Development of a Method to Generate a Simplified Finite Element Model for an Electrical Switchboard Cabinet

Electrical switchboards are one of the key pieces of equipment used in operations of most critical facilities such as hospitals and emergency services buildings. Unfortunately, past observations have shown that the switchboard cabinet and its contents may be vulnerable to damage or failure during an earthquake. An electrical switchboard cabinet is a complex structure typically constructed using cold-formed steel frame members enclosed by steel panels and containing a variety of switchgear and bus bars. The panels are usually fastened to the steel members by screws, and the steel members are connected together by bolts or screws. The structural behavior of the cabinet can be evaluated using shake table testing and/or high fidelity finite element models. However, these methods are relatively expensive, highly specific, and interpretation of the results may be difficult. Therefore, a method to formulate a simplified finite element model for the cabinet is proposed in this study. The simplified model consists of beam elements (Timoshenko), shell elements and springs. This model can be constructed and executed computationally at a lower cost, and interpretation of the results is a simpler assignment. The present model has the capability to capture the effect of warping deformation in the frame members and possible nonlinear behaviors of the cabinet, such as: local buckling at the end of frame members due to high bending moments, failure of the screw connections and buckling of the panels. The simplified model is validated using a high fidelity model of the cabinet under 1st-order and 2nd-order pushover analyses. Future work to incorporate structural models for the internal components is also discussed

Incorporation of Elastic Local Buckling in a Plain Channel Section Beam Subjected to Double-Curvature Bending: An Effective-Width Approach

When electrical cabinets are subjected to lateral loads, such as earthquakes, the beams of the cabinet frame typically experience double-curvature bending deformation. These beams are usually constructed from cold-formed plain channel sections so they are vulnerable to elastic local buckling near their ends, where high stresses from applied loads are more likely to develop. To capture local buckling behavior, structural engineers typically use high-fidelity finite element models, but this approach can be complex and computationally expensive. A Timoshenko beam element model is simpler and less computationally costly but it is not capable of capturing local buckling behavior. In this paper, a hybrid Timoshenko beam element model augmented with nonlinear nodal springs is proposed to capture elastic local buckling. Local buckling behavior is computed using cross sectional moment-curvature data generated by an effective-width equation, and the results of computations are validated using a high fidelity finite element model (referred to as the benchmark model) of the beam. The resulting reduced rotational stiffness is incorporated in nonlinear elastic rotational nodal springs introduced at the beam ends. A comparison of the hybrid and benchmark model results is presented to confirm the accuracy of the hybrid model

IPO Earnings Forecast, Corporate Governance and Earnings Management——Empirical study based on the IPO of A-share Mainboard companies

IPO盈利预测披露的问题一直以来都获得了众多学者的重视，因为它对于资本市场有着十分重大的意义。对投资者来说，IPO盈利预测代表着公司对于未来经营业绩的一种预期和描述，向广大投资者提供了支撑决策的信息，提升了市场对于公司的信心，降低了上市公司内部管理者与外部利益相关者之间的信息不对称，帮助投资者进行股票估值和投资决策。因此IPO盈利预测可以提高整个市场的信息效率。但是IPO盈利预测也会带来一个负面的问题，那就是管理层为了迎合预测而进行的盈余管理。 随着我国IPO盈利预测披露制度由强制性转变成了自愿性披露，IPO公司可以自愿选择是否披露盈利预测，这就可能导致披露预测的公司为了降低预测误差而有更强...The disclosure of IPO earnings forecast has always been a focus of study because it is significant for the capital market. For investors, IPO earnings forecast represents the expextation and description for the company’s performance in the future, which provides information for the investors for decision-making, enhances the confidence the market has for the company, reduces information asymmetry...学位：管理学硕士院系专业：管理学院_会计学学号：1752012115111

Advanced seismic design methods for precast cladding

Issued as Progress report, and Final report, Project E-20-60

Ductile cladding connection systems for seismic design

Issued as Final report, Project E-20-W9

Out-of-Plane Capacity and Rehabilitation of Partial Height Masonry Partitions

This project examined the behavior of nonstructural components present in essential facilities in Mid-America. School buildings were chosen for detailed studies because of the vulnerability of their occupants and the importance of these particular facilities to post earthquake emergency response. An inventory of nonstructural components was made for this class of essential facilities using the categorization of components developed by FEMA. In addition, the results of an inventory of schools and other essential facilities from Project SE-1 (Inventories of Essential Facilities in Mid-America) were used in this study. Partial height interior unreinforced masonry walls were found in many schools and because of their clear vulnerability to seismic forces were selected as the focus of this study. The primary objective of the present investigation was to evaluate and then suggest retrofit strategies for these components to enable them to meet the life safety and/or immediate occupancy performance levels specified in current FEMA guidelines. Additional objectives were to assess the accuracy of current evaluation methods recommended by FEMA and if necessary to develop improved analysis procedures, rehabilitation guidelines, and performance measures.published or submitted for publicatio

Response Modification Applications for Essential Facilities

This study examined the application of passive energy dissipation systems for response modification of essential facilities in the Mid-America region. Essential facilities are defined as buildings that support functions related to post-earthquake emergency response and disaster management. For such buildings simply insuring life safety and preventing collapse are not sufficient, and the buildings must remain operational during or suitable for immediate occupancy after a major earthquake. A regional inventory of essential facilities (MAE Center project SE-1) revealed that unreinforced masonry (URM) is the most common type of construction for essential facilities, and such material is well known to be highly vulnerable to strong earthquakes. As a result, response modification for this type of building, and particularly for low-rise firehouses, was the focus of this study.National Science Foundation EEC-9701785published or submitted for publicatio

Mechanics of Materials

xx, 1098 p. : Ill.; 25 cm

Rapid Assessment of Fragilities for Collections of Buildings and Geostructures

This report describes the results of research to develop a way to rapidly assess the fragility of structures and geostructures over a specified region. Structural performance under future earthquakes cannot be predicted with certainty. This is primarily due to the fact that an earthquake is a random phenomenon in nature, but another source of uncertainty comes from the structures themselves. For an individual structure or geostructure, the uncertainty arises largely from material properties and construction methods, but for a collection of structures whose individual characteristics are not known, additional uncertainty arises from macro-level parameters such as structural type, base planform, orientation, as well as vertical and planform irregularities, and the applicable design codes. Since detailed analysis of each structure or geostructure in the collection is impractical, this report addresses the problem by developing a methodology based on the use of computationally efficient metamodels to represent the overall structural behavior of the collection. In particular, response surface metamodels are developed using a Design of Experiments approach to select the most influential parameters. Monte Carlo simulation is carried out using probability distributions for the parameters that are characteristic of the target collection of structures or geostructures, and the fragility of the collection is estimated from the computed responses.National Science Foundation EEC-9701785published or submitted for publicatio