Fire Design Research Articles

An experimental and numerical analysis of the fire resistance of concrete elements incorporating ROBOVOID void formers

Disposal of plastic waste poses a significant scientific challenge due to its non-biodegradable properties, increasing volume of production, and low recycling rate. One potential solution is its’ manufacture into void formers for use in concrete building elements. However, plastics soften and decompose when exposed to high temperature fire which poses a challenge for fire safety design and certification of construction elements. A combined experimental and numerical study is presented to determine the fire resistance of concrete building elements that incorporate a novel recycled plastic void former (ROBOVOID, US patent No. 11,352,789). Multiple experimental fire exposure tests are performed to determine fire resistance and assess thermally induced damage for various building elements incorporating ROBOVOID. The fire resistance of the voided elements increased as the concrete content increased, or the fire intensity or exposure duration decreased. A finite element model is presented that can predict the thermal response of the building elements when subject fire representative of the Australian Standard Bushfire Attack Level (AS 1530.8.1), Building-to-Building (AS 5113) and Fire Resistance Level (AS 1530.4) conditions. The analysis indicates that polymer-based void formers can be incorporated into concrete structures while maintaining a high level of fire resistance for a variety of fire conditions.

Fire Resistance Test and Numerical Simulation on the Tube Structure of Steel–Concrete–Steel Immersed Tube Tunnel

To provide references for the fire prevention design of steel–concrete–steel immersed tube tunnels, four types of test conditions—no fire protection, fireproof coating insulation, single-layer seam fireproof boards, and double-layer seam fireproof boards—were carried out using partial full-size structural test members. Additionally, the thermal insulation effects of various fireproofing technology solutions were contrasted and analyzed. Combined with the numerical simulation analysis, the temperature distribution law inside the tube structure under various fireproofing measures and the temperature rise law of measuring points at different depths were studied, and the protective effect of the fireproof layers on the tube structure under high fire temperature was demonstrated. The results of the numerical simulation and the experimental data agree well. The results show that adding fireproof layers can significantly lower both the steel shell’s surface temperature and the depth of fire impact. Without fire protection, the surface temperature of the bottom steel shell exceeds 300 °C at 69 s, and the member bursts. The fireproof coatings are cracked and flaking and cannot meet the fire resistance limits. Both single-seam and double-seam schemes of calcium silicate boards can meet the fire resistance limit requirements and the latter has a better heat insulation effect.

Study on smoke propagation in tunnel construction of a hydropower station: A full-scale fire experiment

In this study, full-scale fire experiments were conducted in a hydropower station to investigate smoke propagation during tunnel construction. The flame height, smoke temperature and stratification, smoke descent and spread velocity were analyzed via measurements and on-site observations. The initial combustion stage was largely affected by ignition source during tunnel construction for diesel pool fire, and the average flame height in the fully developed stage could reach 1.4–2.1 m in experimental fire scenarios. The gradient of the smoke temperature evolution near the fire was the opposite for the upstream and downstream regions. The longitudinal temperature distribution was concentrated in a small range at the heights of the smoke layer, and gradually decreased by air entrainment as the height decreased, while further increasing in the lower half of the tunnel height in the near-fire region under heat radiation from the fire source. Moreover, distinct and stable smoke stratification formed during the fully developed combustion stage, and the smoke layer interface was at approximately half the tunnel height. Smoke descent was aggravated in the decay stage of combustion, and the fire risk remained high after the fully developed period. The smoke front spread velocity was empirically determined for the full-scale tunnel fire scenarios. Conclusions from full-scale experiments can support smoke control design and on-site fire emergency response plans for hydropower stations.

Shear resistance and design of stainless steel plate girders in fire

In this paper, the shear resistance and design of stainless steel plate girders at elevated temperatures are investigated. A broad range of parameters influencing the structural response of stainless steel plate girders in fire are taken into account, considering (i) austenitic and duplex stainless steel grades, (ii) rigid and non-rigid end posts, (iii) different aspect ratios for the unstiffened portions of the plate girders, (iv) various web slendernesses and (v) different elevated temperature levels. The influence of these parameters on the behaviour of stainless steel plate girders at elevated temperatures is considered. Currently, there is an absence of specific design rules on the fire design of stainless steel plate girders in the European structural steel fire design standard EN 1993-1-2. Considering this, an accuracy assessment of the room temperature stainless steel plate girder design recommendations of the European structural stainless steel design standard EN 1993-1-4 applied with the elevated temperature material properties of stainless steel is performed. The results indicate that this approach leads to unsafe and scattered ultimate strength estimations for stainless steel plate girders in fire. New fire design recommendations for stainless steel plate girders that are in accordance with the existing design provisions of EN 1993-1-2 and EN 1993-1-4 are proposed. The accuracy and safety of the proposed new design recommendations are comprehensively verified against the results from nonlinear finite element modelling.

