Iranian Journal of Science and Technology - Transactions of Civil Engineering

Published by Shiraz University
Print ISSN: 2228-6160
Adsorption of Reactive Yellow 145 (RY145) and Remazol Black RL (RBRL) onto pine needles (PN) was investigated with respect to initial dye concentrations, adsorbent dosage, and pH in a batch manner. The obtained data in the study were described according to the Langmuir and Freundlich isotherm models and the Langmuir model describes the experimental data very well with a q(max) value of 13.831 and 7.225 for RBRL and RY145 respectively. As the pH decreased, adsorption density increased gradually and the highest adsorption density was obtained at pH 2 for both adsorbents (91.57 and 64.77% for RBRL and RY145 respectively). Equilibrium adsorption rates of 70.15% with RY145 and 86.72% with RBRL onto PN were observed at 90 min. In order to better model the kinetics of adsorption, first order, pseudo second order and second order models were applied. Among these models, the pseudo-second order kinetic model provided a good correlation for the adsorption of RY145 and RBRL by PN with a R-2> 0.999. Results showed that pine needles have great potential to remove Reactive Yellow 145 (RY145) and Remazol Black RL from aqueous solutions.
This paper has experimentally investigated the simultaneous effect of the pier shape and position on scouring in a sharp 180-degree bend. Several experiments were performed on the bend for nine different pier shapes at three different positions, and the corresponding shape factors coefficients (ratio of maximum scour depth to that of a circular pier) were evaluated for all pier shapes at each position. The presented results show that the shape factor coefficient (Ks) is mostly affected by the pier geometric shape and the effect of position of the piers is small. Furthermore, the piers with low width and sharp nose create shallow and low-volume scour hole. In contrast, deeper holes are created around the piers with wide nose and sharp edges with larger volumes. Also, the results showed that the maximum scour depth is equal to 4.22 times the pier width in the case of rectangular pier located at 90-degree bend position and the lowest scour is equal to 2.12 times the pier width that was created around the pier located at the 120-degree bend position. The maximum scour depth for the pier installed at the 120-degree position has decreased by 50% compared to that for the rectangular pier placed at the 90-degree position.
Scouring around the bridge's piers is one of the major causes of serious damage to the bridge pier. A laboratory modelling method has been utilized in this research to study the effect of level and thickness of collar on scouring around the pier. The experiments were carried out in a channel with a 180° bend and a relative curvature radius equal to 2. This channel is composed by the straight upstream- and downstream-directed paths, respectively, 6.5 and 5.1 m long and 1 m wide. All experiments were conducted with a constant discharge capacity equal to 0.07 m3⁄s. The obtained results indicated that the installation of the collar at the initial bed surface and 0.4 pier width under the initial bed level with thickness of 0.12 and 0.06 pier width helped gain the best results in reducing the amount of scouring when placing the pier at 90° of the bend. It also decreased 70% of the maximum depth of the scour hole in comparison with when the collar was not implemented. In the positions of 60° and 120°, the thickness parameter has no appreciable effect on scouring, and the best level of collar in this positions is same as the pier located at 90° of bend.
In this paper, the scouring around a triad series of vertical bridge piers located in a bend is investigated using SSIIM software. To this end, some of the most essential parameters such as the relative radius and the bridge pier position in both transverse and longitudinal directions to the flow have been examined. Then the bed topography variations have been detected within a flume. It is worth mentioning that the experiments have been conducted in a 180-degree sharp bend in the presence of the bridge piers. The available experimental results were used to ensure correctness of the simulated output data. Accordingly, it is evident that the simulated model not only is capable of estimating the amount of the maximum scour and sedimentation but also can effectively predict their position using an experimental model. Based on the results, it is indicated that the maximum scour depth is reported in the case of the bridge pier transverse to the flow installed at the 60-degree position of the bend with a relative radius of 5. Under these circumstances, the maximum depth of scour is evaluated to be 1.14 times the depth of flow at the beginning of the bend. Also, the maximum volume of scour around bridge piers has been detected in this case.
This paper presents a hybrid numerical model for morphodynamic flow simulation in open channels. For this purpose, a deviatoric version of the Saint Venant’s equations is solved using the Beam and Warming implicit finite difference scheme. The Exner sediment continuity equation is solved using a simple finite difference scheme. The hydrodynamic and the sediment transport models are then coupled using the semicoupled approach. Due to the use of the deviatoric version of the governing equations, the model can efficiently handle the undulated river bed. Secondly, the present model can also use larger time step due to its implicit nature. Moreover, the implicit scheme is also iteration free and can smoothly handle transcritical flow regime. The model is tested in several test cases with bed slopes ranging from −0.244 to 0.086. The results obtained are compared with results of some existing models and found to be capable of handling varied situations with sufficiently high time steps.
Land use/land cover (LULC) changes have emerged as a major concern on global as well as on the local stage because of its considerable impact on climate and environment, especially in rapidly developing areas. Therefore, accurate mapping of LULC and ongoing changes over a time period have drawn a lot of attention in recent years. Remote sensing images from Landsat series satellites are a major information source for LULC change analysis. The present study mainly focuses on the evaluation of three classification techniques, namely maximum likelihood classifier (MLC), artificial neural network (ANN) and support vector machine (SVM) using multi-temporal Landsat images in order to choose the best method among them. The overall analysis based on accuracy measures indicates that the SVM is superior to ANN and MLC. The classification results achieved by the best recognized technique (SVM) were applied to assess the spatio-temporal changes in LULC that occurred in a fast growing Varanasi district of India over a period of 14 years (2001–2014). A paired samples t test was also carried out to determine the statistical significance of changes in LULC between different studied time periods. The results reveal the rapid expansion in built-up area resulted in substantial decrease in agricultural land and other LULC classes. This study also highlights the importance of Landsat images to provide accurate and timely LULC maps that can be used as inputs in a number of land management and planning activities.
