Comparative Study of Conventional Braces and Buckling Restrained Braces in Steel Frame Structure

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Comparative Study of Conventional Braces and Buckling Restrained Braces in Steel Frame Structure

Mr. Dipak Vasantrao Patil Civil Engineering Department SKN,

Sinhgad Collage of Engineering, Korti Pandharpur..

Mr. C. M. Deshmukh Assistance Professor,

Civil Engineering Department SKN, Sinhgad Collage of Engineering, Korti Pandharpur.

Mr. S. S. Kadam Assistance professor,

Civil Engineering Department SKN,Sinhgad Collage of Engineering, Korti Pandharpur.

AbstractA conventional moment resisting steel frame undertakes large level of lateral deformation when subjected to strong ground motion or wind forces. If this deformation is excessive, structural and non-structural damage is evident, which damages structural integrity. To avoid such large deformations, various types of systems have been used in steel frames. Diagonal elements, called braces, have been implemented as additional structural member that increase the stiffness and energy dissipation, and control relative inter story deformation in an effective way, thus protecting the structure against damage and improving the overall behavior.

The BRBs permits very high compression strength. Because there is no reduction in the available material strength due to instability, the effective length of the core can be considered zero. By confining inelastic behavior to axial yielding of the steel core, the brace can achieve great ductility. Thus, the hysteretic performance of these braces is similar to that of the material of the steel core. Braces with core materials that have significant strain hardening also will exhibit strain hardening. Because the strains are not concentrated in a limited region such as a

plastic hinge, the braces can dissipate large amounts of energy. Testing has established the braces low-cycle fatigue life; this capacity is well in excess of demands established from nonlinear dynamic analysis. Such analyses also show that using braces with this type of hysteretic behavior leads to systems with very good performance. Drifts are expected to be significantly lower than the specially concentric braced frame (SCBF) due BRBs behavior. BRBFs response to seismic loading provides a much higher confidence level in adequate performance than does the behavior of concentrically braced frame (CBF). Analytical studies of the response of BRBF also have been used to estimate the maximum ductility demands on BRBs. BRBs must be designed and detailed to accommodate inelastic deformations without permitting undesirable modes of behavior, such as overall instability of the brace or bearing of the non-yielding zones of the core on the sleeve.

Key words: Lateral load resisting systems, Buckling Restrained Brace, Conventional Braced frame.

I. INTRODUCTION

Lateral load brings a major concern in structural design of tall buildings. For many years, various design and construction technologies have been developed, aiming at enhancing the lateral load resisting performance of building structures.

They achieve this through the decoupling of the stress- resisting and flexural buckling resisting aspects of compression strength. Axial stresses are resisted by a shaped steel core. Buckling resistance is provided to that core by a casing, which may be of steel, concrete, composite, or other construction. Because the steel core is restrained from buckling, it develops almost uniform axial strains. Plastic hinges associated with buckling do not form in properly designed and detailed BRBs.

The brace, which is basically a steel inner core that sustains the lateral forces acting on the respective frame story. The encasing member, formed by reinforced concrete, steel tubes, or reinforced concrete panels surrounding the inner brace, acts as a restraining element that provides lateral stiffness when the inner core tends to deform laterally. The following figure shows a typical cross section of one type of BRB commonly used in actual engineering practice.

2. OJECTIVES

  1. To compare the frame behavior with buckling restrained braces using the same brace but placed in hollow tube to restrain its buckling

  2. To arrive at measure of effectiveness of buckling restrained braces under different lateral loading on different frames such as bare frame, frame with ordinary brace and frame with buckling restrained brace for two, three and four numbers of bays.

    III. MATERIALS AND METHODS

    Following methodology will be adopted for proposed research work;

    1. Literature Survey:

      This will be through journals, proceedings, reference books, technical magazines &moreover through Internet for latest available literature

    2. In this project we will do

      1. Analysis and Design of frame model using STADD pro software

      2. Experimental setup

        After the Analysis and Design of frame model using STADD pro software. We Create the Frame Using the Dimension. This Frame Fitted with Using the Bolted Connection on the I Section (C.I.).This are fitted with the ground floor in concrete.

