This document provides an overview of multi-storey steel structures. It discusses:
- The early history of steel structures beginning in the late 18th century with cast iron buildings and progressing to steel I-beam structures in the mid-19th century.
- Famous early skyscrapers from the late 19th century including the Home Insurance Building and Monadnock Building which helped popularize the technology.
- Structural systems for tall buildings including rigid frames, braced frames, rigid core structures, and tubular designs capable of supporting 70-120+ stories.
- Design considerations like building shape, foundation tolerance, wind loading, and seismic provisions like ductile connections and a rigid base.
While Designing a High rise Load & Structural Analysis is major factor to consider. Here we analyzed some data and try to describe briefly. We hope that it will help you lot :) Done by Neeti Lamic, Bayezid, Sykot Hasan
Video Lecture: https://youtu.be/zoj6DYMvg2I
Structural System in High Rise building or Tall Building
Emporis standards-
“A multi-story structure between 35-100 meters tall, or a building of unknown
height from 12-39 floors is termed as high rise.
The International Conference on Fire Safety –
"any structure where the height can have a serious impact on evacuation“
Massachusetts, United States General Laws –
A high-rise is being higher than 70 feet (21 m).
Buildings higher than 100m is termed as skyscraper according to emporis.
Buildings 300m or higher is termed as super tall and buildings 600m or taller is termed as mega-tall.
Tall structures are ;
Flexible, low in damping, slender and light in weight.
Sensitive to dynamic wind loads.
Adversely affect the serviceability and occupant comfort.
Oscillations are observed in the along-wind and crosswind directions and in torsional mode.
Behaviour of wind response is largely determined by building shapes.
Aerodynamic optimization of building shapes is the most efficient way to achieve wind resistant design.
In ancient China, tall buildings appear to be those of traditional pagodas.
In support of:
• Building Support Structures, Analysis and Design with SAP2000 Software, 2nd ed., eBook by Wolfgang Schueller, 2015. The SAP2000V15 Examples and Problems SDB files are available on the Computers & Structures, Inc. (CSI) website: http://www.csiamerica.com/go/schueller
• The Design of Building Structures (Vol.1, Vol. 2), rev. ed., PDF eBook by Wolfgang Schueller, 2016, published originally by Prentice Hall, 1996, 868 pages
While Designing a High rise Load & Structural Analysis is major factor to consider. Here we analyzed some data and try to describe briefly. We hope that it will help you lot :) Done by Neeti Lamic, Bayezid, Sykot Hasan
Video Lecture: https://youtu.be/zoj6DYMvg2I
Structural System in High Rise building or Tall Building
Emporis standards-
“A multi-story structure between 35-100 meters tall, or a building of unknown
height from 12-39 floors is termed as high rise.
The International Conference on Fire Safety –
"any structure where the height can have a serious impact on evacuation“
Massachusetts, United States General Laws –
A high-rise is being higher than 70 feet (21 m).
Buildings higher than 100m is termed as skyscraper according to emporis.
Buildings 300m or higher is termed as super tall and buildings 600m or taller is termed as mega-tall.
Tall structures are ;
Flexible, low in damping, slender and light in weight.
Sensitive to dynamic wind loads.
Adversely affect the serviceability and occupant comfort.
Oscillations are observed in the along-wind and crosswind directions and in torsional mode.
Behaviour of wind response is largely determined by building shapes.
Aerodynamic optimization of building shapes is the most efficient way to achieve wind resistant design.
In ancient China, tall buildings appear to be those of traditional pagodas.
In support of:
• Building Support Structures, Analysis and Design with SAP2000 Software, 2nd ed., eBook by Wolfgang Schueller, 2015. The SAP2000V15 Examples and Problems SDB files are available on the Computers & Structures, Inc. (CSI) website: http://www.csiamerica.com/go/schueller
• The Design of Building Structures (Vol.1, Vol. 2), rev. ed., PDF eBook by Wolfgang Schueller, 2016, published originally by Prentice Hall, 1996, 868 pages
In this presentation, the nonlinear seismic behavior of three ordinary moment-resisting concrete space frames with unsymmetrical plan in three, four and five stories are evaluated. The three buildings were originally designed according to existing Iranian codes. Seismic loads are calculated and distributed over the height of the frame using both rectangular and triangular forms. It has been found that the obtained capacity curves have been affected greatly by the forms of loading. Results have been also produced in form of story drifts to establish the performance level of these buildings. The results show that all of the frames in both directions are within the life safety performance level.
