International Journal of Civil Engineering
Volume:15 Issue: 4, 2017

Most rehabilitation codes have a special part for regular masonry infill panels. However, they are completely silent for infills improved by concrete covers, probably for the lack of sufficient experimental test data. Shotcreting one side or both sides of the existing infills is one of the best methods to improve structural seismic behavior. Therefore, this paper focuses on the ultimate strengths and modification factors of this type of infill panels, based on the existing experimental data of the literature. The existing formula of the codes is improved to estimate ultimate strength of such infill panels. Furthermore, modification factors of primary and rehabilitated specimens are calculated and compared. In this regard, envelopes of the load–displacement behavior of the specimens are applied, as well. It is shown that envelops give more conservative values for the m-factor, compared with the standard backbone curves. It is shown that modification factor of masonry infill panels is decreased when rehabilitated by concrete covers; however, for clay tile infills, it remains almost unchanged.

An experimental program was carried out to investigate the usability of recycled coarse aggregate (RCA) concrete with and without ground granulated blast furnace slag (GGBFS). The RCA was derived from concrete having compressive strength of 47.6 MPa. Twelve concrete mixtures having various RCA (0–25–50–100%) and GGBFS (0–30–60%) replacement levels were designed with a water-to-binder (w/b) ratio of 0.50. Fresh concrete properties were observed through workability and slump loss. Compressive strength, tensile splitting strength, bond strength, ultrasonic pulse velocity, water absorption and density of hardened concretes were also determined at 7 and 28 days and the relations between physical properties and mechanical properties of RCA concretes with/without GGBFS were investigated. The RCA content significantly improved the tensile splitting strength of the concrete according to the compressive strength and the use of 60% GGBFS content in RCA concrete had a marginal increasing effect on the tensile splitting strength. The mixes containing 100% RCA was found to be noticeably beneficial in terms of the bond strength and the highest bond strengths were obtained with the use of 60% GGBFS content in RAC for all series at 28 days. However the lowest density and the greatest water absorption was obtained for RAC and an inverse relationship between the density and the water absorption ratio was determined.

The motorcycle is considered one of the most applicable transportation modes for various trips in Iran. According to a 2011 report by Iran’s Police Department, motorcyclists and their passengers accounted for almost 25% of all crash fatalities. The objective of this study is to identify the most important factors that contribute to the fault of motorcyclists involved in crashes. The classification and regression trees model is used in this research to differentiate between at-fault and not-at-fault cases. The results show collision type to be the most determining factor for at-fault probability of motorcyclists. According to this fact, the probability of rear-end collision is the highest, while the probability of side collisions is the lowest. Other factors involved vary according to the collision type. Factors affecting rear-end collisions the most are passenger characteristics and the rider’s age. However, side collisions are mainly due to lighting conditions and area types (urban and rural roads). Finally, this paper suggests that training riders and installing warning systems that warn drivers when they are too close to motorcycles can reduce rear-end and side collisions to a great extent.

The paper presented an attempt to assess service life of steel girders in military bridges (or bypass temporary bridges) when fatigue cracks are detected in them. A function describing the geometry of fatigue cracks, the so-called crack shape factor Y, for two different, assumed calculated models, was presented. The function was used to plot sample graphs allowing assessing the remaining service life of such structural elements or engineering structures in a simple way. This method of analyzing can be used not only for the military bridges but also for other steel structures with existing cracks. The work also presented assessments of possible applications of two FEM calculated models using shell elements to test stress and deformation at the top part of a fatigue crack located in a web of a steel girder used in the military bridges. The results of the conducted numerical analyses were compared with the results obtained in experimental research conducted in laboratory conditions using extensometers.

The current work deals with the comparison between two different computer formulations, namely, force- and displacement-controlled approaches for non-linear FE analyses of an RC beam in flexure with partially developed and asymmetric steel reinforcement. Instead of inputting load–slip data of direct tension pullout test to ANSYS code for defining the bond property, a different approach is adopted. In the study, load slip data are extracted from bond stress model of Yousaf (Performance of self-compacting concrete in bond at beams intersection. PhD dissertation, 2015) where the model was developed using data of digital strain gauge mounted on main steel bar in flexural beam testing. The load slip data are fed to computer as a set of real contestants choosing large-deformation non-linear plastic analysis scheme, discrete modeling approach for material modeling and program-chosen incremental scheme following the Newton–Raphson method. Complete harmony is found in computer and experimental results advocating the correctness and validation of the approach adopted for computer analysis. Among both formulations adopted for ANSYS analysis, the results reveal that the displacement-controlled approach is easy and efficient in terms of time-saving and less disk space requirement along with the ability to give falling branch of load–deflection response, if element displacement capacity still exists. Furthermore, it gives an early estimate of the load carrying capacity of the structural element along with suitable values of convergence and non-linear solution parameters. On the other hand, force-based analysis for a beam with unsymmetrical reinforcement detailing seems to yield more realistic and practical results in terms of mid-span deflection and beam cracking behavior compared with assumed symmetric displacement-controlled technique. From the study, the superiority of the force-controlled approach in comparable conditions is established through observed performance simulation with that of practical beam results along with the applicability of the approach adopted in the study. A comparison of ANSYS and experimental stress of partially developed rebar shows that the used bond model performs extremely well.

