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Jazan University College of Engineering
Civil Engineering Department
SEICMIC ACTIVITIES OF JAZAN AREA
Case Study: Seismic Analysis of a Multi-Story R. C.
Building in Abu Arish City
By
Team Members:
Ahmed Mohamed AhmedNashily201110659 Ibrahim Hassan HamedAmri 201020242
Majed Mohamed AbduMashrqy201020256
Supervisor:
AssistantProf. Dr. Ali EltomHassaballa
A Senior Project Final Report submitted in partial fulfillment
of the requirements for the degree of BACHELOR OF Science (B.Sc.), in
Civil Engineering (Completion Date: Dec. 2015)
Jazan University College of Engineering
Civil Engineering Department
SEICMIC ACTIVITIES OF JAZAN AREA
Case Study: Seismic Analysis of a Multi-Story R. C.
Frame Building in AboArish City
APPROVAL RECOMMENDED:
� Examination committee: 1. Prof Dr.HossamEldin Mohamed Sallam 2. Prof Dr.Ahmed Ahmed El-Abbasy 3. Dr.Fathelrahman Mohamed Adam
� PROJECT SUPERVISOR (s)Date
Dr. Ali EltomHassaballa
� DEPARTMENT HEADDate Dr. MohamedMobarki
� COURSE INSTRUCTORDate
APPROVED � DEAN, COLLEGE OF ENGINEERINGDate
Prof. Dr. Jebril Ahmed Khamaj
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I
ABSTRACT
Jazan area is located in the most active seismic zone region of the Kingdom
of Saudi Arabia where there is a complicated geological structures and
tectonics. This project reviews the seismic activities occurred in Jazan area
together with reviewing the Saudi Building (Seismic) Code (SBC-301-
2007). A multi-story reinforced concrete building in aboArish city was
seismically analyzed using the Equivalent Lateral Force Procedure with the
aid of STAAD PRO software. The building, which was Ordinary Reinforced
Concrete Moment Resisting Frame (ORCMRF), analyzed in compliance
with the provisions of (SBC-301-2007). The most important parameters
governing the analysis of this frame were dead load, live load and seismic
loads. Seismic loads were computed as pairs of accelerations versus times.
The damping ratio was taken as 0.05 (5% of the critical damping).
The ground accelerations versus time periods were calculated using SBC-
301-2007 together with parameters necessary to be used as input data for the
program to calculate the seismic parameters, i.e., reactions, displacements,
base shear, bending moments, shearing forces, drifts. The obtained results
show effects of earthquake ground motions on building studied herein is so
greater for the higher increases of the values of outputs resulting from
seismic load comparing to that due to static load only.
Finally, the results obtained, clearly, show the importance of taking the
Saudi seismic code provisions into account when analyzing and designing
multi-story buildings in abu arish city.
II
DEDICATION
To my Families who, through his financial and moral support was the source of
inspiration and the mainstay in my attaining an education, I dedicate this project.
III
ACKNOWLEDGEMENT
This project was written under the direction
and supervision of Associated
Prof.Dr. Mohammed Noor Nahir H. Maghrabi
and Assistant Prof. Dr. Mubarak Abd Alla
Aldoma Adam. Who were abundantly helpful
and offered invaluable assistance, support
and guidance.
iv
IV
TABLE OF CONTENTS
PAGE ABSTRACT DEDICATION ACKNOWLEDGEMENT TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES CHAPTER (1) INTRODUCTION
1-1 Genaral entroductin 1.2 Statement of Research Problem 1-3 objective of Research 1-4 Methodology of Research 1.5 Research Outlines
CHAPTER (2) DYNAMICS OF STRUCTURES AND EARTHQUAKE ENGINEERING Dynamic of Structures: 2.1 Introduction 2.1.1 Deterministic analysis .. 2.1.2 Nondeterministic analysis 2.2 Types of Prescribed Loadings 2.3 Definitions 2.4 Lateral Stiffness of Simple Structures 2.5 Analysis of Vibration Frequencies for Undamped Systems Earthquake Engineering 2.6 Definition 2.7 Faulting 2.8 Causes of earthquakes 2.9 Seismic Waves 2.10 Elastic Rebound Theory . 2.11 Measures of Earthquake Size 2.11.1 Magnitude 2.11.2 Earthquake intensity 2.11.3Earthquake energy (E) 2.12 Structural Damage 2.13 Damage as a Result of Soil Problems 2.13.1 Liquifaction 2.13.2 Landslides 2.13.3 Weak clay
I II III IV VI VII VIII
1 1 3 3 4 4
5 5 5 5 6 7 9 11 12 12 12 13 14 17 18 18 19 20
21 21 21 22 22
V
. 2.14 Damage as a Result of Structural Problems . 2.14.1 Foundation failure .2.14.2 Foundation connections 2.14.3 The lack of a secure connection to foundation 2.14.4 Soft story 2.14.5 Torsional moment 2.14.6 Shear 2.14.7 Flexural failure CHAPTER (3) Part One SEISMIC ACTIVITIES IN JAZAN AREA 3.1 Location of Jazan 3.2 Jazan Region and its Importanc 3.3 Earthquakes Data Base of the Arabian Peninsula 3.4 Samples of Earthquakes in Jazan Area Part Two SAUDI SEISMIC CODE 3.5 Seismic Ground Motion Values 3.5.1 Mapped acceleration parameters 3.5.2 Site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters 3.5.3 Design Response Acceleration Parameters 3.5.4 Design Response Spectrum 3.6 Equivalent Lateral Force Procedure 3.6.1 Calculation of Base Shear (V) 3.6.2 Lateral distribution of seismic forces 3.6.3 Horizontal shear distribution 3.6.4 Overturning moment 3.6.5 Story drift determination CHAPTER (4) SEISMIC ANALYSIS OF A MULTI-STORY R. C. BUILDING 4.1 Introduction 4.2 Frame Details and Study Case 4.3 calculations of acceleration 4.4 Discussion of the Analysis CHAPTER (5) CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions 5.2 Recommendations
REFERENCES
23 23 23 23 24 24 25 26
27 27 27 29 30 33 33 33
33 34 34 35 35 37 38 39 39
41 41 41 44 54
56 56 57 58
VI
LIST OF FIGURES FIGURE No DESCRIPTION PAGE
(2.1) Characteristics and sources of typical dynamic loadings 6
(2.2) Free vibration of an idealized one-story undamped structure 8
(2.3) a. Idealized pergola; b. idealized water tank;
c. free vibration due to initial displacement [v(0)] 9
(2.4) Lateral displacements and rotations of beam-column joints 10
(2.5): Earthquake Terminology 12
(2.6) Fundamental fault mechanisms (left), San Andreas
fault in California (right) 13
(2.7) Diagrams illustrating the forms of ground motion near the
ground surfacein four types of earthquake waves 15
(2.8) Massive tsunamis 16
(2.9) Tsunami occurrence mechanism (left), tsunami causes (right) 16
(2.10) Elastic rebound theory of earthquake generation 17
