نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال پنجاه و یکم شماره 1 (پیاپی 102، بهار 1400)

Morrison et al. (2015) proposed a controlled heating process for steel in which every property of steel remains constant except its strength (i.e. yielding strength). This novel idea is used for the weakening of beam sections as reduced beam section (RBS) moment connections do. Therefore, plastic hinges develop away from the column face. In this paper, in addition to study the near-fault effects on this type of moment connections, parametric analyses are performed. Moreover, the seismic performance of this new weakened connection is evaluated using nonlinear static analyses. With regards to the obtained results, the best region of beam for heating is determined and seismic performance factors are proposed.

It is almost three decades that finding the release time and location of pollutant sources in rivers has attracted the researchers’ and pundits’ attention. In most of the current studies related to finding the release time and the location of pollutant sources, each of the researchers has considered their own specific circumstances in kind of hypotheses and problem solution methods. In a more general study, in previous studies researchers have used three approaches for solving the inverse problem of the pollutant transport equation. The first approach (simulation-optimization methods) includes characteristics such as combining an optimization algorithm with other numerical methods of solving transport and hydrodynamic equations. The need to use computers with strong processors for solving inverse problem is a type of computational costs that can be counted as a weakness for this method (Mazaheri et al., 2015). The second approach (probabilistic and geostatistical methods) focuses on using probabilistic and geostatistical distribution. Furthermore, using this method would assist to decrease computational volume for finding inverse problem answers, and finally would reduce number of simulations. So, that is an advantage for this method.

Masonry Infills are assumed as non-structural elements and are not considered in the design process of the infilled frames while their presence can affect the local or global behavior of infilled frames. In the present study, the out-of-plane behavior of masonry infilled frames was studied numerically in the finite element software of DIANA. To have an accurate numerical model, an experimental test was performed and the numerical model was validated based on the experimental results. The influence of different parameters such as the presence of central opening and Infill's mechanical and geometrical properties were thoroughly investigated. The results showed that the presence of a central opening can have a major influence on the out-of-plane response of the infilled frames. It is also concluded that infills with higher compressive strength and larger thickness present better out-of-plane response in terms of strength and stiffness. Finally, it is obtained that using infills with higher tensile strength does not increase their out-of-plane strength.

The pavement engineering approach in recent decades has been to develop the use of cement in pavements, including concrete pavement, in particular roller concrete pavement. Some problems with the implementation and application of this type of procedure have led researchers to focus on the subject matter of this type of pavement. In this respect, one of the problems with the level of roller concrete, which, in technical terms, is “surface wear” Known as surface abrasion and surface cracks. Surface abrasion, in addition to reducing the thickness of the pavement layer and defective bearing capacity, in the amount of surface friction and creating a driver safety problem due to the dispersion and throwing of aggregates, it also has a negative effect on the surrounding and passing vehicles. Repair and maintenance is an optimal and economical solution in road pavement management. The use of Chip Seal as preventive maintenance is a two option maintenance for low-volume traffic in highway pavements (Vaitkus et al., 2018, Khabiri, 2005), In previous studies, micronutrient aggregate has been used more than usual, as an example of research on the effect of surface aggregates and bitumen on the performance of peeled aggregates in chip seal (Aktas et al., 2013). The main purpose of this research is to use a fine grading and emulsion bitumen with a rubber powder additive in roller compacted concrete pavement.

Progressive collapse of building structures typically occurs when an abnormal loading condition causes a sudden loss in the structural capacity of one or more critical members, which leads to a chain reaction of failure and ultimately catastrophic collapse (Tohihi et al, 2014). In this research, based on alternative load path (ALP) approach, with using three-dimension (3D) finite element (FE) method, numerical studies were conducted for investigation progressive collapse resistance of beam-column joints in reinforced concrete (RC) frame under loss of exterior ground column. The paper presents a simple and reliable FE model that predicted the nonlinear load-deflection response of tested RC joints conducted by other researchers. Experimental models including two set of interior and exterior subassemblages were analysis under monotonic loading to simulate gravity load on the damaged frame after a blast. In the numerical simulations, the nonlinear behavior of materials was modeled by appropriate constitutive laws. The comparisons between numerical and experimental responses highlighted the reliability of proposed FE model. In addition, a parametric study is conducted using the validated models to investigate effect of slab on the behavior of the subassemblages and the transverse reinforcement ratio and slab effects on performance of substructures that covering both the interior and exterior joints.

Iran is one of the most seismically active areas in the world. Railway tunnels are an integral part of the infrastructure of modern society. Railway tunnels built in areas subject to earthquake activity must withstand both seismic and static loading. In this manner, some railroad tunnels need retrofitting. They have been designed without considering the seismic loading and can damage in future earthquakes. Thus, these tunnels should be evaluated, seismically. This paper, presents a summary seismic analysis and evaluation of railroad tunnels with stone masonry lining. 68 railroad tunnel is investigated, in this manner, as a case study.

In the present paper, results of experimental and numerical investigations on the stress concentration factor (SCF) distribution in internally ring-stiffened tubular KT-joints of offshore structures are presented. In this research program, experimental study was followed by a set of parametric stress analyses for 118 steel ring-stiffened KT-joints subjected to axial loads. The analysis results were used to present the general remarks on the effect of geometrical parameters on the SCF distribution along the weld toe, and to establish a new set of SCF parametric equations.

