Analytical model for hybrid RC frame-steel wall systems

Y.L.Mo,S.F.Perng 국제구조공학회 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.2

Effect of loading rate on softening behavior of low-rise structural walls

Mo, Y.L.,Rothert, H. Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.6

Cracked reinforced concrete in compression has been observed to exhibit lower strength and stiffness than uniaxially compressed concrete. The so-called compression softening effect responsible is thought to be related to the degree of transverse cracking and straining present. It significantly affects the strength, ductility and load-deformation response of a concrete element. A number of experimental investigations have been undertaken to determine the degree of softening that occurs, and the factors that affect it. At the same time, a number of diverse analytical models have been proposed by various this behavior. In this paper, the softened truss model thoery for low-rise structural shearwalls is employed using the principle of the stress and strain transformations. Using this theory the softening parameters for the concrete struts proposed by Hsu and Belarbi as well as by Vecchio and Collins are examined by 51 test shearwalls available in literature. It is found that the experimental shear strengths and ductilities of the walls under static loads are, in average, very close to the theoretical values; however, the experiment shear strengths and ductilities of the walls under dynamic loads with a low (0.2 Hz) frequency are generally less than the theoretical values.

Analytical model for hybrid RC frame-steel wall systems

Mo, Y.L.,Perng, S.F. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.2

Reinforced concrete buildings with shearwalls are very efficient to resist earthquake disturbances. In general, reinforced concrete frames are governed by flexure and shearwalls are governed by shear. If a structure included both frames and shearwalls, it is generally governed by shearwalls. However, the ductility of ordinary reinforced concrete is very limited. To improve the ductility, a series of tests on framed shearwalls made of corrugated steel was performed previously and the experimental results were compared with ordinary reinforced concrete frames and shearwalls. It was found that ductility of framed shearwalls could be greatly improved if the thickness of the corrugated steel wall is appropriate to the surrounding reinforced concrete frame. In this paper, an analytical model is developed to predict the horizontal load-displacement relationship of hybrid reinforced concrete frame-steel wall systems according to the analogy of truss models. This analytical model is based on equilibrium and compatibility conditions as well as constitutive laws of corrugated steel. The analytical predictions are compared with the results of tests reported in the previous paper. It is found that proposed analytical model can predict the test results with acceptable accuracy.

Seismic shear behavior of rectangular hollow bridge columns

Mo, Y.L.,Jeng, Chyuan-Hwan,Perng, S.F. Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.12 No.4

An analytical model incorporating bending and shear behavior is presented to predict the lateral loading characteristic for rectangular hollow columns. The moment-curvature relationship for the rectangular hollow sections of a column is firstly determined. Then the nonlinear lateral load-displacement relationship for the hollow column can be obtained accordingly. In this model, thirteen constitutive laws for confined concrete and five approaches to estimate the shear capacity are used. A series of tests on 12 model hollow columns aimed at the seismic shear behavior are reported, and the test data are compared to the analytical results. It is found that the analytical model reflects the experimental results rather closely.

Integrated Safety and Tolerability of Daclatasvir plus Asunaprevir in Patients with Chronic HCV Genotype 1b Infection

( L. Wei ),( K. Chayama ),( W. L. Chuang ),( S. H. Bae ),( J. Y. Jang ),( R. Bhore ),( V. Vazquez ),( L. Mo ),( M. Linaberry ),( M. Treitel ),( H. Kumada ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: The combination of daclatasvir (DCV) plus asunaprevir (ASV)has demonstrated high sustained virologic response (SVR) rates andis generally well tolerated in clinical studies. This integrated analysisevaluated the safety profile of DCV (60mg once daily) and ASV (100mgsoftgel capsule or 200mg tablets twice daily in genotype 1b (GT1b)infected patients enrolled in four phase 3 and two phase 2 clinicalstudies conducted globally, including Asia.Methods: Integrated safety data from 1218 treatment-naive or treatment-experienced patients were analyzed for adverse events (AEs),serious AEs, discontinuations due to AEs and grade 3/4 AEs andlaboratory abnormalities reported on-treatment.Results: Patients were 58% female, median age was 58 years and23% had compensated cirrhosis. DCV+ASV was associated with infrequentserious AEs and discontinuations due to AEs (Table). Twelvepatients reported treatment-related serious AEs. The most commonAEs (any grade) were diarrhea, nausea, fatigue, and headache. Onepatient died due to coronary heart disease (not treatment-related).The most common grade 3/4 laboratory abnormalities were aminotransferaseelevations (more frequent among Japanese patients); however,all grade 3/4 laboratory abnormality occurred in <5% of patientsoverall. Grade 3/4 total bilirubin elevations were reported in <1%of patients. The DCV+ASV safety profile was similar in patients withor without cirrhosis.Conclusions: DCV+ASV was generally well tolerated across globalnon-Asian patient populations and in Asian patients from Japan, mainlandChina, Korea, and Taiwan.

Shear Cracking of Prestressed Girders with High Strength Concrete

Emad L. Labib,Y. L. Mo,Thomas T. C. Hsu 한국콘크리트학회 2013 International Journal of Concrete Structures and M Vol.7 No.1

Prestressed concrete (PC) is the predominant material in highway bridge construction. The use of high-strength concrete has gained wide acceptance in the PC industry. The main target in the highway industry is to increase the durability and the life-span of bridges. Cracking of elements is one aspect which affects durability. Recently, nine 7.62 meter long PC I-beams made with different concrete strength were designed according to a simple, semi-empirical equation developed at the University of Houston (UH) (Laskar et al., ACI Journal 107(3): 330?339, 2010). The UH Method is a function of shear span-to-depth ratio (a/d), concrete strength f¹c, web area bwd, and amount of transverse steel. Based on testing these girders, the shear cracking strength of girders with different concrete strength and different shear span-to-depth ratio was investigated and compared to the available approaches in current codes such as ACI 318-11 (2011) and AASHTO LRFD Specifications (2010).

