Joost Walraven

Delft University of Technology | TU · Department of Civil ENgineering

The Netherlands has a large number of thin, transversely prestressed concrete bridge decks, cast in-situ between flanges of prestressed concrete girders dating back to the 1960s and 1970s. These bridges are critical in shear when analyzed using EN 1992-1-1:2005; however, in reality, they show no significant signs of distress, possibly because of re...

Most of the Dutch bridges were built around middle of the last century and it is vital for designers to find out if these bridges can still be considered safe for the traffic of modern times. The capacity in shear is especially critical as it was not considered in design recommendations before 1976. Therefore, experiments on a 1:2 scale model of a...

Discussions have been underway in fib (Fédération Internationale du Béton) about advancing the fib Model Code for concrete structures. These include the fib international workshop in The Hague (June 2015), the fib MC2020 Core Group meeting in Madrid (December 2015), and a series of follow‐up worldwide consultations on the fib ambition regarding the...

All over the world, the safety of old structures is a question that has become increasingly important with the passage of time. In the Netherlands, there are a large number of thin, transversely prestressed concrete bridge decks, cast in-situ between the flanges of long prestressed concrete girders. These bridges date back to the 60’s and 70’s of t...

An experimental program was carried out to investigate the shear capacity of High-Performance Fiber-Reinforced Concrete (HPFRC) I-beams. The main parameters were assigned as the fiber content and presence of shear reinforcement. To study the effect of these main parameters on the shear capacity, testing of six I-beams and other control specimens wa...

An experimental program was carried out to investigate the shear capacity of High-Performance Fiber-Reinforced Concrete (HPFRC) I-beams. The main parameters were assigned as the fiber content and presence of shear reinforcement. To study the effect of these main parameters on the shear capacity, testing of six I-beams and other control specimens wa...

The paper investigates the effect of various geometrical and material parameters on the bearing (punching shear) capacity of transversely prestressed concrete deck slabs by numerical methods. Experiments on a 1:2 scale model of such a bridge were carried out in the laboratory and a 3D nonlinear finite element (FE) model was developed in the finite...

The purpose of this paper is to investigate the feasibility of using artificial neural network programming for the prediction of the fresh properties of self-compacting concrete. The input parameters of the neural network were the mix composition influencing the fresh properties of self-compacting concrete namely, the cement content, the dosages of...

This paper presents a new concept to evaluate the shear capacity of reinforced concrete beams without shear reinforcement having flexural shear failure. Based on experimental observations, it is proposed that the opening of the critical inclined crack can be considered as the lower bound for the shear capacity of a structural member. It is also pro...

Reinforced concrete short-span solid-slab bridges are used to compare Dutch and North American practices. As an assessment of existing solid-slab bridges in the Netherlands showed that the shear capacity is often governing, this paper provides a comparison between Aashto (American Association of State Highway and Transportation Officials) practice...

In the Netherlands, most of the bridges were built more than 50 years ago and it is essential for bridge authorities to find out if these bridges are still safe for modern traffic loads for which they were not designed initially. Experiments on a 1:2 scale were carried out in the laboratory of the Delft University of Technology (TU Delft) to invest...

In Anbetracht steigender Verkehrslasten und geringer angesetzter Tragfähigkeiten in den vor Kurzem eingeführten Eurocodes steht in den Niederlanden die Querkrafttragfähigkeit vieler bestehender Brücken mit Stahlbetonmassivdecke zur Debatte. In den Normvorschriften werden jedoch günstige Wirkungsmechanismen, wie die Querkraftverteilung in den Platte...

Synopsis This paper presents a new theory for the shear capacity of reinforced concrete members without shear reinforcement. While recognizing that there are multiple failure mechanisms, the theory attributes the opening of a critical flexural shear crack as the lower bound of the shear capacity. It proposes that the shear displacement of an existi...

The main objective of the study presented in this paper was to investigate the feasibility using support vector machines (SVM) for the prediction of the fresh properties of self-compacting concrete. The radial basis function (RBF) and polynomial kernels were used to predict these properties as a function of the content of mix components. The fresh...

A 55-year-old bridge showed large cracking in the approach bridge caused by restraint of deformation and support settlement. After repair, it was uncertain at which crack width the traffic loads on the bridge should be further restricted. The shear capacity was calculated by counting on the aggregate interlock capacity of a supposedly fully cracked...

It is widely recognized that Compressive Membrane Action (CMA), also called Arching Action, increases both the bending and punching capacities of reinforced concrete (RC) structures. In this paper a non-linear finite element (NLFE) approach which adopts multi-layered shell modeling of RC slabs is presented. NLFE analyses (NLFEA) were carried out wi...

