Raft foundation analysis and design example pdf documentation

This code, code of practice for foundations 2017 the 2017 code is issued upon completion. Current design practice is based on conventional group pile or block failure theory, that ignore the bearing contribution from the raft. A guide for practicing engineers seismic design of reinforced concrete mat foundations has advanced significantly in the last twenty years. Instructional materials complementing fema p751, design examples foundation design 3. Design of raft foundations methods and calculations. The best is to define supports is to add elastic soil in the definition of the panel raft foundation thickness. Hello there, i am designing a raft foundation usign autodesk robot 2014 and i am facing some problems first question.

Raft foundation analysis and design example free download as pdf file. The raft foundation is a very commonly used type of foundation system. It explores the assumptions that are made in the analysis of soil structure interaction, together with the associated calculation methods. Appendix c, foundation capacities tables, provides design capacities for foundation uplift and withdrawal, based on the foundation type chosen wood, concrete masonry or castinplace. Halfspace analysis for threedimensional systems, in addition to the substructure techniques, is available in the extended program version. Definition of raft foundation along with working principle, when to choose raft, types of raft foundation, materials of raft foundation, raft construction steps etc are discussed below. Design of raft footings the structural design of raft foundations can be carried out by two methods. Determine the stress distribution beneath the foundation 5. These approaches make their own assumptions and deal with ideal raft, symmetrical in shape and loading.

Dec 23, 20 this book covers complete design of raft foundations including piled rafts, starting from their need, type, all the approaches suggested so far in published literature, effect of assumptions made and values of variables selected, on the design values of stresses, and brings out the limitations of these approaches using actually constructed rafts. This approach is generally referred to as the compensated foundation design and is extremely useful when structures are to be built on very soft clays. Transfer of seismic forces strength and stiffness shallow and deep foundations elastic and plastic analysis the subtitles are effectively a table of contents although the topics are not really treated in that. The use of a limited number of piles, strategically located, may improve.

The reactions from the loads imposed on the example building are calculated, the loads on the foundation elements. Raft foundations e optimized design of piled raft foundations has been actively investigated in recent years 1920 21 22, focusing on the mechanisms of different pile arrangements and. L1084 32 abingdon villas page 35 of 70 pringuerjames consulting engineers ltd. In order to reduce the costs and improve the overall performance of building systems, the static optimized design with variable rigidity of piled raft foundations has been widely used in recent years.

A raft foundation is a reinforced concrete slab under the whole of a building or extension, floating on the ground as a raft floats on water. To get a better idea about when to use raft foundation, it is important to understand how raft foundation works. A combination with the other fea programs is also possible. Instructional materials complementing fema p751, design examples. A method of analysis is presented for piled raft foundations where the piles exhibit non linear loaddeflection behaviour. Design of a raft foundation a pile foundation analysis and design using experimental. Mat footing furthermore, mat footings are helping to reduce the varying settlements caused by construction on nonhomogenous soils or uneven load distribution on the footing. Essential to the foundation engineers study is a rational method of design, whereby various foundation types are systematically.

A conventionally reinforced mat raft foundation is selected, proportioned and designed, such as to. The mathematical solution of the raft is based on the finite. Basic design criteria concentrically loaded d2 all sides c critical section for twoway shear b critical section for oneway shear a critical section for flexure outside face of concrete column or line midway between. Curve 3 represents the case in which piles are positioned in such a way to act as a settlement reducers. Analysis of the performance of a large ribbed mat foundation supporting building 333. The soil in this method is replaced by an infinite number of isolated springs. This type of foundation tends to be heavily overdesigned for three major reasons. Optimization technique has been applied for a raft foundation. The raft is analysed through the use of finite element methods, while the. Ppt design of mat foundations powerpoint presentation.

Between the geotechnical design parameters of bearing capacity and settlement, which are independent, if the design just satisfies bearing capacity, settlement will be over satisfied i. Instructional materials complementing fema 451, design examples foundation design 141 foundation design proportioning elements for. Mat or raft foundation is a large concrete slab supporting several columns in two or more rows. Strengthening of structure structual inspection structural detailing. The eccentricity of the load and the pressure distribution below the raft which is considered to be linearly varying are taken into account in this analysis. The calculations presented herein cover the principal steps in the design of the mat raft foundation as it would be carried out in a structural engineering consultants office. Raft foundation is one of the types of foundation that is composed of a thick mat or slab that supports the entire structures. Foundation analysis and desing foundation design 1. The document may be downloaded subject to terms and conditions stipulated in the website. The building is located in seismic zone iii on a site with medium soil. Compensated foundation the net pressure increase in the soil under a mat foundation can be reduced by increasing the depth d f of the mat.

