The cold-formed steel framed shear walls with steel sheets and wood-based sheathing are both code approved lateral force resisting system in light-framed construction. In the United States, the current design approach for cold-formed steel shear walls is capacity-based and developed from full-scale tests. The available design provisions provide nominal shear strength for only limited wall configurations. This research focused on the development of analytical models of cold-formed steel framed shear walls with steel sheet and wood-based sheathing to predict the nominal shear strength of the walls at their ultimate capacity level. Effective strip model was developed to predict the nominal shear strength of cold-formed steel framed steel sheet shear walls. The proposed design approach is based on a tension field action of the sheathing, shear capacity of sheathing-to-framing fastener connections, fastener spacing, wall aspect ratio, and material properties. A total of 142 full scale test data was used to verify the proposed design method and the supporting design equations. The proposed design approach shows consistent agreement with the test results and the AISI published nominal strength values. Simplified nominal strength model was developed to predict the nominal shear strength of cold-formed steel framed wood-based panel shear walls. The nominal shear strength is determined based on the shear capacity of individual sheathing-to-framing connections, wall height, and locations of sheathing-to-framing fasteners. The proposed design approach shows a good agreement with 179 full scale shear wall test data. This analytical method requires some efforts in testing of sheathing-to-framing connections to determine their ultimate shear capacity. However, if appropriate sheathing-to-framing connection capacities are provided, the proposed design method provides designers with an analytical tool to determine the nominal strength of the shear walls without conducting full-scale tests.

In order to predict the strength of shear wall with cold-formed steel framing members, analytical models were reviewed. Multiple analytical models were studied, as well as twenty-one connection tests were performed. The connection tests consist of 50-ksi cold-formed steel framing track, different fastening configurations, and different sheathing thicknesses (1/8" and 1/2"). No.12 screw resulted in the highest peak load of all fastening configurations, while the rivet connection had the lowest peak load. In addition, failure modes were observed after conducting the connection tests including shear in fastening, screw pullout, and bearing in the sheathing. However, only the rivet and No.10 screw fastening configurations were used in the prediction analysis of the shear wall by the elastic model. Six shear wall tests were conducted on both panels (1/2"and 1/8" thickness). After doing the comparison between the experimental and the elastic model, the percentage difference for the 1/8" and the 1/2" polymer composite panels (3''along the edge and 6''along the chord stud), was very small. It was 6.2% for the 1/8" and 2.96% for the 1/2" panels. This means the analytical model can predict the shear wall peak load. However, the percentage difference was slightly higher being 7.4% for the 1/2" polymer composite panels with 6" along the perimeter with the 12" at the chord stud. After comparing the experimental values to the predicted value of shear walls, it was concluded that this model is the most appropriate analytical method for predicting the shear wall capacity framed with cold-formed steel sheathed with polymer composite panels. Many of these configurations were used in a prototype shelter that was constructed and built at the structural testing laboratory at the University of North Texas.

The purpose of this study is to model and analyze the nonplanar shear wall assemblies of shear wall-frame structures. Two three dimensional models, for open and closed section shear wall assemblies, are developed. These models are based on conventional wide column analogy, in which a planar shear wall is replaced by an idealized frame structure consisting of a column and rigid beams located at floor levels. The rigid diaphragm floor assumption, which is widely used in the analysis of multistorey building structures, is also taken into consideration. The connections of the rigid beams are released against torsion in the model proposed for open section shear walls. For modelling closed section shear walls, in addition to this the torsional stiffness of the wide columns are adjusted by using a series of equations. Several shear wall-frame systems having different shapes of nonplanar shear wall assemblies are analyzed by static lateral load, response spectrum and time history methods where the proposed methods are used. The results of these analyses are compared with the results obtained by using common shear wall modelling techniques.

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The purpose of this study is to analyze the foundation beam linked between two shear walls in the presence of lateral loads. Mat foundation with shear walls is one of the most commonly used reinforced concrete structural systems to resist the lateral load. When two independent walls are connected with a link beam, also known as the coupling beam, the overturning resistance of the building is largely increased. However, the coupling beams are relatively weaker structures and can develop larger stresses. When there is a mat foundation, or pile cap in case of pile foundation, the part of the foundation which is right below the coupling beam where no shear wall is present, will also get large stresses due to the highly rigid nature of adjacent shear walls. Most of the lateral deformations are imposed only on the coupling beams and foundation beam. There is not much literature or design procedure found in books and codes to mitigate the high risks associated with the foundation beam between shear walls on its design vulnerability. This thesis is focused on the risks associated with exceptionally high forces on the foundation beam due to earthquake forces.

