Joint Sealants Research Articles

Sealing of cut-off wall joints at the Wiehl Dam at maximum operating level

Sealing of cut-off wall joints at the Wiehl Dam at maximum operating level

Structural Design and Performance Analysis of a Deep-Water Ball Joint Seal

To overcome the current difficulties of high-precision machining and the high manufacturing and maintenance costs of spherical seals for deep-water drilling ball joints, a new spherical seal technique is proposed in this paper. The spherical seal is mainly composed of silicone rubber and polytetrafluoroethylene (PTFE). Rational structural design makes the seal independent from the ball and other components, making it easy to replace if leakage occurs at its surface. PTFE can elastically deform over a certain deformation range, which guarantees that two sealing surfaces fit tightly together. O-Ring and PTFE elasticity makes up for any lack of accuracy during spherical machining and decreases the machining precision requirements for spherical surfaces. Using a finite element technique and nonlinear theory, the performance of the spherical seal under the influence of various factors is determined. The results show that the spherical seal designed in this paper exhibits excellent sealing performance under low-temperature and high-pressure conditions. The spherical seal, a combination of an O-ring and PTFE, has the advantages of cheap manufacturing and maintenance costs and excellent sealing performance.

Current concepts in revision hip arthroscopy.

Hip arthroscopy is an evolving procedure and its indications have expanded. The number of patients undergoing this procedure has increased significantly as well as the number of surgeons being trained. This has resulted in a notable increase in post-operative complication rates creating the need to develop advanced hip arthroscopic techniques. Revision hip arthroscopy is often complex and many factors should be considered to achieve a satisfactory clinical outcome. Careful pre-operative planning and agreement of expectations between the physician and patient regarding the procedure are important. This review describes several advanced treatment options that are used mainly in revision or complex primary hip arthroscopy cases. Labral reconstruction or augmentation technique is used in cases of severely deficient acetabular labral tissue to restore the fluid seal mechanism. In cases of symptomatic (often post-operative) adhesion formation, a spacer between the labrum and the joint capsule is useful for pain relief and prevention of future adhesions. Large defects of the capsule due to previous unrepaired capsulotomy or any other cause can be addressed with the capsular reconstruction technique. Ligamentum teres reconstruction using an anterior tibialis allograft is indicated in patients with hip instability and persistent pain after previous debridement or with complete tears of this structure. The senior author's treatment of choice in cases of previous over-resection of CAM impingement is the remplissage technique to restore the bony defect of the femoral head-neck junction and preserve the joint seal.

Performance of selected polyurethane joint sealants in concrete structures

Often underestimated and neglected, joint sealants in concrete structures play an important role in protecting the structure against its premature deterioration. The focus of the presented paper lays upon the issue of sealing of joints in concrete structures. Concrete is one of the most difficult materials to seal since there are always small particles of dust and the material itself. In this paper, the joint will be viewed as traditional expansion joint. Two representatives of flexible one component polyurethane sealants were selected. The main reason for this selection was that conventional repair materials are usually very rigid and easily incline towards the formation of cracks and gaps. The aim of this paper is not only to verify the suitability of selected materials but also to demonstrate that polyurethane sealants might be a better and long-lasting solution for filling of joints and patching of cracks within concrete structures.

Design Optimization and Fatigue Analysis for Seal Joint of Control Rod Drive Mechanism

Two kinds of seal joint thickness of control rod drive mechanism seal house were analyzed on stress and fatigue by using finite element method, and it provides analytical basis for equipment optimization, design manufacturing and problem handing. In the fatigue computing, all the transients were grouped into several groups, so as to separate the transients not at the same stage obviously. Meanwhile, the transients can be respectively combined in every group to reduce the redundant conservatism of computation. The elastoplastic strain correction factor was modified by analyzing thermal and mechanical load separately referring the rules of RCC-M 2002.By comparing the stress of two thickness joints, the results are found that the fatigue results of the thinner thickness are safer, but this is contrary to the rule of other results. The fatigue usage factor can be reduced by using modified elastoplastic strain correction factor when the amplify of the primary and secondary stress is large produced by both thermal load and mechanical load.

