https://doi.org/10.14311/APP.2022.33.0473 Acta Polytechnica CTU Proceedings 33:473–479, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague LATERAL LOAD BEARING CHARACTERISTICS OF LIGHT GAUGE STEEL AND LIGHTWEIGHT CONCRETE SHEAR WALLS Chunri Quana,∗, Qiang Huangb, Dongbin Lic, Yong Chend a Osaka Institute of Technology, Department of Architecture, 5-16-1 Omiya, Asahi-ku, 535-8585 Osaka, Japan b China BIM Union, Department of Management, No.30 Beisanhuandonglu, 100013 Beijing, China c China Building Technique Group Co., Ltd., Engineering Technology Research Center, No.30 Beisanhunadonglu, 100013 Beijing, China d ARSE Building Engineering Technology Co., Ltd., Design Department, No.365 Dongsihuannanlu, 100023 Beijing, China ∗ corresponding author: chunri.quan@oit.ac.jp Abstract. In China, there is a new structural system named light gauge steel and lightweight concrete (LSLC) structure, which used lightweight concrete as structural material in composite way with cold- formed steel. Here, the shear walls are the main structural members for the LSLC structure, which are assembled with the light gauge steel lattice columns and horizontal braces, and filled with lightweight concrete. In this study, the LSLC shear walls are experimentally investigated to evaluate their failure mechanism and lateral load bearing capacity. For this purpose, several specimens with different shear span ratio are designed and tested under static cyclic loading. This paper presents the damage state and hysteresis loops of the specimens detailly. Then, the lateral load bearing characteristics of the LSLC shear walls are discussed according to the failure mechanism, such as shear and flexural failure. Finally, the calculation methods of lateral strength for the LSLC shear walls are proposed based on the diagonal strut mechanism and sectional force equilibrium. Keywords: Failure mechanism, lateral load bearing characteristic, light gauge steel and lightweight concrete structure, shear wall. 1. Introduction Cold-formed steel structure has been widely used in the low-rise buildings due to its high strength, ease of construction, and low cost [1]. On the other hand, due to low self-weight, good workability, excellent performance on thermal insulation, fire resistance and sound absorption, lightweight concrete was primarily utilized as non- and semi-structural material in the past building construction [2]. Motivated by the in- dustrialized performance of cold-formed steel struc- ture, good integrity of cast-in-situ concrete struc- ture and advantages of the lightweight concrete, a new structure system named light gauge steel and lightweight concrete (LSLC) structure, which used expanded polystyrene concrete or foamed concrete as the structural material in composite way with the cold-formed steel, was proposed and applied to the building construction in China [3]. Compared with the traditional reinforced concrete structure, the LSLC structure can reduce seismic load significantly based on the use of lightweight concrete to decrease the self-weight of overall structure. Compared with the cold-formed steel structure, the LSLC structure has great advantages in features such as fire protec- tion, thermal insulation and sound absorption. In the past several years, the studies of the LSLC structure were focused on the members such as shear walls and slabs, furthermore their design method has been developed based on the considerable tests. This paper describes the design details and testing method for the LSLC shear wall specimens, with dif- ferent shear span ratio as the experimental param- eters. Then, the damage state and hysteresis loops of specimens are presented detailly, and the seismic capacity of the LSLC shear wall is evaluated based on the cyclic lateral loading test results. Finally, the lateral load bearing characteristics of the LSLC shear walls are discussed, and the calculation methods of lateral strength for the LSLC shear walls are pro- posed. 