Seismic Shear Performance of Beam-column Subassemblages in Multistory R/C Structures PDF Download

Author: El Mostafa Higazy
Publisher:
ISBN:
Category :
Languages : en
Pages : 496

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Author: Sayed Ahmed Aly Attaalla
Publisher:
ISBN:
Category :
Languages : en
Pages : 600

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Author: Shannon D. Paboojian
Publisher:
ISBN:
Category : Columns
Languages : en
Pages : 454

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Book Description
Abstract: "An experimental study was undertaken to investigate the cyclic strength and ductility of composite columns subjected to simulatedseismic loading conditions. Eight two-thirds scale specimens were tested, each consisting of a structural steel shape encased in reinforcedconcrete. Parameters studied in the test program included: the degree of concrete confinement required to achieve adequate ductility; the effectiveness of shear studs for developing flexural stiffness and capacity under combined loading; the distribution of transverse shear resistance among the elements of the composite column; and concrete compressive strength. The results of the test program indicate that composite columns possess exceptional ductility and strength under cyclic loading if the buckling of longitudinal reinforcement is inhibited. Furthermore, the steel shape provides the primary resistance to transverse shear during overloading, and shear studs are not effective in enhancing the resistance against lateral loading. The elastic secant stiffness of the composite section corresponding to initial yielding of the longitudinal reinforcement was found to be well approximated by using one-half the gross moment of inertia (0.5I[subscript g]) in conjunction with Young's modulus for concrete. A prediction method based on superimposing the individual strengths of the reinforced concrete and structural steel shape was found to provide good agreement with test results. Current AISC LRFD provisions were determined to grossly underestimate the flexural capacity of the test specimens, which were axially loaded to 20% of their nominal pure axial load capacity [sic]."

Author: Yasser Helal
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Old reinforced concrete buildings are vulnerable to seismic actions as they were built in accordance with non-seismic code provisions and suffer from poor material quality and/or reinforcement detailing. Moreover, many buildings were constructed without even basic design code recommendations. Consequently, their structural components, in particular beam-column joints, suffer from a wide range of deficiencies. These joints may deteriorate severely under seismic actions leading to extensive damage and collapse. The current study aims to develop an understanding of the behaviour of exterior beam-column joints with shear strength and anchorage deficiencies, and to examine a strengthening solution using post-tensioned metal strips in upgrading their performance. A multiphase experimental programme was conducted including small and medium-scale beams with inadequate lap splices loaded in tension and deficient isolated full-scale exterior beam-column joints subjected to quasi-static cyclic loading. In the beam tests, deficient splices were investigated under different confinement conditions, namely, unconfined, internally confined by steel stirrups, and externally confined by metal strips. Test parameters included concrete cover, confinement ratios, concrete quality, and bar diameter. Providing post-tensioned external confinement had a considerable impact on the behaviour, and resulted in sizable enhancements in strength and ductility. Parametric studies were conducted to identify the parameters most influencing the contribution of external confinement to bond. A bond stress-slip model is proposed that can be used to predict and simulate the behaviour of splices strengthened by post-tensioned metal strips. This model was implemented in FE models of beams and showed good correlation with the measured response. In the joint tests, four full scale exterior RC beam-column joints were tested under cyclic loading. The joints experienced severe cracking and damage including a shear mechanism in the panel zone. The joints failed prematurely at about 50% of their nominal flexural strength. Strengthening the joints with post-tensioned metal strips led to an improved performance, higher energy dissipation and more controlled shear failure along with moderate damage in the beam. An enhanced ACI-based strut-and-tie joint model is proposed and verified against the current test results and results by others. The model can be used for strengthened specimens as well as unconfined exterior joints and it accounts for different beam anchorage lengths. A quad-linear shear stress-strain model is proposed to simulate the behaviour of strengthened joints. The model was implemented in a finite element panel-zone scissors model. The scissors model was incorporated in nonlinear static and cyclic analyses. The simulated response was found to represent the joint behaviour reasonably well. A full-scale two storey reinforced concrete framed building was designed and tested on a shaking table, in cooperation with different researchers and academic partners. The building was substandard with a multiple range of deficiencies in the joint regions and connecting elements. The bare building suffered severe damage under small seismic intensities. Upgrading the structure with schemes of post-tensioned metal strips led to a considerably enhanced performance.

