نشریه مهندسی عمران
سال پنجاه و سوم شماره 10 (دی 1400)

In this study, four concrete types, including ordinary Portland cement concrete, fly ash concrete, slag concrete, and slag-fly ash concrete, are taken into account in order to estimate their compressive strength by two novel machine learning methods (genetic algorithm and soccer league competition algorithm), and four types of regressions (linear, 2nd order polynomial, exponential, and logarithmic). Subsequently, the precision of prediction models are compared based on performance indicators, and the most accurate models are applied in the optimization problem modeling. Drawing on results, the most precise model to estimate the compressive strength of ordinary Portland cement concrete is the genetic algorithm, and the soccer league competition is the most accurate model to estimate the strength of other concrete types. Afterward, a model is developed so as to design mixture proportions of 40MPa concretes. Fly ash concrete, slag-fly ash concrete, and slag concrete reduce the unit cost by 35.2%, 29.9%, and 23.1%, respectively, compared with ordinary Portland cement concrete. Fly ash concrete, slag-fly ash concrete, slag concrete, and ordinary Portland cement concrete require 217.25 kg, 150.47 kg, 102 kg, and 414.64 kg cement to be manufactured. Furthermore, the slag concrete can reduce the amount of cement in the mixture proportion by 75.4%, and it is the most eco-friendly concrete.

In this study, flow characteristics and pressure parameters of hydraulic jumps has been investigated in a laboratory flume. The results for different incident Froude numbers (Fr1), at the downstream of an Ogee spillway on the typified USBR II stilling basin bed were compared with the USBR type I basins. Dimensions of the Ogee spillway and stilling basin were designed according to the USBR criteria. The pressure data of the points on the basin bed were recorded using pressure transmitters with 20 Hz frequency. Experimental parameters including flow depth and velocity at the start and end points of free jumps (Y1, Y2, V1 and V2), and submerged jumps (Y3, Yt, V3 and Vt) were measured. In the present study, dimensionless parameters of energy dissipation efficiency (εt), mean pressure head (Ψ*X), standard deviation of pressure fluctuations (Φ*X), maximum positive pressure fluctuation coefficient (CP+), maximum negative pressure fluctuation coefficient (CP‒), total pressure fluctuation coefficient (CP) and skewness coefficient (Ad) were investigated. Pressure parameters are dependent on Fr1, the point position (Γ*X), and the submergence degree (S). The results showed that by reducing the values of Fr1, parameter εt decreases. The parameter Φ*X max in the USBR type II basin decreases around 30% compared to the type I basins in free jumps. The reduction of Φ*X max values in the submerged jump with S=1.4 is about 29% than free jumps. The values of CP+max and |CP‒|max coefficients in the submerged jump with S=1.4 in comparison with free jumps decreases about 15% and 17%, respectively.

It is necessary to provide seismic design criteria for structural systems in order to optimally design bending reinforced concrete frames with steel shear wall. Researchers have used energy requirements as one of the most important and efficient tools to measure and minimize cumulative damage to structures, which depend strongly on the time and duration of the earthquake. Therefore, this study attempts to investigate the energy response properties of an equivalent single degree of freedom versus near pulse species acceleration accelerometers to estimate the maximum energy types and its relation to a multi degree of freedom for three reinforced concrete structures with steel shear walls, low-rise, mid-rise and high-rise under ductile coefficients of 1, 2, 3, 4 and 5. The results of the study of the changes in the ratio of cyclic energy to total energy wasted in the structures show that in the multi-degree system the period is independent of the periodicity to the extent that the effect of higher modes is negligible. Also, by increasing the ductility coefficient, this ratio for the multi-degree system is closer to the results of the one-degree system and, in a sense, increasing the ductility coefficient results in a decrease in the effects of higher modes.

