Frame Wall Research Articles

T-joint Fillet Laser Welding of High-Strength Stainless Steel for Curtain Wall Frames

The aim of this study is to develop a frame for exterior facades of architectural curtain walls using numerical and experimental analyses of stainless steel T-joint fillet laser welds. The main characteristics required for this frame are that it should have an aesthetic surface from the narrow bead width and exhibit improved tensile strength at the joints. In this study, a method for optimizing the welding conditions was developed to simulateneously improve two mutually exclusive properties. It is essential to achieve more than 80% penetration of the weld zone to guarantee tensile properties. Laser welding parameters such as power, welding speed and focus height are the main variables. In addition, when high-strength stainless steel is applied as a curtain wall frame, its structural performance improves compared to conventional stainless steel.

The impact of wooden studs on the moisture risk of timber frame constructions

Since timber frame constructions can help to reduce CO2-emissions and lower the embodied energy of buildings, the market share of timber-based buildings is growing across Europe. Unfortunately, timber frame constructions are found to be susceptible to moisture damage, such as interstitial condensation, mould growth and wood rot. To avoid moisture damage, a correct design of the wall composition is crucial, with special emphasis on the ratio between vapour resistance of wind and vapour barrier. Given that experimental investigations are time-consuming and expensive, numerical tools are common to assess the hygrothermal behaviour of building components. And although timber frame constructions are inherently two- or even three-dimensional due to the embedded wooden elements, most often, 1D-simulations focussing on the basic configuration with insulation between wind and vapour barrier are conducted. This paper investigates to what extent neglecting the embedded wooden elements influences the risk assessment of the wall. Three different wall configurations have been considered and their hygrothermal response, as predicted by 1D- and 2D-numerical simulations, are compared. Variability of the exterior climate is included by using four distinct different climate regions. Contrary to common assumptions, buffering of moisture in wooden elements does not always lower the risk on moisture damage, but might even increase it. While the predicted risk on mould growth was found to be similar between 1D and 2D-simulations, the opposite was found for the risk on interstitial condensation. Mainly for cold climates and wall configurations with hardly any other hygric buffering capacity, levels of interstitial condensation were found to be significantly higher when taking the wooden elements into account in the numerical simulations. Hence, care should be taken when assessing the reliability of timber frame walls based on 1D-simulations only.

Numerical analysis of timber frame wall filled with hemp concrete

This paper presents a numerical study of the lateral load-carrying capacity of hemp concrete as infill material in timber frame walls. The parameters that significantly affect the lateral resistance of hemp walls were investigated. For this purpose, vertical stud timber frame walls measuring 2.5 m in height and 1.2 m in length were used as the benchmark to validate earlier experimental work. A numerical study of three timber walls filled with hemp concrete was conducted to assess the effect of wall length on the lateral load-carrying capacity of hemp concrete. Three vertical stud timber frame walls with a standard height 2.5 m and different lengths (1.2 m, 1.6 m and 2.4 m) were investigated using Abaqus software. This study confirms, firstly, that the length of a timber wall plays a significant role in the lateral load-carrying capacity of hemp concrete. Secondly, the contact and bonding between the hemp concrete and timber wall have a significant effect on the lateral load-carrying capacity of hemp concrete as infill material in timber frame walls. It was clear, from the numerical results, that increasing the length of the wall significantly increases the contribution of hemp concrete to lateral resistance. Good contact and bonding between the hemp concrete and the timber elements also increase the lateral strength of the hemp wall.

Analysis of the Performance of Natural Composite Materials Reinforced with Sago Sheath Fibers as an Alternative Material in Overcoming the Effect of Urban Heat Islands on Buildings

