Abstract
This study investigates the influence of strong ground motion orientation on seismic response of a single-story reinforced concrete (RC) structures. For this purpose, three dimensional, single-story, single-bay asymmetric RC structure tested on shake table and its symmetric version are used. The numerical models of the structures in which reinforcement slip deformations taken into account are established according to the modelling technique validated in the "Blind Prediction Contest" conducted at the 15th World Conference on Earthquake Engineering. 30 pairs of near-field ground motion records are selected for bi-directional nonlinear time-history analyses. Horizontal components of ground motions are rotated from 0o to 360o with 10o increments. Selected and rotated ground motion records are scaled to get compatible with the target spectrum. Nonlinear time-history analyses are performed by applying simultaneously the horizontal components of those ground motions to the numerical models. The results for both asymmetric and symmetric structural models revealed that change in the ground motion incidence angle may result almost 4 times larger story drift ratio demands compared to the result obtained by using as-recorded ground motion records. However, when the averages of the maximum story drift ratio demand obtained from all analyses are considered, the change in the demands depending on the ground motion incidence angle remains around 15%.
Key Words
3d model; bi-directional nonlinear time-history analyses; ground motion orientation; near-field ground motions; shake table
Address
Deniz B. Kayi: Department of Civil Engineering, Bursa Technical University, Bursa, Turkey
Beyhan Bayhan: Earthquake Engineering Research Center, Bursa Technical University, Bursa, Turkey
Gökhan Özdemir: Department of Civil Engineering, Eskişehir Technical University, Eskişehir, Turkey
Abstract
Investigating the negative bending moment dynamic load allowance (NBMDLA) is crucial for characterizing dynamic response under moving loads in continuous girder bridges. This study proposes a recommended value for NBMDLA based on field test of continuous girder bridges under natural traffic flow. Firstly, strain signals in the negative bending moment zone and natural traffic flow information were collected from three continuous girder bridges. Then, NBMDLA was analyzed factors such as vehicle speed, vehicle type, and vehicle lateral driving position. Finally, a recommended NBMDLA value was proposed through statistical regression. Results indicate that NBMDLA increases significantly with rising vehicle speed. Lighter vehicles tend to result in larger NBMDLAs. Vehicle lateral driving position has a significant effect on NBMDLA, though without a clear linear trend. A recommended value of 0.3 is proposed as a design reference for new continuous girder bridges.
Key Words
continuous girder bridge; dynamic load allowance; natural traffic flow; negative bending moment; recommended value
Address
Chenkai Jiao, Yuxin Xue, Yongjun Zhou, Yuan Jing, Yu Zhao and Xiayu Li: School of Highway, Changan University, Xian, 710000, China
Abstract
To investigate the effects of different variables on the temperature and structural response of assembled superimposed single-compartment pipe galleries during the entire fire process, as well as the differences in damage, single-compartment pipe galleries with varying haunch heights and reinforcement ratios were designed for a full-process fire study. This included static tests under normal temperature, thermal-mechanical coupling tests during the fire, and post-fire static tests. Model tests and finite element simulations were employed to analyze the temperature gradient across the pipe gallery cross-section, longitudinal temperature distribution patterns, structural failure modes, displacement responses, strain responses, and residual bearing capacity evolution. Results indicate that the significant temperature difference between the inner and outer surfaces of the pipe gallery's top slab generates thermal stress, leading to the degradation of concrete performance. Fire exposure causes severe damage to the pipe gallery, while increasing haunch height and reinforcement ratio effectively enhances its bearing capacity and ductility throughout the fire process. Based on observed residual bearing capacity phenomena, a calculation method incorporating high-temperature material degradation and structural shear failure modes is proposed. Experimental data were compared with numerical simulations and validated through finite element analysis. Considering the temperature characteristics and structural performance of the pipe gallery, practical engineering improvement recommendations are provided. The research outcomes offer theoretical support for the study and application of assembled superimposed pipe galleries.
