The precise characterization of ground motions incorporating site, source, distance and other effects and the accurate prediction of seismic demands at the component and system level are essential requisites for advancing performance-based design and evaluation methodologies. This research effort focuses on issues related to ground motion characteristics with particular emphasis on near-fault records and its interrelationship with seismic demand and ultimately in developing enhanced procedures for estimating deformation demands in structures for performance-based evaluation. Recent earthquakes have revealed an enhanced level of hazard imposed by ground motions recorded in the vicinity of causative faults associated with directivity effects. Both forward-rupture directivity and fling effects produce ground motions characterized by a strong pulse or series of pulses of long period motions. To highlight their potential damaging effects on building structures, the energy content of near-fault records were investigated by devoting special attention to forward-rupture directivity and fling effects and the influence of apparent acceleration pulses. A new demand measure called the effective cyclic energy (ECE) is developed and defined as the peak-to-peak energy demand imparted to structural systems over an effective duration that is equivalent to the time required for reversal of the system effective velocity. This energy term led to the evolution of a non-dimensional response index ( y cff ) as a new descriptor to quantify the destructive power of near-fault records. Based on validation studies conducted on numerous instrumented buildings, the ECE spectrum is proposed to estimate the input energy demand of multi-degree-of-freedom (MDOF) systems without performing nonlinear-time-history (NTH) analysis. In the final phase of the study, a new pushover analysis methodology derived from adaptive modal combinations (AMC) is developed to predict seismic demands in buildings. This procedure integrates concepts built into the capacity spectrum method recommended in ATC-40 (1996), the adaptive method originally proposed by Gupta and Kunnath (2000) and the modal pushover analysis advocated by Chopra and Gael (2002). A novel feature of the procedure is that the target displacement is estimated and updated dynamically during the analysis by incorporating energy based modal capacity curves in conjunction with constant-ductility demand spectra. Hence it eliminates the need to approximate the target displacement prior to commencing the pushover analysis. The methodology was applied to several vertically regular instrumented steel and reinforced concrete (RC) moment-frame buildings, and also validated for code-compliant vertically irregular steel and RC moment frame buildings. The comprehensive evaluation study including individual and statistical comparisons with benchmark responses obtained from NTH analyses demonstrate that the AMC procedure can reasonably estimate key demand parameters such as roof displacement, interstory drift, plastic rotations for both far-fault and near-fault records, and consequently provides a direct reliable tool for performance assessment of building structures.
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Design of a high-rise office building~ like any engineering design. is a complex
multidisciplinary process with the objective to discover~ detail and construct a system to
fulfill a given set of performance requirements. The success of this process is highly
dependent upon the cooperation taking place between the members of the design team.
Although present-day engineering computer technology allows for precise analysis and
design of the different subsystems of an high-rise building. it does not readily provide
insight for choosing among alternatives of these subsystems to arrive at the best overall
design.
This research study presents a computer-based computational method for optimal
cost-revenue conceptual design of high-rise office buildings. Specifically, a Multicriteria
Genetic Algorithm (MGA) is applied to conduct Pareto optimization that
minimi~es capital and operating costs and maximizes income revenue for a given
building project, subject to design constraints imposed by building codes and fabrication
requirements.
The conceptual design process involves the coordinated application of
approximate analysis, design and optimization. To commence the design process, a
population of different alternative designs are generated. Using approximate analysis and
design based on pre-developed data bases, the values of the conflicting cost-revenue
objective criteria are established for each design. Then, a MGA is used to explore the
design space and find improved designs having enhanced values of the objective criteria.
The results, for a given building project, is a set of Pareto-optimal conceptual designs that define the "trade-off' relationships between the three competing objective criteria to
minimize capital cost, minimize operating cost and maximize income revenue. The
corresponding three-dimensional criteria space is populated by feasible conceptual
designs that are 'equal-rank optimal' in the sense that each design is not dominated for all
three objective criteria by any other feasible design possible for the building. Life-cycle
costing is introduced to investigate the profit potential of building designs over time. The
conceptual design of four example office buildings are conducted from a variety of
viewpoints to illustrate the capability of the computational procedure to create
comprehensive computer-generated colour graphic representations of optimal costrevenue
trade-off relationships for office buildings taking into account architecturat
structural, mechanical and electrical systems. While this study focuses on office
buildings and corresponding cost-revenue criteria, the proposed computer method for
conceptual design is directly applicable to any type of artifact and related objective
criteria.
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Linear and Non- Linear Flexural Stiffness Models for Conc Walls in High-Rise Buildings
Author: Ahmad M. M. Ibrahim | Size: 5.76 MB | Format:PDF | Quality:Unspecified | Publisher: Ahmad M. M. Ibrahim | Year: 2000 | pages: 167
In the seismic design of high-rise wall buildings;, the fundamental period of the building and the building drift are usually determined using linear elastic dynamic analysis. To carry out this analysis, designers need to assume a linear flexural stiffhess of the wall sections that account for
cracking. The commentary to the 1994 Canadian concrete code (CPCA 1995) suggests a stiffness value of 70% of the gross moment of inertia (I g) of the wall section. The commentary to the 1995 New Zealand Standard (NZS 3101 1995) suggests much lower stiffhess values. A wall subjected to axial compression of 10% of fc! Ag is suggested to have half what is recommended in the CPCA Handbook (i.e. 0.35 lg). The NEHRP Guidelines for the Seismic Rehabilitation of
Buildings (FEMA 273) suggests stiffness values of 0.8 Ig and 0.5 Ig for uncracked and cracked concrete walls, respectively. While it is not clear which of the recommended stiffness values should be used, it is certainly clear that the choice of stiffness value will have a significant
influence on the predicted period and drift of the building.
