Iranian Journal of Science and Technology, Transactions of Civil Engineering最新文献

A few investigations on clear water local scour around vertical bridge piers on clay-sand mixed (cohesive sediment) beds are found in the literature. However, no research has been reported on local scour around inclined bridge piers for clay-sand mixed cohesive beds. This research work was carried out to investigate the impact of dual inclined bridge piers (convergent-vertical piers) on maximum scour depth installed in flow direction on four beds containing different clay contents from 20–80% with sand. Three different pier shapes of different cross sections were tested (circular, rectangular & diamond) in each case. The effect of inclination (0°, 5°, 10°, 15°, 20°) with the vertical on the same beds was analyzed and discussed. The results revealed a considerable reduction in maximum scour depth with inclined bridge piers in comparison with vertical bridge piers. The least scour depth was observed around 10° inclination for rectangular and circular shaped sections and 5° for diamond bridge pier. On average 53.25%, 57.25%, and 72% reduction in scour depth was observed for inclined rectangular, diamond, and circular bridge piers respectively as compared to the vertical bridge piers. The circular bridge pier proved the most effective inclined pier, exhibiting the least scour depth among the three pier shapes. Furthermore, no equation was found in the literature to predict the maximum scour depth around inclined bridge piers on clay-sand mixed beds, so three non-linear regression-based equations for three different upstream collinear piers as a function of clay content percentage and inclination were predicted which reasonably described the experimental data.

Two types of corrugated steel plate shear walls, namely low-yield point (LYP) and convention, are investigated in terms of strengthening reinforced concrete (RC) frames. Within LYP corrugated steel plate shear walls, two layouts are considered: half and full plate. A total of 24 models are considered to assess their performance in the aspect of ultimate strength, stiffness, and mechanical analysis. The objective of this research is to compare and analyze the effectiveness of LYP corrugated steel plate shear walls in enhancing the seismic resistance of RC frames. Based on force analysis and finite element modelling, the equivalent support model is proposed to verify the validity of the models. The deviation was between 1.76 and 14.27%. The findings reveal that LYP corrugated steel plate shear walls demonstrate comparable bearing capacity to conventional methods, with the added advantage of improved ductility. The maximum top displacement increases by 35% and 68% in the case of half and full plate. Although there is minimal variation (9.86%) in stiffness, these characteristics collectively contribute to enhanced seismic resistance and overall performance of the reinforced concrete frames.

In recent years, research has explored using glass fiber-reinforced polymer (GFRP) bars as a corrosion-resistant alternative to steel reinforcement in concrete columns. Design guidelines have been established in ACI 440.11–22 for GFRP bars. However, there's currently no specific code for Basalt fiber-reinforced polymer (BFRP) bars in concrete columns due to limited experimental data. This study investigates using BFRP bars and ties as an alternative to steel reinforcement in concrete columns. It presents results from testing 11 columns under concentric loads. The test variables included the longitudinal BFRP reinforcement ratio, BFRP tie spacings, BFRP tie diameter, and reinforcement type. The experimental results showed a resemblance in the performance of concrete columns reinforced with BFRP and steel bars. Longitudinal BFRP bars contributed between 6.4 and 17.2% to the ultimate load-carrying capacity. A reduction in tie spacing was observed to slightly improve the load-carrying capacity. Moreover, when using the same volumetric reinforcement ratio, employing smaller diameter bars with closer spacings proved to be more efficient than using larger diameter bars with greater spacings. The study also introduced two models for predicting the maximum load capacity of BFRP-reinforced concrete columns, and the proposed models showed high accuracy compared to existing models in the literature.

This paper presents the results of experimental and analytical investigations of an unreinforced masonry wall (URM) exposed to continuous tensile-compressive cyclic loading. For the experimental investigation, a sample masonry wall (SMW) was designed inside a rectangular steel frame carried by pinned supports and built over a distance of 1200 mm in length by 1500 mm in height. The SMW was made of bricks whose dimensions were 285 mm × 185 mm × 130 mm. Under the influence of cyclic loading, damages appeared as diagonal or scattered cracks. The SMW was retrofitted by using carbon fiber-reinforced polymer (CFRP). An epoxy resin-based product and layers of CFRP were placed on the damaged SMW according to the crack patterns to acquire better recovery, effective strengthening, and enhanced performance. The retrofitted SMW underwent the same cyclic loading to obtain the effects of CFRP on the load–displacement capacity of the damaged masonry wall. Furthermore, an operational modal analysis test was conducted over SMW (the undamaged, the undamaged and retrofitted with CFRP) to determine their real dynamic characteristics. For analytical investigations, finite element analysis (FEA) was implemented in ABAQUS software with a simplified micro-modeling approach and damages were considered only in terms of displacement in this work. Nonlinear cyclic analysis was performed to obtain crack patterns and displacements. To determine modal parameters such as mode shapes and frequencies, modal analysis was also conducted. The obtained results such as displacements, damage patterns and modal parameters from analytical investigations were compared with experimental investigations. In the comparison of analytical and experimental studies, the results showed that the dynamic characteristics such as mode shapes and natural frequencies of SMW were changed. The use of CFRP increased up to 36% of the frequencies of the damaged sample wall. Furthermore, the shear strength capacity of SMW retrofitted by CFRP was significantly increase.

