نشریه مهندسی عمران
سال پنجاه و دوم شماره 11 (بهمن 1399)

Reactive powder concrete (RPC) is a new type of high performance concrete (HPC) which due to using fine powder and puzzolanic materials as well as high amount of materials which are hydraulically active, is known as this name. RPC characteristics have a high sensitivity to type and characteristics of materials used in RPC; therefore, in order to achieve desired physical and mechanical properties, it is necessary to carefully consider selection of materials and mix proportions. The purpose of this research was to investigate the effect of water to ementitious materials ratio (W/CM), amount of cementitious materials (CM), silica fume to cementitious materials ratio (SF/CM), cement type and grading of silica sand on compressive strength of RPC. To do so, 21 RPC mixes were designed and made. In each step of this research, one of the effective parameters were studied and accoding to obtained results, the next steps were performed. RPC specimens were cured in 90 oC water for 7 days. Results showed that by using cement type V, cementitious materials of 1100 kg/m3, water to cementitious materials ratio equal to 0.2, silica fume to cementitious materials ratio equal to 0.2 and use of silica sand with the the finest grading, the highest compressive strength can be achieved.

Adobe constructions are considered vulnerable subjected to lateral loading so that their failure in the past earthquakes has caused severe casualties and structural damages. Nonetheless, numerous adobe buildings are still being used in seismic-prone regions worldwide, including Iran, many which are of historical background. Therefore, evaluation of their lateral behavior and retrofitting stands of high priority and can lead to preserving these national assets. In this study, the cyclic lateral behavior of adobe walls made of adobe units and mud mortar was investigated under different constant axial load. The experimental specimens were comprised of four adobe wall panels measuring 1000 mm in length, 900 mm in height, and 200 mm in thickness. The main experimental parameter was the magnitude of axial compression applied on the wall. The experimental results were compared in terms of load-displacement hysteretic curves, cracking pattern, failure mode, stiffness degradation, cumulative energy dissipation, and hysteretic damping. With increasing axial stress from 0.1 to 0.7 MPa, the failure mode was changed from shear to shear-compression. Also, due to increased axial stress, lateral resistance increased, but the corresponding displacement decreased.

In recent years, Vibration Based System Identification (VBSI) as a powerful tool to disclosure a mathematical expression of dynamic behaviors of structures, is taken into consideration for structure engineers. Among developed strategies for VBSI, the strategies identifying under ambient vibration tests without using input data, with no limitation in serviceability and no need to complex excitation tools, have been more desirable. In some cases, regarding to high numbers of Degrees Of Freedom (DOFs) and impossibility of recording in whole DOFs, it is necessary to identify physical characteristics beside modal parameters with recording in limited numbers of DOFs. Among those physical characteristics, stiffness parameter is more important. The main goal of this paper is to present a method for identification of story stiffness in shear type buildings using incomplete structural responses. At the first, the sub matrix of structural stiffness matrix is identified by the proposed method based on the structural dynamics theory and the realization theory-based Stochastic Subspace Identification (SSI) method and then story stiffness will be available. Since the presence of noise is imaginable in ambient vibration tests, effects of noise also been investigated. To evaluate the proposed method, a five-story analytical shear building is studied. Extensive analysis show the high ability and accuracy of proposed method in correct identification of story stiffness from incomplete output records even in presence of noise.

Polycyclic aromatic hydrocarbons (PAHs) attract great attention because of their toxicity, stability, lipophilicity, bioaccumulation, carcinogenesis and mutagenic characteristics. Urban runoff contains significant amounts of PAHs, which transfer to receiving environments and cause significant environmental and health risks. Because of their hydrophobicity characteristic, transport of these compounds in aquatic environment, mainly coupled to suspended particles and sediments. Therefore, assessment of sediments is considered as a medium that affect fate and transport of PAHs. Present study evaluates the concentrations and sources of PAHs in sediments of Tehran runoff. The samples were taken from three main subcatchments of Tehran city in April 2017 and concentration of 16 PAHs and organic carbon were measured and their probable sources were determined using five diagnostic ratios. The total PAHs concentration ranged from 57 to 978.2 ng/g dry weight. Also, the concentrations in the sub- catchment 2(57-976.6 ng/g) was higher than the sub-catchment 1(84.4 -773.2 ng/g) and sub-catchment 3(76.3 – 978.2) due to its location in the center of the city and the diversity of pollutant sources. Moreover, a significant and strong correlation is observed between total organic carbon and PAHs, while its coefficient varied in each sub-catchments. At all stations except station C1S27, 3 and 4 rings compounds had significant dominance. Four indexes show the origin of compounds is pyrogenic while LMW/HMW index indicates that the source of contamination in 30% of the stations is petrogenic. Generally, the portion of pyrogenic sources is significantly higher due to high population density, traffic and human activities.

