Seismic Design With Base Isolation

Seismic Isolation for Designers and Structural Engineers

This book provides both theory and design aspects of seismic isolation. This will be useful for structural engineers and teachers of engineering courses. For other structural components (concrete frames, steel braces etc) the. engineering student is taught the theory (lateral loads, bending moments) but then also the design (how to select sizes, detail reinforcing, bolts). This book will do the same for seismic engineering. The book provides practical examples of computer applications as well as device design examples so that the. structural engineer is able to do a preliminary design that wont specify impossible constraints. The book also addresses the steps that need to be taken to ensure the design is code-compliant.

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Performancebased seismic design

From around the 1980s there was a growing awareness that building codes, in general, provided a good level of life-safety protection, but were significantly less reliable in minimizing property damage in moderate and even small earthquakes. This concern led to the birth of performance-based seismic engineering, or performance-based seismic design. Work by the Structural Engineers Association of California (SEAOC) resulted in the publication of tentative design guidelines on this subject as an Appendix to the SEAOC (1999) Blue Book. The following brief discussion is based on that publication. Finally, it is noted that at the time of writing (2009) performance-based seismic design is mainly used in research and in some retrofitting projects, and is as yet little used for the design of new structures. A drawback to its use is its inability to incorporate torsional effects.

Mechanical Properties of Seismic Isolation Systems

Northern Architectural Systems

A seismic isolation system is the collection of all individual seismic isolators and may be composed entirely of one type of seismic isolator, a combination of different types of seismic isolators, or a combination of seismic isolators acting in parallel with energy dissipation devices (i.e., a hybrid system). The most popular devices for seismic isolation in the United States may be classified as either elastomeric or sliding. Examples of elastomeric isolators include high-damping rubber bearings (HDR), low-damping rubber bearings (RB), or low-damping rubber bearings with a lead core (LRB). Sliding isolators include flat assemblies or those with a curved surface, such as the friction-pendulum system (FPS).

The Design and Construction Process Performance Based Seismic Design

Earthquakes provide architects, engineers, constructors and enforcers with a number of important considerations foreign to the non-seismic design and construction process. As some of these criteria are fundamental in determining the form of the 'structure', it is crucial that adequate attention is given to earthquake considerations at the correct stages in the process. To this end, a simplified flowchart of the design and construction process for earthquake resistant infrastructure is shown in Figure 8.1.

Seismic Design Highlights ASCE 702 IBC03 NFPA 5000

ASCE 7-02 utilizes spectral response seismic design maps to quantify seismic hazards on the basis of the contours. These maps were prepared by the U.S. Geological Survey (USGS), along with a companion CD-ROM. This CD-ROM provides mapped spectral values for a specific site based on the site's longitude, latitude, and site soil classification. Examples are shown in Figs. 2.43 and 2.44. Longitude and latitude for a given address can be found at Web sites such as www.Oeocode.com. Use of the CD-ROM is recommended for establishing spectral values for design, since the maps found in ASCE-7 and at Web sites are at too large a scale to provide accurate spectral values for most sites. The origin of present-day (2004) seismic codes may be traced back to the 1971 San Fernando Valley earthquake, which demonstrated that design rules of that time for seismic resistance had some serious shortcomings. Each subsequent major earthquake has taught new lessons. Seismic codes such as ASCE-7 have endeavored...

Performance based seismic design

A number of recent seismic codes including AASHTO-LRFD (2007) and Eurocode 8 (2004) have promoted the adoption of performance based seismic design for bridge Background and guidance on analysis methods for performance-based design is provided in FEMA-440 (FEMA, 2005) and the LRFD Seismic Design Guidelines (Multidisciplinary Center for Earthquake Engineering Research, 2000).

Seismic Design

Earthquakes result from the sudden movement of tectonic plates in the earth's crust. The movement takes place at fault lines, and the energy released is transmitted through the earth in the form of waves that cause ground motion many miles from the epicenter. Regions adjacent to active fault lines are the most prone to experience earthquakes. The map in Fig. 20.1 shows the maximum considered ground motion for the contiguous 48 states. The mapped values represent the expected peak acceleration of a single degree-of-freedom system with a 0.2 sec period and 5 percent of critical damping. Known as the 0.2 sec spectral response acceleration Ss (subscript s for short period), it is used, along with the 1.0 sec spectral response acceleration (mapped in a similar manner), to establish the loading criteria for seismic design. Accelerations Ss and S, are based on historical records and local geology. For most of the country, they represent earthquake ground motion with a 'likelihood of...

Seismic Isolation

Seismic Isolation Base Cabinets

Seismic isolation is a viable design strategy that has been used for seismic rehabilitation of existing buildings and in the design of a number of new buildings. In general, this system will be applicable to the rehabilitation and design of buildings whose owners desire superior earthquake performance and can afford the special costs associated with the design, fabrication, and installation of seismic isolators. The concepts are relatively new and sophisticated, and require more extensive design and detailed analysis than do most conventional schemes. In California, peer review of these new concepts is required for all designs that use seismic isolation. Figure 8.34a. Design concept for base-isolated buildings Top curve D shows the forces in the structure if it were to remain elastic during an earthquake. The conventional design approach is to build ductility into the structure to absorb the difference in forces between B and D. By providing seismic isolation, the maximum force...

Isolation from seismic motion

Seismic Isolation Pier Mobile Home

The principle of isolation is simply to provide a discontinuity between two bodies in contact so that the motion of either body, in the direction of the discontinuity, cannot be fully transmitted. The discontinuity consists of a layer between the bodies which has low resistance to shear compared with the bodies themselves. Such discontinuities may be used for isolation from horizontal seismic motions of whole structures, parts of structures, or items of equipment mounted on structures. Because they are generally located at or near the base of the item concerned, such systems are often referred to as base isolation (Figure 8.13), although the generic term seismic isolation is preferable. The layer providing the discontinuity may take various forms, ranging from very thin sliding surfaces (e.g. PTFE bearings), through rubber bearings a few centimetres thick, to flexible or lifting structural members of any height. To control the seismic deformations which occur at the discontinuity, and...

Eccentrically braced frames

Deformed Braced Frame

Figure 8.11 Deformed shape of eccentrically braced frame subjected to lateral sway, showing potential for substantial secondary damage to floors and non-structure. Reproduced by permission of the Earthquake Engineering Reseach Institute Figure 8.11 Deformed shape of eccentrically braced frame subjected to lateral sway, showing potential for substantial secondary damage to floors and non-structure. Reproduced by permission of the Earthquake Engineering Reseach Institute

Sources of accelerograms and response spectra

Earthquake engineers experienced at working outside basic code requirements have developed sources of information of their own, through government and university organizations specializing in seismology and earthquake engineering. As the problem of availability of information varies so widely from place to place and as the situation is changing so rapidly, this section will simply discuss a few of the chief sources of data presently existing. (ii) Accelerograms of simulated earthquakes. Many earthquake engineering research organizations throughout the world have computer programs for generating artificial earthquakes. Software for the generation of simulated earthquakes such as PSEQGN is available at a small cost from the National Information Service for Earthquake Engineering (NISEE) at the University of California, Berkeley, PEER Building 451 RFS, 1301 South 46th Street, Richmond, CA 94804-4698, USA (email info nisee.berkeley.edu).

Hybrid structural systems

While hybrid systems are often unavoidable and can provide good seismic resistance, care must be taken to ensure that the structural behaviour is correctly modelled in the analysis. Interaction between the different components can be large, and is not necessarily obvious, and many papers have been written on this subject. For example, for low-rise buildings it may be reasonable in many cases to assume that the walls or the braced bays resist the entire horizontal earthquake load, and the moment resisting frame is not required to resist horizontal earthquake forces. However, deformations are still imposed on the moment resisting members, requiring some seismic design consideration such as detailing for ductility.

