Wall Strength Research Articles

3D Discrete Fracture Network Modelling from UAV Imagery Coupled with Tracer Tests to Assess Fracture Conductivity in an Unstable Rock Slope: Implications for Rockfall Phenomena

The stability of a rock slope is strongly influenced by the pattern of groundwater flow through the fracture system, which may lead to an increase in the water pressure in partly open joints and the consequent decrease in the rock wall strength. The comprehension of the fracture pattern is a challenging but vital aspect in engineering geology since the fractures’ spatial distribution, connectivity, and aperture guide both the water movement and flow quantity within the rock volume. In the literature, the most accepted methods to hydraulically characterise fractured rocks in situ are the single borehole packer test, the high-resolution flow meters for fractures, and the artificial tracer tests performed in boreholes. However, due to the high cost a borehole requires and the general absence of wells along coastal cliffs, these methods may not be appropriate in rockfall-prone areas. In this study, an unsaturated rocky cliff, strongly affected by rockfalls, was investigated by combining kinematic analysis, Discrete Fracture Network (DFN) modelling, and artificial tracer tests. The DFN model and potential rock block failure mechanisms were derived from high-resolution 3D virtual outcrop models via the Structure from Motion (SfM) photogrammetry technique. An artificial tracer was injected using a double ring infiltrometer atop the recharge zone of the slope to determine the infiltration rate and validate the DFN results. The DFN and tracer test methods are frequently used at different spatial scales and for different disciplines. However, the integration of digital photogrammetry, DFN, and tracer tests may represent a new step in rockfall and landslide studies. This approach made possible the identification of groundwater flow patterns within the fracture system and revealed about a 10-day tracer transit time from the injection area and the monitored slope, with similar conductivity values gathered from both the DFN and tracer test. Planar and wedge failures with volumes ranging from 0.1 and 1 m3 are the most probable failure mechanisms in the areas. The results were consistent with the delay between the intense rainfall and the slope failures previously documented in the study area and with their mechanisms.

Structural reliability and partial safety factor assessment of unreinforced masonry in vertical bending

ABSTRACT This paper focuses on a structural reliability-based assessment of clay brick unreinforced masonry (URM) walls subjected to uniformly distributed out-of-plane loads in one-way vertical bending. Stochastic models combining finite element analysis (FEA) and Monte Carlo simulations (MCS) are used to account for spatial variability of the flexural tensile bond strength when estimating the wall failure loads. The strength of URM walls is known to be influenced by the flexural tensile bond strength, which is subject to high spatial variability as batching, workmanship, and environmental exposure alter the strength of this bond. For this assessment, single skin walls have been considered with bond strength statistics seen in typical construction. The model error statistics available for similar walls are combined with the results of the spatial stochastic FEA and probabilistic load models to determine the reliability index corresponding to the Australian Standard for Masonry Structures AS 3700 design of members in vertical bending. It was found that existing levels of reliability exceed target reliabilities, and the capacity reduction factor can be increased from 0.60 to 0.65 for URM walls in one-way vertical bending while still providing an acceptable level of reliability. A sensitivity analysis showed this finding to be robust.

Analysis of the Seismic Performance of a Masonry Structure with RC Frames on the First Story with Concrete-Filled Steel Tubular Dampers

The concrete shear walls of masonry structures with RC frames on the first story are low-rise shear walls with a height–width ratio of less than 1. The strength, stiffness, and ductility of these low-rise shear walls are not matched, resulting in poor seismic performance. Based on the idea of the passive control theory and multi-seismic defensive lines, the scheme of a masonry structure with RC frames on the first story with a concrete-filled steel tubular (CFST) dampers is proposed in this paper. To explore the seismic mitigation effect of CFST dampers applied to a masonry structure with RC frames on the first story, the seismic performance under low-reversed cyclic loading of the frame with the CFST dampers is first compared with that of the energy-dissipated low-rise concrete shear wall proposed by previous researchers and the ordinary low-rise concrete shear wall. Furthermore, the response of the masonry structure model with RC frames on the first story with CFST dampers and two other comparative structural models under earthquake action are discussed. The results show that a masonry structure with RC frames on the first story with CFST dampers has a fuller hysteretic loop, lighter pinching, better energy dissipation ability, and better seismic performance. Compared with the other two structures, the energy dissipation capacity of the masonry structure with RC frames on the first story with CFST dampers is significantly improved, by 1.25~1.5 times. The amplification effect of the deformation angle allows the CFST dampers to play a significant role in energy dissipation, whereas the main structure still undergoes a small deformation. The CFST dampers can dissipate more seismic energy to protect the main structure from damage and improve the seismic performance of masonry structures with RC frames on the first story.