The growth of the transportation network has led to a special need to the life cycle cost analysis and increase the lifespan of asphalt mixtures. There are several ways to improve the performance of asphalt mixtures, one of which is bitumen modification using modifiers. In recent years, with the invention and expansion of the production of nanomaterials, special attention has been paid to the use of nanomaterials to improve the rheological properties of bitumen. Accordingly, this study evaluates the effect of copper nanooxide on the rheological behavior of bitumen and the mechanical properties of the asphalt mixture. Therefore, the dynamic shear rheometer is used to determine the specifications of bitumens at medium and high temperatures, as well as fatigue and dynamic creep tests to investigate the performance of asphalt mixtures against fatigue cracking and rutting. The results of bitumen rheological experiments show that the use of copper nanooxide at 1 and 2 percent by weight of bitumen improves the rutting parameter in unaged and short-term aged bitumen from 49-343 and 57-257 percent, respectively, and also improves the fatigue parameter in long-term aged bitumen from 11-40 percent. The results of fatigue tests show that the fatigue life of samples containing 1 and 2 percent of this additive at 5 and 20 °C will improve by 9-16 percent and 6-31 percent, respectively. Also, the results of the rutting potential show that the use of 1 and 2 percent of nanooxide has reduced the permanent deformation change of 13-35 and 18-18 percent, respectively.

It has been used to preserve structures and extend their useful life, retrofit damaged structures. Concrete slabs, as a key structural member, play an important role in the load distribution and structural behavior, and lack of resolving the damage to concrete slabs can lead to irreparable damage. In this experimental study, the one way reinforced concrete slabs were strengthened with using high performance fiber-reinforced cementitious composite laminates in the slab's tensile side. Its lateral surfaces are then strengthened with carbon fiber reinforced polymer laminates to increase shear capacity. This study is summarized in three steps. In the first step, the mixing design and mechanical properties of fiber-reinforced cement composites were investigated. In the second step, the flexural capacity of fiber-reinforced cement composite laminates was determined separately before bonding to the slab. In the final step, shear and shear reinforced concrete slabs were tested for shear behavior investigation. The results showed that the strengthening of the lateral sides of the specimens was improved the flexural capacity, fracture pattern, stiffness, and energy absorption by examining the shear behavior of the specimens. Also for one-way slabs strengthened with fiber-reinforced cement composite laminates, if the concentrated load is applied to the slab so that the shear Span-to-effective height ratio is less than 2.5, even If it is strengthened at the lateral surfaces to increase the shear capacity of the cross-section, the failure pattern will certainly be shear.

As data collection costs decrease, transportation systems have shifted from systems requiring data to systems requiring data analysis. Since the accuracy of these data varies with the sources of data collection, acquiring higher accuracy data from a combination of multiple sources is the main challenge of working with such data. Data fusion is a very efficient mechanism can interconnect data from different sources to increase the accuracy of data in line with the purpose of the study.The main goal of this article is to get the most accurate travel time possible from multiple sources.Among the data fusion methods are the Kalman filter, Bayesian inference, artificial neural networks and Dumpster-Scheffer theory,from which the Bayesian inference is used and its results are investigated.It is proposed that by combining different data sources with different temporal and spatial coverage, the most accurate travel time with maximum spatial and temporal coverage would be achieved.The Niayesh tunnel in Tehran was selected as a case study,where extensive equipment for intelligent transportation systems is installed. After determining the accuracy of each source with floating car data, the fused travel time of one day in which multiple sources data were available was calculated.In this study, considering the possibility of simultaneous access to multiple data sources at the same location,the following source, Google travel time data, Bluetooth travel time data and Inductive loop detectors were fused. The improved travel time can increase the accuracy of travel time costs in transportation planning, information on variable message signs and routing software.

In the present study, laboratory methods were used to investigate the drainage conditions of the steady-state with the surface recharging. In the study, fine and coarse sandy soil samples were used to study changes in groundwater level. The test specimen was poured into a large-scale flume, with 5.4 m long, which led to uniform vertical precipitation and vertical drainage on both sides. The parameters of precipitation rate, soil gradation and water level within the drains were investigated as variables in this study. The results showed that the maximum change in water height in coarse sand due to increasing water height in drains from 0 to 40 cm is equal to 56.9 cm and 72.5 cm, respectively, which caused an increase of 15.6 cm. However, in fine sand these changes are very small (2 cm) and equal to 87.2 cm in free drainage conditions and equal to 89.2 in water conditions of 40 cm inside the drains. The obtained laboratory results were compared with the Dupuit-Forchheimer analytical relationship, according to which this relationship is able to accurately predict the level of water in the fine sand, but in coarse sand, the relationship underestimates the water table height in the soil.