Estimating Casualties

Table 7.4 Deaths by structural and other causes in the 1994 Northridge, California, earthquake. (Reprinted from Durkin, ME (1996) Casualties patterns in the 1994 Northridge, California earthquake. 11th World Conference a Earthquake Engineering, Paper No. 979, with permission from Elsevier Science) Table 7.4 Deaths by structural and other causes in the 1994 Northridge, California, earthquake. (Reprinted from Durkin, ME (1996) Casualties patterns in the 1994 Northridge, California earthquake. 11th World Conference a Earthquake Engineering, Paper No. 979, with permission from Elsevier Science)

Stiffness to control deformation

The importance of deformation control in enhancing safety and reducing damage and thus improving the reliability of construction in earthquakes is now well recognized (Section 8.2). The stiffness levels required to control damaging interaction between structure, cladding, partitions and equipment vary widely, depending upon the nature of components and the function of the construction, but stiff construction is obviously better than flexible in this regard. The seismic deformations of conventional construction can be greatly reduced by the use of seismic isolation (Section 8.5), so that relatively flexible moment resisting frames may be able to satisfy the design deformation criteria, and P-delta column moments will be greatly reduced.

Defining design events

To further illustrate the point, Kuala Lumpur in Malaysia is located at the rather remote distance of about 400 km from the Alpide earthquake belt, and historically has therefore had little concern for earthquakes. However, from the 1970s, with the advent of taller buildings some instances of alarming swaying and cracking occurred, but only in tall buildings. The author has been involved in investigations which causally linked these phenomena with large-magnitude events occurring 400 km away. Many other sites around the world located at similar distances from large earthquake sources, while safe for most traditional construction, may merit seismic design checks for longer-period construction.

Earthquake Risk and Hazard

Fortunately, an authoritative attempt has been made to overcome this difficulty through the publication by the Earthquake Engineering Research Institute's glossary of standard terms for use in this subject (EERI Committee on Seismic Risk, 1984). Their terminology will be used in this book.

Dynamic analysis of soilstructure systems

Comprehensive dynamic analysis of soil-structure systems is the most demanding analytical task in earthquake engineering. The cost, complexity, and validity of such exercises are major considerations. There are two main problems to be overcome. First, the large computational effort which is generally required for the foundation analysis makes the choice of foundation model very important five main methods of modelling the foundation are discussed in the next section. Secondly, there are great uncertainties in defining a design ground motion which not only represents the nature of earthquake shaking appropriate for the site, but also represents a suitable level of risk.

Steel beams

Moment Column

For the adequate seismic design of the steel beams, and the associated connections and columns, the moment-curvature or moment-rotation relationship should be known. A long stable plastic plateau is required which is not terminated too abruptly by lateral or local buckling effects, such as indicated by terminating at points A, B and C in Figure 10.6. The curves terminating at D and E are typical of the desired behaviour achieved by well-designed beams under moment gradient and uniform moment, respectively. The

Indian Plants Kasuda

Bhattacharya S (ed.) (2007) Design of Foundations in Seismic Areas Principles and Applications. National Centre of Earthquake Engineering, Indian Institute of Technology, Kanpur. Kramer SL (1996) Geotechnical Earthquake Engineering. Prentice Hall, Upper Saddle River, NJ. Penzien J (1970) Soil-pile foundation interaction. In Earthquake Engineering. (ed. RL Wiegel). Prentice Hall, Englewood Cliffs, NJ, pp. 349-381. Whitman RV and Liao S (1984) Seismic design of gravity retaining walls. Proc 8th World Conf on Earthq Eng, San Francisco III 533-540.

Earthquake Insurance

The role of insurance in earthquake risk management has been discussed in simplistic terms in Section 1.3.1, and methods of modelling losses have been discussed in earlier parts of this chapter. More information on earthquake insurance is available in Earthquake Engineering Research Institute (2000), Walker (1997) and Smolka (2000).

Shallow foundations

In the seismic design of deep box foundations, designers must rely mainly on normal structural and geotechnical static design techniques, supplemented where appropriate by consideration of known seismic phenomena, such as seismically enhanced soil pressures. The natural stiffness and strength of box-shaped foundations should be utilized to

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Map Greyhawk Ull

Figure 4.37 Comparison of the median spectral acceleration from the Abraham and Silva (1997, 2008) models for vertical strike-slip earthquakes for RJB 1 km. (For this case, RJB is the closest distance to the coseismic rupture plane). Reproduced by permission of the Earthquake Engineering Reseach Institute Figure 4.37 Comparison of the median spectral acceleration from the Abraham and Silva (1997, 2008) models for vertical strike-slip earthquakes for RJB 1 km. (For this case, RJB is the closest distance to the coseismic rupture plane). Reproduced by permission of the Earthquake Engineering Reseach Institute

Seismic response and design

Bridges are the most vulnerable transportation network component to damage from natural disasters as compared to roads and railway lines. It is therefore of priority to adequately design new bridge structures and reassess the response of existing bridges in areas subjected to earthquake hazard. This chapter briefly addresses a number of topics related to seismic response and design of bridges, namely damage observations in previous earthquakes, conceptual design and modern seismic codes. Commonly observed bridge failure modes following damaging earthquakes are presented. This shows that despite the advancement in seismic design practice, there are repetitive damage patterns due to the increased number of bridges of complex configurations and the heightened consequences of bridge damage in developed societies. Features of layout and configuration that are favourable to controlled and predictable seismic response of bridges are also discussed. Various options available from foundations...

Catholic University of Louvain Atelier Lucien Kroll

Lucien Kroll

From the very start, it was the group's intention, in Kroll's words, to express the diversity of individuals and not the authority of institutions. 81 Everywhere in the final design this intention is manifest. Kroll states The building forms are not static. Walking through the site they change constantly, always in an unexpected fashion. The materials of the windows, their colors, curtains, balconies, and plants increase the sense of diversity. They reinforce the individuality and the autonomy of the occupants, and not the power of the central administration. 82 This richness of diversity is not merely on the surface. For example, Kroll spent considerable time convincing structural engineers to investigate structural design in more creative ways. For one building Kroll proposed a plan of wandering columns, 83 a system where columns were not arranged in the normal grid, either horizontally or vertically. Kroll felt that the regular grid of equal bays was too conformist, that it risked...

Asce 702 Ibc 2003 And Nfpa 5000 Seismic Provisions

In 1971, the San Fernando earthquake demonstrated that the code provisions in place at the time were inadequate and that major revision was necessary. To accomplish this, the Applied Technology Council (ATC) was founded to perform the research and development necessary to improve the code. This effort culminated in 1978, with publication of ATC3.06, a report titled Tentative Recommended Provisions for Seismic Regulation of Buildings. The Structural Engineers Association of California (SEAOC) incorporated many of the recommendations in that report into the 1988 edition of the UBC. Perhaps more important, however, was that publication of this report coincided with the adoption of the National Earthquake Hazards Reduction Program (NEHRP). Design for seismic resistance involves providing structures with proper configuration and continuity, adequate strength and stiffness, and structural detailing capable of resisting inelastic cyclic loading. The NEHRP provisions deal with all these...

Ship and barge collision

Kinetic Architecture Timber

Multidisciplinary Center for Earthquake Engineering Research (2001) Recommended LRFD Guidelines for the Seismic Design of Highway Bridges (NCHRP Project 12-49). Multidisciplinary Center for Earthquake Engineering Research. Maguire J. A. and Wyatt T. A. (2002) Dynamics, An Introduction for Civil and Structural Engineers, 2nd edn, Thomas Telford, London. Wilson E. L., Farhoomad I. and Bathe K. J. (1973) Nonlinear dynamic analysis of complex structures. Earthquake Engineering and Structural Dynamics, 1, 241-252.

