نشریه مهندسی عمران فردوسی
سال بیست و هفتم شماره 2 (تابستان 1395)

Deep beams are type of beams which their behavior is different from conventional beams because of their particular type of geometry. In this paper, the retrofitting of these beams is considered and 10 deep beams are tested experimentally and discussed about retrofitting methods. Experimental studies indicate that the use of CFRP bands in the direction perpendicular to diagonal cracks in comparison with the use of CFRP in vertical direction are appropriate in condition that many CFRP with less width be used instead of using wide CFRP with lower number. The comparison of the experimental results is conducted with the results of existing relations in literature. The comparison shows that the existing relations cannot correctly predict the behavior and ultimate load of deep beams retrofitted by FRP tested in this paper.

This paper discusses the arching effect as the formation of a stable arch in granular materials. For this aim, a developed trapdoor apparatus is designed in order to investigate the arch dimensions in term of the internal friction angle, average size and base angle of materials. Observations show that for all tested granular ensembles, width and height of the arch increase with an increase in trapdoor width and a decrease in base angle. It is also found that the shape of the whole arches is governed by a parabola. In addition, for both constant values of trapdoor width and base angle, the increase in both the internal friction angle and density of granular materials leads to the increase in arch dimensions.

The effect of Welding residual stresses that was created in thin infill plate of steel plate shear wall system during constructional processes was studied in this research. Residual stresses in a welded structure is the result of the non-uniform expansion and contraction and plastic deformation of the weld and surrounding base metal due to heating and cooling cycle, during welding process, this issue could affected SPSW`s behavior. In this research ABAQUS finite element software is utilized to simulation of welding process and steel plate shear wall behavior. Sequentially coupled thermo-elastic–plastic finite element computational procedure is developed to calculate temperature field and welding residual stresses in SPSW. The result shows that residual stresses created in infill plates of three story steel plate shear wall with rigid beam-column connection due to welding process makes yielding load, ultimate load, stiffness, ductility and energy absorption, decrease 1.4%, 1.26%, 7.6%, 7.3%, 3.4% respectively in model with residual stresses in comparison with model without residual stresses. Thus, the ignore of residual stresses effect due to welding in prospect of thin steel plate shear walls(SPSWs) behavior is negligible.

Scour around bridge piers is one of the most important fields of hydraulic research. Local Scour around bridge piers and abutment is one of the main reasons of bridge failures. In the field of scour at the bridges, researches are more focus on scour of piers in compare with abutment. While the available information on the bridge failures required cost, the major problems are related to abutment. Therefore, most costs have spent in this part. One of the methods used to reduce of scour around bridge piers and abutment is installing collar. The collars protect the river bed against vortex flow in the vicinity of the piers and abutments . In this research the effect of two types of collar, include complete and L-shaped collar, were investigated on abutment scour reduction and application diagram is proposed. Results show that increasing dimensions of collars will increasing the efficiency of performance. Comparing of both collars indicated, that if the length of collars is larger than half the length of the abutment, the L-shaped collar is more effective in compare with complete collar. The L-shaped collar doesn’t prevent sediment movement due to lift vortex in downstream of abutment and for this reason it is shown more effective performance than the complete collar. Also, using the L-shaped collars with less area is more cost effective.

In this study, for evaluating ductility of ordinary concentrically braced frames (OCBFs) and special concentrically braced frames (SCBFs) which are X- braced in two adjacent middle spans, 16 steel ordinary concentrically braced frames and 16 special concentrically braced frames are studied. The results confirm that, although most of ordinary concentrically braced frames, which are X-braced, cannot experience the corresponding target displacement, but because of their high designing force level expected ductility can be obtained. Also results confirm that the response modification factor of SCBFs which is proposed by Iranian seismic design code (2800 standard forth edition), R=5.5, is more logical than ASCE's one, R=6. According to the results, the response modification factor of 5 is proposed for special concentrically braced frames, which have an analytical period of more than one second (frames more than 10 stories).

In this paper, an algorithm is presented for the formation of optimal null basis vectors corresponding to sparse flexibility matrices. For controlling the independence of the vectors, a generator is selected in each corresponding self-equilibrating systems, and the sequence of generators is modeled as decision variables. Since the equilibrium conditions and uniqueness of generators consists a underdetermined linear system, a linear mixed integer programming model is presented for finding sparse solution. In charged system search algorithm, the movement of charged particles is tracked in a continuous domain, therefore it is modified for using in a discrete binary space, and also a new operator called probability of mutation is defined in this paper. The numerical examples shows that the proposed method enables to find suboptimal solution, while using short computational time and resulting good accuracy.

Structural dynamic parameters: natural period, shape modes and damping ratio of vibration, play a decisive role on the seismic behavior of those structures. There are several methods for determining of the structural dynamic parameters, such as: free vibration, ambient vibration and force vibration tests. In this research the structural response of a three-story building (the natural frequencies of vibration and the structural damping values) are monitored by a two-frequency GPS device mounted on the structure. The time in full oscillation of the structure will be the natural period of vibration. The damping ratio is determined using logarithmic formulation. The results from analytical method are the same as the experimental results approximately. For example, the natural period in X direction was determined 1.07 and 0.93 Hz using GPS and analytical methods. Comparing the results of the experiments and the results of the computer analysis shows the good accuracy in determining the parameters.