(2.11) Accelerogram from El Centro earthquake,
May 18, 1940 (N-S component) 18
(2.12) Common types of damage during large earthquakes 21
(2.13) Liquifaction caused building failure in Niigata, Japab 21
(2.14) About 75% homes were damaged as a result of
Turnagain heights slide 22
(2.15) Broken piles under bridge (left), Piles penetrating
bridge deck (right) 23
(2.16) House that fell from its foundation during the 1971 San
Fernardino earthquake (left), Failure of column
to pile shaft connection. 23
(2.17) Soft story collapse in San Francisco during
the 1989 Loma Prieta earthquake 24
VII
(2.18) Plan view of nine-story SRC building in Kobe (left),Nine-story SRC
Building immediately after the 1995 Kobeearthqake (right). 24
(2.19) Damage to north side of Mt. McKinley apartments,California
(left),Shear failure of Pier 150 on Kobe Route3 (right) 25
(2.20) Flexural damage to columns at lower level of Dakki subway
during the 1995 Kobe earthquake (left),Pier 585on Kobe
Route 3 duringthe 1995 Kobe earthquake (right). 26
(3.1) Seismograph stations of the Saudi National Seismic Network 30
(3.2) Seismicity up to 2013 including historical and instrumental earthquakes
above Ml 3 (Saudi geological survey database) 31
(3.3) Distributed of instrumental earthquakes in Jazan area and vicinity 32
(3.4) Sabkha corrosion action on structures 32
(3.5) Design Response Spectrum 34
(3.6) Deflection of frame structure 40
(4.1) Plan and elevation joint numbers of the studied frame 43
(4.2) Dimensions and member numbering of the frame 43
(4.3) Design Response Spectrum for Abo Arish City 46
(4.4) Relation between horizontal reactions (Fx) due to L/C1 and L/C2 47
(4.5) Relation between verticalreactions (Fy) due to L/C1 and L/C2 47
(4.6) B.M. at supports of the frame due to L/C1 and L/C2 48
(4.7) Relation between nodal resultant displacements due to L/C1 and L/C2 50
(4.8) Axial forces of columns due to combinations L/C1 and L/C2 53
(4.9) B.M. in beams due to combinations L/C1 and L/C2 54
VIII
LIST OF TABLE TABLE No DESCRIPTION PAGE (3.1) Governorates and number of population of Jazan region 28
(4.1) Samples of calculated accelerations versus times for Abo Arish City 46
(4.2) Reactions of supports of the studied frame 46
(4.3): Nodal displacements of the studied frame in Abu Arish city 49
(4.4) Column end forces of the studied frame 51
(4.5) Beam end forces of the studied frame 53
1
Chapter One
INTRODUCTION
1.1 General Introduction Earthquakes are broad-banded vibratory ground motions, resulting from a
number of causes including tectonic ground motions, volcanism, landslides,
rock burst, and man-made explosions. Of these, naturally occurring tectonic-
related earthquakes are the largest and most important. These are caused by
a fracture and sliding of rock along faults within the earth's crust. The study
of strong earthquake ground motions and associated seismic hazard and risk
plays an important role for the sustainable development of societies in
earthquake prone areas. There are a great number of historical and recent
earthquake have occurred in the southern red sea and southwestern Saudi
Arabia. Jazan area is located in most active region in the KSA where there is
a complicated geological structures and tectonics. This project reviews the
seismic activities occurred in Jazan area and conducts seismic analysis for a
R.C. building located in Abu Arish City. Many researchers conducted
researches and studies relating to Saudi Arabia in general and southwestern
Saudi in particular such as: S.A. Ashour and H.H. Abdel-Rahman, in 1994,
who presented a paper on "Application of Seismic Risk Analysis and
Earthquake Simulation Methods to the Western Region in Saudi Arabia" [1].
2
A comparative study on seismic provisions made in UBC-1997 and
Saudi buiding code (SBC-301-2007) for RC buildings was prepared by
Nazar and M. A. Ismaeil (2014) [2]. A technical report on "Earthquakes
Data Base of the Arabian peninsula" was written by Abdullah M. Alamri in
1998 [3]. The report describes the seismological problems associating with
rifting in the Red Sea and the geometry of the plate margins in the west and
southwest. Abdullah M. Al-Amri, Arthur J. Rodgers, Tariq A. Al-Khalifa,
presented a paper on "Improving the level of seismic hazard parameters
in Saudi Arabia using earthquake location", (2008)[4].
Awad Ali Al-Karni (2009) [5], studied the evaluation of the liquefaction
potential of the soil at the location of Jazan university in Jazan city which
lies on the east side of Red Sea. M.N. Fatani and A.M. Khan (1993)[6],
presented a conference paper on "Foundation on salt bearing soils of
Jizan",in order to present the geotechnical aspects of the area concentrating
on the foundation design and construction practice. Furthermore, the
geotechnical aspects of Jazan soil were studied by many authors as
(Dhowian et al., 1987 [7]; Erol, 1989 [8]; Dhowian, 1990 [9]; Al-Shamrani
and Dhowian, 1997) [10].
3
1.2 Statement of Research Problem
Jazan area is located in the most active seismic region in the KSA where
there is a complicated geological structures and tectonics. The area has a
new urban communities and big cities with heavy populations implementing
and promising with many strategic and developmental projects.
Furthermore, most of the buildings in this area do not follow the Saudi
seismic design considerations although it is affected by many earthquake
events. For all these reasons, it is necessary to perform studies and
researches related to southwestern part of KSA in general and Jazan area in
particular.
1.3 Objectives of Research
1. To study the seismic activities in Jazan area.
2. To analyze, in accordance with the Saudi Seismic Code, a
reinforced concrete building in Abo Arish city subjected to
earthquake loading.
3. Compare and discuss the results obtained and extract valuable
conclusion and recommendations concerning buildings constructed
in Abo Arish city.
4
1.4 Methodology of Research
The following steps will be followed to fulfill the objectives of the
project
1. Collection of data necessary for the project from different sources.
2. Analysis of a R.C. building under moderate earthquake loading in
Abo Arish City by the method of Equivalent Static Lateral Force
Procedure using STAAD-Pro program.
