Lumped system model for elastic steel-concrete beams with partial interaction

2019 ◽  
Vol 16 (1) ◽  
pp. 121-133
Author(s):  
Ahmed M. Ellakany ◽  
Mohamad Ali ◽  
Mohamed A. El-Gohary ◽  
Mohamed Elkholy
Keyword(s):  
Numerical Model ◽  
Shear Layer ◽  
Transfer Matrix ◽  
Composite Beam ◽  
Composite Beams ◽  
Elastic Support ◽  
Dynamic Responses ◽  
Content Type ◽  
Elastic Composite ◽  
Lower Beam

Purpose The purpose of this paper is to introduce a numerical model to investigate static response of elastic steel-concrete beams. The numerical model is based on the lumped system with the combination of the transfer matrix and the analog beam methods (ABM). The beams are composed of an upper concrete slab and a lower steel beam, connected at the interface by shear transmitting studs. This type of beam is widely used in constructions especially for highway bridges. The static field and point transfer matrices for the element of the elastic composite beam are derived. The present model is verified and is applied to study the static response of elastic composite beams with intermediate conditions. The intermediate condition is considered as an elastic support with various values of stiffness. The elastic support can be considered rigid when the stiffness has very high values. The influence effect of shear stiffness between the upper slab and lower beam, and the end shear restraint on the static behavior of the composite beams is studied. In addition, the change in the stiffness of the elastic support is also highlighted. Design/methodology/approach The objective of this study is to introduce a numerical model based on lumped system to calculate the static performance of elastic composite bridge beams having intermediate elastic support by combining the ABM with the transfer matrix method (TMM). The developed model is applicable for studying static and dynamic responses of steel-concrete elastic composite beams with different end conditions taking into account the effect of partial shear interactions. The validity of the lumped mass model is checked by comparing its results with a distributed model and good agreements are achieved (Ellakany and Tablia, 2010). Findings A model based on the lumped system of the elastic composite steel-concrete bridge beam with intermediate elastic support under static load is presented. The model takes into consideration the effect of the end shear restraint together with the interaction between the upper slab and the lower beam. Combining the analogical beam method with the TMM and analyzing the behavior of the elastic composite beam in terms of shear studs and stiffness, the following outcomes can be drawn: end shear restraint and stiffness of the shear layer are the two main factors affecting the response of elastic composite beams in terms of both the deflection and the moments. Using end shear restraint reduces the deflection extensively by about 40 percent compared to if it is not used assuming that: there is no interaction between the upper slab and the lower beam and the beam is acting as simply supported. As long as the shear layer stiffness increases or interaction exists, the deflection decreases. This reduced rate in deflection is smaller in case of existence of end shear restraint. The effect of the end shear restraint is more prevailing on reducing the deflections in case of partial interactions. However, its effect completely diminishes in case of complete interaction. Presence of the end shear restraint and shear layer stiffness produces almost the same variations in the components of the bending moments of the composite beam. Finally, for a complete interaction, comparing the case of using end shear restraint or the case without it, the differences in the values of the deflections and moments are almost negligible. Research limitations/implications The following assumptions related to the theory of ABM: shear studs connecting both sub-beams are modeled as a thin shear layer, each sub-beam has the same vertical displacement and the shear deformation in the sub-beams is neglected. Practical implications The developed model can be effectively used for a quick estimation of the dynamic responses of elastic composite beams in real life rather than utilizing complicated numerical models. Social implications The applications of this model can be further extended for studying the behavior of complex bridge beams that will guarantee the safety of the public in a quick view. Originality/value Previous models combined the TMM with the ABM for studying the static and free-vibration behaviors of elastic composite beams assuming that the field element is subjected to a distributed load. To study the dynamic response of elastic composite beams subjected to different moving loads using transfer matrix ABM, it was essential to use a massless field element and concentrate the own weight of the beam at the point element. This model is considered a first step for studying the impact factors of elastic composite beams subjected to moving loads.

