Publications de Alain Nussbaumer

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In the evolution of structural glass beam elements, the requirements for post-fracture load bearing capacity and safe failure behaviour have led to the development of reinforced and post-tensioned beams. Maximum bending capacity in the post-fracture state ...

Tubular space trusses for bridge applications use thick-walled tubes. The reduction in fatigue resistance due to geometrical size effects is thus an important issue. In order to carry out a thorough study, both fatigue tests on large-scale specimens and ad ...

This paper is devoted to the experimental and numerical assessment of residual stresses created by welding in the region surrounding the weld toe of tubular K-shaped joints (i.e. region most sensitive to fatigue cracking). Neutron-diffraction measurements ...

The local undercut defects at the weld toe provide a potential initiation site for fatigue cracks and significantly impact the structure's fatigue strength. The influence of continuous undercut depth on fatigue performance is widely studied, but the resear ...

Many laboratory studies have shown the beneficial effects of weld improvement methods on the fatigue strength of welded details. However, no structural codes systematically include weld improvement methods in detail classification. The purpose of this paper is to discuss the possibilities of using these methods in practice on either new or existing structures. This paper provides the reader with practical rules for designing and computing the fatigue strength of improved welded joints. A computation method

The modelling of randomness and uncertainty in fatigue resistance and fatigue load variables are presented in some detail. This is followed by a review of the specifics of reliability analysis for fatigue limit states and a background on the semi-probabili ...

In this study, the high-cycle fatigue behavior of bridge connections subjected to distortion-induced loadings (generating multiaxial stresses) and strengthened with prestressed elements were experimentally investigated. Thereafter, appropriate critical pla ...

This study aimed to identify the fatigue crack initiation site of high-frequency mechanical impact (HFMI)-treated high-strength steel welded joints subjected to high peak stresses; the impact of HFMI treatment residual stress relaxation being of particular ...

This paper investigates the high cycle tensile fatigue behavior of steel rebar reinforced − UHPFRC elements, at a fatigue load ratio, i.e., R-ratio of 0.3, representative for structural applications. Prior to testing, magnetoscopy is conducted on each spec ...

• Tensile fatigue under repeated two-level block loading is first studied, representing simplified service loading. • Partial recovery of deformation and stiffness during the lower stress cycles is first identified, analogous to damage-retardation mechanism in steels. • Fatigue cycles below the constant amplitude fatigue limit can be damaging. The tensile fatigue behavior of Ultra-High-Performance Fiber-Reinforced-Cementitious Composites (UHPFRC) is critical for the long-term performance of UHPFRC structure

The objective of this Round Robin is to assess the software influence on the structural/local stress values as determined by means of various methods. In particular the influence of (a) FEM software solver, (b) potentially software-depending element charac ...

Part 2 of the Eurocode 3 (EN 1993-2) proposes a straight forward fatigue verification method using a single heavy vehicle model (FLM3) and a damage equivalent factor, lambda, to represent the fatigue damaging effects of the real traffic on road bridges. Th ...

Prestressed composite patch bonded on cracked steel section is a promising technique to reinforce cracked details or to prevent fatigue cracking on steel structural elements. It introduces compressive stresses that produce a crack closure effect. Moreover, it modififies the crack geometry by bridging the crack faces and so reduces the stress intensity range at the crack tip. Fatigue tests were performed on notched steel plate reinforced by CFRP strips as a step toward the validation of crack patching for fa

Pre-stress bonded composite patch is a promising technique to reinforce steel member damaged by fatigue. ifhe effectiveness of this technique was verified by fatigue tests on notched steel plates. Results showed that the application of carbon fibre reinforced plastic (CFRP) strips and, eventually, the introduction of a compressive stress by pretension of the CFRP strips prior to bonding produced a significant increment of the remaining fatigue life. In this paper, the stress intensity factor in the notched

In HSS welded structures, HFMI allows fatigue strength improvement factors by inducing compressive residual stresses, cold-worked surface region and modifying the weld toe shape. According to the literature, the factors are proposed based on failures at CA ...

This paper describes the numerical analysis method used to estimate welding induced residual stresses in K-shape tubular bridge joints. The knowledge of residual stress distribution is required to design the geometry of K-joints loaded under fatigue stresses. Numerical simulations are focused on the arc welding MAG process, generally used to weld joints in bridge construction. Thermomechanical analyses are performed in 3D using two finite element codes: ABAQUS® and MORFEO®. ABAQUS has the advantage to offer

Retrofit of existing steel buildings often requires strengthening of the connection regions. One common connection, the bolted beam-column connection, is often strengthened in design using stiffened extended endplates, or with continuity plates welded betw ...

A new technique using prestressed carbon fiber laminates (CFRP – Carbon Fiber Reinforced Polymers) is being developed to repair fatigue cracks or prevent fatigue cracking on riveted bridge members. High fatigue resistance and high tensile strength of carbon fibres allows the use of bonded CFRP-plates for crack patching. Prestressed CFRP-plates bonded on cracked steel sections slow down or stop completely crack propagation by acting in three different ways: (1) by increasing the stiffness of the cracked stee

To explore the governing mechanism underlying the tensile fatigue behavior of Ultra-high Performance Fiber Reinforced Cementitious Composites (UHPFRC), this study tested eight specimens using four advanced non-destructive measurement techniques. First, mag ...

Fatigue crack growth observed in tubular K-joint specimens, typical of tubular bridge structures, always initiates at the chord crown toe locations whether the applied stress range is tensile or compressive. Even though other locations around the weld have ...

Alain Nussbaumer

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Exploring the potential of the critical shear crack theory for reinforced and post-tensioned glass beams: Initial analysis and experiments

Size effects in the fatigue behavior of welded tubular bridge joints

Numerical modelling and experimental investigation on welding residual stresses in large-scale tubular K-joints

Strain-based analysis on the influence of local undercut geometry on fatigue crack initiation life

On the practical use of weld improvement methods

Models and methods for probabilistic safety assessment of steel structures subject to fatigue

Multiaxial fatigue criteria for prestressed strengthening of steel connections

Damage-Based Assessment of the Fatigue Crack Initiation Site in High-Strength Steel Welded Joints Treated by HFMI

High cycle tensile fatigue behavior of steel rebar reinforced - UHPFRC at high R-ratio

Two-level block fatigue behavior of UHPFRC uniaxial tension specimens

Round robin on local stress evaluation for fatigue by various FEM software

Fatigue Damage Factor Calibration for Long-Span Cable-Stayed Bridge Decks

Crack growth induced delamination on steel members reinforced by prestressed composite patch

Analysis of cracked steel members reinforced by pre-stressed composite patch

Fatigue properties of as-welded and post-weld-treated high-strength steel joints: The influence of constant and variable amplitude loads

Residual stresses in as-welded joints: finite element modeling and neutron diffraction stress measurements

Experimental testing and simulation of bolted beam-column connections having thick extended endplates and multiple bolts per row

Repair of riveted bridge members damaged by fatigue using CFRP materials

Deciphering tensile fatigue behavior of UHPFRC using magnetoscopy, DIC and acoustic emission

Neutron diffraction investigations on residual stresses contributing to the fatigue crack growth in ferritic steel tubular bridges