Wall Joints Research Articles

Tests of Joints in AAC Masonry Walls

Abstract The paper presents the results of the Authors’ tests on the joints in AAC masonry walls. The shape of the tested element and the test stand were fitted innovatively based on the Authors’ own experience as well as on the literature overview and numerical analysis. Cracking morphology and mode of failure were investigated. The relationship between the load and displacement for different types of joins was compared. The obtained results were also compared to the results obtained on the reference model, which was a model with a traditional masonry bond. In the remaining testing elements, the connection was realized with the use of steel connectors. Various mechanisms of cracking and failure have been observed as well as the behaviour and load-bearing capacity of joints were different. The obtained results encourage to further analyses focused on detailing the joints and application of new methods in the construction of the joints.

Assessment of the compressive strength of lime mortar in the joints of brick walls - case study

The paper presents the test results of lime mortar compressive strength in the joints of brick walls. The tests were carried out with the Double Punch Test (DPT) method and with the use of an impact penetrometer (penetrometric test PT) on original samples taken from the structure of a building erected in the 1880s. The obtained results have shown that the predictions of the mortar compressive strength using both methods were very consistent (the difference 6%). The penetrometric method also made it possible to assess the homogeneity of the mortar in the direction of the wall thickness.

Optimization of Process Parameters and Comparative Study on Bi-Metallic Joints Developed by High Temperature Nicrobrazing, Laser and GTAW Joining Processes

High Temperature Nicrobrazing of AISI 316 and 316 L stainless steels has been studied by comparing with pulsed laser and gas tungsten arc welding processes. Fabrication of instrumented irradiation capsule for evaluating the irradiation performance of fuel and structural materials in a nuclear reactor requires development of thin wall joints capable of withstanding high temperature and/or internal pressure. Thin wall joints for high temperature (∼550 °C) applications can be made by Laser Beam Welding (LBW), Gas Tungsten Arc Welding (GTAW) and High Temperature Brazing (HTB) methods. Using these methods, joints have been prepared and tests such as helium leak test (HLT) and microhardness test have been carried out. Microstructures were also evaluated. A comparative study has been performed on these joining methods to identify the suitable methods for high temperature applications. No observable leak was found during HLT. Microstructures of joints shows variation in solidification morphology due to difference in heat sources. It has been observed that the joint prepared by high temperature brazing process is having higher microhardness value than the joints prepared by LBW and GTAW processes. Further, it has been observed that LBW joints have better mechanical properties than GTAW joints and HBW joints.

A Study of Laser Beam Welding, Gas Tungsten Arc Welding and High Temperature Brazing Processes on Micro hardness and Tensile Strength of AISI Type 316 Stainless Steel

Thin wall joints for elevated temperature (~550 °C) applications can be prepared by Laser Beam Welding (LBW), Gas Tungsten Arc Welding (GTAW) and High Temperature Brazing (HTB) methods. The joints have been made and tests such as helium leak test (HLT), micro hardness test and tensile test were carried out. A study has been performed on these joining techniques to recognize the suitable method for high temperature applications. No observable leak was identified during HLT. Microstructures shows dissimilarity in solidification morphology due to disparity in heat sources. It has been identified that the joint made by brazing process having higher micro hardness value. Further, it has been observed that LBW joints have better mechanical properties than GTAW joints and HTB joints.

PENINJAUAN EFEK PENGEKANGAN DINDING PADA HUBUNGAN KOLOM , BALOK DAN DINDING AKIBAT BEBAN BERULANG LATERAL SERTA IMPLEMENTASINYA PADA PEMBANGUNAN RUMAH TAHAN GEMPA DI KABUPATEN ACEH BESAR

The function of wall which arranged from brick even from concrete in function as partition could increase strength and durability of frame structure, but actually the contribution of wall in increasing strength and ductility is often ignored. It is happened because of lack of acknowledge of behavior of frame and wall caused of axial loading that consist of cyclic lateral loading as the effect of wind load and earthquake.. In this case study it was aimed to observe the effect of wall confinement at column, beam and wall joint caused of lateral cyclic loading and it implementation on earthquake resistant housing building in Aceh Besar sub district. The strength and ductility increasing on the frame with wall and without wall (Husna, 2008) proofed that there were contribution of the increasing of strength and ductility of frame. Drift ratio of frame with wall without bed joint was 0.74. % and drift ratio of frame with wall and bed joint was 0.84 %.. In the other hand drift ratio of portal without wall was 44.85 %.Key words : strength, ductility, frame, full wall, partial wall, axial cyclic loading

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.

