Alejandro Pérez Caldentey

Effect of load distribution and variable depth on shear resistance of slender beams without stirrups

The shear resistance of elements without stirrups has mainly been investigated by test setups involving simply supported beams of constant thickness subjected to one- or two-point loading, and most of the formulas included in codes have been adjusted using this experimental background. It is a fact, however, that most design situations involve constant or triangular distributed loading (such as retaining walls or footings) on tapered members. Furthermore, there seems to be few shear tests involving cantilever structures subjected to distributed loading. These structures, which are common in everyday practice, fail in shear near the clamped end, where the shear forces and bending moments are maximum (contrary to simply supported beams of tests, where shear failures under distributed loading develop near the support region for large shear forces but limited bending moments). In this paper, a specific testing program undertaken at the Poly- technic University of Madrid (UPM), Madrid, Spain, in close collab- oration with Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland, is presented. It was aimed at investigating the influence of load distribution and tapered beam geometrics on the shear strength. The experimental program consists of eight slender beams without stirrups. Four specimens had a constant depth, whereas the others had variable depths (maximum depth of 600 mm [23.6 in.]). Each specimen was tested twice: one side was tested first under point loading, and then (after repairing) the other side was tested under either uniform loading or triangular loading. The setup allowed direct comparisons between point and distributed loading. The experimental results showed a significant influence of the type of loading and of tapered geometries on the shear strength. On the basis of these results, and using the funda- mentals of the critical shear crack theory, a consistent physical explanation of the observed failure modes and differences in shear strength is provided. Also, comparisons to current design provisions (ACI 318-08 and EC2) are discussed.

Experimental Study of Thermal Actions on a Solid Slab Concrete Deck Bridge and Comparison with Eurocode 1

This paper presents extensive temperature measurements obtained during a period of 4 years in an integral solid slab prestressed concrete bridge deck. There is very little experimental information available for this bridge typology. The quality of the measured temperature data are validated by comparing experimentally measured displacements at the ends of the bridge with theoretical displacements determined with the recorded temperature components. The measured temperatures are also compared with common design parameters made considering the specifications for thermal actions proposed by Eurocode 1. The results corroborate that the Eurocode 1 formulations are generally adequate to represent thermal actions on bridges; however, it may need to be complemented to define maximum and minimum temperatures for bridges in locations with daily temperature variations greater than 10°C.

Uncertainties of Crack Width Models

Crack widths for verification of serviceability limit states can be calculated by simplified formulas provided by codes of practice or by numerical analysis based on nonlinear finite element methods. Authors performed a pilot study with the aim to develop a methodology for assessment of model uncertainty involved in the crack width analysis. Experimental data of four beams were used as a reference of real physical evidence for model validation. Two crack models were investigated, namely the model proposed by the fib Model Code 2010 and the numerical model based on fracture mechanics and finite element method. The results indicate that both models tend to underestimate the maximal crack width. The mean crack widths are well simulated by the numerical model.

Analysis of TBM Lining Rings under Lack of Gap Fill: Practical Case of Ovalization and Crack Patterns

AbstractThis paper presents a practical approach to the study of defects in a tunnel-boring machine (TBM) ring due to the lack of gap filling during the construction phases. This lack of gap fill c...

Bases de cálculo del Eurocódigo 7. Un cambio en la metodología para el proyecto de cimentaciones

Resumen El Eurocodigo 7 supone un importante cambio en la forma de abordar el proyecto de las cimentaciones, respecto a la practica tradicional en Europa, ya que implica pasar de los metodos basados en tensiones admisibles, a los metodos de calculo basados en los estados limite y la introduccion de los coeficientes parciales en el ambito de la ingenieria geotecnica, de forma que las bases de calculo del proyecto geotecnico sean acordes con las establecidas en los demas Eurocodigos para el proyecto del resto de la estructura. En el articulo se describen con detalle los diferentes estados limite, tanto ultimos como de servicio, que el Eurocodigo 7 establece que hay que verificar en el proyecto de las cimentaciones, explicando la forma de aplicar en cada caso los coeficientes parciales que afectan a las acciones, a los materiales del terreno y a las resistencias.