that is load transfer to cast in rebars via the concrete bond between them that is strut and tie model. The new rebar will; the load will be transfer from new rebar to old rebar, the existing rebar through this strut and tie principal that, here the modes of failure will be steel failure, bond failure that is steal will cut off, bond will fail. (Refer Slide Time: 11:14)

17 And splitting because of closed spacing, I mean splitting because of edge and spalling because of closed spacing. These are all the 4 failures observed in this theory and there is other theory as I said rebar without splice, where in no rebar in the parent material to splice with. So, here the modes of failure will be steel failure, bond failure, splitting, spalling and concrete shear, concrete cone also will try to come out, when there is no reinforcement in the parent material that is PCC. (Refer Slide Time: 11:38) When you are inserting rebar in a PCC, concrete shear is also expected. So, these 2 approaches will take us to a design and again for rebarring also, we have separate software for doing this, say this is typical software for extending a slab and this is a software for; this is a system for

18 extending a beam from a column that is simply support a structure and other is cantilever structure. So, here lots of bending; bending diagrams is also analysed in the software. (Refer Slide Time: 12:07) And shear, tension also analysed and that will be given as a report and then we can submit a design proposal for that. Some of the application for post installation of rebars are; diaphragm wall fixing, slab connections or extension of slabs. (Refer Slide Time: 12:16) Misplaced bars, vertical or horizontal connections like extending your column or beam. (Refer Slide Time: 12:21)

19 A wall strengthening as I said, here new rebars will be fixed and the connecting these rebars by using shear connectors that is concrete stitching. (Refer Slide Time: 12:32) And a new slab connection, extension of slabs, some joint strengthening and cantilever balconies, most of the residential application, they will be interested in balcony fixings, so that also we support them. (Refer Slide Time: 12:40)

20 And slab widening in bridge applications, some structural up gradations, slab strengthening and sidewalk way upgrade. (Refer Slide Time: 12:47) And this is a shear connectors where in the rebar will be bent as U, so that the proper load transfer will be ensured, this is what I am saying, this is U. (Refer Slide Time: 13:01)

21 What you are saying is a bridge deck over concrete over lay, where in the thickness of the pathway is increased by using the shear connectors, these are all shear connectors and these are all main rebars and these are all shear connectors. These shear connectors are inserted by using our chemical. (Refer Slide Time: 13:18) The depth will be decided by our technical team and there are certain rebars from rock as I said, if we need to do raise a foundation from a rock, so we can insert rock; starter bars from rock and then you can cast a rebar, cast a footing. So, this is basically to avoid earths up thrust pressure, so that the pressure is measured and accordingly depth has been calculated. So, that the complete pressure has been arrested by using this rebars. This is how we fix it as such.

22 (Refer Slide Time: 13:48) And one of the important support that we do is; we do site pull out testing, we do not charge anything for the site pull out testing and these all the testing system. (Refer Slide Time: 13:59) This is a complete set up, where in you have a load cell to pull the rebar out and you have a pump to run the fluid; to run the pressure and we have a gauge to measure the pressure how much it withstood and at last about the installation system that is what; all about post installed rebar connections. (Refer Slide Time: 14:23)

23 And at last installation systems, where this installation can be very much useful is to where in your welded support is been avoided, where a project site is avoiding welded support. (Refer Slide Time: 14:34) There we have this kind of application where in can take a support from ISBN channel system and also from the concrete. We have separate BOQ, BOM for everything, these are beam clamps to take a support from ISBN web and a pipe rings to run a pipes on top of a; from a ceiling and accessories like pushbutton, anchors and all which will transfer the loads and connections, this connectors just to ensure the angle connectors connecting between these channels and the horizontal and vertical channels and modular channels. (Refer Slide Time: 15:12)

24 These are the channels; these all the main members that will take the complete loads. Last but not the least, the HILTI technical support, where we can support contractor is; selection of anchors we have separate team for selecting these anchors based on the system what we discussed just a while back and design of anchor arrangement for insert plate fixing etc, by using the software. (Refer Slide Time: 15:46) And we have this fastening technology manual and a technical literature documents are required approvals for anchors will be given by us and depth calculation for post installed rebar connection by using the (15:42) coarse and the testing of rebars or anchors at site, that what we discussed. So, why HILTI because you get a superior added value through a reliable partnership.

