Scientia Iranica
Volume:23 Issue: 2, 2016

Sensitivity analysis is considered as an important part of evaluating the performance of mathematical or numerical models. One-factor-at-a-time (OAT) and differential methods are among the most popular sensitivity analysis (SA) schemes employed in the literature. The two major limitations of the above methods are lack of addressing the correlation between model factors and being a local method. Given these limitations, its extensive use among modelers raises concern over the credibility of the associated sensitivity analyses.This paper proposes proof of the inefficiency of the aforementioned methods drawing from experimental designs, and provides a novel technique based on principal component analysis (PCA) to address the issue of the correlation among input factors. In addition, proper guidelines are suggested to handle other conditions.

Transportation Discrete Network Design Problem (TDNDP) aims at choosing a subset of proposed projects to minimize the users’ total travel time with respect to budget constraint. Because TDNDP is a hard combinatorial problem, recent research has widely addressed heuristic approaches and ignored the exact solution. This paper is going to explore how application of parallel computation can affect the performance of an exact algorithm in TDNDP. First, we show that the Branch-and-Bound (B&B) algorithm proposed by LeBlanc is well adapted to a parallel design with synchronized Master-Slave (MS) paradigm. Then we develop a parallel B&B algorithm and implement it with two search strategies of Depth-First-Search (DFS) and Best-First-Search (BFS). Detailed results over up to 16 processing cores are reported and discussed in an illustrative example of the Chicago Sketch network. The results suggest an almost linear speedup for both strategies which slightly drops as more processing cores are added. When using 16 processing cores the speedup values of 11.80 and 12.20 are achieved for DFS and BFS strategies respectively. Furthermore, the BFS strategy reveals a very fast parallel performance by finding the optimal solution via the minimum computational effort.

The California Bearing Ratio (CBR) value of the soils is very important for geotechnical engineering and earth structures.A CBR value is also affected by the type of soil and different soil properties. With this in view, in this paper, an attempt has been made for investigating the factors that affect theCBR value of some Aegean sands collected from nine different locations in Manisa (Turkey). The sand samples were tested for mineralogy, particle shape and size, and specific gravity. In addition, the CBR tests were performed on these samples corresponding to different dry densities and the influence of dry density, relative density, water content, particle shape and size on theCBR value was examined. Multiple regression analysis (MRA) was performed to predict the CBR value of the sands by using the experimental results. It has been demonstrated that the MR equation proposed in this paperis efficient in determining the CBR value of Aegean sands and the computed values are in good agreement with those obtained from the experimental investigations. Moreover, several performance indices such ascoefficient of correlation, variance account for, mean absolute error, and root mean square error were calculated to check the prediction capacity of the MR equation proposed. The obtained indices make it clear that the equation, derived from the samples used in this study, apply well with an acceptable accuracy to be used for the CBR estimation at the preliminary stage of site investigations.

Precast construction projects are associated with many activities, numerous parties, enormous effort and different processes. For effective communication, this requires delivering appropriate and up-to-date information to enhance collaboration and improve integration. The purpose of this paper is to develop the system architecture and prototype of Context-Aware Cloud Computing Building Information Modeling (CACCBIM) for precast supply chain management. The findings of this research are grounded through the literature of cloud computing, context-awareness, building information modeling and, ultimately, the analysis of interviews with stakeholders in precast construction. Findings determine that lack of integration, improper planning and scheduling, poor production timing, poor coordination, lack of good communication among parties, wrong deliveries, poor control and supervision are the major issues within the precast supply chain. These issues could result in adverse consequences for the objectives and success of the precast project.Eventually, to reduce and eliminate these issues, the proposed prototype will support appropriate deliveries,efficient monitoring, the facilitation of coordination and collaboration with improved communication. It is anticipated that this research will establish a unique perception of the precast construction industry which will finally enhance its productivity, improve its efficiency and maximise its effectiveness.

