Problems in foundation engineering are the selection of suitable beds and foundation for high rise building is one of the known problems in high rise building. In no of cases it has been discovered that the designing of building foundations goes beyond the limits of normative documents and their construction. As per requirement to ultimate strength bearing capacity especially for high rise building designs are extremely strict.
Beds and foundations are quite important phenomena in design and construction of high rise building foundation. There are currently recommended foundation types where piles, combined pile-raft foundations and mat foundations are considered.
Ground engineering known as geo-technical design procedures consists on several stages to gain the design of a foundation which is carried out from feasibility study to final geo-technical design followed by concept realisation and soil investigation.
Researches has been carried out in accordance to design of high rise building foundation and no of ideas has been brought forward in which anchored slab foundations, raft piled foundations, mat foundations and group of piles or piles can be used for high rise buildings.
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Typically for high rise building foundations normally piles or group of piles are used for less than thirty floors with the diameter of 0-8 meters having length of 1-40 meters in the case of using wall in the soil ground assuming a parameter structure wall with reinforcement concrete having thickness of 60-1.5 meter which includes basement walls.
While considering foundations for high rise building a major part is to aim the reduction of settlement in the new built structure to ensure the safety and sustainability with subject to long life of foundation. In most cases there can be possibilities that the soil type and ground conditions may lead to deep foundations with respect to transfer the high ultimate loads to the soil with the high bearing capacities.
In case of bearing capacity of foundation which depends upon soil type, in case of high rise building foundation piles or combined piled-raft foundations are used to accommodate the allowable bearing capacity with subject to soil type and site conditions.
In some cases ground water improvement is also necessary especially in urban areas to improve the volume of voids in the soil in order to built high rise building foundation to get the allowable bearing capacity and allowable foundation settlement to resist the failure of foundation.
The literature review shows that a very little research work has been carried out to understand the types of foundation with subject to settlement and bearing capacity of soils effect on high rise building foundations.
In view of foregoing ,by using the advance computer modelling techniques by considering case study, a no of numerical model based on standard finite-element method will be developed to investigate the behaviours of high rise building foundation by proposing a reliable foundation for high rise building with subject to settlement of foundation considering the simplified hand calculations comparing with the finite element which will be gained from computer modelling with accordance to load and other factors affecting on proposed foundation. Further in case study investigation will be carried out to examine sensitivity and limits of foundation settlements, factors affecting on settlement of foundation in accordance to load and displacement finally, a set of suggestions will be framed for future improvements of design criteria for foundations.
The selected topic of the project "modelling and design of high rise building foundation" is based on advanced computer based numerical modelling and a case study.
Aim and objective of the project:-
The selected project aims to understand the behaviour of foundations for high rise building
The factor of settlement with respect to load and how the displacement occurs.
How the ground improvements can take place.
Bearing capacity of soils in case study with respect to the foundation type.
Application of advanced computer based numerical modelling techniques will be utilised to compare the hand calculated results.
The comparison of experimental results (case study) versus numerical modelling will be carried out to analysis the degree of agreement of both results.
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The scope of this project is to study the behaviour of foundations which can be used for high rise building structures.
The effect of load and displacement will be carried out with subject to settlement, bearing capacity of soils and ground water improvement
The trend of modes of failure will be carried out on the performance of designed foundation
Based on investigation and previous carried out a conceptual model will be developed with the help of case study.
The potential risks of this research work are given below.
A very limited time to complete the project
The complexity of software and its usage.
The risk of self learning of computer modelling techniques within scheduled period of time.
The short of knowledge and intensive understanding of the topic.
The limitation of simulating and modelling the natural site condition and interaction of soil with the pile foundation subject to corrosion induced cracking.
The production of invalid results.
The following steps will be taken to mitigate or avoid the above noted risks
The appropriate work plan under the guidance of project supervisor will be revised.
The selection of appropriate and user friendly computer package will be discussed with the supervisor.
In view of complexity of usage of computer package and difficulty of self learning, an appropriate help of supervisor will be sought.
A confident user of software will be identified and an additional help will be requested.
In order to avoid the production of invalid results, close liaison and the scheduled meeting will be held with the project supervisor.
The stipulated completion period for this research project is three and half months. A number of tasks under various phases have been scheduled to accomplish the research project within fixed time scheduled.
(Task 1 & 2): A comprehensive literature review will be carried out. The gaps and possible direction for research project will be outlined. The capabilities and limitations of campus based available software will be explored. And the most appropriate software available at campus will be selected and learnt to accomplish the project work.
Deliverable: A report comprises the gaps and possible direction for the project will be prepared and submitted to the supervisor for correction and further guidance.
(Task 3): A numerical calculation will be carried out to determine the behaviour and mechanism of propagation of corrosion product. The rate of corrosion propagation subject to various environmental factors will be investigated and quantified.
Deliverable: A detail report of numerical calculation, tabular and graphical representation of results will be prepared and submitted to the supervisor for correction and further guidance.
(Task 4): The procedure of computer based modelling will be outlined and model development process based on advance computer application will be carried out. The behaviour of pile foundation under the composite influence of corrosion induced cracking and soil conditions will be modelled.
