Automation in Construction xxx (xxxx) xxx Please cite this article as: Xuhong Zhou, Automation in Construction, https://doi.org/10.1016/j.autcon.2020.103468 0926-5805/© 2020 Elsevier B.V. All rights reserved. Automated locating of replaceable coupling steel beam using terrestrial laser scanning Xuhong Zhou a, b , Jiepeng Liu a, b , Guozhong Cheng a, b, * , Dongsheng Li a, b, * , Y. Frank Chen c a Key Laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University), Ministry of Education, Chongqing 400045, China b School of Civil Engineering, Chongqing University, Chongqing 400045, China c Department of Civil Engineering, The Pennsylvania State University, Middletown, PA 17057, USA A R T I C L E INFO Keywords: Replaceable coupling steel beam Terrestrial laser scanning Automated locating Bolted connection ABSTRACT The replaceable coupling steel beam (RCSB) is an optimal component of earthquake-resilient structures. In practice, the RCSB is connected to RC shear wall using numerous bolts with a small construction tolerance of 2 mm. However, conventional methods to locate the bolt holes are mainly manual and rely on an approximate measurement, thus time-consuming and subjective. Addressing this issue, this paper describes a fully-automated method to locate the bolt holes in RC shear walls using the terrestrial laser scanning. Specifcally, the bolt holes can be frst detected by an effective boundary detecting technique and then accurately ftted with a robust random sample consensus algorithm. The proposed technique is validated with the experimental results including the radius and relative position estimations of bolt holes. The fully-automated method can therefore be adopted to locate the RCSBs. 1. Introduction The reinforced concrete coupled shear wall (RCCSW) is an effcient structural system for resisting lateral forces, which has been widely used in high-rise buildings [1–3]. The RCCSW system consists of two indi- vidual reinforced concrete (RC) shear walls connected by the coupling beams (CBs) positioned along the wall height, as shown in Fig. 1. The CBs are expected to undergo signifcant inelastic deformation and dissipate earthquake-induced energy. For an earthquake resilient structure, it is anticipated that the damaged CBs are replaceable after a severe earthquake. However, the repair of damaged CBs can be very costly and even impractical, especially for cast-in-place RC structures [4,5]. To improve the repairability of CBs, the replaceable coupling steel beam (RCSB) has been proposed and shown to be effective [6,7]. Two main types of the connection between the RCSB and RC shear walls are illustrated in Fig. 1. In practice, the RCSBs are connected to RC shear walls using bolts with a small construction tolerance of 2 mm according to the Chinese code [8]. A large number of bolts are usually required to be placed simultaneously on a single steel plate, which complicates the on-site installation. The steel components must be of good quality to maintain the high stiffness and the on-site construction process is a chain of different tasks which should be followed with great precision. However, conventional methods for assessing the structural dimensions are mainly manual and rely on an approximate measurement, thus time- consuming, expensive, and subjective. Moreover, construction workers often have to manually adjust the hole diameters at the construction site for proper matching [9]. Therefore, a new assessment approach for RCSBs is warranted. For end plate connections (Fig. 1), a minor adjustment in y-axis direction is not allowed due to the required high stiffness in steel components, implying that a much higher degree of accuracy and precision is required. Addressing this issue, an U-shape plate connection is proposed in this study, where all bolt holes are on the same plane and an adjustment of 2 mm is permitted. To ft the RCSBs with U-shape plate to RC shear walls, all the bolt holes in the RC shear walls need to be accurately located and the RCSBs with U-shape plates can then be fxed and manufactured based on the measured positions of bolt holes. However, a fully-automated method for locating the bolt holes in RC shear walls is currently unavailable. The closely related work with this study is the virtual trial assembly technology on steel members with bolted connections (Fig. 2), where the dimensional assessment is based on the building information model (BIM) and the bolt holes are measured by the total station [10–12]. However, this approach is deemed non-automated. Photogrammetry is an optical measurement technique where the three-dimensional (3D) * Corresponding author at: Key Laboratory of New Technology for Construction of Cities in Mountain Area (Chongqing University), Ministry of Education, Chongqing 400045, China. E-mail addresses: chengguozhong@cqu.edu.cn (G. Cheng), lds@cqu.edu.cn (D. Li). Contents lists available at ScienceDirect Automation in Construction journal homepage: www.elsevier.com/locate/autcon https://doi.org/10.1016/j.autcon.2020.103468 Received 2 June 2020; Received in revised form 15 November 2020; Accepted 16 November 2020