Design and Analysis of Mini Fire Fighting Robot

Abstract: Fire Incident is a disaster that can potentially cause the loss of life, property damage and permanent disability to the affected victim. The Victim of Fire Incident can also suffer from prolonged psychological and trauma. Fire fighters are primarily tasked to handle fire incidents, but they are often exposed to higher risks when extinguishing fire, especially in hazardous environments such as in nuclear power plant, petroleum refineries and gas tanks. They are also faced with other difficulties, particularly if fire occurs in narrow and restricted places, as it is necessary to explore the ruins of buildings and obstacles to extinguish the fire and save the victim. With high barriers and risks in fire extinguishment operations, technological innovations can be utilized to assist firefighting. Therefore, this paper presents the design of a firefighting robot dubbed that can extinguish fire without the need for fire fighters to be exposed to unnecessary danger. It is designed to be compact in size than other conventional fire-fighting robot to ease small location entry for deeper reach of extinguishing fire in narrow space. It is also equipped with an ultrasonic sensor to avoid it from hitting any obstacle and surrounding objects, while a flame sensor is attached for fire detection. This resulted in It demonstrating capabilities of identifying fire locations automatically and ability to extinguish fire remotely at distance

A New, Green, Recyclable Fireproof Insulation Board for Use in Integrated Composite Structure Fire Protection Systems

A fireproof insulation board can be recycled, and the raw materials used in its production are very environmentally friendly, non-toxic and non-hazardous, and bring no harm to the human body and the surrounding environment. One practical application of fireproof insulation board is in an integrated composite structural fire protection system, which is a multidimensional comprehensive structural fire protection system proposed for the combined construction of buildings with different functions, such as horizontal and vertical, to ensure overall safety in the event of a building fire. The specific new technology of this new system includes an integrated structural fire protection system composed of a 3.00 h fire insulation board, which comes from the collection of textile scraps consisting of metals and buttons removed from clothes. To prove the effectiveness of this fireproof insulation board, its parameters were collected and put into FDS (FirG Dynamics Simulator, a CFD model of fluid flow during combustion developed by the National Institute of Standards and Technology), the fire safety goals considering the safety of building and personnel were established, and fire scene design based on the statistics of fire data and building codes was generated to test the safety of evacuation. To ensure the reliability of simulation results, an on-site physical fire test was conducted with the recycled insulation board. The result shows that the function of recycled board optimizes the phased evacuation design plan of personnel and solves the design difficulties of expanding fire zones and long evacuation distances when used in warehouses. Through the innovative design of the roof opening rate set at 30% and a hole spacing of 60 m, this underground fireproof insulation board is guaranteed to possess natural smoke exhaust conditions and can be used to improve public safety areas.

An advanced computational method for nonlinear inelastic thermo-mechanical analysis of spatial steel frames in fires

A novel advanced computational method incorporating the stability functions and the distributed plasticity model into the fiber beam-column element is proposed for the first time to predict the nonlinear inelastic thermo-mechanical behavior of spatial steel frames in fires. The space spread of plasticity is captured by tracing the uniaxial temperature-stress–strain relation of each fiber on sections at integration points. The element stiffness matrix is integrated via the Gauss-Lobatto numerical integration scheme. The nonlinear material behavior is captured by adopting the distributed plasticity model with the force-based interpolation function whereas the geometric nonlinearity of P-δ and P-Δ effects are considered by using the stability functions and a geometric matrix, respectively. The shear deformation and residual stresses which normally exist in steel frames are also considered. For the implementation, a nonlinear thermal incremental-iterative solution scheme based on the Newton-Raphson and Gaussian Elimination algorithm is also developed to address the nonlinear problems due to thermal expansion and material degradation. By taking advantage of the computational benefits of stability functions and the force-based interpolation function, the proposed method offers a novel computational framework for nonlinear structural analysis in a fire with excellent computational efficiency. The reliability and accuracy of the proposed program are verified by comparing the obtained results with results from test data, existing studies, and Abaqus. In addition, the computational performance of the proposed numerical program is about 10 times more effective than the Abaqus commercial software, thus would offer an extremely valuable tool for practical fire resistance designs.

