Technical Transactions iss. 6. Civil Engineering iss. 1-B

Technical Transactions iss. 6. Civil Engineering iss. 1-B

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Collection items (9)


Redistribution of bending moments in multi – span R/C beams and slabs subjected to fire

Kowalski, Robert, Urbański, Marek
Article
2013
This paper shows consideration of decrease in cross-section stiffness in commonly used in practice R/C beams and slabs in cases when only reinforcing bars or only concrete compressed zone is subjected to fire. Analyses were based on: a) standard fire curve, b) 500°C Isotherm Method assumptions, c) mechanical properties of reinforcing steel when heated to high temperatures. Afterwards, based on the estimated decrease of cross-sections stiffness, the redistribution of bending moments was calculated in some cases of two-span R/C beams and slabs subjected to fire from their bottom face. Due to the bending moment redistribution, one could expect a reduction of bending moments in span cross-sections and an increase of the support bending moment. As a result of this phenomenon, the ultimate limit state of the structural multi-span elements might occur after a shorter fire duration than could be expected when redistribution of bending moments is neglected.

Numerical model for analysis of early-age thermal–moisture effects in an RC wall

Klemczak, Barbara, Knoppik-Wróbel, Agnieszka
Article
2013
The paper presents the original numerical model for simulation of thermal, moisture and mechanical effects in concrete structures with an example of application. The influence of different curing conditions on the temperature and moisture distribution in RC wall was investigated. The stress state and the damage intensity factor were determined and the areas of possible cracking were selected as well.

Behaviour of unreinforced and reinforced masonry wallettes made of ACC blocks subjected to diagonal compresion

Kałuża, Marta, Kubica, Jan
Article
2013
For more than 10 years, masonry units made of ACC turned out to be one of the most popular materials used in the construction of residential buildings in Poland and other European countries. The recommended technology for erecting such structures requires using thin bed joints and non-filled head joints. Unfortunately, masonry buildings erected using this technique are prone to damage and cracks. One of the methods to guarantee improvement of cracking resistance of this type of structure is using a special prefabricated reinforcement to be placed in bed joints. The main objective of the investigation presented here was to analyse the behaviour of unreinforced and reinforced, with prefabricated truss-type called MURFOR®, masonry walletts. All specimens were subjected to diagonal compression. Three groups of specimens were tested, each using a different mortar coating Testing was especially focused on the main technological problem of the proper adhesion between mortar and the reinforcement surface.

Redistribution of forces between reinforcement bars and profiles in the intermediate support zone in the double span, double combined beams

Habiera, Elżbieta, Czkwianianc, Artem
Article
2013
The aim of the study was to analyse the behaviour of the innovative precast beams, where the prestressed concrete and specially prepared steel profile were combined. This paper deals with the results of the tests and the analysis of redistribution of internal forces between reinforcement bars and steel profiles in the intermediate support zone in the proposed double span beams.

Dissipative forces in joint surface of composite reinforced concrete floors

Gromysz, Krzysztof
Article
2013
It is assumed that longitudinal shearing in joint surface (interface) of composite floors is balanced by: elastic forces, force of cohesion and kinetic friction. Moreover, internal friction occurs in the interface. Due to their nature, not all the above mentioned phenomena occur at the same time; however they are together responsible for deformation of interface. The paper discusses dissipative forces (non elastic). An interface model is built and test results of six floors are presented. All slabs are the same size – 3 m span and 0.6 m width and 0.18 m high. All slabs have the same longitudinal reinforcement. There are four types of join surface tested: smooth, very smooth, with eliminated adhesion and indented.

CFRP strengthening of bent RC beams using stiff and flexible adhesives

Derkowski, Wit, Kwiecień, Arkadiusz, Zając, Bogusław
Article
2013
The paper presents new research on the use of a flexible adhesive layer in CFRP strengthening applications for bent RC beams, which was carried out at the Cracow University of Technology. The Flexible Joint Method, developed at the Cracow University of Technology, uses PU polymers as adhesives in bonding FRP composites to concrete structures. In the tests, reinforced concrete beams were strengthened with CFRP strips, using an epoxy adhesive and five kinds of polymer adhesives of different flexibility. The beam strengthened by means of CFRP strips on middle hard flexible polymer, demonstrates the most uniform CFRP strain distribution along its length and the smallest deflection. The use of the presented technology could allow for the overcoming of some obstacles which occur when repairing concrete structures, however it is obvious that a lot of tests on such adhesives have to be carried out.

Structural fire design methods for reinforced concrete members

Chudyba, Krzysztof, Seręga, Szymon
Article
2013
The paper presents methods for determining fire resistance of reinforced concrete members according to Eurocode 2-1-2 (simplified methods based on the effective cross-section and incremental-iterative approach) [3]. Results of conducted calculations are compared with fire test results taken from the literature. The main parameters considered in the conducted analysis are: concrete class, values of normal force eccentricity and cross-section shape. General conclusions are formulated as to the accuracy of simplified methods and practical limitations of their application within the analysed scope of variable material and geometrical parameters.

Methods for determining masonry walls fire resistance

Chudyba, Krzysztof, Matysek, Piotr
Article
2013
In the paper, the general procedures for masonry wall design in fire situations are presented together with methods for determining the fire resistance according to EN 1996-1-2 [1] and its Polish version, PN-EN 1996-1-2 [2]. Special attention is paid to the practical application of presented methods (tabulated data and simplified methods based on reduced cross-section) and to pointing out possible problems and shortcomings. There is also brief comments on the process of introducing Euro code 6 (EN 1996-1-1 [3], EN 1996-1-2 [1]) for the design of masonry structures in Polish practice (codes: PN-EN 1996-1-1 [4], PN-EN 1996-1-2 [2]).