3. Computer programs were used to achieve the objectives of this
research such as STAAD PRO, ORIGIN and EXCEL.
1.5 Research Outlines
This research consists of six chapters that can be briefly resumed as follows: Chapter one: contains a general introduction, problem statement, objectives, methodology and outlines of the research. Chapter two: contains the dynamics of structures and earthquake engineering. Chapter three: reviews the seismic activities occurred in Jazan area and short notes about the Saudi Seismic Code. Chapter four: presents and discusses the seismic analysis of a R.C. building in Abo Arish city. Chapter five: covers the conclusions and proposes future recommendations.
5
Chapter Two
DYNAMICS OF STRUCTURES AND EARTHQUAKE ENGINEERING
Dynamics of Structures
2.1 Introduction:
The term dynamic may be defined simply as time-varying; thus a dynamic
load may be any load of which its magnitude, direction, and/ or position
varies with time. Similarly, the structural response to a dynamic load, i.e.,
the resulting stresses and deflections, is also time-varying, or dynamic.
Two basically different approaches are available for evaluating structural
response to dynamic loads: deterministic and nondeterministic.
2.1.1 Deterministic analysis:
If the time variation of loading is fully known, even though it may be highly
oscillatory or irregular in character, it will be referred to herein as a
prescribed dynamic loading; and the analysis of the response of any
specified structural system to a prescribed dynamic loading is defined as
deterministic analysis.
2.1.2 Nondeterministic analysis:
If the time variation is not completely known but can be defined in a
statistical sense, the loading is termed a random dynamic loading; and its
corresponding analysis of response is defined as a nondeterministic analysis.
6
2.2 Types of Prescribed Loadings
There are two basic categories:
i. Periodic loading: exhibits the same time variation successively for a
large number of cycles as shown in Fig. 1(a and b).
ii. Non-periodic loading: loadings may be either short-duration impulsive
loadings or long duration general forms of loads. A blast or explosion is a
typical source of impulsive load; for such short duration loads, special
simplified forms of analysis may be employed. On the other hand, a general,
long-duration loading such as might result from an earthquake can be treated
only by completely general dynamic analysis procedures as shown in Fig. 1
(c and d).
Fig. (2.1): Characteristics and sources of typical dynamic loadings: (a)
simple harmonic; (b) complex; (c) impulsive; (d) long-duration.
7
A structural dynamic problem differs from its static loading in two
important respects:
1. The time varying nature of the dynamic problem because both loading
and response vary with time.
2. The effect of inertial forces which resist accelerations of the structure in
this way are the most important distinguishing characteristic of a structural
dynamics problem.
2.3 Definitions:
- Periodic Motion: The motion which repeats after a regular interval of time
is called periodic motion.
- Frequency ( f) or (fn): The number of cycles completed in a unit time is
called frequency. Its unit is cycles per second (cps) or Hertz (Hz).
- Time Period: T or (Tn ) is time period of vibration
Time taken to complete one cycle is called periodic time. It is represented in
seconds/cycle.
- Amplitude (uo): The maximum displacement of a vibrating system or
body from the mean equilibrium position is called amplitude.
- Free Vibrations: When a system is disturbed, it starts vibrating and keeps
on vibrating thereafter without the action of external force.
- Natural Frequency (w) or (wn): When a system executes free vibrations
which are undamped, the frequency of such a system is called natural
frequency.
Fig. (2.2) explains graphically these definitions.
8
Fig. (2.2): Free vibration of an idealized one-story undamped structure
- Forced Vibrations:
The vibrations of the system under the influence of an external force are
called forced vibrations. The frequency of forced vibrations is equal to the
forcing frequency.
- Resonance:
When frequency of the exciting force is equal to the natural frequency of the
system it is called resonance.
- Degrees of Freedom:
The degree of freedom of a vibrating body or system implies the number of
independent coordinates which are required to define the motion of the body
or system at given instant.
9
2.4 Lateral Stiffness of Simple Structures:
Simple structures such as pergola and elevated water tank shown in Fig. 2.3
can be idealized as a concentrated or a lumped mass (m) supported by a
massless structure with stiffness (k) in the lateral direction.
Fig. 2.3: a. Idealized pergola; b. idealized water tank;
c. free vibration due to initial displacement [v(0)]
Where
m = the mass of roof
k = the sum of stiffnesses of individual pipe columns
v = lateral displacement
10
a. b. c.
Fig. (2.4) Lateral displacements and rotations of beam-column joints
Consider the frame of Fig. 2.4 a with length (L), height (h), elastic modulus
(E), and moment of inertia for beam (Ib)and for columns (Ic). The lateral
stiffness (k) of the frame can be determined for the two extreme cases:
i. If the beam is rigid [i.e., flexural rigidity EIb = ∞ (Fig. 2.4b)]
(2.1)
ii. For the beam with no stiffness [i.e., flexural rigidity EIb = 0 (Fig.2.4c)]
(2.2)
To a frame with L = 2h and EIb = EIc, and for rotational DOFs, the lateral
stiffness is:
K = (2.3)
11
2.5 Analysis of Vibration Frequencies for Undamped Systems
The equation of motion for a freely vibrating undamped system:
(2.4)
In which 0 is a zero vector. Since it is simple harmonic equation (2.4) may
be expressed for a MDOF system as
(2.5)
= shape of the system, = phase angle.
Taking the second time derivative for equation (2.5), the accelerations in
free vibrations are
(2.6)
Substituting equation (2.5) and (2.6) into equation (2.4) gives
Which (Since the sine term is arbitrary and may be omitted) may be written
(2.7)
By Cramer's rule the solution of this set of simultaneous equation is
( 2.8)
Hence a nontrivial solution is possible only when the denominator
determinant vanishes. In other words, finite-amplitude free vibrations are
possible only when
(2.9)
Equation (2.9) is called the frequency equation of the system.
The vector made up of the entire set of modal frequencies, arranged in
sequence, is called frequency vector (w).
12
Earthquake Engineering
2.6 Definition:
An earthquake is manifested as ground shaking caused by the sudden release
of energy in earth's crust.
The actual point at which the release occurs is known as the focus. The
epicenter is the point on the surface immediately above the focus as shown
in Fig. (2.5). The focus may be close to the surface (Kobe, 1995) or many
10s of Kilometres down.
Fig. (2.5): Earthquake Terminology
2.7 Faulting:
A fault is termed as the resulting fracture in the earth's crust when two
groundmasses move with respect to one another, Fig. (2.6).
Earthquakes are generated by sudden fault slips of brittle rocky blocks,
starting at the focus depth and observed at a site located at the epicentral
distance.