Author: James Otis Jirsa
Publisher:
ISBN:
Category : Architecture
Languages : en
Pages : 546

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Author: Duane L. N. Lee, James K. Wight
Publisher:
ISBN:
Category :
Languages : en
Pages : 226

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Author: Brian Forzani
Publisher:
ISBN:
Category : Columns, Concrete
Languages : en
Pages : 124

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Author: Amer Mohammad Elsouri
Publisher:
ISBN:
Category :
Languages : en
Pages : 338

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Book Description
Wide and concealed beam- narrow column joints constitute an important part of reinforced concrete building structural systems in Lebanon and the region. Because Lebanon and most of the region are seismically active, evaluating the performance of these joints when subjected to earthquake loads becomes particularly important. A two-part experimental investigation was carried out. Part 1 concentrated on evaluating the seismic response of wide and concealed beam-narrow column joints when designed and detailed under gravity load in accordance with local design and construction practices (as-built). Part 2 focussed on exploring means for improving the seismic performance of the joints through adequate reinforcement detailing, guided by the ACI Building Code. Aspects of the seismic behavior that were evaluated throughout the research program included: (i) mode of joint failure, (ii) flexural and shear capacity, (iii) bond performance of the reinforcing bars, (iv) lateral drift capacity or ductility, (v) stiffness degradation, (vi) energy absorption and dissipation capacity under cyclic loading, and (vii) shear capacity of the joint core. In the first part of the investigation (Part 1), four full-scale interior and exterior beam-column sub-assemblages were tested under quasi-static cyclic loading. All specimens experienced extensive shear cracking within the joint core, and at drift ratios between 4.0% and 4.5%, the joint core experienced damage beyond repair. It was concluded that unless detailed to prevent or limit shear failure, the as-built joints under investigation are significantly weak to be considered as part of the earthquake lateral-load-resisting system. In the second part of the investigation (Part 2), four additional full-scale joints were tested under quasi-static cyclic loading. The joints, referred to as earthquake-resistant joints, were similar to the four joints tested in Part 1, except that the reinforcement details were improved in part in accordance with ACI 318-08 provisions for earthquake-resistant structures. The joints satisfied some of the ACI Building Code design and steel detailing requirements, but still violated the dimension limitations specified in the same code or recommended by ACI-ASCE Committee 352-02. The corresponding joints displayed a considerably improved seismic performance, manifested by preventing or delaying joint shear failure, higher lateral load and drift capacities, lower stiffness degradation, larger energy dissipation capacities and stable overall hysteretic response when compared with the as-built joints. In addition to the main two parts of the investigation described briefly above, the potential of upgrading the seismic-resistant joints tested in Part 2 using a combination of epoxy injection for repairing the major cracks and carbon fiber reinforced polymers (CFRP) composites for strengthening was also explored and experimentally evaluated. The repair and strengthening procedure used in this study, which was carried out with minimum labor and cost, resulted in significant improvement of the structural performance of the damaged joints. This improved performance was manifested by substantial stiffness recovery, enhanced lateral load capacity and low strength degradation under large lateral drifts, controlled cracking and damage, and reasonable regain of energy absorption and dissipation capacity.

Author: Suthipoul Viwathanatepa
Publisher:
ISBN:
Category :
Languages : en
Pages : 184

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Author: Konstantinos G. Megalooikonomou
Publisher: Cambridge Scholars Publishing
ISBN: 1527530361
Category : Technology & Engineering
Languages : en
Pages : 387

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Book Description
Reinforced concrete columns play a very important role in structural performance. As such, it is essential to apply a suitable analytical tool to estimate their structural behaviour considering all failure mechanisms such as axial, shear, and flexural failures. This book highlights the development of a fiber beam-column element accounting for shear effects and the effect of tension stiffening through reinforcement-to-concrete bond, along with the employment of suitable constitutive material laws.