Taking the Shorter Road the Fuller Construction Company of the Orient 19201926

After these young architects returned to Japan, they seemed unable to move beyond what William Starrett characterized as a kind of 'banal' architecture that generated 'thick exterior walls . . . and cumbersome interior cross walls, all in a country of soft and soggy bottoms, where lightness of construction and scientific engineering should have been the first consideration' (Brock, 1981). Starrett theorized that one reason the Japanese architects had not managed to overcome banality was that, upon their return from foreign schools, they had been unable to collaborate with structural engineers, as American architects had done when they returned from European stints

Ionica Headquarters Cambridge UK

Ionica Building Cambridge

Design architect for the project was David Emond. A graduate of the Sheffield University School of Architecture with several years of experience in commercial and other projects with different London practices, he joined the Cambridge-based RH Partnership in 1992 at the start of the Ionica project (Emond, 1998). Guy Battle of Battle McCarthy provided environmental consulting. A building services engineering graduate of the Bath School, from the era when architects, structural engineers and building services engineers followed an integrated learning programme, Battle had worked for Ove Arups for some years before forming a partnership with structural engineer Chris McCarthy (Battle, 1998).

Methodologies For Seismic Vulnerability And Seismic Resistance Assessment

Masonry Structures

The method RAN-Z, where the seismic vulnerability is assessed as well, was developed in 1995 (Perus et al. 1995). This method uses similar parameters as the previous one the structural type, the regularity, the amount of structural walls, the existing damage extent, the confinement, the height of the building and the seismic zone. Beside the difference in the range of their values, the method is based upon the use of neural network and this represented the main step further. The data base, that the neural network uses to identify the correlation between the values of input parameters and the values of seismic vulnerability assessment, has been prepared with the results of a questionnaire, fulfilled by six top experts of earthquake engineering in Slovenia. The vulnerability is numerically evaluated

From the Engineers Desk

Good Straw Tower

Structural Engineers The stamp of a structural engineer for straw bale home plans is a must in many jurisdictions. Structural engineers can work from completed plans or can often do the design and drafting work as well. They ensure that the plans, as drawn, are feasible, structurally sound, and meet code and safety requirements. The stamp of a structural engineer can help circumvent the concerns of a building official and allow you to get approval for your straw bale building plans. If you have drawn your own plans or purchased plans that require adaptations or minor changes, it may be better to take them to an engineer rather than to an architect.

The Dilemma of Technology

Low Tech Reinforced Concrete

The structure of the architectural and construction professions reflects this long history. In most Western societies, especially in Europe. architecture remains with medicine and the law one of the liberal professions. This comes from those simpler times when one man could expect to understand how to build, and instruct others in what to do. Those days have long disappeared. First there were specialists. Structural engineers, like myself, calculated how a building would resist gravity and other environmental forces. Then came services engineers, deciding on plumbing, heating, cooling. In the beginning this was welcomed it offered architects and designers a wonderful new freedom. But slowly all the functional aspects of construction were controlled by their specialists. The architect consulted and worked with them and. by teamwork, together they designed the building. This is where we are today. But this implies that the architect and his design team control the process of building....

Gravity resisting structure

As explained above, the architectural integration of seismic and gravity resisting structure and architect-structural engineer collaboration is best begun early in the design process. In the early days of seismic design when suspended floors were cast-in-place rather than utilizing The move away from two-way frames reduces structural redundancy. Now fewer elements provide seismic resistance. The search for economy of structure leads to the concentration of seismic structure rather than its more even distribution. Seismic and gravity structures are separated. The limit of this rationalization is reached with a seismic resistant structure consisting of two one-bay moment frames or two shear walls in each orthogonal direction (Fig. 6.8). Given the lack of redundancy, structural engineers need to be especially careful in the design, detailing and construction of the few critical structural elements and to design the slender gravity-only columns to accommodate horizontal seismic...

Seismic Strengthening Details

Transverse Reinforcement Walls

A thorough understanding of existing construction and seismic retrofit objectives acceptable to owners and to the building official is an important consideration before a seismic retrofit is undertaken. The importance of considering global and elemental deformations at expected levels of seismic forces, not at code or design levels, cannot be overstressed. This is because even with the use of amplification factors, the deformations are at best an approximation, particularly when applied to complex multistory and multidegree-of-free-dom systems. It should be kept in mind that detailing in existing buildings often does not meet the requirements of new construction, and that the strength and stiffness of existing elements may not be comparable with new upgraded systems and elements. Thus, verification of elements for deformation compatibility becomes even more important. This criterion is secondary only to the requirement of providing a continuous load path that is sufficiently stiff and...

Seismic Importance Factor IE

In seismic design, the importance factor I is used to increase the margin of safety against collapse. For example, I 1.50 for essential facilities, I 1.25 for hazardous facilities, and I 1.15 for special occupancy structures. Essential structures are those that must remain operative immediately following an earthquake such as emergency treatment areas and fire stations. Hazardous facilities include those housing toxic or explosive substances. Examples of special occupancy structures are those not classified as special or hazardous, and required for continuous operation. Standard occupancy structures such as office buildings, hotels, and residences are designed for I 1.0. The above values of I apply to facilities designed under the regulations of the 2001 California Building Code (2001 CBC). For buildings designed under the 1997 UBC, the values of I are as follows (Table 16-K, UBC 1997)

Introduction Terminology and Disciplines

Structural engineers also often find it difficult to appreciate the process of traditional building, which they label low technology. R.J.S. Spence and D.J. Cook (1983) accurately point out the differences of the low technology approach, but unfortunately they use as their example the manufacture of fire brick, not a very useful illustration because such brick is far less used in traditional building than other materials.

General Design Requirements

The building's lateral loads were originally taken by the mass brick exterior walls as a box system with some interior masonry walls being used to act as bearing and shearwalls. These augmented the exterior walls and added strength due to the building's ell shape. The design basic wind speed of 120 mph for Norwich produced the greater building design lateral loading as opposed to the seismic lateral requirement. Connecticut is in a moderate seismic zone, with the State's ground accelerations per Code analysis producing less forces in the building's lateral resisting structural elements. Two factors contributed to this result. First, the building's height (5 stories for the Wauregan and 6 stories for the Clarendon Annex) presented a substantial area for wind loads, and second, the light weight wood floor did not contribute substantial mass in the earthquake's lateral load formulas. The wind's total base shear was thus in excess of that produced by seismic analysis. It is worth noting...

Reinforced and Posttensioned Masonry

Brickwork and blockwork, like concrete, have high com-pressive strength but relatively low tensile resistance. So, as with concrete, reinforcing and post-tensioning can be used to carry or relieve the tensile stresses. Reinforced brickwork has been used in India and Japan since the First World War and in America since the Second World War. In Britain reinforced and prestressed masonry is also used by structural engineers for structures such as retaining walls, tanks and footbridges.

First Interstate World Building Los Angeles Floor Plan

Cityspire Tower Ground Floor Plan

Figure 8.19. 21st Century Tower, China (a) model photographs (1), (2), and (3) (b) bracing system (c) framing plan, levels 19, 28, and 37 (d) structural action in primary columns and braces (e) typical interior core bracing. Architects Murphy Jahn Inc., Chicago, structural engineers John A. Martin & Associates Inc., Los Angeles, and Martin & Huang, International, Los Angeles. Figure 8.21. Fox Plaza, Los Angeles (a) building photograph (b) floor framing plan. Architects Johnson, Fain & Perei structural engineers John A. Martin & Associates Inc., Los Angeles. Although the building is regular both in plan and elevation and is less than 240 ft (78 m) in height, because of transfers at the base (Fig. 8.23b), a dynamic analysis using site-specific spectrum was used in the seismic design. The dynamic base shear was scaled down to a value corresponding to the static base shear. To preserve the dynamic characteristics of the building, the spectral accelerations were scaled down without...

