Showing papers on "Shear wall published in 2013"

Behavior of Precast Concrete Shear Walls for Seismic Regions: Comparison of Hybrid and Emulative Specimens

Abstract: This paper discusses the lateral load behavior of two, 0.40-scale, hybrid, precast concrete shear wall test specimens and the behavior of a third precast specimen designed to emulate monolithic cast-in-place RC shear walls. The walls had identical overall geometry and were constructed by placing rectangular precast panels across horizontal joints. The hybrid walls used mild steel bars [Grade 400 (U.S. Grade 60)] and high-strength unbonded posttensioning (PT) strands for lateral resistance, whereas the emulative wall used only mild steel bars. The mild steel bars crossing the base joint were designed to yield and provide energy dissipation, with the PT steel in the hybrid walls reducing the residual displacements of the structure. The mild steel bars at the base of the emulative wall and one of the hybrid walls used Type II mechanical splices, while the other hybrid wall used continuous bars grouted into the foundation. Because of the lack of PT steel, the emulative wall developed a large residual ...

Viscoelastic coupling dampers (VCDs) for enhanced wind and seismic performance of high‐rise buildings

Abstract: SUMMARY As high-rise buildings are built taller and more slender, their dynamic behavior becomes an increasingly critical design consideration. Wind-induced vibrations cause an increase in the lateral wind design loads, but more importantly, they can be perceived by building occupants, creating levels of discomfort ranging from minor annoyance to severe motion sickness. The current techniques to address wind vibration perception include stiffening the lateral load-resisting system, adding mass to the building, reducing the number of stories, or incorporating a vibration absorber at the top of the building; each solution has significant economic consequences for builders. Significant distributed damage is also expected in tall buildings under severe seismic loading, as a result of the ductile seismic design philosophy that is widely used for such structures. In this paper, the viscoelastic coupling damper (VCD) that was developed at the University of Toronto to increase the level of inherent damping of tall coupled shear wall buildings to control wind-induced and earthquake-induced dynamic vibrations is introduced. Damping is provided by incorporating VCDs in lieu of coupling beams in common structural configurations and therefore does not occupy any valuable architectural space, while mitigating building tenant vibration perception problems and reducing both the wind and earthquake responses of the structure. This paper provides an overview of this newly proposed system, its development, and its performance benefits as well as the overall seismic and wind design philosophy that it encompasses. Two tall building case studies incorporating VCDs are presented to demonstrate how the system results in more efficient designs. In the examples that are presented, the focus is on the wind and moderate earthquake responses that often govern the design of such tall slender structures while reference is made to other studies where the response of the system under severe seismic loading conditions is examined in more detail and where results from tests conducted on the viscoelastic material and the VCDs in full-scale are presented. Copyright © 2013 John Wiley & Sons, Ltd.

Acoustic emission monitoring of a reinforced concrete shear wall by b-value-based outlier analysis

Abstract: Reinforced concrete shear walls are critical structural components in gravity and lateral force resisting systems. The objective of this work is to design and validate a monitoring system capable of rapid and automated damage assessment of reinforced concrete shear walls. The proposed system is based on a sparse array of piezoelectric transducers to receive acoustic emissions distributed across the wall and a statistical pattern recognition algorithm capable of identifying critical structural conditions to inform decision makers on the need for repair to ensure safe operation of the structure. The proposed system was validated on a full-scale reinforced concrete shear wall subjected to quasi-static cyclic loading.

Approximate R-Factor for Cross-Laminated Timber Walls in Multistory Buildings

Abstract: Cross-laminated timber (CLT) is a wood construction technology that has been utilized in Europe for several decades and has become even more popular recently. Although the technology has been in existence for approximately 20 years, its seismic performance has been explored only recently by a handful of researchers. Interest in bringing CLT to the North American construction market necessitates a full understanding of the seismic behavior of CLT systems and the development of a response-modification factor, known as the R-factor, for use in force-based seismic design codes. In this paper, a nonlinear, load-resistance model for CLT shear walls is developed based on reversed-cyclic test data and explained. An estimation of a possible R-factor is obtained by developing a design for a 6-story CLT apartment building, based on computed peak interstory drifts, to achieve good performance in a high seismic region of the United States. It is concluded that using the equivalent lateral force procedure with ...

