scholarly journals Design of slender reinforced concrete rectangular columns subjected to eccentric loads by approximate methods

2012 ◽  
Vol 5 (4) ◽  
pp. 548-554 ◽  
Author(s):  
J. M. Calixto ◽  
T. H. Souza ◽  
E. V. Maia
Keyword(s):  
Reinforced Concrete ◽  
Second Order ◽  
Order Effects ◽  
Test Results ◽  
Approximate Methods ◽  
Design Procedures ◽  
Load Combination ◽  
Second Order Effects ◽  
The Stability ◽  
Slender Columns

Reinforced concrete codes worldwide establish that the design of slender columns must ensure that under the most unfavorable load combination, there is neither instability nor material failures. Thus, it is mandatory to consider material as well as geometrical nonlinearities. The consideration of second order effects can be done using simplified methods or the general method. This work analyses second order effects based on the approximate methods shown in NBR 6118 [1]: approximate curvature method and approximate stiffness procedure. Due to the importance of the columns in the stability of buildings is essential that these simplified design methods provide safe solutions for the design of columns. In this scenario, the objective of this study is to evaluate these simplified design procedures in terms of safety, precision and economy with respect to test results of RC slender columns subjected to eccentric loads found in the literature. The comparative analysis reveals that the approximate stiffness procedure provides better results.

scholarly journals Statistical analysis of second order effects variation with the stories height of reinforced concrete buildings

2017 ◽  
Vol 10 (2) ◽  
pp. 333-357
Author(s):  
D.M. OLIVEIRA ◽  
N.A. SILVA ◽  
C.C. RIBEIRO ◽  
S.E.C. RIBEIRO
Keyword(s):  
Reinforced Concrete ◽  
Statistical Analysis ◽  
Second Order ◽  
Order Effects ◽  
Reinforced Concrete Buildings ◽  
First Order ◽  
Concrete Buildings ◽  
Ideal Situation ◽  
Second Order Effects ◽  
The Ideal

Abstract In this paper the simplified method to evaluate final efforts using γ z coefficient is studied considering the variation of the second order effects with the height of the buildings. With this purpose, several reinforced concrete buildings of medium height are analyzed in first and second order using ANSYS software. Initially, it was checked that the (z coefficient should be used as magnifier of first order moments to evaluate final second order moments. Therefore, the study is developed considering the relation (final second order moments/ first order moments), calculated for each story of the structures. This moments relation is called magnifier of first order moments, "γ", and, in the ideal situation, it must coincide with the γ z value. However, it is observed that the reason γ /γ z varies with the height of the buildings. Furthermore, using an statistical analysis, it was checked that γ /γ z relation is generally lower than 1.05 and varies significantly in accordance with the considered building and with the presence or not of symmetry in the structure.

Evaluating second-order effects in rigid wall-flexible roof diaphragm buildings

2020 ◽  
Vol 36 (4) ◽  
pp. 1864-1885
Author(s):  
John Lawson ◽  
Maria Koliou
Keyword(s):  
Rigid Wall ◽  
The United States ◽  
Second Order ◽  
Order Effects ◽  
Building Stock ◽  
Stability Coefficient ◽  
Multistory Buildings ◽  
Flexible Diaphragm ◽  
Second Order Effects ◽  
The Stability

When evaluating seismically induced second-order effects in buildings, engineers and researchers are most familiar with these concerns in the context of multistory buildings with rigid diaphragms. However, similar concerns are valid for short single-story concrete or masonry-walled buildings with larger flexible diaphragms, which is a significant portion of the building stock in the United States. These rigid wall-flexible diaphragm (RWFD) buildings may have significant diaphragm drifts causing induced second-order effects. The stability coefficient currently found in ASCE 7 has traditionally been used by practitioners to evaluate the relative risk of P-delta instability in multistory buildings, but this indicator can be adapted for use in RWFD buildings. Using numerical studies following the Federal Emergency Management Agency (FEMA) P-695 collapse assessment methodology to evaluate the risk of collapse for a set of RWFD archetype buildings, a modified stability coefficient for RWFD buildings is found to capture the trend toward P-delta collapse and can act as a reasonable indicator without the need for heavy computational efforts.