13
There are three types of earthquakes depending on focal depths:
i. Shallow earthquakes: have focal depths in the range of 5-15 km.
ii. Intermediate earthquakes: focal depths of 20-50 km.
Fig. (2.6): Fundamental fault mechanisms (left), San Andreas fault in
California (right)
2.8 Causes of earthquakes:
i. Tectonic plate movements.
ii. Dislocation of the crust.
iii. Volcanic eruption.
iv. Man-made explosions.
v. Collapse of under-ground cavities, such as mines or karsts.
vi. Large reservoir-induced.
14
2.9 Seismic Waves:
Earthquake waves can be classified in three types (Fig. 2.7):
i. Primary or compressional waves (P-waves)
P-waves are compression waves (like sound) traveling with the highest
speeds (25,000 km per hour, or 7 km per second) and will reach a distant
observer first. They push rocks and vibrate backwards and forwards and can
travel through liquids.
ii. Shear or secondary waves (S-waves)
S-waves travel at about 13000 km per hour or 3.6 km per second reaching
after P-waves.S waves are characterized by a sideways movement. The rock
materials are moved from side to side as the wave passes, moving at right
angles to the direction of wave motion.
iii. Love waves (L-waves)
It is the surface waves that are most damaging as they cause the earth's crust
to undulate. The L-waves travel along the surface of the earth from the point
directly above the quake or epicenter. These waves are the ones that cause
most of the damage.
15
Fig. (2.7): Diagrams illustrating the forms of ground motion near the ground
surface in four types of earthquake waves
iv. Tsunami (Tsunamis) or Seismic sea wave:
A tsunami "harbor wave" known as a seismic sea wave or as a tidal wave, is
a series of waves in a water body caused by the displacement of a large
volume of water, generally in an ocean or a large lake. Earthquakes, volcanic
eruptions and other underwater explosions (including detonations of
underwater nuclear devices), landslides, and other disturbances above or
below water all have the potential to generate a tsunami. Wave heights of
tens of meters can be generated by large events, Fig. (2.8). A tsunami can
travel at well over 970 kph (600 mph) in the open ocean - as fast as a jet
flies. Fig. (2.9) shows tsunami occurrence mechanism and tsunami causes
(right)
16
Fig (2.8): Massive tsunamis
Fig. (2.9): Tsunami occurrence mechanism (left), tsunami causes (right)
17
2.10 Elastic Rebound Theory:
It was from study, by H. F. Reid, of the rupture which occurred along the
San Andreas fault during the San Francisco earthquake in 1906. Reid
concluded that the specific source of the earthquake vibration energy is the
release of accumulated strain in the earth's crust, the release itself resulting
from the sudden shear-type rupture as shown in Fig. (2.10).
Fig. (2.10): Elastic rebound theory of earthquake generation: (a) before
straining; (b) strained (before earthquake); (c) after earthquake.
18
2.11 Measures of Earthquake Size
2.11.1 Magnitude:
Magnitude is the amount of strain energy released at the source. Richter
magnitude is the (base 10) logarithm of the maximum amplitude measured
in micrometers (10-6 m) of the earthquake record obtained by a Wood-
Anderson seismograph corrected to a distance of 100 km:
ML = log A – log A0 (2.10
Where
ML = local magnitude
A = maximum amplitude in micrometers
A0 = a standard value[ calibration amplitude (0.001 mm)]
Fig. (2.11): Accelerogram from El Centro earthquake, May 18, 1940 (N-S
component)
19
Earthquakes of magnitudes less than 5 are not expect to cause structural
damage, whereas for magnitudes greater than 5 potentially damaging ground
motion will be produced.
We can measure the size of earthquakes using moment magnitude as in
equation (2.11):
M = ()[log(M0) – 16.05] (2.11)
Where M0 is the seismic moment defined as
M0 = GAD
Where
G = shear modulus of rock (dyne/cm2)
A = area of the fault (cm2)
D = the amount of slip or movement of the fault (cm)
2.11.2 Earthquake intensity:
Seismic intensity is a measure of effect, or the strength of an earthquake
hazard at a specific location measured by many scales such as the modified
Mercalli scale (MMI). MMI defines the level of shaking at specific sites on a
scale of I to XII as shown in Table (2.1).
20
2.11.3Earthquake energy (E):
Earthquake energy can be obtained by
Log E = 11.8 + 1.5 M (2.12)
Where
E = amount of earthquake energy released
M = magnitude of earthquake
By the above formula, the energy increases by a factor of 32 for each unit
increase of magnitude.
Table (2.1) Modified Mercalli Intensity scale (MMI) of earthquakes
21
2.12 Structural Damage:
During large earthquakes the ground is jerked back and forth, causing
damage to the element whose capacity is below the earthquake demand as
shown in Fig. (2.12).
Fig. (2.12): Common types of damage during large earthquakes
2.13 Damage as a Result of Soil Problems:
2.13.1 Liquifaction
Liquifaction occurs when loose saturated sand, silts, or gravel are shaken,
the material consolidates, reducing the porosity and increasing pore water
pressure. The ground settles, oven unenenly, tilting and toppling structures
that were formerly supported by the soil as shown inFig. (2.13)
Fig. (2.13):Liquifaction caused building failure in Niigata, Japan
22
2.13.2 Landslides
When a steeply inclined mass of soil is suddenly shaken, a slip-plane can
formed and the material slides downhill, during a landslide, structures sitting
on the slide move downward and structures below the slide are hit by fallen
debris.
Fig. (2.14): about 75% homes were damaged as a result of Turnagain heights
slide
2.13.3 Weak clay
The problems encountered at soft clay sites include the amplification of the
ground motion as well as vigorous soil movement that can damage
foundations. Several bridges suffered collapse during the 1989 Loma Prieta
earthquake due to the poor performance of weak clay, shown in Fig. (2.15).
23
Fig. (2.15): Broken piles under bridge (left), Piles penetrating bridge deck
(right)
2.14 Damage as a Result of Structural Problems
2.14.1 Foundation failure
Usually, it is the connection to the foundation or an adjacent member rather
than the foundation itself that is damaged during a large earthquake.
2.14.2 Foundation connections
2.14.3 The lack of a secure connection to foundation
It can cause damages to electrical transformers, storage bins, lifelines
facilities and a variety of other structures as in Fig. (2.16).
Fig. (2.16): House that fell from its foundation during the 1971 San
Fernardino earthquake (left), Failure of column to pile shaft connection.
24
2.14.4 Soft story
Buildings are classified as having a "soft story" if that level is less than 70%
as stiff as the floor immediately above it, or less than 80% as stiff as the
average stiffness of the three floors above it as shown in Fig. (2.17).