In this research, the relationships of the discharge coefficient of the sharp-crested U shape plan form labyrinth weirs (one cycle) have been investigated experimentally and numerically. Also, from 3 groups of weirs with heights of 10, 12.5, and 15 cm and at each height, the length of different arches to the values of 40.82, 45 and 48.10 cm have been tested. The main purpose of the present study is to determine the overflow discharge from the weir by providing relationships for the discharge coefficient experimentally. Dimensional analysis was used by 𝜋 Buckingham method to extract the relationship. Three-dimensional simulation of weirs was performed numerically with equations governing the finite volume method using FLOW-3D software, then compared with laboratory results. The results of the present study show that the proposed relationship can predict discharge values with very high accuracy and an error of 4.79% in the ratio of the head-to-height weir of 0.1 to 1.2. As the length of the weirs arch increases, the flow interference increases, and the discharge efficiency decreases. Although with increasing the length of the weirs, the length of the crest increases, the weirs efficiency decreases, the maximum throughput efficiency decreases in this case, It is at 7.01%. With constant arc length and increase in weirs height, it was observed that the throughput efficiency decreases significantly, which shows a maximum volume of flow through the weirs of 4.82%.

Increasing active school trips is a strategy for children’s health. Despite that the route features may associate with higher amounts of walking school trips, the majority of previous studies have focused on buffer-level characteristics of the built environment. Moreover, the role of children’s interest has not been widely examined in previous studies. The present study investigates the associations between the route-level features of the built environment, socio-economic, and cognitive characteristics on children’s walk to school. A total of 340 questionnaires were distributed among 7-12 year-old pupils across three primary schools in a neighbourhood in Tehran. For each route to school the environmental features were collected by means of the Pedestrians First (PF) instrument, which is a tool for measuring the walkability. Results revealed that the number of motorcycles, and the distance from home to school were negatively, and the non-residential land use and the proportion of favourable sidewalks were positively related to the children’s walk to school. Parental worry about children’s walking to school negatively associated with children’s walk to school. Analyses, however, found the children’s interest in walking non-significant in their walk to school. The results had important ramifications for planning the walk to school programs in the neighbourhood level. Furthermore, findings underlined the provision of multi-facet long-term policies such as land use changes and school allocation patterns across the neighbourhood, when preparing master and land use plans, to enhance walking school travels for health reasons.

In cost-benefit analysis and prioritization of safety countermeasure, it is necessary to estimate the social costs of accidents. One of the crash costs is the cost of users' time loss due to delays caused by accidents. In most studies, this factor has been ignored or considered only as a general estimate and no specific method has been considered for it. In this research, an analytical method has been proposed to calculate the cost of the delay caused by the accident and the factors affecting it have been investigated. Another objective of this paper is to investigate and compare the cost of time loss to road users in different types of accidents according to type of vehicles and roads. In a case study, total time loss of users in various accidents is calculated according the roads and vehicles types. The results show that accidents on arterial roads and especially heavy vehicle accidents, cause the most wasted time for users. Total time loss in each injury or fatal accident on the freeway-highway, main road and secondary road is 2039.65, 700.39 and 95.90, respectively. Also, it is found that the share of freeway-highway, main and secondary roads from the total time lost in rural accidents is 43.69, 54.92 and 1.39 percent, respectively. The average time lost in each rural accident is 869 people - hour and its cost in 2016 is equal to 27.3 million Rials, which is about 0.6% of the total cost of rural accidents.

