نشریه مهندسی سازه و ساخت
سال نهم شماره 12 (پیاپی 65، اسفند 1401)

The computational complexity of performance based seismic design methods makes most engineers prioritize the use of simpler force-based methods. Having a practical relationship between force and performance methods can solve this challenge. The hybrid force/displacement method has the advantages of the design method based on the performance and computational ease of force design methods. In this research, frames with 3, 6, 9, 12, 15 and 20 story with 3 bays with a width of 5 meters have been considered. The length of the link beam is defined as another parameter affecting the response, 1, 1.75 and 2.50 meters. The studied models have been developed by designing the method of load and resistance factor design method, for 3 performance levels of immediate occupancy, life safety and collapse prevention, as well as the first occurrence of the plastic joint. The final models are analyzed under 20 pulse-type near-fault records using time history analysis. Finally, using the genetic algorithm, the corresponding experimental relationships are presented to determine the behavior factor, local and global ductility. The proposed relationships are influenced by geometric characteristics such as the number of stories, the stiffness ratio of the columns, the slenderness of the braces, the length of the beam and the ductility levels. The results of the hybrid force/displacement seismic design of structures outside the range of the defined database, in comparison with the force methods, show the accuracy of this method in estimating the seismic needs of divergent bracing frames.

Engineering ethics is the study of decisions, policies, and values that are an acceptable ethical standard in engineering practices. Maintaining and promoting trust in the engineering profession in society can only be established in the organizational culture of the profession through ethical approaches to the behavior of committed individuals. Organizational behavior strategy includes general relationships and the way employees behave in performing services. The present research, in terms of applied purpose and type of research method, is descriptive-analytical. After establishing its face validity, content validity, structural validity, and reliability using Cronbach's alpha, the primary study instrument was a survey questionnaire. Due to the importance of this topic, it is necessary to conduct this research in order to assess the performance of engineers in professional ethical behavior with employers and colleagues based on the approved code of ethics for engineering professionals and to predict the effect of components in dealing with employers and colleagues using a structural equation model. The statistical population consisted of Kermanshah engineers, whose data was collected using a simple random sampling technique. The statistical analyses were performed using SPSS & AMOS software, and descriptive and inferential statistics revealed a significant positive relationship between the hypotheses and the proper performance of engineers. The evaluation criteria of the model as a whole are desirable and standard, and it has a high level of reliability for measuring the ethical behavior of engineers with employers and colleagues.

Despite the fact that in most operating conditions, concrete components, compaction and curing affect the performance of concrete, but premature failure of concrete structures due to problems with the durability of concrete structures also occurs a lot. Due to the lack of information on the effect of type and strength of aggregates on the durability of self-compacting concrete, in this article, using the tests of "friction transfer" and "drilled core" to investigate the effect of strength of different aggregates on the reliability of concrete Self-compacting has been exposed to sodium sulfate. 9 types of stones with the names of travertine, granite, basalt, andesite, marble, green stone tuff, crystal green tuff, rhyolite and limestone have been used to make self-compacting concretes. Compressive strength tests of self-compacting concretes cured with water and sodium sulfate solution were performed at ages 7, 14 and 28. The results showed that the volume change of rocks with higher water absorption percentage was less and there is a direct relationship between the compressive strength of self-compacting concretes treated in water and sodium sulfate solution with the strength of the parent rock. We also see an increase in compressive strength of self-compacting concrete placed in sodium sulfate solution at a young age compared to samples placed in water. There is also a linear relationship with a high correlation coefficient between the results of the friction transfer test and the core correction test. Compressive strength of crystalline green tuff, green tuff, andesite, rhyolite, travertine, lime, marble, granite and basalt are 31.76, 33.12, 39.92, 43.43, 48.41, 51/97, 59.66, 62.17 and 75.41 Mpa, respectively. With increasing compressive strength, the results of friction transfer test also increased so that for the mentioned rocks are equal to 132.4, 146.9, 155.9, 168, 176.3, 185.3, 189.8, 5 / 198 and 9/207 Nm.

