Course Report:Composite Structures Edit by Chen Shiming College of Civil Engineering Tongji University 2015
Course Report: Composite Structures Edit by Chen Shiming College of Civil Engineering Tongji University 2015
Contents 1.Moment redistribution and load carrying capacity continuous composite beams …Bagatti Alessia 2.A comparison of design method for steel encased concrete columns and steel reinforced concrete columns Claudio De Filippis 3.Glued composite beams:Fatigue test and interface comparision …Farradeche Ghislain 4.A comparative study of concrete filled composite columns and steel reinforced C0 ncrete c0 lumns… …Mattia Girolomini 5.A comparative study of concrete filled composite columns and steel reinforced concrete columns …Irene Josa Cullere 6.Design of composite beams for different degree of shear connection -LYU Ruoshi 7.Structural performance of ultra shallow composite floor beam ...................................................................Marti carrera comamala 8.Design of composite beams for different degree of shear connection Alice 9.Research review:The finite element models of the composite beam of steel and concrete …Wang Changjiang 10.Design method of load carrying capacity for composite slabs with steel profiled sheeting ....Wang Junhao 11.A comparative study of Chinese and foreign specification of concrete filled composite columns ...Zhou Shuangning
Contents 1. Moment redistribution and load carrying capacity continuous composite beams ····························································································Bagatti Alessia 2. A comparison of design method for steel encased concrete columns and steel reinforced concrete columns ···················································Claudio De Filippis 3. Glued composite beams: Fatigue test and interface comparision ··································································································Farradeche Ghislain 4. A comparative study of concrete filled composite columns and steel reinforced concrete columns ·····································································Mattia Girolomini 5. A comparative study of concrete filled composite columns and steel reinforced concrete columns ·····································································Irene Josa Culleré 6. Design of composite beams for different degree of shear connection ················································································································LYU Ruoshi 7. Structural performance of ultra shallow composite floor beam ··························································································Martí Carrera Comamala 8. Design of composite beams for different degree of shear connection ··········································································································Salomoni Alice 9. Research review: The finite element models of the composite beam of steel and concrete ····················································································Wang Changjiang 10. Design method of load carrying capacity for composite slabs with steel profiled sheeting ···························································································Wang Junhao 11. A comparative study of Chinese and foreign specification of concrete filled composite columns ···································································Zhou Shuangning
Moment redistribution and load carrying capacity of continuous composite beams Bagatti Alessia 1436375 A.Y.2014/2015 School of Civil Engineering,Tongji University 1.Introduction n EuroCode 4(part 1.1)[2]continuous composite beams are defined as internal supports or is joined by full-strength and rigid connections,with connection between the beams and each support such that it can be assumed that the support does not transfer significant bending moment to the beam.At the internal support the beam may have either effective reinforcement or only nominal reinforcement." Continuous composite beams represent an efficient structural method in many structural systems,such as buildings and bridges,due to additional advantages associated with the dis th n easier serviceability chec owever,the de esign and analysis of continuous composite beams is rathe complicated due to their different behaviour in positive(or sagging)and negative(or hogging) moment regions.Moreover,in regions of hogging moments,e.g.at the internal support regions of continuous members,a large part of the steel beam section is subjected to compressive stresses,thus the bottom flange and the web are susceptible to local instabilities. 2.Description of structural components The following figure shows a typical continuous composite beam and the forces that can be developed at the beam-column connection.The tensile force acting in the slab area may be carried out by additional reinforcement and the compressive force acting across the column may be carried out by additional web stiffeners.Other important factors that must be taken into account are: -the presence of longitudinal shear force between the concrete slab and the steel -the fact that the bottom part of the steel section is in compression and therefore both flange and web are prone to buckling
