## 1 Introduction  
Vertical members in a high-rise building, such as columns and shear walls, receive vertical loads that subsequently lead to axial shortenings of the members. Factors that influence the extent of the shortening of a vertical member include the stress ratio induced in the member during construction, the reinforcement ratio of the section, and other environmental conditions surrounding the member [1]. The vertical members in a high-rise building will not shorten by the same amount since the vertical members have different loading and design conditions, so differences between the amount of shortening of adjacent vertical components inevitably occur. This differential shortening can deteriorate the quality of construction by causing slab distortions, separation of elevator guiderail brackets, unexpected deformation of interior drywalls, and damage to cladding systems [2, 3]. In practice, to minimize the effect of differential shortening on structural and nonstructural elements, compensation for the estimated differential shortenings is made during construction [1]. Thus, during construction, to compensate for differential shortening, the formwork along one edge may be raised by the estimated amount of the differential shortening. However, it is almost impossible to accurately predict the amount of shortening through an estimation formula due to the idealization of material properties and the assumptions in analytical models [4, 5, 6]. Therefore, a field monitoring program is used to obtain actual shortenings of walls and columns and to compare them with the estimated shortenings. For a proper compensation of differential shortening [7, 8], the comparison between measured and estimated shortenings is made at selected floor levels, where strain sensors are installed, throughout the height of the building. There have been many cases in which the amount of shortening was measured in the process of constructing actual high-rise buildings [2, 9, 10, 11, 12, 13]. As shown in Figure 1, conventional field sensing systems for measurement of column shortenings during construction may fall into three categories. One method, for manual data acquisition, is to use a manual instrument to take direct measurements from each sensor [13]. A second method, for wired data acquisition, is to install a data logger on each floor where sensors are installed, connect the data logger and sensors with a cable, and connect this to the server for automatic measurement. The third method, for wireless data acquisition with a conventional data logger, is to connect the sensors and a conventional data logger with lengthy cables and then connect this to a wireless communication device to send to the server [12, 14]. In practice, the most widely used practice is to connect a local area network (LAN) or wireless communication device to the data logger to collect data automatically, such as in the second and third method. However, these methods necessitate connecting the sensors on each floor to the data logger with cables or wires, which can disturb the construction process and cause significant time and effort for management of lengthy cables. Additionally, no research on the automatic monitoring system for shortenings of vertical members in high-rise buildings during construction, which can confirm the data collected in the server in real-time for the prompt management as well as measure the shortenings automatically, has been reported. Therefore, to solve the problems associated with cables during construction and monitor the collected data in real-time, an automatic field monitoring system using a wireless sensor network (WSN) is necessary [15, 16, 17]. An automatic field monitoring system based on a WSN is convenient to install and manage during construction. Also, a lot of data can easily be measured from numerous sensors, and the extent of column shortenings in a high-rise building caneasily be analyzed according to the construction process. This can enhance the precision and safety of the construction of a high-rise building.