Distribution of load effects and reliability of reinforced concrete frames: intact and with columns removed

Abstract

The design of reinforced concrete (RC) frames is made on a member-by-member basis. Similarly, in the literature, the reliability of RC beams and columns is often studied in isolation from the rest of the structure. Yet, in the construction of regular frames, symmetry and regularity are often exploited, resulting in the same design for each element type. This is despite of different load effects on different parts of the structure, which leads to significant variations in the failure probability of the elements. Hence, in this paper, we investigate the reliability of members and the distribution of load effects in regular RC frame buildings, considering intact and column loss cases, where symmetry is lost. Results show that the ratios of normal-to-bending loads change significantly along building height, and this has a significant impact on reliability of individual columns.

Reliability analysis of reinforced concrete frames subjected to post-construction settlements

“…The example used to evaluate structural safety is a four floors plane frame, as described in Facholli and Beck [4]. Figure 2 presents the geometry of the structural frame, which has three spans of 5 meters and a floor height of 3 meters.…”

“…All elements were considered to be constituted by a concrete with characteristic compressive strength of 30 MPa, and tangent and secant modulus of elasticity according to item 8.2.8 of ABNT NBR 6118 [13] (granite type aggregate). The beams are subjected to a live load to dead load ratio of 0.61 (𝐷𝐷 𝑘𝑘 = 26.38 𝑘𝑘𝑘𝑘/𝑚𝑚, 𝐿𝐿 𝑘𝑘 = 16 𝑘𝑘𝑘𝑘/𝑚𝑚) as described in Facholli and Beck [4]. The live loads are established considering a residential building, with the rooms classified as "Pantry and laundry area", with 2.0 kN/m 2 .…”

“…For permanent loads, a total of 3.30 kN/m 2 is considered. The building slabs have a thickness of 0.10 meters [4]. It is worth noting that usual cases of the 𝐿𝐿/𝐷𝐷 ratio for reinforced concrete beams of buildings can vary between 0.1 and 0.60 [17].…”

“…Some authors have dedicated themselves to studying and evaluating the safety level of existing structures using such a theory. Works such as Facholli and Beck [4] and Beck et al [5] have employed reliability theory to evaluate the safety level in structural element loss events. Küttenbaum et al [6], Mankar et al [7] and Souza et al [8] evaluated the variations of the mechanical properties of materials and their impact on the system's reliability in situations of structure use.…”