Intersecting cylindrical shells are frequently encountered in various types of engineering structures. Despite their common occurrence, reliable and accurate analytical methods have not been generally available. To contribute to the understanding of the stress concentration phenomena and possible solutions for them, finite element analyses are carried out for shells with holes, shells with reinforced holes and cylinder-to-cylinder intersections. The overall agreement between the finite element predictions and experimental results is a very good one.
10 THINGS THEY DON'T TEACH IN MARKETING SCHOOLSGuillaume Rigal
Here are ten skills or competencies I believe every aspiring marketer should learn. Yet it is not part of usual marketing courses.
1. Give / receive creative feedback
“Don’t keep a dog and bark yourself”
2. Vlookup and other Excel voodoo tricks
Marketers shouldn’t be afraid of numbers.
3. History of advertising
The marketer should be a voracious reader and an inquisitive historian of his trade.
4. How to manage upward / stand your ground
Marketing is no department for the pushover.
5. Fractions and basic % calculation
It’s always good to impress people in the room and be noticed as number-inclined.
6. Project management
Learn and apply the basics of project management and you will become a strong asset in any marketing job and to any leader.
7. Storytelling
Great marketers and leaders tell stories. You should too.
8. Bargaining
Don’t be a fool and think bargaining is beneath you or a salesman’s job. Or else, as Bon Scott sang, risk “getting had / getting took”.
9. Sketching / mapping
Know how to convey your point of view visually in a strategic manner.
10. Endurance
It’s tough out here for Marketers. Know it, build a thick skin, and be a pitbull.
A skyscraper is a very tall, building. The minimum height requirement currently to be accepted as skyscraper is 800 feet (244 meters). The word skyscraper was first known to such buildings in the late 19th century, which reflects public amazement at the tall buildings that are being built in New York City. The structural definition of the word skyscraper was later refined by architectural, historians, based on engineering developments of the 1880's that had enabled construction of tall multi-story buildings. This definition was based on the steel skeleton as opposed to constructions of load-bearing masonry, which passed their practical limit in 1891 with Chicago's Monadnock Building.
Thus, this PDF deals with the construction and details of various skyscrapers along with their advantages and challenges both technically as well as in general perception. Necessary diagrams are given along with proper explanations.
Design & Analysis of High rise Building With & Without Floating Column Using ...IJSRD
At present buildings with floating column is a typical feature in the modern multistory construction in urban India. There are many projects in which floating columns are adopted, especially above the ground floor, where transfer girders are employed, so that more open space is available in the ground floor. As the load path in the floating columns is not continuous, they are more vulnerable to the seismic activity. Sometimes, to meet the requirements these type of aspects cannot be avoided though these are not found to be of safe. Hence, an attempt is taken to study the behavior of a G+15 multi storey building in which some storey’s are considered for commercial purpose and remaining storey’s are for residential purpose. This paper studies the comparison & seismic analysis of the multistory buildings with floating column and without floating column. Finally, analysis & results in the high rise building such as storey drifts, storey displacement, and Base shear were shown in this study. Design and Analysis was carried out by using Extended Three Dimensional Analysis of Building Systems (ETABS) Software.
