Seismic Detailing of RCC Structure as per BNBC 2020

Seismic detailing

Seismic Detailing of RCC Structure as per BNBC 2020

বিএসসি ইন সিভিল ইঞ্জিনিয়ারিং পাশ করার পর যদি কেউ চাকরী বা প্রফেশনাল প্র্যাক্টিস করা শুরু করতে চায় তাহলে তার উচিত অন্তত বাংলাদেশ ন্যাশনাল বিল্ডিং কোড টা ভাল ভাবে অধ্যয়ন করা । সব না বুঝলে ও পুরো কোড টা একবার দেখতে হবে । কোথায় কি আছে জানতে হবে । অন্তত এটুকু বুঝতে হবে – কোডের কোন অংশ কোথায় প্রয়োজন হবে । যা বুঝতে পারছেন না নোট করে রাখ । সব একবারে বুঝতে পারার কোন প্রয়োজন নেই । এখন অনেকে প্রশ্ন করবে BNBC কোন version অধ্যয়ন করব। আমরা নিশ্চয়তা দিয়ে বলতে চাই তুমি #BNBC_2020 অধ্যয়ন কর । এটা পাশ না হলেও প্র্যাকটিস করতে পারবে । অনেক বড় বড় প্রজেক্টে ব্যাবহার হচ্ছে । এরপর যদি #BNBC_2006 নিতান্তই দরকার হয় তুমি সহজে বুঝতে পারবে কারন তোমার BNBC 2020 জানা আছে । এই কোর্সটা তোমাদের প্রফেশনাল জীবনে পথ চলাকে সহজ করার জন্য আমাদের প্রয়াস। আশা করি ভাল লাগবে, উপকারে আসবে।

The Civil Engineers who want to start their professional career in Bangladesh after completing BSc in Civil Engineering, should study Bangladesh National Building Code (BNBC) thoroughly. Even if you don’t understand some parts of BNBC, try to complete reading all the related Geotechnical and Structural related portions. You have to know the contents – which part, where are they located. If you don’t understand something, please note down. Now, question is which version of BNBC should be studied. We suggest to study BNBC 2020. It is going to be approved soon. Even it is not approved, you can practice it. In some big projects of government, BNBC 2020 have been used. If you need BNBC 2006, you can use BNBC 2006 easily, because there are many common things in both the version. This course is our endeavor to assist you in your professional development. We hope that you would like it and it would be benefit you.

What you'll learn

  • General requirement of seismic detailing
  • Special, Intermediate, Ordinary Seismic Detailing of Column, Beam, Joint.
  • Strong Column – Weak Beam concept
  • Intermediate Seismic Detailing of Flat plate
  • Seismic Detailing of Foundation

Prerequisite / Eligibility

  • BSc, MSc or PhD in Civil Engineering
  • Level 4 or 4th year student of bachelor’s in civil engineering
  • AMIEB students of IEB

Course Teacher

Professor Dr. Jahangir Alam, Department of Civil Engineering, BUET, Dhaka, Bangladesh

Brief Biography of Course Teacher

Education

  • PhD in Geotechnical Earthquake Engineering, the University of Tokyo, Japan, 2005
  • MSc in Civil and Geotechnical Engineering, BUET, Dhaka, Bangladesh, 2002
  • BSc in Civil Engineering, BUET, Dhaka, Bangladesh, 1998

Biography

Professor Dr. Engr. Md. Jahangir Alam is faculty member at the Department of Civil Engineering, BUET, Dhaka-1000, since 1999. He completed his PhD from University of Tokyo in Geotechnical Earthquake Engineering in 2005 as a Monbu-Kagaku-sho Scholar. He was research fellow in Ecole Centrale Paris in 2008. Professor Jahangir did his BSc in Civil Engg with major in Structure and MSc in Civil and Geotechnical Engineering from BUET.

Professor Jahangir has multidisciplinary research interests and has publications in international journals and conferences. His current research topics are “Risk Sensitive Land Use Planning of Mega City”, Physical and Numerical Modeling of Liquefaction Hazard, Mitigation against Seismic Liquefaction, Cyclic Behavior of Non-plastic silt, Reinforced Earth, Earthquake Resistant Foundation in Soft Soil, Climate Resilient Concrete, Climate Resilient Road.

Professor Jahangir was involved in many consultancy projects where he designed/checked high rise RCC buildings, Communication towers, Jetty, Shore Pile, Embankment, Container Terminal, Ground Improvement, Bridge Foundation etc. He supervised many MSc and PhD students. He was involved in pile load testing, pile integrity testing, concrete mix design and development of laboratory and field-testing equipment.

