Sharif Journal of Civil Engineering

Three-dimensional analyses are conducted to study the effects of ground motion and the presence of velocity pulse on the pile responses in liquefiable soils. Liquefaction of soils is an important issue in geotechnical engineering. Soil liquefaction occurs when saturated or partially saturated soil substantially loses strength and stiffness in response to applied stress, such as shaking during an earthquake or other sudden changes in stress conditions. The forward directivity effect, which includes a large velocity pulse at the beginning of the velocity time history of the ground motion and contains most of the seismic energy from the rupture, is the most damaging phenomenon observed in near-field ground motions. To investigate the effect of near-field ground motions on the seismic response of a soil-pile system, a three-dimensional model consisting of the two-layered soil and the pile is constructed. Modeling is conducted by using the FLAC 3D software. The P2PSand model is applied for the modeling of sandy soil. P2PSand model refers to a Practical TWO-surface Plastic SAND constitutive model for general 3D geotechnical earthquake engineering applications aimed at capturing essential soil dynamic characteristics. The model is a modified extension of the fabric-dilatancy-related sand plasticity DM04 model developed by Dafalias and Manzari. The Dafalias-Manzari two-surface model (DM04) is a critical-state compatible and state parameter-related plasticity model developed in the framework of Bounding Surface theory, which has been widely implemented and studied. Dynamic analyses are conducted for the soil-pile system under the excitations of four selected ground-motion suites that were recorded on the rock. The results show that near-field velocity pulses have a considerable effect on the behavior of the system and cause sudden large displacement demands on the piles and soil. The pulse in the record of near-field ground motion has caused the pore water pressure coefficient (Ru) to increase and liquefaction in the upper soil layer.
Keywords: Liquefaction  FLAC 3D  Seismic Response  Soil-pile Interaction  Pulse-like ground motion

Three-dimensional analyses are conducted to study the effects of ground motion and the presence of velocity pulse on the pile responses in liquefiable soils. Liquefaction of soils is an important issue in geotechnical engineering. Soil liquefaction occurs when saturated or partially saturated soil substantially loses strength and stiffness in response to applied stress, such as shaking during an earthquake or other sudden changes in stress conditions. The forward directivity effect, which includes a large velocity pulse at the beginning of the velocity time history of the ground motion and contains most of the seismic energy from the rupture, is the most damaging phenomenon observed in near-field ground motions. To investigate the effect of near-field ground motions on the seismic response of a soil-pile system, a three-dimensional model consisting of the two-layered soil and the pile is constructed. Modeling is conducted by using the FLAC 3D software. The P2PSand model is applied for the modeling of sandy soil. P2PSand model refers to a Practical TWO-surface Plastic SAND constitutive model for general 3D geotechnical earthquake engineering applications aimed at capturing essential soil dynamic characteristics. The model is a modified extension of the fabric-dilatancy-related sand plasticity DM04 model developed by Dafalias and Manzari. The Dafalias-Manzari two-surface model (DM04) is a critical-state compatible and state parameter-related plasticity model developed in the framework of Bounding Surface theory, which has been widely implemented and studied. Dynamic analyses are conducted for the soil-pile system under the excitations of four selected ground-motion suites that were recorded on the rock. The results show that near-field velocity pulses have a considerable effect on the behavior of the system and cause sudden large displacement demands on the piles and soil. The pulse in the record of near-field ground motion has caused the pore water pressure coefficient (Ru) to increase and liquefaction in the upper soil layer.
Keywords: Liquefaction  FLAC 3D  Seismic Response  Soil-pile Interaction  Pulse-like ground motion

The understanding of architecture as an ecology of interactive systems moves past limitations and restricted tendencies toward spatial environments that are adaptive, perceptual, and behavioral. In this framework, the environment seeks to build interaction scenarios to activate relationships between components. In this case, architecture moves away from well-known models that always lead to disciplined responses and toward understanding adaptive ecologies that include active particles for communication and exploration. The current research investigated and discussed the design of a system that can replace the current methods of planning the construction of infrastructure units in the future. The result is the simulation of a cellular self-assembly system that can produce and rebuild its structure when needed. Therefore, there is a revolution in construction and a complete revision of architectural standards and construction planning, disremembering demolitions and laborious construction costs. This study aims to explore the function of quorum sensing, a mechanism of intra-species communication that serves as the central regulatory system in the formation and concurrent response to environmental changes. The algorithmic design features of the system's constituent units were also examined. During the assembly process, extracellular matrices act as the milieu in which individual cells interact with one another and the desired environment as constructed building blocks. This allows for parallel assembly and error correction at a general level, both automatically, and has significant implications for the field. The proposed model uses a two-level control system (micro-macro) to ensure that the interactions among the components, on the one hand, and between the components and their environment, on the other hand, are in line with the objectives of the plan and the balance of the whole system. This two-level approach primarily follows a bottom-up process at the scale of the interaction of its constituent particles and subsequently utilizes a top-down process during the overall regulation of the system through the extracellular matrix. Ultimately, the simulation results obtained using Grasshopper3d software were shown in three scales: small (chair), medium (shelter), and large. This approach has been demonstrated to be effective in previous research and offers a promising framework for further investigation in this field. This research can take essential steps in developing simulator machines to build a construction self-assembly system based on sequential configurations and numbers.
Keywords: Adaptive Ecologies  Self-assembly  Living Architecture  Diffusion Limited Aggregation  Reversible Fabrication