A macro‐element with bidirectional interaction for seismic analysis of unreinforced masonry walls

AbstractPrior to implementing retrofitting measures for seismic action, it is necessary to evaluate the global capacity of unreinforced masonry (URM) buildings. Even with simplified assumptions, equivalent frame (EF) modeling adequately captures global responses and failure mechanisms in existing buildings, making it a popular modeling strategy among structural engineers. However, macro‐elements employed in the EF modeling of URM walls consider in‐plane (IP) and out‐of‐plane (OP) behaviors separately by decoupling their interaction and require independent verification for OP failure involving limit analysis. Such decoupling of interaction is justifiable if proper wall‐wall/wall‐floor connections and rigid‐diaphragm action of slabs are ensured; however, OP failure is likely a result of inadequate connections. Multiple components of ground motion excitation and plan eccentricity in buildings can activate bidirectional interaction in such circumstances. Due to OP damage, the interaction reduces the full IP strength of a URM wall, resulting in overestimating its lateral capacity. This paper proposes a frame‐like 3D macro‐element incorporating the effect of OP action on the IP shear response of URM piers under static and monotonic lateral loads. Only two parameters modifying IP shear stiffness and capacity are required to account for the interaction. Analytical expressions for the interaction parameters are proposed from a detailed micro‐modeling study. The paper also demonstrates, within the EF modeling, the applicability of the proposed macro‐element for seismic analysis of regular URM shear walls with openings.

Efficient boosting-based algorithms for shear strength prediction of squat RC walls

Reinforced concrete shear walls have been considered as an effective structural system due to their optimal cost and great behavior in resisting lateral loads. For the slender type of these walls, failure modes are mainly related to flexure, while for the squat type with height-to-length ratios less than two, shear is the dominant factor. Thus, accurate estimation of shear strength for squat shear walls is necessary for design applications and can also be complex due to the various effective parameters. In order to address this issue, first a comprehensive dataset with 558 samples of squat shear walls is conducted, and three hybrid models consisting of genetic algorithms and boosting-based ensemble learning methods, i.e., XGBoost, CatBoost, and LightGBM, are used for estimation of shear strength. The results showed high prediction accuracy, with a coefficient of determination of at least 98.6% for all three models. Genetic algorithm has been proven to be an effective method for tuning boosting-based algorithms compared to manual testing. In addition, the results of the algorithms are compared to their default hyperparameters and other conventional regression Models. Also, multicollinearity and principal component analysis (PCA) were studied. Furthermore, the performance of three tuned models is compared with that of a mechanics-based semi-empirical model and other genetic programming (GP)-based models. Finally, parametric and sensitivity analyses were performed, to demonstrate the ability of the models to identify the most critical parameters with significant influence on shear strength.

Analytical Model of Wellbore Stability Analysis of Inclined Well Based on the Advantageous Synergy among the Five Strength Criteria

The proper drilling mud density is vital for wellbore stability maintenance, which relies on both stress distribution on the borehole wall and rock strength. Thus, the selection of rock strength criterion is vital for wellbore stability analysis (WSA), and several strength criteria have been developed and employed to perform WSA, but the real collapse pressure does not comply with any single strength criterion. Therefore, to accurately predict the critical mud weight against wellbore collapse, an analytical model of WSA was proposed for inclined wells based on the advantageous synergy among the five types of strength criteria, such as the Mohr-Coulomb criterion, Mogi-Coulomb criterion, Drucker-Prager criterion, modified Wiebols-Cook criterion, and modified Lade criterion. The predicted results among these analytical and five conventional models were compared under three kinds of typical stress regimes, such as normal, strike-slip, and reverse faults. Finally, five kinds of typical oil and gas field data were collected to further verify the accuracy of this new model. The results indicated that different models predicted different collapse pressure, owing to the Mohr-Coulomb criterion ignoring the intermediate principal stress ( σ 2 ), so as to always give the greatest collapse pressure, followed by the present analytical model and the Mogi-Coulomb criterion, while the other three types of strength criteria gave different results, because of the difference in the influence of σ 2 , while the present analytical model integrated the advantageous synergy among the five strength criteria. The prediction error of the conventional analytical model ranges from 9.4 to 34.2% with an average of 22.1%, while the prediction error of this new model ranges from 2.3 to 12.5% with an average of 7.1%, so that the present analytical model has much higher accuracy than that of any single strength criterion. In addition, this new analytical model can be simplified as the conventional analytical model by adjusting the weight coefficients.

