Floor slabs can range from a simple residential basement slab to a heavyduty industrial floor. What is grade slab and what is the difference between. Concrete slab on grade thickness analysis for slab subjected to single wheel loading from vehicles with pneumatic tires per pca slab thickness design for industrial concrete floors on grade figure 3, page 5. Reading the fine print i realized that the army manual is using a safety factor of 5. This type of foundation differs from house foundations with basements in this respect. Aci 302 guild for concrete floor and slab construction and aci 360 design of slab on grade provides the design methodology for this type of slab. As crosssectional area in square inches of steel per lineal foot of slab width f friction factor. From this table and accompanying text i know that means simply to define a 6in. It addresses the planning, design, and detailing of slabs. F numbers provide architects and contractors a method of determining the flatness and levelness of a concrete floor slab.
The engineering community understands shrinkage cracking for the most part, but the gen. Type b, reinforced only for shrinkage and temperature. While videother floor slabs have performed satis factorily, floorthe economy of the designs is unknown. Ufactorb skylightb u factor glazed fenestrationb,e shgc ceiling rvalue wood frame wall rvalue.
Very good reference for designing concrete slabs on grade. Many of the simplifications and enhancements developed for comcheck have provided the technical basis for code changes submitted to the international code council icc. Stresses in floor slabs on grade resulting from vehicular loads are a function of floor slab thickness, vehicle weight and weight distribution, vehicle wheel or track configuration. Mar, 2019 other basic assumptions used in the flexural analysis of the slab on grade worksheet are as follows. Background information on design theories is followed by discussion. The losses are from the edges of the slab and insulation on these edges will significantly reduce the heat losses. Clarifying slabongrade insulation in ashrae standard 90. Online concrete slab on grade analysis calculator for slab subjected to interior concentrated post or wheel loading assuming slab is reinforced for shrinkage and temperature only. From the below fig, it is clear that the wall stands on a footing and the grade slab is resting on a layer of gravel and moisture barrier. Slab thickness design for industrial concrete floors on grade and concrete floors on ground by pca and they have helped somewhat.
F factor for slabs with both vertical and horizontal insulation. F factor the perimeter heat loss factor for slab on grade floors, expressed in btuhft f. Download rhode island department of state nellie m. The concrete slab is generally positioned on a layer of sand in order to improve drainage conditions and to act as a cushion. Theoretical concepts, practi cal applications, basis of. Tm 580912 concrete floor slabs on grade subjected to.
A new method for designing floor slabs on grade due to the. F friction factor w weight of concrete slab psf f s allowable steel stress, use 23 to 34 of the steel yield point psi 2 assumes that the slab will move shrink an equal distance from each end towards the center l slab length between free ends, in feet. An interior load condition is assumed for flexural analysis. For grade 60 rebar as f l w2 fs where f the subgrade friction factor 1. I am working on a very large church complex 45,000 sqft with about 80 spaces.
Keeping the construction industry informed for over 70 years. Floor flatness tends to be very important for spaces where equipment must be set perfectly level spaces like tv studios, warehouses that use airpallet jacks, and some research laboratories require floors that are flatter than a typical concrete slab. Flooring grade insulation sheets laid prior to pouring. Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. So you could try using an edge r of zero and a floor u based on 6inch thick concrete and see what result you get. Advantages and disadvantages of each of these slab designs are provided, including the ability of some slab designs to minimize cracking and curling more than others.
Ive just input floor areas through the wizard and selected the type of foundation insulation i have from the. How to use the new ground heat transfer slab model integration in energyplus 8. After this publication, it was subsequently adopted by the uniform building. The major structural components of a slabongrade foundation are the floor slab itself and either grade beams or foundation walls with footings at the perimeter of the slab see figures 42 and 43. Title 24 require the underground wall constructions and slabsongrade or underground floors not to exceed certain maximum values of cfactor and ffactor. The configuration of insulation and the ffactors for the baseline building are shown in bookref idbaselinebuildingffactorcriteriaforslabongradefloors. This group of objects describes the physical properties and configuration for the building envelope and interior elements. Introduction concrete slabs on grade are a very common type of concrete construction. The structural design of a concrete floor slab on grade is primarily controlled by the stresses caused by moving live loads and in some cases the stationary loads.
