NGUYEN VAN NAM MODELING OF STRUCTURES SEISMICALLY ISOLATED...

MINISTRY OF EDUCATION AND TRAINING

DANANG UNIVERSITY

NGUYEN VAN NAM

MODELING OF STRUCTURES SEISMICALLY

ISOLATED BY FRICTION BEARINGS

MAJOR : MECHANICAL ENGINEERING

CODE : 62.52.01.01

SUMMARY OF DOCTOR OF ENGINEERING DISSERTATION

Danang - 2017

The work was finished at

University of Science and Technology - Danang University

Science Advisor:

1. Assoc. Prof. Dr. HOANG PHUONG HOA

2. Assoc. Prof. Dr. PHAM DUY HOA

Reviewer 1: Prof. Dr. PHAN QUANG MINH

Reviewer 2: Assoc. Prof. Dr. LUONG VAN HAI

Reviewer 3: Dr. NGUYEN THE DUONG

This Dissertation was defended at The Doctor of Engineering

committee at Danang University on 17 of 4, 2017

For the detail of the dissertation, please contact:

- Information and Library Center of Danang University.

- National Library of Vietnam.

1

INTRODUCTION

1. Motivation of Study

Earthquake is one of the serious disasters caused by natural for

human life, constructions and economy in general. Throughout

history, the world has seen occuring of many strong earthquakes,

killed a lot of human lifes, destroyed a lot of buildings and lost

millions of dollars in economic each year due to the earthquakes.

Although Vietnam is not in the dangerous zone of the

epicenter of strong earthquakes in the world, it is still a country

located in areas with high seismic hazard. It is reported by scientists

at the International Workshop "Dangerous earthquake, tsunami and

the early warning system for Asia - Pacific" hold by the Institute of

Geophysics - Institute of Science and Technology Vietnam within

two days (5 and 6-9.2011). Some large urban areas are currently

located on the fault zone and are possible to get very strong

earthquakes such as Hanoi located on the Hong river fault zone,

Chay river, Ma river, Son La river is forecasted to suffer level 8

concussions according to the Richter scale.

Recently, the vibration caused by earthquakes appeared in

many provinces and cities, especially Hanoi, Ho Chi Minh City and

Danang where have of a large number of buildings, large bridges

and demands of construction of large projects are growing in number

as well as in height. Those are very sensitive to ground acceleration

of earthquakes.

With these facts as above, the constructions should have

seismic resistant design, particularly modern seismic resistant design

standpoint associated with the term "structural vibration control" and

is still new in Vietnam. Therefore, the research about them is

2

essential, has scientific meaning and high practice. This is also the

motivation for the author to research the title: “Modeling of

structures seismically isolated by friction bearings” to provide a

solution to reduce the harm caused by earthquakes for constructions.

2. Purpose of Study

Research the numerical modeling for base isolated structures

with the friction pendulum bearings including SFP, DFP and TFP

bearings subjected to earthquake load. Evaluate the seismic reduction

effectiveness of the base isolation bearings for constructions. From

there, application research of TFP bearings for high-rise buildings

built in Hanoi, Vietnam.

3. Object and Scope of Study

The objects of the study in dissertation are the friction

pendulum bearings including SFP bearing, DFP bearing and TFP

bearing.

The scope of the study including: Research response of

structures with single bearing (don’t consider the work together of

many bearings in a construction), ignoring torsion; The superstructure

behavior is linear and the bearing behavior is nonlinear.

4. Dissertation content

- Identify the structure, working principle of the seismic

isolation bearings: SFP, DFP and TFP.

- Numerical modeling for base isolated structures with the

friction pendulum bearings above subjected to earthquake. Evaluate

the seismic reduction effectiveness of these bearings for

constructions.

- Research to develop a new model for TFP bearing.

- Application research of TFP bearing for high-rise buildings

3

in Vietnam according to ASCE 7-2010 Standard design.

5. Methodology of study

Investigate a theoretical model, the research results were

simulated by Matlab and compared to an experimental model results

of other authors have been published by NEES (Network for

Earthquake Engineering Simulation) to verify.

6. Contributions of the dissertation

- Numerical modeling for base isolated structures with the

friction pendulum bearings: SFP, DFP and TFP. Evaluate the seismic

reduction effectiveness of these bearings for constructions.

- Improve the TFP bearings model. Via improved model,

details of each slider displacement on the spherical surfaces and

effects of vertical component of ground acceleration are also clearly

calculated for TFP bearings.