Fig. (2.17): Soft story collapse in San Francisco during the 1989 Loma Prieta
earthquake
2.14.5 Torsional moment
Curved, skewed and eccentrically supprted structures often experience
atorsional moment during earthquakes as shown in Fig. (2.18).
Fig. (2.18): Plan view of nine-story SRC building in Kobe (left),Nine-story SRC
buildingimmediately after the 1995 Kobeearthqake (right).
25
2.14.6 Shear
Most building structures use shear walls or moment-resisting frames to resist
lateral forces durng earthquakes. Damage to these system varies from minor
cracks to complete collapse, see Fig. (2.19).
Fig. (2.19): Damage to north side of Mt. McKinley apartments,California
(left),Shear failure of Pier 150 on Kobe Route3 (right)
26
2.14.7 Flexural failure
Flexural members are often designed to form plastic hinges during large
earthquakes as shownin Fig. (2.20). A plastic hinge allows a member to
yield and deform while continuing to support its load. However, when there
is insufficient confinment for RC members, a fleural failure will occur
instead accompanied by compression or shear damage as the capacity of the
damage area has been lowered.
Fig. (2.20): Flexural damage to columns at lower level of Dakki subway
during the 1995 Kobe earthquake (left),Pier 585on Kobe Route 3 during the
1995 Kobe earthquake (right).
27
Chapter Three
Part One
SEISMIC ACTIVITIES IN JAZAN AREA
3.1 Location of Jazan:
Jizan, or more properly Jazan, was known in ancient times as Almikhlaf
Alsulimani. Jazan is located on the southwest corner of Saudi Arabia on the
coast of the Red Sea and directly north of the border with Yemen. Jazan City
lies in an active zone of earthquakes classified as zone 2B with maximum
applied horizontal acceleration of 0.2g.Saudi Arabia is divided into 25
zones, each zone having its specific building code covering not only seismic
activity but other criteria as well.”
3.2 Jazan Region and its Importance
The Province of Jazan lies in the south west section of the Kingdom of Saudi
Arabia. It has a population of approximately 1,365,110 at the 2010 census
and covers an area of 40,000 km2 including some 5,000 villages and cities.
Jizan, is home to the Port of Jizan, Saudi Arabia’s third most important port
on the Red Sea. It stretches some 300 km along the southern Red Sea coast,
just north of Yemen. The region includes over 100 islands in the Red Sea.
The Farasan Islands, Saudi Arabia’s first protected wildlife area, is home to
the endangered Arabian gazelle and, in winter, receives migratory birds from
Europe.
28
The region is subdivided into14 governorates as shown in Table(3.1)
.
Table (3.1) Governorates and number of population of Jazan region
Name
Census
15 September 2004
Census (Preliminary)
28 April 2010
Abu Arish 123,943 197,112
Alddair 49,239 59,494
Alddarb 52,062 69,134
Ahad Almasarihah 70,038 110,710
Alaridah 62,841 76,705
Alaydabi 52,515 60,799
Alharth 47,073 18,586
Alraith 13,406 18,961
Baish 58,269 77,442
Damad 62,366 71,601
Farasan 13,962 17,999
Jazan 255,340 157,536
Sabya 198,086 228,375
Samtah 128,447 201,656
Total Province 1,187,587 1,365,110
Jazan is one of the Kingdom's richest agricultural regions, remarkable for
both the coffee beans, grain crops (barley, millet and wheat) and fruit
(apples, bananas, grapes, lemons, mangoes, oranges, papayas, plums and
tamarinds).
29
Jazan Economic City:
is an economic city in the Jizan Province of the Kingdom of Saudi Arabia,
with a focus on the energy and manufacturing industries. Arab News
reported in January 2011 that when the city is completed, an estimated
500,000 new jobs will be created. Jazan Economic City focuses on four
areas: heavy industries, secondary industries, human capital and lifestyle.
The proposed city will provide an environment for key industries,
technology exchanges, commerce and trade, employment opportunities,
education and training, housing and a broad spectrum of socio-economic
activities for a projected population of 300,000 people.
Jazan University is located at Jazan city with its campuses at Jazan, Sabya,
Abu Arish, Samtah, Addarb, Addair, Al Ardhah and Farasan Island. Arrayth
is one of the most beautiful mountains in the south of Saudi Arabia.
3.3 Earthquakes Data Base of the Arabian Peninsula
Recently, there are two independent analog seismic telemetry networks in
Saudi Arabia. The King Saud University (KSU) network was established in
1985 and consists of 30 stations with denser sub-networks in the Gulf of
Aqabah region (12 stations) and the southwestern part of Saudi Arabia (8
stations). A network run by King Abdulaziz City for Science and technology
(KACST) was established in 1993 with 11 short-period stations in the Gulf
of Aqabah and the southwestern part of Saudi Arabia adjacent to the Yemen
border. Saudi Arabia will set up an additional 50 advanced earthquake
monitoring stations.
30
The Kingdom already has 150 earthquake monitoring stations called the
Saudi National Seismic Network (SNSN), and the new ones will boost the
capability by providing precise data collection [14]. Fig. (3.2) shows the
distribution of seismograph stations of Saudi Arabia.
Fig. (3.1) Seismograph stations of the Saudi National Seismic Network
3.4 Samples of Earthquakes in Jazan Area
In 2014, a magnitude-5.1 earthquake struck in the southwestern part of the
Kingdom, 50 km northeast of Jazan, at a depth of 10 km followed by 37
aftershocks of magnitudes ranging 0.94 - 5.1 in Richter scale[14].
Its impact was felt by inhabitants in the Asir and Najran regions. Generally,
there were many earthquakes struck Jazan area and north of Yemen in the
years 859, 1121, 1191, 1269, 1481, 1630,1710, 1941, 1947 (of magnitude 6,
killed 1200 of people), 1955, 1982, 1993 (of magnitude 4.8) as shown in
Fig. (1). Earthquakes of magnitude 6 are common along the spreading axis
of the Red Sea but generally they are not felt onshore and appear to pose
little risk to infrastructure.
31
Fig. (3.2) shows earthquake epicenters greater than magnitude 3 in the Saudi
Geological Survey (SGS) catalogue for all years up to 2013. Fig.(3.3) shows
the distribution of instrumental earthquakes in Jazan area and its vicinity.
Fig. (3.2) Seismicity up to 2013 including historical and instrumental
earthquakes above Ml 3 (Saudi geological survey database)
32
Fig. (3.3): Distributed of instrumental earthquakes in Jazan area and vicinty
Because Jizan is located on the sea-shore, water immigrates to the surface
leaving a salt crust on the top surface, which is known as 'Sabkha' soil. This
salt bearing (saline) soil and the salt dome affected the foundation
performance in the area, see Fig (3.4).