Recently, the excellent performance of graphene-based materials has attracted civil engineering researchers in its application in cementitious mixtures. However, the application of graphene is hindered by its high cost and the agglomeration phenomenon in cementitious mixtures. In this regard, it is necessary to choose a dispersing agent with the ability to effectively separate graphene layers as well as improve mechanical properties and impermeability of cementitious mixtures. In this study, the effect of surfactant as a graphene separating agent from graphite on the mechanical properties and microstructure of cement paste containing water-dispersed graphene was investigated. The microstructure of the produced graphene reveals that the process of manufacturing graphene by peeling the surfactant leads to fragmentation and rupture of graphite. After 7 days of curing, the compressive strength of cement paste containing a mixture of 5 g / l graphite and 0.56 g / l surfactant increased by 28.66% compared to the control mixture. The crystallography and thermogravimetric results showed that graphene accelerates the formation of CH and C-S-H due to its nucleating effect in the cement matrix. Furthermore, the incorporation of graphene and surfactant into cement paste reduced the voids by 18.6%. This study shows that graphene dispersed in water produced by 0.56 g / l surfactant has the potential to be used as a novel additive in cement-based mixtures.

Earthquake induced pounding between adjacent buildings could be the source of different architectural and structural damages. A minimum distance is required in references, including seismic design codes. These differences motivate an investigation to evaluate the accuracy of each criterion. In this research, the criteria mandated by modern seismic design codes are evaluated based on the separation distances predicted by nonlinear time history analyses. The study is carried out on steel and concrete buildings with different story numbers and lateral systems. A set of 7 far and 7 near – fault records compatible with the design spectrum provided in the seismic design code of Iran (Standard No. 2800 – 4th ed.) were used in the analyses. The separation distances are obtained based on SRSS and ABS compared to the criteria mandated by IBC-2009, Euro Code 8, Standard No. 2800, and NBCC 2005. Based on the results, since the ABS method results are larger than SRSS, the criterion in standard No.2800 should be reformed. It is also indicated that the criteria should be different for far and near – fault earthquakes. For moment frames, SRSS in far fault earthquakes and ABS in near fault earthquakes are suggested. For braced frames, however, a separation distance larger than or equal to one percent of the height is required in both the far fault and near fault earthquakes.

The durability of concrete is one of the main criteria in the implementation and operation of concrete structures exposed to environmental risks. One of the most important causes of rebar corrosion is the presence of chloride ions. Therefore this paper investigated the effect of using xanthan gum, which is a type of polysaccharide, on the durability characteristics of self-compacting concrete. By selecting step xanthan additives in the amount of 0.2% by weight of cement, Silica fume in the amount of 5, 7, and 10% by weight of cement, and Nano silica in the amount of 2, 3, and 4% by weight of cement, mechanical and durability characteristics have been evaluated experimentally. In this paper, by controlling the rheological properties of self-compacting concrete, the parameters of migration coefficient; Chloride penetration refers to the depth to which chloride ions from the environment penetrate into the concrete; electrical specific strength and compressive strength of concrete were evaluated. Self-Compacting Concrete Benefits and the expansion of its application, multi-parameter evaluation is needed to be considered. The results indicate that xanthan gum additive improves viscosity, reduces slump flow, and reduces the separation of self-compacting concrete, and its effect on improving durability characteristics such as specific strength, migration coefficient, and penetration depth of chlorine ion, combined with each other is better than used separately. Microstructural images indicated the formation of a stable composition in the three-additive design and xanthan gum, Silica fume, and Nano-silica were evaluated to provide the desired viscosity, strength, and durability of self-compacting concrete, respectively.

