The slab on grade worksheet assumes a structurally unreinforced slab, aci360type b, reinforced only for shrinkage and temperature. This provides 105 percent of the concrete needed for the slab. Find the following parameters for design moments in step 2 per unit width step 4 note. This introduction of internal stresses is called prestressing and is usually accomplished through the use of tendons that are tensioned or pulled tight prior to being anchored to the concrete.
The infills keep the weight of the floor to a minimum and are then covered with insitu concrete to form the ribs and the floor slab. It serves as a walking surface but may also serve as a load bearing member, as in slab homes. Tips for pouring a concrete slab most concrete cracks can be minimized if the base is well prepared reinforce slabs with weldedwire fabric during layout, i cut the fabric about 6 in. This is the prestressed concrete a fundamental approach 5th edition solution manual by edward g. The minimum spacing of reinforcing bars should preferably be 6 in.
Slab design reading assignment chapter 9 of text and, chapter of aci31802 introduction aci318 code provides two design procedures for slab systems. Sections dealing with slabs, hollowcore and both prestressed and non prestressed beams have been examined to include recent revisions in a23. The study provides a recommendation with regard to how the virginia department of. Consequently, the dead load weight of the structure is decreased which results in reduced consumption of materials. Asce, secb course content slab on grades construction. This compression is produced by the tensioning of highstrength tendons located within or adjacent to the concrete volume, and is done to improve the performance. In second figure there are beams on all four sides with a intermediate beam. This design example was not intended to follow the design and detailing practices of any. Prestressed concrete is structural concrete in which internal stresses have been introduced to reduce potential tensile stresses in the concrete resulting from loads.
Offering an essential background for a thorough understanding of building code requirements and design procedures for slabs, reinforced concrete slabs, second edition provides a full treatment of todays approaches to reinforced concrete slab analysis and design. In any span, the max cable sag, zd depends on the concrete cover requirements and the tendon dimensions. Design of slab for flexure 067 m unit width of slab. Therefore, polished concrete with the addition of hardeners improves the cement mpa by 3 4 time times to 75 100 mpa. Design of prestressed concrete flat slabs mafiadoc. Nawy prestressed concrete solution manual pdf solution manual prestressed concrete nawy scribd. This document is intended for the use of individuals. According to builders plaque, this structure was built by cecil county in 1931. A process of preparing concrete slabs and beams for extra strength by pouring concrete over tightly drawn steel cables, steel rods. Precast concrete beams and precast slabs reinforced concrete or prestressed with a composite insitu topping or precast concrete walls with precast concrete slab system figure 3. Fy 20 average % breakdown of overall project costs for. This example will use the standard deck slab design as explained in the design guide. The idea of prestressed concrete has been around since the latter decades of the 19th century, but its use was limited by the quality of the materials at the time.
Unit weight, wc 150 pcf top slab reinforcing yield, fy 60000 psi subgrade modulus, k 200 pci concentrated load, p 0. Prestressed concrete bridge an overview sciencedirect. Pci manual for the design of hollow core slabs second edition by donald r. Precast prestressed concrete institute pci certified plant insures a quality product manufactured under strict regulations product overview hollowcore is an extruded, prestressed concrete slab with continuous voids to reduce weight and cost. The result is a much harder floor surface than standard concrete and a more decorative finish. This design should always be used unless approval to use a thinner deck is obtained from the state bridge engineer. Use a 2 x 4 in a sawing motion to level and remove excess concrete. Longitudinal steel should be detailed in a 2bar alternating pattern, with one of the bars continuous through the slab. Now if length to width ratio is 2 or greater, slab is one way even though supports are provided on all sides.
Prestressed slabs ducon concrete domesticore concrete. Hollowcore is an extruded, prestressed concrete slab with continuous voids to reduce weight and cost. Prestressed concrete is used in a wide range of building and civil structures where its improved concrete performance will allow for longer spans, reduced structural thickness and materials savings to be realised compared to reinforced concrete. The designer shall insure that the width of the pier cap or the seat of the abutment is sufficient for locating the anchor bolts. Floor slabs can range from a simple residential basement slab to a heavyduty industrial floor.
The construction and design of concrete slabs on grade. Aasho girders type ii, iii, and iv 5000psi 10x10, 12x12, 14x14. How to calculate concrete needed to pour a slab hunker. Download prestessed concrete by n krishna raju this book is popular among engineering teachers, students, and those who are practicing structural engineering. Use hand tools for cutting and bending reinforcement steel bars. Hollowcore is very economical and provides great design flexibility. In this model, the cracked concrete is regarded as cracks with concrete between cracks. In this case the structural action of the slab is essentially one way. Concrete slab, a very common and important structural element, are constructed to provide flat, useful surfaces.
