Design Of Steel-concrete Composite Beam Of The Floor Structure
Saimaa University of Applied SciencesThe Faculty of Technology, LappeenrantaDouble Degree Programme in Construction and Civil EngineeringAleksei PashkoDesign of steel-concrete composite beam of the floorstructureBachelor’s Thesis 2015
CONTENTS1. INTRODUCTION . 42. BUILDING CODE REQUIREMENTS FOR FLOOR SYSTEM OF RESIDENTIALBUILDING . 62.1. Fire safety of buildings . 62.2. Corrosion protection . 103. DESIGN OF STEEL AND CONCRETE COMPOSITE BEAM . 113.1. Load estimation. 143.2. I stage Steel Beam calculation . 163.2.1. Beam Section . 173.2.2. Strength verification. 183.2.3. Serviceability limit state . 193.2.4. Overall stability . 203.2.5. Flange local stability . 213.2.6. Fillet weld strength verification . 223.3. II stage Composite beam calculation . 243.3.1. Static Calculation . 243.3.2. Composite beam section. 243.3.3. Strength verification. 263.3.4. Serviceability limit state . 273.3.5. Anchor shift verification . 283.3.6. Local concrete crumbling verification . 304. COMPARISON OF THE CREATED ALGORITHM WITH EXPERIENCE ANDCOMPUTER-AIDED CALCULATION . 314.1. Computer-aided calculation of the steel beam . 314.2. Computer-aided calculation of the composite beam . 334.3. Ruukki test . 405. CONCLUSION. 42Figures . 43Tables . 44Charts . 44REFERENCES . 45APPENDICES . 46APPENDIX 1 Automatized design of the composite beam “Calculation program” . 462
AbstractAleksei PashkoDesign of steel-concrete composite beam of the floor structure, 49 pages, 1 appendix.Saimaa University of Applied Sciences, LappeenrantaTechnology, Civil and Construction EngineeringDouble Degree Programme in Civil and Construction EngineeringBachelor’s Thesis 2015Instructors: Lecturer Petri Himmi, Saimaa University of Applied SciencesManaging Director Denis Pronin, Ruukki Rus.The purpose of the thesis was to design a steel-concrete composite beam of the floorstructure for a multi-storey residential building according to the Building Codes. Thework was commissioned by the company Ruukki Rus, specialized in steel construction.The thesis should be of interest to Ruukki, any customer, design engineers and otherconstruction companies dealing with civil engineering especially residential building.Data for this study were collected by Russian and European building codes, books ofconstruction disciplines and Ruukki specifications and reports.The first part of the thesis contains general guidance, requirements and restrictions forthe floor system in a residential building that takes place in Building Codes.The second part includes calculation points. It contains load estimation, I stage steelbeam design and II stage composite beam design.The last part is a comparison of the results obtained by the created program withexperience and computer-aided calculation accomplished by means of SolidWorks.As a result of this project, the guidance for a designer with calculation algorithm of steeland concrete composite beam was made as soon as the program of the compositebeam calculation was made in Microsoft Excel Software.Keywords: Steel-concretecalculations, ,
1. INTRODUCTIONRecently the application of steel frame and light-weight envelope structures isdeveloped in residential construction in Russia. Frame structural system provides a freebuilding space division that can be changed during building operation. Both light-weightbuilding envelope and internal vertical partition structures are already widespread in theconstruction. Thus, in order to achieve a minimum of dead load of the buildingdesigners have worked up composite light-weight flooring systems. Composite floorsusing profiled sheet decking have become very popular for non-residential multi-storeybuildings. Its success is due to the strength and stiffness that can be achieved, with aminimum use of materials.Steel-concrete composite structure has already been used in the XIX century. In theend of the century scientists noticed that steel beam with concrete cover made forincreasing a fire proof has more strength and stiffness than it was required. And in 1923it was approved by the experiments in England. The typical steel beam with concretecover can be seen in figure 1.1. Based on the discovery they decided to divide functionsbetween concrete that is a brittle material and steel that is an elastic material. Concreteis good to resist compression while steel has good tensile strength. Thus, this was areason to apply a composite structure, one part of which resists on tensile forces,another one is in compression.The purpose of the project is to design a steel-concrete composite beam with lightweight concrete as a part of a composite floor structure that is more efficient than acommon reinforced concrete floor structure with heavy-weight concrete. Application oflight-weight concrete reduces permanent load acting on the floor and the frame of thebuilding. As a result of the work, an algorithm of the composite beam calculation wascreated in compliance with the requirements and limitations from Building Codes andalso