نشریه مهندسی عمران
سال پنجاه و پنجم شماره 6 (شهریور 1402)

Various improvement methods have been proposed to improve the mechanical and physical characteristics of soil for the construction and the other similar matters. One of the improvement methods is using of the environmentally-friendly elements such as Persian herbal gum as a renewable hydrocolloid biopolymer. Regarding this, in the present laboratory study, the effect of adding this gum to the Firouzkooh sand (No 161) was investigated. Persian gum-water mixture was added in different percentages relative to the weight of dry soil, and the created samples were subjected to unconfined compressive strength test to identify the optimal conditions of the composition. In spite of the variability of the weight percentages of water and gum added to the soil, the effect of the weight of the soil, curing temperature (room or oven temperature), and curing time (7 to 56 days) were investigated. To interpret the effect of Persian gum addition, several scanning electron microscope tests were performed on selected dry samples. The results clearly revealed an increase in the unconfined compressive strength of the samples improved with Persian gum up to 4 MPa due to the presence of many carboxyl and hydroxyl groups in the gum. Samples cured at room temperature with relative humidity of 15% displayed lower unconfined compressive strength than similar samples cured in an oven temperature due to the hydrophilic properties of herbal gum and increased flexibility of the created bonds.

This research includes an analytical approach on the subject of vulnerability of structures with resistant skeleton consisting of multiple cells of moment frames, based on the seismic resilience approach. There are two considered studied structures consisting of a 24- and a 48-story bundled framed tube resistant skeleton. The results of this study have been obtained and evaluated through performing incremental dynamic analyses (IDA) and statistical evaluations of structural fragility curves. The seismic fragility analysis has been applied with respect to the assigned FEMA provisions in order to calculate the probability for the structure to exceed six performance levels. Then, by determining the damage coefficients according to the HAZUS 2005 instructions and applying the proposed formulation of the damage function in the report MCEER-09-0009, the seismic resilience strength index of the studied structures was calculated.Based on the results of nonlinear dynamic analyses, it was observed that the bundled framed tube structural systems have relatively good safety and resilience against collapse mode under strong near-field records containing velocity pulses. Also, based on the evaluation of the probabilistic values calculated for the occurrence of the assigned limit states, it was known that the studied bundled framed tube structures handle the gradual processes of stiffness deterioration and strength degradation, with a more comprehensive formation of the geometric nonlinear behavior. In accordance with the processed results of the fragility curves, it was known that the application of bundled framed tube structures in high-rise buildings can produce a high capability of dynamic stability .

Runoff production is due to watershed response to rainfall event. Various researches have been performed in order to accurately determine the watershed response. In most response models, as in kinematic wave-based models, require detailed input data such as cover characteristics, slope, initial moisture, and soil infiltration properties. In this study, a time-area histogram extraction technique was presented via genetic algorithm optimization and deconvolution methods and results were evaluated in theoretical and real watersheds. In the model presented, a set of rainfall-runoff events in matrix form were called as inputs while the corresponding time-area diagrams were extracted. The results showed that the accuracy of the model in estimating the response of a theoretical watershed was 99%, while similar accuracy in direct approach was 74%. The accuracy of the model in estimating the response of the V-shaped geometric watershed and the real Walnut Gulch watershed reached an average of 99%. Therefore, the model introduced in this research is effective in determining the time-area diagram of the V-shaped watershed and may be used in other basins.

In this study, the quantitative effects of the construction of Seymareh Dam in the Karst site of this structure on the fluctuations of groundwater level and discharge of springs have been investigated. According to 10-year measurements, it was found that there is a direct hydraulic relationship between the water surface of the dam reservoir and the water level of observation wells. The results revealed that a significant difference in the amount of water level of the North Edge wells compared to the South Edge wells, especially in the right abutment and the right abutment wells compared to the left abutment can be clearly seen, respectively, the evidence and confirmation of an Asmari core with Low permeability is along the axis of the anticline and also more efficiency of the sealing curtain on the right side is another reason for this difference. Changes in the total discharge of the total springs measured on both banks (right and left) have a similar trend to the changes in the discharge of the left bank springs, which is due to the more discharge of the left abutment springs. The results showed that with increasing the water level of the reservoir to 660 meters, the amount of discharge of springs in the region reached 1400 liters per second and with decreasing the level of reservoir water in the next year this amount decreased and again with increasing level to 704 meters, the amount of discharge to 1800 Liters per second has increased.

In this article, the performance of Eccentrically Braced Frames with Vertical Shear Links against progressive collapse has been investigated based on GSA guidelines and the alternative path method. For this purpose, three frames of 5, 10, and 15 floors have been investigated, and their performance was estimated by the method of nonlinear dynamic analysis with SAP2000 software. By removing the middle column for all three frames, it was observed that the displacements are regular and perform well in progressive collapse. However, with the removal of the corner column, the five-story frame collapsed, and for the 10-story frame, an increase of about 3 times the floor displacement was observed. But for the 15-story frame, the behavior of the frame under progressive collapse is very suitable. The removal of the corner column in the frames creates a more critical condition than the removal of the middle column. In the scenario of removing the middle column, the maximum vertical displacement on the last floor of the 5-story frame was equal to 9.21cm, in the 10-story frame it was equal to 6.37cm and in the 15-story frame, it was equal to 4.25cm. For comparison, in the scenario of removing the corner column, the maximum vertical displacement obtained on the last floor of the 5-story frame was unknown due to collapse, and in the 10-story frame it was equal to 21.88cm and in the 15-story frame, it was equal to 7.65cm. Results show that as structure height