- Propose the optimal parameters of TFP bearings for high-rise

buildings in Hanoi and evaluate the seismic reduction effectiveness

of them.

7. Dissertation layout

The Dissertation consists of the introduction, four chapters and

conclusion, the recommendations, all content of the dissertation is

contained in 133 A4 pages and is organized as follows:

Introduction

Chapter 1. Overview

Chapter 2. Modeling of friction bearings

Chapter 3. Improved model of triple friction pendulum bearing

Chapter 4. Seismic reduction effectiveness of TFP bearings for

high-rise buildings in Ha Noi

Conclusions and recommendations

4

Chapter 1

OVERVIEW

1.1. Overview of earthquakes and earthquake resistant design

1.1.1. Earthquakes

An earthquake is a very strong shaking phenomenon of the

surface of the earth when large energy are released in a very short

time due to the sudden cracked in the crust or in the upper mantle of

the earth [10], [ 62].

Earthquakes have the following original: Earthquake

originated from plate tectonics, from the faults; Other originals: from

the expansion in the hard rock crust of the earth, by explosions,

volcanic activity,…

The important parameters of ground motion in seismic

resistant design including: the largest amplitude, duration of strong

motion, frequency content, magnitude earthquake, the distance to the

fault, soil conditions at site.

1.1.2. Approachs of earthquake resistant design

Earthquake resistant design of structures is a required duty, a

major challenge for structural engineers. There are two earthquake

resistant design perspective: traditional earthquake resistant design

and modern earthquake resistant design.

Earthquake resistant design with modern standpoint associated

with the structural vibration control engineering with 3 main groups

as follows: passive control, active control and semi-active control.

1.2. Seismic base isolation technology

1.2.1. Concept of seismic base isolation

Seismic base isolation is a passive control technique for

structure and very effective in earthquake resistant design. The main

5

idea of this technique is the isolation between superstructure and

basement by using the soft bearings, called seismic isolation bearings.

1.2.2. Types of isolation devices

The types of bearing used in seismic base isolation technique

usually involves two common types: rubber bearings (elastic bearing,

Figure 1.6) and friction bearings made from stainless steel.

Friction bearings 3 main categories:

- Single friction pendulum bearings: structure shown in Fig. 1.7,

including 1 spherical surface with radius R, 1 slider slides on spherical

surface with friction coefficient and ability of displacement is d.

dR,

a. Cutaway view b. Cross section

Figure 1.7. Single friction pendulum bearings (EPS, 2011)

- Double friction pendulum bearings: structure shown in Fig.

1.8, including spherical surfaces 1 and 2 and a slider inside.


Figure 1.8. Double friction pendulum bearings (Fenz, 2008e)

Triple friction pendulum bearings: Structure shown Fig 1.9,

including 4 spherical surfaces with the radius R1, R2, R3 and R4. Inside,

3 sliders slide on 4 spherical surfaces with friction coefficient i.

6


Figure 1.9. Triple friction pendulum bearings (Fenz, 2008e)

1.2.3. Brief history of seismic base isolation technology application

Seismic base isolation technology has been studied and

applied in recent decades. However, the idea appeared more than 100

years ago by the invention of the Touaillon. In recent years, the

application of this techniques for structure subjected to earthquakes

becomes popular in the US, Japan, New Zealand,... and some

countries in Europe.

1.3. Overview of research for isolated friction bearings

1.3.1. The studies outside the country

- The studies of SFP bearings: the first study is published in

1987 by Zayas. The outstanding studies are published by other

authors: Mokha, Constantinou, Reinhorn, Nagarajaiah, Mosqueda,...

The studies focused on analysis structure and movement of the SFP

bearing. Effectiveness of reduce seismic of bearings was evaluated

through theoretical and experimental models.

- The studies of DFP bearings: Tsai and Constantinou research

groups are considered systematically. In addition, many individual

studies on this bearing also should concern such as Kim and Yun

(2007), Malekzadeh (2010),...

- The studies of TFP bearings: TFP bearing with it’s

7

advantages began to be produced around the year 2007. The

outstanding studies can mention such as Constantinous and Fenz

(University of Buffalo); Steve Mahin, Troy Morgan and Tracy

Becker (UC Berkeley); Ryan’s research group (University of

Nevada, Reno), The latest publication of TFP bearing almost belongs

to this group, the publication can be listed as: Dao [36], [37, [38],

Okazaki [80], Ryan [86], [87], [88]. In addition, some studies of

other authors on the TFP bearing also published as: Fadi [41],

Ghodrati [52], Moeindarbari [67], Sarkisian [89], Tsai [103], [104].

