1

effect of seismic on soil type

یر الزالزل على نوع تربة التأسیستأث

2

تأثیر الزالزل على األبنیة

Effects of Earthquakes on Buildings Seismic Terminology Ground shaking (pushing back and forth, sideways, up and down) generates internal forces within buildings called the Inertial Force (FInertial), which in turn causes most seismic damage. FInertial = Mass (M) X Acceleration (A).

التسارع× قوى العطالة = الكتلة

The greater the mass (weight of the building), the greater the internal inertial forces generated.

Lightweight construction with less mass is typically an advantage in seismic design

Greater mass generates greater lateral forces, thereby

increasing the possibility of columns being displaced, out of plumb, and/or buckling under vertical load (P delta Effect).

Earthquakes generate waves that may be slow and long, or short and abrupt.

The length of a full cycle in seconds is the Period of the wave and is the inverse of the Frequency.

All objects, including buildings, have a natural or fundamental period at which they vibrate if jolted by a shock

The natural period is a primary consideration for seismic design, although other aspects of the building design may also contribute to a lesser degree to the mitigation measures.

If the period of the shock wave and the natural period of the

building coincide, then the building will “resonate” and its vibration will increase or “amplify” several times.

3

Fig. 4. Height is the main determinant of fundamental period—each object has its own fundamental period at which it will vibrate.

The period is proportionate to the height of the building. یزداد مع ارتفاع البناء دور البناء T The soil also has a period varying between 0.4 and 1.5 sec.,

very soft soil being 2.0 sec. Soft soils generally have a tendency to increase shaking as much as 2 to 6 times as compared to rock.

Also, the period of the soil coinciding -with the natural period of the building can greatly amplify acceleration of the building and is therefore a design consideration.

Fig. 5. Tall –

buildings will undergo several modes of vibration, but for seismic purposes (except for very tall buildings) the fundamental period, or first mode is usually the most significant

4

5

حادثة الطنین في الحركات االھتزازیة من الریاح والزالزل

اءنھي عندما یتساوى دور اھتزازالبحادثة الطنینT1 T2 التربةمع دور اھنزاء

وعوضا عن ان تمتص التربة وتشتت قسم من قوى

وقد تتضاعف قوى العطالة بسبب تساوي الزلزال تزداد

قوى وجھود لحدوث وینھار المنشأ T1=T2 الدورین

داخلیة اكبر من التي صمم علیھا المنشأ عطالة

التربة الصخریة ربالنسبة لتجنب حادثة الطنین و تساوي دوT1

في الریاح والزالزل والحركات االھتزازیة T2 المنخفض مع دور البناء

فھذا یحدث فقط في األبنیة ذات االرتفاع القلیل كما في الفلالت

القلیل كما في األبنیة T الجمل القصیة الجاسئة والدورواألبنیة ذات طایق واحد الى اثنان الحجریة والبلوك

اختیار البناء من الترب الصخریة یفضللذلك في

Tوزیادة دورھا نوع الھیكلي وجملة القص مرنة

لیست جدران قصیة فقط بل إطارات او جمل ثنائیة

لجعل البناء اكثر مختلطة من جدران القص واالطارات

الدور عن دور الترب الصخریة T وتكبیرالدور مرونة

البلوك والطوب یفضل استعمال البناء الحجري اووفي حال

لتجنب وتكتیف الجدران وزیادة المرونة إطارات خرسانیة

حادثة الطنین وتصدع البناء

6

- في حال الترب الرملیة والطینیة ذان الدورT1 العالي

2Tانقاص دورھا العالي البرجیة الىالى العكس في األبنیة نلجأ

وذلك بزیادة صالبتھا واضافة جدران قصیة او تكبیر المقطع

او اضافة مخمدات زالزل لكي ال تحدث عملیة الطنین

T1لیصبح اقل من دور التربة

7

المیاه تأثیر الزالزل على نوع تربة التأسیس و

او تواجد میاه مع الترب وذلك عند تواجد تربة سیئة طینیة

فھذا غیر مرغوب في الزالزل الرملیة او الغضاریة

تربةوخاصة في حیث اھتزاز التربة اسفل اساسات البناء

رملیة مع تواجد میاه

اللبشة سیؤدي الى غربلة التربة وھروب ذرات التربة وفي حال خارج اللبشة وتزداد نسبة المیاه وتمیع التربة لھروب الذرات

مما یزید میالن البناء وحتى انقالبھ وتصدعھ

لذلك غي حال الترب السیئة الطینیة وارتفاع منسوب المیاه وخاصة في حال اللبشة (الحصیرة) یفضل تواجد تقریر تربة

8

یوصي بعمل إحالل واستبدال تربة

من الخوازیق او استعمال اساسات عمیقة

- الى األعماق( حصیرة) مع النزول ویمكن استعمال لبشة مع عدد من طوابق األقبیة

البناء حیث تصبح قاعدة او بناء جدران ساندة على محیط

ذرات التربة خارج األساس كصندوق مغلق یمنع ھروب

حدود قاعدة اللبشة ویمنع حادثة التمیع

whirring incident in the vibrational animations of wind and earthquakes

Incident whirring is when the period T1 of building equal With the period of soil T2 Instead of the soil absorbs and dispersion part of

the earthquake forces But increases and doubles inertia forces becuse of equal The two periods T1=T2 and building collapses to a strong stress internal inertia is greater than that designed the building on

• For an incident to avoid whirring and equal periods

9

Between rocky soil Low period T1 and building period T2 in case wind, earthquakes and seismic animations

This occurs only in buildings with little height as in apartments One floor to two and buildings with rigid shear sentences Where T as small as the period at the stone buildings and blocks

So in the rocky soil prefer to choice of construction structural type and sentence shear flex type, such as frames

not only the shea walls, but frames or joint sentences

Mixed shear walls and frames to make the building more Flexibility and increase the period T from a period of rocky soils

In the case of construction stone or brick blocks ,the prefer to use concrete frames surround walls to increase flexibility

In case sandy soils and clay with a period of higher T1 Resort to the opposite in buildings tower to relieve high period T 2 By increasing the stiffness and adding Shear walls or Maximize section Earthquake dampers or add to whirring process does not occurTo become less than the period of soil

10

effect of seismic on soil type & water

11

12

13

14

And when presence poor clay soil or presence water with sandy soils it is undesirable in terms of earthquakes shake the soil beneath the foundations of the building, especially in sandy soil with the presence of water

In the case of foundation mat will lead to a filtering the soil and the soil particles escape Outside the mat and increasing ratio of water and dilute the soil to escape the atoms And it increases the slope of building even rotation and cracking

Therefore, in the event of poor clay soil and high water levels Especially in the case of (the mat) prefer to presence soil report

recommends doing substitution and replacement of soil Or use of deep foundations Piles

- can be used (mat) with go down to the depths with a number of floors basements

Or the design of walls building supported on the perimeter of the base where they become The foundation a closed box prevents the escape of soil particles outside the boundaries of the base mat and prevents incident liquefaction

15

Dr Youssef Hamid a