Shear Cracking of Prestressed Girders with High Strength Concrete

Labib, Emad L.,Mo, Y.L.,Hsu, Thomas T.C. Korea Concrete Institute 2013 International Journal of Concrete Structures and M Vol.7 No.1

Prestressed concrete (PC) is the predominant material in highway bridge construction. The use of high-strength concrete has gained wide acceptance in the PC industry. The main target in the highway industry is to increase the durability and the life-span of bridges. Cracking of elements is one aspect which affects durability. Recently, nine 7.62 meter long PC I-beams made with different concrete strength were designed according to a simple, semi-empirical equation developed at the University of Houston (UH) (Laskar et al., ACI Journal 107(3): 330-339, 2010). The UH Method is a function of shear span-to-depth ratio (a/d), concrete strength $\sqrt{f^{\prime}_c}$, web area $b_wd$, and amount of transverse steel. Based on testing these girders, the shear cracking strength of girders with different concrete strength and different shear span-to-depth ratio was investigated and compared to the available approaches in current codes such as ACI 318-11 (2011) and AASHTO LRFD Specifications (2010).

Multiscale modeling of reinforced/prestressed concrete thin-walled structures

Laskar, Arghadeep,Zhong, Jianxia,Mo, Y.L.,Hsu, Thomas T.C. Techno-Press 2009 Interaction and multiscale mechanics Vol.2 No.1

Reinforced and prestressed concrete (RC and PC) thin walls are crucial to the safety and serviceability of structures subjected to shear. The shear strengths of elements in walls depend strongly on the softening of concrete struts in the principal compression direction due to the principal tension in the perpendicular direction. The past three decades have seen a rapid development of knowledge in shear of reinforced concrete structures. Various rational models have been proposed that are based on the smeared-crack concept and can satisfy Navier's three principles of mechanics of materials (i.e., stress equilibrium, strain compatibility and constitutive laws). The Cyclic Softened Membrane Model (CSMM) is one such rational model developed at the University of Houston, which is being efficiently used to predict the behavior of RC/PC structures critical in shear. CSMM for RC has already been implemented into finite element framework of OpenSees (Fenves 2005) to come up with a finite element program called Simulation of Reinforced Concrete Structures (SRCS) (Zhong 2005, Mo et al. 2008). CSMM for PC is being currently implemented into SRCS to make the program applicable to reinforced as well as prestressed concrete. The generalized program is called Simulation of Concrete Structures (SCS). In this paper, the CSMM for RC/PC in material scale is first introduced. Basically, the constitutive relationships of the materials, including uniaxial constitutive relationship of concrete, uniaxial constitutive relationships of reinforcements embedded in concrete and constitutive relationship of concrete in shear, are determined by testing RC/PC full-scale panels in a Universal Panel Tester available at the University of Houston. The formulation in element scale is then derived, including equilibrium and compatibility equations, relationship between biaxial strains and uniaxial strains, material stiffness matrix and RC plane stress element. Finally the formulated results with RC/PC plane stress elements are implemented in structure scale into a finite element program based on the framework of OpenSees to predict the structural behavior of RC/PC thin-walled structures subjected to earthquake-type loading. The accuracy of the multiscale modeling technique is validated by comparing the simulated responses of RC shear walls subjected to reversed cyclic loading and shake table excitations with test data. The response of a post tensioned precast column under reversed cyclic loads has also been simulated to check the accuracy of SCS which is currently under development. This multiscale modeling technique greatly improves the simulation capability of RC thin-walled structures available to researchers and engineers.

Seismic interaction of flexural ductility and shear capacity in reinforced concrete columns

Howser, Rachel,Laskar, A.,Mo, Y.L. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

The seismic performance of reinforced concrete (RC) bridge columns is a significant issue because the interaction of flexural ductility and shear capacity of such columns with varied amounts of lateral reinforcement is not well established. Several relationships between flexural ductility and shear capacity have been proposed by various researchers in the past. In this paper, a parametric study on RC bridge columns is conducted using a nonlinear finite element program, "Simulation of Concrete Structures (SCS)", developed at the University of Houston. SCS has been previously used to predict the seismic behavior of such columns. The predicted results were compared with the test results obtained from experiments available in literature. Based on the results of the parametric study performed in this paper, a set of new relationships between flexural ductility and shear capacity of RC columns is proposed for seismic design.

Seismic interaction of flexural ductility and shear capacity in reinforced concrete columns

Rachel Howser,A. Laskar,Y.L. Mo 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.5

The seismic performance of reinforced concrete (RC) bridge columns is a significant issue because the interaction of flexural ductility and shear capacity of such columns with varied amounts of lateral reinforcement is not well established. Several relationships between flexural ductility and shear capacity have been proposed by various researchers in the past. In this paper, a parametric study on RC bridge columns is conducted using a nonlinear finite element program, “Simulation of Concrete Structures (SCS)”, developed at the University of Houston. SCS has been previously used to predict the seismic behavior of such columns. The predicted results were compared with the test results obtained from experiments available in literature. Based on the results of the parametric study performed in this paper, a set of new relationships between flexural ductility and shear capacity of RC columns is proposed for seismic design.