Journal of Structural Engineering & Applied Mechanics

Adeel Arif Elif Boru Osman Kırtel

In seismic performance assessment of reinforced concrete structures, member stiffness is believed to be a critical modelling decision. In realistic conditions, the effective stiffness and flexural stiffness of members reduce due to lateral earthquake loads. The existing design codes, such as TBDY-18 and ASCE 41-17, recommend that stiffness modifiers be used to compensate for this decrease in linear elastic analysis procedures. Although this modelling option is significant, there are still very few systematic comparative studies that quantify the variations in seismic demand between gross and code-prescribed effective stiffness assumptions, especially when structures are evaluated under the conditions of Turkish seismic hazard. This work is a comparative linear time history analysis of a four-story, regular reinforced concrete moment-resisting frame simulated in ETABS. Three assumptions of the stiffness model were considered: gross section properties as a baseline; TBDY-18 effective stiffness modifiers; and ASCE 41-17 effective stiffness modifiers. Eleven pairs of spectrum-matched ground motions, which are compliant with the DD-2 hazard level and site conditions in Sakarya Province, Turkey, were used and verified against TBDY-18. The fundamental period was found to be increased by around 30-38% by adopting effective stiffness assumptions opposed to the baseline stiffness model through model analysis. Besides, the story displacement and inter-story drift ratios were recorded to increase under linear time history analysis, as the ratios of inter-story drift increased by 26-66% and top-story displacements by 46-59%. However, under effective stiffness models in the X and Y directions, the base shear was reduced by 21-23% and the overturning moments by 23-25% compared to the gross section baseline. The results show that gross stiffness assumptions underestimate deformation demands but overestimate force demands. Thus, effective stiffness modifiers are necessary to avoid non-conservative performance assessments in code-based linear seismic analysis.

https://doi.org/10.31462/jseam.2026.649

Yunus Emre Gündoğdu Berivan Yılmazer Polat

This study, which was conducted in the Pülümür district of Tunceli, was carried out in an area with high seismic risk due to the region's proximity to the Bingöl-Yedisu Fault. In the study, the earthquake safety of the existing building stock was assessed using visual inspection methods. In this context, 172 buildings in the Pülümür district of Tunceli province were examined in detail in terms of earthquake safety using the Canadian Seismic Screening Method. In the analyses, seismic safety levels of the buildings, structural and nonstructural risks were taken into consideration and seismic priority indexes (SPI) were determined. The results of the study revealed that a large portion of buildings in the Pülümür district carry different levels of risk of earthquake. Specifically, the evaluated building stock was entirely constructed before the critical year of 2007 and exhibits high seismic vulnerability. This critical threshold is technically attributed to two main regional factors: the design practices predating the 2007 Turkish Earthquake Code and the absence of ready-mixed concrete technology in Tunceli province prior to that year. Furthermore, based on the method’s classification, it is suggested that buildings with a Seismic Priority Index (SPI) greater than 20, which indicates "High" to "Very Hazardous" risk levels, should be prioritized for detailed assessment and retrofitting, and that local governments should develop incentive policies for these mitigation efforts.

https://doi.org/10.31462/jseam.2026.651

Gülnur Başer Berk Aygün

Carbon fiber–reinforced plastics (CFRPs) are extensively utilized in aerospace, defense, automotive, and marine applications owing to their high specific stiffness and strength. Although unidirectional (UD) prepreg systems provide superior mechanical performance, their high material and processing costs have motivated increasing interest in textile-based reinforcements and out-of-autoclave manufacturing techniques, such as vacuum-assisted resin infusion (VARI). In VARI processes, laminate thickness is not constrained by a rigid mold cavity and is therefore strongly governed by the reinforcement architecture and resin uptake behavior. In this study, the influence of the areal weight (AW) of unidirectional carbon fiber reinforcement on laminate thickness in vacuum-infused composites is systematically investigated. Non-crimp stitched UD carbon fabrics, with measured carbon areal weights ranging from 596.6 to 634.9 g/m², were manufactured by varying the tow density across the fabric width. The compaction behavior of dry fabrics was evaluated using 100-ply stacks under vacuum, while the thickness and fiber volume fraction of cured laminates were determined from 20-ply infused specimens. The results demonstrate a strong linear correlation between carbon AW and cured ply thickness (CPT) (R² ≈ 0.93), indicating that laminate thickness increases predictably with increasing reinforcement mass per unit area. Specifically, an increase of 10 g/m² in carbon AW corresponds to an average increase of approximately 0.035 mm in CPT. Similarly, the dry stack thickness under vacuum exhibits a strong linear dependence on AW (R² ≈ 0.90), whereas the fiber volume fraction (FVF) shows a slight decreasing trend with increasing AW. These findings provide quantitative design guidelines for thickness prediction and reinforcement selection in infusion-based manufacturing of unidirectional CFRP laminates, particularly for applications where geometric constraints are minimal or absent.

