Test Method to Measure the Relative Capacity of Wall Panels to Evacuate Moisture from Their Stud Cavity

Rainwater penetration is the source of moisture that causes the greatest damage to building envelope assemblies. The building envelope should be designed to reduce the amount of rainwater penetration by deflection and drainage. Since it is not realistic to assume a perfect wall without any leakage, the envelope should have the drying capacity to tolerate defects that may arise from the design, construction, and aging of the exterior wall system. Systems with a greater capacity to evacuate moisture from the stud cavity are less likely to undergo moisture damage. A new testing method is developed and deployed to evaluate the relative drying capacity of six wood-framed wall panels of different configurations built into a test hut and tested within a large scale environmental chamber. The wall panels used plywood, oriented strand board (OSB), or fiberboard as sheathing, but did not include cladding. A uniform moisture source was introduced in a water tray set on a load cell at the bottom of each stud cavity. The protocol is based on the hypothesis that the potential for moving a water molecule from the bottom plate to the exterior of the stud cavity is independent of the previous journey of that molecule, i.e., whether it has traveled from the interior of the bottom plate to the surface of the plate or whether it comes from free water in a tray at the level of the bottom plate. For a given set of boundary conditions, this potential is a function of the characteristics of the wall panel, and is identified as the drying capacity of the panel or its drying by evaporation index (DEI). The value of DEI corresponds to the evaporation rate. The moisture response of wall materials enclosing the stud cavity and the evaporation rate of the moisture source were monitored. The results show that this index can be used as an indicator of the relative drying capacity of different wall systems.     

Response of Conventional Steel Stud Wall Systems under Static and Dynamic Pressure

This research effort focuses on the evaluation of existing design standards for cold-formed steel stud?walls and the development of retrofit wall systems. Full-scale wall systems are tested under uniform static pressure using a vacuum chamber. The resistance functions obtained are used to model the dynamic behavior of the walls and to predict performance under blast conditions. This paper focuses on defining the static resistance of nonload-bearing steel stud walls with slip track connections and their performance under external explosions. Simple modifications to existing design practice have significantly improved the blast performance of the steel stud walls. Maximum blast resistance is achieved by using steel angles connected to the studs and anchored to the floor and ceiling. The static and dynamic performances of five full-scale steel stud wall systems are presented in this paper.     

Use of Precast Concrete Walls for Blast Protection of Steel Stud Construction

This research study examines the use of a precast concrete panel system for blast protection of facilities with exterior light gauge metal stud walls. The structural retrofit is designed for the specific case where internal operation of the facility cannot be interrupted. To meet this design requirement, a series of precast concrete panels are installed exterior to the building envelope with connections to the foundation at ground level and to the steel building frame at upper floor levels. To validate the retrofit concept, two explosive detonations representing relatively low and high blast threat levels are examined. An exterior insulation and finishing system (EIFS) clad stud wall and a precast concrete protected stud wall are examined under each demand level. The measured responses of both systems are compared with each other and with basic dynamic predictive models. In addition, a finite element study of the connection is conducted to estimate support demands for the blast retrofit. The research results show that the precast wall system provides effective protection of the exterior wall. The research also shows that EIFS clad metal stud wall systems retain significant resilience under blast demands. The dynamic responses of the systems are predictable using standard elastic-plastic dynamic modeling assumptions.     

Determination of Hydraulic Conductivity Using Piezocone Penetration Test

An elastoplastic, finite-strain, coupled theory of mixtures in an updated Lagrangian reference frame is applied to the piezocone penetration test to estimate the hydraulic conductivity of the soil via analysis of the steady-state excess pore pressure generated during piezocone penetration. The results of this approach were compared with piezocone penetration test data. It showed that reliable hydraulic conductivities can be estimated conveniently without performing pore pressure dissipation tests. This study also shows that the change in the dimensionless excess pore pressure (excess pore pressure is normalized by the effective overburden pressure) at the cone tip is almost constant when the dimensionless hydraulic conductivity (hydraulic conductivity is normalized by the penetration speed and cone radius, hereafter called DLHC) is less than 10?7 or greater than 10?4. It is also shown that the drainage condition around the cone tip is close to a fully undrained condition when the DLHC of the soil is less than 10?7, while it is close to a fully drained condition when the DLHC of the soil is greater than 10?4.     