Previous experimental research indicated an increased shear capacity for slabs under concentrated loads as compared to beams. Expressions have been derived for this increase, including the definition of an appropriate effective width. It is unknown, however, if the uniformly distributed loads on solid slab bridges - for example, due to dead loads -...

For the shear assessment of existing concrete slab bridges in the Netherlands, different levels of approximation are used. Shear stress resulting from the dead loads and live loads is determined in a spreadsheet or from a linear finite-element model. In a spreadsheet-based approach the effective width for the wheel prints needs to be assumed and in...

The ModelCode 2010 introduced the concept of levels-of-approximation (LoA) as a strategy for simplifying the procedures involved in preliminary design stages, or in the design of non-critical structural elements, while still providing the tools for engineers to use state-of-the-art techniques in the assessment of existing structures or in advanced...

+ Show Description The long-standing problem of shear in structural concrete elements is typically studied as one-way shear in beams, or as two-way shear in slab–column connections. The problem of one-way shear in slabs, as encountered by bridge engineers when considering the concentrated live loads on slab bridges, is not described by codes. This...

Selected chapters from the German concrete yearbook are now being published in the new English "Beton-Kalender Series" for the benefit of an international audience. Since it was founded in 1906, the Ernst & Sohn "Beton-Kalender" has been supporting developments in reinforced and prestressed concrete. The aim was to publish a yearbook to reflect pro...

In slabs subjected to concentrated loads close to the support, shear is verified for two limit states: beam shear over an effective width, and punching shear on a perimeter around the concentrated load. In current practice, the beam shear strength of slabs is calculated as for beams, and thus the beneficial effects of transverse load redistribution...

In part I of this paper, dedicated to the subject of shear resistance under sustained loading (Sarkhosh 2015), a series of tests on reinforced concrete beams without shear reinforcement was described, which were subjected to high sustained shear loads close to the short-term failure load. The goal of this research project was to investigate the beh...

In the Netherlands, there are a large number of transversely prestressed concrete bridge decks that have been built in the 60's and 70's of the last century and are found to be shear-critical when assessed using the recently implemented EN 1992-1-1:2005 (CEN 2005). To check the safety of such bridges against the wheel print of the Eurocode Load Mod...

Several experiments were carried out on reinforced concrete beams without shear reinforcement subjected to high sustained shear loads close to the short-term failure load. The goal was to investigate the behaviour of shear-critical concrete beams under sustained loading. The beams were subjected to the load for a minimum period of three months. Mea...

The use of constitutive equations from the standards to model flat suspended slabs reinforced only with plastic fibres leads to an overestimation of the experimental response of these elements. To address such problem, a parametric study is conducted. In this study, the influence of the parameters from the constitutive equations on the structural b...

Code provisions for one-way shear assume a linear relation between the shear capacity of a reinforced concrete member and its width. For wide members subjected to a concentrated load, an effective width in shear should be introduced. To study the effective width and the influence of the member width on shear capacity, a series of experiments was ca...

Shear in reinforced members has been a topic of study for many decades. Recently, the shear capacity of slabs subjected to concentrated loads – the case between one-way shear (also called beam shear) and two-way shear (or punching shear) – has been given more attention because this case is encountered in bridge engineering. This paper aims to give...

Fibre reinforcement technology has advanced significantly in recent years and, as a result, expanded into different applications. In particular, steel fibre-reinforced concrete has been successfully employed in flat slabs of several buildings in Europe with fibres as the only reinforcement. However, design methods for fibre-reinforced concrete (FRC...

As a result of the heavier live load models and more conservative shear approaches prescribed by the recently implemented Eurocodes, a large number of existing reinforced concrete solid slab bridges in the Netherlands were found to be shear-critical. The beneficial effect of the transverse load redistribution in slabs under concentrated loads is no...

The research subject of this paper is the bearing capacity of transversely prestressed concrete bridge decks between concrete girders under concentrated loads. Experiments on a 1:2 scale model of this bridge were carried out in the laboratory and a 3D nonlinear finite element model was developed in the FEA software package DIANA to study the struct...

Der Eurocode 2 (EN 1992-1-1) beschäftigt sich mit der Bemessung und Konstruktion von Stahlbeton- und Spannbetontragwerken. Eine eingehende Betrachtung und der Vergleich der nationalen Anhänge sind notwendig, um die Unterschiede der national festgelegten Berechnungsparameter zu verifizieren. Dieser Aufsatz gibt einen Überblick über die gegenwärtige...

