نشریه مهندسی سازه و ساخت
سال نهم شماره 3 (پیاپی 56، خرداد 1401)

Installation of traditional piles in urban and coastal environments has many challenges, such as the need for heavy drilling equipment and machinery, the lack of access, enforcement problems in soft and problematic soils and environmental problems such as vibration and noise pollutions. Meanwhile, according to the development of different hydraulic and mechanical equipment, new model of piles have been introduced which can be considered as a useful alternative to traditional piles. This model of piles bring the advantage of minimum executive problems such as less vibration and noise pollution and high speed installation procedure at low accessible areas. In the present study, using different hydraulic and electronic equipment, the behavior of the two models of conventional screw piles and a new innovated pile model were studied in Bandar Anzali with an embedment depth of 3.20 m. Also, a tubular steel pile was tested as the basis for comparing the behavior of driven piles with screw piles with the same dimensions and embedment depth. Overall, five compressive static loading tests were carried out on the implemented piles. The results indicated that this model of piles have an acceptable loading capacity and can be introduced as a suitable substitute for traditional piles in urban and coastal constructions.

Due to the high land volume in urban areas, maximum-slope excavation has become an inseparable part of the construction of a building. The sensitive nature of the excavation operation in terms of cost and safety requires an accurate knowledge of the soil’s behavior, making it an important research field. Most of studies investigate the soil’s behavior using numerical methods, which are accompanied by a certain level of inaccuracy. To sidestep the unavoidable errors associated with numerical methods, this study uses a small-scale physical modeling methodology to investigate soil behavior. The phased excavation of an unsupported vertical sandy soil trench has been experimentally modeled using three small-scale physical models with/without an externally applied load. Three models with different lengths and constant cross-sections were constructed to assess the effects of length (the third dimension) on the trench’s deformation and stability. The results show that during excavation with no external loading, increasing the model’s length does not significantly increase horizontal and vertical deformations. However, in tests in which the system was subjected to an applied load, decreasing the length caused substantially larger vertical and horizontal deformations in the soil. Increasing the models’ length-to-height ratio decreased the discrepancies among the deformations created during loading. In other words, increasing the length caused the deformations of the models to converge toward a similar value. It was observed that the 3D-to-2D deformation ratios are dependent on the load applied to the trench. These ratios decreased as the model approached failure.

Completing the project in the shortest possible time, at the lowest cost, at the highest level of quality, can play a decisive role in profitability and competition. Time, cost and quality are the most important goals of any project, and their optimization is one of the topics in project planning and control. The aim of this study is to find the optimal combination of time, cost and quality in conditions of limited resources. The theory of constraints in project management has led to a new approach to project management and control called the critical chain. In this research, using the critical chain technique and the high ability of the tabu search algorithm (TS) in optimization, the problem of multi-objective optimization of time, cost and quality in conditions of resource constraints has been solved. The proposed algorithm was extracted with MATLAB coding software and the desired results were extracted. To validate the proposed model, two case studies with 7 and 18 activities have been solved. Also, a project with 60 activities in which time, cost and quality optimization was done, was used to validate the proposed algorithm in the research and the results were extracted and compared. The results showed that the tabu search algorithm had a correct and acceptable performance. In such a way that it has the ability to create multiple Pareto answers with different values ​​of the three objective functions of time, cost and quality. This allows project managers to choose the best solution in terms of time, cost and quality according to their needs and policies.

In this study, structures equipped with friction dampers under the influence of far-field and near-field earthquakes are investigated. How they slide and vibrate, which includes displacement, velocity and acceleration, is calculated by numerical analysis. And the response of the structure under the effect of far-field and near-field earthquakes on the one hand and also considering the simple friction model of Columbus and the more complete model of velocity-dependent friction (Stribeck friction) is compared. Although the possibility of a far-field earthquake is very likely, but the occurrence of large earthquakes near cities that are near faults is undeniable, and these earthquakes have certain specifications that distinguish them from far-field earthquakes. Some of these specifications are such that if neglected, they will lead to underestimation of the seismic force in the design of structures. Examples of these specifications are fling step effect and the presence of velocity pulse in the component perpendicular to the fault that is caused as a result of the phenomenon of forward directivity.Due to the nonlinear behavior of the damping force (FD), programming has been used to perform nonlinear analytical dynamics. Also, behavioral models in Open Sees software are used to investigate the behavior of Stribeck friction for friction damper and to compare its results with the results obtained from accurate analysis. The results show that simplifications of the sliding friction model, on the one hand, and lack of focus on near-field earthquakes, on the other hand, result in underestimation of displacements, especially in member forces. Considering Stribeck friction, error rate is reduced and results are improved.