Client has a family room that was slab on grade with nothing between the concrete and dirt. The u factor is a measure of heat transmission, in this case through a concrete slab, either from the ground into the enclosed space or vice versa. The second set of values for unheated and heated slabs should be for vertical insulation, not horizontal. A concrete slab does not have a crawlspace underneath it. What would you recommend to warm up the floor, esp, something that doesnt send. Comparing the values found in this table with the values found in table 11 in designing floor slabs on grade there is a huge disparity. This video shows you how to calculate the amount of concrete required to pour a concrete slab on ground with splayed edge beam and a rebated. Modulus of subgrade reaction k is used to represent the. Concrete slab on grade analysis calculator for post or wheel. Note that cfactor doesnt include soil or air films. The ufactor for concrete slabs concrete construction. The design procedure set forth in that publication had at that time been in use by the author for about 15 years.
Matching these slabongrade construction layersinsulation will mean youre achieving the target ffactor for your perimeter zones. Perimeter is the part of the foundation or slab nearest to the surface of the ground outside. Title 24 require the underground wall constructions and slabsongrade or underground floors not to exceed certain maximum values of cfactor and f factor. They had a berber carpet over cheap pad, but they like to walk around the house barefoot and the floor feels cold to their feet, esp. The construction and design of concrete slabs on grade. Slab thickness design for industrial concrete floors on. If the slab is too thin, it may break under load and fail before its time.
Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabs onground. Jan 30, 20 designing floor slabs on grade by boyd c ringo and robert b anderson this comprehensive book will help you select the most costeffective. That is, the concentrated post or wheel load is assumed to be well away from a free slab edge or corner. Slabongrade heat loss estimation hvacr engineering. Difference between structural concrete slab and plain. Thats why designing an industrial floor to withstand anticipated loading conditions is critical to satisfactory performance. That is, the walls, roofs, floors, windows, doors for the building.
If the slab is too thick, it costs more than it should. I asked this a couple of days ago on the hap users forum and no one has responded so hopefully ill have better luck here. Supported grade slab or slab on grade foundation is chosen when the traditional footings are already framed on site to raise the columns. A new method for designing floor slabs on grade due to the difficulty of applying simplified design methods, amongst them being the portland cement association pca and wire reinforcement institute wri methods. I changed the last column from a u value to an effective r value. Learn more about construction procedure with video explanation.
Limiting factors on the width of the slab edge insulation in this situation are determined by attachment of floor finishes and width of foundation. Ground heat transfer calculations using c and f factor constructions. It is expressed in btus per hour, per square foot, per degree fahrenheit, referring to the temperature difference between the slab s upper and lower surfaces. Slab on grade definition what does slab on grade mean in. Be f o r e an ove r all productivity efficiency is obtained, the estimator must first arri v e at estimates of six important production elements that will affect the efficiency of the crews the six classifications of production elements a r e.
Slab viewed as a plate on a liquid foundation with full subgrade contact subgrade modeled as a series of independent springs also known as winkler foundation. The ffactor diet book discover the secret to permanent weight. It defines an effective r value that is based on the loss per foot of perimeter. Ffactors scientifically proven approach allows you to achieve results without hunger, deprivation, or denial. So under structural plans in the project browser, lets go to level one. In contrast to the ufactor for floors, the ffactor for slabongrade floors is expressed per linear foot of building perimeter. Tm 580912 concrete floor slabs on grade subjected to heavy. Best fix for cold slabongrade family room floor fine. Perimeter is the part of the foundation or slab nearest to the surface of the ground. I could not find a better reference that covered the subject matter like this book does. Where heated slabs are below grade, belowgrade walls shall comply with the f factor requirements for heated slabs. Designing floor slabs on grade civil engineering community. Asce, secb course content slab on grades construction. Slab on grade or floating slab foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground.
Stresses in floor slabs on grade resulting from vehicular loads a re a function of floor slab thickness, vehicle weight and weight distribution, vehicle wheel or track configuration. Nov 17, 2009 secondary reinforcement is not considered in determining the load carrying capacity of the slab. I dont consider it to be a fully insulated slab since the horizontal insulation only extends 24 inwards, and a6. Unheated slab on grade floors are all other floors in contact with ground. Slab on grade ffactor for a large building leeduser. The architect intends to use 24 of r10 insulation in the vertical plane which should be an f factor of 0.
For myself i would recommend pl200 squirt between the footing and the styrofoam, or a permanently fle. Stepbystep procedures, sample solutions, and commentary. Im currently working on a warehouse in which i have to specify the slab on grade thickness and reinforcing. The slab on grade worksheet assumes a structurally unreinforced slab, aci360. The method used in the heat loss calculator is based on the ashrae fundamentals chapter on heat loss.
