Lakusic et al.  developed a study about the buckling curve for lateral-torsional buckling resistance of cas- tellated beams considering an experimental and a numerical analysis based on finite elements models. Accord- ing to the obtained results, the use of the buckling curved for welded beams -, category in which castel- lated beams are included, instead of the buckling curve c for rolled sections, leads to a severe value for the reli- ability index target i.e. 3.8 associated to the structure class RC2. Radic et al.  performed a numerical analy- sis of castellated beams considering two different procedures for the calculation of the elastic critical moment for lateral torsional buckling comparing FE results and Eurocode 3 procedures -. The research results show that the web opening of the castellated beams has little influence on the value of the elastic critical mo- ment for the lateral-torsional buckling. Other works can be cited concerning the web openings beams behaviour. Basher et al.  investigated the effects of circular or square web openings on the ultimate strength of horizon- tally curved composite plate girders. Hagen et al.  and Hagen and Larsen  performed some numerical simulations in order to provide data for the development of a design model for the shear capacity of steelgirders with web openings, with and without transverse stiffeners and opening reinforcements. Lagaros et al.  studied an optimum design of 3D steel structures having perforated I-section beams. Lian and Shanmugan  reported that on plate girders curved in plan containing centrally placed circular web openings, the ob- served failure mechanism in the tests was similar to that observed in plate girders without web openings,
In this experimental program, a series of thirteen small-scale deteriorated steelbeams were tested to examine the behaviour of the unstrengthened and strengthened deteriorated steelgirders. Each specimen was cut to a length of 2.0 m and was tested with a clear span of 1.6 m. The clear span selected to have a (h/L) ratio equal to 0.1, where (h/L) is the ratio of the total depth to the clear span of the tested beam. The tested beams were divided into four group: group one (Gl) consisted of four beams with different percentage of deterioration to investigate the behaviour of the deteriorated beam and to determine the remaining capacity, while the other three groups were designed to evaluate the effectiveness of the proposed retrofit schemes. Four beams were strengthened with CFRP sheets bonded to the tension flange and were tested in group two (G2) to characterize the static behaviour of steelbeams strengthened with CFRP sheets. Group three (G3) consisted of two beams strengthened with high-modulus CFRP laminate strips, which were externally bonded to the bottom flange of the tested beam. Unbonded CFRP sheets were used to strengthen three deteriorated steelbeams in group four (G4) by using ductile anchorage system.
The SPGs are structural bending members in which the appropriate combination of steel plates is used to make them. In the cases when existing rolled steel profiles are not able to withstand the applied loads to the bending members, employing the beams made of plates is inevitable. In addition to having good performance against the applied loads, the SPGs are also economically more cost-effective than the rolled steelbeams. Meanwhile, the SPGs vastly serve as main structural members in the construction of bridges and overpasses with relatively large spans, ordinary buildings with large spans as well as frames of industrial structures.
Ferritic stainless steel, which has low or even no nickel content, is considered to be a good alternative to austenitic and duplex stainless steels with a lower initial material cost, which is largely a function of nickel content. Although the lower nickel content results in reduced ductility and corrosion resistance compared to austenitic stainless steel, but ferritic stainless steel offers higher 0.2% proof stress of 36.3-47.9 ksi (250-330 MPa) in the annealed condition (CEN 2009). One of the main elements is chromium, which contributes to a minimum of 10.5% in ferritic stainless steel (Cashell and Baddoo 2014). The most commonly used ferritic grades are EN 1.4003 and EN 1.4016. Ferritic grades EN 1.4509, EN 1.4521 and EN 1.4621 can be obtained by adding stabilizing elements such as niobium and titanium. The ferritic grades with stabilizing elements offer similar corrosion resistance to austenitic grades EN 1.4301 (304) and 1.4401 (316) (Cashell and Baddoo 2014). The current European design specification (CEN 2006) only covers ferritic grades EN 1.4003, EN 1.4016 and EN 1.4512. Generally, the ferritic stainless steel can provide an attractive, competitive and economical alternative for the use of stainless steel.
