M. Farzam, University of Tabriz, Iran N. A. Fouad, Institut für Bauphysik, Leibniz University,Germany J. Grünberg, Institut für Bauphysik, Leibniz University,Germany M. Y. Fard, University of Tabriz, Iran
The main objective of this paper is to study the effect of eccentricity of loads on the ultimate punching resistance and rotational capacity of slabs. A mechanical model recently proposed by Muttoni, which has been developed to predict the punching capacity of slab-column connections under concentric loads, is developed in the same manner as that of Broms to be applicable for the investigation of rotational capacity of slabs under eccentric loads. Furthermore, the effect of eccentricity of load on the ultimate punching resistance and the rotational capacity of slabs with respect to column is numerically studied performing a non-linear finite-element analysis using Atena. The numerical analyses consist of calculations of selected punching tests. The factors affecting the behaviour of the connections, such as the ratio of tension reinforcement, the type of reinforcement steel and the concrete compression strength are studied parametrically. The results of the analyses are compared with Eurocode 2 and ACI code predictions and with the mechanical model previously proposed by Broms and the model developed by Muttoni.
Placement of concrete underwater is necessary in the implementation of most in-shore, and off-shore structures. The pouring of underwater concrete is considered to be a challenge for engineers, even during the design stage or during implementation and supervision. This is because many precautions must be taken to ensure the success of the casting process. The most important of these is to protect the fresh concrete from the water during the casting process to avoid the risk of wash-out of the cement past and segregation of aggregates. Concrete can be placed underwater successfully through good design of the concrete mix and choosing the most suitable method for placing of the concrete. There are new techniques for underwater concreting such as grouted aggregate; this is known as the two-stage concrete method. The main objective of this paper is to present the capability of pouring concrete underwater using this method. A laboratory model was prepared, visually investigated and tested by extracting core samples, then performing compressive, tensile and ultrasonic pulse velocity tests. From the results obtained it has been observed that concrete can be poured successfully underwater using the two-stage method, and it is recommended that this research may be developed by using different water-cement ratios and cement-sand ratios to obtain the optimum mix design; also, different types of aggregates, which are available in local quarries, may be used.
Torsion strengthening of RC beams with carbon fibre composites
J. J. Holtz Silva Filho, PUC-Rio, Brazil E. de Souza Sánchez Filho, Fluminense Federal University, Brazil M. de Souza Lima Velasco, PUC-Rio, Brazil
This paper presents the results of an experimental and theoretical study designed to evaluate the behaviour of reinforced concrete beams subjected to torsion and strengthened with carbon fibre composites. A total of seven beams, each with the dimensions 200x400x4200 mm, were tested. Test results reveal marked increases in the torsion capacity of 38% and 40% for each series of beams. The effective axial stress of a theoretical model for bonding the carbon fibre composites is incorporated in the space truss with softening model. The predictions of this proposed model are then compared with tests results. A high degree of agreement is verified between the experimental and theoretical values.
Deformations at flexural yielding of members with continuous or lap-spliced bars
Dionysis Biskinis, University of Patras, Greece Michael N. Fardis, University of Patras, Greece
Models are developed and calibrated for the moment, the chord rotation and the secant stiffness at flexural yielding of reinforced concrete beams, rectangular columns or walls and members of T-, H-, U- or hollow rectangular section, on the basis of a databank of tests on members with continuous bars. Criteria are developed for the identification of adverse shear effects on the yield moment. The models apply only to members whose yield moment is not reduced by shear effects. They employ simple, explicit expressions suitable for practical application without moment-curvature analysis. They are extended to members with bars lap-spliced starting at the end section. The effect of biaxial loading on member yielding is examined. Most of the models have been adopted in Eurocode 8, Part 3.
Experimental investigations of partially-damaged RC beams and columns
Andrew Pullen, Imperial College London, UK Ali Abbas, Imperial College London, UK
This paper summarises experimental investigations of undamaged and partially damaged reinforced-concrete beams and columns. The aim of the work was to establish and carry out experimental methods for determining the load-deformation behaviour and strength of these simple structural elements under varying levels of localised pre-damage (such as weakening or partial loss of concrete material). In particular, the effect of such partial/local damage on the overall behaviour and, crucially, its contribution to structural collapse, were also studied. There is little experimental evidence to validate predictions obtained from analysis or numerical modelling of partially damaged concrete members. Often, the ultimate capacity is the primary output of interest and it is usually determined using specimens that have no prior local damage. The present study produced data that led to a comparative study between the structural behaviour of both damaged and undamaged structural elements in order to help understand the effect of local damage and its contribution to structural collapse. The experimental results can also be used for future modelling and validation purposes.
Deformation of continuous reinforced concrete beams during patch repair
John Cairns, Heriot Watt University, UK Eoin Coakley, Conventry University, UK
This paper describes an experimental and numerical investigation examining the effect of reinforcement exposure during the patch repair process on the behaviour of continuous beams. Particular attention is paid to moment transfer and change in strain patterns during concrete breakout. The test programme embraced a range of parameters including the length and position of breakout and a variety of reinforcement arrangements. Moment transfer during concrete breakout was monitored to assess whether breakout at one location would cause overstressing in other parts of the structure. Results from tests and numerical analysis show increases in section deformations away from the breakout were small when compared to those within the breakout length. It is surmised that there is little danger of overstraining in locations away from the breakout zone while breakout does not extend past a point of contraflexure.