Research on Floor Heave Mechanisms and Control Technology for Deep Dynamic Pressure Roadways

In order to study the influencing factors of floor deformation and floor heave mechanisms of deep mining roadways, this paper takes the deep dynamic pressure mining roadway of a mine as the engineering background and adopts a research method combining theoretical analyses, numerical simulations and field observations to study the influence of various factors on floor deformation and floor heave mechanisms. It is determined that the influencing factors on floor heave are a large buried depth, a long duration of dynamic pressure, unique characteristics of the surrounding rock and an insufficient support strength. A bearing mechanics model of the roadway floor beam is established, and it is determined that the displacement of the roadway floor is negatively correlated with the elastic modulus and floor thickness and positively correlated with the buried depth of roadway, the roadway width and the width of fracture zone. A numerical simulation method is used to study the influence of the original geological conditions, strengthening the elastic modulus of floor, strengthening the strength of the side wall rock and increasing the thickness of the floor rock on the displacement of the roadway floor. It is determined that increasing the thickness of floor rock controls the floor heave the most, followed by strengthening the elastic modulus of the floor rock and then strengthening the strength of the side walls. The results of the numerical simulation agree well with those of the theoretical analysis. After the control method of “bottom lifting + bottom angle bolt + floor bolt ” is adopted on site to treat the floor heave, the floor heave volume of the roadway is small during the service period of the 303 working face return air roadway, which meets the application requirements of the roadway. Meanwhile, the theoretical analysis and numerical simulation results are indirectly verified.

Shear Strength of Reinforced Concrete Squat Walls

Squat shear walls are widely used in various structures to resist earthquake loads. However, the relevant design expressions found in building codes and literature do not incorporate the influence of all crucial parameters and provide inconsistent peak shear strength estimations. This study adopts the artificial neural network (ANN) to predict the peak shear strength of squat walls using an extensive database that includes the results of 487 walls with wide-ranging test parameters. The ANN models consider the effect of concrete strength, the wall aspect ratio, vertical and horizontal reinforcements, vertical reinforcement of boundary elements, and axial load ratio. These accurately predicted the available test results. They implemented it to carry out parametric and sensitivity analysis to investigate the effect of the main parameters on the peak strength and to give information about the factors that contribute most to the shear response. In addition, a softened strut and tie method is proposed, considering the variables that substantially influence the shear strength. A nonlinear regression analysis is employed to determine the coefficients of the proposed model using the available database. The performance of the proposed model is measured using the existing models, which results in the best favorable agreement with the test results. Doi: 10.28991/CEJ-2023-09-02-03 Full Text: PDF

Higgsless simulations of cosmological phase transitions and gravitational waves

First-order cosmological phase transitions in the early Universe source sound waves and, subsequently, a background of stochastic gravitational waves. Currently, predictions of these gravitational waves rely heavily on simulations of a Higgs field coupled to the plasma of the early Universe, the former providing the latent heat of the phase transition. Numerically, this is a rather demanding task since several length scales enter the dynamics. From smallest to largest, these are the thickness of the Higgs interface separating the different phases, the shell thickness of the sound waves, and the average bubble size. In this work, we present an approach to perform Higgsless simulations in three dimensions, producing fully nonlinear results, while at the same time removing the hierarchically smallest scale from the lattice. This significantly reduces the complexity of the problem and contributes to making our approach highly efficient. We provide spectra for the produced gravitational waves for various choices of wall velocity and strength of the phase transition, as well as introduce a fitting function for the spectral shape.