Influence of Surrounding Soil Conditions and Joint Sealing on Seepage Resistance of a Sheet Pile Wall, Three Dimensional Numerical Analyses

The aim of this article is to present 3D numerical calculations results of the seepage resistance of sheet pile (SP) wall with sealed joints. In the present work the leakage through SP wall was determined for one joint of full length. In the analysed example, the SP wall passed through one kind of soil but some conditions (permeability of joint and of surrounding soil) changed depending on the adopted assumptions.To find the distribution of the total head in the calculation area Laplace equation was used. To determine the velocity field Darcy's law was adopted.In the first step, the discharge flowing through the single joint of SP wall based on 3D numerical simulations was determined. In the next step, the joint resistance was estimated and the discharge was found analytically. The results obtained using these two methods were compared. And the conclusions are as follows: it seems possible to estimate the „joint permeability” coefficient using numerical methods, in some conditions the analytical results are far away from numerical ones, due to the nonlinear pressure distribution along the joint, it is necessary to collect in-situ data to confirm the usefulness and reliability of obtained solutions and to proposed more complete methods of determination of SP wall seepage resistance.

고체 로켓 모터의 체결 볼트와 오링에 대한 베이지안 접근법 기반 모수 추정과 신뢰성 해석

로켓 모터와 같은 일회성 시스템은 매우 높은 신뢰도를 요구하기 때문에 합리적인 신뢰성 설계방안이 필요한데 아직 국내에서는 단순히 각 부품별로 안전 계수를 부여하는 설계 방법을 적용해 왔다. 고전적인 신뢰성 해석에서는 한계 상태 함수에 사용되는 변수가 단일 값으로 입력되고 몇 개의 실험 데이터에 대하여 단순히 평균과 표준 편차를 취한 뒤 그 값을 신뢰성 해석에 사용하기 때문에 로켓 모터와 같이 높은 수준의 신뢰도를 요구하는 시스템에서 위험한 결과를 도출할 수 있다. 본 연구에서는 로켓 모터의 체결 볼트와 오링을 대상으로 베이지안 접근법을 활용하여 입력 변수를 통계적으로 추정하고 이를 통한 신뢰성 해석을 수행하였다. 추정된 변수는 확률 분포 형태로 도출되며 신뢰성 해석 결과로 계산되는 실패 확률 역시 분포로 주어지기 때문에 객관적이고 정량적인 설계 기준을 설정할 수 있다.

Performance Analysis of the Joint Sealing Materials for the Cement Concrete Pavements in Civil Airports

Cement concrete pavements in airfields need to be sealed with all kinds of sealants to prevent the ingress of water or incompressible materials into their joints. Airfield cement concrete pavements have unique in-service conditions, and the sealants in these environments are not only exposed to climatic effects and heavy traffic loads but also to jet fuel and fluids. By analyzing the causes of damage and selecting four types of typical joint sealing materials for cement concrete pavements in civil airports (e.g., silicone, polyurethane, polysulfide, and polythiourethane), the basic physical properties, adhesion, and resistance of these materials are tested. By combining the experimental results with the relevant technical specifications and standards at home and abroad, these materials are divided into high elastic modulus and low elastic modulus based on 23℃ tensile modulus. The surface drying time, cone penetration, elastic recovery rate, tensile modulus, low temperature tensile elongation, tensile bond, fuel immersion characteristics, resistance to heat ageing, and flame resistant properties of these materials are used as performance indices and provide a technical reference for the construction of airport cement concrete pavements.