The seismic performance of the frame shear wall tall building with and withou...eSAT Journals
Abstract Recently, High-rise buildings are developed very quickly to satisfy the production and peoples’ living needs and development. There are so many reasons for large number of developments of the high- rise building, commercialization, industrialization and urbanization. This quick development of the high-rise building necessitates study and analysis of the seismic performance of high-rise buildings, especially when the high-rise building has irregularity in its horizontal plan or vertical section. In this present study, main focus to analyze the relative earthquake performance for the tower portion of a 34 storey Reinforced Concrete (RC) with 103.4m total height frame-shear wall buildings with and without setbacks subjected to an earthquake excitation scaled down to be of peak ground acceleration appropriate for China, and analyze the setback influence on this high-rise building to identify weakness positions in the high-rise building structure. The comprehensive use of SAP2000 software V16.1 for the elastic calculations aid to assess nonlinear time history analysis for their applicability to tower models (first model with setbacks, second model without setback) of height-rise frame-shear wall building under same conditions of the site category, earthquake acceleration type and standards in structural design. This study is carried out first to judge the shear for the tall building model 1 belongs to which type of the torsion, second to study how the vertical (elevation) setback impact in tall building resisting seismic activity. Key Words: Setback; SAP2000; Irregular high-rise building; Frame-shear wall; Seismic analysis; Time history analysis.
This slide explains different structural systems used in high rise buildings.what is the true meaning of high rise building ?
aims of high rise? objectives of high rise?
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
"Impact of front-end architecture on development cost", Viktor TurskyiFwdays
I have heard many times that architecture is not important for the front-end. Also, many times I have seen how developers implement features on the front-end just following the standard rules for a framework and think that this is enough to successfully launch the project, and then the project fails. How to prevent this and what approach to choose? I have launched dozens of complex projects and during the talk we will analyze which approaches have worked for me and which have not.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
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GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Search and Society: Reimagining Information Access for Radical FuturesBhaskar Mitra
The field of Information retrieval (IR) is currently undergoing a transformative shift, at least partly due to the emerging applications of generative AI to information access. In this talk, we will deliberate on the sociotechnical implications of generative AI for information access. We will argue that there is both a critical necessity and an exciting opportunity for the IR community to re-center our research agendas on societal needs while dismantling the artificial separation between the work on fairness, accountability, transparency, and ethics in IR and the rest of IR research. Instead of adopting a reactionary strategy of trying to mitigate potential social harms from emerging technologies, the community should aim to proactively set the research agenda for the kinds of systems we should build inspired by diverse explicitly stated sociotechnical imaginaries. The sociotechnical imaginaries that underpin the design and development of information access technologies needs to be explicitly articulated, and we need to develop theories of change in context of these diverse perspectives. Our guiding future imaginaries must be informed by other academic fields, such as democratic theory and critical theory, and should be co-developed with social science scholars, legal scholars, civil rights and social justice activists, and artists, among others.
2. C.Teleman_S.S.III_Curs8
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SHORT HYSTORY
Reliance Building, Chicago -designers Burnham &Root
(extended 14 storeys), 1890
1801- Salford-Manchster, U.K, 7 storeys building with beams and columns made of cast iron, designed by
Boulton&Watt;
1845- William Fairbanks uses iron I sections for a several storey factory;
1879- Chicago, Willim La Baron Jenney designes “Leiter Building”, 7 storeys and Home Insurance Building,
11 storeys;
In the same period Monadnock Building is designed by Burnham & Root : 16 storeys, brick masonry.
3. • Structures that are placed in down town where the price of land is high so the surface on
the ground is restricted.
• The homeland-America, associated with the economic boom from the end of XIX-th
century to the middle of the XX-th.
