Purpose: Throughout the years numerous studies have been made that concludes thatcombining steel and wood results in improved strength. Under optimal conditions woodis an effective structural material, as it’s both cheap and durable. Steel on the other handunder right circumstances has considerably higher strength than wood. To combinewood and steel has over the last years gathered more attention. Studies shows thathybrid structures can lead to an economical advantage when building multiple storeybuildings, as it can replace or complete pure steel frames. The purpose of this paper isto increase the knowledge and understanding of how steel and wood cooperate and tofind out the advantages and disadvantages of using a flitched beam, as well as compareit’s strength to structural wood and glulam.Method: The paper comprises a quantitative study with two different kinds of datacollection methods, Literature studies and calculations. The literature study consists ofscientific papers and papers published by known institutions and will help the paperanswer the first issue. The calculations has been made with the help of Tekla Tedds,which follows the Eurocode design principles. Which will help the authors answer bothof the papers issues.Findings: The paper has found that the flitch beam has improved strength overstructural wood and glulam, but a significantly higher price. The flitch beam also has amuch higher self weight than structural wood and glulam. The flitch beam can also spanlonger than structural wood and glulam with the same applied load.Implications: The study have concluded that it’s hard to motivate the usage of flitchedbeams in floor designs as they have such high price. The flitch beam has higher strengththan both structural wood and glulam. Which makes the flitch beam a good option asload bearing beam that requires slim dimensions. The added strength of the flitch beamcan motivate the high price under the right circumstances.Limitations: The paper has limited the calculations to an enclosed environment andwill not take moisture or any other type of exposure in to account, As a dry indoorenvironment is optimal for both steel and wood. The calculations the paper uses arebased on Eurocode and all other forms of dimension principles will not be taken intoaccount. / Syfte: Genom åren har forskning gjorts som tyder på att när man kombinerar stål ochträ kommer det bidra till en ökad hållfasthet. Under optimala förhållande är trä ettotroligt effektivt och bra alternativ inom byggande då det är billigt och tåligt. Närstålbalkar däremot placeras i optimala förhållande kan de bibehåll betydligt mer ochstörre krafter än vad trävirke kan göra. Att kombinera stål och trä har de senaste årethaft ett ökat intresse. Studier visar att hybridbalkar kan vara till stor ekonomisk fördelvid byggnation av flervåningshus, då det kan ersätta eller komplettera rena stålstommar.Syftet med arbete är att öka kunskapen och förståelsen för hur stål och trä samverkarsamt ta reda på för och nackdelar hos de stålförstärkta träbalkarna samt jämföra deraslastkapacitet med konstruktionsträ- och limträbalkar.Metod: Arbetet omfattar en kvantitativ studie där två typer av datainsamlingsmetoderhar använts. Dessa två typer är beräkningar samt litteraturstudier. Litteraturstudienbestår av vetenskapliga artiklar som har hjälpt besvara en av frågeställningarna.Beräkningarna har använts för att besvara båda frågeställningarna, de har gjorts idimensioneringsprogrammet Tekla tedds som följer alla Eurocodes beräknings- ochdimensioneringsregler.Resultat: Resultaten visar på att den stålförstärkta träbalken har högre kapacitet änlimträ och konstruktionsvirke, både med hänsyn till nedböjning och brott men betydligthögre pris och egentyngd. Den stålförstärkta träbalken klarar även av längrespännvidder vid samma belastning.Konsekvenser: Utifrån de resultat rapporten kommit fram till är det svårmotiverat attanvända sig av de stålförstärkta balkarna i bjälklag på grund av det höga priset Denstålförstärkta träbalken klarar dock av högre laster än vad konstruktionsvirke och limträgör, vilket kan göra balken användbar som avväxlingsbalk. Att använda denstålförstärkta träbalken som avväxlingsbalk kan motivera det höga priset då den kanhålla mindre dimensioner än limträ och konstruktionsvirke vilket kan vara önskvärt iolika sammanhang.Begränsningar: De begränsningar som sattes för rapporten var att utesluta alla typerav miljörisker på balkarna som tillexempel fukt och solljus vid beräkningarna, då entorrmiljö är en optimal miljö för både trä och stål. Beräkningarna som arbetet baseraspå grundar sig på Eurocodes dimensioneringsregler. Andra typer av dimensioneringsprinciper har uteslutits.