Moment redistribution and load carrying capacity of continuous composite beams Bagatti Alessia 1436375 A.Y. 2014/2015 School of Civil Engineering, Tongji University 1. Introduction In EuroCode 4 (part 1.1) [2] continuous composite beams are defined as: “A beam with three or more supports, in which the steel section is either continuous over internal supports or is joined by full-strength and rigid connections, with connection between the beams and each support such that it can be assumed that the support does not transfer significant bending moment to the beam. At the internal support the beam may have either effective reinforcement or only nominal reinforcement.” Continuous composite beams represent an efficient structural method in many structural systems, such as buildings and bridges, due to additional advantages associated with the favourable redistribution of internal forces across the member and the easier satisfaction of serviceability checks. However, the design and analysis of continuous composite beams is rather complicated due to their different behaviour in positive (or sagging) and negative (or hogging) moment regions. Moreover, in regions of hogging moments, e.g. at the internal support regions of continuous members, a large part of the steel beam section is subjected to compressive stresses, thus the bottom flange and the web are susceptible to local instabilities. 2. Description of structural components The following figure shows a typical continuous composite beam and the forces that can be developed at the beam-column connection. The tensile force acting in the slab area may be carried out by additional reinforcement and the compressive force acting across the column may be carried out by additional web stiffeners. Other important factors that must be taken into account are: - the presence of longitudinal shear force between the concrete slab and the steel; - the fact that the bottom part of the steel section is in compression and therefore both flange and web are prone to buckling
eshear Fig.1 Geometry and forces acting on con ous composite beam In order to develop the mo have asimilar rigid beam column connection. Because the concrete slab in capable to withstand high compression forces,usually the resisting moment in the sagging region is really high.On the other hand in hogging region at the support)the concrete slab is in tension,and so it is likely to be cracked and all the tension forces must be carried by steel reinforcements. An intrinsic assumption is done in the analysis of continuous composite beams,and it is that the ection is able to tate to a degre the re ting moment.Thus the beam-co fficut to adapt with the requirements for serviceabbecauseh e concrete will crack when the tension reinforcement within it strains beyond yield.To minimise these cracks the reinforcement must be well distributed and preferably relatively small diameter bars. It is the case that the effective breadth of the slab section is less in this region and is disturbed by the presence of the column continuing between floors.The effective breadth of the slab over the support is taken as be=lo/8. Another appear due to the compressed eof the steel section at the ne high cal moments can cause local buckn the constituent plates and or lateral torsional global mode. This may be particularly acute for local buckling as the lower part of the beam will have reached and possibly exceeded yield.For this reason it is important to ensure that the lower part of the web is classified correctly.Eurocode 33]propose a classification of the steel beam section to ensure that the resulting strains can be accommodated without a reduction in resistance below the plastic moment.Limitations must be placed on the slender ness of the elements of the cross. i compression. the cros -section mine whether or not l cal buc ection to develop its plastic moment resistance and the rotations necessary for the redistribution of internal moments
Fig. 1 Geometry and forces acting on continuous composite beam In order to develop the moment capacity of a fully continuous beam the overall section must have a similar capacity in the hogging and sagging regions. This leads to the concept of a fully rigid beam column connection. Because the concrete slab in capable to withstand high compression forces, usually the resisting moment in the sagging region is really high. On the other hand in hogging region ( at the support) the concrete slab is in tension, and so it is likely to be cracked and all the tension forces must be carried by steel reinforcements. An intrinsic assumption is done in the analysis of continuous composite beams, and it is that the beam column connection is able to rotate to a certain degree whilst carrying the design resisting moment. Thus the beam-column connection requires certain ductility. This is often difficult to adapt with the requirements for serviceability because the concrete will crack when the tension reinforcement within it strains beyond yield. To minimise these cracks the reinforcement must be well distributed and preferably relatively small diameter bars. It is the case that the effective breadth of the slab section is less in this region and is disturbed by the presence of the column continuing between floors. The effective breadth of the slab over the support is taken as . Another problem can appear due to the compressed lower flange of the steel section at the support. The high