(Task 5 & 6): A parametric metric study will be undertaken to quantify the effects of various factors on propagation of cracks in concrete cover of pile foundation. An intensive analysis of data and post-processing and detailed examination will be carried out.
Deliverable: A detail report of results and analysis will be prepared and submitted to project supervisor for guidance.
(Task 7, 8 & 9); the comparison of final results and case study will be made. The compilation of analysis of results, summary of conclusions and recommendation for possible future research work will be carried out. A draft of dissertation report will be written. The same will be submitted to supervisor for review and necessary correction and modification.
Research Methodology and approach:-
The project is principally concerned with modelling and design of high rise building foundations with subject to uses of foundations for high rise. A case study will be carried out in terms of design and model which will be appropriate for high rise in literature review the types of foundations will be investigated with subject to high rise.
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By applying the previous techniques and formulae for the design of foundation the results will be recorded and a comparison will be carried out with the computer software package in case study.
The comparison will be carried out in terms of load versus deflection, settlement calculations by using previous methods and finite element with the choosed case study using computer modelling programme.
The exploratory and quantitative methodology for the behaviour analysis of high rise building foundation will be adopted .In view of which a comprehensive model will be adopted and explored the results will be extracted from computer modelling of the problems and will be compared with the results gathered from case study results .a range of results will be produced in terms of graphical and in tabular form. The results will be analysed and compared with the results obtained from case study. The behaviour of foundation for high rise used in case study will be explored in terms of numerical modelling based on finite element.
ANCHORED-SLAB FOUNDATIONS FOR HIGH-RISE BUILDINGS
Reference: Soil Mechanics and Foundation Engineering, Vol. 42, No. 4, 2005 pg; 127-130 E. A. Sorochan and D. S. Konyukhov.Scientific-Research Institute of Foundations and Underground. Structures and, Moscow State Civil-Engineering University.
According to Sorochan & Konyukhov; ''It is proposed to use foundations with anchors for the construction of high-rise buildings. Friction piles rigidly fixed to a monolithic reinforced-concrete slab are used as anchors. A 70-story 210-m-high building is analyzed for different types of foundations. Settlements and Tilts based on mathematical modelling are compared with reliable values established by the Construction Rules and Regulations''.
Design of piled raft foundation on soft ground
Reference: report from; Y.C.Tan director, Gue & partners Sdn Bhd, Kuala Lampur,Malaysia. & C.M.Chow Senior Geo-technical Engineer, Gue & Partners Sdn Bhd, Kuala Lampur,Malaysia.
According to Y.C.Tan & C.M.Chow; A design approach for piled-raft foundation system using settlement reducing piles on soft ground is presented. The design approach is divided in to two categories, i.e for low rise and medium high rise the piled raft system is generally based on the concept of settlement reducing piles to control local deformation where piles of short length are strategically located beneath concentrated loads. for medium rise buildings, piles of varying lengths with the longest piles in the middle and progressively shorter piles towards the edge are adopted to control differential settlement within allowable limits. Various design cases must be considered for the design of piled-raft using settlement reducing piles to ensure adequate provisions of pile and design of strip raft for low rise buildings while an interactive analysis to model pile -soil-structure is proposed to analyse medium-rise buildings.
BEDS AND FOUNDATIONS OF HIGH-RISE BUILDINGS.
Reference: Soil Mechanics and Foundation Engineering, Vol. 40, No. 5, 2003 pg; 173-175 by S. B. Ukhov, Scientific-Research Institute of Foundations and Underground Structures.
According to Ukhov; ''Bed and foundation problems occupy a special place in the design and construction of high-rise buildings. This results from the fact that the average pressures over the footprints of the buildings reach 0.5-0.8 MPa, and occasionally more. For the relatively deep bedrock in Moscow, these pressures are frequently transmitted onto soils of Quaternary deposits possessing elevated compressibility. At the same time, requirements for limiting deformations of the beds, especially for their non uniformity and tilting of the buildings remain extremely rigid.
The following are currently recommended as basic types of foundations for high-rise buildings: pile, combined piled-raft, and slab, including foundations with increased stiffness (box foundations). Deep foundations, which are supported on fissured limestone's, as has occurred, for example, in the construction of the "underground bridge" in the zone where the third transportation beltway intersects the "Lenin Avenue" metro station in the area of Gargarin Square, can be used for heavily loaded foundations in particularly complex cases''.
GEOTECHNICAL PROBLEMS ASSOCIATED WITHTHE CONSTRUCTION OF HIGH-RISE BUILDINGS.FOREIGN EXPERIENCE AND DOMESTIC PRACTICE
Reference; Soil Mechanics and Foundation Engineering, Vol. 40, No. 5, 2003,pg 176-184 V. M. Ulitskii, A. G. Shashkin, and K. G. Shashkin Saint Petersburg State University for means of Communication; and, Scientific-Production Union Georekonstruktsiya Fundamentproekt.