This study investigated the structural behaviors of reinforced concrete shear walls containing opening and slab. A series of three half-scale shear wall specimens were tested: a solid wall (WS-Solid), a wall with opening and slab (WS-023), and a wall with opening but no slab (WB-0.23). Using the experimental results, the reduction in the load-carrying capacity of the wall due to the loss of cross section was evaluated. Its contribution to the moment resisting capacity of the total system of coupling elements and its structural behavior was also examined. The results of experiments conducted on the WS-0.23 specimen with artificial damage due to installation of the opening, and showed that the load-carrying capacity of the wall decreased as a result of the opening. It is apparent that the influence of cutting reinforcing bars and the reduction of effective sectional area lead to early first yield of the reinforcing bars before the allowable limit of the drift ratio of the shear walls is reached. This decrease in the load-carrying capacity of the shear wall because of installation of openings is significantly different from the results of previous studies. This is because slabs and the remaining wall function as coupling elements for the shear wall. The contribution of slabs and residual wall to the lateral load resisting system was investigated via an empirical test and finite-element analysis. During the experiment, a U-shaped critical section of coupling slab was observed and its effective width and the total length of the critical section examined. The critical section of coupling slab that functions as a coupling element for shear wall varied marginally from the results of previous studies. The results of the analysis conducted show that slabs and residual walls contribute approximately 30% to the lateral load resisting system.

Bridges normally undergo nonlinear deformations during a near-field strong ground motion resulting in a critical deviation of their columns from the plumb state due to considerable residual deformations. The conventional hysteresis models formulated for typical concrete columns are normally used for this purpose which most of times fail to correctly predict the residual deformations occurred as a result of a one-sided or directivity pulse excitation. The present research aims at development of a peak-oriented hysteresis model being able to regenerate residual deformations more reasonable compared with the conventional hysteresis models. This multi-linear peak-oriented model considers strength deterioration in each half cycle in addition to stiffness degradations in unloading cycles. Yielding points differ in both positive and negative sides of the hysteresis model that enables us to define a different elastic stiffness of both sides in asymmetric concrete sections. This work also compares the obtained results to the conventional hysteresis models, namely bilinear, Clough, Q-Hyst, Takeda, and Bouc-Wen in terms of prediction of residual nonlinear deformations in cyclic analysis or dynamic analysis of reinforced concrete single-column bridge piers. The obtained results prove higher relative accuracy of the proposed model.

This paper presents comparative numerical research on the overall seismic behavior of RC frames with different types of rebar (normal versus high-strength rebar). A nonlinear numerical model is developed and is validated using experimental results. Comparing the numerical and experimental behaviors shows that the developed model is capable of describing the hysteretic behavior and development of plastic hinges in experimental RC frames with longitudinal steel bars of various strengths. The validated model is then used, considering the influences of axial load ratios and volumetric ratio of longitudinal rebar to investigate the effects of reinforcement strength on the overall seismic behavior of RC frames. The simulation results indicate that utilizing high-strength reinforcement can improve structural resilience, reduce residual deformation, and achieve a favorable distribution pattern of plastic hinges on beams and columns.

One kind of the irregularities in structures, with considerable effect on seismic performance, is setback in elevation that causes large damage especially in the vicinity of the irregularity. The main objective of this research is to propose and develop drift-based index to estimate damage to reinforced concrete moment resisting frames with setback. For this purpose, first, inelastic dynamic time-history analysis is performed on several frames with different types of setbacks subjected to various earthquake records and damage to them is computed by the Park–Ang damage index. Then, the two relations between the damage and drift are derived by applying irregularity indices to account for setback effects. It is shown that the proposed damage indices are capable to estimate the damage index of setback frames.