Innovative Wall System for Construction Industry

This paper describes an innovative wall system for use in residential and commercial construction projects that is reusable, uses less dimensional lumber, and is faster to assemble and install compared to traditional stud wall systems. The wall system is an engineered wall design composed of components fabricated from 5.08 × 5.08 cm (2 in.) (nominal dimensions) nailing strips and oriented strand board fins located in the midsection of the nailing strip. Components can be connected to one another by hinges allowing the system to be collapsible. Laboratory testing has shown that this wall system has significantly improved racking capabilities compared to the traditional stud wall system both with and without sheathing. Additional research is required, however, to enhance this wall system's structural characteristics in bending and axial loads. An economic analysis showed that material costs are cheaper for this wall and assembly, and installation times are less compared to traditional stud wall construction. In its present form, this wall system could be used for non-load-bearing applications (e.g., partition walls within a load bearing structure).     

Wall Stud-to-Track Gap: Experimental Investigation

Because of an increasing interest in the use of cold-formed steel for commercial and residential framing, both design and installation guidelines are needed. The wall framing, which typically consists of axial load bearing C-section studs, is laterally braced and attached at the bottom and top of the wall to a track section. The common bottom and top attachment consists of the wall stud and track of nominally the same cross-section depth. Because the nominal depths of the C-section and the track are similar, a tight connection is often not achieved and a gap occurs. The Standard for Cold-Formed Steel Framing—General Provisions specifies that the gap between the wall stud and track in a wall assembly must not exceed 1/8?in. This gap dimension is consistent with the gap specified by ASTM C 1007. The value of 1/8?in. is based on industry experience and practice but had not been experimentally verified. To explore both the stud-to-track connection strength and the aesthetic concerns associated with a gap between the axial load bearing stud and the track in a typical cold-formed steel wall assembly, a test program was initiated at the University of Missouri-Rolla. Based on the findings of the 54 wall assembly tests and short column tests performed in this experimental study, design guidelines are proposed for a typical wall stud assembly.     

Mechanics and Test Study of Two-Dimensional Flexible Membranes

Numerous enclosure wall systems as well as roof systems employ membranes that are not fully adhered, common examples being mechanically attached roofing membranes and housewraps in screen-type exterior wall systems. Under a negative air pressure differential, these membranes can deform or balloon. Ballooning of the membrane will affect many aspects of performance. For instance, it will change the volume of the air chamber in screen-type wall systems and will, therefore, affect both the extent of screen pressure moderation and the nature of ventilation within the wall. This paper develops the structural mechanics for flexible membranes ballooning in two dimensions under an air pressure differential. The governing differential equation is derived and solved numerically. A second-order parabola is assumed to describe the ballooning shape of the two-dimensional flexible membrane. Alternative theories for the ballooning shape are reviewed and compared. A series of physical tests were carried out to confirm the deformed shape and the magnitude of the peak deflection.     

A Quantitative Model of Keyhole Instability Induced Porosity in Laser Welding of Titanium Alloy

Quantitative prediction of the porosity defects in deep penetration laser welding has generally been considered as a very challenging task. In this study, a quantitative model of porosity defects induced by keyhole instability in partial penetration CO₂ laser welding of a titanium alloy is proposed. The three-dimensional keyhole instability, weld pool dynamics, and pore formation are determined by direct numerical simulation, and the results are compared to prior experimental results. It is shown that the simulated keyhole depth fluctuations could represent the variation trends in the number and average size of pores for the studied process conditions. Moreover, it is found that it is possible to use the predicted keyhole depth fluctuations as a quantitative measure of the average size of porosity. The results also suggest that due to the shadowing effect of keyhole wall humps, the rapid cooling of the surface of the keyhole tip before keyhole collapse could lead to a substantial decrease in vapor pressure inside the keyhole tip, which is suggested to be the mechanism by which shielding gas enters into the porosity.     

Determining Operating Inlet Pressure Head Incorporating Uniformity Parameters for Multioutlet Plastic Pipelines

An important objective of a microirrigation system is to determine the proper operating inlet pressure head, ensuring the desired level of water application uniformity as well as the allowable pressure head variation along the multioutlet pipeline. This paper offers, simple, direct, but sufficiently accurate, relationships incorporating different microirrigation uniformity parameters, such as Christiansen uniformity coefficient, coefficient of variation of emitter discharge, and allowable pressure head variation, to determine the operating inlet pressure head (i.e., pressure head and outflow profiles) for multioutlet plastic pipelines. In this analysis some mathematical expressions were deduced to relate three uniformity parameters; then the operating inlet pressure head is simply reformulated by taking into account a multiplying factor α to the required average outlet pressure head, in terms of three uniformity parameters. Resulting, the influence of different uniform pipe slopes on the water application uniformity and the operating inlet pressure head for various emitter discharge exponents, was evaluated. In addition, to cover various design combinations an extensive comparison between the proposed equations and those of the previous studies was also presented. Examination of the results from this research indicated that, the performance of the proposed technique is sufficient in comparison to those of the recent analytical and numerical procedures.     