Unsealed joints in urban concrete pavements for buses

Urban pavements for buses need to resist high traffic demands without regular invasive maintenance interventions that affect the pavement clients. Although jointed plain concrete pavements can provide these requirements, sealing the joints and keeping them sealed for 10 years costs up to 45% more than unsealed joints. The objective of this paper is to evaluate the performance of unsealed transverse joints in urban pavements for buses. The field measurements made after 8 years in-service (average) in 270 unsealed joints in Chile, 150 on bus corridors and 120 on their adjacent lanes, show that only ten joints of the bus corridors were affected by very low spalling (30 mm) due to the construction process and not due to the performance of the unsealed joints. The adjacent lanes have zero joints affected by spalling. Furthermore, no pumping or measurable joint faulting was detected even after 5 million accumulated equivalent single-axle loads. These results, the 50 years of Wisconsin's experience in the USA and the deficiencies of joint seals place unsealed joints as a cost-effective alternative to optimise urban pavements for buses, considering the needs of the pavement clients – that is, users and municipal transportation agencies.

Improved Infiltration Modeling for Partially Sealed Joints in Concrete Pavement Design

AbstractThe primary purpose for sealing joints in rigid pavement—besides limiting incompressible material—is to prevent or reduce the amount of water infiltrating into the pavement structure. The p...

Effect of axial play on the sealing ability of the radial single-lip seal in an abrasive environment

The results of research focused on the specifics of frictional interaction between contacting surfaces of radial seal working in the environment with high abrasive content have been presented. The effect of the abrasive penetration through sealing during its axial play on the shaft, called the pumping effect, which results in the wear of the sealed friction joint parts and leads to the premature failure, has been found.

Field study of the building physics properties of common building types in the Inner Himalayan valleys of Bhutan

Traditionally, buildings in the Inner Himalayan valleys of Bhutan were constructed from rammed earth in the western regions and quarry stone in the central and eastern regions. Whilst basic architectural design elements have been retained, the construction methods have however changed over recent decades alongside expectations for indoor thermal comfort. Nevertheless, despite the need for space heating, thermal building performance remains largely unknown. Furthermore, no dedicated climate data is available for building performance assessments. This paper establishes such climatological information for the capital Thimphu and presents an investigation of building physics properties of traditional and contemporary building types. In a one month field study 10 buildings were surveyed, looking at building air tightness, indoor climate, wall U-values and water absorption of typical wall construction materials. The findings highlight comparably high wall U-values of 1.0 to 1.5W/m²K for both current and historic constructions. Furthermore, air tightness tests show that, due to poorly sealed joints between construction elements, windows and doors, many buildings have high infiltration rates, reaching up to 5 air changes per hour. However, the results also indicate an indoor climate moderating effect of more traditional earth construction techniques. Based on these survey findings basic improvements are being suggested.

Submodeling Analysis of Joint Sealing Material in Vertical Joint of Concrete Face Slab

At present, spalling failure has begun to appear in concrete slab of high concrete rockfilled dam (CFRD). Based on known displacement on cushion surface of a high CFRD, the model including face slab and cushion was set up using submodeling technique. The effect of different joint sealing materials in vertical joint on stresses of face slab was analyzed. The results show that the two joint sealing materials mentioned in the paper can effectively decrease the maximum pressure and strain in horizontal direction. Birch board can also decrease the maximum pressure and strain in slop direction. It is helpful to prevent spalling failure in face slab. So Birch is more suitable and suggested as joint sealing material in vertical joint.

Adhesion and Cohesion Testing of Joint Sealants after Artificial Weathering – New Test Method

The use of construction sealants is an important area not just of the building construction. Each building requires a careful processing of all details and façades are no exception. From today's point of view we may note that sealing of façade joints and different types of cracks, fissures or gaps is nothing unusual and, therefore, it is astonishing that there still occur defects that often cause a significant decrease of the durability of the structures and sealed structures. This paper deals with testing of a selected group of construction sealants at a so-called ‘real joint’. The real joint is a term defining a set of testing samples when the testing body contains a sealant applied in a manner corresponding to its real application. Cement bonded particleboard board was representing the façade cladding in this research since during the sealing there often occur complications with adhesion of sealants. For the presented experiment the existing testing methods that are used for verification of adhesion of cladding materials were studied and modified. According to the opinion of the authors those modified methods simulate well the parameters of the external environment and thus also the negative influences that may have a significant impact on the sealed joint in practice. The measured results prove that in the application of the sealants it is very important to follow the technology discipline and namely it is necessary upfront to verify whether the chosen materials are compatible. In most tested cases, diversion from the above-given steps resulted in failure of the sealed joint.

