Base isolation systems are preferably applied in low-rise buildings since the
vibration period of the structure can be shorter, so that it performs more rigidly to
maximize the benefit from the isolation system. Mid-rise and high-rise base-isolated
buildings are expected to have different and variable response characteristics compared to
low-rise base-isolated buildings, and may not perform as well as low-rise or relatively
stiffer base-isolated buildings. However, in this study, the benefit of seismic isolation in a
9-story is comparable or even better than a low-rise (3-story) isolated building that was
investigated thoroughly in a previous study (Sayani et al. 2011) with respect to peak floor
acceleration, peak story drifts, and peak plastic rotation.
A pair of 9-story isolated and conventional buildings were designed by
Forell/Elsesser, using the same design philosophy as 3-story buildings that were
investigated earlier. Both 9-story and 3-story buildings were designed to satisfactorily
meet the current building code standards (ASCE 2005). OpenSees and SAP 2000 were
used to develop analytical models of the 9-story buildings for independent purposes. The
SAP model was used primarily for model analysis and to perform a design check with
standard response spectrum analysis procedures. The OpenSees model was used for
nonlinear pushover analysis and nonlinear response history analysis to suites of ground
motions representing various probability of occurrence events.
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The P-Delta effect occurs when a frame or structure is laterally displaced by either seismic or wind loadings. As the structure is being displaced laterally, gravity begins to act on the members causing a secondary effect on the forces and moments which in turn cause additional displacement.
The purpose of this study is to investigate the P-Delta effect on multi-story steel framed structures with welded flange plate connections. The traditional method regarding the calculation of the P-Delta effect assumes the lateral displacement of the steel columns is due to lateral deflection only and does not take joint rotation into account. In this study, a finite element analysis using computer models will be used to investigate the additional lateral displacement from the P-Delta effect due to the addition of joint rotation.
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The P-delta effect is a second order effect experienced by any structure when subjected to lateral loads like earthquake or wind loads, and is originated by an additional destabilizing moment generated due to the gravity acting on the laterally deflected member further displacing it. For the purpose of this research, displacement is considered as the study parameter to analyze the second order P-Delta effects.
The main objective of this study is to investigate effects of forces causing P-Delta effects on Single Story Single Bay Steel Moment Frames with Reduced Beam Section Connection (RBS). FEMA-350 and AISC Seismic Design Manual suggest that, if the specified conditions are satisfied, there is no need to provide additional panel zone reinforcements as continuity and doubler plates. This study makes an effort to observe the effects of panel zone strength in formation of plastic hinges and in shifting fracture zone away from the column face on frames with RBS connections under P-Delta effects and find whether further increasing the stiffness of panel zone will have beneficial outcome or not.
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Inelastic behavior in steel special moment frames occurs through the development of plastic hinges at locations near the ends of the beam. The main objective of using a reduced beam connection is to force the formation of plastic hinges to be formed at the reduced beam section rather than at the ends of the beam which otherwise would lead to brittle failure of the beam-column connections. The beam has two reduced beam sections, each located at a certain distance from the face of the column, so that the plastic hinges are formed symmetrically at each of this section. When acted upon by lateral loads, the maximum moments occur at the ends of the beam. Therefore, the plastic hinges form at the reduced beam section. However, when a frame is subjected to a combination of gravity and lateral loads, the plastic hinge formation at one of the reduced beam section is not so clear and further analysis has to be done to study the effect. FEMA 350 indicates that the desired plastic hinge location is only valid for beams with gravity loads representing a small portion of the total flexural demand. If gravity demands significantly exceed 30% of the girder plastic capacity then further plastic analysis of the frame should be performed to determine the appropriate hinge locations.
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This research investigates the analytical lateral load responses of unbonded posttensioned
cast-in-place concrete special structural walls with bonded or debonded
longitudinal mild steel reinforcement under the action of monotonic lateral load. Two sets
of generalized closed-form expressions are derived for estimating the lateral load
responses, base moment and lateral drift, of the walls for critical limit states. First set of
equations is for cast-in-place special structural walls with bonded longitudinal
reinforcement and the second for cast-in-place special structural walls with
predetermined length of debonded longitudinal reinforcement at the base of the wall.