Microleakage of new dentin bonding systems using human and bovine teeth

The objective of this study was twofold: to evaluate the microleakage behavior of three dentin bonding systems and to determine if bovine teeth are comparable substrates to human teeth when studying the microleakage of various materials. The materials evaluated were Scotchbond Multi-Purpose Adhesive, Prisma Universal Bond 3, and All-Bond 2. All three bonding systems were used in combination with Prisma APH hybrid composite for comparison of microleakage behavior. Sixty class 5 preparations were cut at the cementoenamel junction for groups containing 30 human and 30 bovine teeth. A 1 mm 45 degree bevel was placed at the enamel margin. Teeth were grouped according to the dentin bonding system used and then restored according to the manufacturer's directions. After restoration, the teeth from each group were stored in distilled water at 37 degrees C for 3 days. The teeth were then thermocycled between 4 degrees C and 58 degrees C for 100 cycles and returned to distilled water at 37 degrees C for an additional 4 days. The teeth were then sealed with nail polish up to 1 mm from the margins of the restoration and placed in 45Ca isotope for 2 hours. The teeth were then sectioned and placed on x-ray film to produce autoradiographs. Microleakage was evaluated for the enamel and dentin margins separately using the following scale: 0 = no leakage, 1 = penetration of isotope to less than 1/2 the distance to the axial wall, 2 = penetration of isotope greater than 1/2 of the distance to the axial wall but short of the axial wall, and 3 = penetration of isotope to the axial wall or beyond. The materials were compared to each other using the Mann-Whitney U and Kruskal-Wallis tests. The gingival margins were compared to the incisal margins for all materials. No statistically significant differences in microleakage were revealed between the incisal and gingival location for human substrates, but there was statistically significant greater gingival microleakage for bovine substrates. All-Bond 2 leaked significantly more than Scotchbond Multi-Purpose for human substrates at the incisal margin. All-Bond 2 had significantly more microleakage than Prisma Universal Bond 3 at both dentin and enamel margins for the bovine substrate. There were no statistically significant differences in microleakage among the bonding systems for the human substrate. No statistically significant differences between the microleakage behavior of human and bovine substrates were found. These results support the use of bovine teeth for in vitro microleakage studies.     

Deep Jet-Grouted Cut-Offs in Riverine Alluvia for Ertan Cofferdams

Constructing the 245-m-high, double curvature concrete arch Ertan Dam required two high cofferdams (the upstream one exceeding 60 m) and the removal of 40 m of alluvium from the riverbed. Full penetration and partial penetration cut-offs were created at Ertan with jet-grouting techniques. Dewatering between the cofferdams and behind the cut-offs was successful and was maintained for more than 2 years against 40–70 m of water heads. This paper describes in detail the design rationale and main features, as well as the construction methods of both cut-offs. The treatment by conventional grouting of the rock below the jet-grouted wall is also outlined.     

Hydraulic Property Estimation Using Piezocone Results

Governing underground water flow, hydraulic properties such as hydraulic conductivity or coefficient of consolidation are major geotechnical parameters. Determination of hydraulic properties, however, is traditionally time consuming and expensive. This research proposes an easy and economical way of determining the hydraulic properties of soils through piezocone penetration tests. Pore pressure responses of soils from piezocone penetration tests are numerically analyzed herein by the coupled theory of mixtures, which is based on the large strain elastoplasticity. Using the numerical results, the effects of input parameters are evaluated. Simple equations are also derived for a faster estimation of the hydraulic conductivity or the coefficient of consolidation of soils. The hydraulic properties predicted by these derived equations agree reasonably with the measured results.     

