Henk Kolstein

Sandwich system for renovation of orthotropic steel bridge decks

A sandwich system of two steel faces and a polyurethane core is studied as a renovation system for orthotropic steel bridge decks. An experimental program has been carried out aiming to better understand the sandwich beam flexural behavior. The temperature significantly affects the sandwich flexural behavior. Increase in the temperature decreases the sandwich stiffness and strength. The stiffness is more difficult to predict at high temperatures due to the viscoelastic behavior of the core. Stiffer and stronger renovation solutions can be achieved by putting the extra weight on the core thickness rather than on the faces thickness. Stresses on the deck plate can be reduced by 60—95% using this renovation system.

Structural monitoring of a strengthened orthotropic steel bridge deck using strain data

Orthotropic steel bridges have experienced early fatigue cracks at several welded connections in the steel deck plate. One of the possible strengthening systems to enlarge the fatigue life of the existing decks consists of bonding a second steel plate to the existing deck. This renovation technique was for the first time applied on the orthotropic deck of the movable bridge Scharsterrijn. This article describes the results of the structural monitoring carried out to evaluate the short-term and long-term performance of the strengthening system. Static and dynamic controlled load tests were carried out using a calibrated truck. Strain history measurements were recorded continuously during 1 year from the normal traffic running on the bridge. The short-term measurements show significant decrease of the stress level at the bridge deck after the renovation, especially at the deck plate details. The stresses at the welds between the deck plate and the stiffener web reduce approximately 55% at the deck plate side and 35% at the stiffener web side. Due to this reduction, the fatigue life of these welds is expected to increase 11 times at the deck plate side and 3.6 times at the stiffener side. The long-term measurements do not show significant changes in the stress level at the bridge deck during the year of monitoring. The strengthening system has demonstrated good performance reliability to prolong the life span of the movable orthotropic bridges.

Parametric Study on the Interface Layer of Renovation Solutions for Orthotropic Steel Bridge Decks

Abstract:i¾?The article presents renovation solutions for orthotropic steel bridge decks consisting of bonding a second steel plate to the existing steel deck in order to reduce the stresses and enlarge the life span of the orthotropic bridge deck. Two solutions for the interface layer between the existing deck plate and the second steel plate are presented: thin epoxy bonded system and thick polyurethane sandwich system. A parametric study based on analytical solutions is carried out on flexural behavior of beams representing the renovation solutions. The influence of geometrical, mechanical and structural parameters on the stiffness and stress reduction factor of the system is studied. Maximum values of stiffness and stress reduction are achieved when maximizing the interface layer thickness and minimizing the second steel plate thickness with in certain practical limits. Based on the weight restrictions one can choose the most efficient interface layer regarding thickness and mechanical properties.

Moisture Absorption/Desorption Effects on Flexural Property of Glass-Fiber-Reinforced Polyester Laminates: Three-Point Bending Test and Coupled Hygro-Mechanical Finite Element Analysis

Influence of moisture absorption/desorption on the flexural properties of Glass-fibre-reinforced polymer (GFRP) laminates was experimentally investigated under hot/wet aging environments. To characterize mechanical degradation, three-point bending tests were performed following the ASTM test standard (ASTM D790-10A). The flexural properties of dry (0% Mt/M∞), moisture unsaturated (30% Mt/M∞ and 50% Mt/M∞) and moisture saturated (100% Mt/M∞) specimens at both 20 and 40 °C test temperatures were compared. One cycle of moisture absorption-desorption process was considered in this study to investigate the mechanical degradation scale and the permanent damage of GFRP laminates induced by moisture diffusion. Experimental results confirm that the combination of moisture and temperature effects sincerely deteriorates the flexural properties of GFRP laminates, on both strength and stiffness. Furthermore, the reducing percentage of flexural strength is found much larger than that of E-modulus. Unrecoverable losses of E-modulus (15.0%) and flexural strength (16.4%) for the GFRP laminates experiencing one cycle of moisture absorption/desorption process are evident at the test temperature of 40 °C, but not for the case of 20 °C test temperature. Moreover, a coupled hygro-mechanical Finite Element (FE) model was developed to characterize the mechanical behaviors of GFRP laminates at different moisture absorption/desorption stages, and the modeling method was subsequently validated with flexural test results.

Numerical Analysis of High Strength Steel Endplate Connections at Ambient and Elevated Temperatures

This paper deals with the behaviour of high strength steel (HSS) endplate connections at ambient and elevated temperatures using ABAQUS. The detailed FE model considers material and geometric non-linear effects, large deformations and contact interactions. This paper highlights the main challenges in modelling endplate connections. Validation against experimental results shows that the proposed FE model can reproduce the behaviour of mild steel endplate connections with reasonable accuracy. Using HSS instead of mild steel as endplate material, this model is able to predict the performances of HSS endplate connections both at ambient temperature and under fire condition. By a parametric study, it is found that a thinner HSS endplate enhances the ductility of connection both at normal condition and under fire condition, and achieves the same load-bearing capacity with mild steel endplate connection. This finding is promising for further investigations on improving the robustness of endplate connections in fire.