Fig. (3.4):Sabkha corrosion action on structures
33
Part Two
SAUDI SEISMIC CODE
3.5 Seismic Ground Motion Values:
3.5.1 Mapped acceleration parameters
The Kingdom of Saudi Arabia has been divided into seven regions for
determining the maximum considered earthquake ground motion. The
parameter Ss shall be determined from the 0.2 second spectral response
accelerations shown on Figures 9.4.1(b) through 9.4.1(i) (SBC-301-
2007).The parameter S1 shall be determined from the 1.0 second spectral
response accelerations shown on Figures 9.4.1(j) through 9.4.1(q) (SBC-
301-2007).
3.5.2 Site coefficients and adjusted maximum considered earthquake
spectral response acceleration parameters
The Maximum considered earthquake spectral response acceleration for
short periods (SMS) and at 1-sec (SM1), adjusted for site class effects, shall be
determined by the Equations:
SMS = Fa SS (3.1)
SM1 = FV S1 (3.2)
34
S1 = the mapped maximum considered earthquake spectral response
acceleration at a period of 1-sec as determined in accordance with section
9.4.1 (SBC-301-2007).
SS = the mapped maximum considered earthquake spectral response
acceleration at short periods as determined in accordance with section 9.4.1
where site coefficients Fa and Fv are defined in Table 9.4.3a and Table
9.4.3b, respectively(SBC-301-2007).
3.5.3 Design Response Acceleration Parameters
Design earthquake spectral response acceleration at short periods, SDS, and at
1-sec period, SD1, shall be determined from the following Equations:
SDS = SMS (3.3)
SD1 = SM1 (3.4)
3.5.4 Design Response Spectrum
1. For periods less than or equal to T0, the design spectral response
acceleration, Sa, shall be given by (as shown in Fig. 3.5):
Sa = SDS (0.4 + 0.6 ) (3.5)
Fig. (3.5) Design Response Spectrum
35
2. For period greater than or equal to T0 and less than or equal to TS, the
design spectral response acceleration, Sa, shall be taken as equal to SDS.
3. For period greater than TS, the design spectral response acceleration, Sa,
shall be given by:
(3.6)
SDS = the design spectral response acceleration at short periods, at 1-sec
SD1 = the design spectral response acceleration at 1-sec periods, in units of g-
sec.
T = the fundamental period of the structure (sec):
T0 = 0.2SD1/SDS
TS =SD1/SDS
3.6 Equivalent Lateral Force Procedure:
3.6.1 Calculation of Base Shear (V)
According to "SBC-301-2007" the total base shear (V) can be calculated in
accordance with the following equation:
V = Cs W (3.7)
Where:
Cs = the seismic response coefficient determined in accordance with Section
10.9.2.1.
(3.8)
36
SDS = the design spectral response acceleration in the short
period range as determined from Section 9.4.4 (SBC-301-2007)
R = the response modification factor in Table II.
I = the occupancy importance factor determined in accordance with section
9.5
The value of the seismic response coefficient, (Cs), need not be greater than
the following equation:
(3.9)
But shall not be taken less than
(3.10)
SD1= the design spectral response acceleration at a period of 1.0 sec, in unit
of g-sec, as determined from section 9.4.4.
T = the fundamental period of the structure as determined in section 10.9.3.
The approximate fundamental period (Ta), in seconds, shall be determined
from the following equation
(3.11)
Where
hnis the height in (m) of the base to the highest level of the structure, and
Ctand xare determined from Table 10.9.3.2.
Or Ta, for structures no exceeding 12 stories in height, can be determined
from the following equation Ta = 0.1 N (3.12)
37
Where
N = number of stories
Ta for masonry or concrete shear wall structures shall be permitted to be
determined from
(3.13)
Cw is calculated from the following equation
(3.14)
Where
AB = the base area of the structure m2.
Ai = the area of shear wall "i" in m2.
Di = the length of shear wall "i" in m.
n = number of shear walls in the building.
3.6.2 Lateral distribution of seismic forces
The lateral seismic force (Fx) (kN) induced at any level shall be determined
by the following equations:
Fx = CvxV (3.15)
and
(3.16)
38
Where
Cvx=vertical distribution factor
V = total design lateral force or shear at the base of structure, (kN).
wi and wx= the portion of the total gravity load of structure (W) located or
assigned to level i or x.
hi and hx= the height "m" from the base to level i or x.
k = an exponent related to the structure period as follows:
for structures having a period of 0.5 sec or less, k = 1
for structures having a period of 2.5 sec or less, k = 2
for structures having a period between 0.5 and 2.5 sec,
k shall be 2 or shall be determined by linear interpolation between 1 and 2.
3.6.3 Horizontal shear distribution
The seismic design story shear in any story (Vx) (kN) shall be determined
from the following equation:
(3.17)
Where Fi = the portion of the seismic base shear (Vx) (kN) induced at level i.
39
3.6.4 Overturning moment
The overturning moments at level x (Mx) (kN.m) shall be determined from
the following equation
(3.18)
Where
Fi= the portion of the seismic base shear (V) induced at level i.
hi and hx= the height "m" from the base to level i or x.
3.6.5 Story drift determination
The design story drift (∆) shall be computed as the difference of the
deflections at the top and bottom of the story under consideration.
The deflections of level x at the center of the mass (δx) "mm" shall be
determined in accordance with the following equation:
(3.19)
Where
Cd = the deflection amplification factor in Table 10.2
δxe= the deflections determined by an elastic analysis
I = the importance factor determined in accordance with section
9.5.
Story drift (∆x) =δx - δx-1, as shown in Fig. (3.6)
40
Fig. (3.6) Deflection of frame structure
41
Chapter Four
SEISMIC ANALYSIS OF A MULTI-STORY
R. C. BUILDING IN ABO ARISH CITY
4.1 Introduction
In this project, an office 10-story R.C. frame, located in Abo Arish city, has
been seismically analyzed aiming to investigate the seismic performance of
a reinforced concrete moment resisting frame building under an earthquake
ground motion. The building was analyzed in accordance with the Saudi
Building Code (SBC-301-2007) using STAAD PRO software. Abo Arish
city lies in an active zone of earthquakes classified as zone 2B with
maximum applied horizontal acceleration of 0.2g
4.2 Building Details and Study Case An office ten-story regular reinforced concrete frame building located in
Abo Arish City, with 16 m X 20 m plan as shown in Fig. (4.1), was analyzed
to investigate its seismic performance. The most important parameters
governing the analysis of this frame were dead load, live load and seismic
loads. Seismic loads were computed based as pairs of accelerations versus
times.
