Mahmut Bassurucu

The 7.7 and 7.6 magnitude Pazarcık and Elbistan earthquakes that struck Kahramanmaraş on 6 February 2023 caused widespread structural damage across many provinces and are considered rare in seismological terms. While many reinforced concrete (RC) buildings designed under current earthquake regulations sustained significant damage, some older RC buildings with outdated designs sustained only moderate damage. This study aims to analyze the seismic performance of such older RC buildings to understand why they did not collapse or suffer severe damage. An 8-story RC building in Adıyaman province, damaged by the earthquake, was considered for analysis. The region’s seismicity and local site conditions were assessed through borehole operations, geotechnical laboratory tests, and seismic field tests. The soil profile was modeled, and one-dimensional seismic site response analyses were performed using records from nearby stations (TK 4615 Pazarcık and TK 4612 Göksun stations) to determine the foundation-level earthquake record. Nonlinear static pushover analysis was carried out via SAP2000 and STA4CAD, utilizing site response analysis and test results taken from the reinforcement and concrete samples of the building. The findings, compared with the observed damage, provide insights into the performance of older RC buildings in this region.

6 Şubat 2023 tarihinde meydana gelen Mw=7.7 ve Mw=7.6 büyüklüklerindeki Kahramanmaraş merkezli depremler Adıyaman’ın da aralarında bulunduğu 11 ili önemli ölçüde etkilemiştir. Adıyaman ilindeki betonarme yapılarda bulunan yapısal sorunlar, depremlerde felaketin boyutlarını önemli ölçüde arttırmıştır. Bu nedenle, betonarme yapılarda yapısal elemanlar açısından önemli hasarlar ve toptan göçmeler gözlemlenmiştir. Bu çalışmada, Adıyaman il merkezindeki betonarme yapılar için yapım uygulamalarının değerlendirilmesi amacıyla saha araştırmaları gerçekleştirilmiştir. Bulgular, birçok betonarme yapının yapısal ve/veya işçilik hataları nedeniyle hasar aldığını veya toptan göçtüğünü göstermiştir. Sonuç olarak, Adıyaman ilindeki betonarme yapıların deprem performansını iyileştirmek için gelecekte yapılacak yapım ve güçlendirme çalışmaları açısından bazı kritik öneriler yapılmıştır.

An experimental study was herein presented focusing the effect of different type, shape and volume fraction of fibers on the hardened properties of concrete including compressive, splitting tensile and flexural strengths at 7 and 28 curing days. A control concrete mixture with no fiber was prepared and six fiber reinforced concrete mixtures were designed by using two different types of fibers which were steel fibers with different shapes (short straight and hooked end) and polypropylene fiber with the volume fraction of 0.4% and 0.8%. The load-deflection curves and toughness of the specimens were analyzed based on ASTM C1609. The results showed that the utilization of short straight steel fibers with 0.8% volume fraction was most efficient at improving the compressive strength while the use of 0.8% long hooked end steel fibers provided better splitting tensile and flexural strengths. Besides, the long hooked end steel fibers with the volume fraction of 0.8% contributed to an excellent deflection hardening behavior resulting in higher load deflection capacity and toughness at peak load, L/600 and L/150. On the other hand, with incorporation of polypropylene fiber, all strength values were decreased regardless of the volume fraction and curing days.

There are only a few studies related to the effect of the hybrid fiber reinforcement on the flexural behavior of full‐scale beam specimens having lap‐spliced length. Thus, this study will ensure important experimental data about the effect of macro steel fibers blended with micro steel fibers on lap‐spliced length. The aim of this study was to investigate the influence of hybrid steel fiber reinforcement on the flexural behavior of full‐scale reinforced concrete beams having different lap‐spliced bars. A sum of three traditional concrete mixtures including a total of 1% fiber by volume fraction was adopted: control mixture without steel fiber, only macro steel fiber and hybrid steel fiber reinforced mixtures. For this purpose, 18 full‐scale beams (200 × 300 × 2000 mm) having three different lap‐spliced length (15, 25, and 35Ø) as tension steel bars were produced and tested under four‐point bending to examine flexural behavior, mode of failure, ductility, and energy absorption capacity properties. In conclusion, the hybrid fiber reinforcement caused the highest increase in the load carrying capacity of the beam specimens. Besides, the hybrid fiber reinforced beam specimens exhibited excellent ductility and energy absorption capacity compared to single fiber reinforced beam specimens. On the other hand, it can be addressed that the hybrid fiber reinforced structural elements had a vital important to compensate the application errors and carelessness in steel bar workmanship, inadequate the lap‐spliced length as per the codes. It can be emphasized that the lap‐spliced length as per the building codes can be reduced in 40% by containing hybrid steel fiber (0.8% macro‐0.2% micro) reinforced concrete without a reduction in load carrying capacity, ductility, and energy absorption capacity compared to control beam specimens without fiber.

In this study, experimental and statistical analyses were conducted to reveal the effect of micro steel and/or polypropylene (PP) fibre with macro steel fibre as binary and ternary hybridization on the fresh, mechanical and flexural performance of hybrid fibre reinforced self-compacting concrete (HFR-SCC). For this purpose, some tests were conducted related to fresh and hardened properties. It was seen that PP had negative effect on the fresh properties of HFR-SCC mixtures compared to micro steel fibre. Moreover, multiple linear regression (MLR) was used to estimate the fresh and hardened properties of HFR-SCC as function of the percent of fibres by volume while ANOVA analysis determined the contributions of parameters. It was obtained from statistical analysis that there was a good correlation between experimental results and predicted values with approximately R²=0.91 except for compressive strength. Finally, the use of PP with micro steel fibre as ternary hybridization increased the compressive, splitting, flexural tensile strengths, toughness and ductility of HFR-SCC with 1.1%, 13.2%, 18.8%, 14.9% and 26.3%, respectively, while the inclusion of PP into the mixture as binary hybridization had less positive effect on the hardened properties compared to binary steel fibre reinforced SCC with 0.25% micro steel fibre.