One of the main damages of the nonstructural masonry walls during an earthquake is its instability and collapse on the combination of deformation at the in-plain direction caused by lateral inter-story drift of structures and out-of-plane inertial forces applied to the wall because of earthquake acceleration. In most of the researches, only one of these actions was investigated, or their interactions were not directly investigated.
In this research, a combination of in-plane and out-of-plane loadings was carried out, and the effect of reinforcing on the nonstructural walls by using fiber mesh reinforced mortar and bed joint rebar has been investigated.
For this purpose, three wall specimens with scale of 1 to 1 were made of Leca blocks. Walls were subjected to a combination of in-plane cyclic loading and out-of-plane loading. The results showed that nonstructural walls, without reinforcement, failed under out-of-plain force in low in-plain drift, and the test process was stopped. On the other hand, strengthening the nonstructural wall with fiber mesh reinforced concrete caused an increase of 15% and 54% in the drift ratio related to the reduction of the wall resistance and the maximum in-plane force compared to the nonstructural wall, which was strengthened with bed joint reinforcement.
Keywords : Masonry wall  TRC  Textile Reinforced Mortar  Bed joint reinforcement  Hysteresis behavior

One of the most common methods of identifying modal parameters in the field of operational modal testing is the method of identifying sub-random space and frequency domain analysis. Unfortunately, the scope of these methods' application is limited to static signals with a long pick-up time, and if the above conditions are violated, the results will be erroneous; This is in the context that the above two conditions are not met regarding the earthquake signal, and so far the reliability of these methods and their error rate in the face of this group of signals have not been studied. In this regard, in this study, the performance of these methods in earthquake conditions (both conditions are violated) is studied.
For this purpose, an numerical model of two two-dimensional frames with different heights (five and ten floors) is created and stimulated by using 20 earthquake records in the near and far fields. Using the obtained results and comparing them with the results of the numerical model, the error values for the modal parameters are obtained; Also, with the statistical study of the errors in the estimation of the frequency of the structure, the probability distribution function of the error and an estimate of the distance of the error are suggested .The results of the study showed that (a) the method of identifying random subspace has a better performance than the method of frequency domain analysis; (B) The random subspace detection method is not able to detect the first modes and is proposed to identify higher modes; (C) the efficiency of the frequency domain decomposition method decreases with increasing structural height; (D) By optimizing and locating the sensors, the performance of the frequency domain analysis method is dramatically improved. However, in the random subspace detection method, the detectability increases with the number of sensors.
Keywords:
Operational modal analysis  Frequency domain analysis  identification of random subspace  structural health monitoring
Main Subjects

Nonlinear Time History Analysis (NTHA) contains a complex and rigorous process for structural seismic evaluation. Nonlinear static (Pushover) analysis can simplify this process. This paper aims to develop an energy-based seismic assessment methodology using pushover analysis. This methodology can estimate the response of mid-rise buildings with much fewer computational operations than NTHA and consider higher mode effects. Other advantages of the proposed procedure include using the capacity curve of Multiple Degrees Of Freedom (MDOF) systems directly instead of the Equivalent Single Degree Of Freedom (ESDOF) and computing the energy demand of the structure based on the mean spectrum corresponding to the desired hazard level instead of the various earthquake record spectrums. The proposed methodology converts the pushover capacity curve to the energy capacity curve for each mode, and the energy demand curve is superimposed on it. The intersection of these two curves is considered the target response. NTHA and Modal Pushover Analysis (MPA) are employed to validate and compare the proposed methodology with other ones. Also, 4, 8, and 9-story steel moment frame buildings are selected, modeled, and analyzed using OpenSEES software. The results show that the proposed methodology can estimate the responses of the building with reasonable accuracy compared to the mean results of the NTHA. Also, the proposed method significantly reduces the error of the responses compared to the MPA. Nevertheless, it can be concluded that the proposed energy-based methodology can be a simple, efficient, and rapid alternative for NTHA.
Keywords:
Seismic Evaluation  Pushover Analysis  Energy-based Methodology  Higher Mode Effects  Steel Frames