Concentrically braced frames exhibit adequate stiffness against lateral loads. However, a critical issue with these frames lies in the connection between the brace and beam/column. The compressive and tensile forces in the braces induce significant shear at the end of the beam, leading to yielding of the beam and failure of the connection to the column. Additionally, in many cases, welds at the edge of the gusset plate to the beam experience premature failure due to stress concentration before brace yielding or buckling. In this study, it is proposed to replace the I-shaped beam with a double channel beam (2-UNP) and to allow the gusset plate to pass continuously through the beam. Consequently, in consecutive stories, there will be a continuous connection plate passing through. The research results demonstrate that in this configuration, the stress level in the beam web, connection of the beam to the column, and weld at the edge of the connection plate are significantly reduced. In frames with through gusset plates, as a portion of the brace force is transferred through the connection plate passing through the U-shaped beam, less force is absorbed by the weld, preventing premature brace yielding or buckling before weld failure. Furthermore, due to increased allowable drift in frames with through gusset plate, the ductility of the frame enhances compared to frames with a conventional gusset plate.

This paper presents the results of experimental and numerical investigations on precast concrete sandwich panels (PCSPs) as one-way slab tested under flexural load. These panels consist of three layers: an ordinary reinforced concrete layer as the upper layer, a thick lightweight concrete layer as the core, and a lightweight concrete and tension-resistant reinforced ordinary concrete layer as the bottom layer. The common method to join the layers together against the inter layer shear force is carid out by means of truss shear connectors. As a novel method an egg-shaped shear connector were proposed and tested in this research. The behavior of four PCSPs were studied under four-point displacement control monotonic test. The sandwich panels with egg-shaped shear connectors exhibited higher ductility and toughness under flexural loading than those with truss-shaped shear connector. In addition, the sandwich panels with two concrete layers had a smaller linear region stiffness than those with three concrete layers. Furthermore, finite element (FE) models were developed in the ABAQUS to investigate the effects of orientation of shear connectors. Eventually, analytical computation was performed to obtain the ultimate flexural capacity of the panels and were compared with the results of experimental and FE models. The results showed a significant degree of accuracy. Therefore, the PCSP slab can serve as an alternative to the normal concrete slab system in buildings.

In this study, the impact of a saline soil environment at low temperatures on the durability of cement-based materials is investigated. Specifically, we examine the effects of varying limestone powder content and fineness on the sulfate attack capability of cement-based materials with limestone powder (CMLP). The study includes a comparative analysis, and the sulfate attack life of CMLP is predicted under the influence of an electric pulse based on the Wiener process model. Our findings revealed that CMLP experiences more pronounced damage with higher limestone powder content and fineness during both sulfate immersion and accelerated erosion induced by an electric pulse. Moreover, the electric pulse enhances the sulfate attack compared to immersion across samples with different limestone powder content and fineness. Notably, at a low temperature of 5 °C, the formation of gypsum, ettringite, and thaumasite was observed in the samples, with the characteristic peaks of erosion products becoming more apparent with increased limestone powder content and fineness. Using the Wiener model, the reliability degradation analysis indicated that the accelerated erosion life of samples with 10% and 20% limestone powder content, as well as specific surface areas of 1468 and 1785 m²/kg, under accelerated erosion by electric pulse, were 310, 160, 208, and 165 days, respectively. Overall, our study underscores the importance of considering the content and fineness of limestone powder when harnessing it as a constituent material in cement-based materials, especially in low-temperature saline soil environments.

In this research, the topology optimization method was used to decrease the significant amount of induced distributed loads on surrounding boundary elements of unstiffened steel plate shear walls, which are produced due to the development of tension field action. Therefore, after validating the finite element modeling and optimization methods of steel plate shear walls in ABAQUS, the infill panel’s internal shear forces within the specified strip zones around it were considered as the objective function while the infill panel’s volume and its geometric symmetry were the constraints of the optimization problem. By evaluation of single and combined objective functions for the shear forces, the obtained optimized configurations were superimposed in AutoCAD and regarding the results of 54 considered models, a practical optimized configuration was proposed. Then, a detailed parametric study was performed to find the most optimum geometrical dimensions of the proposed practical configuration considering the amount of stiffness, energy dissipation capacity, out-of-plane deformation and shear forces of the boundary elements. Finally, the required flexural stiffness of the boundary elements of the selected optimized model was examined and it was concluded that the coefficient of the equation, which is proposed by AISC341 provisions for the stiffness of boundary elements, was reduced by 22.58%.

Currently, unmanned aerial vehicles (UAVs) have a variety of applications in the civil construction industry, including activities related to evaluating the condition of buildings. The objective of this article is to organize information on the use of UAVs in inspecting and evaluating heritage buildings through a Systematic Literature Review. The methodology involved selecting 34 articles from the Scopus and Web of Science databases from the past five years. In general, UAVs are combined with other technologies for data acquisition to produce more precise results, such as Terrestrial Laser Scanning and digital cameras. The most used product of UAVs is a 3D model, which integrates different platforms such as Building Information Modeling and Finite Element Modeling. While UAVs are an important tool for providing accurate diagnoses and evaluations, further research is needed on their limitations in cultural heritage. For example, the applicability of UAVs depends on factors such as flight autonomy, location system, and standardization of procedures. More in-depth research is necessary for both data processing and improving the physical components of UAVs to establish their use in inspecting and evaluating heritage buildings.

It is thought that structural control systems developed for structures exposed to earthquake warnings may have an important place in the future as well as today. Among these, base isolation systems offer effective and practical solutions by damping earthquake-induced vibrations at the ısolatıon level. However, due to the lack of self-adaptation feature against some near- or far-field earthquakes, semi-active and active control systems have been proposed by some researchers. These systems, which use an external power source, also need a control algorithm in order to take action in the event of an earthquake. In other words, in order for the control system to adapt to any earthquake and act as a vibration damper, a passive device, energy to activate the device and a control algorithm are needed. This review covers important studies on passive, semi-active, hybrid and active control systems recommended for the protection of structures against vibrations caused by earthquakes. The advantages and disadvantages of the studies on these control systems compared to each other have been determined. As a result of the study, some inferences were made about what kind of control system would be recommended in the future, taking into account the deficiencies in the literature.