Temperature changes the engineering behavior of clay soils. Clay soils are used as a protective cover for burial of high-level wastes (HLWs), where the soil is exposed to medium to high temperature regimes. Marls are a type of sedimentary deposits consisting of clay minerals and calcium carbonate. These two components can substantially influence the behavior of marl soils from an engineering standpoint. The present study focuses on the engineering characteristics of marl soils under various temperature regimes with an emphasis on the microstructural changes in permeability coefficient, settlement, and compressive strength Therefore, after determining the geotechnical properties of the marl soil, its samples were exposed to temperatures from 25℃ to 900℃. The changes in marl soil properties were analyzed via mechanical tests (measuring permeability, consolidation, and uniaxial compressive strength), and microstructural tests (measuring pH and X-Ray diffraction), and scanning electron microscopy (SEM). The microstructural analysis of marl soil samples indicates that due to the deterioration and formation of new minerals as well as soil particle arrangement and microscopic texture; temperature regimes increase the permeability coefficient. However, at 700℃ the formation of cement compounds reduces permeability coefficient by an approximate factor of 50,000.

Accurate prediction of flow and sediment discharges, as basic information, is important for many river engineering projects. To calculate the bed load in the rivers, many experimental and semi-experimental equations have been developed but depending on the hydraulic conditions and sediment profiles in each river, some of these equations may yield better results. In this research, by developing an applied software, the abilities of 27 equations of estimating bed load in rivers of Golestan province (Chehel-Chay, Khormaloo and Soosra), in which bed load is measured, have been evaluated. It should be noted that in this developed software quasi-two-dimensional models can be used for computing speed distribution in width of the river and also in estimating sediment loads. The software is also able to increase the accuracy of estimations by calculating calibration coefficients in the studied river. The results showed that by using the developed software, the best method for estimating bed load in the studied rivers is Yang's method. In this case, the abundance of discrepancy ratio between 0.5 to 2 for the rivers Chehel-Chay, Khormaloo and Soosra is 43.8%, 50% and 30.8% respectively. Also, using quasi-two-dimensional models, increases discrepancy ratio between 0.5 to 2 for the rivers Chehel-Chay, Khormaloo and Soosra by 6.3%, 6% and 8%, respectively. Results also showed that by calculating and applying a calibration coefficient, accuracy of methods can be improved for the studied rivers.

In this paper, focusing on structure-soil-structure interaction, dynamic behavior of two adjacent structures with flexible base is studied. The main identifiers of this structure-soil-structure interaction system are defined with dimensionless parameters. With considering a logical range of the parameters, various states including most practical cases are calculated. Soil flexibility and dynamic correlation between two adjacent structures through the soil are accounted for using springs and dashpots at the base of the structures. The equations of motion are solved in time and frequency domains for two adjacent single degree of freedom systems to make it possible to study parametrically the effect of structure-soil-structure interaction on the responses. As a result of harmonic analysis, natural frequencies with and without considering damping, damping ratios and amplitude of the system’s dynamic responses are calculated and compared with those of the single building (no adjacency). Also, the cases prone to a possible pounding are recognized. By analyzing such a system in both time and frequency domain, it is shown that with appropriate arrangements, both of the analysis procedures result in the same responses for an interaction problem.

