مهندسی عمران و نقشه برداری
سال:1398 | دوره: | شماره: |تعداد مقالات:12

Building industry as one of the greatest industries in Iran comprises a significant share of waste generation in the country. Since a large quantity of the generated construction waste is buried due to the lack of a recycling protocol, it leads to an undesired waste of resources and causes severe environmental issues. This paper provides a study on the problem of material loss/construction waste in the Iranian Building Industry regarding the impact of relevant shortcomings in the stages of design, construction and supervision as the main phases of construction process. This paper includes the case studies from Isfahan, Mazandaran, Qazvin and Zanjan provinces, with a focus on the most important elements underlying construction waste generation. It also presents the experts points of view on prefab and conventional construction methods considering construction waste generation through a questionnaire-based survey. In general, the results show that Iranian project managers, engineers, contractors and workers believe that from 40 to 100 percent of construction wastes can be reduced via application of prefab construction methods. The results indicate that prefabrication can be considered as a solution to waste reduction in the Iranian Building Industry, whereas there is a dominant conventional method application in the industry.

The elements of the concrete structure are most frequently affected by cracking. Crack detection is essential to ensure safety and performance during its service life. Cracks do not have a regular shape, in order to achieve the exact dimensions of the crack; the general mathematical formulae are by no means applicable. The authors have proposed a new method which aims to measure the crack dimensions of the concrete by utilizing digital image processing technique. A new algorithm has been defined in MATLAB. The acquired data has been analyzed to obtain the most precise results. Here both the length and width of the crack are obtained from image processing by removing background noise for the accuracy of measurement. A semi-automatic methodology is adapted to measure the crack length and crack width. The applicability of the program is verified with the past literature works.

The present study compared the performance of soldier pile and concrete bearing pad anchored wall facings. Using Abaqus finite element software, two case studies have been precisely represented for the facing designs and effects of the parameters of soil type, spacing of anchors and facings, surcharge and facing sizes were investigated. The analysis results indicate that the soldier pile method can efficiently reduce anchored wall deformation, especially at the wall crest. The horizontal deformation at the top of the anchored soldier pile wall was about half of the wall anchored with concrete bearing pads. Soil arching between the anchors in the horizontal direction was more effective in the soldier pile wall and the bending moment of the laggings in the soldier pile wall was considerably less than that of the anchorage with bearing pads.

After the failure of an element in a structure, its loads should be redistributed on the other elements and the structure must provide some new paths to carry the load. If such new load paths are not provided, collapse progression will begin in the structure. As the beginning of progressive collapse in a structure is more sensitive to the missing of an element, the location of that element is more important to be found. The most sensitive element is called the key element. In this paper, sensitivity analysis is modified following GSA and DoD guidelines and used for finding the key element of symmetric structures with different heights. Four structures with different heights have been analyzed for every column missing event and the load carrying conditions of the structures have been monitored. The results showed that the location of the key element in the plan and height of the structure is different in structures with different heights.

This paper evaluates the effect of slot existence with limited length between flanges and web junction of I-shaped beams at the region of moment connections on vertical force and shear stress distribution in beam flanges and web at connection section in comparison with classical theory of stress distribution. The main purpose of this research is to evaluate the efficiency of the slot in connections such as slotted web beam to column connection in modern age. The issue of the slot has many benefits but very little studies have been done on it. Accordingly, one hundred and twenty models with two moment connections under the concentrated static load in mid span have been made for doing parametric study in ANSYS Workbench finite element software. The linear static analysis was done on all constructed models. Variable parameters in these models for parametric study include slot length between flange and web junction in connection region (from 0 to 190 mm), beam length, beam section height and Poisson’ s ratio of beam material. In all models the amount of shear stress in section height over the section vertical axis in connection region and also the devoted contribution from force which goes to flanges and web under the concentrated load on mid span have been calculated. Performed studies have shown that vertical shear stress distribution in beam to column connection section with moment connection differs a lot from what is stated in mechanics of materials equations. Practically the available equations in regulations which state that web receives the entire vertical shear and ignore the contribution of flanges are not reliable. In addition, studies have shown that the slot existence in junction of web and flanges in connection section with limited length can has great effect on the quality of vertical shear stress distribution over the section of connection and also the slot existence has great effect on the reduction of shear stress in flanges and increase in shear stress in web according to classical theory. As a total result, nowadays slotted web beam to column connection can be used as a fantastic and simple idea to improve modern connections behavior.

Among all of the slope stability methods, use of stone columns and geosynthetic elements can be a good way for stabilizing. One of the efficient ways in order to reinforce earth slopes is Geogrid Encased Stone Column (GESC). This technique can dramatically increase bearing capacity and decrease settlement rate. The aim of this paper is experimentally to investigate a comparison between the behavior of Ordinary Stone Column (OSC) and GESC for reinforcing of sand slopes. The slope was constructed using raining technique and reinforced using GESC. The slope saturated through precipitation and loading procedure applied. The obtained results compared and verified with 3D Finite Difference Method (3DFDM). Both experimental and numerical analyses indicated that location of GESC in middle of the slope increases the bearing capacity of slope crown 2. 17 times than OSC.

