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EARTHQUAKE RESITANT BUILDINGS CONUSTRUCTION AGNIESZKA MACHALSKA

VIA UNIVERSITY COLLEGE DENMARK

Bachelor of Architectural Technology and Construction Management

October 2011


Earthquake resistant buildings construction

© Agnieszka Machalska October 2008

VIA University College, Horsens, Denmark

3rd semester elective subject Bachelor of Architectural Technology and Construction Management Consultant: Leila Kæmsgaard Pagh Schmidt

3 Copies - Bookman Old Style 11

All rights reserved – no part of this publication may be reproduced without the prior permission of the author.

NOTE: This dissertation was completed as part of an Architectural Technology and Construction Management degree course – no responsibility is taken for any advice, instruction or conclusion given within!

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I would like to thank Mrs. Leila KĂŚmsgaard Pagh Schmidt for her helpful advices and support as a consultant.

ABSTRACT This report gives an overview of earthquake resistant construction of buildings. It introduces the nature of earthquake, its distribution and act upon the building construction. The main idea is to present different structures, their seismic response and methods used to improve the design, so it is earthquake resistant. It briefly explains all important steps that have to be taken into the consideration before and during the design process. Starting from the methods of seismic analysis for structures, the determination of site characteristics and ending with detailed description of different structures, their analysing and the choice of best solution.

KEY WORDS: earthquake resistant construction, damages to building, building structures, load distribution, seismic response, seismic analysis

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TABLE OF CONTENTS LIST OF ILLUSTRATIONS....................................................................................4 REPORT BACKGROUND.....................................................................................5 NATURE OF EARTHQUAKE................................................................................6 DAMAGE STUDIES.............................................................................................7 MODIFIED MERCALLI SCALE AND EMS............................................................9 SEISMIC CODES .............................................................................................10 EARTHQUAKE RESISTANT DESIGN.................................................................11 FRAME TYPES FOR STRUCTURAL SYSTEM.....................................................13 SHEAR WALLS.................................................................................................16 CLOSELY LOOK ON THEORY IN PRACTICE...................................................16 SUMMARY OF WORKING PROCESS.................................................................20 CONCLUSION...................................................................................................20 REFERENCES..................................................................................................21

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LIST OF ILLUSTRATION

Fig. 1 Earthquake sources location (Booth and Key 2008, p.21)........................................................7 Fig. 2 Modified Mercalli scale............................................................................................................9 Fig. 3 A SYNOPSIS OF THE EUROPEAN MACROSEISMIC SCALE (EMS 98)………………………10 Fig. 4 Categories of function within a building (Booth and Key 2008, p.97)...................................11 Fig. 5 Soil classification from Eurocode 8 (Booth and Key 2008, p.98-99)....................................12 Fig. 6 Moment-resisting frame types: (a) grid frame (b) perimeter frame (Booth and Key 2008, p.105).................................................................................................................................................14 Fig. 6 (Booth and Key 2008, p.107)..................................................................................................15 Fig. 8 Eccentrically braced frames (Booth and Key 2008, p.109)...................................................15 Fig. 9 Knee-braced frame (Booth and Key 2008, p.110).................................................................16 Fig. 10 The Archive of Historical Earthquake Data (AHEAD) contains data on all the most significant damaging historical earthquakes in Europe. Here large and extra large earthquakes in 1900-1963..17 Fig. 11 Number of Earthquakes Worldwide for 2000 – 2011………………………………………………..17 Fig. 12 Largest and Deadliest Earthquakes by Year 2000-2011…………………………………………..18 Fig. 13 Data from USGS PDE data base.............................................................................................18 Fig. 14 Recent earthquakes map (USGS)...........................................................................................19 Fig. 15 Van, Turkey; October 23rd,2011...........................................................................................19

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REPORT BACKGROUND This report was written as a part of the 3rd semester of the education as Bachelor of Architectural Technology and Construction Management. I decided to focus on the topic relative to the Structural Design classes. Design and technical aspects are taken into consideration. During the design phase it is relevant to make sure that a building not only looks well but mainly is sustainable. The architectural and engineering profession always have to cope with earthquakes dilemma. The earthquake risk covers almost entire globe, social and economical consequences are enormous. We cannot influence on the natural physics processes, but we can improve design of the buildings to bring down aforesaid consequences. I find it crucial and interesting. At the same time as a 3rd semester student I have bigger knowledge about structures in the buildings. That is why I want to take a closely look on the earthquake resistance in constructions.