Tension stiffening effect, which is due to participation of concrete in resisting tension between cracks, results in the reduction of strains of reinforced concrete member relative to pure bars. In some researches, this effect was involved at strain – stress behavior of concrete after cracking that few researches investigated FRP reinforced concrete. In Present investigation, comparison of experimental data with results of layered nonlinear analysis of wide collection FRP-reinforced concrete beams relative to prior researches was used for extracting of concrete strain – stress after cracking. The resulting model unlike previous models was developed for all type of FRP bars. The constants of model are obtained from optimization method based on genetic. 78 curves from 87 curves of FRP – reinforced concrete beams under four-point bending are used for deriving of model coefficients and the others are used for investigating of optimal model. Furthermore, 20 percent of load – deflection data of 78 beams are also randomly selected for controlling of optimal model instead of developing of model. The average natural logarithm of experimental/calculated deflection ratios for randomly selected data by applying initial model and optimal model is 1.0457 and 0.2668, respectively. According to ideal value of zero for natural logarithm of experimental/calculated deflection ratio, applying optimal model has improved this statistical parameter by 74 percent. Responses of nonlinear analysis by using initial model and optimized model are compared with those of code relations.

In the present study, to investigate and compare the effect of Nanosilica nanoparticles and water-soluble polymer of cationic polyelectrolyte on a set of physical, mechanical and chemical properties of CL clay, a series of laboratory tests were performed on untreated soil samples, treated with Nanosilica and treated with cationic polyelectrolyte. Nanosilica was added to soil with 0.5, 1, 2 and 3% dry weight of soil and cationic polyelectrolyte with concentrations of 3, 6, 9 and 12 gr/liter based on optimum water content and their effects on the soil details has been investigated in 3,7,14 and 28 days of processing. Despite the differences in the effectiveness mechanisms, these materials showed similar effects on the variety of soil samples characteristics in this study. By adding of both materials to the soil, optimum water content, liquid limit, unconfined compressive strength, and water retaining potential of soil have been increased and Maximum dry density and free swelling percentage of soil decreased remarkably. On the other hand, regarding small changes of plastic limit and increasing of liquid limit, plasticity index increases. Also, for various amounts of additives, there is no significant change in soil pH.

Building collapse is a level of the structure performance in which the amount of financial and life loss is maximized, so this event could be the worst incident in the construction. In this study, the collapse of low and mid-rise Regular special steel moment frames with 3, 6, and 9 story were designed by ETABS according to code guidelines and then the collapse of mentioned frames has been evaluated by nonlinear static pushover and incremental dynamic (IDA) analyses with SeismoStruct. The nonlinear static pushover analyses with three lateral load patterns were used to determine the likely location of the plastic hinges at the moment of probable failure mechanism for the mentioned frames and the nonlinear incremental dynamic analyses were used to assess the seismic intensities corresponding to form each failure mechanisms. Thus, the intensity of earthquake and the values of drift corresponding to the failure of studied frames were calculated. To perform nonlinear dynamic analyses, 10 far-fault records were used. The results of this study showed that the collapse of studied frames occurs under the far-fault records in different drifts and seismic intensities and the value of relative drift equivalent to the collapse limit varies from 2 to 5 percentage and It was also found that the collapse capacity of 3 and 6-story frames is 3.3 g and 3.4 g respectively in the uniform lateral load method and in 9-story frame, the collapse capacity of the first mode and linear lateral load methods is more and equals to 2.5 g.

Mechanical specification of the interface of soil and reinforcement is one of the most important parameters of the design and construction of reinforced soil systems. Anchorage length of the reinforcement is determined based on the soil-reinforcement interface parameters. Required long anchorage lengths restricts the application of reinforced soil systems. Improving the mechanical parameters of the soil-reinforcement interface could be used to develop the applications of reinforced soil structures in projects with limited space. In this research, the cement treatment of the interface of the soil and reinforcement was employed to improve the pull-out capacity of the reinforcement and consequently to reduce the anchorage length. The effect of the cement treatment on the pull-out capacity of the reinforcement was studied in the laboratory. Also, the effect of the increased thicknesses of the reinforcements resulted from the cemented layers adhered to the reinforcement surface was investigated. The laboratory tests conducted using specially developed pull-out test device. The tests conducted on high-strengths woven geotextiles with different thicknesses with both pristine and cement treated interfaces. Cement treatment carried out with 1.5 g/cm2 portland cement sprayed on water saturated geotextile. The results of tests conducted on pristine reinforcements with different thicknesses showed that increasing the thicknesses of the reinforcements increase the pull-out capacity. Also, the cement treatment increases the pull-out capacity of reinforcements.