the calculation program was made in Microsoft Excel Software. It is simple in usewith a small instruction. The program provides a design of the composite beam.As it was told earlier, the composite flooring system has been designed at first for nonresidential building. A widespread composite flooring system is a concrete slab restingupon downstand steel I-beams (see figure 1.2). Collaboration of steel and concreteparts of the structure is provided by anchors welded on the upper flange of the I-beam.In order to apply a composite flooring structure in residential building it is important tominimize the thickness of the floor for effective space usage. Therefore the designedfloor structure was developed to provide a minimum depth. A downstand beam isreplaced by partially encased into a concrete slab steel beam.Along the letter notation axis the flooring system is presented by a continuousmonolithic ribbed slab. It is poured by means of retained formwork as steel profiledsheet. As a reinforcement of the slab bar mat reinforcement and reinforcing mesh areused.In another direction it is a steel-concrete composite beam with I-section. The steelbeams are partially encased in the slab that eliminates the fire protection costs and4
improve the flexibility of layout. The usage of light-weight concrete and T-section ofsteel beam leads to reducing the overall dead weight.The flooring system that is designed will be applied in the residential 11-storey building.The total height of the building is about 33 m. The frame system is one of the modernmixed systems called Column-slab with rigid core. The durability of the designedbuilding is 50 years as large-scale housing construction according to GOST 542572010.Building Code requirements to the floor structure are mainly referred to fire-resistanceand corrosion protection as soon as strength, stiffness and stability.The flooring system reduces loads on the building frame, the overall costs of the loadbearing structure in comparison with a typical reinforced concrete floor, has lessthickness of the floor, weight of steel and concrete mass than a composite floor with Isection steel beams. If we take the following unit price of structural materials: 1 t of steel– 30 000 rubles; 1 m3 of steel – 230 000 rubles, 1 m3 of concrete - 2500 rubles; we willsave as a minimum 1000 rubles per 1 m of steel beam by using the designed flooringsystem.Figure 1.1 Steel beam with the concrete coverFigure 1.2 Widespread composite flooring: concrete slab resting upon downstand steelbeams.5
2. BUILDING CODE REQUIREMENTS FOR FLOOR SYSTEM OFRESIDENTIAL BUILDING2.1. Fire safety of buildingsThe fire class of a building should be known in order to define the required fire class forits load-bearing structures. In this case we are taking the residential 11-storey building.The fire class of the building is P1 defined by National Building Code of Finland E1, fireload is less than 600 MJ/m2. In according to National Building Code of Finland E1 arequired fire class for load-bearing structures is R120 that means the load-bearingstructure carries 120 minutes under the fire.The fire class of the designed building is II defined by the building height in SP54.13330.2011. According to SNiP 21.01-97 “Fire Safety of buildings and works” arequired fire class for load-bearing structures is R90. Load-bearing structure is astructure that takes part of providing the overall stability and geometric invariability of abuilding. For building envelope integrity and insulation should be guaranteed at thesame time. Flooring system is both load-bearing structure and building envelope. So itshould be REI 90.Steel structure has low limit of fire-resistance that is increased by enclosure steelsurface from the fire by a layer like suspended ceiling, fireproof coating. According toManual 2013 Steel T-section beam fire-resistance limit is R 9 as the given metalthickness is tred 4,9 mm. As told in SP 54.13330.2011 “Multicompartment residentialbuilding”, essential level of load-bearing structure fire-resistance must be provided onlyby structural fire protection like flame retardants of ROCKWOOL, Technonicol.The given thickness is defined by the following formula:(2.1)perimeter of the section, see figure 2.1.6
Figure 2.1 Beam parameters for given thicknesscalculationMainly there are three ways for fire protection of building structures in the contemporaryconstruction: fireproof plaster on reinforcing mesh, fireproof thermally intumescent paintand facing with fireproof plate materials. A fireproof plate may be gypsum board,vermiculite slab and magnesite board. Fire-protective plaster SOSCH1 increases thefire-resistance of a structure up to REI 150.It is obvious that the most appropriate way of fire protection of the composite beams isfacing with fireproof plate materials. Suspended ceiling is foamed by fireproof plates. Inaddition, application of thermally intumescent paint for steel beam may be realized asan extra fire protection.Design of appropriate device (structure) of the fire protection depends on properties ofused materials that are mainly thermal conductivity and thermal capacity. Firstly limit ofheat flow rating is provided by the material with low thermal conductivity. The next layeris made of high thermal capacity material that is slowly heated during the conflagration.Essential thicknesses of each layer are defined depending on the device of the fireprotection and properties of the layers. It may be accomplished by the programSolidWorks. Heat flow rating is a design load in the fire resistance calculation. The valueof the fire load equals. The value of heat flow of normal conditions isabout.There are material parameters in Table 2.1 that are used in the fire resistance analysisrealized by the Solidworks.7