As an alternative to strengthening or repairing steel structures with welded or bolted plates, bonded CFRP laminates can be used. The improvements that can be expected are increased stiffness and strength and an extension to the fatigue life of the strengthened member. One advantage of using CFRP is its high tensile strength and stiffness compared with its low self-weight. The strengthening scheme is less labour intensive compared with other existing techniques, which makes it even more interesting as a system for repairing and/or strengthening existing structures. Laminate bonding relies on the strength of the adhesive layer. Both theoretical work and laboratory tests have shown that this strength is governed by stresses along the bond line, which occur due to differences in strain, caused by external loads or the difference in coefficients of thermal expansion between the steel beam and the laminate. Concentrations of interfacial stresses occur in the vicinity of the geometric discontinuities; in particular, at the end of a bond line but also at the location of a crack in the substrate or a bond defect in the adhesive layer.
For multiple heat/cool cycles (Table 1), steps 1 - 7 are repeated for each heat/cool cycle separately, with the results from step 7 for a specific cycle constituting the initial conditions for the following cycle. If for example the girder from the previous paragraph (heated to 299C (570F)) was cooled to ambient conditions, then heated to 354C (670F), the temperature increase in the 2 nd heating cycle ( ∆ T = 354C – 21C = 333C (670F – 70F = 600F)) would be subdivided into six intervals ( ∆ T i = 55.6C (100F)) and thermal analysis (steps 1 – 7) performed with the results from the final step 7 (after cooling, previous paragraph) being the initial value. Such an analysis was carried out by Brockenbrough (Brockenbrough 1970a) to compare experimental results obtained from the US Steel study. However, was this not the case for fabrication aids (Brockenbrough 1972, 1973) where only one heat/cool cycle was considered.
In the present work, high strength steel fibre reinforced concrete (HSSFRC) compositions were designed to provide an effective medium for the fibre reinforcement, in order to compet with steel stirrups for the shear reinforcement of HSC laminar structures. For the characterization of the post-cracking flexural behaviour, three point notched-beam bending tests were carried out according to the RILEM TC 162-TDF recommendations . Performing an inverse analysis with the obtained force-deflections curves, the fracture mode I parameters of the HSSFRC were obtained. These values were used to characterize the crack opening component of a smearead crack constitituve model, which can also simulate the crack sliding component with the current concept of shear retention factor or with the use of a crack-shear softening diagram. The influence of these two alternatives for modeling the crack shear behaviour, on the response of the tested beams is analyzed in the numerical session of the present paper.
Although standard joists, including KCS-Series, are designed specifically to support uniformly distributed loads applied to the top chord, research con- ducted by the Steel Joist Institute, using second-order inelastic analysis, has demonstrated that the localized accumulation of uniform design loads of up to 100 pounds within any top or bottom chord panel has a negligible effect on the overall performance of the joist, provided that the load is applied to both chord angles in a manner which does not induce torsion on the chords. Concentrated loads in excess of 100 pounds, or which do not meet the criteria outlined above, must be applied at joist panel points or field installed web members must be utilized as shown in the detail above. NMBS can provide a specially designed joist with the capability to take point loads without the added members if this requirement and the exact location and magnitude of the loads are shown on the structural drawings. Also, NMBS can consider the worst case for both the shear and bending moment for a traveling load with no specific location. When a traveling load is specified, the contract drawings should indicate whether the load is to be applied at the top or bottom chord, and at any panel point, or at any point with the local bending effects considered.
Modern civilization relies upon the continuing performance of civil engineering infrastructure ranging from industrial building to power station and bridges. A structural member composed of two or more dissimilar materials joined together to act as a unit is referred as composite structure. It is a powerful construction concept in which compressive strength of concrete and the tensile strength of steel are almost effectively used.