One of the main components of pavement management system (PMS) is pavement evaluation. Several indices have been defined for the evaluation of existing pavement. The Pavement Condition Index (PCI) is a common index used for pavement evaluation. In order to calculate PCI, a significant volume of condition data-based on distress surveying-is required. The objective of this research is to reduce the volume of required data by introducing a new sample unit definition. For this reason, “ wheel path sample units” were defined and used instead of the standard sample unit (according to ASTM D6433). The analysis of results showed that not only there is no significant difference between standard and wheel path PCIs, but also there is a good correlation between standard PCI and both wheel path PCI (PCIw) and outside wheel path PCI (PCIow), corresponding to R2 = 0. 929 and R2 = 0. 874, respectively. Also, PCIow saves a great amount of time and energy.

With respect to disasters, earthquake is one of the leading causes of death. Its aftermath can be abated if proper actions take place before the onset of the earthquake. Various sectors in a country are responsible for managing disasters, but the lack of knowledge about the positive effects of their actions makes them reluctant to act decisively. Retrofitting buildings and structures, positioning humanitarian goods, retrofitting transportation links, and devising a disaster response plan all make a city more resistant. The main aim of this paper is to present a robust model to investigate the effect of considering recovery costs on decision making. In this model, the importance of each region changed with due attention to imposed costs to the region without any action. The result shows a 13 percent improvement compare to the previous model. Also, this paper highlights the significance of pre-disaster action on the recovery costs and the importance of taking action before it is too late.

Polymers not only possess repairing functions concerning the concrete structures, but also due to their properties are used in making different types of polymer cements and improving the matrix structure of cement materials, enhancing the viscosity, mechanical, and stability power of concretes. Today, there is limited knowledge on the use of SBR in structural light aggregate concrete. In the present research, light expanded clay aggregate was used to produce light weight concrete weighing 1740 to 1780 kg/M3. Unlike the previously conducted studies in which the desirable properties of concrete were achieved by increasing the compressive strength, in the current study we have used C25 light concrete without any cement supplements. SBR latex copolymer was incorporated in concrete directly (additive) and indirectly (light aggregates coating) each based on a combinational performance of 28 and 60 days. The results revealed that based on the used cement matrix, the optimal performance of the latex in the direct method was enhanced by increasing the bending and tensile strength rather than the compressive strength. The indirect presence of latex not only imposed a new limit in ITZ, but also had no interfering role in modifying the chemical mechanism of cement hydration. Thus, the behavior of this concrete did not show any enhancement in the mechanical properties as it did in the case of direct implication of latex. The study also showed that the presence of latex in both methods led to reduced permeability of the concrete. This research also looked into the impact of cement matrix capability, latex consumption rate, curing age and method and the effect of copolymer ratio on improving the light weight concrete stability and mechanical properties.

This paper analyzes how feasible it is to use electric arc furnace slag as coarse aggregate, and blast furnace dust as fine aggregate in the manufacture of hot asphalt concrete for roads. Three mixtures were designed using the Ramcodes methodology, the M1 mixture of control with conventional materials, the M2 mixture replacing 50% and the M3 mixture replacing 100% of the conventional aggregates, which were submitted to tests to evaluate the susceptibility to moisture damage and plastic deformation, as well as others to determine the resilient modulus and the fatigue laws for each type of mixture. The mixtures with EAF and BFD presented better mechanical characteristics than the mixture with natural aggregates, met the acceptance requirements and the results of the performance tests are within the required requirements.

This paper evaluated an integrated water resources management approach through linked WEAP-MODFLOW model. Study area is Ravasnar-Sanjabi plain located in Kermanshah province in the west of Iran. A MODFLOW model was evaluated and then, accepted as a groundwater model for the region in present research. Schematic WEAP model was provided as representing general features of water resources system after designing a conceptual model for the study area. The simplified rainfall-runoff model in WEAP was used to perform hydrological simulations. In the second step of present research, the groundwater model was linked to WEAP dynamically. Simulation years with 12 time steps per year included years of 2007-2015 for creating and verifying WEAP-MODFLOW model and years of 2015-2030 for performing scenarios. Statistical criteria included mean absolute error (MAE), root mean square error (RMSE), and Nash-Sutcliffe (NASH), with Box plot diagram being selected to assess accuracy of calibrated model. Four scenarios were implemented for 2015 until 2030. They included unchanged present situation and situations with 35%, 45% and 57% reduction of groundwater and surface water withdrawal. Results showed that the fourth scenario with a 57% decrease in the extraction of surface water and groundwater resources was the best one. Based on this scenario, exploitation of the system will be sustainable, with the system recovering as 0. 023 meter rising per year. Finally, the results of present study indicated that the approach was feasible for planning and managing water resources in spite of the lack of some data.

In the recent years, non-connected piled raft foundation has been considered as an economical and practical deep foundation in the situation that high shear and concentrated loads may occur at the connection of the raft and pile head. This paper was presented an experimental study of a square foundation on the effects of parameters such as S/D, L/D and etc. in two cases of connected or non-connected piled raft system under the eccentrically loaded raft. The results was showed that square raft in the case of S/D = 3 and L/D = 8, the bearing capacity of the non-connected piles is more than that of the connected piles. The results of the experiments was showed pile length is more effective than the pile spacing in connected pile raft system. However by decreasing pile spacing, bearing capacity is increased in non-connected pile raft and pile spacing is more effective than the pile spacing in non-connected pile raft system. Comparison of bearing capacity and settlement indicated in the non-connected piled raft system, the longer piles not only has not much effect in increasing bearing capacity significantly, but also has lower effect on the reduction of the settlement. Also in non-connected piled raft system by increasing the pile spacing reduced BPI (bearing pile index) wile in connected piled raft system increased.