Abstract One of the main concerns about FRP-reinforced concrete (RC) structures is the performance of the FRP reinforcement under fire exposure. Previous studies showed that fire resistances above 90 min can be attained if proper anchorage of the rebars is provided and splicing is avoided along spans exposed to fire. However, this topic has not yet been investigated in a comprehensive way. This paper presents experimental investigations on the fire resistance of concrete slab strips reinforced with sand-coated GFRP bars. GFRP-RC (and steel-RC) slab strips were simultaneously subjected to the ISO 834 standard fire and a sustained service load applied in four-point bending. The influence of the following parameters was assessed: (i) concrete cover (2.5 cm and 3.5 cm); (ii) presence of lap-splices with different overlapping lengths (30 cm to 65 cm) directly exposed to fire, and (iii) concrete strength. The results obtained confirm that GFRP-RC slabs can attain relatively long fire resistances provided that the anchorage zones of the rebars (where temperatures were continuously monitored), remain sufficiently cold: the average temperature of the reinforcement along the anchorage length was kept below 108 °C in all tests, slightly above the Tg of the rebars (98 °C). The slab strips reinforced with continuous GFRP rebars attained fire resistances between 80 min and 150 min, failing due to tensile rupture of the reinforcement at midspan for temperatures in the rebars above 570 °C, long after the bond to concrete was lost in most of the heated span. For slab strips with bar splices exposed to heat, the fire resistance was reduced to less than 20 min, highlighting the remarkable impact of this constructive detail on the fire performance. For 30 cm long lap splices, premature failure occurred due to slippage in the splices for a temperature (105 °C) close to the Tg; in slabs with longer overlap lengths, slippage occurred for moderately higher temperatures (146 °C to 176 °C). As expected, the increase in concrete cover, provided an additional thermal protection to the rebars, but resulted only in a slight fire resistance increase. Slab strips with lower concrete strength presented lower fire resistance, due to more extensive cracking, which led to higher (localized) heating of the reinforcement.

中文翻译：

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涂砂GFRP筋加固混凝土板条的防火性能

摘要 FRP 钢筋混凝土 (RC) 结构的主要关注点之一是 FRP 钢筋在火灾暴露下的性能。先前的研究表明，如果提供适当的钢筋锚固并避免沿暴露于火灾的跨度拼接，则可以达到 90 分钟以上的耐火性。然而，这个话题还没有得到全面的研究。本文介绍了用砂涂层 GFRP 钢筋加固的混凝土板条的耐火性试验研究。GFRP-RC（和钢-RC）板条同时经受 ISO 834 标准火灾和四点弯曲应用的持续服务载荷。评估了以下参数的影响：（i）混凝土覆盖层（2.5 厘米和 3.5 厘米）；(ii) 存在不同重叠长度（30 厘米至 65 厘米）的搭接接头直接暴露在火中，以及 (iii) 混凝土强度。获得的结果证实，GFRP-RC 板可以获得相对较长的耐火性，前提是钢筋的锚固区（连续监测温度）保持足够冷：沿锚固长度的钢筋平均温度保持在 108°以下在所有测试中为 C，略高于钢筋的 Tg (98 °C)。用连续 GFRP 钢筋加固的板条在 80 分钟到 150 分钟之间达到了耐火性，由于钢筋在跨中的拉伸断裂，钢筋温度高于 570 °C，在大部分时间与混凝土的粘合消失很久之后加热跨度。对于带有暴露于热的钢筋接头的板条，耐火性降低到不到 20 分钟，突出了这一结构细节对防火性能的显着影响。对于 30 cm 长的搭接接头，由于接头在接近 Tg 的温度 (105 °C) 内滑动而发生过早失效；在重叠长度较长的板坯中，在适度较高的温度（146 °C 至 176 °C）下会发生滑动。正如预期的那样，混凝土覆盖层的增加为钢筋提供了额外的热保护，但仅导致耐火性略有增加。混凝土强度较低的板条具有较低的耐火性，这是由于更广泛的开裂，导致钢筋的（局部）加热更高。由于在接近 Tg 的温度 (105 °C) 下接头滑动而导致过早失效；在重叠长度较长的板坯中，在适度较高的温度（146 °C 至 176 °C）下会发生滑移。正如预期的那样，混凝土覆盖层的增加为钢筋提供了额外的热保护，但仅导致耐火性略有增加。混凝土强度较低的板条具有较低的耐火性，这是由于更广泛的开裂，导致钢筋的（局部）加热更高。由于在接近 Tg 的温度 (105 °C) 下接头滑动而导致过早失效；在重叠长度较长的板坯中，在适度较高的温度（146 °C 至 176 °C）下会发生滑动。正如预期的那样，混凝土覆盖层的增加为钢筋提供了额外的热保护，但仅导致耐火性略有增加。混凝土强度较低的板条具有较低的耐火性，这是由于更广泛的开裂，导致钢筋的（局部）加热更高。但仅导致耐火性略有提高。混凝土强度较低的板条具有较低的耐火性，这是由于更广泛的开裂，导致钢筋的（局部）加热更高。但仅导致耐火性略有提高。混凝土强度较低的板条具有较低的耐火性，这是由于更广泛的开裂，导致钢筋的（局部）加热更高。