      3. Loading arrangement

      4. Number of test

      5. Result

      6. Conclusion

      7. References

4 EXPERIMENTALPROGRAM –

For the STADD analysis the model of steel frame two bay and two story with storey height and bay width equal with lateral load acting at each story level as shown in fig. 4.1 is taken. The sections of frame and braces are so finalize that, when loaded the braces should fail first and then frame members.

Figure 4.1 Proposed Loading Arrangement

Figure 4.2 Actual Loading Arrangement

Following fig.4.3 shows the failed members when loaded with static lateral load

fig.4.3 Failed members when loaded with static lateral load.

Fig. 4.5 Conventional Brace

Following Figure 4.4 Utility Ratio and Failed Members

Table 4.1 Utility Ratio

Table 4.2 Failed Member

From the above analysis finalized sections of frame and brace are

Column 25x25x2.6 Rectangular Tube Beam 25x25x2.6 Rectangular Tube Conventional Brace 6mm dia. Circular bar.

Buckling Restrained Brace 6mm dia. Bar surrounded by circular pipe.

Following fig.4.5 and Fig. 4.6 shows Conventional Brace and Buckling Restrained Brace

Fig. 4.6Conventional Brace

  1. Frame with two bay-

    In this test a frame with two bays is tested under different lateral load with the following three condition i.e.

    Un-braced frame, Frame with conventional brace and Frame with buckling restrained brace. The lateral load applied at the top is half the load applied at bottom storey. The test results obtained are as following

    1. CBF-

      Table1 Applied load vs. storey deflection for CBF

      (Kg)

      2.5

      TOP

      1.05

      App5lied

      BOSTtoTrOeyM

      Deflec0t.i2o9n(mm)

      Lo5ad

      TOP

      3.42

      10

      BOTTOM

      0.84

      7.5

      TOP

      5.6

      15

      BOTTOM

      1.42

      10

      TOP

      5.89

      20

      BOTTOM

      2.95

      12.5

      TOP

      9.85

      25

      BOTTOM

      2.55

      15

      TOP

      10.85

      30

      BOTTOM

      2.69

      Load (KG)

      Load (KG)

      Following fig.5.1 shows the graphical presentation of load vs. deflection for top and bottom storey

      CBBF

      CBBF

      40

      30

      20

      10

      TOP

      BOTTOM

      40

      30

      20

      10

      TOP

      BOTTOM

      0

      0

      0

      5

      Deflection (mm)

      10

      0

      5

      Deflection (mm)

      10

      Figure.1 Load vs. Deflection for CBF

      Fig.2 Two bays frame with conventionalbrace.

    2. BRBF

      Table 2 Applied load vs. storey deflection for BRBF

      Fig.4 Two bays frame with buckling restrained brace

      load vs.

      Applied Load

      Storey

      Deflection

      2.5

      TOP

      0.81

      5

      BOTTOM

      0.04

      5

      TOP

      1.10

      10

      BOTTOM

      0.60

      7.5

      TOP

      1.25

      15

      BOTTOM

      0.85

      10

      TOP

      2.72

      20

      BOTTOM

      1.09

      12.5

      TOP

      3.95

      25

      BOTTOM

      1.55

      15

      TOP

      4.29

      30

      BOTTOM

      2.07

      Applied Load

      Storey

      Deflection

      2.5

      TOP

      0.81

      5

      BOTTOM

      0.04

      5

      TOP

      1.10

      10

      BOTTOM

      0.60

      7.5

      TOP

      1.25

      15

      BOTTOM

      0.85

      10

      TOP

      2.72

      20

      BOTTOM

      1.09

      12.5

      TOP

      3.95

      25

      BOTTOM

      1.55

      15

      TOP

      4.29

      30

      BOTTOM

      2.07

      Following fig.5.3 shows the graphical presentation of Deflection for top and bottom storey

  2. RESULT

    This frame is tested under three cases i.e. bare frame, frame with conventional brace and frame with buckling restrained brace. The Un-braced frame had the maximum deflection of 10.85 mm at top storey and 2.69 mm at bottom storey

    for load of 15 kg and 30 kg respectively. The conventionally braced frame had the maximum deflection of 7 mm at top storey and 2.3 mm at bottom storey for load of 15 kg and

    30 kg respectively. And the frame with buckling restrained brace had the maximum deflection of 4.29 mm at top storey and2.07 mm at bottom storey for load of 15 kg and 30 kg respectively.

