14 research outputs found
Connection and Reinforcement Design Details for Pultruded Fiber Reinforced Plastic (PFRP) Composite Structures
No full text This paper aims at introducing some suggested design detail recommendations for connections and stiffeners for pultruded fiber reinforced plastics (PFRP) structural shapes. It also serves as a practical design reference for PFRP fabricators in selecting the appropriate connection configurations. The anisotropic nature of the material has been considered in preparing these structural details. This paper is divided into three interrelated parts: 1) connection design details for PFRP frame structures; 2) simplified stiffening details to reinforce and increase the structural capacity of PFRP open-web profiles; and 3) experimental evaluation of stiffened PFRP beams. In the first part, connections for new construction using customized FRP Universal Connectors (UC), developed by the author, are presented along with the required stiffeners to minimize the localized deformation and to overcome the premature failure of PFRP open-web profiles. This common localized failure PFRP open-web profiles was reported earlier in several papers by the author and others. In addition, shear and flexural stifrening details are presented. To solve the problems associated with existing PFRP frame structures, suggested details for transfer elements and stud stiffeners are also presented. These additional stiffening details to existing PFRP structures are not costly, and will assist in increasing both the reliability and safety of such structures under excessive loading conditions. Consequently, this will reduce the risk and the liability imposed on both the designers and the fabricators. In addition, experimental results of both stiffened and unstiffened simply supported PFRP H- beams are presented to demonstrate the importance of using additional stiffeners to off-theshelf pultruded profiles. The result of this experiment indicates that an increase up to 65% of the ultimate loading capacity of the section can be achieved compared to unstiffened specimens. In addition, an increase in both critical buckling stress and post-buckling strength was the result of adding these stiffeners. </jats:p
A numerical and experimental analysis on the mechanical behavior of bolted joints between pultruded profiles and T-Stubs of glass fiber reinforced polymer
No full text2010 - 2011In the last decades, FRP composites have been widely used for constructing entire civil structures.
One of the challenging issues for building with pultruded FRP composites is understanding the
behavior of bolted joints. In this paper, the results of a numerical analysis performed on different
types of bolted composite joints with different geometry and subjected to tensile loads are reported.
The aim of this study is to examine the distribution of shear stresses among the different bolts by
varying the number of rows of bolts as well as the number of bolts per row. The study also
considers the presence of variable diameter washers and their influence on the bearing stresses of
composites with different fibre orientations.
For verification of the validity of the analytical models, numerical results are compared to
experimental results reported elsewhere. The results of this study showed that in multi-bolt joints,
the load is not distributed equally due to varying bolt position, bolt-hole clearance, bolt-torque or
tightening of the bolt, friction between member plates and at washer-plate interface. The results also
indicated that in the presence of washers, the stress distributions in the fibre direction, varying fibre
inclinations, are decreasing for each value of washer pressure. [edited by Author]X n.s
Mechanical characterization of a unidirectional pultruded composite lamina using micromechanics and numerical homogenization
No full textIn this paper, analytical and numerical homogenization methods are proposed to effectively simulate the macroscopic characteristics of a pultruded composite lamina. A continuum damage model was implemented via user material subroutine to model fiber failure, while the Mohr-Coulomb plastic criterion is employed to model matrix damage. In order to simulate the damage of the fiber-matrix interface, the relationship between traction and displacement is established. The proposed theoretical and numerical models were verified by tensile, compressive, and shear test results. The outcomes of this study indicated that both theoretical, numerical prediction values agree well with experimental verification results confirming the validity of the proposed methodology in providing a reliable reference for structural design of pultruded fiber reinforced polymeric (FRP) composite structures.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure
Mechanical behavior of web-flange junctions of thin-walled pultruded fiber-reinforced polymer profiles: an experimental and numerical evaluation
No full text2012 - 2013Fibre-reinforced polymer (FRP) composites represent a class of advanced materials whose use has spread from the aeronautical, mechanical and naval industry to civil infrastructure, which has generated a new set of challenges.