In this paper, the parameters required for the ice and concurrent wind loading case, including the radial equivalent ice thickness and the concurrent wind speed for the return periods in the structures of the power transmission lines, are determined according to the standard criteria of IEC 60826. Loading parameters have been calculated using two-variable hazard curves and compared with simplified methods in IEC 60826. Ice and concurrent wind hazard curves are prepared using data recorded in 15 selected meteorological stations in the cold regions of the country (including heavy and ultra- heavy areas according to the climate-zoning map of the transmission lines). Numerical simulations have been used to determine the thickness of ice formed around the conductor of the transmission lines due to the lack of direct data from the measurement. The results show significant conservatism of the reduction factors of the ice and concurrent wind in IEC 60826 standards at most of the studied meteorological stations. Accordingly, using the ice and wind hazard curves at the stations, the reduction factors are determined and presented to calculate the values of loading parameters in ice and wind loading case in terms of their reference values (which are available in the zoning maps). The proposed reduction factors are consistent with the standards of IEC 60826 and are suitable for use in loading and designing the structures of transmission lines with different return periods in the cold regions of the country.

The application of composite sections in recent years is increasing because of its great advantages in advanced countries.The purpose of this study is to investigate the effective parameters on loading capacity of steel columns covered with concrete under the simultaneous impact of axial and cyclic lateral loading, including steel compound shape, concrete strength and retrofit with carbon polymer fibers. The use of a concrete-covered steel column in comparison to a single steel column or reinforced concrete column will increase the capacity of the final capacity significantly. In other words, composite columns have a very high load capacity. for this purpose, in order to study the behavior of steel columns covered with concrete under the simultaneous effect of axial and cyclic lateral loading, After validating the modeling in abaqus finite element software, the behavior of these columns in different cases of steel composite section, 28 day compressive resistance of a different concrete, and impact of retrofitting with carbon polymer fibers on ultimate capacity, is investigated. the results show that the parameters such as the shape and dimensions of section of steel column, the 28 - day compressive resistance of a different concrete and retrofitting with carbon polymer fibers have a significant effect on increasing or decreasing the ultimate capacity of these columns. Finally, the cracking pattern in the concrete has been investigated and due to the crack propagation pattern, retrofitting with carbon polymer fibers have been applied on the concrete surface to reduce corrosion crack.

If unpredictable loads are applied to the flat slab-column connections, punching shear failure occurs with almost no warning signs. According to the brittle manner of this failure, the load carried by the slab-column connection redistributes to adjacent supports and causes overloading to these supports. Due to this overloading and brittle nature of punching shear failure, progressive collapse may happen both horizontally or vertically. In order to prevent the progressive collapse of flat slab-column connections, it is necessary to provide a secondary load carrying mechanism after punching shear. In this Paper, Suggestions for establishing a supporting mechanism in the flat slab connections after punching failure are proposed. For this purpose, an experimental study was performed to investigate the post-punching behavior of 9 slab specimens with various reinforcement layouts and concrete covers. The effects of integrity, compressive and bent-up reinforcements, diameter of tensile reinforcements, and concrete cover of tensile reinforcements on the post-punching behavior of slab-column connections were studied. The results of the experiments show that the integrity reinforcements significantly improve the post-punching strength. The compressive reinforcements may not increase post-punching strength. The increase of the concrete cover of the tensile reinforcements and decrease of the diameter of the tensile reinforcement result in an increase of the post-punching strength. The bent-up reinforcement increases the punching and post-punching strengths, simultaneously.

