MS15.2 - Nonlinear Dynamics and Dynamic Stability

The occurrence of moderate to high-intensity earthquakes in countries like Chile and New Zeeland, has shown damage to well-detailed reinforced concrete wall buildings designed according to seismic-resistant regulations, which leads to a questioning about the level of damage that would be expected, in intermediate and high buildings structured with industrialized reinforced concrete walls, according to construction and design practice in Colombia, especially when considering the coupling provided by the floor system acting as a diaphragm. This study presents the nonlinear analysis of an intermediate building located in Bucaramanga, Colombia, a city in a high seismic hazard zone, with concrete walls well detailed with confined edge elements whose thicknesses are between 15 and 30 cm. The model consists of a three-dimensional computational representation in the OpenSees software of the building using the Multiple-Vertical-Line-Element-Model-3D (3D-MVLEM) for modeling the walls, which are connected through a four-node finite element called ShellNLDKGQ that represents the slab. The simulation of flexure-dominated reinforced concrete wall behavior which is characteristic of intermediate and high buildings is allowed by this model. Results from static nonlinear analyses, shows a twofold shear capacity due to the coupling effect to this building. In addition, they show that axial forces vary because of the shear transferred through the slab.

Abstract—This paper defines the methodology of designing Control Room Buildings for Vapor cloud explosion (VCE). Intensity of blast forces has not been standardized. Companies have their own specifications based on internal research relying on the interpretation of damages suffered in real life scenarios. There has been a paradigm shift in quantifying the blast forces over the years. While earlier design was based on equivalent static load approach for a blast force of 21 KN/sq.m, the current norms demand that the design to be based on impulse load that can reach up to 270 KN/sq.m Taking guidance from numerous publications - this paper demonstrates a step-by-step approach by idealizing the various components building as SDOF system, diaphragms and shear wall. A numerical integration approach has been adopted to determine the structural response for the dynamic load. The underlying philosophy is to make the building flexible enough to absorb the energy, and avoiding progressive collapse and retaining the basic integrity of the structure. In other words the building design has to be "Robust". Nonlinear characteristics of concrete strain and formation of plastic hinges at the location of maximum moment are the essential features of this method Keywords—Blast. SDOF, Nonlinear Robust

Nonlinearities significantly limit the size and complexity of numerical models. The present work presents a general method to simulate kinematic nonlinear structures more efficiently. An efficient basis formulation that increases the number of basis vectors without increasing the number of unknown basis coordinates is used. The basis is organized from a Taylor series that includes the system mode shapes and their complete first-order modal derivatives. The Taylor series predicts fixed linear relations between the modal coordinates of the system mode shapes and the modal derivatives, respectively. Thus, the complete solution is known solely by determining the modal coordinates of the mode shapes. The fixed coordinate relation significantly minimizes the computational costs. Furthermore, it is illustrated that the stability of the Taylor basis is dependent on the mode shape frequencies only, allowing the applied time steps to be significantly larger than in standard nonlinear basis analysis. It is illustrated that the computational time can be decreased by one order of magnitude using a Taylor basis formulation compared to a standard basis formulation, including identical basis vectors.