Steel Beam And Steel Column Without Concrete Encasement

Composite Construction Column Junction

Seismic design factors are R 5, 2, and Cd 4.5. Buildings in SDC D or E are permitted with a height limitation of 160 feet. The height limit for buildings in SDC F is 100 ft. Composite eccentrically braced frames are permitted for buildings in SDC A, B, or C without any height restrictions. The values for seismic design factors are R 8, 2, and Cd 4. For buildings in SDC D or E, the height limit is 160 feet, and for

Historical note on bridge codes in Europe the USA and Japan

The history of European practice in seismic design is rather recent, and cases of bridge damage in European earthquakes are very few indeed. For Europe, the interest in seismic design of bridges arises from two main considerations, namely the potential for disastrous effects and the export market. With regard to the former, several thousand bridges in Italy are potentially subjected to considerable earthquake risk, while major projects for bridge construction are under way in Greece, among several other European nations with a large bridge population and non-negligible exposure. Whereas national codes in Europe included seismic provisions for bridges, these were rather minimal considerations and intended to support European consultants working abroad. It was through the development of Eurocode 8 Design of Structures for Earthquake Resistance (CEN, 2004 CEN, 2005) that concerted efforts were dedicated to the development of seismic design guidelines for bridges in Europe. The first...

Rigid Frames Moment Frames

Seismic Design Criterion

The Northridge, Richter magnitude 6.7 earthquake of January 17, 1994 in California, which caused damage to over 200 steel moment-resisting frame buildings, and the January 18, 1995, Richter magnitude 6.8 earthquake in Kobe, Japan, have shaken engineers' confidence in the use of the moment frame for seismic design. In both of these earthquakes, steel moment frames did not perform as well as expected. Almost without exception, the connections that failed were of the type shown in Fig. 3.3. The majority of the damage consisted of fractures of the bottom flange weld between the column and girder flanges. There were also many instances where top flange fractures occurred. In view of the observed brittle fracture at the beam-to-column intersections, new connection strategies have been developed, and most building codes are being revised. The new game plan typically consists of designing beams such that the plastic hinges form away from the column face. Current moment frame design practice...

Composite Gravity Systems

In seismic design, the term diaphragm applies to a horizontal element that transfers earthquake-induced inertial forces to vertical elements of the lateral-force-resisting systems. To do so requires a collective action of diaphragm components including chords, collectors, and ties. In buildings, typically floors and roofs provide for the diaphragm action by connecting building masses to the primary vertical elements of the lateral-force-resisting system. Diaphragm Design Summary Buildings Assigned to SDC C and Above. Typical steps in the seismic design of a diaphragm are as follows

Uniform Building Code 1997 Edition Seismic Provisions

A redundancy-reliability factor, p, also new in the 1997 UBC, has been incorporated to promote redundant lateral-force-resisting systems. Nonredundant systems are penalized through higher lateral load requirements, while super-redundant systems are not rewarded with less stringent seismic design requirements.

Keymer Take Home Owner Back To Massachusetts

The crocodiles at Paignton Zoo Environmental Park in Devon have no fear of their pools running dry thanks to the Sika Watertight Concrete system. Often associated with keeping water out of structures, in this case the system has been used to keep the water in. Structural Engineers Winward Dexter specified Sika Watertight Concrete for the five pool enclosures within the swamp - an ideal and cost effective solution in fulfilling the design brief for this project. Hanson Premix supplied 200 cubic metres of watertight concrete to the project. Sika Watertight Concrete is based upon two Sika admixtures. Sika Viscocrete Superplasticiser reduces the amount of water required in concrete production, whilst offering good workability and in turn reducing the volume of capillary pores within the concrete. Sika 1+ blocks the pores to give effective protection down to 100 metres head of water.

Dynamic Analysis Theory

A good portion of the loads that occur in buildings can be considered static, requiring static analysis only. Although almost all loads except dead loads are transient, meaning that they change with time, it is customary to treat them as static. For example, lateral loads imposed by transient wind pulses are usually treated as static loads and even in earthquake design, one of the acceptable methods of design, particularly for buildings with regular configuration, is to use an equivalent static force procedure. Under these circumstances, the analysis of a structure reduces to a single solution for a given set of static loads. Although the equivalent static method is a recognized method, most building codes typically mandate dynamic analysis for certain types of buildings such as those with irregular configurations (see ASCE 7-03, Table 9.5.2.5.1). It is therefore necessary, particularly in seismic design, to have a thorough understanding of dynamic analysis concept.

The specialisation of designers

This distinction is recognised to some extent by the profession in the United Kingdom. The Institution of Structural Engineers, with a membership of chartered engineers (MIStructE and FIStructE) in the UK of approximately 9,000, caters for the minority of designers, and the Institution of Civil Engineers, with a chartered UK membership (MICE and FICE) of approximately 36,000, represents the majority of more general civil engineers. In order to become a member of the Institution of Structural Engineers, suitably qualified graduates with about three years experience in industry have to pass an examination that tests their knowledge as designers of structures, while similarly experienced graduates applying for membership of the Institution of Civil Engineers are subjected to a written assignment that tests their more general suitability to take professional responsibility. However, the distinction is

History And Seismicity Of Anatolia

An important number of historical buildings that date back to different periods keep lighting the past of the land. This is the reason that people from all around the world visit Anatolia to see the traces of their civilizations to understand the lives of their ancestors. On the other hand, it is unfortunate that most of the historical buildings in Anatolia are in poor situations today. Anatolia is a potential source for earthquake engineers to carry research on earthquake behaviour of the existing structures. It has a strong seismic activity. Several severe earthquakes throughout history have caused significant damages in some regions. Movements of the Eurasian Plate, African Plate, Arabian Plate and Anatolian Plate are what that causes earthquakes. The Arabian, African and Eurasian Plates move to north and south towards each other. As a result of this, the Anatolian Plate is squeezed out westwards. This westward movement results from differences in rates of motion between the...

The Edification Subject Of Intervention

Cabinet, (2) Coordination of Post-Graduation Program of Faculty of Education Coordination. (3) Golden room (Fig. 3). Under the supervision of the head architect, a multidisciplinary team was gathered, composed by urban plagues biologists experts, structural engineers, and a proficient firm specialized in wood structural restoration. The practice work evolved, therefore, in three lines. In the first one, biologists determined the termites infecting species, in order to guarantee the efficiency of the plagues control program. In the second one, structural engineers calculate the remaining section of each wood beam, to make the structural assessment. Finally, the practice restoration work was carried out according to the engineers strengthening project.

Structural Analysis And Assessment For The Building

Structural responses of the building to static loads and earthquake action were calculated. The static loads and earthquake action were determined by the actual condition of the structure and the Chinese building codes. In the static analysis, floor dead load was taken as 1.5 kN m2 for the timber floor and 3.5 kN m2 for the concrete floor, and roof dead load was 2.0 kN m2 for the timber trusses supported area and 2.5 kN m2 for the steel trusses supported area. In the seismic analysis, the earthquake intensity was taken as grade 7 according to the Chinese Code for Seismic Design of Buildings (GB50011-2001).

Innovative structural configurations

The search for innovative structural configurations to outwit quakes is still very much alive, after having exercised many minds over the centuries. Indeed, the list of those searching has included more than structural engineers. Witness a physician's patent for base-isolation, and architect Frank Lloyd Wright's commendable yet flawed attempt to use soft ground as a seismic isolation system for the Tokyo Imperial Hotel.11 The discovery of the ultimate 'earthquake-proof' system or configuration remains tantalizingly elusive.

Cooperatively Assessing Space Needs

Meeting with key stakeholders early in the design process to determine the overall guiding principles of the interior design is important. These meetings ideally include all disciplines involved, including the architectural designer, interior designer, mechanical engineer, structural engineer, and staff who are going to be working in the space. Each component of a building's design affects the overall aesthetic of the environment. For example, the lobby at Saint Alphonsus Regional Medical Center in Boise, Idaho, was created by a team of individuals representing several disciplines. The charge from those involved with aesthetics was to design a welcoming, relaxing transition space that reflected the culture and spirit of Boise. The electrical engineer was integral in creating an even distribution of light that was comfortable as a transition from the outside world. The structural engineers were responsible for making sure the suspended sculptural artwork and waterfall were supported...

