Lateral load design of tall buildings

Abstract

Because of the wish for, and the necessity of the multiple use of space the amount of tunnels and buildings in close proximity of roads are increasing. Meanwhile the number of transports of dangerous goods is also increasing. Therefore it would be desirable to have a highway network which is fully accessible for the transport of dangerous goods. In order to make this possible the effect of an incident with dangerous goods on the buildings along the road should be known. This study focuses on the effect of an explosion blast on a building. It aims to propose a method to determine this effect, and to propose several structural solutions for buildings, situated alongside the road, to make them more resistant against the blast load from an explosion on the road as a result of an incident with an LPG tank truck. Of all the possible situations on the Dutch highway network some are discussed and three are chosen to study the effect of an explosion. These situations are: in the tunnel, at the tunnel mouth and on the open road with buildings beside the road. Of all types of explosions and effects that can occur, this study only focuses on the effect of a blast wave on a building as a result of a BLEVE of an LPG tank truck of 50 m3. A BLEVE is a Boiling Liquid Expanding Vapour Explosion. The to liquid compressed gas will evaporate explosively when the vessel ruptures, which results in a blast wave. The overpressure at the building can be schematised by in instant increase of the pressure to the peak overpressure, after which it decreases linearly to zero after a certain positive phase duration. The impulse is the surface under the pressure-time curve. An explosion in a tunnel results in the building-up of pressure. To determine how the overpressure exits the tunnel and reaches the building, an estimation of the increase of volume and the wave front surface is made. For an explosion in the open field five different methods are discussed. These range from a TNT equivalence method to a gas-dynamic modelling. The calculated values for the overpressure differ a lot and not all methods give a value for the impulse. Based on the described methods it is concluded that an explosion on the open road gives a larger blast load on the building than an explosion in the tunnel or the tunnel mouth. The blast-wave of an explosion of an LPG tank truck can cause damage to the buildings. Several aspects of the blast-wave are discussed, and how they determine the load that is transferred to the main load bearing structure. These aspects are among others the reflection, dynamic blast load, adjacent buildings, distribution of the blast load on the façade of a building, and glass failure. For several of these aspects methods are given to determine the load on the building. The peak reflected overpressure on a defined model building of 35 m high is 101 kPa and the impulse is 1,97 kPa*s. After this the mechanical properties of a building as a whole and of the building elements that determine its response to this load are determined. These are the static strength, natural frequency and ductility. After the loading, all the response aspects and the structural properties are determined and an estimation of the damage to the building and its elements is given with methods that calculate the chance of collapse, the equivalent static load and the required ductility. From sensitivity analyses of the damage methods it is concluded that it is possible to make a building able to withstand the blast from an LPG explosion by choosing the right parameters. The most sensitive parameters of the blast load and the mechanical properties of the building are the tank volume, the distance to the explosion, the horizontal design load and the height of the building. A higher building results in a larger design load and a smaller angular rotation.