investigation of hybrid beam – column joints under …€¦ · yield strength of the concrete...

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International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 5, May 2018, pp. 218–228, Article ID: IJCIET_09_05_025

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=5

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

INVESTIGATION OF HYBRID BEAM –

COLUMN JOINTS UNDER CYCLIC LOADING

A S. Srinivasan

M.Tech, Structural Engineering, SRM Institute of Science and Technology,

Kattankulathur, Kanchipuram, Tamil Nadu

S. Pradeep (O.G)

Assistant Professor, Civil Engineering Department, SRM Institute of Science and

Technology, Kattankulathur, Kanchipuram, Tamil Nadu

ABSTRACT

In this paper, the investigation is about the behavior of beam-column joints under

cyclic lateral loading. Where maximum stress at the joints is resisted by using steel -

profile mechanism for both external and internal beam-column joints. The behavior of

steel-profile is validated through Ansys 18.2 FEM software. Static analysis is carried

out to find the behavior of frame structure and the fatigue lifespan at the beam-column

joints is evaluated using constant amplitude method of cyclic loading. The frame

model is designed as per experimental parametric investigation and this study is

carried out for two frame specimens.

Keywords: Beam - Column Joints, Steel Profile, Fatigue, Cyclic Loading, Von-Mises.

Cite this Article: A S. Srinivasan and S. Pradeep (O.G), Investigation of Hybrid

Beam – Column Joints under Cyclic Loading, International Journal of Civil

Engineering and Technology, 9(5), 2018, pp. 218–228.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=5

1. INTRODUCTION

This research paper mainly is to ensure the joints strength under the lateral force. Due to

seismic force acting on the structures leads to failure at the beam-column joints. Normally

maximum shear bending in the structure will occurs at beam-column joints so; the life factor

is less at the joint area. To increase the strength at the joints many engineers implemented vast

area of research to enhance joint strength. By means of material replacement, mechanism

enhancement etc., in this paper introducing the steel-profile mechanism at beam-column joints

to increase stiffness at joints, also analytical investigation shows that the fatigue life of the

structure is improved when compared to the controlled specimen. Static analysis is carried out

to check the behavior of the steel-profile mechanism at the joints. Steel profile mechanism

mainly designed for practical implementation at the construction situations, where the steel

profile mechanism is placed at the both external and internal beam-column joints which are

used to reduce stress at that critical zone.

A S. Srinivasan and S. Pradeep (O.G)


Figure 1 Behavior of frame due to lateral force.

Fig 1 shows the shear bending of the body due to lateral load. In this structure beam-

column joints having maximum shear force. So, these points are referred as the critical zone

to consider for the safety enhancement to the joints, this particular zone has to be more

stiffened than any other critical zone. So innovative design of steel profile is introduced at

those points to resist shear bending at the joint area. Also, steel profile is able to resist

maximum shear force acting at critical zone that shown as analytical representation in this

paper.

Figure 2 Shear force due to lateral loads.

Shear bending plot shows the maximum force is acting at the joint area shown in Fig 2,

this is due to lateral load causes heavy stress at beam-column joints resulting the joint zone

has minimum life factor. Here in the earthquake resistance design, the way is to reduce shear

bending is by increase in material strength, dimension of structure, and reinforcement area. In

this paper research proposed through reinforcement enhancement at maximum working stress

at the joints to resist stress by a reinforcement.

2. FRAME MODEL

Frame model is done through SolidWorks, CAD software for better designing. High-

performance CAD modelling tool is useful for dimension accuracy and better graphics

experience. Additional simulation for model is facilitated in solid works to perform the cross-

check for the model and its used to reduce errors in the model, which is more beneficial for

Investigation of Hybrid Beam – Column Joints under Cyclic Loading


designing a CAD model for an engineering research. Exported the model as (parasolid.exe)

format, then the file is imported into Ansys for numerical analysis.

2.1. Frame Parameters

Frame model is of one story with 2 bays in the structure, where this frame model is very

beneficial to find out the behavior at the both external and internal beam-column joints. This

framed model perfectly suits for lateral load deformation simulation and for designing

suitable reinforcement at beam-column joints. Concrete and Structural Steel material is

defined for the structure. Here for the applied lateral force, the stress will get transmitted to

the supports. Hence the failure begins at that support area first. So, to reduce the stress at the

supports, gradual increase in dimension at the base (1/3) of the column length. Therefore, for

applied lateral load the stress will take place first at the beam-column joints. Hence steel

profile mechanism is easy to validate at the joints.

Figure 3 SolidWorks CAD Model.

2.1.1. Beam Parameters

Sl. No. Parameters Descriptions

1 Clear Length 500mm

2 Width 90 mm

3 Depth 100 mm

4 Reinforcements Top & Bottom – 2nos of 6mm diameter bars

5 Stirrups 6mm diameter bar at 95mm C/C

6 Clear Cover 25 mm

2.1.2. Column Parameters

Sl. No. Parameters Descriptions

1 Clear Length 600mm

2 Width 100 mm

3 Depth 90 mm

4 Reinforcements 4nos of 6mm diameter bar

4 Stirrups 6mm diameter bar at 100mm C/C

5 Clear Cover 20 mm



Figure 4 AutoCAD Reinforcement detailing.

