Prestressed continuous composite beams (PCCBs) have been widely used in constructions. While the open literature contains notable works that examine the behavior of PCCBs at ambient conditions, the behavior of these members at elevated temperatures has rarely been addressed. As such, this paper focuses on investigating fire resistance of PCCBs by means of advanced numerical simulation. For this purpose, a finite element model was developed to predict the fire response of PCCBs and this model was validated through utilizing actual observations from newly conducted fire tests. Furthermore, a series of parametric studies were carried out to investigate the effect of key parameters on fire response of PCCBs. These parameters include magnitude of applied load, prestressing level, size of external tendons and ratio of span to depth of cross section. The outcome of this parametric study shows that the load ratio has an adverse influence on the fire resistance of PCCBs. For instance, the greater the magnitude of applied loading was, the slower the transient prestress in the external tendons decreased with increasing temperature, and the lower the critical temperature was. Further, when temperature was below 375°C, the larger the prestress ratio was, the slower the deflection increasing rate was. Calculated sagging moment capacity gradually decreased with the temperature rise, reaching the minimum at 150°C, then the moment increased with the increase of temperature. Meanwhile, hogging moment at middle support increased with the increase of temperature during the initial heating phase, then gradually decreased with increasing temperature. For PCCBs with different span-to-depth ratios, the difference of critical temperatures was negligible when the load ratio was constant, and their deflections were very close. When the ratio of span to depth was > 10, the effect of span-to-depth ratios on behavior of PCCBs can be ignored.

中文翻译：

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预应力连续钢-混凝土组合梁耐火性能数值研究

预应力连续组合梁（PCCBs）已广泛应用于建筑中。虽然公开文献中包含了一些着名的工作，这些工作检查了 PCCB 在环境条件下的行为，但很少涉及这些成员在高温下的行为。因此，本文侧重于通过先进的数值模拟研究 PCCB 的耐火性。为此，开发了一个有限元模型来预测 PCCB 的火灾响应，并通过利用新进行的火灾测试的实际观察来验证该模型。此外，还进行了一系列参数研究，以研究关键参数对 PCCB 火灾响应的影响。这些参数包括施加载荷的大小、预应力水平、外部钢筋束的尺寸以及跨度与横截面深度的比率。该参数研究的结果表明负载比对 PCCB 的耐火性有不利影响。例如，外加载荷的大小越大，外筋中的瞬态预应力随温度升高而降低的越慢，临界温度越低。此外，当温度低于375℃时，预应力比越大，挠度增加速度越慢。计算的下垂弯矩能力随着温度的升高逐渐减小，在150℃时达到最小值，然后随着温度的升高而增大。同时，在加热初期，中间支撑处的中拱力矩随着温度的升高而增加，然后随着温度的升高而逐渐减小。对于具有不同跨深比的 PCCB，当载荷比恒定时，临界温度的差异可以忽略不计，并且它们的挠度非常接近。当跨深比 > 10 时，跨深比对 PCCB 行为的影响可以忽略不计。