Research and Practice of Rebar Engineering Quantity Calculation for Underground Diaphragm Wall of Intercity Railway Based on BIM and Planar Representation Method of Rebar

Underground diaphragm wall is a typical form of deep foundation support for intercity railroad, which has the characteristics of high wall strength, high stiffness and large amount of steel reinforcement. In the process of quantity calculation, there are problems such as unreasonable calculation method of reinforcement quantity and inaccurate and non-uniform calculation results. This paper briefly discusses the research on quantity calculation based on BIM model by combining the classification form of underground diaphragm wall, sorting out the rules of quantity calculation and steel flat method labeling. It also discusses the functions of the rebar information extraction system based on the rebar flat method labeling and the flow structure of the rebar quantity calculation process of intercity railroad underground diaphragm wall based on BIM and rebar flat method labeling. Finally, the accuracy of the calculation results of the diameter, length and number of longitudinal bars, hoop bars and tension bars of the underground diaphragm wall of the intercity railroad is compared with the traditional calculation mode by combining the calculation model. The data showed that the accuracy rate of calculation based on BIM and steel flat marking method was higher than that of traditional calculation mode, and the accuracy rate of BIM and steel flat marking method reached 97.9% on average, while the accuracy rate of traditional calculation mode was only about 85% on average. Therefore, it is verified that the calculation of intercity railroad underground diaphragm wall reinforcement based on BIM and steel flat method has good effect.

Model trees and stepwise regressions for accurate in-plane shear strength predictions of partially grouted masonry walls

The behaviour of partially grouted (PG) masonry shear walls is complex due to masonry's anisotropic nature and the nonlinear interactions among its constituents. Currently available code- and research-based shear strength equations provide highly variable results when predicting the in-plane shear strength of PG masonry walls. It is crucial to develop a greater understanding in this area, as sudden shear failures of masonry walls can lead to catastrophic losses of human life and property. This study presents the development of several new in-plane shear strength models for PG masonry walls using stepwise regression and model trees with data compiled from 292 experimentally tested walls. The models are found to significantly outperform existing code- and research-based shear strength equations. It was found that, of the variables studied, the most significant ones are the axial load, wall geometry, compressive strength of mortar, and area of interior vertical reinforcement.

A Collapse Strength Model for a 7” Crescent-Worn Casing Connection Considering Sealing Integrity

Collapse failure under external pressure is one of the common failure forms of casing. Much research has been performed on the casing body, but few on the threaded connection, in view of the general belief that the threaded connection has a thicker wall and larger collapse strength than the casing body. However, under external pressure, the sealing capacity of a worn casing connection will decrease due to deformation of the sealing structure, so the influence of sealing ability should be considered to determine the collapse strength of casing. In this paper, we established a three-dimensional finite element model of a 7” crescent-worn casing connection and calculated the collapse strength of the connection under different wear depths. Meanwhile, the stress distribution characteristics on the sealing surface were obtained and the influence of wear on the sealing performance of the casing connection under external pressure was analyzed. The results showed that when the wear rate exceeds a certain value, the collapse strength of the connection based on sealing integrity was lower than that of the casing body. Based on these, a collapse strength model for a 7” crescent-worn casing connection considering sealing integrity was developed and a safety evaluation method of the collapse strength of the worn casing string was proposed.

Seismic performance evaluation of steel and GFRP reinforced concrete shear walls at high temperature

Fire-induced structural damage to the seismic performance of reinforced concrete shear walls is critical in the event of a fire-earthquake scenario. However, only few researchers have studied the seismic performance of reinforced concrete shear walls at high temperatures. This study focuses on the seismic performance of fiber reinforced concrete shear walls at high temperatures by using finite element (FE) software, ABAQUS. The experimental test available in a literature on seismic behavior of shear walls exposed to fire and thermal properties of glass fiber reinforced polymer (GFRP) bars were used to validate the FE model and showed good agreement and thus used in the simulation.The FE results showed that exposure of RC shear wall to fire reduced the strength of the wall. The strength of walls at the maximum applied drift of 3.2% with concrete cover thicknesses of 20 mm, 25 mm, and 30 mm was dropped by about 70%, 76%, and 85% of the reference shear wall, respectively. Similarly, the strength of RC walls was reduced by about 80%, 75%, and 68% of the reference shear wall for the duration of fire exposure of 30 min, 60 min, and 120 min, respectively. Additionally, the strength of walls due to one side, two sides, or all sides’ exposure to fire was decreased by about 68%, 56%, and 50% of the reference shear wall, respectively. It can generally be concluded that the fire exposure sides has largely affected the strength of the shear wall compared to the other parameters and GFRP bars were more sensitive to temperature than steel bars.