Two-way two-lane (TWTL) carriageway comprises a considerable portion of the road network in developing countries. Thus, reliable road capacity estimation is of great importance for road design, operation, and planning. Furthermore, heavy vehicles’ presence causes an extreme variation in roads’ operation and level of service, especially on different slopes. This paper investigates the effects of heavy vehicles in the traffic stream by using the concept of passenger car equivalent (PCE) from Highway Capacity Manual 2016 (HCM2016) and then calibrates it for developing countries such as Iran. This research aims to determine PCE factors for heavy vehicles in Iran’s TWTL roads with diverse geometrical and traffic conditions. Accordingly, PCEs were calculated by two approaches, and the results were compared with HCM factors. The conclusion indicates that by increasing the TWTL road slope, PCE factors increase, but when the traffic volume increases, PCE factors decrease. However, the extent of PCE increase or decrease was not always equal to the correspondent values specified in HCM2016. It was observed that as the length and the slope increase, the PCE values reported by HCM have a higher rate than the ones estimated for Iran. For 5.5–6.5% slopes, the HCM PCE factors were almost twice Iran’s calculated ones.
Shiraz flash flood of March 25, 2019, at the eve of Iranian New Year had 21 fatalities and 164 injured. Lack of methodologies to estimate design discharges in ungauged catchments has contributed to the inadequate design of the flood control infrastructure. Here, we make a physically informed conceptual model of the catchment to estimate the flood discharges associated with return periods used in hydrological designs. Lack of historical precipitation and temperature data is compensated for with the application of historic regional climate models (RCMs) from Coordinated Regional Downscaling Experiment (CORDEX) ensemble. Model consists of eleven sub-catchments (SOCONT basin model) and four river elements (kinematic wave flow routing) and is calibrated to reproduce the flood event. Generalized extreme value theory is used to estimate return levels for the flood based on the model outputs for 12 simulations with RCM as climatic drivers. Return level of 2019 flash flood with estimated discharge of 55 m3/s is about 75 years. Flash flood discharge with a return period of 100 years is estimated to be 95 m3/s which is much higher than capacity of the pipe installed in the expressway. The methodology provided here overcomes lack of data in ungauged catchments susceptible for flash floods. Peak discharge and peak arrival time are shown to be effective as constrains for model construction. The results show that the current infrastructure is not adequate for the flood control and should be augmented and expanded to properly facilitate flood flow discharge from the catchment.
Rayyan stadium location plan
Transport general model proposed by SC for stadiums hosting FIFA World Cup 2022. SC Competition Venue Requirements: Spaces and Systems, Rev 1, May 2016
Bus stand and spectator queuing area
Typical intersection-VISSIM layout and LOS. Note: The link sections in red indicate traffic congestion due to high density of vehicles and the sections in the green indicate low density of vehicles and thereby less congestion
Spectator profile comparison
The State of Qatar has made extensive preparation to successfully host the upcoming FIFA 2022 World Cup, a tournament that will be held for the first time in the Middle East and the North Africa region. In preparation for this tournament, a wide-ranging operational strategy is being developed for each of the stadiums separately. This paper looks into the preparation stages of master planning and transport strategy for one of the hosting venues, which is located in Al Rayyan, Qatar. An overview of the Fédération Internationale de Football Association (FIFA) tournament, its assumptions, spatial planning, traffic modeling, Temporary Traffic Management, and the required mitigations from the transport operations perspective alongside the lessons learned are discussed in the paper.
Current design codes have prepared linear analysis methods instead of nonlinear ones in order to reduce time, cost and other factors such as less need of these methods for expert knowledge. In linear analysis method, elastic strength demand of structure is decreased by applying a response modification factor called behavior factor (R) and by considering the design code regulations, structure members will be permitted to experience nonlinear response (in the time of middle-to-severe earthquakes). Because of different assumptions for linear (force-based method that has deficiencies) and nonlinear methods and whereas seismic stability or instability is not merely related to the strength of structure, rather it depends largely on the capability of structure to resist drifts, seismic performance evaluation of structures designed by linear procedure appears to be necessary using standards for evaluation. In this research, seismic performance of steel moment frames once designed based on 3rd edition of 2800-Iranian seismic code and allowable stress design (ASD) method and another time based on new ones, the 4th edition of 2800 seismic code and load and resistance factor design (LRFD) method, are compared with each other through nonlinear pushover and time-history analyses according to ASCE/SEI 41–13. Results showed positive change of design codes procedure with respect to alteration of design method in both types of ductile design, intermediate and special. Since mean of overstrength values and mean of ductility values have increased a little, mean of behavior factor values has become closer to the recommended values of the new seismic code. Also, a small number of structures met total collapse during nonlinear time-history analyses.
Sluice gates commonly control water levels and flow rates in rivers and channels. They are also used in wastewater treatment plants and to recover minerals in mining operations and in watermills. Hence, scour phenomena downstream of sluice gates have attracted the attention of engineers to present a precise prediction of the local scour depth. Most experimental studies of scour depth downstream of sluice gates have been performed to find an accurate formula to predict the local scour depth. However, an empirical equation with appropriate capacity of validation is not available to evaluate the local scour depth. This study presents the application of multivariate adaptive regression splines (MARS) to evaluate the local scour depth downstream of sluice gate using 228 experimental case studies of the scour depth downstream of sluice gates with an apron. MARS is used to develop empirical relations between the scour depth and various control variables, including the sediment size and its gradation, apron length, sluice gate opening, and the flow conditions upstream and downstream of the sluice gate. Six non-dimensional variables were given to determine a functional relationship between the input and output parameters. The efficiency of MARS model is investigated with ANN model in the training stages. On the other hand, performances of the testing results for this model are compared with the ANN model and traditional approaches based on regression methods. The uncertainties prediction of the MARS was quantified and compared with ANN model. Also, sensitivity analysis was performed to assign effective parameter on the scour depth prediction.
This study describes series of experimental investigations on the uplift capacities for 3D models of belled anchors and formation of respective nonlinear failure surfaces in sand around 2D panels. The variation in uplift capacities due to the influence of embedment ratios of 3, 4 and 5, diameter ratios of 0.28, 0.33, 0.38 and 0.46, and bell angles of 45°, 54°, 63° and 72° in dry sand is evaluated by 3D model study, and the present 62.5% experimental data are within a range of + 12.46 to − 15.14% variation based on a few previous multiple regression models. The observation on the variation of nonlinear failure pattern in sand around 2D panels is correlated with the effects of variable parameters. In order to visualise the pattern of failure surfaces clearly, 3-mm-thick layers of dyed sand are placed within 18-mm-thick non-dyed sand layers maintaining the same density of sand. The horizontal extent of failure points and corresponding embedment depth are plotted in X–Y coordinate. The mobilised shear and dead-weight of each slice wedge are evaluated by horizontal slice method, and vertical equilibrium is implemented for elementary forces. The variation in analytical uplift capacities is used to illustrate the effects of variable parameters. The variation of maximum horizontal extent of failure points at sand surface and passive, transition and active zones within failure domain is also illustrated. The experimental 81.25% data are within + 10.08 to − 9.74%, and rest are within + 15.85 to − 17% variation with respect to the analytical uplift capacities.