Monotonic and fatigue assessment of steel-concrete composite beams strengthened with externally post-tensioned tendons

2018 ◽  
Author(s):  
◽  
Ayman Elzohairy
Keyword(s):  
Numerical Model ◽  
Composite Beam ◽  
Composite Beams ◽  
Fatigue Tests ◽  
Flexural Behavior ◽  
Bending Test ◽  
Steel Beam ◽  
Premature Failure ◽  
Post Tensioning ◽  
Post Tensioned

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The steel-concrete composite beam represents a structural system widely employed in both buildings and girder bridges. The coupling between steel beams and concrete flanges assures both economic and structural benefits because of quick construction of steel structures and large increase in stiffness due to the presence of concrete. Strengthening with external post-tensioning (PT) force is particularly effective and economical for long-span steel-concrete composite beams and has been employed with great success to increase the bending and shear resistance and correct excessive deflections. Applying external PT force to the steel-concrete composite beam is considered an active strengthening technique that can create permanent internal straining action in the beam which is opposite to the existing straining action due to the applied service loads. The most benefits of using this system of strengthening are an elastic performance to higher loads, higher ultimate capacity, and reduction in deformation under the applied loads. Under service loads, bridge superstructures are subjected to cyclic loads which may cause a premature failure due to fatigue. Therefore, fatigue testing is critical to evaluate existing design methods of steel-concrete composite beams. ... This research presents static and fatigue tests on four steel-concrete composite specimens to evaluate the effect of externally post-tensioned tendons on the ultimate strength and fatigue behavior of composite beams. Fatigue tests are conducted to a million cycles under a four-point bending test. In addition, final static tests are performed on fatigued specimens to evaluate the residual strength of the strengthened specimen. A numerical model is described to predict the fatigue response of the composite beam by considering the fatigue damage in the concrete flange. The accuracy of the developed numerical model is validated using the existing test data. The static test results indicate that the external post-tensioning force improves the flexural behavior of the strengthened specimen by increasing the beam capacity and reducing the tensile stress in the bottom flange of the steel beam. The fatigue results demonstrate that the external post-tensioning significantly decreases the strains in the shear connectors, concrete flange, and steel beam. The tendons demonstrated an excellent fatigue performance, with no indication of distress at the anchors.

Shear tab connection with composite beam subjected to transient-state fire temperatures

2019 ◽  
Vol 10 (4) ◽  
pp. 411-434 ◽  
Author(s):  
Mohammad Hajjar ◽  
Elie Hantouche ◽  
Ahmad El Ghor
Keyword(s):  
Composite Beam ◽  
Transient State ◽  
Composite Beams ◽  
Slab Thickness ◽  
Bottom Flange ◽  
Rational Model ◽  
Content Type ◽  
Geometrical Properties ◽  
Axial Forces ◽  
Shear Tab

Purpose This study aims to develop a rational model to predict the thermal axial forces developed in shear tab connections with composite beams when subjected to transient-state fire temperatures. Design/methodology/approach Finite element (FE) models are first developed in ABAQUS and validated against experimental data available in the literature. Second, a parametric study is conducted to identify the major parameters that affect the behavior of shear tab connections with composite beams in the fire. This includes beam length, shear tab thickness, shear tab location, concrete slab thickness, setback distance and partial composite action. A design-oriented model is developed to predict the thermal induced axial forces during the heating and cooling phases of a fire event. The model consists of multi-linear springs that can predict the stiffness and strength of each component of the connection with the composite beam. Findings The FE results show that significant thermal axial forces are generated in the composite beam in the fire. This is prominent when the beam bottom flange comes in contact with the column. Fracture at the toe of the welds governs the behavior during the cooling phase in most FE simulations. Also, the rational model is validated against the FE results and is capable of predicting the thermal axial forces developed in shear tab connections with composite beams under different geometrical properties. Originality/value The proposed model can predict the thermal axial force demand and can be used in performance-based approaches in future structural fire engineering applications.

Composite beams under fire loading: numerical modeling of behavior

2016 ◽  
Vol 7 (2) ◽  
pp. 142-157 ◽  
Author(s):  
Kristi L. Selden ◽  
Amit H. Varma
Keyword(s):  
Composite Beam ◽  
Failure Modes ◽  
Concrete Slab ◽  
Material Model ◽  
Composite Beams ◽  
Bottom Flange ◽  
Stress Strain ◽  
Content Type ◽  
Beam Deflections ◽  
Fire Loading