The actual influence of cracking on the flexural stiffness of a concrete wall subjected to seismic loading is nonlinear. Nonlinear static analysis is increasingly used to capture this influence provided that an appropriate nonlinear model is used for the materiaL In this thesis, a simple nonlinear flexural (bending moment-curvature) model for concrete walls
in high-rise buildings is proposed. To validate the model, a 40ft high slender concrete wall was constructed and tested under simulated earthquake loading. Results from the test were compared with the proposed model and showed good agreement. Based on the proposed piece-wise linear model, a general method to determine the linear "effective" flexural stiffness of concrete walls was developed. Results from the general method for the effective flexural stiffness showed that the large variation in effective stiffness that is recommended by various design guidelines does actually exist for different wall configurations under certain conditions. The general method presented in this thesis gives the appropriate stiffness for a particular wall considering all important parameters that influence the stiffhess. A study was conducted to examine the influence of a variety of parameters on the stiffness of concrete walls and a set of simplified
expressions are proposed for the effective flexural stiffness of concrete walls.
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Six full-scale high-strength concrete columns were tested under cyclic lateral force and a constant axial load equal to 20% to 34% of the column axial load capacity. The 510 mm (20 in.) square columns were reinforced with 4 No. 29 (ASTM No.9) and 4 No. 36 (ASTM No.ll) bars constituting a longitudinal steel ratio of 2.6% of the column gross sectional area. The main experimental parameter was transverse reinforcement detail. It was found that the hysteretic behavior and ultimate deformability of high-strength concrete columns are significantly influenced by the amount and details of transverse reinforcement in the potential plastic hinge regions as well as the axial load levels. Excellent hysteretic behavior achieving a drift ratio of 6% without degradation of load carrying capacity was developed by columns with 82% or more of confinement specified in the seismic design provision of the ACI 318-95 code, when the axial load ratio was 20%. However, similar columns only achieved an ultimate drift
ratio of3% when the axial load was above 30% ofthe column axial load capacity. Reasonably good hysteretic behavior up to an ultimate drift ratio of 4% was possible for columns reinforced with transverse reinforcement providing as low as 57% of confinement required by the ACI code, when the axial load ratio was 20%. For the same transverse reinforcement configuration and testing condition,
improved behavior was observed for the model column where the transverse reinforcement was of a higher strength. New performance-based design for required transverse reinforcements for high-strength concrete columns subjected to seismic loading is investigated. Macro-analysis was performed to predict the column behavior at various stages of seismic loading. The analytical results show that currently available confined high-strength concrete stress-strain theories
implemented in a new curvature-based moment-curvature program analysis is able to predict the lateral shear versus displacement relationship of the specimens. A micro-analysis was performed with ADINA (Automatic Dynamic Non-linear Analysis), a finite element analysis software, by constructing three-dimensional finite element models. The results, with all parameters properly prescribed,
provide good correlation with the experimental values. The finite element method can provide detailed analytical results of stress and crack distributions and provide insights in stress and crack variations during the stages of loading as well as verification of the experimental results.
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Riddington J.R., Ghazali M.Z. [1988] "Shear strength of masonry walls," Proceedings of the Eigth International Brick and Block Masonry Conference, Dublin, Ireland.
Hamburger R.O. [1993] "Methodology for seismic capacity evaluation of steel-frame buildings with infill unreinforced masonry," Proceedings of the US National Conference on Earthquake Engineering, Memphis, Tennesse, USA.
Liauw T.C., Lee S.W. [1977] "On the behaviour and the analysis of multi-storey infilled frames subjected to lateral loading," Proceedings of Institution of Civil Engineers, Part 2, Vol. 63, pp. 641-656.
Author: Ahmed A. Shabana | Size: 3.6 MB | Format:PDF | Quality:Unspecified | Publisher: Cambridge University Press | Year: 2010 | pages: 386 | ISBN: 9780521154222
Dynamics of Multibody Systems, Third Edition, introduces multibody dynamics, with an emphasis on flexible body dynamics. Many common mechanisms such as automobiles, space structures, robots, and micromachines have mechanical and structural systems that consist of interconnected rigid and deformable components. The dynamics of these large-scale, multibody systems are highly nonlinear, presenting complex problems that in most cases can only be solved with computer-based techniques. The book begins with a review of the basic ideas of kinematics and the dynamics of rigid and deformable bodies before moving on to more advanced topics and computer implementation. This revised third edition now includes important new developments relating to the problem of large deformations and numerical algorithms as applied to flexible multibody systems. The book's wealth of examples and practical applications will be useful to graduate students, researchers, and practicing engineers working on a wide variety of flexible multibody systems.
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A comprehensive and practical guide to surveying for archaeologists, with clear instructions in archaeological mapping, recording field work and detailed case studies from the UK, Europe and the US. Philip Howard provides a user’s guide to methods and instruments of surveying to enable archaeologists to represent their own fieldwork confidently and independently. Archaeological Surveying is an invaluable resource which:
- provides beginner’s instructions to software used in computerised surveying, including IntelliCAD 2000, Terrain Tools, Christine GIS and Global Mapper
- introduces the archaeologist to a range of surveying instruments such as GPS, electronic distance measures, theodolites and magnetic compasses
- includes low-cost software.
This textbook is an essential read for any field archaeologists who are in need of an introduction to surveying, or simply wish to update their techniques.
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