42
As per SBC-301-2007 the following selected load combinations were
selected for the analysis of the studied frame:
Load Case 1 (L/C1) is static load (dead and live):
1.4 DL + 1.7 LL (4.1)
Load Case 2 (L/C2) is static load + Earthquake loads:
1.2 DL + + 1.0 E + f1 LL (4.2)
Load Case 3 (L/C3) is dead + Earthquake) loads:
0.9 DL + 1.0 E (4.3)
Where
f1 = 1.0 for areas occupied as places of public assembly, for live loads in
excess of 0.5 kN/m2 and for parking garage live load.
f1 = 0.5 for other live loads.
In this analysis, the live load is taken as 3.5 kN/m2.
From the frame shown in Fig. (4.1), Joints' numbers 6, 11, 16, 21, 26, 31,
36, 41, 46, 51 were selected to calculate their nodal displacements for the
different loading cases.
43
Fig. (4.1) Plan and elevation joint numbers of the studied frame
Member numbering Dimensions
Fig. (4.2) Dimensions and member numbering of the frame
plan Joint number
44
One frame was analyzed using STAAD PRO program. The ground
accelerations versus time periods were calculated using SBC-301-2007
together with parameters necessary to be used as input data for the program
to calculate the seismic parameters, i.e., reactions, displacements, base
shears, bending moments, shearing forces, drifts. The damping ratio was
taken as 0.05 (5% of the critical damping).
• Typical columns' sections = 30 mm x 30 mm,
• Typical beams' sections = 30 mm x 45 mm, and
• Typical slab thickness = 150 mm.
Some members of the frame building were selected for the purposes of the
analysis. The selected members, which are shown in Fig. (4.2) were:
Columns: 2, 11, 20, 29, 38, 47, 56, 65, 74, and 83.
Beams: 6, 7, 8, and 9.
4.3 calculations of acceleration:
Calculations of mapped and design spectral response accelerations for
Abo Arish City:
Using the Saudi Building Code (SBC-301-2007) equations shown in
chapter three the following parameters have been calculated to be used as
input data for seismic analysis of the R.C. Building located in Abo Arish
City (Abo Arish City lies in region 6). The calculated results of these
parameters are as follows:
45
• SS = the mapped maximum considered earthquake spectral response
acceleration at short periods.
SS= 0.448 Fig 9.4.1(h) 5% damped
• S1 = the mapped maximum considered earthquake spectral response
acceleration at a period of 1-sec
S1= 0.128 Fig 9.4.1(p) 5% damped
Fa and Fv = site coefficients
Fa = 1.86 (Table 9.4.3a) of (SBC-301-2007).
FV = 3.4 (Table 9.4.3 b) of (SBC-301-2007).
• SMS = The Maximum considered earthquake spectral response
acceleration for short periods , adjusted for site class effects
SMS = Fa SS =1.866 x 0.448 = 0.836
• SM1 = The Maximum earthquake spectral response acceleration for at
1-sec periods , adjusted for site class effects
SM1 = FV S1= 3.416x 0.128 = 0.437 SDS = the design spectral response acceleration at short periods.
SDS = (2/3) x SMS = (2/3) x 0.836 =0.557
• SD1 = the design spectral response acceleration at 1-sec periods.
SD1 = (2/3) x SM1 = (2/3) x 0.437=0.291
• T = the fundamental period of the structure (sec):
T = 0.1 N = 0.1 x 10 = 10 sec
T0 = 0.2SD1/SDS = 0.2x2.87/5.5 = 0.104 sec
TS =SD1/SDS = 2.87/5.5 = 0.523 sec
• R = the response modification factor in Table II:
R = 2.5 (for ordinary R.C. resisting moment frame)
46
Fig.(4.3) Design Response Spectrum for Abo Arish City
• I = the occupancy importance factor determined in accordance with
section 9.5 (SBC-301-2007):
I = 1 (for occupancy category I and II)
No Time (Sec)
Accelerations (m/s2)
1 1.000 0.291
2 2.000 0.146 3 3.000 0.097 4 4.000 0.073 5 5.000 0.058 6 6.000 0.049 7 7.000 0.042 8 8.000 0.036 9 9.000 0.032 10 10.000 0.029
Table (4.1) Samples of calculated accelerations versus times for Abo Arish City
47
Fig. (4.4) Relation between horizontal reactions (Fx) due to L/C1 and L/C2
Fig. (4.5) Relation between vertical reactions (Fy) due to L/C1 and L/C2
48
Fig. (4.6) B.M. at supports of the frame due to L/C1 and L/C2
49
Table (4.3): Nodal displacements of the studied frame in AboArish city
Resultant (mm) Z (mm) X (mm) Y (mm) L/C Node No.
