Max A.N. Hendriks

Simulation of Unreinforced Masonry Beams Retrofitted with Engineered Cementitious Composites in Flexure

AbstractA two-dimensional non-linear finite-element analysis micro-modeling approach to simulate unreinforced masonry beams in bending is extended to include a retrofit with a thin layer of ductile fiber-reinforced cement-based material referred to as engineered cementitious composite (ECC). The retrofit method is one that has been demonstrated to add significant ductility to unreinforced masonry infill walls under in-plane cyclic loading and is further expected to enhance out-of-plane bending resistance. The objective of the research is to identify and propose a modeling approach for this complex system of four materials and three different types of interface using basic material properties and established model parameters for future analyses of the retrofit system in structural applications. Of the two geometric models investigated, a simplified approach using expanded brick units with zero-thickness mortar elements is recommended and validated. Brick-mortar interface opening, cracking of the ECC layer ...

Numerical Analysis of Tunnelling Effects on Masonry Buildings: The Influence of Tunnel Location on Damage Assessment

The architectural heritage is subjected to various risk factors like the lack of maintenance, the material decay and the external solicitations. Nowadays, due to the ever-increasing demand for urban space, a relevant cause of structural damage that the historical buildings experience is the ground settlement due to excavation works. In the city of Amsterdam, for example, the construction of the new North-South metro line will involve an area characterized by the presence of many ancient masonry buildings. A fundamental phase of the design of this kind of projects is the assessment of the risk of subsidence which can affect the existing structures. The actual method to perform this assessment provides for a preliminary screening of the buildings located in the area surrounding the excavation, in order to evaluate which structures are at risk of settlement induced damage. It is based on the simplification of the building as a linear elastic beam and the assumption of the absence of interaction between the soil and the structure. An improved classification system should take into account the main parameters which influence the structural response, like the nonlinear behaviour of the building and the role played by the foundation in the soil-structure interaction. In this paper, the effect on the damage mechanism of the excavation advance and the location of the tunnel with respect to the building is evaluated. Numerical analyses are performed in order to understand the effect of different settlement profiles of the ground. A coupled model of the structure and the soil is evaluated, taking into account a damage model for the masonry building and the nonlinear behaviour of the soil-structure interaction. This paper demonstrates the importance of 3D modelling; neglecting the tunnel advance can lead to an underestimation of the damage.

Influence of the alkali-silica reaction on the mechanical degradation of concrete

The alkali-silica reaction (ASR) is an important problem that has yet to be completely understood. Owing to the complexity of this phenomenon, a number of studies have been conducted to characterize its kinetics, its impact on the material, and its structural consequences. This paper focuses on the deteriorating impact of ASR on concrete material, not only in terms of concrete swelling but also in consideration of the induced mechanical degradation. The relationships between concrete expansion and various engineering properties, which are key parameters in structural assessments, are investigated. First, new mechanical test results are presented. Second, available literature data on the evolution of engineering properties of ASR-affected concrete under free-expansion conditions are collected and statistically analyzed. The elastic modulus was found to be the best indicator for identifying the progression of ASR in concrete. Conversely, the evolution of compressive strength was observed to potentially mask damage resulting from the ASR. The tensile behavior of the affected concrete was better represented by the splitting tensile test.

Damage Functions for the Vulnerability Assessment of Masonry Buildings Subjected to Tunneling

This paper describes a new framework for the assessment of potential damage caused by tunneling-induced settlement to surface masonry buildings. Finite element models in two and three dimensions, validated through comparison with experimental results and field observations, are used to investigate the main factors governing the structural response to settlement. Parametric analyses are performed on the effect of geometrical and structural features, like the building dimensions, the nonlinear behavior of masonry, and soil-structure interactions. These results are used to create a framework of an overall damage model that correlates the analyzed parameters with the risk of the building being damaged by a given level of settlement. The proposed vulnerability framework has the potential to be developed as a decision and management tool for the evaluation of the risk associated with underground excavations in urban areas.

Reliability Assessments of Large Reinforced Concrete Structures Using Non-linear Finite Element Analyses: Challenges and Solutions

The use of non-linear finite element analyses for reliability assessments of reinforced concrete structures has gained much attention during the last decade, particularly with the introduction of semi-probabilistic methods in fib Model Code 2010. In a recent PhD project, the topic has been elaborated on with a special focus on the applicability to large concrete structures like dams and offshore platforms. Such structures usually require the use of relatively large solid finite elements and large load steps in order to reduce the computational cost. In this paper, the main findings from the project, including a proper material model for concrete, quantification of the modelling uncertainty and treatment of uncertainties from different sources, will be discussed. Unanswered questions that has been raised during the project will be highlighted.