Effect of foam porosity on absorption, capillary absorption and chloride ingress was studied. Performance of mixes with w/c ratio of 0.5 and foam contents of 20, 35 and 50% were determined and compared to those of a base mix with the same proportions but without foam incorporation. A structural grade foam concrete with w/c ratio of 0.4 and foam content of 20% was also considered together with a conventional concrete of equal strength level. The results show that foam incorporation results in decreased absorption and capillary absorption and increased chloride diffusion. The discrepancy is due to presentation of absorption results on total concrete volume basis. By considering these results on paste volume basis, which is the penetrable phase, absorption results show the same trend as the chloride diffusion results. Incorporation of 20, 35 and 50 percent foam into the base mix resulted in increases of 12, 27 and 50 percent in paste absorption and 18, 55 and 155 percent in chloride diffusion values respectively. Increased foam volume resulted in larger and more connected air voids. Despite the negative effect of foam incorporation on penetration characteristics, the structural grade foam concrete with its lower w/c ratio achieved similar levels of performance as the base mix and performed better than the conventional concrete of equal strength level.

Due to the high consumption of mortar and concrete, especially in structures and the increasing demand for cement production, considering the environmental degradation effects of this substance, it seems necessary. One of the solutions is to produce environmentally friendly materials and reduce the damaging effects of Portland cement production, Such as slag geopolymer mortar and concrete. The purpose of this paper is to experimentally investigate the statistical approach of the mechanical and resistive properties of cement mortar and geopolymer fibers mortar. Four mix design including three geopolymer mix design with 0, 0.5, and 1% steel micro-fibers and a conventional mortar mix design were considered. A total of 320 specimens were made, each consisting of 20 cubic specimens, 20 cylindrical specimens, 20 small beam specimens, and 20 small disc specimens. The results indicated that by increasing the percentage of steel microfibers up to 1% in geopolymer samples, the compressive strength, tensile strength and modulus of rupture increased by 6.39, 60.86, and 63.40%, respectively. The number of destruction resistance blows was also about 25 times higher. In all compressive, tensile, flexural, and impact strengths tests, the non-fiber geopolymer specimens had better behavior than conventional cement mortar specimens. In all geopolymer specimens with increasing fiber percentage, standard deviation and coefficient of variation increased as a result of data dispersion.

Granular soils have complex macroscopic response under seismic loading. Due to the many uses of the results of cyclic triaxial tests, the numerical modeling of these tests is needed to facilitate the prediction of soil behavior and reducing the cost of laboratory tests. The aim of the present research is to evaluate the ability of the discrete element method to investigate the dynamic behavior of sand by simulating a number of drained stress controlled cyclic triaxial tests under three-dimensional conditions. In addition, the effect of parameters such as number of loading cycles, soil relative density, cyclic stress ratio, particle shape and loading paths on the dynamic properties of soil (shear modulus and damping ratio) is also considered. The results indicate that numerical simulation by discrete element method can accurately represent the variations of soil dynamic properties with the considered variables. The comparison of experimental results from the literature and numerical models carried out in this study shows that the rate of decreasing in shear modulus and increasing in damping ratio of the samples with non-spherical particles with shear strain is higher in the given cyclic stress ratio and porosity. The cyclic stress ratio does not have significant effect on the shear modulus, damping ratio and coordinate number of samples. The coordinate number of the sample with spherical and non-spherical particles (e=0.3) is obtained 7.7 and 6.4, respectively, at the end of the simulation test. In the same condition, the samples with non - spherical particles have undergone more deformations.

Carbonate sediments are among the problematic soils in geotechnical engineering. These soils are different from quartz soils both in terms of production origin and in engineering behavior. In this paper, for comparison of resistivity parameters, Bandar Abbas carbonate sand and Firoozkooh quartz sand under ordinary triaxial tests and simple static shear tests were used. Experiments were performed under the same conditions of grain size, relative density and stress. Parameters such as physical properties, shear behavior, stress path, modulus of elasticity, shear modulus and internal friction angle of maximum were compared. The results showed that Bandar Abbas carbonate sand had higher shear strength than quartz quartz sand under the same conditions of relative density and all-round stress. The maximum internal friction angle values of carbonate sand due to its intrinsic webbing in both triaxial and shear tests were higher than quartz sand. The dilation angle for both experiments increases with decreasing stress. In carbonate sands, due to the fragmentation and fragility of the grains, the degree of dilution is greater than quartz sand. Also, in loose samples than in dense samples, because of less locking and closing of the grains, the degree of dilatation is greater than the dense one. Due to differences in the values and slope of the stress path of the two experiments, the results of the triaxial test are on average 10 to 15% higher than the simple shear test.