1.3.2. The studies inside the country

In Vietnam, base isolation was mentioned in Vietnam design

standards 375: 2006 in 2006. The study is very limited, the

outstanding studies such as: Nguyen Van Giang and Chu Quoc

Thang (2006), Tran Tuan Long (2007), Le Xuan Huynh et al (2008),

Do Kien Quoc (2009), Le Xuan Tung (2010, 2012).

1.4. Comments, the need of new findings

- Earthquake resistant design is a necessary requirement.

Using seismic isolation bearings in the structural vibration control

technology subjected to earthquakes is new perspective bringing high

efficiency, should be studied and more widely applied.

- The studies of friction sliding bearing need to be

implemented in this dissertation as follows: indicate the mumerical

model and evaluate the sseismic reduction effectivenes of SFP, DFP

and TFP bearing; research to develop a improved model of TFP

bearing from the simple model of previous studies. This model must

have the reliability and improve than the existing models; A

application research on TFP bearing for high-rise buildings built in

the ground conditions in Hanoi need been implemented.

8

Chapter 2

MODELING OF FRICTION BEARINGS

2.1. Basis of the theory

2.1.1. Basis of earthquake resistant design for buildings

- Numerical model: with these assumptions in structural

dynamics, numerical model of an n-storey building subjected to

earthquakes will be presented as shown in Figure 2.1.

ug

m1

m2

mn

k1

k2

kncn

c2

c1

1st storey

ug

k1

c1 m1

u1

k2

c2 m2

u2

kn

cn mn

un

uga. b. c.

2nd storey

Nth storey

a. N-storey frame; b. Ideal numerical model;

c. Equivalent model

Fig. 2.1. Multiple DOFs structure model subject to earthquakes

- Equations of motion: the differential equations of motion of

the structural model are established by displacement method

(stiffness matrix method) as Equation 2.1.

- Determination method of structural response: this study will

use the direct integration method (time-history analysis). This

method is the most accurate results, reflect nature of the dynamic

problem, is suitable for research problems.

2.1.2. The choice of numerical method in research

System of differential equations of motion of seismic isolated

structures subjected to earthquakes in this research is complex. We

9

have to use the numerical method to solve them. Runge – Kutta

method will be selected in this study with the it’s advantages.

2.1.3. Calculation model of friction force in friction bearings

Friction force in motion with the laws of nature is relatively

complex. It depends on many factors such as surface material,

pressure, sliding velocity and load history,... There are many models

established to determine the dynamic friction force. The model used

in the study of friction sliding bearing such as: Coulomb model,

modified Coulomb model, plasticity model (Viscoplasticity model,

Bouc - Wen model). In particular, the plasticity model give the most

accurate results, used in this study.

2.2. Modeling of single friction pendulum (SFP) bearings

2.2.1. The relationship between force and horizontal displacement

The general equation of motion of SFP bearings represents the

relationship between force and the horizontal displacement of the

bearings as Equation 2.25, hysteresis loop shown in Figure 2.5.

r

WF u WZ F

R (2.25)

where: 1st component of the equation is the restoring force, the 2

nd

component is the friction force, the force of impact is the 3rd

. F/W

u

1/R

Figure 2.5. Hysteresis loop of SFP bearings

2.2.2. Modeling of seismic isolated structure with SFP bearings

The model is presented as Figure 2.6.

10

ug

k1

c1m1

u1

k2

c2 m2

u2

kn

cn mn

unkb

d

ub

mb

SFP bearing

Fig. 2.6. The model of seismic isolated structure with SFP bearing

System of differential equations of motion including (n + 1)

equations subjected to ground acceleration is written as Equation

2.26 (according to the d'Alembert principle).

