Development of a Formwork Deflection Measurement System for Construction Site Safety and Quality Assurance

Abstract. In this study a low-cost real-time monitoring system to detect deflection of scaffolding for the formwork is designed and it is implemented on construction sites. The developed system uses HC-SR04 ultrasonic distance sensors to measure the distance between the ground and the ceiling formwork. Successive distance measurements relieve the deflection of scaffold components and the data is transmited to a central computer via 433 MHz RF modules. The distance measurements are based on the speed of sound and in order to enhance the accuracy of the measurements a DHT11 temperature sensor is incorporated into the system to account for temperature induced changes in speed of sound. The use of low-cost, easily replaceable sensors ensures usability of the developed system on construction sites where against environmental conditions such as physical impacts and heavy dust are commonly encountered. The ultrasonic sensors are activated sequentially to reduce interference and more accurate distance measurements are obtained. The system is designed to ensure easy installation which makes it adaptable to various construction environments. The distance data collected by the sensors are processed through a central computer. Recent measurements with baseline data gathered at the beginning of the concrete placement process are compared. This assists detecting significant changes on the scaffolding system such as excessive settlement or deformation, which could jeopardize the safety of the formwork structure. The proposed system offers an efficient, cost-effective, and scalable solution for real-time monitoring of the deflection of the scaffolding for the formwork. Consequently it ensures structural stability, construction safety, and quality of concreting tasks.