Download - Brief Report of Research Done by EERI-VJTI Student Chapter's 1st Team VJTI Unshakeables

7/31/2019 Brief Report of Research Done by EERI-VJTI Student Chapter's 1st Team VJTI Unshakeables

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Brief Report Of Research done by EERI-VJTI Student Chapter's 1st team VJTI Unshakeables

By

1. Kunal Chopda2. Prathamesh Khanolkar3. Ronak Jain4. Sameer Dhuri5. Saurabh Humbre6. Shivam Mishra7. Sumit Ghogale8. Tanmay Kamble9. Vatsal Mehtalia10.Yogendra Borse

Guided by

1. Dr Mrs M. A. Chakrabarti , HOD , Structural Dept , V.J.T.I.2. Dr K. K .Sangle, Prof Structural Dept, V.J.T.I.1. Introduction :

We are a team of undergraduate students fromVeermata Jijabai Technological Institute (VJTI),Mumbai. Our team

members are driven to make a mark in the field of earthquake sustainability. As a part of this, we students participated

inSeismic Design Competition 2012which is organized byEERI (Earthquake Engineering Research Institute). We

to share this experience with ISSE. We were the 1st

team from India to participate in this competition. With this

discussion, more undergraduate students will develop interest in this field.

The objectives of competition were to promote study of earthquake engineering among undergraduate students. It gave

opportunity to work on a hands-on project designing and constructing a cost-effective frame building to resist seismicloading and understand the fundamentals of Structural Dynamics and Earthquake.Our team was hired to submit a desi

for a multi-story commercial office building. Our task was to design and construct a cost-effective structure to resist

seismic loading.

2. The overall framework of competition is as follows:

To verify the seismic load resistance system, a scaled balsa wood model must be constructed and tested. The model is

be subjected to three ground motions, which represent different return period earthquakes. In order to ensure life safety

the building model must not collapse during shaking. In addition, the response of the model in terms of roof drift and r

acceleration will be measured during the shaking. For each ground motion, the value of the roof drift will be used to

estimate the monetary loss due to damage in the structural and non-structural building components. Likewise, the roof

acceleration will be used to estimate the monetary loss due to damaged equipment that is contained inside the buildingcollapse occurs, the monetary losses will account for demolishment, reconstruction, and downtime. Finally, the annual

seismic cost will be obtained as the sum of the economic loss estimated for each of the earthquakes divided by its retu

period.A cost-benefit analysis will be carried out to determine the most cost-effective building. This will be done by

balancing the revenue with the initial building cost and seismic cost.

Project Constraints:

The model has to comply with the conditions provided by the organizers as follows:
http://www.vjti.ac.in/http://www.vjti.ac.in/http://www.vjti.ac.in/http://slc.eeri.org/SDC2012.htmhttp://slc.eeri.org/SDC2012.htmhttp://slc.eeri.org/SDC2012.htmhttp://www.eeri.org/http://www.eeri.org/http://www.eeri.org/http://slc.eeri.org/SDC2012.htmhttp://www.vjti.ac.in/


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2.1 Building DimensionsThe building must comply with the following dimensions.

Max floor plan dimension: 15 in x15 in

Min individual floor dimension: 6 in x 6 in

Max and min number of floor levels: 29 and 15

Floor height: 2 in Lobby level height (1st level): 4 in

Min and max building height: 32 in and 60 inMax rentable total floor area: 4650 in2 (3 m2)

2.2 Weight of Scale ModelThe total weight of the scale model, including the base and roof plates and any damping devices, should not exceed

4.85 lbs (2.2 kg). The approximate weight of Model Base Plate and Roof Plate 1.1 Kilograms.

2.3 Structural Frame Members

Structures shall be made of balsa wood. The maximum member cross section dimensions are:

Rectangular member: 1/4 in x 1/4 in and Circular member of dia 1/4 in (6.4 mm).

2.4 Shear WallsShear walls constructed out of balsa wood must comply with the following requirements:

Maximum thickness: 1/8 in Minimum length (plan view): 1 in.

Shear walls must span at least one floor. Structural members can attach to the ends of a shear wall.2.5 Structural LoadingDead loads and inertial masses will be added through steel threaded bars tightened with washers and nuts. These will b

firmly attached to the frame in the direction perpendicular to shaking.

Floor weight: (1.18 kg)Roof weight: (1.59 kg)

Weight spacing: Increments of 1/10th the height (H/10)

Length between weights on bar: 16 in Threaded bar diameter: 1/2 in

The dead load will be placed at nine floor levels in increments of (H/10), corresponding to (1/10) x H to (9/10) x H. In

cases where a floor does not exist at an exact increment of (H/10), the weight will be attached to the nearest higher flo


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Figure 1. Testing of model on shake table with the loads applied

3. Our aim

To achieve balance of a stiff and flexible structure in design with Simple structural configuration. The design must be

Cost effective and feasible.

