Repeated Loading Behavior of CFRP-Strengthened Continuous RC Beams: Experimental Investigation, Finite Element Analysis, and Predictive Modeling

Abstract

This study investigates the repeated-loading performance and moment redistribution of continuous reinforced concrete (RC) T-beams strengthened with carbon fiber-reinforced polymer (CFRP) using a combined experimental and numerical approach. The experimental part studies the effect of reinforcement percentage and the CFRP strengthening configuration, while the FE model validates the effect of compressive strength of concrete, ratio of span to depth, CFRP reinforcement percentage, CFRP length percentage, loading frequency, and yield strength of steel on the behavior of the structure under repeated loadings. Five half-scale two-span RC T-beams having different reinforcement percentages and CFRP configurations were experimentally tested under repeated loading. CFRP strengthening increased load capacity by up to 16% and improved ductility, energy dissipation, stiffness degradation, and crack distribution; noticeable benefits were observed with the hybrid-strengthening system. The maximum ductility ratio increased from 2.7 in the control beam to 4.8 in the reinforced beams. In summary, the conflict between the stiffening effect and rotational capacity was found to be the key factor controlling the moment redistribution process. Three-dimensional non-linear finite element (FE) modeling was performed, which showed good agreement with the experimentally obtained load-displacement curve, stiffness degradation, strain evolution, and cracking pattern trends. Utilizing the validated FE database, a predictive model based on multiple regression analysis with a power-law multiplicative formulation was constructed. ABSTRAK: Kajian ini menyiasat prestasi berterusan rasuk T konkrit bertetulang (RC) yang diperkukuh menggunakan polimer gentian karbon (CFRP) di bawah beban berulang, serta tingkah laku pengagihan semula momen melalui gabungan pendekatan eksperimen dan numerik. Pengaruh nisbah tetulang dan konfigurasi pengukuhan CFRP dinilai melalui eksperimen. Manakala model unsur terhingga (FE) digunakan bagi mengesah kesan kekuatan mampatan konkrit, nisbah rentang kepada kedalaman, nisbah tetulang CFRP, nisbah panjang CFRP, frekuensi pembebanan, dan kekuatan luluh keluli terhadap tindak balas struktur di bawah pembebanan berulang. Lima rasuk T (RC dua bentang) berskala separuh dengan nisbah tetulang dan konfigurasi CFRP berbeza telah diuji secara eksperimen di bawah beban berulang. Penggunaan pengukuhan CFRP meningkatkan kapasiti beban sehingga 16% serta menambah baik kemuluran, pelesapan tenaga, degradasi kekakuan, dan taburan retakan, dengan prestasi terbaik dicapai pada konfigurasi pengukuhan hibrid. Nilai maksimum nisbah kemuluran meningkat daripada 2.7 bagi rasuk kawalan kepada 4.8 bagi rasuk pengukuhan. Secara keseluruhan, dapatan menunjukkan bahawa keseimbangan antara peningkatan kekakuan dan kapasiti putaran merupakan faktor utama mengawal proses pengagihan semula momen. Pemodelan tiga dimensi unsur terhingga (FE) tak linear menunjukkan padanan baik dengan dapatan eksperimen dari segi lengkung beban–sesaran, degradasi kekakuan, evolusi regangan, dan corak keretakan. Berdasarkan pangkalan data FE yang telah disahkan, satu model ramalan berasaskan analisis regresi berganda menggunakan formulasi hukum kuasa multiplikatif telah dibangunkan.