The current building codes provide limited prescriptive guidance on design for protection of buildings due to progressive collapse. Progressive collapse is a situation in which a localized failure in a structure, caused by an abnormal load, such as explosions or other happenings. Three procedures, often employed for determination of the structural response during progressive collapse i.e. linear static procedure (LSP), nonlinear static (NSP) and nonlinear dynamic (NDP) analyses. In nonlinear static analysis, a force-based method is applied and the structure is pushed down to the target force. In this research, a new displacement-based method will be proposed for nonlinear static analysis. In displacement-based method, the structure is pushed down to target displacement instead of target force (similar to the one in seismic pushover analysis). To make a nonlinear static analysis, instead of increasing the load around the area of the removed column, a maximum displacement is calculated and the upper node of the removed column is pushed up to target displacement. Here, to determine the target displacement, results from nonlinear dynamic and linear static analyses are compared. This paper tries to present a formula to calculate the target displacement using the linear static rather than the nonlinear dynamic analysis. For this reason, 3 buildings with 3, 5 and 10 stories have been seismically designed and studied. The results show that, this method is much more accurate in comparison to the recommended approach in current codes. Also, this method does not have the limitations of force-based nonlinear static analysis.

Upstream blankets, drains and cutoff walls are considered as effective measures to reduce seepage, uplift pressure and exit gradient under the foundation of hydraulic structures. To investigate the effectiveness of these measures, individually or in accordance with others, a large number of experiments were carried out on a laboratory model. To extend the investigation for unlimited arrangements, the physical conditions of all experiments were simulated with a mathematical model. Having compared the data obtained from experiments with those provided from the mathematical model, a good correlation was found between the two sets of data indicating that the mathematical model could be used as a useful tool for calculating the effects of various measures on designing hydraulic structures. Based on this correlation a large number of different inclined angles of cutoff walls, lengths of upstream blankets, and various positions of drains within the mathematical model were simulated. It was found that regardless of their length, the blankets reduce seepage, uplift pressure and exit gradient. However, vertical cutoff walls are the most effective. Moreover, it was found that the best positions of a cutoff wall to reduce seepage flow and uplift force are at the downstream and upstream end, respectively. Also, having simulated the effects of drains, it was found that the maximum reduction in uplift force takes place when the drain is positioned at a distance of 1/3 times the dam width at the downstream of the upstream end. Finally, it was indicated that the maximum reduction in exit gradient occurs when a drain is placed at a distance of 2/3 times of the dam width from upstream end or at the downstream end.

Steel-concrete hybrid systems are used in buildings, in which a steel structure has been placed on a concrete structure to make a lighter structure and have a faster construction. Dynamic analysis of hybrid structures is usually a complex procedure due to various dynamic characteristics of each part, i.e. stiffness, mass and especially damping. Dynamic response of hybrid structures has some complications. One of the reasons is the different stiffness of the two parts of structure and another reason is non-uniform distribution of materials and their different features such as damping in main modes of vibration. The available software is not able to calculate damping matrices and analyze these structures because the damping matrix of these irregular structures is non-classical. Also an equivalent damping should be devoted to the whole structure and using the available software. In the hybrid structures, one or more transitional stories are used for better transition of lateral and gravity forces. In this study, an equation has been proposed to determining the equivalent uniform damping ratio for hybrid steel-concrete buildings with transitional storey(s). In the proposed method, hybrid buildings are considered to have three structural systems, reinforced concrete, transitional storey and steel. Equivalent uniform damping ratio is derived by means of a semi-empirical error minimization procedure.

Due to the nonlinear relationship between storage and discharge existing in the nonlinear forms of the Muskingum model, the model parameters and outflow cannot be directly determined. The traditional routing procedure has been widely applied to model calibration and flood routing. However, most studies have focused only on the accuracy of parameter estimation methods which adopt the traditional routing procedure, ignored the correctness and effectiveness of routing procedure itself. In this study, three routing schemes of traditional routing procedure are evaluated by simulation experiment and the results demonstrate that the routing scheme 1 is the best, and scheme 3 is followed, the worst one is scheme 2. But the scheme 1 and 3 yield parameters estimates and corresponding outflow hydrographs lead to violation of the routing equations in terms of residuals. The scheme 2 is legitimate, however, the accuracy is not high enough. As an alternative, a new routing procedure based on iterative method is proposed for parameter estimation and flood routing of the nonlinear Muskingum models. The proposed routing procedure is applied to model calibration and flood routing for three examples involving single-peak, multi-peak, and non-smooth hydrographs. The results show that the proposed routing procedure is not only satisfying the routing equations for all time stages in the routing process, but also superior to the routing scheme 2. Therefore, it can confidently be applied to parameter estimation and flood routing for the nonlinear Muskingum models.