Investigation of Various GFRP Shear Connectors for Insulated Precast Concrete Sandwich Wall Panels

Abstract: Glass fiber–reinforced polymer (GFRP) shear connectors provide much reduced thermal bridging in insulated concrete sandwich panels compared to steel connectors. In this study, 50 specimens with dimensions of 254×254×900 mm representing segments of a precast sandwich wall comprising two concrete wythes and a concrete stud surrounded by insulation foam have been tested in a double-shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymer connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors, including the effect of friction between concrete and foam, ranged from 60 to 112 MPa, significantly higher than polymer connectors but lower than steel connectors. As the connectors bridge...

Seismic Analysis of RCC Building with and Without Shear Wall

Abstract: In the seismic design of buildings, reinforced concrete structural walls, or shear walls, act as major earthquake resisting members. Structural walls provide an efficient bracing system and offer great potential for lateral load resistance. The properties of these seismic shear walls dominate the response of the buildings, and therefore, it is important to evaluate the seismic response of the walls appropriately. In this present study, main focus is to determine the solution for shear wall location in multi-storey building. Effectiveness of shear wall has been studied with the help of four different models. Model one is bare frame structural system and other three models are dual type structural system. An earthquake load is applied to a building of ten stories located in zone II, zone III, zone IV and zone V. Parameters like Lateral displacement, story drift and total cost required for ground floor are calculated in both the cases replacing column with shear wall.

Monitoring Crack Propagation in Reinforced Concrete Shear Walls by Acoustic Emission

Abstract: In the last two decades, several efforts have been made to monitor the cracking behavior in RC structures. A technique that shows promise is acoustic emission (AE). This paper presents the results of an experimental study aimed at monitoring fracture processes in a large-scale RC shear wall using one of the most important AE parameters, that is, the b-value. The specimen was subjected to a displacement controlled reversed cyclic loading. A Gaussian filter is proposed to improve the interpretation of b-value data obtained during the test. In addition, a cluster analysis based on the k-means is presented to automatically classify the signal into tensile and shear cluster. Finally, a new algorithm called Sifted b-value (Sb) analysis is introduced to monitor the evolution of each crack mode. The proposed approach is capable to identify the initial yielding and eventually provide an early warning for the planning and implementation of remedial action to the structure at a point at which it is less expe...

Steel sheathed/CFS framed shear walls under dynamic loading: Numerical modelling and calibration

Abstract: This paper describes the numerical modelling using OpenSees of shear walls constructed of cold-formed steel (CFS) framing and flat steel sheathing. The first phase comprised non-linear models calibrated using existing reversed cyclic shear wall test data. The second phase involved more advanced models calibrated using data from dynamic shake table tests of single- and double-storey shear walls and additional ancillary component testing. These advanced models were able to accurately reproduce the shear strength and displacement time history and hysteretic response of the dynamically tested shear walls. The use of a building model that incorporates the second phase wall models is demonstrated for the evaluation of representative CFS framed structures using non-linear time history dynamic analyses.

Dynamic Testing of Single- and Double-Story Steel-Sheathed Cold-Formed Steel-Framed Shear Walls

Abstract: This paper describes an experimental investigation of steel-sheathed cold-formed steel-framed shear walls by means of dynamic shake table tests. The objective was to evaluate the seismic performance and to identify whether the shear-wall behavior was consistent with past static tests, to obtain measures of damping and natural period of vibration, to investigate the influence of a second story, and to validate and improve the accuracy of the numerically predicted force-deformation response. The scope of study comprised five single-story and five double-story walls of the platform framing technique. Each wall was subjected to a suite of excitations: impact test to measure the linear-viscous damping ratio, harmonic excitation to estimate the natural period of vibration, and ground motions representative of the seismic hazard in Canada. An overview is presented of the test setup and dynamic loading protocols, as well as the test results and numerical model.

