Asian journal of civil engineering
Volume:11 Issue: 1, Feb 2010

The purpose of this study is to investigate the effectiveness of the least-squares based finite element models in solving the beam bending problems to overcome shear and membrane locking and predict generalized forces accurately. This study is conducted using the Euler- Bernoulli and Timoshenko beam theories applied to straight beams. The solution accuracy of the least-squares finite element models with conventional finite element models is also assessed.

An efficient methodology is proposed to design optimization of structures subjected toearthquake time history loading considering nonlinear structural response. It is clear that the structural optimization for transient time history loading is a computationally intensive task, especially when the nonlinear response is concerned. In the proposed hybrid methodology particle swarm optimization (PSO), genetic algorithm (GA), probabilistic neural network (PNN), radial basis function neural network (RBFNN) and wavelet transforms (WT)techniques are combined to achieve the optimization task. In order to investigate the efficiency of the proposed methodology, a 72-bar space steel tower is designed for optimal weight for El Centro earthquake. The numerical results demonstrate the efficiency and computational advantages of the proposed methodology.

The objective of the present investigation is to obtain the performance of the concrete by the microbiologically induced special growth/filler. One such thought has lead to thedevelopment of a very special concrete known as Bacterial Concrete where bacteria isinduced in the mortars and concrete to heal up the faults. Researchers with differentbacteria’s proposed different bacterial concrete’s. Here an attempt was made by using thebacteria “Bacillus subtilis”. Calcite formation by Bacillus subtilis is a model laboratorybacterium, which can produce calcite precipitates on suitable media supplemented with acalcium source. Cement mortar cubes with four different cell concentrations were cast and control specimen was also cast. This study showed a significant increase in th compressive strength was observed due to the addition of bacteria for a cell concentration of 105 cells per ml of mixing water. From Scanning Electron Micrography analysis, it is noted that pores were partially filled up by material growth with the addition of the bacteria. Reduction in pore due to such material growth will obviously increase the material strength. Concrete cubes with and without addition of bacteria were cast and it is observed that there is an improvement in the compressive strength for the cubes with the addition of bacteria. Concrete cylinders with and without addition of bacteria were cast and it is observed that there is an improvement in the Split tensile strength for the cylinders with the addition of bacteria. From the durability studies, the percentage weight loss and percentage strength loss with 5% H2SO4 revealed that Bacterial concrete has less weight and strength losses than the conventional concrete and it also revealed that bacterial concrete is more durable in terms of “Acid Durability Factor” and “Acid Attack Factor” than conventional concrete.

The strengthening of aging steel structures has become a task for civil engineers in recentyears. The steel girders in aging bridges are among the structures which can be effectivelystrengthened by epoxy bonding carbon fiber reinforced polymers (CFRP) laminates to thedamaged tension face of the girders. Though this method is very simple to use, it usuallysuffers from the problem of debonding failure of CFRP strip used for strengthening of steelmembers. Therefore it is worthwhile to provide a proper and practical bonding enhancement detail. In this paper, a method of adding steel patch plates on CFRP strip is introduced.Eight steel beam specimens which are artificially damaged at their mid-span (notched) andthen repaired with CFRP laminates are tested through a four-point loading setup. Also,double-lap shear tests are performed to validate the effect of using the proposed method in comparison with another anchoring method known as mechanical clamping. The effect of different bonding lengths of the CFRP laminates is investigated, too. The experimental results of the repaired steel beam specimens show that adding small pieces of steel plate (patches) over CFRP laminate and beam’s flange at high stress concentration zones can increase the bonding strength about 50% in comparison with the beams repaired with no patches. The results of double-lap shear tests show that the methods of adding steel patches and mechanical clamping increase the bonding resistance up to about 59% and 35%, respectively, in comparison with the cases of without patches or clamps.

Membranes are widely used in various engineering applications such as the design stage ofmicrophones, pumps, pressure regulators, and other acoustical applications. This paperinvestigates the numerical aspects for free vibration analysis of homogeneous and nonhomogeneous rectangular and square membranes. The method of discrete singularconvolution is employed. The results are obtained for different density case and aspectratios. Numerical results are presented and compared with that available in the literature.The results show that the regularized Shannon delta kernel based discrete singularconvolution algorithm produces accurate frequency values.

The present paper describes the analysis of high-rise steel buildings frames with Steel plateshear walls (SPSWs) by using SAP- 2000 FEA programme. The primary variable in theanalysis were presence of steel plate shear walls, thickness of plate (5 mm to 10 mm) andaspect ratio (0.833 to 1.667 width-to-height ratio). From the results obtained it is observed that, with the use of steel shear walls in the buildings, the bending moments in the beams are observed to reduce. The increase of shear wall thickness has a little effect on the bending moments and shear forces of the beams and there is small decrease in the lateral deflections.The storey drift increases with increase of aspect ratio while bending moment and shearforce show a considerable increase.

The Big Bang–Big Crunch (BB–BC) optimization algorithm is a new optimization methodthat relies on the Big Bang and Big Crunch theory, one of the theories of the evolution of the universe. In this paper, a discrete Big Bang–Big Crunch algorithm is presented for optimal design of structures. The BB–BC is employed to optimize different types of skeletalstructures with discrete variables including trusses and frames. The results demonstrate the efficiency of the discrete BB–BC algorithm compared to other heuristic algorithms.

Base isolation is an acknowledged means to reduce the transmission of earthquakeaccelerations from the ground into the structure. Of particular interest here are systemswhere the bearing slides on a concave surface which produces a self-centering forcerestoring the building to its original position. While the idea behind the technology isstraightforward, the numerical simulation of the structural response is difficult, since thecontact between the bearing and the sliding surface changes continually between stickingand sliding in a nonlinear process. The research presented here aims at developing acomputational model for base-isolated building which would allow the engineer to simulatethe structural response in the time domain in order to find an optimum design of bothbuilding and isolator. It has been shown that a compact 1-DOF system suffices to expressthe general isolated layer response during the excitation. For more general details such asstructural accelerations and drift a set of coupled differential equations must be solved.Finally, through comparison of the behavior of an isolated structure with a fixed-base one,the efficiency of sliding isolation is demonstrated.

A detailed study of box girder bridge cross-sections namely Rectangular, Trapezoidal andCircular has been carried out in the present investigation. Commercially available softwareSAP-2000 has been used to carryout linear Analysis of these box girders. Three dimensional 4-noded shell elements have been employed for discretization of domain and to analyze the complex behavior of different box-girders. The linear analysis has been carried out for the Dead Load (Self Weight) and Live Load of Indian Road Congress Class 70R loading, for zero eccentricity as well as maximum eccentricity at mid-span. The paper presents a parametric study for deflections, longitudinal and transverse bending stresses and shear lag for these cross-sections. The Finite element computational model has been validated by comparing few obtained results with the published literature. Effectiveness of four noded shell elements for analysis of box girder bridges is also presented. It is found that the rectangular section is superior to other two sections. It can be stated that the obtained results will provide guidance to the bridge designers.