Composites have unique features, such as high corrosion resistance, electromagnetic transparency, low maintenance costs and high strength-to-weight ratio. During the past few decades, pultruded fibre-reinforced polymer (PFRP) composites have been used in several successful applications related to corrosive environments such as cooling towers, mining and petrochemical facilities, water and wastewater treatment plants, as well as, off-shore structures. By mid-1990s, major applications of these materials were initiated in the field of seismic and corrosion repair and strengthening of existing reinforced concrete bridges and buildings.
Historically, off-the-shelf PFRP composites were developed and designed by the pultrusion industry and were intended for low-stress applications. Recently, composites have been introduced as primary structural members to replace or complement other conventional materials, such as steel, concrete and wood, in critical applications such as bridge decks, pedestrian bridges, and recently in highway bridges and other infrastructural systems. ... [edited by Author]XII n.s
MAS-NMR studies of glasses and glass-ceramics based on a clinopyroxene-fluorapatite system
No full text21/09/12 MEB. Author version attached, OK to publish
Durability of High-Performance Fiber Reinforced Cementitious Composites Subjected to Freeze–Thaw Cycles
No full textThe application of high-performance fibre-reinforced cementitious composites (HPFRCCs) represents one of the most advanced solutions in the civil engineering field for both mitigating the criticisms of ordinary concrete while ate the same time enhancing its overall mechanical performances. Moreover, due to its significant durability resistance, HPFRCC material is highly recommended also in the view of reducing the cost for the long-term maintenance of reinforced concrete elements. More specifically, the capability of resisting against freezing promotes its possible use in cold regions where freeze–thaw cycling can lead to significantly degradation of cement-based composites. In this context, this study summarized the key results of an experimental campaign aimed at investigating the degradation processes generated by freeze–thaw actions on the resulting HPFRCCs. Furthermore, a numerical simulation is also performed for unveiling the degradation effect induced by the freeze–thaw cycles. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland A
Material-structure integrated design optimization of GFRP bridge deck on steel girder
No full textDesign optimization of fiber-reinforced polymeric (FRP) composite products is essential to facilitate their applications in engineering structures. For bridge structures, the main design optimization goals are the reduction of FRP material consumption and the structure weight, which aim to reduce the initial construction cost and achieve a longer bridge span. Compared with conventional steel–concrete composite bridges, FRP-steel composite bridges possess more design variables and more complex design process, which necessitate the simplified optimization models. This paper aims to propose a two-scale design optimation method for FRP bridge deck on the steel girder. The macro behavior of the pultruded FRP composite bridge deck is analyzed. Regarding the micro level, the equivalent properties of pultruded GFRP lamination are calculated by combining micromechanics and classical lamination theory (CLT). The above-mentioned macro pultruded GFRP bridge level and the micro fiber/resin level were bridged based on the assumption that the micro-component effective homogenized strain equals to the corresponding macro strain. The two-scale lamination optimization of pultruded GFRP bridge deck is finally achieved by finding optimized two-scale design variables that can achieve the minimum bridge weight or the lowest initial construction cost with all listed constraint requirements satisfied. A pultruded FRP deck supported on equally-spaced steel girders was selected as a case study to show how to obtain the optimized two-scale parameters by using this proposed optimization method. The optimized results of the top flange thickness, tu, the bottom flange thickness, tl, the web height, hw, and the web thickness per meter, tw, are 46.02 mm, 45.86 mm, 300.0 mm and 37.42 mm, respectively. Results also showed that the optimized ratio of the 0°-lamina, 45°-lamina, and the 90°-lamina are77.9%, 17.1%, 5.0%. The optimized fiber volume fraction is 65.2%
The Effects of Fiber Length and Volume on Material Properties and Crack Resistance of Basalt Fiber Reinforced Concrete (BFRC)