25 (Refer Slide Time: 15:54) And creating enthusiastic customer everywhere, everything. Now, we will go to the second half of the session that is, I can show you some samples of anchoring system what we have discussed quite a while back. (Refer Slide Time: 16:08) This is the anchoring system; we have complete range of anchor fasteners. (Refer Slide Time: 16:21)

26 This is the mechanical anchor fastener which works on a combination of friction and keying principal. This is the nut; this will be inside the concrete and this will be exposed to; it will be open to the atmosphere and upon tightening it, the bottom portion will try to expand and this sleeve will act as a friction media, and this is how the which stands for the load over here. And upon expansion, this red colour sleeve; plastic sleeve will break, so which will indicate the anchor completely expanded, so we will have to stop accordingly and then this red colour head will be shearing off, so as to ensure the proper torque is ensured in this anchor. This anchor is one of the heavy duty anchor in our portfolio and we use this anchor for power plant, boilers nuclear fixings, nuclear plant applications and all. (Refer Slide Time: 17:24)

27 These as approval for a seismic zone, tensile zone and cycling loading, dynamic approvals and all other approvals we have. This is one of the heavy duty anchor for us, this you called it as HSL3. One of the other mechanical anchor which is very simple, which is medium duty anchor, this does not have any complication as that anchor has like expansion system. This is a sleeve and this is the nut, making a hole, concrete will be going inside. (Refer Slide Time: 18:11) Upon tightening, this head will try to come out, this head will try to come out and this sleeve will expand and form a friction media and that is how this anchor works basically. These are all mechanical expansion anchors and this is light duty or medium duty anchor. This anchor is applicable for something like an insert plate fixings, pipe rack fixings and all and the other

28 anchor in form of plastic anchors are; this is the plastic sleeve anchor, where in this red colour sleeve combined with the screw. Red colour sleeve combined with the sleeve will form as an anchor and you can see here the expansion fins and all, so upon tightening it, this spring try to expand and form a friction bond and this is how this anchor works. This anchor is basically for light duty application like door frame fixing and TV board fixing, any sort of fixing in gypsum board and all, for that application we can use this anchor. (Refer Slide Time: 18:58) And one of the other plastic sleeve anchor; one of the other plastic sleeve anchor is HKD. This is basically it is a kind of butterfly kind of anchor actually HLD; this is HLD anchor and this is the; we have to fold this and insert into a hole and upon tightening here, automatically it expands inside the gypsum partition. This anchor is will be very much good for a cavity kind of base material like gypsum partition and hollow blocks. (Refer Slide Time: 19:28)

29 And this is simple a sleeve anchor where in any external screws can be used for making it expand. This basically used for an electrical plumbing application, wiring application and all. (Refer Slide Time: 19:43) And next comes the chemical anchor where in the sleeve, this capsule and this bolt will be the forming as the chemical media, where in first making a hole, insert the chemical and then drive this anchor; drive this bolt by using a drilling machine. So, by driving this, the chemical particle inside the capsule will get mixed with this threads and then form a proper bonding system, where in chemical bonding is ensure and then load can be transferred after this chemical is getting set. (Refer Slide Time: 20:35)

30 And this is one of the system of; one of the very older system of chemical grouting and there is one more chemical grouting system, where in base material is hollow. This is the base material and this is the anchor which is getting fixed. What it will do? There is a sleeve inside the thing, after expanding, after inserting chemical gets expanded and this will form as a key, to avoid anchor to come out of the base material. This works on again keying principal. This is mainly for the masonry fixing, brick wall, to take support from brick walls and all. (Refer Slide Time: 21:06) And at last, here comes the rebarring system, where in rebar as I explained you post installation of rebars that is taking a dowels from an existing column or any concrete. Say, let us assume this is the concrete and the we make a hole and inject the chemical, later on we insert the rebar, that is

31 how the bonding system happens. The same chemical injection bonding principle only, again here there are 3 sorts of failure as I explained in my presentation. One is steel failure that is steel is getting cut and other is concrete cone failure that is the major chunk of concrete is coming out and the last is the bond failure, where in the bond alone comes out with the anchor. So, these 3 failures will be analysed and will be design accordingly. So, now I am going to explain you about the anchor, how anchor; chemical anchor, mechanical anchor works basically. (Refer Slide Time: 21:57) This is the base material and making a hole and inserting an anchor, so you will have; as I said you will have a sleeve inside anchor and you have a nut here, upon tightening, this head will try to come out, while coming out, the sleeve will expand and form a chemical; proper friction and this friction is responsible for the tension force applied over here and the next is; this is mechanical anchors. (Refer Slide Time: 22:33)

32 And the next is chemical anchors, where in a making a hole, filling the chemical and then inserting the bolt and there is a bond between chemical and the base material and also chemical and the rod. So, that bond strength will decide the pull out capacity of this anchor. So, that is how this chemical anchor works. (Refer Slide Time: 22:59) And the next is post installation of rebars; post installed rebars. Ideally, when you have a column and if you want to; this is the column available and if you want to take a beam outside, you have a 4 bars to be taken out. So, what we do is, normally, it will be; drilling will be done and the chemical injection will be done and then dowel bars will be taken out. So, from this dowel bars main reinforcement can be tied in, that is how the things happen.