Recently, in developed countries, a variety of self-centering structural systems have been developed using precast concrete bends and Accelerated Bridge Construction (ABC) method to reduce construction time, increase safety, reduce seismic damage, reduce repair and reconstruction costs, and increase seismic resiliency. In this system, bridge bents are constructed by precast elements tied together with post-tensioned tendons such that under the effect of lateral seismic forces, they are able to rock and self-center back to their original configuration. The use of this system greatly reduces the residual displacements and the seismic damage. Also, due to the use of prefabricated elements, the construction speed of the bridge is significantly increased. This paper compares the seismic performance of one type of the self-centering structural system with the conventional structural system for three typical highway bridges constructed in Iran. An analytical model for simulating nonlinear behavior due to the rocking motion in the self-centering system is first developed and verified by comparing the analytical response with the experimental results. Then, the concrete bends of the three typical bridges in Iran are modeled and analyzed once as a conventional system and once as a self-centering system, and the seismic performance of these two systems is compared with each other. The results of this study indicate that in spite of a modest increase in maximum lateral drifts, the residual drifts are substantially reduced when the conventional system is replaced by the self-centering system.

In this paper, the results of the effect of exposure of CFRP strengthened and coated 150mm concrete cubes, to harsh environments are presented. The harsh environment included: wet and dry and freeze and thaw cycles as well as different temperature changes. It is anticipated that, the intended environmental conditions harm the performance of the CFRP sheet by reducing the compressive strength of concrete and at the same time, increase its permeability. The test specimens used in this investigation, include 150mm CFRP strengthened concrete cubes with and without protective coating layers. The methods employed were "Cylindrical chamber" permeability, mortar capillary water absorption and mortar compressive strength tests. The results obtained tend to indicate that the proper selection of protective coating had a significant impact on the performance of the CFRP coated concrete cubes that were under harsh environmental condition. Application of suitable coatings on to the CFRP layer caused respective reductions of about 28%, 34%, and 36%, on the permeability of specimens after being exposed to specified wet - dry, freeze - thaw and temperature change cycles.

At the present time, population growth in the world has led to increasing need for water resources in agriculture, industry and urban, and it is necessary to planning for optimal and sustainable use of limited available water resources. In this paper, supply water demands with controlling changes in groundwater level, especially in agricultural lands with maximizing economic profits, has been defined as objectives of Numerical simulation and multi-objective nonlinear optimization modeling. In the model, combined use of optimization and simulation techniques has been used as a useful and powerful way to determine management strategies for optimal utilization of water resources. The optimization approach shows that the amount of water allocated to the agricultural sector decreased by nine percent, and this amount of savings in water consumption led to raised only one percent crop cost in the cultivation. Environmental sustainability and Aquifer saving improved in the amount of 3/03 million cubic meters per year, and this has been achieved while maintaining profits in addition to agricultural economy, supply of drinking water and industry in the region that has been fully provided

Asphalt recycling or, in other words, reuse of pavement is one of the latest technologies in the field of road construction that is now more accepted than other pavement construction methods. In addition to better environmental protection, this technology results in significant cost savings. Still, one of the major concerns of its use is the creation of undesirable properties in asphalt mix, such as bitumen aging and reduced cracking resistance. The use of rejuvenation agent and WMA (warm mix asphalt) additive are of the solutions to improve the performance of asphalt mixers containing RAP (reclaimed asphalt pavement) materials. Hence, in this research, in order to evaluate the effect of using RAP on the fracture resistance of WMA mixtures, the RAP materials with two dosages of 25% and 50%, one type of rejuvenation agent and Sasobit, as a WMA additive, were employed. To study the fracture resistance of the mixtures at the temperatures of -15 C and 25 C under mode I loading, semi-circular bending test was selected, and different fracture parameters including critical fracture load, fracture energy, flexibility index, cracking resistance index and fracture toughness were calculated. The results exhibited that the addition of RAP material to the mixture had negative effect on the fracture parameters at different temperatures, and resulted in the reduction of these parameters. While, the mixtures containing rejuvenator showed more elastic behavior than those without rejuvenator. Therefore, the use of rejuvenator led to the improvement of the fracture parameters.

