seismic performance on non- structural elements – … · structural elements were observed in the...

http://www.iaeme.com/IJCIET/index.asp 1005 [email protected]

International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 11, November 2017, pp. 1005-1017, Article ID: IJCIET_08_11_099

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=8&IType=11

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

SEISMIC PERFORMANCE ON NON-

STRUCTURAL ELEMENTS – AN

EXPERIMENTAL INVESTIGATION AND

NUMERICAL ANALYSES

B. Powrna

Department of Civil Engineering, Anand Institute of Higher Technology, Tamilnadu, India

R. Rajkumar

Department of Civil Engineering, SSN College of Engineering, Tamilnadu, India

R. Aravindh


B. Gokula Krishnan


ABSTRACT

Non-structural elements are more important for the structure. This study is more

interested in knowing the response of non-structural elements which may lead to make

the structural element not to achieve the immediate occupancy performance level. The

response of a non-structural element depends on the response of its supporting building,

size and weight of element, location of the element in the building (for example, the first

floor or roof), flexibility of the component, etc. Earthquake design of non-structural

elements is quite crucial for important buildings and lifeline structures. However, as

progress was made with regard to seismic safety of main structures, and failures of non-

structural elements were observed in the past earthquakes, seismic codes incorporated

design provisions for these elements. The main aim is to study the seismic performance

of the non-structural element mounted within buildings to withstand the forces and

displacement that arise from the seismic response of the structure. Non-structural

elements transfer the inertia force to the structural elements. Observation of non-

structural element in the past earthquake that had happened in Northrigde, Nisqually

and Bhujwere observed. In these earthquakes, the major damage is due to non-

structural elements. This study includes the physical characteristics of non-structural

element, response characteristics of non-structural elements, acceleration of non-

structural elements and importance of non-structural elements. Various analysis

methods of non-structural elements such as Equivalent static analysis, Linear dynamic

analysis, Non-linear static analysis, Non-linear dynamic analysis and Response

B. Powrna, R. Rajkumar, R. Aravindh and B. Gokula Krishnan


spectrum analysis are presented. Dynamic interaction of the structural and non-

structural elements is studied. Evaluation of the mid period dynamic response and short

period dynamic response of the non-structural elements are studied and reported. It is

concluded that as the displacement goes higher the acceleration decreases respectively

and the stress increases accordingly.

Key words: Earthquake, Response Spectrum, Displacement, Non-Structural.

Cite this Article: B. Powrna, R. Rajkumar, R. Aravindh and B. Gokula Krishnan,

Seismic Performance on Non-Structural Elements – An Experimental Investigation and

Numerical Analyses, International Journal of Civil Engineering and Technology, 8(11),

2017, pp. 1005-1017.

http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=8&IType=11

1. INTRODUCTION

Floor vibration is the oscillatory motion of the building and occupants (vertical and horizontal

direction). This vibration causes damage to non-structural elements. Human activities induce

sinusoidal loading to the floor slab and the machines induce impact loading on the floor slab.

External forces like traffic and so on can also cause floor vibration. The frequency of human

walk is 1.6 to 2.2 Hz. There will be periodic loading so superimposition of frequencies occurs.

So, they get malfunctioned depending on the motion, duration, and layout of the building. For

better vibration performance steel construction has been implemented because it is cost

effective, light weight solution and good vibration damping. If the mass of the structure gets

increased the magnitude of the vibration response gets decreased. Perceptible reduction in

vibration amplitude can change mass, stiffness or damping of the floor system.

2. TRANSMISSION PATH OF VIBRATION

The parameters that govern the vibration response of a floor system are its mass, modulus of

elasticity and damping.

2.1. MASS

The mass to be used in analysis is that of the floor system and its superimposed load. It is

expressed as (W/g), where “W” is the weight of the objects attached to the floor that faithfully

follows its displacement and “g” is the gravitational acceleration taken as 9.81 m/sec2. Applied

forces without mass that do not affect structure’s stiffness are not included in the vibration

response of a floor.

2.2. MODULUS OF ELASTICITY

The elastic modulus for vibration analysis is larger than the static values, in particular when

high strength concrete is used. Recommended values are 25% higher than the static modulus.

2.3. DAMPING

Damping has an inherently high variability that is difficult to determine before a floor system

is placed in service. The recommended values from reference vary from 2-3% for steel floors.

3. EXPERIMENTAL SETUP

The experiment was performed on the specimen made of acrylic and steel material. Base plate

is of steel material. A flexible box like structure has been considered. Two set of earthquake

vibration has been performed. The first set was carried out for point 1 and point 4. The next set

was carried out for point 2 and point 3.