Successful implementation of civil projects is one of the key factors for the economic development of each society. Every year, a major part of the country’s capital allocates to civil and infrastructure projects. Most of these projects are implemented with delay. Analyzing the factors affecting delays in these projects is essential with the aim of omitting the factors and timely implementation of the projects. Over the years, professionals and researchers have investigated various aspects of delays. For example, causes of delay in large construction projects in Saudi Arabia were studied by Assaf and Al-Hejji (2006). Sweis et al. (2008) identified and classified causes of construction delays in residential projects in Jordan. Factors affecting delays in Indian construction projects were analyzed by Doloi et al. (2012). Aziz (2013) identified various factors causing delay in construction projects in Egypt. Delay causes of road construction projects in Egypt were explored by Aziz and Abdel-Hakam (2016). Arditi et al. (2017) studied the effect of organizational culture on delay in construction. In this paper, after a revision of related researches and considering experts' opinions, different factors affecting projects delay in Iran are identified. Then the factors are prioritized by using the analytical hierarchy process (AHP).

One of the most used deep foundations are piles. The piles are tall members that are used to transfer the foundation loads from the weak layers of the soil to the ground at a deeper and stronger layers. In some structures, the piles may be exposed to uplift forces, including those subjected to extreme overturning moment, such as power towers or docks. During numerical modeling in relation to vertical pile under axial load, it was observed that the axial load bearing capacity of the pile was reduced at the presence of lateral loading (Abdel-Rahman and Achmus, 2006). For the pile under load, the ultimate vertical load ratio (p < sub>u) to the lateral loading (p < sub>L) was greater than 1, with a maximum resistance to load times, when the load angle was 30 degrees. The ratio p < sub>u/p < sub>L was between 0.18 and 0.72, and for the angle of 60 degrees, p < sub>u/p < sub>L less than 0.18 ratio, the ratio value is maximized at 90 degrees (Chattopadhyay and Pise, 1986). Baki et al. (2013) reported that the optimal load bearing of the piles under tensile loading is achieved in rough piles in anchored sand. By changing the angle of application of the tensile loading from zero to 60 degrees relative to the vertical, the pile frictional resistance only turns to the side resistance with the lateral side of the earth, and both components contribute to the final capacity. The study of piles behavior under oblique tension loadings showed that tensile loads are depending on the buried length ratio (L/d), the ratio of the enlarged base diameter to the pile diameter (B/d), the loading angle (α) and the relative density of the soil around the pile (Dr). The ultimate resistance of pile increases with increasing the ratios of (L/d), (B/d) and soil density. The analysis of the results showed that the critical angle (αcr) which the pile reaches its maximum tensile strength depends on the ratio (L/d), (B/d) and soil density (Mandal et al., 2002). The tensile load capacity of the buried enlarged base pile in the sand was studied using physical modeling tests. Analysis of the results showed that the uplift tensile capacity of pile increases significantly with increasing the ratio of buried length to pile diameter more than two and also, increasing the relative density of the sand. The results also showed that the increase in the pile diameter leads to tensile load of the pile (Nazir et al., 2015). A series of laboratory study and numerical analysis of finite element were performed to evaluate the efficiency of enlarged base piles with increasing cross-section at different levels of the pile length in order to improve its uplift capacity. The results of the study showed that with increasing the cross-section of the pile at different levels, the tensile capacity of piles increased, and the amount of sand deformation around the pile decreased (Moayedi and Mosallanezhad, 2017).

Understanding the ultimate and the working strength and stiffness of the connections is required for the design of spatial structures. Comparison of numerical modeling with the experimental results is the most useful method to investigate the structural behaviour of the joints. The geometry and proportions of a particular connection depend on various factors such as the magnitude of forces, the size of the structural members, the end-details of the elements, the method of construction and economic factors. This paper studies the structural behaviour of the joints of a steel lattice cooling tower. A good number research on spatial structures is devoted to obtain the strength and stiffness of the nodes and/or assembly of nodes and structural members. For instance, Maalek (1999) presents the results of experimental and numerical works on Akam socket joints. In this work, Akam spherical socket nodes of diameter 250 mm of ST37 and ST52 are subjected to various biaxial combinations of tensile and compressive forces. Chenaghlou et. al. (2014) study the behaviour of a type of ball joint and propose a model for obtaining its rotational rigidity and strength under various loading conditions. Davoodi et. al. (2012), study the nonlinear behaviour of a ball joint used in spatial structures. Ahmadizadeh and Maalek (2014), investigate the effect of the flexibility of the socket joints in spatial structures.

Wind turbines are installed in windy coastal and offshore regions to extract the wind energy with high efficiency (Barari et al. 2017). The construction cost of the foundation of offshore wind turbines is about 30% of the cost of all superstructure and foundations. Therefore, the economic design of the foundation is critically important and many researchers have focused on it. Offshore wind turbines are usually constructed on gravity-based or monopiles. Bucket foundations or skirted foundations are widely used in offshore regions, oil and gas industries. The use of bucket foundations has been increased in offshore regions especially for foundations of wind turbines over the past two decades (Byrne and Houlsby 2004; Eid, 2013). The behavior of tripod and pile foundations in liquefied soils was investigated. But there are limited reports and studies on the behavior of bucket foundation in liquefied soils (Yu et al., 2015). Conducted some centrifuge tests on wind turbine models with suction caisson foundations to study the behavior of bucket foundations in liquefied soils. It was found that increasing the foundation diameter and length of the skirt had the highest impact on the reduction of pore pressure. Moreover, an increase in the skirt length had the highest impact on the reduction of settlement.

Marly soils have a relatively good resistance in the dry state, but these characteristics tend to significant degradation in contact with water (Ouhadi & Yong, 2003, Hosseini et al. 2012). The Failure to identify the behavior of clayey fine-grained soils, and especially marls, can challenge the structures constructed on such soils. Because of the extent and distribution of this type of soil in many regions of Iran, especially in southern Iran, and the high potential for the construction of hydraulic structures in these areas, it is necessary to study the behavior of these soils. Accordingly, the purpose of this study is to investigate the geotechnical characteristics of marl soils and provide a solution for improving the engineering properties of these soils.