Performance assessment on high strength steel endplate connections after fire

Purpose – This study aims to reveal more information and understanding on performance and failure mechanisms of high strength steel endplate connections after fire. Design/methodology/approach – An experimental and numerical study on seven endplate connections after cooling down from fire temperature of 550°C has been carried out and reported herein. Moreover, the provisions of European design standard for steel structures, Eurocode 3, were validated with test results of high strength steel endplate connections. Findings – In endplate connections, a proper design using a thinner high strength steel endplate can achieve the same failure mode, similar residual load bearing capacity and comparable or even higher rotation capacity after cooling down from fire. It is found that high strength steel endplate connection can regain more than 90 per cent of its original load bearing capacity after cooling down from fire temperature of 550°C. Originality/value – The post-fire performance of high strength steel endplate connection has been reported. The accuracy of Eurocode 3 for endplate connections is validated against test results. Keywords Numerical study, Experimental study, High strength steel, After fire, Endplate connection

Coupled Hygro-Mechanical Finite Element Method on Determination of the Interlaminar Shear Modulus of Glass Fiber-Reinforced Polymer Laminates in Bridge Decks under Hygrothermal Aging Effects

To investigate the mechanical degradation of the shear properties of glass fiber-reinforced polymer (GFRP) laminates in bridge decks under hygrothermal aging effects, short-beam shear tests were performed following the ASTM test standard (ASTM D790-10A). Based on the coupled hygro-mechanical finite element (FE) analysis method, an inverse parameter identification approach based on short-beam shear tests was developed and then employed to determine the environment-dependent interlaminar shear modulus of GFRP laminates. Subsequently, the shear strength and modulus of dry (0% Mt/M∞), moisture unsaturated (30% Mt/M∞ and 50% Mt/M∞), and moisture saturated (100% Mt/M∞) specimens at test temperatures of both 20 °C and 40 °C were compared. One cycle of the moisture absorption–desorption process was also investigated to address how the moisture-induced residual damage degrades the shear properties of GFRP laminates. The results revealed that the shear strength and modulus of moisture-saturated GFRP laminates decreased significantly, and the elevated testing temperature (40 °C) aggravated moisture-induced mechanical degradation. Moreover, an unrecoverable loss of shear properties for the GFRP laminates enduring one cycle of the moisture absorption–desorption process was evident.

Effects of Adhesive Connection on Composite Action between FRP Bridge Deck and Steel Girder

The FRP-steel girder composite bridge system is increasingly used in new constructions of bridges as well as rehabilitation of old bridges. However, the understanding of composite action between FRP decks and steel girders is limited and needs to be systematically investigated. In this paper, depending on the experimental investigations of FRP to steel girder system, the Finite Element (FE) models on experiments were developed and analyzed. Comparison between experiments and FE results indicated that the FE models were much stiffer for in-plane shear stiffness of the FRP deck panel. To modify the FE models, rotational spring elements were added between webs and flanges of FRP decks, to simulate the semirigid connections. Numerical analyses were also conducted on four-point bending experiments of FRP-steel composite girders. Good agreement between experimental results and FE analysis was achieved by comparing the load-deflection curves at midspan and contribution of composite action from FRP decks. With the validated FE models, the parametric studies were conducted on adhesively bonded connection between FRP decks and steel girders, which indicated that the loading transfer capacity of adhesive connection was not simply dependent on the shear modulus or thickness of adhesive layer but dominated by the in-plane shear stiffness .

Fatigue experiments on connections made of very high strength steels

An effective application of Very High Strength Steels (VHSS) can be expected in truss-like structures, typically made of hollow sections. Improved design of VHSS truss structures could incorporate the application of cast joints, since an appropriate design of cast joints limits the stress concentrations in the joint and welds are shifted out of critical zones. The main objective of the research was to determinate the fatigue strength of welded connections made of VHSS. Truss specimens made of circular hollow sections (CHS) and cast joints were fatigue tested. In the Vgirth- welded connections of cast steel joints and CHS made of S690-G10MnMoV6-3 and S890- G18NiMoCr3-6, weld root cracks were initiated by applying cyclic loading. The fatigue results of the truss specimens exceeded detail class 71, although the detail class for girth welds is only valid for wall thickness t < 12,5 mm, whilst the average wall thickness of the specimens was 23 mm.

Moisture Diffusion in FRP Adhesively-Bonded Joints under Hot/Wet Environments

Fibre Reinforced Polymer (FRP) bridge deck systems are finding increasing usage in the constructions of new bridges and renovations of old bridges. Especially hybrid structures are competitive, i.e. steel girders combined with a pultruded FRP bridge deck. Adhesive bonding which provides smoother load transition is often the most attractive joining technique for the connection between steel girders and FRP decks. However, the long-term performance of this connection is not clearly defined. So the durability modelling and life-time prediction of the adhesively bonded joint are still issues which designers and engineers have to face. As a first step of the PhD research, moisture diffusion in FRP adhesively bonded joints is discussed and analyzed numerically. The moisture concentration distribution of FRP adhesively bonded joints after 70 years was obtained, which can subsequently be used as input for the next step stress-strain analysis allowing for the incorporation of moisture-dependent mechanical properties in the FE model.