PROBLEM STATEMENT What exactly is involved in designing buildings that are earthquake resistant or earthquake proof?

DELIMITATION In this report I focus mainly on Europe, however, include other continents in my researches. I examine different types of structures, materials and components in a buildings and theirs interaction with seismic loads. I want to find what kind of problems in building construction may be caused by earthquake (mainly passed experience) and what can be done to create earthquake resistant structures.

RESEARCH QUESTIONS     

What is the effect of earthquakes on the building structures? Which forces have an effect on the building during earthquake and how do they deform its structure? What building construction materials are used for earthquake resistance? How do such materials react to earthquake vibrations and earth movements? What specific examples of earthquake resistant engineering can I document - how are earthquake resistant structures actually constructed? 5


RESEARCH METHODS I will use secondary research methods – collecting facts, information and opinion mainly through the internet, books and official documents.

WORKING METHOD I divide report on two main parts – theoretical and practical. After gaining knowledge from theory I will examine practical aspects of the topic.

The death toll caused by earthquake effects is very big every year. Depending on the place on the Earth and sophistication of each country it can be more or less tragic. Only in year 2011 thousands of people died in two serious earthquakes: Tōhoku, Japan and Van, Turkey. Many of them was killed by buildings collapse. Even in well developed and well prepared country like Japan number of destroyed buildings exceeded 100 000. By dint of earthquake resistant construction we could possibly elude similar tragedies.

NATURE OF EARTHQUAKE Engineers have to deal with primary and secondary sources of earthquake damage. First one can be simply described as a violent shaking of the ground. It might affect an area hundreds kilometres in radius and directly effect on building structure. Inertia forces set up by the ground acceleration are dangerous primary damage sources, while secondary sources might occur. I want to mention the most serious once like the collapse of one structure on another, the outcome due to fire following the earthquake. The release of noxious chemical and radioactive materials may also arise, but it does not cause major problems.

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Sudden release of energy in Earth’s lithosphere begins surface movements at planes of weakness or fractures in the crust. The points where failure occurs are called fault planes. Focus is where the failure starts.

Fig. 1 Earthquake sources location (Booth and Key 2008, p.21)

We can define strength of the earthquake by two measures. Intensity – shaking strength at any given place on the Earth’s surface, describe by earthquake effects on people and buildings and magnitude – size of event itself. The larger the epicentre distance the lower intensity. Magnitude as a quantitative measure of earthquake size is not directly related to the released energy and is independent of the place of observation.

DAMAGE STUDIES Apart from the knowledge about earthquakes gained from reading, the experience should be the base for stating the conclusions. Engineers always take closer look on the past events. Importance of post-earthquake feedback for designers is hard, because they have to know a set of design rules and feel what may happen to their construction. We have to remember that laws of nature do not respect theories and calculations. It means that even minor faults in construction like wrongly placed reinforcement, poorly compacted concrete, fallen masonry blocking escape paths, window frames separating from wall etc. may put lives at risk. Ground behaviour during and after earthquake is very important, mainly because its huge impact on piles, underground pipelines and installations, however, I will focus more on what happens to the particular constructions. Starting with structural collapse it might be result of torsional or lateral displacement, foundation movements and local failure of supporting members. In many cases although the building has not collapsed it is damaged so badly it must be demolished. Whether it does not make any difference from economical point of view (insurance, costs etc.) it is crucial for people who occupy the building. 7