In this paper, a novel Hp-Cloud approximate function with Kronecker delta property, named herein as HPCK, is utilized in a meshless finite volume method for two-dimensional elasticity problems. Using the enrichment parts in the HPCK approximate functions leads to excessive unknowns corresponding to nodal points. Therefore, the obtained equations from the ordinary finite volumes method (FVM) are underdetermined. We tackled this problem by proposing an algorithm that considers more control volumes (CVs), known as enrichment CVs (ECVs), inside the main CVs. Following the fulfillment of the equilibrium equations on these ECVs, sufficient equations are obtained to solve the unknowns. In the proposed FVM with HPCK approximate function, the boundary conditions are easily and directly enforced due to Kronecker delta property of HPCK. Moreover, the proposed method leads to a fast convergence and highly accurate results for the studied test problems. In addition, unlike approximation functions like MLS, this method does not involve matrix inversions, which leads to low computational costs and CPU usage while achieving desirable accuracy levels.
Roller-compacted concrete (RCC) is very lean with its lower content of cementitious materials and water to control the heat of hydration. The quality of such concrete mainly depends on the performance of the coating condition of aggregates with cement paste/mortar, which itself is in very lean and serves as the binder. The prototype mixer, BR-100, was developed to verify the 2n mixing theory based on the kneading and lapping mechanism. Very lean mortar, to be used in RCC, was mixed in the BR-100 mixer to compare its compressive strength and flexural strength. Twenty-eight-day compressive strength of lean mortar mixed with a combination of conventional and the new mixing method was 28.6 MPa, which was increased by more than 36% than that of mixed in the only conventional method. Similarly, the flexural strength of lean concrete mixed with the first method was 6.3 MPa, greater by more than 31% than that of conventional methods (4.8 MPa). It was concluded from the investigative research work that the 2n mixing theory enhances both compressive strengths and flexural strengths of lean mortar with the nice coating of paste around the surface of aggregates with the significant effect of kneading and lapping mechanism.
This paper presents a realistic as well as detailed 3D finite element model within the framework of concrete damage plasticity model in ABAQUS software to predict the behavior of CFRP-confined concrete short columns with various rectangular and square cross-sectional areas subjected to compressive monotonic loading. Considering a suitable yield criterion, orthotropic behavior of concrete is taken into account. Furthermore, to account for the hydrostatic-pressure-dependence behavior of concrete, a non-associated flow rule based on Drucker–Prager potential function is adopted in the simulation. As an intrinsic behavior of concrete, the phenomenon of variation of Poisson’s ratio is modeled by using the USDFLD subroutine available in the software package, and the effect of Poisson’s ratio variation on the responses is investigated. To this end, nineteen specimens examined in three previous studies are numerically modeled using the proposed approach for two cases, namely fixed and variable Poisson’s ratio (totally 38 numerical models). Comparisons between experimental and numerical results corroborate that the proposed numerical approach is very appropriate for estimating both the ultimate axial strain and the axial stress–strain behavior of the CFRP-confined concrete columns.
Data collection related to the flow pattern has always been associated with outliers due to various reasons. Outlier detection in flow pattern experiments is of high importance and results in a better and more accurate understanding of the flow pattern. In this study, six data mining methods have been used to identify the outliers in flow pattern experiments. The discussed methods include box plot, histograms, linear regression, k-nearest neighbors, local outlier factor, k-medoids clustering, multilayer perceptron, and self-organizing map. The main aim of this study is to detect the outliers in data collection in order to conduct flow pattern experiments using the data mining methods. These methods have been analyzed and compared with each other in a case study and their performance evaluated. The experimental outliers under investigation were emanated from flow pattern experiments around a spur dike located in a 90° bend using Vectrino velocimeter (ADV). The range of velocity measurement of this device is between ± 0.01 and ± 4 m/s, and measurement accuracy is 1 mm/s. Also, the frequency is set at 50 Hz. The comparisons of different outlier detection methods results demonstrated that the box plot and the local outlier factor methods have the best performance.
Presented is a method of three-dimensional stability analysis of convex slopes in plan view based on the Lower-bound theorem of the limit analysis approach. The method's aim is to determine the factor of safety of such slopes using numerical linear finite element and lower bound limit analysis method to produce some stability charts for three dimensional (3D) homogeneous convex slopes. Although the conventional two and three dimension limit equilibrium method (LEM) is used more often in practice for evaluating slope stability, the accuracy of the method is often questioned due to the underlying assumptions that it makes. The rigorous limit analysis results in this paper together with results of other researchers were found to bracket the slope stability number to within ±10% or better and therefore can be used to benchmark for solutions from other methods. It was found that using a two dimensional (2D) analysis to analyze a 3D problem will leads to a significant difference in the factors of safety depending on the slope geometries. Numerical 3D results of proposed algorithm are presented in the form of some dimensionless graphs which can be a convenient tool to be used by practicing engineers to estimate the initial stability for excavated or man-made slopes.
In this paper, three dimensional discrete element method simulations of true triaxial test are presented. During simulations, the major, the intermediate and the minor principal strains are monitored to maintain the b-value constant. The effect of intermediate principal stress on the frictional parameters of granular materials is studied. Furthermore, the micromechanics of samples using the Stress–Force–Fabric (SFF) relationship is investigated. The SFF relationship is comprised of anisotropy tensors of fabric, contact normal and tangential forces. Results show that, the mobilized friction angles in simulations with different b-values have very good agreements with results of the so-called general stress tensors, which are made of force and position vectors at contact points. It is observed that the evolution of anisotropy in the sample is at the origin of different responses of granular materials in macro scale. The frictional properties of granular materials is observed sensitive to the intermediate principal stress both at macro and grain scale. Our observations highlight the important role of intermediate principal stress, and are consistent with experimental studies of true triaxial tests on granular materials.