2.3. Modeling of double friction pendulum (DFP) bearings


DFP bearing is structured as Fig. 1.8. The motion including 3

different sliding stage. Stage I: sliding begins on surface 1 (surface 2

not yet sliding). Stage II: surface 2 will slide together with surface 1

(sliding on surface 1 and 2). Stage III: Slider on restrainer of surface

1, sliding on surface 2. Equations of motion show the relationship

between force and displacement in the stages expressed as Eq. 2.30,

2.35 and 2.36. Hysteresis loop of the stages shown in Fig. 2.8.

f=F/W

u

2

2

2

1

uII

uI

uIII =d1+d2

Figure 2.8. Hysteresis loop of DFP bearings (----: stage I, II)

2.3.2. Modeling of seismic isolated structure with DFP bearings

The model of seismic isolated structures subjected to earthquake

is presented as Fig. 2.9. System of differential equations of motion is

11

written as Eq. 2.42 (according to the d'Alembert principle).

ug

k1

c1m1

kb1

d1

u1ub1

mb1

k2

c2 m2

u2

kn

cn mn

unkb2

d2

ub2

mb2

DFP bearing

Fig. 2.9. The model of seismic isolated structure with DFP bearing

2.4. Modeling of triple friction pendulum (TFP) bearings


The motion of bearings including 5 stages are described in

detail by Fenz and Morgan. Stage I: sliding on surface 2 and 3 only;

Stage II: sliding on surface 1 and 3; Stage III: sliding on surface 1

and 4; Stage IV: sliding on surface 2 and 4; Stage V: sliding on

surface 2 and 3. Motion equation corresponding stage as Eq. 2.51,

2.55, 2.59, 2.63 and 2.67. Hysteresis loop shown in Fig. 2.11.

f=F/W

u

uI

2

4

uII

uIII

uIV

uV

2

22

1

Figure 2.11. Hysteresis loop of TFP bearings (----: stage I to IV)

2.4.2. Modeling of seismic isolated structure with TFP bearings

The model of seismic isolated structures with TFP bearings

subjected to earthquakes such as Fig 2.12 shows. System of

differential equations of motion is written as Eq. 2.84.

12

ug

k1

c1m1

kb1

e

d1e

u1ub1

mb1

k2

c2 m2

u2

kn

cn mn

un

TFP bearing

kb3

d3e

ub3

mb3

kb2

d2e

ub2

mb2

e e

Fig. 2.12. The model of seismic isolated structure with TFP bearing

2.5. Analysis of numerical example

To illustrate the results of study, an example of a 5-storey

structure was isolated by different friction bearings include: SFP, DFP

and TFP bearing subjected to earthquake is analyzed. Examples will

illustrate the value of the physical characteristics of the structure,

seismic isolation bearings and structural response.

- The 5-storey structure: the same mass per floor mi= 450/g

(kN.s2/mm), stiffness ki = 80 kN/mm and damping ratio %,

fundamental period of structure T1 = 0.529 s.

- Parameters of the bearing: dimensions and parameters of the

bearings are presented as Figure 2.13.

- Ground acceleration parameters: including 7 real acceleration

data of different earthquakes found from the Pacific Earthquake

Engineering Research Center (PEER), as shown in Table 2.1

- Analysis results:

Analysis results including hysteresis loop (Fig. 2.14 to 2.20),

effectiveness of reduce shear for 1st floor (Fig. 2.21 to 2.27) and

reduce absolute acceleration 5th floor (Fig. 2.28 to 2.34). Results of

displacement of bearing is according to relative displacement spectra

and effectiveness of reduce seismic of the bearings is approximately

80% (suitable for previous studies). Comparing the effects of three

13

bearings SFP, DFP and TFP presented in the Fig. from 2.35 to 2.41.

The results show that the effectiveness of TFP bearing is the best.

2.6. Conclusion of Chapter 2

The research results including: 1. Indicate basis of calculation of

earthquake resistant structure; 2. Present the principle of motion SFP,

DFP and TFP bearings and modeling seismic isolated structures with

SFP, DFP and TFP bearings subjected to earthquake; 3. Present an

example to illustrate the results of research. Via the analysis of the

example, the seismic reduction effectiveness is evaluated detailly,

results is suitable for previous studies. In this example, the advantages

of TFP bearing is considered better than the SFP and DFP bearings.

Chapter 3

IMPROVED MODEL OF TFP BEARING

3.1. Introduction

In the Chapter 3 of the dissertation, an improved model for

TFP bearing is studied. The behaviors not yet mentioned in previous

studies of TFP bearing will be analyzed in this model.

3.2. Establishing improved model

The improvements of the model shown in the following: a.

The model considers movement in three-dimensional (two horizontal

x, y and vertical z) of ground acceleration; b. The friction force is

calculated according to a general model, the friction coefficient

depends on sliding velocity and surface pressure of bearing.

