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1. Design of Reinforced Concrete Beam-Column Joint For Seismic and Non-Seismic CE-5 15 -241 Project By: Moneef Yahya Mohammed Qaid (G202390070) Instructor: Dr. Abbas Albu Shaqraa Date: 10 th Dec. 2024

2. Outlines

3. Introduction Beam-Column joints are considered the critical zone in the reinforced concrete frame since it is the crucial element that subjected to greater loads during acute ground shakes . Beam-column joints are critical components in reinforced concrete structures, especially in seismic regions. Their design and detailing significantly impact the overall structural integrity and performance.

4. Introduction Most reinforced concrete failures occur not because of any faults in analysis of the structure or in design of the members but because of inadequate attention to the detailing of reinforcement. Most often, the problem is at the connections (Joints) of main structural elements

5. Types of beam-column joints according to loading conditions and structural behavior : classifies structural joints into two categories: 1- Type 1 joint connects members in an ordinary structure designed on the basis of strength to resist gravity and normal wind load . 2- Type 2 joint connects members designed to have sustained strength under deformation reversals into the inelastic range, such as members in a structure designed for earthquake motions, very high winds, or blast effects.

6. Types of beam-column joints according to the location of joint in the structure the joints are classified in three groups as follows. 1-Interior joint 2-Exterior joint 3-Corner joint

7. Earthquake behavior of joints

8. Earthquake behavior of joints Under pull-push forces, beam-column joints experience geometric distortion. One diagonal of the joint lengthens, while the other shortens. If the column's cross-sectional size is inadequate, diagonal cracks form in the joint's concrete.

9. Some related studies Reference Focus Key Findings Uma et al. (2006) Review of design and detailing codes for beam-column joints Extensive research underscores the importance of safe joint behavior. Kang et al. (2009) Seismic anchorage of headed bars Improved understanding of cyclic loading on joints during seismic events. Le-Trung et al. (2013) Seismic performance criteria for joints in RC moment frames Joint shear stress levels significantly impact seismic behavior. Lee et al. (2013) Experimental study on seismic behavior of joints with headed bars Proposed design improvements for better joint performance during earthquakes. Ou et al. (2017) Anchorage performance of headed bars under cyclic loading Contributed to understanding joint behavior under seismic conditions. Pauletta et al. (2020) Semi-empirical models for shear strength of RC interior joints under cyclic loads Advanced models to predict shear strength, enhancing joint safety in seismic applications.

10. 5. Types of failure of beam-column joint Tow types of failure generally occurs at beam-column joint: 1-shear failure Occurs when excessive shear forces exceed the material's strength, leading to cracks in the concrete. Splitting cracks, typically horizontal or diagonal. 2-Anchorage failure Involves a loss of the joint's ability to secure structural elements and is classify into three types: A. Side splitting failure: lateral forces. B. Local compressive fracture: Compression overload C. Raking-out failure: inadequate anchorage.  classified,

11. failure of beam-column joint. When the earthquake occurs, it affects the buildings . especially in joints between column and beams as shown image.

12. failure of beam-column joint.

13. Procedure for Checking the Capacity of a Beam-Column Joint According to ACI Standards

14. Check the distribution of the column bars and lay out the joint ties (Type 1) A beam-column joint shall be considered to be restrained if the joint is laterally supported on four sides by beams of approximately equal depth. The area of all legs of transverse reinforcement shall be at least the greater of (a) and (b): shall be distributed within the column height not less than the deepest beam or slab element framing into the column

15. Check the distribution of the column bars and lay out the joint ties (Type 2) Amount of transverse reinforcement shall be in accordance with Table (1). The concrete strength factor kf and confinement effectiveness factor kn are calculated according to Eq. (a) and (b). where nl is the number of longitudinal bars or bar bundles around the perimeter of a column core with rectilinear hoops that are laterally supported by the corner of hoops or by seismic hooks. Table (1). Transverse reinforcement for columns of special moment frames[8]

16. Joint classification Beam-Confined Joint : A joint face is confined by a beam if its breadth is at least three-quarters of the joint width. Interior Joints : Beams must cover three-quarters of the joint's width and depth. If criteria are not met, the joint should be analyzed as an exterior joint. Exterior Joints : Beams on opposite faces should cover three-quarters of the joint width. If criteria are not met, the joint should be analyzed as a corner joint. This ensures proper joint strength and stability based on beam configuration. Typical beam-to-column joints[6]

17. Calculation of Shear Forces in Joints T3 C3 Y CT Vcol   N T1 C1 Vj C2 T2 Vcol T4 C4 M CU M BL M BR M CL A SLL A SLR A SUR A SUL T1 = C1 =A SUR beam * α * fy T2 = C2 =A SLL beam * α * fy T3 = C3 =A SUR column * α * fy T4 = C4 =A SLL column * α * fy MBR=T1*Y CT MBL=T2*Y CT MCU=T3*Y CT MCL=T4*Y CT VCOL= (MCU+ MCL)/H Vj =T1+C2-VCOL Vj =T1+T2-VCOL Exterior joints: V j = T1 -V COL V j =C1 -V COL α Joint forces Factor α adjusts for higher actual yield strength and strain-hardening at large deformations, set at a minimum of 1.0 for low-ductility frames and 1.25 for high-ductility frames [3][7] .