3D printer is the device that quickly produces the models designed on the computer using different materials without the need for a mould. In this study, the properties of the 3D printer developed by Iston and the complementary components such as concrete pump, concrete transmission hose, printer nozzle head which are synchronized with this printer are given. In addition, the mix design of fibre-reinforced and grain size limited high-performance concrete, which is used in this printer, and properties of fresh and hardened concrete are examined. In this context, mechanical properties of casted and printed specimens were compared. In addition, mechanical behaviour of printed samples in different directions was also investigated. Results of both compression and flexural tests show the mechanical properties of the printed specimens differed slightly in directions. When the casted and printed samples are compared, the strength of the casted samples is slightly higher than the printed samples. Although the mechanical properties of the casted and printed samples differed, targeted results were obtained for the strength of the printed samples. In the last part of the study, examples of street furniture produced in 3D printer using white cement mixture for decorative purposes are given. Although there are studies in the literature about 3D concrete printing, there are not any studies on street furniture produced in 3D printer.
Sluice gates are widely used in irrigation networks, in order to control the water level and regulate the flow that enters the intakes. Creating a sill under the sluice gate reduces the height of the gate and the construction costs of the irrigation network and also affects the discharge coefficient. The main aim of this study is evaluation of the effect of the shape, height and location of the sill on the sluice gate’s discharge coefficient. In order to evaluate the effect of the shape and height of the sill on the hydraulic flow, Flow-3D model was employed and two different sill shapes (rectangular and semicircular) with different heights were used under the sluice gate. The results indicate that creating a sill under the sluice gate increases the discharge coefficient and the shape and height of the sill are the most important factors in its increase. When the ratio of the rectangular and semicircular sills’ height to the gate opening is 2 and 0.5, respectively, the discharge coefficient is maximum value and 8.3% and 23% more than the case without sill, respectively. In order to correct the discharge coefficient of sluice gate with sill, equations for rectangular and semicircular sills have been presented.
The 3D textile-reinforced cementitious composite applications have various and large area of utilization. The studies have been performed on the 3D spacer fabrics, and its applications are especially on the improvement of the mechanical properties of the fabrics. However, the durability properties of the 3D spacer fabrics are also important for the 3D spacer fabric applications. Due to the lack of studies on this subject, this research attempts to investigate the performance of 3D textile-reinforced cementitious composite under elevated temperature. For this purpose, 3D textile-reinforced cementitious composite specimens were exposed to 150, 200, and 300 °C temperatures for two hours. Tensile and flexural tests were performed for determination of the performance of 3D textile-reinforced cementitious composite specimens before and after exposure to elevated temperatures. Test results indicate that the 3D textile-reinforced cementitious composite lost its bearing capacity at 300 °C.
This paper investigates the earthquake in Sarpol-e-zahab County, Kermanshah Province, Iran on November 12, 2017. For this purpose, the seismological aspects and the earthquake source are investigated. The ground motion is studied and its response spectra are compared with the Tabas earthquake response spectra and also the design spectra of the Iranian seismic design code (Standard No. 2800). The maximum pseudo-acceleration responses of the longitudinal and transverse components of Sarpol-e-zahab fall between 0.3 and 0.6 s. The structures' period in most of the buildings in this region has the same value. This resulted in severe damage to most of the buildings in the region due to the resonance effect. Finally, the seismic behavior of different structural buildings in this region is studied, and the buildings' damages are outlined. The study presents field observations of damage to the buildings since the damage appearing in the buildings may be the result of such elements as site effect, poor construction quality, poor material, poor detailing, soft stories, weak stories, and inadequate reinforcement.
Worked example of using design charts to compute the bearing capacity of non-associative sand
Collected database of footing load tests on sand
Following the recent work of the authors in development and numerical verification of a new kinematic approach of the limit analysis for surface footings on non-associative materials, a practical procedure is proposed to utilize the theory. It is known that both the peak friction angle and dilation angle depend on the sand density as well as the stress level, which was not the concern of the former work. In the current work, a practical procedure is established to provide a better estimate of the bearing capacity of surface footings on sand which is often non-associative. This practical procedure is based on the results obtained theoretically and requires the density index and the critical state friction angle of the sand. The proposed practical procedure is a simple iterative computational procedure which relates the density index of the sand, stress level, dilation angle, peak friction angle and eventually the bearing capacity. The procedure is described and verified among available footing load test data.
A trapdoor system has frequently been used to study soil arching and its development. The load transfer in the fill of embankments is very similar to a trapdoor system. In order to study the displacement mode of the embankment and the influence of soil arching effect on the earth pressure on culvert crown, a series of model tests on controlled settlement were carried out using three different diameter aluminum rods with analogical embankment backfill. In the process of controlling the settlement of aluminum rods, photographs of aluminum rods with different relative displacements were taken by a digital camera, and the MATLAB software was used to run a program to extract the whole-field displacement values of aluminum rods from the image acquisition of the photographs by particle image velocimetry technique. The evolution law of soil arching on culvert crown was investigated under different differential settlement (Δs) and different filling heights (H). The results show that with the change in Δs, the soil arching has experienced three stages, which are formation, evolution, and stability. The height of soil arching in a critical state is about 1.5 times of the culvert width (D), and the inclination angle of the shear plane (θ) is 15° after the stabilization of the embankment settlement. The calculation of earth pressure on the culvert crown considering the soil arching effect is proposed as (1) earth pressure on culvert crown considering incomplete soil arching; (2) earth pressure on culvert crown considering complete soil arching. Finally, by comparing the calculated results with the measured values, the difference is about 10%, which illustrates the applicability of the proposed calculation method of earth pressure on culvert crown considering the soil arching effect.
Infrastructure development projects in Oman are at a peak which results in a huge requirement for the construction materials. Aggregates are one of the most common materials naturally available and used in both cement and asphalt concrete apart from being used as under laying material. The evaluation of aggregates physical, chemical and mechanical properties thus becomes important as it directly affects the product in which they are used as a constituent. Aggregates should be hard and tough enough to resist crushing, degradation and disintegration from any associated activities including manufacturing, stockpiling, production, placing and compaction. In this article, an attempt is made to develop a modified method to determine the abrasion resistance of aggregates. Different sizes of aggregates obtained from two natural sources in Oman were tested in the laboratory using both the standard and modified Los Angles Abrasion (LAA) test, and a mathematical relationship is developed. Based on this relationship, the standard LAA value can be determined from the modified method results. In the modified LAA test method, the time required for the test is reduced by 24 h, apart from reducing the resources required for the test. Since the modified LAA method is developed considering Oman climatic and geological conditions, there is a possibility that this method and mathematical relationship may not be valid in a region when these conditions are changed. In such satiation, the modified LAA test method and mathematical relationship described in this article may need to be validated before it is adopted.