Nonlinear behavior of friction force is governed by modified Bouc-

Wen model; c. The model can check the position of the slider on the

surface at each time; d. The accuracy of the model will be validated

by experimental results on many different ground acceleration data.

14

3.2.1. Numerical model

One-dimensional behavior (1D): 1D movement of the TFP

bearing including 5 stages is modeled by Fenz [47], [50] with three

groups of friction elements connected as shown in Figure 3.1. The

physical parameters of the model as Tables 3.1.

1e

d1e

2e

d2e

3e

d3e

F/W

kb1 kb2 kb3

F/W

Figure 3.1. The series model of TFP bearings (Fenz, 2008a)

Developing model: The general model of seismic isolated

structure with TFP bearings subjected to movement of ground in 2

dimensions x and y is shown in Figure 3.2

ksx

csx ms

kb1

e

d1e

usxub1x

mb1

kb3ub3x

kb2ub2x

ksy

csy

kb

1

e

d1

e

ub

1y

mb

1

ugx

ugy

usy

x

y

mb2 mb3

ee

d2e d3e

kb

2

e

d2e

ub

2y

mb

2

kb

3

e

d3

e

ub

3y

mb

3TFP bearing

TF

P b

earin

g

Figure 3.2. The general model of seismic isolated structure with

TFP bearing

15

From the model shown in Figure 3.2, the system of differential

equations of motion of structure isolated by TFP bearing subjected to

ground acceleration in each direction established on the basis of the

d'Alembert principle (Equation 3.1 and 3.2). Friction coefficient of

the movement in both 2 directions is calculated by Equation 3.3,

where the hysteresis variable Z is determined according to Equation

3.5. The vertical component of ground acceleration will be calculated

according to Equation 3.7 and included in the model through the total

weight of superstructure.

3.2.2. Model verification

Theoretical model simulated by Matlab is verified by

experimental results performed by Ryan et al in 2013 [87]. The

experimental full-scale model is a 5-storey building having a total

weight of over 5000 kN (Figure 3.3 to 3.6), is isolated by 9 TFP with

1.4 m in size (Figure 3.7) subjected to 19 different ground

acceleration data. Extracted from some of verify results such as the

following figure.

a. Results of displacement bearing in the x and y directions

16

b. Results of hysteresis loop in the x and y directions

Figure 3.13. Comparing the analytical result to experimental

result subjected to 90TAB motion

a. Results of displacement bearing in the x and y directions

b. Results of hysteresis loop in the x and y directions

Figure 3.26. Comparing the analytical result to experimental

result subjected to 115TAK motion

17

3.3. Detailed calculation slider displacements

Slider displacements on 4 surfaces are calculated as follows:

1

1 1 1

2

2 2 2 1

1

3

3 3 3 4

4

4

4 4 4

( )

( )

( )

( )

eff

f r

eff

f r

eff

eff

f r

eff

eff

f r

Ru F F F

WRW

u F F F uR W

RWu F F F u

R W

Ru F F F

W

(3.9)

Where the force components are determined from solving the

system of differential equations of motion.

3.4. Effects of the vertical component of ground acceleration

The model considering of the effects of vertical component of

ground acceleration is verified with the model of Dao [36]. Analysis

of 5-storey building model with 7 different ground acceleration data

in 2 cases with/without vertical component. The results showed that

displacement bearing has not changed much but absolute

acceleration and shear force in the floor were increased significantly.

Therefore, we can not ignore this component as previous studies.

Figure 3.46 and 3.47 illustrate a case with 88RRS motion.

a. Absolute acc. b. Shear

Figure 3.46. Structural behavior with 88RRS motion

18

Hình 3.47. Hysteresis loop of bearing with 88RRS motion


Developing a new model for seismic isolated structure with

TFP bearing from the one-dimensional (1D) equivalent model of

Fenz et al (2008). Via this model, the displacement of the slider on

surface is calculated in detail and affect of vertical component of

ground acceleration is evaluated clearly.

Chapter 4

SEISMIC REDUCTION EFFECTIVENESS OF TFP

BEARING FOR HIGH-RISE BUILDINGS IN HA NOI

4.1. Introduction

As predicted, Hanoi may occur earthquake level 8. Earthquake

resistant design of buildings for this area is required in the recent

constructions. However, seismic resistant design method is still

traditional. In the study of this chapter, seismic resistant design

method with seismic base isolation technology by TFP bearing for

high-rise buildings was implemented.