• Most reprezentative:
Leiter Building, Chicago, 1879, architect William le Baron Jenney; 11 storeys
Monadnock, Chicago, Burnham & Root, 16 storeys
1890 Industrial producing of steel with Thomas and Siemens-Martin kilns
Invention of the elevator (Ottis)-important moment
Empire State Building, New York, 1931, Al Smith, 381m, 102 storeys
World Trade Center, New York, 1963, 411m , 110 storeys
John Hancock Center, Chicago, 1968, 337 m
Sears Tower, Chicago, 1974, 442 m, 120 storeys
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SHORT HYSTORY
9. C.Teleman_S.S.III_Curs8
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Cartier La Defense, Paris, 560 hectares (5.6 million square metres) area, 72 glass and steel buildings
and skyscrapers, 180,000 daily workers, and 3.5 million square metresof office space.Around its
Grande Arche and esplanade ("le Parvis"), La Défense contains many of the Paris urban area's tallest
high-rises, and is home to no fewer than 1,500 corporate head offices, including those of 15 of the
top 50 companies in the world
12. STRUCTURAL SYSTEMS
Rigid frames both
directions-unbraced;
Braced frames with
articulated connections
between beams and griders-
vertical and horizontal and
on both principal directions
directions
Frames with rigid
connections on one direction
and articulated connection
on the other;
Structures with rigid core
(steel or reinforced concrete)
and suspended columns on
periphery
Tubular structures
1- Rigid joints: 20-25 storeys;
2, 3, 4- rigid joints and vertical bracing: 70-80 storeys;
5- external rigid tube made of columns closely placed and internal rigid
core: 80-90 storeys;
6- articulated joints and vertical bracing externally placed: 90-100
storeys (John Hancock Centre, Chicago);
7- external and internal tubes , columns placed very closely and rigid
connection- (World Trade Centre) :100-110 storeys;
8- frames with rigid joints and vertical plus horizontal bracing both
directions: 110-120 storeys (Sears Tower, Chicago)
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13. PLANE-SHAPES
• Regular shapes: rectangular or compound from several rectangles (Other shapes are
used also);
• In plane:
• a - symmetry necessary to avoid torsion effect under horizontal actions;
• b- distance between columns on both directions 4...10 m.
Optimization of the distances between the axes
of the columns:
L-spans; Wc- weight of columns; Wb - weight of
beams; Wt – total weight
Plane shapes of the high-rise buildings
and in plane grid
C.Teleman_S.S.III_Curs8
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14. EXAMPLESOFSTRUCTURALSOLUTIONS
Rigid core of reinforced concrete and rigid
connections between columns and beams
both directions
Rigid core that takes and transfers the loads from floors to the
foundations; columns are in tension
Beams very close placed transversally, longitudinal beam rigidly connected to the columns and
horizontal bracing externally and internally
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15. BRACEDFRAMES
Braces in tension
dissipation in lower part, close to the interface with the column
V shape braces in tension and compression
Eccentric braces – dissipation in the bottom flange of the beams ;
Braces in K –rigid, non-dissipative
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16. EFFICIENTSOLUTIONSFORTOLERANCEDISTANCES
• Preventing the effects of temperature variation:
a- limitation in plane length: 70...100 m;
b- tolerance between the structural elements of the building on the whole height or at least at the top of the structure
(reduces the cumulative linear deformations of beams);
c- Design the walls at the first storey independent: avoid the shear stresses in the external walls at the first floor level
due to the variations in dimensions.
• Preventing the effect of uneven settlements of the foundations-two adjacent buildings with different weights and/or
heights or laying on different ground soils, will settle differently at the foundations level:
- the foundations will be designed separately (soil cannot take important stresses);
- the foundations will be designed as a common rigid plate.
Shear of the external wall at the ground
level: t
he first storey is designed
independent from the others in order to
avoid this phenomenon
Effects of the variation of temperature upon the
structural elements:
a) line O of horizontal displacements in the
middle of the building and cumulative
deformations at the edges;
b) reducing the cumulative linear deformations
by introducing internal tolerances at the top level
C.Teleman_S.S.III_Curs8
16
Foundations need tolerance
distances when the structural units
weight differ or the ground
foundaton condtions are different
17. POSITIONOFTHECONFERENCEHALLSINPLAN
• at the ground level as an independent structure ► enables the access and the evacuation easily
(needs a bigger surface of terrain);
• at the top level ► the structural in plane shape undisturbed and doesn’t increase the surface of
ground affected (the evacuation of the people from inside is much more difficult);
• at intermediary level ► insures a quicker evacuation the continuity of the columns being
interrupted and the structure is provided with a powerful truss in some cases on the height of a
storey taking over and transferring the stresses from the columns above).