North-western Iran (Azerbaijan province), one of the most seismic regions of the country, has experienced many seismic events during its long history. The recent dual earthquake with Mw = 6:4 and Mw = 6:3 struck the Ahar-Varzaghan area in Azerbaijan province in 2012.8.11 and caused a lot of fatalities. In this paper, the varieties of several seismic parameters, such as the b-value of the Gutenberg-Richter relation and standard deviation, Z, have been investigated to explore the temporal and spatial changes of seismicity patterns. Calculating and comparing these data before and after the occurrence of earthquake demonstrate some information about anomaly preceding main shocks. Temporal variations of b-value show a clear decrease before the 2012 Ahar- Varzaghan dual earthquakes. Considering the spatial changes in the b-values, it is possible to recognize a zone with abnormal low b-values around the epicenter of these events. The variation of the b and Z-values around the epicenter shows preparedness of the region before the occurrence of the main shock of Ahar-Varzaghan earthquake.

By locating a steel shear panel at the intersection point of the X-braces, concentrically or eccentrically braced shear panel (CBFSP and EBFSP) is formed. In this paper, to perform parametric study, 1-story CBFSP and EBFSP models with span length greater or less than height are considered. Using linear static analyses, the effects of size and location of the shear panel on the lateral stiffness of the frame with respect to the moment resisting frame with the same member sections are investigated. Next, for 1- and 3-story models, maximum displacement along with base shear and the ratio between the dissipated energy and input energy are examined under 4 ground motion records. Behavior of the truss elements in cross-strip model for nonlinear dynamic analyses is validated based on a performed experimental program. The findings show that the optimum state is achieved by decreasing size of the shear panel and situating it at the middle of the frame or to some extent upper. Furthermore, in this study, tentative values of the over-strength, deflection amplification and response modification factors, which are estimated by pushover curves, are proposed. Using linear regression, an equation is obtained for estimation of the fundamental period of CBFSP and EBFSP.

Since placing continuity plates in panel zone of columns is difficult, and also has too much cutting and welding in connection area, it reduces the reliability of the connection, so the continuity plates are removed from inside of the column and are replaced with internal elements such as horizontal reinforcement network and with external elements such as Trapezoidal stiffeners. In this study, through finite element modeling and geometric- material nonlinear analysis under pushover and cyclic loading to investigation of loading. Results show that beam to Box column connection with and without in-filled with concrete with arrangement stiffeners using of concrete in model- with continuity plates causes to an increase of 0.12 percent in restraint, 4.98 percent in ductility and 96.92 percent in final resistance. More ever, in the proposed model, using of concrete leads to an increase of about 2 percent in restraint, 52.51 percent in resistance, while ductility connection formation was reduced, and all parameters have shown a significant increase with binding reinforcement by horizontal reinforcement networks. Therefore, a new proposed connection has satisfied all seismic parameters as well in present study, and this is a good alternative for continuity plates which are inside of the column.

Steel structural members are likely exposed to corrosive environments, and thus corrosion is one of the dominant life-limiting factors of steel structures. Extensive studies on the effectsof pitting and uniform corrosion on the strength performance of steel structural members under a wide variety of loading conditions have been undertaken to assess the relationship between pitting corrosion intensity and residual strength. The aim of this study is to investigate the ultimate compressive strength characteristics of steel web plate elements with pit and uniform corrosion wastage. A series of ABAQUSnonlinear elastic-plastic large deformation finite element analyses are carried out on I-shapedsection steel girder models with varying pittingcorrosion intensities. Artificial pitting of different intensities is considered on the web plates and a uniform loading applied vertically on the upper flange section. The ultimate load-carrying capacity of deteriorated models with different levels of uniform thickness loss is also studied. The results are applied to assessing the ultimate compressive strength of web plates with different pitting corrosion intensities and a uniform loss thicknessby developing design formulae that represent the average loss thickness versus the ultimate load-carrying capacity.

Settlement based design for shallow foundation realizing consolidation aspect is a major task of geotechnical engineer. Compression index (Cc) from the odometer test is used to estimate the consolidation settlement of clays. Since the determination of Cc from odometer tests is relatively time-consuming, empirical equations based on index properties can be useful for settlement estimation. Empirical correlations have been proposed to relate the Cc of clay deposits to other soil parameters. New polynomial models are proposed for correlation. In order to assess the merits of the proposed approach, a database containing 352 data points have been compiled from case histories via geotechnical investigation sites in the province of Mazandaran, along southern shoreline of the Caspian Sea, Iran. We compare our results involving polynomial fitting with earlier results of statistical correlation relations among Cc with other geotechnical soil properties. The predicted values using our model are checked with the measured ones to evaluate the performance of the polynomial model. The results suggest that the newly proposed approach of correlation provides a means for recognizing more efficiently the patterns in the data and reliably predicting the Cc.

