Iranian Journal of science and Technology (B: Engineering)
Volume:34 Issue: 4, August2010

In this paper, harmony search algorithm is utilized for the optimum design of slab-formwork. This method is a numerical optimization technique developed recently that imitates the musical performance process when a musician searches for a better state of harmony.The cost of the form components involved is considered as the objective function of the optimization problem. Constraints for the optimization problem are bending moment, shear, maximum deflection and imposed ACI code provisions. The use of the harmony search to formwork design problems provides optimum cross sections and optimum spacing of the form members (joist and stringer), while minimizing the total cost.

This paper studies the stress and displacement distributions of transversely isotropic rectangular plates with continuously varying thickness and simply supported at four edges. On the basis of three-dimensional elasticity theory, the general expressions for the displacements and stresses of the plate under static loads, which exactly satisfy the governing differential equations and the edge conditions of the plate, are analytically derived. The unknown coefficients in the solutions are approximately determined by using the double Fourier sinusoidal series expansions to the upper surface and lower surface conditions of the plate. Convergence and comparison studies demonstrate the correctness and effectiveness of the proposed method.

In the present research, an explicit dynamic analysis is conducted on a typical multi-storey Steel Plate Shear Wall (SPSW) designed according to AISC requirements. The SPSW model is subjected to a base earthquake acceleration record to simulate the time history response of the structure. The analysis utilizes a finite element method involving both material and geometric nonlinearities. The energy dissipation behavior and distribution of storey shear over height of the model are investigated through time history response of the system. In addition, this paper proposes a new definition of energy ductility, which can be used in the investigation of the dynamic response of SPSWs. The ductility demand based on the proposed definition as well as shear resistance contribution of the web plate and Vertical Boundary Elements (VBE) of SPSW are evaluated.

Although Polypropylene (PP) fibers have advantageous characteristics, the weak bond with the cement matrix as a result of their smooth surface and chemical inertness remains a large limitation. It has been demonstrated that the fiber-matrix bond strongly affects the ability of fibers to stabilize crack propagation in the matrix. As the bond between fiber and matrix is mainly mechanical, it seems that incorporating nano-SiO2 into fiber reinforced cement composites provides a better bond with the matrix through pore refinement and better distribution of the hydration products. Hence, in this paper an effort was made to study the effect of PP fibers on the mechanical and physical properties of mortars incorporating nano-SiO2. Four fiber volume fractions, 0, 0.1%, 0.3% and 0.5% were considered. Compressive and flexural strength, water absorption and shrinkage of mortars were reported. SEM observation was also conducted to evaluate the effect of nano-SiO2 on the microstructure of cement paste. Results showed that nano-SiO2 significantly improved the mechanical and water absorption characteristics of mortars. It was observed that the microstructural characteristics of cement paste can be effectively improved by incorporating nano-SiO2, as the presence of nano-SiO2 enhanced the PP fibers effectiveness in strengthening mortar properties.

In this study, loss of concrete-steel bond strength of lightweight and ordinary concrete under monotonic and cyclic loading is examined for plain and deformed steel bars. Here, lightweight and ordinary concrete-steel bond strength is determined by pull-out test for a variety of specimens in various configurations. For each specimen, a bond strength-slip curve is obtained through monotonic loading. Following this process, an identical specimen is subjected to cyclic loading under similar conditions using the same test setup. These examinations reveal several insights. Lightweight concrete-steel bond strength is greater than the ordinary concrete-steel bond strength for plain steel bars under monotonic loading. Ordinary concrete-steel bond strength is greater than lightweight concrete-steel bond strength under both monotonic and cyclic loading for deformed steel bars. The loss of concrete-steel bond strength is greater in plain bars than in deformed bars.

In this work a considerable number of papers regarding the cracked beam like structures in the literature are cited. A new and general governing differential equation for eigenvalue analysis of cracked members is derived. Buckling analysis of cracked columns, lateral free vibration of cracked beams, axial free vibration of cracked bars, torsion free vibration of cracked shafts etc. may be considered as special cases. The proposed standard ordinary differential equation is solved and the exact analytical solutions for eigenvalues and mode shapes of these members are determined. Through customizing the general solutions for special conditions the predefined solutions are obtained and the accuracy and robustness of the present study is verified.

