Why are there different ffactors for the same horizontal insulation. The thickness of the plain concrete slab is determined by the properties of the concrete used in the slab. That is, the walls, roofs, floors, windows, doors for the building. Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. The construction and design of concrete slabs on grade. Slabongrade and underground floors defined with ffactors. F f numbers can be taken for slabs on grade as well as elevated slabs. Unheated slab on grade floors are all other floors in contact with ground. Where heated slabs are below grade, belowgrade walls shall comply with the f factor requirements for heated slabs. Thats why designing an industrial floor to withstand anticipated loading conditions is critical to satisfactory performance. 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. Ive just input floor areas through the wizard and selected the type of foundation insulation i have from the. F factor the perimeter heat loss factor for slab on grade floors, expressed in btuhft f. Difference between structural concrete slab and plain.
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. The configuration of insulation and the ffactors for the baseline building are shown in bookref idbaselinebuildingffactorcriteriaforslabongradefloors. This grade slab acts as the foundation for a home or building, and provides a stable base for w. A concrete slab does not have a crawlspace underneath it. 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. 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. For concrete slabs, most of the heat loss occurs around the edges of the slab.
Slab on grade definition what does slab on grade mean in. 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. Slab on grade or grade slab types construction procedure. The concrete slab is generally positioned on a layer of sand in order to improve drainage conditions and to act as a cushion. Point loads applied to slab on grade structural engineering.
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. 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. Heated slab on grade floors include all floors that are heated directly in order to provide heating to the space. 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 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. From this table and accompanying text i know that means simply to define a 6in. It defines an effective r value that is based on the loss per foot of perimeter. The slab on grade worksheet assumes a structurally unreinforced slab, aci360. Supported grade slab or slab on grade foundation is chosen when the traditional footings are already framed on site to raise the columns. 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. It is important to note that fl numbers generally only apply to slabs that are placed on grade. Very good reference for designing concrete slabs on grade.
Slabongrade heat loss estimation hvacr engineering. Tm 580912 concrete floor slabs on grade subjected to. Stepbystep procedures, sample solutions, and commentary ringo, boyd c. For grade 60 rebar as f l w2 fs where f the subgrade friction factor 1. The construction and design of concrete slabs on grade d. What is grade slab and what is the difference between. That is, the concentrated post or wheel load is assumed to be well away from a free slab edge or corner. 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.
Ffactors scientifically proven approach allows you to achieve results without hunger, deprivation, or denial. Learn more about construction procedure with video explanation. What would you recommend to warm up the floor, esp, something that doesnt send. Ufactorb skylightb u factor glazed fenestrationb,e shgc ceiling rvalue wood frame wall rvalue. For myself i would recommend pl200 squirt between the footing and the styrofoam, or a permanently fle. F numbers provide architects and contractors a method of determining the flatness and levelness of a concrete floor slab. Assembly u factor, c factor or f factorbased method. Client has a family room that was slab on grade with nothing between the concrete and dirt. 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. 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.
Matching these slabongrade construction layersinsulation will mean youre achieving the target ffactor for your perimeter zones. The c factor for the belowgrade exterior walls of the building envelope, as required in accordance with table c402. Elevated concrete slabs are problematic since those. Mar, 2019 other basic assumptions used in the flexural analysis of the slab on grade worksheet are as follows. Asce, secb course content slab on grades construction. Type b, reinforced only for shrinkage and temperature. 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.
A new method for designing floor slabs on grade due to the. Title 24 require the underground wall constructions and slabsongrade or underground floors not to exceed certain maximum values of cfactor and f factor. Ive just input floor areas through the wizard and selected the type of foundation insulation i have from the dropdown lists. Reading the fine print i realized that the army manual is using a safety factor of 5. 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. Many of the simplifications and enhancements developed for comcheck have provided the technical basis for code changes submitted to the international code council icc. 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. The engineering community understands shrinkage cracking for the most part, but the gen. I dont consider it to be a fully insulated slab since the horizontal insulation only extends 24 inwards, and a6. The architect intends to use 24 of r10 insulation in the vertical plane which should be an f factor of 0. Keeping the construction industry informed for over 70 years.
