s. m. mirhosseini

Successful civil projects are one of the key factors in the economic development. Civil projects are always criticized for time and budget wastage. Delays in the execution of these projects sometimes not only waste national resources and cause social damages, but also may ultimately render the project economically unjustifiable, to the extent that the direct and indirect damages from delays can sometimes exceed the actual value of the project. However, despite all government efforts, projects in Iran still suffer from delays. Therefore, managing the delays in construction projects in Iran for optimal utilization and proper management is essential. This research proposes a delay management model for construction projects based on evaluating the effective factors on the delay of construction projects in Iran using system dynamics and optimization methods. Finally, a model suitable for the managerial situation in top-ranked contracting companies in Tehran province was presented. The validation and credibility assessment of the proposed model in managing the delay of construction projects in Iran indicated that, by combining these two approaches, project managers can improve project performance under dynamic system conditions. This innovation can be utilized in different industries, especially in the construction industry. In fact, this study provides an optimal response to the management of delays in construction projects by changing the planning horizon using integrated tracking methods and identifying the best strategy and planning horizon for policymakers. Through this, an optimal planning horizon for managing delays in construction projects in the real world is achieved.

The experience of past earthquakes and the weak seismic performance of some structures have highlighted the need for modern seismic systems. Therefore, further examination of lateral seismic systems, such as energy dissipation dampers, is essential for improving the seismic performance of existing systems. Energy dampers can generally be divided into two categories: velocity-based dampers, such as viscous dampers, and displacement-based dampers, such as yielding and friction dampers. Friction dampers are one of the most effective energy dissipating devices in structures, capable of dissipating seismic energy through friction without causing damage (yielding). This paper studies a new system combining a knee-braced frame (KBF) with a friction damper (KBFD). The damper used is a linear friction damper with a slotted bolted connection. The goal of incorporating the friction damper in this configuration is to help prevent out-of-plane buckling of the brace equipped with the damper and to maximize the capacity of damper to improve the seismic performance of the KBF. In this paper, the finite element model of the KBFD was first validated using experimental results. Then, six types of KBFD frames, with varying pre-tension forces in the friction damper considered as a variable parameter, were studied. These studies included performing pushover analysis to calculate the seismic parameters of the structure, such as ductility and behavior factors. The results of these analyses indicate an improvement in the seismic performance of the KBFD compared to the KBF, with both the ductility and behavior factors increasing. Based on the results, with increasing pre-tension force, the behavior factor also increases and is suggested to range between 7.9 and 9.0. Additionally, these frames were subjected to cyclic loading to further study their seismic behavior. The results of the frame analyses were reported as hysteresis curves, initial and secant stiffness, frame resistance, ductility, behavior factor, dissipated energy, and equivalent viscous damping. The results demonstrate that the friction damper effectively reduces the seismic demand on the braces and columns. Furthermore, the obtained hysteresis curves show a high level of input earthquake energy dissipation and appropriate seismic performance of the frames with the proposed configuration.

Acceptable seismic performance, ease and low cost in design and implementation are advantages of passive dampers, but fixed performance parameters corresponding to the type and amount of input energy reduce their efficiency. In this research, a new two-level passive damper in rigid connections with variable stiffness, strength, and energy absorption capacity is introduced and its seismic performance in 5, 10, and 15-story steel frames is evaluated with nonlinear dynamic analysis using SAP2000 software. The results show that, despite the different dynamic parameters in the selected seismic records, such as the frequency content and duration of ground motions, the performance of the structures under all earthquakes has improved significantly, which confirms the effectiveness of the proposed damper in rigid connections on improving the seismic performance structures. Besides, results prove the proposed damper effectiveness on decreasing the structural response such as maximum displacement and base shear. The average displacements reduced by 61%, 51% and 16% compared to those of BSEEP-4ES connections for the 5, 10 and 15-story frames, respectively. Besides, maximum base shear forces reduced by average of 29% and 15% compared to those of BSEEP-4ES connections for the 5 and 10-story frames, respectively.