This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges. The procedure includes ambient vibration tests under operational conditions, finite element modeling using special software and finite element model updating using some uncertain parameters. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. Because of the fact that the bridge is the sole in this part of Fırat, it has a major logistical importance. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the beam compartment is investigated. Three dimensional finite element model of the beam compartment of the bridge is constituted using SAP2000 software to determine the dynamic characteristics analytically. Operational Modal Analysis method is used to extract dynamic characteristics of the beam compartment by using Enhanced Frequency Domain Decomposition method. Analytically and experimentally identified dynamic characteristic are compared with each other and finite element model of the beam compartment of the bridge is updated by changing of some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the differences between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %46.7 to %2.39 by model updating. Also, a good harmony is found between mode shapes after finite element model updating.

The cavitation erosion induced by high flow velocities is very prominent in high head and large unit discharge tunnel. Air entrainment is an effective technology to solve this problem. In this study, numerical simulation and physical model test are applied to the comparative study of air-water flows on bottom and lateral aerator in tunnel. The flow pattern, aeration cavity, air concentration and pressure distribution were obtained and there is a close agreement between the numerical and physical model values. The hydraulic characteristic and aeration effect of anti-arc section are analyzed. The results indicated that added lateral aeration facilities on 1# and 2# aerator can weaken backwater and increase the length of the bottom cavity, but it is limited to improve the air concentration and protect sidewall downstream of the ogee section. Air concentration improved on side walls downstream of anti-arc section when added lateral aeration facility on 3# aerator. The black water triangle zone disappeared and the floor and side walls well protected.

Soil contamination by heavy metals is a worldwide environmental challenging issue. Due to the industrial activities, a site located in North West of Shiraz (Fars Province, Iran) has the potential to be contaminated by different heavy metals. The objective of this study was to assess the effectiveness of dicalcium phosphate (DCP) and sodium tripoly phosphate (STPP) for immobilizing lead, copper and cadmium in contaminated soils. Leaching column tests performed on the soil without any stabilizing agent demonstrated a uniform leachate of metals in the effluent during the experimental period. After mixing DCP or STTP with the contaminated soils, the release of all three heavy metals through the effluent was ceased. The results further indicated that 0.1 to 0.2 percent by weight of these stabilizers is effective for immobilizing of applied metals through the experimental soil. Penetration of acid sulfuric solution with pH of 5 had no influence on stabilizing efficiency and almost whole the applied heavy metals seem to be immobilized through the soil media.

A study has been conducted on the bearing capacity of strip footings over sandy layered soils using the stress characteristic lines method. Traditional bearing capacity theories for specifying the ultimate bearing capacity of shallow foundations are based on the idea that the bearing layer is homogenous and infinite. However layered soils are mainly happening in practice. The stress characteristic lines method is a powerful numerical tool in order to solve stability problems in geotechnical engineering. In the present paper, an appropriate algorithm is derived for estimating the static bearing capacity of strip footing located on two layered soils using the stress characteristic lines method. Some numerical and experimental examples are presented in order to validate the proposed algorithm. Some graphs and equation are presented for initial estimating the effective depth of strip footings located on two layered soils.

Currently, there is no reliable design procedure which considers all aspects of liquefaction effects on shallow foundations. There are many light and heavy structures resting on saturated sand with high liquefaction potential in seismic areas. The aim of this experimental and numerical study is to evaluate the performance of two shallow foundations with different contact pressures in liquefaction. The results of the centrifuge experiment of shallow foundations with surcharges of three-story and nine-story buildings on liquefiable sand are presented in detail. Although entire soil profile liquefied, no liquefaction observed under the foundations. There was a clear difference in settlement mechanisms observed beneath the shallow foundation and in the free-field. The heavy foundation fluctuated more strongly compared with the lighter one. The effect of soil permeability and contact pressure on foundation response was investigated during numerical study. The experiment was simulated two dimensionally using a fully coupled nonlinear constitutive model (UBCSAND) implemented in a finite difference program, FLAC-2D. The results show that settlement of foundations increased with the increase of soil permeability. Trends of excess pore water pressure were captured reasonably by the soil model, but the settlement mechanisms were different. The soil model underestimated total liquefaction-induced settlement of shallow foundation, especially for light foundation.