Leachate is a hazardous liquid that leads to numerous environmental problems. Soil pollution is one of the most important of these problems caused by poor leachate management facilities and limited land availability. Studies show that soil characteristics change during contamination, and these changes are a function of the type of soil and leachate. Therefore, it is necessary to evaluate the static and dynamic behavior of soils after contamination with leachate. Despite the importance of this issue, studies in this field are limited only to static behavior, and the effect of leachate on the dynamic behavior of soils remains almost unknown. Hence, an experimental effort has been made in this study to evaluate the effect of waste leachate sampled from the Alborz landfill on the dynamic parameters of three different clays under different overburden pressures (6.29, 18.88, and 31.47 kPa). For this purpose, the amount and type of heavy metals in the leachate were first determined using an inductively coupled plasma (ICP) spectrometer. Then, cylindrical soil samples were prepared in three different leachate contents (0%, 6%, and 12.5%) and subjected to a simple dynamic shear test. Moreover, the samples were photographed using an SEM microscope to investigate the effect of leachate on the soil texture. Based on the hysteresis loops obtained from simple shear tests and, subsequently, amounts of shear modulus (G) and damping ratio (D) calculated from them, it was found that pollution and its increase cause an increase in the shear modulus and a decrease in the damping ratio so that the growth of the shear modulus and the decrease in the damping ratio are affected by the type of soil and are more pronounced in soils with a lower paste range. It was also observed that the greatest effect of leachate on improving the shear modulus of the soil can be seen at lower levels of pollution. The increase in the influence of shear modulus and damping ratio of clay from overburden pressure was identified as one of the effects of soil contamination with leachate, which was more evident in clays with high paste range.
Keywords:
Waste leachate  Shear modulus  Damping ratio  Clay

Traditional patterns could be an effective solution for water consumption and pollution-related problems in the construction industry. However, the water footprint of traditional buildings in Iran has not been investigated. Iran has rich experience in constructing traditional buildings. This paper presents a comprehensive analysis of the grey and blue water footprints of the construction of traditional buildings in Iran with emphasis on different climate zones. The results are compared with modern buildings (concrete and steel). High-quality data related to 11 materials factories and 34 traditional buildings (stone, wood, clay, and brick) are presented. Blue and grey water footprints of building materialization are calculated using the water footprint network and life cycle assessment methods. The focus is on the structures of buildings. The grey and blue water footprints of modern structures are 327 times and 1.5 times larger than the grey and blue water footprints of traditional structures, respectively. Steel and cement production are influential parameters in the greywater footprint of modern structures. Employee meals have the greatest impact on the water footprint of traditional structures. The blue water footprint dominates the water footprint of traditional structures, which is 2.26 times larger than the greywater footprint. Stone structures have a blue water footprint of 0.85 m3/m2, which is dominated by the blue water footprint of employees' food (38.82%) at construction sites. They have a smaller blue water footprint than adobe and brick structures (1.41 - 1.42 m3/m2) and are close to the water footprint of wooden structures. The water footprint of brick structures is mainly influenced by the energy used (57.04%) for brick production. On the other hand, the greywater footprint dominates the blue water footprint of modern structures, which is 99.61 times larger than the blue water footprint. Steel structures have a blue water footprint of 1.86 m3/m2 and a greywater footprint of 208 m3/m2, the main pollutant of which is cadmium. Concrete structures have a blue water footprint of 1.60 m3/m2 and a greywater footprint of 137 m3/m2, with mercury as the main pollutant. From the water footprint viewpoint, it is better to use concrete structures than steel structures if both have suitable properties for the conditions they are used in. According to the results, the non-use of traditional buildings leads to an increase in water consumption and pollution.
Keywords:
Blue water footprint  Greywater footprint  Traditional structures  life cycle assessment

Autonomous vehicles are a proper option for children's school trips due to their high potential. Parents are the main decision-makers in choosing their children's school trip mode, and it is essential for policymakers to be aware of their behavior and willingness, especially when technology is not yet available to the public. Previous studies of self-driving cars (SAVs) have focused on the rejection or acceptance of this technology by adult users, while SAVs are an attractive option for students' educational trips. Few studies in this field emphasize the need to do it, but in the current study, unlike previous studies, the factors affecting the behavior of parents who are unable to make a decision in this regard have been investigated using mathematical modeling. The virtual link of the current study questionnaire (in six sections) was uploaded by the school principals in the educational groups of the selected schools with the parents after experimental questioning and correction. Data analysis shows that almost a high percentage of parents (29%) have not been able to give a definite opinion about whether or not their child uses autonomous vehicles. In this article (for the first time), the factors affecting the inability of parents to make decisions are studied. The binary logit model on the May 2021 questionnaire of parents of fourth to ninth-grade students in Kerman schools (1435 cases) has a correct estimation percentage of 77.1 and a good fit coefficient equal to 0.4. The estimated model shows that the behavioral characteristics and accidental history of parents influence their decisions. In the case of Kerman, parents who have a history of fatal accidents in close relatives and who have a high level of concern about the way they drive and the possibility of a high-traffic accident in public transportation have not been able to decide whether to reject or accept this technology.
Keywords

