Cantilever slab reinforcement

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Cantilever Slab Design

Students Click Here. Related Projects. Home Forums Structural Engineers Activities Structural engineering general discussion Forum Cantilever slab - how far back into the anchor span to extend rebar.

Given: Cantilever reinforced concrete balcony slab of typical condo apartment. Say balcony cantilever spans 1. The anchor slab spans 6 m east-west and is supported by reinforced concrete shear walls.

Reinforcement Detailing of Reinforced Concrete Slabs

Assume there is a reinforced concrete beam at the supported end of the cantilever. Assume live load of cantilever is 4. Should it be 1. I suppose a finite element analysis might give and answer, but without doing that, is there an answer?

This question pertains to a typical detail I am reviewing. The top bars should extend at least the development length of the bar beyond the support. Our old BS Code used to say 2 x cantilever length. Eurocode i think says 1. I stick with 2!Sign Up to The Constructor to ask questions, answer questions, write articles, and connect with other people.

VIP members get additional benefits. By registering, you agree to the Terms of Service and Privacy Policy. Lost your password? Please enter your email address. You will receive a link and will create a new password via email. Sorry, you do not have permission to ask a question, You must login to ask question. Become VIP Member. Reinforcement detailing of a slab is done based on its support conditions.

Slab may be supported on walls or beams or columns. Slab supported directly by columns are called flat slab. Slab supported on two sides and bending takes place predominantly in one direction only is called One Way Slab. On the other hand, when slab is supported on all four sides and bending take place in two directions are said to be Two Way Slab.

In one way slab main reinforcement is parallel to shorter direction and the reinforcement parallel to longer direction is called distribution steel. In two way slab main reinforcement is provided along both direction. Slabs could be simply supported, continuous or cantilever. In two way slab the corners may be held down by restraints or may be allowed to lift up. Additional torsion reinforcement is required at corners when it is restrained against uplifting as shown in Fig.

Thickness of the slab is decided based on span to depth ratio specified in IS Minimum reinforcement is 0. The diameter of bar generally used in slabs are: 6 mm, 8 mm, 10 mm, 12mm and 16mm. Maximum spacing of main bar is restricted to 3 times effective depth or mm whichever is less.

For distribution bars the maximum spacing is specified as 5 times the effective depth or mm whichever is less. Minimum clear cover to reinforcements in slab depends on the durability criteria and this is specified in IS Generally 15mm to 20mm cover is provided for the main reinforcements. Alternate main bars can be cranked near support or could be bent at 0 at the edge and then extended at the top inside the slab as shown in Fig. Curtailment and cranking of bars and is shown in Fig.

Torsion reinforcement shall be provided at any corner where the slab is simply supported on both edges meeting at that corner and is prevented from lifting unless the consequences of cracking are negligible. It shall consist of top and bottom reinforcement, each with layer of bars placed parallel to the sides of the slab and extending from the edges a minimum distance of one fifth of the shorter span.Slab and girder bridges are used when the economical span limit of solid slab bridges is exceeded.

For simply supported spans, this limit is generally found to be nearly 10 metres and for continuous or balanced cantilever type structures, this limit is 20 to 25 metres. The deck slab of a slab and girder bridge spans transversely over the girders which run longitudinally spanning between abutment or pier supports.

The spacing of the girders depends on the number of girders to be provided in the deck which again is related to the cost of materials, shuttering, staging etc. Closer beam spacing means lesser thickness of deck slab and consequently savings in concrete and steel in deck slab but since the number of beams is more in that case, this increases the quantity of concrete, shuttering and reinforcement for girders and for longer spans where bearings are required, the number of bearings.

Therefore, the most economical arrangement of bridge deck varies from place to place depending on the cost of materials, shuttering, staging etc. It has been observed that three beams deck is generally found economical than two, four or five beams deck having a carriageway for two lanes.

For proper functioning, at least two cross-beams at two ends and one at the centre are essential. A spacing of about 4. Sometimes in long bridges, it is necessary to keep provision for carrying pipes gas, oil or watercables etc. If no gap between the deck slab and the cross beams is maintained, the slab panel becomes a two-way slab continuous in both the direction. In designing the girders, the dead load of deck slab, cross-beams, wearing course, wheel guard, railing, etc.

The distribution of the live loads, on the other hand, is not a simple one. It depends on many factors such as the span-width ratio, properties of the bridge deck and the position of the live loads on the girders. Therefore, the sharing or distribution of live loads on the girders and consequently the live load moment varies from girder and as such this aspect requires to be considered carefully.

Design a slab and girder bridge with 7. The deck may consist of 3 girders spaced at 2, 45 m. The bridge deck will have no footpaths. Since the deck slab is monolithic with the cross-beams, it will be designed as a two-way slab supported on longitudinal girders and cross-beams with continuity on all sides. The method outlined by M. Pigeaud deals with the effect of concentrated load on slabs spanning in two directions or on slab spanning in one direction where the width-span ratio exceeds 3.

A synopsis of the method is given here. It has been advocated that due to continuity, the mid-span moments may be reduced by 20 percent and the same moment may be taken as the support negative moment also. In the example, Class R tracked vehicle will govern the design. Taking mid span and support moment as 80 percent of the above as stated before and allowing for 25 percent. The effect of Class R tracked or wheel load will not be maximum since it is to be placed 1.

