BSDEs with diffusion constraint and viscous Hamilton-Jacobi equations with unbounded data

We provide a stochastic representation for a general class of viscous Hamilton-Jacobi (HJ) equations, which has convexity and superlinear nonlinearity in its gradient term, via a type of backward stochastic differential equation (BSDE) with constraint in the martingale part. We compare our result with the classical representation in terms of (super)quadratic BSDE, and show in particular that existence of a solution to the viscous HJ equation can be obtained under more general growth assumptions on the coefficients, including both unbounded diffusion coefficient and terminal data.Comment: to appear in Annales de l'Institut Henri Poincar{\'e} (B), Probabilit{\'e}s et statistiqu

Axial Impact Resistance of FRP-Confined Concrete

This study investigates the impact resistance of fiber-reinforced polymer (FRP) confined concrete. Concrete cylinders were wrapped with carbon FRP (CFRP) or glass FRP (GFRP) with a varied number of layers and wrapping schemes. The impact tests were conducted by using drop-weight apparatus at different impact velocities. Dynamic behavior of the specimens has been investigated. The experimental results have shown that the failure modes are very different than those from static tests. Identical specimens experienced different damage as the impact velocities changed. The dynamic rupture strain of FRP was found to be substantially lower compared with that under static loads. As a result, the FRP efficiency factors were 0.17 and 0.56 for CFRP and GFRP, respectively. Interestingly, although GFRP has lower tensile strength and elastic modulus, it showed much better performance against impact compared with CFRP in terms of both the strength and ductility. The higher rupture strain of GFRP compared with CFRP results in higher confinement efficiency of GFRP under impact loads. A confinement model is proposed to predict the confined concrete strength under impact

Effect of the plastic hinge and boundary conditions on the impact behavior of reinforced concrete beams

This study numerically investigates the effect of the plastic hinge and boundary conditions on the behavior of reinforced concrete (RC) beams under slow-impact-velocity events. Numerical models are developed by using LS-Dyna and verified against experimental results. The effect of different factors including the impact velocity, projectile weight, and concrete strength on the impact behavior of RC beams is examined. The numerical results have shown that the effect of boundary condition is marginal on the impact force but significant on the displacement and damage of relatively long beams. Determining the structural stiffness of a beam in an equivalent single degree of freedom model for predicting the impact load should consider the plastic hinge formation and stationary location. And this model is not necessarily suitable for predicting the peak beam response since it is independent of the boundary conditions when the impact velocity is fast. The negative bending moment of the simply-supported beam occurs with a large magnitude which needs to be taken into account in the design. The residual displacement is more sensitive to the boundary conditions than the peak displacement. Varying concrete strength from 20 MPa to 100 MPa does not noticeably change the impact force and displacement but significantly affects the failure mode of the beam

Flexural behaviour of precast segmental concrete beams internally prestressed with unbonded CFRP tendons under four-point loading

This study investigates the use of carbon fibre reinforced polymer (CFRP) tendons on precast segmental beams (PSBs) to tackle the corrosion problems which are likely to occur at joint locations of PSBs prestressed with steel tendons. Up to date, the use of CFRP tendons was extensively documented for monolithic beams while their application on PSBs has not been reported yet. Three precast segmental T-section beams including two beams with unbonded CFRP and one with steel tendons were built and tested under four-point loads in this study. The test results showed that CFRP tendons can be well used to replace the steel tendons on PSBs. The beams with CFRP tendons demonstrated both high strength and high ductility as compared to the beam with steel tendons. However, the stresses in the unbonded CFRP tendons at ultimate loading conditions of the tested beams were low, ranging from only about 66% to 72% of the nominal breaking tensile strength. The type of joints i.e. dry and epoxied, greatly affects the initial stiffness of the beams but has no effect on the opening of joints at ultimate loading stage. Moreover, a comprehensive examination on four existing code equations to predict the stress in the unbonded tendons showed that the four examined codes predicted well the stress at the ultimate loading condition of the unbonded steel tendons, however, they significantly under predicted those in the CFRP tendons. A modification in the strain reduction coefficient used by ACI 440.4R for predicting the stress increment in unbonded CFRP tendons of monolithic beams is therefore proposed for PSBs based on the experimental results