Based on observations we can come up with a few findings and principles. Firstly buildings placed close or connected with movement joint during the earthquake will pound against each other. That is why the closeness of buildings (especially in case of floor levels differ), flexibility of structures is so relevant while designing. Secondly appendages to buildings (penthouses, cladding, masonry parapets, roof tanks) tend to act faultily. Moreover designer has to remember that sometimes the contents of building have greater value and importance than the building itself. Then it is important to avoid the contents damage. Unfortunately the situation where the building is relatively unharmed itself, but the contents of it suffer major damage is often, especially in more flexible buildings. Proper tying varying components can slow down or even prevent the failure in the buildings. Lack of tying is quickly exposed by earthquake shaking, for example in older buildings timber floor joist are poorly tied to supporting walls. What is more, failures are commonplace also in anchorages of components into masonry or casted-in concrete. It happens, because they are almost invariably fragile in tension and shear, in this manner unable to accommodate any movements. Lets draw out brief conclusions about different types of construction. It is proved that reinforced concrete beams and columns frames which are not braced by walls in a building are highly vulnerable to earthquakes. Failure of beam-column joints, bursting failures in columns and shear failure in columns, anchorage failure of main reinforcing bars in beams and columns are main reasons for vulnerability of this construction. In contrast shear walls which provide contribution to lateral resistance are less vulnerable. Clear example from 1988 in Armenia where precast concrete wall buildings survived without endangering their habitants (but suffered in compression failure of outer edges), while precast concrete frame buildings suffered total collapse. Structural steelwork suffers more from earthquakes. Common types of damages showed by structural steel work are brittle failure, member buckling, uplift of braced frames, local failure of connection element, bolt slip, high deflections in unbraced frames and failure of connections between steel elements and other building members. It is a lot different in failures of unreinforced masonry. Because they are so common they are taken for granted. European codes allow low-rise unreinforced masonry housing as long as stringent conditions are met during US codes ban the use of unreinforced masonry. Nevertheless, it is still widely used in due to economic reasons. The way the masonry construction perform depends on its type. Random rubble and adobe masonry (poor areas) perform the worst, so 100% of destruction can be expected. In big official building where the good quality rock blocks the total collapse is less possible, but they may suffer from damage. However, the ability to remain stable after experiencing cracking in good-quality masonry is impressive. Next type, free-standing masonry is liable to toppling failure which may be reduced by mechanical connections at the sides and head of a wall. Other very common failure in-plane for both reinforced and 8


unreinforced masonry. Because it is very stiff in-plane, the forces transmitted by ground shaking are high. It can either collapse or “x” crack and of course damage will be often worse around openings. Timber seems to have best performance when we talk about earthquake resistance. The reason why is good tensile strength a favourable strength-toweight ratio. On the other hand, timber as a organic material is susceptible to parasites attack and fungal decay which can totally reduce seismic resistance. Besides, the fire - dangerous, secondary source of earthquake arise more often in cities with timber houses. I have to also mention the base for every building – foundation. Its failure is mainly a result of failure of the supporting soil (while liquefaction the soil loses its shear strength). Even though the failing soil is unable to transmit strong shaking to the structures, its failure can cause gross settlement. “At any level on a multi-storey building the ground motion will be modified by the motion of the building itself.” What we know by now is that suspended non-structural elements like ceiling or light fittings, appendages (parapets) perform badly. If any very stiff content or the one with natural frequency of own close to that of building suffers from greater forces than the one would be mounted at ground level. That is why we know that damage increases towards the roof on multi-storey structures, where penthouses and roof tanks are subjected to high forces. But when we are talking about non-structural elements failures due to not only the inertia forces but also to relative displacement can appear. If there is no provision for movement, then elements connected to more than one level (cladding, windows) will fail.

MODIFIED MERCALLI SCALE AND EMS (98) I do not find it necessary to review different seismic scales, however, MM EMS are two scales I want to focus on. They are very important, while talking about construction vulnerability. Briefly about MM: it measures earthquake intensity and scale effects of an earthquake on the Earth’s surface, humans, objects of nature and man-made structures.