Key Words
haunch height; prefabricated composite single-compartment pipe gallery; reinforcement rate; temperature and structural performance; test and finite element analysis; whole process of fire
Address
Yanmin Yang, Chengyin Wang: School of Civil Engineering, Jilin Jianzhu University, Changchun, 130119, China
Xing Yuan: Zhongqing Construction Co. Ltd., Changchun, 130022, China
Abstract
Concrete is the most diverse and widely used building material . The production of Portland cement is associated with the production of a large amount of carbon dioxide, which causes air pollution. It is inevitable to find an alternative material for Portland cement. Removal of cement is one of the greatest advantages of using geopolymer concrete. In this article, the results of tests on the fracture parameters of lightweight fly ash C class-based Geopolymer concrete (LWFCGC) as a material that has both
advantages of lightness and use of green cement, are presented. These tests include three-point bending test on 49 beams with different activator to binder ratios. Also, compressive strength and tensile strength tests were performed on hardened concrete after 24 hours of processing at 80oC. In these experiments, three mix designs with 0.4, 0.5 and 0.6 activator to binder ratios were considered. By changing the activator to binder ratio from 0.6 to 0.4, compressive strength increased from 18.9 MPa to 28.4 MPa, fracture toughness improved from 19.65 MPa mm0.5 to 23.29 MPa mm0.5, total fracture energy (GF) increased from 59.20
N/m to 65.99 N/m, and the GF/Gf ratio decreased from 3.42 to 3.15.
Key Words
fracture parameter; geopolymer concrete; high temperature processing; lightweight geopolymer concrete
Address
Mohammad Reza Abbasi Zargaleh: Faculty of Civil and Earth Resources Engineering, Department of Structure, Islamic Azad University, Central Tehran Branch, Iran; Department of civil Engineering, National University of Skills (NUS), Tehran, Iran
Moosa Mazloom: Department of Structural and Earthquake Engineering, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Iran
Mojtaba Jafari Samimi: Faculty of Civil and Earth Resources Engineering, Department of Structure, Islamic Azad University, Central Tehran Branch, Iran
Mohammad Hassan Ramesht: Faculty of Civil and Earth Resources Engineering, Department of Structure, Islamic Azad University, Central Tehran Branch, Iran
Abstract
The effectiveness of bonded composite patch repairs in extending the service life of damaged aircraft structures is largely influenced by the mechanical behavior of the adhesive layer, particularly shear stresses. Adhesive or cohesive failure due to debonding remains a major concern, yet the degradation mechanisms are not fully understood. This study employs finite element simulations to analyze the impact of patch geometry, specifically thickness distribution, on repair efficiency. Three patch configurations with varying thickness distributions were developed, demonstrating that repairs using inhomogeneous-thickness patches significantly outperform conventional uniform-thickness patches. Compared to a standard rectangular patch of constant thickness, the optimized patches led to lower stress intensity factors (SIF) and a substantial reduction in shear stresses within the adhesive layer. Notably, a stair-shaped patch and a digressive stair patch provided the best performance, effectively distributing stresses while minimizing peak concentrations. These findings highlight the potential for advanced patch geometries to enhance repair durability and reliability in aerospace applications.
Address
Mohammed Baghdadi, Mohammed Amine Bellali, Boualem Serier: LMPM, Department of Mechanical Engineering, University of Djillali Liabes, BP 89, Cité Ben M'hidi, 22000 Sidi Bel Abbes, Algeria
Raul D.S.G. Campilho: ISEP-School of Engineering, Polytechnic of Porto, Porto, Portugal
Abstract
This paper presents an optimized design approach for hollow-structured fan blades, aiming to improve both fatigue life and weight reduction. The design process incorporates static and dynamic analyses to evaluate fatigue loads, structural stability, and key design variables for hollow structures. The model focuses on the PW-4000 engine fan blade, utilizing Ti-4Al-6V alloy and an e59 airfoil profile. Stress, modal and fatigue analyses confirmed structural safety under high-speed rotation and identified critical factors influencing fatigue life. The optimization employed the Box-Behnken design and the modified extensible lattice sequence (MELS) method to refine the blade's cross-sectional shape. The third iteration of optimization achieved the best performance, balancing a target fatigue life of over 10,000 cycles and weight reduction. The study emphasizes that optimizing the blade's internal structure can enhance reliability while maintaining lightweight design goals, minimizing both overdesign and the risk of structural failure.
Key Words
fan blade optimization; fatigue life; hollow structure design; structural safety; weight reduction
Address
Jinung Lee, Sejin Ki, Sunghun Kim, Yonggyung Shin: School of Aerospace and Mechanical Engineering, Korea Aerospace University, 76 Gonghangdaehak-ro, Deokyang-gu, Goyang, Gyeonggi 10540, Republic of Korea
Seongpil Cho: Department of Aeronautical and Astronautical Engineering, Korea Aerospace University, 76 Gonghangdaehak-ro, Deokyang-gu, Goyang, Gyeonggi 10540, Republic of Korea