33 (Refer Slide Time: 23:52) So, here what we do is, we analyse this modes of failure that is pull out force and all and next I was explaining about the software also; Profis software. This software basically we have profis for anchors and rebars. For profis anchors, for anchor it is called as profis anchors and for rebar, it is called as profis rebar. What is the difference between the anchors and rebar is basically, if you want to connect a concrete or any RCC to steel, we can use profis anchor And if you want to connect RCC to RCC, we can use profis rebar. That is what the basic difference between anchoring and rebarring. Anchoring is all about connecting steel member to a concrete and a rebarring is all about connecting RCC member to RCC. So, here the concept of doubling will be coming and here the concept of insert plate fixing will be coming. For both the connections, we support moment, tension and shear. (Refer Slide Time: 25:23)

34 Same here; moment, tension and shear. So, all these force will be analysed based on the given force, we decide this dimension that is how both the thing works actually and the next I was discussing about installation system. Basically, this works on modular supports that what we have MQ channel. That channels what we have shown here is basically a square channel, c kind of channel where you can take the support from C channel and you can run a pipe ring or you can suspend a pipe ring. This C channel can be supported from a concrete, this is how this normally our installation system works. Apart from that, we can also go ahead with welded support, where in some site will not support welded support. So, basically for where you avoid welding, where in this case, we can use this installation systems and this installation systems can used in HVAC and the pipe electrical MEE and lot many factories like for truss fixing, for truss bottom fixing and all, for that kind of things, we can use this modular supports. And this is what wanted to convey to you and with this, I would like to conclude the seminar and I would like to thank you for the opportunity given for me for show casting our company and our products and services. I am sure this will help you out in your academic career. Thank you. I like to thank Mr. Vinoth Kumar, for the nice explanation about the HILTI products available. We know that HILTI is a world leader in terms of anchors.

35 Professor - student conversation starts Couple of questions; what are the different materials used in the anchor systems like what is the type of plastic and what is the type of chemical use, can you tell us something? Yes, in case of a mechanical anchor like we do, we have this galvanized steel and we have this high corrosive resistance, all these material are MS steel only; MS steel and stainless steel. And all these MS steel will be coated with a galvanised for 0.5 microns to avoid corrosion effect and also we have separate stainless anchor to avoid complete corrosion for the facade applications and all. This is same applicable for all the mechanical anchors and for plastic sleeve anchor, the sleeve it is the combination of sleeve and the screw. The screw is basically made of carbon steel only, it is a mild steel and which is again coated with galvanised coated and the plastic sleeve is made of polyamide plastic which is flexible and this is not brittle because the plastic sleeve should expand, it should not break that is how, so these are all polyamide plastic and for chemical, we have 3 different; we have 2 different thing; one is powdered chemical is basically urethane methacrylate that is a chemical name of the capsule. And all these injection chemical and all will be falling under 2 categories; one is hybrid mortar and epoxy. Hybrid mortars are epoxy are cementitious grout basically, which is non shrink grout that is use for machine foundation and rock anchoring and all. This is as good as a concrete with the higher grade of concrete that is what the chemical is What would be the expected life of these different systems that you have? All our anchors are basically based on European standard. We have separate standard for estimating the lifetime of these anchors and as per the standard it is estimated to be around 30 years of lifetime. So, the anchor when it is passing through 80 years standard, it should with stand 30 years of lifetime, so all of our anchors are rated for those lifetimes. And do these anchors differs from one geographic location to the other because there will be climatic changes so, for India would you have specific anchors that are tailor made for Indian conditions. Yes, but not completely mechanical anchors and all does not depend on the

36 temperature or external atmosphere. Where in chemical anchor, it varies with the setting time, so for coldest countries and all, we need the anchor should know which should not set quickly. Whereas hot country like India and all, it should have a higher setting time because it needs a lot of temperature for making the chemical to gelled up. So, that is how the resin and bond mixture will be varying. Otherwise, chemical changes will not be there, country to country but the proportionate mixture will change from country to county. But we have these anchors specifically made for Indian condition. Sir, what are the application of this cartridge system of chemical anchors and capsule system of chemical anchors? Cartridge system is basically it is an injection kind of chemical, where in both the thing varies with the case to case. For example, when you are installing an anchor on several heights, where in the cartridge, you can expect the manpower to inject the chemical and then insert the rebar. So, there cartridge directly goes inside and then tighten it, then anchor it, that is it. Where in, other applications like doweling or rebarring; this concept of rebarring, where RCC to RCC connection has been there. So, there we will have to go for injection system, where in chemical is being injected and the rebar will be inserted. So, ideally both the thing will have a similar bond strength, only thing is cartridge will have no setting time, which means once it is install, you can start loading, whereas sorry capsule system. Cartridge system will have some setting time which means after installing after some half an hour only we can load it, so that also; loading thing also; when you want to load immediately, you can use capsule or you have some time one or 2 days time after installation you can go for injection. So, both the thing remains the same, I mean varies with the application that is how it is, okay. Professor - student conversation ends. So, I would like to thank you; thank one and all for listening this presentation and I am sure this will be benefiting you for your thing and on behalf of the company; I would like to thank

37 Professor Gettu for giving us opportunity for show casting our products and services. Thanks a lot again.