Mechanical modeling for predicting the axial restraint forces and rotations of steel top and seat angle connections at elevated temperatures

2017 ◽  
Vol 8 (3) ◽  
pp. 258-286 ◽  
Author(s):  
Sana El Kalash ◽  
Elie Hantouche
Keyword(s):  
Mechanical Model ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Experimental Results ◽  
Fe Model ◽  
Content Type ◽  
Analysis And Design ◽  
Axial Forces ◽  
Fe Simulations ◽  
Seat Angle

Purpose This paper aims at developing a mechanical-based model for predicting the thermally induced axial forces and rotation of steel top and seat angles connections with and without web angles subjected to elevated temperatures due to fire. Finite element (FE) simulations and experimental results are used to develop the mechanical model. Design/methodology/approach The model incorporates the overall connection and column-beam rotation of key component elements, and includes nonlinear behavior of bolts and base materials at elevated temperatures and some major geometric parameters that impact the behavior of such connections when exposed to fire. This includes load ratio, beam length, angle thickness, and gap distance. The mechanical model consists of multi-linear and nonlinear springs that predict each component stiffness, strength, and rotation. Findings The capability of the FE model to predict the strength of top and seat angles under fire loading was validated against full scale tests. Moreover, failure modes, temperature at failure, maximum compressive axial force, maximum rotation, and effect of web angles were all determined in the parametric study. Finally, the proposed mechanical model was validated against experimental results available in the literature and FE simulations developed as a part of this study. Originality/value The proposed model provides important insights into fire-induced axial forces and rotations and their implications on the design of steel bolted top and seat angle connections. The originality of the proposed mechanical model is that it requires low computational effort and can be used in more advanced modelling applications for fire analysis and design.

scholarly journals BEHAVIOUR OF MINERAL WOOL SANDWICH PANELS UNDER BENDING LOAD AT ROOM AND ELEVATED TEMPERATURES

2020 ◽  
Vol 12 (1) ◽  
pp. 25-31
Author(s):  
Ashkan Shoushtarian Mofrad ◽  
Hartmut Pasternak
Keyword(s):  
Parametric Study ◽  
Elevated Temperatures ◽  
Sandwich Panels ◽  
Mineral Wool ◽  
Bending Stiffness ◽  
Experimental Results ◽  
Fe Model ◽  
Analysis And Design ◽  
Bending Load ◽  
Panel Thickness

This paper presents a parametric study for the bending stiffness of mineral wool (MW) sandwich panels subjected to a bending load. The MW panels are commonly used as wall panels for industrial buildings. They provide excellent insulation in the case of fire. In this research, the performance of sandwich panels is investigated at both ambient and elevated temperatures. To reach that goal, a finite element (FE) model is developed to verify simulations with experimental results in normal conditions and fire case. The experimental investigation in the current paper is a part of STABFI project financed by Research Fund for Coal and Steel (RFCS). The numerical study is conducted using ABAQUS software. Employing simulations for analysis and design is an alternative to costly tests. However, in order to rely on numerical results, simulations must be verified with the experimental results. In this paper, after the verification of FE results, a parametric study is conducted to observe the effects of the panel thickness, length and width, as well as the facing thickness on the bending stiffness of MW sandwich panels at normal conditions. The results indicate that the panel thickness has the most significant effect on the bending stiffness of sandwich panels.

Study on the residual performance of RC beams exposed to processed temperatures and fire

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sachin Vijaya Kumar ◽  
N. Suresh
Keyword(s):  
Failure Modes ◽  
Elevated Temperatures ◽  
Slow Heating ◽  
Maximum Temperature ◽  
Rc Beams ◽  
Heating Rates ◽  
Fast Heating ◽  
Content Type ◽  
Temperature Increment ◽  
Residual Performance

PurposeThe Reinforced Concrete(RC) elements are known to perform well during exposure to elevated temperatures. Hence, RC elements are widely used to resist the extreme heat developing from accidental fires and other industrial processes. In both of the scenarios, the RC element is exposed to elevated temperatures. However, the primary differences between the fire and processed temperatures are the rate of temperature increase, mode of exposure and exposure durations. In order to determine the effect of two heating modalities, RC beams were exposed to processed temperatures with slow heating rates and fire with fast heating rates.Design/methodology/approachIn the present study, RC beam specimens were exposed to 200 °C, to 800 °C temperature at 200 °C intervals for 2 h' duration by adopting two heating modes; Fire and processed temperatures. An electrical furnace with low-temperature increment and a fire furnace with standard time-temperature increment is adapted to expose the RC elements to elevated temperatures.FindingsIt is observed from test results that, the reduction in load-carrying capacity, first crack load, and thermal crack widths of RC beams exposed to 200 °C, and 600 °C temperature at fire is significantly high from the RC beams exposed to the processed temperature having the same maximum temperature. As the exposure temperature increases to 800 °C, the performance of RC beams at all heating modes becomes approximately equal.Originality/valueIn this work, residual performance, and failure modes of RC beams exposed to elevated temperatures were achieved through two different heating modes are presented.