Analytical models for walls, with the two configurations of longitudinal reinforcement,
using fiber elements are also presented for nonlinear analysis of walls under monotonic
lateral load. In general, results of the closed-form expressions are in good agreement with
the results of analytical models.
The analytical models and the closed-form expressions are also used for investigating
effects of six design parameters in the lateral load response of the walls. The parameters
considered are area of post-tensioning steel with constant initial prestress; initial prestress
in post-tensioning steel with constant area of post-tensioning steel; constant initial
prestress force with varying area and initial prestress; area of boundary longitudinal
reinforcement; area of web longitudinal reinforcement; and spacing of web longitudinal
reinforcement.
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Hi friends
Please share this article; The Stability of Liquid-Filled Cylindrical Shells Under Dynamic Loading
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If anyone here has GS AFES Tutorial, please kindly share..
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Hi friends
Please anybody can share this article; Effect of Openings on Elephant’s Foot Buckling of Large Oil Tanks
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Publishing information
This British Standard is published by BSI Standards Limited, under licence from The British Standards Institution, and came into effect on 31 May 2012. It was prepared by Technical Committee ISE/104, Concrete reinforcing and prestressing
steels. A list of organizations represented on this committee can be obtained on request to its secretary.
Supersession
This British Standard supersedes BS 5896:1980, which is withdrawn.
Relationship with other publications
This standard has been revised to follow BS EN 10138-1 (in preparation).
Definitions, symbols, steelmaking and manufacturing processes, routine inspection and testing, test methods, identification of the manufacturer and technical class and verification of mechanical properties in the case of dispute may be taken from BS EN 10138-1, when published.
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Engelhardt, Michael D.; Popov, Egor P. - Behavior of Long Links in Eccentrically Braced Frames
Author: Engelhardt, Michael D.; Popov, Egor P. | Size: 59.6 MB | Format:PDF | Quality:Scanner | Publisher: UNIVERSITY OF CALIFORNIA AT BERKELEY | Year: 1989 | pages: 414
This report describes an experimental investigation and associated studies on the behavior of long, flexural yielding links in seismic-resistant Eaentrically Braced Frames (EBFs). EBFs provide ductile behavior under severe earthquake loads by restricting yielding to beam segments called "links". Short, shear yielding links are preferred because of their demonstrated excellent plastic rotation and energy dissipation capacities. Longer, flexural yielding links, however, can offer important architectural advantages and have been used on a number of recently constructed EBFs. Little experimental data has been available on the behavior of long links under cyclic loading.
The central focus of this report is an experimental investigation on fourteen 213 scale subassemblages subject to cyclic loads. The subassemblages model a portion of a single-diagonal EBF with the rinks attached to the columns. 'The testing program showed that the dominant failure mode for long links attached to columns is fracture of the link flange at the link-to-column connection. Rased on this experimental program, the recommendation is made that long links attached to columns not be used in EBFs. The test results suggest, however, that long links located between two braces can provide acceptable perfamance, although short Iinks are still preferred for best overall performance.
Because of the very high axial force and bending moment typically carried by the beam segment outside of the link, this member can buckle before link inelastic rotation is fullydeveloped, with a consequent loss in the overall system perfomance. Problems with the beam can be avoided by adhering to capacity design principles. A preliminary design procedure based on capacity design concepts is developed for the beams and braces of an EBF.
Based on the findings of this investigation, combined with the results of previous EBF research, preliminary design recommendations are provided for the use of long links not attaclled to columns. Included are recommendations on the design yield strength, ultimate strength, plastic rotation capacity and stiffening requirements for long links. The testing program has also demonstrated the suitability of selected brace-to-link connection details for use in EBFs with long or short links.
This book was posted in this thread closed with dead link
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