Effect of Beam Transverse Position on the Behavior of Reinforced Concrete Beam Column Joints Under Quasi-Static Loading

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Effect of Beam Transverse Position on the Behavior of Reinforced Concrete Beam Column Joints Under Quasi-Static Loading

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Ehab Hediba, Ezz El-Deen M. Salah b, Mahmoud R. Lashan c, Amr H. Zaher d, Ayman H. Hosny d

a Assistant Lecturer, Department of Building and Construction Engineering, H.I.E, 6 October City

b Assistant Professor, Department of Civil Engineering, Faculty of Engineering, Ain Shams University c Assistant Professor, Department of Concrete Structure, Housing & Building National Research Center d Professor, Department of Civil Engineering, Faculty of Engineering, Ain Shams University

Abstract:- The study of the beam-column joints is essential for developing a structure with better characteristics. An experimental investigation carried out on the reinforced concrete exterior beam-column joint subjected to Quasi-Static loading is reported in this paper. The objective of this study aimed to attaining a better understanding of the effect of beam transverse position on the behavior of reinforced concrete beam column joints, three real scale beam-column joints were casted, with different eccentric-beam column connections with the same reinforcement. Parameters such as ultimate load, energy dissipation capacity, stiffness degradation, and crack behavior of concrete were examined and the results showed that the concentric beam position is the best position for beam in joint, also is better in the displacement, energy dissipation capacity, stiffness degradation and strength decay.

1. INTRODUCTION

Reinforced concrete moment resisting frames, which typically consist of a framework of beams and columns, are among the most commonly used lateral load resisting systems. For the first half of the twentieth century, the design of the area where beams and columns join was overlooked. Several earthquakes demonstrated that the beam-column joint in such a system is the weakest link under lateral load. Since the late 1960s, a substantial amount of research has been conducted on the performance of beam-column joints and design codes started to incorporate related design and detailing guidelines [1].

The integrity of beam-column joints in reinforced concrete (RC) frames, especially in a crucial zone, is essential for the satisfactory performance of the whole structure. Therefore, the behavior of external connections between beams and columns is a significant parameter affecting the performance of such R.C frames. An important influence in this regard is the concrete compressive strength, joint reinforcement and relative stiffness of beam and column in each connection [2], which is itself determined by considerations of geometry and reinforcement percentage.

Eccentric joint means the beam and column centerline does not coincide with each other [3]. Most of researchers have studied the eccentric in joints consist of wide beams. Based on study made on various design codes, Li and Kulkarni [4] indicated that the BS8110, British Standards 1997 strictly restricts the use of wide beam-column connections to resist earthquake loads. Such geometric restrictions are often based on historical design practices. However, in the United States, beam width is restricted of (bc +1.5hb), where hb is the beam depth and bc is the column width. Whereas in New Zealand, the beam width restriction is the lesser of (bc + 0.5hc) and 2bc, where hc is the column depth.

Several experimental and theoretical studies have been conducted to investigate the overall conduct of beam-column joints. A.K.Kaliluthin, et al [5], focused on the general behavior with specific structural properties of common types of joints in reinforced concrete moment resisting frames to be aware of the fundamental theory of the joint for better efficiency. A beam- column joint is a very critical zone in reinforced concrete framed structure where the elements intersect in all three direction .The behavior of joints was found to be dependent on a number of factors related with their geometry; amount and detailing of reinforcement, concrete strength and loading pattern.

Subramani et al. [6] carried out an analytical study using ANSYS for traditional T-shaped concrete frame building joints with strong beam-weak columns. They found that both axial forces and beam to column linear stiffness ratio had impacts on joint capacity and ductility behaviour of the specimens.

The earliest test conducted by Abrams [7] indicated that compressive strength of concrete was sensitive to the rate of loading. Since then, numerous experimental studies have been carried out to investigate the dynamic mechanical properties of concrete over a wide range of strain rates.

The energy absorption and carrying capacity of plain concrete subjected to both static and dynamic loading were investigated by Atchley and Furr [8] using cylinders. The conclusion was that the compressive strength and energy absorbed increased with an increase in the rate of loading, with evidence of becoming a constant value at the higher rates of loading. Based on previous experimental results, Bischoff and Perry [9] and Malvar and Ross [10] summarized the effect of loading rate on the properties of concrete compressive and tensile strength, respectively,

To contribute a better understanding of the behavior of external beam column joints under reversed cyclic loading, in this paper three specimens of beam-column joints with 100mm (0.25 tc) (tc: column length), 75mm (0.18 tc) and zero eccentricity

distance between C.G of beam and C.G of column were constructed and analyzed. The main parameter is to study effect of beam position on the behavior of reinforced concrete beam column joints under quasi-static loading.

2. MATERIALS CHARACTERIZATION:

2.1 Concrete2.2 Steel3.1 Specimens detailsTime3.2 Test Set-Up4.1 Cracks patterns and failure mode4.2 Failure mode and load- displacement curves:J4J2DISPLACEMENT(MM)JointJoint4.3 ENERGY DISSIPATIONDisplacement(mm)4.4 STIFFNESS DEGRADATIONDisplacement (mm)4.5 STRENGTH DECAY

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