scholarly journals Analysis of the global second-order effects on irregular reinforced concrete structures using the natural period of vibration

2019 ◽  
Vol 12 (2) ◽  
pp. 408-428 ◽  
Author(s):  
F. F. LEITÃO ◽  
G. H. SIQUEIRA ◽  
L. C. M. VIEIRA JR. ◽  
S. J. C. ALMEIDA
Keyword(s):  
Reinforced Concrete ◽  
Bending Moment ◽  
Second Order ◽  
Order Effects ◽  
Concrete Frames ◽  
Natural Period ◽  
Asymmetric Structures ◽  
Mass Matrices ◽  
Modes Of Vibration ◽  
Second Order Effects

Abstract The χT parameter, a simplified method recently presented, allows to estimate the global second-order effects on reinforced concrete frames using the natural period of vibration. This parameter was developed based on the fact that both natural period of vibration and global second-order effects depend essentially on the stiffness and mass matrices of the structure, being thus related. In this paper, numerical analyses are conducted on nine models with different patterns of irregularity in terms of geometry in plan and stiffness. The main purpose of these analyses is to evaluate the applicability of the χT parameter in asymmetric structures as well as that can present torsional modes as the fundamental mode of vibration. In addition, different hypotheses are tested in order to verify the influence of the different modes of vibration in the structural sensitivity to global second-order effects. Results of the simplified analyses were compared to the final bending moment values obtained through a nonlinear numerical analysis considering the P-Δ effect. It is observed that the parameter χT is a promising indicator for a simplified estimation of the global second-order effects for concrete frames, especially when higher modes of vibration are taken account in the analysis.

scholarly journals COMPARATIVE STUDY OF NON-LINEAR SIMULATIONS OF A REINFORCED CONCRETE SLENDER COLUMN USING FINITE ELEMENT METHOD AND P-DELTA

2019 ◽  
Vol 3 (1) ◽  
pp. 1-11
Author(s):  
Régis Marciano de Souza ◽  
Ricardo Rodrigues Magalhães ◽  
Ednilton Tavares de Andrade
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Reinforced Concrete ◽  
Iterative Process ◽  
Second Order ◽  
Order Effects ◽  
Non Linear ◽  
Slender Columns ◽  
Slender Column ◽  
Element Method

This paper analyzes the non-linear geometric behavior of reinforced concrete slender columns. This approach is due to the fact that there is a tendency to reinforced concrete slender constructions, which may have significant second order effects. This research aimed at comparing different formulations for the analysis of non-linear behavior of reinforced concrete slender columns by comparing results from simulated problem (slender column with ten load scenarios) between the Finite Element Method (FEM) and the Iterative Process P-DELTA(P-Δ). Numeric results revealed that the Iterative Process P-Δ presented different results from FEM and that the second order effects are significant for reinforced concrete slender column problems.

Simplified Approach Based on the Natural Period of Vibration for Considering Second-Order Effects on Reinforced Concrete Frames

2018 ◽  
Vol 18 (05) ◽  
pp. 1850074 ◽  
Author(s):  
Daniel G. Reis ◽  
Gustavo H. Siqueira ◽  
Luiz C. M. Vieira ◽  
Ronald D. Ziemian
Keyword(s):  
Reinforced Concrete ◽  
Amplification Factor ◽  
Flexible Structures ◽  
Second Order ◽  
Order Effects ◽  
Concrete Frames ◽  
Natural Period ◽  
Reinforced Concrete Frames ◽  
Order Analysis ◽  
Second Order Effects

Recent studies have demonstrated the existence of a relationship between a structures susceptibility to second-order effects and its natural period of vibration ([Formula: see text]) given that both these properties are fundamentally dependent on the structure stiffness and mass properties. The main advantage of the use of this characteristic is that [Formula: see text] can be obtained easily by the existing structural analysis software. In this study, different formulations are developed in order to propose an amplification factor ([Formula: see text]) to multiply first-order analysis results and satisfactorily obtain results of a second-order analysis. These formulations are based on D’Alembert’s principle, Rayleighs method, and the use of generalized coordinates to represent the dynamic displacement of flexible structures. It is observed that [Formula: see text] provides values closer to and in fact, more conservatively than, those obtained by the conventional simplified methods currently used by structural design engineers. Thus, the amplification factor [Formula: see text], which is based on the natural period of vibration, is proposed to be used as (i) an indicator of a structure susceptibility to second-order effects and (ii) an amplification factor to describe the second-order effects on reinforced concrete frames.