It is used where the supporting soil has low bearing capacity. This type of foundation, which is sometimes referred to as a raft foundation, is a combined footing that may cover the. Elpla has models for analyzing single pile, pile groups, piled raft foundation. In this section, only the rigid method will be covered. Raft foundation design raft design software raft analysis. If there is a layer of compressible clayey soil extending to a great depth or if there is a compressible soil at lower depth, a greater compression is produced in the soil under the center of the footing causing a dishshaped ground surface as shown in. For a raft foundation walls and columns act as objects to transfer load from the above part of a building rather than supports. Residential footing design policy for all of its residential footing designs.

This book examines alternative design procedures for plain and piled raft foundations. Pdf analysis of piled raft foundations researchgate. The raft foundation is a kind of combined footing that may cover the entire area under the. Raft foundation design and analysis with a practical. Design of raft footings is detailed in the following steps. Design applications of raft foundations this book examines alternative design procedures for plain and piled raft foundations.

Small analysis of piled raft analysis of piled raft systems is an extension of the raft analysis above. In this particular post we are going to consider the analysis and design of the same foundation using manual calculations according to the principles of the eurocodes. The factored soil pressure under the raft is 80knm2 and a linearly varying soil pressure due to 0 2000 4000 6000 8000 0 12000 14000. Pro for analyzing mat foundations for different types of loads. Raft foundation when to use, types, construction civil. The design engineer must determine the appropriate. What are the difference between tender and contract documents. The duty of the foundation design specialist is to establish the most economical design that safely conforms to prescribed structural criteria and properly accounts for the intended function of the structure.

Comprehensive treatment of the subject makes the book helpful to the design engineers, engineering teachers, students and even those who are engaged in further research. Pdf optimization of raft foundation design researchgate. The program geo5 slab can be used for the design of mat foundations or slabs of any shape on elastic subsoil, using the finite element method. Once logged in, you will be able to download the document using the download button on the right. In raft foundation design, the stresses developed underneath the mat could be different from the calculated values due to following reasons. Under these situations, the addition of a limited number of piles may improve the ultimate load capacity, the settlement and differential settlement performance, and the required thickness of the raft. To demonstrate the analysis procedures, an example problem of a cprf is solved. A structural designer engaged in the design of raft foundations finds it hard to select. It is desired to design the raft slab shown below to support the column loads for a building as given below.

Raft foundation analysis and design example scribd. All columns are 230 x 450mm, the grade of concrete f ck is 30 nmm 2, and the yield strength of the reinforcement f yk is 500 nmm 2. The second phase of the research project is underway. In this research, the economic advantages of using raft foundations, pile group foundations and piled raft foundations are discussed based on the geotechnical design. The difference being that many of the repetitive numerical reports generated by the analysis and design program used adaptmat are. This type of foundation spreads the load of the building over a larger area than other foundations, lowering the pressure on the ground. Foundation analysis and design examples chapter 3 described the types of loads considered in this manual. The emphasis of the present document is the implementation of nonlinear analysis procedures used primarily for the estimation of the demand on a bridge structure, not the evaluation of its capacity for design purposes. Raft foundations are essentially large plan area foundations built either solidly or in cellular form. Elpla can analyze foundation of arbitrary shape with real subsoil model. Raft foundation design using csisafe the structural world. Raft foundation design and analysis with a practical approach.

Piled raft foundations provide an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. Module 5 lectures 17 to 19 mat foundations topics 17. Raft foundation analysis and design example foundation. The geotechnical design of foundations for taller wind turbines has also become complicated presenting unique challenges for each location. This type of foundation is used when there are larger column loads to support and when soil bearing capacity is too low. Shallow foundations geotechnical software geo5 fine. Sometimes area covered by raft may be greater than the contact area depending on the bearing capacity of the soil underneath. Force on a pile eq on unloaded pile pile supporting structure. Design of raft foundations methods and calculations according to is 2950. Design of raft foundation excel sheet raft foundation is a thick concrete slab reinforced with steel which covers the entire contact area of the structure like a thick floor. A linear elastic stiffness matrix will be generated for the halfspace processing, therefore a superpositioning is possible. The use of softwares to design mat foundation had been introduced to track the current era of computers. The program also calculates the settlement and rotation of the foundation and allows designing reinforcement for the foundation. They may be employed for lightly loaded structures on soft natural ground or on other ground where weak zones exist.