Plastic viscosity (PV), yield point (YP), fluid loss volume, thickening time, and compressive strength of cement are the main parameters that are necessary for a successful operation. In this study, 25 tests were done to design different slurries and find the effect of various additives, including extenders (bentonite and sodium silicate), accelerators (calcium chloride and sodium chloride), retarders (calcium lignosulfonate and CMHEC), and fluid loss controller (FLC). Calcium chloride provides acceptable results up to 6% by the weight of cement. For more than 6%, it provides unpredictable results. The sodium chloride in high concentrations (30%) acts as a retarder. Calcium lignosulfonate slows down thickening timeless than CMHEC, while CMHEC can retard the slurry more and increase the closing time. The ratio of the increase in slurry setting time to the increase in calcium lignosulfonate is almost linear while for CMHEC this is not the case and this increase increases nonlinearly. addition of FLC on cement water causes water to be retained in the slurry system and this causes the increase of this additive in the slurry to increase the setting time of cement and reduce its short-term strength (24 hours).

Self-compacting concrete (SCC) containing fibers is a continuous compound, in which the fibers are dispersed throughout the concrete matrix and reduce shrinkage and microcracks. Furthermore, SCC properties such as filling capability and high efficiency produce a homogeneous mixture that could remove many problems of the conventional concrete. In this study, 10 mix designs were examined and tested, one of which was considered for the control sample and the other 9 designs included 0.25, 0.5, and 0.75 v/v% of steel, single-strand macrosynthetic (MEX 100), and carbon fiber reinforced polymer (CFRP) fibers. The rheological behavior of fresh SCC was investigated by the rheometer test as well as common tests used to determine the properties of fresh SCC, including slump flow, J-ring, L-box, U-box, and V-funnel tests. Then, the behavioral model of the hardened concrete was analyzed by tests determining mechanical properties such as compressive strength and modulus of elasticity. The results indicated adding fibers to fresh concrete reduced self-compacting and rheological properties of concrete; this effect became more visible with increasing the volume percentage of fibers, so that the greatest effect was observed in the design containing CFRP fibers. Results of mechanical properties of hardened concrete showed adding low volumes of fibers to SCCs improved some of these properties. However, using high volumes of fibers increased ductility and, thus, reduced compressive strength and modulus of elasticity in SCCs.

Determining suitable lands for urban development is one of the most important and complex decisions of city managers. The main approach of the present study is to determine suitable lands for physical development of Bandar Abbas, to achieve which, one of the effective components including geological criteria (6 sub criteria), geotechnical (13 sub criteria) and environmental (4 sub criteria) Was used. ANP method was used to weight the criteria. After creating the information layers, fuzzy operators AND, OR, SUM, Product, gamma 0.9, gamma 0.7 and gamma 0.5 were used to superimpose the criteria. OLS was used to select the best operator to show suitable lands for urban development and clustering of neighborhoods was done by K-mean method. The results showed that the weights of geotechnical, environmental and geological criteria were 0.584, 0.280 and 0.135, respectively. The results of OLS showed that among the fuzzy operators, the SUM algebraic operator had the highest correlation with the research criteria and provided the best map for determining urban development lands. The results of K-mean method showed 4 clusters for urban development of Bandar Abbas. In the first cluster, 53.6% (30.5 km2) of the lands located in the eastern and northeastern regions of Bandar Abbas, are quite suitable for the physical development of the city. Is; 30.7% (17.5 km2) of suitable land is located in the northwestern part; About 13.1 percent (7.5 km2) of unsuitable lands and 2.4 percent (1.4 km2) of completely unsuitable lands.

In this study, optimal sensor placement (OSP) which plays a key role in the health monitoring of large-scale structures, is investigated using the genetic algorithm. The OSP problem is among permutation problems that it's challenging to define the crossover operator in this kind of problems. In this study, a new hybrid crossover operator is proposed to find the optimal location for sensors, and two different strategies are investigated for selecting members to form the next generation population. Also, the two-structure coding method has been used instead of the typical binary coding method to create the chromosomes of the population members. The objective function and fitness is defined based on the modal assurance criterion (MAC) matrix that is calculated with identified mode shapes and analytical mode shapes. The efficiency of the proposed method was investigated on a high-rise structure. The results show that the mode shapes identified by the optimal placement obtained from the proposed method are identical to the analytical mode shapes of the finite element model. Also, the comparison between the sensor locations obtained by conventional operators and the proposed operator shows that the proposed hybrid crossover operator outperforms other operators in terms of accuracy and convergence speed.

Using wave barriers is one of the effective measures for seismic wave attenuation. The barriers have different geometries and are arranged in periodic configurations. Considering the complex barrier behaviors and their miscellaneous characteristics, many research is conducted in recent years to find effective barriers. This paper proposes a new unit cell as a wave barrier to reduce the propagation of surface waves. Unlike the common practice in which harder and heavier materials are placed in the center and soil around it, the suggested unit cell consists of undisturbed soil as a core and a foam layer on both sides as a soft coating material. Firstly, a unit cell is considered in an infinite periodic lattice using solid-state physics concepts and periodic theories and is modeled using COMSOL Multiphysics FEM software. The dispersion curve can be obtained by changing the wave vector in the first irreducible Brillouin zone and calculating the corresponding eigenfrequencies. Then, the bandgaps are defined in the dispersion curves. Following that, because constructing an infinite lattice is impractical, a finite lattice of the unit cell is simulated to explore the unit cell efficiency in a more realistic setting. The time and frequency domain analyses are carried out using the finite lattices. The findings reveal that the proposed soil-foam unit cell with a height of four meters can effectively reduce the waves in the bandgap range in infinite and finite lattices. The obtained bandgap range is between 12.75 to 17.61 Hz.