The reinforced concrete bifurcation in hydropower station is consistently under high internal water pressure, and its diameter is usually larger than common duct junctions. To diminish or to decrease the heavy plastic zone and stress concentration, structure rounding is commonly used on bifurcation. This will bring some changes to the flow characteristic of bifurcation, and it is an interesting attempt to figure out the influence of structure rounding optimization. The realizable k–ε model was employed in computational fluid dynamics numerical simulation. The water pressure distribution was compared quantitatively at several certain sections. Furthermore, uneven pressure is analyzed by relative standard deviation. Hydraulic characteristics are discussed as well, including flow pattern, excavation volume and head loss in different working conditions. The results indicate that the pressure of the pipe wall is uneven, and the maximum and minimum pressure value has a differential of 0.3–1.2 % compared to the relative static water pressure. The pressure unevenness will increase after structure rounding, and it has a positive correlation with structure rounding radius. At the same time, it is more reasonable for structure rounding in the obtuse angle region than that in the acute angle region, on account of well-distributed flow conditions and better economic benefit.

In this paper, the probabilistic seismic performance of vertically irregular steel buildings, considering soil–structure interaction effects, is evaluated. Various irregular distributions of structural properties, including mass, stiffness and strength along the height of three-dimensional moment resisting steel frames were intended. The finite element model of soil medium was created with solid elements below the structure. The nonlinear material behavior of soil was considered as well. Nonlinear incremental dynamic analysis was performed to evaluate the flexible-base structural performance in the framework of probabilistic performance-based earthquake engineering. According to the median curves of intensity demand of structures, it is concluded that non-uniform height-wise distribution of lateral resistance properties of steel structures varies the displacement demand and the seismic capacity of the irregular frames, compare to the regular structure. The capacity variation of most irregular frames is more obvious at the nonlinear phase of structural behavior. Due to the foundation flexibility, the damage concentration raises in the bottom floor and the irregularity increases the seismic demands of the lower floors of the system. Among all the irregular steel frames, the average increase of the displacement demand and reduction of the seismic capacity are maximal for the strength and concurrent variation of stiffness and strength irregularity models, respectively. Additionally, mass irregularity shows minor influence in the seismic demand and capacity variations of the steel frames. The predominant influence of stiffness and strength irregularities (soft and weak story) is observed in reduction of the structural ductility factor and the mean annual frequency of exceeding limit states.

The study presents a model for the evaluation of construction projects from the point of view of the client (e.g. developer company). The problem lies in choosing the best solution from the point of view of many criteria. The proposed model is based on a multi-criteria comparative analysis using fuzzy logic. The first part of the paper presents a selection of criteria describing the construction project along with their description. The set of attributes describing the analysed object was determined on the basis of the synthesis of specific proposals for the parameters of construction projects. The set of criteria has been divided into two groups: technical, technological and organisational criteria and separately the economic criteria. Then, the number of variables describing the observations was checked using principal component analysis (PCA). Course of action was presented in the event of multiple criteria analysis using the fuzzy set theory. Both the weights and the evaluations of individual criteria were modelled using membership functions due to the fact that when describing a construction project, or the validity of the criteria of describing variables, they are approximate. An analysis of the correlation of selected project criteria was presented. The proposed decision support model of assessing a construction project makes possible to compare various variants based on 11 factors identified. The use of fuzzy logic has enabled more accurate description of the phenomenon analysed when the exact parameters of the project in the planning and preparation stage of the project are not known.

This paper presents an evaluation on lateral cyclic behaviors of precast concrete columns using a steel box connection through experimental investigation. The test consisted of one monolithic reinforced concrete column as a reference and five precast concrete columns. All specimens had identical dimensions of 0.25 × 0.25 m2 cross-sectional area and 1.7 m height with a longitudinal reinforcement ratio of 0.0152. Materials used for all specimens were also from the same batch. The study was aimed at understanding the design concept of the steel connecting box and detailing of column reinforcement for avoiding the brittle failure of precast concrete frame buildings. The experimental results show that without premature failure in welding or nut slipping, depending largely on the reinforcement details, the precast system with a steel box connection can be effectively used. Flexural failure mode with a ductile mechanism can be achieved to resemble the monolithic one. With a higher relative stiffness and capacities of the designed connecting box, the precast columns show a higher capacity as the failure section was shifted to an upper level. Hence, it can be said that the proper details of precast concrete columns contain acceptable seismic performances, e.g. ultimate capacity, stiffness, energy dissipation, and capacity degradation under repeated loading.

Stilling basins and hydraulic jumps are designers’ favorable choice for energy dissipation downstream of spillways and outlets. A properly designed stilling basin can ensure considerable energy dissipation in the short distance of a basin. In this study, experiments have been conducted to evaluate effects of a perforated sill and its position on the length of a favorable B-type hydraulic jump in a stilling basin. Perforated sills with different heights and ratio of openings were placed in different positions of the stilling basin. Tests were carried out for three tail water depths to assess the sensitivity of the jump to tail water. The hydraulic characteristics of the jump were measured and compared with continuous sill-controlled and free hydraulic jumps. Results of the experiments confirmed significant effect of the perforated sill on dissipation of energy and development of the jump in a shorter distance. Results are also presented in the form of mathematical models for estimation of the sill height, sill position, and basin length with the inflow measurable parameters of depth and velocity.

