Frans Bijlaard

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.

High Strength Steel in Buildings and Civil Engineering Structures: Design of Connections

There is an increasing demand for high strength steel in the construction of buildings and civil engineering structures. However, there is a significant lack of knowledge of the behaviour of this type of construction. Research must focuses on the characterization of the strength and ductility of members (tension, compression and flexural members) and joints. In view of the severe deformation demands that are placed on many type of joints, particularly bolted connections, a special emphasis is given to assess current joint design criteria to understand what is expected of the high strength steel material. To address these topics, an experimental investigation was undertaken on moment connections with end plates made from high strength steel S460, S690 and S960 (yield stress of 460 N/mm2, 690 N/mm2 and 960 N/mm2, respectively) to provide insight into the nonlinear behaviour of this joint type. Test results show that the extrapolation of current design philosophy based on the semi-continuous/partially-restrained concept gives accurate strength predictions and that these connections can achieve reasonable rotation demands.

Monotonic Loading Tests on Semi-Rigid End-Plate Connections with Welded I-Shaped Columns and Beams

8 specimens of beam-to-column bolted end-plate connections with various details and welded I-shaped section columns and beams were tested under monotonic loads. Based on the specification for the end-plate connection rotation proposed, the contribution of the panel zone and the gap between the end-plate and column flange to the joint rotation have been obtained. The influences of both flush and extended types, column stiffeners, end-plate rib stiffeners, bolt sizes and end-plate thicknesses etc on the joint behaviour have been compared. The test results indicate that all these connections tested are typically semi-rigid. For the flush and extended end-plate connection, the joint rotation mainly derives from the relative deformation between the end plate and the column flange and the shearing deformation of the panel zone respectively. Using a special method to measure bolt strain, the bolt tension forces and their development and distribution have been depicted and studied, and two bolt tension force distribution models for end-plate connections using pretensioned bolts are recommended.

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.

Guidance for the Design of Spliced Columns

Steel columns in sway and nonsway frames that are spliced along their length generally have a lower strength capacity in compression. This load capacity can be further reduced owing to the inevitable presence of small geometrical imperfections in the form of the out-of-straightness of the column and column segment misalignment. The current work examines the buckling behavior of a framed spliced column with initial imperfections and the possibility of a nonuniform cross section. A geometrically nonlinear model accounting for imperfect elastic buckling behavior is formulated using the differential equations of equilibrium. This is followed by a study of the imperfection sensitivity to the linearly evaluated critical load. A discussion on the variation of the load-carrying capacity with the level of imperfections on a practical spliced column is also presented. The findings suggest that a spliced column can be considered equivalent to a prismatic Euler column, with an appropriate effective length, for design purposes. In this context, some implications for design are deduced from the presented analysis.

Analysis on Adhesively-Bonded Joints of FRP-steel Composite Bridge under Combined Loading: Arcan Test Study and Numerical Modeling

The research presented in this paper is an experimental study and numerical analysis on mechanical behavior of the adhesively-bonded joint between FRP sandwich bridge deck and steel girder. Generally, there are three typical stress states in the adhesively-bonded joint: shear stress, tensile stress, and combination of both. To realize these stress states in the adhesively-bonded joint during tests, a specific loading device is developed with the capacity of providing six different loading angles, which are 0°(pure tension), 18°, 36°, 54°, 72° and 90°(pure shear). Failure modes of adhesively-bonded joints are investigated. It indicates that, for the pure shear loading, the failure mode is the cohesive failure (near the interface between the adhesive layer and the steel support) in the adhesive layer. For the pure tensile and combined loading conditions, the failure mode is the combination of fiber breaking, FRP delamination and interfacial adhesion failure between the FRP sandwich deck and the adhesive layer. The load-bearing capacities of adhesive joints under combined loading are much lower than those of the pure tensile and pure shear loading conditions. According to the test results of six angle loading conditions, a tensile/shear failure criterion of the adhesively-bonded joint is obtained. By using Finite Element (FE) modeling method, linear elastic simulations are performed to characterize the stress distribution throughout the adhesively-bonded joint.

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