The position of the conference halls
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18. VARIATIONOFTHECROSSSECTIONOFTHEBUILDING
Alternatives for the variation of the cross
section of the high-rise buildings: constant
cross section and variable in steps;
a- elastic part; b- rigid part.
Anti-seismic provisions
The most important provisions are:
1. Design of a structure with a high degree of
redundancy that insures an important reserve of
loading capacity in plastic domain and
consequently allow its accommodation to a new
static scheme which results in certain cases of
collapse;
2. The adoption of a symmetric shape in plan
parallel with avoiding of the unequal repartition
of the weight for reducing the torsion effects;
3. Design of a rigid base for the building;
4. Gravity centre lower to the ground level (by
compensating the weight of the underground
level);
5. Steels with high performances of strength and
ductility must be used- the ration fu/fy≥1,2 and
elongation under ultimate stress ≥ 15%;
6. Structural connections with mechanical fasteners
will be done with high strength bolts (group
8.8…10.9).
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19. ACTIONSANDCOMBINATIONOFACTIONS
•Vertical actions
1.Permanent actions: self-weight of the structure, including
the weight of the floors and of the walls an empirical formulae
being used for a preliminary evaluation:
• [daN/m3]
where:
•G- the total weight of the structure;
•n - total number of the storeys;
•K – amplifying coefficient (influence of bracing system, stairs,
lifts, building services (K=1,10...1,15);
2.Variable actions:
2.1. Live loads, usually uniformly distributed, in [daN/m2]
according with the function of the building (e.g., residential
building, hotel, etc.) and in particular with the destination of
every space inside this building (rooms, halls, lobbies, stairs
etc.);
2.2. Snow on the roof (terrace)-uniform distributed.
•Horizontal actions
•Variable actions - wind on the envelope of the building;
•Accidental actions – earthquake, fire, explosions.
The distribution of the variable actions in various schemes is
presented, the most familiar cases of loading being considered
in the static computation of the multi-storey buildings.
2
n
12K10G
Simplification of the static computation
Separation of the spatial structure into plane frames:
1- transversal frame; 2- longitudinal structural element
(girder); 3- longitudinal frame
Loading schemes of vertical and horizontal actions on
multi-storey buildings: a)- permanent actions;
b)- variable actions (live loads); c) variable actions
(wind); d) accidental actions (earthquake)
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20. WindDynamicAction
Different loading diagrams for wind action and for combined gravitational and wind loading on structure
Classification of the steel structures considering the wind dynamic effects
Hz
H
100
4,0n
5,1
0
Hz
H
n
40
0
20
2
1
ii
ii
ym
yW
n
Hz
H
d
n
1,0
1 4
Hm
E
nr
r=1 r=2 r=3 r=4 r=5 r>5
=3,52 =22,4 =61,7 =121,0 =200 *
2
2/12* r
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21. STATICANALYSIS
•Slope-deflection method- smaller number of unknown elements; whenever is possible the
advantages of structural symmetry (geometric, elastic, mechanic) must be taken into
account.
• Some assumptions are prior set off:
1.-moments of inertia- constant along the bars;
2.-influence of shear forces neglected;
3.-in the first order computation the effect of axial forces upon the deformations of the bars
is neglected;
Computer design of the structure implies that the elastic characteristics of the cross section
of the elements are known. These characteristics may be determined with the help of
approximating methods.
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22. Structural systems for the high rise
buildings: 1-rigid joint; 2- column; 3-floor;
4- horizontal bracing; 5-vertical bracing; 6-
hinged joints
Rigid frames both transversally and longitudinally; the
connections are designed to the moments induced by the vertical
and horizontal loads. These structures have rather a small number
of stories (20 to 30 storeys) and a big amount of maneuvre at the
building site is necessary.
Rigid frames transversally with braced frames articulated
with vertical braces longitudinally; the frames take over vertical
loads and the horizontal forces are transferred to the vertical
bracing of the structure;
Frames with both rigid and articulated joints, for ex. transversal
rigid frames and longitudinal braced frames with articulated joints
which have at the lower part of the structure articulated joints and
the frames are provided with vertical bracing; rigid frames are used
at the top of the structure;
Rigid frames braced both directions: used for up to 70-80 storeys
Bracing system may also be adopted for the limitation of the
horizontal displacements. If braces are missing, then
important horizontal displacements due to horizontal actions
(wind, earthquake etc.) have to be taken into account affecting
the joints of the structure.