Seismic behavior of skew bridges, backbone of modern transportation networks, has not been well studied. Such bridges have experienced intensive damages due to girder unseating under torsional effects of seismic responses coupling in longitudinal and transverse directions, which would be aggravated by pounding between adjacent spans and abutments. Since bridges are usually supported on Cast-In-Drilled-Hole extended pile shafts and the inelastic behavior of superstructure during an earthquake is profoundly dependent on supporting soil strength, the main purpose of research is evaluating the seismic responses of reinforced concrete skew overcrossings to variations in structural parameters by applying models including backfill-abutment and soil-pile nonlinearities under near-fault records with high velocity pulses and comparing the results with fixed-base model. Nonlinear time-history analyses were conducted using seven pulse-like records with three orthogonal components on a two-span skewed bridge. The effects of skew angle, base condition modeling approach and soil strength on demands was assessed and compared for flexible- and rigid-base conditions. Various analyses were conducted with respect to possible changes in soil properties from soft to stiff for clayey and loose to dense for sandy soils. Despite the changes in soil properties, most of the demands were sensitive to increase in skew angle as a factor of structural stiffness and will increase incrementally with this angle but deck rotation significantly affected by these variations. Considering foundation flexibility by a set of nonlinear springs can refine responses, particularly by Direct Method and will cause an improved effect on various demands rather than the fixed-base condition.

Instability of earth slopes in open channels have been always considered by hydraulic engineering. In present study, application of lime and nano lime in control of failure in side slope of earth channel has been investigated experimentally. Results showed, lining of 20% lime and 5% nano lime, increased angle of internal friction 24.4% and 35.5%, respectively and cohesion reached a value of 3.3 kPa. In feeding, for slopes of 26.5, 33, 45 and 53 degree failure occured in water levels of 560 mm, 460 mm, 460 mm and 410 mm, respectively. For seepage situation, slope of 26.5 degree was stable and slopes of 33 and 45 became instable in water level of 510 mm. Slopes of 45 degree with 10% lime and 53 degree with 20% lime were stable in maximum level of 660 mm. Potential variation behind the slope showed curve procedure with lime percent. Lining of side slop with lime and nano lime decreased seepage discharge in same water level. Also, application of lime and nano lime changed shape of failure zone and using nano lime decreased cracks in size. In feeding, without and with lime lining, curved failure surface and crack observed on slope.

Stepped spillways are used to discharge excessing floods entering the reservoirs, through which the energy is exposed to highly dissipation rates. It consists of a series of steps along the spillway to ensure a uniform flow along the spillway. Steps improve the rate of energy dissipation along the spillway, which consequently affect the flow characteristics and energy dissipaters at the downstream. The flow over stepped spillways is divided into three regimes of nappe, transition and skimming flows. So far, limited number of studies have been performed on the basis of analytical and empirical information to check the features and nature of nappe flow. Limitations on physical model studies is also important to mention. As a result, few relationships have been suggested to describe nappe flow characteristics over stepped spillways. In this study, experiments were performed on three large-scales hydraulic spillway models of SiahBishe upper and lower dams and Zhaveh dam, which cover six spillway slopes and 24 flow rates. Measurements of depth, velocity, and static pressure were made at 40 different cross sections along the chutes. Major effective geometrical and hydraulic parameters on energy dissipation in nappe flow regime over spillways were analyzed, based on measurements made in this study. A relationship was then suggested to calculate the rate of energy dissipation in nappe flow regime. This study showed that the ratio of critical depth to height of spillway is the most important parameter in predicting energy dissipation, the increase of which reduces the relative energy dissipation in nappe flow.