Ignoring the primary damage to structural components due to blast load or fire is the alternate load path (APM) method's weakness in progressive failure analysis. The new technique used in this study examines the structure's more realistic responses by considering the initial cause of the failure. Also, buckling-restrained braces (BRBs) are applied to diminish the potential for progressive failure in braced steel buildings. Variables include the type of primary local loading (APM, blast loading, and heat caused by fire), the position of column removal in the plan (inner and outer frame), the type of brace (BRB and CB), and the number of stories (3, 5, and 8 stories). The buildings were simulated using ABAQUS. The results showed that BRBs in steel buildings under blast load, compared to conventional braces, reduce the potential of progressive failure. The use of BRBs provides much more energy absorption than conventional bracing systems due to brace buckling prevention.

The idea of using paper wastes in concrete to reduce environmental pollution and Silica fume to improve the properties of concrete is a huge transformation in the building industry. In this study, the effect of waste paper ash along with silica fume on mechanical properties of concrete was investigated experimentally. The cement was replaced with different percentages of paper waste ash (0, 2.5, 5, 7.5, and 10%) and Silica fume (0, 2.5, 5, 7.5, and 10%). Then, 25 mix designs were prepared. Compressive strength, indirect tensile strength, flexural tensile strength, slump, ultrasonic pulse velocity, and impact tests are performed for all concrete specimens at different ages. Also, creep was presented for concrete-containing waste paper ash and silica fume based on existing equations and they were compared with the concrete code of USA and concrete code of Iran. These equations were suggested to predict the behavior of concrete-containing waste paper ash and silica fume. It was also observed that at a constant water cement ratio and for all ages, Silica fume and paper waste ash increased. Also, based on the results of this study, empirical relationships were presented for the relationship among indirect tensile strength and 28-days compressive strength of concrete, tensile strength due to flexural and 28-day compressive strength of concrete specimens, compressive strength and specific weight. Thus, these equations could be used to predict the behavior of concrete-containing paper waste ash and Silica fume. The tensile strength/compressive strength ratio of ordinary concrete was about 10. However, this ratio was between 13.55 and 17.79 in concrete specimens containing waste paper ash and silica fume. The compressive strength ratio of 28 days to 90 days was between 0.67 and 0.81. However, this ratio was between 0.55 and 0.65 in ordinary concrete, which indicates the higher initial strength of specimens containing waste paper ash and silica fume.

Light hierarchy is a secondary but highly influential issue in the perception of space and forming a unique experience in architecture. Light hierarchy is due to a light gradation which presents the priority of space content and leads the users into the space around him. This is a significant subject in Iranian-Islamic architecture that is considered in constructing a pleasant building in various ways.

To identify the factors contributing to the Light hierarchy, experts in the field of Iranian-Islamic architecture were surveyed by the Delphi method to identify the factors and their role as fundamental, main or complementary factors. To be specific, experts were also asked to rate the role of factors in the creation of light hierarchies with a Likert scale of 5 degrees. Wilcoxon test was used to analyze data at the last part.

The factors were divided into three categories: “Lighting Elements” (such as normal opening and lattice opening), “Intermediate communication with outer space”, and “Decorating”.

Experts believed that the “normal opening” had a significant effect on the “fundamental factor” in creating a light hierarchy. In addition, “lattice opening” and “architectural spaces” were identified as the “main factor” factors controlling the light, and decorations as the “complementary factor” influence the light hierarchy.

Investigating the behavior of the box-shaped column panel zone has been one of the major concerns of scientists in the field.  In the American Institute of Steel Construction the shear capacity of I-shaped cross- sections with low column thickness is calculated. This paper determines the shear capacity of panel zone in steel columns with box-shaped cross-sections by using artificial neural network (ANN) and genetic algorithm (GA). It also compares ABAQUS finite element software outputs and AISC relations. Therefore, neural networks were trained using parametric information obtained from 510 connection models in ABAQUS software. The results show that the predicted shear capacity of the NN and the GA in comparison with the AISC relations use a wide range of all effective parameters in the calculation of the shear capacity of panel zone. Therefore, the use of artificial intelligence can be a good choice. Finally, the GA, along with optimization of a mathematical relation, has been able to minimize the error in determining the shear capacity of panel zones of steel-based columns, even at high column thicknesses.

