Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described

Credit Market Imperfections in Middle Income Countries

In this paper we document three credit market imperfections prevalent in middle income countries that can help explain the boom-bust cycles as well as other macroeconomic patterns observed at higher frequencies across these countries. These imperfections are: the existence of financing constraints that affect mainly the nontradables sector, currency mismatch and systemic bailout guarantees.

Flexural Buckling of Steel Cold-Formed Hollow Profiles in the Framework of Eurocodes

The use of cold-formed hollow structural (CFHS) steel has been growing in the past decade due to several advantages such as superior behavior towards lateral-torsional buckling, aesthetic structures, and feasibility of using internal volume to increase load-carrying capacity. The cold-forming process can change drastically the shape of the stress-strain curve and strength parameters of the base material. There are several investigations on buckling tests of hollow section columns; however, studies on cold-formed hollow sections are still lacking. This shortcoming of experimental data becomes more pronounced when the corner behavior of CFHS is under consideration. Only a limited number of corner coupon tests can be found in international literature. This Ph.D. thesis is developed in line with the progress of the European project INNOvative 3D JOINTS for Robust and Economic Hybrid Tubular Construction (INNO3DJOINTS). The primary objective is to advance, through analytical and experimental research, knowledge on the flexural buckling behavior of CFHS columns. An extensive experimental program ( 21 flexural buckling tests) on SHS and RHS columns has been carried out varying the steel grade (i.e. S275 and S355) and the overall slenderness ratio. This database serves as the basis for the assessment and improvement of the flexural buckling curve for CFHS. The stress-strain behavior of the sections was investigated by performing tensile coupon tests (81 tests) from both flat and corner areas. special effort was made to obtain the static stress-strain data by pausing the test for 60 seconds during the test. We also employed an innovative method to perform the coupon test on the corner area of CFHS. This procedure will reduce the secondary effect results from methods such as welding a plate or flattening the end grip, and therefore reduce the bias in the results of the corner area. A comprehensive discussion on the definition of safety and the adopted safety levels in EN1990 and EN1993-1-1 has been presented. The results show some potential criticisms of the application of current rules for plastic design and analysis of such a column and a further investigation is required on the matter. In addition, it is shown that the current material test procedures in BSI and ATM standards may lead to misevaluate the static strengths of material which is required for the design of structures

Credit Market Imperfections in Middle Income Countries

In this paper we document three credit market imperfections prevalent in middle income countries that can help to explain boom-bust cycles, as well as other macroeconomic patterns observed at higher frequencies across these countries. These imperfections are: the existence of financing constraints that affect mainly the nontradables sector, currency mismatch and guarantees that cover lenders against systemic crises. In MICs T-sector firms have access to international capital markets, while most N-firms are bank-dependent and are financially constrained. Systemic guarantees generate incentives for borrowers to take on insolvency risk by denominating debt in foreign currency. This currency mismatch makes movements in the real exchange rate – the relative price between N and T goods – the driving element in the amplification of shocks.

Essays in financial economics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, 2013.Cataloged from PDF version of thesis.Includes bibliographical references.In Chapter 1, we seek to understand the relation between liquidity and market imperfections from two dimensions: 1) Across liquidity measures, we compare the influence of imperfections on two commonly used measures, Kyle's lambda and price reversal; 2) Across imperfections, we study the interaction between two sources of market imperfection, information asymmetry and participation cost. We show that the two liquidity measures may be affected in opposite directions by the same imperfection, or may not capture liquidity changes at all; imperfection interactions can cause the market to appear "less illiquid" than single-imperfection benchmarks. Our model also suggests that imperfections and liquidity shocks may influence expected returns in opposite directions, which complicates the liquidity-asset price cross-sectional relation. In Chapter 2, joint with Andrew Lo, we perform an empirical comparison of systemic risk measures. In a recent survey paper, Bisias et al. (2012) provide a summary of 31 proposed measures for systemic risk in the financial system. In this paper we examine a subset of these measures to determine their time series properties before, during, and after the Financial Crisis of 2007-2009. By comparing their empirical properties over time, we hope to identify which measures were most informative for navigating through the 1998 and the 2007-2009 crises. By constructing rolling-window estimates of these measures using only prior data, we control for the most blatant forms of look-ahead bias to assess the value of these measures as "early-warning signals". Finally, we explore the possibility of combining these measures to produce even more informative indicators of systemic risk. In Chapter 3, joint with Andrew Lo and Silvia Sgherri, we construct two global systemic In Chapter 3, joint with Andrew Lo and Silvia Sgherri, we construct two global systemic risk indicators as well as a panel of regional indicators, using monthly hedge fund data. Results show that our geographic-focus global indicator provided contemporaneous characterization of financial distress; the hedge fund style-category global indicator generated early-warnings for the 2007 quant crisis and the 2011 European debt crisis, and typically led the geographic-focus indicator by 1~2 months. In addition, we use Granger causality network to visualize the interconnectedness of regional risks and track the transmission of crisis over time.by Yifan Zhou.Ph.D