No full textBasalt fiber reinforced concrete (BFRC) has been widely utilized in various constructions such as buildings, large industrial floors, and highways, due to its excellent physical and mechanical properties, as well as low production cost. In order to address the influence of basic parameters such as fiber volume fraction (0.05∼0.40%), fiber length (12∼36 mm) of BF, and compressive strength (30, 40, and 50 MPa) of concrete on both physical and mechanical properties of BFRC including compressive strength, tensile and flexural strength, workability, and anti-dry-shrinkage cracking properties, a series of standard material tests were conducted. Experimental results indicated that clumping of fibers may occur at relatively higher fiber volume fraction resulting in mixing and casting problems. Based on experimental values of mechanical properties and anti-dry-shrinkage cracking resistance of BFRC, the reasonable basalt fiber length and fiber volume fractions are identified. The addition of a small amount of short basalt fibers can result in a considerable increase in both compressive strength and modulus of rupture (MoR) of BFRC and that the proposed fiber length and content are 12.0 mm and 0.10%∼0.15%, respectively. As the length of basalt fibers increases, the development of early shrinkage cracks decreases initially and then increases slowly and the optimal fiber length is 18.0 mm. Results of the study also indicated that early shrinkage cracks decrease with the increase of fiber volume fraction, and when the volume fraction of 0.20% is used, no cracks were observed. All the findings of the present study may provide reference for the material proportion design of BFRC.Steel & Composite Structure
Electrophysiological studies versus high-resolution nerve ultrasound in diagnosis of Guillain–Barré syndrome
No full textAbstract Background Guillain–Barré syndrome (GBS) is polyneuropathy characterized by inflammation and immune-mediated processes that is classified into many subtypes based on electrophysiological and pathological criteria. The diagnosis of GBS can be confirmed using electrophysiological studies. However, electrophysiological studies may be normal when carried out early within 1 week in the course of the disease (Berciano et al. in J Neurol 264:221–236, 2017). One of the most useful imaging modalities for peripheral nerve diseases is ultrasonography (US). Nerve US in combination with electrophysiological studies provides an appropriate method in evaluating diseased peripheral nerves. This study aimed to enhance the reliability of early GBS diagnosis by correlating the findings of electrophysiological studies and nerve ultrasound. The nerve conduction studies (NCSs) in 37 GBS patients and 37 controls combined with cross-sectional area (CSA) assessment with US within the first 3 days of onset of symptoms and on day 14 after disease onset were evaluated. Results At presentation, patients and controls did not differ significantly in NCS parameters (p ≥ 0.05) except for a significantly longer F-wave minimum latency in the median, ulnar, and tibial nerves in patients (p 0.05). Conclusion Electrophysiological results in GBS are crucial in diagnosing the disease and understanding its pathophysiology, but serial NCSs are required. Ultrasound shows structural aspects of the nerve, so ultrasonography is a reliable tool which can be used in diagnosis and follow-up of early GBS. As a result, combining the two investigations has a complementary effect in the diagnosis and prognosis of GBS
Rationale for simplifying the strength formulae for the design of multi-row bolted connections failing in net tension
No full textHart-Smith [1] developed a set of closed form strength formulae for a semi-empirical approach to determine the net tension strength of multi-row bolted connections with composite materials. Mottram [2] showed that, for a pultruded fibre reinforced polymer material, the approach to be reliable (and conservative) for the configuration comprising two rows with a single bolt per row. This led to the formulae being developed into clauses in an American pre-standard for Load and Resistance Factor Design (LRFD) of Pultruded Fiber-Reinforced Polymer (FRP) Structures [3]. Because the expressions in the Hart-Smith formulae are not simple, the message coming from the practitioners, on the ASCE/SEI Fiber Composites And Polymers Standards committee (FCAPS) tasked with developing the pre-standard [3] into a standard, is that they would not use them when designing bolted connections. Taking stock of the specified geometries, bolt details and design parameters permitted by the pre-standard [3] the author conducted an analytical
parametric study using the Hart-Smith formulae with the aim of establishing simplified forms that could be routinely used in the design office. Presented in this paper is the provenance to this code-specific work when the connection has more than a single row of bolts. A presentation is given to what has been lost, in terms of calculated net tension strength, by providing the
simplified strength formula in the mandatory part to the standard. To enable the designer to be able to take full advantage of the Hart-Smith design approach [1, 2], the ‘complicated’ formulae and their accompanying mandatory-style text are to be found in an appendix with the standard’s commentary [3]