Prestressed concrete prestressed concrete, invented by eugene frevssinet in 1928 is a method for overcoming concrete s natural weakness in tension. Start pulling and pushing the concrete around until you fill it to the top of the forms. How to attach new concrete to old concrete with pins hunker. Concrete 1 concrete a composite material that consists essentially of a binding medium, such as a mixture of portland cement and water, within which are embedded particlesorfragmentsofaggregate,usuallyacombination of. The precast prestressed concrete voided slab structure is a popular bridge design because of its rapid construction and cost. This bridge type often rates insufficient according to the. Posttensioned concrete is used for castinplace concrete and for bridges, large girders, floor slabs, shells, roofs, and pavements. A large subset of the dutch bridge stock consists of reinforced concrete slab bridges. This, in turn, makes it simpler to calculate the number of yards youll need for your concrete order. A slab strip of unit width is analysed using simple beam theory. As a guideline aggregate has an mpa of approximately 180.
As well as the prestressed wire reinforcement the half slabs have steel mesh embedded in the lower part to further increase the element strength. Forensic investigation of two voided slab bridges in the virginia department of transportations richmond district june 2017. Behavior and design of spread prestressed concrete slab. Design step 5 design of superstructure prestressed. Foreword this report is intended to serve as a manual of good practice for the design of prestressed concrete flat slabs in addition to the recommended procedures, other methods are described for the sake of completeness and to compare different methods of design. Over time this expansion and contraction, especially if they occur at different rates due to the sections of concrete being exposed to different temperatures, will work the sections apart, and the crack will widen. Units are supplied with prestressing strands complying with bs 5896. You will need extra concrete to allow for spillage, waste or any unforeseen events. Pdf seismic design criteria for slabcolumn connections. For slabs with light loads, as those for homes, include wire mesh midway up the thickness of the slab to reduce cracking. The adopted structural model is the aforementioned one employed by sapountzakis and katsikadelis 5. Rapid construction conserves energy versatility of design precast prestressed concrete. Among bridges, the pamban road bridge at rameshwaram, tamilnadu, remains a classic example of the use of prestressed concrete girders definitions the terms commonly used in prestressed concrete are explained. The concrete and clay infill blocks can be laid in two layers.
Jul 31, 2014 first, the polyethylene film acts as a slipsheet between the underside of the concrete and the subbase. It also has chapters on materials for prestressed concrete. The design procedure includes determining slab thickness based. I n this paper the analysis of prestressed concrete slab andbeam structures is presented.
In the present paper, the ultimate load of the reinforced con crete slabs 16 is determined using the finite element method and mathematical programming. Ask the concrete truck driver to mix the concrete between a 5 and 6 inch slump. That is, the concentrated post or wheel load is assumed to be well away from a free slab edge or corner. Once the concrete has hardened to the required strength, the steel tendons are inserted and stretched against the ends of the unit and anchored off externally, placing the concrete into compression. The slab on grade and on piles is not a good solution either as it anchors the slab on grade while the soil may want to swell. Cpci design manual canadian precast prestressed concrete. In this case the soil pushes up on the slab and the piles hold it down at the connections between the pile and the slab. Introduction concrete slabs on grade are a very common type of concrete construction. Comprehensive, uptodate coverage of reinforced concrete slabsfrom leading authorities in the field.
Prestressed concrete members are able to bear reversal of stresses, impact, vibration and shock due to the absence of cracks. A primary reason for using continuity with precast, prestressed girders is the elimination of the maintenance costs associated with. This help file describes input and analysis features of slab bridge designer 2. The earliest prestressed concrete poles were designed in 1933 by freyssinet, a french engineer. In maine we install a lot of slabsongrade for houses and garages. Hurst the purpose of this book is to explain the fundamental principles of design for prestressed concrete structures, and it is intended for both students and practising engineers. Prestressed concrete prestressed concrete concrete. Because of the brittle nature of shear failures, conservative design is necessary.
The behaviour of the concrete between cracks is simulated by the conventional theory of plasticity. Bridge piers bridges castinplace into falsework continuous beams with composite slab easy to use. This report is intended to serve as a manual of good practice for the design of prestressed concrete flat slabs in addition to the recommended procedures, other methods are described for the sake of completeness and to compare different methods of design. Prestressed concrete a fundamental approach 5th ed nawy. Slab beam bridges are commonly used in texas for short spans in low clearance areas where precast prestressed concrete slab beams are placed in a sidebyside configuration. The construction and design of concrete slabs on grade d. Further, when combined with timely surface curing, a polyethylene vapor barrier under the slab is an asset, retaining moisture in the concrete to improve hydration during setting. Concrete slab resting on grade containing steel reinforcement which consists of either a welded wire fabric or deformed reinforcing steel bars. When the concrete reaches a specified strength, the strands are released from the abutments. Typical uses for reinforced concrete are street and highway paving, sidewalks, foundation walls and slabs and almost any other solid concrete form where most of the pressure will be compression. Keep pouring the concrete until you have enough on the ground to work with.
Proof load testing of reinforced concrete slab bridges in the. Cosfb is a deepembedded concrete dowel connecting insitu concrete with the steel section, ensuring a composite action without an increase in the floor. Concrete is by far the most versatile and most widely used construction material worldwide. The prestressed floor slabs are used where the loosely reinforced slabs are close to their limits, with regards to load and span width. Prepared for the pci hollow core slab producers committee john e.
Longer span length increases untroubled floor space and parking facilities. The design procedure includes determini ng slab thickness based. Prestressed concrete is a form of concrete used in construction. Advantages and disadvantages of prestressed concrete.