Investigation of the real contact area of tensile fractures with different normal stresses and sizes by using pressure-sensitive films

More than 240 experimental tests were conducted and the characteristics of real contact area of the mated tensile fractures were investigated by using pressure-sensitive films. The effects of normal stress, fracture size as well as rock type on the real contact area of mated tensile fractures were evaluated and discussed. The results show that the real contact area of the mated rock fractures has a parabolic increasing relationship with the normal stress ratio (the ratio of the applied normal stress on the fracture surface to the uniaxial compressive strength of the joint wall). Also, the size of the tensile fracture can affect its real contact area, and the larger the applied normal stress is, the more significant the size effect of the rock fracture on the real contact area is. Furthermore, lithology has a significant influence on the real contact area of the structural plane, which is also related to the applied normal stress. Under the same stress condition, the real contact areas of shale and granite fractures are the smallest, while that of green sandstone fractures is the largest. By analyzing the nominal normal stress and the real normal stress on rock fractures, it was found that even if the nominal normal stress applied on the rock fractures is only 1.5 MPa, the average real normal stresses can reach 20 MPa ∼ 45 MPa, which is about 15–30 times the nominal applied normal stress. The contact characteristics of tensile fractures were analyzed by adopting the cutting methods. It was revealed that within a mated tensile fracture, the smaller the JRC of an area is, the larger the real contact area will be. The results of this study are of great significance for revealing the characteristics and laws of the contact areas of tensile fractures, and the 248 sets of data specimens obtained from the tests can provide important support or reference for establishing mechanical models for rock mass contact.

Numerical Investigation of the Effects of Opening on the Strength of Masonry Wall

Masonry is used as a construction material since old age. It is a cheaper construction material compared to R.C.C. and also requires comparatively less construction skills. During an earthquake, the masonry wall constructed following the codal provisions shows preliminary behaviour in the in-plane direction of wall and it has lesser deformation in the out-of-plane direction of the wall. Although, the strength and stiffness of the Un-Reinforced Masonry (URM) walls were reduce due to sizes and positions of openings, the relationship between the seismic capacity of the walls and the position and size of opening in walls are not clear. Researchers in the past mostly explored the in-plane behaviour of solid masonry wall without opening. Considering the openings in these walls can significantly affect the strength of the masonry wall. Hence, in the present study, an attempt is made to understand the effect of varying opening sizes (4 different combinations of door and/or window openings) in unreinforced masonry wall using finite element software CATIA. From this software, URM walls were modeled and load based quasi-static analysis were done in in-plane direction. The collapse mechanisms of the masonry walls and crack patterns are studied from the analysis and a key output from this work is the characterization of the relationships between the sizes and positions of openings and the in-plane performance of masonry walls.

Experimental and Numerical Study on Unreinforced Brick Masonry Walls Retrofitted with Sprayed Mortar under Uniaxial Compression

The use of shotcrete or sprayed mortar is a common construction alternative to retrofit unreinforced brick masonry (URM), and extensive research has already been carried out in this area. However, most studies have been conducted on lateral strength, for example, eccentric compression or seismic forces. On the other hand, there are few studies about uniaxial compression, and the results of most studies confirm a strong relationship between the thickness of the retrofitting layer and whether it is a double-sided retrofitting section. However, most studies are exclusively experimental, with few samples, and lack numerical analysis; therefore, deeper research is required on this issue. In this sense, this paper combined experiments and finite element (FE) simulations to further study the uniaxial compression. A series of cyclic uniaxial compression experiments on URM retrofitting with sprayed mortar were performed. The experimental results were used to calibrate the FE model. Using these calibrated FE models, more variable parameters were run so that more reference results could be obtained. Moreover, the resulting damageable model of FE will be useful for studying the behavior in the inelastic phase. Results found that the compression strength of most composite walls retrofitted with sprayed mortar increases with the thickness of the sprayed layer and can improve the construction defects of the masonry itself. An over-thin sprayed layer reduces the range of the elastic phase of the composite wall. This phenomenon tends to stabilize with increasing thickness. The ultimate strength of the composite masonry is generally positively correlated with the overall increase in the thickness of the sprayed mortar but may cause a negative contribution to the ultimate strength of the composite masonry when the sprayed layer is too thin. The contribution of double-sided spraying to the ultimate strength of the composite wall was not as large as expected, but the contribution to the improvement of the elastic modulus of the wall was significant.

