scholarly journals Strengthening of seismically deficient exterior beam-column connections using embedded steel bars

2019 ◽  
Vol 276 ◽  
pp. 01007
Author(s):  
Ridwan ◽  
Samir Dirar ◽  
Yaser Jemaa ◽  
Marios Theofanous ◽  
Mohammed Elshafie
Keyword(s):  
Shear Stress ◽  
Tensile Stress ◽  
Superior Performance ◽  
Rc Beam ◽  
Control Specimen ◽  
Concrete Core ◽  
Novel Technique ◽  
Principal Tensile Stress ◽  
Steel Bars ◽  
Joint Shear

Several techniques for improving performance of reinforced concrete (RC) beam-column (BC) connections have been developed in last two decades, but these techniques have been criticized for being labourintensive and susceptible to premature de-bonding. To overcome these shortcomings, a novel technique utilising embedded steel bars has been developed in this study for strengthening seismically deficient RC BC connections. This technique involves drilling holes within the joint core. After the drilled holes are cleaned, they are partially filled with epoxy. Finally, steel bars are inserted in the epoxy-filled holes. Two exterior BC connections were constructed and loaded under displacement-controlled cyclic loading. The first specimen was a control specimen designed in accordance with the pre-1970s building codes to represent BC connections requiring strengthening. The second specimen was strengthened with eight 8 mm steel bars embedded within the concrete core in the joint area and epoxied to maintain the bond between the concrete and the steel bars. The strengthened specimen had superior performance compared to that of the control specimen in terms of joint shear stress, normalised principal tensile stress demand and stiffness degradation. The results show that shear stress of the joint was enhanced by about 8% whereas the enhancement in the principal tensile stress demand was 24% compared to that of the control specimen. The results showed that the proposed technique is capable in upgrading the seismic performance of seismically deficient RC BC connections.

A Simplified Approach to Joint Shear Behavior Prediction of RC Beam-Column Connections

2012 ◽  
Vol 28 (3) ◽  
pp. 1071-1096 ◽  
Author(s):  
Jaehong Kim ◽  
James M. LaFave
Keyword(s):  
Shear Stress ◽  
Parameter Estimation ◽  
Estimation Method ◽  
Stress And Strain ◽  
Rc Beam ◽  
Peak Response ◽  
Experimental Database ◽  
Key Points ◽  
Shear Stress And Strain ◽  
Joint Shear

An extensive experimental database of reinforced concrete (RC) beam-column connections subjected to cyclic lateral loading has been constructed. All cases within the database experienced joint shear failure, either in conjunction with or without yielding of longitudinal beam reinforcement, representing damage within a joint panel that was the main contributor to total lateral deformation. (Cases having damage within a joint panel caused by other premature failure modes (e.g., anchorage failure) are not included in the database.) Using the experimental database, envelope curves of joint shear stress vs. strain behavior were developed by connecting key points such as cracking, yielding, and peak loading. Joint shear stress and strain models at peak response have been developed by a Bayesian parameter estimation method based on the experimental database. At other key points, important influence parameters are also identified by constructing joint shear stress and strain models in conjunction with the Bayesian parameter estimation method. Then, a complete RC joint shear stress vs. strain model (including post-peak behavior) is suggested using simplified joint shear stress and strain models at peak response; effects of key parameters on the suggested behavior models are evaluated. Finally, the ASCE/SEI 41 joint shear behavior model has been examined using the constructed database—specific joint shear strength factors and plastic joint shear deformation values are recommended for use when following that approach.

scholarly journals Improvement Methods for Reduction of the High Stress of Ultra-High Asphalt Concrete Core Dams

2019 ◽  
Vol 9 (21) ◽  
pp. 4618
Author(s):  
Jun Gao ◽  
Faning Dang ◽  
Zongyuan Ma ◽  
Yi Xue ◽  
Jie Ren
Keyword(s):  
Shear Stress ◽  
Internal Friction ◽  
Tensile Stress ◽  
Stress Level ◽  
Asphalt Concrete ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
High Shear ◽  
High Shear Stress ◽  
Concrete Core

With the rapid development of asphalt concrete core rockfill dams (ACCRDs), the construction of ultra-high asphalt concrete core rockfill dams (UACCRDs) has been improved significantly. However, the security problems of asphalt concrete core (ACC) become very prominent with the increase of dam height. The shear failure control standard and tensile failure control standard of ACC are suggested. The mechanisms of ACC that generate high shear stress and high tensile stress are investigated. Based on the definition of stress level and the transmission mechanism of arch structures, the improvement methods that reduce the high shear stress and high tensile stress of ultra-high asphalt concrete core (UACC) are proposed and investigated. The results show that the stress level of ACC can be reduced significantly by the increase of the strength parameters of ACC (failure ratio, cohesion, and internal friction angle). The following value ranges of the failure ratio, cohesion, and internal friction angle of ACC for the suitable construction of UACCRDs are recommended: Rf ≥ 0.75, C ≥ 0.30 MPa, and φ ≥ 28.5° (h = 150 m), with the growth gradient adjusted by 5%, 15%, and 5%/25 m. The tensile stress and tensile stress area can be reduced obviously by the new type of dams (curved asphalt concrete core rockfill dams (CACCRDs)). The value ranges of the curvature of CACC (k ≥ 1.0 × 10−3) for the suitable construction of UACCRDs are recommended.

scholarly journals A Nonlinear Macro-Model for the Analysis of Monotonic and Cyclic Behaviour of Exterior RC Beam-Column Joints