Autonomous vehicle  School trip  Binary logit model  Policy making  Demand

In this research, the experimental investigation of the inertial interaction of soil-pile raft structure has been conducted for slender structures supported by the combined pile-raft foundation with emphasis on the new concept of design method (performance-based design). Most of the former studies based on this concept have focused on the surface foundation, where the surface foundation's rocking motion acts as a source of energy dissipation to protect the superstructure. Meanwhile, less attention has been paid to the surface foundation combined with piles (Combined pile-raft foundation) as an economic support system for high-rise and heavy structures. Mainly, the focus of optimizing these foundations through parametric analysis has been on variables such as pile arrangement and pile length for vertical static loading. When the heavy structures are subjected to the lateral load caused by the earthquake, the foundation experiences significant inertial moments. Thus, the nonlinear behavior of the foundation is not far from expected. The present research intends to examine the rocking behavior of combined pile-raft foundations as the foundation of slender structures. Evaluating the response of the superstructure and its possible benefit from the nonlinear behavior of the foundation is the principal goal of this research. In this regard, using experimental models, some characteristics of combined pile-raft foundations, such as the arrangement of piles and the relative length of the piles, have been investigated on the response of the superstructure. Three physical models were constructed in the laboratory. Each model contained a single degree of freedom superstructure supported by a floating pile raft foundation in sandy soil. Two characteristics were considered for evaluating pile raft characteristics: pile configuration and pile length ratio. The superstructure was identical in all three physical models. An experimental procedure based on forced vibration tests was presented to assess the dynamic response of the models at different levels of foundation nonlinearity. According to the experimental measurements, the nonlinear behavior of the foundation has a significant role in the response of the superstructure. Dynamic demand reduction as well as drift reduction are the two most important factors that benefit the superstructure from foundation nonlinearity. Accordingly, the dynamic behavior of the models is divided into two individual phases. Also, comparing the results of the models showed that the arrangement of piles and the relative length of the piles in the combined pile-raft foundation have a significant impact on superstructure response.
Keywords

Soil-pile-structure interaction  Performance-based design  Pile-raft foundation  Nonlinear response  Forced vibration

In some roadway projects, especially in a mountainous region, the mechanically stabilized earth walls must be constructed in front of stable features such as a rockface for a variety of reasons, including the construction of new roadways, widening of urban transportation corridors, and reduction of rockfall risk. There has been limited research into the dynamic performance of the MSE wall adjacent to the rock slope; thus, the seismic behavior of this retaining system is still poorly understood. The most common methods for seismic stability analyses of reinforced-soil retaining walls are based on pseudo-static limit-equilibrium approaches, where seismic coefficients are applied to the potential failure soil mass. In the pseudo-static method, the assignment of an appropriate lateral seismic coefficient (Kh) that would be able to simulate the seismic inertial force induced in the sliding wedge has a considerable effect on the accuracy of the analyses. Since earthquake acceleration is the main cause of the inertial force induced in the failure mass, the seismic acceleration coefficient (Kh) is determined mostly based on the peak ground acceleration at the wall base level. The seismic events are transient in nature, and the earthquake-induced forces vary in intensity during vibrations. However, in the pseudo-static method, the seismic force is applied to the failure soil mass indefinitely. Therefore, the use of peak ground acceleration could lead to over-conservative results. To overcome this limitation, the seismic coefficient is usually expressed as a fraction of the peak ground acceleration for design purposes. The value of this fraction has not been clearly defined for reinforced-earth retaining walls. Most of the proposed methods for calculating the seismic acceleration coefficient are based on theoretical assumptions, and the validation of this important parameter has not been evaluated based on an experimental approach. In this study, initially, the seismic behavior of the polymeric-strip reinforced-earth retaining walls built on the rock foundation is investigated using shaking table tests. Then, the assumptions of the pseudo-static approach are simulated by push-back pressure tests. To apply back pressure to a model wall, a special apparatus was designed and made in the Tarbiat Modares University laboratory. Finally, the horizontal seismic coefficient is estimated by comparing and adjusting the result of the shaking table and push-back pressure tests. The results presented are based on the acceptable seismic performance of the retaining wall and are compared with the previously proposed relations and AASHTO design code.
Keywords:
Reinforced-earth retaining wall  rock foundation  seismic acceleration coefficient  shaking table test  push-back pressure test