Local knowledge of a region is an asset that encourages the identification of a region. Hence, the specificity, uniqueness, and character that animates a particular city can distinguish it significantly from other cities. Sago tree fronds are widely applied to buildings as an alternative material for making tiles for roofs and other parts of buildings. The sago palm has long been used for making roofs and walls, especially in traditional houses. Few previous studies have used sago fronds as a manufacturing material for traditional houses. However, based on data in the field, many traditional houses still use sago fronds as a roof and wall framing material. This is also an effort to overcome the urban heat island phenomenon (UHI) in buildings. The UHI phenomenon is a phenomenon of urban development that highly affects environmental quality conditions and causes microclimate changes where air temperature conditions in urban areas are higher than the surrounding air temperatures. Sago midrib fiber is a natural composite material used as a reinforcing material for natural composite materials due to its thermal and mechanical properties. Composite materials using the hand lay-up technique—with characterization methods including the impact test and the DSC test, variations in NaOH levels, and variations in the resin–catalyst matrix—were used in this study. The results obtained were then compared with those in the literature. The results showed that 6% NaOH obtained the most significant impact value of 2.1 J, and the resin–catalyst matrix variation of 97.5%:2.5% obtained the most significant impact value, which was 2.4 J. Meanwhile, the DSC test results showed that the material’s best value for retaining heat was at 4% NaOH content variation and a resin–catalyst matrix variation of 97.5%:2.5%.

Nonlinear Static Analysis of Core Wall RCC Framed Buildings

RCC framed buildings mainly consists of shear walls and columns for resisting lateral force due to earthquakes. In most of the framed buildings shear walls are provided in the outer frames. In addition to shear walls provided in the outer frames, RCC lift -well (core wall) is also provided in the inner core of the buildings to accommodate lift. Core wall also acts as shear wall contributing to the lateral resistance to the buildings. In the present study, nonlinear static analysis is performed to study the behaviour of high rise RCC buildings, the buildings have a centralised lift core wall with a door opening and shear walls in outer frames. The flange of core wall is joined together at regular interval by floor and slabs and connecting beams to provide proper connection in between flange. This Residential G+14 RCC framed building is lying in seismic zone 4 and analysed as per guidelines of is 1893 (part 1) 2016 and ETABS 17.0.1. Responses namely lateral loads, story drift, base shear, story displacement and the formation of plastic hinges compared for two types of buildings, namely with core wall and without core wall to understand the effect of core wall against the lateral loads.

Using a decision-making tool to select the optimal industrial housing construction system in Tehran

ABSTRACT Industrial dwelling construction (IDC) combines offsite and onsite construction methods. The current work proposes a multiple-criteria decision-making assistant system (DMAS) approach for evaluating home buildings, selecting decision agents, and determining acceptable IDC types and characteristics for large-scale housing enhancement. Using the analytical hierarchy process (AHP), a multicriteria DMAS was planned. Literature reviews and expert interviews were used to assess thirty decision agents. To validate the procedure, five IDCs were analyzed as case studies. Thirty professionals analyzed decision agents' and housing systems' priority vectors using questionnaires. Three decision agents were identified: (1) user needs, (2) the building industry, and (3) the supply chain. Consequently, Prefabricated Reinforced Concrete Slab, Beam, and Column Blocks (PRCSBCB) and Light Steel Frame Wall Panels (LSFWP) can be used to construct suitable dwellings. These construction options are low-cost, lightweight, and easy to install. They also use inexperienced local workers. Results showed the method's potential and usefulness with so many choices and decision agents. This research examines knowledge and skill gaps in Iran's IDC and encounters a shortage of IDC specialists and mass-construction variants. The study identifies key decision-agents and housing options for quick, appropriate, and cost-efficient mass housing and helps professionals, entrepreneurs, and decision-makers make better decisions.

Effect of Outstanding Flanges on Stress Concentration in Box Beam

Background of the research: A conventional box-type structure is generally used in constructing the core/shear wall, internal frame, and steel box girders. Tube-in-Tube with single and multiple tubes reduces the shear lag effect and lateral deformation in a tall tubular structure. Purpose: However, the present study focuses on the behavior of a modified form of the conventional box beam, i.e., a box beam with outstanding flanges. Thus, this study analyzes a box beam with outstanding flanges and compares the shear lag effect (Stress concentration) and lateral deformation with a conventional box beam. Methodologies: The minimum potential energy principle is applied to analyze the models and validated with the finite element results. Principal results: The transformation is observed to be reducing the shear lag effect at the web-flange junction and lateral deformations of the beam. In addition, the transformation also controls stress reversal. The modification demonstrated in the present study is stiffer than the conventional box-type structure as a core/shear wall or internal frame. Major conclusions and contributions to the field: This modification may be an integral part of tall tubular buildings producing significantly lowered stress concentration and lateral deformation. The present study is also applicable to strengthening steel box girders. It is possible to extend the bottom plate with the outstanding flange to increase the load-bearing capacity or strengthen the existing steel box girder. Therefore, the transformed box beam can be utilized as an economical alternative in constructing tall tubular buildings and retrofitting the steel box girder bridge. It is convenient and straightforward as there is no need to stiffen any part of the core/shear wall or internal frame. Additionally, there is no need to remove elements from the existing girder or alter its dimensions. Add the remaining flange by welding or bolting it onto the bottom flange to extend it. Limitation of the study and future research: A different assumption of stress function can be used in the flange and web when an orthotropic membrane theory is adapted to analyze the frame tube structure.