Field performance of cold- and hot-applied joint sealants

Stone mastic asphalt (SMA) and thin surfacing have been used in the UK for over 15 years. The primary location of failure and deterioration on the majority of thin surfacing is along the longitudinal joints. Traditionally, contractors used hot bitumen as the joint edge sealant material. More recently, many contractors used cold-applied bituminous edge sealants. This paper presents the findings of field and laboratory investigations aimed to explore which method provides the optimum performance of longitudinal joints. Dynamic shear rheology (DSR), indirect tensile strength (ITS), pull-off, permeability and air void content tests were performed. The results of the DSR tests showed that cold-applied sealant could outperform the field performance of the hot-applied 40/60 pen bitumen sealants. However, the adhesion and ITS tests showed that hot-applied sealant was more effective than the cold-applied sealant in creating a good bond between two asphalt mats. There was no significant difference in the permeability of joints constructed using either sealant. The survey of roads constructed using hot- and cold-applied sealants showed that both methods are capable of constructing durable longitudinal joints on roads with low-to-medium traffic volume.

Design of Stilling Basin Linings with Sealed and Unsealed Joints

AbstractOne of the main causes of lining damage in stilling basins and at the toe of chute spillways is the global instantaneous uplift forces due to the difference in pressure acting on the upper and the lower surface of protection slabs or rock elements. Spillway stilling basin linings can be built according to two different techniques: using sealed joints or unsealed joints. In the case of sealed joints, the pressure underneath the slab is constant and the uplift force results from the pressure fluctuations acting on the slab. In the case of unsealed joints, the pressure propagation at the lower surface of the slab, being transferred through the joints, should also be considered. The aim of the paper is to study, define, and compare the design criteria in these two cases. In the present study, the pressure field on the slab is evaluated according to a recent method based on the Taylor hypothesis, whereas the pressure propagation under the slab is computed by a new 3D model based on unsteady flow analys...

Elastic lateral-torsional buckling of glass beams with continuous lateral restraints

Lateral-torsional buckling is a typical buckling mode for slender members loaded in bending, which is characterized by the lateral and torsional displacement of the cross-section along the complete member length. Structural glass members are often connected to the encompassing structure by means of a silicone sealant joint along the member length, which acts as a partially rigid lateral connector, restraining the movement of this side of the member. While this will increase the lateral-torsional buckling resistance of these members, this is currently not considered during the design. In this paper the behaviour of glass beams with a continuously restrained top edge, loaded by a line load or central point load along this edge, will be investigated by executing a numerical parametric study. In this study, the restraint provided by the silicone sealant joint is modelled by lateral springs along the edge of the beam. The influence of the spring stiffness on the critical load and corresponding eigenmode shape will be determined in an eigenvalue analysis, considering both monolithic and laminated glass beams. The results of this study will give some first insights in the influence of lateral restraints on the lateral-torsional buckling behaviour.