18. Nominal joint shear strength Vn (For Type 1 )   Use the minimum . If this is not satisfied either We will increase the size of the column or the amount of shear being transferred to the joint will need to be decreased.   γ values are for Type-1 joints[3]. Beam and column dimensions used to calculate width of joint , bj [3]. Aj = bj hc bj = the effective width of the joint. hc = the column dimension parallel to the shear force in the joint. α=1

19. Nominal joint shear strength Vn (For Type 2 ) =0.75   Nominal joint shear strength Vn for seismic joints[7 ]. Use the minimum . Effective joint area[7]. If this is not satisfied either either We will increase the size of the column or the amount of shear being transferred to the joint will need to be decreased[3].   Don’t forget here α=1.25

20. Development length check For Non-seismic joint (Type 1) Development of deformed bars and deformed wires in tension Development length ℓd for deformed bars and deformed wires in tension shall be the greater of (a) and (b): Length calculated in accordance with a-2 using the applicable modification factors of in a-3 . 12 in . For deformed bars or deformed wires, ℓd shall be calculated by: in which the confinement term ( cb + Ktr )/ db shall not exceed 2.5, and Where n is the number of bars or wires being developed or lap spliced along the plane of splitting. It shall be permitted to use Ktr = 0 as a design simplification even if transverse reinforcement is present [8][3][1]. a-2 a-3 -Modification factors for development of deformed bars and deformed wires in tension[8]. Cb (Bond Strength Coefficient)

21. Development length check For seismic joint (Type 2) i . Development length of bars in tension For bar sizes No. 3 through No. 11 terminating in a standard hook, ℓdh shall be calculated by the following Equation: ℓdh shall be at least the greater of 8db and 6 in . for normal-weight concrete and at least the greater of 10db and 7.5 in . for lightweight concrete .

22. Check the Minimum flexural strength of columns [ For seismic joints in special frames ] Strong Column-Weak Beam Concept: The strong column-weak beam design concept is a structural engineering strategy for enhancing buildings' seismic performance . The goal is to keep columns stronger than beams , allowing beams to absorb and disperse energy during an earthquake. This prevents catastrophic failure and helps the structure remain stable. ΣMnc is sum of nominal flexural strengths of columns framing into the joint, evaluated at the faces of the joint. ΣMnb is sum of nominal flexural strengths of the beams framing into the joint, evaluated at the faces of the joint Partial collapse and full collapse ? illustrate for two different structural systems under shear forces Plastic hinge should be in the beam

23. Conclusions The detailing of beam-column joints (BCJs) is crucial for structural integrity in reinforced concrete construction. Structural failures often arise from inadequate detailing rather than design flaws. Improved reinforcement detailing practices and standardized guidelines are necessary. A comprehensive investigation into factors affecting joint performance is essential to mitigate failures. Adherence to ACI codes and modern materials can enhance structural resilience. Special attention to BCJ design is vital in seismic regions to ensure safety. Enhancing detailing practices contributes to the overall success of engineering projects, especially in earthquake-prone areas.

24. References [1] C. W. Dolan and A. H. Nilson , Design Concrete, vol. 12, no. 2. 2022. [2] Concrete Reinforcing Steel Institute (CRSI), “Design Guide on the ACI 318 Building Code Requirements for Structural Concrete,” Am. Concr . Inst., pp. 1–998, 2020. [3] W. H. Dilger , Reinforced concrete: mechanics and design, vol. 27, no. 6. 2000. doi : 10.1139/l00-087. [4] S. R. Uma and S. K. Jain, “Seismic design of beam-column joints in RC moment resisting frames - Review of codes,” Struct . Eng. Mech., vol. 23, no. 5, pp. 579–597, 2006, doi : 10.12989/sem.2006.23.5.579. [5] K. Z. Sayed, “Design Requirements of Reinforced Concrete Beam-column Joints in International Codes and ECP-RC-2018,” vol. 16, no. 6, pp. 16–27, 2019, doi : 10.9790/1684-1606031627. [6] J. A. Committee, J. F. Bonacci , C. E. French, L. E. García , R. T. Leon, and J. K. Wight, “ACI 352R-02 Recommendations for Design of Beam-Column Connections in Monolithic Reinforced Concrete Structures,” vol. 02, no. Reapproved, pp. 1–38, 2010. [7] American Concrete Institut , “318M-19: Building Code Requirements for Concrete and Commentary,” Aci 318-19M, no. October 2019, p. 628, 2019. [8] A. A. C. I. Standard, ACI 318M-14. [9] A. K. Tiwary et al., “Behavior of RC Beam–Column Joints Strengthened with Modified Reinforcement Techniques,” Sustain., vol. 14, no. 3, pp. 1–19, 2022, doi : 10.3390/su14031918.

25. Thanks