2. Outline of experiment 2.1. Configuration of the LSLC shear wall Shear wall is the main structural member of the LSLC structure system. Figure 1 shows the standard con- figuration of the shear wall with thickness of 180mm and concrete cover thickness of 20mm. Light gauge steel frame is assembled with the light gauge steel lat- tice columns and horizontal braces, then filled with lightweight concrete. The lattice columns composed of two or four square steel tubes, which were com- bined and fixed by batten plates and bolts with 600 mm spacing as shown in Figure 2. Steel strips with 473 https://doi.org/10.14311/APP.2022.33.0473 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en C. Quan, Q. Huang, D. Li, Y. Chen Acta Polytechnica CTU Proceedings Self-drilling screws Brace Two-tube lattice column Four-tube lattice column Lightweight concrete Figure 1. Configuration of the LSLC shear wall. Figure 2. Installation of batten plates in the lattice column. Specimen Height × Width × Thickness (mm) Shear span ratio Axial force ratio S0.8-A0.4 1650 × 2062.5 × 180 0.8 0.4 S1.5-A0.4 2250 × 1500 × 180 1.5 0.4 S2.5-A0.4 2250 × 900 × 180 2.5 0.4 Table 1. Experiment parameters. W-shaped cross section were installed as horizontal braces with spacing of 600mm, which were connected to the lattice columns by self-drilling screws. 2.2. Design of specimen The test specimens are designed according to the standard design method of LSLC shear wall men- tioned above. In this study, five full-scale specimens with different shear span ratio and axial force ratio as the experimental parameters are tested under in- plain cyclic loadings. Table 1 and Figure 3 show the experiment parame- ters and design details of specimens. The light gauge steel lattice columns of each specimen are composed of four and two square steel tubes at the side and the middle of the wall, respectively. Then, the lattice columns are anchored in the reinforced concrete rigid beam (stub). The horizontal braces are installed with spacing of 600mm, which are connected to the lattice columns by three self-drilling screws. 2.3. Material characteristic Table 2 and table 3 show the material test results, where the values represent the mean value of 3 sam- ples in each test. The light gauge steel is designated as S350GD conform to the Chinese National Standard GB/T2518 [4]. which requires the yield strength and tensile strength not less than 350MPa and 420 MPa, respectively. In addition, No.4.8 self-drilling screw given in the ISO15481 [5] is adopted as fastener. The expanded polystyrene concrete with design- ing density of 1000kg/m3 is used as lightweight con- crete. Here, test samples with dimensions 100 mm × 100 mm × 100 mm are prepared in casting process of each specimen, then the compressive strength and density are measured according to the Chinese Na- tional Standard GB/T50080 [6]. 474 vol. 33/2022 Lateral Load Bearing Characteristic of Shear Walls 水平拉条墙体 底梁 顶梁 自攻钉 矩形钢管 矩形钢管拼装扣板 brace stub stub wall screws batten plate steel tube Figure 3. Details of specimens (unit: mm). Member Yield strength Tensile strength Young’s modulus Cross-section [MPa] [MPa] [MPa] [mm] Lattice column 361.5 484.3 2.02 × 105 Horizontal brace 352.1 462.2 1.98 × 105 Table 2. Mechanical properties and cross-section size of light gauge steel. Density Compressive strength Young’s modulus [kg/m3] [MPa] [MPa] 1058 6.36 0.72 × 104 Table 3. Mechanical properties of lightweight concrete (expanded polystyrene concrete). 2.4. Loading program The loading system and history are shown in Figure 4 and Figure 5, respectively. The lateral cyclic loading is performed by load control system until the yielding of light gauge steel. Then, it is switched to displace- ment control, and peak drift angles (the ratio of lat- eral deformation to wall height) are planned by the times of displacement (∆) when the light gauge steel is yielded. Here, two cycles for each peak drift are imposed. The axial load is applied to each specimen based on the axial force ratio. 