Purpose The purpose of this study was to develop a three-dimensional (3D) finite element modeling (FEM) technique using the commercially available program ABAQUS to predict the thermal and structural behavior of composite beams under fire loading. Design/methodology/approach The model was benchmarked using experimental test data, and it accounts for temperature-dependent material properties, force-slip-temperature relationship for the shear studs and concrete cracking. Findings It was determined that composite beams can be modeled with this sequentially coupled thermal-structural 3D FEM to predict the displacement versus bottom flange temperature response and associated composite beam failure modes, including compression failure in the concrete slab, runaway deflection because of yielding of the steel beam or fracture of the shear studs. Originality/value The Eurocode stress-strain-temperature (σ-ε-T) material model for structural steel and concrete conservatively predict the composite beam deflections at temperatures above 500°C. Models that use the National Institute of Standards and Technology (NIST) stress-strain-temperature (σ-ε-T) material model more closely match the measured deflection response, as compared to the results using the Eurocode model. However, in some cases, the NIST model underestimates the composite beam deflections at temperatures above 500°C.

Spectral finite element method for wave propagation analysis in smart composite beams containing delamination

2020 ◽  
Vol 92 (3) ◽  
pp. 440-451
Author(s):  
Namita Nanda
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Composite Beam ◽  
Spectral Element ◽  
Equation Of Motion ◽  
Composite Beams ◽  
Piezoelectric Composite ◽  
Content Type ◽  
Propagation Analysis ◽  
Spectral Finite Element

Purpose The purpose of the study is to present a frequency domain spectral finite element model (SFEM) based on fast Fourier transform (FFT) for wave propagation analysis of smart laminated composite beams with embedded delamination. For generating and sensing high-frequency elastic waves in composite beams, piezoelectric materials such as lead zirconate titanate (PZT) are used because they can act as both actuators and sensors. The present model is used to investigate the effects of parametric variation of delamination configuration on the propagation of fundamental anti-symmetric wave mode in piezoelectric composite beams. Design/methodology/approach The spectral element is derived from the exact solution of the governing equation of motion in frequency domain, obtained through fast Fourier transformation of the time domain equation. The beam is divided into two sublaminates (delamination region) and two base laminates (integral regions). The delamination region is modeled by assuming constant and continuous cross-sectional rotation at the interfaces between the base laminate and sublaminates. The governing differential equation of motion for delaminated composite beam with piezoelectric lamina is obtained using Hamilton’s principle by introducing an electrical potential function. Findings A detailed study of the wave response at the sensor shows that the A0 mode can be used for delamination detection in a wide region and is more suitable for detecting small delamination. It is observed that the amplitude and time of arrival of the reflected A0 wave from a delamination are strongly dependent on the size, position of the delamination and the stacking sequence. The degraded material properties because of the loss of stiffness and density in damaged area differently alter the S0 and A0 wave response and the group speed. The present method provides a potential technique for researchers to accurately model delaminations in piezoelectric composite beam structures. The delamination position can be identified if the time of flight of a reflected wave from delamination and the wave propagation speed of A0 (or S0) mode is known. Originality/value Spectral finite element modeling of delaminated composite beams with piezoelectric layers has not been reported in the literature yet. The spectral element developed is validated by comparing the present results with those available in the literature. The spectral element developed is then used to investigate the wave propagation characteristics and interaction with delamination in the piezoelectric composite beam.

Experimental validation of the proposed technique for condition monitoring of structure using limited noisy modal data

2019 ◽  
Vol 11 (1) ◽  
pp. 45-59
Author(s):  
Jafar Ali ◽  
Debasish Bandyopadhyay
Keyword(s):  
Numerical Model ◽  
Practical Problem ◽  
Experimental Validation ◽  
Structural Parameters ◽  
Measured Data ◽  
Dynamic Responses ◽  
Element Level ◽  
Inverse Dynamic ◽  
Content Type ◽  
Modal Data