Upon assessment of existing reinforced concrete short-span solid slab bridges according to the recently implemented Eurocodes that include more conservative shear capacity provisions and heavier axle loads, a number of these structures were found to be shear-critical. The results from recent experimental research on the shear capacity of slabs indi...

For the evaluation of existing slab bridges in the Netherlands, the governing shear stress resulting from composite dead load and live loads is determined from a finite element model. It is necessary to determine over which length (expressed as a multiple of the effective depth) the peak shear stress can be distributed for comparison to the design...

In this paper results are presented from a by STW funded research project "spalling of concrete due to fire exposure" between Eindhoven University of Technology and Delft University of Technology and aimed at developing an integral spalling model. In this paper two coupled Finite Element based models are presented in which the first model describes...

The design shear resistance of an existing structure can be evaluated with analytical design procedures and numerical procedures provided by non-linear finite element analyses. The new fib Model Code 2010 proposes different calculation methods that fall into four different levels of approximation. As the level of approximation rises, so the complex...

Many models to determine the shear capacity of shear reinforced beams are based on the truss analogy. Various proposals have been formulated in recent years, all of which differ with regard to the limits of strut inclination. Remarkably, those limits do not depend on the type of concrete, which could be expected to be critical for the shear frictio...

Previous experimental research at Delft University of Technology indicated an increased shear capacity of slabs under concentrated loads as a function of decreasing distance to the adjacent line support. Expressions have been derived for this increase, including the definition of an appropriate effective width. However, it is unknown if the uniform...

The capacity of reinforced concrete solid slab bridges in shear is assessed by comparing the design beam shear resistance to the design value of the applied shear force due to the permanent actions and live loads. Results from experiments on half-scale continuous slab bridges are used to develop a set of recommendations for the assessment of slab b...

Long-term tests on large-scale Concrete beams without shear reinforcement, which are tested for more than two years under sustained loading close to the ultimate shear capacity (load ratio ranging from 87% to 95%) under climate controlled condition, show that sustained loading has no significant effect on the shear capacity. Although many flexural...

The experimental program presented in this paper deals with the influence of the spatial variation of the concrete strength in width direction on the shear capacity of one way slabs. Two test series are designed, in which the spatial variation of the concrete strength is exaggerated. The influence of the concrete strength variation on the inclined...

The paper presents a research program dealing with the shear capacity of existing solid slab bridge decks without shear reinforcement. The widely applied design formula in Eurocode regarding beam structures without shear reinforcement is evaluated as a reference. The research program is subdivided into several test series. The research topics inclu...

Dieses Kapitel beinhaltet: Einführung Grundlagen zur Herstellung ultrahochfester Betone Mechanische Eigenschaften des Festbetons Dauerhaftigkeit Grundlagen der Bemessung Verbindungen Ausgeführte Beispiele Danksagung Literatur

One-way slabs under concentrated loads are generally designed for shear by checking the beam shear resistance and the punching shear resistance over an effective width. Only a small number of test data regarding the shear resistance of one-way slabs subjected to concentrated loads is currently available. To be able to better evaluate the shear resi...

Due to an unfortunate turn of events this article is published on the preceding pages with an erroneous version of Eq. 12. Please find below the correct Eq. 12 that should be regarded by the reader as the final version. (Formula presented).

The Model Code for Concrete Structures 2010 is a recommendation for the design of structural concrete, written with the intention of giving guidance for future codes. As such, the results of the newest research and development work are used to generate recommendations for structural concrete at the level of the latest state of the art. While carryi...

Existing solid slab bridges under a combination of wheel loads and distributed traffic loads sometimes do not fulfil the code requirements for shear. However, reinforced concrete slabs loaded close to the support are subjected to shear stresses which might result in a failure mode of combined punching and shear. This behaviour is studied in a first...

Under sustained loading, the propagation of cracks in concrete is assumed to be related to the elastic deformation, material parameters and time. Based on the fictitious crack model (FCM), a finite element method is proposed to explain the behavior of cracks in time using current constitutive relations to approximate the time-dependent crack strain...

Some damages observed in tunnels constructed with tunnel-boring machines are caused by contact deficiencies between segments, which are the result of the sum and accumulation of several types of tolerances. Because the relation among the tolerances, the contact deficiencies, and the structural damage is not quite clear, the segmented lining is usua...

Damages observed in tunnels constructed with tunnel boring machines affect the overall quality of the structure and the efficiency of the construction process. Most of these damages are caused by contact deficiencies between segments that are generated by the sum of several tolerances on the shape and on the placement of the lining. Moreover, the i...