Construction of structures on sandy soils of northern part of Iran encounters problems due to lack of proper strength properties. In recent years, bottles of Polyethylene terephthalate (PET) such as water bottles caused an environmental threat due to their prolonged persistence. Utilization of these materials for soil improvement seems to be a sustainable approach. In this study, the effect of recycled PET on mechanical properties of Babolsar sandy soil is investigated through an experimental program using direct shear and consolidated drained (CD) triaxial compression tests. Various contents of PET were added to sand with 3%, 5% and 7% cement contents. Curing time and relative density of samples were 7 days and 70%, respectively. Results showed that addition of fiber improves strength parameters such as cohesion and internal friction angle. Furthermore, the effect of the fiber is less marked with an increase in cement content. The samples with 3% cement demonstrated better results in both direct shear and tiaxial tests. By adding 0.5% and 1% PET fibers to the samples containing 3% cement at 100 kPa pressure, the ratio of strength in direct shear tests increased 13% and 24%, respectively, and in the triaxial test, it increased 50% and 93%, respectively.

In this paper, the discrete method of eigenvectors of covariance matrix has been used to weight minimization of steel frame structures. Eigenvectors of Covariance Matrix (ECM) algorithm is a robust and iterative method for solving optimization problems and is inspired by the CMA-ES method. Both of these methods use covariance matrix in the optimization process, but the covariance matrix calculation and new population generation in these two methods are completely different. At each stage of the ECM algorithm, successful distributions are identified and the covariance matrix of the successful distributions is formed. Subsequently, by the help of the principal component analysis (PCA), the scattering directions of these distributions will be achieved. The new population is generated by the combination of weighted directions that have a successful distribution and using random normal distribution. In the discrete ECM method, in case of succeeding in a certain number of cycles the step size is increased, otherwise the step size is reduced. In order to determine the efficiency of this method, three benchmark steel frames were optimized due to the resistance and displacement criteria specifications of the AISC-LRFD, and the results were compared to other optimization methods. Considerable outputs of this algorithm show that this method can handle the complex problems of optimizing discrete steel frames.

Coastal sandy soils cover a large part of the soil of northern part of the country. These soils will have problems due to loose characteristic and lack of proper strength properties for roads building. Beach sand is encountered with the wash-out phenomenon due to uniform gradation and lack of cohesion at the time of the water flow in an unconfined state. To solve the problem of these soils, various methods such as reinforcement with different materials are used. In this research, the effect of adding various percentages of polypropylene fibers to non-cemented and cemented sand on the mechanical characteristics of sandy soils of Babolsar beach was investigated by performing direct shear tests and triaxial tests. According to the results, adding these fibers improves the internal friction angle, cohesion, maximum strength, Failure strain and residual strength of sand. Comparison of the results of direct shear tests and triaxial tests showed that, due to the proper orientation of the fibers relative to the direction of main tensile strains in triaxial tests, the efficiency and their effect on the soil resistance behavior in triaxial samples were more significant than direct shear tests.    

To implement asphalt roads in an area, in many cases, especially in poor and swampy areas, there is a need for improvement. In recent years, the use of reinforced soil is common for the design of roads, foundations and retaining walls. On the other hand, the solid waste management, in terms of large volume and longtime decomposition of wastes such as sack polypropylene fibers, in addition to its effective role in the economic cycle is as one of the important indicators of development at the macro level in developing countries. Therefore, reinforcing of soil with the use of waste materials has a particular importance. In this research, by performing a laboratory experiment, the effect of adding various percentages of sack polypropylene fibers on the behavior and values of strength parameters of non-cemented and cemented sand (with three weight ratios of 3, 5 and 7% and 7-day treatment time) were investigated. The results show that the presence of these fibers has a significant effect on the behavior of non-cemented and cemented sand. Adding these fibers improves the strength parameters (φ and C), increase the maximum strength, failure strain and residual strength of soil. The effect of these fibers on the all studied parameters in non-cemented soil is higher than that of cemented soil. Also, their effect becomes less by increasing the percentage of cement in cemented soil. According to the research, these materials can be used in the road beds, which has environmental benefits, in addition to economic benefits