2021 ◽  
Vol 8 ◽  
Author(s):  
Ernesto Grande ◽  
Maura Imbimbo ◽  
Annalisa Napoli ◽  
Riccardo Nitiffi ◽  
Roberto Realfonzo
Keyword(s):  
Shear Stress ◽  
Linear Regression Analysis ◽  
Material Model ◽  
Joint Interface ◽  
Model Parameters ◽  
Multivariate Linear Regression Analysis ◽  
Rc Beam ◽  
Stress Strain ◽  
Experimental Database ◽  
Joint Shear

The study presents a numerical investigation on exterior reinforced concrete (RC) beam-column joints under seismic actions based on a macro-modelling approach proposed by the authors in a recent paper. The followed approach makes use of the well-known “scissors model” where two nonlinear rotational springs arranged in series were introduced to schematize the shear behavior of the joint panel and, moreover, the possible occurrence of the debonding of longitudinal steel rebars at the beam-joint interface. In this paper, the scissor model is employed in the context of a novel predictive approach with the twofold objective to: 1) develop a new model for the estimate of the maximum shear strength of RC joints by performing a multivariate linear regression analysis on a set of experimental tests and, 2) define a new multilinear backbone joint shear stress-strain law to be assigned to one of the mentioned springs. In particular, the identification of the shear strain parameters is obtained by performing a sensitivity analysis in which a number of monotonic load-drift numerical curves are derived by varying the strain values in ranges opportunely a-priori defined and compared with the experimental ones to investigate their accuracy. Finally, cyclic analyses on RC joints collected in the experimental database are carried out by considering the backbone joint shear stress-strain law identified in the calibration process. The analyses are performed by using the nonlinear open-source finite element platform, OpenSees, in which the “pinching4” uniaxial material model, available in the software library, is implemented to set the parameters governing the hysteresis rules and pinching effect. To this purpose, five literature proposals suggesting the values to use for such parameters are taken into account and their assessment is presented in the paper. The obtained outcomes have allowed, on the one hand, to identify the proposal providing the best numerical simulations of the experimental results and, on the other end, to draw useful indications on how to further improve the cyclic modelling by opportunely modifying the setting of the “pinching4” material model parameters.

Experiment Study on Cyclic Behavior of Concrete Filled Steel Tube (CFST) Column-Reinforced Concrete (RC) Beam Connections

2009 ◽  
Vol 417-418 ◽  
pp. 833-836 ◽  
Author(s):  
Qing Xiang Wang ◽  
Shi Run Liu
Keyword(s):  
Reinforced Concrete ◽  
Tube Wall ◽  
Plastic Hinge ◽  
Steel Tube ◽  
Reinforced Concrete Beams ◽  
Cyclic Behavior ◽  
Concrete Core ◽  
Concrete Filled Steel Tube ◽  
Steel Bars ◽  
Moment Resisting

The test results of six connections under cyclic loading are presented in the paper. Each test specimen was properly designed to model the interior joint of a moment resisting frame, and was identically comprised of three parts that including the circular concrete filled steel tube columns, the reinforced concrete beams, and the short fabricated connection stubs. Energy dissipation was designed to occur in the beams during a severe earthquake. Steel bars which were embedded into concrete core and welded to the connection stubs, were used to transfer the force distributed by the reinforcing bars of concrete beam to the concrete core. The results indicated that the embedded steel bars were very efficient in eliminating the stress concentration on the tube wall and there was no visible deformation occurred on the tube wall until the collapse of the specimen. Furthermore, the connection of each specimen had enough capacity and thus the plastic hinge appeared in the beams. As results, the ductility of this new type structure directly depended on the RC beams.

Limits to elastic response. Yielding and failure

2020 ◽  
pp. 357-368
Author(s):  
Lallit Anand ◽  
Sanjay Govindjee
Keyword(s):  
Shear Stress ◽  
Tensile Stress ◽  
Critical Value ◽  
Maximum Principal Stress ◽  
The Body ◽  
Elastic Response ◽  
Elastic Behaviour ◽  
Pressure Independent ◽  
Yield Conditions ◽  
Is Failure

This chapter presents conditions for determining the limits of elastic behaviour for isotropic materials. The stress invariants of equivalent pressure, equivalent shear stress, and equivalent tensile stress are defined. These are then used to define common yield conditions, viz. the pressure-independent Mises and Tresca yield conditions, as well as the pressure-dependent Coulomb-Mohr and the Drucker-Prager yield conditions. Rankine’s failure criterion for brittle materials in tension, that is failure in a brittle material will initiate when the maximum principal stress at a point in the body reaches a critical value, is also discussed.

Optimum Design of Ribbon and Wire Wound Cylinders for Metal Forming Dies

1977 ◽  
Vol 99 (3) ◽  
pp. 733-737 ◽  
Author(s):  
J. Gro̸nbaek ◽  
T. Wanheim
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Tensile Stress ◽  
Optimum Design ◽  
Metal Forming ◽  
Working Pressure ◽  
Internal Working ◽  
Shrink Fit

The ribbon winding process enables the manufacture of metal forming dies with higher allowable internal working pressure than is possible by conventional shrink-fit constructions. Varying the tensile stress in the ribbon in the winding process, the stress distribution in the die can be given a predetermined shape. Based on the assumption that all ribbon layers carry the same shear stress when the internal working pressure is acting, a new winding theory is derived. This method permits the internal working pressure to be increased about 30 percent compared to that of the previously known winding theories and about 60 percent compared to that of shrink-fit constructions.

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