Professor Jahangir actively involved in National and International professional bodies. He is life member and was Treasurer of Bangladesh Society for Geotechnical Engineering (BSGE), which is Bangladesh Chapter of ISSMGE. He is life fellow of Institute of Engineers Bangladesh (IEB). He is life member of Bangladesh Earthquake Society (BES). He was Treasurer of Bangladesh Earthquake Society (BES).

Certificate of Attendance

Certificate of attendance will be awarded after completion of all video lessons and quizzes

Related Courses

  • Earthquake Load as per BNBC 2020
  • Wind Load as per BNBC 2020
  • Soils and Foundations as per BNBC 2020

Free Courses

  • Design Issues for Large Earth Structures: Stress, Deformation, FOS and Liquefaction
  • Webinar on Dynamic Analysis

Features of ourPROFESSORs.com

Frequently Asked Questions (FAQ)

Course Preview

Detail Course Outline

Detailing of Reinforcement in Concrete Structures

  • General requirements of detailing: Standard and seismic hook, Minimum bend diameter, Tolerance for placing reinforcement, Spacing of reinforcement, Bundled bar, Exposure condition and cover, Column detailing, Temperature and shrinkage bars, Structural integrity, Development length.
  • Seismic detailing: Occupancy Category, Importance factor, Seismic design category (OMRF, IMRF, SMRF), Flexural Members of Special Moment Frames (SMRF – beam), Special Moment Frame Members Subjected to Bending and Axial Load (SMRF – Column), Minimum flexural strength of columns , Special, Structural Walls and Coupling Beams, Requirements for Intermediate Moment Frames , Requirements for ordinary moment frame members, Comparison between OMRF, IMRF and SMRF.

BNBC intensive outline

1
BNBC intensive outline

CONTENTS

  • BNBC Part 6, Chapter 1 – Definition and General Requirement
  • BNBC Part 6, Chapter 2 – Load (wind and earthquake load)
  • BNBC Part 6, Chapter 3 – Soils and Foundations
  • BNBC Part 6, Chapter 8 – Seismic Detailing of RCC Structures
  • Software implementation of wind load and earthquake load


2
All Documents of Seismic Detailing of RCC Structure as per BNBC 2020

Seismic Detailing

1
General requirement of seismic detailing, Part-1

DETAILING OF REINFORCEMENT IN CONCRETE STRUCTURES

( According to BNBC 2017 )


Contents of this presentation

·        General requirements of detailing

•      Standard and seismic hook

•      Minimum bend diameter

•      Tolerance for placing reinforcement

•      Spacing of reinforcement

•      Bundled bar

•      Exposure condition and cover

•      Column detailing

•      Temperature and shrinkage bars

•      Structural integrity

•      Development length



Standard hooks


For free end of bar,

  • 180o bend plus an extension≥4db 65 mm 
  • 90o bend plus an extension ≥ 12db 

§ For stirrup and tie anchorage:

  •   For db≤16mm, 90o bend plus an extension ≥ 6db 
  •  For 19≤db≤25mm, 90o bend plus an extension≥12db
  •   For db≤25mm, 135o bend plus ≥ 6db   
  •  For closed ties and continuously wound ties, 135o bend plus an extension ≥      4db 65 mm 



For free For stirrup and tie anchorage of bar

Seismic Hook

  • Seismic hook bend should be ≥ 1350
  •  Circular hoops bend should be ≥ 900 

·        Seismic hook extension ≥ 6db, 75mm


Minimum bend diameters

The minimum diameter of bend for standard hook and for tie and stirrup hooks if db ≥16mm

Bar Size------------------------------Minimum Diameter of Bend

10 mm ≤ d_b ≤ 25 mm---------6d_b

25 mm < d_b ≤ 40 mm----------8d_b

40 mm < d_b ≤ 57 mm----------10d_b


·        For stirrups and tie hooks, if db≤16mm, inside diameter of bend ≥4 db


Spacing of Reinforcement

·        The minimum clear spacing between parallel bars of slab ≥1db , 25 mm

·        1.33* maximum nominal size of coarse aggregate

·        Where parallel reinforcement is placed in two or more layers, clear distance between layers ≥25 mm

·        For compression members, the clear distance between longitudinal bars ≥1.5 db , 40 mm

·        1.33* maximum nominal size of coarse aggregate

·        In walls and one-way slabs the maximum bar spacing ≤3*wall or slab thickness h, 450 mm

·        For two-way slabs, maximum spacing of bars ≤ 2* slab thickness h, 450 mm

·        For temperature steel, maximum spacing ≤ 5* slab thickness h , 450 mm



Bundled bars

·        Groups of parallel reinforcing bars bundled in contact to act as a single unit shall be limited to four.