RIGID AND HINGED FRAMES IN VARIOUS COMBINATIONS
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23. Cross sections of steel buildings
with rigid core and dual core
Design of the rigid core: a)made of reinforced concrete;
b) made of steel trusses
Rigid core structures with columns and/or tensioned elements on the perimeter; external core made
of columns closely situated and connected to very stiff girders and internal columns sustaining the
floors;
VI Rigid cores and pendulum columns: vertical bracing are placed in the external walls all the height of
the building and the columns inside the perimeter sustain the floors;
VII Dual core tubular structures: two concentric tubes formed of columns closely spaced connected at
every level with stiff girders; the internal core may be made of reinforced concrete or steel columns;
VIII Other combined systems
HIGH RISE BUILDINGS WITH RIGID CORES
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24. THESTIFFNESSOFTHESTRUCTURALFRAMES
•P- effect – analysis that allows the structural classification into two categories: non-sway (stiff, rigid)
and sway (flexible) frames
•rigid steel frame: during the evaluation of the structural response to horizontal actions the additional
stresses due to horizontal translations of the connections may be neglected.
•V- vertical total reaction determined at the bottom of the columns in a certain level;
•H- horizontal total reaction;
• - horizontal relative translation of the storey determined in a I order computation, based on the vertical
and horizontal actions on the structure and in addition horizontal equivalent forces due to imperfections.
•Imperfections: ENV 1993-1-1:
•-global;
•-local geometrical imperfections and residual stresses variation of the yield strength
1,0
H
V
h
Types of structures considering the classification of the stiffness: a- structures for which the relationship is relevant;
b- structures for which the relationship is not relevant
C.Teleman_S.S.III_Curs8
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25. PRINCIPALASPECTSOFBRACINGSYSTEMDESIGN
ai – horizontal translations at the i level in the braced system due to horizontal force H;
si - horizontal translations at the i level in the un-braced system due to horizontal force H.
•In other words, the stiffness of the braced frame is 5 times greater than the stiffness of the un-braced
frame:
5
i
si
a
sa R5R
sR - stiffness of the un-braced structure.
- stiffness of the braced structure;
H
Ra
C.Teleman_S.S.III_Curs8
25
Braced steel frame is considered: if the horizontal translations of the joints are reduced in a 80%
proportion due to the presence of braces
The bracing system is a plane girder, fixed in foundations (at
the ground level). The connection between any vertical
bracing and the adjacent columns is obtained with
longitudinal elements- girders that are considered with
infinite stiffness.
Under this supposition, the horizontal forces acting in the
joints of the vertical bracing system at a certain level will
determine translations of the ends of the columns
identical with the joints of the bracing elements.
NOTE
26. Limitation of the sway by placing vertical bracing on the height: left- sway to a frame with rigid joints and to
a braced frame; middle- interaction between the two frames; right- deformation of the whole building
EFFECT OF VERTICAL BRACING SYSTEM
C.Teleman_S.S.III_Curs8
26
27. P- EFFECT
• The joints of the bracing system suffer horizontal
translations under a linear variation on the height of
the structure:
• The force necessary to fix the elements in the
connection will then be (the angle is very small):
•
• and at the level i the whole force acting on the
bounded connections will then be:
• The real behaviour is presented, the variation of the
horizontal translations being in fact different from
level to level. The effect P- will then be described
by the horizontal force at the level i:
• Then the real total force acting at the level i will be:
The P- effect
H
1
iiiiiii VtgVDDDDH 11 sin
ii VH
iiiii DDH 11
iiiii DDH 11 Systems of horizontal in-plane translations due to
imperfections: a- braced frames; b- un-braced frames
C.Teleman_S.S.III_Curs8
27
28. BRACINGSYSTEMOFMULTI-STOREYSTEELSTRUCTURES
• Vertical braces: placed in the plane of
the vertical frames and insure the
necessary stiffness on both directions
and to take in plane torsion effects.