4.2. Analysis of the effectiveness of TFP bearings for high-rise

buildings in Hanoi

4.2.1. Structure parameter

The 9-storey reinforced concrete building, assuming the

absoluted hard slab, mass and stiffness of the floor the same

19

assumptions, including: mass mi = 100 N.s2 /mm, stiffness ki = 150

kN/mm, damping ratio fundamental period of structure T1 =

1 s (suitable for various projects).

4.2.2. Selection of analyzed ground acceleration parameters

With performance - based seismic design and time history

analysis, ground acceleration are selected according to the provisions

of ASCE 7-2010 including 7 acceleration data and each motion is

recorded both 2 directions. Structure is analyzed and evaluated with 3

different levels of earthquakes including SLE (Service Level

Earthquake) level, DBE (Design Base Earthquake) level and MCE

(Maximum Considered Earthquake) level. The magnitude of data for

each level is adjusted by SF coefficient as Eq. 4.3. Results acceleration

data is selected as the Table 4.1 and SF coefficient is calculated as

Table 4.2. Fig. 4.2 and 4.3 illustrate the average of SRSS spectra

acceleration and target spectra magnitude after adjustment.

2

1

2

1

2

( ) 1.3

T

SRSS a

T

T

SRSS

T

f SF S S dT

SF

S dT

(4.3)

Figure 4.2. Target spectra MCE compare to the average of SRSS

in isolated base structure

20

Figure 4.3. Target spectra MCE compare to the average of the

SRSS in fixed base structure

4.2.3. The choice of the optimal parameters for TFP bearing with

ground conditions in Hanoi

As structure, there will be 7 parameters of bearing need be

chosen icluding: 2 3 ; 2 3eff effR R ; 2 3d d ; 1; 4; Reff1 = Reff4; d1

= d4 ensuring sliding must occur on 5 stages. The criteria to select the

optimal parameters are given: 1. Adapt many earthquake levels; 2. The

structural response is the smallest. Process of choosing the optimal

parameters for TFP bearing is performed as schematic in Figure 4:24.

The results of the optimal parameters of bearing following: R2 = R3

=500 mm; R1 = R4 = 4000 mm; 2 = 3 = 0.01 - 0.02; 1 = 0.02 - 0.06;

4 = 0.04 – 0.08; d2 = d3 = 40 mm; d1 = d4 = 170 mm.

4.2.4. Seismic reduction effectiveness of the bearing for buildings

We analyze the structure of the two cases: fixed base and

isolated base with TFP bearing. Seismic reduction effectiveness is

evaluated through absolute acceleration and relative displacement of

the floors. With MCE level, the results shown in Figure 4.20 and

4.21. SLE and DBE levels for the same results. Displacement of

bearing, base shear in 2 cases and seismic reduction effectiveness of

21

TFP bearing is calculated in detail in Table 4.4.

Figure 4.20. Absolute acceleration in the floors, MCE level

Figure 4.21. Relative displacement in the floors, MCE level

Table 4.4. Displacement bearing and effectiveness of reducing

base shear in isolated base 9-storey structures with TFP bearings

Level

Disp bearing, ub

(mm) Base shear, Fb (kN)

Fixed

base

Isolated

base

Fixed

base

Isolated

base

Effectiveness

(%)

SLE 0 65.8 2415 697 71

DBE 0 176 5183 1103 79

MCE 0 311 7791 1451 81

From the results of structural response, the horizontal force

conditions in the bearing (in 17.2.4.4, ASCE 7-2010) and the initial

assumption parameters are tested satisfactorily.

22

Fig. 4.24. Determining schematic the parameters for TFP bearing


TFP bearing device is very effective in performance-based

seismic design. Application TFP bearing for high-rise buildings

subjected to earthquake in Hanoi according to ASCE 7-2010 bring high

efficiency (about 70% - 80%). A determining method of the optimum

parameters for TFP bearing is presented. Accordingly, the optimal

parameters used for high-rise building in Hanoi were found.

- Determine the reasonable 1 < 4

- Analyze varied Reff1 = Reff4 with 1 < 4 above

+

- Size of structure

- Construction site

Design spectrum 1. Structural parameters calculation.

2. Choice of parameters for bearing:

- According to experience: Reff2 = Reff3 ; d2 = d3;

2 = 3

- Preliminary: d1 = d4

- Preliminary: Varied Reff1 = Reff4.

- Preliminary: Varied 1 < 4.

Choose and adjust

ground accl.

