Experimental investigation of shear behavior in deep flexural members exposed to elevated temperatures

Abstract Fires frequently affect building structures, yet the mechanical behavior of deep flexural members, especially after exposure to high temperatures, remains inadequately understood. Current design codes for concrete structures at ambient temperatures do not sufficiently account for the residual capacity of these members following fire‐induced damage. Given the specific and complex mechanical properties of deep flexural members, particularly under varying shear span and shear‐depth ratios, a gap exists in predicting their post‐fire performance. Addressing this gap is critical to improving the safety and resilience of fire‐exposed structures. Here, the shear behavior of eight deep flexural members was experimentally investigated at both normal temperatures and post‐high‐temperature conditions (200°C, 350°C, and 500°C). The specimens were subjected to tests with shear span ratios between 0.3 and 1.2, and shear‐to‐depth ratios of 2 and 3. Key performance metrics—including failure modes, ultimate bearing capacity, load‐deflection relationships, steel strain, and maximum crack width—were analyzed. Additionally, the empirical formula in existing design codes was modified using a layered method to better predict the residual shear capacity of deep flexural members after fire exposure. The results demonstrate that high temperatures and shear span ratios significantly affect shear performance. Shear capacity initially improved and then declined as temperature increased. A higher shear span ratio intensified bending effects, transitioning failure modes from shear failure to bending‐shear failure, and progressively reduced ultimate bearing capacity. The proposed empirical formula provides a reliable means of calculating or predicting the residual bearing capacity of fire‐damaged deep flexural members, offering sufficient safety margins. These findings contribute to refining post‐fire structural assessments and enhancing building safety.