Nowadays, soil stabilization has a vital importance due to the population growth, the necessity of construction and unsuitable natural soil for structure construction. The use of additives such as lime and cement is one of the ways that can be applied for soil stabilization. Among new additives for soil stabilization, it can be pointed out that Nano-Material is a more efficient and most cost-effective method with respect to traditional additives. One of this Nano-Material is Nano-Lime that can be used for soil improvement. Therefore, in this study, the effect of Nano-Lime on soil resistance parameters was investigated. For this purpose, unconsolidated undrained triaxial test is performed on the soil specimens containing 0.5, 1 and 2% by weight of soil at 7, 14, and 28 days curing. According to the results, the values of maximum deviator stress are increased by adding Nano-Lime to the soil specimens, and this trend grows with an increasing percentage of Nano-Lime in the soil as well as curing days. That said, the 28-days maximum deviator stress of clean soil is increased by 21.3 to 38.3%, 27 to 59.3% and 29.6 to 70.8% with including 0.5%, 1% and 2% nano-lime for cell pressure 100, 200 and 300 kPa, respectively. Moreover, it can be seen that stiffness of specimens containing Nano-Lime rather than clean soil specimen is increased. Also, the obtained results show that the cohesion of soil increased due to effect of Nano-Lime on soil samples, which this trend increased with curing time.

Side weirs are a type of hydraulic structures that can be used as a deviator structure for controlling and dispensation of discharge in flood and high velocity flows. The flow on these structures is spatially varied flow type with decreasing discharge. Due to the applications of side weirs for transferring and controlling discharge in flood flows and considerable velocities, its very likely to have supercritical flow on these kind of structures. Piano key and labyrinth side weirs can be used, when the width of the weir opening is limited. The increase in side weir's effective length relative to its opening is one of the advantages of these side weirs. The majority of studies done on the Piano key weirs had been limited to experimental methods, due to the limited conditions of laboratory, high cost and recent development in numerical models, its important to simulate these weirs in fluid dynamics software’s. In this research side weirs with different plans have been simulated by FLOW-3D. The FLOW-3D numerical model has been calibrated and verified for simulating side weirs using experimental results. Determination and presentation of the relation between the kinetic energy correction factor () and the momentum correction factor (β), discharge coefficient for Piano key side weirs in supercritical flow and comparing the shapes of piano key side weirs are some of the results of this research. These results can be used in designing these side weirs.

In the present era, Climate change and its impact on available water resources are one of the main challenges. In this regard, temporal and spatial analysis of temperature and precipitation, which are important parameters in determining the status of water resources, can be used to assess the hydro-climatological conditions of the watershed and appropriate management policies. In this research, the trend in precipitation and temperature distribution over 30 years testing period of 1981-2010 was investigated using non-parametric tests such as Man-Kendal, Spearman, Sen’s Slope, and Pettit. Afterward, interpolation techniques, such as IDW, LPI, GPI, and RBF were used to detect spatially trends at the watershed. The results showed that precipitation decreased by 14.3% during the period 1981-2010 and the temperature increased by 3.5%, with changes in precipitation and temperature occurring in 2004 and 1985, respectively. However, the negative trend in precipitation was not significant in contrast to the positive temperature trend during the study period. A comparative analysis of interpolation techniques shows that Ordinary Kriging and Radial Basis Functions with least error are the best methods for spatial analysis of precipitation and temperature, respectively

Concrete is the most important consumable in constructional construction, which is increasing. Cement is used as a constituent of concrete to produce it, and on the other hand it produces 8% of the world's carbon dioxide produced. In this study, the mechanical properties and durability of concrete made with copper smelting slag, iron melt slag and metalaoleene as a substitute for cement have been investigated. A total of 384 samples were made up of 16 mixing designs with varying degrees of replacement of copper smelting slag, iron smelting, and metalaole waste. Mixing scheme According to the American ACI 211.1 regulations and the conditions for the SSD materials, dry aggregates then cement materials after that, and finally the supernatant, were gradually added to the mixture. On the designs in a fresh state, a slump test, and in a hardened condition at the age of 7, 14, 28, and 90 days, the compressive strength was tested according to standard BS 1881 and at 28 days of pressure test in accordance with DIN 1048-5. In all designs containing pozzolan, we see a decrease in water absorption compared to a pozzolan design. In, the constant percent displacement of water under pressure is related to the designs containing metalaole and the most related to the plans containing copper smelting slag.