Ive just input floor areas through the wizard and selected the type of foundation insulation i have from the dropdown lists. Heavy loads in building s such as warehouses include moving load s, stationary live loads, and wall loads. For concrete slabs, most of the heat loss occurs around the edges of the slab. A 2 2area 2 a c 2 2 posttensioned concrete design table 11 list of symbols used in the aci 31808 code cp area enclosed by the outside perimeter of the section, in a g gross area of concrete, in a 2 l total area of longitudinal reinforcement to resist torsion, in a o area enclosed by the shear flow path, sqin a oh area enclosed by the centerline of the outermost closed. Slabs which are directly laid on the earth to support walls and other structural elements are called as slab on grade or grade slabs. They are calculated using the standards set forth in astm e1155, which is the standard test method for determining f f floor flatness and f l floor levelness numbers. The concrete is then placed into the mold, leaving no space between the ground and the structure. What id like to do in the video is to create basically a slab on grade. Heated slabongrade floors include all floors that are heated directly in order to provide heating to the space. Your 12 inches of r5 horizontal insulation has an ffactor of 0.
The construction and design of concrete slabs on grade d. Guide for concrete floor and slab construction aci 302. F f numbers can be taken for slabs on grade as well as elevated slabs. Slab thickness is a major factor in the cost of a concrete floor, so theres often pressure, which can become intense, to make the slab as thin as possible. T h e r e are five commonly used p ro c e d u r es for designing industrial floor slabs. Slab with reinforcement on both faces with diagram of stress and figure c12. Following are the rcc slab design and detailing guidelines. Shallow foundations include spread footing foundations, mat slab foundations, slab on grade foundations, pad foundations, rubble trench foundations and earthbag foundations. A shallow foundation is a type of building foundation that transfers building loads to the earth very near to the surface, rather than to a subsurface layer or a range of depths as does a deep foundation.
Stepbystep procedures, sample solutions, and commentary ringo, boyd c. There are two different types supported slab on grade and monolithic slab on grade. Concrete slab on grade analysis the engineering community. It is important to note that fl numbers generally only apply to slabs that are placed on grade. Floors ctr wall ld thickness calculate the required thickness of a concrete slab on grade floor to support a wall load at the centerinterior or on a joint. Combined slabs figure 11 d b b b t f t f t f t f t effective width of t beams slab segments. Floor slabs on grade structural engineering general. Another special slab on grade situation, is the presence of water under the slab. Calculate the maximum wall load that the maximum wall load that a concrete slab on grade floor can support at a joint or at the centerinterior of the slab. Slabongrade and underground floors defined with ffactors. Ground heat transfer calculations using c and f factor.
The perimeter heat loss factor for slab on grade floors formula in book heated slab slab on grade construction in which the heating elements, hydronic tubing, or hot air distribution system is in contact with, or placed within or under, the slab. The thickness of the plain concrete slab is determined by the properties of the concrete used in the slab. Reinforced concrete slab design and detailing guidelines for depth of slab, loads on slab, reinforcement guide for oneway and twoway slabs as per is 456. Why are there different ffactors for the same horizontal insulation. Reinforced concrete slab design and detailing guide is456. The pca and wri slab on grade design methods for industrial floors led to a design for concrete fatigue, even though 2. Elevated concrete slabs are problematic since those. This will constitute the need for the engineer to design a pressure slab, to withstand any uplift that.
Point loads applied to slab on grade structural engineering. The c factor for the belowgrade exterior walls of the building envelope, as required in accordance with table c402. Assembly u factor, c factor or f factorbased method. Guide to design of slabs onground reported by aci committee 360 aci 360r10 this guide presents information on the design of slabs onground, primarily industrial floors. Note that this is an effective r value based on the slab perimeter, not the slab area. Duncan is right, especially when you factor in the flake factor of building inspectors and their own take on what they think the code requires. Flat concrete structure built on top of the soil at ground level and does not require support from underground footers or foundation walls. The steady state heat transfer through the floor is calculated as, q area u eff t air,out t air,in t air,out t air,in p exp ffactor where, q is the steady state heat transfer through the floor in watt. Concrete slab on grade thickness analysis for slab. Since 1946, bni building news has been the nations most comprehensive source of construction books, building codes, legal forms, cost estimating tools and other reference materials for the building trades. If this is the case, then the design of the slab on grade is an engineered structural slab, that will span any settlement that may occur within the sub grade. Department of energy under contract deac0576rl01830 rescheck tm technical support document march 2019 rw schultz r bartlett. Modulus of subgrade reaction which one should be used.
Slab on grade or grade slab types construction procedure. As such it cannot be compared to r values that are defined in the usual way based on area. Department of energy doe and pacific northwest national laboratory pnnl intend to refine and enhance the comcheck materials over time in response to needs expressed by users. One of two classes for floors in contact with ground. Design of slabs on grade aci 360r92 by american concrete institute from aci manual of concrete practice, 1999 4.
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