3. Test results 3.1. Failure patterns Figure 6 shows the crack patterns in each specimen at the safety limitation, where it is defined as the moment in which the maximum lateral strength of the LSLC shear wall deteriorates to its 85%. 3.1.1. S0.8-A0.4 specimen A shear crack at the middle of wall is observed at the drift angle of 0.11% with the width of 0.15mm. Loaded to 0.25%, some vertical cracks occur at the upper of wall along the light gauge steel lattice columns. At the drift angle of 1.88%, clear shear cracks are observed at the diagonal of wall. 3.1.2. S1.5-A0.4 specimen A shear crack at the bottom of wall is observed at the drift angle of 0.11% with the width of 0.1mm. Loaded to 0.36%, some vertical cracks and flexural cracks oc- cur in succession. At the drift angle of 3.02%, the vertical cracks and flexural cracks continue to extend and the width increases. 475 C. Quan, Q. Huang, D. Li, Y. Chen Acta Polytechnica CTU Proceedings 45 5056 50 3740 Positive direction Negative direction Figure 4. Test setup (unit: mm). - 7 - 6 - 5 - 4 - 3 - 2 - 1 0 1 2 3 4 5 6 7Δ Δ Δ Δ Δ Δ Δ Δ Δ Δ Δ Δ Δ Δ Load control 1cycle 2cycles 2cycles 2cycles 2cycles 2cycles 2cycles Displacement control Yielding of steel Figure 5. Loading history. 3.1.3. S2.5-A0.4 specimen There are some flexural and flexural-shear cracks are observed at the drift angle of 0.21% with the maxi- mum width of 0.15mm. Loaded to 0.34%, vertical and horizontal cracks occur along the light gauge steel lat- tice columns and braces. At the drift angle of 3.04%, the width of flexural cracks increases, and local crush of lightweight concrete cover is observed at the bot- tom of wall. 3.2. Hysteretic characteristics Figure 7 shows the relationship between lateral strength and drift angle. 3.2.1. S0.8-A0.4 specimen The maximum lateral strength of 295.5kN is recorded at the drift angle of 0.59%. Then, remarkably rapid strength deterioration is observed until the drift angle of 1.53%, which is the safety limitation of the speci- men. It shows typical shear failure characteristics. 3.2.2. S1.5-A0.4 specimen The maximum lateral strength of 146.2kN is recorded at the drift angle of 1.15%. Then, relatively slow strength deterioration is observed until the drift an- gle of 2.10%, which is the safety limitation of the specimen. It shows flexural-shear failure characteris- tics. 3.2.3. S2.5-A0.4 specimen The maximum lateral strength of 73.8kN is recorded at the drift angle of 0.46%. Then, slow strength de- terioration is observed until the drift angle of 1.23%, which is the safety limitation of the specimen. It shows typical flexural failure characteristics. 4. Seismic capacity evaluation 4.0.1. Lateral load bearing capacity Figure 8 shows the relationship between maximum lateral strength and shear span ratio. The maximum lateral strength decreases with the increase of the shear span ratio. Compared with the S0.8-A0.4 spec- imen, the maximum lateral strength of the S2.5-A0.4 specimen decreases by 75.0%. It can be considered that the flexural failure characteristics of shear wall gradually dominates with the increase of the shear span ratio. 4.1. Deformation capacity Figure 9 shows the relationship between ductility co- efficient and shear span ratio. Herein, the ductility coefficient (µ) of the LSLC shear wall is calculated as the ratio of failure displacement (∆u, displacement of safety limitation) to yield displacement (∆y), which is defined as shown in Figure 10. It is difficult to de- termine the internal relationship between the shear span ratio and the ductility coefficient of the LSLC shear wall. However, the ductility coefficient of each specimen is larger than 4, showing better deforma- tion capacity compared with the reinforced concrete shear walls [7]. 