Outdoor mmWave Channel Modeling for Fixed Wireless Access at 60 GHz

AbstractThe large bandwidths that are available at millimeter wave (mmWave) frequency bands allow high‐throughput wireless communication systems that enable fixed wireless access (FWA) applications. In FWA networks, a stationary link is created between antennas installed at building facades or street furniture, such as lampposts. A Line‐of‐Sight (LOS) scenario is preferred, but to guarantee the quality of service to the user, communication should remain possible when the LOS path is obstructed. In this paper, outdoor channel models at 60 GHz are presented that can be used for the design and optimization of FWA networks, based on measurements with the Terragraph wireless system using IEEE Std. 802.11ad radios. LOS path loss measurement data is analyzed and building reflection loss, diffraction loss, and vegetation loss are measured. There is limited diffuse scattering, but reflections on the wall frame structure result in reflected paths with low losses. Existing vegetation models that are based on measurement campaigns at lower frequencies underestimate vegetation loss at mmWave frequencies, as measured excess attenuation values range from 15 to 25 dB for distances lower than 14 m. The presented channel models are used for link budget calculations for FWA networks.

The wall–frame interaction effect in CLT-steel hybrid systems

Behaviour and capacity of cross-laminated timber (CLT) infills built inside steel frames have been given increasing research attention in recent years. It is widely accepted that when the CLT wall panel is built in tight contact with the bounding steel frame to participate in the load sharing, its inherently large in-plane stiffness will attract additional forces to the frame area and change the behaviour of the hybrid system. If not designed properly, the structural integrity of both the infill and the frame will be compromised. It is thus crucial to accurately evaluate the contribution of the infill CLT wall panel to the stiffness and strength of the hybrid system. To that end, a finite element study was performed to investigate the frame-wall interaction effect on the behaviour of hybrid systems. The lateral stiffness, lateral load capacities and hysteretic characteristics of the hybrid systems with frictional and connected interfaces were investigated. The load-sharing effect between the CLT wall and the steel frame was studied. The numerical results showed that the connected models were very effective as the infill absorbed a substantial part of the lateral load, during the initial stages of loading.

Optimization design method of pressure pentamode materials

Pentamode materials have broad application prospects in the control of underwater elastic waves. It is of great significance to design pentamode materials configuration with certain compressive resistance to promote the underwater application of pentamode materials. Based on the particle swarm optimization algorithm, a multi-objective optimization design method considering structural pressure resistance is proposed. The optimization objective consists of three parts: pentamode attribute matching degree, underwater compression ability test, and target density and target modulus matching degree. Aiming at the octagonal frame structure with a fan-shaped mass block in the inner corner, the multi-objective optimization design method is adopted to optimize the thickness of the frame wall t, the radius of the mass block R, and the limit lengths l2 and h2. After optimization, the pentamode attribute matching degree of the material is 0.998. When the safety factor is equal to 1.5, it can withstand the hydrostatic pressure of more than 200 m water depth. In the frequency domain of 3 K to 6 kHz, the average value of the total scattering cross-section of the material is 0.055, which is similar to the sound propagation in pure water. The research shows that the multi-objective optimization design method of pentamode materials can be used to design the configuration of pentamode materials considering both underwater pressure resistance and sound transmission performance. The research results are expected to provide a method reference for the configuration design of underwater pressure-resistant pentamode materials.

