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

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.

This study proposes and implements an automated design optimization program for steel plate shear wall (SPSW) systems and evaluates the effect of design conservatism level on the seismic collapse performance of SPSW archetypes. Initially, a MATLAB program is prepared that develops elastic and inelastic SPSW models with variable geometric and loading conditions and automates the manual seismic design process of these structures. The program is connected to a set of OpenSees scripts for computing the required response parameters. SPSW archetypes with 4, 8, 12 and 16 stories are then designed twice, using the genetic optimization algorithm and manual iterations. The seismic collapse performances of the two design sets are finally investigated with respect to the FEMA P695. The results indicate that design optimization leads to a weight reduction of up to 27%, and can still lead to acceptable collapse margin ratios (CMRs) according to FEMA P695. In addition to the buildings weight and CMR, the distribution of ductility and inter-story drift demands are assessed along heights when the manual design is replaced with an optimization procedure. In general, design optimization has shown more pronounced effects on the studied low-rise structures in terms of economy and seismic performance.

Water is an indispensable resource in modern social life, and the surface is composed of 71% water and 29% land. It is also an indispensable resource in both daily life and industrial production. In recent years, water resource pollution has become increasingly severe, and industrial wastewater discharge has had a huge impact on the entire water ecological environment. Faced with the increasingly serious pollution of the environment, traditional sewage treatment methods are gradually difficult to cope with. This article compared the suspended biological filler technology using aquatic environmental materials with green products using traditional activated carbon materials. The experimental results showed that the average service life of the designed green product based on aquatic environmental materials was 6.125 years, while the average service life of activated carbon was around 3.5 years. The average difference was 2.625 years. In order to optimize the pollutant removal rate of the product, the average removal rates of various harmful substances using suspended biological fillers based on water environment materials in 9 rounds of testing were 93.7, 89.7, 73.3, and 84.4%, respectively. The average removal rates of each hazardous substance in the nine rounds of tests were 81.8, 81.7, 65.9, and 74.0% for activated carbon based on the physical method, respectively. For the optimized green product wastewater treatment efficiency, the average reduction in the treatment of suspended biological fillers based on water environmental materials was 441.1 mg/L, and the average reduction in the treatment of activated carbon adsorption technology based on physical methods was 398.3 mg/L. Therefore, compared to using activated carbon, applying suspended fillers based on water environment to the optimization design of green products can effectively improve the service life and pollutant removal rate of green products, resulting in lower decontamination costs and higher pollutant treatment efficiency.

In today’s modern city life, shopping centers have become a part of the urban identity. Erzincanpark Shopping Center, which was put into service at the city’s western entrance in 2022 in Erzincan, created an additional traffic volume causing inadequacies and accidents in urban transportation. This study aimed to identify these problems and inadequacies and develop possible solutions and suggestions. To examine the importance of coordination between junctions, traffic flow, and phase arrangements, Erzincanpark was chosen as the study area, and the junctions on Halitpasa Street were examined. The study used the traffic impact analysis method to examine traffic counts at junctions, signal optimization, travel time, queue length, delay, CO₂, NOx, VOC emissions, and fuel consumption values. The study results showed that Yildiz and Nedim Muratoglu junctions should be modern roundabouts to ensure the optimum situation. Furthermore, it was determined that there was no change in the parameters studied in the design of Ergan Junction in 3 different ways: signaled, 4-way (without an island), and modern roundabout. Analytical Hierarchy Process (AHP), one of the multi-criteria decision- approaches, was used to find the feasible result, considering safety and construction costs.