Today in the world that most of communities rely on advanced technology, there are many risk factors threaten structures and buildings. There is also no complete and stable security and there are always fear for irreparable damage due to accidents and painful events, especially fire. Hospitals and treatment centers are important in preventing and fighting against fire because on the one hand the patients are hospitalized and disabled and on the other hand due to many expensive equipments. As result, preventive measures and strong management are necessary at the time of the fire. This study was conducted to evaluate the safety status of hospitals in term of ability to prevent and combat the fire in Babol as the most populous city in Mazandaran province in north ofI iran.In this descriptive, analytical. and field study conducted at 2017, the status of fire safety in five biggest hospitals in the Babol district are evaluated. Following the coordination and obtaining the necessary permissions from the hospitals, the standard checklists included Information on safety indicators completed. Then the situation of the hospitals measured in comparison with each other. And data analysed with SPSS program for evaluation of mean and standard deviation. Finally, the hospital's safety status and risk factors have been identified in the form of reports and suggestions, and delivered to the responsible authorities for improvement the safety status.Safety indicators of hospitals are as follow as: Rohani 86.65% ± 10.80; Beheshti;75.01%± 18.96; Yahya nezhad 60.09%± 23.42; Babol clinic 74.12%± 11.21; Mehregan 97.39%± 4.26.the highest percentages of implementation of safety requirements are related to the Emergency Response Safety(95.71%) and the least is related to the safety index of the structure (55.71%).Safety status of 8.57% of hospitals is weak, 34.29% of them is moderate, and 57.14% of them is favorable.

In the present paper, the effect of rotation with different angles in the Structural bearing system was investigated by irregular non-parallel systems in the concrete structure with the dual design bearing system of the moment frame and the concrete shear wall. The structure was examined in two different modes, first without rotation in the bearing system and analyzed at an angle of zero degrees. Then, the bearing system was seismically analysed by rotating at angles of 15, 30, and 45 degrees to create irregularities in non-parallel systems. The results of structural behavior were performed by comparing the values of base shear, drift, and torsion effect in the structure. The results of the present study showed that the amount of drift and base shear of the structure in the state that has irregularity of non-parallel systems in the structure is more than the state of the structure without irregularity of the non-parallel system. Comparing the amount of base shear for the angels and other modes increases the amount of base shear by increasing the rotation angle of the bearing system, which increases the amount of rotation angle, imposes more force on the structure. The amount of base shear for the angle of 30 degrees of rotation of the Structural bearing system in the main direction of the building is more than other angles. The analysis results also showed that the non-parallelism of the central core of the structure reduces the lateral bearing capacity of the whole system. As a general conclusion, it can be stated that the higher the rotation angle of the bearing system, the higher the amount of displacement and drift, which is the most critical state for the 30-degree angle and the best performance in the structure for the zero degrees angle.

Estimating the cost of building construction, especially in the early stages of studies, is a topic of interest and importance for employers and investors. The high inflation of the country's economy in recent years and the sharp fluctuations in the price of construction materials have doubled the importance of estimating the cost of building construction, even in small urban projects. However, until the design of the building is completed and the final plans are not prepared in full detail, it is not possible to measure the project and estimate the construction costs with acceptable accuracy. On the other hand, the proposed approximate methods for initial estimates are associated with many differences from reality that are not consistent with the existential philosophy of project economic estimation. Therefore, in this study, using training capability of Artificial Intelligence and Artificial Neural Network algorithms, the weight of rebar used in concrete buildings of concrete moment frame, without complete design and preparation of executive plans is calculated and the results are compared with real values. The proposed artificial neural network model is a multilayer feeder type feeder with post-diffusion learning algorithm and is based on the parameters of number of openings in longitudinal and transverse direction, floor height, number of floors, number of columns per floor, floor area and seismic base shear. The weight of rebar used in the studied buildings has been estimated. The results indicate that the proposed neural network model can estimate the weight of rebar used in regular buildings with 95% accuracy and in irregular buildings with 80% accuracy.

