Fully coupled multi-physics nonlinear analysis of structural space frames subjected to fire using the direct stiffness method

2018 ◽  
Vol 22 (6) ◽  
pp. 1266-1283
Author(s):  
P. Ravi Prakash ◽  
Gaurav Srivastava
Keyword(s):  
Reinforced Concrete ◽  
Pore Pressure ◽  
Solution Procedure ◽  
Structural Members ◽  
Space Frames ◽  
Structural Space ◽  
Stiffness Method ◽  
Direct Stiffness ◽  
The Stability ◽  
Fully Coupled

This article develops a fully coupled hydro-thermo-mechanical formulation based on the direct stiffness method for analysis of steel and reinforced concrete structural space frames. The superiority of the developed formulation lies in developing the direct stiffness method for fire analysis, which enables use of a much coarser spatial mesh when compared to existing fire analysis frameworks. Effects of temperature-dependent material properties, damage due to fire and pore pressure, nonlinear thermal gradients, and large deformations of structural members are directly integrated into the stability and bowing functions in the construction of the member stiffness matrix. This alleviates the need to perform element-level numerical quadrature, typically required by all existing finite element–based approaches. Full coupling between the pore pressure, thermal and mechanical solvers is considered through a two-level spatial discretization strategy with a staggered scheme for the numerical solution procedure. Five numerical examples are presented to demonstrate the accuracy and efficacy of the developed formulation in analysis of steel and reinforced concrete structural members and frames.

Numerical Modelling of Time-Dependent Behaviour of Reinforced Concrete Structure with Use of B3 Model

2014 ◽  
Vol 14 (2) ◽  
pp. 38-45
Author(s):  
Jiří Koktan ◽  
Jiří Brožovský
Keyword(s):  
Reinforced Concrete ◽  
Time Dependent ◽  
Technical Standard ◽  
Reinforced Concrete Structure ◽  
Concrete Frames ◽  
Creep Analysis ◽  
Stiffness Method ◽  
Direct Stiffness ◽  
Time Dependent Behaviour ◽  
Dependent Behaviour

Abstract The paper proposes an implementation of creep analysis of reinforced concrete structures which utilizes the B3 model and the direct stiffness method for reinforced concrete frames. The analysis is based on a numerical integration and it is implemented in an algorithmic programming language. There is presented a solution with the mentioned approaches which is compared with solution based on the EN 1992-1-1 technical standard.

scholarly journals Calibrating a New Constitutive Tension Model to Extract a Simplified Nonlinear Sectional Analysis of Reinforced Concrete Beams

2021 ◽  
Vol 11 (5) ◽  
pp. 2292
Author(s):  
Alaaeldin Abouelleil ◽  
Hayder A. Rasheed
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Compressive Strain ◽  
Design Criterion ◽  
Reinforced Concrete Beams ◽  
Secondary Outcome ◽  
Shear Stresses ◽  
Structural Members ◽  
Flexural Member ◽  
Smeared Crack

Nonlinear analysis of structural members is vital to understand the behavior and the response of reinforced concrete members. Even though most design procedures concentrate on the ultimate stage of response towards the end of the post-yielding zone as the decisive design criterion, the structural members usually function at the service load levels within the post-cracking zone. Therefore, cracking is a critical aspect of concrete behavior that affects the overall response of reinforced concrete beams. The initiation and the propagation of the cracks are affected directly by the tension and shear stresses in the beam. In flexural beams, the tensile stresses dominate the crack onset and its growth. Cracks in reinforced concrete flexural beams leave non-cracked regions in between the cracked sections. In order to apply a consistent analysis strategy, the smeared crack approach averages the behavior of these different cracked sections and uncracked in between regions to generate an accurate global response of the entire beam. This study presents a numerical constitutive tensile model that captures the complete tensile response of the reinforced concrete flexural member, in terms of averaged/smeared crack response. As a second step, this model was examined against a large pool of experimental data to validate its accuracy. Overall, the main objective of this study is to develop a representative constitutive tensile model for reinforced concrete flexural members and validate its accuracy against experimental results. The full nonlinear sectional response is analytically realized, based on the assumed trilinear moment–curvature response and the assumed trilinear moment–extreme fiber compressive strain response. This is considered as the secondary outcome of the present study.

scholarly journals Inclusion of CFRP-Epoxy Composite for End Anchorage in NSM-Epoxy Strengthened Beams

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Md. Akter Hosen ◽  
Mohd Zamin Jumaat ◽  
A. B. M. Saiful Islam
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Concrete Cover ◽  
Structural Members ◽  
Premature Failure ◽  
Near Surface ◽  
Steel Bars ◽  
Near Surface Mounted ◽  
Separation Failure ◽  
Concrete Cover Separation

Nowadays, the use of near surface mounted (NSM) technique strengthening reinforced concrete (RC) structural members is going very popular. The failure modes of NSM strengthened reinforced concrete (RC) beams have been shown to be largely due to premature failure such as concrete cover separation. In this study, CFRP U-wrap end anchorage with CFRP fabrics was used to eliminate the concrete cover separation failure. A total of eight RC rectangular beam specimens of 125 mm width, 250 mm depth, and 2300 mm length were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM steel bars and the remaining four specimens were strengthened with NSM steel bars together with the U-wrap end anchorage. The experimental results showed that wrapped strengthened beams had higher flexural strength and superior ductility performance. The results also show that these beams had less deflection, strain, crack width, and spacing.

