A New Pull-Out Technique for In-Place Estimation of Concrete Compressive Strength

A new type of postinstalled wedge anchor (B15G) is presented. A refined geometry of the anchor bolt and a careful choice of all the technical details allow the insert to work also in tensile stress states and to avoid much of the practical uncertainties that affect the commonly used procedures. The calibration of the procedure has been performed on 3 classes of concrete and for 5 stress distributions (medium and low compression, vanishing stress states, inhomogeneous compressive stresses, and inhomogeneous tensile stresses). It has been found that the correlation curves, pull-out force versus compressive strength, are not linear and depend on the stress state; besides, the statistical scattering of the calibration tests never exceeds 7-8% of the average values

A semi-random field finite element method to predict the maximum eccentric compressive load for masonry prisms

An accurate prediction of the compressive strength of masonry is essential both for the analysis of existing structures and the construction of new masonry buildings. Since experimental material testing of individual masonry components (e.g. masonry unit and mortar joints) often produces highly variable results, this paper presents a numerical modelling based approach to address the associated uncertainty for the prediction of the maximum compressive load of masonry prisms. The method considers numerical model to be semi-random for a masonry prism by adopting a Latin Hyper cube simulation method used in conjunction with a parametric finite element model of the individual masonry prism. The proposed method is applied to two types of masonry prisms (using hollow blocks and solid clay bricks), for which experimental testing was conducted as part of the 9th International Masonry Conference held at Guimarães in July 2014. A Class A prediction (presented before the tests were conducted) was generated for the two masonry prisms according to the proposed methodology, and the results were compared to the final experimental testing results. The root mean square deviation of the method for prediction of eccentric compressive strength of both types of prisms differed by only 2.2KN, thereby demonstrates the potential for this probabilistic approach.This work was sponsored with funding from the European Union's Grant ERC StG 2012-307836-RETURN. The experimental testing program and student blind competition was sponsored by the European Lime Association (EuLA)

Masonry compressive strength prediction using artificial neural networks

The masonry is not only included among the oldest building materials, but it is also the most widely used material due to its simple construction and low cost compared to the other modern building materials. Nevertheless, there is not yet a robust quantitative method, available in the literature, which can reliably predict its strength, based on the geometrical and mechanical characteristics of its components. This limitation is due to the highly nonlinear relation between the compressive strength of masonry and the geometrical and mechanical properties of the components of the masonry. In this paper, the application of artificial neural networks for predicting the compressive strength of masonry has been investigated. Specifically, back-propagation neural network models have been used for predicting the compressive strength of masonry prism based on experimental data available in the literature. The comparison of the derived results with the experimental findings demonstrates the ability of artificial neural networks to approximate the compressive strength of masonry walls in a reliable and robust manner.- (undefined

Assessment of masonry bridges: numerical and theoretical approaches

The mechanical response of masonry bridges is still only partially known. Recent tests on reduced scale models and on real scale bridges showed that masonry bridges are complex structures in which all the elements take part in the load carrying system. The assessment procedures rely on some commonly accepted assumptions and make largely use of Limit Analysis, which assumptions are not fulfilled by brickwork. Recent tests showed that only deep arches can be reasonable dealt with Limit Analysis procedures while the collapse of shallow arches is not a bending collapse, that is typical of collapse mechanisms, but it is ruled by the axial force, collapse being attained because of compressive crushing of some sections. In this paper a comprehensive view of the assessment procedures is given underlying pros and cons of every approach. An example provides an application of the discussed issue

Collapse of an industrial shed: a case study for basic errors in computational structural engineering and control procedures

Collapses that do not produce other than economic losses remain often unknown either to the public and to the community of engineers. The technical causes of any collapse deserve attention even if no scientific research is needed since they often show that design and control procedures and code provisions may fail in preventing errors both in the design and in the building phase of standard structural engineering. In this paper the collapse of an industrial steel shed, under a 10cm layer of fresh snow, is discussed showing that its collapse resulted from a chain of errors, in the design phase, during its assemblage and in the final inspection and control phas

Dynamic Validation of DDBD Procedures for Masonry Structures

Direct Displacement Based methods make use of over-damped SDOF systems, equivalent to the actual structure, to perform either the design or the assessment procedures. The equivalence criteria for masonry structures are discussed in this paper. A constitutive model for masonry structures, able of reproducing the main features of the response also in dynamic analyses, is discussed. Energy dissipation related to ductility is used to set an equivalent viscous damping as a function of the ductility demand. The effectiveness of the equivalent SDOF system is estimated comparing the response of a DDBD procedure with that of full non linear dynamic analyses that make use of several natural and generated time histories, either original and scaled to take into account also severe pga. The outcomes show that DDBD procedures are reliable also for simple masonry structures provided energy dissipation is carefully considered along with the limited values of ductility of masonr

Deep trench, landslide and effects on the foundations of a residential building: A case study

The case study discussed in this paper deals with the excavation of an excessively deep and long trench in a clay slope made at one edge of an urban connection road. The subsequent failure of the top portion of the slope did not cause any human casualty but severe damage to a neighbouring retaining wall and to an adjacent building. The works aimed at the stabilization of the slope are suspected to have increased the damage to the foundation system of the building. The aim of this paper is that of showing that all the events could be foreseen just relying on the basic concepts of mechanics and on proper engineering practice. The causes for the landslide, and subsequent problems, are to be found in an excessive confidence in soil cohesion and in the application of standard engineering procedures in a non-standard cas

Masonry bridges: static and dynamic response through reduced scale models

For the assessment of masonry bridges a crucial aspect the identification of the actual load bearing structure. To identify and quantify the contribution of all the elements of a bridge, static and dynamic tests on 1:3 prototypes have been performed; similarity to the real bridges has been retained by reducing not only the geometric scale but also the material properties. The models have been tested in different settings: bare arch, arch+fill, arch+spandrel; dynamic tests have been carried out at different levels of load-induced damage. In this way, it has been demonstrated that all the elements contribute to the load bearing structure and their contribution grossly estimated. Damages may be recognized only if their extent is large enough to be detected also visually, so that dynamic tests are useful to discover some hidden element, such as internal spandrels, rather than for estimating the structural damage. Some issue for retrofitting of these bridges is discussed on the basis of the experimental results obtained

A heuristic approach to microcracking and fracture for ceramics with statistical consideration

none2Microcracking damage and toughening are examined for ceramics. These effects have been found to depend on the material microstructure and macrocrack growth. Isotropic damage, attributed to random distribution of microcrack location, length and orientation can be associated with a disordered microstructure and of a non-uniform residual stress field. When the applied stress is the main cause of cracking, the microcrack distribution is no longer random such as a system of quasi-parallel cracks. To highlight the effect of crack interaction, discrete models are advanced where damage is simulated by a distribution of microcracks. The dilute concentration assumption is invoked to simplify the analysis. The two-dimensional discrete model is based on a phenomenological approach that is statistical in character. Interaction of microcracks and with a macrocrack are considered by means of a boundary element technique [1, 2] where both isotropic and anisotropic damage could be treated. Comparison with other results are made to show that the model can be applied to analyze the fracture behaviour of many materialsA. BRENCICH; CARPINTERI ABrencich, Antonio; Carpinteri, A