Contemporary architecture in seismic regions

Seismic design and architecture 105 of light-weight construction reduces the potential architectural impact of the requirements of seismic structure. Irregularity also features in Japanese examples with their juxtaposition of geometric forms, long cantilevers and sculptural qualities. Generally, Japanese construction materials are heavier and, while there is greater visual evidence of seismic resisting structure, once again there is no sense of, nor mention of architectural creativity having been hindered by seismic design requirements. Irrespective of these findings there is no avoiding the fact that buildings in moderate- to high-seismicity regions require increased horizontal strength and stiffness in two orthogonal plan directions, as well as torsional resistance. Additionally, the requirement for a hierarchy of member strengths, particularly in moment frames with their weak beams and strong columns, set seismic resistant structures apart from structures in non-seismic regions....

The 2nd Intervention Phase

Designed with the collaboration of the structural engineers Giulio Mirabella Roberti from the University of Pavia, and Adolfo Alonso and Arturo Mart nez of the Universidad Polit cnica of Valencia. The consolidation will use stainless steel braces, reinforcements and profiles that adapt themselves to the shape of the bell tower and the complex connection between the bell tower and the church. These elements will be installed in most cases in non visible places (like the interior of the round stairway, under the roof eaves of the church, in the hidden space between the vaults and the roof of the church ), will be reversible and inspectionable. Each element has been specifically studied and designed to fit the existing bell tower and solve the structural requirements and stresses.

Federal Emergency Management Agency FEMA httpwwwfemagov

Publications for US architects and engineers including procedures for rapid assessment of earthquake damaged buildings, information on school safety, techniques for seismic retrofitting and (2004). Primer for Design Professionals Communicating with owners and managers of new buildings on earthquake risk (FEMA 389). Detailed guidance on managing and reducing seismic risks together with seismic design and performance issues for a range of building types and facilities.

Design and Detailing Requirements

The seismic design and detailing requirements are cascading meaning that requirements pertaining to a lower category also apply to a higher category. Therefore, SDC A requirements also apply to SDC B, SDC B to SDC C, and so on. 2.4.5.1. Seismic Design Category A (ASCE 7-02 Sect. 9.5.2.6.1) 2.4.5.2. Seismic Design Category B (ASCE 7-02 Sect. 9.5.2.6.2) 2.4.5.3 Seismic Design Category C (ASCE 7-02, Sect. 9.5.2.6.3) 2.4.5.4 Seismic Design Category D (ASCE 7-02, Sect. 9.5.2.6.4) 1. The familiar formula for the design of diaphragms

ASCE 702 Detail Description of Seismic Provisions

Traditionally, the magnitude of the seismic force and level of seismic detailing were strictly a function of structure location. With the latest seismic design provisions, these are now a function of Seismic design category (SDC) has replaced the seismic zone factor Z as the trigger for seismic design requirements including the choice of analysis procedure, the required level of strength and detailing, and the permissible irregularities and the height of buildings. A major departure from 1997 UBC is that detailing and other seismic restrictions are now dependent on the soil characteristics at the site of the structure. The type and usage of the building establishes the seismic use group (SUG) for the building. The SUG is based on the occupancy of the building and the consequences of severe earthquake damage to the building. Three seismic hazard groups are defined. Traditionally, for seismic design, engineers on the U.S. west coast have used a ground acceleration, with a 10 probability...

Code Provisions For Seismic Upgrade

When building codes prescribe full compliance with their current seismic provisions, they are rarely explicit in telling users what measures to take to upgrade the building. There are exceptions, of course. On the U.S. west coast, San Francisco's building code requires upgrading of existing structures to 75 of the strength required by the code for new construction. On the east coast, the Commonwealth of Massachusetts Building Code offers an elaborate path for determination of required remedial measures. In some cases it allows lower seismic forces than those used for new construction. In some regions of high seismic activity, state and local codes and ordinances may require a seismic upgrade even for buildings that are not undergoing renovation. Perhaps the best known of these is California's Senate Bill 1953, a seismic retrofit ordinance adopted on Feb. 24, 1994, in the wake of the Northridge earthquake. It requires more than 450 acute care facilities to submit seismic evaluation and...

Interdisciplinary interaction

5 Mehdian, F., Naderzadeh, A. and Moinfar, A.A. (2004). A comprehensive master plan study on urban seismic disaster prevention and management for Tehran City. Proceedings of the 13th World Conference on Earthquake Engineering,Vancouver, August 1-6. Paper no. 913, 14 pp. 6 Balamir, M. (2004), Urban seismic risk management the earthquake master plan of Istanbul (EMPI). Proceedings of the 13th World Conference on Earthquake Engineering,Vancouver, August 1-6. Paper no. 9005, 22 pp. 7 Kuroiwa, J. (2006). Peru's sustainable cities program 1998-2005 and its application to large built-up areas. Proceedings of the 8th US Conference on Earthquake Engineering, April 18-22, San Francisco. Paper no. 269, 10 pp. 8 Hosseini, M and Shemirani, L.N. (2003). The role of urban planning and design in lifeline-related seismic risk mitigation. In Advancing mitigation technologies and disaster response for lifeline systems. Proceedings of the Sixth US Conference and Workshop on Lifeline Earthquake...

Comparison of provisions

A number of studies comparing seismic codes from the USA and other countries is available in the literature (e.g. Rojahn et al., 1997 Kawashima, 2000b Yen et al., 2003). A comparative study between the seismic design specifications for highway bridges of the US and Japan was reviewed and compared by Yen et al. (2003). In the comprehensive study of Rojahn et al. (1997), the USA codes, namely AASHTO, ATC and Caltrans, were compared. Also included in the latter study were the codes of New Zealand, Japan and Eurocode 8. Kawashima (2000) also presented a brief comparison of design philosophy, design force and ductility requirements for the European, New Zealand, Japanese, AASHTO and Caltrans ATC-32 codes. A comparison is reproduced in Table 2 for a subset of codes compared in the above-mentioned references. The Caltrans provisions are selected to represent the US codes in preference to AASHTO, for the reasons outlined in the previous section. For brevity, only the provisions of the...

On The Theory Of The Ellipse Of Elasticity

The theory of the ellipse of elasticity can be considered as a main icon of the so-called Graphical Statics, the discipline which often characterised the resolving approach of practical design problems during the 2nd half of the 19th century. It represents a very elegant and practical method for the analysis of the flexural response of an elastic structure. It is based on an intrinsic discretisation of a continuous elastic problem. This theory is basically associated to the two outstanding figures of Culmann and Ritter, but also of people, like Giulio Rothlisberger, that were formed at the time at the Polytechnical Schools in Europe and that became later structural engineers and designers and largely contributed in the practical and effective application of the method.

Structural design approaches

Two new approaches to structural design are gathering momentum within the structural engineering profession. Of the two, ' displacement-based design' has fewer implications for architects although it does provide a more rational basis for achieving acceptable levels of performance in design earthquakes. Rather than a structural engineer commencing a seismic design by calculating the stiffness and natural period of a building and then determining inertia forces, displacement-based design begins by specifying a maximum acceptable displacement and then determines the forces that condition causes.16 Displacement-based design will probably eventually replace the current method of force-based design. Performance-based Seismic Design, which has considerably more ramifications for architects and their clients, is the second new design approach. FEMA 349 offers an explanation The concept of Performance-based Seismic Design (PBSD) is to provide engineers with the capability to design buildings...