Comment on "Basis for Derivation of Matrices for the Direct Stiffness Method"

AIAA Journal ◽  
1964 ◽  
Vol 2 (6) ◽  
pp. 1161-1161
Author(s):  
E. L. COOK ◽  
R. E. CHAPEL ◽  
W. D. BERNHART
Keyword(s):  
Stiffness Method ◽  
Direct Stiffness

Comparative study of finite element analysis of steel silos with rectangular and I stiffeners

2021 ◽  
Vol 10 (1) ◽  
pp. 9
Author(s):  
Prasad Lakshmi ◽  
Neethu Elsa Anil
Keyword(s):  
Reinforced Concrete ◽  
Element Analysis ◽  
Plate Structures ◽  
Steel Reinforced Concrete ◽  
Wide Range ◽  
Earthquake Load ◽  
The Stability ◽  
Dynamic Loading Conditions ◽  
Steel Silos ◽  
Static And Dynamic Loading

Silos are used by a wide range of industries to store bulk solids in quantities ranging from a few tones to hundreds or thousands of tones. They can be constructed of steel or reinforced concrete. Steel bins range from heavily stiffened flat plate structures to efficient unstiffened shell structures. They can be closed or open. They are subjected to many different static and dynamic loading conditions, mainly due to the unique characteristics of stored materials. Wind and earthquake load often undermine the stability of the silos. A steel silo with and without stiffeners is adopted and static structural analysis and dynamic analysis is done. The analysis is done by idealizing geometry, material and boundary conditions. Keywords: steel, reinforced concrete, silos.

scholarly journals Temperature influence on creep of reinforced concrete

2020 ◽  
Vol 13 (6) ◽  
Author(s):  
Edmilson Lira Madureira ◽  
Brenda Vieira Costa Fontes
Keyword(s):  
Reinforced Concrete ◽  
Moisture Content ◽  
Alternative Model ◽  
Sustained Load ◽  
Structural Members ◽  
Temperature Influence ◽  
Stress Increase ◽  
Concrete Members ◽  
Over Time ◽  
Creep Strains

abstract: The creep of concrete promotes strains over time in structural members kept under sustained load. It causes the stress decrease on the concrete and the steel stress increase in reinforced concrete members. The moisture content and temperature influence significantly such phenomenon. The creep strains model of the NBR 6118/2014 [1] is, applicable, solely, to those cases of constant stress magnitudes. Reinforced concrete members exhibit variations on the stress magnitudes and, in this way, requires the use of an alternative model for the prediction of the creep strains as the so known the State Model. This report refers itself to temperature influence analysis upon creep strains of reinforced concrete structural members. The results have revealed that temperature speeds up the creep effects and, in this way, the steel yielding caused by the stress increase on the reinforcement bars occurs at earlier ages.

scholarly journals STUDY OF A STRUCTURE SUSPENDED FROM A SYSTEM OF STEEL COLUMNS AND TRUSSES (SYSTEM AND STABILITY)

2020 ◽  
Vol 9 (9) ◽  
pp. 43-54
Keyword(s):  
Reinforced Concrete ◽  
Lateral Force ◽  
Concrete Slabs ◽  
Structural Constraints ◽  
Steel Columns ◽  
Force Method ◽  
Reinforced Concrete Slabs ◽  
The Stability

Throughout history, men always wanted to build structures that are each more impressive than the next, while rising higher in the air. In this process, men were not satisfied with making sure that these structures were beautiful, impressive and majestic, but that they could also be very useful, that they fulfilled a function, and that they were able to resist the various structural constraints that will be imposed on it, or that could be imposed on it. With this in mind, we thought of creating a structure that could both inspire this side of wonder and structural beauty, while being useful and resistant to the loads imposed on it. In this work, we are going to talk about a building suspended to its foundation, in the sense that the building does not rest directly on the ground, but is suspended nearly eight meters from the ground by each of the three columns which support the said building by a system of trusses. The structure is made of steel with reinforced concrete slabs, which gives it a significant advantage in terms of weight. Another advantage is that it reacts quite well to earthquakes, showing only very small deflections using the equivalent lateral force method. In this work we will focus on the stability of the members of the system that carries the building and the stability of the building in general.

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