Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening of damaged concrete columns due to its excellent material properties. Most of the existing compressive strength models for FRP-confined concrete columns have been established through regression analyses of experimental data, and only a few models were established based on theoretical derivation. Therefore, to extend these compressive strength models based on theoretical derivation, a new strength model based on the Drucker-Prager yield criterion was established in this article, which is suitable for predicting the strength of FRP-confined circular and square concrete columns with loaddamaged, fire-damaged and strain rate. To study the strength model of FRPconfined concrete columns, the author collected 675 test data from published literature and built a large database containing cross-section type, damage type, damage degree and strain rate. In this database, most of the existing strength models in the published literature and the model proposed in this article were evaluated. The evaluation results show that the model can accurately predict the compressive strength of FRP-confined circular and square concrete columns with undamaged, load-damaged, fire-damaged and strain rate.

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Ultra-high-performance concrete (UHPC) has the advantages of high compressive and tensile strength, high bending strength, good durability, remarkable corrosion resistance, and low self-weight. In this study, ten UHPC specimens were designed based on three fundamental parameters, including the ratio of the gross supporting area Ab to the bearing plate area Al (local area aspect ratio Ab/Al), the ratio of core area Acor to the bearing plate area Al (core area aspect ratio Acor/Al,), and the reinforcement ratio pv, to investigate mechanical behaviors and bearing capacity. Failure modes, cracking load, crack propagation, wedge features, the relationship between local compression and deformation, and the local bearing capacity was investigated. Finite element models (FEMs) were built to simulate and validate the observed behavior of the anchorage zone under compressive loading. The experiment results demonstrate that the pv significantly increases the bearing capacity. When the reinforcement ratio increased from 4.5% to 3.7%, the bearing capacity increased by 23%, and the effect of Acor/Al was not obvious. In addition, decreasing the Ab/Al from 11.1 to 6.3 increases the bearing capacity to 19%. Furthermore, a model was proposed to predict the bearing capacity of the UHPC specimens reinforced with stirrups. The calculated values, numerical predictions, and experiment results showed good agreement.

<p>This paper investigated the seismic performance of steel frames under earthquake motion. Two- story steel frames were designed based on a code-design method for a medium and high-risk seismic zone. The frame's nonlinear static and dynamic analyses have been performed using OpenSees software and sap2000. We consider diverse configurations, concentrated plasticity, and fiber-model were employed. The results obtained in the analytical study concluded that the user design method was reasonable and the mean maximum drift of the frames under the ground motion sets was in an acceptable range.</p>