SEISMIC DESIGN OF BUILDING STRUCTURES PDF
order to study its dynamic behaviour under seismic loads. Is this hypothesis realistic? Can we really design earthquake resistant structure without damages?. a pdf file at sppn.info Design: Brotbeck Corporate Design, Biel. Impression: knowledge on seismic design of buildings by translat- ing this FWOG BP 15 In skeleton structures, separate non-structural masonry walls by joints! To promote the implementation of existing knowledge in the seismic design of engineering . In building structures these regions are termed plastic hinges.
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Seismic Design of Building sppn.info - Free ebook download as PDF File . pdf) or read book online for free. Request PDF on ResearchGate | SEISMIC DESIGN OF CONCRETE BUILDING STRUCTURES | This contribution presents an overview of the salient aspects of. PDF | On Jan 1, , R. P. Dhakal and others published Structural Design Framework for performance based seismic design of buildings . The method to design structures to resist earthquake induced forces (commonly.
Seismic Design of Building Structures.pdf
Placing the elements in a closely spaced diagrid pattern provides sufficient resistance against vertical and lateral loads. In mega core systems, floor slabs are E R cantilevered from the core shear wall.
In this case, floor slabs are supported by the core shear S walls and discontinuous perimeter columns. Perimeter columns are supported by strengthened cantilever slabs repeated on some storeys. Strengthened cantilever slabs protrude from the core, and are strengthened in order to support the load coming from the storeys above.
E R A M S -The core may be centrally located with outriggers extending on both sides or it may be located on one side of the building with outriggers extending to the building columns on one side. When subjected to lateral loads, the column-restrained outriggers resist the rotation of the core, causing the lateral deflections and moments in the core to be smaller than if the freestanding core alone resisted the loading.
K I L i Simplicity: E R A M ii Uniformity: Concentrations of stresses or large ductility demands cause premature collapse. It may be necessary to subdivide the entire building into independent units by using seismic joints. Structural symmetry means that the centre of mass and centre of resistance are located at, or close to, the same point. K I L Eccentricity produces torsion and stress concentrations. Redundancy primarily arises E path after any component failure. R from the capacity of structures to provide an alternative loading A M v Bidirectional resistance and stiffness: High horizontal stiffness is effective in limiting excessive displacements that may lead to instabilities e.
In this respect, arrangements in which the main elements resisting the seismic actions are distributed close to the periphery of the building present clear advantages. K I L A vii Diaphragm behaviour at storey level: These collect and transmit inertia forces to the vertical elements of lateral resistant A M systems, i. They also ensure that vertical components act together under gravity and seismic loads.
S viii Adequate foundation: Buildings with isolated foundation elements should utilize a foundation slab or tie beams between these elements in both main directions. Vertical irregularities are defined in terms of strength, stiffness, geometry, and mass. Firstly, they minimize the distance in plan between the CoM and CoR.
Remember that even with a perfectly symmetrical structural K I L configuration some degree of A torsion still occurs due to torsional motions within the E R ground shaking.
Like the y direction shear walls, they react against the movement that deflects them. They apply equal and opposite reaction forces upon the diaphragm creating another moment couple. Even though no x direction seismic I L forces act on the building, because these two shear walls orientated K parallel to the x axis are strongly connected to the diaphragm, they A nonetheless participate in resisting torsion.
Even if the new walls are identical to the perimeter walls because they are closer to the CoR they are subject to 50 per cent smaller displacements when the diaphragm twists and the leverarms between them are less. With a lesser resisting I L force proportional to horizontal displacement and half the lever K arm their torsion-resisting contribution is only 25 per cent of that provided by the perimeter walls.
Replace the shear walls with one- or multi-bay moment frames and the principles outlined above still apply.
The building will be less torsionally stiff due to the lesser stiffness of the frames but still perform adequately, especially if the frames are located on the perimeter of the building.
In the examples considered so far, a recommended torsion-resistant structure comprises a minimum of four vertical elements, like shear walls or moment frames, with two in each direction.
However, in some situations the number of elements can be reduced to three Any y direction forces are resisted by one shear wall, and x direction forces resisted K I L by two walls. When torsion induces A E R diaphragm rotation, the two x direction walls, in this case with a long lever-arm A M between them, form a moment couple. They provide torsional stability or S equilibrium irrespective of the direction of loading — but only so long as they remain elastic.
The system becomes torsionally unstable. I L This configuration consisting of three vertical structural K elements is described by structural engineers as a torsionally A unbalanced system.
It is not recommended unless the x E R direction walls or frames are much stronger than minimum requirements. They must be capable of resisting horizontal A M forces with little or no ductility demand and therefore possibly possess far more strength than normal.
K I L Although re-entrant A geometries can take many shapes, what they share E R A M in common from a seismic design perspective, is their S potential damage resulting from for the different dynamic properties of each wing. Typical re-entrant corner forms. For example, when the building in the right Fig is shaken in the y direction, the left-hand area of the building, and the wing to the right, react quite differently.
The left-hand area deflects horizontally a relatively small amount due to its greater K I L depth and inherently greater A horizontal stiffness.
It swings about the stiffer area, possibly damaging floor diaphragms at the junction of the two wings. The building might best be separated into two independent structures. Irregular plan configurations improved by seismic separation gaps.
Building services, including air ducts and pipes also need to pass through floor slabs I L and in the process introduce potential weaknesses into diaphragms. A M S A slot in the diaphragm destroys its ability to span between shear walls for y direction forces. X direction structure not shown.
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A continuous two-span diaphragm. Where the length of a bracing element — such as a shear wall — is short in plan with respect to the width of the diaphragm transferring forces into it, the interface between the horizontal and vertical K I L element may be too weak to A transfer the forces between them.
