Leandro Mouta Trautwein

Punching of reinforced concrete flat slabs with holes and shear reinforcement

Punching shear is a possible type of failure that occurs in reinforced concrete flat slabs, which can develop with an ultimate load below flexural capacity. Several researchers have studied the punching resistance of flat slabs over recent years. Although they have made great advances, there are codes that show different approaches to a singular design. Some codes show that there exist contradictions, even in the simplest situations, such as concentric loads. Most codes prescribe empirical expressions based in a theoretical model to analyze punching strength, but for flat slabs with holes around the column and shear reinforcement there are divergences between codes, justifying research in this area. This paper presents an experimental analysis of nine square reinforced concrete flat slabs under concentric loading (width: 1800 mm; thickness: 130 mm). The main variables used in the tests were: a) two square openings (150 mm) adjacent to the smallest side of the column and b) the use of shear reinforcement containing 3 layers, with 6 or 8 elements in each layer and radially distributed around the column. The research concludes that openings adjacent to the column affect punching shear strength, while the correct use of the shear reinforcement can minimize and even compensate this loss.

Analysis of the influence of column reinforcement anchorage length in a concrete two-pile cap

Resumo This paper describes the parametric analysis applied to assess the influence of column anchorage-reinforcement length on concrete two-pile caps under uniform compression. The non-linear numerical analysis was conducted with the bi-dimensional elements of ATENA 2D software, considering perfect adherence between steel and concrete. Simulation was based on the experimental reference model by Munhoz [1], which was the parameter adopted to validate the numerical modeling. From the validated model, four different anchorage reinforcement lengths were adopted, 34,0 cm, 20,0 cm, 10,0 cm e 3,0 cm, in order to compare pile caps behavior after these changes. Pile cap simulations presented similar behavior, i.e., column anchorage reinforcement length is not a preponderant factor for the internal mechanisms that regulate the function of these elements.

Aspects of Finite Element Modeling of Punching Shear Behavior of Reinforced Concrete Flat Slabs

A series of nonlinear FE analyses was conducted in this paper to model the punching shear failure of RC flat slabs. The analyses were carried out in the software DIANA using three-dimensional continuum elements. These analyses involve the test of different modeling choices in order to evaluate their influences on punching shear failure modeling. The parameters examined are the size of the FE mesh, the convergence methods and the concrete material input parameters. These parameters were investigated by comparing the results of load carrying capacity, load-deflection response and crack patterns from the FE analyses with a reliable experimental test. From the results obtained, it could be concluded that the numerical model was able to reproduce accurately the behavior of the tested slab and capture the punching shear failure.

Análise experimental da contribuição do concreto na resistência ao cisalhamento em vigas sem armadura transversal

Resumo There are many theories and empirical formulas for estimating the shear strength of reinforced concrete structures without transverse reinforcement. The security factor of any reinforced concrete structure, against a possible collapse, is that it does not depend on the tensile strength of the concrete and the formation of any collapse is ductile, thus giving advance warning. The cracking from tensile stress can cause breakage of the concrete and should be avoided at all cost, with the intent that any such breakage does not incur any type of failure within the structure. In the present research study, experiments were performed in order to analyze the complementary mechanisms of the shear strength of lattice beams of reinforced concrete frames without transverse reinforcement. The experimental program entails the testing of eight frames that were subjected to a simple bending process. Two concrete resistance classes for analyzing compressive strength were considered on the construction of frames, 20 MPa and 40 MPa . To resist the bending stresses, the beams of the frames are designed in domain 3 of the ultimate limit states. Different rates and diameters of longitudinal reinforcement were used, 1.32% and 1.55% with 12.5 mm diameter and 16.0 mm in longitudinal tensile reinforcement. From the obtained results, an analysis was made of the criteria already proposed for defining the norms pertinent to the portion of relevant contribution for the shear resistance mechanisms of concrete without the use of transverse reinforcement and the influence of the concrete resistance and longitudinal reinforcement rates established in the experimental numerical results.

A Comparative Study of the Shear Strength Prediction for Reinforced Concrete Beams without Shear Reinforcement

This paper focuses on the assessment of the shear strength prediction established in the brazilian concrete code, NBR6118/2007[1], for reinforced concrete beams without web reinforcement. The values obtained by using the brazilian code equation are compared with a significant number of available experimental data and with those predicted by the expressions of other national and international codes, such as CEB-FIP MC90[2] and ACI-318/11[3]. The brazilian concrete code regarding shear capacity of reinforced concrete elements are explicitly assumed to be valid only for concrete strengths up to 50 MPa. It is shown that the code equation may be unconservative in a large number of cases. This discrepancy increases with increasing concrete strength, decreasing longitudinal reinforcement ratio and increasing beam depth.

Development of Multimedia Environment for Viewing the State of Stress in a Differential Element

The aim of this work is to present a tool developed in a multimedia environment of a cilitate the understanding of the state of plane stress at an infinite simal element, which is directed to lectures in Mechanics of Materials courses. This multimedia resource was developed in Java 3D API, liked an applet, as it is a simple language whose programs can run on all operating system platforms, using the virtual machineconcept. The multimedia resource determines the strains caused by forces acting in a solid body. Usingthis tool the learning process can be more efficiently, and the view of results at an differential element in the state of plane stress can be easier too.

Study of Density and Modulus of Elasticity of Lightweight Concrete with Brazilian Aggregate

Concrete is one of the oldest building materials and applying known to humankind. From 1800s, with the advent of Portland cement concrete has taken a prominent place among the construction materials due to large values of strength, durability and versatility it offered compared to other products, allowing the molding of the various architectural forms. Until the early 80s, the modern concrete remained only as a mixture of cement, aggregates and water, however, in recent decades, due to the development of new techniques and products, the concrete has been undergoing constant changes [. This article discusses the application of technology of lightweight aggregates for concrete production, for use in building elements such as structural panels or fence. Developed an experimental program for the analysis of concrete, with the primary objective to characterize the properties of the parts in the hardened state. The results showed that the lightweight aggregate concrete with Brazilian expanded clay are extremely suitable for the production of prefabricated elements slender, mainly due to the reduction in density and excellent performance in mechanical properties, especially modulus of elasticity, despite the low toughness of lightweight aggregate.