Cement grout is grouted in rock joints of the foundations of dams to prevent water leakage and strengthen the foundation. One of the techniques used to control the grouting operation is the grouting intensity number (GIN), which is equal to the sum of the grouting pressure and volume and represents the grouting energy. Pressure in the rock joints creates a hydraulic lifting force that should not exceed its allowable limit so as not to lead hydraulic jacking and failure. The maximum pressure and grouting intensity number are determined accordingly. Simplifying the plan of the grouted joint, which is modeled as a thin cylinder with a radius of the grouting extension radius, the present study determines the relationship between hydraulic lifting force with grouting pressure and grouting intensity number. In this regard, the joint aperture coefficient was defined and determined based on the rock permeability (the amount of joint aperture). Then, following the geometry of rock-soil mass at the top of the joint, which is considered as a truncated cone with a β angle, for the first time approximate and exact mathematical equations were obtained to determine the permissible hydraulic lifting force (based on the approximate and exact formulas of truncated cone volume). Besides, its approximate and exact mathematical equations were compared. Then, following the principle that the hydraulic lifting force should not exceed the allowable limit, the maximum pressure and grouting intensity number were determined. Finally, by defining two parameters the normal pressure and the normal spreading length, the maximum normal pressure was set so that the hydraulic lifting force to be within the allowable range and prevent hydraulic jacking and failure

The present study deals with the punching shear capacity of reinforced concrete (RC) flat slabs reinforced with Fiber Reinforced Polymer (FRP) bars. A total of 49 reinforced concrete (RC) column-slab connections were simulated using ABAQUS finite element software. The numbers of six interior column-slab connections, five edge column-slab connections, and three corner column-slab connections were selected from the previous test results and were simulated to evaluate the software's ability. The simulation results were so satisfactory in terms of failure mode, initial and propagation of cracks that the tested to simulated punching shear capacity of interior and edge column-slab connections were about 0.86 to 0.92, 0.85 to 0.95, and 0.91 to 0.95 respectively. The punching shear capacity was predicted by ACI 440.1R-15, CSA S806-12, JSCE-97, and BSI 8110-97. The punching shear design equation based on ACI 440.1R-15 underestimated the punching shear capacity with 2.91 to 4.75 (Interior column-slab connections) and 2.01 to 2.99 (Edge column-slab connections), respectively. The numbers of 23 specimens were simulated to investigate the punching shear capacity of reinforced concrete (RC) flat slabs with carbon fiber-reinforced polymer (CFRP) reinforcing bars. The results showed that the replacement of CFRP bars instead of GFRP bars has played a significant role in increasing the punching shear capacity of reinforced concrete (RC) column-slab connections. To investigate the effect of increasing slab thickness, the numbers of six specimens were simulated. With increasing the thickness of the flat slab, the punching shear capacity will increase from 27.05% to 49.50%. It should be noted that with the increase of column dimensions in the form of simulation of six specimens, the punching shear capacity of the specimens has increased about 11.84% to 17.89%.

A seismic-resistant structure not only should provide safety for the residents but also it should minimize the financial loss resulting from the earthquake. Therefore, it must be demonstrated that the structure will remain in acceptable situation after the earthquakes with various intensities. The past has shown that, the financial loss of earthquake for the structures that have been designed based on performance objectives of current seismic codes, is considerable and this results in additional problems. Therefore, it seems that upgrading performance objectives for structures can significantly reduce earthquake losses. Improving the performance objectives of structures is associated with increasing the initial cost of the project. But reducing the damage of resilient structures and the cost of repairing of damaged components in these structures can reduce the ratio of initial cost to total cost.In this study, the effect of enhanced performance objectives in increasing the initial cost of the project and reducing the costs of repairing the damaged components of concrete structures is discussed. To investigate this issue, 3, 5, 10 and 15 storey regular concrete frame structures are modeled and designed based on Design Basis Earthquake of current seismic codes (DBE) and also based on Maximum Considered Earthquake (MCE) for the same performance objectives. The loss and repairing cost of the structures are evaluated according to FEMA-P58 guideline and using PACT software under 6 near-field and 5 far-field records. The results of this study show that, enhancing the design objective of concrete frame structures increases initial cost of lateral resisting frames (beams and columns) and the total cost of the building by 23% and 5%, respectively. Whereas the repair costs of the structure and the whole building are reduced by 43% and 18%, respectively, which ultimately leads to reduction of the life cycle cost for the structures by 13%.