M Tomazevic I Klemenc P Weiss

ABSTRACT The efficiency of improving the seismic resistance of heritage masonry buildings by means of seismic isolation and strengthening of structure with CFRP laminate strips has been investigated. Five models of a simple two-storey brick masonry building with wooden floors without wall ties have been tested on the shaking table. Besides control model, two models, isolated by either damp proof course or seismic isolators, have been tested. Models four and five have been strengthened with CFRP laminate strips, simulating the wall ties placed horizontally and vertically at floor levels and corners of the building, respectively. One of the CFRP strengthened models has been placed on seismic isolators. Tests have shown that the damp proof course, unless adequately designed, cannot be considered as seismic isolation. The isolators have also not improved the behavior in the case of the building without wall ties. However, both models confined with CFRP strips exhibited significantly...

Building Deformations

The basic design procedure for new structures consists of the selection of lateral forces appropriate for design purposes, and then providing a complete, appropriately detailed, lateral-force-resisting system to carry these forces from the mass levels to the foundations. Although deformations are checked, experience has shown that new structures with modern materials and ductile detailing can sustain large deformations while experiencing limited damage. Older structures, however, do not have the advantage of this inherent ductility. Therefore, control of deformations becomes an extremely important issue in the design of seismic retrofits. Determination of the deformations expected in a structure, when subjected to the design earthquake, is the most important task in seismic rehabilitation design. There are three types of deformations that must be considered and controlled in a seismic retrofit design. These are global deformations, elemental deformations, and interstructural...

The Robustness of Masonry Structures

Robustness is a requirement that all structural engineers must consider in their design work. It was previously implied in many structures which had a cellular form and in which elements were automatically tied to each other as a result of construction practice. The partial collapse of a block of flats at Ronan Point in 1968 led to a change in Part A of The Building Regulations, which required structural engineers working on certain buildings to consider disproportionate collapse in their design. The requirement of clients and architects for lighter structures with cladding systems and open-plan layouts has led to further amendments to the The Building Regulations, Part A. The revised rules specify tying requirements and the building types which must now be designed to meet these rules. Careful design and consideration of these rules should not adversely affect the choice of masonry as a structural material.

Engineering Education

Using masonry as a solution to a design problem will require the masonry industry from suppliers, structural engineers and contractors to rethink their approach to design and construction and to see the many opportunities that structural masonry offers clients, users and the general public.

Alternate Design Philosophy

The principle behind the two-phase approach may be explained by recalling the primary goal in seismic design, which is to provide capacity for displacement beyond the elastic range. Any combination of elastic and inelastic deformations is possible to attain this goal. For example, we could design a structural system that would remain elastic throughout the displacement range. This system would have a high elastic strength but low ductility. Conversely, it is entirely possible to have a system with relatively low elastic strength but high ductility, meeting the same design objective of remaining stable. It may be easier to understand the methodology if it is recognized that a specific earthquake excitation causes about the same displacement in a structure whether it responds elastically or with any degree of inelasticity. This is the approach used in the seismic retrofit design of existing buildings. Since buildings of pre-1970 vintage do not have the required ductile detailing, the...

Bucklingrestrained Braced Frame

Detailing Buckling Restrained

Since BRBFs are a recent development, they are not yet addressed by building codes such as IBC-03 or AISC seismic provisions (AISC 341-02). Therefore, to facilitate wider use of this system, the Structural Engineers Association of Northern California (SEAONC) has developed, in conjunction with the SEAOC seismology committee and AISC TC9, a set of design provisions. Their work has resulted in a document, Recommended Provisions for Buckling-Restrained Braced Frames (SEAONC 2001). The provisions are currently under review for inclusion in future building codes and seismic provisions.

Seismic Rehabilitation of Existing Buildings

Failure of nonstructural architectural elements can also create life-threatening hazards. For example, windows may break or architectural cladding such as granite veneer with insufficient anchorage may separate from the building, causing injury to pedestrians. Consequently, a seismic retrofit program should explore techniques for dealing with nonstructural components such as veneers, lighting fixtures, glass doors and windows, raised computer access floors, and ceilings. Similarly, because damage to mechanical and electrical components can impair building functions that may be essential to life safety, seismic strengthening should be considered for components such as mechanical and electrical equipment, ductwork and piping, elevators, emergency power systems, communication systems, and computer equipment.

Distribution within the Structural Floor

Electrical and communications wiring may be embedded in the floor slab in conventional conduits. For greater flexibility in buildings where patterns of use are likely to change over time, systems of cellular steel decking over steel framing, or cellular raceways cast into a topping over concrete slabs, may be selected. These provide a treelike structure The trunk is a wiring trench that runs from the electrical closet to the outside wall of the building, and the branches are the hollow cells that run in the perpendicular direction. Electrical and communications wires and outlets can be added, removed, or changed at any time during the life of the building. Cellular steel decking can affect the layout of the beams and girders in a steel-framed building For optimum distribution of wiring, the cells in the decking generally run parallel to the wall of the core, and for structural reasons the cells must run perpendicular to the beams. This requires close coordination among the architect...

Deformation Compatibility

The 1994 Northridge earthquake taught a number of lessons in seismic design, one of which is the importance of satisfying the so-called deformation compatibility requirement. This requirement, extensively revised in 1997 UBC after observations from the Northridge earthequake, strives to achieve parity in seismic performance of framing elements and connections not required by design to be part of lateral-force-resisting systems, with those required by design. This is because we know now, from the Northridge earthquake, that even in a building with a properly designed and detailed lateral system, collapse can occur if all structural elements are not capable of deforming with the building during the event. Likewise, if certain nonstructural elements in the building are not capable of deforming with the building, the resulting falling hazards may threaten life safety or impede egress from the building.

Preface to the Third Edition

The original Structural Masonry Designers' Manual was viewed by many in the industry as a seminal reference for structural engineers designing masonry structures. The authors were founding members and directors of Curtins Consulting Engineers, a civil engineering consultancy practice, which was synonymous with the innovative and creative use of structural masonry in the latter part of the last century (1970s onwards). Both Bill Curtin and Gerry Shaw were educated in the old way which consisted of working by day and studying by night. This engendered a passion for their subject, which is evident in the previous editions of this book. One major change is the transition from British specifications for materials to European Standard specifications. European specifications are based on performance criteria rather than prescriptive criteria and this will require structural engineers to be more aware of the materials that they specify. Many changes have taken place in masonry construction...

Figure 207

Successful seismic design of frames requires that the structures be proportioned so that hinges occur at locations that least compromise strength. For a frame undergoing lateral displacement, such as shown in Fig. 20.8 , the flexural capacity of the members at a joint (Fig. 20.8 ) should be such that the columns are stronger than the beams. In this way, hinges will form in the beams rather than the columns, minimizing the portion of the structure atfected by nonlinear behavior and maintaining the overall vertical load capacity. For these reasons, the weak beam-strong column approach is used to design reinforced concrete frames subject to seismic loading.

Panel Zone Effects

Typical Bending Moment Diagrams

Structural engineers involved in the design of high-rise structures are confronted with many uncertainties when calculating lateral drifts. For example, they must decide the magnitude of appropriate wind loads and the limit of allowable lateral deflections and accelerations. Even assuming that these are well defined, another question that often comes up in modeling of building frames is whether or not one should consider the panel zones at the beam-column intersections as rigid.

Reentrant corners

Seismic Collectors Entrant Corners

Buildings that have suffered seismic damage due to re-entrant corners occasionally feature in earthquake reconnaissance reports. Although re-entrant geometries can take many shapes, what they share in common from a seismic design perspective, is their potential for damage resulting from the different dynamic properties of each wing (Fig. 8.10). For example, when the building in Fig. 8.11 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 depth and inherently greater horizontal stiffness. The more flexible wing moves further and at a different period of vibration. It swings about the stiffer area, possibly damaging floor diaphragms at the junction of the two wings. As a result of the large horizontal deflections, the right-hand end columns of the right-hand wing might also sustain damage. Effectively, the right-hand wing is subject to...

