Asian journal of civil engineering
Volume:18 Issue: 2, Mar 2017

In the present research, inelastic behavior of cold-formed steel frames with strap bracing was studied under cycling loading using finite element (FE) method. All of frame members including tracks, studs, and braces were modeled using two dimensional shell elements. The screw connections of braces to studs were simulated using connector elements. The shear and axial strength of screws were determined considering the screw pull-out and hard contact of braces to studs. The failure mechanism and resultant base shear were compared with the experimental measurements. The results showed a good agreement between developed FE model and experimental data. The shear and tensile forces of screws at different stages of loading, as well as the behavior in elastic and inelastic regions, were evaluated using the developed model. It was concluded that the buckling and yielding of braces are the most effective factors on the cyclic behavior of cold-formed steel frames; and that cyclic behavior of cold-formed steel frames with strap bracing can be accurately determined using the proposed FE model.

This paper contains geometric nonlinear shallow shell of revolution analysis under static loading. Consideration is given to the action of evenly distributed vertical force for various support types. Critical force and stress are found considering geometric nonlinearity (flexibility) of steel and ferro-cements shell. Critical force coefficient and stress of shells are found by Bubnov-Galerkin method. Stresses, critical force - shape parameter dependence are presented.

Wrapping technology is one of the effective ways of strengthening concrete elements. Several researchers reported the effectiveness of Glass fiber reinforced polymers and carbon fiber reinforced polymers for improving the strength of the concrete elements. Wrapping on three sides is one of the effective methods for strengthening the beams supporting slabs. Very less literature is available on the strength enhancement of “U” wrapped concrete elements subjected to torsional loads. In this investigation an attempt is made to quantify the improvement in twist of “U” wrapped rectangular concrete members subjected to torsional loads “U” wraps. Carbon fiber has taken the driver‟s seat as a wrapping material in developed countries. From cost effective point of view ferrocement can be used as a wrapping material in place of FRP. Beams were cast with different number of mesh layers, different torsional reinforcement, different grades of concrete and mortar. The beams were analyzed with MARS. Analytical model was developed to predict secant stiffness at cracking torque. The predictions for twist at cracking torque are in good agreement with experimental test results.

The quality of concrete of the most of Algerian construction sites is often low. In the case of low compressive strength results, non-destructive tests such as rebound hammer and ultrasonic pulse velocity are performed to check these results. Correlations curves from either equipment manufacturers or from the literature are used by quality control laboratories in order to estimate concrete strength. The estimation of strength based on these correlations is often subject to confusion and contradictory results when compared with the core test results. This clearly shows the need for appropriate correlations for concrete made with local materials and under local environmental conditions. The main objective of this paper is to propose appropriate simplified correlations for concretes made by local materials and for compressive strength levels reflecting the conditions and current practices on building sites in Algeria. This study presents some models established between destructive and individual or combined nondestructive tests (Rebound hammer and ultrasonic pulse velocity) in order to obtain a better estimation of concrete strength on site. The results show the reliability of the combined methods and the important difference in concrete strength estimation as compared to the models available in the literature.

Different arbitrary shapes of plates are used in civil, marine and aerospace engineering. They may undergo large deflections due to large transverse loads and hence, the nonlinear analysis must be carried out on the structures. In view of the above an elegant finite element formulation is developed for analyzing the geometrically nonlinear static behavior of arbitrary shaped thin plates using superparametric element. This element is capable of accommodating different geometries just like isoparametric element. The efficacy of the element is shown by presenting different numerical examples.

The study presented in this paper develops a statistical model which could predict the failure mode of an RC interior beam-column connection under seismic load. A database has been compiled by assembling the details of 150 test specimens loaded to failure under quasi-static cyclic loading, selected from past research. Multinomial logistic regression was employed to develop the model to predict the joint response with three possible outcomes such as shear failure, beam failure and beam-joint failure. Performance analysis of six interior connection specimens, designed to be seismic-resistant with varying aspect ratios, concrete compressive strength, and beam bar yield strength, has validated the statistical model.

This paper evaluates comprehensively seismic inelastic demand of eccentrically braced frames (EBFs) with vertical members. In this configuration, two zipper-struts are added to connect each end-point of the shear links in all stories. To investigate the efficiency of this system versus conventional EBFs, pushover and incremental dynamic analyses were performed. Results show that in this system, the fully-plastic hinges are almost simultaneously developed in all stories while damage in a conventional EBF concentrates only in a few floors. Moreover, the ductility and energy absorption capacity of this configuration are noticeably higher than those of the conventional EBFs.

The steel tubular column filled with steel reinforced concrete (SRCFT), is formed by inserting a steel section into a concrete filled steel tube. In the current paper, a new shape, namely Castellated Cruciform Steel Section (CCSS), for reinforcing of CFT columns has been proposed to improve the compressive strength and hysteresis behavior of these columns under moderate and severe earthquake excitations. A comprehensive study has been conducted to investigate the strength of SRCFT columns reinforced with castellated and traditional cruciform steel sections, made with thin-walled, welded I-section. The paper describes and presents the results of the testing of four small size (155 mm*155 mm) and short column specimens. The experimental results indicate that the new steel section causes high strength and better post yield behavior of SRCFT columns, because of the increase of shear and bending strength, torsion resistance and interaction between the hollow steel section and concrete. In addition, the axial compressive capacities of those steel sections are investigated in a numerical way in the current study. The obtained results of nonlinear analyses of these columns revealed that strength and buckling behavior of castellated cruciform steel columns far outweighs and is more appropriate than that of the traditional cruciform steel columns.

Punching shear of flat slabs is a local, brittle failure that may occur before the more favourable ductile flexural failure. This study develops an artificial neural network (ANN) modelling for the prediction of punching shear strength of flat slabs using 281 test data available in the literature. The paper also evaluates the current design codes for the prediction of punching shear capacity of reinforced concrete flat slabs using the test results reported in the literature. Furthermore, a parametric study was conducted using the trained ANN to establish the trend of the main influencing variables on the punching shear capacity of flat slabs. The results were, then, employed to develop a simplified equation for the prediction of the characteristic/design punching shear strength of flat slabs based on the design assisted by testing approach proposed in Annex D of EN 1990.

In this paper shape and size optimization of truss structures subjected to frequency constraints is addressed utilizing a newly developed multi-agent meta-heuristic algorithm called Tug of War Optimization (TWO). The algorithm considers each candidate solution as a team participating in a series of rope pulling competitions. Frequency constraint structural optimization corresponds to highly non-linear, discontinuous, and non-convex search spaces including several local optima. Such problems call for properly balanced competent optimization algorithms. Here, viability of TWO is demonstrated using four numerical examples.