نشریه مهندسی عمران
سال چهل و هشتم شماره 3 (پاییز 1395)

The Construction industry is known as one of the most dangerous industries in the, work-related mortality, injury rates and workers compensation payment. Industrial accidents are due to inefficiency of conventional methods of risk assessment and performing activities, regardless of safety standards, that it will affect extremley on health and safety staffs. Thus identifying and assessment risks is an essential step in this industry. The safety analysis is an effective act for the identification, assessment and control of risks in this industry. This paper uses systematic and integrated AHP-DEA methodology for safety risk assessment. In the case study of Iran's common construction projects, 20 danger potential activities with high potential of hazards, 10 accident caused by these activities and 12 factors for identification of causes of accidents are enacted. They were evaluated using judgment of safety experts and projects supervisors by questionnaire. Finally, excavation activities and work in elevations were recognized the most risky activity in terms of safety, that strategies were presented to improve and prevent accidents caused by these activities.

Water management in urban areas includes wastewater control and developing efficient drainage systems. Developing the maps of areas with potential of flood-inundation could be an appropriate tool for urban planning and urban developing strategies. Vulnerability analysis of different urban areas is a complex process because it depends on several spatial and temporal parameters and criteria. The purpose of this research is to prepare flood hazard maps to determine more accurate decisions in urban flood management using a combination of multi-criteria decision making and geographic information system (GIS) as a planning support system (PSS). The final flood hazard map shows that regions in the southeastern of the study area have a high hazard with regarding to the flood potential map. It should be mentioned that these regions are located in low-land (with low elevation) areas that their slope are less than 2.5 percent. In addition, in order to evaluate the spatial multi criteria decision making model, the capability of spatial modeling by an intelligent model, artificial neural network, is assessed. The advantages of using the SMCDM (Spatial Multi Criteria Decision Making) model in developing flood management strategies are discussed using the case study.

Structural health monitoring is of great importance in order to ensure safe and reliable performance of structures during the service life. Offshore platforms have been widely used in offshore oil and gas exploitation and are highly susceptible to damage since a major part of these structures is under water exposed to corrosive ocean environments. Utilizing signal processing tools is one of the effective methods in identifying the structural damages. In this paper, first a jacket platform model is introduced and various damage patterns are applied to the model through members’ stiffness reduction. Then, structural response is recorded under the Gaussian white noise excitation. At this stage, the recorded acceleration response is decomposed at different levels via wavelet packet transform and then by using the concepts of energy entropy and performing a sensitivity analysis, damage sensitive components are selected. The results show that the selected damage sensitive components have good efficiency even in low intensity damages and also the rate of change of these components is markedly related to the severity of the damage.

The aim of this study was to evaluate the effect of self-consolidating concrete mixture components on yield stress (static and dynamic yield stress), and plastic viscosity. Accordingly, mixtures with different water-cement ratio and the amount of limestone powder were made. In addition, cement has been replaced with different percentages of silica fume, slag and metakaolin. The results show that increasing of water to cement ration cause decreasing of yield stress and plastic viscosity. On the other hand, increasing in limestone content leads to yield stress reduction. Over time, this yield stress increased while the plastic viscosity of mixtures showed no significant change. By replacing the silica fume, yield stress increased but plastic viscosity unchanged while metakaolin cause increasing in both parameters. The aim of this study was to evaluate the effect of self-consolidating concrete mixture components on yield stress (static and dynamic yield stress), and plastic viscosity. Accordingly, mixtures with different water-cement ratio and the amount of limestone powder were made. In addition, cement has been replaced with different percentages of silica fume, slag and metakaolin. The results show that increasing of water to cement ration cause decreasing of yield stress and plastic viscosity. On the other hand, increasing in limestone content leads to yield stress reduction. Over time, this yield stress increased while the plastic viscosity of mixtures showed no significant change. By replacing the silica fume, yield stress increased but plastic viscosity unchanged while metakaolin cause increasing in both parameters.

In this research, behavior of portal frame withhollow section steel columns (box sections)is investigated against explosive loading. In order to increase the resistance of the frame two strategies are suggested: first, using synthetic fiber ropes with initial slackness as x brace; second, filling the frame column on blast side with concrete which is referred to as composite column. The finite element analysis software used is the commercialized ABAQUS code, and to analyze the finite element, an explicit dynamic method was used in the numerical solution. This study indicates that the use of synthetic fiber rope brace, especially in large blasts that intense snap loads appears in the rope, improves the total displacement of the frame. However, it has not been capable of reducing the plastic deformation of the local points of the frame, which are subject to direct blast. This problem wasrectified greatly using composite columns. Filling the frame column on blast side can reduce the total displacements and local deformations of the frame significantly. The remarkable thing in studying frames with composite columns is that by applying strain rate, concrete with lower strength behaves like stronger concrete.

