A high percentage of reinforced concrete (RC) buildings in Portugal were designed and built before the introduction of modern seismic codes. This research aims to assess the seismic capacity and vulnerability of RC buildings in the city of Lisbon. For that purpose, nonlinear static procedures have been used and fragility curves have been developed. These buildings are reaching the end of their nominal life. Therefore, ageing effects have been taken into account, as well as the presence of smooth rebar. To do so, a sensitivity analysis has been performed by considering the chloride-induced corrosion of the reinforcement steel rebar and the degradation of the concrete cover. To illustrate the effects of ageing and the procedure adopted for the seismic fragility assessment of old RC structures, three RC buildings with masonry infills have been selected as case studies. They were all built between 1960 and 1980, and they are representative of the current building stock in Lisbon. The seismic capacity of the buildings has been determined by means of nonlinear static analyses of three-dimensional numerical models. The N2 method and its extended version have been considered to determine the target displacement. The seismic safety of the buildings has been estimated in terms of the demand/capacity ratio for each vertical structural element (columns and walls) according to the bending and the shear failures. Then, a set of fragility curves has been developed for all buildings to represent the probability of RC elements reaching or exceeding the significant damage limit state. Results have shown that the concrete strength degradation has had more influence than reduction of the rebar diameter in the seismic capacity. When considering steel corrosion, it has been demonstrated that the corrosion rate has reduced the capacity more than the time of exposure. It can be concluded that ageing affects the seismic behaviour of RC structures, increasing the vulnerability of these buildings.

在引入现代地震法规之前，葡萄牙设计和建造了很大比例的钢筋混凝土（RC）建筑物。这项研究旨在评估里斯本市钢筋混凝土建筑的抗震能力和脆弱性。为了这个目的，已经使用了非线性静态程序并且已经开发了脆性曲线。这些建筑物的使用寿命即将结束。因此，已经考虑到了老化效应以及光滑钢筋的存在。为此，已经通过考虑氯化物引起的钢筋钢筋腐蚀和混凝土表层的退化进行了敏感性分析。为了说明老化的影响以及旧钢筋混凝土结构的地震脆性评估所采用的程序，案例研究选择了三座带有砖石填充物的RC建筑物。它们全部建于1960年至1980年之间，代表了里斯本目前的建筑存量。通过三维数值模型的非线性静态分析确定了建筑物的抗震能力。已考虑使用N2方法及其扩展版本来确定目标位移。根据弯曲和剪切破坏，根据每个垂直结构元件（柱和墙）的需求/承载力比率，估算了建筑物的地震安全性。然后，为所有建筑物绘制了一组脆性曲线，以表示RC元素达到或超过重大破坏极限状态的可能性。结果表明，混凝土强度的下降比减小钢筋直径对抗震能力的影响更大。当考虑钢的腐蚀时，已证明腐蚀速率与暴露时间相比降低的能力更大。可以得出结论，老化会影响钢筋混凝土结构的抗震性能，从而增加这些建筑物的脆弱性。