نشریه مهندسی سازه و ساخت
سال دهم شماره 3 (پیاپی 68، خرداد 1402)

One Of the effective parameters in the final strength and durability of self-compacting concrete is post-fabrication curing. External Curing with water Supply and moisture retaining coating are commonly used despite the limitation of these methods. Internal curing is one of the main issues in the implementation of reinforced concrete and bulk concrete structures with much less restrictions, especially in high performance concrete. The aim of this study was to investigate the effect of internal curing of self-compacting concrete using superabsorbent polymers on mechanical properties and durability of concrete. These polymers absorb some water and gradually release it during the hydration process. Using this method, the curing process is performed more efficiently, not only on the surface but also in the depth of concrete elements. Two types of superabsorbent polymer powders based on sodium and potassium with two different amounts have been used in this research. Concrete samples at 7 and 28 days of age were subjected to compressive strength, electrical resistance, water permeability, thaw-freeze cycle and microstructure tests including SEM, XRD and XRF. Compressive strength of samples with internal curing increased by 11.4% compared to control samples. In terms of durability parameters, the samples with internal curing show a reduction of more than 100% in water permeability and 16.7% improvement in electrical resistance. The result of microstructural experiments showed an improvement in evolution of the hydration process by at least 2.4% and at most 8.3% due to internal curing.

The formation of the Industrial Revolution led to great variations in dealing with nature, population increase, industry progress, construction technology improvement, widespread usage of fossil fuels, increase in dependence on cars, etc. It disturbed the balance between humans and nature. Climate change is one of the main crises that threaten human beings today. Due to the incidence of environmental crises, such as energy crisis, increased pollution, and climate change caused by population increase and high energy consumption, the quality of life, especially in urban environments, has been reduced. In this paper, a list of effective factors was prepared by conducting library studies and reviewing previous research, then a questionnaire based on the Likert scale was used to collect the opinions of experts in the field of urban planning and development in Kerman city. Then they were analyzed in SPSS software. Afterward, the decision matrix was formed based on the desired indicators and criteria and was ranked using a questionnaire related to the Fuzzy Vikor method based on the criteria of "impact rate", "importance" and "existence of necessary tools". Based on the research outcomes among all the identified influential factors, ten of the most important influential factors include: "providing easy access to public transportation", "locating local facilities and services at the closest distance", "accessibility", “Easy access to the natural environment without harming it "," Design and location of green spaces for both recreational and air purification "," Establishment of advanced waste recycling systems (waste as a source of energy production) "," Using national and religious teachings ", "reducing energy consumption", "minimal dependence on fossil and non-renewable energy sources", "Investing in lighter, greener, cheaper and smarter infrastructure", "Using new technologies to use clean energy", "Paying special attention to waste segregation", “Sewage collection network”, “converting waste to Biogas" were identified.

Solving the problem with the meshless method is based on selecting a series of points from inside the computational area and boundaries without meshing. In the present study, the phenomenon of seepage below the dam under steady and unsteady flow conditions has been investigated by combining the Meshless method and the Finite Difference Method. Problem solving and calibrating operations were done by coding in MATLAB software. The Meshless method was used for spatial sentences and the Finite Difference Method was used for the discretization of temporal sentences. The results showed that the shape factor (α) for low points is 0.85 and for high points is 0.52, which indicates the proximity of the initial approximations to the main answer. Considering that, the shape factor depends on the geometry and the governing equation, so the same shape factor was obtained for the steady and unsteady conditions equal to 0.52. In the unsteady condition, with the water level behind the dam remaining constant, the water head below the dam also reaches a constant value over time. Also, examination of the results showed that in numerical problem solving, a low error is not a criterion and among the various basic functions, only the MQ function has the better hydraulic performance to draw equipotential lines, so that for 133 points, the shape factor and root mean square error index are 0.52 and 0.0108, respectively.

Self-centering controlled rocking steel braced-frame (SC-CR SBF) is an innovative seismic resistant system that reduces structural earthquake damages compared with conventional structural systems. In addition, the self-centering behaviour could reduce or eliminate building residual deformation and simplify the required repair after an earthquake. These benefits make this system an ideal alternative for conventional lateral force resisting systems such as moment-resisting frames or shear walls. Along with this issue, asymmetric structures are more vulnerable to earthquake excitations and require special seismic design considerations. Therefore, in this study, it is tried to improve the seismic behaviour of asymmetric SC-CR-SBF systems with proper distribution of strength. In this regard, the behaviour of low-rise uni-directional mass asymmetric SC-CR-SBF buildings is studied under bi-directional horizontal ground motions using OpenSEES software. The results show that the appropriate distribution of the strength of SC-CR SBFs in the plan reduced adverse torsional effects and based on these distributions, the proper configuration of mass and strength centers is introduced. Finally based on the results with appropriate arrangement of the centers, the maximum drift of the asymmetric structure decreases as much as roughly 14%. In other words, the maximum drift of the asymmetric SC-CR-SBF buildings of this study are acceptably close to the symmetric case.