4.2. Energy absorption capacity Since the absolute value of dissipated energy de- pends on the scale of the specimen such as the cross- sectional area, the normalized equivalent damping ra- tio (heq) is applied to evaluate the energy absorption capacity of the LSLC shear wall. Herein, the equiva- lent damping ratio is calculated from the energy ab- sorbed in one cycle (∆W ) and equivalent potential energy (We, strain energy) as shown in Figure 11. Figure 12 shows equivalent damping ratio of each specimen. The maximum value of the equivalent damping ratio for each specimen is recorded 17.19 ∼ 19.27%. After loading to the drift angle of 0.5%, the equivalent damping ratio of the LSLC shear wall shows the relatively stable values as 12 ∼ 20%. Com- pared with the reinforced concrete shear walls [8], the LSLC shear walls show lower energy absorption ca- pacity in this experimental study, and it can be con- sidered that the severe slip of the LSLC shear wall reduced the hysteretic dissipated energy. 5. Calculation methods of lateral strength In this paper, the past experimental results of eleven specimens are employed to calculate the lateral 476 vol. 33/2022 Lateral Load Bearing Characteristic of Shear Walls 正向加载 负向加载 Positive loading Negative loading Figure 6. Crack patterns. -5 -4 -3 -2 -1 0 1 2 3 4 5 -400 -300 -200 -100 0 100 200 300 400 θ=0.25%，第一条竖裂缝 荷 载 P/ kN 位移角θ/% θ=1.53%，85%最大荷载 θ=0.59%，最大正向荷载 θ=0.11%，第一条斜裂缝 -80 -60 -40 -20 0 20 40 60 80 位移Δ/mm -5 -4 -3 -2 -1 0 1 2 3 4 5 -400 -300 -200 -100 0 100 200 300 400 位移角θ/% θ=0.11%，第一条斜裂缝 θ=0.20%，第一条竖裂缝 θ=0.36%，第一条横裂缝 θ=1.15%，最大正向荷载 θ=2.10%，85%最大荷载 -90 -60 -30 0 30 60 90 位移Δ/mm -5 -4 -3 -2 -1 0 1 2 3 4 5 -400 -300 -200 -100 0 100 200 300 400 θ=0.21%，第一条斜裂缝 位移角θ/% θ=0.34%，第一条竖裂缝 θ=0.46%，最大正向荷载 θ=1.23%，85%最大荷载 -90 -60 -30 0 30 60 90 位移Δ/mm Drift angle (R, %) Displacement (mm) 30 40 50 Lo ad (k N ) R=0.25%, vertical crack R=0.11%, shear crack R=0.59%, maximum load R=1.53%, safety limitation Drift angle (R, %) Displacement (mm) R=2.10%, safety limitation R=0.20%, vertical crack R=0.11%, shear crack R=0.36%, horizontal crack R=1.15%, maximum load Drift angle (R, %) Displacement (mm) R=1.23%, safety limitation R=0.34%, vertical crack R=0.21%, shear crack R=0.46%, maximum load Figure 7. Lateral strength and drift angle relation. 0 50 100 150 200 250 300 0 0.5 1 1.5 2 2.5 3 La te ra l s tre ng th (k N ) Shear span ratio S0.8-A0.4 specimen S1.5-A0.4 specimen S2.5-A0.4 specimen Figure 8. Maximum lateral strength. 0 3 6 9 12 15 0 0.5 1 1.5 2 2.5 3 D uc til ity c oe ffi ci en t Shear span ratio S0.8-A0.4 specimen S1.5-A0.4 specimen S2.5-A0.4 specimen Figure 9. Ductility coefficient. 0 Δy Δu Δ A1 A2 A1=A2 P Pmax Py 0.85Pmax μ = Δu / Δy Figure 10. Characteristic points of P − ∆ curve. heq = (1/4π)×(ΔW /We) P Δ ΔW We Figure 11. Definition of equivalent damping ratio. 477 C. Quan, Q. Huang, D. Li, Y. Chen Acta Polytechnica CTU Proceedings 0 4 8 12 16 20 24 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 S0.8-A0.4 S1.5-A0.4 S2.5-A0.4 Drift angle (%) Eq ui va le nt d am pi ng r at io (% ) Figure 12. Equivalent damping ratio. Figure 13. Concept and calculation results of diagonal strut mechanism. Figure 14. Concept and calculation results of sectional force equilibrium. 478 vol. 33/2022 Lateral Load Bearing Characteristic of Shear Walls strength for the LSLC shear walls, which are showed shear failure [9]. 5.0.1. Diagonal strut mechanism The lateral strength Qsu for the LSLC shear walls could be calculated based on the diagonal strut mech- anism, as shown in Equation 1, 2, and 3 [10]. Here, fc is the compressive strength of lightweight concrete, weq is the equivalent strut width, t is the thickness of LSLC wall, θ is the strut angle to LSLC wall length, Lw is the length of LSLC wall, Nc is the axial force of lightweight concrete, Ac is the sectional area of lightweight concrete, σN is the compressive stress of LSLC wall, ft is the tensile strength of lightweight concrete, respectively. As shown in Figure 13, the cal- culation results of the lateral strength for the LSLC shear wall based on the diagonal strut mechanism show good agreement with the experimental results. Qsu = fc weq t cos θ (1) weq = ! 