Effects of air change rate and moisture load related to moisture index and the expected moisture performance of a wall assembly

Mould may grow in wood frame wall assemblies when subjected to excessive moisture load over prolonged periods of time. To permit estimating the moisture risk in wood-frame wall assemblies, one approach is to use hygrothermal simulations. This process requires access to relevant climate data and as well, knowledge and experience regarding the use of hygrothermal simulation tools. As well, it may not be practical to undertake such an analysis for each different type of wall being considered for a given location and use. In this regard, the moisture index is usually considered when designing measures for protection from precipitation as it is a useful indicator that reflects the intensity and duration of moisture loads to which a building envelope may be subjected over time. Hence, in the study described in this paper, consideration was given to determining the correlation between mould growth index and moisture index as this would be beneficial to building practitioners in determining the level of protection to mould growth as may be achieved in different climate regions having a particular value for moisture index. The mould growth indices were generated for Oriented Strand Board (OSB) incorporated within a wood-frame vinyl-clad wall assembly located in selected Canadian cities from which moisture indices were derived. Effects of moisture load and air change rate were also taken into account when assessing the correlation between the two indices. The results indicate that when the air change rate and moisture load are favourable to maintain a humid environment, strong correlations were observed between the two indices, vice versa.

Study on the influence of constructional column on the seismic performance of infilled wall frame structure

Aiming at the problems of poor construction quality and low efficiency in the construction of cast-in-situ constructional columns, this paper puts forward a kind of fabricated constructional column. Through four full-scale model tests and numerical simulation, the hysteretic energy consumption, stiffness degradation and deformation capacity of infilled wall frames with fabricated constructional columns were studied. The results showed that the specimens with fabricated constructional columns have good in-plane seismic performance. The test phenomenon showed that the crack development mode of masonry infilled wall was changed by the setting of cast-in-situ constructional columns, and its failure was mainly the “X" shaped shear crack. The failure of the infilled wall without any constructional column or with the fabricated constructional column was mainly caused by the horizontal slip cracks. Compared with the cast-in-situ constructional column specimens, the fabricated constructional column specimen has low damage characteristics under the same drift. Finite element simulation can effectively fit the failure and seismic performance of the specimens. This paper can provide references for the application of the new construction technology.

Case Study in Modular Lightweight Steel Frame Construction: Thermal Bridges and Energy Performance Assessment

This paper proposes an improvement of the conventional Lightweight Steel Frame (LSF) wall structure suitable for the design of high-performance modular buildings. A mobile module, named MUZA, is used as a case study building to analyse the performance of such LSF structures in terms of their thermal bridging effect on the U-value of the opaque envelope elements, linear heat losses at junctions, and moisture condensation risk, as well as thermal bridging effect on the overall energy performance of the building. The study included an additional climate- and orientation-dependent analysis that examined the performance of MUZA under various conditions. The main conclusion is that the steel studs increase the U-value from 28.4% to 41.6% compared to cases without the studs, which consequently increases transmission losses through opaque elements. Thanks to the continuous covering of the metal studs with thermal insulation, the thermal bridges at the element junctions are minimized, and in almost all cases, the Ψ-values are well below 0.1 W/(m·K) and are free from moisture condensation. The overall impact of thermal bridges on heating energy demand is significant, while the impact on cooling energy is less pronounced. The designed module with the proposed LSF wall structure can meet the Croatian requirements for Nearly Zero-Energy Buildings (NZEB), but the shading devices and photovoltaics orientation must be optimized depending on the climatic conditions and the orientation of the large transparent openings. MUZA can be a promising solution for post-disaster housing, providing better indoor environmental quality, healthy living conditions, and low energy bills for the affected people. In addition, it can also be used for permanent housing when a fast and robust modular construction is required which is also energy efficient and sustainable.

In-plane seismic behavior of lightweight steel drywall façades through quasi-static reversed cyclic tests

A lightweight steel (LWS) drywall façade is one of the most widely used architectural non-structural components in a building. This paper presents the results of in-plane quasi-static reserved cyclic tests carried out on 14 different full-scale façades made with LWS framing. The main goal of the study is to investigate the effect of various construction details on the seismic response of the selected facades. The investigated parameters include single or double frame walls, type of sheathing panels, presence of finishing, variation in surrounding constructional elements, absence of track members, type of connection to the surrounding constructional elements, and presence of protrusion. The effect of the construction parameters on the lateral response of the façades was examined in terms of strength, stiffness, force–displacement hysteretic response, and damage mechanisms. Therefore, the damage phenomena observed during the tests are reported, associating them with the three damage limit states based on the level of damage. For the definition of seismic vulnerability, the fragility curves for different façade typologies are also presented. Finally, based on the fragility data, the evaluation of seismic performance according to IDR limits for non-structural components given by Eurocode 8 is also performed.