Tall Buildings

The intent in seismic design then is to limit building movements, not so much to reduce perception of motion but to maintain the building's stability and prevent danger to pedestrians due to breakage and falling down of nonstructural elements. The earthquake hazard is also highly dependent on the geographic region. The effects of earthquake are relatively small for very tall buildings in all regions of the world, including the seismic area of California. The flexibility of a very tall building of, say, 80-plus stories generally allows the building to sway back and forth to the ground motions without developing forces nearly as large as those produced by design wind loads. Therefore, even in a severe seismic area, tall building design is generally controlled by wind loads. However, even then the detailing of the building components and connections should conform to seismic design requirements. This is because the actual seismic forces, when they occur, are likely to be significantly...

Approaches

Shear Failure Tower

2, we now step back and take a wider perspective to examine the current philosophy of seismic design. This chapter begins with a brief historical overview of earthquake resistant design, outlining some of the key developments directly relevant to the seismic design of buildings. This is followed by a review of the philosophy of seismic design as generally adopted internationally. Several important architectural implications are briefly noted before a concluding discussion on ductility. Ductility, one of the principal concepts of contemporary seismic resistant design practice, was introduced in Chapter 2. Its application for each of the main structural seismic resisting systems - structural walls, cross-braced frames and moment frames - is described in Chapter 4. However, before that detailed examination of ductility this chapter explains in general terms how architects and structural engineers achieve ductile structures that is, structures that endure earthquake shaking strong enough...

Plan layout

Figure 9 Large longitudinal displacements of bridge span causing damage to abutment during the 2001 Bhuj Earthquake in India (courtesy of Dr. Kerstin Pfyl-Lang and the Swiss Society for Earthquake Engineering 'SGEB') Figure 9 Large longitudinal displacements of bridge span causing damage to abutment during the 2001 Bhuj Earthquake in India (courtesy of Dr. Kerstin Pfyl-Lang and the Swiss Society for Earthquake Engineering 'SGEB')

Selected References

Farzad Naeim, ed., The Seismic Design Handbook. New York Van Nostrand Reinhold, 1989. 17. N. M. Newmark and E. Rosenblueth, Fundamentals of Earthquake Engineering. Englewood Cliffs, NJ Prentice-Hall, 1971. 59. Seismic Design Guidelines for Upgrading Existing Buildings, PB 89-220453. Departments of the Army, the Navy, and the Air Force, Washington, DC, 1988. 62. Recommended Lateral Force Requirements and Commentary (Blue Book), 7th ed. Seismology Committee, Structural Engineers Association of California, Sacramento, CA, 1999. 67. 2000 IBC Structural Seismic Design Manual, vols. 1, 2, and 3. Structural Engineers Association of California. ICC Publications. 68. S. K. Ghosh, Seismic Design Using Structural Dynamics, in 2000 International Building Code. ICC Publications. 72. Wai-Fah Chen and Charles Scawthorn, eds., Earthquake Engineering Handbook. ICC Publications. 73. Yousef Bozorgnia and Vitelmo V. Bertero, eds., Earthquake Engineering From Engineering Seismology to Performance-Based...

Case Studies

Building Standard Height Per Floor

The main purpose of this section is to introduce the reader to various structural systems normally considered in the design of tall buildings. Presently it will be seen that design trend is toward using composite systems that include such components as megaframes, interior and exterior super-braced frames, spine structures, etc. The case studies highlight those aspects of conceptualization that are timeless constants of the design process and are as important for understanding structural design as is the latest computer software. The case histories are based on information contained in various technical publications and periodicals. Frequent use is made of personal information obtained from structural engineers-of-record. Figure 8.6. MTA headquarters, Los Angeles (a) building elevation (b) typical floor framing plan. Architects McLarand Vasquez & Partners, Inc. Structural engineers John A. Martin & Associates, Inc., Los Angeles.

Types of Foundations

Two Story Building Sections

Houses and small frame buildings do not need complicated foundation systems. A simple inverted-T foundation is all that is normally needed to support the structure under normal conditions. Larger and more complex buildings impose a heavier burden on the foundation system and need to be carefully designed by structural engineers. Foundations for large commercial buildings perform the same functions as those for light-frame structures. The main difference in the foundations for a commercial building and that for a small residence is often the thickness of the concrete and the amount of reinforcing steel.

System Selection

Autovideur Bateau

Code requirements define structures by type of construction regarding materials and systems ranging form type I to type V for least and most restrictive, respectively, of the Uniform Building Code (UBC) for example. Each type of construction has requirements for fire resistance, maximum allowable floor area, building height, and occupancy group. Codes also have detailed requirements regarding seismic design notable structures are categorized by ductility to absorb seismic energy and related height limits. Some code requirements are related to other criteria described in the respective section.

List of contributors

Parke, University of Surrey, Guildford M. J. Ryall, University of Surrey (retired), Guildford N. E. Shanmugam, National University of Malaysia P. Tindall, Hyder Consulting (UK) Ltd, London P. A. Thayre, Atkins Global, Epsom P. R. Vassie, University College London, London M. Wells, Techniker Ltd, Consulting Structural Engineers, London M. Xu, Tsinghua University, Beijing

News

Aibara followed the event by introducing TPS colleague Dr Colin Morrison at a meeting of the Institution of Structural Engineers in April. The presentation, on the subject of Design for the effects of Blast on Glazed Facades was held at the University of Surrey, England.

Renovation Building

The LEED rating system recognizes the benefits of building reuse by awarding up to three points for maintaining 100 of a building's exterior and 50 of the interior structure, excluding non-structural roof materials and windows. It's often necessary to replace or upgrade a roof, and of course, you may want to install more energy-efficient windows in the building (replacing windows is harder for historic renovations). One drawback older buildings were designed long before we knew much about earthquake engineering. So, in seismically active zones, there is often a significant cost associated with structural reinforcement to protect people and property in the case of an earthquake.

Contractor

Traditionally, architects communicate their design intent to the contractor through plans and specifications. The success of this approach depends on the clarity with which information is presented, the care with which the contractor reads the contract documents and the degree of familiarity the contractor has with the construction detailing as drawn. Where contractors are not familiar with aspects of seismic design and detailing the seismic safety of buildings may be jeopardized. explain what Capacity Design is and how it has been incorporated into the structural design. Consider revising Table 13.2 to customize it for your project and use it as a checklist. Not only do contractors appreciate being informed and are empowered by this knowledge but they discover like all of us that, from time-to-time some of their long-held assumptions need revision. Seismic design is more sophisticated and the performance of seismic resistant structures more sensitive to construction variations than...

Expected Results

The PROHITECH project is an important opportunity to develop knowledge and technology in the field of the seismic protection of the Euro-Mediterranean cultural heritage (Mazzolani 2007a, b). The innovative character of the technical solutions proposed for seismic retrofitting is mainly based on the concept of RMTs. The main expected results of the research activity are the following. New and up-to-dated information on the problem of seismic protection will be disseminated, thanks to the participation of acknowledged institutions, belonging to both Europe and Mediterranean basin, all of them widely experienced in the field of seismic design and with an ongoing significant research activity in such area. Young engineers and architects, as well as researchers involved in seismic design, will have the opportunity for a qualified training and research activity, aimed at an enrichment of existing skills in the field of structural engineering.

Peter Clegg

The bulk of the buildings are therefore built into the earth. One simple rectilinear building, however, floats free from the hillside and helps enclose a funnel-shaped arena which forms the entrance to the site. A canopy stretches across this trapezoidal-shaped space and shelters the ticket booths and main entrance area. The canopy designed with Atelier One Structural Engineers is a distorted timber space frame (Figure 11.3) constructed using roundwood poles of indigenous softwood with galvanised steel connectors.

