## 1 Introduction  
Seismic design and construction technologies have improved considerably over the years, but unexpected earthquake damage to reinforced concrete (RC) structures continues to occur. In previous earthquakes (e.g., the Chi-Chi earthquake in Taiwan (1999), Maule earthquake in Chile (2010), and Pohang earthquake in South Korea (2017)), many researchers have attributed the undesired failures in some RC structures to construction quality defects, including poor quality materials and inadequate reinforcement details [1; 2; 3]. Typical types of failures due to poor construction practices during earthquake loads include: (i) brittle shear failure of columns and/or beams due to insufficient shear reinforcement [4; 5], and (ii) buckling of longitudinal bars or shear failure in beam-column joints due to inadequate spacing or lack of transverse stirrups [6; 7; 8]. In particular, the Pohang earthquake (\(\mathrm{M_{w}}\) 5.4) was the most damaging event in South Korea due to the relatively shallow depth (7 km) and the location in the Pohang basin which consists of non-marine to deep marine sedimentary strata. The most structural damage was caused by poor construction practices of pilot-type low-rise RC buildings and schools. As shown in Figure 1, the failure of many RC columns in the seismically designed buildings was observed due to excessive concrete cover, the inclusion of drainage pipes in the column members, the inadequate spacing of the shear reinforcement, or the poor anchorage of ties. The seismic vulnerability of RC structures can increase significantly due to the uncertainties of material strengths and section properties caused by construction practices. All construction processes, including manufacturing, transporting, and pouring, can affect the quality of the material, and aging can degrade its strength. The shear and flexural strengths of members can be also significantly reduced due to the wide tie spacing and the cover thickness, respectively. Many studies have been published concerning the sensitivity of the seismic demand or fragility to the modeling parameters of RC structures. In the literature, materials, modeling strategies, and geometric configuration have been considered as uncertain variables and their tangible impact on seismic vulnerability has been revealed through sensitivity and reliability analyses [9; 10; 11; 12]. For example, [PERSON] and [PERSON] [4] analyzed the sensitivity of concrete strength, yield strength, and damping ratio on the seismic response of staggered wall structures. The Tornado Diagram Method (TDM) and First Order Second Moment (FOSM) method were employed to assess the sensitivity of modeling uncertainties. It was concluded that the sensitivity of each material uncertainty could depend on the ground motion intensity, while damping ratio variation could be more sensitive regardless of its intensity. In addition to structural variables, the effect of ground motion was evaluated as well [13; 14; 15; 16]. [PERSON] and [PERSON] [15] showed that the seismic vulnerability of bridge components could be notably affected by the uncertainty in ground motion rather than geometric or modeling uncertainties. Both [PERSON] and [PERSON] [13] and [PERSON] and [PERSON] [14] carried out sensitivity analyses of uncertainties in materials, structural properties, and ground motion for RC frames through the FOSM method. It was reported that the uncertainty in seismic loads is more important than uncertain structural variables in terms of the effects on the vulnerability of the analyzed structures. However, a very limited number of studies have investigated the effect of construction quality defects on the seismic vulnerability of RC structures. For instance, [PERSON] and [PERSON] [17] evaluated the effect of construction quality variability on the seismic behavior of a six-story RC structure. The variabilities in the construction quality accounting for the material and structural detailing were categorized into three levels, 'poor', 'average', and 'good'.