Fragility assessment for new and deteriorated portal framed industrial buildings subjected to tropical cyclone winds

Low-rise portal framed industrial buildings are widely used as warehouses, workshops and storage facilities. Damage surveys following severe tropical cyclones have shown that both structural and non-structural damage can occur to these buildings. While non-structural damage to the building envelope of portal framed industrial buildings are considered by several existing fragility models, almost none exist that include structural failures in the wind fragility assessment. This study develops a fragility assessment method for portal framed industrial buildings that accounts for wind-induced damage to both structural (steel portal frame and end wall frame) and non-structural (metal cladding system and fenestration) building components. Fragility curves are developed for a prototype industrial building located on the cyclone-prone east coast of Australia considering four damage states with increasing damage severity. A Monte Carlo simulation incorporating probabilistic models of the spatio-temporal variable wind pressures, wind-induced demands and component capacities is employed to conduct the fragility assessment for both individual building components and the building system under critical failure modes. It was found that the fragility of structural framing is non-negligible when wind speed exceeds 80% of the design level. Structural framing failure is a major contributor to the most severe damage state and is a necessary inclusion in the fragility assessment for this type of building. A sensitivity analysis also showed that fastener corrosion can significantly increase the fragility of deteriorated buildings near to coastlines, particularly for low levels of damage.

Numerical analysis of the in-plane behaviour of decoupled masonry infilled RC frames

Damage of reinforced concrete (RC) frames with masonry infill walls has been observed after many earthquakes. Brittle behaviour of the masonry infills in combination with the ductile behaviour of the RC frames makes infill walls prone to damage during earthquakes. Interstory deformations lead to an interaction between the infill and the RC frame, which affects the structural response. The result of this interaction is significant damage to the infill wall and sometimes to the surrounding structural system too. In most design codes, infill walls are considered as non-structural elements and neglected in the design process, because taking into account the infills and considering the interaction between frame and infill in software packages can be complicated and impractical. A good way to avoid negative aspects arising from this behavior is to ensure no or low-interaction of the frame and infill wall, for instance by decoupling the infill from the frame. This paper presents the numerical study performed to investigate new connection system called INODIS (Innovative Decoupled Infill System) for decoupling infill walls from surrounding frame with the aim to postpone infill activation to high interstory drifts thus reducing infill/frame interaction and minimizing damage to both infills and frames. The experimental results are first used for calibration and validation of the numerical model, which is then employed for investigating the influence of the material parameters as well as infill’s and frame’s geometry on the in-plane behaviour of the infilled frames with the INODIS system. For all the investigated situations, simulation results show significant improvements in behaviour for decoupled infilled RC frames in comparison to the traditionally infilled frames.

Shaking table test and seismic behavior of Ningbo Hengda Tower

SummaryA super tall building named Ningbo Hengda Tower is located in Ningbo City, China. It has 91 stories with a total height of 450 m. The structure system of the building consists of three parts, that is, the reinforced concrete core, the outer frame system, and the outrigger trusses connecting the core wall and outer frame. The unique outer frame system is spindle shaped with oblique columns. The outrigger trusses are located at three different levels above the ground, thus strengthening the building and creating irregularities in the stiffness of the structure along the building height. Great challenges are existed in seismic design and analysis of the building. Shaking table test was carried out for a 1/40 scaled model of the building under a series of different base excitations with increasing amplitudes. The dynamic properties, seismic responses, and failure mechanism of the structure are investigated. Test results show that the structure behaved well under designed level earthquakes. The weak points of the structure are identified based on visible damage of the tested model, and some suggestions are made for the improvement of the seismic behavior of the building. It is suggested that measures be taken to improve the ductility of the building from floor 71 to floor 79 and the adjacent floors.