    Following fig.6.1 shows the comparative load carrying capacity and storey deflection for top storey with three types of bracing arrangement.

    Figure Error! No text of specified style in document..3 Load vs. Deflection for BRBF

    Fig. 6.1 Comparison Between Load VS Storey Deflection

    Fig. 6.2Comparison Between Load VS Storey Deflection.

    The Un-braced frame had the average deflection of 6.11

    mm at top storey level and 1.79 mm at bottom storey The conventional braced frame had the average deflection of 3.56 mm at top storey level and 1.22 mm at bottom storey level and the frame with buckling restrained brace had the average deflection of 2.35 mm at top storey level and 1.03 mm at bottom storey level.

    Following fig.6.3shows the comparative Storey Level and storey deflection for top and Bottom storey with

    three types of bracing arrangement.

    Fig. 6.3 Comparison Between Storey Level VS Storey Deflection

  3. CONCLUSION

    Lateral deflection of frame for a specific horizontal

    load is much less in buckling restrained frame as compared to conventional braced frame, using the

    same cross section of a brace.

  4. REFERENCES

  1. Fahnestock L. A.Ricles J.M., and Sause R. (2007) Experimental Evaluation of a Large-Scale Buckling – Restrained Braced Frame Journal of Structural Engineering © ASCE, Pp-1205-1214.

  2. HussainSaif, Benschoten P. V., Satari M.A., Lin S. (2005) Buckling Restrained Braced Frame (BRBF) Structures: Analysis, Design and Approvals Issues Coffman Engineers, Inc. Los Angeles, CA.

  3. Iwata Mamoru,(2004) Applications-design Of Buckling Restrained Braces In Japan 13th World Conference on Earthquake Engineering Vancouver, B.C., Provisionsand Buildings.-BUREAU OF INDIANpp-1-6.

  4. Junxian Zhao, Bin Wu and JinpingOu (2012) FlexuralDemand on Pin-Connected Buckling-Restrained of Practice.Braces andDesign Recommendations journal of structural engineering © asce,pp-1398-1415

  5. Palazzo G., López-Almansa F., Cahís X. and F. Crisafulli X. (2008) Individual testing of dissipative buckling restrained braces, The 14th World Conference on Earthquake Engineering, Beijing, China,pp-21-29.

  6. RoholaRahnavarda,, Mohammad Naghavib, Maryam Aboudia(2018)Investigating Modeling Approaches Of Buckling-Restrained Braces Under Cyclic Loads, Case Studies in Construction Materials 476-488

  7. Bhargava Laxmi Goli1, Himath Kumar Yerramasetty (2017)Analytical Study Of Buckling Restrained Braced Frames Under Lateral Loads Using Etabs, International Journal of Pure and Applied Mathematics ISSN-1311-8080.

  8. AtushiWatande(2018) Design and Application of Buckling Restrained Braces, International Journal of High Rise Building Vol.7,PP-215-221.

  9. Mr. Y. D. Kumbhar, Dr. M. R. Shiyekar (2014) Study Of Buckling Restrained Braces In Steel Frame Building,International Journal Of Engineering Research And Applications ISSN : 2248-9622, PP- 71-74.

  10. Toru Takeuchi (2014) Buckling-Restrained Brace: History, Design And Applications, 9th International Conference On Behavior Of Steel Structures In Seismic Areas Christchurch.

  11. M. Alborzi, H. Tahghighi, A. Azarbakht (2019) NumericalComparison On The Efficiency Of Conventional And HybridBuckling restrained Braces For Seismic Protection Of Short ToMidRiseSteel Buildings,International Journal of Advanced .

CODES:

  1. IS 1893 (Part1):2002- Criteria for Earthquake Resistant Design Of Structures Part 1 General .

  2. IS 800:2007 -General Construction of steel Code.

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