Retrofit of Reinforced Concrete Moment Frames in NZ Using Dual Supplemental Damping

Adding braces to moment frames is considered to be quite an efficient technique for increasing the global stiffness and strength of the structure. It has not only been used in steel moment frames, but also in reinforced concrete (RC) moment frames in recent years. It certainly can increase the energy absorption capacity of structures and also decrease the demand imposed by seismic ground motions. Steel braces are anchored firmly to boundary beams and columns. They are modeled as truss elements and increase earthquake resistance of the building. Buckling restrained braced frames (BRBFs) in which members yield under both tension and compression without significant buckling have been used in recent years in order to ensure the desired seismic performance of special concentrically braced frames. BRBFs are similar to the special concentrically braced frames in that seismic accelerations are resisted by a building-frame members and diagonal braces whereas the design procedure is different. BRBs should be designed to permit ductile yielding both in compression and tension. In this paper, flat-slab RC building with two different configurations of buckling restraint braces (BRBs) is studied. The buildings have 4-storey with 5 bays in both X-and Y-directions and have been designed according to Turkish Specification of Reinforced Concrete Design (TS 500). In order to explore overall behavior up to failure and lateral load resisting capacities for these buildings, nonlinear static analyses have then been performed using SAP 2000-V14.1. Pushover analysis under constant gravity loads and monotonically increasing lateral forces during an earthquake until a target displacement is reached is generally carried out as an effective tool for performance based design. The major outcome of a pushover analysis is the capacity curve which shows the base shear vs. the roof displacement relationship and represents the overall performance of the building. The results of the analyses are presented in terms of capacity curve and energy dissipation.

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Simplified Time-Dependent Column Shortening Analysis in Special Reinforced Concrete Moment Frames

Periodica Polytechnica Civil Engineering ◽

10.3311/ppci.10679 ◽

2017 ◽

Vol 62 (1) ◽

pp. 232-249 ◽

Cited By ~ 1

Author(s):

Mohammad Jalilzadeh Afshari ◽

Ali Kheyroddin ◽

Majid Gholhaki

Keyword(s):

Reinforced Concrete ◽

Frame Structures ◽

Moment Frames ◽

Moment Frame ◽

High Rise ◽

Geometrical Characteristics ◽

Time Changes ◽

The Moment ◽

Long Term Behavior

Necessity for adaption of high-rise reinforced concrete structures’ design and practical steps of implementation through nonlinear staged analysis by consideration of long-term behavior of concrete have always been strongly recommended by researchers in recent years. Cumulative column shortening in conventional analyses is the most important consequence of neglecting the above issues. In this article, numerous modeling and extensive nonlinear staged analyses are carried out on structures with different geometrical characteristics and extremely simple empirical equations to estimate column shortening caused by creep, shrinkage and time changes of modulus of elasticity are provided in such a way that these relations can be independent of conventional parameters of ACI209R-92 regulations used in prediction of mentioned axial strains. Results obtained from validation of the proposed equations show high compliance of all proposed equations for up to 30 floors and also show accuracy of proposed shrinkage equation for the moment frame structures higher than the studied range.

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The Finite-Element Simulation for Reinforced Concrete Frames Including the Softening Behaviour

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.204 ◽

2011 ◽

Vol 243-249 ◽

pp. 204-208

Author(s):

Wei Guo Jiang

Keyword(s):

Finite Element ◽

Reinforced Concrete ◽

Design Method ◽

Nonlinear Static Analysis ◽

Moment Frames ◽

Concrete Frames ◽

Element Analysis ◽

Softening Behavior ◽

Performance Based Seismic Design ◽

Seismic Design Method

In performance-based seismic design method, it is very important to have a good command of the nonlinear performance of a structural system, including in the collapse stage. In this paper, a nonlinear finite-element analysis on reinforced concrete moment frames is carried out. After studying the forces and deformations behavior in beam-column elements, the element stiffness matrix of distributed plasticity beam-column element is deduced using the Cotes scheme with 5 integration points. During the occurrence and development of plastic hinges, sections at some integration points will experience loading, unloading and reverse loading and the stiffness of these sections will experience various status. A quadrilinear form moment-curvature relationships with curvature- softening behavior and the hysteretic modes are used in the nonlinear static analysis program. The numerical analysis is carried out and the numerical results validate the load-displacement relationships and the yield mechanism of experiment frames.

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