In this paper a hybrid method is developed for optimum design of castellated beams by combining two meta-heuristic algorithms, namely the colliding bodies optimization (CBO) and particle swarm optimization (PSO). In this hybrid algorithm (CBO-PSO), positive features of PSO are added to the CBO. Two common types of laterally supported castellated beams are considered as design problems: beams with hexagonal openings and beams with circular openings. These beams have found widespread usage in buildings because of great savings in materials and construction costs. Here, the minimum cost is taken as the design objective function and the new hybrid method is utilized for obtaining the solution of some benchmark problems. Comparison of the results of the CBO-PSO with those of some other metaheuristics demonstrates the capability of the presented optimization algorithm. For most of the examples, the results obtained by the CBO-PSO have less cost in comparison to those of the other considered methods. It is also concluded that the beams with hexagonal openings require smaller amount of steel, hence being superior to the beams with cellular openings.

An experimental program was carried out to investigate the effectiveness of a novel near surface mounted (NSM) technique using innovative manually made CFRP rods (MMRs) and manually made CFRP strips (MMSs) for flexural strengthening of reinforced concrete (RC) two-wayslabs with low clear cover thickness. Four full-scale RC slabs (1500×1500×120 mm) were tested under monotonic four-point bending. One slab was kept un-strengthened as the control specimen, one slab was strengthened using NSM GFRP rods, and the other two slabs were strengthened using NSM CFRP MMRs and NSM CFRP MMSs. The load-deflection responses, strain measurements, and failure modes of the tested slabs were studied and discussed. The behavior of slabs strengthened with this technique was compared to the behavior of the slab strengthened with GFRP rods. The test results confirmed the feasibility and efficacy of this technique in improving the flexural behavior of RC two-way slabs. Strengthened slabs showed an increase in flexural capacity between 279 and 394% over the control specimen. A 3D nonlinear numerical model was developed using the finite element (FE) method to predict the flexural behavior of the tested slabs. A good agreement between experimental and numerical results was observed.

Dome structures are elegant and economical structures used for covering large areas. In this paper, an optimum topology design is performed using the Colliding Bodies Optimization (CBO) method and its enhanced version (ECBO). The Schwedler and ribbed domes are studied determining the optimum number of rings, the optimum number of joints in each ring, the optimum height of crown, and tubular sections of these domes. The minimum volume of each dome is taken as the objective function. A simple procedure is de ned to determine the con gurations of Schwedler and ribbed domes. This procedure includes calculation of the joint coordinates and element constructions. The design constraints are implemented according to the provision of LRFD-AISC. First, a comparative study for domes using di erent algorithms is carried out, and then the e ect of choosing di erent number of joints in each ring on the optimal topology is investigated for Schwedler domes to verify the suitability of design procedure and to demonstrate e ectiveness of the ECBO.

A new method for structural optimization is presented for successive approximation of the objective function and constraints in conjunction with Lagrange Multipliers Approach. The focus is on presenting the methodology with simple examples. The basis of the iterative algorithm is that after each iteration it brings the approximate location of the estimated minimum closer to the exact location gradually. In other words, instead of the linear or parabolic term used in Taylor expansion which works based on a short step length, an arc is used that has a constant curvature but a longer step length. Using this approximation, the equations of optimization involve the Lagrange multipliers as the only unknown variables. The equations which depend on the design variables are decoupled linearly as these variables are directly obtained. One mathematical example is solved to explain in details how the method works. Next the method is applied to the optimization of a simple truss structure to explain how the method can be used in structural optimization. The same problems have been solved by penalty method and compared. The results from both methods have been the same. However because of the long step length and reduction in the number of variables, the speed of convergence has been higher in the presented method.