Second-order effects in URM walls subjected to compression and out-of-plane bending: From numerical evaluation to proposal of design procedures

2020 ◽  
Vol 209 ◽  
pp. 110130
Author(s):  
Marco Donà ◽  
Paolo Morandi ◽  
Massimiliano Minotto ◽  
Carlo Filippo Manzini ◽  
Francesca da Porto ◽  
...  
Keyword(s):  
Numerical Evaluation ◽  
Second Order ◽  
Order Effects ◽  
Design Procedures ◽  
Out Of Plane ◽  
Plane Bending ◽  
Second Order Effects

scholarly journals Considerations about the determination of γz coefficient

2013 ◽  
Vol 6 (1) ◽  
pp. 75-100
Author(s):  
D. M. Oliveira ◽  
N. A. Silva ◽  
C. F. Bremer ◽  
H. Inoue
Keyword(s):  
Reinforced Concrete ◽  
Structural Model ◽  
Steel Structures ◽  
Second Order ◽  
Order Effects ◽  
Simplified Models ◽  
Simplified Analysis ◽  
Second Order Effects ◽  
Conservative Values

In this work, the γz coefficient, used to evaluate final second order effects in reinforced concrete structures, is studied. At the start, the influence of the structural model in determination of γz coefficient is evaluated. Next, a comparative analysis of γz and B2 coefficient, usually employed to evaluate second order effects in steel structures, is performed. In order to develop the study, several reinforced concrete buildings of medium height are analysed using ANSYS-9.0 [1] software. The results show that simplified analysis provide more conservative values of γz. It means that, for structures analysed by simplified models, large values of γz don't imply, necessarily, in significant second order effects. Furthermore, it was checked that γz can be determinated from B2 coefficients of each storey of the structures and that, for all the analysed buildings, the average values of the B2 coefficients are similar to γz.

scholarly journals A Simple Approach for the Design of Ductile Earthquake-Resisting Frame Structures Counting for P-Delta Effect

Buildings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 216
Author(s):  
Shehu ◽  
Angjeliu ◽  
Bilgin
Keyword(s):  
Order Effect ◽  
Simple Approach ◽  
Second Order ◽  
Frame Structures ◽  
Order Effects ◽  
Lateral Loads ◽  
Stability Coefficient ◽  
Internal Forces ◽  
Second Order Effects ◽  
The Stability

In the last decades, the possibility to use the inelastic capacities of structures have driven the seismic design philosophy to conceive structures with ductile elements, able to obtain large deformations without compromising structural safety. In particular, the utilization of high-strength elements combined with the purpose of reducing inertial masses of the construction has highlighted the second-order effect as a result of the “lightweight” structure’s flexibility. Computational aspects of inclusion of the second-order effects in the structural analysis remain an open issue and the most common method in the current design practices uses the stability coefficient θ. The stability coefficient estimates the ratio between the second-order effect and lateral loads’ effects. This coefficient is used then to amplify the lateral loads’ effects in order to consider the second-order effects, within a certain range proposed by codes of practices. In the present paper, we propose a simple approach, as an alternative to the stability coefficient method, in order to take into consideration P-Delta effects for earthquake-resisting ductile frame structures in the design process. The expected plastic deformations, which can be assessed by the behavior factor and the elastic deformations of the structure, are expected to magnify the P-Delta effects compared to those estimated from an elastic approach. The real internal forces are approximated by modifying the stiffness matrix of the structure in such a way as to provide a compatible amplification effect. This concept is herein implemented with a three-step procedure and illustrated with well-documented case studies from the current literature. The obtained results show that the method, although simple, provides a good approximation compared to more refined and computationally expensive methods. The proposed method seems promising for facilitating the design computations and increasing the accuracy of the internal forces considering the second-order effects and the amplification from the inelastic deformations.

Sign in / Sign up

Export Citation Format

Share Document