https://doi.org/10.31462/jseam.2026.654

Abdulhamit Nakipoğlu Muhammed Cemaloğlu Mahmud Sami Döndüren

Worldwide standards give details about the standard size and dimensions of specimen that should be used to determine the compressive strength of concrete. However, these relationships are generally available for plain concrete. Limited information is available regarding the effect of geometry of the test specimen on the compressive strength of concrete incorporating additive materials such as rubberized concrete. In the current work, the effect of incorporation of tire rubber on the compressive strength of concrete has been experimentally investigated. Fine tire rubber particles were added to concrete by 0%, 2%, 4%, and 6% by volume. The results revealed that the compressive strength of concrete decreases linearly as the content of rubber increased. The results also showed that the compressive strength of rubberized concrete depends on the specimen size and slenderness ratio, decreasing as the slenderness ratio increases. Results also revealed that standard cylindrical-to-cubic compressive strength for plain concrete (generally 0.8) may not be applied directly for concrete containing additive materials such as tire rubber. This ratio was found to be equal to approximately 0.72 for C16/20 grade rubberized concrete. Regardless of the test specimen geometry, a strong linear relationship was observed, with each 1% increase in fine rubber content (by volume) reducing the compressive strength of concrete by approximately 6%.

https://doi.org/10.31462/jseam.2026.688

Elif Toplu Osman Kırtel

This study evaluates the predictive performance of Turkey-adjusted NGA-West1 and global NGA-West2 Ground Motion Prediction Equations (GMPEs) using strong-motion data from the 2022 Gölyaka (Mw 5.9) and 2023 Pazarcık (Mw 7.7) earthquakes. Three analysis scenarios were developed based on Vs30 site classifications defined by TBEC 2018: Vs30 = 180–360 m/s records from both earthquakes and Vs30 = 360–760 m/s records from the Pazarcık event. Median spectral values predicted by GMPEs were compared with observed medians within the period range T = 0–10 s. Multiple statistical techniques including Likelihood (LH), Log-Likelihood (LLH), Euclidean Distance Ranking (EDR), Mean Distance Error (MDE), and the √κ indice were applied to assess model performance. Results show that GMPE performance varies significantly by earthquake magnitude, source characteristics, and soil class. The results indicate that GMPE performance varies significantly depending on earthquake magnitude, source characteristics, and site conditions, and no single model provides superior performance across all scenarios. Turkey-adjusted models generally showed strong performance, particularly under medium-to-soft soil conditions, while some models demonstrated improved predictive capability for the Pazarcık earthquake under rock and stiff-soil conditions. In contrast, several models showed comparatively lower agreement with the observed data. Overall, the findings highlight the significant influence of site classification on GMPE selection and support the use of multi-model logic-tree approaches to reduce epistemic uncertainty in probabilistic seismic hazard analysis (PSHA).The results indicate that GMPE performance varies significantly depending on earthquake magnitude, source characteristics, and site conditions, and no single model provides superior performance across all scenarios. Turkey-adjusted models generally showed strong performance, particularly under medium-to-soft soil conditions, while some models demonstrated improved predictive capability for the Pazarcık earthquake under rock and stiff-soil conditions. In contrast, several models showed comparatively lower agreement with the observed data. Overall, the findings highlight the significant influence of site classification on GMPE selection and support the use of multi-model logic-tree approaches to reduce epistemic uncertainty in probabilistic seismic hazard analysis (PSHA).

https://doi.org/10.31462/jseam.2026.694

Mohammed Hassan Ali Pembe Merve Karabulut

In this study, the frictionless receding contact problem of a functionally graded (FG) orthotropic layer, orthotropic punch, and half-plane system was investigated using the finite element method (FEM). Numerous contact mechanics problems have been solved using singular integral equations in the literature. In these studies, to simplify the mathematical solution, the punch transferring the load was assumed to be rigid and its deformations were neglected. However, assuming the punch to be rigid is an idealized situation, and in reality, materials deform under load. As a result, some changes are expected in both the contact stresses and lengths, and the behavior of the entire system. The results obtained in this study were compared with other results obtained in the literature, assuming a rigid punch. The effect of punch stiffness on stress and strain was examined. The aim of this study is to contribute new results for elastic punch problems to the existing literature.

https://doi.org/10.31462/jseam.2026.706