After the Northridge earthquake, a set of prequalified connections were introduced by international design codes. Thease connections include reduced beam secrion (RBS) moment connection, bolted unstiffended and stiffended extended end-plate moment connection, bolted flange plate (BFP) moment connection, welded unreinforced flange-welded web (WUF-W) moment connection, kaiser bolted bracket (KBB) moment connection, conxtech conxl moment connection, sideplate moment connection, simpson strong tie strong frame moment connection, double tee moment connection, slottedweb (SW) moment connection. After ensuring the seismic performance of this set during earthquakes, concerns surfaced that forming plastic hinges in beam elements would result in either making repairs impossible or incredibly expensive in the event of a moderate or severe earthquake. Hence, a type of replaceable connections was introduced wherein plastic hinges would be placed in pre-determined elements. Their intuitive replaceability feature would make repairs and reutilization of the structure a much easier task. In this study, the experimental investigations of 4 full-scale samples of a replaceable rigid connection under cyclic loading were carried out. The results of the experiments demonstrated that in the proposed connection, the plastic hinge is formed in the fuse element while the beam and the column maintain their elasticity, allowing the connection to be replaced. Also, taking into account the early buckling of the fuse plates installed on the beam flanges, the moment capacity of the connection is decreased by 22 percent compared to the moment capacity of the fuse. According to the results obtained from the backbone diagrams, stiffness of the connection after replacing the fuse plates in P12 and P15 samples has decreased by 8.61% and 6.14%, respectively; this could be due to slight changes on the holes on the beam web and flanges as well as changes in the pre-tensioning forces of the bolts. Investigations have revealed that, the 20% increase in the moment capacity of the fuse (using 15 mm-steel plates instead of 12 mm in the fuse plates of the beam flanges) has increased the cumulative energy dissipation of the connection by 12%.
Keywords

Rigid connections  replaceability  fuse  cyclic loading  prequalified connections

In most buildings, concrete and steel are used side by side, and according to the type of loads, various stresses are created at their interface. When the repair layer is in direct contact with the steel or reinforcement, the stresses caused by the shrinkage of the mortars as well as temperature changes have a negative effect on the adhesion between the repair mortar and the steel. According to the CEB-FIP MODEL CODE standard, the shear adhesion between mortar and simple reinforcement is equal to τ=0.3√(fc). But it has not provided conditions to consider the type of implementation. Considering that shrinkage causes shear stresses at the interface of mortar and steel, therefore, in this article, by using the in-situ twist-off test, the shear adhesion strength between mortar and plain steel has been evaluated under different processing conditions. The results of the twist-off test show that the above equation is used if the sample is under processing until the moment of the test, otherwise there will be a big drop in the amount of adhesion, which even reaches 50%. The results of the shear adhesion strength obtained from the twist-off test for the samples that were processed in water until the time of the test, at a young age are almost equal to the equation provided by the CEB-FIP Model Code standard. At older ages, the shear bond strength results from the twist-off test between mortar and steel are on average more than 10% higher than the equation provided by the CEB-FIP Model Code standard. For the samples that were processed for a week and then left in the open space, it is observed that there is a big difference between the shear adhesion strength obtained from the twist-off test and the equation provided by the CEB-FIP Model Code standard. For practical cases where processing is usually done for about seven days, it is suggested that the shear adhesion strength between steel and mortar is measured for samples that have been subjected to wet processing for at least one week and prepared and stored under appropriate conditions. According to the equation, τ=0.15√(fc) should be considered. The amount of 90-day shrinkage for mortar treated in water and left in open space is 0.1083 and 0.2679%, respectively. The amount of shrinkage for mortar processed in water is 59% less than the shrinkage of mortar left in the open space.

The durability of the rebar used in a concrete structure is very important for the safe and long-term use of that structure, and therefore, the root and the main cause of reducing the life and durability of that structure, which is corrosion, is of great importance. In this study, medium carbon steel bars with a diameter of 14 to 40 mm and a number of epoxy coated and fiber bars have been tested and the effect of simulated corrosion on the samples has been investigated by measuring the mechanical properties. The results obtained from this research can be effective in the field of rebar size selection according to its production method in different conditions. This result has been obtained according to the experiments. Mechanical properties are the main properties of steel rebar affected by corrosion that have been tested in this paper. In the measurement of mechanical properties by universal device, slight changes were seen depending on the type of device. In order to measure the rebar cross section more accurately, machining has been used to prepare the rebars after corrosion. The results of this research also showed that in 14 mm size rebar, with the progress of corrosion up to 0.68 mm, the amount of force tolerated decreased by 16.7% (from 102 KN to 85 KN). Also, in the next step, with 0.62 mm of corrosion progress, the amount of this force has reached 76.3 KN from 85 KN (i.e., 10.2% reduction). In the third stage, with the progress of 0.96 mm, the amount of force borne by the rebar has reached 69.7 KN from 76.3 KN, which is equivalent to a 2.5% decrease. Finally, considering the economic and various application conditions, suggestions have been made to improve the performance and increase the durability and long-term use of the structures with more confidence.