Shallow foundation rocking movement include the nonlinear behavior of the foundation and soil material during strong earthquake motions that it has been proposed by researchers in recent years as a change in traditional design. In this research, the performance of rocking motion and flexibility of shallow foundations with curved surface have been discussed. For this purpose, the behavior of this type compared to normal shallow foundation and its effect on the behavior of concrete wall-foundation system with different aspect ratios have been studied. Six models of shear wall system with simple and curved foundation modeled by BNWF (Beam on Nonlinear Winkler Foundation) method in OpenSees software. In BNWF method, a series of distributed independent nonlinear soil springs are generated along the footing length and connected to footing elements to simulate the foundation movement including sliding, rocking and settlement. For investigation the behavior of wall-foundation system the pushover and force-settlement curves are extracted. In the results obtained from OpenSees software, the curved foundation with shear wall has lower base shear and ultimate settlement than a simple foundation that with increasing shear wall height the base shear difference was 30 percent increased. In the time history analysis results was observed that the maximum base shear was decreased between 14 to 17 percent in the system with curved foundation, and also has lower critical contact area that with increasing shear wall height was decreased and self-centering coefficient of wall-foundation system was increased.

The energy absorber device improves the seismic behavior of structures against seismic loads. Despite the proper performance of the dampers against seismic loads, they impose additional costs on the structure. Therefore, in this paper, a new damper is introduced which, in addition to improving the seismic behavior, imposes a small cost on the structure. To evaluate the performance of the proposed damper, 15 numerical samples were simulated by Abacus software. under cyclic loading. The study of cyclic behavior was performed on a steel frame of one story-one bay and the sensitivity of cyclic behavior was studied based on the parameters of thickness, length and dimension to the thickness of the brace and slenderness of brace. The thicknesses of the damper are, respectively, 12, 21 and 30 mm, the length of the damper is 400, 500 and 600 mm, the geometry of the damper is arc and the thickness of the brace is 12, 21 and 30 mm. Numerical simulation was performed. The results of this study showed that this type of damper has a good performance in energy dissipation imposed on the structure. Although the proposed damper improves the energy absorption of the structure, it will also reduce the stiffness.

Ever-increasing demands of the modern world and the growth of industry requirements toward more accurate analyses have made the engineering community develop the first fundamental step and meet the needs by extending the previous prevalent linear methods into nonlinear areas. In this regard, the improvement of linear modes as one of the most pervasive and widespread analytical methods opens a new window to analyses with more closeness to reality. In this paper, after the deep identification of Nonlinear Normal Modes, an approach is proposed to analyze the multi-degree-of-freedom structures with nonlinear material under undamped free vibration. Afterward, through an in-depth investigation of the calculation methods, a novel algorithm for identifying Nonlinear Normal Modes was proposed, and by expanding this algorithm to the existing invariable motion equation used in free vibration analysis, the possibility of the extraction of all Nonlinear Normal Modes has emerged. After that, to investigate the functionality of the proposed approach, the Finite Elements Method-based Model of a 2-story steel structure was developed and, after verification, it was used to form the invariable differential equations. Finally, after verifying the Independent Periodic Method, pseudo-continuous masses of Nonlinear Normal Modes and Frequency-Energy curves of the mentioned structure were calculated. It is worth noting that the independency of resulted response to previous points, the possibility of capturing Nonlinear Normal Modes with different frequencies in each degree-of-freedom, the potential of capturing all internal resonances, the expendability of Finite Elements Model to a set of invariable motion equations, and considering material nonlinearity are among achievements of the current paper.

By studying steel buildings, civil engineers are always looking to design joints that, in addition to increasing the rotational capacity of the joint, prevent the brittle failure of the structure and allow the structure to be repaired after an earthquake. Steel dampers are suitable elements to achieve this goal and simple construction and use, has given them a relatively high advantage over other dampers. These dampers also provide the possibility of reconstruction and low cost of the building by preventing the severe destruction of steel beams and columns during an earthquake.In this study, by comparing several samples of these dampers, their energy dissipation, damping and effective stiffness have been investigated by modeling in ABAQUS software. According to the results, SPD and DPD type dampers have better seismic behaviors and with increasing height, the seismic performance of all dampers have improved. Also, by simulating the behavior of dampers in SAP software, two-dimensional frames of 3, 7 and 15 story with and without dampers have been investigated under the acceleration of 7 earthquakes. The frame response does not give the same results at different accelerometers. However, by adding dampers and creating suitable conditions for the steel beam rotation, an increase in frame energy absorption has been observed in all models with dampers.