With the architecture, Engineering and Construction (AEC) industry representing a significant share of global energy consumption and greenhouse gas (GHG) emissions, developing sustainable design and reducing buildings environmental impacts has become a priority over the past decades. Adopting building information modelling (BIM) tools and implementing them into life cycle analysis (LCA) techniques at early stages of design has proven to be one of the most effective methods for a buildings sustainability evaluation. It’s quite often that some of these attributes are overlooked due to their insignificance or in order to facilitate the analysis. With our environment constantly going through changes it is reasonable that the construction industry should also aim to adapt to these changes and make use of them. However, the role of local climate features and its effects on a buildings energy output is often so neglected. This research aims to consider the role of climatic attributes and local weather characteristics of a building by using BIM-LCA integration techniques, and see how it affects that buildings energy performance. It is witnessed that by using the proper equipment and construction materials, that matches the respective climate, up to 28% of the buildings energy consumption during the operational phase, can be saved. Admitting changes to the model however, can cause up to 3% increase in the models GHG emissions. Moreover, this work develops a prototype to validate the results.

In this study, the shear-lag effects are evaluated on the performance of L-shaped reinforced concrete (RC) shear walls. At first, 42 L-shaped RC shear walls are simulated employing the FlashLab program, and then, the numerical analyses are performed due to the cyclic loading applied within the framework of ABAQUS software. Based on the results of the numerical studies and taking into account the shear-lag effects, axial strain as well as axial deformation distribution are obtained for L-shaped RC shear walls. Thereafter, on the strength of the evolutionary polynomial regression (EPR) and genetic algorithm, new expressions have been developed and introduced for L-shaped sections which allow quick estimation of the axial strain and deformation distributions. The reliability of the proposed expressions has then been examined based on the coefficient of determination, of which the average values for the axial strain and deformation are 80 and 72 percent, respectively. Also, the results of the proposed expression are compared with those of the previous studies for non-rectangular RC shear walls. Finally, on account of the Mean Absolute Relative Error (MARE) index attained for the proposed expressions to that of the previous studies available in the literature, the uniform distribution exhibits the best performance in the response prediction of L-shaped RC walls. Furthermore, calculation of the MARE values indicates that the established formulations can respectively predict the axial strain and deformation of L-shaped RC shear walls with average error of 65 and 54 percent of the MARE values of the available expressions addressed in the literature.

Continuity and doubler plates are used to strengthen the panel zone of rigid connections in steel structures. Unless columns are cut in every story of the building, it is not possible to connect these plates to rigid I-shaped beam-to-circular column connections. To overcome this problem, many researchers have employed external stiffeners. In 2019, a new detailing scheme was introduced for these connections using external stiffeners. Six full-scale experimental samples were built and tested under cyclic loading. Even though the efficiency of the new connection was established using laboratory tests, the study did not discuss the issues relating to the design process. In the present study, to formulate design criteria and relationships, numerical models have been constructed inside ABAQUS and verified using the experimental data. The results obtained from more than 60 finite element models have revealed that the proposed detailing scheme meets all of the code-specified criteria of rigid beam-column connections in special moment resisting frames. Further, based on the thickness of the channel profile and the stiffeners, the proposed detailing can be categorized as either rigid or semi-rigid. Finally, design criteria have been proposed and these connections can be considered as a suitable detailing for I-shape beam to tube column connections.

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

In this research, the progressive collapse of the reinforced concrete frames following the middle column removal has been investigated based on the sensitivity and robustness indexes. At first, the numerical model of the reinforced concrete frame was simulated and verified with Li et al. model in SeismoStruct software. After developing the numerical model, the performance levels and the number of plastic hinges in the frames were obtained. The frames were subjected to the column removal in the first story and their vulnerability to progressive collapse was investigated under nonlinear static push down analysis. In the present research, parametric study including change in the number of stories, span length, story height, concrete compressive strength, rebar yield strength, poisson's ratio and damping ratio of the structure in the progressive collapse of the frames was performed based on the sensitivity and robustness indexes. The results showed that increasing the number of stories from 5 to 20 story, reducing the span length from 5.5 to 3 m, reducing the story height from 4.45 to 3.20 m, increasing the concrete compressive strength from 21.3 to 51.3 MPa, increasing the rebar yield strength from 234 to 350 MPa, increasing the Poisson's ratio from 0.12% to 0.25% and increasing the damping ratio from 5% to 15% decreases and increases the sensitivity and robustness indexes, respectively. Thus, the condition of the frames in progressive collapse improves. Finally, the effect of simultaneous removal of several columns in the progressive collapse of the frames showed that the case 5 of the column removal has the lowest sensitivity index and the highest robustness index, thus having better conditions in progressive collapse.