Seismic Performance on Non-Structural Elements – An Experimental Investigation and Numerical

Analyses


The hanging exciter is used to produce the earthquake vibration. The accelerometers are

used to determine the acceleration. Analysis has been found using burst random, random, sine

and sweep sine. Pairs of accelerometers extending over a region of space can be used to detect

differences (gradients) in the proper acceleration of frames of references associated with those

points. Because this investigation incorporated the horizontal component of the vibration

record, it was important to characterize the typical ratio of vertical excitation to the horizontal

excitation.

The total height of the specimen is 1.01m. The dimension of the Plexiglas box is 1.25m x

1,25m x1m. The dimension of the base plate is 2m x 2m. The diagrammatic sketch is shown in

Fig 1. The excitation is given at the 0.22m from the top of the specimen. The structural element

taken into consideration is a plate with a length and width of 2m and thickness of the plate as

0,01m. The experimental set up is shown in Fig 2.

Figure 1 Line diagram showing the schematic setup

Figure 2 Specimen with hanging excitation

4. FLOW CHART OF THE SETUP

The specimen is excited using a hanging exciter. To avoid the overheating of the exciter it is

connected to the air cooling unit. One of the output channel is also taken from the exciter and

connected to the power amplifier to amplify the signal. Then signal is connected to the signal

mobiliser. The response of the base plate from which the acceleration is to be determined is

taken based on the direction as the two set of responses. The response is carried to the signal

mobiliser to stabilize the signal. The response is taken from the base plate. The two-response

channel and the force channel is connected to the personal computer through the LAN. The

excitation force of 0.03kN is given to the specimen. A nonlinear time history analysis has been

performed to evaluate the dynamic parameters of interest. Also, the type of input excitation

assumes importance in the evaluated dynamic parameters, which is to be studied further in the

project.

Experimental sweep sine investigation has been performed on the plate. The sweep sine

investigations have been carried out for the frequency range of 2 to 25 Hz and the transfer

functions have been evaluated. Time and frequency domain analysis have been conducted and



the salient features are noted. Experimental investigation has been carried out to determine the

response of the plate under excitation. The material of the plate used for the study is steel. The

end conditions are fixed. The experimental setup for the transient excitation consists of

accelerometers and modal shaker. Modal shaker has been used for giving the sweep sine and

excitation. The time history of force and response are obtained in the form of real and

imaginary.

The piezo accelerometer is placed at four corners of the plate so that acceleration response

at those points can be determined. The obtained responses are then amplified using an amplifier.

The amplified signals in time domain are fed into the digital spectrum analyzer. This spectrum

analyzer converts the signal in the time domain to frequency domain. The resultant graph

representing the responses is displayed on the monitor. From the computer, the obtained result

could be processed for determining the acceleration parameters of the plate. The line diagram

of the setup is shown in Fig 3 and the photograph of the setup is presented in Fig 4.

Figure 3 Schematic sketch of flowchart of the setup

Figure 4 Flowchart of experimental setup

5. RESULTS AND DISCUSSION

5.1. RESPONSE OF THE ACCELEROMETERS

The acceleration response of the base plate is taken with the help of the software as shown in

Fig 5. This gives the frequency and time domain of the force and response channels.


Analyses


Figure 5 Acceleration response of the base plate

5.2. HALF POWER BANDWIDTH

Half power bandwidth has been made use to determine the damping. Damping in mechanical

systems may be represented in numerous formats. As per half power bandwidth the structural

damping,

Q = ��

�� =

��

= �

(1)

Where, ε = viscous damping ratio

Q= amplification or quality factor

The Q value is equal to the peak transfer function magnitude for a single-degree-of freedom

subjected to base excitation at its natural frequency.

The natural frequency of the plate is

C� ��

� � (2)

= 0.56 (19.26)

= 15.41 Hz

Figure 6 Acceleration spectrum of the accelerometer at point 1

As per the half power bandwidth theorem the damping ratio is determined as follows, the

peak value of acceleration is (48.75, 0.00152) as evident from Fig 6.



� = 0.00152

2� = 65.89

Q = 64.102

=0.780%

6. NUMERICAL ANALYSIS

The construction of solutions to engineering problems using FEA requires either the

development of a computer program based on the FEA formulation or the use of a commercially

available general-purpose FEA program such as ANSYS. The ANSYS program is a powerful,

multi-purpose analysis tool that can be used in a wide variety of engineering disciplines. The

computational expense should be balanced against the accuracy of the results.

Fig 7 depicts the flow chart for the ANSYS program carried out in this study.