Reinforcing fiber and silica fume of concrete can be considered as one of the most widely used additives. In this study, with a review of the history and advantages of using silica fume and polypropylene fibers in concrete, 380 concrete laboratory samples were constructed, of which 25 mixing designs with water–cement ratio of 0.35 and fiber content of 0.2, 0.3, 0.4 and 0.5 of concrete volume and 7% silica fume were prepared according to the ACI standard in their manufacturing. In the present research, samples of Kevlar fiber containing silica fume were tested under flexural strength, abrasion resistance and hydraulic conductivity coefficient. According to achieved results, the optimum amount of fiber used for flexural strength is 0.4% and the hydraulic conductivity coefficient and abrasion resistance of 0.3% volumetric concrete with 7% silica fume were used in concrete mixing.
Liquid containing tanks are very common civil engineering systems used chiefly for storage purposes. Very often, the tank is placed atop a primary structure and contains considerable amount of liquid mass, sufficient for designing the tank to function as an inertia-based supplemental damping device for the primary structure under lateral excitation. However, due to low inherent energy dissipation capacity and a high proportion of impulsive liquid mass, the proper utilization of deep tanks as dynamic vibration absorbers (DVAs) has not taken place. It thereby requires special attention and innovative design modifications. In this paper, the characteristics of liquid motion in a laterally excited deep tank are first analyzed to explain its inadequate inherent damping. A state-of-the-art review of existing literature on the special design of deep tanks as DVAs is then carried out. A brief comparative performance study on a deep tank, with and without baffles, and a shallow tank, as well as a cost analysis of a deep liquid-containing tank as a DVA for structures, are presented. It is seen that available deep tanks fitted with flow damping devices have the potential to serve as very effective and economical structural vibration control devices. The means to further enhance the effectiveness of deep tanks is also identified.
Seismic safety of super tall buildings is of paramount importance, since if they get damaged, their repair is very costly on the one hand, and their service interruption requires a substitute space for the occupants, which is very difficult, if not impossible, on the other. Regarding these facts, in seismic design of super tall buildings the desired performance level (PL) is immediate occupancy (IO), and it is obvious that achieving this PL is not possible with conventional seismic design procedures. On this basis, in this paper, the efficiency of using specific energy absorbing stories (SEASs) in improvement of seismic behavior of a set of super tall steel buildings with 50, 60, 70 and 80 stories, with tubular frames combined with X-bracing, as their lateral load bearing system, has been investigated. To create SEASs in each building, in every other few stories the bracing elements have been substituted by dampers, as the additional energy absorption sources. The optimal number and the locations of SEASs in each case have been obtained by an optimization technique based on combination of crossover and mutation. Numerical results show that by considering SEASs in almost one tenth of the buildings’ stories, an optimal design is achieved in each case, and that the optimal use of the SEASs reduces the maximum drifts more than 50% in all considered buildings, resulting in a remarkably higher PL, comparing to that of the buildings designed based on conventional methods.
In light of the vast potential for the application of modern energy absorption systems in the structures, the effectiveness of each system should be tested, analyzed, and proved before convincing the structures design companies to use them. In this research, the effectiveness of applying base isolators, viscous and friction dampers and a hybrid system consisted of lead rubber bearing with friction dampers are studied. To quantify the impact of each system, a control structure without any energy absorption system is considered. Base isolators and damper systems are designed according to available international codes. American concrete institute’s codes were used to design the concrete structure frames. All of the considered systems therewith hybrid systems including lead rubber base isolation and viscous dampers have been modeled in ETABS 2018 software. The control structure has an intermediate moment resisting frame with high importance located in a high seismic hazard zone. These models were subjected to time history analysis by using Manjil, Loma prieta, and Imperial Valley Earthquakes records. It was observed that the structural design parameters such as base shears and story drifts were significantly reduced by 76–86% and 44–92%, respectively, compared to the structure without any energy absorption system. Also, the total energy dissipated in the structures equipped with modern energy absorption systems was decreased between 32 and 86% compared to the friction dampers. It should be noted that the studied devices may be used either for the design of a new structure or seismic rehabilitation of the existing structures.
Steel sandwich panels are widely used in various fields because such panels have lower density, high strength-to-weight ratio, easier fabrication and higher energy absorption compared with monolithic plates. In this study, a numerical investigation on a novel steel sandwich panel with slotted I-core under air blast loading is presented. Numerical results are compared with experimental data, and agreement between the two is found to be good. The influences of different parameters such as charge weight, standoff distance, strain rate and boundary conditions are considered. The obtained results emphasize the importance of charge weight and standoff distance on overall dynamic response. Boundary conditions drastically affect the blast behavior of the models; displacement in free edges can exceed the deflection at the center of the panel. Dynamic response of the proposed sandwich panel is also compared with equivalent structures, i.e., traditional I-core panels and equivalent monolithic plate. According to the results, slotted I-core sandwich panels outperform in comparison to equivalent structures when subjected to air blast loading.
Extreme floods become more frequent and is the reason rising load on structures in rivers and the risk to be damaged. The methods of scour calculation at bridge abutments are based on that design flood up to 1% probability (Arneson et al. 2012) accepted by many authors is constant during the maintenance period of the bridge and the equilibrium depth of scour often used for foundation design. Inspite of that equilibrium depth of scour sometimes can be overestimated, because in nature scour is formed under unsteady flow. The bridge abutments usually are constructed on the floodplain, where is no sediment movement, here we considering scour at clear water conditions and estimating scour evolution when sediments are removing out of scour hole. As a basis, the equation of the bed sediment movement was used and a semi-analytical model for computing depth of scour evolution under unsteady flow at the abutments is elaborated. The tests were made in flume for free surface flow conditions, for rigid and sand bed of the bridge crossing model with different contraction rate, depth, discharge, Froude number, steady and unsteady flow, with uniform or stratified bed. To study different parameters impact on scour at the abutment, More than 50 tests were made. Tests results are in good agreement with calculated data by model presented. In the paper is presented the relative local and critical velocities evolution, impact the bed material, flow contraction and unsteady flow on scour depth under clear water conditions at vertical wall abutment.