The stone columns, as a method of soil improvement, significantly reduce soil settlement due to incoming loads and increase soil load-bearing capacity. Adding geotextile as a stone column encasement has a considerable impact on this relationship. In this study, the amount of loose sandy soil settlement was investigated by numerical modelling of stone columns with the Plaxis 3D Foundation software, and the results were validated by using laboratory modelling,. For this purpose, a single stone column was modelled in two modes of rainfall density and compacted states and continuously the group mode in the soil was investigated. Also, the effect of adding geotextile encasement to the inner part of stone column investigated as a central core. So, a 6 centimetre diameter of central core that surrounded with geotextile encasement has considered inside of a 10 centimetre diameter of stone column in both rainfall density and compacted state. The results of experimental and numerical modelling were well-matched with each other. Also, it was clear that the increasing of stone column number and compaction can enhance soil bearing capacity, considerably. The adding of central core has had considerable effect on soil bearing capacity, too. This is due to the increase of all-round stress in the interior of the stone columns. The results showed that the stone column with a diameter of 10 cm increased the bearing capacity compared to unreinforced soil by 36%, while in the stone column with central core in rainfall density and compacted states, this amount is 43% and 54%, respectively. Also by evaluation of appearance deformations in stone columns after loading showed that increasing the density and adding geotextile encasement to the central core has a considerable effect on the created deformations and prevention of local ruptures and the process of deformation becomes more favorable.

One of the effective parameters in performance-based design methods is the determination of lateral displacement demand. Due to the existence of uncertainties in the parameters of analytical models such as mechanical properties of structures and model simplifications, accurate calculation of structural responses is associated with complexities. The use of training-based prediction methods can be a good alternative to accurate analysis in assessing the seismic behavior of a building structure. In this paper, an efficient training approach for modeling and predicting the response of building structures with nonlinear behavior is studied. To perform the training process, an adaptive scheme of fuzzy inference system with the TSK model combined with Multi-Verse optimization algorithm is used to model the seismic behavior of structures. The proposed training model is implemented by optimizing the parameters of the TSK model using the optimization algorithm based on comparing the previous time steps responses. To implement the adaptive design and increase the accuracy of the prediction, three training cases based on the responses of 2, 5, and 10 previous time steps were used. To train this system, the data collected from the results of nonlinear time history analysis under 100 seismic events with different characteristics have been used. Also, 10 events were used to test the inference system. The performance of the proposed design was evaluated on a shear frame structural model with nonlinear hysteresis behavior. The results show that the inference system of the TSK model by combining the optimization method is an efficient computational method for predicting the response of nonlinear structures. The average MSE for the test group ground motions, using three training modes with 2, 5, and 10 previous time steps, 2.817e-03, 1.228e-03, and 2.953e-04, respectively. By increasing the number of time steps from 2 to 10, the prediction error decreases by 89.52%.

Analysis of structural components under fatigue loading due to the complexity of the loading is one of the most challenging problems in civil and structural engineering field. In order to find the fatigue life of a structural member, the costly and time-consuming experiments must be conducted while the collected data is very scattered and cannot be used for other conditions and problems. Therefore, finding effective numerical models to analyze a member subjected to fatigue load, could reducing time and expenses while could offer a systematic and general solution in variety of conditions. In this research, using the findings of a previous experimental study, the behavior of CFRP retrofitted and unretrofitted notched steel beams under fatigue loading has been studied by finite element by numerical modeling in a commercial finite element software. In this study, 11 notched CFRP retrofitted and unretrofitted steel beams (hot-rolled W5×10 made of A36 steel) were modeled and fatigue loaded until failure with stress range between 207 and 379 MPa under frequency of 5 to 10 Hz. The results of numerical modeling were compared with the results of previous experimental study and several equations were presented to estimate the fatigue life of unretrofitted and retrofitted specimens. The normalized stiffness losses of specimens were investigated as well. The verifications showed that numerical models and extracted equations have good agreement with the experimental results.