The Gender Effects of Audit Partners on Audit Outcomes: Evidence of Rule 3211 Adoption

This paper investigates whether the impact of PCAOB Rule 3211 on the quality and cost of audit services differs between female and male audit partners. We find that the improvement of audit quality is more pronounced for female audit partners than male partners after Rule 3211 adoption. Female audit partners are also associated with higher increases in fees and report lags than male counterparts after the adoption of Rule 3211. Further, we find that the presence of female CFOs (or female audit committee members) attenuate the audit fees and report lag increases in the post-adoption periods. Overall, our findings confirm the importance of the gender effect on audit outcomes, which needs further consideration by standard setters. Our study also provides empirical evidence of the benefits of gender equality in the workplace

Rectangular Stress-block Parameters for Fly-ash and Slag Based Geopolymer Concrete

Although there has been a numerous quantity of studies investigating the mechanical properties of geopolymer concrete (GPC), parameters for designing GPC structures are still not systematically investigated and carefully justified. ACI rectangular stress-block parameters are able to predict well the strength of conventional concrete structures but their applicability for GPC is questionable. This study aims to establish new sets of rectangular stress-block parameters for GPC with a broad range of the compressive strength up to 66 MPa. The proposed rectangular stress-block parameters in this study are based on two analytical concrete stress-strain models and measured curves from previous studies of GPC materials. The results from this study show that the use of ACI recommendations for concrete structure in designing GPC beams is still acceptable with high accuracy. However, the axial load-carrying capacity of GPC columns computed by ACI parameters deviate significantly from the experimental results while the proposed parameters provide a good correlation with these experimental data. The significant difference is mainly due to the modification of k3, which is the ratio of concrete strength in real structures to standard cylinder samples. This study suggests that the assumption of k3 = 0.9 in previous studies for conventional Portland concrete is not suitable for use in deriving the stress-block parameters of GPC. In some cases, this ratio should be reduced to 0.7 depending on the curing condition

Tax policy and housing prices: evidence from Vietnam using event study approach

This paper examines the effect of tax policy on housing prices in Vietnam for the period from October 2004 to September 2016 using event study approach. The authors find that all five key changes made to the personal income tax, corporate income tax and non-farm land use tax have caused the housing prices to decline on average 6-11% during the event window, but only the impact of the personal income tax changes is statistically significant. The fact that changes in housing prices are mostly seen prior to the effective date of the tax policy change implies that tax policy change indeed has influenced the housing prices in Vietnam. Although this research has not examined the mechanism through which tax policy has influenced the housing prices, the findings offer some implications for the government in terms of using tax policy for controlling housing prices in Vietnam. The research is also of very few papers in this literature that use the event study approach

Impact response and energy absorption of single phase syntactic foam

© 2018 Elsevier Ltd. This study experimentally investigates the static and impact response of a new single phase syntactic foam which has been newly developed for impact energy absorption. The syntactic foam had different densities ranging from 172 kg/m3to 366 kg/m3depending on the thickness and composition of the coating layers. The impact response and impact energy absorption were investigated by using instrumented drop-weight impact tests. Under static loads, the mechanical properties of the syntactic foam including the compressive strength, the yield stress, and Young's modulus increased with the density but the rate of increment decreased at higher densities. There were two types of progressive failures of the syntactic foam under impact loads. The failure propagation was examined and found to be dependent on the material density and the impact velocity. Interestingly, the densification only occurred in the low-density specimens while this phenomenon was not observed for the specimens with the density greater than 288 kg/m3. The impact energy absorption capacity increased significantly with the density and the wall thickness of the macrospheres