Journal of Structural Engineering & Applied Mechanics
Ali Sahin Tasligedik
Strength hierarchy assessment is a method developed to be able to identify the governing failure mechanisms at reinforced concrete (RC) beam-column joints. The main failures that can be identified in this method are: i) beam plastic hinge; ii) column plastic hinge/shear failure; iii) beam-column joint shear failure. Through the identification of the governing failure mode in a joint, the validity of the capacity design principles can be checked for the considered RC beam-column joint. The obtained observations can then be used in finding the most optimal repair/strengthening application. This method has been going through updates and developments in the last decade and new applications have emerged. In this article, a state-of-the-art summary of the procedure is reported with its most recent updates as well as its practical engineering applications.
Mehmet Fırat Karapınar
The current paper presents a seismic performance assessment of a low-story RC building through the time history analysis and a retrofitting proposal accordingly. The seismic analyses were repeated for the retrofitted building model and the effectiveness of the retrofitting proposal was determined. In the first stage of the study, the design project and material characteristics of the building were examined. Using these data, a 3D model of the building was prepared on the Midas Gen program. Next, a total of 11 earthquake records were selected and scaled for nonlinear time history analysis. Using the analysis results with the codes written on the Matlab program, the damage states of the load-bearing members were determined and the building’s performance was measured. The results indicated that some load-bearing members have insufficient strength and a retrofitting proposal was made accordingly. A building model was then prepared considering the retrofitting proposal and the retrofitted building model was found to satisfy controlled damage performance criteria envisaged in the local seismic code. It is believed that the methodology presented in this study can be effectively used in similar buildings with poor structural strength for identifying structural performance and selecting proper retrofitting practices.
Ayşe T. Daloğlu
The teaching-learning optimization (TLBO) technique is applied to unbraced steel frames with semi-rigid beam-to-column connections and semi-rigid column-to-base connections. The algorithm for design produces optimized steel frames by choosing appropriate sections from a set of standard steel sections. These standard steel sections, including wide-flange profiles (W), are provided by the American Institute of Steel Construction (AISC). The first example is subjected to the displacement, inter-story drift, and stress constraints of AISC-Load and Resistance Factor Design (LRFD) regulations. In addition, the displacement and stress limitations of the AISC-Allowable Stress Design (ASD) standard and the geometric (size) requirements are implemented in the last two examples. In finite element analysis, optimal designs of three alternative unbraced frames are performed with and without semi-rigid beam-to-column and column-to-base plate connections. All optimization techniques are encoded in the high-level programming language C# version 17.4.4 to integrate with SAP2000 version 22's Open Application Programming Interface (OAPI). The analysis results indicate that the rigidity of connections is determining parameter in the weight optimization of unbraced steel frames.
Gülten Tandoğan Kibar
Esra Lakot Alemdağ
Cross-laminated wood (CLT) material, which has many advantages, has been widely used in architectural designs as a building element and building material in recent years. It has been proven that CLT can also show high performance against ground vibrations, but it is also mentioned in the literature that some problems such as rupture, snagging, and breaking occur in the elements used in the connections of the walls to the floor and the ground. This study was conducted to examine the performance of fasteners used in CLT walls against lateral load. In this context, 4 CLT walls were produced and then 5 metal profiles were designed to be used in the connection of these walls with the foundation ground. CLT wall and connection profiles, created according to ASTM E 72 standards, have been tested in an experimental setup with different detail options. According to the test results, it was observed that some of the CLT walls and connection profiles showed high performance at maximum load, displacement, and stiffness values. As a result, it has been determined that the resistance of the CLT material against lateral earthquake load can be increased with the right fasteners, and the collapse time of the structure in the event of an earthquake can be indirectly extended.
Punching resistance in flat slab systems in reinforced concrete structures is often provided with drop panels or shear reinforcement around columns. Shear studs are effectively used in these structures as shear reinforcement. However, factory-made shear studs may not be available in all locations and small quantities for small projects. Therefore, cheap shear studs that can be manufactured from widely available materials in small quantities can be very useful in certain cases. In this study, shear studs manufactured from threaded bars, widely available in hardware stores, are used for providing punching resistance to flat slabs. Stud heads were formed with T-section nuts. Four slab specimens, two with shear studs and two without, were cast and tested under concentrated loads at their mid-point. The slabs had 2150×2150×150 mm dimensions and they were cast with two different longitudinal reinforcement ratios. Test results showed that manufactured shear studs significantly increased the load and deformation capacities of the slabs. Slabs with shear studs were able to show up to three times higher bending deformations and they were able to sustain up to 50% higher loads. The study has shown that these studs can be effectively used for punching strengthening purposes in flat plate systems or in other cases where punching resistance is needed.
Mehmet Emin Arslan
In this study, the fracture and mechanical behavior of glass fiber reinforced concrete (GFRC) are investigated comparatively. For this purpose, three-point bending tests were carried out on notched beams produced using GFRC with 1, 2, and 3 kg/m3 fiber contents and the dimension of 6, 12, and 24 mm to determine the fracture energy. Fracture energy values of the GFRC specimens were calculated by analyzing load versus crack mouth opening displacement (CMOD) curves. Compressive strength was determined using cube samples with the dimension of 150x150mm. Tensile strength and Modulus of elasticity were determined using notched beams with the dimensions of 48010050 mm. Also, notched beams were produced and tested in accordance with RILEM recommendations. In addition, microstructural analyses were performed based on Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations. The results showed that the effects of fiber contents on fracture energy were very significant. However, the effect of fiber addition on the compressive strength and modulus of elasticity values was not significant.
Ayşegül Durmuş Demir
Reinforced concrete grouped silos-commonly employed in the industry to store granular materials- also needs to be designed in earthquake-prone areas. Silos experience a higher rate of structural failures than the majority of other types of construction. And one of the main causes of silo failure is the dynamic overpressures caused by stored materials under seismic loads. However, the principles determining loads on such structures and requirements for their structural analysis aren’t precisely specified in relevant codes of design. Instead of emphasizing grouped silos that interact strongly, the present dynamic design only concentrates on a single silo which can lead to unrealistic solutions for grouped silos. Therefore, it is necessary to determine the seismic behavior of grouped silos more accurately. This paper aims to investigate the seismic behavior of RC on-ground grouped silos compared to single ones by using a numerical model because of its adaptability, which allows for the analysis of a wide range of silo problems. In this context, a three-dimensional finite element model, that considered the interaction between stored material and silo wall as well as the continuity of the silo walls, was performed using ANSYS software. Two different aspect ratios and three different internal loading cases were taken into account for the parametric study to demonstrate their influences on dynamic overpressures and equivalent base shear forces in RC-grouped silos. It is concluded that designing the on-ground slender grouped silos with a high aspect ratio as individual single silos is unreasonable and may produce very low values for the base shear force.