Doctrines of earthquakes and also the latest approaches of earthquake resistant building design in standards need to be revised periodically. While the revisions and updates in the American standards occur over periods of three or five years including limited subjects, in Turkey the same revisions are done once over long periods including the whole subjects of the standards. As examples the standards of 1975, 1998, 2007 and finally 2018 could be given. Especially, in 2018 standard (TBEC-2018) many changes were made over concepts and criteria. The procedure of calculating the earthquake loads in 2018 standards is similar to the one in the American standards of (ASCE-7-16), however for the element design the changes are shown as developments over the one of 2007 earthquake standard (TEC-2007). The changes made by 2018 standard for calculations of earthquake loads and their effects on civil engineering are very important factors of new building design. The earthquake load affecting a building which is the first factor of earthquake resistant building design shows important differences according to the condition changes in the standard. Based on this motivation in this study reinforced concrete frame type buildings of different elevations were researched by using ETABS (structural software for building analysis and design) according to linear equivalent seismic load method. According to the analysis results of the chosen buildings, a comparison forthe base shear force, top displacement and relative story displacement between TEC-2007, TBEC-2018 and ASCE 7-16 standards was carried out. From the analysis results, it is found that for most of the soil classes while the maximum base shear forces in 3 and 5-story buildings are achievedat TEC-2007, the maximum base shear forces in 7 and 9-story buildings are achieved at TBEC-2018. Also, it is predicted that the higher increment in the design forces of buildings with higher elevations is obtained at TBEC-2018 for strong soils, and at TEC-2007 for weak soils. By considering cracked sections at TBEC-2018 the calculations displacement and period was affected as periods in TBEC-2018 were increased by almost 34% respected to TEC-2007. The same increment ratio was determined for ASCE 7-16 as 45%. Also, as a response for the increments in period, the spectral acceleration determined from the elastic spectrum diagram was decreased. At the end of the study, nonlinear performance analysis was also performed and performance points were determined according to the demand spectra of the seismic codes. ASCE's demand displacement values are in any case lower than Turkish codes. TBEC-2018 reveals less displacement demands in high-rise buildings than TEC-2007. The closest results for the three regulations occurred on the softest grounds.According to the results obtained from the static pushover analysis, a ductile behavior occurred in all of the structural systems and plastic hinge mechanism started from the beams firstly.
In this paper, discrete design optimization of a cantilever retaining wall has been submitted associated with a detailed parametric study of the wall. In optimal design, the minimum wall weight is treated as the objective function. Through design algorithm, the optimal design variables (base width, toe width, thickness of base slab and angle of front face) yielded minimum structural weight of the wall and satisfied stability conditions have been determined for different soil parameter values. At the end, a detail parametric study searching the effect of change of soil parameters on the retaining wall design has been conducted with 120 optimized wall designs for different values; eight values of the angle of internal friction, three values of the unit volume weight and five values of wall heights. The obtained results from optimization analyses indicate that change of the angle of internal friction more effective than change of the unit volume weight on the optimal wall weight. Economic wall design with optimization analysis is achieved in a shorter time than the traditional method.
Two different large-scale industrial structures that were destroyed by fires in 2011 and 2012 in Turkey were examined. The structural framework in the first structure was constructed as prefabricated concrete, while a prefabricated concrete–steel (hybrid) was the structural framework in the second. The post-fire performance of the structures was evaluated according to the structural system properties of the buildings and tests on concrete core and steel reinforcement samples obtained from the structures. Since the fire durations of the two buildings examined were slightly different, in addition to the structural framework differences, material test results were comparatively interpreted for the two structures. The concrete used in the building exposed to the longer fire duration suffered a substantial loss in mechanical properties, the concrete cover in the reinforced concrete elements failed completely, and there was a significant loss in the yield strength of the steel reinforcement. In the second structure, which experienced a fire of shorter duration, although the concrete cover had failed similarly to the first case, there was not a substantial loss in the mechanical properties of the reinforcement and concrete. It was observed that damage to the steel structural framework in the second structure (a prefabricated concrete–steel hybrid) triggered damage in the prefabricated concrete system. The precautions that need to be taken in terms of fire, especially in industrial structures, were evaluated based on either the load-carrying system or the section, and suggestions for improvements are made.
In this study, earthquake performance of the structures was tested which were modeled according to the minimum criteria of simplified analysis approach proposed in TBEC-2019. For this purpose, 144 reinforced-concrete building models were designed according to parameters such as earthquake design class, building height (number of storey), number of spans, soil type and three different simplified formulas suggested in the code. The level of structural performance of buildings models was determined by the linear (L) and nonlinear performance analysis (NL) methods that given in TBEC-2019. The base shear force, top displacements and over-strength factor (Ω) of each structural model were obtained, and performance analysis was performed by comparatively. As a result of the structural analyses, it was seen that some of the buildings model designed according to minimum column sectional criteria given in simplified methods could not meet the suggested seismic performance level. While the number of structural models that provide the controlled damage (CD) level in the L analysis method is 44 (30.55%), it is 107 (74.3%) in the NL analysis method. The insufficient performance was obtained in both L and NL methods in models which have over-strength values below 3. It has been observed that multi-criteria of building performance are not met with the weakening of local soil conditions. It was also seen that the L method chosen in the performance analysis gave more conservative results with this study.
In this paper, the investigation of the optimum designs for two types of concrete cantilever retaining walls was performed utilizing the artificial bee colony algorithm. Stability conditions like safety factors sliding, overturning and bearing capacity and some geometric instances due to inherent of the wall were considered as the design constraints. The effect of the existence of the key in wall design on the objective function was probed for changeable properties of foundation and backfill soils. In optimization analysis, wall concrete weight which directly affect parameters such as carbon dioxide emission and the cost was considered as the objective function and analyzes were performed according to different discrete design variables. The optimum concrete cantilever retaining wall designs satisfying constraints of stability conditions and geometric instances were obtained for different soil cases. Optimum designs of concrete cantilever retaining wall with the key were attained in some soil cases which were not found the feasible optimum solution of the concrete cantilever retaining wall. Results illustrate that the artificial bee colony algorithm was a favorable metaheuristic optimization method to gain optimum designs of concrete cantilever retaining wall.
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