The objective of this video is to give a quick introduction to deflection in concrete. Allowable deflection limits refer to table 1 of the appendix. Pdf shortterm deflections in twoway rc slabs using deflection. Designing deflections in concrete slabs and beams london. In this paper, an experimental investigation was carried out to study the flexural behaviour of prestressed concrete beams with eccentricity. These showed that the concrete tensile strength, extent of cracking and elastic modulus are the most significant parameters. Slabs are usually used in floor and roof construction. Evaluation of deflections of prestressed concrete beams. The anchorages to posttensioned members must distribute a large load to the concrete, and must resist bursting forces as a result.
Adequate control of deflections can usually be achieved for in situ reinforced concrete beams and slabs by compliance with specified spandepth ratios. Deflection of concrete slabs concrete slab deflection. Deflection curves for experimental and theoretical values for. Reinforced concrete slabs on columns were initially developed in the u. Deflections in concrete slabs and beams technical report pdf. The methodology for calculating deflections of reinforced. If these options are implemented properly, the result could be more cost effective compared to elements that either show deflections. It is based on the recommendations of aci318 as expounded in adapt technical note tn292.
For the specified concrete material of 65 mpa cube. Greater accuracy may be achieved by considering small increments of span and computing relevant curvatures and thus overall deflections. The strands or tendons are fed through the ducts stage 1 then tensioned stage 2 and then anchored to the concrete stage 3. How to calculate the max deflection of the cantilever portion. Factors affecting deflections of reinforced concrete beams and slabs.
Deflections in slabs and beams the concrete society. This paper is concerned with calculating the maximum deflection of steel concrete composite beams with partial shear interaction. Twoway concrete slab with beams spanning between supports. Causes of excessive deflections in reinforced concrete slabs. Effect of shrinkage restraint on deflections of reinforced self. Eigelaar thesis presented in partial fulfilment of the requirements for the degree of masters of science of engineering at.
This paper proposes a method for calculating longterm deflections of reinforced concrete beams by considering creep and shrinkage effects separately. To predict the deflection of frp prestressed concrete psc beams, the american concrete institute aci utilizes a semiempirical equation of effective moment of inertia ie, originally developed. Checking slab deflection is included in the beam design section of bs 8110 part 01. Mineral products association mpa is the trade association for aggregates, asphalt, cement, concrete, dimension stone, lime, mortar and silica sand industries. Gives guidance on procedures for design of concrete structures at the serviceability limit state, concentrating on deflection. Various measures to control deflections of rcc beams and slabs are explained in this article.
Deflections of reinforced concrete beams and columns. The deflection prediction methods and the spaneffective depth verification procedures are. Such stiffened slabs are often called waffle slabs because of the geometric analogy with a waffle. A computer program is written by the author and coded by fortran 77 to carry out the numerical calculations. Hopkins and park 27 tested a 14scale, ninepanel reinforced concrete slabbeam floor system. In this method, the concrete has already set but has ducts cast into it. Deflections due to creep are generally much greater than deflections resulting from all other timedependent effects combined and are of primary interest 1. Chao and naaman proposed the simplified equation to predict deflection for prestresssed concrete members based on finite element analysis 2.
There is a lack of longterm tests on beams and slabs under. Punching shear strength of reinforced concrete slabs without. The image part with relationship id rid102 was not found in the file. Amin and ramez proposed prediction model of longterm deflection for prestressed concrete beams 4. In most cases design of reinforced concrete beams and slabs is governed by deflection rather than strength.
Deflections in concrete beams reinforced concrete design. Pdf traditional reinforced concrete slabs and beams are widely used for building. Permissible deflection in beams and oneway slabs permissible deflections in a structural system are governed primarily by the amount that can be sus. Unless computations show that deflections will be small table 9. Guide to the design and construction of reinforced concrete. Design criteria for deflection capacity of conventionally. However, as flat slab structures become more slender, serviceability is increasingly governing their design. Deflections of reinforced concrete flat slabs citeseerx. Maximum deflections of reinforced concrete beams and slabs as per aci 318.
Pdf deflection prediction of reinforced concrete beams by. Pdf deflection of steelconcrete composite beams with. The allowable calculated deflection varies between l240 and. Types of slabs in reinforced concrete construction, slabs are used to provide flat, useful surfaces. This limit may be exceeded if camber is provided so that the total deflection minus the camber does not exceed the limitation. Note that it is not the summation of the initial and incremental deflections. N a ccr h b d nas concrete beam 26 jkm cracking of the concrete in tension.