Bearing capacity prediction of shallow foundation is one of the most important problems in geotechnical engineering practices, with a wide variety range of methods which have been introduced to forecast it accurately. Recently, soft computing methods such as Artificial Neural Networks (ANNs) and Support Vector Machines (SVMs) have been used for prediction of the ultimate bearing capacity of shallow foundation. However, in these methods the modeling process is complex and are not as easy to use as the empirical equations. In this paper, M5P model tree as a new soft computing method has been used for prediction of the ultimate bearing capacity of shallow foundation. The main advantage of model tree is that, compared to ANN and SVM, they are easier to use and more importantly they represent understandable mathematical rules. Laboratory experimental tests of shallow foundations on cohesionless soils were used with parameters of the internal friction angle, the unit weight of the soil, and the geometry of a foundation considers depth, width, and length to develop and test the model. The results achieved from the proposed model was compared with those obtained from the Meyerhof, Hansen and Vesic computation formulas. The results indicate that M5P model tree perform better than the mentioned theoretical methods.

Energy costs comprise considerable amount of operation costs in water distribution networks. Optimal management of energy costs to provide required water for consumers with desired quality is of high importance. To achieve this, optimization is defined as a powerful tool. In this paper, by focusing on operation phase, multi-objective optimization of water supply network considering hydraulic, quality and integrated reliability measures is performed. In each of these cases, the first goal is to minimize energy costs and maximization of each reliability measure is considered as the second objective. Therefore, it is necessary to set the performance schedule of the pumps over a period of time, one day, such a way that pumping schedual changes based on consumption variation during the day. In addition, it is required to maximize the hydraulic, quality and integrated reliability measures in the network. In this paper, in order to adapt more pump operating modes of pump station, both constant and variable speed pumps are used. In order to optimize performance of water distribution network, due to the high efficiency and simplicity of ant colony algorithm, the NA-ACO-CD (Non-Dominated Archiving Ant Colony Optimization with Crowd Distance) algorithm has been coded in Visual Studio C. The efficiency of NA-ACO-CD algorithm is tested with mathematical functions and proved to be applicable on water distribution networks. The proposed method is evaluated on Anytown water distribution network and required pareto curved are produced. It is concluded that the methodology cannot be attained to a combination of pump speeds such that all three pump, hydraulic and quality reliabilities will be maximized simultaneously.

Earthquakes could have catastrophic impacts on tunnels and buried structures. Liquefaction phenomenon is one of the most destructive effects of earthquakes. Liquefaction results in decreasing effective stress and this consequently leads to decreases in shear strength of the soil. As a result, large deformation in both soil and buried structure occurs. Moreover, liquefaction causes soil boiling, lateral spreading, structure settlement and the uplift of buried structure. In many earthquake cases, uplift of the buried structure due to liquefaction was reported as one of the major damaging factors. This research sought to model earthquake induced uplift of buried structures including tunnels in the soil susceptible to liquefaction under seismic loading. Two dimensional finite difference modeling is employed to simulate centrifuge experiments. The UBCSAND model was adopted as constitutive model in numerical simulations. The modeling results are compared with the measurements of centrifuge experiment and the capabilities of the model to predict the liquefaction of soil around tunnels are assessed.

Damages due to Northridge and Kobe earthquakes were expressive of considerable effects of vertical components of earthquakes compared to the horizontal ones. On the other hand, thin steel plate shear wall is one of the newest resistant systems which until now it`s behavior haven’t been investigated under vertical component of earthquake. Therefore, in this article, effects of vertical component on seismic responds such as displacement and stories shear and forces of columns and beams with usage of non-linear time history dynamic analysis under several ground motions of vertical and horizontal components of earthquakes in 3, 10 and 20 frames is studied. Results of analysis show that vertical component of earthquake has considerable effect on seismic responds of steel shear walls.

Molecular diffusion is one of the important contaminant transport mechanisms through soil and rocks. In this study the molecular diffusion coefficient of marl stone and sand stone from the Urmia City landfill site was determined using the best fit method of the observed laboratory data and the predicted theoretical data. The marl stone and sand stone samples were tested under the conditions of “through diffusion” and “in diffusion”, respectively, and the observed chloride concentrations were determined. The computer code of Pollute was used for theoretical calculations. The average diffusion coefficients of 2.48x10-10 (m2/s) and 2.55x10-10 (m2/s) were obtained for marl stone and sand stone, respectively, which show the similarity of this parameter in both samples due to the compatibility of the effect of physical parameters of the samples such as porosity and density. The results of the sensitivity analysis of the affecting parameters in molecular diffusion in modeled stones showed that the parameters of time and diffusion coefficient have more effect on the concentration of chloride ion at the end of the migration path through stone. The good agreement between the data of the experimental and theoretical models shows the accuracy of the adopted experimental methods and theoretical model. The results of this study could be used in contaminant transport calculations in the design of solid waste landfills situated on bed rocks.