Reinforcement solid body place inside the concrete body with the help of assembling tool

in the SolidWorks CAD Software. Removal of reinforcement volume from the concrete body,

were the steel area is subtracted from the concrete. Then again placing the reinforcement body

at the subtracted area.

3. ANSYS INPUTS

Ansys setup requires some information to proceed numerical analysis. Material properties are

the major inputs to consider for all the bodies, Structural steel material is applied for

reinforcement bodies and M25 Grade design is taken into account for the concrete body.

Contacts between the concrete and reinforcement are taken into consideration to cross check

the bonding between concrete and reinforcements. Fatigue data is needed for both concrete

and structural steel to evaluate the life factor of structural members for continuously applied

load. Constant amplitude method is adopted for cyclic loading.

3.1. Material Properties

Table 1 Concrete Properties

Parameters Value Units

Density 2300 Kg/m3

Elastic Modulus 25000 N/mm2

Poisons Ratio 0.17 -

Yield Tensile 2.25 N/mm2

Yield Compressive 25 N/mm2

Ultimate Tensile 2.5 N/mm2

Ultimate Compressive 31.2 N/mm2

Table 2 Structural Steel 250 Properties


Density 7850 Kg/m3


Poisons Ratio 0.3 -

Yield Tensile 250 N/mm2


Ultimate Tensile 415 N/mm2

Ultimate Compressive 415 N/mm2



Table 3 Structural Steel 415 Properties


Density 7850 Kg/m3


Poisons Ratio 0.3 -

Yield Tensile 415 N/mm2


Ultimate Tensile 550 N/mm2

Ultimate Compressive 550 N/mm2

3.2. Body contacts

Bonded Contact is applied b/w Concrete and reinforcement in the model. Resulting both

behaves as a Single structural element in the Modal. Where Pre-Stressed Body Required

Frictional Contact between the elements due to frictional loss. Designing for normal RCC

structure doesn’t require frictional contacts between elements for analysis.

3.3. Fatigue data

Fatigue data is the collection of data for the material, which is subjected to repeated cyclic

load resulting data taken as total life of the material. It’s the progressive and localized

structural damage that occurs when a material is subjected to cyclic loading. Below data

analytically use to find out the total life of the materials.

Figure 6 Fatigue data for Structural Steel and Concrete

4. JOINT MECHANISM

The maximum shear force is acting at beam-column joints shown in fig 2, hence critical zone

taken into consideration for enhancing the joint strength. In this paper brief discussion is

about steel profile mechanism, Where Two-Types of steel profile is designed and provided at

joints, one is T- Shape provided at the external joint and the other is Cross-Shape provided at

the internal beam-column joint. Steel Profile mechanism reinforcement design is formulated

according to the structural variation. Design of steel profile is cost effective with more

beneficial enhancement at the both external and internal beam-column joints.



Figure 7 Steel-Profile Mechanisms at Joints.

4.1. Formulation

• Area of reinforcement - Lesser than 0.5% of C.S (if >200mm).

• Area of Reinforcement - Equal to 0.5-0.55% of C.S (if <200mm).

Length of Steel Profile - User Defined According to Max Bending stress at joints. Should

not be more than 1/3 of the Clear length.

Total length of the bars along beam is 160mm and the column is 150mm, area of

reinforcement is 57 mm2

whereas 2nos of 6mm diameters bars are provided at the beam-

column joint. Same for external and internal joints, here in this analytical study shows that the

external steel profiles give more life to the joints than internal steel profile mechanism.

5. ANALYSIS

Static analysis is done for the Frame Specimens using Ansys FEM. Mesh for the concrete

body is 35mm and Steel Body is 10mm along longitudinal direction, Frame model divided up

to 450780 mesh elements. Various lateral loads were applied to the frame to find out the safe

load for the structure, where safe load processed for cyclic loading “constant amplitude

method” chosen to calculate the maximum life at the joints. Load concentrated on the body

varying from 5kN to 100kN. Ansys numerical result shows that the ultimate load carrying

capacity of the joints is around 50kN without any damage. Here its factor to 42.5kN for the

Uncracked Structural safe load to be considered for analysis of structure.

5.1. Static Structural Analysis

Figure 8 Loading Point and Boundary Conditions.



A 50kN lateral load applied at the external beam-column joint, where the stress exceeds the

yield strength of the concrete material at joints area. Here concrete yield strength considered

as 25MPa, Material failure takes place when the applied load causes the stress at the joints

which exceeds yield strength of the material 25MPa. So, considering design load as 50kN, so

factored to 42.5kN for safe behavior at beam-column joints. Experimental load for heavy

destruction at beam-column joint load is around 75 to 80kN. Results evaluated by von mises

stress component is preferred by a designer, which represents the behavior of the structure due

to applied load and boundary condition. Von Mises stress shows that the failure occurrence at

the body point, when the stress exceeds the yield strength of the material. So, an engineer can

able to design a structure in the way to execute in the fields.