Table 2.1 Material parameters MaterialThermalconductivity123Magnesite plateConlit 150 (Rockwool)Air*Thermal 60,050,16-4Concrete D12000,31840KM0*- thermal conductivity of air is taken greater as correction due to convection. The actualair value of thermal conductivity is. Classification of inflammabilityaccording to Chapter 3 Asset 13 Federal Law published 22.07.2008 123-FLOne of the versions of the flooring system is shown in figure 2.2.Figure 2.2 Section of the composite flooring systemThe specification of the structure is listed in table 2.2.Table 2.2 Specification of the flooring structure NameVerticalsize1Floor covering7,5 mm2Cap30 mm3Concrete slab220 mm4Steel profiled sheet153 mm5Conlit 150 (Rockwool)20 mm6Magnesite plates12,5 mm7Steel fasteners (cold-formedmembers)-8Function of the layerCoverSlab protection, levelingLoad-bearing and envelopeLoad-bearing and formworkBeam fire protectionFloor fire resistanceFastening, air layer – floorfire resistant component.
The structure shown in figure 2.2 is a preliminary version to provide the fire resistanceof the flooring system that is confirmed by the model thermal analysis realized by theprogram Solidworks. The model is an approximate slab structure that consists ofmagnesite plate 12,5 mm, air layer, concrete D1200 and steel bar. The model forthermal analysis is shown in figure 2.3.Figure 2.3 Model for thermal analysisThe result of the analysis is presented in figure 2.4.9
Figure 2.4 Thermal analysis result made in SolidWorksIn order to accept the final decision of the envelope structure additional tests arenecessary to approve the design proposal. It contains a fire-resistance limit of thestructure that is determined in compliance with GOST 30247 and a fire hazard class ofa structure that is set in compliance with GOST 30403.2.2. Corrosion protectionThe flooring system serves in two zones: non-aggressive and slightly aggressive. Thetee section steel structures can be designed in non-aggressive and slightly aggressivezones. Steel beams are protected on the factory by paint coating. The protective layerconsists of ground coat and varnish. A manufacturing process is automatized in theRuukki factory.There are no special requirements on reinforcement protection in the zones in Buildingcodes.10
3. DESIGN OF STEEL AND CONCRETE COMPOSITE BEAMThe composite beam shown in figure 3.1 is a steel beam and a reinforced concrete slabthat take up the load together. The joint between steel and concrete parts is provided bysteel anchors. The brace is steel bars that are placed along the beam by essential step.The bracing is necessary in order to ensure integrity of the structure. The steel beamhas tee cross section. A design section of the composite beam is a steel part andeffective slab section. A floor surface consists of a cap with a required thickness andfloor covering represented by laminated plastic. A ceiling structure is a gypsumcardboard layer attached to steel cold-foamed bars that are parallel to the compositebeam. A layer that is set under the steel beam flange provides required fire-resistanceof the structure.Figure 3.1 Steel and concrete composite beamThe calculation is complicated by two stages: construction and operation. On the firststage the steel beam is calculated in compliance with SP 16.13330.2011 and SP20.13330.2011. On the second stage the steel and concrete composite beam iscalculated in compliance with SNiP 52-01-2003, SP 63.13330.2012, EuroCode 1994.The total deflection of the composite beam is a sum of the steel beam of the I stage andthe composite beam of the II stage deflections. The total state of stress is also formedby construction and operation stage stresses. There are no district requirements forsupporting the beam during casting. Steel beam is designed in such a way as a realdeflection of the steel beam is less than limit deflection, I stage load is taken. But thisimplementation is appropriate only for the composite beam as the part of steel-concretecomposite flooring system. Usually steel studs are used as an additional supporting ofsteel sheet.11
