Numerical evaluation of pin-bearing strength for the design of bolted connections of pultruded FRP material

This paper presents finite-element predictions for the strength of a pultruded fiber-reinforced polymer (FRP) material subjected to pin-bearing loading with hole clearance. One of the distinct modes of failure in steel bolted connections is bearing. It is caused by the compression action from the shaft pressing into the laminate, and when there is no lateral restraint the mechanism observed at maximum load shows brooming for delamination failure. Each lamina in the glass fiber polyester matrix material is modeled as a homogeneous, anisotropic continuum and a relatively very thin resin layer is assumed to contain any delamination cracking between stacked layers. A cohesive zone model is implemented to predict the size and location of the initial delamination, as well as the load-carrying capacity in a pin-bearing specimen. Finite-element simulations (as virtual tests) are performed at the mesoscale level to validate the modeling methodology against experimental strength test results with delamination failure, and to show how pin-bearing strength varies with parameter changes. For an example of the knowledge to be gained for the design of bolted connections, the parameteric study in which the mat reinforcement is either continuous strand or triaxial (+45°/90°/−45°/chopped+45°/90°/−45°/chopped strand) shows the latter does not provide an increase in pin-bearing strength

Finite element guidelines for simulation of fibre-tension dominated failures in composite materials validated by case studies

This paper presents a finite element modelling methodology to predict the initiation and damage progression in notched composite laminated plates subjected to increasing in-plane tension load. An important feature of the methodology is it does not rely on customized user-subroutines but solely on the analysis capabilities of the general purpose software Abaqus; thus ensuring that the numerical results can be universally reproduced. The methodology presented copes with intralaminar failure modes and uses the Hashin failure criterion to predict the onset of failure (cracking). To account for damage progression after crack initiation there is a fracture energy calculated for each of four failure modes. Four open-hole laminated plates taken from the literature are used for benchmark examples. The predicted ultimate strength based on the analytically-obtained stress-displacement curve was found to be within 10% of the experimental observations. To study the influence of the interaction of having two or three holes across the mid-plane of a pultruded open-hole tension specimen, a parametric study was carried out. The paper ends giving guidelines for the generalized modelling methodology using Abaqus without user-subroutines

Bolted connections of pultruded GFRP : implications of geometric characteristics on net section failure

The results of a three-dimensional finite element study of the net section dominated failure behaviour of pultruded open-hole specimens are presented. Computer models are developed using the general-purpose software Abaqus. Several issues are addressed in the study with respect to the notched plate geometry: (i) thickness of plate, (ii) transverse centre-to-centre spacing of holes (gauge), and (iii) distance from the centre of the hole to the nearest edge. The analytical results provide information on basic performance and the effects of these parameters on strength and damage tolerance performance, thereby furthering the current understanding of pultruded plate-to-plate connection behaviour under static loading. Based on the results, design recommendations for minimum edge distance and gauge spacing for bolts are given

Virtual characterization of delamination failures in pultruded GFRP angles

This paper deals with the application of cohesive zone models to study delamination failures in leg-angles of pultruded glass fibre reinforced polymer material using the general-purpose finite element software Abaqus. The objective of the study is present a finite element modelling methodology that can, for example, help to fill-in knowledge gaps in the available experimental data pertaining to the tying force resistance of angle-cleated jointing in frame construction. It may be used to optimize cleat shape and laminate lay-up (dependent on composite processing method) for the strongest cleat against a minimum cost requirement. A benchmark example taken from literature is used to show that the numerical predictions from the authors’ simulations are reliable. The approach is next used to analyse an equal leg-angle component where one leg is fixed and the other orthogonal leg is being deformed by a tensile force applied over the free end surface. Numerical results from Abaqus are used to show that a lamination produced by the pultrusion processing method fails unstably by delamination cracks radiating around the curved region and extending into the leg panels. As a preliminary study to show the potential of the new modelling methodology it is used to show the influence of the radius of curvature at the junction between the legs on the tying force resistance; based on the load at delamination onset a smaller radius reduces the cleat’s strength

INFLUENCE OF SPLICES ON THE STABILITY BEHAVIOUR OF COLUMNS AND FRAMES

Abstract. The paper presents a study on the influence of splice connections on the stability behaviour of compressed steel columns. The column is modelled as two independent prismatic parts connected by a rotational spring at the splice location and rotational and extensional springs at the column ends to represent the effect of the adjacent structure. The general behaviour is characterized using a polynomial Rayleigh-Ritz approximation substituted into the potential energy function, in combination with the Lagrange's method of undetermined multipliers, and based on this model the critical load is found. The load-carrying capacity is analysed with respect to the following variables: (i) location and rotational stiffness of the splice, (ii) change in the column section serial size and (iii) column end-restraints stiffness coefficients. A nonlinear regression model is developed to predict simple relationships between the critical load and the relevant column characteristics

INFLUENCE OF SPLICES ON THE STABILITY BEHAVIOUR OF COLUMNS AND FRAMES

Abstract. The paper presents a study on the influence of splice connections on the stability behaviour of compressed steel columns. The column is modelled as two independent prismatic parts connected by a rotational spring at the splice location and rotational and extensional springs at the column ends to represent the effect of the adjacent structure. The general behaviour is characterized using a polynomial Rayleigh-Ritz approximation substituted into the potential energy function, in combination with the Lagrange's method of undetermined multipliers, and based on this model the critical load is found. The load-carrying capacity is analysed with respect to the following variables: (i) location and rotational stiffness of the splice, (ii) change in the column section serial size and (iii) column end-restraints stiffness coefficients. A nonlinear regression model is developed to predict simple relationships between the critical load and the relevant column characteristics

A review of the behaviour and analysis of bolted connections and joints in pultruded fibre reinforced polymers

Medicago truncatula is a model legume, whose genome is currently being sequenced. Somatic embryogenesis (SE) is a genotype-dependent character and not yet fully understood. In this study, a proteomic approach was used to compare the induction and expression phases of SE of both the highly embryogenic line M9-10a of M. truncatula cv. Jemalong and its non-embryogenic predecessor line, M9. The statistical analysis between the lines revealed 136 proteins with significant differential expression (P < 0.05). Of these, 5 had a presence/absence pattern in M9 vs M9-10a and 22 showed an at least twofold difference in terms of spot volume, were considered of particular relevance to the SE process and therefore chosen for identification. Spots were excised in gel digested with trypsin and proteins were identified using matrix-assisted laser desorption ionization-time of flight/time of flight. Identified proteins indicated a higher adaptability of the embryogenic line toward the stress imposed by the inducing culture conditions. Also, some proteins were shown to have a dual pattern of expression: peroxidase, pyrophosphatase and aspartate aminotransferase. These proteins showed higher expression during the induction phases of the M9 line, whereas in the embryogenic line had higher expression at stages coinciding with embryo formation

Influence of splices on the stability behaviour of columns and frames

The paper presents a study on the influence of splice connections on the stability behaviour of compressed steel columns. The column is modelled as two independent prismatic parts connected by a rotational spring at the splice location and rotational and extensional springs at the column ends to represent the effect of the adjacent structure. The general behaviour is characterized using a polynomial Rayleigh-Ritz approximation substituted into the potential energy function, in combination with the Lagrange’s method of undetermined multipliers, and based on this model the critical load is found. The load-carrying capacity is analysed with respect to the following variables: (i) location and rotational stiffness of the splice, (ii) change in the column section serial size and (iii) column end-restraints stiffness coefficients. A nonlinear regression model is developed to predict simple relationships between the critical load and the relevant column characteristics