Fire resistance and design assessment of Q355 circular hollow section joints

This paper presents an experimental investigation on fire resistance of circular hollow section (CHS) T-, Y- and K-joints. A total of 15 specimens subjected to brace axial load were heated inside an electric furnace, including 5 T-joints, 5 Y-joints and 5 K-joints. The temperature inside furnace follows ISO 834 standard fire curve. The principal parameters considered in this study include the dimensionless geometric parameters of joints β and γ, as well as the load ratio n. It is found that the failure mode of the axially loaded CHS joints under fire is chord plastification. Referring to the temperature-deformation curves of these CHS joints, it is suggested to adopt 1.5% ovalisation of the chord diameter as the failure criteria of the CHS joints under fire. The fire resistance of the CHS joints is seriously reduced with an increase in the load ratio n. By comparing the temperature development and the critical temperatures of the CHS joints obtained in the tests with the ones predicted by design codes, it is found that the measured temperature development curves of the CHS joints are significantly different from the calculated ones before the joint temperature reaches 550 °C. Further investigation is essential for temperature development analysis of CHS joints, especially in the aspects of the section factor Am/V of CHS joint. The fire resistance performance of CHS T- and Y-joints is shown to be reasonably estimated with the resistance method provided in modern design codes, even though the estimation on CHS K-joints is relatively conservative.

Numerical and Experimental Investigation on the Effect of Mechanical Smoke Extraction Caused by External Wind in Subway Station Halls

When fires break out in subway station halls, traditional smoke extraction (TSE) systems are employed with the aim of preventing smoke from spreading to the platform and passageways. The functionality of TSE systems under the influence of external winds needs to be further explored. Based on a numerical method, this study investigated the effect on TSE systems under the influence of external wind. A numerical model was established and validated by means of full-scale field tests to ensure accuracy. Subsequently, the validated model was applied to study the effect of the external wind directions and speeds on the smoke diffusion distance. The results showed that when all entrances and exits were on the windward side, the external wind direction led to serious longitudinal diffusion of the smoke toward the side with fewer entrances and exits of the station hall, and the diffusion distance increased with increasing wind speed. The diffusion distance reached a maximum value of 61.32 m when the outdoor wind was 5 m/s, which was 67.9% higher than that under no wind. When all the entrances and exits were on the leeward side, the external wind had little influence on the degree of smoke spread, with the greatest smoke diffusion distance being only 4.76% longer than that under no wind. When two entrances and exits were on the windward side and the other on the leeward side, the external wind caused smoke to spread to a passageway, and the degree of smoke spread was more unfavorable at higher wind speeds, with the longest diffusion distance being 7.28 m. To prevent smoke from spreading to passageways and to effectively shorten the longitudinal diffusion distance of smoke, an optimized smoke control (OSC) system was proposed, employing center and passageway smoke barriers, which were able to shorten the diffusion distances by 35.45%, 13.64%, and 2.35%. In particular, smoke diffusion did not occur in passageways. This study provides a reference for the fire safety engineering design of subway stations.

Simulation-Based Investigations of the Load-Bearing Behavior of Concrete Hollow Sphere Slabs Exposed to Fire

This paper concerns the investigations of the flexural capacity of concrete slabs with integrated concrete hollow spheres that are subjected to fire and their mass saving potential compared to solid slabs. (1) Background: The overuse of concrete in construction contributes considerably to global CO2 emissions; therefore, the potential for mass reduction in structural components must be fully exploited. However, the design regulations for weight-minimized components, particularly slabs with internal voids, are often not explicitly covered by standards, such as the fire design standard relevant to this paper. (2) Methods: Based on the design guidelines for statically determinate structures in Eurocode 2-2 and DIN 4102-4, a solid slab and a concrete slab with concrete hollow spheres are designed and evaluated with regard to their weight and flexural capacity when subjected to fire. The temperature profiles within the slab cross-section exposed to fire are simulated using ABAQUS finite element software, considering the physically nonlinear, temperature-dependent material behavior of concrete and steel. Using these results, the strain distribution corresponding to the maximum flexural moment is iteratively determined at the weakest cross-section, which exhibits the largest void. (3) Results: All components show sufficient flexural capacity for the target fire duration of 90 min. (4) Conclusion: In the context of this study, the design guidelines according to Eurocode 2-2 and DIN 4102-4 are proven to be fully applicable also for concrete hollow sphere slabs.