4. We proceeded for our project as follows:

Before we could start working on actual model, various tests were performed. Following points were considered first:

4.1 TESTING

4.1.1Material


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Figure 2. Three point flexure test

4.1.1.1 BALSA wood:The material which is very close to steel is BALSA wood, which is very delicate to handle, as well as tough to work o

As it is brittle, it is liable to fracture and slicing and hence incapable to take considerable strain and deformations. Thr

point flexure test was performed (refer Figure 2) to determine Elastic modulus of balsa wood from formula E =

(5wl4)/384Iy.

4.1.1.2 Adhesives:

The joint with the different adhesives were tested for tension and shear failure. And from results, Fevikwik was

finalized.

Table 1. Strength of Adhesives

4.1.2 Connection

Adhesive Tensile strength Shear Strength

Fevikwik- 9.5 kg/mm2 0.4 kg/mm2

Araldite 4.8 kg/mm2 15.8 kg/mm2

Fevicol 3.1 kg/mm2/mm2 11.08 kg/mm2


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Figure 3. Gusset plate connection in model

No connection was supposed to be made with nails or binding wires etc. Only method to connect to members was to uGroove Joint, Butt Joint, Tongue & Groove Joint, and Oblique Cross Halving Joint to enhance the strength of joint. Al

Gusset Plate is used as moment connection; it increased surface area of contact and joint fixity.

4.1.3 Compression testing of columnA prototype of beams and column of 2 storeys is subjected to compression test and the model with desired level is

adopted.(refer Figure 4)

Figure 4. Compression test of prototype (buckling of columns at middle beam joints)

4.2 EXPERIMENTS:


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To achieve our final model, we made 3 models before.

First, the scheme framework of model was tested in ETABS software. Model with the optimum solution was chosen to

erected. The model is then tested on the shake table to study the effect of vibration on the structure simulating to the

earthquake force.

.

Figure 5: Primary models without bracing

First model was made of pine wood due to unavailability and then actual balsa wood is used for rest of the models. Tu

In Tube form is used for model 1 and 2. No bracing were provided to understand the behavior of the columns and beam

only. Also, the method of erection was improvised from experience. In first model, no more than 3 people could work

the model. But later, it was erected in parts and the structure was made horizontal while assembly. So proper level is

achieved.

4.3 Conceptual input in final model :

From the experiments, we modified our structure to achieve final model. The features are:

4.3.1 Stiffen the structure:


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Structure becomes stiffer if the internal force is more direct, more uniformly distributed and small. This concept is

explained with the equations:

Deflection of pin jointed structure is = (Ni2Li / EiAi) For i= 1 to m

Stiffness of pin jointed structure is = 1/ (Ni2Li / EiAi) = 1/ Ni

2fi

Where,

Ni: is the ith internal force induced by a unit load at the critical point;

Li: is the length ofith member;

Ei: Youngs modulus of the ith member;

Ai: area of the ith member;

fi=Li/Ei*Ai is known as the flexibility of the ith member.

Hence to increase the stiffness conceptual solution used are

1. As many force components as possible should be zero.

2. No one force component should be significantly larger than the other non-zero forces.

3. The values of all non-zero force components should be as small as possible.

4.3.2 Core area was increased.

4.3.3 Shear Walls:

We tried Tapered shear walls which cause reduction in cost, requirement of lesser material, faster completion of proje

But it led to formation of soft-storey mechanism due to gradual reduction of shear resisting area, and the structure faile

torsion. Hence, we decided to use continuous shear wall for full height of the structure.

4.3.4 Super Column

General super column theory consists of provision of columns having large dimensions and concrete columns having ssections.

They are extended to the top of the structure and provide a high degree of rigidity and generally adopted for tall structu

This was used to design huge right angled triangle shaped hollow columns formed by connecting 3 vertical shear wall

the 4 diagonal corners of the structure

This helped to concentrate max weight along the edges and hence use the weight of the structure with maximum benef

It was made using three shear walls converging to form right-angled triangles at the four corners of the structure. This

gave very good performance during software modeling in spite of absence of a core and provision of outriggers.

Also, it provided an overall stiffness and symmetry to the structure due to them having high stiffness and being at larg

distances from the centroid of the structure. This design causes lower amount of torsion. Also very large spans could b

provided which is always welcomed by the developers.


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4.3.5 BracingBracing systems may be used for transmitting loads and increasing lateral structural stiffness. There are many options

arrange bracing members and there are unlimited numbers of bracing patterns, as evidenced in tall buildings, scaffoldi

structures and temporary grandstands. Five criteria, based on the first concept derived in the last section, have been

suggested for arranging bracing members for a structure. The five criteria can be presented as follows:

Criterion 1: Bracing members should be provided in each story from the support (base) to the top of the structure.

Criterion 2: Bracing members in different stories should be directly linked. Criterion 3: Bracing members should be linked linearly wherever possible.

Criterion 4: Bracing members in the top story and in different bays should be directly linked where possible.

Criterion 5: If extra bracing members are required, they should be linked following the above four criteria.

