Condensation Risk – Impact of Improvements to Part L and Robust Details on Part C -Interim report number 7: Final report on project fieldwork

This report sets out, in draft1, the results of the fieldwork phase of research into the impacts of the 2002 revisions to Part L of the building regulations (Approved Document L1 - DTLR, 2001), and the adoption of Robust Details (RDs - DEFRA 2001) on the extent of condensation risk in the construction of dwellings (Oreszczyn and Bell, 2003). The objective of the fieldwork was to explore the practical application of the revised Part L and its associated robust details by housing developers. This was done through a qualitative evaluation of the design and construction of 16 housing schemes designed in accordance with the revised part L and making use of robust details2. The results of the analysis are to be used to enable condensation modelling that takes into account not only the guidance of robust details but also the way in which construction details were actually designed and, perhaps more importantly, constructed. To this end the report identifies 7 areas of construction detailing (yielding some 15 separate detail models) that are to be included in the condensation modelling phase of the project

Cable Median Barrier Failure Analysis and Remediation Phase II

Cable median barrier crashes from a total of 12 states were analyzed. Crash data included scene diagrams, photographs, and field measurements, crash narratives, although the availability of data in each crash varied. Major contributors to penetration crash propensity were identified: diving underride, in which the front end of the vehicle dropped below the bottom cable; prying, in which the vehicle profile caused cable separation or lifting; override; bouncing override, in which the vehicle rebounded after contact with the back slope and bounced over the top of the barrier; system failure, in which one component failure or design failure prevented the cables from adequately engaging the vehicle; and large vehicle crashes, such as tractor trailers, buses, and single-unit trucks into TL-3 systems. Major contributors to rollover were identified: steep median slopes, in which the slope caused unstable bouncing or abrupt changes in slope profiles acted as trip points for the tires; broadside skid, in which the vehicle was skidding with a sideslip angle of nearly 90 degrees prior to contact with the barrier; contact with post, in which the post acted as a trip point; and other factors such as towing trailer units, median anomalies, or with large vehicles such as tractor-trailers, buses, or motor homes. Recommended improvements to cable median barrier systems included: minimum top cable height of 35 in. (890 mm); maximum top cable height of 15 in. (381 mm); minimum of 4 cables supported by posts; higher lateral cable-to-post attachment strength at bottom and lower strength at top; low strong-axis strength post sections; and to eliminate cable entrapment in a vertical slot in the post when initial cable contact occurs at a post location. A summary of factors and how they contributed to penetration, rollover, and severe crash probability is shown in Table 1

Control of welding residual stress for dissimilar laser welded materials

The most common problem of welding dissimilar metals (DMWs) with respect to residual stresses is the differences in the coefficient of thermal expansion and heat conductivity of the two welded metals. In the present work, a CO2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless steel and low carbon steel plates. The Taguchi approach with three factors (selected welding parameters) at five levels each (L3-25) was applied to find out the optimum levels of welding speed, laser power and focal position for CO2 keyhole laser welding of dissimilar butt weld. The responses outputs were the residual stresses at different depth in the heat affected zone (HAZ). The Hole-Drilling Method technique was applied to measure the residual stress of dissimilar welded components. The results were analysed using analysis of variances (ANOVA) and signal-to-noise ratios (S/N) for an effective parameters combination. Statistical models were developed to describe the influence of the input parameters on the residual stress at different specimen levels; to predict there value within the limits of the variables under investigation. The result indicates that the developed models can predict the responses satisfactorily

Fragility analysis of building envelope components subject to windborne debris impact hazard

This thesis presents a methodology for developing windborne debris (WBD) impact fragility curves for building envelope components (BECs) by using stochastic finite element (FE) models. These fragility curves provide the probabilistic description of the impact resistance of BECs subject to an impact event described by an appropriate intensity measure (IM). Accurate fragility curves are essential in the development of a general probabilistic performance-based engineering framework for mitigation of WBD impact hazard. Monte Carlo simulation is used in combination with the FE method to propagate uncertainties in the BEC’s model parameters and WBD impact location. As an application example, the fragility curves relative to different damage measures are derived for aluminum storm shutters subjected to WBD impact. It is found that (1) the missile kinetic energy at impact is a sufficient IM for BECs with ductile behavior subjected to WBD impact, and (2) the performance of storm panels in terms of penetration of WBDs is critically dependent on the details of the panels’ installation

Design of the Highly Uniform Magnetic Field and Spin-Transport Magnetic Field Coils for the Los Alamos National Lab Neutron Electric Dipole Moment Experiment