It collects forces compression, S from the diaphragm acting in either tension or depending upon the direction of force at that instant of time and Collector or tie members transfer transfers them into the wall.
K The slot destroys the ability of the diaphragm to span to the right- A hand wall. If the purpose of the slot is to introduce light or services E R through the diaphragm one option is to bridge the slot by introducing a section of steel bracing.
The only option is to no longer consider that wall as a shear wall but to provide a new shear wall to the left of the penetration. A serious diaphragm discontinuity occurs where a potential floor diaphragm consists of more than one level. If a relatively small area is raised or lowered it can be treated, as far as seismic K I L behaviour is concerned, as if A it were a penetration. This could lead to their premature failure and so the best approach would be to separate the diaphragms and their supporting members into two independent structures.
Plan irregularities: In each case the directions of strength of the vertical structures are angled with respect to any sets of orthogonal K I L axes.
A E to resist horizontal forces and R The ability of each configuration M torsion is understood by A S considering the length of each vertical system as a strength vector. A vector can be resolved into components parallel to, and normal to, a set of axes. Two examples of non-parallel systems. For this reason codes S insist that structural engineers model non-parallel systems in 3—D in order to capture these effects and design for them. A non-parallel system showing the orthogonal force components of each wall and secondary diaphragm stresses for a y direction force.
Rather than earthquake energy absorbed by ductile yielding of K I L steel reinforcing bars, or A E hinge zones, or structural fuses R structural steel sections in plastic A M throughout the whole structure as shown in Fig. Serious damage is caused especially to the columns of that soft storey. Of all vertical configuration problems, the soft storey is the most serious and is by far the most prevalent reason for multi- storey building collapses.
So many buildings, located in seismically active regions throughout the K I L world possess relatively open A E soft storey mechanism forming.
R ground floors and are at risk of a A M A soft storey building is doomed, S since columns in the soft storey usually lack the resilience to absorb seismic damage and still continue to support the weight of A collapsed building with weak the building above. Soft storeys are also caused by other configuration irregularities as illustrated in the next figure. However, the structural I L engineer must undertake special analyses and provide members K within that storey with additional strength and ductile detailing.
In more severe soft storey cases even the most advanced structural design cannot prevent poor performance in a design-level earthquake. K I L A So the questions arise: How can you achieve this presumably architecturally desirable layout without creating a hazardous weak column—strong beam configuration? One of two strategies is employed: The internal moment frames and shear walls of the next Fig. They are designed so as the perimeter frames need only carry gravity forces.
It has to undergo the same horizontal drifts as the stronger alternative seismic resisting structure without distress while, at the same time, resisting gravity forces. Begin by accepting that the frames with such a flexible and soft storey must be excluded from the primary seismic resisting system.
I L So keep their irregular configuration and design them to resist gravity forces only. Once again provide an alternative stiffer structure to K A resist all seismic forces. At least two other approaches are possible. E R First, introduce beams without floor slabs.
This may achieve the intended A M spaciousness of the double-height storey yet avoid a soft storey by S restoring the regularity of the moment frame. Now that the weight of the level without a floor is far less than that of the floor above, a special engineering analysis and design is a Provided beams without slabs required. If the idea of inserting beams to create regularity is unattractive, consider a mega-frame solution. The moment frame storey height is extended to two storeys.
At alternate storeys floor beams are pinned at their ends to prevent them participating as moment frame elements. The main disadvantage of the K I L mega-frame solution is that A the frame member sizes are considerably larger E than R A M normal in order to control the increased drift and bending columns S and shear stresses due to the increased storey heights.
The must also be designed to resist mid-height inertia forces acting at b Create a two-storey mega-frame by pinning alternate storeys. Two columns together, one that is half the height of the other, resist a horizontal force. The shorter column therefore eight times is K I L stiffer than the other, so A it tries to resist almost eight times as much E R force as the longer A M column. It is unlikely to S be strong enough to resist such a large proportion of the horizontal force and may fail.
Two unequal height columns resisting seismic force. Of course, that creates a soft storey scenario M that then needs to be addressed. If the piles are monolithic with columns and protected from contact with the ground by sleeves or casings that allow unrestrained horizontal drift, then a short column is avoided. The problem is that the free-length is too E R short to allow for the A M development of a ductile plastic hinges.
S In the event of seismic overload the column fails in shear. Comparison between a regular and a short column subject to horizontal drift.
Methods to avoid a short column configuration with reinforced concrete infills. We are grateful to every reader who Lakes ofter the time to help us improve the quality of our books by pointing out an error.
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No part of this publication may be reproduced, stored in a retrieval system, or transwnitted, ja any form or by any means, electronic, mechanical photocopying, recording, or otherwise. CA www ppidpass. Seistnie design of building stenetures: Lindebnrg, with Majid Baradar. Includes index: ISBN pbk. Barthqnake engineeting--Californin--Problems, exercises. Civil engineering-California, 1. L56 More From S Dutta.
Seismic Design of Building Structures.pdf
S Dutta. Hemant Yadav. Sanka Seneviratne. Mila Ljubisavljevic.Enter the email address you signed up with and we'll email you a reset link. K I L Although re-entrant A geometries can take many shapes, what they share E R A M in common from a seismic design perspective, is their S potential damage resulting from for the different dynamic properties of each wing. All rights reserved. This is due to the rather long list of things we do not know and can not do, as well as uncertainties in the things we do know and can do.
The podium and tower form represents a rather severe setback configuration. On the other hand, EBFs, I utilize axis offsets to intentionally introduce flexure and shear in K preselected beam segments to increase ductility.
E R A M S -The core may be centrally located with outriggers extending on both sides or it may be located on one side of the building with outriggers extending to the building columns on one side.
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