Figure 3.2 steel studs as an additional supporting of steel sheetThere are different stress situations in I and II stages. Stress distribution is beingchanged since a concrete slab begins to harden. The neutral axis is changing itsposition because of modification of the beam section. When upper concrete flange ofthe composite beam hardens, it will take most part of the compressive stress.Stress diagram changes by the following way, see figure 3.3 and 3.4:Figure 3.3 Steel and concrete composite beamSteel beam resists a bend. There are bending moment and shear force action in thesections of the beam. A lower part of the steel beam that is mainly a flange resiststension. An upper part – it is only steel web – is under the compression.12
Steel beam should be enough strong, stiff and stable to provide good conditions forconcrete slab foaming. At the time as a concrete slab hardened, concrete and steelparts of the composite beam start bearing together. See figure 3.4.Figure 3.4 Steel and concrete composite beamConcrete slab represents an upper flange of the composite beam that resists thecompression. Thus, the whole section of the beam is I-section. Stress distribution ispresented in figure 3.4.In order to realize the benefits of the composite structures at the maximum level thereshould be a strong and stiff joint between steel and concrete structures. The joint isprovided by steel anchors. The brace is steel bars that are placed along the beam byessential step. The bracing is necessary in order to ensure integrity of the structure.13
3.1. Load estimationThere are two stages in load estimation. The first stage is a steel beam deflection underthe first group of loads: dead weight of steel beam, profiled sheet, reinforced concreteas soon as sustained load of additional reinforcement and assemblage load. Thesecond group of loads that makes a composite beam deflection contains floor covering,temporary useful and temporary partition load.According to SP 20.13330.2011 Safety factor for each group of loads is the following: Temporary working (useful) and temporary partition loads Dead weight of steel structures and additional barsDead weight of steel structures and floor covering, capDead weight
with a small instruction. The program provides a design of the composite beam. As it was told earlier, the composite flooring system has been designed at first for non-residential building. A widespread composite flooring system is a concrete slab resting upon downstand steel I-beams (see figure 1.2). Collaboration of steel and concrete
4. Composite beams have higher stiffness, thus it has less deflection that steel beams. 5. Composite construction is faster because of using rolled steel and pre-fabricated components than cast-in-situ concrete. 6. Encased steel beam have higher resistance to fire and corrosion. II. DIFFERENT SYSTEM OF CAGING . A. Steel-concrete composite system
fullest extent. Generally in steel-concrete composite beams, steel beams are integrally connected to prefabricated or cast in situ reinforced concrete slabs. There are many advantages associated with steel concrete composite construction. Some of these are listed below: The most effective utilisation of steel and concrete is achieved.
Composite beam is a combination construction of different type of materials but the most common use of the materials is when the concrete as a slab and steel as a beam in composite beam. Steel and concrete are very different in nature, but these two materials complement one another; concrete as a slab is efficient in compression and steel as beam
The concrete on the top crushes before the steel yields (brittle) The steel yields before concrete crushes (ductile) The concrete will fail in compression at a concrete strain of 0.003-0.004. The steel will yield at a steel strain of fy/Es or a steel stress of fy. N A ccr h b d nAS Concrete Beam 26 jkm Cracking of the Concrete in Tension
for permanent loads. For normal-weight concrete the short-term ratio of modulus of elasticity of steel to that of concrete are recommended by AASHTO-LRFD [4]: (12.1) FIGURE 12.1 Steel-concrete composite girder bridge (I-880 Replacement, Oakland, California) TABLE 12.1 Minimum Mechanic Properties of Structural Steel Material Structural Steel .
Types of composite: A) Based on curing mechanism: 1- Chemically activated composite 2- Light activated composite B) Based on size of filler particles: 1 - Conventional composite 2- Small particles composite 3-Micro filled composite 4- Hybrid composite 1- Chemically activated, composite resins: This is two - paste system:
It is shown that for the studies conducted on one-way frames, composite CFT column construction with beam end-plate connections was generally more expensive than conventional steel column construction. INTRODUCTION A steel-concrete composite structural member contains both structural steel and concrete elements
ISO 14001:2004 and ISO 9001:2000 15 Annex B (informative) Correspondence between OHSAS 18001, OHSAS . Standard vi List of tables Table A.1 – Correspondence between OHSAS 18001:2007, ISO 14001:2004 and ISO 9001:2000 15 Table B.1 – Correspondence between the clauses of the OHSAS documents and the clauses of the ILO-OSH Guidelines 20 Summary of pages This document comprises a front cover .