Purpose Condition monitoring (CM) of structures is important from safety consideration. Damage detection techniques, using inverse dynamic approaches, are important tools to improve the mathematical models for monitoring the condition of structure. Uncertainties in the measured data might lead to unreliable identification of damage in structural system. Experimental validation is crucial for establishing its practical applicability. The measurement of dynamic responses at all degrees of freedom (DOFs) of a structure is also not feasible in practice. In addition the effect of these uncertainties and constraint of limited measurement are required to be studied based on experimental validation. This paper aims to discuss these issues. Design/methodology/approach Proposed numerical model based on measured natural frequencies and mode shapes is found suitable for CM of framed structures in the framework of finite element model with limited dynamic responses. The structural properties, namely, axial rigidity and bending rigidity are identified at the element level in the updated models of the system. Damage at the element level is identified by comparing the identified structural parameters of the updated model of the system with those of the undamaged state. Proposed numerical model is suitable for practical problem, as it is able to identify the structural parameters with limited modal data of first few modes, measured at selected DOFs. Findings The model is able to identify the structural damage with greater accuracy from the noisy dynamic responses even if the extent of damage is small. Experimental studies, on simple cantilever beams, establish the potential of the proposed methods for its practical implementation. Research limitations/implications The greater random noise will lead to unreliable identification of structural parameters as observed. Thus, filtering of noise technique may be required to be adopted prior to consideration of the measured data in the proposed identification approach. Practical implications Requirement of higher modal data seems to be difficult in case of real life practical problem. Thus, simulation technique like condensation or SEREP technique may be adopted. Social implications Structural health monitoring of infrastructural system is significantly important. CM of those structures from global response with limited measured data seems to be an effective tool to ensure safety and durability of structures. Originality/value The modal testing and subsequent extraction of modal data have been carried out at the authors’ laboratory. The numerical code based on inverse dynamic approach has been developed independently with original contribution.

scholarly journals SIMULAÇÃO NÚMERICA DO COMPORTAMENTO DE VIGAS MISTAS DE AÇO E CONCRETO PROTENDIDAS [ Numerical behavior analysis of prestressed steel-concrete composite beams ]

2018 ◽  
Vol 15 (1) ◽  
Author(s):  
Elder Nogueira Da Silva ◽  
Alex Sander Clemente De Souza
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Finite Elements ◽  
Composite Beam ◽  
Concrete Slab ◽  
Constitutive Relations ◽  
Composite Beams ◽  
Experimental Results ◽  
Finite Element Models ◽  
Shear Connectors

RESUMO: O presente trabalho apresenta uma metodologia para análise numérica de vigas mistas de aço e concreto protendidas utilizando o pacote computacional ABAQUS®, que permite modelagens via método dos elementos finitos. A metodologia aborda aspectos relacionados a escolha dos elementos finitos utilizados, geometria das malhas, relações constitutivas dos materiais, condições de acoplamento e vinculação entre os materiais e procedimentos de aplicação dos carregamentos, com o objetivo de simular o comportamento da estrutura. A interação entre laje de concreto e viga de aço foi modelada com conectores e elementos de contato e considerando somente o acoplamento das redes de elementos finitos da laje e da viga. A validação do modelo numérico foi realizada através da correlação entre os resultados numéricos e experimentais disponíveis na literatura. Para ambas as formas de vinculação laje-perfil, o modelo numérico representou de forma satisfatória o comportamento observado experimentalmente. Nos casos em que foram modelados os conectores de cisalhamento as vigas apresentaram menor rigidez e consequentemente melhor correlação entre resultados numéricos e experimentais.ABSTRACT: This paper reports a methodology adopted to represent the behavior of prestressed steel concrete composite beam by finite element models using software ABAQUS®. The methodology presents aspects related to the choice of finite elements types, mesh geometry, constitutive relations of materials, boundary conditions, steel-concrete interaction and sequence of loading.  The interaction between the concrete slab and the steel profile was carried out modeling the shear connectors, using contact elements to modeling the interface and after was carried out using TIE constraint. The validation of the numerical model was carried through the correlation between the numerical and experimental results and it was adequate to simulate the experimentally tested beams for both forms of slab profile bonding, especially for the cases where the shear connectors were modeled, because the beams presented lower stiffness and consequently greater proximity of the experimental results.

scholarly journals Longitudinal shear capacity of the slabs of composite beams

1976 ◽  
Vol 3 (4) ◽  
pp. 514-522 ◽  
Author(s):  
M. N. El-Ghazzi ◽  
H. Robinson ◽  
I. A. S. Elkholy
Keyword(s):  
Composite Beam ◽  
Shear Failure ◽  
Concrete Slab ◽  
Compressive Force ◽  
Longitudinal Shear ◽  
Composite Beams ◽  
Shear Capacity ◽  
Slab Width ◽  
Two Parameters ◽  
Concrete Elements