A wide ranges of variables effect on the medical errors such as job involvement and organizational commitment. Coincidental relationship between two variables on medical errors during outpatients’ visits has been investigated to design a model. A field study with 114 physicians during outpatients’ visits revealed the mean of medical errors. Azimi and Allen-meyer questionnaires were used to measure Job involvement and organizational commitment. Physicians divided into four groups according to the Job involvement and organizational commitment in two dimensions (Zone1: high job involvement and high organizational commitment, Zone2: high job involvement and low organizational commitment, Zone3: low job involvement and high organizational commitment, Zone 4: low job involvement and low organizational commitment). ANOVA and Scheffe test were conducted to analyse the medical errors in four Zones by SPSS22. A guideline was presented according to the relationship between errors and two other variables. The mean of organizational commitment was 79.50±12.30 and job involvement 12.72±3.66, medical errors in first group (0.32), second group (0.51), third group (0.41) and last one (0.50). ANOVA (F test=22.20, sig=0.00) and Scheffé were significant except for the second and forth group. The validity of the model was 73.60%. Applying some strategies to boost the organizational commitment and job involvement can help for diminishing the medical errors during outpatients’ visits. Thus, the investigation to comprehend the factors contributing organizational commitment and job involvement can be helpful.

Linguistically, the use of indefinite article in Arabic language is considered as one of the significant subjects that has attracted a lot of attention. Scholars such as Jorjani and Zamkhshari have understood some noticeable points with regard to indefinite article usage in the Arabic language. To do so has special reasons. In other words, indefinite article usage in Arabic makes our speech more eloquent. Accordingly, the use of indefinite article in Arabic is preferable to that of definite one since it is more consistent with the message the speaker wants to convey.Hence, the reasons why I am determined to deal with indefinite article usage in Arabic are, at first I want to prove how eloquently Ali (AS) used indefinite article in Nahj-ol-Balagheh. In reality, nobody could use it as efficiently as he did. And secondly I want to answer affirmatively those who have some doubts about the fact that Nahj-ol-Balagheh was written by Ali. Only those who are skilled in speechmaking such as Iman Ali can cope with an impromptu speech, while using both eloquent and simple speech style. In fact, his speechmaking style serves all the purposes of speech under any conditions.The current paper has tried to present a scientific classification of indefinite article usage in Nahj-ol-Balagheh in order to display its importance in eloquent speech making. The usage of indefinite article in Imam Ali’s speech has different purposes such as greatness, profusion, diminution, and kind. The aforementioned items are both consistent with eloquent speech style and effective in purpose and focal points of eloquent speech.