carried moments can cause local buckling of the constituent plates and or lateral torsional global mode. This may be particularly acute for local buckling as the lower part of the beam will have reached and possibly exceeded yield. For this reason it is important to ensure that the lower part of the web is classified correctly. Eurocode 3 [3] propose a classification of the steel beam section to ensure that the resulting strains can be accommodated without a reduction in resistance below the plastic moment. Limitations must be placed on the slenderness of the elements of the crosssection which are in compression. Eurocodes introduce the concept of cross-section classification to determine whether or not local buckling limits the ability of the cross-section to develop its plastic moment resistance and the rotations necessary for the redistribution of internal moments
Continuous composite beams have different advantages and disadvantages with respect to simply supported ones. ADVANTAGES higher span/depth ratios can be used,for given limits to deflections; greater load capacity due to redistribution of moments; cracking of the top surface of a floor slab near internal columns can be controlled,so that the use of brittle finishes is feasible; the floor structure has a higher fundamental frequency of vibration,and so is less susceptible to vibration caused by movements of people; robust(e.g.in resisting the effects of or explosion) DISADVANTAGES more complex design:actions on one span cause action effects in adjacent spans,and the stiffness and bending resistance of a beam vary along its length; susceptibility to buckling in the negative moment region over internal supports; two forms of buckling may be involved:local buckling of the web/or bottom flange and lateral torsional buckling complex than for a simply su pported nd connections are involved.However the design of Distribution of internal moments is dependent on the ratio of the negative (hogging)moment of resistance to that in positive('sagging')bending.When elastic analysis is used to determine internal moments and forces (global analysis),moment may be redistributed from internal supports to allow for cracking of concrete and yielding of steel.The extent of the redistribution is dependent on the classification of the steel section at each internal support and on the concerning flexural rigidity in the negative moment regions ed sectior sed to the fle al rigidity for ever cross-sectior ng the beam ('uncra section method). Alternatively,it may be assumed that over a fixed length on each side of interal supports,the properties are those of the cracked section(cracked section method"). It is not possible to predict accurately the stresses or deflections in a continuous beam for a given set of actions,because should be considered also the variation over time caused by the shrinkage and creep of concrete,which can cause effects of cracking of concrete.For what
Fig. 2 Classification of cross section Continuous composite beams have different advantages and disadvantages with respect to simply supported ones. ADVANTAGES - higher span/depth ratios can be used, for given limits to deflections; - greater load capacity due to redistribution of moments; - cracking of the top surface of a floor slab near internal columns can be controlled, so that the use of brittle finishes is feasible; - the floor structure has a higher fundamental frequency of vibration, and so is less susceptible to vibration caused by movements of people; - greater stiffness; - the structure is more robust (e.g. in resisting the effects of or explosion). DISADVANTAGES - more complex design: actions on one span cause action effects in adjacent spans, and the stiffness and bending resistance of a beam vary along its length; - susceptibility to buckling in the negative moment region over internal supports; - two forms of buckling may be involved: local buckling of the web/or bottom flange and lateral torsional buckling. Usually the global analysis for continuous beams is more complex than for a simply supported ones, because the properties of columns and connections are involved. However the design of hogging moment regions of the beams is the same. Distribution of internal moments is dependent on the ratio of the negative (‘hogging’) moment of resistance to that in positive (‘sagging’) bending. When elastic analysis is used to determine internal moments and forces (global analysis), moment may be redistributed from internal supports to allow for cracking of concrete and yielding of steel. The extent of the redistribution is dependent on the classification of the steel section at each internal support and on the assumptions made concerning flexural rigidity in the negative moment regions. The properties of the uncracked section may used to determine the flexural rigidity for every cross-section along the beam (‘uncracked section method’). Alternatively, it may be assumed that over a fixed length on each side of internal supports, the properties are those of the cracked section (“cracked section method”). It is not possible to predict accurately the stresses or deflections in a continuous beam for a given set of actions, because should be considered also the variation over time caused by the shrinkage and creep of concrete, which can cause effects of cracking of concrete. For what