Comparison of the seismic and wind analyses of two tower cranes

Abstract

Tower cranes act as essential support equipment for the development of the city’s construction projects, not only for new projects but also in the rehabilitation of old structures. In the present study, we analyze and compare two different tower cranes, where the differences are essentially based on the geometry, weight, and consequently the reach and load capacity of each structure. In general, these types of structures correspond to slender steel structures designed to carry high loads. Despite the great importance given to these structures, many disasters have occurred causing damage to people or to urban equipment in the vicinity due to total or partial collapse. We developed a 3-D mathematical linear model of the structures in SAP2000 and compared the analytical frequencies with in situ measurements. The maximum error for the first two translationally identified modes in the x and y directions was 4.9 %. These structures are very flexible, with frequencies below 0.5 Hz. We then applied and evaluated the impact of two types of exceptional action, seismic (maximum reference acceleration of 1.5 m/s2 and 1.7 m/s2) and wind load characteristics of an urban area (surrounded by buildings), for the two structures not carrying any load. The effects resulted in no serious consequences, with wind being the most severe action in certain cross-sections and seismic action in others. One very important and innovative aspect of this study was the in situ characterization of the frequencies and the verification that the mathematical model reproduced the behavior of the real structure very well. We complemented this study by measuring four more structures and proposing a law to estimate the frequency as a function of the length of the tower plus jib. However, we also found from a literature review of recently published work that, contrary to the six structures that we analyzed, it is difficult to extrapolate this law for other types of tower cranes.