Effect of Steel Framing for Securing Drywall Panels on Thermal and Humidity Parameters of the Outer Walls

Abstract The paper analyses the effect of steel framing used to secure drywall panels on thermal and humidity properties of outer walls. In the practice of building a light structure, the most popular components are steel and wood studs. They are used to obtain framing for building a wall (an outer wall in this study). Analysis presented in this study concerned the corner of the outer wall build using the technology of light steel framing. Computer simulation was used to perform thermal and humidity analysis for the joint of the outer wall.

Probabilistic assessment of groundwater leakage in diaphragm wall joints for deep excavations

A probabilistic method is proposed for conducting groundwater-related hazard assessments that are useful for the risk management of deep excavations in saturated soils in urban areas. The design of deep excavations, construction procedures and execution methods aimed at realizing underground infrastructure are characterized by major uncertainties related to soil properties, construction imperfections and hydrogeological site conditions. During the construction stages, geometrical imperfections and ineffective technologies to control wall seepage can strongly affect the level of risk to the adjacent built environment, leading to severe damages. The aim of this study is to provide an assessment of the leakage probability in reinforced concrete (RC) retaining walls. We model the main geo-structural factors that influence trench stability and the key geometric and technological parameters that affect construction imperfections as relevant random variables. Moreover, through Bayesian updating, useful recommendations are provided regarding the effectiveness and influence of the monitoring phase on reducing the failure probability.

Stress Behaviour in Compression of Contact-Monolithic Joint of Self-Supporting Wall of Large Panel Multi-Storey Building

The article deals with the behaviour of a contact-monolithic joint of large-panel buildings under compression. It gives a detailed analysis and the descriptions of the stages of such joints failure based on the results of the tests and computational modelling. The article is of interest to specialists who deal with computational modelling or the research of large-panel multi-storey buildings. The text gives a valuable information on the values of their bearing capacity and flexibility, the eccentricity of load transfer from upper panel to lower, the value of thrust passed to a ceiling panel. Recommendations are given to estimate all the above-listed parameters.

Structural, mechanical and corrosion studies of Cr-rich inclusions in 152 cladding of dissimilar metal weld joint

Cr-rich inclusions were discovered in 152 cladding at the inner wall of domestic dissimilar metal weld joint, and their morphologies, microstructures, mechanical properties and corrosion behaviors were systematically characterized by SEM, TEM, nanoindentation and FIB. The results indicate that the Cr-rich inclusions originate from large-size Cr particles in 152 welding electrode flux, and they are 50–150 μm in size in most cases, and there is a continuous transition zone of 2–5 μm in width between the Cr inclusion core and 152 cladding matrix, and the transition zone consists of Ni & Fe-rich dendritic austenite and Cr23C6 and Cr matrix. The transition zone has the highest nanoindentation hardness (7.66 GPa), which is much harder than the inclusion core (5.14 GPa) and 152 cladding (3.71 GPa). In-situ microscopic tensile tests show that cracks initialize preferentially in transition zone, and then propagate into the inclusion core, and creep further into 152 cladding after penetrating the core area. The inclusion core and its transition zone both share similar oxide film structure with nickel-base 152 cladding matrix in simulated primary water, while those two parts present better general corrosion resistance than 152 cladding matrix due to higher Cr concentration.