The first criterion is obvious to ensure proper transmission of loads. If bracing is not provided over the entire height of

structure, its performance will be significantly reduced. There are a number of ways to achieve this criterion; but the

second and the third criteria suggest using the shorter force path. The first three criteria mainly concern the bracing

arrangements in different stories. For a temporary grandstand structure, however, the number of bays is usually larger

the number of the stories. To create a shorter force path, or more zero force members in a structure, the fourth criterion

gives a means to consider the relationship of bracing members across the bays of the structure.

The fifth criterion suggests that when extra bracing members are required, usually to reduce bracing member forces an

distributes them more uniformly, they should be arranged using the previous criteria.

4.3.6. Roof frame:

As the roof frame was subjected to loading, the frame of roof was made of thicker section to avoid local failure.

(Refer Figure 6)


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Figure 6: Thicker members in Roof grid

4.3.5.1 ETABS

To decide what kind of bracing configuration to be used on the final model various models were made based upon the

above concepts in E-tabs. The models were so prepared that other than bracing configuration nothing was changed. Th

models were analysed for a given time history function and based upon the deflection the final pattern of bracing

configuration was decided.

Characteristic of testing were

Period: 1sec

Number of steps per cycle: 20

Number of cycle: 5

Amplitude: 0.101 g


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Figure 7. FFT analyzer to convert the time domain response to frequency domain

Figure 8: Trial models in ETABS for different types of bracings


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Table 2. Model testing results using ETABS software

Model Displacement

mmNatural period

secNatural

frequency Hz

Trial one 0.5738mm 0.127641 7.8344

Trial two 0.5408mm 0.123654 8.0870

Trial three 0.5166mm 0.120926 8.2695Trial four 0.4900mm 0.117978 8.4761

Trial five 0.4891mm 0.117896 8.4820

We tested several designs in ETABS and decide to construct more better structure every time. (Refer figure 8 and tabe

The effect of construction errors can significantly hamper the performance of building during earthquakes thus

emphasizing the importance of quality assurance.

The performance prediction of scaled building models were exactly matching with software modelling due to accuate

assumptions of material properties, joint fixity and geometry and precise construction. There was considerabel differen

in actual model (refer figure 9) and software consideration of centre to centre joint. We need to make some assumption

and changes in input for ETABS model.Say, connection doesnt offer total rigidity to the joint, in ETAB model, we

reduced the value of fixity of joint in the software model hence achieving similarity between software model and theactual model.

Figure 9: Difference of connection in software and in actual model

4.4 Final testing

In the final testing, the joint of structure to the base plate failed. The reason being, we practiced using M seal to conne

the structure to the base plate, which transmits the vibration to the model. But the same was ineffective due to increase

setting time in the lower temperature then.


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Figure 10. Final model


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Figure 11. Testing of our model at EERI (VJTI student with the president

5. Conclusions

This project has imparted us a great exposure to the field of structral engineering and its parts like structural dynamics

experimental mechanics, structural analysis to earthquake engineering, finite element analysis, geotechnical

engineeering.every field has its equal importance and in together they help us to make megastructures stand every natu

calamities like earthquake, storm etc


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We made it to US and landed in the 18th position /34 universities & 6th amongst the Broken Structures category. We

were the only team to have exact roof Drift & acceleration prediction in EERI SDC 2012.

References

1. Improving the Earthquake Resitance of Small Buildings, Houses and Community Infrastructure.-Gregory A. JSzakats 12th WCEE.

2. FEMA 451-B Concepts of Earthquake Engineering3. Practical Three Dimensional Nonlinear Static PushoverAshraf Habibullah, and Stephen Pyle- ETABS.4. Dynamic Analysis using Mode Superposition- CSI5. IBC Internatioal Building Code-20096. NEHRP -Code 7(National Earhquake Hazard Risk Prevention)7. Earthquake Tips C. V. R Murthy-NICEE (National information Center of Earthquake Engineering)8. The Design Integration of Structural Efficiency, Architectural Expressiin and High Performance Exterior W

Sytems.- Mark Sarkisian CTBUH(Conference of Tall Buildings and Urban Habitat.

9. Seismo Resisting Architecture on Building Scale- H Guliani , M I Yacante, A M Campora.10. Design Example of a Six Storeyed Building- Sudhir K Jain

6. About author:This are the students of VJTI and founders of EERI-VJTI Student Chapter. They can be reached at

http://www.vjtiunshakeables.com/

[email protected] competition results testing of Video are on the following links-

http://slc.eeri.org/SDC2012.htm,

http://www.youtube.com/watch?v=MtfTBGrZMiw
http://www.vjtiunshakeables.com/http://www.vjtiunshakeables.com/mailto:[email protected]:[email protected]://slc.eeri.org/SDC2012.htmhttp://slc.eeri.org/SDC2012.htmhttp://www.youtube.com/watch?v=MtfTBGrZMiwhttp://www.youtube.com/watch?v=MtfTBGrZMiwhttp://www.youtube.com/watch?v=MtfTBGrZMiwhttp://slc.eeri.org/SDC2012.htmmailto:[email protected]://www.vjtiunshakeables.com/

Download - Brief Report of Research Done by EERI-VJTI Student Chapter's 1st Team VJTI Unshakeables

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