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Behavioral Study of Precast Concrete Structure with Fixity at Different Levels – Part II

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C A Prasad1, Dr. N.H. Kulkarni2, R.A.Takalkar3
1Director Metey Engineering and Consultancy Pvt. Ltd.
2Associate ProfessorCivil Engineering Department, SGGSIE&T, Vishnupuri, Nanded
3(M.Tech) from SGGSIE&T,Vishnupuri, Nanded

 

4. Two Successive Story’s Released (Zone-II)
Story Displacement
Observations for Two Successive Story’s Released Structure in Zone-II

a. Story displacement: -The structure is stable, deflections are within the limits (i.e. H/500) in both the directions. Column sizes are required to be increased to 1.2M*1.2M corresponding to 6th and 5th floor release, to control the displacements.When the 3rd and 2nd story releases are given, the column size needs to be further increased to 1.5M*1.5M to control the displacements.

b. Story drift: – Inter-story drifts are within the Allowable limits of 0.004xfloor height in both the directions.

c. Column reinforcement: -When story releases are given to 9th and 8th floors, column reinforcements are observed as 1.20%.Corresponding to 6th and 5th floor release, when column size was increased to 1.2M*1.2M, reinforcement in the columns are observed as 1.15% Corresponding to 3rd and 2nd story releases, the column sizes were increased to 1.5M*1.5M. the reinforcement in the columns are nearly nominal (0.80%)

d. Modal Mass Participation: – The structure is getting the first mode in x-direction with the corresponding release at 9thand 8th floor.Thereafter, with releases to structure at 6th and 5th,3rd and 2nd floor, the structure is getting the 1st mode in the y-direction instead of in x-direction.The mass participation values are happening between 67% to 73%. The torsion is occurring only in the 3rd mode.

Table 4 Story Displacement in x and y-direction
Table 4 Story Displacement in x and y-direction

 

 

 

 

 

 

Column Reinforcement

Table 5 Column Longitudinal Reinforcement
Table 5 Column Longitudinal Reinforcement

 

 

 

 

Modal Mass Participation

 

Table6 Modal Mass Participation
Table6 Modal Mass Participation

 

 

5 Alternate Story Released (ZONE-III)

The results ofanalysis for alternate story released structure in zone -III are presented in the following tables.

Observations for Alternate Story’s Released Structure in Zone-III

a. Story displacement: – The structure is stable, and deflections are within the limits (i.e. H/500) in both the directions.
b. Story drift: -Inter-story drifts are within the Allowable limits of 0.004xfloor height in both the directions.
c. Column reinforcement: – Column reinforcements are nearly nominal for the story releases corresponding to 9th and 7th floors.Thereafter, its demand is increasing when the 5th and 3rd floor releases are given.In addition to 9thand 7th floor, when 5th and 3rd floors are also released, the increased deflections (still within Allowable limits) and the reinforcement percentages are observed in the columns.
d. Modal Mass Participation: -The structure is getting the first mode in x-direction with the corresponding release of 9thand 7th floor.After the release of 5th and 3rd floor the first mode is shifting into the y-direction instead of in x-direction.The mass participation values are happening between 68% to 73%. The torsion is occurring only in the 3rd mode.

Story Displacement

Table 7 Story Displacement in x and y-direction
Table 7 Story Displacement in x and y-direction

 

 

 

 

 

 

 

Column Reinforcement

Table 8 Column Longitudinal Reinforcement
Table 8 Column Longitudinal Reinforcement

 

 

 

 

 

Modal Mass Participation

Table 9 Modal Mass Participation
Table 9 Modal Mass Participation

 

 

 

6. Two successive Story’s Released (Zone-III)
STORY DISPLACEMENT

Table 10 Story Displacement in x and y-direction
Table 10 Story Displacement in x and y-direction

 

 

 

 

 

 

Column Reinforcement

Table 11 Column Longitudinal Reinforcement
Table 11 Column Longitudinal Reinforcement

 

 

 

 

Modal Mass Participation

Table 12 Modal Mass Participation
Table 12 Modal Mass Participation

 

 