Assume TD

and TM

Fixed Reff1 = Reff4, analyze with varied 1 < 4

Calculate and check

TD and TM

- Determine the reasonable Reff1 = Reff4

- Determine the parameters fully

Analyze structure with

parameters above Check horizontal

force conditions

Optimal parameters

+

- -

23

CONCLUSIONS AND RECOMMENDATIONS

1. Conclusions

Within the scope of the dissertation, conclusions are drawn as

follows:

1. Based on the the structure and movement principles of the

friction bearings including: SFP, DFP and TFP bearings from

previous studies, dissertation established the model of isolated base

structures with the bearings subjected to earthquakes. Contents

including: indicate numerical model, establish differential equations

of motion and suggest methods to solve them to find out the response

of structures. Dissertation performed a simulation example of the

structure subjected to different ground acceleration data to evaluate

the effectiveness of the devices. The results show that the bearings

are very effective in seismic reduction. From the results of

simulation examples, the advantages of TFP bearing is considered

the best in comparison to SFP and DFP bearing.

2. With the advantages of TFP bearings evaluated, the

dissertation established an improved model for TFP bearings. The

reliability of the model was verified with experimental results.

3. From improved model, the calculation of each slider

displacement inside the bearing is performed. The results are

evaluted detailly of each location of slider at each time of the

movement. The significance of this work is to determine precisely

the surphus displacement of each slider at the end of the earthquake.

4. Effects of vertical component of ground acceleration on

response of the structures isolated by TFP bearings is carefully

analyzed in the dissertation. This result shows that, with some

earthquakes having large peak value or large vertical acceleration

24

will cause the response of structures increased significantly, can not

be ignored in the design, which is almost neglected in previous

studies, especially the absolute acceleration of the floor.

5. Application research of TFP bearings for high-rise buildings

with seismic conditions in Hanoi is performed in the dissertation.

Content of this study is to find an optimal parameters for TFP

bearing with seismic conditions in Hanoi, evaluate the seismic

reduction effectiveness of the TFP bearing for buildings.

2. Recommendations

In terms of research and the scope of the dissertation, a

number of issues have not yet been mentioned and clarified, need to

have the following research, specifically:

1. It’s necessary to study a reasonable impact model to

simulate structural behavior when the slider reaches the displacement

limit. The impact occurs between the slider and the hard boundary

will effect on the structural response.

2. When the slider slides on the spherical surface, the

temperature at the contact surface between the slider and the surface

will increase, take effect on the friction coefficient of the bearing.

This problem also need to be studied and clarified.

3. Seismic base isolation system usually has a large horizontal

displacement. It is nessesary to study structural control combining

other devices with those bearings to limit horizontal displacement of

large superstructure.

4. It’s nessesary to be further study of the problem of multi-

objective optimization to find the optimal parameters for TFP

bearings with all buildings and different ground conditions in

Vietnam.

LIST OF PUBLISHED WORKS

1. Published scientific papers

1.1. Domestic Publishing

1. Nguyen Van Nam, Hoang Phuong Hoa, Pham Duy Hoa (2013),

Seismic reduction effectiveness of TFP friction isolation

bearings, compare to SFP bearings, Proceedings of the 9th

Vietnam National Congress on Mechanics, Hanoi, December

08-09, 2012, ISBN: 978-604-911-435-9, pp. 397- 405.

2. Pham Dinh Trung, Nguyen Van Nam, Nguyen Trong Phuoc

(2014), Analyzing the seismic reduction effectiveness of friction

bearings combines with Magneto-Rheological damper

connecting two structures subjected to earthquakes”, Journal of

Science Ho Chi Minh City Open University, Vol. 1 (34) 2014,

ISSN 1859-3453, pp. 102-115.

3. Tran Quoc Khanh, Hoang Phuong Hoa, Nguyen Van Nam

(2014), Seismic reduction effectiveness of friction pendulum

bearing for continuous beam bridge subjected to earthquake

load, Proceedings of the Vietnam National Congress on

Mechanical engineering for the 35th Anniversary of the

Foundation of the Institute of Mechanics, Hanoi, April 09, 2014,

ISBN: 978-604-913-233-9, pp. 81-86.


Seismic reduction effectiveness of TFP friction bearings for

high-rise buildings, Proceedings of the Vietnam National

Congress on Mechanical engineering for the 35th Anniversary

of the Foundation of the Institute of Mechanics, Hanoi, April 09,

2014, ISBN: 978-604-913-233-9, pp. 155-150.