It is the intent of this chapter to establish the practices and specific requirements of the structure and bridge division for the design and detailing of prestressed and posttensioned concrete members. The depth of a concrete slab floor is very small compared to its span. Design step 5 design of superstructure prestressed concrete bridge design example task order dtfh6102t63032 547 design step 5. Followings are the advantages of prestressed concrete. It is primarily used as a floor and roof deck system. Under a prescriptive specification, the means are verified. In the past decades, prestressed concrete poles have become famous and have replaced the traditional poles made of timber, steel or reinforced concrete. The first prestressed concrete bridge was built in 1948 under the assam rail link project. Oneway slabs normally design as a beam with cables running in the direction of the span at uniform centres. Apr 18, 2018 next, multiply the surface area by the thickness of the slab. Performance specifications for durable concrete current practice and limitations each of these requirements is actually a means to an end, and durable concrete is likely to be but not always the result of following these means. Seismic design criteria for slabcolumn connections article pdf available in aci structural journal 1044. When joining new concrete work to old concrete work, the joint will always develop a crack and will be a point of expansion and contraction.
Tm 580912 concrete floor slabs on grade subjected to heavy. Practically, dead loads are neutral in a prestressed concrete beam. The result is a lightly reinforced slab designed to offset the effects of temperature and shrinkage of the concrete. Sep 03, 2011 reinforced concrete sk 33 section through slab showing stress due to moment. This will is the volume of cubic yards of concrete needed for the concrete slab. It is substantially prestressed during production, in a manner that strengthens it against tensile forces which will exist when in service 35 this compression is produced by the tensioning of highstrength tendons located within or adjacent to the concrete and is done to improve the performance of the concrete. This book starts off with an introduction that explains the basics about the topic. Calculate for overage multiply the volume of cubic yards determined in step 4 by 1. A new example on partial prestressing has been added, and all examples dealing with shear and torsion have been evaluated in the context of the new a23. Structural concrete structures reinforced concrete construction. Concrete slab how to install a slab from start to finish. The width, depending on the production procedure, is up to 3 m, thickness of the concrete board is 80 120 mm.
A flat piece of concrete, put on the walls or columns of a structure. Pdf prestessed concrete by n krishna raju book free. It took until the 1920s and 30s for its materials development to progress to a level where prestressed concrete could be used with confidence. When zd is determined, the prestressing force required to balance an. As the concrete sets, it bonds to the tensioned steel.
The invention relates to a prestressed slab element 10, in particular a concrete slab element, manufactured according to the insitu concrete method or prefabricated in a concrete precasting plant which in top view of its surface 11 comprises at least one hollow element region 20 with hollow elements 21 contained therein and at least one support region 30 for supporting or. Forensic investigation of two voided slab bridges in the. Reinforced concrete slab is the most popular floor slab system used in residential building construction in sri lanka. Reinforced concrete solid slabs can be either oneway spanning or two way. A new example on partial prestressing has been added, and all examples dealing with shear and torsion have been. A slab foundation is usually less expensive to install than a full concrete wall foundation with a concrete floor.
Slabs may be supported on two sides only or have beams on all four sides. The analysis of slab and beam floor with prestressed wire. Because airentrained concrete is more workable than standard concrete and because the entrained. It doesnt have a foundation or any concrete walls under it or around it.
Quality controlled products prestressed slabs are ce approved and manufactured in a controlled environment. A numerical model for material nonlinear analysis of concrete slabs supported on soil is described in this work. This mix is easy enough to move around, but not too wet to weaken the concrete. Comprehensive design example for prestressed concrete. This reduces the chance of exposing the wire at the edges and allows. It is a horizontal structural component, with top and bottom surfaces parallel or near so. Convert the thickness into feet so that youll get the volume product in cubic feet. Determination of the reinforced concrete slabs ultimate. A floor is usually made of half slabs with hollow blocks concrete or clay or polystyrene infills. An interior load condition is assumed for flexural analysis. Difference between reinforced concrete and prestressed. Pdf analysis of prestressed concrete slab and beam.
Slabs cast with an opening are reinforced by steel bars and slabs with a sawn up opening are strengthened with carbon fibre reinforced polymers cfrp. Pdf prestressed and posttensioned concrete yatniel. Application of lb ratio in first figure slab is supported on two opposite sides only. Concrete floor slabs on grade are subjected to a variety of loads and loading conditions. In most cases, youll need to provide the amount of. Thinner slabs, that are important for high rise building as with the same amount of cost, it can construct more slabs than traditional thicker slabs. With minimal mesh or fibre reinforcement and pumped concrete, the completed floor can quickly follow. Concrete floor slabs on grade are subjected to a varie ty of loads and loading conditions. Placing the concrete concrete must be placed within half an hour of mixing. The designer should avoid whenever possible the mixing of 30 and 40 wide slab sections. This compresses the concrete, arches the members, and creates a builtin resistance to service loads. The type of reinforced or prestressed concrete bridge deck depends mainly on the functional requirements, the structural form, and the main span length of the construction.
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