According to V. M. Ulitskii, A. G. Shashkin, and K. G. Shashkin; ''The concept of the piled-raft foundation assumes the transfer of some of the load from the building through the lower surface of the slab grillage . Here, the fraction of the load taken up by the slab grillage plays a basic role in the design. According to experience gained with the design of pile foundations at the Institute of Geo-technics in Darmstadt, the portion of the load taken up by the grillage slab is assigned by the designer. It is assumed that during deformation, excess loads from the piles will be transmitted onto the grillage slab; this will, as a result, also lead to an assumed distribution of pressure. Here, of course, it is considered that the settlements of the piled-raft foundation may be appreciably higher than those of a pile foundation, and may approach the settlements of a building on a slab in terms of value. It is precisely this situation that has obviously prohibited application of the concept of the piled-raft foundation to the building housing Commerce Bank II for which the requirements regarding settlements were extremely stringent. Observations made with respect to pressure transducers indicated that a slab grillage does not transmit pressures to the bed soil''.
''On the whole, worldwide experience gained with the design and construction of high-rise buildings indicates that only high technologies of work production combined with profound analytical drafting of the design, and detailed investigations of interaction between the bed soils and building structures will make it possible to erect high-rise buildings in a fail-safe manner, including those constructed under the complex geotechnical conditions of Saint Petersburg. There is no doubt that beyond the dependence on the construction site, the erection and subsequent occupancy of high-rise buildings should be accompanied by a set of scientific measures, including a system of observations on the interaction between the basic bearing structures and bed soils''.
USING SETTLEMENT-CONTROL PILES TO ENHANCE MAT FOUNDATION OF A HIGH-RISE BUILDING IN ORLANDO.
Reference; Amr M. Sallam, Ph.D., P.E., M. ASCE, Associate Vice President, Nodarse & Associates, Inc., Winter Park, Florida, USA:firstname.lastname@example.org.
S.E. "Jim" Jammal, P.E., M. ASCE, Executive Vice President, Nodarse & Associates, Inc., Winter Park, Florida, USA:email@example.com.
According to Amr M Sallam & Jim Jammal ; A piled raft foundation is a system in which the total structural load is supported partially by the raft (mat) through contact with the soil and the piles usually by friction. A piled raft foundation is economical because the utilized piles are usually short since they do not have to extend to a sound bearing layer. The piled raft foundation undergoes settlement that is more than that of pile foundations and less than that of mat foundations. Piled raft foundations were used to support bridges, high rise buildings, and heavy industrial plants. Most of the piled raft research concentrated on the load distribution between that mat and the piles. Analytical solutions as well as linear and nonlinear two and three dimensional Finite Element Analysis are available to optimize the piled raft design. Although a pronounced piled raft foundation was not utilized in the presented case history, the authors utilized the idea of using short frictional piles to control settlement of the mat foundation.
A peer review and additional exploration study was performed by the authors to evaluate the most economical foundation system for a Downtown Orlando mixed-use building. Original design called for deep foundations in the form of Augered-Cast-In-Place piles. An alternative foundation system that consisted of solid mat foundations with settlement-control piles was recommended. The settlement-control piles were utilized below the heavily loaded column, where higher contact pressure were observed. This foundation system required continuous coordination between the geotechnical and structural engineer. The settlement-control piles was modeled in the mat structural analysis program as points of higher stiffness than the mat. The results of two static pile load tests were used to estimate the actual pile stiffness within the design load of the pile. A number of columns were monitored for settlement during and after construction. The measured settlement were substantially lower than the predicted settlement, which proved the efficiency of the recommended mat foundation with settlement-control piles.
SLAB-PILE FOUNDATION FOR A HIGH-RISE BUILDING
Reference: Soil Mechanics and Foundation Engineering, Vol. 45, No. 1, 2008 pg; 17-22. R.A.Mangushev, A.V.Igoshin, N.V.Oshurkov, and A.B. Fadeev Saint Petersburg State Architectural and Civil Engineering University.
According to R.A.Mangushev, A.V.Igoshin, N.V.Oshurkov, and A.B. Fadeev; A slab-pile foundation (SPF) belongs to that group of floating piles with a low slab grillage, which provides for the transfer of a portion of the load onto the soil directly through the lower surface of the grillage. SPF had become popular after several high-rise buildings had been erected on them in Frankfurt (Germany) on a thick stratum of indigenous clay. As compared with a purely slab foundation, an SPF has insignificant settlement and a lower probability of tilting. At the same time, it is more economical than a purely pile foundation where the entire load is transferred onto the piles. SPF hold promise for widespread use in the construction of tower buildings, large tanks, and other similar entities.
According to author; It is difficult to analyze the causes of significant deviations in computed SPF settlements from the actual settlement based on one-time analyses. More probably, settlements on the high side, which were obtained by layer-by-layer summation even with a limitation placed on the depth of the compressible stratum with respect to a criterion of 0.5, are caused by data presented by survey organizations, where the compression modulus of the soils had been appreciably underestimated. The experience gained with installation of the SPF has therefore been successful. The actual settlement of the building is lower than the computed value, and lower than the limiting allowable settlement. There is virtually no tilt. The iteration method used to analyze the settlement of the SPF is guaranteed devoid of gross errors, and yields a cautious and, not-underestimated assessment of expected settlement.