S a n d s i n n a t u r e g e n e r a l l y c o n t a i n p l a s t i c a n d n o n-p l a s t i c f i n e s. P r e v i o u s r e s e a r c h h a s b e e n m a i n l y f o c u s e d o n t h e c y c l i c b e h a v i o r o f s a t u r a t e d c l e a n s a n d. R e c e n t s t u d i e s, h o w e v e r, r e v e a l t h a t t h e c y c l i c b e h a v i o r o f s a t u r a t e d s a n d c o n t a i n i n g p l a s t i c f i n e s i s q u i t e d i f f e r e n t f r o m t h a t i n c l u d i n g n o n-p l a s t i c f i n e s. M o r e o v e r, m o s t l i q u e f a c t i o n s t u d i e s h a v e c o n c e n t r a t e d o n s t r e s s-c o n t r o l l e d c y c l i c t r i a x i a l t e s t i n g o f c l e a n s a n d, w h i l e s t r a i n-c o n t r o l l e d t e s t i n g a l l o w s a m o r e f u n d a m e n t a l a s s e s s m e n t o f p o r e p r e s s u r e g e n e r a t i o n. I t i s d u e t o t h e s t r o n g r e l a t i o n s h i p b e t w e e n s h e a r d e f o r m a t i o n a n d p o r e p r e s s u r e g e n e r a t i o n. I n t h i s s t u d y, t h e e f f e c t s o f p l a s t i c a n d n o n-p l a s t i c f i n e s o n t h e p o r e w a t e r p r e s s u r e b e h a v i o r o f s a t u r a t e d s a n d a r e s t u d i e d b y m e a n s o f a s t r a i n c o n t r o l l e d c y c l i c t r i a x i a l t e s t s. T o t h i s a i m, a l l s p e c i m e n s a r e p r e p a r e d b y m o i s t t a m p i n g u s i n g t h e u n d e r c o m p a c t i o n t e c h n i q u e. S p e c i m e n s a r e s u b j e c t e d t o 50 s i n u s o i d a l c y c l e s o f a x i a l s t r a i n a t a l o a d i n g r a t e o f 0.1 H z. F u r t h e r m o r e, s h e a r s t r a i n l e v e l s a r e a p p l i e d i n t h e r a n g e o f 0.003% t o 0.3%, a n d p o r e p r e s s u r e i s d i r e c t l y m e a s u r e d i n t h e s p e c i m e n s. T h e r e s u l t s d e m o n s t r a t e t h a t t h e s p e c i m e n s w i t h u p t o 15% n o n-p l a s t i c f i n e (s i l t) c o n t e n t g e n e r a t e a l o w e r v a l u e o f p o r e w a t e r p r e s s u r e t h a n t h a t o f c l e a n s a n d. I n c r e a s i n g s i l t c o n t e n t t o 30% l e a d s t o a p o r e p r e s s u r e c l o s e t o t h a t o f c l e a n s a n d. O n t h e o t h e r h a n d, i n s a n d s p e c i m e n s w i t h u p t o 20% p l a s t i c f i n e s (k a o l i n i t e), g e n e r a t e d e x c e s s p o r e w a t e r p r e s s u r e i s m o r e t h a n t h a t o f c l e a n s a n d. U p t o t h i s p l a s t i c f i n e c o n t e n t, s a n d g r a i n s s t i l l g e t i n t o u c h w i t h e a c h o t h e r, a n d c l a y p a r t i c l e s p l a y a r o l e l i k e a l u b r i c a n t f i l m b e t w e e n t h e m. T h e r e s u l t i s a m o r e c o l l a p s i b l e f a b r i c a s t h e s a n d-s k e l e t o n t r i e s t o r e a r r a n g e i t s e l f i n t o a m o r e s t a b l e s t r u c t u r e. B y i n c r e a s i n g p l a s t i c f i n e s u p t o 30%, t h e e x c e s s p o r e w a t e r p r e s s u r e n o t i c e a b l y d e c r e a s e s t o a l e v e l t h a t i s l e s s t h a n t h a t o f c l e a n s a n d. T h i s c o u l d b e a t t r i b u t e d t o t h e f a c t t h a t a t l a r g e r f i n e c o n t e n t, t h e s a n d-s k e l e t o n v o i d r a t i o i s l a r g e r t h a n t h e m a x i m u m v o i d r a t i o f o r c l e a n s a n d. T h e r e f o r e, t h e s a n d g r a i n s a r e n o l o n g e r i n c o n t a c t, f l o a t i n g i n t h e k a o l i n i t e m a t r i x. T h u s, t h e s p e c i m e n s h o w s a c l a y-l i k e b e h a v i o r. C o n s e q u e n t l y, t h e b e h a v i o r o f t h e s p e c i m e n i s c o n t r o l l e d b y t h e f i n e s, s o t h a t t h e s p e c i m e n i n d i c a t e s c y c l i c m o b i l i t y b e h a v i o r. T h i s i n v e s t i g a t i o n r e v e a l s t h a t t h e c o n v e n t i o n a l c r i t e r i a f o r l i q u e f a c t i o n a s s e s s m e n t, s u c h a s t h e s t a n d a r d p e n e t r a t i o n t e s t (S P T), d o n o t c o n s i d e r t h e e f f e c t o f t h e p l a s t i c i t y o f f i n e s. T h e r e f o r e, t o e v a l u a t e t h e l i q u e f a c t i o n p o t e n t i a l o f s a n d s c o n t a i n i n g f i n e s, o n e s h o u l d r e s o r t t o o t h e r p r e c i s e t e s t s, s u c h a s c y c l i c t r i a x i a l t e s t s.