Analytical study on seismic force modification factors for cross-laminated timber buildings

Abstract: With two producers in operation and over 20 buildings already constructed or in planning process, use of cross-laminated timber (CLT) is gaining popularity in Canada. Since CLT as a structural system is currently not included in the National Building Code of Canada (NBCC), one of the most important issues are the values for the force modification factors for seismic design of CLT structures when NBCC equivalent static force procedure is used. In this study, a test-calibrated numerical model for CLT shear walls was applied to develop the design resistances for typical CLT wall configurations. An estimation of a possible range of Rd-factors was obtained by developing design variations for three multi-storey CLT apartment buildings. By specifying the desired seismic performance in terms of inter-storey drift, it is concluded that an Rd-factor of 2.0 will likely provide desirable building performance during the design earthquake level event in Vancouver, B.C.

Analytical Study on Plastic Hinge Length of Structural Walls

Abstract: This study was organized to derive an analytical expression for the estimation of plastic hinge length for cantilever structural walls using the results of comprehensive nonlinear finite-element analyses. For that purpose, a parametric study was conducted. The variation of plastic zone length at the base of the cantilever shear wall models was determined on the basis of analysis results that depend on several parameters, such as the wall length, wall height, axial load ratio, and the ratio of wall boundary element and the web horizontal reinforcement. In light of the parametric investigation, a plastic hinge length expression was proposed dependent on wall length, axial load ratio, wall horizontal web reinforcement ratio, and shear-span-to-wall-length ratio. Existing plastic hinge length prediction formulations were also compared with the plastic hinge length obtained from finite-element analyses. Finally, the accuracy and reliability of the proposed plastic hinge length equation was verified by u...

Real-time Seismic Damage Detection of Concrete Shear Walls Using Artificial Neural Networks

Abstract: Concrete shear walls are widely employed in buildings as a main resistance system against lateral loads. Early identification of seismic damage to concrete shear walls is vital for deciding post-earthquake occupancy in these structures. In this article, a method based on artificial neural networks for real-time identification of seismic damage to concrete shear walls was proposed. Inter-story drifts and plastic hinge rotation of concrete walls were used as the inputs and outputs of a MLP neural network. Modal Pushover Analysis was employed to prepare well-distributed data sets for training the neural network. The proposed method was applied to a five-story concrete shear wall building. The results from the network were compared with those obtained from Nonlinear Time History Analysis. It was observed that the trained neural network successfully detected damage to concrete shear walls and accurately estimated the severity of seismic-induced damage.

Numerical Modeling of Slender Reinforced Concrete Shear Wall Shaking Table Tests Under High-Frequency Ground Motions

Abstract: This article presents the numerical modeling of large-scale shake table tests of slender 8-story reinforced concrete (RC) shear wall specimens. Nonlinear time history analyses are carried out using reinforced concrete fiber elements (OpenSees, OS) and the finite element (FE) methods (VecTor2, VT2). The effects of the modeling assumptions are investigated, including: (a) the tension stiffening effect, (b) damping, (c) smeared vs. lumped reinforcement, and (d) the use of effective shear stiffness in OS. Good agreements are obtained between the numerical and experimental results. Using the proposed numerical modeling strategy, it is possible to investigate the nonlinear dynamic responses of slender RC wall structures with confidence.

Corotational Model for Cyclic Analysis of Light-Frame Wood Shear Walls and Diaphragms

Abstract: This paper presents a new two-dimensional shear-wall and diaphragm model developed as part of a Network for Earthquake Engineering Simulation (NEES) Project entitled NEES-Soft: Seismic Risk Reduction for Soft-Story Woodframe Buildings. A large portion of the older multistory buildings in the California region were constructed with a deficiency that makes them vulnerable to collapse in the first story during earthquakes. This deficiency is referred to as soft-story. The new model presented in this paper was developed using a corotational formulation, which makes it suitable for modeling the side-sway collapse of wood shear walls under large displacement as well as estimating the in-plane stiffness of floor diaphragms. To achieve high computational efficiency, a nodal condensation technique is used to eliminate the degrees of freedom (DOFs) associated with the nail connections from the global DOFs of the model. To verify the validity of the new model, the model was coded into a computer program and ...