Seal spot welding of steel and aluminium alloy by resistance spot welding: dissimilar metal joining of steel and aluminium alloy by Zn insertion

This research concerns a dissimilar metal joining of steel and aluminium (Al) alloys by means of zinc (Zn) insertion. The authors propose a joining concept for achieving strong bonded joints between Zn-coated steel and Al alloys. A eutectic reaction between Zn in the Zn coating and uniform Al–Fe intermetallic compound (IMC) layer at the joint interface, leading to a strong bonded joint. The ultimate aim of this research was to apply this joining concept in the resistance spot welding process for manufacturing vehicle bodies. As a practical issue characteristic to joints of dissimilar metals, anticorrosion measures against electrochemical corrosion must be undertaken. If there is moisture near a joint interface of dissimilar metals, electrochemical erosion will progress. Therefore, a sealing function that could prevent moisture intrusion is required. By applying the above-mentioned welding process to a set of metals with thermosetting resin spread in between, we realized seal spot welding, which not only prevented moisture intrusion but also retained high tensile strength. In this research, first, a cyclic corrosion test was performed on the seal spot-welded joint of galvanized (GI) steel, a steel grade widely distributed in Japan, and Al alloy was bonded by seal spot welding, and the following topics are discussed. Complete removal of sealant from the joint interface is the key to realizing the high tensile stress joint, because remaining sealant will lead to reduction in tensile strength. Therefore, heat generation at the interface was monitored by measuring electrical current and potential difference between the two electrodes, and a precise temperature control was performed. Moreover, the bonding process was clarified by stepwise analysis of the joint interface using optical microscopy, and a guideline for producing strong joints was proposed. And finally, a TEM observation also confirmed that the interface structure of the seal spot-welded joint was the same as joints without the resin; a thin and uniform Al–Fe IMC layer was formed and a strong metallurgical bonding was achieved.

Uncracked joints in plain concrete pavements: causes, effects and possibilities of improvements

During the construction of Jointed Plain Concrete Pavements (JPCPs) in Chile, it was observed that joints remained uncracked. The objectives of this paper are to evaluate the effects of uncracked joints (UnCrJ) in JPCPs and to propose possible solutions or improvements to avoid or minimize this phenomenon. Considering low thermal amplitude as cause of UnCrJ, a rational-based, detailed and empirically validated model is used to predict UnCrJ and crack width. The modelled results are not only due to material changes but also to the location of the series of cracks in time in the JPCP system. The paper contributes with this rational approach, instead of an empirical-simplified one, to achieve the objectives. For the modelled conditions, the “as-built” slab length range is 8 m to 56 m instead of the 4 m designed one. Then, more curling, joint faulting, water infiltration in sealed joints and load transfer efficiency ≤ 70% are expected. The alternative solutions proposed are associated to innovations as short joints spacing, unsealed joints and saw-cuts up to 50% thickness made with thin blade (≤ 3mm), which was verified with new field evidence provided in the article.

Experimental study on the thermal conductivity and moisture ingress in closed-cell mechanical pipe insulation systems at below ambient conditions (ASHRAE RP-1646)

Mechanical pipe insulation systems are commonly used around chilled water pipes to reduce heat gain from the ambient. Often water vapor condensate accumulated inside the pipe insulation and it might lead to a degradation of the insulation thermal conductivity. There are not any standardize test methods for characterizing this phenomena and literature showed that the values of the thermal conductivity of pipe insulation systems are different from flat slabs due to the radial configuration and the presence of split joints. This article first introduces work on the improvement of a novel test apparatus for measuring pipe insulation thermal conductivity at below ambient temperature. Then, measured from the improved experimental devices, new experimental findings on the thermal conductivity of three closed-cell pipe insulation systems, that is, cellular glass, elastomeric rubber and PIR, are presented. The first two of these insulation materials were tested without a sheet or film vapor retarder whereas the third was tested with a sealed polyvinylidene chloride plastic film vapor retarder. Data showed that these closed-cell pipe insulation systems were resistant to the moisture ingress, and the thermal conductivity slightly increased with the moisture content. The impacts of joint sealant and vapor jacket were key factors to the system moisture ingress and should be carefully considered during system design and installation. The results in this article showed the importance of including appropriate insulation thickness safety margins due to the presence of insulation joints and the possible joint sealant in order to achieve condensation control.