The integration of building information modelling and fire evacuation models

This paper presents a framework for integrating fire evacuation models into Building Information Modelling (BIM). The framework is intended to enhance coordination between stakeholders from diverse disciplines involved in the domain of fire evacuation design. It supports a full in/out data loop linking BIM and evacuation design tools, which enables professionals and authorities to review building design models coupled with evacuation data and perform comprehensive assessments more efficiently. The development of the framework is discussed along with the associated data exchange from a fire safety engineering perspective. Additionally, the benefits of two-way data flow between BIM and fire evacuation design tools are demonstrated by implementing a prototype system for coupling Revit, a popular BIM platform, and Pathfinder, a widely used evacuation simulator. This open source tool is named Evac4BIM and has been systematically tested to demonstrate its applicability in building design.

Discussing the development of domestic and foreign fire protection technical regulation and fire protection technical standard systems

This paper reviews the composition, development, and operation mechanism of domestic and foreign fire protection technical regulations and standards. Considering the development and problems of China's fire protection standard system and fire protection technical standards, this paper recommends fire safety professional engineering design specialization, suggests key research fields pertaining to fire protection technical standards, and elucidates how a performance-based fire protection technical standard system can be established.

Structural safety assessment of concrete tunnel lining subjected to fire

The basis of a possible fire design and verification approach to the linings of RC tunnels, using the performance-based approach, is presented. Starting from an extensive literature review, a selection of the most relevant tunnel fires was analysed. The study of structural consequences of these real fires may be considered as experimental data of tunnel in fire, to define the possible fire damage levels. Back analyses were carried out to define the main parameters controlling each damage state, whose temperature range is determined via fluid-dynamic analyses based both on fire zone models and Computational Fluid Dynamic Modelling. Therefore, the novelty of this paper is that the proposed methodology introduces the structural damage levels for the tunnel lining in fire, according to a performance-based approach.In the second part of the paper, the proposed approach was applied to a real concrete tunnel to assess its potential fire damage level. First of all, the expected damage level of the underground structure was identified through the gas temperatures reached during different real fire scenarios, where no fire damage was observed. This result was confirmed by analysing both the temperatures and the stresses of the structural lining, through advanced thermo-mechanical analyses.

Application of travelling behaviour models for thermal responses in large compartment fires

Large open-plan compartment fires in modern buildings may exhibit a local burning region travelling across the floor plan as a ‘travelling fire’. This phenomenon has been found in the forensic investigations of fire accidents and in the large compartment fire tests. The fire impact in a large compartment is spatially non-uniform and time-variant, which can cause severe local damage to structural components. Advanced from the previous models assuming constant travelling, the natural fire model established in this paper comprises time-variant and test-based travelling behaviour models and localised fire models of various modes. It is demonstrated with the fast-spread Veselí fire test and the slow-spread Malveira fire test. A generic structural model is set up within OpenSees for fire to examine the thermal impact on structural members under various travelling fire scenarios of different travelling parameters, fire travelling directions, and beam sizes. Locally much higher thermal responses are represented after introducing behaviour models while adopting the same design fire load. Based on the work in this paper, a library of design fire models can be potentially enabled to examine the fire safety performance of structures regarding the realistic fire load and fire impact aiming for discovering unknown worse fire scenarios.