Risk allocation is the definition and division of responsibility associated with a possible future loss or gain arising from an identified risk. Quantitative approaches to risk allocation have been developed to overcome the limitations of qualitative approaches, especially the issue of the amount of risk to be borne by each party. This paper presents a cooperative-bargaining game model for quantitative risk allocation that extends the previous existing system dynamics SD-based model. The behavior of contracting parties in the quantitative risk allocation process is modeled as the players’ behavior in a game. The proposed model accounts for both the client costs and the contractor costs to perform the quantitative risk allocation process. To evaluate the performance of the proposed model, it has been employed in a pipeline project. Quantitative risk allocation is performed for the inflation as one of the most important identified risks. It is shown that using the proposed cooperative-bargaining game model, both the client and contractor costs are decreased in comparison to the previous SD-based risk allocation approach.

Various methods have been applied to construction crew productivity problem. This paper additionally introduces the use of two novel artificial intelligent methods which are Self Organizing Maps and Artificial Bee Colony. It first presents the results of the prediction performances of these two methods and then focuses on the visualisation ability of SOM through the presentation of two dimensional maps produced for the current problem. The prediction performances are compared by comparing MAPE, MAE and MSE values obtained during seven fold cross validation. Two dimensional maps produced by SOM based model are additionally presented in order to analyse the relationship between labour related factors of crew size, age and payment method with productivity rates of ceramic tiling crews.

The contribution of concrete to inelastic deformation capacity and shear strength of reinforced concrete (RC) columns failing in shear has been investigated extensively by various researchers. Although RC members are designed to have shear strengths much greater than their flexural strengths to ensure flexural failure according to the current codes, shear degradation of RC columns failing in flexure has not been studied widely. The aim of this study is to investigate the shear degradation of RC columns using finite element analyses (FEA). The results of FEA are compared with the results of experimental studies selected from literature, and it is observed that the lateral load-deflection curves of analysed columns are compatible with the experimental results. Twenty-six RC columns were analysed under monotonically increasing loads to determine the concrete contribution to shear strength. The results of analyses indicate that increasing the ratio of shear to flexural strength reduces the concrete contribution to shear strength of the columns.

This paper presents a novel approach to solve the double-track railway rescheduling problem, when an incident occurs into one of the block sections of the railway. The approach restricts the effects of an incident to a specific time, based on which the trains are divided into rescheduled and unchanged ones, so that the latter retain their original time-table after the incident. The main contribution of this approach is the simultaneous consideration of three rescheduling policies: cancelling, delaying and re-ordering. A mixed-integer optimization model is developed to find optimal conflict-free time-table compatible with the proposed approach. The objective function minimizes two cost parts: the cost of deviation from the primary time-table and the cost of train cancellation. The model is solved by CPLEX 11 software which automatically generates the optimal solution of a problem. Also, a meta-heuristic solution method based on simulated annealing algorithm is proposed for tackling the large-scale problems. The results of an experimental analysis on two double-track railways of the Iranian network show an appropriate capability of the model and solution method for handling the simultaneous train rescheduling. The results indicate that the proposed solution method can provide good solutions in much shorter time, compared with the time taken to solve the mathematical model by CPLEX software.

The behavior of Chamkhaleh sand and three other recognized sands namely, Babolsar, Firouzkuh and Standard (Ottawa) sands are compared using triaxial apparatus under undrained monotonic loading conditions. Chamkhaleh and Babolsar sands are supplied naturally from southern Caspian Sea shorelines, whereas artificial Firouzkuh and Standard sands were supplied commercially. Samples were prepared using wet tamping with regard to the reduced compaction effect at relative density of 15% under isotropic consolidation pressures of 100, 300 and 500 kPa. The results of triaxial tests have indicated that Chamkhaleh sand has much more dilation tendency than the other sands. In order to evaluate the reasons behind this behavior, the spherecity and roundness of all the four sand particles were measured using an image processing method. It was revealed that the spherecity of the four sands is not much different, but Chamkhaleh sand is more angular than the other sands. For comparison of the dilative response of the sands in undrained triaxial tests, a “dilation tendency index” is introduced. This index may be used as a criterion for measuring the dilation of sands in undrained tests. Results have shown that the internal friction angle under the steady state condition is more dependent on the shape of particles than the maximum strength condition. For spherecities greater than 0.5, the dependency rate of sand behavior on the roundness is decreased.

This study proposes a prediction model about the trajectories a vehicle, in isolated conditions, along a curve of a road. As we know, the road environment induces stress on users and, under certain conditions, influences driving behavior. It is of advantage then, to isolate and identify those conditions from among the numerous variables, which are actually the most significant so as to prevent or mitigate the occurrence of dangerous maneuvers. On the basis of an experiment performed using an instrumented vehicle, we collected a data base to which we subsequently applied Neuro-Fuzzy techniques for the selection of the most representative variables. We then used these data to prepare a nonlinear dynamic Hammerstein-Wiener’s model able to predict the track paths along curves. The findings were encouraging since almost all the results obtained from the validation checks proved satisfactory. This research is the first step in the identification of complex systems and could be applied in road safety measures and design of new and existing roads.