This paper discusses the effect of intentional deformation of a flexible formwork after casting of the concrete and the influence of the characteristics of concrete in the fresh state on the quality of a concrete element. This deformation is intended to bring the concrete element in its desired final shape; the deformation typically takes place in...

This paper aims at providing a link between fiber orientation and the properties of FRC, the structure to be built and its respective production process. Since the proposed framework is to a large extent new, the main components are described in the beginning. Then, two major subjects are approached from a theoretical perspective: fiber orientation...

Energy consumption and CO2-emission of concrete can be reduced when cement is replaced by secondary materials such as residual products from other industries. However, for the design of such environmentally friendly concretes, predicting its performance is very important. In this article a cyclic design method is presented, which can predict the st...

For the design of defined-performance concrete, predicting the material properties of concrete becomes more and more important. To be able to select the right type of fillers and control the water demand in such mixtures, an extension to the compressible packing model was developed to optimize the particle packing of aggregates as well as powders i...

The capacity of solid slab bridges in shear is assessed by comparing the design beam shear resistance to the design value of the applied shear force due to the permanent actions and traffic loads. The transverse distribution of loads which occurs in slabs is thus not taken into account. Experiments on slabs under concentrated loads are carried out...

In de afgelopen decennia zijn verkeerslasten en de verkeersintensiteit op de Nederlandse wegen en kunstwerken drastisch toegenomen. Veel van die kunstwerken zijn uitgevoerd als plaatviaducten zonder schuifwapening. De vraag bestaat of het afschuifdraagvermogen van deze viaducten nog steeds voldoende is. Op basis van experimenteel en literatuuronder...

In reinforced concrete one-way slabs, two limit states related to shear need to be checked: beam shear over an effective width at the support and punching shear on a perimeter around the load. Current code provisions are based on shear tests on heavily reinforced slender beams under point loads. The question remains if these procedures are valid fo...

The use of self-compacting concrete (SCC) eliminates the need for compaction, which has benefits related to economic production, the durability, the structural performance and working circumstances. SCC is able to transport fibers which can replace in some structures conventional reinforcement. By taking into account tailor-made concrete characteri...

A High Performance Fiber Reinforced Cementitious Composite (HPFRCC) is a tensile-hardening cementitious material with a post-cracking ten-sile strength equal to or higher than that of an un-cracked cross-section. As a con-sequence, the tensile strength can be taken into account for the structural design, which allows sophisticated computational met...

The annual production of Portland cement, estimated at 3.4 billion tons in 2011, is responsible for about 7% of the total worldwide CO2- emission. To reduce this environmental impact it is important to use innovative technologies for the design of concrete structures and mixtures. In this paper, it is shown how particle packing technology can be us...

Optimizing concrete mixtures with regard to cement content is one of the most important solutions in sustainable concrete design. Workability of these low cement content or ecological mixtures is very important. Eleven mortar mixtures are presented, which show how a higher packing density can be used to obtain mixtures that require less water. High...

The longitudinal forces introduced by tunnel boring machines (TBMs) to the segmental tunnel linings influence their structural response. The analyses of the linings construction process and the ground–structure interaction mechanisms have shown the influence of the lining creep on the progressive loss of the initial longitudinal force. An analytica...

Several authors have described the main mechanism of formation of cracks in the segmented lining during the construction of tunnels with tunnel boring machines. The most frequent types of cracks are caused by a condition of uneven support generated by contact deficiencies between the segments. This paper analyzes the influence of these contact defi...

The fib Model Code is a recommendation for the design of reinforced and prestressed concrete which is intended to be a guiding document for future codes. Model Codes have been published before, in 1978 and 1990. The draft for fib Model Code 2010 was published in May 2010. The most important new element in this Model Code is “Time” in the sense of s...

The orientation of fibers has a pronounced influence on the tensile behavior of steel fiber reinforced concrete (SFRC) and, consequently, this aspect should be considered in modeling the material constitutive law. Previous works have shown that the tensile strength of SFRC is directly related to the average orientation of the fibers. However, few s...

When assessing the capacity of existing reinforced concrete slab bridges under the increased traffic loads prescribed in the current codes, shear may become the critical failure mode. To better evaluate the shear capacity of reinforced concrete slab bridges, a series of experiments is carried out on continuous one-way slabs loaded close to the supp...

Reinforced concrete one-way slabs subjected to concentrated loads are designed for shear by checking beam shear over an effective width and punching shear. Only a limited number of test data regarding the shear capacity of one-way slabs subjected to concentrated loads is available. To better evaluate the shear capacity of reinforced concrete one-wa...