The design of foundations for tall buildings is a challenging task for geotechnical engineers as they are required to consider all geotechnical aspects of the project, with the aim of identifying and managing the geotechnical risks. In the design of foundations for tall buildings, lateral loadings are of great importance as are the vertical loadings. A small rotation at the foundation will be magnified to a very large magnitude at the top of the structure due to the height of the building, which will affect the serviceability and functionality of the building.
This paper presents the foundation design process for two cases - the 1km high Nakheel Tower in Dubai and the 151 storey Incheon Tower in South Korea. The role of the authors as an internal reviewer of the analyses and an engineer undertaking the numerical analyses during the different project phases will be discussed. Analyses of the proposed foundation were carried out by computer programs using the boundary element method and 2D & 3D finite element methods based on the limit state approach. Key issues, in particular the overall performance of the foundation, will be addressed.
The paper concludes with a summary of the design processes and the basic design criteria for tall buildings.
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Foundation design for the Emirates Twin Towers, Dubai
Author: Harry George Poulos and Andrew J. Davids | Size: 0.81 MB | Format:PDF | Quality:Unspecified | Publisher: Can. Geotech. J. 42: 716–730 (2005) | Year: 8 june 2005 | pages: 15
This paper describes the foundation design process adopted for two high-rise buildings in Dubai, the Emirates Twin Towers. The foundation system for each of the towers was a piled raft, founded on deep deposits of calcareous soils and rocks. The paper outlines the geotechnical investigations undertaken, the field and laboratory testing programs, and the design process and describes how potential issues of low skin friction and cyclic degradation of skin friction due to wind loading were addressed. An advanced numerical computer analysis was used for the design process, which was carried out using a limit state approach. This necessitated analysis of a large number of load cases, and the paper describes how the information was processed to produce design information. A comprehensive program of pile load testing was undertaken, and class A predictions of both axial and lateral load–deflection behaviour were in fair agreement with the load test results. Despite this agreement, the overall settlements of the towers observed during construction were significantly less than predicted. The possible reasons for the discrepancy are discussed.
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Seismic Analysis and Design of a Concrete Arch Bridge Direct Displacement-based Design Approach to Seismic Isolation
Author: Trausti Hannesson | Size: 7.3 MB | Format:PDF | Quality:Unspecified | Publisher: Technical University of Denmark Bjarni Bessason, University of Iceland | Year: APRIL 2010 | pages: 119
In this thesis the response of a concrete arch bridge to seismic loads corresponding to the South Iceland Seismic Zone (SISZ) is calculated. The analyzed bridge was originally designed for non-seismic load conditions. The South Iceland Seismic Zone is an active seismic zone and several times since
the settlement of Iceland structures have collapsed and casualties been reported in earthquakes in that area.
The main objective of this thesis is to evaluate the e ect of changing the bridge location and come up with a suitable design alternative. Linear response spectrum analysis is performed with the general purpose FE-program
SAP2000 from which it is clear that the bridge is in need of redesign to withstand the seismic loads occurring in the South Iceland Seismic Zone. A direct displacement-based design approach is employed to design an isolation system using lead rubber bearings. Linear response spectrum analysis is performed using equivalent linear sti ness and damping to model the nonlinear behavior of the base isolation. The nonlinear behavior of the isolation system was then further investigated with nonlinear time history analysisVusing arti cial ground motions.
The study shows that by introducing lead rubber bearings as the only change to the original design the response to seismic loads can be signi cantly improved.
The direct displacement-based design approach to the design of
seismically isolated structures proved to be simple and to o er control of the total structural response. Simple hand calculations were veri ed by
linear response spectrum analysis but considerable di erence was observed
between the linear and nonlinear methods in terms of expected displacement
of the bridge deck and hence section forces. Results from response spectrum
analysis were in all cases conservative.
Keywords: seismic engineering, bridge engineering, direct displacement-based design,
seismic isolation, lead rubber bearings
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SEISMIC ANALYSIS OF MULTISTOREY BUILDING WITH FLOATING COLUMN
Author: Sukumar Behera | Size: 1.2 MB | Format:PDF | Quality:Unspecified | Publisher: Department of Civil Engineering, National Institute of Technology Rourkela- 769008 | Year: may2012 | pages: 93
In present scenario buildings with floating column is a typical feature in the modern multistory
construction in urban India. Such features are highly undesirable in building built in seismically
active areas. This study highlights the importance of explicitly recognizing the presence of the
floating column in the analysis of building. Alternate measures, involving stiffness balance of the
first storey and the storey above, are proposed to reduce the irregularity introduced by the
floating columns. FEM codes are developed for 2D multi storey frames with and without floating column to study
the responses of the structure under different earthquake excitation having different frequency content keeping the PGA and time duration factor constant. The time history of floor displacement, inter storey drift, base shear, overturning moment are computed for both the
frames with and without floating column.