Numerical Modelling of FRCM Materials Using Augmented-FEM

2019 ◽  
Vol 817 ◽  
pp. 23-29
Author(s):  
Santi Urso ◽  
Houman A. Hadad ◽  
Chiara Borsellino ◽  
Antonino Recupero ◽  
Qing Da Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
The United States ◽  
Design Guidelines ◽  
Constitutive Law ◽  
Analytical Models ◽  
Fiber Reinforced Polymers ◽  
Fe Model

The use of externally-bonded composite materials for strengthening and rehabilitation of existing structures is among the most popular reinforcement techniques. Technologies, such as Fabric Reinforced Cementitious Matrix (FRCM) have been recently developed to address some of the issues of Fiber Reinforced Polymers (FRP), such as sensitivity to elevated temperatures and UV, impermeability, restricted application in presence of moisture or uneven substrate. For a detailed strengthening design with FRCM composites, the mechanical properties of the materials are required. Analytical models in literature discuss the interaction between the FRCM matrix and fabric using a fracture mechanics approach. These analytical laws were simplified using a trilinear curve in which a constant branch correlated to the friction is added. In the United States, “Acceptance Criteria AC434” includes the test methods to evaluate the mechanical properties of the FRCM through a direct tensile test which uses clevis grips. The material characterization per AC434 is in harmony with ACI 549.4R design guidelines. This study deals with the analysis of FRCM materials using 2D Augmented-Finite Element Method (A-FEM) approach. Constitutive material behaviors were used to implement on A-FE model, which can predict the failure modes of the composite material. The damage of the mortar was described by a trilinear curve, and the number and position of the cracks were fixed preliminarily. The fabric was modelled as a continuum layer attached to the mortar with no-thickness cohesive elements. The cohesive law between fabric and mortar was taken from the literature. The tensile test on the FRCM coupon with one layer of fabric was numerically modeled and compared to the experimental stress-strain curves. Results show that the numerical curves matched the experimental ones and capture the three branches of the FRCM constitutive law as well as the failure mode. This modelling tool will allow researchers to predict the constitutive law of an FRCM mater

Experimental model for predicting the semi-rigid connections’ behaviour with angles and stiffeners

2016 ◽  
Vol 20 (6) ◽  
pp. 884-895 ◽  
Author(s):  
Mahyar Maali ◽  
Mahmut Kılıç ◽  
Merve Sağıroğlu ◽  
Abdulkadir Cüneyt Aydın
Keyword(s):  
Energy Dissipation ◽  
Experimental Model ◽  
Failure Modes ◽  
Bending Moment ◽  
Experimental Results ◽  
Rotation Curves ◽  
Rotation Capacity ◽  
Seat Angle ◽  
Eurocode 3 ◽  
Global Moment

This article presents the experimental results of nine specimens of steel bolted beam-to-column connections with top-and-seat angle and stiffener. All of the connections have the angles and beams reinforced with stiffeners in the extended parts. The results are analysed on the basis of the global moment–rotation curves. The main parameters observed are the failure modes, the evolution of the resistance, the stiffness, the rotation capacity, the ductility of a joint and the energy dissipation. The aim was to provide necessary data to improve the Eurocode 3. While the stiffness decreased with the increased thickness of beam stiffeners of 5–10 mm, the maximum bending moment (Mj.max) increased with the increased length of top-and-seat angle.

Punching in two-way RC flat slabs with openings and L section columns

2019 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Valdemir Colares Pinto ◽  
Vitor Branco ◽  
Denio Ramam Oliveira
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Failure Modes ◽  
Computational Simulation ◽  
Experimental Results ◽  
Design Codes ◽  
Nonlinear Simulation ◽  
Content Type ◽  
Flat Slabs ◽  
Failure Loads