·        Bundled bars shall be enclosed within stirrups or ties.

·        Bars larger than 32 mm diameter shall not be bundled in beams.              

·        Individual bars within a bundle terminated within the span of flexural members shall terminate at different points with at least 40db stagger.

·        Where spacing limitations and minimum concrete cover are based on bar diameter db, a unit of bundled bars shall be treated as a single bar of a diameter derived from the equivalent total area

·        Exposure Condition and Minimum Cover



Exposure Condition and Recommended Cover

·        Cast-in-place concrete :

  • Minimum concrete cover (permanently exposed to earth)= 75 mm.
  • Concrete exposed to earth or weather, the minimum clear cover shall be as under

    19 mm to 57 mm bar diameter:                                  50 mm

    16 mm diameter bar and smaller:                                               40 mm

 

 

Concrete in Corrosive Environments

  1. A specified concrete cover for reinforcement not less than 50 mm for walls and slabs and not less than 65 mm for other members may be used. For precast concrete members a specified concrete cover not less than 40 mm for walls and slabs and not less than 50 mm for other members may be used.
  2. Minimum compressive strength of concrete  for the corrosive environment or other severe exposure conditions shall be 25 MPa with minimum cement of 400 kg per cubic meter. Coarse aggregate shall be 20 mm down well-graded stone chips and fine aggregate shall be coarse sand of minimum FM 2.20.
  3. For any non-structural member like drop wall, railing, fins etc., 12 mm down well graded stone chips may be used as coarse aggregate.
  4. Use of brick chips (khoa) as coarse aggregate is strictly prohibited for the corrosive environment or other severe exposure conditions.
  5. Water cement ratio shall be between 0.4-0.45. Potable water shall be used for all concreting

8.1.9 Lateral Reinforcement for Columns



Spiral:

·        Size of spirals for cast in situ construction ≥ 10 mm diameter

·        Clear spacing between spirals 25 mm ≤ s ≤ 75 mm

·        Anchorage of spiral reinforcement shall be provided by 1.5 extra turns of spiral bar or wire at each end of a spiral unit.

·        Lap Splices ≥      48 spiral diameter for deformed uncoated bar or wire, 72 spiral diameter for other cases, 300 mm

 

Ties:

·        Vertical spacing of ties ≤ 16 db   ,  48 dtie,  Least dimension of column

 

 

8.1.8 Reinforcement Details for Columns

Offset Bars: Offset bent longitudinal bars shall conform to the following:

(a)   The maximum slope of inclined portion of an offset bar with axis of column shall not exceed 1 in 6.

(b)   Portions of bar above and below an offset shall be parallel to the axis of column.

(c)    Horizontal support at offset bends shall be provided by lateral ties, spirals, or parts of the floor construction. Horizontal support provided shall be designed to resist 1.5 times the horizontal component of the computed force in the inclined portion of the offset bars. Lateral ties or spirals, if used, shall be placed not more than 150 mm away from points of bend.

(d)   Offset bars shall be bent before placement in the forms (see Sec 8.1.3).

(e)   Where the face of the column above is offset 75 mm or more from the face of the column below, longitudinal bars shall not be permitted to be offset bent. The longitudinal bars adjacent to the offset column faces shall be lap spliced using separate dowels. Lap splices shall conform to Sec 8.2.14.

(f)     The lowest tie in any storey shall be placed within one-half the required tie spacing from the top most horizontal reinforcement in the slab or footing below.

(g)   The uppermost tie in any storey shall be within one-half the required tie spacing from the lowest horizontal reinforcement in the slab or drop panel above.

(h)   Where beams or brackets provide concrete confinement at the top of the column on all (four) sides, top tie shall be within 75 mm of the lowest horizontal reinforcement

(i)     Ties shall be arranged such that every corner and alternate longitudinal bar shall have lateral support provided by the corner of a tie with an included angle not more than 135o.

(j)     No vertical bar shall be farther than 150 mm clear on each side along the tie from such a laterally supported bar



Shrinkage and Temperature Reinforcement

·        Area of shrinkage and temperature reinforcement shall provide at least the following ratios of reinforcement area to gross concrete area:

·        In any case, the reinforcement ratio shall not be less than 0.0014.