F factor for slabs with both vertical and horizontal insulation. In contrast to the ufactor for floors, the ffactor for slabongrade floors is expressed per linear foot of building perimeter. Title 24 require the underground wall constructions and slabsongrade or underground floors not to exceed certain maximum values of cfactor and ffactor. 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. Modulus of subgrade reaction which one should be used. Slab thickness design for industrial concrete floors on grade and concrete floors on ground by pca and they have helped somewhat. Ground heat transfer calculations using c and f factor constructions. I could not find a better reference that covered the subject matter like this book does. The ffactor diet book discover the secret to permanent weight.
Floor slabs can range from a simple residential basement slab to a heavyduty industrial floor. Flooring grade insulation sheets laid prior to pouring. 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. Concrete slab on grade thickness analysis for slab. If the slab is too thick, it costs more than it should. 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. Im currently working on a warehouse in which i have to specify the slab on grade thickness and reinforcing. Your 12 inches of r5 horizontal insulation has an ffactor of 0. Ground heat transfer calculations using c and f factor.
One of two classes for floors in contact with ground. Download rhode island department of state nellie m. Limiting factors on the width of the slab edge insulation in this situation are determined by attachment of floor finishes and width of foundation. Note that this is an effective r value based on the slab perimeter, not the slab area. 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. Modulus of subgrade reaction k is used to represent the. Nov 17, 2009 secondary reinforcement is not considered in determining the load carrying capacity of the slab. As crosssectional area in square inches of steel per lineal foot of slab width f friction factor. Stepbystep procedures, sample solutions, and commentary.
If the slab is too thin, it may break under load and fail before its time. After this publication, it was subsequently adopted by the uniform building. I am working on a very large church complex 45,000 sqft with about 80 spaces. 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. Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabs onground.
Clarifying slabongrade insulation in ashrae standard 90. 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. Theoretical concepts, practi cal applications, basis of. Design of slabs on grade aci 360r92 by american concrete institute from aci manual of concrete practice, 1999 4. Reinforced concrete slab design and detailing guide is456. 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. Concrete slab on grade analysis the engineering community. This group of objects describes the physical properties and configuration for the building envelope and interior elements. Heavy loads in building s such as warehouses include moving load s, stationary live loads, and wall loads. 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. 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. 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. Another special slab on grade situation, is the presence of water under the slab.
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. While videother floor slabs have performed satis factorily, floorthe economy of the designs is unknown. Heated slabongrade floors include all floors that are heated directly in order to provide heating to the space. 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. The method used in the heat loss calculator is based on the ashrae fundamentals chapter on heat loss. Designing floor slabs on grade civil engineering community. Guide for concrete floor and slab construction aci 302. The ufactor for concrete slabs concrete construction. Slab thickness design for industrial concrete floors on. The design procedure set forth in that publication had at that time been in use by the author for about 15 years. This will constitute the need for the engineer to design a pressure slab, to withstand any uplift that.
Introduction concrete slabs on grade are a very common type of concrete construction. As such it cannot be compared to r values that are defined in the usual way based on area. 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. T h e r e are five commonly used p ro c e d u r es for designing industrial floor slabs. So under structural plans in the project browser, lets go to level one. What id like to do in the video is to create basically a slab on grade. 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. How to use the new ground heat transfer slab model integration in energyplus 8. There are two different types supported slab on grade and monolithic slab on grade. Slab with reinforcement on both faces with diagram of stress and figure c12. 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. Perimeter is the part of the foundation or slab nearest to the surface of the ground outside. Floor slabs on grade structural engineering general. 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.
Shallow foundations include spread footing foundations, mat slab foundations, slab on grade foundations, pad foundations, rubble trench foundations and earthbag foundations. 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. I changed the last column from a u value to an effective r value. Heat loss calculations and principles ced engineering. 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. Flat concrete structure built on top of the soil at ground level and does not require support from underground footers or foundation walls. The losses are from the edges of the slab and insulation on these edges will significantly reduce the heat losses. Note that cfactor doesnt include soil or air films. The second set of values for unheated and heated slabs should be for vertical insulation, not horizontal.
Best fix for cold slabongrade family room floor fine. 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. Perimeter is the part of the foundation or slab nearest to the surface of the ground. Slab on grade ffactor for a large building leeduser. Tm 580912 concrete floor slabs on grade subjected to heavy. The concrete is then placed into the mold, leaving no space between the ground and the structure. An interior load condition is assumed for flexural analysis. Department of energy under contract deac0576rl01830 rescheck tm technical support document march 2019 rw schultz r bartlett. Combined slabs figure 11 d b b b t f t f t f t f t effective width of t beams slab segments. 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.
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