Jens Henrik Nielsen

• PhD
• Professor (Associate) at Technical University of Denmark

A novel experimental setup for dynamic material characterisation that combines a ring-on-ring test configuration for equibiaxial flexural testing with a modification of the well-known split-Hopkinson pressure bar (SHPB) is presented. The design is generic, but in the present paper intended for and validated by experiments on flat circular glass sam...

The presented experimental work investigates the performance of window glass panes exposed to radiant heat flux. Such performance is of interest, as the cracking and fallout of window glass panes during a fire strongly influences the fire duration and thereby the structural response and the safety of fire brigades and rescue services. This study fo...

A ring-on-ring test configuration for the equibiaxial flexural testing of flat samples was integrated into a novel modified split-Hopkinson pressure bar (SHPB) setup. The established modifications enabled high-speed cameras for fracture assessment and non-contact optical deflection measurements using stereo digital image correlation (stereo-DIC). I...

The present paper is concerned with deriving simplified design equations and charts for modelling in-plane expansion of fractured thermally pre-stressed soda-lime-silica glass panes using the method of equivalent temperature differences (ETD) together with a thermal expansion analogy for strains. The starting point is a theoretical method based on...

A ring-on-ring test configuration for the equibiaxial flexural testing of flat samples was developed and integrated into a novel modified split-Hopkinson pressure bar (SHPB) setup. The established modifications enabled the application of high-speed cameras for fracture assessment and non-contact displacement measurements using stereo digital image...

Infolge variierender Produktionsbedingungen erfolgt der thermische Vorspannprozess von Gläsern nicht vollständig homogen. Daraus entstehen lokale Unterschiede in den Eigenspannungen. Um die statistischen Verteilungen von charakterisierenden Größen des Eigenspannungsprofils in thermisch vorgespanntem Flachglas zu bestimmen, wurden mehr als 100 Probe...

A novel experimental setup for dynamic material characterisation that combines a ring-on-ring test configuration for equibiaxial flexural testing with a modification of the well-known split-Hopkinson pressure bar (SHPB) is presented. The design is generic, but in the present paper intended for and validated by experiments on flat circular glass sam...

The present paper is concerned with deriving simplified design equations and charts for modeling in-plane expansion of fractured thermally pre-stressed glass panes using the method of equivalent temperature differences (ETD) together with a thermal expansion analogy for strains. The starting point is a theoretical method based on linear elastic fra...

The present paper is concerned with deriving simplified design equations and charts for modelling in-plane expansion of fractured thermally pre-stressed glass panes using the method of equivalent temperature differences (ETD) together with a thermal expansion analogy for strains. The starting point is a theoretical method based on linear elastic fr...

In most literature, the residual stress distribution is assumed to be a symmetrically 2nd order polynomial with compressive stresses near the surface, balanced by tensile stresses in the centre. This assumption leads directly to the assertion that the thickness of the compressive layer is 21.1 % of the total thickness. The present paper experimenta...

Soda-lime-silica glass is a widely used material in society today and its strength over various loading times is of major engineering concern. This paper reviews studies from the published literature, which report on the time-dependent tensile behaviour of soda-lime-silica glass. Furthermore, current normative definitions are reviewed and compared...

Glass Structures & Engineering has recently added a new dimension to the journal: the Glassinars! In these live online events, recent papers of the journal are highlighted through short presentations by the authors, followed by Q&A sessions. By means of the Glassinars we provide a direct interaction between the readers and authors, so to initiate a...

A new issue is ready and the world is still trapped in the pandemic of COVID19. Many of us work from home, at least partially. Traveling, especially in an international context, is restricted. Performing research and providing education is challenging. Although we aim for physical distancing only, social distancing is one of the negative effects of...

This paper presents a novel concept for improving the long-term load-bearing performance of reinforced glass beams (hybrid beams). The concept of reinforcing glass beams using steel or other (ductile) materials have been investigated over the last couple of decades utilising the fracture pattern of annealed glass to ensure a ductile behaviour. Howe...

The failure of glass has been studied extensively by many researchers. However, the focus has previously been on the static to quasi-static, rate-independent behaviour. It is commonly accepted that the strength of glass is sensitive to the applied loading time, however, the amount of research in the field of loading rate dependency seems very limit...

A numerical model used to predict the behavior of 3D printed concrete in the early age phase up until the point of collapse is presented. An incremental creep model for the material including aging and temperature effects is suggested. Furthermore, kinematic nonlinear effects are included in order to predict instability. The input parameters to the...

The Glass Structures & Engineering journal performs very well and a stunning 1500 pages were published over the past 4 years! This equals to more than 100 articles which in total are downloaded over 100.000 times so far. This performance is achieved thanks to the contributions and support of our authors, reviewers, board members and of course our r...