Review of the NRC Canada Studies on Fire Resistance of Walls: Results, Research Gaps and Design Guidelines

The National research council Canada conducted three major fire resistance studies on the interior party walls, interior fire separation walls and exterior walls. The fire resistance results of these studies were published over the past three decades and the publications were short in suggesting design guidelines for practioners’ use and gaps for future research. This paper summaries the fire resistance results of 35 full-scale wall tests, suggests design guidelines and identifies future research gaps for interior party walls, interior fire separation walls and exterior walls. The result summary includes the effect of different design parameters on the fire resistance performance of wall assemblies such as the stud type and spacing, number of stud rows, number of gypsum board layers and thickness, mid-height blocking, resilient channels installation and spacing, screws spacing for attaching gypsum board to either wall faming or resilient channels, insulation type and exterior wall sheathing type on the fire resistance of loadbearing and non-loadbearing wall assemblies. The summary results was used as the basis for suggesting design guidelines for practioners’ use and identifying gaps for future research to improve the fire resistance performance of wall assemblies. For example, the use of a reduced screw spacing from 406 mm o.c. to 203 mm o.c. in the gypsum board field and from 406 mm o.c. to 150 mm o.c. at the board joints was suggested for future research to keep the protective gypsum board layer attached to studs or resilient channels longer for a better fire resistance performance of wall assemblies. Also, fire resistance design guidelines are suggested, for examples, the use of rock fibre insulation for non-load bearing interior party walls to achieve 1.5-h fire resistance, the use of cellulose fibre insulation for loadbearing fire separation walls to achieve 2-h fire resistance rating and the use of reduced screw spacing in attaching the gypsum board to wall framing from 406 mm o.c. to 203 mm o.c. for loadbearing exterior wall assembly with gypsum board glass mat sheathing to expand the fire resistance rating from non-useful 30-min to a useful code compliance 45-min fire resistance rating assembly. Additional suggested examples for future research gaps and design guidelines are also provided.

Analysis of the critical temperature on load bearing LSF walls under fire

Light Steel Frame (LSF) walls are widely used in building structures, used as partition walls and load bearing walls. The LSF is usually protected by layers of homogeneous plates or composite plates, with or without insulation materials in the cavity. This investigation presents the simulation results of composite LSF walls in reduced scale and full scale, based on variable load levels (20 to 80%). The numerical model uses a hybrid model approximation, based on the experimental tests to accurately determine the temperature field. The numerical model is validated with experimental results, at reduced and full scale, both at room temperature and under fire conditions. This modelling technique can follow the thermal and mechanical degradation of the protection layers of the LSF wall and determine the fire rating for load bearing (R) and insulation (I). The fire resistance (R) decreases with the increase of the load level. The insulation ability is also predicted for different protection materials. Relevant conclusions are presented to increase the insulation ability of LSF walls, especially when using non combustible double protection layers. The insulation ability to sustain fire usually increases with the number of studs and with the application of insulation material in the cavity region. The ability to sustain the load under fire also increases with the number of studs, especially for higher load levels. The ability to sustain the load also increases with the number of protection layers, changing from 16% at 20% load level, to 42% at 50% load level.A new proposal is presented for the critical temperature of the LSF, based on the maximum temperature of the LSF during the fire, allowing the calculation of the critical temperature, based on the load level of the specimen. This relation can predict the fire resistance time, based on the preliminary thermal analysis of the specimen. The reduced scale specimens present higher critical temperatures when compared to the full scale specimens, due to the typical failure mode (local modes for the reduced scale and global modes for the large scale).

Critical Temperature of Load Bearing LSF Walls Under Fire

AbstractLight Steel Frame (LSF) walls are widely used in building structures, used as partition walls and load bearing walls. The LSF is usually protected by layers of homogeneous plates or composite plates, with or without insulation materials in the cavity. This investigation presents the experimental and the simulation results of composite LSF walls in reduced scale and full scale, based on variable load levels (20 to 80%). The numerical model is validated with experimental results, at reduced and full scale, both at room temperature and under fire conditions. This modelling technique can follow the thermal and mechanical degradation of the protection layers of the LSF wall and determine the fire rating for load (R) and insulation (I). The fire resistance (R) decreases with the increase of the load level, being the critical temperature of the steel structure presented by the maximum temperature of the Hot Flange (HF). A new proposal is presented for the critical temperature of the LSF, based on the maximum temperature of the LSF during the fire. The insulation ability is also predicted for different protection materials. Relevant conclusions are presented to increase the insulation ability of LSF walls.