Observations for Two Successive Story’s Released Structure in Zone-III

a. Story displacement: -Column sizes are required to be increased to 1.5M*1.5M corresponding to 3rd and 2nd story release, such that deflections are within the limits.
b. Story drift: – Inter-story drifts are within the Allowable limits of 0.004xfloor height in both the directions.
c. Column reinforcement: -When story releases are given to 9th and 8th, 6th and 5th floors, column reinforcements are nearly 1.0% and 1.60% respectively.Thereafter, the column sizes are also required to be increased to 1.5M*1.5M corresponding to 3rd and 2nd story release for controlling increased deflection. Reinforcement in the columns are nearly nominal (0.80%)
d. Modal Mass Participation: -The structure is getting the first mode in x-direction with the corresponding release at 9thand 8th floor.Thereafter, with releases to structure at 6th and 5th,3rd and 2nd floor, the first mode is shifting to the y-direction instead of in x-direction.The mass participation values are happening between 67% to 73%. The torsion is occurring only in the 3rd mode.

The plan above shows the structure is requiring extra shear walls for structural stability purpose in Zone IV, when alternate floors releases are given to the structure. The releases can be given for the 9th and 7th floors without the necessity of the extra shear walls. For successive story releases also, the extra shear walls are required and thus it is not cost effective for releases to be given in zone-IV area.

Similarly, it is observed that the structure in zone-V area, releases to the structure are not preferable as it demands more number of shear walls for structural stability purpose.

7. Summaryof Observations

Based on the details presented above, the following observations are made:

  • The structure is analyzed corresponding to seismic zones-II, III, IV and V. The structure analyzed is of 10 story high with bay size of 8m*8m and 7 bays in each direction.
  • Precast hollow core slabs with structural topping will give the diaphragm action.
  • As precast hollow core slabs are one-way slabs, all the internal frames are moment resistant frames connected by the floor slab perpendicular to it.
  • In the Y-direction, all are moment resistant frames are in y- direction
  • In the x- direction,two internal frames and two peripheral frames + shear walls are provided as Moment resistant frames to resist lateral forces initially for zone II and III

 

Zone-II and III

Alternate story release: – Alternate story release concept is recommended for zone II and III and is cost effective too.
Two successive story releases: -Successive story releases concept is also effective for zone II and III, even though, it demands increased column sizes of 1.5m* 1.5m compared to 1.0m*1.0m. However, few shear walls can be introduced in y- direction too, and there by retain the same column size will be further studied and reported

Zone-IV and V

Additional shear walls are required to be provided internally too for zone-IV and V areas and thus they are not cost effective and thereby, releases to the structure in Zone IV and V is not recommended

References

The references adopted for the preparation of this paper are listed below:

  • Andrea Belleri, “Displacement based design for precast concrete frames with not-emulative connections”.Engineering Structures 141 (2017) 228–240
  • R. B. Nimse; D. D. Joshi; and P. V. Patel“Experimental Study on Precast Beam Column Connections Constructed Using RC Corbel and Steel Billet under Progressive Collapse Scenario”.Structures Congress 2015 1101 382481.
  • F. Biondini, L. Ferrara and G. Toniolo “Capacity design criteria for connections in precast structures” The 14th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China
  • HalukSucuoglu“Effect of Connection Rigidity on Seismic Response of Precast Concrete Frames” PCI Journals.
  • Ahmad Baharuddin Abd. Rahman, Dennis Chan Paul Leong, A. Aziz Saim, Mohd. Hanim Osman “Hybrid beam-to-column connections for precast concrete frames”(APSEC 2006)
  • Hossein Parastesh, Iman Hajirasouliha, Reza Ramezani“A new ductile moment-resisting connection for precast concrete frames in seismic regions: An experimental investigation”Engineering Structures 70 (2014) 144–157.
  • Dongzhi Guan, Cheng Jiang, Zhengxing Guo &HanbinGe“Development and Seismic Behavior of Precast Concrete Beam-to-Column Connections”Journal of Earthquake Engineering ISSN: 1363-2469.
  • Fib 43“Structural connections for precast concrete buildings”The role of structural connections in prefabricated concrete building structures chapter.
  • Kim S. Elliot and team “Precast concrete structure handbook” what is precast concrete chapter.
  • IS1893:2002, “Criteria for Earthquake Resistant Design of Structures”.
  • IS 456:2000, “Plain and reinforced concrete-code of practice”

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