The empirical models of liquefaction-induced lateral ground deformation have the most common applications for the routine projects. Beside the inherent uncertainties of such models, estimation of geotechnical, geometrical, and design earthquake parameters also involves measurement errors. These sets of error may considerably affect the final estimation of ground deformation and lead to questionable designs. Several empirical models are in-use in the current practice; however, a comprehensive study seems to be required in order to evaluate and compare their performances. This papers aims to present: (1) parametric study of the available empirical models of lateral spreading, consideration of the most recent database, and developing a new empirical model, and (2) Reliability analysis of the developed model through FORM, SORM, and Monte Carlo methods. In the first part, unreliable data points with only one observation borehole located farther than 5m from the point of ground deformation are removed from the database. The new empirical model has acceptable accuracy compared with the previous models. In the second part, effect of the geotechnical parameters variability in the estimated values of ground deformations are estimated and the results are presented in terms of probability of exceedence from a certain level of permissible displacement versus the ground slope.

In this paper, the influence of soil type and distance between adjacent buildings on structural dynamic properties (natural frequencies and damping ratios) is investigated. For this purpose equations of motion for two adjacent buildings, which affect each other’s dynamic responses, are developed. For modeling soil and its effects, springs and dampers in the base level is used. Finally, by studying a real building, its dynamic properties in case of being located adjacent to another same building and individually are calculated and compared. In previous researches, these dynamic properties were calculated by experimental methods. By comparing analytical and experimental results, it is found this proposed model calculate the values of dynamic properties with good precision.

Compilation of appropriate strategies for the improvement of road safety requires full data of the road specifications. The use of Mobile Mapping System as a method for the road safety audit is a trend that provides a comprehensive database of information including video images and geographical information. The goal of this paper is to introduce an automatic method which can control the safety standards related to speed limit signposts before the curve by analyzing the collected data and maintain sufficient accuracy in controlling the safety standards and economize on time and cost. The proposed method analyzes the coordinates of the centerline axis points of the road and determines the geometrical specifications of the horizontal curves in first phase and processes the images in order to identification and distinction of the speed limit signs before the horizontal curves in second phase, finally safety standards related to placement and limitation of speed sign before the curve is controlled. The final results substantiate a high percentage of success in identification and accuacy in the analyzing of geographical date phase and image processing phase. The accuracy of the proposed method for horizontal curves was proved to be 90% for the horizontal curve radius calculation and it was 97% for the beginning point of the horizontal curve determination. Besides application of support vector machine leads to 92% accuracy in identification of the signs and 97% accuracy in speed limit distinction.

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradient at the ýoutlet of such structures rested on permeable foundations.ýþ þSo far, for analysis of seepage under hydraulic ýstructures much research work has been conducted in the form of numerical models. However, less field and ýlaboratory works have been done to study boiling phenomena for evaluating of the numerical models. In the ýpresent research work, a laboratory model was made to simulate seepage and its controlling measures under ýcoastal dikes. The model consist of a flume 2.2m long, 0.8m deep and 0.4m wide, in which vertical sheet pile ýwere provided by Perspex sheets. The flume was made of steel frame and Perspex as well as thick glass ýsheets. The foundation material was made of clean, fine sand, compacted to a uniform density and covered ýthe bottom 40cm of flume. Perspex sheets were employed sheet pile variable depth. The piezometric heads at ýthe both downstream and upstream side of dike were measured using small diameter clear plastic tubes. The ýeffect of position and depth of the sheet pile on the seepage flow and exit gradient have been demonstrated in ýform of dimensionless curves. The results show that the depth of the sheet piles d/D=0.46 with the maximum ýupstream water level h/hm=1.0 boiling phenomenon does not occur and the seepage rate and hydraulic ýgradient in the area are favorable.ý

Optimization of underground stope is defined as looking for a boundary with the highest profit considering technological and geometrical constraints. The first algorithms were presented about five decades ago for optimization of mining limits. Most of algorithms, presented till now, have been applied for optimization of open pit limits. Few algorithms have been presented for Underground cases, most of which have been tailored for a specific mining method or lack rigorous techniques. There are, however, some rigorous algorithms but they fail to provide 3D solution,. In this paper, a new algorithm is introduced to optimize stope layout using integer programming (IP) technique. The algorithm is implemented on a specific model, derived from conventional block model. It is a rigorous algorithm and provides a realistic optimum solution, compared to its alternatives. For the first time, two more constraints, namely the minimum width of rib pillars and the maximum stope height, are considered in the proposed algorithm.

Concentrically braced frames, CBFs, are the common systems to provide lateral stiffness and strength in buildings that in Comparison with other systems such as moment resisting frames and eccentrically brace frames have less seismic energy dissipation and ductility. This defect caused many studies in the recent years to improve the ductility and seismic performance of them. In this paper, by making hole in the middle or end gusset plates on diagonal and X-braces samples by doing nonlinear static analysis with ABAQUS software, it was tried to provide more ductility and to improve the seismic performance of the brace. This performance is based on the brace buckling prevention. Therefore, holes should be designed in such a way that have less axial capacity than brace critical buckling load to help earthquake energy dissipation. Hysteresis Curves show ductile behavior enhancing energy dissipation during cyclic loading of the final specimens and postponing the occurrence of buckling in the brace members until displacement about 2 cm while normal braces buckled in 1 cm displacement. The reduction of frame stiffness approximately 8-57% and 12-17% increment of equivalent damping prove more ductility and better seismic behavior of the proposed system.