Abstract— Cellular beams became popular day by day as an efficient structural form in steel construction since their introduction. Their design and making process provides greater flexibility in beam proportioning for strength, depth, size and location of circular holes. The advantages of manufacturing these beams is to increase overall beam depth, the moment of inertia and section modulus, which results in greater strength and rigidity. Cellular beams are used as primary or secondary floor beams in order to achieve long spans and service integration. They are also used as roof beams, and are the best solution for curved roof applications, combining weight savings with a low-cost manufacturing process. Even though it had many advantages, some failure modes are associated with this type due to the presence of openings which is not presented on solid beams. Stiffeners are the best solutions to overcome the failures and resist buckling of beams. The first part of the research program focuses on the finite element modelling of cellular steelbeams with and without stiffeners in ANSYS software. In the second part of the research, finite element analysis program is used to perform elastic buckling analysis and predict critical loads of all steel cellular beams with and without stiffeners.
Due to certain limitations, further work is anticipated to focus on the optimisation of the opening shapes to be employed in the topo- logically optimum web opening architecture. Investigations of the ultimate load carrying capacities and the associated failure modes of the topologically optimum web opening conﬁgurations are deemed necessary. Following preliminary analyses, it was consid- ered of paramount importance to investigate the results of various complex loading and support conditions as well as depth-to-span ratios which may trigger other failure modes. Similarly to the design of cellular, castellated, and other perforated beams with var- ious standard and non-standard web opening shapes, the diversity of loading and supports conditions is to be dealt in the beam design process as well as introducing web and ﬂange stiffeners and/or using partial factors. In case of a steel frame structure is considered, the engineer is able to use the optimised beams as formed by the periodical position of the short sections, and treat each beam of the frame whilst using its equivalent static properties assuming constant cross-section along its length (Euler beam theory). The ultimate aim of this research project is the development of design equations that can be used in the routine design of beams employ- ing such optimum web opening conﬁgurations.
Based on the results presented and discussed, it is evident that the combinations of kenaf fibres and steel fibres have the potential to serve as part of shear reinforcement in reinforced concrete beams. The increase in strength of the reinforced concrete beams was not consistent during the testing as the beams with fibres were not fully dried and hardened. Therefore, the full capability and capacity of the fibre reinforced concrete in increasing the strength consistently with the increase in the fibre content was not observable. However, for the case of three beams with reduce in shear reinforcement, it can be clearly seen that the fibres improved the load carrying capacity of the beam up to 29% and 25% for KFSF-RC beams with V f
carbonization which subjects them to a high-temperature treatment of around 1,000 °C in an inert atmosphere. The carbonized fibres are further graphitized at a higher temperature of about 3,000 °C to achieve higher carbon content and higher Young’s modulus. The final step of the process is post- treating the relatively inert surfaces of the carbon fibres to improve their adhesion to composite matrices . The carbon fibre fabrics can be categorized in terms of their mechanical properties into ultra high modulus (>500 GPa), high modulus (>300 GPa), intermediate modulus (>200 GPa), low modulus (>100 GPa), and high strength (>4 GPa) carbon fibres . The disadvantages of carbon fibre fabrics are its high cost and chances of galvanic corrosion when used with other metals like steel. Glass fibre fabrics is made by mixing silica sand, limestone, boric acid, and other minor ingredients. The mixture is heated to about 1260 °C until it melts. The molten material is then passed through fine holes forming fine strands. The strands are then cooled, gathered, and wound. The fibres are then drawn to increase the unidirectional strength. The fibres are finally woven into various form for use in composites. Some additives are also used during the fabrication process to improve different properties of the fabrics as required. Glass fibre fabrics are ideal for use in the construction market because of their dimensional stability, high strength at low densities, good impact and corrosion resistance and good insulating properties. However, glass fibres are sensitive to moisture especially in presence of salt and alkalinity. Most common Glass fiber fabrics used are E-glass (Electrical type) and S-glass (High-performance type) .
