Asian journal of civil engineering
Volume:16 Issue: 7, Dec 2015

This paper describes a series of experiments conducted on cold-formed built-up square sections with intermediate flange and web stiffeners under axial compression with hinged end conditions. The specimens were formed using angle sections with edge, intermediate flange and web stiffeners connected by self- tapping screws. 27 columns were tested by varying the cross section dimensions of the specimen. The column lengths of the specimens varied from 840 mm to 2240 mm. Tensile coupon tests were conducted to find the material properties of the sections. Local buckling, distortional buckling, flexural buckling and interaction of these buckling were observed during the test. The column strengths obtained from the experiments were compared with the design strength calculated using direct strength method (DSM) in the North American Specification for cold-formed steel structures. The reliability of the DSM method was evaluated using reliability analysis. It is shown that, strengths calculated by using direct strength method are reliable and slightly unconservative. Finally, a design recommendation was proposed for DSM to calculate the ultimate strength of cold formed built-up square sections with intermediate flange and web stiffeners.

Utilization of industrial waste products in concrete is gaining importance all around the world due to the rise of environmental consciousness. Rubber from worn out tyres is one such waste material thought of by the researchers. Recycled rubber aggregates produce more elastic concrete, which has higher resistance to specific loads (impact loads, vibration and cyclic loads) compared to conventional concrete. Therefore, in this paper, the effect of crumb rubber on properties of Ordinary Portland Cement (OPC) Concrete and Ternary Blended Cement (TBC) Concrete of M40 grade are investigated with fly ash and silica fume as powders along with cement. TBC concrete has shown high energy absorption and higher strengths compared to OPC concrete.

The idea of expansion has a long history in mathematics and structural mechanics. In mathematics, Whitehead [1] used an expansion process for the characterization of topological spaces. In structural mechanics, Müller Breslau and Henneberg [2,3] employed simple expansion for the classification of trusses. In this paper, the latter idea is generalized and applied to the calculation of degree of statical indeterminacy (DSI) and degree of kinematical indeterminacy (DKI) of different types of skeletal structures, such as rigid-jointed planar and space frames, pin-jointed planar trusses and ball-jointed space trusses. Such a calculation not only simplifies the evaluation of DSI and DKI, but it also provides an insight to the problem of the formation of sparse statical and kinematical basis matrices required for efficient analysis of structures by the force method and displacement approach, respectively.

Self-compacting concrete (SCC) due to several economical and technical advantages is increasingly used in construction industry. It can be improved on strength behavior when the fibers are added. Although the workability as a significant factor for this concrete must be maintained. This investigation experimentally evaluated the effects of steel and PET (polyethylene terephthalate) fibers separately on the properties of either fresh or hardened SCC. Fresh properties of concrete have been investigated by slump flow, V-funnel and L-box tests. Hardended properties were tested for compressive strength, splitting tensile strength, flexural strength, shrinkage and ultrasonic pulse velocity (UPV) tests. The results showed that 30 Kg/m3 Steel and 3 Kg/m3 PET fibers can be considered as suitable contents regarding to fresh and hardened properties of SCC. However, the addition of PET fibers have caused a slight decrease in compressive strength.

This study is focused on behaviour of bolted cold formed steel angle members under tension. L-shaped specimens with different dimensions tested by using single-line bolted connections were discussed in this study. Sixteen numbers of single plain and lipped angle specimens were tested in a Universal Testing machine using black bolts of 10mm diameter. The thickness of the steel sheet used in this study was 2 and 3mm. Various types of connection failure, Load vs deflection behaviour were studied. The comparisons are made between the test results and predictions computed based on specifications using BS 5950(Part V)-1998, AS/NZS 4600:2005.

In this paper, an analytical approach is presented for free vibration analysis of tall structures with various lateral resisting systems and variable properties along the height. Primarily, according to replacement beam theory, the tall structure is modeled by a non-prismatic Timoshenko beam with shear and global bending stiffness which is supported laterally by a beam with local bending stiffness. The vibration frequencies of shear beam, bending beam and as well as Timoshenko beam are calculated and the vibration frequencies of tall structure are obtained by combination of the obtained vibration frequencies. Presented analytical approach is also used to calculate the mode shape functions and internal forces of the tall structure. The efficiency and accuracy of the current approach are confirmed through comparison of the numerical results to those obtained using available finite-element software and other references.

The effect of superplasticizer on various properties of concrete made with 100% recycled coarse aggregate (RCA) was studied in this paper. Two grades: normal strength concrete (M20) and medium strength concrete (M30) were designed with 100% recycled coarse aggregate with and without addition of superplasticizers. Controlled concrete mixes of same grades (M20 & M30) with and without addition of superplasticizers were also prepared with natural aggregate to evaluate the behaviour of recycled aggregate concrete in comparison to normal concrete. Workability, compressive, split tensile and flexural strengths; stress-strain characteristics, rebound number and ultrasonic pulse velocity tests were performed during the investigation. The test results reveal that with the addition of superplasticizer in RAC, it may be possible to achieve the normal and medium strength concrete (M20 and M30) as it was achieved the same with natural aggregate without addition of superplasticizer.

In the present study, light expanded clay aggregate (LECA) and fly ash aggregate (FAA) were used as self-curing agents in self-compacting concrete (SCC). FAA and LECA were used as an internal water reservoir. The coarse aggregate was replaced by 5% LECA and the fine aggregate was replaced by the various proportions of FAA from 0% to 50% by weight of fine aggregate. Test results showed that SCC mix with 40% FAA attained higher strength under conventional water curing. Besides, SCC mix with 30% FAA showed higher strength under self-curing. It is concluded that SCC with LECA and FAA could be successfully used as self curing agents where conventional curing is not effective.

Evaluating strong ground motion propagation in soil is one of the issues in geotechnical engineering which has caused heated debate among engineers and it is utilized for computing ground surface motions. This paper, presents analyses to acquire hazard curves and uniform hazard spectra for Andimeshk site considering the influences of the site and soil characteristics. Several recorded accelerograms of the past earthquakes at the abovementioned site and adjacent zone (radius of 200Km) are used to determine the region-specific source parameters. Seismic hazard curves are first acquired by using the Crisis software based on the records of Andimeshk catalog and then uniform hazard spectra obtain considering site effects by modeling the soil profile of Andimeshk and performing the nonlinear analysis in time domain by DeepSoil software. The results are compared to Iranian Seismic Code and significant differences are shown. Moreover, this paper provides further suggestions for using new spectrum (2/3 of 2% in 50 years) for engineering design purposes.