Urban runoff as one of the most important emission sources of heavy metal to the environment has potential environmental and health risks. This study aimed to evaluate the content of ten heavy metals in runoff of Sorkheh Hesar catchment, Tehran for this purpose, Runoff samples were taken from the outlet of Sorkheh Hesar catchment during three flood events in 2018- 19 and the total concentration of heavy metals was determined by ICP-MS. Fe, Mn, Zn, Pb, Cu, Cr, Ni, As, Mo and Cd had the highest abundance in all samples, respectively. The results of Spearman's rank correlation coefficient showed strong correlation between most metals, especially Fe, Mn, Zn, Pb, Ni, Cd and Cu, which indicating the same input sources and similar geochemical behavior. Also the mean values of Contamination Index, Heavy Metal Evaluation Index and Heavy Metal Pollution Index were 24.7, 30.1 and 130.2, respectively which indicated most of the samples were in contaminated and high contaminated level, due to high concentration of three elements including Fe, Mn and Pb in compare to standard permissible values.

Stone column is one of the cost effective techniques for improving soft soil layers. Since in the construction process of stone column, weak soil is replaced with stiffer material, appropriate method to bury the waste materials e.g. reclaimed asphalt pavement (RAP) and scrap tires, is to use as stone column materials. The aim of this study is the application of scrap tires for enclosing stone columns and RAP mixed with gravel for stone column, to provide an environmental friendly and cost-effective improvement method for weak layers. In order to investigate the behavior of such stone columns, experimental modeling of the unit cell consisting of a single stone column with reclaimed asphalt pavement as filler material and encasing it by scrap tires has been carried out. RAP contents of 0%, 25%, 50%, 75% and 100% are selected to investigate effects of different mixing ratios. Loading capacity tests were performed on encased and non-encased stone column specimens. Results of loading capacity tests show that encasing of stone columns with scrap tires improves the loading capacity significantly. On the other hand by increasing the RAP ratio from 0% to 100%, the stone column loading capacity changes. However the amount of change in the bearing capacity is not significant and therefore the use of stone column made of 100% or any percentage of RAP is reasonable.

Load capacity and ductility are two main characteristics of the flat slab-column connection in high seismic areas. To date, different methods have been employed to strengthen the connection against shear punching, including column capital, drop panel, high strength concrete, and shear reinforcement. In the current experimental study, the effect of using Engineered Cementitious Composite (ECC) to upgrade the strength shear punching behavior of flat slabs under an unbalanced moment was investigated. ECC can provide the composite with features such as the ability to spread multiple cracks under load, strain hardening, shear force and scabbing strength, and high deformation. For this purpose, seven reinforced concrete flat slab specimens with a dimension of 1000mm*1000mm*100 mm under the load with the eccentricity of 150mm were examined. The slabs were made from two layers of normal concrete and ECC in their thickness. The variable parameters included the unbalanced moment effect, improved interaction of the two materials, and ECC thickness. It was observed that improving the contact surface of normal concrete and ECC increases the shear capacity. In addition, the replacement of slab concrete with ECC increases the punching capacity and post-punching strength of the slab without a large and sudden drop in load. The change in failure mechanism was observed from a sudden and abrupt failure to a formable failure with high-energy absorption when using more ECC layer thicknesses.

This paper presents a computational approach to the analytical performance of modal pushover method (MPA) in predicting nonlinear response parameters of tall buildings compriding hybrid framed tube with large scale zipper elements. The accuracy of the results based on MPA is evaluated by comparing the benchmark responses obtained through conducting two sets of nonlinear time history analyses (NLRHA). Also, the effect of higher modes on the structural response parameters is measured by considering three computational vectors of the ordered lateral loading prepared according to the participation of the basic mode as well as the first 3 and 5 transitional modes, separately. In this study, the determination of the target displacement in MPA was set based on the results of NLRHA under two groups of near and far field records. The variation range of response parameters of the three high-rise 30storey studied structures was evaluated based on conducting a series of MPA as well as NLRHA analyses. The computational outputs of the MPA are compared with the results of the NLRHA (as exact values) and the standard error percentage is estimated. Evaluation of the results represented in this study demonstrates the relatively desirable computational capability of the MPA method in predicting the behavior characteristics of tall building structures with symmetric and regular rigid skeleton at plan and height. Moreover, it was observed that the presence of large-scale zipper elements in resistant system can reduce the seismic response parameters and also relatively increases the overall dynamic stability of high-rise structural skeleton.