Collapsible soils are one of the moisture sensitive soils that experience sudden and significant settlements due to wetting. These soils are widely distributed and constitute about 10% of the total land area of the world, which are typically located in arid and semi-arid areas. In foundation engineering, the most important issue in dealing with these soils is to measure their collapse potential with different water infiltration patterns. The effect of parameters such as initial soil conditions, loading conditions and gradation quality on the behavior of these soils has been investigated. The amount of clay in the soil is considered as an important factor in the behavior of the collapsible soils. Water enters the soil from different sources, but the existing devices and tests to measure the collapse potential are not capable of modeling water infiltration patterns. In this study, an apparatus was used that simulates different water infiltration patterns based on the direction of water movement (from top or bottom) and type of water distribution (point or wide). The results show that in oedometer tests and tests with the ability to simulate the water infiltration patterns, with the increase in the amount of clay in the sample, the collapse potential increases, but the amount of increase is not the same in different tests. The amount of increase in collapse potential due to the increase of clay in the sample is greater in single and double oedometer tests than in tests with the ability to simulate the water infiltration patterns, and for a more accurate prediction of the collapse potential, tests with the ability to simulate the water infiltration patterns should be used. Among the different water infiltration patterns in the soil, for the sample with  clay compared to the sample without clay, the highest increase in collapse potential is related to the top-point water infiltration pattern ) and the lowest increase is related to the bottom-wide water infiltration pattern( ). But for the sample with 23% clay compared to the sample without clay, the highest increase in collapse potential is related to the top-wide water infiltration pattern( ) and the lowest increase is related to the bottom-wide water infiltration pattern( ). 

Keywords: Clay percent, Collapse potential, Water infiltration pattern, Experimental apparatus, Collapsible soil.

Mass nonlinear dynamic analysis is unavoidable in many fields of earthquake and structural engineering, such as incremental dynamic analysis, probabilistic performance-based design, and optimization approaches. Using simplified models with fewer degrees of freedom instead of detailed original models to a great extent reduces the computational cost and prevents extremely time-consuming analysis. Among different simplified models for steel moment frames, stick models (such as shear beam models) only use the global story stiffness to estimate the original model responses, which do not consider the structural configuration. The stick models are only suitable for obtaining the general responses of the structure, such as global and interstory drift. However, simplified frame models are the more accurate simplified models that consider the details of the original frame, such as beam and column elements, nonlinear plastic hinge springs, and joint rotations. Substitute Frame is one of these models, which is a one-bay frame that predicts the structural responses for concrete and steel moment frames with very high accuracy. The purpose of this research is to develop a substitute frame model for steel moment frames with unequal bay lengths. For this purpose, the beam stiffness and nonlinear behavior of rotational springs were modified based on linear and nonlinear structural analysis approaches and the proposed model is called Modified Substitute Frame. In the following, to evaluate the accuracy of the proposed model, three types of 12-story buildings with unequal bay lengths were designed using ASCE7-16 and AISC 341-16 criteria and subjected to three different ground motion data sets, i.e., far field, near field with pulse and without pulse ground motions. The nonlinear time history analysis results showed that the Modified Substitute Frame predicts the original frame responses with very high accuracy. Moreover, the Modified Substitute Frame prediction was more precise than the Improved FishBone model which was recently presented for moment frames with unequal bay lengths.

Current methods of splicing columns with different depth sizes have a long total load path as well as large and expensive details. These details are sometimes overly complicated and hard to fabricate. To shorten the load path and make fabrication easier and more economical, a middle plate is proposed in this study to be placed between the two columns to connect them. The plate is butt-welded to both the lower and the upper portions of the column.  Although this type of splice has been used occasionally in steel structures, its behavior is mainly unknown and research and code specifications regarding this type of splice are very limited. The current research studied the overall behavior of columns connected by this type of splice and obtained the minimum plate thickness required for typical columns to meet codes provisions. To provide the possibility of filling potential hollow sections with concrete, it is recommended to use a hallow plate in box-shaped columns. This study conducted finite element analysis on box- and H-shaped columns with different upper column depths. The influence of the plate thickness and shape on the strength and stiffness of splice in each combination was studied and minimum plate thickness was obtained. The splice exhibited satisfactory strength and stiffness in regular combinations. In combination with an upper column depth reduction of less than 5cm in box-shaped profiles and less than 7.5cm in the H-shaped profiles, the splice plate with a thickness of 5cm or more meets the criteria for both strength and stiffness. Decreasing the upper column depth increases the demand on the splice plate and a thicker plate is needed. Moreover, the shape of the splice plate, i.e., hollow plate or regular plate, had a large impact on the column behavior as the required thickness was greater in hollow plates. Results of stiffness analysis showed that decreasing the upper column depth and overall height of the column decreases the axial stiffness of the column.