The longitudinal shear failure of the slab of composite beams is constrained to occur at a predetermined shear surface. A method for calculating the longitudinal shear capacity of the slab of simply-supported steel–concrete composite beams is presented. The method is based on analyzing the stresses at failure of the concrete elements located at the slab shear surface.A design chart based on estimating the transverse normal stress required within the concrete slab to achieve the full ultimate flexural capacity of the composite beam is proposed. Alternatively, using elastic–plastic stress distribution across the concrete slab, the longitudinal compressive force due to bending and hence the applied moment can be predicted for any longitudinal shear capacity of the slab. The proposed design and analysis when compared to previous tests and analysis showed good agreement.The slab width and the shear span of the composite beam are found to be two important parameters which cannot be neglected when estimating the longitudinal shear capacity of the slab. These two parameters have been neglected in the empirical solutions previously adopted.

3-D elastic coupling vibration and acoustical radiation characteristics of cracked gear under elastic support condition

2015 ◽  
Vol 23 (9) ◽  
pp. 1548-1568 ◽  
Author(s):  
Shao Renping ◽  
Purong Jia ◽  
Xiankun Qi
Keyword(s):  
Dynamic Response ◽  
Support System ◽  
Three Dimensional ◽  
Elastic Support ◽  
Dynamic Responses ◽  
Tooth Root ◽  
Support Condition ◽  
Elastic Boundary ◽  
Root Crack ◽  
Elastic Disc

According to the actual working condition of the gear, the supporting gear shaft is treated as an elastic support. Its impact on the gear body vibration is considered and investigated and the dynamic response of elastic teeth and gear body is analyzed. On this basis, the gear body is considered as a three-dimensional elastic disc and the gear teeth are treated as an elastic cantilever beam. Under the conditions of the elastic boundary (support shaft), combining to the elastic disk and elastic teeth, the influence of three-dimensional elastic discs on the meshing tooth response under an elastic boundary condition is also included. A dynamic model of the gear support system and calculated model of the gear tooth response are then established. The inherent characteristics of the gear support system and dynamics response of the meshing tooth are presented and simulated. It was shown by the results that it is correct to use the elastic support condition to analyze the gear support system. Based on the above three-dimensional elastic dynamics analysis, this paper set up a dynamics coupling model of a cracked gear structure support system that considered the influence of a three-dimensional elastic disc on a cracked meshing tooth under elastic conditions. It discusses the dynamic characteristic of the cracked gear structure system and coupling dynamic response of the meshing tooth, offering a three-dimensional elastic body model of the tooth root crack and pitch circle crack with different sizes, conducting the three-dimensional elastic dynamic analysis to the faulty crack. ANSYS was employed to carry out dynamic responses, as well as to simulate the acoustic field radiation orientation of a three-dimensional elastic crack body at the tooth root crack and pitch circle with different sizes.

scholarly journals Experimental Study on Timber−Lightweight Concrete Composite Beams with Ductile Bolt Connectors

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2632
Author(s):  
Yafeng Hu ◽  
Yang Wei ◽  
Si Chen ◽  
Yadong Yan ◽  
Weiyao Zhang
Keyword(s):  
Composite Beam ◽  
Lightweight Concrete ◽  
Experimental Testing ◽  
Composite Beams ◽  
Strengthening Effect ◽  
Bending Performance ◽  
Maximum Deformation ◽  
Bending Failure ◽  
Push Out ◽  
Timber Beams

A timber–lightweight−concrete (TLC) composite beam connected with a ductile connector in which the ductile connector is made of a stainless−steel bolt anchored with nuts at both ends was proposed. The push−out results and bending performance of the TLC composite specimens were investigated by experimental testing. The push−out results of the shear specimens show that shear–slip curves exhibit good ductility and that their failure can be attributed to bolt buckling accompanied by lightweight concrete cracking. Through the bending tests of ten TLC composite beams and two contrast (pure timber) beams, the effects of different bolt diameters on the strengthening effect of the TLC composite beams were studied. The results show that the TLC composite beams and contrast timber beams break on the timber fiber at the lowest edge of the TLC composite beam, and the failure mode is attributed to bending failure, whereas the bolt connectors and lightweight concrete have no obvious breakage; moreover, the ductile bolt connectors show a good connection performance until the TLC composite beams fail. The ultimate bearing capacities of the TLC composite beams increase 2.03–3.5 times compared to those of the contrast beams, while the mid-span maximum deformation decrease nearly doubled.

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