Literature review of modelling approaches for ASR in concrete: a new perspective

Abstract The assessment of concrete structures affected by alkali–silica reaction (ASR) is a complex problem due to the multiscale nature of this long-term phenomenon. The reaction starts within the concrete constituents and developed at aggregate level by inducing swelling and deterioration of concrete material, which eventually affect the capacity of the structure. Due to this multiscale nature of the phenomenon, the problem is studied by various researchers in numerous manners. In this paper, a literature review of the main modelling approaches for ASR in concrete is presented within a new perspective. The models are categorised on the basis of their input and output parameters, instead of adopting the classical classification on the base of the scale (e.g. micro, meso and macro). The main aim of the review is to understand to which extent the available models are able to describe the deteriorating impact induced by ASR in concrete material and if the approaches can ultimately be extended to structural analyses.

Lattice Modelling of the Onset of Concrete-Ice Abrasion

The last decades the concrete-ice abrasion process has been well known as a concrete surface degradation mechanism due to ice sliding. The topic is especially relevant for concrete gravity based structures in the Arctic offshore. The article presents a numerical model in which the onset of wear in the concrete-ice abrasion process is simulated. The simulations are performed on meso-scale, which means that concrete is modelled as a three-phase material in which paste, aggregates and the interface transition zone are distinguished. Lattice modelling is adopted for the numerical modeling. Hertzian contact theory which predicts excessive tensile stresses on the concrete surface due to sliding of ice asperities is used as an analytical basis for the numerical model. It was concluded that such model is able to capture both surface and subsurface cracking in the concrete.

Building response to tunnelling- and excavation-induced ground movements: using transfer functions to review the limiting tensile strain method

Abstract In this paper, limiting tensile strain method (LTSM) is reviewed, and advantages and disadvantages resulted from the simplicity of this method are examined in the light of the findings of the existing experimental and numerical studies. Using the viewpoint of the transfer functions for the LTSM, a more independent sight for the interpretation of the relationships between deflection ratio, structure’s geometry, longitudinal/shear stiffness ratio and the limiting tensile strain is provided. In addition, the effect of average horizontal strain is included simply in the modified deep beam equations. Using reported data and observed damage classes of real and simulated case studies available in the literature, back-calculations for the coefficients of the transfer function are made. After comparing the back-calculated coefficients to the original coefficients of the LTSM, it is shown that observed damage and measured crack widths are reasonably compatible with the proposed limiting tensile strain boundaries. Also, it is shown that for the cases in which moderate or higher damage was observed, the original deep beam equations tend to underestimate the resultant damage.

Evaluation of Current Crack Width Calculation Methods According to Eurocode 2 and fib Model Code 2010

The background theory for the crack width calculation methods according to Eurocode 2 and fib Model Code 2010 is discussed to evaluate the applicability for the more general case of relatively thick beams, slabs and shells. Essentially, the formulas originate from the maximum transfer length and the difference in steel and concrete strains over this length. It is shown that the formulas are based on both a slip and a no-slip theory, two theories using exactly opposite assumptions. The slip theory assumes that a physical slip occurs in the interface between concrete and steel and, also, that plane sections remain plane. The no-slip theory assumes that no physical slip occurs between concrete and steel and, thus, that plane sections no longer remain plane. The theories were merged pragmatically in an attempt to describe the physical reality related to cracking. This resulted in a formula for the transfer length composed by two linear terms. Such a formulation, however, leads to inconsistencies that opposes the basic principles in solid mechanics. It is argued that these inconsistencies limits the application for the more general case. The observations in this paper suggests that a more robust and consistent calculation method should be formulated. A possible way is by improving the bond assumptions in the interface between concrete and steel, and thoroughly studying the geometry and configuration of cracks experimentally and theoretically.

A two-stage numerical analysis approach for the assessment of the settlement response of the pre-damaged historic Hoca Pasha Mosque

ABSTRACT The current article presents a case study of the settlement response of the historic Hoca Pasha Mosque that involves uncertainties arising from the complex excavation activities, soil properties, building materials, and geometry and the presence of pre-existing cracks in the mosque’s walls. The objective is to demonstrate the added value of a two-stage numerical analysis approach for the assessment of the settlement response of the building. The first stage comprises analyses of the structural behavior using the monitored settlements for each wall. The second stage examines the behavior of the complete building as a whole. The effects of soil-structure interaction and the pre-existing cracks are considered through discrete interface elements. It is shown that executed simulations can reasonably reproduce the overall settlement response, resulting stresses and the pre-existing crack activities. The parametric analyses in the second stage also produce generalizable results, of use beyond the specific case. Namely, as the soil/structure stiffness ratio increases the settlement-induced vulnerability increases. Including soil-structure interaction in the analyses reduces tensile strains due to differential settlements. Including pre-existing cracks reduces tensile strains in the vicinity of the cracks but results in an increase of stresses in neighboring sections.