The Development of Penetration Charges for Increasing the Efficiency of the Interventions of Fire Rescue Service Units

During building fires is often necessary to deliver nozzles with water to the desired point of intervention and the wall or ceiling must be penetrated for energy supply and the entrance of persons. Access openings for extinguishing are created with hand tools or explosives, but it is a very time-consuming activity and fragmented material may endanger persons. Another possibility is the use of charges with a water layer, which absorbs the shock wave of the explosion at the back and at the same time significantly suppresses the fragmentation of the building element on which the charge acts. The penetration charge developed in two versions allows a sufficient penetration of the partitio

Optimization approaches for standard repairs in a concrete element

After extreme events, structural elements can result damaged and repairs are needed to restore safe functionality of structure. This thesis investigates the design approaches for typical repairs in concrete elements. A methodology for automatic design and cost estimation of common elements will be developed, which is useful for decision taking in performance-based design

Study on the dynamic response of subway tunnel by viaduct collapsing vibration and the protective measures of reducing vibration

Collapsing vibration caused by demolition blasting of buildings has large effect on the buildings and underground structures nearby. Combined with the demolition blasting of a viaduct, numerical simulation was carried out to investigate dynamic response of subway tunnel subjected to collapsing impact load. The paper put forward composite protective structures of steel-rubber tires and makes safety checking calculation of the subway tunnel on the basis of composite protective measures by numerical simulation. In order to ensure the safety and stability of subway tunnel in the practical operation of demolition blasting of the viaduct, the composite protection system was further optimized, which may provide a good reference for the related engineering practices

Numerical simulation on ground vibration caused by the demolition of a 200 m high chimney

A chimney-soil model was built using finite element method to simulate the demolition of a chimney and the subsequent ground vibration. The acceleration history of ground vibration at observed point was obtained. The simulated results were compared with on-site measured data and good agreement was found with errors of less than 2.88 % for maximum acceleration amplitudes. It was also demonstrated that the element disappearance in the model did not affect the vibration response

Full Scale 13-Story Building Implosion and Collapse: Effects on Adjacent Structures

Two dormitory halls at the University of Nebraska-Lincoln known as Cather and Pound halls were demolished via controlled implosion on December 22, 2017. Cather and Pound halls were two thirteen-story reinforced concrete structures. The demolition of these two structures included the implosion of controlled charges at selected columns on alternating floors which initiated the progressive collapse of these structures. Three nearby structures in the vicinity of Cather and Pound halls were instrumented with high sensitivity uniaxial piezoelectric accelerometers to record the response of the adjacent structures during the event of the implosion and the progressive collapse. While these two thirteen-story reinforced concrete structures were also instrumented with sacrificial accelerometers to record the real-time response of the structures during implosion and progressive collapse, the focus of this thesis is the responses observed at the adjacent structures during the demolition sequence. The primary objective is to understand how a group of nearby structures response and interact during the implosion and progressive collapse of multistory buildings. To this end, ground motion parameters at three free field positions nearby these adjacent structures have been quantified to observe the variation of free field ground motions during the demolition event. Likewise, the acceleration response data obtained from adjacent structures and free field positions have been analyzed in the time and frequency domains. The analysis of response data has also been presented separately in terms of the blast and collapse sequence to differentiate and understand the response of adjacent structures during the blast and progressive collapse of the two 13-story reinforced concrete structures. An input-output study of the responses observed within three adjacent structures with respect to the ground motion recorded at free field positions indicated that secondary effects, such as the air wave generated by the blast, contributed to the structural response. Two of the adjacent structures are numerically modeled with a lumped mass approach in LS-DYNA, and the responses of these numerical models are compared to the experimental recordings. The numerical study further emphasized the significance of the air wave. Advisor: Christine E. Wittich and Richard L. Woo

Numerical and experimental verification of finite element mesh convergence under explosion loading

Explosions inflict severe damage to building structures and threaten national security as well as social stability; their scope of impact and damage level is subject to the energy contained in the shock waves. Explosion testing is limited by the test site and amount of explosive used; a large scale explosion test is not viable. Therefore, numeric analysis is adopted as the preferred research method instead of an actual field test. The application of finite element analysis requires consideration of the complexity of an analysis model and the mesh density. An explosive load violent enough to cause distortion to mesh cannot reveal the actual mechanical behavior and will compromise the convergence and accuracy of the results. The purpose of this study is to analyze the optimal mesh density of the finite elements under an explosive load, in order to explore the element mesh convergence and to compare the results with the experimental. The results of this study can reasonably simulate an explosion effect, achieve the convergence as indicated by calculation results, and provide a foundation upon which future dynamic mechanic studies may establish numerical models. To enhance the calculation accuracy, this study adopts a fluid dynamic analysis program, LS-DYNA, finite element analysis software, to conduct Fluid-Solid Interaction (FSI). A TNT free-field explosion simulation is analyzed for mesh density convergence under an explosive load. The analysis results reveal a pattern where the shock wave diminishes as it moves further away from the explosion point. The results may serve as reference for studies involving the numeric analysis of explosions