·        Area of shrinkage and temperature reinforcement for brick aggregate concrete shall be at least 1.5 times that provided in above.

·        Spacing of shrinkage and temperature reinforcement ≤ 5*slab thickness, 450 mm



Brick aggregate concrete

Area of shrinkage and temperature reinforcement for brick aggregate concrete shall be at least 1.5 times that provided in above.



Development of Deformed Bars and Deformed Wires in Tension

·        Development length for deformed bars and deformed wire in tension, ld ≥300 mm

·        For deformed bars or deformed wire, ld shall be as follows:


Clear spacing of bars or wires being developed or spliced not less thand_b, clear cover not less than d_b, and stirrups or ties throughout l_d not less than the Code minimum

Or, Clear spacing of bars or wires being developed or spliced not less than 2d_b and clear cover not less than d_b *****

((f_y ψ_t ψ_e)/(2.1λ√(f'_c ))) d_b

Where

·        ld=development length

·        fy=yield strength of the tension rebars (Mpa)

·        fc’=compressive strength of concrete (Mpa)

·        db=bar diameter (mm)

·        ψt=rebar location factor that accounts for the position of rebars in freshly placed concrete

·        ψe=rebar coating factor reflecting the effects of epoxy coating

·        ψs= rebar size factor

·        λ= lightweight aggregate concrete factor


The factors used in the expressions for development of deformed bars and deformed wires in tension are as follows:

·        Where horizontal reinforcement is placed such that more than 300 mm of fresh concrete is cast below the development length or splice, ψt=1.3. For other cases, ψt=1.0.

·        For epoxy-coated bars or wires with cover less than 3db, or clear spacing less than 6db, ψe=1.5. For all other epoxy-coated bars or wires, ψe=1.2. For uncoated and zinc-coated (galvanized) reinforcement, ψe=1.0. However, the product ψt ψe need not be greater than 1.7.

·        For 19 mm diameter and smaller bars, and deformed wires, ψs=0.8. For 20 mm diameter and larger bars, ψs=1.0.

·        Where lightweight concrete is used, λ shall not exceed 0.75 unless fct is specified. Where normal weight concrete is used, λ=1.0.

o  Development of Deformed Bars and Deformed Wires in Compression

·        Development length for deformed bars and deformed wire in compression, ldc  ≥ 200 mm

·        Development length for deformed bars and deformed wire in

     compression, ldc≥ (0.24f_y d_b)/(λ√(f_c^' )) 0.043f_y d_b

Where the constant 0.043 carries the unit of mm2/N



Lap splices in bundled bar

·        Lap splices of bundled bars shall be based on the lap splice length required for individual bars within the bundle.

·        Individual bar splices within a bundle shall not overlap. Entire bundles shall not be lap spliced.




Splices of Deformed Bars and Deformed Wire in Tension

·        The minimum length of lap for tension splices shall be as required for Class A or B splice, but not less than 300 mm, where the classification shall be as follows:

Class - A splice: 1.0 L

Class - B splice: 1.3 L


·        Lap splices of deformed bars and deformed wire in tension shall be class B splices except that Class A splices are allowed when the area of reinforcement provided is at least twice that required by analysis over the entire length of the splice, and one-half or less of total reinforcement is spliced within the required lap length.



Minimum Splices in Compression

·        The minimum length of lap for compression splice shall be 0.071f_y d_b for f_y =420 N/mm2 or less or (0.13f_y-24)d_b for f_y greater than 420 N/mm2, but not less than 300 mm. For f_c^' less than 21 N/mm2, length of lap shall be increased by one-third.

·        Development length and lap length will increase 33% for brick aggregate concrete

·        Development length and lap length will increase 30 - 50% for epoxy coated rebar




2
General requirement of seismic detailing, Part-2
3
General requirement of seismic detailing, Part-3
4
General requirement of seismic detailing, Part-4
5
General requirement of seismic detailing, Part-5
6
General requirement of seismic detailing, Part-6
7
General requirement of seismic detailing, Part-7
8
How to determine seismic detailing category

Special Seismic Detailing

1
Seismic detailing principles

EARTHQUAKE-RESISTANT DESIGN PROVISIONS

(According to BNBC 2017)


