The paper presents analysis of the stress and deflections changes due to creep in statically determinate composite steel-concrete beam. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. an elastic law for the steel part and an integral-type creep law of Boltzmann — Volterra for the concrete part. On the basis of the theory of the viscoelastic body of Arutyunian-Trost-Bažant for determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time “t”, two independent Volterra integral equations of the second kind have been derived. Numerical method based on linear approximation of the singular kernal function in the integral equation is presented. Example with the model proposed is investigated.The creep functions is suggested by the model CEB MC90-99 and the “ACI 209R-92 model. The elastic modulus of concrete Ec(t) is assumed to be constant in time ‘t’. The obtained results from the both models are compared.
<p> The paper presents analysis of the stress-strain behaviour and deflections changes due to creep in statically determinate composite steel-concrete beam according to EUROCODE 2, ACI209R-92 and Gardner&Lockman models. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. an elastic law for the steel part and an integral-type creep law of Boltzmann – Volterra for the concrete part considering the above mentioned models. On the basis of the theory of the viscoelastic body of Maslov-Arutyunian–Trost-Zerna-Bažant for determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time “t”, two independent Volterra integral equations of the second kind have been derived. Numerical method based on linear approximation of the singular kernel function in the integral equation is presented. Example with the model proposed is investigated.</p>
auftreten, während sich in der Stahlbewehrung nur elastische Verformungen bilden, die von der äußeren Lasteinwirkung herrühren.Als Ergebnis dieser Verformungen und wegen der Tatsache, daß durch den Kleber auf Epoxid-Grundlage eine feste Verbindung zwischen Bewehrung und Holzmaterial des Trägers hergestellt wird, tritt in jedem Querschnitt, der ständiger Einwirkung des äußeren Moments M o unterliegt, in der Zeit t eine neue, zusätzliche, sich selbst im Gleichgewicht haltende Kräftegruppe auf: M h (t); M a (t) (Bild 2). Die Größe dieser Zur Bestimmung der Umlagerungsgrößen in Holz in der Zeit t wurde nach der Theorie des viskoelastischen Körpers für das Kriechen des Holzes eine Volterra-Integralgleichung der zweiten Art abgeleitet. Für die Lösung dieser Gleichungen wird eine analytische Methode vorgeschlagen, die Laplacesche Transformationen ausnützt. Die Anwendung wird an einem Beispiel gezeigt.Creep behaviour of steel reinforced timber beams. The paper presents analysis of the stress changes due to creep of the wooden members in simply supported timber beams with tension reinforcement. For determining the redistribution of stresses in beam section between wooden and tension reinforcement with respect to time t, a Volterra integral equation of the second kind have been derived on the basis of the theory of the viscoelastic body. An analytical method, which makes use of Laplace transformation for solving these equations, is proposed. The application of the method is explained with the aid of an example.
The paper presents analysis of the stress-strain behaviour due to creep in statically determinate composite steel-concrete beam according to AAEM method of Bažant in comparison with numerical method. The analysis is based on the results obtained by numerical solution with Volterra integral equations derived for determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time "t" and creep of concrete according EC2 provisions. On the basis of the theory of the viscoelastic body of Arutyunian-Trost-Bažant it is analysed the migration of stresses from concrete plate to steel beam using two independent Volterra integral equations of the second kind and two independent algebraic equations, during the period of 70 years. The closeness of the results obtained by the two methods is shown with an example from the bridge practice.
<ul><li> <p>The paper presents analysis of the stress changes due to creep in statically determinate composite steel-concrete beam according to (AAEM) method of Bažant in comparison with numerical solution using Volterra integral equations based on EC2 provisions for creep of concrete. The mathematical model involves the equation of equilibrium, compatibility and constitutive relationship, i.e. an elastic law for the steel part and an integral-type creep law of Boltzmann – Volterra and algebraic-type creep law of Trost - Bažant for the concrete part considering the above mentioned models. It is analyzed the migration of stresses from concrete plate to steel beam using two independent Volterra integral equations of the second kind and two independent algebraic equations. The closeness of the results obtained by the two methods is shown with an example from the bridge practice.</p></li></ul>
Abstract-The aim of the study is an analysis of some constructive systems in Bulgarian architecture in 19th century and in the beginning of 20th century. In the historical development of Bulgaria this is the time of changes in all areas of life. The period is connected with the transition from the Middle Ages to the Modern Era and the perception of the changes brought about by the industrial development in Europe. The wooden and steel constructions used in cult and public buildings and facilities have been explored. The use of different types of materials for these structures is related to the functions of the facilities, their social and industrial significance. In the course of the study, the hypothesis of the unity of the construction system and its relation to the terrain is confirmed. The unity of the construction system is considered as a significant problem, because builders during this period follow the local historical tradition and good knowledge of the craft. Following the tradition they work with historic, traditional materials such as wood and stone. The change with the constructions and the materials comes with the liberation of the Bulgaria in 1878. At that time an accelerated development of industrial production began. The active construction of buildings and road facilities is connected with steel structures of prefabricated elements. Often, they also come into use due to the compromised peculiarities of the terrain. In the study in chronological order were analyzed cult buildings with brick massive constructions, with wooden constructions and industrial steel structures. A cult building rare for the Bulgarian architecture, such as the church in Istanbul, is accented. It is assembled from pre-fabricated steel profiles in order to be reversible, portable and easily replaceable structural elements.Index Terms-Bulgarian buildings and road facilities; historical stone, wooden and steel constructions; industrial production; pre-fabricated steel profiles.
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