A detailed investigation has been conducted to study the shift location of the point of the maximum scour depth for both bridge abutment-collar and pier-collar arrangements. In the present study, an experimental program has been conducted for abutment-collar arrangements and additionally, the data obtained from the literature for the pier-collar arrangements have been revisited and analyzed to complement the framework of this study. For the abutment-collar arrangements, a series of experiments under clear-water conditions were carried out for different abutment lengths with fixed values of collar location and collar width. For pier-collar arrangements, data used from the literature have been involved constant pier diameter with various collar sizes at various elevations. To describe the locations of these maximum scour depths, their coordinates with respect to the location of the abutment or the pier were obtained. Results from this investigation showed that when a collar placed on or below the bed level was used as a countermeasure against scouring, either on an abutment or on a pier, it was observed that the maximum scour depth was routed downstream of the bridge structure.
Perfect plastic load-displacement diagram [17] Displacement
Presented is a method of three-dimensional stability analysis of slopes due to earthquake forces based on the Lower-bound theorem of the limit analysis approach. The method's aim is to determine the factor of safety of such slopes using numerical linear finite element and lower bound limit analysis to produce seismic stability charts for three dimensional (3D) homogeneous slopes. The rigorous limit analysis results in this paper together with results of other researchers were found to bracket the slope stability number and therefore can be used to benchmark for solutions from other methods. It was found that using a two dimensional (2D) analysis to analyze a 3D problem will lead to a significant difference in the factors of safety depending on the slope geometries. Numerical 3D seismic results of the proposed algorithm are presented in the form of some dimensionless graphs which can be a convenient tool to be used by practicing engineers to estimate the initial stability for excavated or man-made slopes.
The four main influencing parameters affecting traffic flows are human, environments, vehicles, and roads, and the human is the most influential parameter in this case. This study is a thorough investigation on the use of psychology in traffic safety to find the effects that personality traits have on the number of accidents and the frequency of fines. A questionnaire was distributed among 200 university students who had active driver’s license. The questionnaire consisted of three sections: personal information, questions related to the subject under review, and the Neo test. In this study, a confirmatory factor analysis method was used based on structural equations and then carried out using the maximum likelihood or likelihood estimation (ML) method. Then, the hypotheses were considered and tested by the AMOS software. These analyses are individually categorized into three categories of hazardous behaviors: aggressive, disagreeable, and lack of attention to health. The non-separation of high-risk behaviors is also considered. Finally, the results show that personality traits have a meaningful relationship with the number of fines and the number of accidents, as well as the tendency to show aggressive behaviors, disagreement, and lack of attention to personal health. According to the results, eating and drinking while driving have the greatest impact among other high-risk behaviors.
Sample distribution Regional directorates ACCIDENT group (Number of level crossings in which accident occurred) CONTROL group (Number of level crossings in which no accident occurred)
Normality test of independent variables)
Results of non-parametric "Mann-Whitney U" Test
Chi-square test for categorical independent variables
Logistic regression model based on traffic moment components: average daily traffic counts of trains and vehicles
The sections where risk of accidents is the highest in railway transport are the level crossings. In many countries, accidents that occur on the level crossings lead to loss of goods and lives. Therefore, governments have adapted some regulations to prevent accidents that occur at level crossings. In this study, we have examined the data of level crossings belonging to particular years in Turkey. The effects of physical and traffic characteristics of the level crossings, which are determined in the framework of the related regulation, are interpreted by logistic regression modeling method. As a result, it was determined “the width” and “the type” of level crossings are independent determinants of accidents, while “traffic moment” is not. Since the traffic moment parameter is not an independent determinant, the sub-parameters forming the traffic moment are used as inputs for the new model. In the new model, which sub-parameters of traffic moment, the type and width of the level crossing parameters are used as input, “the number of annual average traffic value of vehicles” and “the type of level crossing” parameters are found as independent determinants of accidents while the number of annual average traffic value of trains and the width are not.
Many optimization techniques based on swarm intelligence have been developed for size optimization of skeletal structures. Cuckoo search algorithm, artificial bee colony algorithm, colliding bodies optimization, artificial coronary circulation system (ACCS) are only some examples of these algorithms. In these methods, the sizing variables are often assumed to be continuous. However, in most practical structural engineering design problems, the design variables are discrete. The aim of this study is to present an optimization algorithm based on the ACCS algorithm for the discrete optimum design of truss structures. Here, the discrete search strategy using the ACCS algorithm is presented by three different scenarios in detail and their effectiveness and robustness are compared to those of the recently developed discrete optimization methods. The ACCS optimization algorithm uses the visual center point of populations in each iteration and simulates the process of growing coronary arteries of heart. Finally, it is shown that the discrete ACCS has the fastest convergence rate among the considered algorithms and can be effectively used to solve optimal design of truss structures with discrete variables.
This article adopts four high-accuracy machine learning-based approaches for the prediction of discharge coefficient of a Piano Key Weir (PK-weir) under subcritical condition located on the straight open-channel flume. These approaches consist of least-square support vector machine (LS-SVM), extreme learning machine (ELM), Bayesian ELM (BELM), and logistic regression (LR). For this purpose, 70 laboratory test results are used for determining discharge coefficient of PK-weir for a wide range of discharge values. Root-mean-squared error (RMSE), Nash–Sutcliffe model efficiency coefficient (NSE), the coefficient of correlation (R), threshold statistics (TS), and scatter index (SI) are used for comparing the performance of the models. The simulation results indicate that an improvement in predictive accuracy could be achieved by the ELM approach in comparison with LS-SVM and LR (RMSE of 0.016 and NSE of 0.986), while the BELM model’s generalization capacity enhanced, with RMSE of 0.011 and NSE of 0.989 in validation dataset. The results show that BELM is a simple and efficient algorithm which exhibits good performance; hence, it can be recommended for estimating discharge coefficient.
In spite of various methods applied for determining scouring depth around piers, the empirical models are the ones utilized in practice more than others. In this regard, the accuracy of empirical equation used plays the key role in the estimation of scouring depth in numerical software. In this paper, a new accuracy-improved empirical model is proposed to estimate scour depth around piers. The new model, which considers three equations based on the ratio of flow velocity to the critical velocity for the mean particle diameter, is developed using a powerful hybrid method based on various reliable field databases. The performance of the proposed model is compared with those of six common empirical ones available in the literature, artificial neural network, and genetic programing. The empirical models include the two models used in HEC-18, the model developed by Florida Department of Transportation (known as FDOT), Froehlich’s equation, Jain–Fischer’s equation, and Afzali’s equation. According to the obtained results, it is concluded that the new model achieves more precise results comparing with the other conventional and practical available models for the considered data.
