Asian journal of civil engineering
Volume:18 Issue: 5, Aug 2017

In this paper, a new nature-inspired population-based meta-heuristic algorithm is presented. The algorithm, called Cyclical Parthenogenesis Algorithm (CPA), is inspired by reproduction and social behavior of some zoological species like aphids, which can reproduce with and without mating. The algorithm considers each candidate solution as a living organism and iteratively improves the quality of solutions utilizing reproduction and displacement mechanisms. Mathematical and engineering design problems are employed in order to investigate the viability of the proposed algorithm. The results indicate that the performance of the newly proposed algorithm is comparable to other state-of-the-art meta-heuristic algorithms.

This paper presents development of spectral finite strip method for dynamic analysis of thin rectangular plates subjected to moving loads. Dynamic stiffness matrix of a plate strip in frequency domain is derived. For obtaining dynamic response of plate subjected to moving loads, both Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) are utilized. Numerical examples are presented to validate accuracy of the presented method.

Instead of the complicated non-linear response history analysis (NL-RHA), engineers are more likely to use simplified non-linear static procedures (NSPs). Because of various deficiencies of the conventional pushover procedures, different researchers presented advanced NSPs. Some of these advanced NSPs used first two modes of the structure and the others offered using more than first two modes. In this study, the higher mode contributions in the structural responses are investigated through NSPs including modal pushover analysis (MPA) and modal shear-based pushover (MSP) procedures for far-field and near-field ground motions. Finally, the optimized number of considered modes for different situations is suggested.

The early age behavior of concrete is a complex phenomenon because of the chemical, physical and mechanical characteristics that evolve in time, with climate being one of the essential conditions influencing this evolution. The objective of our present work is based on the study by numerical simulation, in 3- dimensions, of concrete behavior at an early age during the first 24 h of hydration under severe conditions of temperature and wind speed using a COMSOL Multi-physics.
The temperature was maintained at 55°C for the first 7 h, then from the 8th hour to 24th hour decreasing down to 25°C, with a 12km/h wind speed. The model describes two divided domains air and the concrete slab. The obtained results allow us to better understand the temperature variation phenomena in the slab by heat transfer taking into account the release of heat due to the exothermic reactions of cement hydration as well as the influence of a high wind speed, while varying the thickness of the slab studied and the w/c ratio.

Dynamic ratcheting (DR) is a phenomenon that occurs in nonlinear systems and one aspect of complicated nonlinear dynamic behaviors. DR behavior have a strong effect on the magnitude of plastic deformation in single-degree of freedom (SDOF) hysteretic damping systems, therefore there is need to precisely examine this phenomenon caused by earthquake excitations. DR-inducing frequencies of ground excitation are called “active frequencies”. A new method is proposed in this study to identify active frequencies of DR-inducing ground excitation using wavelet transform. The identification method is based on a reduced dimensionality and filtered frequency content of original record according to closeness of displacement time history of SDOF system under both original and modified record. The objective of this study is divided into two main parts: In the first part of this study, applying the proposed method for a DR- inducing ground motion and it was an example that how the method could be utilized to identify active frequencies of DR- inducing ground motion. The second part of this study is devoted to identify the DR- inducing ground motions between a set of ground motions records, containing 504 records up to the year 2012, in Iran. The reduced representation of ground motion is a useful technique for extracting active frequencies from ground motion.

The study herein presents the investigation on the cyclic response of post-tensioned prestressed concrete beam retrofitted with precured fibre reinforced polymer plates with different orientations and thicknesses. The load carrying capacity and deformation capacity of the precured glass fibre reinforced polymer plates were evaluated. The experimental results revealed that the prestressed concrete beams retrofitted with unidirectional glass fibre reinforced polymer plates attained a maximum increase in ultimate load. The stiffness has greatly reduced in post-tensioned prestressed concrete beam as the load progresses till the failure of beams. The retrofitted prestressed concrete beam sustained more number of cycles than the control prestressed concrete beam. The prestressed concrete beams retrofitted with fibre reinforced polymer showed a delamination and rupture of glass fibres.

The present study focuses on the performance of a 0.6 scale new moment resisting precast concrete beam-column connection subjected to cyclic loading by conducting experiments. The precast connection considered for this study was a beam-column connection where beam is connected to column with inverted E corbel. The experimental results of the precast specimens have been compared with that of the reference monolithic connection. The performance of the precast connections in terms of the ultimate load carrying capacity, load-displacement hysteresis behaviour, energy dissipation capacity, equivalent viscous damping ratio and ductility factor were compared with that of the monolithic beam-column connection.

Historical masonry structures frequently present an unsatisfactory behavior under exerted seismic loads.Because ofcultural values and vulnerability of these kinds of structures to seismic loads, they must be protected and retrofitted in a way which is both safe and non-destructive. In this paper, Zein-o-din minaret, one of the Iranian historical structures in Kashan built in13th century was selected in order to find a solution which can be applied to other similar historic towers. First, some information on the geometric characteristics of the minaret was collected and afterwards by conducting related experiments, the mechanical properties of the materials were determined. Then, using ambient vibration testing, the structural dynamic behavior such as the main natural frequency of the minaret was obtained. Dynamic analyses of this minaret were implemented through ABAQUS software and the resulted natural frequency from the numerical analysis was compared to the corresponding value from ambient vibration testing. Finally, by utilizing the verified numerical models, various options were proposed for rehabilitation of the Zein-o-din minaret. The outcomes illustrated that using high strength grout for filling the gaps between the bricks and seams would be the best solution for renovation of this historical minaret.

Assessing the effects of near-field ground motions shows that the directivity effects in velocity histories of these ground motions leads to one or more impact pulses with large amplitudes that yield in increased ductility demand of rigid structures placed in near source areas. In this study, the cumulative Park-Ang damage index has been used for comparing the damage potential brought about by the two acceleration components of ground motions that are normal to the fault direction or parallel to it. Two-dimensional steel moment frames with 4, 7, 10, 15 and 20 stories have been nonlinearly modeled and analyzed using the Opensees software. The investigations have been performed in different performance levels corresponding to target ductility values equal to 2, 3 and 4. The utilized ground motion records include 40 records divided equally to the normal and parallel sets regarding the fault direction. The scaling of the record sets have been performed so that the studied frames have met the considered target ductility values. The results show that the lower stories are more frequently affected by the normal records, therefore, more intense damages are attributed to these records. That is while, the parallel records have been found to affect mostly intermediate and especially upper stories. The results also show that increasing the target ductility values leads to an increased damage potential for the studied structures.

This paper presents a finite element analysis of the response of a grouted splice sleeve under tension. The connection is modelled in different bar embedded lengths (75, 125 and 175 mm) and sleeve diameters (50, 65 and 75 mm), and analysed by using ANSYS®. The results obtained include the load-displacement response, mechanical properties and failure mode. These results are verified with the experimental results, and found to have a variation exceeding ±10%. Nevertheless, based on the understandings obtained through modelling, the thickness and diameter of the sleeve can be reduced to 2.5 and 40 mm, respectively, to reduce the material cost by 60% without causing any decrease in the tensile capacity.