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Abstract: The dynamic strength enhancement of concrete under different initial static loadings is investigated in this paper. The mechanism of the influence of the inertia effect on the dynamic strength of concrete is discussed first by analyzing a single dimension of freedom system, which shows that the inertia effect only influences the dynamic loading part. The dynamic strength of concrete at initial static loading is calculated assuming a single crack model with consideration of free water viscosity using dynamic fracture mechanics. The dynamic stress intensity factor of the crack under linearly increasing loading on the basis of an initial static loading is achieved. The relationship between the dynamic strength increase factor and the static stress level is obtained. The comparison between the results by the model proposed in this paper and those by experiments in some available references indicates a good agreement. [Copyright &y& Elsevier]

This paper presents experimental and analytical studies on the flexural behavior of fully composite steel-concrete I-girders strengthened by externally bonded carbon fiber reinforced polymer (EB-CFRP) sheets. The experimental program consisted of four reduced-scale specimens composed of a hot-rolled steel I-girder section acting compositely with topping reinforced concrete slab using two rows of properly designed shear studs along the entire length of the girder flange. One girder was un-strengthened to act as a reference girder, while the remaining three girders were strengthened with 2, 3 and 4 layers of CFRP sheets mounted on the bottom side of the steel girder's tension flange considering complete anchorages of the CFRP sheets at both ends. The composite girders were tested under a four-point loading system in order to obtain a comprehensive overview of the flexural behavior of both un-strengthened and the CFRP-strengthened girders. Finally, an analytical design procedure was proposed in order to obtain the moment of resistance of the composite girders. Then, the proposed methodology was verified against the current experimental results as well as the experimental results obtained by other researchers. The comparison showed good agreement between the proposed analytical results and the experimental findings with a maximum variation less than 10%. Thus, the proposed equations for moment of resistance of CFRP-strengthened composite girders can be used by design engineers with confidence. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of an experimental program developed to study the feasibility of producing prestressed concrete girders using lightweight concrete. During the experimental campaign, bond tests were performed in push-in (TL bond test) and pull-out (FB bond test) types of specimens. To-scale prestressed concrete elements were produced, implemented, and tested. The variables studied were the type of concrete, the test age, and the delayed effects of bond. The TL bond test allowed the behavior of the transfer length to be characterized, governed by the Hoyer effect. Equations have been calibrated to identify the upper and lower transfer lengths using the experimental results of this trial. The proposed equations delimit the safety boundaries of the experimental transfer length values obtained in the experiments performed on the beams. The results obtained in the experimental phase discourage the use of the studied lightweight concrete for producing pre-tensioned concrete elements. [Copyright &y& Elsevier]

Abstract: This paper describes the development of a hybrid model for a concrete batching and mixing plant. The model is sufficiently detailed so as to ensure that it can be used to establish the control system within an industrial monitoring and control framework. Since the concrete batching and mixing plants are hybrid systems, Global Automata were used to build the model of the physical system, since they provide greater “modeling power” being suitable for modeling of a wider variety of systems than other types of automata. Various modeling methods based on the classical hybrid systems theory are rather applied in research works with academic orientation and usually are far from the engineers of industry. A fundamental objective of this work was to adopt a development environment which will be familiar to the industrial people. The developed model entails a hierarchical structure with an automaton as supervisor and several other interactive automata describing the subsystems of the plant. The model was then used to understand the influence of various design and operating parameters on plant performance. The model was also used to establish the control strategy. Both were implemented in a SCADA (Supervisory Control and Data Acquisition) environment which monitors and controls the overall operation of the plant. This framework has been applied on a real plant of West Greece with success in all realistic tests concerning either the control operation or the model validation. [Copyright &y& Elsevier]

Abstract: This paper presents a spatial time-dependent reliability analysis to predict the likelihood and extent of cracking for reinforced concrete structures exposed to chloride ion attack. A reinforced concrete surface is discretised into a large number of smaller elements and random field methods used to simulate the variability of the concrete damage over the entire area. Models predicting corrosion initiation and propagation, crack initiation and crack growth are used to track the evolution of the corrosion process for each element and thus allow the extent of damage as a function of time to be determined. A range of durability design specifications are investigated and maintenance thresholds are defined as being reached when a specified proportion of the bridge deck is damaged, say 1%. This will enable the minimum time to first repair to be estimated. The results provide a comparative tool to assist designers in selecting design specifications and possible maintenance regimes to achieve an optimal outcome in terms of service-life and life-cycle cost of the structure. [Copyright &y& Elsevier]

Abstract: The paper gives the results of an analytical method proposed to predict the load deflection behaviour of partially restrained slab strips. The effect of deflection prior to yield line load on the development of compressive membrane forces was incorporated in the theoretical analysis. An experimental programme was designed to cast and test ten partially restrained slab strips with different edge rigidity. A comparison has been made between the results of the proposed and one of the other methods available in the literature. The results indicate that the proposed method can predict the load deflection behaviour satisfactorily. A parametric study has been made on the load enhancement beyond yield line load and the results are presented. [Copyright &y& Elsevier]

Abstract: In the present paper the results of a finite element study of single headed stud anchors loaded in tension (concrete cone failure) are discussed. Anchors with extremely large embedment depths (up to 1500mm) for which few experimental data is available are investigated. Many such anchors are used in engineering practice, therefore, the aim of the study was to investigate their safety. The numerical analysis is performed using a three-dimensional finite element code based on the microplane model. Calculated concrete cone capacity for large anchors with small heads shows good agreement with the current LEFM based design formula for anchors. The numerical study and the available test data show that the ultimate strength of anchors with larger heads is higher than predicted by the design code formula. Furthermore, the size effect on the ultimate load of these anchors is less pronounced. It is shown that the current design formula is conservative for anchors with large heads. A correction factor is proposed to account for the effect of the size of the headed stud and to improve design formula. Further theoretical, experimental and numerical work is needed to investigate the performance of large single anchors and anchor groups and to verify and improve current design recommendations. [Copyright &y& Elsevier]