0.25 + 0.85 Nc Ac fc " Lw (2) θ = 90◦ − cos−1 #! σN σN + 2 ft " $ 2 % (3) 5.1. Sectional force equilibrium The lateral strength Qsu for the LSLC shear walls could be calculated based on the sectional force equi- librium, as shown in Equation 4, 5 [3]. Here, Qc is the strength shared by lightweight concrete, Qsv is the strength shared by horizontal brace, QN is the increased strength by axial force, λ is the shear span ratio of LSLC wall, ft is the tensile strength of lightweight concrete, fa is the tensile strength of light gauge steel, Ac is the sectional area of lightweight con- crete, Aah is the sectional area of horizontal brace, s is the space of horizontal brace, hw0 is the equivalent length of LSLC wall, N is axial force to LSLC wall, γRE is the seismic adjustment coefficient (here, 0.85), respectively. As shown in Figure 14, the calculation results of the lateral strength for the LSLC shear wall based on the sectional force equilibrium show conser- vative evaluation, compared with the experimental results. Qsu = Qc + QN + Qsv (4) Qsu = # 1 λ − 0.5 (0.3 ft Ac + 0.06 N) + 0.2 fa Aah s hw0 %$ γRE (5) 6. Conclusions Seismic performance of the light gauge steel and lightweight concrete shear wall was experimentally in- vestigated under in-plane cyclic loadings. The major findings can be summarized as follows. 1. The effects of shear span ratio on the lateral load bearing capacity of the LSLC shear wall were grasped quantitatively. 2. The ductility coefficient of each specimen was larger than 4, showed better deformation capacity compared with the reinforced concrete shear walls. However, the equivalent damping ratio of the LSLC shear wall was calculated the values of 12 ∼ 20%, showed lower energy absorption capacity compared with the reinforced concrete shear walls. 3. The lateral strength of the LSLC shear wall cal- culated based on the diagonal strut mechanism showed good agreement with the experimental re- sults. However, the calculation results based on the sectional force equilibrium showed conservative value compared with the experimental results. Acknowledgements The financial support of the Self-funded Project of China Academy of Building Research Co., Ltd (for Applied Technology Research, Grant No. 20151802330730055) is gratefully appreciated. References [1] N. Balh, J. DaBreo, C. Ong-Tone, et al. Design of steel sheathed cold-formed steel framed shear walls. Thin-Walled Structures 75:76-86, 2014. https://doi.org/10.1016/j.tws.2013.10.023. [2] M. R. Jones, A. McCarthy. Preliminary views on the potential of foamed concrete as a structural material. Magazine of Concrete Research 57(1):21-31, 2005. https://doi.org/10.1680/macr.2005.57.1.21. [3] Ministry of housing and urban-rural development. Technical specification of lightweight steel and lightweight concrete structure China, 2016. [4] Chinese National Standard. Continuously hot-dip zinc-coated steel sheet and strip, Beijing: Standards Press of China, 2008. [5] International Standards Organization. Cross recessed pan head drilling screws with tapping screw thread, 1999. [6] Chinese National Standard (GB/T50080). Standard for test method of performance on ordinary fresh concrete, Beijing: Architecture Industrial Press of China, 2001. [7] T. Shimazu, Y. Fukuhara, T. Satoh T, et al. New reinforced concrete structure Japan, 2002. [8] H. Tomatsuri. Proceedings of the Japan Concrete Institute 31(2):409-14. [9] China Building Technique Group Co., Ltd. An experimental report of light gauge steel and lightweight concrete shear walls Beijing, 2015. [10] S.-J. Hwang, W.-H. Fang, H.-J. Lee, et al. Analytical Model for Predicting Shear Strengthof Squat Walls. Journal of Structural Engineering 127(1):43-50, 2001. https://doi.org/10.1061/(asce )0733-9445(2001)127:1(43). 479 https://doi.org/10.1016/j.tws.2013.10.023 https://doi.org/10.1680/macr.2005.57.1.21 https://doi.org/10.1061/(asce)0733-9445(2001)127:1(43)