Study on bonding strength of hot-cast anchors subject to elevated temperature

Appropriate assessment of the fire resistance of pre-tensioned steel structures depends largely on the ability to reasonably predict anchors response at elevated temperature. The bond strength of hot-cast anchors has been explored at room temperature, whilst that at elevated temperature has been less deeply scrutinised. The aim of this research is to experimentally and numerically investigate the behaviour of hot-cast anchors at elevated temperature. A total of twenty-two sets of hot-cast anchors are prepared for pull-out test at elevated temperature to investigate the ultimate load capacity and failure modes. The tests observe the failure mode including filler fully melted, filler partially melted with bond steel wires slipping and filler slipping with bond steel wires. The three types of failure modes of hot-cast anchors are dependent on the tension force ratio and target heating temperature. A charge-couple device camera (CCDC) system is used to capture the slipping displacement at the end of bonding strands accurately, which experiences linearly slipping, accelerated slipping and jump slipping phase. It takes longer heating time to achieve the critical tension force of hot-cast anchors than jump slipping points. It indicates that filler of hot-cast anchors can provide enough bond strength before jump slipping at elevated temperature. On the basis of examination of all test data, the failure criterion of hot-cast anchors at elevated temperature has been proposed herein that when the slipping displacement of bond steel strands reaches the value of 8.5% of its nominal diameter at elevated temperature, hot-cast anchors would be failed. The transient temperature distribution of hot-cast anchors is investigated by tests, simple method and thermal numerical analysis respectively. A simple method is employed to determine the characteristic temperature of hot-cast anchors as hot-cast anchors fail. Finally, a critical temperature method is generated to check the fire resistance and design fireproof for hot-cast anchors.

Proposed design fire scenarios for underground hard rock mines

Given the complexity and uniqueness of underground hard rock mines, the application of the design fire scenario approach is recommended when evaluating fire safety in mines. Providing a full set of design fire scenarios – ensuring that several important life safety aspects are covered – for a mine can be challenging. The question is whether a catalogue of potential clusters of design fire scenarios could be developed, covering important aspects found underground? Given the general lack of research into design fires in the mining industry, this paper provides a unique analysis of design fire scenarios in underground hard rock mines. Taking advantage of several different and diverse data sources, a comprehensive analysis with holistic character is provided where several proposed clusters of design fire scenarios and analyses of what criteria to apply when evaluating the scenarios are presented. The analysis of suitable criteria highlights the toxicity of the emitted smoke and decrease in visibility as potential criteria underground. The proposed scenarios focus on influencing parameters such as the fire behaviour, position of fire, fire load, and smoke spread. The proposed clusters of design fire scenarios will provide a key tool when evaluating fire protection measures in an underground mine.

Mechanical properties under high-temperature and fire resistant limit of carbon fiber reinforced polymer cable

To fully understand the fire resistant performance of Carbon fiber reinforced polymer (CFRP) cable with high-temperature-resistant resin matrix, both steady state and fire resistant tests were conducted on specimens. The degradation law for axial tensile properties of CFRP cable without pre-tension load under high temperature from 100 to 600 °C was uncovered in steady state tests in order to develop the corresponding constitutive models. Failure temperatures and fire-resistant limits of CFRP cables with pre-tension load heated following the equivalent standard temperature rise process were obtained in fire resistant tests, and were compared to the predicted results using the developed constitutive models and finite element thermal analysis. Then, a practical calculation model for determining fire-resistant limit of CFRP cable was developed and the effect of temperature-load path on mechanical properties of CFRP cable under high temperature was identified. The obtained results demonstrate that the rupture morphologies of tensile failure of CFRP cable in both steady state and fire resistant tests varied with the failure temperature. In steady state tests, mechanical properties of CFRP cable at high temperature are closely correlated with glass transition temperature Tg = 211.6 °C and decomposition temperature Td = 409.6 °C, and effect of high temperature on elastic modulus is more significant than that of tensile strength. In fire resistant tests, failure temperature and fire resistance limit of CFRP cable gradually decreased as pre-tension ratio increased. The fire resistance limits of CFRP cables with pre-tension ratios of 0.2 ∼ 0.6 vary from 3.26 to 15.40mins and its fire performance are very poor. The presence of pre-tension load with ratio R from 0.6 to 0.7 resulted in acceleration of damage for CFRP cable at high temperature. The developed constitutive models of mechanical properties under high temperature and the practical calculation model of fire-resistant limit with high accuracy can be adopted in fire resistant design and analysis of the structures with CFRP cable.