Airtightness improvement solutions for log wall joints

The air leakage rate of handcrafted log wall and window joint and handcrafted log wall corners using Scandinavian saddle notch or dovetail notch were measured in the laboratory in an airtight measuring chamber. In the first test setup, the joint between the log wall and a window frame was sealed using various commonly practiced methods. Commonly used sealing methods were applied on both corner notches and the joint between logs to evaluate the effectiveness of these sealing methods.The best natural sealing material was peat moss that reduced air leakage of Scandinavian saddle notch by 77% and that of the dovetail notch by 84%. The best modern sealing material was special joint sealant that reduced air leakage of Scandinavian saddle notch by 87% and that of the dovetail notch by 70%. After improving the dovetail notch with PU foam, the air leakage reduced to 94% compared to the original unsealed version.

Analysis of Physical Parameters for External Partition Wall Joints Insulated from The Inside

The article introduces material and technological characteristics in insulation of external partitions from the inside. Selected joints of external partition walls were analyzed: corner joint of external walls and wall-window joint in a frame cross-section. The numerical calculations were performed using TRISCO and WUFI software with various isolation thickness and location. Basic physical parameters were defined: linear heat penetration coefficient Ψ, temperature distribution, temperature factor fRsi and real pressure distribution of steam and saturated steam, and humidity increase of external walls and their joints for insulation applied from the inside. Based on calculations and analyzes performed design recommendation were formulated resulting from application of insulation from the inside, arising from binding requirements for heat and humidity.

Seismic design of floor–wall joints of multi-storey CLT buildings to comply with regularity in elevation

The effects of irregularity in elevation of cross-laminated timber buildings have not been fully analysed in literature to provide useful information for the design. In this work, a number of building configurations, regular or irregular in elevation, characterized by a different arrangement per storey of the floor–wall joints have been analysed by means of non-linear dynamic analyses. Comparative results in terms of ratio between the behaviour q-factor of the investigated irregular configurations and that of reference regular ones, show that less dissipative capacity can be expected if the building is irregular due to a disequilibrium among storeys between the actual and the required strength provided by the floor–wall joints. A correlation method to estimate the behaviour q-factor for perfectly regular cross-laminated timber buildings is here presented and extended to in-elevation irregular ones. A new empirical formulation to assess the reliable corrective factor accounting for the irregularity in elevation of cross-laminated timber buildings, according to Eurocode 8 provisions, is also proposed. A final discussion about the implications of in-elevation irregularity on the building design is reported.

Nonlinear shear behavior of rock joints using a linearized implementation of the Barton–Bandis model

Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing, inducing dilation and resulting in nonlinear joint shear strength and shear stress vs. shear displacement behaviors. The Barton–Bandis (BB) joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints. The BB model accounts for asperity roughness and strength through the joint roughness coefficient (JRC) and joint wall compressive strength (JCS) parameters. Nevertheless, many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr–Coulomb (M−C) model, which is only appropriate for smooth and non-dilatant joints. This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior. To bridge the BB and the M−C models, this paper aims to provide a linearized implementation of the BB model using a tangential technique to obtain the equivalent M−C parameters that can satisfy the nonlinear shear behavior of rock joints. These equivalent parameters, namely the equivalent peak cohesion, friction angle, and dilation angle, are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing. The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre- and post-peak regions of shear displacement, respectively. Likewise, the pre- and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established. Verifications of the linearized implementation of the BB model show that the shear stress-shear displacement curves, the dilation behavior, and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.

Effect of Different Wall Roughness on the Frictional Behavior of Rock Joints

ABSTRACT Rock discontinuities play a crucial and critical role on the deformational and failure behavior of the rock mass. In most investigations, both the surfaces of the rock joints are considered to have same roughness. But, in nature, the walls of a fresh joint is only expected to be complimentary and to have same roughness. Weathered and water percolating rock joint is most likely to develop different surface roughness on the two opposite walls. So, the shear strength and frictional response behavior derived from the single joint roughness coefficient (JRC) assumption cannot be used in such a condition. To address this shortcoming, we have prepared sandstone blocks with different surface roughness and conducted experiments in a tribometer. The static friction, shear stiffness and coefficient-of-friction of the joint surfaces were calculated and their changes with increasing normal load were noted. One of the major findings of this paper is that, shear strength of the joints may not have a direct correlation with the increasing JRC value of the individual joint walls. Hence, some of the joint walls having higher cumulative JRCs were found to show lower shear strength than those with lowers roughness. This is because, the opposing walls of such joints are not anymore complementary and the frictional resistance is completely controlled by the height and contact area of the asperites.