This paper presents the design concept of a ring-on-ring test configuration arranged in a novel split Hopkinson pressure bar (SHPB) inspired setup. It is a generic design, but in this case, intended for investigating the equibiaxial flexural strength of small circular soda-lime-silica glass specimens at high strain-rates. As these kinds of results...

Architectural and structural glass basic engineering knowledge

Architectural Glass basics

The tempering process introduces a residual stress field to the glass that only allows a drilling depth of approximately 20% of the thickness (compressive zone) before fragmentation will be initiated. The present paper investigates post-drilled holes in tempered glass that can be used for a novel assembling technique leading to an increased accurac...

Offshore structures are constantly exposed to a multihazard marine environment that threatens their structural integrity. This imposes a high risk for extensive structural failures while various deterioration mechanisms may degrade the available capacity of the structures. Thus, no reliable decisions can be reached regarding design, operation, and...

A novel ring-on-ring test setup was developed for investigating the biaxial flexural strength of small circular soda–lime–silica glass specimens at high loading rates in a high-speed test rig. Such rate effects becomes important when designing for extreme events such as impact and blast, which are highly relevant for glass used in e.g. façades. The...

Launching a peer-reviewed journal is a challenge. While the few first online-first articles of Glass Structures and Engineering had already been downloaded 676 times by the end 2015, we saw download numbers explode to over 16,000 in 2016 and further increase to almost 25,000 in 2017. These great numbers illustrate further the growing impact this jo...

Barely 20 months after the publication of the first ever issue of Glass Structures & Engineering, (GS&E) we find ourselves with five issues, containing a total of over 800 pages of double-blind peer-reviewed leading-edge research and trailblazing practical applications of structural glass. This is topped with GS&E's recent indexing in the Emerging...

The present paper is adding to the current knowledge by experimentally investigating the change of strain in a fragment of tempered glass. This is done by comparing the surface shape before and after fracture. The present work also aims at validating a FE-model for estimating the remaining strain energy and thereby the stress in a fragment post fai...

Welding‐induced residual tensile stresses and distortion have become a major concern in relation to the structural integrity of welded structures within the offshore wind industry. The stresses have a negative impact on the integrity of the welded joint, as they promote distortion, reduce fatigue life, and attribute to the corrosion cracking and br...

When tempered glass breaks, it shatters into relatively small pieces depending on the residual stress state in the glass. This has been known for centuries and is currently used in standards for classifying whether a piece of glass is tempered or not. However, the process of fragmentation is complex and only a few, relatively simple, models have be...

This work presents 3D results of the thermal tempering simulation by the Finite Element Method in order to calculate the residual stresses in the area of the holes near edges and corners of a tempered glass plate. A viscoelastic material behavior of the glass is considered for the tempering process. The structural relaxation is taken into account u...

Heat soak testing of tempered glass is a thermal process required after the tempering process itself to bring glasses of commercial soda-lime-silica-glass to failure that are contaminated with nickel sulphide inclusions, diameter 50 mm to 500 mm typically. Thus, the tests avoid a so-called “spontaneous” breakage of the glass in building elements at...

The use of bolted connections in glass installations is common place in contemporary architecture. However, it is difficult to predict the load bearing capacity of these connections accurately due to the several factors that influence the strength of glass in the region of the bolt hole, namely: the complex stress state, the inherent strength of gl...

The present paper develops and validates a 3D model for the simulation of glass tempering. It is assembled from well-known models of temperature dependent viscoelasticity and structural relaxation and predicts both transient and steady-state stresses in complex 3D glass geometries. The theory and implementation of the model is comprehensively given...

This work presents a full 3D numerical study of the residual stresses in tempered (toughened) glass near holes using Narayanaswamy’s model for the tempering process. It is the objective of the paper to elucidate the influence on the minimal residual compressive stresses at holes from variations in: the far-field stress, plate thickness, hole diamet...

Toughened glass is often used in load carrying elements due to the relatively high tensile strength compared with float glass. The apparent tensile strength of toughened glass is a combination of the pure material strength and the residual stresses imposed by the toughening process. This paper is concerned with an experimental characterization of t...

This work presents experimental observations of the characteristic fracture process of tempered glass. Square specimens with a side length of 300mm, various thicknesses and a residual stress state characterized by photoelastic measurements were used. Fracture was initiated using a 2.5mm diamond drill and the fragmentation process was captured using...

The present paper is a study on how to obtain a ductile behaviour of a composite transparent structural element. The structural element is constructed by gluing a steel strip to the bottom face of a float glass beam using an epoxy adhesive. The composite beam is examined by four-point bending tests, and the mechanisms of the beam are discussed. Ana...

The paper is a study on how to obtain a ductile behaviour of a composite transparent structural element. The structural element is constructed by gluing a steel strip to the bottom face of a float glass beam using an epoxy adhesive. The composite beam is examined by four- point bending tests, and the mechanisms of the beam are discussed. Analogies...