Maximum ratios of computed deflection to span l for beams. Deflection of frp prestressed concrete beams request pdf. A reinforced concrete slab is a broad, flat plate, usually horizontal, with top and bottom surfaces parallel or nearly so. These factors are categorized into two group with parameter identified prior to construction and factors unidentified prior to construction. Pdf estimation of deflections in rc slabs is important in the limit state design. Founded in 1904 and headquartered in farmington hills, michigan, usa, the american concrete institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensusbased standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design. Ce 433, fall 2006 deflection of a reinforced concrete beam. Abhinav and valsson studied the behaviour of prestressed beams based on finite element analysis 3. Deflection of prestressed concrete beams externally strengthened using parafil ropes article pdf available in magazine of concrete research 551. Structural calculations for posttensioned beam and oneway slab construction.
It is necessary to take into account and evaluate different factors which influence deflections of reinforced concrete beams and slabs before starting design and construction. Check deflection of slabs for bs 8110 part 1 method of checking the deflection of the slabs are similar to the checks of beam deflection. This narrative outlines the procedure for deflection check in design of posttensioned floor systems. Pdf deflections of reinforced concrete beams and columns. In the 1950s, flat slabs without capitals started to become prevalent. Comparison of various methods for measuring deflection on slabs getec. May 31, 2018 according to eurocode you can calculate the deflection of structural members based on rigorous method or simplified method. Deflections interview questions for structural engineers part b. The steel will yield at a steel strain of fyes or a steel stress of fy. Effective moment of inertia and deflections of reinforced. How to reduce deflection of reinforced concrete beams and slabs.
Deflection of concrete floor systems for serviceability1 bijan o aalami2 deflection control is a central considerations in serviceability of floor systems. Aci 318 has the recommendations given in tables 2 and 3. The midspan deflection of a beam in such a frame is affected by the stiffness of the members framing into. Jan 15, 2017 how to control deflection of reinforced concrete beams and slabs. The paper presents an advanced methodology for calculating deflections of reinforced concrete beams with allowance for discrete cracking. First part of the video demonstrates the background of the deflection by illustrating a bending moment. Longterm deflections of reinforced concrete beams scholarship. Tn292 deflection of concrete floor systems for serviceability. The theoretical approach is based on the basic principles of nonlinear deformation model and also takes into account nonlinear concrete and reinforcement behaviour.
Pdf deflection of prestressed concrete beams externally. They are commonly used in the usa for the foundation of houses or any. Twoway concrete floor slab with beams design and detailing design the slab system shown in figure 1 for an intermediate floor where the story height 12 ft, column cross sectional dimensions 18 in. Rational model for calculating deflection of reinforced concrete beams and slabs.
Deflection of reinforcedconcrete beams and slabs civil. The simplified method for calculation of deflection is shown in the figure below. It is concluded that this method reflects the actual behavior of reinforced concrete slabs with respect to the estimated cracking and service load deflections. Mar 18, 2010 our aim is to enable all those involved in the design, use and performance of concrete and masonry to realise the potential of these materials. It then considers the more rigorous methods contained in the codes, which consider the. Under the guidance of various current design codes, this. Design of composite beams using precast concrete slabs. Structural calculations for posttensioned beam and oneway. Tr 58 deflections in concrete slabs and beams, concrete society.
Deflections in concrete slabs and beams, 2005, or how to design concrete structures using eurocode 2. Aug 27, 2015 guide to the design and construction of reinforced concrete flat slabs contents membersof the projectsteeringgroup list of tables vii iv list of figures v 1. Ce 433, fall 2006 deflection of a reinforced concrete beam overview the deflection of reinforced concrete beams is complicated by several factors. Controlleddeflection design method for reinforced concrete.
Deflections of reinforced concrete flat slabs estee m. How to control deflection of reinforced concrete beams and slabs. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Pdf deformation of multistorey flat slabs, a site investigation. Maximum deflections of reinforced concrete beams and slabs. Deflections of beams and slender columns computed using this program are compared with the. This publication is concerned with situations where prediction of deflections is. Feb 19, 2015 the objective of this video is to give a quick introduction to deflection in concrete. The report is divided into three parts design, worked examples and spreadsheets, and background. Pdf the paper statistically investigates accuracy of predictions of shortterm deflections.
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