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Earthquake Design
Short Course Presentation by Prof. Mete A. Sozen
Author: Prof. Mete A. Sozen | Size: 45 MB | Format:RAR | Quality:Unspecified | Year: 2013
This presentation i get from short course of earthquake design presented by Prof. Mete Sozen in Indonesia at August 2013.
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I need an RC building modeled (with reinforcement) in Revit Structure. I have used the software a lot, but I need a good way to do the reinforcement of beams and columns in this program and get practical bar bending, column and beam schedules.
Meanwhile, I have extensions installed, but extensions do not give good bar bending schedule. If wrong please guide me.
A parametric study of linear and non-linear passively damped seismic isolation systems for buildings
Author: Cenk Alhan, Henri Gavin | Size: 0.5 MB | Format:PDF | Quality:Unspecified | Publisher: Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708-0287, USA | Year: 2004 | pages: 13
The effects of near-field ground motions with large velocity pulses have motivated passive damping requirements for the protection of seismically isolated structures. Structures in which the first mode damping exceeds 20% or 30% typically do not exhibit classical modes, and simulation via a simple superposition of uncoupled second order equations is not possible. When the damping is produced by viscous or linear visco-elastic devices, we can, however, gain insight into the dynamic behavior of these structures using a convenient first-order formulation and frequency domain methods. When the damping effects are created by nonlinear mechanisms such as yielding or friction, the behavior of the structure is amplitude dependent and analyses are commonly carried out in the time domain. In this paper, frequency domain analysis and earthquake time history analysis are applied to study the influence of isolation damping on higher-mode effects and inter-story drift ratios. Because higher mode effects, plan irregularities, and bi-directional ground motions are all important attributes of the dynamic behavior of these structural systems, a simple comparison of isolation damping mechanisms can not be carried out via simple single or two degree of freedom realizations. In order to incorporate these important details in the study of the dynamic behavior of these structures, a set of 8-story proto-type building models with L-shaped floor plans, different isolation periods, isolation damping characteristics, and levels of isolation stiffnesses are examined.
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Author: Matthew Grey | Size: 4.8 MB | Format:PDF | Quality:Unspecified | Publisher: A thesis submitted for the degree of Master of Science by Research at the University of Oxford | Year: 2006 | pages: 166
Guyed masts are a specialized type of structure commonly used in the broadcasting industry to support equipment at substantial heights. The dynamic analysis of these structures under seismic loading is a much understudied field that requires investigation. The complex nature of their analysis arises from the nonlinear force-deflection relationship of the cable supports as well as P-D effects in the mast. These lead to the structure exhibiting significant nonlinear characteristics even under working load conditions. Full nonlinear analysis of guyed masts is rarely performed as it is complex and time consuming. Masts are usually designed by equivalent static methods for wind and ice loading only, with the seismic load case often assumed to be less onerous. The validity of this assumption is investigated as part of this research.In this project four existing guyed masts in the UK with heights ranging from 99m to 312m are accurately analysed under various seismic loading conditions using SAP2000 structural analysis software. The research aims to gain an understanding into the distribution and magnitudes of forces developed during typical seismic and design wind events, establish indicators and trends that may aid in guyed mast design, and identify the circumstances in which seismic loading may be the governing load case. Investigations into the ‘travelling wave’ effect, the significance of vertical motion, and the suitability of a response spectrum analysis are also undertaken. Applicable sections of Eurocode 8 are followed wherever possible.It is shown that when subjected to substantial seismic events with peak ground accelerations in the region of 4m/s2 , significant forces can develop in masts that are comparable to those
produced during a wind assessment using the Patch Load method. The distribution of forces can be appreciably different from a wind loading analysis and any regions with irregular or inconsistent distribution of wind response forces can be vulnerable to seismic loading, particularly when mean hourly design wind speeds are less than 22m/s. It is also shown that enough common or predictable seismic behaviour exists between masts to suggest that the development of a simplified seismic analysis method for guyed masts is feasible.
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Author: João Luís Domingues Costa | Size: 2.8 MB | Format:PDF | Quality:Unspecified | Publisher: DANMARKS T E K N I S K E UNIVERSITET | Year: 2003 | pages: 101 | ISBN: ISBN 87-7877-129-9
The work has been carried out at the Department of Structural Engineering and Materials, Technical University of Denmark (BYG•DTU) under the supervision of Professor, Dr. techn. M. P. Nielsen.
The author would like to thank his supervisor for giving valuable advice and inspiration as well as valuable criticism to the present work.
Thanks are also due to the author’s co-supervisor M.Sc. Ph.D. Rita Bento, Instituto Superior Técnico, Lisbon, Portugal, who has given important and useful comments and suggestions. A word of appreciation should also be addressed to Civil Engineer Ph D Junying Liu, COWI A/S, for providing the example used in the case study and for assistance in carrying out the study. The Portuguese institution for scientific research Fundação para a Ciência e Tecnologia – FCT, sponsors the Ph.D. project under which this report was done. The author grateful acknowledges this support.
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