In general, the behavior indicates that using a closer stirrup spacing increases the overall shear capacity of the beam. Furthermore, using a smaller spacing reduces the transverse strain at any given load level. This is particularly clear for the C-M and M-M cases, however is not as defined for the C-C case. While beam C-C-6 yields at a much lower load level, resulting in significantly higher transverse strains than the other two beams, it has the same shear capacity as C-C-3. This could partially be attributed to the higher a/d ratio present in testing beam C-C-6 It is important to note that these comparisons do not account for the changing shear span to depth ratio between beams with six inch stirrup spacing, and those with three and four inch spacing.
construction is to make two materials to combine together in resisting the external load. An experimental investigation was carried out on 8 simply supported beam specimens to understand the flexural performance. Two beams were control beams and the remaining six beams were composite beams. Six composite beams were provided with different configuration of the shear transfer mechanism. The cross section of the beams were kept such that, span to depth ratio varied from 6 to 9 and shear span to depth ratio varied from 2.5 to 3. The grade of concrete was M30 and the grade of steel was kept Fe415. Composite action is predominant over the fundamental mechanism of load slip, load transfer and shear transfer. Sound bond between the two materials under flexure- shear is to be achieved during the design and construction of composite structures. The connection between the steel and the concrete section of this work was established using T-shear connectors. T-shear connectors were used in three different configurations. The beam specimens were tested by subjecting them to two point loading. The cracking load, load-deflection behavior, ultimate load and failure pattern of the beam specimens were studied. The experimental results indicate that, the load carrying capacity of the composite beams were increased by 38.09% to 214.28%. The experimental results have also indicated that, the span to depth ratio and shear span to depth ratio have an influence on the increase in the load carrying capacity of the composite beams. The mid-span deflection at ultimate load for the composite beams were reduced by 50% when compared to control beams. It was observed that, the steel-concrete composite beams failed due to shear-compression failure in the shear span. Key Words: Composite beams, shear connector, Cracking load load-deflection, ultimate load etc.
The design of unbraced cold-formed steelbeams must consider lateral-torsional buckling due to the low torsional stiffness associated with open cross-sections. The American Iron and Steel Institute incorporated design equations for the critical elastic lateral-torsional buckling stress in the North American Specification for the Design of Cold-Formed Steel Members. These equations are based on elastic theory for singly-symmetric and doubly-symmetric sections. However, the equation for point-symmetric sections is only a rough approximation. Furthermore, there are no provisions for lateral-torsional buckling of non-symmetric sections, or sections oriented to non-principal axes. This paper investigates and develops a general formulation of the lateral-torsional buckling equation to broadly cover all cold-formed steel cross-sections.
The gravel used in this work was local one having specific gravity and volume weight of 2.53 and 1.52 gm/cm 3 , respectively and maximum nominal size of 20 mm. Sand from natural sources having a specific gravity 2.63, volume weight and fineness modulus of 1.73 gm/cm 3 , 3.19, respectively, were used. Ordinary Portland cement was used in this study, the specific gravity 3.15, surface area 3200 cm 2 /gm, initial setting time 2.25hr and final setting time 4.25 hr. The concrete mix was designed to have a 28 days cubic strength of about 27 N/mm 2 . The concrete mix proportion is details in table (3). Longitudinal reinforcing steel and steel plate (CFS) were mild steel of grade 24/35.
In the current research, distortional buckling of cold-formed stainless steel open-section beams was investigated. Four-point bending tests of eight C-section stainless steelbeams, made of S30401 alloy, were carried out with global and local buckling precluded by careful design of specimen and test rigs. A detailed finite element model based on ABAQUS was developed and verified against test data. Parametric study was carried out with the verified model, covering four types of sections (C, Z, SupaCee, and SupaZed), three stainless steel alloys (S30401, S44330, S32101), and a series of section slenderness. A convenient method to identify distortional buckling point in either experimental or numerical study was discussed. Existing design formula for stainless steel and steel structure were assessed with the available data. Revised formula based on Direct Strength Method was proposed.