Back analysis of an ancient rockslide at Lake Fundudzi, Limpopo Province, South Africa

A massive rockslide occurred in the Soutpansberg Mountains of the Limpopo Province ~20,000 years ago that blocked the course of the eastern flowing Mutale River forming Lake Fundudzi, which is the only known true inland lake in South Africa. The landslide occurred in the northwestward dipping and highly jointed Fundudzi Formation of the Soutpansberg Group. The failed slope was observed to be a homogenous jointed sandstone rock slope which is quartzitic in places. Cluster analysis, which uses fuzzy clustering in Rocscience Dips, revealed three major joint sets (JS1, S0 and JS3) in the rock mass with an average dip and dip direction of 85°/237°, 15°/283° and 73°/157°, respectively. The main failure plane best correlated with JS3, which dips towards the lake. The kinematic analysis also revealed that the mechanism of failure was planar which is in agreement with site observations. The strong rock material classification of the sandstone from a laboratory index and mechanical tests was one of the indicators that failure could have been mostly structurally controlled. The technique of back-analysis was employed using RocPlane in order to investigate the geotechnical conditions that may have resulted in failure. The results obtained from the sensitivity analysis in RocPlane showed that the joint roughness coefficient (JRC) followed by the residual basic friction angle (ϕ r) were the main influential shear strength parameters on the factor of safety, F, as opposed to the joint wall compressive strength (JCS) which has very little impact on F for the range of values considered. Results from back-analysis show a range of possible combinations of JRC and ϕ r values under different groundwater and seismic conditions. Whilst the groundwater shows more impact than the seismic coefficient, the field evidence points to seismic activity as a more plausible trigger than groundwater. This study shows the usefulness of back-analysis techniques in assessing various conditions of failure that may have resulted in ancient rockslides. Although it may not result in a unique set of geotechnical parameters that may have resulted in failure, it, however, gives an insight into probable causes of failure and, thus, can be useful in mitigation of future failures.

The Role of Mortar Microstructure in Providing the Face Wall Structural Integrity

The basic condition for proper function of a face wall in external environment is providing structural integrity within its entire period of usage. Structural integrity can be defined as construction ability to maintain bearing capacity, functionality and shape within acceptable ranges without arising state of emergency during exploitation. Wall structural integrity results first of all from construction mortar which, except for bearing function should also provide protection from entering water into the wall interior. The processes of water capillarity, drying, and freezing are dependent on microstructure and open porosity.In the article there are introduced tests of three mortars (cement, cement with plasticizer, and cement-lime based) formed in wall joints. In order to prepare mortar samples from joints of wall elements for porosimetry tests, mortar was separated from bricks in such way that whole joint was left intact. By breaking, each layer of mortar was divided parallel to the joint surface into three parts – two parts adjacent to brick base (each 1/4 of layer thickness) and the middle part sized 1/2 of joint thickness. By Mercury Intrusion Porosimetry the basic microstructure parameters were measured, as well as pore volume distribution in the function of their diameters as integral and differential relation. The analysis of pore volume variation for integral distribution let us state the pore sizes which as additional, are formed in mortar in the area of joint adjacent to wall element surface. Independently of mortar type, in this area there are additional pores created, which are responsible for capillary flow. In cement mortars there are additionally macropores created which decides about water migration through a joint and about its gas permeability.