Class A wheel load as shown in Fig.While casting slab of Ground floor slab, We missed a portion of the slab as you can see the 'missing part' in the attached picture, There is no steel going out except for stairs reinforcement from from GF to FF. Can anyone help me how to sort this out? How to cast this portion?

cantilever slab reinforcement

Chipping up to cm and connecting with the HB reinforcement will sort it out? When I poured new slabs to exsisting slabs, we would drill into exsiting slab 12" to 16" and epoxy rebar into the holes. We then tied the new slabs reinforcment to these bars. The epoxy we used had a compressive strength of 12, psi, stronger than the concrete itself. This might be an option you can use. I think the forum deserves to hear that lame excuse explanation.

Happened in Qatar! And forgot from the start! I mean there was no form workno reinforcement! Why it happened? Lack of proper supervision! I came at the time of concrete, just checked lap lengths, heights, covers etc! Now can we get back to the topic! A solution came in my mind! Let me share it with you! S we try Light weight high grade concrete? I have a suspicion that you should remove and replace the incorrectly cast concrete that was designed to be monolithic.

I have a suspicion that is your suspicion as well. Field fixes of this magnitude drive us crazy.

Cantilever Slab Design

To answer it you need to know what the engineer intended, which way it was supposed to span, what reinforcing was supposed to be there. Only the original engineer knows what elements have the capacity to support this. What makes you thing that an engineer was ever involved here? Sounds like a typic engineering design from here in AZ. Constantly have to field fix engineering problems.

Thank goodness for field experienced personal fixing desk experienced PEs. You beat me to it. I was thinking of the same thing but was not going to post it because it wasn't really that funny a joke in this context. Best you talk with the engineering consultancy company that produced the original design and get them to sign-off on a suitable fix that wont endanger the public.To browse Academia.

Skip to main content. Log In Sign Up. Download Free PDF. Cantilever Slab Design. Ramjan Shehzaad. Under the loads, it bends and the directions of its bending depend on its shape and support conditions. A beam bends only in one direction, i. Therefore, slabs may have different names depending upon its bending, support conditions and shapes. For example, a slab may be called a One-way simply supported rectangular slab, b Two-way simply supported or restrained rectangular slab, c Cantilever rectangular slab, d Fixed or simply supported circular slab, etc.

One-way slab means it bends only in one direction and, therefore, reinforcement for bending i. A slab supported on all sides bends in all the directions so the main reinforcements provided shall be such that they may be effective in all directions. For ease of analysis and convenience of reinforcement detailing, the bending moments in a slab are calculated in two principal directions only and, therefore, such a slab is called a two-way slab.

A slab is designed as a beam of unit width in the direction of bending. In this unit, only the most commonly used rectangular slabs, with uniformly distributed load is described.

For solid slabs, the values given below : Overall or or Depth of more less Slab mm K 1. Temperature and shrinkage reinforcement is provided along the direction perpendicular to the span.

This is illustrated through the following example. Example 4. Load data and design parameters are given below : Load Data Lime terrace topping of mm thickness is provided over the slab. Figure 4. The detailing of the reinforcement has been shown in Figure 4. Only temperature and shrinkage reinforcement is provided along the long span. The top of slab is covered with mm lime terrace. Imposed Design a roof slab simply supported on all its four edges of effective spans load may be taken as 1.

Substituting all the values in the above equation. Distribution Steel 0. Reinforcement detailing has been shown in Figure 4. The other specifications for design and detailing for the slab are the same as those for simply supported beams Section 3.

Describe the maximum horizontal distance between parallel main bars and that between parallel temperature and shrinkage bars. Being monolithic with the beams, the corners are prevented from lifting and, therefore, torsional reinforcements are provided to resist the resultant torsional moments. Main reinforcements are provided along both the principal axes to resist corresponding moments Mx and My, respectively.

Detailing of reinforcement is done in the following manner : a A slab is divided in edge strips and a middle strip in both directions as shown in Figure 4. Table 4. Interior Panels : Negative moment at 0. One Short Edge Discontinuous : Negative moment at 0.Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website.

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cantilever slab reinforcement

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cantilever slab reinforcement

Minimum reinforcement in either direction shall be 0. Main reinforcement which is based on the maximum bending moment shall not be less than 0. The pitch of the main bars shall not exceed the following:. Distribution bars are running at right angles to the main reinforcement and the pitch shall not exceed.

The diameter of main bars may be from 8 mm to 14 mm. The maximum bending moment per meter width of slab. Suppose a slab is supported at the ends and also at intermediate points on beams, the maximum sagging and hogging moments to which the slab is subjected to due to uniformly distributed load, can be computed as follows:.

Your responses were successfully submitted. Thank you! Kindly check your email and confirm the same to receive your free ebook. This table is not related to loads. BS provides a table for span to depth ratio which is based one total unfactored dead and imposed load.

Design of Cantilever Slab Spreadsheet

I have a project to design a classroom block. Kindly assist on how to go about it. This method is obsolete. I dont think designers practically use Working stress method any more!!! Sign Up Sign Up to The Constructor to ask questions, answer questions, write articles, and connect with other people.

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