Contents

  1. Occupancy Category
  2. Importance factor
  3. Seismic design category (OMRF, IMRF, SMRF)
  4. Flexural Members of Special Moment Frames (SMRF – beam)
  5. Special Moment Frame Members Subjected to Bending and Axial Load (SMRF – Column)
  6. Minimum flexural strength of columns
  7. Special Structural Walls and Coupling Beams
  8. Requirements for Intermediate Moment Frames
  9. Requirements for ordinary moment frame members
  10. Comparison between OMRF, IMRF and SMRF








Seismic zone


1.      Southwestern part including Barisal, Khulna, Jessore, Rajshahi,

·        Seismic Intensity= Low,

·        Seismic Zone Coefficient, Z =0.12


2.      Lower Central and Southwestern part including Noakhali, Dhaka, Pabna, Dinajpur, as well as Southwestern corner including Sundarbans

·        Seismic Intensity= Moderate,

·        Seismic Zone Coefficient, Z =0.20


3.      Upper Central and Northwestern part including Brahmanbaria, Sirajganj, Rangpur

·        Seismic Intensity= Severe,

·        Seismic Zone Coefficient, Z =0.28


4.      Northeastern part including Sylhet, Mymensingh, Kurigram

·        Seismic Intensity= Very Severe,

·        Seismic Zone Coefficient, Z =0.36



 Building and Structure Occupancy Categories:


Nature of Occupancy: Buildings and other structures that represent a low hazard to human life in the event of failure, including, but not limited to:

  1. Agricultural facilities.
  2. Certain temporary facilities.
  3. Minor storage facilities

Occupancy Category - i


Nature of Occupancy: All buildings and other structures except those listed in Occupancy Categories I, III and IV.

Occupancy Category - ii


Nature of Occupancy: Buildings and other structures that represent a substantial hazard to human life in the event of failure, including, but not limited to:

  1. Buildings with more than 300 people.
  2. Buildings with day care facilities with a capacity greater than 150.
  3. Buildings with elementary school or secondary school facilities with a capacity greater than 250.
  4. Buildings with a capacity greater than 500 for colleges or adult education facilities.
  5. Healthcare facilities with a capacity of 50 or more resident patients, but not having   surgery or emergency Treatment facilities.
  6. Jails and detention facilities.

Occupancy Category - iii


Nature of Occupancy: Buildings and other structures designated as essential facilities, including, but not limited to:

  1. Hospitals, Fire, rescue, ambulance, and police stations and emergency vehicle garages.
  2. Designated earthquake, hurricane, or other emergency shelters, emergency preparedness, communication.
  3. Power generating stations, Ancillary structures, Electrical substation structures, Aviation control towers, air traffic control centers.

Occupancy Category - iv


Site Dependent Soil Factor and Other Parameters Defining Elastic Response Spectrum

Soil type---------S--------TB (s)------TC (s)---------TD (s)

SA---------------1.00-------0.15-------0.40-----------2.0

SB---------------1.20-------0.15-------0.50-----------2.0

SC---------------1.15-------0.20-------0.20-----------2.0

SD---------------1.35-------0.20-------0.20-----------2.0

SE----------------1.40------0.15-------0.50-----------2.0

 

Site Class---Occupancy Category I---------III-Occupancy Category IV

----------Zone 1-Zone 2-Zone 3-Zone 4--Zone 1-Zone 2-Zone 3-Zone 4

SA---------B--------C--------C-------D--------C--------D-------D-------D

SB---------B--------C--------D-------D--------C--------D-------D-------D

SC---------B--------C--------D-------D--------C--------D-------D-------D

SD---------C--------D--------D------D---------D-------D-------D-------D

S1, S2-----D-------D--------D-------D--------D--------D-------D-------D




2
Special detailing of Beam longitudinal rebar
3
Special detailing of Beam stirrup
4
Strong Column – Weak Beam concept, Part-1
5
Strong Column – Weak Beam concept, Part-2
6
Special detailing of transverse rebar of Column, Part-1
7
Special detailing of transverse rebar of Column, Part-2
8
Special joint detailing

Intermediate Seismic Detailing

1
Intermediate detailing of Beam
2
Intermediate detailing of Column

Other Seismic Detailing

1
General requirement of Flat plate, Part-1
2
General requirement of Flat plate, Part-2
3
Intermediate detailing of Flat plate
4
Ordinary detailing of Beam and Column
5
Special detailing of Foundation
6
BNBC Quiz 6 : Seismic Detailing
10 questions
4.7
4.7 out of 5
3 Ratings

Detailed Rating

Stars 5
2
Stars 4
1
Stars 3
0
Stars 2
0
Stars 1
0

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