5.2. Fatigue Analysis

Linear and non-linear structural analysis do not show the fatigue life of the structure its shows

the behavior and evaluates components like stress, strain and deformation for applied load and

boundary conditions accordingly. If the analysis assumptions are observed and the calculated

stress are within the allowable limits, application concludes that the total fatigue life cycle of

the body which can withstand the maximum number of a cyclic load at each and every node

in the model. Static structural studies are used for numerical fatigue analysis. The maximum

number of cycles required for fatigue failure to occur at any location is depended on the

material and the yield stress acting on the body.

5.2.1. Stages of failure

Stage 1 Cracks development in the concrete is mainly due to honeycomb in the body which is

not visible for naked eyes. Irregular mix design will cause surface cracks in the concrete. Also due to human errors like material handling, transportation etc.

Stage 2 Cracks formation due to continuous cyclic loading in the structure. Which results in

breakage of material at certain cyclic loading?

Stage 3 The ability of the design to carry the maximum load applied continuously till failure

take place in the structure.

In this study fatigue, life cycle monitored at the starting point of the cracks at the beam-

column joints.

5.2.2. Correction methods

The fatigue analysis is programmed by using three different algebraic formulations which

designer should adopt as per field and requirement.

• For brittle material “Goodman method” is suitable for evaluating life.

• Ductile material “Gerber method” formulation shows accurate results.

• General adoption is “Soderberg Method” for conservative analysis.

Here in this paper, Goodman method is adopted to calculate total life cycle of Concrete

material which is brittle in nature.

5.2.3. Fatigue events

Two Types of fatigue events is carried out by using Ansys FEM: Constant amplitude method

and variable amplitude method. In this study, constant amplitude method is preferred because

the maximum load already designed for the structure to apply. Hence constant amplitude

method is adopted to find total life cycles at the joints.

Outputs: fatigue analysis shows components like life, damage, & factor of safety. The

Program based on the loading ratio determines a corrected alternating stress from the static



study stress value for each node can able to select or probe nodal value of specimen as shown

in figure 12&13.

Zero Based Analysis (LR=0): Here load is 42.5kN cyclically applied as shown in fig.

Where the load varies from 0 to 42.5kN then gradually reduced to “Zero” respect to time (t) in

Sec. Cyclic loading continuously applied till evaluation of material life of the structure.

Figure 9 Zero Based (LR=0) Constant Amplitude.

6. RESULTS AND DISSCUSSIONS

Here in this investigation, steel profile mechanism behavior is monitored exactly with the help

of Finite element analysis which is resulting over stiffening at the beam-column joints. Extra

reinforcement enhancement that is provided at joints is act as antilock mechanism at joints,

twisting of member at the joints area seems to be reduced at a certain level. The area around

the beam-column joints shows that the stress is reduced, were stress decreased around 1.5MPa

to 2MPa. The output results clearly show that the tensile performance at joints is increased.

Two types of results shown below 1) Static analysis results which shows the behavior of the

structure and 2) Fatigue analysis which shows the maximum life factor of the structure for

applied load and boundary conditions, zero based analysis is carried out for the frame, load is

applied continuously from “0” to “42.5kN” again to “0” as shown in fig 11.

6.1. Static analysis results

Figure 10 Von-Mises stress for concrete



Figure 11 Von Mises stress for structural steel

Frame is stressed up to 95MPa, maximum stress inducing in structural steel and concrete

is stress up to 23MPa at joints for applied load. Normally in RCC structure the steel is always

has maximum stress than concrete, due to lateral force, tensile stress is maximum at structural

steel, shown in Fig 10 and 11.

6.2. Fatigue analysis results

Figure 12 total fatigue life at critical point (Frame without Steel-Profile)

Figure 13 total fatigue life at critical point (Frame with Steel-Profile)



Hence the fatigue life at the joints is increased when compared to frame without steel-

profile. Here external joints life is increased from 1574 to 1804 cycles, Internal joints life is

increased from 1055 to 1205 cycles, shown in fig 12 and 13. Finally concluded that the steel

profile mechanism act as good load resistor at beam-column joints.

7. CONCLUSIONS

• Provision of steel profile is found to improve structural behaviour at beam-column

joints.

• Steel Profile reinforcement could able to resist the shear stress up to 47MPa at both

the joints. So, Reduction in Joint Shear deformation.

• Steel Profile Bars stressed up to 82MPa at the joints. Hence load-carrying Capacity of

the member is slightly increased.

• Stiffness at the beam-column joints increased which results in the improvement of

fatigue life at the joints, when compared to the controlled specimen.

• Initial Crack Formation due to yield stress is reduced. Hence life of the structure will

get increased.

• Steel-Profile reinforcement is cost effective and increase in mechanical behaviour at

joints.

• More research is required to validate steel profile mechanism for the future

construction applications.

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investigation of hybrid beam – column joints under …€¦ · yield strength of the concrete...

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