Purpose This study aims to contribute to a better understanding of the influence of the position of openings around L cross-section columns in reinforced concrete flat slabs through a nonlinear computational analysis compared to experimental results. Design/methodology/approach Tests on four reinforced concrete flat slabs of 1800 x 1800 x 120 mm3 were carried out under symmetrical punching; one slab was referenced (without hole) and three had square holes of 100 x 100 mm2 close to columns and with centroid on the critical perimeter at 0.5 d and 2.0 d of the loaded area. A nonlinear analysis of the slabs was performed to aid the interpretation and preview of the experimental results, and to estimate the ultimate loads and failure modes. These estimates followed recommendations of ACI 318, Eurocode 2, NBR 6118, MC 2010 and critical shear crack theory. Findings The results showed that the presence of holes in the analyzed regions does not influence significantly the behavior of the slabs, leading to conservative structural design once the ultimate load estimates are low, while the computational results adequately estimated the slabs’ behavior. Research limitations/implications A few limitations were observed on how to implement the correct modeling system for computational nonlinear simulation. Practical implications All design codes underestimated failure loads and the theoretical method was not much better. The nonlinear computational simulations were satisfactory, presenting results close to experimental ones (97 per cent accuracy). Computational simulation also showed that the presence of holes does not significantly influence the load-vertical displacement behavior or failure loads. Social implications Structural and civil engineers and designers can observe with better details the punching phenomenon and make take secure decisions to building projects. They can preview accurate cases that are not cited in design codes and literature. Originality/value This is a very rare subject in literature that interests the entire scientific community and especially reinforced concrete designers. Presenting a new methodology to nonlinear flat slab with openings modeling to punching shear provoked by L cross section columns, case that is not cited in literature and design codes.

Tensile and shear strength for a self-drilling screw and transition of failure-modes and shear-strengths for self-drilling screwed connections at elevated-temperatures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuminobu Ozaki ◽  
Ying Liu ◽  
Kai Ye
Keyword(s):  
Shear Strength ◽  
Test Temperature ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
High Strength ◽  
Shear Loading ◽  
The Self ◽  
Content Type ◽  
Steel Sheets ◽  
Loading Tests

PurposeThe purpose of this study is to clarify both tensile and shear strength for self-drilling screws, which are manufactured from high-strength, martensitic-stainless and austenitic stainless-steel bars, and the load-bearing capacity of single overlapped screwed connections using steel sheets and self-drilling screws at elevated temperatures.Design/methodology/approachTensile/shear loading tests for the self-drilling screw were conducted to obtain basic information on the tensile and shear strengths at elevated temperatures and examine the relationships between both. Shear loading tests for the screwed connections at elevated temperatures were conducted to examine the shear strength and transition of failure modes depending on the test temperature.FindingsThe tensile and shear strengths as well as the reduction factors at the elevated temperature for each steel grade of the self-drilling screw were quantified. Furthermore, either screw shear or sheet bearing failure mode depending on the test temperature was observed for the screwed connection.Originality/valueThe transition of the failure modes for the screwed connection could be explained using the calculation formulae for the shear strengths at elevated temperatures, which were proposed in this study.

Radial Buckling of Tensile Armor Wires in Subsea Flexible Pipe—Numerical Assessment of Key Factors

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Alireza Ebrahimi ◽  
Shawn Kenny ◽  
Amgad Hussein
Keyword(s):  
Three Dimensional ◽  
External Pressure ◽  
Axial Stiffness ◽  
Parameter Study ◽  
Fe Model ◽  
Key Factors ◽  
Flexible Pipe ◽  
Analysis And Design ◽  
Axial Forces ◽  
Out Of Plane

Flexible pipes can be used as risers, jumpers, and flowlines that may be subject to axial forces and out-of-plane bending motion due to operational and environmental loading conditions. The tensile armor wires provide axial stiffness to resist these loads. Antibirdcaging tape is used to provide circumferential support and prevent a loss of stability for the tension armor wires, in the radial direction. The antibirdcaging tape may be damaged where a condition known as “wet annulus” occurs that may result in the radial buckling (i.e., birdcaging mechanism) of the tensile armor wires. A three-dimensional continuum finite element (FE) model of a 4 in. flexible pipe is developed using abaqus/implicit software package. As a verification case, the radial buckling response is compared with similar but limited experimental work available in the public domain. The modeling procedures represent an improvement over past studies through the increased number of layers and elements to model contact interactions and failure mechanisms. A limited parameter study highlighted the importance of key factors influencing the radial buckling mechanism that includes external pressure, internal pressure, and damage, related to the percentage of wet annulus. The importance of radial contact pressure and shear stress between layers was also identified. The outcomes may be used to improve guidance in the engineering analysis and design of flexible pipelines and to support the improvement of recommended practices.

Experimental and numerical study on the fire response of cold-formed steel beams with elastically restrained thermal elongation

2016 ◽  
Vol 7 (4) ◽  
pp. 388-402 ◽  
Author(s):  
Luis Laím ◽  
João Paulo C. Rodrigues
Keyword(s):  
Cross Sections ◽  
Failure Modes ◽  
Numerical Study ◽  
Research Work ◽  
Experimental Tests ◽  
Steel Beams ◽  
Structural Behaviour ◽  
Content Type ◽  
Axial Forces ◽  
Cold Formed Steel