Until recently, the hot-rolled steel members have been recognized as the most popular and widely used steel group, but in recent times, the use of cold-formed high strength steel members has rapidly increased. However, the structural behavior of light gauge high strength cold-formed steel members characterized by various buckling modes is not yet fully understood. The current cold-formed steel sections such as C- and Z-sections are commonly used because of their simple forming procedures and easy connections, but they suffer from certain buckling modes. It is therefore important that these buckling modes are either delayed or eliminated to increase the ultimate capacity of these members. This research is therefore aimed at developing a new cold-formed steel beam with two torsionally rigid rectangular hollow flanges and a slender web formed using intermittent screw fastening to enhance the flexural capacity while maintaining a minimum fabrication cost. This thesis describes a detailed investigation into the structural behavior of this new Rectangular Hollow Flange Beam (RHFB), subjected to flexural action The first phase of this research included experimental investigations using thirty full scale lateral buckling tests and twenty two section moment capacity tests using specially designed test rigs to simulate the required loading and support conditions. A detailed description of the experimental methods, RHFB failure modes including local, lateral distortional and lateral torsional buckling modes, and moment capacity results is presented. A comparison of experimental results with the predictions from the current design rules and other design methods is also given. The second phase of this research involved a methodical and comprehensive investigation aimed at widening the scope of finite element analysis to investigate the buckling and ultimate failure behaviours of RHFBs subjected to flexural actions. Accurate finite element models simulating the physical conditions of both lateral buckling and section moment capacity tests were developed. Comparison of experimental and finite element analysis results showed that the buckling and ultimate failure behaviour of RHFBs can be simulated well using appropriate finite element models. Finite element models simulating ideal simply supported boundary conditions and a uniform moment loading were also developed in order to use in a detailed parametric study. The parametric study results were used to review the current design rules and to develop new design formulae for RHFBs subjected to local, lateral distortional and lateral torsional buckling effects. Finite element analysis results indicate that the discontinuity due to screw fastening has a noticeable influence only for members in the intermediate slenderness region. Investigations into different combinations of thicknesses in the flange and web indicate that increasing the flange thickness is more effective than web thickness in enhancing the flexural capacity of RHFBs. The current steel design standards, AS 4100 (1998) and AS/NZS 4600 (1996) are found sufficient to predict the section moment capacity of RHFBs. However, the results indicate that the AS/NZS 4600 is more accurate for slender sections whereas AS 4100 is more accurate for compact sections. The finite element analysis results further indicate that the current design rules given in AS/NZS 4600 is adequate in predicting the member moment capacity of RHFBs subject to lateral torsional buckling effects. However, they were inadequate in predicting the capacities of RHFBs subject to lateral distortional buckling effects. This thesis has therefore developed a new design formula to predict the lateral distortional buckling strength of RHFBs. Overall, this thesis has demonstrated that the innovative RHFB sections can perform well as economically and structurally efficient flexural members. Structural engineers and designers should make use of the new design rules and the validated existing design rules to design the most optimum RHFB sections depending on the type of applications. Intermittent screw fastening method has also been shown to be structurally adequate that also minimises the fabrication cost. Product manufacturers and builders should be able to make use of this in their applications.

The results of a pilot series of tests, designed to investigate the influence of the presence of a composite floor slab on the performance of steel beam-to-column connections, are reported. Direct comparisons against equivalent bare steel tests show improvements in moment capacity (up to 15 times), with reinforcement anchorage being the main controlling factor. Thus joints to internal columns where the deck runs parallel to the beams and relatively small numbers of bars supplement the basic mesh reinforcement may be expected to give the best performance.