Fig. 2 Modified Mercalli scale

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MM contains twelve intensities, still only VI-XII are important for us, because MM6 (VI) is when slightly damage may occur in construction and MM12 (XII) means total damage. EMS (98) – European Macroseismic Scale, which final version was ended at 1998, is mainly created for better co-operation between seismologists and engineers.

Fig. 3 A SYNOPSIS OF THE EUROPEAN MACROSEISMIC SCALE (EMS 98)

SEISMIC CODES Seismic codes are essential tool for seismic designers and they establish minimum requirements. For example in US the IBC code is used, in Europe – Eurocode 8. Because the requirements are very similar in other codes I will mainly focus on European system. The codes specify how to calculate a minimum lateral strength which later on is applied to the structure. The lateral strength requirement is calculated with below parameters: building mass, basic seismicity, earthquake type, site classification, building function, structural factor and building period. Building mass is simply sum of structural mass arising from dead load and live load. Basic seismicity means “the design peak ground acceleration expected on rock sites, for return period of 475 years”. Earthquake type in Eurocode 8 is given as two site types – dominated by large-magnitude earthquakes and 10


by smaller-magnitude but closer events. The national annex for this shows which of the design response spectrum shapes apply to particular region. For building function the specific factor is used to multiply the design ground acceleration on the rock. It is very important, because some of the buildings like emergency hospitals might need better protection during an earthquake. Besides that codes include requirements for strength, deflection (storey drifts) to limit damage to non-structural elements, detailing to ensure adequate ductility, foundation to make sure that “the intended plastic yielding can take place in the superstructure without substantial deformation occurring in the foundation�, non-structural elements and building contents to make sure that items attached to more than one part of structure can stand deformation. Load combination (Ed – design action effect) in Eurocode 8 is unfactored combination of dead, earthquake and reduced amount of variable loads (live or snow). Seismic loads does not include wind loads.

EARTHQUAKE RESISTANT DESIGN All the decisions made during conceptual phase of the design are later on difficult to change so their performance understanding is important from the very beginning. It is useful to find out the principal analysis of functions and how they affect the structural skeleton. One of the principals considers it in vertical direction

Fig. 4 Categories of function within a building (Booth and Key 2008, p.97)

Establishing of optimum locations for service cores and for stiff structural elements continuously to the foundation at early stage is main aim. Not only for seismic design, but in general essential thing at the basis of it is to obtain data on the soil conditions and ground water level at the site, because it has major influence on that design. The data must be made sufficing so the site might be classified into standard profile, described in codes. 11


Fig. 5 Soil classification from Eurocode 8 (Booth and Key 2008, p.98-99)

The next thing should be considered while designing is structural layout. Observations and experience show that well tied buildings with well-defined, continuous load-paths to the foundation perform better during earthquakes. Also the degree of symmetry meaningful for earthquake resistance. Damages caused by earthquake are found to be five to ten times finer in essentially regular structures, compared to those with definite irregularity. It is mainly because sudden changes cause concentration of stress and potential failure points. The gratest possible regularity, compactness and torsion resistance should be considered for the layout of the lateral load-resting vertical elements. Moreover, separation joints should be provided for irregular plan shapes which should be divided into compact shapes. Masses placed lower down produce less unfavourable effects than the masses placed high in the building. It is implied by the characteristic swaying mode of building during earthquake. Where it is possible the heavy plant rooms and massive roofs should be avoided. The adequate reserve to meet an extreme earthquake attack without collapse is also needed. Here the main focus is ductile and brittle responses. “A ductile 12