Inactivation of the mitogen-activated protein kinase Mps1 from the rice blast fungus prevents penetration of host cells but allows activation of plant defense responses

The rice blast fungus, Magnaporthe grisea, generates enormous turgor pressure within a specialized cell called the appressorium to breach the surface of host plant cells. Here, we show that a mitogen-activated protein kinase, Mps1, is essential for appressorium penetration. Mps1 is 85% similar to yeast Slt2 mitogen-activated protein kinase and can rescue the thermosensitive growth of slt2 null mutants. The mps1-1Delta mutants of M. grisea have some phenotypes in common with slt2 mutants of yeast, including sensitivity to cell-wall-digesting enzymes, but display additional phenotypes, including reduced sporulation and fertility. Interestingly, mps1-1Delta mutants are completely nonpathogenic because of the inability of appressoria to penetrate plant cell surfaces, suggesting that penetration requires remodeling of the appressorium wall through an Mps1-dependent signaling pathway. Although mps1-1Delta mutants are unable to cause disease, they are able to trigger early plant-cell defense responses, including the accumulation of autofluorescent compounds and the rearrangement of the actin cytoskeleton. We conclude that MPS1 is essential for pathogen penetration; however, penetration is not required for induction of some plant defense responses.     

钻孔密封材料的微观特性及其对密封性能的影响

研究了钻孔密封材料聚氨酯和膨胀水泥冻复合材料(PD复合材料)的微观特性,并考察了其对钻孔密封性能的影响作用.实验模拟了煤矿井下钻孔封孔过程,利用FEIQuantaTM250环境扫描电子显微镜对聚氨酯、PD复合材料本身,以及两者与煤壁的结合、渗透和发展进行微观对比和分析.PD复合材料的渗透系数约为聚氨酯瓦斯渗透性系数的1/48.聚氨酯为蜂窝网状结构,内部孔隙较大,与孔壁结合处存在空白区域;PD复合材料结构严实,内部孔隙极小,在孔壁处与煤体结合密实.PD复合材料比聚氨酯更容易克服钻孔周围裂隙区内瓦斯压力、水锁效应等各种阻力的作用,在钻孔周围裂隙内逐渐渗透,且其自身可以继续在钻孔周围残余裂隙和孔洞内发展.      

Computation of Cavity Expansion Pressure and Penetration Resistance in Sands

A cavity expansion-based theory for calculation of cone penetration resistance qc in sand is presented. The theory includes a completely new analysis to obtain cone resistance from cavity limit pressure. In order to more clearly link the proposed theory with the classical cavity expansion theories, which were based on linear elastic, perfectly plastic soil response, linear equivalent values of Young's modulus, Poisson’s ratio and friction and dilatancy angles are given in charts as a function of relative density, stress state, and critical-state friction angle. These linear-equivalent values may be used in the classical theories to obtain very good estimates of cavity pressure. A much simpler way to estimate qc—based on direct reading from charts in terms of relative density, stress state, and critical-state friction angle—is also proposed. Finally, a single equation obtained by regression of qc on relative density and stress state for a range of values of critical-state friction angle is also proposed. Examples illustrate the different ways of calculating cone resistance and interpreting cone penetration test results.     

Innovative Central Opening Strut System for Foundation Excavation

A central opening strut system is used to support a diaphragm wall for foundation excavation. This system contains at least one regular polygon module and a number of straight strut members. These strut members connect the diaphragm wall and the regular polygon module together, so that the earth pressure acting on the diaphragm wall in one direction can be transmitted to the diaphragm wall in the other directions by the arch action of this polygon module. In this research, the basic structural behavior of the central opening strut system is examined. A full-scale structural testing of the joint subassemblage is also performed to examine the ultimate strength of the joint. A construction site with five excavation stages and four layers of strut systems is chosen as the case study. The ABAQUS finite-element program is employed in the study of the behavior of this system during various construction stages. From these studies, it is found that the proposed central opening strut system is able to provide a large working space and greatly increases the efficiency of the construction work. Through proper design of the member and the joints, this system provides a better safety factor as compared with the traditional strut system.     

Penetration Resistance of Offshore Skirted Foundations and Anchors in Dense Sand

Penetration of skirts is an essential design issue for offshore skirted foundations and anchors in sand. Skirts may not penetrate far enough into dense sand by the available submerged weight alone. It may therefore be necessary to apply underpressure inside the skirt compartment to produce an increased driving force and to reduce the penetration resistance. This paper recommends procedures to calculate penetration resistance and required underpressure for skirts penetrated in dense sand with and without interbedded clay layers. The recommendations are based on interpretation of skirt penetration data from prototypes, field model tests, and laboratory model tests in dense sand. The paper first presents a model to calculate the penetration resistance of skirts penetrated by weight, or other external vertical load that does not cause flow of water in the sand. Two models are considered; one based on bearing capacity equations with friction angles from laboratory tests, and the other one based on empirical correlations with CPT tip resistance. The bearing capacity model gives more consistent correlations with the empirical data than the CPT model. Thereafter, a model to account for the effect of underpressure applied inside the skirt compartment is proposed. This model is developed based on interpretation of available prototype and model test data from skirts penetrated by underpressure. The results show that underpressure facilitates skirt penetration in sand considerably by providing both an additional penetration force and a reduced penetration resistance. It is also shown that interbedded clay layers can prevent flow of water through the sand and eliminate the beneficial reduction in penetration resistance.     