Six new species of the lichen genus Pyrenula (Pyrenulaceae) from Northeast Brazil

Six new Pyrenula species are described as new to science, viz. Pyrenula aurantiothallina C. O. Mendonça, Aptroot & M. Cáceres, with orange thallus with KOH+ purple anthraquinone, simple low conical ascomata, inspersed hamathecium, and ascospores 3-septate, 19.5–22.5 × 7–8.5 µm, generally somewhat constricted at the septa; Pyrenula coccinea C. O. Mendonça, Aptroot & M. Cáceres, with yellowish brown thallus and ascomata with 6 to 25 together immersed in a pseudostromata with partly fused outer walls but separate, apical ostioles, covered with red pruina, ascospores 3-septate, 15–18(–20) × 5–6 µm; Pyrenula diamantinensis C. O. Mendonça, Aptroot & M. Cáceres, with thallus yellowish brown, corticate, partly with a layer of whitish pruina, with (often eroded) pseudocyphellae, ascomata flattened to subglobose, numerous, partly covered by a layer of whitish pruina, 0.3–0.5 mm diam., mostly with 2–10 sideways touching but not totally fused, clypeus in upper half much thicker than below, ascospores 3-septate, 26–33 × 11–16 µm, lumina mostly obliquely quadrangular; Pyrenula lilacina C. O. Mendonça, Aptroot & M. Cáceres, with lilac thallus, simple ascomata, and ascospores 3-septate, 31–37 × 11–14 µm; Pyrenula supralaetior C.O. Mendonça, Aptroot & M. Cáceres, which is similar to P. laetior Müll. Arg., but with ascospores 25–31 × 11–13 µm; and Pyrenula violaceastroidea C. O. Mendonça, Aptroot & M. Cáceres, with ascomata pyriform, aggregated by 3–6 perithecia with a shared ostiole but without joint walls (parmentarioid), ostiole, ascomata and thallus partly covered by wine-red to purplish, KOH+ purple, anthraquinone. They were all found by the first author during several recent field trips in the North and Northeast of Brazil.

Evaluation of a technical survey and the renovation needs of old rural wooden houses in Estonia

Wooden detached houses represent the majority of buildings in rural areas in Estonia. The design service life of these rural wooden building is nearing its end. Before starting major renovation of these houses, a comprehensive survey of the buildings is required in order to determine all the visible and hidden damage of constructions. A renovation plan may be composed after the houses’ technical condition has been examined completely. This paper provides a description of the issues that need to be reported in a technical survey of an old log house. The relevant survey method was tested on 50 houses in Estonia. Besides describing survey components and methods, detailed information is given about building envelope elements and possible variations. All detected damage is described and illustrated with drawings and photographs. Every envelope component of a house should be checked for possible damage during an inspection. There are hidden components, especially below the floor where opening the construction or using a flexible camera is needed for an inspection. Most often, rot damage was found in foundation wall and log wall joints, the main reasons for it being broken or missing rain protection or waterproofing for the edge of the foundation. Often damage was identified in crawl spaces (floor beams) and near water leaks in the roof.

해석 방법에 따른 창호-벽체 접합부의 결로 방지 성능 비교

The purpose of this paper is to compare calculation results of performances of condensation resistance of joints of windows and walls according to analysis standards, simulation programs, and modeling methods and also analyze the causes. Domestic and relevant foreign criteria were reviewed, and Heat transfer simulation was conducted targeting double and triple glass windows. Also, an improved modeling plan was proposed comparing performance of condensation Resistance depending on the modeling approach. The analysis results, from different calculation methods of effective thermal conductivity of cavity spaces showed significant differences in accordance with the analysis standards. It appeared that automatic calculation of effective thermal conductivity by ISO 15099 was impossible using Physibel Bisco. Therefore, an improved and simplified modeling method using respective heat transmission coefficients for window panes and frames was proposed. It was confirmed that compared to the simple modeling, the improved modeling method decreased errors of surface temperature on joints of windows and walls by up to 10% and compared to the detail modeling, all modeling cases were within 10% or less.