Modeling of friction bearings in structures subjected to

earthquakes: SFP bearing, Proceedings of the Vietnam National

Congress on Mechanical engineering, Danang University, ISBN

978-604-84-1273-9, pp. 479 - 486.

6. Nguyen Van Nam, Hoang Phuong Hoa, Nguyen Hoang Vinh

(2015), Modeling of friction bearings in structures subjected to

earthquakes: DFP and TFP bearings, Proceedings of the

Vietnam National Congress on Mechanical engineering, Danang

University, ISBN 978-604-84-1273-9, pp. 487 - 494.

7. Hoang Phuong Hoa, Nguyen Van Nam, Pham Duy Hoa (2016),

Study the effects of dimension parameter on behavior of double

friction bearings subjected to earthquakes, Journal of

Construction (Vietnam Ministry of Construction), ISSN 0866-

0762, Vol. 01(2016), pp. 87-90.


Effects of vertical components of strong earthquakes on the

response of base isolated structures with TFP bearings, Journal

of Science and Technology - Danang University, ISSN 1859-

1531, Vol. 1(98), pp. 46-49.

9. Hoang Phuong Hoa, Nguyen Van Nam, Pham Duy Hoa (2016),

Designing the optimal dimensions single friction bearings for

high-rise buildings subjected to earthquake, Journal of

Construction (Vietnam Ministry of Construction), ISSN 0866-

0762, Vol. 3(2016), pp. 106-109.


The effectiveness of SFP seismic isolation bearings for high-rise

buildings subjected to earthquakes considering of vertical

excitation component, Journal of Construction (Vietnam

Ministry of Construction), ISSN 0866-0762, Vol. 3(2016), pp.

34-36.

11. Nguyen Hoang Vinh, Nguyen Van Nam, Hoang Phuong Hoa

(2016), General modeling of seismic isolated structures with

SFP bearings, Journal of Construction (Vietnam Ministry of

Construction), ISSN 0866-0762, Vol. 3(2016), pp. 102-105.

12. Hoang Phuong Hoa, Nguyen Van Nam, Ngo Thanh Nhan

(2016), Effect of SFP bearing parameters on response of seismic

isolated structures, Journal of Transportation (Vietnam Ministry

of Transport), ISSN 2354-0818, Vol. 6(2016), pp. 52-54.

13. Thai Van Ngai, Nguyen Ba Ngo, Hoang Phuong Hoa, Phan

Hoang Nam, Nguyen Van Nam (2016), Research the methods of

seismic reduction for cable-stayed bridge at Nga Ba Hue

intersection - Danang City subjected to earthquakes,

Proceedings of National Conference on Transport infrastructure

with sustainable development, Danang, September 17-18, 2016,

ISBN 978-604-82-1809-6, pp. 603-608.

14. Dang Xuan Binh, Nguyen Van Duan, Hoang Phuong Hoa, Phan

Hoang Nam, Nguyen Van Nam (2016), Research the methods of

seismic reduction for roundabout structure at Nga Ba Hue

intersection - Danang City subjected to earthquakes,

Proceedings of National Conference on Transport infrastructure

with sustainable development, Danang, September 17-18, 2016,

ISBN 978-604-82-1809-6, pp. 597-602.

1.2. International Publishing

1. Nam V.Nguyen, Hoa P.Hoang and Hoa D.Pham (2016),

Predicting the responses of triple friction pendulum bearings

using an improved model with variant friction coefficient,

Proceedings of The Fourteenth East Asia-Pacific Conference on

Structural Engineering and Construction (EASEC14),

HochiMinh City, 6-8 Jan, 2016, ISBN: 978-604-82-1684-9, pp.

1578-1585.

2. V. Nam Nguyen, P. Hoa Hoang, H. Nam Phan and Fabrizio

Paolacci (2016), A Modeling Approach of Base Isolated High-

Rise Building with Double Friction Pendulum Bearings,

International Conference on Advanced Technology Sustainable

Development ICATSD2016. Ho Chi Minh City, 22-23, August

2016, ISBN 978-604-920-040-3, pp. 235-240.

2. Science research work

1. Ministry level research: Application Research of seismic

isolation solutions for constructions subjected to earthquakes.

Code: B2016.DNA.03. (In progress, expected to report in 2017,

Responsibility: members).

NGUYEN VAN NAM MODELING OF STRUCTURES SEISMICALLY ISOLATED...

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