Cyclic response of reinforced concrete walls with different anchorage details: Experimental investigation

Abstract: Previoustestsofstructuralwallshaveroutinelyusedcontinuousreinforcementextendingfromthefoundationtothetopofthespec- imen. This detailing is consistently different from that of multistory walls in the field, which incorporate splices in the wall longitudinal rein- forcement above the wall-foundation interface. As a result, the performance of walls incorporating continuous reinforcement in the laboratory may not be representative of walls in the field that use lap splices or mechanical couplers near the wall base. This paper investigates lateral load behavior of three nominally identical structural walls with continuous reinforcement, lap splices, and mechanical couplers in the plastic hinge region, and quantifies the differences in their responses using force-displacement response, lateral deformation components, and energy dissipation estimated using equivalent viscous damping. DOI: 10.1061/(ASCE)ST.1943-541X.0000732. © 2013 American Society of Civil Engineers. CE Database subject headings: Anchorages; Cyclic loads; Plastic hinges; Reinforced concrete; Seismic design; Shear walls; Experimentation. Author keywords: Anchorage; Lap splice; Mechanical coupler; Cyclic loads; Plastic hinges; Reinforced concrete; Seismic design; Shear walls.

Effects of mortar layers in the delamination of GFRP bonded to historic masonry

Abstract: Externally bonded fiber reinforced polymers (FRPs) used as strengthening for shear historic masonry walls increase tensile capacity so as to support combined compression and high shear forces released during earthquakes. The local and global capacity of FRP strengthened shear walls depends on delamination. This paper deals with the anchorage strength of GFRP strips bonded to historic masonry by analysing results obtained in pull–push shear tests carried out on GFRP-to-historic-brick bonded joints. The experimental research also foresaw the analysis of effects deriving from the presence of mortar layers in actual historic brickwork masonry, simulated through the creation of grooves on the surface of mortar filled clay bricks. The experimental results indicated brittle failure of joints due to delamination; results were processed to evaluate failure load values, strain vs. anchorage length diagrams and shear stress vs. slip relationships experimentally. Finally, the anchorage of GFRP-to-historic-brick was theoretically studied to improve the classic solution by incorporating adherent shear deformation. Discussion on the experimental and theoretical data was developed.

Seismic shear forces on RC walls: review and bibliography

Abstract: Effect of higher vibration modes on the seismic shear demand of reinforced concrete cantilever walls has been studied since the 1970’s. The shear amplification becomes more important with increasing fundamental period (tall buildings) and increasing ductility demand (R or q factors). Yet, studying the relevant recommendations of structural engineering researchers and provisions of various seismic codes reveals that there is no consensus regarding the extent of shear amplification and of the inter-wall distribution of shear demand in structural systems comprising walls of different lengths. The paper presents the available formulas for predicting shear amplification in ductile walls and dual systems (wall-frames). One effect that impacts the shear amplification is shear cracking mainly in the plastic hinge zone of the wall near the base leading to appreciably lower shear amplification than previously predicted. Post yield shear redistribution among interconnected unequal walls is also addressed. Finally, an extensive bibliography is provided.

Seismic Behavior of a Modern Concrete Coupled Wall

Abstract: RC core walls are used commonly in modern building construction as the primary lateral load–resisting system. To meet architectural constraints, including elevator, stair, and doorway openings, common configurations include walls coupled together with heavily reinforced, low-aspect-ratio coupling beams. Numerous studies have focused on coupling beams and improved seismic performance and design of coupling beams. However, far fewer research programs have studied the seismic behavior of the coupled wall system. Coupled walls are typically used in mid- to high-rise construction, and understanding their seismic response requires simulation beyond the coupling beam and must include all important yielding components of the system. A research project was undertaken to investigate the response of a midrise coupled wall designed to meet current codes. The advanced testing capabilities of the University of Illinois at Urbana-Champaign George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES)...