1.598 0.000 -1.598 -0.026 DL + LL 6
9.345 0.000 -0.625 9.324 DL + LL + E
3.057 0.000 -3.057 -0.009 DL + LL 11
20.676 0.000 -1.230 20.639 DL + LL + E
4.368 0.000 -4.368 -0.009 DL + LL 16
31.724 0.000 -1.808 31.672 DL + LL + E
5.525 0.000 -5.525 -0.007 DL + LL 21
41.158 0.000 -2.351 42.093 DL + LL + E
6.524 0.000 -6.524 -0.006 DL + LL 26
51.708 0.000 -2.848 51.629 DL + LL + E
7.359 0.000 -7.359 -0.005 DL + LL 31
60.131 0.000 -3.289 60.041 DL + LL + E
8.028 0.000 -8.028 -0.004 DL + LL 36
67.213 0.000 -3.663 67.113 DL + LL + E
8.528 0.000 -8.528 -0.002 DL + LL 41
72.779 0.000 -3.959 72.671 DL + LL + E
8.857 0.000 -8.857 -0.016 DL + LL 46
76.678 0.000 -4.164 76.565 DL + LL + E
9.012 0.000 -9.012 0.108 DL + LL 51
78.979 0.000 -4.264 78.864 DL + LL + E
50
Fig. (4.7) Relation between nodal resultant displacements due to L/C1 and L/C2
51
Table (4.4) column end forces of the studied frame Column Node L/C Axial Shear Bending
Fx (kN)
Fy (kN)
Fz (kN)
My (kNm)
Mz (kNm)
2 2 DL+LL 1830 -0.245 0.000 0.000 -0,287
DL+LL+E 1220 50.291 0.000 0.000 80.022
7 DL+LL -1830 0.245 0.000 0.000 -0.448
DL+LL+E -1190 50.612 0.000 0.000 70.851
11 7 DL+LL 1630 -1.615 0.000 0.000 -1.728
DL+LL+E 1080 52.038 0.000 0.000 78.972
12 DL+LL -1630 1.615 0.000 0.000 -3.116
DL+LL+E -1070 54.157 0.000 0.000 77.141
20 12 DL+LL 1440 -3.974 0.000 0.000 -5.466
DL+LL+E 949.723 48.051 0.000 0.000 72.332
17 DL+LL -1440 3.974 0.000 0.000 -6.454
DL+LL+E -944.215 53.266 0.000 0.000 71.821
29 17 DL+LL 1260 -5.803 0.000 0.000 -8.257
DL+LL+E 832.618 43.485 0.000 0.000 65.318
22 DL+LL -1260 5.803 0.000 0.000 -9.152
DL+LL+E -815.262 51.102 0.000 0.000 65.136
38 22 DL+LL 1070 -7.414 0.000 0.000 -10.741
DL+LL+E 715.855 37.879 0.000 0.000 56.729
27 DL+LL -1070 7.414 0.000 0.000 -11.501
DL+LL+E -690.611 47.610 0.000 0.000 56.907
47 27 DL+LL 890.525 -8.769 0.000 0.000 -12.837
DL+LL+E 599.112 31.399 0.000 0.000 46.850
52
32 DL+LL -890.525 8.769 0.000 0.000 -13.469
DL+LL+E -569.702 42.908 0.000 0.000 47.348
56 32 DL+LL 711.760 -9.881 0.000 0.000 -14.566
DL+LL+E 482.085 24.157 0.000 0.000 35.846
37 DL+LL -711.760 9.881 0.000 0.000 -15.076
DL+LL+E -452.099 37.125 0.000 0.000 36.625
65 37 DL+LL 534.826 -10.718 0.000 0.000 -15.900
DL+LL+E 364.489 16.325 0.000 0.000 23.965
42 DL+LL -534.826 10.718 0.000 0.000 -16.253
DL+LL+E -337.470 30.392 0.000 0.000 25.011
74 42 DL+LL 359.162 -11.524 0.000 0.000 -17.075
DL+LL+E 245.950 7.878 0.000 0.000 11.278
47 DL+LL -359.162 11.524 0.000 0.000 -17.498
DL+LL+E -225.450 23.004 0.000 0.000 12.356
83 47 DL+LL 185.781 -11.670 0.000 0.000 -17.391
DL+LL+E 126.884 -0.294 0.000 0.000 -1.044
52 DL+LL -185.781 11.670 0.000 0.000 -17.619
DL+LL+E -116.954 15.023 0.000 0.000 0.164
53
Fig. (4.8) Axial forces of columns due to combinations L/C1 and L/C2 Table (4.5) beam end forces of the studied frame
Beam Node L/C Fx (kN)
Fy (kN)
Mz (kNm)
6 6 DL+LL -8.799 90.774 42.836 DL+LL+E -0.515 106.258 133.525 7 DL+LL 8.799 101.226 -63.742 DL+LL+E 11.034 113.118 39.507 7 7 DL+LL -10.169 97.061 65.918 DL+LL+E -5.072 99.429 113.173 8 DL+LL 10.169 94.939 -61.674 DL+LL+E 8.275 98.036 32.541 8 8 DL+LL -10.169 94.939 61.674 DL+LL+E -5.072 98.036 113.489 9 DL+LL 10.169 97.061 -65.918 DL+LL+E 8.275 99.429 26.656 9 9 DL+LL -8.799 101.226 63.742 DL+LL+E -0.515 113.118 123.167 10 DL+LL 8.799 90.774 -42.836 DL+LL+E 11.034 106.258 77.303
54
Fig. (4.9) B.M. in beams due to combinations L/C1 and L/C2
4.4 Discussion of the Analysis
The results of the analysis indicated that the horizontal reactions (Fx) of the
building due to L/C2 show larger values, reaching up to 5 times that due to
L/C1 in the outer supports, and this difference increased so many times in
the inner supports as shown in Table (4.1) and Fig. (4.3). The vertical
reactions (Fy) due L/C1 is slightly greater than that due to L/C2 revealing
the effect of static load on reducing lateral movements (see Table 4.1 and
Fig. 4.4). This concept is also true for bending moments (Mz) at supports
that reflects the severe effects of horizontal excitation ground motion on this
building as shown in Fig. (4.5). Table (4.2) and Fig. (4.6) show the results of
the nodal displacements due to different load cases, from which it is clearly
observed that the calculated resultant of nodal displacements due to L/C 2
were about 6 to 10 times the nodal displacements due to L/C1.
55
These values indicated that the horizontal motions have great effects on the
lateral displacements of the studied building.
For columns, axial forces due to L/C1is slightly greater than that due to
L/C2. However, the forces in upper floor columns showed lesser values.
There are large increases in the values of shearing forces and bending
moments at columns when earthquake effects were considered in the
analysis as shown in Table (4.3) and Fig. (4.7). The values of bending
moments due to L/C2 in beams 6, 7, 8, and 9 were found to be about 1.5 -2.0
times the values due to L/C1 as shown Table (4.4) and Fig. (4.8).
56
Chapter Five
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions
Based on the obtained results from the analysis of the reinforced concrete
building in AboArish city, it can be concluded that:
1. It is found that the values of horizontal support reactions generating
from L/C2 were about 5 times that due to L/C1 in the outer supports
and this rate increases much more in the inner supports.
2. It is clearly observed that the calculated resultant of nodal
displacements due to L/C2 were about 6 to 10 times the nodal
displacements due to L/C1.
3. Axial forces of columns due to L/C1is slightly greater than that due to
L/C2 and these forces decrease gradually in the upper floor columns
which showed lesser values.
4. Bending moments in beams due to L/C2 were about 1.5 to 3 times that
values due to L/C1. Where as bending moment in the columns due to
L/C2 showed much larger values compared to that due to the static loads
(L/C1).
57
5.2 Recommendations
From this research and the results obtained, it can be recommended that:
1. Saudi seismic code should be taken into consideration when analyzing
and designing buildings and structures in the country.
2. Seismic risk analysis has to be conducted for major cities of Jazan
area.
3. Further studies and researches, in this field, are needed such as
analysis and design of various structures subjected to earthquake
loading in Fifa, soil dynamic investigation in Jazan area, earthquake
simulation using shake table for Jazan area, methods of rehabilitation
of ancient and historical buildings. Analysis and design of structure
subjected to wind and earthquake loading.
58
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