Figure 7 Flow chart of the ANSYS process

7. MATERIAL PROPERTIES

The young’s modulus of steel and Plexiglas are 207 GPa and 45 GPa. Respectively and the

Poisson’s ratio of steel and Plexiglas are 0.29 and 0.35 respectively

8. MATERIAL MODELLING

If the physical system under consideration exhibits symmetry in geometry, material properties,

and loading, then it is computationally advantageous to model only a representative portion. If

the symmetry observations are to be included in the model generation, the physical system must

exhibit symmetry in all of the following:

• Geometry.

• Material properties.

• Loading.

• Degree of freedom constraints.


Analyses


9. TRANSIENT VIBRATION

To determine the dynamic response of the time dependent loading transient analysis is chosen

instead of the static, modal and harmonic analysis.

Transient dynamic analysis of the floor slab in this study has been performed using ANSYS

software. To evaluate the dynamic response of floor slab in time domain needs to do a transient

dynamic analysis. ANSYS offers three methods of transient dynamic analysis: Full transient,

Modal superposition method, and reduced method. These methods differ in calculation method

and also in range of applicable types of load. In this study, the results from ANSYS are

compared with transient calculations done experimentally and theoretically

For this analytical investigation three type of input loading are considered and the schematic

sketch of the floor to be loaded is illustrated in Fig 8.

1. Trapezoidal wave2. Triangular wave3. Sinusoidal wave

Figure 7 Schematic sketch of floor that is to be loaded

9.1. ANALYTICAL STUDY OF TRAPEZOIDAL PULSE LOAD

Figure 9 Trapezoidal wave is loaded to the model to study the response of the structure

For each loading input the displacement with lower amplitude which is within the elastic

limit is given in case I. Next the displacement with higher amplitude which is beyond the elastic

limit is given in case II. The results are plotted as shown in the form of graphs as shown in Fig

10 and 11 respectively.



Figure 10 Lower amplitude trapezoidal loading wave

Figure 11 Higher amplitude trapezoidal loading wave

The numerical results obtained for the Trapezoidal loading wave are presented in Table 1.

Table 1 Results for the trapezoidal pulse

Point of

Response

Case 1 Case 2

Maximum Stress

value

(kN/m2)

Maximum

acceleration (m/s2)

Maximum Stress

value

(kN/m2)

Maximum acceleration

(m/s2)

1 0.682345E-06 -0.0234902E-09 0.349029E-05 -0.154836E-09

2 0.998767E-06 0.394863E-05

3 0.997631E-06 0.946958E-05

4 0.998616E-06 0.785883E-05

9.2. ANALYTICAL STUDY OF TRIANGULAR PULSE LOAD

Fig 12 shows the triangular wave loaded to the model to study its response. For each loading

input the displacement with lower amplitude which is within the elastic limit is given in case I.

Next the displacement with higher amplitude which is beyond the elastic limit is given in case

II.

0

0.02

0.04

0.06

0.08

0.1

0 0.1 0.2 0.3 0.4

Dis

pla

cem

ent,

mTime period, Sec

0

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4

Dis

pla

cem

ent,

m

Time period, Sec


Analyses


Figure 12 Triangular wave is loaded to the model to study the response of the structure.

9.3. ANALYTICAL STUDY OF HALF SINE PULSE LOAD

Figure 13 Half sine pulse wave is loaded to the model to study the response of the structure

Fig 13 shows the half sine pulse loaded to the model to study its response. For each loading

input the displacement with lower amplitude which is within the elastic limit is given in case I.

Next the displacement with higher amplitude which is beyond the elastic limit is given in case

II.

Fig 14, 15 16 and 17 show the stress response of the model at points 1, 2, 3 and 4

respectively obtained as a result of trapezoidal wave loading on the model for case 1.

Similarly, the stress response corresponding to the higher amplitude are obtained and

presented in Fig 18, 19, 20 and 21 at point 1,2, 3 and 4 respectively.



Figure 14 Stress response of point1 Figure 15 Stress response of point 2

Figure 16 Stress response of point 3 Figure 17 Stress response of point 4

Figure 18 Stress response at point 1 Figure 19 Stress response at point 2

Figure 20 Stress response at point 3 Figure 21 Stress response at point 4


Analyses


The Acceleration response for the lower amplitude displacement and Higher amplitude

displacements are presented in Fig 22 and 23 respectively.

Figure 22 Acceleration response for lower amplitude displacement values

Figure 23 Acceleration response for higher amplitude displacement values

The Contour plots of the trapezoidal wave for lower displacement and Higher displacement

are presented in Fig 24 and 25 respectively.

Figure 24 Contour plot for lower amplitude displacement values

Figure 25 Contour plot for higher amplitude displacement values



10. CONCLUSIONS

Similar responses are obtained for triangular loading and half sine pulse loading on the model.

Graphical results are obtained for lower amplitude and for higher amplitude.