Charge-Parity (CP) violation is one of Sakharov\u27s three conditions which serve as guidelines for the generation of a matter-antimatter asymmetry in the early universe. The Standard Model (SM) of particle physics contains sources of CP violation which can be used to predict the baryon asymmetry. The observed baryon asymmetry is not predicted from SM calculations, meaning there must be additional sources of CP violation beyond the Standard Model (BSM) to generate the asymmetry. Permanent electric dipole moments (EDMs), which are inherently parity- and time reversal- violating, present a promising avenue for the discovery of new sources of CP violation to resolve this outstanding problem. The SM prediction for the neutron EDM, for example, is multiple orders of magnitude smaller than the sensitivity achieved by modern neutron EDM experiments \cite{sm_nedm_estimate}. The measurement of a non-zero neutron electric dipole moment larger than the SM prediction would be a sure sign of BSM CP violation. A experiment searching for the neutron EDM at Los Alamos National Lab (LANL) has been constructed with the goal of improving the current neutron EDM upper limit $d_n \u3c 1.8 \times 10^{-26} \; e \cdot$cm (90\% CL) \cite{ILL-nEDM-2020} by approximately one order of magnitude. The work presented in this thesis has been performed in support of the LANL-nEDM experimental effort. Precise magnetic field control is required to reach the desired measurement sensitivity, specifically a highly uniform $B_0$ holding magnetic field. A multiple-split solenoid with an octagonal cross section was designed and fabricated to meet the gradient specification $\langle | \partial B_z / \partial z | \rangle \u3c 0.3$ nT/m and address engineering challenges related to assembly and magnetometry. Efficient transport of neutron polarization from the polarizing magnet to the storage cells is also essential to accomplish the sensitivity goal. A series of modified, self-shielding cos $\theta$ coils have been designed to maximize polarization as neutrons propagate through penetrations in the magnetically shielded room. The spin-transport coils, in conjunction with the simultaneous spin analyzers, will provide a polarization product $\alpha \u3e 0.8$. The series of coils interfaces with the $B_0$ coil in a pseudo-continuous manner such that the fringe fields do not cause depolarization of the neutrons and do not generate non-uniformities in the storage cell volumes

Composite Interstage Structural Concept Down Select Process and Results

NASA's Advanced Composites Technologies (ACT) project evaluated several composite construction options for the Ares V Interstage to support the Constellation Program's goal of reducing the mass of vehicle dry structures. In Phase 1 of the project, eight candidate construction concepts were evaluated for the Ares V Interstage design. Trade studies were performed using finite element analyses to determine weight estimates for the construction concepts. An evaluation process was then used to down select the construction concepts down to two concepts for further consideration in Phase 2 of the project. In Phase 2 of the project, additional trade studies were performed using detailed finite element analyses of the Interstage and a final down select process was used to choose the recommended Interstage construction concept. The results of the study showed that a honeycomb sandwich design was the most favorable Interstage construction concept based on advantages in manufacturing cost. Details of the Phase 1 and Phase 2 trade studies and down select process with final results are presented in the paper

RF cavity design for a low cost 1 MeV proton source

In this paper we present the design for a low-cost RF cavity capable of accelerating protons from 100 keV to 1 MeV. The system is designed to meet the specifications from the proposed Alceli LTD medical proton therapy linac, to deliver a 1 nA proton beam current with a 1 kHz repetition rate. We present a design of an RF normal conducting (NC) re-entrant Cu cavity operating at 40MHz consisting of a coupled two cavity system, both driven by a single Marx generator. The choice of such a low operating frequency for the cavity system enables us to use a relatively low-cost cost Marx Generator as the RF source. Marx generators work in a similar fashion to a Cockcroft-Walton accelerator (without the expensive components), creating a high-voltage pulse by charging a number of capacitors relatively slowly in parallel, then rapidly discharging in series, via spark gaps. Marx generators can deliver 2.5GW, 1 ns pulses, with rise times of 200 ps, and (relatively) low jitter

Reducing Thermal Bridging and Understanding Second-Order Effects in Concrete Sandwich Wall Panels

Structural engineers have traditionally detailed structures with structural and fabrication efficiency in mind, but often based on a limited understanding of thermal efficiency. Some connection designs can create significant thermal bridging, leading to unnecessary heat transfer and even premature degradation through condensation. Thermal bridging occurs when heat transfer is given a path through a more conductive material like concrete or steel rather than insulation. Concrete sandwich wall panels (SWP) tend to be highly efficient at preventing heat transfer in the middle of panels, with greatest heat transfer occurring at connections. This project identified thermally efficient details for future SWP construction to reduce heat transfer, lessen environmental impact, and increase sustainability of SWP structures. It can be particularly difficult to avoid thermal bridging at corbel connections, so 12 corbel specimens were created and tested to provide alternative corbel design options for engineers. Nine details were successfully created and are presented. Corbel specimens were modeled using the Beam-Spring Method with good agreement. After validating the Beam-Spring Model, a parametric study investigated effectiveness of the PCI Second Order Analysis and the effect of length, panel stiffness, and wythe configuration on SWP behavior under axial and flexural loads