Asian journal of civil engineering
Volume:12 Issue: 3, Jun 2011

A method is used to obtain the fundamental frequency of a retaining wall quite accuratelyand carry out a dynamic analysis of such wall based on modal response technique. Thepresent procedure establishes both the general and particular cases of dynamic response ofretaining wall based on improved Rayleigh-Ritz method. The wall will be assumed to be aflexural member. The fundamental frequency of the retaining wall with soil mass has beencomputed. The results based on proposed method are then used to back propagation neuralnetwork (BPN). In the present work, the fundamental frequency of a retaining wall iscalculated by BPN. A significant benefit of BPN is its ability to learn relationships betweenvariables with repeated exposure to those variables. Therefore, instead of deriving ananalytical relationship from mathematical formulations, the BPN learns the relationshipthrough an adaptive training process. Numerical example shows the merit of the BPN.

This paper presents the seismic behavior of exterior beam-column joints with square spiralconfinement in the joint region along with different reinforcement detailing for anchorage of beam bars, confinement in joint and additional reinforcement in beam and column. Thebehaviour of specimen with square spiral confinement (SS) in the joint region without anyadditional reinforcement in beam or column is compared with SS1, SS2, SS3, SS4 and SS5SS1 indicates specimen with beam longitudinal bars having inclined anchorage and SS2 isthe specimen with additional inclined bars from column to beam. The specimen withadditional beam bars and primary beam bars provided with round hook type anchorage isSS3. SS4 was provided with welded wire mesh in joint region alone whereas SS5 hadwelded wire mesh in beam and column region. The performance of the specimens arecompared in terms of lateral load-displacement hysteresis loop, load ratio, percent of initialstiffness versus displacement curves, total energy dissipation, beam rotation at distances of D and 2D, strain in beam main bars and crack pattern. Among all the specimens, SS2 was the most effective considering all the parameters taken for comparison. It is concluded that inclined bars from column to beam over a specific beam length in SS2 can successfully move the plastic hinge away from the column face.

In this paper, optimum design of steel frames is performed using the Big Bang-Big Crunch(BB-BC) algorithm. The objective of this optimization is to minimize the total weight of thestructures subjected to serviceability and strength constraints in accordance with BritishStandard (BS5950) and AISC-Load and Resistance Factor Design (LRFD). Designs areevaluated for fitness based on their penalized structural weight, which represents the actual frame weight and the degree to which the design constraints are violated. The considered design examples demonstrate the efficiency of the algorithm, and also the design results based on BS5950 and AISC-LRFD specifications are compared. In general, it is shown that the optimum frames designed based on the AISC-LRFD specification are more economical than those designed in accordance with BS5950.

A reliable estimation of seismic demand is an essential part of recently developedperformance based design engineering. In this estimation a Probabilistic Seismic DemandModel (PSDM) must be implemented to predict the mean value of the demand at thespecific value of intensity measure parameter. In this paper it is tried to perform acomparison between the PSDMs which are obtained through the results of nonlineardynamic analysis subjected to a set of scaled records with the models determined throughthe results of incremental dynamic analysis in order to find the proper value for the scalefactor. The results show that model estimation using only a single scale factor is achievablein the case of 3 and 6-storey frames and for 9, 12 and 15-storey frames, the combination of scaled and un-scaled records can lead to reliable estimation of parameters.

The paper presents a short investigation of theoretical prediction models for plain concrete confined with Ferrocement. Although to date scant experimental data is available for a conclusive recommendation, however, ample evidence of the versatility of the model proposed by Waliuddin and Rafeeqi [36] has been provided in this paper. The proposed model possess the capability of predicting strength of plain concrete, confined with Ferrocement for almost all the possible and practical methods of confinement by way of; integrally cast mesh layer, mesh layers in precast shell and wrapped mesh layer on precast core.

The influence of permanent expanded polystyrene formwork on fire resistance of selfcompacting concrete (SCC) is investigated in this paper. A type of SCC is produced andcured at two different conditions, one at traditional condition and the other inside expanded polystyrene forms. A type of normal vibrated concrete with similar compressive strength isalso produced and cured at the same conditions for comparing purposes. The specimens are exposed to different high temperatures. The residual mechanical strengths, phase composition and porosity changes at high temperatures are investigated. The insulating permanent forms raised the risk of spalling of concretes and had important influences on residual mechanical strengths of the concrete.

In this paper a new ribbed bracing system (RBS) is proposed capable of performing as avariable stiffness system that can be used for controlling structural deformations and frequency shifting to compensate seismic energy. RBS has two important advantages. Because of ribbed system, the compressive member is rigidly moved like a piston and a cylinder and therefore it is a buckling prevented system. Also it is possible to use this system as a semi-active system by considering the story drifts and global structural damage and control the system if it is necessary to be open or closed based on the operational criteria assigned in the system. RBS has no need to any actuator and large power supply, but just a battery-size power supply to switch the ribbed mechanism to be on or off. RBS is composed of a ribbed supplemental part and a normal wind-bracing on each floor. Considering an appropriate criterion based on the storey drift, minimum number of bracing systems will be active on the height of struطcture during earthquake. In contrast with completely closed RBS (CC-RBS) by on-off bracing system arranged along the height of the building cause period shifting of the structure to the larger value. Three stages are considered in the numerical studies: conventional bracing frame (CBF), CC-RBS and semi-active RBS (SA-RBS). Damage indices and Fourier transforms arecalculated in order to discuss on the efficiency of the proposed system. Nonlinear dynamicanalysis of system has been carried out and structural behaviour has been investigated. Numerical results show the efficiency of CC-RBS in reducing structural damage andimproving seismic energy. Also base shear is reduced when SA-RBS is used and structuraldamage is more uniform in this case.