During operation, a variety of factors, including earthquakes, wind, fatigue, the environment, and many others, can always cause damage to structures and the characteristics of the structure change as a result of the damage. The availability of low-cost methods for detecting damage in truss bridges makes it possible to examine a greater number of operating bridges and ultimately reduces future losses and risks. As a result, researchers' pursuit of suitable methods for detecting damage in structures has grown significantly over time. Bridges have always been the focus of researchers' efforts to comprehend their behavior and develop methods for identifying damage because of their significance as the infrastructure of every nation. In this study, an eight-span truss bridge was subjected to a moving load in a laboratory process, and the vertical displacement response of only one desired point of the truss lower chord is measured, in the damaged and intact condition. On the other hand, the influence line diagrams of all truss members have been extracted during the modeling in finite element software. The efficacy of this method in detecting damage in truss bridge screw connections has been evaluated using fourteen distinct damage scenarios. The results show that if damage occurs in the bridge connections, the difference diagram of displacement responses of two healthy and damaged states and the influence line diagram of the member whose connections are damaged will match in terms of shape and can be an indicator to identify the damage. This method works for all of the truss bridge's members, and it has worked even when more than one member was damaged. Considering that this method has been numerically validated in the previous study, using a more accurate displacement sensor with less noise and using conditions closer to those of the numerical analysis improves the accuracy of the results.

One of the methods of stabilizing soil slopes or excavated pits is soil nailing. The use of this method is common in different parts of the world and has a history of about four decades. However, the use of this method in cold regions is more limited than other regions with normal temperature conditions due to insufficient studies and lack of necessary information about the response of the soil nail wall under freezing conditions.............

One of the methods of stabilizing soil slopes or excavated pits is soil nailing. The use of this method is common in different parts of the world and has a history of about four decades. However, the use of this method in cold regions is more limited than other regions with normal temperature conditions due to insufficient studies and lack of necessary information about the response of the soil nail wall under freezing conditions. ..............

The advancement of technology with an increasing population has led to the requirement for high-speed mobility trains. High-speed transportation by trains requires passing through soft soil conditions, which requires stability. High-speed trains are used nowadays in developed countries to reduce travel time. When the train moves at a critical speed, it can significantly increase the dynamic responses of the components on the railway lines. The present study examines the results of 3D numerical modeling, considering the impact of the high-speed train passing through the mechanical earth wall stabilized by plate anchors. Numerical modeling was carried out using Plaxis 3D finite element software. The impact of various factors such as the speed of the train (180, 200 & 250 Km/h), the number of plates (single, double, and triple), and the number of train tracks (1 & 2 tracks) have been investigated. The Hardening soil with small strain model has been used for modeling the behavior of the backfill soil. In this study, the geometrical characteristics of the Thalys high-speed train were used to model the train passing through the walls of 6 meters that were stabilized with plate anchors. From the results, it was concluded that Increasing train speed from 160 to 250 Km/h increases the settlement under the rails by 11% and increases the horizontal displacement of the wall by 13%. It was confirmed that increasing train speed will result in an increase in the settlement under the rails and increases the horizontal displacement of the wall in all investigated cases. Increasing the number of plates along with decreasing their dimensions has a positive effect on the wall’s performance with regard to the horizontal displacement of the wall. Also, it should be mentioned that by increasing the number of train tracks from 1 to 2, the settlement under the rails increased by 5%, and the horizontal displacement of the wall increased by 20%.

The retrofitting plan is effective when, in addition to being cost-effective, it minimizes casualties, reduces infrastructure damage, and limits the extent and scope of damages as much as possible. The design and construction of most explosion-resistant barriers in all types of structures are not optimal due to the high cost on the one hand and the low probability of explosion during the life of the structure on the other hand. In this research, the proposal of using the combined method of restraining net along with the blast wave absorber panel as a new model in protecting the building against external explosions has been studied. The rocket is restrained at a certain distance from the main structure by a resistant net and the panel absorbs the wave caused by the explosion. By conducting studies and experiments on various absorbent materials, the selected panel was introduced and its behavior against threats at different distances was evaluated numerically and in the field. The results of the simulations were in good agreement with the field tests, which can be generalized for different amounts of charge.