Purpose This paper is mainly aimed at the structural performance of compound cold-formed galvanised steel beams under fire conditions based on the results of a large programme of experimental tests and numerical simulations. The main objective of this research was to assess the critical temperature and time of the studied beams. Other important goals of this research work were to investigate the influence of the cross-sections (C, lipped-I, R and 2R beams) and, above all, of the axial restraint (0, 0.45, 3, 7.5, 15, 30, ∞ kN/mm) to the thermal elongation of the beam and the rotational restraint at beam supports (0, 15, 80, 150, 300, 1,200 and ∞ kN.m/rad) on the fire resistance of this kind of beams. Design/methodology/approach This paper still provides details of the simulation methodology for achieving numerical stability and faithful representation of detailed structural behaviour and compares the simulation and experimental results, including beam failure modes, measured beam axial forces and beam mid-span deflections. Findings Good agreement between Abaqus simulations and experimental observations confirms that the finite element models developed with the Abaqus/standard solver are suitable for predicting the structural fire behaviour of restrained cold-formed steel beams. Originality/value The results showed above all that the effect of the stiffness of the surrounding structure seems to decrease with the increasing slenderness of the beams.

In-plane stability of shallow concrete arches under fire

2020 ◽  
Vol 11 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Yanni Bouras ◽  
Zora Vrcelj
Keyword(s):  
Thermal Loading ◽  
Failure Modes ◽  
Fe Model ◽  
Uniform Temperature ◽  
Fire Response ◽  
Plane Failure ◽  
Content Type ◽  
Geometric Imperfection ◽  
Inelastic Analysis ◽  
Fire Loading

Purpose Concrete arch structures are commonly constructed for various civil engineering applications. Despite their frequent use, there is a lack of research on the response and performance of concrete arches when subjected to fire loading. Hence, this paper aims to investigate the response and in-plane failure modes of shallow circular concrete arches subjected to mechanical and fire loading. Design/methodology/approach This study is conducted through the development of a three-dimensional finite element (FE) model in ANSYS. The FE model is verified by comparison to a non-discretisation numerical model derived herein and the reduced modulus buckling theory, both used for the non-linear inelastic analysis of shallow concrete arches subjected to uniformly distributed radial loading and uniform temperature field. Both anti-symmetric and symmetric buckling modes are examined, with analysis of the former requiring geometric imperfection obtained by an eigenvalue buckling analysis. Findings The FE results show that anti-symmetric bifurcation buckling is the dominant failure mode in shallow concrete arches under mechanical and fire loading. Additionally, parametric studies are presented which illustrate the influence of various parameters on fire resistance time. Originality/value Fire response of concrete arches has not been reported in the open literature. The authors have previously investigated the stability of shallow concrete arches subjected to mechanical and uniform thermal loading. It was found that temperature greatly reduced the buckling loads of concrete arches. However, this study was limited to the simplifying assumptions made which include elastic material behaviour and uniform temperature loading. The present study provides a realistic insight into the fire response and stability of shallow concrete arches. The findings herein may be adopted in the fire design of shallow concrete arches.

Analysis of exterior beam-column joints under varying column axial load and code comparisons

2022 ◽  
pp. 136943322110509
Author(s):  
Mohammed A Sakr ◽  
Ahmad G Saad ◽  
Tamer M El-korany
Keyword(s):  
Shear Strength ◽  
Axial Load ◽  
Failure Modes ◽  
Experimental Results ◽  
Fe Model ◽  
Joint Shear Strength ◽  
Load Effect ◽  
Interaction Diagram ◽  
Strength Capacity ◽  
Joint Shear

This paper presents a finite element (FE) study of beam-column joints subjected to cyclic loading. This study is primarily dependent on investigating the shear behavior of joints under the influence of different column axial load ratios. Wherefore, a total range of the column axial load ratios, whether in tension or compression has been considered. This paper proposes a two-dimensional (2D) FE model that considers material non-linearity. The proposed FE model was verified with experimental results from literature that tested varying column axial load ratios and different failure modes. The examination among experiential and numerical outcomes demonstrated that the FE model can reenact the conduct of beam-column joints and can catch the different failure modes with acceptable accuracy. A parametric study was established using the proposed FE model and strut-and-tie (ST) model of Pauletta to assess the Eurocode joint shear strength equations. For this purpose, four specimens were designed according to Eurocode recommendations while two other specimens were designed to satisfy all of the Eurocode recommendations except for the required joint confinement. An interaction diagram was introduced for each specimen to express the behavior under varying column axial load ratios. The results of the comparison between Eurocode, FE model, and ST model showed some differences in calculating the joint shear strength capacity, especially under column tension loads. Furthermore, this paper proposed new design equations based on Eurocode equations taking into account the column axial load effect. These proposed equations worked to increase the accuracy in calculating the joint shear strength capacity. Proposed equations were compared to the FE model results and other experimental results available in the literature. The comparison showed that the differences with the FE model decreased and that the proposed equations had better accuracy at different tension and compression loads than the Eurocode.

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