Raft foundation is generally used to support structures like residential or commercial buildings where soil condition is poor, storage tanks, silos, foundations for heavy industrial equipment etc. Whats the difference between defining the stiffness of the soil kz in the thickness of the plate or as a support. Instructional materials complementing fema 451, design examples foundation design 147 reinforced concrete footings. Raft foundation design for a typical 2 storey house example bs8110. Spreadsheets for the analysis of piled raft foundations scielo. Additional cost of analysis methods, which are, however, not exact. Iii to provide documentation leading to appropriate procedures for design. Chapter 6 describes the shallow foundation design process for bridge foundation support on spread footings. The software is specifically designed for civil and structural engineers. Once the values of these constants have been found, the displacement of any intermediate point can be calculated by eqn. British electricity international, in station planning and design third edition, 1991. Seismic design of reinforced concrete mat foundations. It enables verification of bearing capacity of a foundation on both, drained and undrained soil and rock subsoil.

The summation is to be done over all the storeys, including the foundation beam of raft. Raft foundation design and analysis with a practical approach gupta, s. The raft will be used for economical consideration. The analysis and design of piled raft foundations shall take into account the pile soilpile. Appendix b, foundation design load tables, provides design requirements for anchorage of the manufactured home to the foundation and recommended footing sizes. Raft foundations are suitable for medium rise story buildings ranges from four to twelve stories. Design of foundations universiti teknologi malaysia. A number of methods have been proposed based on primarily on two approaches of simplified and truly elastic foundations.

Staad pro retaining wall analysis and design cantilever type 2018 easy method duration. Chapters are written by leading consultants and contractors from around the world who draw on their extensive experience in the uk and overseas. Design example it is desired to design the raft slab shown below to support the column loads for a building as given below. For foundations of such high rise building, normally raft foundation, pile foundation or piled raft foundation are used. Combined footings and mats, manual of concrete practice. Code of practice for design and construction of raft foundations, part 1. A six storey building for a commercial complex has plan dimensions as shown in figure 1. This book covers complete design of raft foundations including piled rafts, starting from their need, type, all the approaches suggested so. Program geo5 slab is designated for analysis of foundation mats and slabs on elastic subsoil.

Concordia university, 20 piled raft foundation is a new concept, which has received increasing recognition in recent years. Solved examples are included for each of the methods recommended. Sachpazis date 230420 chkd by date appd by date raft foundation design bs8110. Available textbooks, handbooks, various publications and papers give widely different approaches for design of raft foundations. Mar 07, 2014 28 raft foundations design and analysis note. A structural designer engaged in the design of raft foundations finds it hard to select the method that can be carried out within the time and cost available for design and give adequate safety and economy. Poulos in situations where a raft foundation alone does not satisfy the design requirements, it may be possible to enhance the performance of the raft by the addition of piles. Code of practice for calculation of settlements of foundations part i. As analytical capabilities have improved, primarily in the form of finite element analysis, the mathematical modeling of.

An approximation for analysis of raft and piled raft foundations. In the design of foundations in piled rafts, a great number of unknown facts are. This appendix demonstrates how these loads are calculated using a sample building and foundation. Chapters 5 and 6, together with the detailed bridge foundation design examples presented in appendix b, provide the practical information necessary to complete shallow foundation design for a highway bridge. Design the structural component of the mat foundation using the stress distribution obtain from 4. This document provides answers to questions on the aspects one must consider when using staad. Raft is a powerful software that can be used for making analysis, design, estimation, costing of rcc raft foundation with adherence to is. The book gives many examples of project applications covering a wide range of structural forms and ground conditions. Technical report documentation page transportation. The piled raft foundation utilises the pile group for the control of settlement, with the piles providing most of the stiffness at the service loads while the raft elements provide the additional capacity at the ultimate load levels. Committee 336, suggested analysis and design procedures for combined footings and mats, aci struct j 1988, pp. Aug 12, 2017 design of raft foundation excel sheet raft foundation is a thick concrete slab reinforced with steel which covers the entire contact area of the structure like a thick floor.