This paper presents a hybrid method for predicting the dynamic responses of bridge structures contemplating the interaction between vehicle–bridge systems. This method is a combination of the theoretical approach and iterative increments as commonly used numerical solutions. it has been shown, the contact force between the vehicle and bridge has a linear relationship with the displacement at the contact point. The parameters of mentioned linear relationship change during the movement of the vehicle on the bridge. In the proposed framework, each increment is initiated with the numerical and iterative parts. Then, according to the analytical part of the proposed framework, the linear relationship of contact force and displacement between the vehicle a bridge is extracted. Consequently, considering the numerical and analytical criteria, the contact displacements and contact forces are calculated. Results indicate that the proposed method offers a framework to predict the dynamic response of bridge and vehicle considering the vehicle-bridge interaction. It was concluded that this method takes a considerably lower computational effort compared to conventional iterative methods In the structures with high contact displacement between the vehicle and structure (for example in the flexible pavement), the suggested method can solve the interaction problems in a considerably lower time and computational effort.

Need to increase urban infrastructure and lack of access to suitable quality soil increased demand for new methods for soil improvement. Recently, improving the parameters of strength, stiffness and permeability of sand under microbial induced calcite precipitation has received much attention from geotechnical experts as innovative and environmentally friendly methods. Therefore, it is very important to study the parameters affecting the biological improvement technique and find the ideal combination to increase efficiency and reduce costs. The main purpose of this paper is to investigate the effect of the variability of cementation solution molarity, bacterial optical density and curing time (three levels of variation for each) on the parameters of deviation and effective stresses for biologically improved sand under undrained triaxial compression test. The sand used in this study is a SP soil according to the unified soil classification system, and the adopted micro-organism is Bacillus pasteurii as the urease-positive bacterium. The response surface methodology was used to optimize the stress parameters in the improved sand and to significantly reduce the number of experiments. The experiments were designed using a Box-Behnken design with five central points. Three-dimensional schemes and regression model contours were used to evaluate and compare the effect of each variable. In this method, according to the analysis of variance for the data, the effect of all variables on the responses was significant and the optimal values for effective and deviation stresses were 958.2 and 1032.4 (kPa), respectively. Due to the slope of the curves, the molarity of the cementation solution had the greatest effect on the responses, and the effect of bacterial optical density on effective stress was less than deviation stress, that may be due to the accumulation of excess bacteria (lack of nutrients) and its impact on excess pore water pressure.

Studies of blast load and its effects on tanks is of particular importance. Blast on liquid storage structures possible to large due to the water crisis and disaster risk human health and the environment due to the spread of chemical substances and a fire hazard will result. Hence, understanding the dynamic behaviors of liquid storage structures under blast loading through numerical simulations is of utmost importance. In the present study, three dimensional (3D) finite element (FE) simulations of a steel water storage tank for different tank aspect ratios, percentages of water stored in the tank, tank wall thicknesses, boundary conditions at the bottom of the tank and magnitudes of blast loading have been performed using the FE software, Abaqus. Also check the behavior of structures resistant to the destructive effects of Blast waves, because of its importance in the design of sustainable structures against blast loading, has long been of interest to researchers. In this study, the numerical simulation of blast wave combined approach coupled as Euler - Lagrangian (CEL) and the ConWep has been paid. In this study, the explosive loading of domed fixed roof tanks with support and self-standing, considering the explosive load of 2000 kg of TNT explosive at a distance of 10 meters from the tanks is considered. To show the amount of stress at different heights on the tanks, four reference points were selected. The results show the critical situation at the reference point number three (corresponding to the empty space section of the tank). At reference point number three, the amount of stress is higher than at other points, and therefore this area is critical.