Investigation on axial resistance of steel reinforced concrete cross-shaped columns exposed to high temperature

Steel reinforced concrete (SRC) special-shaped columns have the advantages of high spatial utilization, flexible layout and good economic benefits, which are used in high-rise buildings. However, this composite structure has the disadvantages of high steel content and large fire area, which makes it easier to suffer damage in fire, and even cause the collapse of buildings. This paper presents mechanical properties of SRC cross-shaped columns exposed to high temperature. Seven SRC cross-shaped column specimens were analyzed. Temperature field distribution, failure mode, deformation and fire resistance of specimens were obtained under different axial compression ratios (0.4, 0.6) and eccentricity (0, 40, 60, 80 mm). The results showed that: (1) All specimens were in a condition of compression failure and section steel had partial bending failure with the concrete falling off. (2) The larger eccentricity and axial compression ratio were, the earlier cracks appeared, and the more cracks appeared, the more serious concrete shedding of specimen were. Moreover, the cracks were concentrated especially on the side of loading point (i.e., two sides close to the point where the applied load is located), and the cracks are adjacent to the support of specimen, which appear in the whole length of specimen. (3) Axial compression ratio had a significant influence on fire resistance of SRC cross-shaped columns, and influence of eccentricity on fire resistance was generally little compared with axial compression ratio. The fire resistance declined by 43.48–69.14% as axial compression ratio increased from 0.4 to 0.6. Fire resistance declined by 5.45–45.31% as eccentricity increased from 0 to 80 mm, and it was significantly reduced by 28.12–45.31% when axial compression ratio was 0.6. Finally, fire resistance calculation method of SRC cross-shaped column was obtained, which provided reference for fire resistance design of SRC structure.

Simplified proposal for the temperature field of steel-reinforced CFST columns exposed to fire

Concrete-filled steel tubular (CFST) columns are composite sections that may contribute to reduce the environmental impact in construction through a more efficient use of resources. By embedding a steel profile inside a CFST section, a new typology is generated, the so-called steel-reinforced concrete-filled steel tubular (SR-CFST) columns, which may enhance not only the structural capacity of these composite columns at room temperature but also their fire performance. This paper focuses on studying the thermal behaviour of SR-CFST columns under fire conditions, for which purpose a two-dimensional finite element model was developed by the authors and validated by comparing the temperature distribution results with experimental tests available in the literature. Subsequently, parametric studies were carried out to analyse the influence of the relevant parameters – cross-section shape, outer tube thickness, inner steel profile dimensions, section factor – over the cross-sectional capacity of SR-CFST columns exposed to a standard ISO 834 fire. Using the data obtained from the parametric studies, a simplified temperature distribution proposal was derived. In the presented proposal, the composite section was divided onto four components (hollow steel tube, concrete infill, inner steel profile web and flanges) and simplified equations and tables were developed through statistical data processing in order to find the representative equivalent temperature of each part of the section. By doing so, the reduced cross-sectional capacity of a SR-CFST column at a given fire resistance period can be easily evaluated by using a single strength and stiffness value for each component of the section corresponding to its assigned equivalent temperature. This simplified approach may be helpful for practitioners in the fire design process of SR-CFST columns, for which the current provisions in Eurocode 4 Part 1.2 do not provide guidance in predicting the temperature field.

Influence of different gypsum plasterboards on the fire performance of cold-formed steel walls

As typical fire protection sheathings, the thermal physical properties of gypsum boards may vary among manufacturers, which may affect the fire performance of gypsum-sheathed cold-formed steel (CFS) walls. Six different gypsum boards were selected for the sheathing of six mid-scale, non-load-bearing, CFS wall specimens, and fire tests were conducted under ISO 834 conditions. The results indicated that the insulation performance of gypsum boards may be related to the density and fibre content of gypsum boards. High-density gypsum boards have an improved heat absorption capacity. Adding fibre to the gypsum boards can effectively delay fire-induced fall-off of the gypsum boards. When gypsum boards with no visible fibre exhibit fire-induced fall off, their cold surface temperature fell between 560 °C and 710 °C, while that for gypsum boards with obvious fibre contained in fire exceeded 780 °C. Hence, from the perspective of safety, the performance variation of gypsum boards caused by different manufacturers should be considered in the fire design of CFS walls. A new prediction criterion was proposed to determine fire-induced fall-off of gypsum boards, namely, the cold surfaces of gypsum boards reaching 550 °C and a heating rate above 40 °C/min. The new criteria can clearly quantify the fire-induced fall-off time and temperature of gypsum boards according to their time–temperature curve. In addition, it is suggested to adopt fire-resistant gypsum boards as face-layer sheathing and to adopt standard gypsum boards as base-layer sheathing to make gypsum-sheathed CFS walls more cost-effective.