The purpose of this paper is to improve the intelligence and universality of classical method for gating control in the SCOOT system. Firstly, we introduce a method to identify spillovers, and use the occupancy threshold for spillover recognition to trigger this special control logic. Then we present an influence rate model for links upstream of the bottleneck link, and a share ratio model for the downstream links, after analyzing the interrelationship of the traffic flows among adjacent traffic links. With known threshold values for the influence rate and share ratio, we propose a rule and process for selecting the intersections that should be included in the sub-area of the gating control. Thirdly, we determine total capacity adjustments for the incoming and outgoing streams of bottleneck links, with the aim of dissipating the queue to a permissible length within a given period of time. After that, the apportion models for the total adjustments among different paths and links are presented, along with the correlation coefficients of the traffic flows between the bottleneck link and the other links. Next, we ascertain the capacity decrements and increments for the gated and benefiting streams, and define the optimization schemes so as to calculate splits for the gated and benefiting intersections. Finally, we evaluate the advanced method using a VISSIM simulation. The results show that new control method brings significant and positive effects to the bottleneck link itself and to the entire control area.

Ship lift is a major navigation structure lifting and lowering ships to shorten the time across the dam. The ship chamber, the key equipment, serves as the carrier for ships. Due to its gigantic body and mass, complicated coupled vibrations occur between the chamber and ship lift structure during seismic process. With the engineering background of the ship lift at the Three Gorges dam, a three-dimensional shell finite element model is established for the ship lift, and then simplified into a three-dimensional truss finite element model through dynamic equivalent principle. And the numerical model of coupled vibration analysis is formed through static condensation, calculating the coupled vibration response between the ship lift structure and the ship chamber. The result shows that no connection and rigid connection between them are both inadvisable. Consequently, three connection devices: spring, viscous liquid damper and magneto-rheological fluid damper are applied to control coupled vibrations during artificial seismic waves. The result shows that the magneto-rheological fluid damper makes better vibration damping effect if suitable semi-active control strategy is applied, in comparison with passive control devices.

Resource allocation project scheduling problem (RCPSP) has been one of the challenging subjects amongst researchers in the last decades. Most of the researches in this scope have used deterministic variables, however in a real project activities are exposed to risks and uncertainties that cause to delay in project’s duration. There are some researchers that have considered the risks for scheduling, however, new metahuristics are available to solve this problem for finding better solution with less computational time. In this paper, two new metahuristic algorithms are applied for solving fuzzy resource allocation project scheduling problem (FRCPSP) known as charged system search (CSS) and colliding body optimization (CBO). The results show that both of these algorithms find reasonable solutions, however CBO finds the results in a less computational time having a better quality. A case study is conducted to evaluate the performance and applicability of the proposed algorithms.

In this article, general procedures for vulnerability assessment and retrofitting of a generic seismically designed bridge are outlined and the bridge’s damage criteria for blast resistance are explained. The generic concrete bridge is modeled and analyzed with the finite element technique implemented in ANSYS LS-DYNA environment and explosion threats are categorized into three main levels. Uncoupled dynamic technique is adopted to apply the blast loads on the bridge structure, damage and performance levels are resulted based on quantitatively verified damage mechanisms for the bridge members. The results show that, amongst different loading scenarios, the explosions that happen under deck are more critical comparing to blasts initiating from over deck sources. Furthermore, two retrofitting methods 1) concrete filled steel tube (CFST) and 2) concrete jacket are applied on the bridge columns. The program AUTODYN is used with coupled dynamic analysis of a column to compare the effectiveness of each method. Afterward, more efficient method for a column is applied to the whole bridge and its efficiency is revaluated. It is shown that CFST can decrease concrete spall, scabbing, rotation, displacements and shear forces more than the concrete jacket. Considering the proposed damage and performance levels, the bridge retrofitted with CFST reacts with lower damage level and higher performance level to blast loads.

The main purpose of this study is to investigate the influence of urban solid waste leachate on the mechanical properties of the soil. Order to provide a more accurate identification of the contaminated soils, Cylindrical specimens of the soil, according to the density curves with different initial conditions (different initial contamination levels) were prepared, then the soil specimens were loaded at different load levels using a direct shear testing equipment and a universal testing machine to apply axial compression on the specimens. By analyzing the results, the stress-strain and failure behavior of the soil specimens containing different percentages of the solid waste leachate was evaluated. The most important result was reducing the mechanical properties of the soil contaminated with different percentages of solid waste. The results of adding lower quantities of leachate, is far more significant compared to the received results from adding higher amounts of leachate.