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The behavior of timber–concrete slab-type structures is not fully understood yet. This is the case of the transversal load distribution in composite floors under concentrated loads. Included in a broader investigation, this article presents the findings for the specific case of a timber–concrete composite floor under the action of a concentrated load. This article aims at studying such transversal load distribution by means of some theoretical methods, which were compared with experimental results. Different finite elements (FE) and analytical models were used. Numerical models using different types of FE were validated based on numerical and experimental results. The analytical model used distribution coefficients. From the study, it was possible to conclude that all the methods were able to detect a non-linear transversal distribution, but there were some deviations when comparing the methods with each other. The analytical method, based on several simplifications presented a larger deviation from the numerical ones. This is discussed in more detail within this article and some practical considerations were added.

The study of torsion in reinforced concrete members began in the early twentieth century but it has become more widespread in the past 60 years. Even today, this topic has not been deeply researched with respect to slabs. This work reports a study on the behavior of reinforced concrete slabs subjected to torsion, with particular attention to the stiffness in state I and state II (uncracked and cracked phase) and to the relation T – θ (torsional moment-twist). It is known that torsional forces lead to a much larger loss of stiffness in state II, due to the strong cracking, than the loss of flexural stiffness. When the member is predominantly subjected to bending moments the K I / K II  ≈ 3–5 is usually admitted, but when torsion has a preponderant role this relationship is not valid. This study may alert the scientific community to a seemingly unknown relation: torsional stiffness of reinforced concrete slabs, in the cracked phase, is about 1/17–1/15 of the stiffness in the elastic phase. For the analysis of slab deformation, particularly under service conditions, accurate knowledge of the slab stiffness in state II is important. The knowledge of T – θ relation is also important to perform a numerical nonlinear analysis. An experimental program was designed and carried out in which 9 slabs were tested until failure. To submit the slabs predominantly to torsional moments, vertical movement at 3 corners was restricted and the action was applied to the fourth corner. Based on the results obtained, the following relations were defined: load–displacement ( P – d ), torsional moment-twist ( T – θ ) and K T,I / K T,II .

A simple computation procedure is developed to predict the general behaviour of reinforced concrete beams under torsion. Both plain and hollow normal strength concrete beams are considered. Different theoretical models are used to reflect the actual behaviour of the beams in the various phases of loading. To pass from a phase to the following one, transition criteria need to be taken into consideration. Such criteria are explained. The theoretical predictions are compared with result from reported tests. Conclusions are presented. The main conclusion is that the calculation procedure described in this paper gives good predictions when compared with the actual behaviour of the plain and hollow beams.

As materials and structural optimization continue to be important in design, structural safety checks for service limit states have become increasingly important. One key aspect of these checks is the controlling of cracks to prevent them from affecting the structure’s function or appearance. However, the authors have found that current regulations do not accurately reflect the reality of crack behavior. This is the case of the crack spacing. To address this issue, the authors conducted experiments on 27 reinforced concrete beams to investigate crack location, cracking moment, corresponding deflection, and crack width values as sag increases. Their main finding was that cracks tend to appear at the stirrup locations, and that crack width increases linearly with the sag-to-free-span ratio up to the yielding point. They also concluded that increasing the amount of tensile reinforcement is an effective way to reduce crack width for the same sag.

Cement-based construction materials, commonly known as “cement concrete”, result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material’s strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%.

Non-destructive tests (NDT) have been used in the last decades for the assessment of in-situ quality and integrity of concrete elements. An important step in the application of NDT methods concerns to the interpretation and validation of the test results. In general, interpretation of NDT results should involve three distinct phases leading to the development of conclusions: processing of collected data, analysis of within-test variability and quantitative evaluation of property under investigation. The analysis of within-test variability can provide valuable information, since this can be compared with that of within-test variability associated with the NDT method in use, either to provide a measure of the quality control or to detect the presence of abnormal circumstances during the in-situ application. This paper reports the analysis of the experimental results of within-test variability of NDT obtained for normal vibrated concrete and self-compacting concrete. The NDT reported includes the surface hardness test, ultrasonic pulse velocity test, penetration resistance test, pull-off test, pull-out test and maturity test. The obtained results are discussed and conclusions are presented.

Reinforced concrete (RC) frame beams are subject to axial restriction at the ends, which plays an important role in the nonlinear behavior of these beams. This paper presents a numerical and theoretical investigation into the flexural behavior of RC beams axially restricted with external steel or fiber reinforced polymer (FRP) reinforcement. A numerical procedure for RC beams axially restricted with external reinforcement has been developed and it is verified against available experimental results. A numerical parametric study is then performed on axially restricted RC beams, focusing on the effect of type, area, and depth of external reinforcement. The results show that axial restriction increases the post-cracking stiffness and ultimate load-carrying capacity but reduces the flexural ductility. The ultimate stress in external reinforcement is substantially impacted by reinforcement type, area, and depth. A simplified model is developed to predict the ultimate load of RC beams axially restricted with external steel/FRP reinforcement. The predictions of the proposed simplified model agree favorably with the numerical results. The correlation coefficient for the ultimate load is 0.984, and the mean difference is −2.11% with a standard deviation of 3.62%.

The ultimate behavior of high-strength concrete hollow beams is studied with respect to their strength and ductility. Sixteen beams were tested and the results are presented herein. The hollow beams had a constant square cross section and were symmetrically reinforced. The variable parameters were the concrete's compressive strength, from 46.2 to 96.7 MPa (from 6699 to 14,022 psi), and the total amount of torsional reinforcement, from 0.30 to 2.68%. The study presented in this paper shows that the torsional ductility is low and that the range of reinforcement ratio where ductility still occurs is very narrow. Different codes of practice were compared in the light of the experimental results. As a consequence, the authors found that ACI Code is the most appropriate for predicting torsional strength and limiting torsion reinforcement, thereby leading to ductile behavior.

This work aims to study the possibility of using alkaline activated fly ash in structural members. The work, of an experimental nature, focuses on the evaluation of the behavior of simply supported beams under two symmetrical loads (four-point tests). For such study, 10 beams were built, of which, five using fly ash and the remaining five using traditional Portland cement. The test results are compared. Conclusions on the practical application of fly ash in structures were explained and, as mention later in this document, there is room for improvement. This is one of very few works on fly ash alkali activated structures and further studies are necessary in the future. Some aspects, such as shrinkage and deformability are presented as some of the negative points concerning the potential use of fly ash. These are two aspects that need more attention in future investigations.

This article presents an experimental study on the plastic behaviour of HSC beams in bending. Nineteen isostatic beams were tested up to failure. The loading consisted of two symmetrical concentrated forces applied approximately at thirds of the span of the beams. The main purpose of the analysis is to characterize the plastic rotation capacity in the beams’ failure section with an experimental parameter. Bearing this in mind, a global plastic analysis of the tested beams is presented. The main variables of this study are the longitudinal tensile reinforcement ratio and the compressive strength of the concrete. The results obtained here are completed with others presented before and the whole set of results is analysed and discussed. The plastic rotation capacity of the tested beams are analysed with the rules of some codes of practice. Finally, a summary of the main conclusions is presented.