A STUDY ON TSUNAMI-RESISTANT REINFORCEMENT EFFECT OF REINFORCED CONCRETE OUTER WALL BY FIBER REINFORCED SHEET

In the 2011 Tohoku Earthquake, many buildings were collapsed or overturned, and a number of outer concrete walls were broken by the hydro dynamic pressure due to Tsunamis. Out-of-plane strength of wall are usually not concerned in the seismic design and a few static loadings tests verify the actual nonlinear out-of-plane response of concrete walls. In a past study, an out-of-plane strength of outer concrete walls damaged by 2011 Tohoku Tsunami was evaluated based on the plastic hinge mechanism. In this study, the strength evaluation method is verified by the hydro static loading test on the concrete walls, and the out-of-plane strength are compared by the test between the bare concrete walls and walls reinforced with the polyester fiber sheets.

The effect of polyurethane foam glue on the strength and deformability of aerated concrete masonry when using it as a masonry mortar

The article presents the results of experimental studies of masonry made of cellular concrete blocks of autoclave hardening YTONG produced by JSC «Kcell-Aeroblock-Center» on the adhesive composition (polyurethane glue) Dryfix (POLYPAG AG). The tests included comprehensive studies of the strength and deformability of masonry walls made of cellular concrete blocks, under various types of stress state of structures: central and off-center compression of masonry walls, axial tension on bandaged and unbound seams, tensile bending on bandaged and unbound seams, shear with an assessment of tangential adhesion. Tests have confirmed the inconsistency of the technology of laying blocks of cellular concrete on the adhesive composition of Dryfix with incomplete filling of seams. This technology has a significant impact on the strength of the masonry during bending: the adhesion of the blocks to each other with such an adhesive composition applied to the surface of the block is significantly lower than the value obtained when testing the blocks for axial tension. According to the results of the experiments, the value of the temporary resistance to axial stretching along the unbound section (normal adhesion) of the masonry, the values of the calculated resistance of the masonry to stretching during bending along the unbound and tied sections, as well as the value of the calculated resistance of the masonry under central compression were determined.

Study on Seismic Performance of Cold-Formed Thin-Walled Steel-Straw Board Composite Wall with Diagonal Brace

The composite wall studied in this paper is based on the original cold-fonned thin-walled steel-straw board composite wall, which is set up with inclined braces and rigid inclined braces to improve its seismic performance. The factors of aspect ratio are analyzed, and the formula of shear bearing capacity of composite wall is deduced. The results show that: (1) When the height-width ratio of the composite wall is 2.4m×1.2m, 1.8m×1.2m and 1.2m×1.2m respectively, the yield strength of the composite wall is 35.78kN, 37.47kN and 54.23kN respectively. The yield strength of the former increases by 4.72 %, and the yield str ength of the latter increases by 44.73 %. (2) Using the effective strip method, the error of the derived shear capacity formula is not large, and the difference between the experimental value and the simulated value is not large, in order to provide some reference for the seismic design of this kind of cold-fonned thin-walled steel-strawboard composite wall with diagonal brace.

Lateral Resistance of Reinforced Light-Frame Wood Shear Walls

In light-frame timber construction, the shear wall is one of the most important components that provide resistance to lateral loads such as earthquakes or winds. According to KDS (Korea Design Standard) 42 50 10, shear walls are to be constructed using wood-based structural sheathing, with studs connected by 8d nails spaced 150 mm along the edge and 300 mm in the field. Even though small-scale residential timber building can be designed to exhibit seismic resistance using light-frame timber shear walls in accordance with KDS 42 50 10, only the abovementioned standard type of timber shear wall is available. Therefore, more types of timber shear walls composed of various materials should be tested to measure their seismic resistance, and the results should be incorporated into the future revision of KDS 42 50 10. In this study, the seismic resistance of shear walls composed of structural timber studs and wood-based structural sheathing with reinforced nailing is tested to evaluate the effects of the reinforcement. For the nailing reinforcement, shear wall specimens are constructed by applying nail spacings of 75–150 mm and 50–100 mm. For the shear wall specimens with one sheathing and reinforced nailing, the shear strengths are 1.7–2.0 times higher than that of the standard shear wall (nail spacing of 150–300 mm). The shear strength of the shear walls with sheathing on both sides is 2.0–2.7 times higher than that of the standard shear wall.