structure is one that can maintain its stability under repeated cyclical deflections considerably greater than its yield deflection. The ductile structure therefore resists the extreme earthquake not by brute force, but by allowing plastic deformations to absorb the kinetic energy induced by the ground shaking. (...) There are two principal means of ensuring ductility. First, the capacity design procedures should be used to ensure that yielding takes place in ductile rather than brittle modes. Second, special detailing is needed to ensure that parts of the structure designed to yield can achieve large post-yield strains. An example is the provision of horizontal confinement steel in columns. Consequently relative horizontal deflections within a building must be limited due to movements and damage of non-structural elements. Besides, sometimes columns in a building might be only designed to resist gravity loads. Then if the seismic loads are taken by other elements, but deflections are too great they will fail, even though they are ductile. Likewise, overall deflections may impact across separation joints within a building and between buildings so that is why should be also limited. Finally, my focal point in conceptual design – structural system. Here the choice of structural material is essential. We already know that concrete has an unfavourable low strength-to-mass ratio and that columns and beams made of it are often brittle in compression and shear. Nevertheless, correct and detailed design may provide excellent ductility in flexure and in compression. Brittle buckling modes of failure are much less likely than in steel. Diversely to concrete strength-to-mass ratio it is high for steel which is obvious advantage over concrete because seismic forces are generated inertia. That also makes steel ductile in both flexure and shear. Masonry suffers from same ratio as steel, but not exhibit ductile failure modes but good-quality stone is very strong in compression. But masonry unlikely steel and concrete structures must be designed elastically to have a big reserve against design earthquake forces, without reliance on ductility. Timber as mentioned before is light and strong, however, as a organic material is quite prone to rack.

FRAME TYPES FOR STRUCTURAL SYSTEM Moment-resisting frames derive their lateral strength from the rigidity of the beam column connection. They consist horizontal beams and vertical columns, commonly use for steel and concrete construction. When choosing overall slenderness seismic and wind loads must be considered, because very slender structures tend to deflect in excessive storey drifts and overall movement. There are two types of unbraced frames: grid frame and perimeter frame. Grid frames are highly redundant and achieve good spread of resistance to seismic forces. “They comprise a uniform grid of frames in both directions. They have very good torsional resistance and coupled lateral response is unlikely to be a problem, even with irregular plan shapes.� Unfortunately, we can find few 13


disadvantages of grid frames. All columns and beams must be designed and detailed for ductility and all columns for biaxial loads. Thus the architectural planning might be tougher and internal spacing may be decreased. Grid frames are commonly used in low- and medium-rise buildings with any shape. Second type of the system is called perimeter frame. In that case internal structure must be able to carry only gravity loads so the spacing between columns can be increased and that creates greater architectural freedom. If the building is rectangular shaped the corner columns suffer from the problems of biaxial loading and possible uplift, while circular plan shapes are less affected by that problem. This type of framing is mainly used for mediumand high-rise buildings with compact plan shape. If we want the high-rise structure to be economical, we should use steel as a structural material.

Fig. 6 Moment-resisting frame types: (a) grid frame (b) perimeter frame (Booth and Key 2008, p.105)

Concentrically braced frames (CBFs) are constructed in a way that the centre lines of the bracing members cross at the main joints in the structure which minimise residual moment in the frame. The advantages and disadvantages of braced framing are opposite to moment framing. The stiffness and strength is provided at low cost, however, ductility is limited. Bracing can also restrict architectural planning.

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Fig. 7 (Booth and Key 2008, p.107)

Eccentrically braced frames (EBFs) members are arranged in such a way they are separated to meet eccentrically. Between those ends the weak, but ductile link is created so it yields before any of other frame members. It is relatively short so the elastic response of the frame is similar to the CBF. The difference is that EBFs end provides much greater ductility and helps avoiding problems of buckling and irreversible yielding. An alternative for EBFs is the knee brace which stay stiff and elastic during earthquakes, but also provides ductility and protection from buckling in extreme events. The big advantage of knee brace is the fact that it can be removed and replaced if damaged after earthquake, because it does not form part of the main structural frame.

Fig. 8 Eccentrically braced frames (Booth and Key 2008, p.109)

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Fig. 9 Knee-braced frame (Booth and Key 2008, p.110)

SHEAR WALLS Shear walls, also known as a structural walls and their flexure behaviour is usually more important than shear behaviour. By shear walls the strength and stiffness is provided by low cost. The excellent behaviour is observed in concrete shear walls, because they are not prone to “pancake” collapse. Overall, shear walls avoid the stress concentration found at the beam-column joint regions. If the ductility is needed it may be found in slender shear walls. Moreover stocky shear walls exist and they might not make ductile, however, the need for ductility is reduced by their large potential strength. Nevertheless, stocky shear walls may need diagonal steel to overcome problems like failing in brittle failure modes (diagonal tension, sliding shear).