• Horizontal braces: stiffness of the
floor when it cannot insure a
satisfactory bond between the vertical
elements (trusses with simple ties or in
X over the whole floor or only in certain
zones).
• Floors made of reinforced concrete or
corrugated steel sheet (composite
structure) insure enough stiffness.
•Sometimes the horizontal bracing is
placed at 3...5 storeys interval on the
height of the structure, considering that
the current floor insures its own
stiffness.
Vertical bracing designed as a rigid core :
actions of the horizontal forces
Different systems for the vertical braces
C.Teleman_S.S.III_Curs8
28
29. ACTIONSONRIGIDFRAMES
• Vertical actions
Loading cases for maximum axial force and maximum bending moments for the marginal (A) and internal joints (B)
Distribution of the bending moments from vertical loading in the internal joints
C.Teleman_S.S.III_Curs8
29
The loading schemes correspond
to maximum axial force and
maximum bending moments in
the end bays and internal bays
Distribution of the
bending moments from
vertical actions and the
static equilibirum in the
structural joint
30. C.Teleman_CM3_Curs7
30
EVALUATION OF INTERNAL FORCES AND BENDING MOMENTS
FROM HORIZONTAL ACTIONS
• In the elastic design it is assumed that the axial internal forces from each level, Nik, are
directly proportional with the distances to the N. A. (rigidity center), dik, at every level;
also, these forces are directly proportional with the cross section area of the columns, Aik.
• We write the equations of equilibrium for the overturning moment under horizontal
actions for each of the current column, k, at the current level i :
ikikjj dNyW
1i1i
ikik
1i
ik
dA
dA
N
N
2
ikik
1i1i
1i
jj dA
dA
N
yW
jj2
ikik
1i1i
1i yW
dA
dA
N
n
1i
ji WV
ij
ik
iik
I
I
VV
2
h
VM ikik
Horizontal actions from wind action on structures with rigid connections and
the internal forces resulted under these forces: axial forces, shear forces and
bending moments
31. DESIGNOFHINGEDSTRUCTURESANDVERTICALBRACING
• Vertical actions
C.Teleman_CM3_Curs7
31
The structural joints are subjected to a
reduced bending moment as a result of
uneven reactions on the edge of the
structural beams :
eRRM
2
l
pR;
2
l
qpR
21
11
Calculation of the bending moment resulted from un-even
reaction from beam convergent in the structural connection
Forces and bending moments resulted from the
distribution of horizontal forces to the bracing system
Horizontal actions
32. C.Teleman_CM3_Curs7
32
The rigidity of the current stiffener i is Fi (equal with horizontal force acting on the bracing system
that results in an unitary translation of the brace).
If a reference stiffness Fo is considered, the stiffness of the current bracing i may be expressed in
relation wih Fo by adopting a factor of proportion, ki:
Horizontal actions
0F
i
k
i
F
2
A
cy
n
1j
ij
n
1j
jxyjk
n
1j
yjF
n
1j
jxyjF
cx
Based on these stiffnness values, the rigidity center will be determined on each level:
Every bracing system parallel with the axis y-y will take the in plane force Nyi’ , component of the
resultant force Ry, distributed based on its rigidity to the “n” braces)
yj
yikyR
n
1j
yjF
yiFyR
'
yiN
Force Nyi” resulted from from th distribution of the bending moment determined by the the eccentricity of
the aplication of the reaction force Ry with respect to the rigidity center, My= Ry· ex to all “n” bracing
systems depend on the rigidity of the braces and on the distance ax from the torsion center:
yixi
yjxj
''
yi
''
yj
Fa
Fa
N
N
yixi
yjxj''
yi
''
yj
Fa
Fa
NN
xj
n
j
''
yj aNM
But: xj
a
yi
F
xi
a
yj
F
xj
an
j
''
yi
NM
n
j yi
k
xi
a
yj
k2
xj
a
''
yi
NM