Reinforcing soils with biaxial geogrids have been shown to be an effective method for improving the ultimate bearing capacity of granular soils. The pull-out resistance of reinforcing elements is one of the most significant factors in increasing bearing capacity. In this research a new reinforcing element that includes attaching elements (anchors) to ordinary geogrid for increasing the pull-out resistance of reinforcements is introduced. Reinforcement therefore consists of a geogrid and anchors with cubic elements attached to it, named (by the authors) Grid-Anchor. Three-dimensional numerical study was performed to investigate the bearing capacity of square footing on sand reinforced with this system. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of the reinforcement layers, the angle of anchors, the stiffness of reinforcement and anchors and the distance that anchors are effective were investigated. Three-dimensional finite element analysis by "PLAXIS 3D Tunnel" software, indicated that when a single layer of reinforcement is used there is an optimum reinforcement embedment depth for which the bearing capacity is greatest (u=0.5B). There also appeared to be an optimum vertical spacing of reinforcing layers for multi-layer reinforced sand (h=0.25B). The bearing capacity was also found to increase with increasing the number of reinforcement layers, if the reinforcement was placed within a range of effective depth (d=1.25B). In addition, analysis indicated that increasing reinforcement and anchor stiffness beyond a threshold value does not result in further increase in the bearing capacity (1kN for anchors and 100 kN/m for geogrid). Results show that the Grid-Anchor system of reinforcing can increase the bearing capacity 2.74 times greater than that for ordinary geogrid and 4.43 times greater than for non-reinforced sand.

Permanent Ground Deformation (PGD), occurring as faulting, liquefaction-induced soil movements and landslides can significantly affect underground lifelines such as buried gas and water pipelines. This paper investigates the response of buried pipelines in sand to transverse PGD with particular attention to the peak forces exerted on the pipe. Available analytical solutions provide a wide range of predicted peak dimensionless forces, but there is limited information regarding the transition of the peak dimensionless force from shallow to deep embedment conditions. There are large uncertainties in the true values since the bounds established by the analytical solutions are large. In order to find the solution and to investigate its failure mechanism, the numerical modeling of soil-pipe interaction is performed for different conditions. The effects of burial depth ratio, pipe size and soil properties are addressed using finite differences analyses. A constitutive model for the continuous strain-hardening/softening and volumetric dilatancy of sand is proposed. The results showed that the transverse soil restraint decreases for larger diameter pipes in the horizontal direction, and there is no effect in the vertical direction. The transverse soil restraint increases with increasing burial depth ratio but it becomes constant at deeper soil profiles.

This paper describes a subroutine for estimation of daily and average annual runoff in a computer model for microcatchment design and prediction of rain-fed grape yield in the Bajgah area, Fars province, Islamic Republic of Iran. In this subroutine, it is assumed that all abstractions arise from infiltration, and a method for determining ponding time and infiltration by using recording rain gage data and soil physical properties was developed based on the Green-Ampt infiltration equation. This subroutine was then incorporated into a previously developed model to design the microcatchment area and grape yield prediction. The developed subroutine resulted in a daily microcatchment runoff coefficient of 0.0737 in the study area which is similar to the measured value of 0.080. The daily threshold rainfall to produce daily runoff estimated by the developed subroutine was 6.5 mm where its measured value was 4.6 mm. The developed subroutine resulted in a microcatchment average annual runoff coefficient of 0.0894 in the study area, which is similar to the measured value of 0.0875. The annual threshold rainfall to produce annual runoff was estimated by the developed subroutine, and was 158.8 mm where its measured value was 106.5 mm. The estimated relationship between annual runoff and rainfall was used in the model and estimated the microcatchment area and grape yield properly. In general, it is indicated that the developed subroutine is able to determine the daily and annual runoff-rainfall relationship to be used in the model for the design of the micricatchment area and prediction of grape yield in the study area.

This article deals with the problem of choosing the best possible shipping alternative among a set of transportation modes based on four decision criteria. An Analytic Hierarchy Process (AHP)-like model was used to solve the problem. The developed model was run on a combination of rail–road–sea transportation, for Turkey. Instead of considering different commodity types, just the textile sector was modeled and studied for simplicity. The proposed model was shown to be very flexible with the considered criteria. Because of time and financial limitations the study area was restricted to Istanbul city. A short poll was conducted to find out the most important decision criterion for shippers. Subsequently, the first four most preferred criteria of the respondents were chosen to be embodied into the model. Finally, the model validity was proven by almost seventy percent accuracy along with the real life choices of the shippers.