In this paper, the mesh-less SPH formulation is modified based on Voronoi diagram to approximate region influence of computational nodal points to achieve higher accuracy. The accuracy of the proposed method is examined for a 2-D elliptical partial differential equation with known analytical solution using both regular and irregular node distributions. In addition, a comparison between the accuracy is accomplished for conventional SPH and the proposed method. The numerical results indicate the accuracy of the proposed method over SPH method especially for irregular node distributions.
In this study, a new model of Laplacian operator is formulated as a hybrid of an incompressible SPH (I-SPH) method with Taylor expansion and moving least-squares method. Accuracy of the proposed Laplacian model in solving 2-D elliptic partial differential equations for a unit square computational domain is compared with the conventional I-SPH Laplacian operator. The results show significant improvement in accuracy for the proposed model on regular, highly irregular and multi-resolution irregular node distributions employed for computational domain discretization. The proposed Laplacian model because of notable accuracy can be applied for more efficient simulation of free surface flows.
The grain size distribution curve of the studied soil
a Direct shear strength test mold; b specimen after testing
Variation of shear stress with normal stress of soil stabilized with PVA for different curing time: a 1 day; b 7 day; c 14 day; d 28 day
Physical composition of MCC used in this study
Improvements in the strength characteristics of soil are noteworthy in geotechnical engineering. Many engineering problems emerge in silty sand soil because the silty fraction generally has low strength properties. High dispersion in such soil at a construction site illustrates the necessity of studying and surveying new methods of improvement of its strength properties. One of the methods used to improve soil strength is chemical additives. In the present research, the effects of the addition of polyvinyl acetate (PVA) and micronized calcium carbonate (MCC) on the strength of silty sand soil have been investigated. PVA and MCC were mixed with soil in different proportions (1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 5% and 6% (wt.)) for unconfined compression testing and (1%, 2%, 3% and 4% (wt.)) for direct shear strength test under different curing time (1, 7, 14 and 28 days). SEM images were acquired before and after mixing to determine changes in the properties of each sample. It was found that the addition of MCC and PVA to silty sand soil increased the unconfined compression strength (UCS) by 2.5% and 4%, respectively, comparing to untreated soil. An increase in the MCC and PVA contents decreased the UCS of the soil. It was also demonstrated that the addition of PVA more effectively improved the soil strength properties than did MCC. The addition of both of materials increased the shear strength of the soil, but this increase was greater for cohesion than for the internal friction angle. It was also demonstrated that increasing the curing time in stabilized samples of both additives increased the UCS more than 80% in the first 14 days.
This paper examines the influence of acetic acid-treated recycled aggregates on the physical, mechanical, and durability properties of self-compacting concrete. Meanwhile, the zero waste technique has been implemented through the addition of waste acetic acid solution from the aggregate treatment, and its effects on fresh behavior, mechanical characteristics, permeability, penetration, absorption, migration, and resistivity, as well as carbonation resistance of the concrete, was investigated. To ensure that waste acetic acid solution (Wac) does not interfere with the pozzolanic activity of metakaolin; preliminary tests were conducted, which revealed a favorable influence of Wac on CH consumption. The findings show that metakaolin in slurry form compensates for the loss of workability in self-compacting concrete caused by the substitution of recycled materials. Furthermore, the self-compacting concrete's mechanical strength, durability, and microstructure have all been successfully improved by the creation of strong resistance to chloride penetration and carbonation. From the various aspects of self compacting concrete investigated, this study has verified the feasibility of using Wac as an admixture in SCC, promoting the use of recycled aggregates that can not only minimize construction waste accumulation but also provide economic benefits.
This paper presents shear strength test results and structural changes in clay soils with acetic acid. Two different clay soils were used, kaolinite and another containing montmorillonite with a mixed mineralogy, while pure water and various contents of acetic acid (20%, 40%, 60% and 80%) were used as pore fluids. Clay-pore fluid slurries prepared with a water content of twice the liquid limit of each acetic acid content were consolidated under a 100 kPa pre-consolidation pressure. Direct shear tests were conducted on samples taken from pre-consolidated mixtures in order to determine changes in shear strength. Additionally, optical microscope images and scanning electron photomicrographs were obtained in order to observe structural changes under the influence of acetic acid. According to the experimental results, significant increases occurred in peak shear strength and shear strength parameter values in both clays in parallel with increasing acetic acid content. These increases were higher in the clay with montmorillonite; in particular, there were substantial changes in the internal friction angle. Increasing liquid limit values with increasing acetic acid contents in kaolinite resulted in a substantial decrease in the other clay. The optical microscope images and scanning electron photomicrographs indicated that lumpy formations occurred in both clays with the addition of acetic acid, and their structures began to resemble that of a silt and fine sand form.
Post-earthquake damage and performance-level evaluations have not been considered in ACI318-19/ASCE07-16 seismic design provisions while designers expect such provisions lead to structure with repairable damages and life-safety performance level after the design seismic event. This study has investigated the post-earthquake damage and performance levels of simplified reinforced concrete (RC) structures designed according to the ACI318-19/ASCE07-16 seismic design provisions through nonlinear-dynamic analyses. The simplified RC structures have been selected to represent a vast range of structural stiffness, strength, and demand ductility and have been classified by their periods (T), R-factors, and demand displacement ductility ratios (μ). The numerical investigation has indicated that nearly 12 percent of structures designed according to ACI318-19/ASCE07-16 seismic design provisions have collapse-prevention performance level and unrepairable damages. Furthermore, ACI-based seismic design is not consistent for linear and nonlinear time history analyses. It has been concluded that the current ACI seismic design provisions cannot assure a life-safety performance level with high reliability. Damage-based seismic design methodology should be adopted instead of current strength-based drift-controlled R-based seismic design.
Cone stem diagram
Efficient water supply systems are necessary for the development and sustainability of human societies. One relevant aspect of these systems is the metering function, recorded employing water meters, which determines the charges levied to the clients and estimates the water losses in the network. Inaccurate measurements are detrimental for both the client and the supplier. For allowing more precise metering, one option is to use an air volume reducing device, an accessory similar to a check valve that minimizes the air volume entrapped in the pipelines, thus improving metering accuracy. This research used an experimental design to determine the influence of four factors and their interactions on the pressure drop across these devices as a preliminary step for allowing their extended use on low-pressure water supply systems. The results showed that the diameter, the spring stiffness, and the flow rate are significant factors in the pressure drop. The shape of the valve stem is statistically significant only when interacting with other factors.