Manufacturing industries synthesize new chemical products every day, which eventually find their way into domestic and industrial wastewaters. As a result, wastewater is becoming increasingly more complex in nature. The emerging pollutants escape the treatment systems and appear in the receiving water bodies. Wastewater treatment plants in India still report effluent parameters in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) at the ppm level, whereas these emerging pollutants, many of whom are non-biodegradable, can be toxic and carcinogenic at the ppb level. Therefore, it is imperative to look for alternatives or upgrade the existing systems which safely remove these harmful compounds from wastewater. In this research, efficiency of electrocoagulation process was assessed in a laboratory-scale setup in removing recalcitrant carbon from a real wastewater. The wastewater was collected from an effluent treatment plant that receives domestic wastewater and industrial effluents from chemical, bulk drugs and allied industries, for treatment. In this study, the wastewater sample was analyzed for total dissolved solids (TDS) and total organic carbon (TOC), and then treated biologically in a respirometer using aerobic microorganisms. After the oxygen uptake curve plateaued, indicating a cessation of biological process, the sample was analyzed for TDS and TOC and put in a lab-scale electrocoagulation setup. Iron and Aluminium electrodes were used in the study and efficiency of the system in removing the recalcitrant/residual carbon and TDS was studied with respect to the reaction time. The results showed that electrocoagulation can be a potential post-biological treatment system for removal of recalcitrant carbon from wastewaters.

In recent years, environmental protection is increasingly becoming a major issue in transportation including asphalt production. Despite the fact that hot mix asphalt (HMA) is widely used around the world, some recent studies suggest that using warm mix asphalt (WMA) technology reduces the production and placement temperature of asphalt mixes. Currently, a common way of producing WMA is through the utilization of additives. This paper firstly characterizes the effect of WMA additives (organic, chemical, water-containing additives) on base bitumen properties. Following the determination of optimum bitumen content of the mixtures with different WMA additives through Marshall test, Hamburg wheel-tracking device is used to measure the permanent deformation characteristics of WMA mixtures. Based on the findings of this study, the utilization of WMA additives helps in the reduction in viscosity values which in return decreases mixing and compaction temperature leading to the reduction in energy costs as well as emissions. Besides, it can be concluded that all WMA mixtures performed better than HMA mixtures in the matter of rut depth.

Sufficient literature is available on approaches to deal with heterogeneous traffic on mid-blocks in developing countries, but not much work is done on roundabouts. The estimation of passenger car unit (PCU) for different vehicles to convert heterogeneous traffic into homogeneous traffic is a well-accepted procedure. But the parameters used for mid-blocks may not be helpful on roundabouts as traffic flow characteristics on the two locations are different. Suggested PCU values on roundabouts from developing countries are not recent, and needs a relook. It is also not clear whether to use static or dynamic PCU values on account of possible temporal and spatial variations across locations. This paper presents an estimation approach for PCUs on roundabouts and suggests using static value instead of dynamic. The problem to deal with re-estimation of PCU values at different locations, due to possible traffic flow variations, is dealt with by proposing a heterogeneity equivalency factor (H-Factor). The factor is multiplicative and converts heterogeneous traffic (veh/h) into homogeneous traffic (pcu/h).

The present work is devoted to a better insight into the identification of carbonation versus efflorescence formation in alkali-activated blast-furnace slag and investigates the relation between the chemical composition of the alkali-activator and the extent of the occurrence of these two phenomena. Obtained results showed that mixes of relatively lower alkali contents suffer not only from weak compressive strength due microstructural defects, but also from carbonation during the first few days. On the other hand, mixes containing relatively higher alkali contents strongly suffer from efflorescence formation in spite of their interestingly high compressive strengths. Carbonation during the first few days can partially neutralize the alkali content of the surface layers of the material which in turn significantly affects the activation mechanism leading to the formation of binding compounds of different molecular structure.

This paper outlines the effects of curing conditions on the strength and hydration products of lime-activated slag cement. The slag cement was prepared by activating the ground granulated blast furnace slag with lime and plaster of Paris. The curing of mortar specimens was done at temperatures of 27°, 45°, 60°, 75 °C and the compressive strength of specimens were determined after curing periods of 3, 7, 28, 56 and 90 days. The curing temperature is found to influence both the early and later age strengths. For the present test conditions the highest 90-day compressive strength was found to be 47.63 MPa for the specimen cured at temperature of 60 °C. Further, the developed strength in mortar specimens were correlated with the hydration products and microstructure using X-ray diffraction and scanning electron microscope results. Generalized reduced gradient technique is adopted to find the optimum curing temperature for the given raw material composition and this is found to vary marginally on curing period.