This study is devoted in understanding the basic principles which govern the floor vibration

induced by the human activities and the external forces. The study emphasizes the importance

of seismic design of non-structural elements and floor acceleration and floor stress due to the

earthquake force. Various codal provisions and modelling approaches available on this topic

have been reviewed. Relative displacement of the non-structural elements should be considered

as the point of view of structural design. Amplification factor and the damping ratio are

determined from the experimental investigation. An analytical study related to the test specimen

has been performed using ANSYS 12 and the necessity of further experimental evaluation using

earthquake simulators have been identified for better seismic performance of important

structures.

From the study, it has been noted that when the displacement goes higher, the acceleration

decreases respectively and the stress increases accordingly. Horizontal acceleration demand is

studied to know about the quasi resonance. The theoretical evaluation of the non- structural

element also has been studied to check the permissible limit of first natural frequency.

REFERENCE

[1] Andre Filiatrault (2001), “Guidelines, Specifications and seismic performance

characterization of non-structural building components and equipment”, PEER 2002/ 0.5,

Pacific earthquake engineering research Centre.

[2] ATC 69 (2008), Reducing the risks of non-structural earthquake damage, Applied

Technology Council; California, USA.

[3] ASCE7 (2016), Seismic design requirements for non-structural components, American

Society of Civil Engineers; Virginia, USA.

[4] “Earthquake engineering practice” (2013), Volume 7, Issue I, National information Centre

of earthquake engineering; Kanpur, India.

[5] FEMA 74 (2005), “Earthquake hazard mitigation for non-structural elements”, Federal

Emergency Management Agency; USA.

[6] Fan Ru Lin (2008), “Development of seismic force requirements for non-structural

components in Taiwan”, 14th world conference on earthquake engineering; Beijing, China.

[7] Gordon Colin G. (1991), “Generic Criteria for Vibration-Sensitive Equipment”, Volume

1619, SPIE Proceedings; Washington, USA.

[8] Goutam Mondal and Sudhir K Jain (2005), “Design of non-structural elements for

buildings”, PP – 22 to 27, Indian concrete journal.

[9] IBC (2006), chapter 8, 11, 12, 29, 30, International building code; California, USA.

[10] John W Van de Lindt, et al (2007), “Non-structural elements in performance-based seismic

design of wood frame structures”, Journal of structural engineering.

[11] Lam N.T.K (2008),”Overturning of non-structural components in low-moderate seismicity

regions”, Special Issue, Electronic Journal of Structural Engineering.

[12] Mario Paz (2004), “Structural Dynamics”, Second edition, CBS Publication, New Delhi,

India.

[13] FEMA273 (1997), NHRP “Guidelines for the seismic rehabilitation of buildings”, Federal

Emergency Management Agency; USA.

[14] Philip J. Caldwell, et al (2004), Phase 2, Task 2.3 “ATC-58 Project Task Report”.

[15] Pampanin S. (2011), “Damage mitigation strategies of non-structural infill walls”,

Proceedings of 9th pacific conference on earthquake engineering.


Analyses


[16] Robert Bachman (2011), “Proceedings of MCEER seminar”, Multidisciplinary Center for

Earthquake Engineering Research, Haiti.

[17] Samit Ray Chaudhiri (2004), “Distribution of peak horizontal floor acceleration for

estimating non-structural element vulnerability”, 13th world conference on earthquake

engineering.

[18] ShahramTaghavi (2008), “Effect of interaction between primary and secondary systems on

floor response spectra”, 14th world conference on earthquake engineering.

[19] Saeed moaveni, “Finite element analysis – theory and application with ANSYS”,

[20] Strukturlabor (2010), “Finite element modeling with ANSYS”, Centre of structure

technologies.

[21] Gaikwad Madhukar V and Prof. Mangulkar Madhuri N, Seismic Performance of Circular

Elevated Water Tank with Framed Staging System, Volume 4, Issue 4, May – June 2013,

pp. 159-167, International Journal of Advanced Research in Engineering and Technology

(IJARET).

[22] Dar, M. H., Chat, Z. A. and Shafi, S. Flaws in Construction Practices of Masonry Buildings

in Kashmir with Reference to Earthquakes (A Case Study). International Journal of

Advanced Research in Engineering and Technology, 6(1), 2015, pp. 70-75.

[23] Dharane Sidramappa Shivashaankar and Patil Raobahdur Yashwant, Role of Ferrocement

Cavity Wall In Earthquake Resistant Structure and Construction Method, Volume 5, Issue

6, June (2014), pp. 108-111, International Journal of Advanced Research in Engineering

and Technology (IJARET)

[24] Wyatt (1989), “Design guide on the vibration of floors”, steel construction institute

publication 076, London.

seismic performance on non- structural elements – … · structural elements were observed in the...

Documents