Engineered cementitious composite is a cement-based composite material that exhibits significantly higher flexural, tensile, and compressive strength compared to ordinary concrete. The initial tensile strain capacity of ECC within the first two days of concreting is approximately 5%. However, as time progresses, the tensile strain capacity decreases to stabilize at a constant value of 3%, a level considerably higher than that of ordinary concrete. Moreover, ECC exhibits exceptional durability in sulfate, chloride, tropical environments, as well as resistance against freeze-thaw cycles. Its significance characteristics, including strain-hardening behavior, multiple cracking, and ductile behavior, distinguish it from the other types of concrete. To produce engineered cementitious composite, special materials such as fly ash and polyvinyl alcohol (PVA) fibers are required, but they are not available in the country. In this research, 13 different engineered cementitious composite mix designs were developed using locally available materials such as slag, limestone powder, industrial pozzolan, silica fume and polypropylene fibers. Then, the mechanical properties of different engineered cementitious composite mix designs, including compressive strength, modulus of rupture, energy absorption, and toughness indices have been investigated. The experimental results showed that optimizing the use of silica fume, and slag at rates of 10% and 28% by weight of cement, respectively, along with the inclusion of industrial pozzolan at a rate of 22% by weight of cement, improves the mechanical properties of engineered cementitious composite. Finally, the best engineering cement composite mix design was reinforced with glass grids (one and three layers) and subjected to a four-point bending and direct tensile tests. According to the results obtained from the four-point bending test of glass grid reinforced engineered cementitious composite panels, it can be concluded that increasing the number of glass grid layers enhances flexural strength, the area under the load-deflection curve, and energy absorption. For instance, the flexural strength of engineered cementitious composite panel reinforced with three layers of glass grid increased by 47.5% and 275%, respectively, compared to the flexural strength of an engineered cementitious composite panel reinforced with one layer of glass grid and an unreinforced engineered cementitious composite panel.

Keywords: Engineered cementitious composite (ECC); micro-silica; industrial pozzolan; mechanical properties.

Global population growth and industrialisation over the past two centuries have been increased the tendency toward increased use of fossil fuels. The rising trend in greenhouse gas emissions brought on by the usage of fossil fuels has contributed to global warming and, as a result, increased environmental hazards. Geothermal energy is a substantial source of clean, sustainable, and renewable energy that is utilized extensively for building heating and cooling and has a big impact on reducing greenhouse gas emissions. Energy piles as a convenient and efficient energy geo-structure receiving a lot of attention worldwide for use in building heating and cooling. Investigating the variables influencing the thermal interaction between the group of energy piles and its impact on reducing the extracted energy from the energy pile group is the goal of this study. The soil porosity, mass flow rate of the circulating fluid, pile diameter, pile length, and pile position have all been investigated using the COMSOL Multiphysics Software. The analysis of the simulation data reveals that as energy piles' diameters increase, so does the amount of extracted energy. The amount of energy extracted is significantly influenced by the soil's porosity, which causes thermal interaction to decrease and energy extraction to increase as porosity increases. It was found that the amount of energy extracted is not significantly affected by the mass flow rate of the fluid circulating in the pipe. If the amount of extracted energy calculated with respect to the pile length, as the length of the pile increases, the average energy extracted per meter of the pile decreases and tends to a constant value. When the pile diameter is kept constant, pile interaction tends to be reduced by increasing the ratio of the pile diameter to the pile spacing (s/D), and as a result, the amount of energy extracted increased. In the group of energy piles, it has also been found that the corner piles are the most and the center piles are the least effective piles.
Keywords: Geothermal energy, Energy pile group, Extracted energy, Interaction, Heat transfer in soil, Comsol

Mortars are heterogeneous construction materials whose raw materials, manufacturing processes and application conditions have continuously evolved throughout time . Mortars are artificial construction materials that consist of;
one or more mineral adhesives whose main function is to connect loose grains using different chemical changes in their mass, aggregates that are used to create volume stability on the mortar mass and water that is used to mix the mortar components into a sticky dough. Materials must be carefully measured and mixed to give the desired balance to bring out its essential properties. Therefore, in this research, 11 mixing plans for mortar, which is a kind of reactive powder concrete, with sand to cement ratios of 4.5, 4.75, 5, 5.25, 5.5, 5.75, 6, 25 6.5, 6.5, 6.75, and 7 were made and the effect of increasing the ratio of sand to cement was evaluated, and by analyzing the results of compressive strength, it was observed that the highest compressive strength was at the age of 1, 7, 14, and 28 days of the sample with a sand-cement ratio of 4.75 and at the ages of 42, 56 and 90 days, it corresponds to the sample with a sand-to-cement ratio of 4.5 and by analyzing the flexural strength results, it was also observed that the highest flexural strength is related to the sample with a sand-to-cement ratio of 4.5. Then the effect of adding 1% of polymer resin to 11 sand-cement ratio was investigated. From the analysis of the results, it was found that adding 1% of polymer resin at the age of 1 day causes a decrease in compressive strength compared to samples without polymer resin. But with increasing age of samples in high sand-cement ratios, an increase in compressive strength is observed. The highest compressive strength at ages 7, 14, 28, 42, 56 and 90 is for the sand-cement ratio of 4.75 and the highest flexural strength was observed at the sand-cement ratio of 4.5.

Keywords: Mortar, Mechanical behavior, Polymer resin, Sand to cement ratio