This research is inserted in the topic of timber buildings. Many construction systems are available for building using timber, with the two main systems in residential ambit being Cross Laminated Timber and Light Timber Frame. Both systems reckon on the presence of shear walls to bear the effects of horizontal loads like seismic events or wind. This thesis deals with timber shear walls, and is divided into two parts: the first part is related to the ultimate and serviceability limit states rules to be included in upcoming versions of the building codes, while the second part presents a novel use of CLT walls as seismic renovation for existing buildings, as part of a European project. The first part of the thesis, which is presented in three papers, is closely related to the process of producing new building codes, and aims at an easier integration between research and codification. The initial focus is the behaviour of Cross Laminated Timber subjected to in-plane loading. Eurocode 5 currently lacks a part concerning this product and the discussion is still ongoing regarding the methods for stresses evaluation and on the strength values to adopt for safety verifications. The first paper tackles this problem by analysing different calculation methods currently available for the evaluation of the in-plane shear stresses, a common notation is introduced in order to have a meaningful comparison between methods proposed by different authors. All methods are then applied to a real case of existing experimental data regarding a four point bending test of CLT beams. Stiffness and strength of CLT are essential parameters for the definition of models to be adopted in codes regarding timber buildings, in particular for the calculation of shear walls. Another very common timber construction system is called Light Timber Frame: an assembly comprising a timber frame and an external sheathing layer mechanically joined to the frame. Consequently LTF walls are considered, the study is directed towards shear wall models for the evaluation of deformations. The second paper focuses on the evaluation of the displacement at the top of LTF walls subjected to horizontal loads. This is a key aspect for designers, since the limitation of deformations ensures that the building retains a satisfactory performance at serviceability limit states. The displacement is due to many different contributions, with the sheathing-to-framing deformation being one of the major ones. The paper presents a comparison between two of the proposed methods to calculate the sheathing-to-framing deformation of LTF shear walls. The influence of the nail slip contribution on the overall displacement of the top of the wall is studied also with parametric analyses, by varying both mechanical properties and geometrical dimensions. Comparison with existing experimental data is also provided. The study on shear walls regards also their lateral capacity, as well as the comparison between LTF and CLT walls of equal aspect ratio and similar restraining. In the third paper, existing cyclic test data on LTF and CLT walls were used to study the different displacement contributions and estimate the influence of the hold-down on the lateral response of the walls. A simplified capacity model is proposed for the walls, based solely on the hold-down forces. The second part of the thesis deals with the use of CLT shear walls as a mean for the retrofit of existing buildings. The need for sustainable renovation solutions and improvement of the performance of existing buildings is at the base of the European project e-Safe. The project presents a multidisciplinary approach on building renovation, from mechanical, energetic, technological and architectural point of view. In this thesis the focus is on the seismic retrofit system called e-CLT: a CLT panel is attached to the outside of existing buildings with a novel connector that acts as a friction dissipation device, thus offering additional energy dissipation in case of strong earthquakes. The fourth paper presents the first experimental campaign on this novel friction connector. Different geometries for the connector are studied and optimised, before being tested under cyclic protocol. The connector is tested on a steel setup, in order to isolate the friction behaviour and study the stability of the hysteresis loops. The results permitted to acquire new information useful for further developments on the system. The fifth paper presents a subsequent experimental campaign on the friction connector. The shape is changed and improved in light of the previous results. The setup is improved and includes also a screw connection between friction connector and CLT panel. The goal is to study the influence of the timber connection on the friction dissipative performance. An analytical model is proposed, fitted on the experimental data.

<p> A general formulation of the analysis of plane coupled shear walls is presented. The "continuous method" of analysis of coupled shear walls is reformulated in terms of deflection variables. The assumption that midpoints of the connecting beams are points of contraflexure is relaxed so that the resulting theory is applicable to the general case where the lateral loading on the piers can be arbitrarily distributed. The governing equation of the structural system under static loading with the appropriate boundary conditions are given. The effect of asymmetry of the structure is discussed. As an application of the derived theory, the problem of shear walls subjected to differential foundation settlement and rotation is studied. Solutions to deflections and internal stresses, under such conditions, are given. Evaluation of the internal stresses was performed on a practical shear wall structure and the results analysed. Through the use of deflection variables, the formulation is extended into the regime of dynamics. The governing equation of motion with appropriate boundary conditions are given. The free vibration of coupled shear walls is studied and design curves for the fundamental natural frequency are presented. The use of substitutive symmetric systems and its effects on the fundamental frequency of asymmetric systems are examined. Theoretical natural frequencies were verified by dynamic testing on two models to show that the proposed theory is sufficiently accurate to provide information for dynamic analysis in seismic design. / Thesis / Master of Engineering (ME)

<p> This thesis describes the construction and testing of small-scale shear wall buildings with rigidly connected floor slabs, but without wall openings. A micro-concrete material was used in the casting of both the basic small-scale shear wall buildings and the floor slabs. The vertically cantilevered buildings were tested by applying a transverse static load at the top of the buildings.</p> <p> The behaviour of buildings with only floor slabs was compared with that of buildings containing only wall openings. The results of static loading of the buildings were compared with those results predicted analytically using Vlasov's thin-walled elastic beam theory.</p> / Thesis / Master of Engineering (MEngr)

An analytical study was performed to evaluate the effect of shear wall ratio on the dynamic behavior of mid-rise reinforced concrete structures. The primary aim of this study is to examine the influence of shear wall area to floor area ratio on the dynamic performance of a building. Besides, the effect of shear wall configuration and area of existing columns on the seismic performance of the buildings were also investigated. For this purpose, twenty four mid-rise building models that have five and eight stories and shear wall ratios ranging between 0.51 and 2.17 percent in both directions were generated. These building models were examined by carrying out nonlinear time-history analyses using PERFORM 3D. The analytical model used in this study was verified by comparing the analytical results with the experimental results of a full-scale seven-story reinforced concrete shear wall building that was tested for U.S.-Japan Cooperative Research Program in 1981. In the analyses, seven different ground motion time histories were used and obtained data was averaged and utilized in the evaluation of the seismic performance. Main parameters affecting the overall performance were taken as roof and interstory drifts, their distribution throughout the structure and the base shear characteristics. The analytical results indicated that at least 1.0 percent shear wall ratio should be provided in the design of mid-rise buildings, in order to control observed drift. In addition / when the shear wall ratio increased beyond 1.5 percent, it was observed that the improvement of the seismic performance is not as significant.

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