CLOSELY LOOK ON THEORY IN PRACTICE Having bigger knowledge about earthquakes impact on different construction I want to verify how the theory is used in practice. First of all I decided to examine different organizations, departments cooperating with governments and so on. Primarily I expected to find enormous amount of information, maps, visualisations and statistics. At the beginning of my report I was explaining the importance of past events and gained experience for future improvement. To do so we need sure-footed data. I looked for it at AHEAD’s website. AHEAD stands for The Archive of Historical EArthquake Data and it contains on all influential historical earthquakes in Europe for the period 1000-1963.

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Fig. 10 The Archive of Historical Earthquake Data (AHEAD) contains data on all the most significant damaging historical earthquakes in Europe. Here large and extra large earthquakes in 1900-1963.

While reading about AHEAD I found out that it is also part of Seismic Hazard Harmonization in Europe. SHARE is a Collaborative Project in the Cooperation program of the Seventh Framework Program of the European Commission. The project aims to establish new standards in Probabilistic Seismic Hazard Assessment (PSHA) practice by a close cooperation of leading European geologists, seismologists and engineers.

Above-mentioned projects and organizations are focused on Europe. Unlike them USGS program was made to reduce effort in earthquake hazard in United States. Nonetheless, worldwide information can also be found there. For example exact statistics like number of all earthquakes, largest and deadliest earthquakes worldwide. Moreover, maps and visualisations giving very good overview of earthquakes, their hazard in US and the rest of the world. Fig. 11 Number of Earthquakes Worldwide for 2000 – 2011

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Fig. 12 Largest and Deadliest Earthquakes by Year 2000-2011

Fig. 13 Data from USGS PDE data base

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Fig. 14 Recent earthquakes map (USGS)

Later on I tried to find some useful detailed information about one of the tragic earthquakes from 2011 I already mention. On a website where they collect all reports I came across CEDIM’s report about passed earthquake in Van, Turkey. It was updated on 25th of October, only few days after tragedy. The size of death toll was not surprisingly big, however, 2262 buildings were destroyed. What even more shocking for me is that as a report says “…collapses of schools remains a critical issue in Turkish earthquakes…”. In my opinion, since KOERI (Kandilli Observatory and Earthquake Research Institute) exists, there should be more focus on buildings damage and collapse prevention. Even if the country has to cope with economical problems, but at the same time there is a risk of the high intensity of earthquakes, according to codes, public buildings should be protected even better.

Fig. 15 Van, Turkey; October 23rd,2011

Finally, one of the books I studied to write this report was written basically according to standard in New Zealand. Therefore, I was trying to find detailed information about the serious earthquake in Chrischurch, NZ from February 22nd, 2011. Luckily, I found a interview about structural 19


damage to buildings with Ziggy Lubkowski who is Arup's seismic business and skills leader. When asked about dependence between magnitude of the event (6,3Rs) and size of destruction, Lubkowski says that damages where relatively bigger than after previous, stronger (7,1Rs) earthquakes, however, event occurred very close to built-up area. I also agree on the stated opinion that upgrading old buildings all around the world is currently serious issue. Nevertheless, it must be solved, because the fact that those building survived past events does not mean the same will happen in the future. We have to remember that every additional seismic load put on the building may easily cause graduating damages which is even more dangerous. As Lubkowski said, the forensic examination must be made before official judgment why so many buildings collapsed in Chrischurch. But what he is sure at the moment, shaking level exceeded design codes. Simply, the motion of the earthquake was much more stronger than the buildings were designed for. It is basically because the buildings are not designed for the strongest earthquake (financial reasons). Main aim is just to design the structures in a way the people will survive. As long as it is possible the requirements are fulfilled, even if the damage is beyond repair. “Generally speaking liquefaction won’t cause collapse; you might get settlements, buried structures may float, but it doesn’t cause collapse. There are different ways in which you can deal with that. You can build things to accommodate those kind of effects or you can improve the ground but again that starts to become very expensive. “ Lubkowski thinks that it is not necessary to focus on liquefaction problem in Chrischurch, the only exceptions might be hospitals etc.. What is more, it has nothing to do with damages caused in a discussed event, because it is more relevant for design itself not for earthquake resistance.