To analyze and design the reinforced concrete structural members correctly, their behavior must be evaluated under different loadings. The efficiency, accuracy and speed of the methods of structural analysis depend on the use of suitable behavior models. In reinforced concrete structures, the concrete will be cracked under normal loadings since it has a relatively low tensile strength. Therefore, it is important to understand stress transfer mechanisms in the cracked surfaces to evaluate the response of reinforced concrete structures. In the present study, an experimental program is developed to identify the cracked surface behavior under shear loading. The test specimens made of ultra-high performance concrete are used to measure the shear transferred by longitudinal bars (dowel action). Based on the results of the tests and other studies, we present a suitable model for the shear mechanism through the bars in the cracked surfaces of ultra-high performance concrete. The results show that inclined crack decreases the dowel capacity, so that the dowel capacity of samples B6, B7, and B8 decreases to 33%, 50%, and 61% compared to sample B5 (with a 90° angle between notch and bar). The results show the proper accuracy of the equations proposed for estimating the dowel shear-displacement curve in which the correlation was in range 0.972–0.997, between the proposed model and test results.
Masonry bridges are vulnerable structural systems to the ground motion excitation and their survival in case of such incidents has to be studied in detail. In this work, a simplified model for dynamic analysis of masonry bridges based on rocking motion of rigid blocks is proposed. Using this model, nonlinear time integration analysis on these bridges can be done with ease and in a short time. The proposed model was used in evaluation of seismic performances of a monumental masonry bridge subjected to both horizontal and vertical seismic actions. The study shows the importance of vertical component of ground motion in determination of internal forces and shear sliding deformation at bottom of the bridge’s pier. The proposed model has also shown its ability in defining the effectiveness of a seismic retrofit approach for the same bridge system in a comparative study. According to this investigation, seismic performances of the bridge can be significantly improved in case of adding ductility to its deck assembly.
Sustainability leads a cementless materials branch in material engineering and science. Geopolymer is one part/leaf of the sustainability branch and has many advantages (i.e., less carbon emission and low energy consumption in production) attracting attention itself. The recent dizzying progress observed in geopolymers has now turned its direction towards environmentally friendly waste-based geopolymers. Accordingly, many types of waste produced in various industries have come to life in geopolymer seeming like a positive approach from the environmental point of view. However, this area is still a virgin and is worth studying. Hence, to contribute to this field, this experimental study was conducted. Accordingly, 25–50–75% basalt powder (BP), limestone powder (LSP), recycled aggregate powder (RAP), and waste marble powder (WMP) (< 63 μm) were employed in the experiments to produce a durable and sustainable metakaolin (MK) based geopolymer with blast furnace slag (BFS). Thirteen mixtures were produced, and reference was included in the experiments. The main binder as a composition of MK, BFS, and an activator (1:2 NaOH/Na2SiO3) was considered. At the first stage of the experiments, the main properties of the geopolymer mortars were determined by conducting the tests of the mechanical properties and the physical properties. Then, the tests of the durability properties were applied to the reference and the best geopolymer specimens selected by different multi-criteria decision support methods (MCDMs). In this point, CDMs are useful tools to find the best choice and two MCDMs, such as TOPSIS and HDM, were considered to obtain the best geopolymer mix. As a result, ages-based evaluation showed that 28-day-old specimens had the high results. BP provided satisfactory results with a dense and compact structure in geopolymer. The best geopolymer mixture included 75% BP and had a significant mechanical and durability performance compared to reference with satisfactory properties. Examining the experimental results with a MCDM may give excellent results than the conventional singular evaluation technique.
This paper presents the effect of activator ratio and silica fume additive on physical and mechanical properties in slaked lime-based alkali-activated mortars which are limited in literature. The binder, which was formed by slaked lime and adding 5%, 10%, 15% silica fume into slaked lime, was activated with sodium hydroxide. The concentration of activator was chosen between 10 and 15 mol. The water/binder ratio was determined to be 0.55, and the binder/sand ratio was chosen as 1/3. After the produced mortar samples were placed in the mold, they were kept at 105 °C for 24 h at the activation temperature. The samples taken out of the oven were kept at room temperature (22 ± 2) ºC for up to 28 days. As a result of the experiments, in the samples containing 85% slaked lime and 15% silica fume, a compressive strength value of 36.46 MPa was determined. Compared with the control samples, it was observed that the flexural strength of the alkali-activated mortars produced with slaked lime increased by 3.72-fold and the compressive strength increased by 5.9-fold. As a result of the regression analysis, sodium hydroxide amount providing optimum flexural and compressive strength was determined as 14.28 mol, silica fume ratio as 10.03%.
Electric arc furnace slag (EAFS) is a material that emerges as a by-product in iron and steel plants and is in need of evaluation. To ensure its recovery by using it in concrete production, it was replaced 10%, 20% and 30% by weight with cement, and only this part of mixture was activated with alkalis. During the hydration of the cement, alkalinity of the environment increases. In order to facilitate the reaction of EAFS, the pH value of the medium was increased by adding alkaline materials from outside. Replaced EAFS was activated with three different alkali solution levels by changing sodium concentrations (4%, 6% and 8%) and silicate moduli (1 and 2). Alkali solution/binder ratio was kept the same as 0.4 for all slightly alkali-activated mixtures, and the binder dosage was 400 kg/m3. The effects of the pH degree of the medium were determined by mechanical and permeability tests. Capillary water absorption, water absorption, pressurized water permeability, gas permeability and rapid chloride permeability (RCP) properties were determined, and results were analyzed statistically to know the effect of each variable. 4% sodium concentration and silica module 1 appear to be quite effective in reducing RCP. When the alkali level is too high, the strength decreased and the permeability increased. The visualization of gel formation in the scanning electron microscope image proved that EAFS can be alkali-activated.
Top-cited authors
A. Kaveh
  • Iran University of Science and Technology
Mahmoud Reza Maheri
  • Shiraz University
Reza Kamgar
  • Shahrekord University
Faradjollah Askari
  • International Institute of Earthquake Engineering and Seismology
Ali Johari
  • Shiraz University of Technology