A permeability barrier in the dorsal wall of the equine hoof capsule

The permeability barrier in the dorsal wall of the equine hoof capsule was studied by means of horseradish peroxidase (HRP) in 0.9 N saline solution as a water soluble tracer. Section were treated with 3'3'-diaminobenzidine tetrachloride (DAB) and before dissection the quality of the horn of feet from 10 horses was assessed and given a subjective grade as either good or poor. Blocks of tissue from each horse were left in either an oven at 60 degrees C or in water for 2 weeks before treatment in HRP, sectioning and DAB solution. Regions observed were i) outer surface, ii) outermost layers of the horn, iii) cut edge of the outer layer, iv) inner layer of horn, v) cut edge of the inner layer and vi) laminae. Horn deemed to be normal horn and of good 'quality' showed very slight penetration of HRP 3-5 cell layers deep in the outer layer. The cut edge of the outer layer of the wall of the 'normal' horn also showed minimal penetration of HRP through the intercellular spaces. The cut edge of the inner layers of the wall of normal, good quality horn showed penetration of the tracer up to 20 cell layers deep, with HRP in both the intercellular spaces and within the cells. In contrast, sections of horn from horses with brittle feet showed deep cracks in the outer surface into which the HRP had penetrated. Good quality horn showed no change in the position of the permeability barrier after soaking in water for 14 days, but the brittle horn showed an increase in permeability to HRP. In brittle horn, reaction product was seen deep within the section in the intercellular spaces of the intertubular horn only. Placing horn in an oven had no effect on the permeability barrier. The permeability barrier of the dorsal wall of the equine hoof capsule differs with the layer of the wall. Horn considered to be of poor quality had a weaker permeability barrier than horn of good quality.     

Seismic Rotational Stability of Waterfront Retaining Wall Using Pseudodynamic Method

Design of waterfront retaining walls under seismic conditions is an important topic of research among the geotechnical engineering fraternity, and recently there have been studies in which the stability of rigid waterfront retaining walls has been assessed. However, an important aspect of seismic rotational stability of such walls is still missing from the literature archives. The present study shows the importance of rotational displacements for the design of the rigid waterfront retaining wall. Consideration has been made for the calculation of the hydrodynamic pressure as well as the seismic forces, both due to the seismic pressure and seismic wall inertia. These seismic forces have been calculated using the pseudodynamic approach. The free water condition has been considered in the analysis, and thus the hydrodynamic pressure has been considered to exist on the downstream face of the retaining wall as well, and a well-known expression approximating the effect of the inertia of the water due to the earthquake has been used for the estimation of this hydrodynamic pressure force. Simple expressions for the calculation of rotational displacement both during and after the earthquake have been proposed, and typical results have been obtained. It is observed that with an increase in the ratio of the water level to the total height of the wall from 0.50 to 1.00 the rotational displacement of the wall increases by about 110%. Similar trend of an increase in the value of the rotational displacement was observed for an increase in the values of the horizontal and vertical seismic acceleration coefficients. Also, the parametric study carried out in the analysis suggested that the rotational displacement is sensitive to other parameters such as the upstream water height, pore pressure ratio, soil, and wall friction angles. Due to nonavailability of the results in which rotational stability of the waterfront retaining wall under the seismic conditions has been studied, the results from the present analysis seem to bring out a unique approach.     

变频调速恒压供水控制系统

概述了金昌冶炼厂原来的供水控制系统的构成及缺陷。介绍了采用法国施耐德公司的ATV-58HD46N4变频器、日本三菱公司的FX2N-32MR可编程控制器、PID调节器和压力传感器构成的新的恒压供水闭环控制系统,该系统只要获得压力给定值和反馈值便可工作,通过输出频率的改变实现泵的转速调节,进行压力闭环控制,保持管网的压力恒定。对新系统的优点作了较为详细的论述,特别在节能效果上与原系统作了详细比较。