SUMMARY OF WORKING PROCESS Before actual writing the report I firstly made a researches. After collecting as much as possible I had to select the sources of information which are the most trustworthy. The writing process began with theoretical part of report. Later on I look trough all practical things like statistics, experts’ opinions etc. to be able to compare them with the knowledge I gained while writing theory part.

CONCLUSION I have finished my report which is an elective subject in the 3rd semester Constructing Architect degree course. I have come across many facts that will be useful for my future career as a constructing architect. First, the overall knowledge about earthquakes and negative effects caused by them for different 20


construction. I also understood why it is important for earthquake resistance to take into consideration past events and what kind of conclusions and future solutions I may arise. I gained knowledge about seismic loads and their influence on different material types. Moreover, I know now which documents I need for detailed conceptual resistant design. I found different opinion about the issue, with some of them I agree, on the other hand I found few of them subjective.

REFERENCES BOOKS “Earthquake design practice for buildings”, E.Booth and D.Key, second edition, 2008, thomastelford “Earthquake resistant building design and construction”, N.B.Green, third edition, 1987, Elsevier “Earthquake resistant design and risk reduction”, D.Dowrick, second edition, 2009, Wiley

INTERNET 1. http://www.nerc.ac.uk/press/releases/2011/09-earthquake-experts.asp (October 27,2011) 2. http://www.bgs.ac.uk/research/earthquakes/yesterdaysearthquakes.html (October 27,2011) 3. http://www.emidius.eu/AHEAD/main/?from= (October 27,2011) 4. http://neic.usgs.gov/neis/qed/ (October 27,2011) 5. http://earthquake.usgs.gov/hazards/designmaps/ (October 27,2011) 6. http://www.worldarchitecturenews.com/index.php?fuseaction=wanappln.commentview&co mment_id=246 (October 27,2011) 7. http://www.eeri.org/ (October 27,2011) 8. http://earthquake-report.com/2011/10/25/new-insights-into-the-october-2011-van-turkeyearthquake-detailed-analysis-by-the-cedim-forensic-earthquake-analysis-group/ (October 27,2011)

REFERANCES TO ILLUSTRATIONS

Fig. 1 Earthquake sources location (Booth and Key 2008, p.21) Fig. 2 http://www.geo.mtu.edu/UPSeis/Mercalli.html Fig. 3 http://www.earthquakes.bgs.ac.uk/macroseismics/ems_synopsis.htm Fig. 4 Categories of function within a building (Booth and Key 2008, p.97) Fig. 5 Soil classification from Eurocode 8 (Booth and Key 2008, p.98-99) Fig. 6 Moment-resisting frame types: (a) grid frame (b) perimeter frame (Booth and Key 2008, p.105)

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Fig. 6 (Booth and Key 2008, p.107) Fig. 8 Eccentrically braced frames (Booth and Key 2008, p.109) Fig. 9 Knee-braced frame (Booth and Key 2008, p.110) Fig. 10 http://www.emidius.eu/AHEAD/main/?from Fig. 11 http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php Fig. 12 http://earthquake.usgs.gov/earthquakes/eqarchives/year/byyear.php Fig. 13 http://earthquake.usgs.gov/earthquakes/world/world_density.php Fig. 14 http://neic.usgs.gov/neis/qed/ Fig. 15 http://www.inquisitr.com/153429/turkey-earthquake-239-killed-rescue-efforts-ongoing/

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