The engineer

'I am not a person who says engineers are a curse on you the most exciting structures are combinations of architects and engineers structural engineers are nearly always creative, as are civil engineers. But traffic engineers - they have become the bogeyman - their strict adherence to codes and rules without thinking of their consequences is the problem. Think of Calatrava today or Brunel, Eiffel, Roebling, Strauss or Khan.19 'Ah, did you know that in the past a mild form of autism was called engineer's disease ' 'As far as anyone can be blamed for the urban mess it is the highway engineer. They don't understand how people, roads and places work.' 'Engineers are bound by performance measures, codes, standards, criteria, guidelines.' 'Their explicit codes contain an implicit culture.' 'The civil engineer will ask, Will the forces operate correctly They will as long as we have laid down the proper criteria. ' 'They tend to have a belief in an optimum - there is the perfectly functioning...

Ground Shaking

Ground Acceleration Map Loma Prieta

Apart from the poorest of communities for whom even partial earthquake protection is unaffordable, most of the disastrous effects of earthquakes are avoidable. Earthquake-resistant construction greatly reduces the loss of life from a damaging quake, as well as lessening economic losses and disruption to societal activities. Architects and structural engineers achieve earthquake-resistant buildings by following the principles and techniques outlined in this book. These are incorporated into new buildings with minor additional cost. The exact per centage increase in construction cost depends on many factors including the type and weight of building materials, the seismicity of the region and local code requirements. However, it is certainly far less expensive than improving the seismic performance of existing buildings. Some predictions, such as a region's maximum credible earthquake, are incorporated into documents like seismic design codes. Based mainly upon geological evidence,...

Shear walls

Of all seismic resistant structural systems, reinforced concrete shear walls have the best track record. During past earthquakes even buildings with walls not specially detailed for seismic performance, but with sufficient well-distributed reinforcement, have saved buildings from collapse. The success of shear walls in resisting strong earthquake shaking has led some leading structural engineers to recommend them, at least for reinforced concrete construction. For example, Mark Fintel a noted US structural engineer who studied the seismic performance of shear wall buildings over a thirty-year period, concludes 'We cannot afford to build concrete buildings meant to resist severe earthquakes without shear walls.'1

Postearthquake

In the aftermath of a destructive quake in an urban area, thousands or maybe hundreds of thousands of buildings require safety assessments. Beginning as soon as possible after the quake the objective of a rapid safety evaluation procedure is to get people back into safe homes and businesses as quickly as possible, and to keep them out of unsafe structures. Building officials, volunteer structural engineers and experienced architects undertake this work. The ideal is for each building in the affected area to receive a quick yet careful assessment. After noting the observed damage on a rapid evaluation assessment form the assessor posts a placard.5

Seating capacity

Seismic Isolation Stadium

Figure 3.1 An example of a stadium planned for phased development. It is the British 'Stadium for the Nineties' proposal by the Lobb Partnership (now HOK Sport Architecture) in association with the Sports Council and the structural engineers YRM Anthony Hunt Associates. Figure 3.1 An example of a stadium planned for phased development. It is the British 'Stadium for the Nineties' proposal by the Lobb Partnership (now HOK Sport Architecture) in association with the Sports Council and the structural engineers YRM Anthony Hunt Associates.

Damping

It is a common practice to lump different sources of damping into a single viscous type of damping. For nonbase-isolated buildings, analyzed for code-prescribed loads, the damping ratios used in practice vary anywhere from 1 to 10 of critical. The low-end values are for wind, while those for the upper end are for seismic design.

Earthquake Load

Recommended Lateral Force Requirements and Commentary. San Francisco, CA Seismology Committee, Structural Engineers Association of California, Los Angeles, CA, 1990. 1.49. Anil K. Chopra. Dynamics of Structures, Theory and Applications to Earthquake Engineering. Englewood Cliffs, NJ Prentice-Hall, Inc., 1995.

Assessment

As mentioned previously, assessment is the first step in the process of retrofitting. The seismic vulnerability of a building must first be ascertained before deciding whether or not to retrofit. Building assessment usually consists of two stages. An initial or preliminary assessment begins the process. Some countries have developed assessment procedures based upon extensive knowledge of their local building types, construction methods and materials and history of seismic code devel-opments.7, 8 After a brief visual inspection to identify any serious structural weaknesses, such as critical configuration problems, structural engineers 'score' a building, expressing its strength as a percentage

Irregular Buildings

The seismic design of regular buildings is based on two concepts. First, the linearly varying lateral force distribution is a reasonable and conservative representation of the actual response distribution due to earthquake ground motions. Second, the cyclic inelastic deformation demands are reasonably uniform in all of the seismic force-resisting elements. However, when a structure has irregularities, these concepts may not be valid, requiring corrective factors and procedures to meet the design objectives.

Component Behavior

Mechanical components are often fitted with vibration isolation mounts to prevent transmission of vibrations to the structure. By increasing their flexibility, the vibration isolation mounts can alter the dynamic properties of the components, resulting in a dramatic increase in seismic inertial forces. Isolation mounts must be specifically designed to resist these increased seismic effects. For example, 1997 UBC requires the design forces for equipment mounted on a vibration isolator to be based on a dynamic amplification factor, ap 2.5, and a component response modification factor, Rp 1.5. Comparable values for a rigid equipment with supports fabricated of ductile materials attached to rigid mounts are ap 1.0 and Rp 3.0. Since the seismic design force is a function of the ratio ap Rp, all other things being equal, the design force for an equipment with vibration isolation mounts would be five times larger than the design force when it is mounted on rigid supports.

Conversion Factors

This section gives general requirements for structural detailing in concrete. A slight departure from these requirements can be expected because each project is different. Individual structural engineers and designer detailers also influence the style of working drawings and schedules. Moreover, structural detailing in concrete can vary since it can be considerably affected by external requirements including those of authorities such as gas, electricity, water, municipal, etc. Full drawings are prepared by structural engineers acting as consultants as part of the tender documentation. The architects are involved in the preparation of the site and other general arrangement plans. The main contractors are involved in preparation of temporary work drawings, including shoring and formwork. During the contract, drawings are sometimes modified by minor amendments and additional details. These drawings are generally updated as the projects progress. The drawings, which are distributed to...

Moment Frames

Based on test results of more than 150 connection assemblies, the Federal Emergency Management Agency (FEMA) published a July 2000 document titled Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings FEMA 350. This publication allows new prequalifications for connection details believed to be capable of providing reliable service when subjected to large earthquake demands. The criteria given in the publication allow the design of steel moment-frame structures to be performed in a straightforward, select-design-detail method, and are believed to provide the reliability incorrectly assumed to exist in pre-Northridge moment-frame connections. For the majority of structures and conditions of use, the designer is now able to select, design, and detail prequalified moment-frame connections using FEMA 350 criteria without the need to perform project-specific prototype qualification testing. For connection details other than those included in FEMA 350, qualification tests...

Adjacent Buildings

One of the basic goals in seismic design is to distribute yielding throughout the structure. Distributed yielding dissipates more energy and helps prevent the premature failure of any one element or group of elements. For example, in moment frames, it is desirable to have strong columns relative to the beams to help distribute the formation of plastic hinges throughout the building and prevent a story collapse mechanism.

Setbacks

A setback is where a plan dimension of a storey above a certain level in a multi-storey building reduces (Fig. 9.21). Seismic codes categorize buildings with abrupt setbacks as irregular. Sophisticated structural analyses quantify the ' notch effect' of a setback, but even though structural engineers avoid notches wherever possible because of stress concentrations, setbacks can be designed satisfactorily. The need for 3D modelling of setback buildings can be appreciated from Fig. 9.21(b) ' Although the irregular vertical configuration in the x direction can be designed for, y direction shaking induces torsion due to the way the positions of the CoM and CoR change at every setback.