Journal of Structural Engineering

The existing models for the prediction of the splitting failure of dowel-type connections loaded perpendicular to grain are determined generally based on crack growth of the entire member cross-section. These models can be appropriate for stocky or rigid fasteners installed through the full thickness of the wood member. However, for slender dowel-type fasteners such as timber rivets, particularly when the penetration depth of the fastener does not cover the whole member thickness, the crack formation is different. Observations from current tests in thick members show that the crack growth across the grain occurs to a depth corresponding to the effective embedment depth of the fastener and propagates along the grain until it reaches its unstable condition. The design method presented in this paper to predict the connection splitting capacity takes into account the observed two possible failure modes of wood: either partial or full width splitting. In the proposed method, the effect of geometry parameters such as connection width and length, fastener penetration depth, loaded and unloaded edge distances, end distance, and member thickness as observed by others are considered. Results of the tests undertaken with laminated veneer lumber (LVL) and glulam manufactured from New Zealand Radiata Pine (RP) and data available from literature confirm the validity of this new method and show that the proposed design approach can be used advantageously in comparison to other existing models for timber rivet connections under transverse loading.

Database-assisted design (DAD) is an integrated methodology that calculates wind loadings and wind-induced internal forces. It can also calculate demand-to-capacity indexes for each structural member, and by checking whether they differ significantly from unity, determine the adequacy of the members’ structural design. Its practical usefulness depends on the availability of comprehensive aerodynamic databases. A public domain aerodynamic database produced in 2003 by the University of Western Ontario (UWO) is not sufficiently extensive to satisfy design needs generally encountered in practice. For this reason, the Tokyo Polytechnic University (TPU) recently developed comprehensive sets of aerodynamic databases that are publicly available and would fill large voids present in the UWO database. This paper presents comparisons of aerodynamic pressures and forces based on TPU and UWO data for low-rise buildings to help assess the extent to which the respective aerodynamic pressure measurements are comparable. In addition, the paper presents a brief review of comparisons between full-scale and UWO wind tunnel measurements of pressures on the Texas Tech University experimental building. The results presented in the paper, though not exhaustive, suggest that TPU and UWO pressure simulations are reasonably equivalent, and may in practice be used for the design of main wind force resisting systems.

Magnetorheological dampers (MR) have the promising ability to mitigate seismic hazard for structures because of their adaptive energy dissipation characteristics and low power requirements that can be met using standby batteries. These attractive characterstics of advanced damping devices, such as MR dampers, are important for achieving the goals of performance-based infrastucture designs. This paper validates the performances of four semiactive control algorithms for the control of a large-scale realistic moment-resisting frame using a large-scale 200-kN MR damper. To conduct this test, a large-scale damper-braced steel frame was designed and fabricated. Four semiactive controllers, namely (1) passive on, (2) clipped optimal controller, (3) decentralized output feedback polynomial controller, and (4) Lyapunov stability based controller, were designed for this frame. Real-time hybrid simulations (RTHS) were carried out for these controllers using three recorded earthquakes. The comparative performance of these controllers was investigated using both RTHS and numerical simulations in terms of reductions in the maximum interstory drifts, displacements, absolute accelerations, and control forces, and comparisons between test and numerical results.

In this paper, the results from a test program focusing on the behavior of eleven fully grouted reinforced masonry (RM) structural walls containing confined boundary elements are analyzed and presented according to force, displacement, and performance-based seismic design considerations. To be consistent with current force-based seismic design codes, analysis is presented to predict the strength, stiffness, displacements, and ductility-related force modification factors using the eleven test specimens. A new estimate of the plastic hinge region for displacement calculations is also proposed which considers the inherent planes of weakness in masonry mortar joints as well as the angle of inclination of shear cracks. Finally, within the context of performance-based design methodologies, the occurrence of specific damage states is identified. A methodology is proposed to estimate crack width in the walls based on curvature measurements which is also verified using digital image correlation analysis. The paper presents key seismic design parameters that are expected to contribute to the adoption of RM walls with boundary elements in the next-generation of North American seismic design codes.

The typical cause of flexural failure of prestressed beams is compression crushing of concrete, which is a progressive softening damage. Therefore, according to the amply validated theory of deterministic (or energetic) size effect in quasi-brittle materials, a size effect must be expected. A commercial finite-element code, ATENA, with embedded constitutive equations for softening damage and a localization limiter in the form of the crack band model, is calibrated by the existing data on the load-deflection curves and failure modes of prestressed beams of one size. Then this code is applied to beams scaled up and down by factors of 4 and $1/2$. It is found that the size effect indeed takes place. Within the size range of beam depths of approximately 152–1,220 mm, the size effect represents a nominal strength reduction of about 30% to 35%. In the interest of design economy and efficiency, a size effect correction factor could be introduced easily into the current code design equation. However, this is not really necessary for safety since the safety margin required by the code is exceeded for the normal practical size range if the hidden safety margins are taken into account. The mildness of the size effect in the normal size range is explained by the fact that the compression softening zone occupies a large portion of the beam and that, at peak load, the normal stress profiles across the softening zone exhibit only a minor stress reduction below the strength limit. Fitting the type 2 size effect law to the data can provide a simple extrapolation to much deeper beams, for which a stronger size effect is expected. But the extrapolation has some degree of uncertainty because of higher scatter of the test data used for calibrations.

Despite significant experimental, numerical and analytical research, the shear behavior of reinforced concrete members remains one of the least well understood mechanisms in reinforced concrete. Because of the complexity of shear behavior, empirical or semiempirical analysis approaches have typically been developed and these are widely employed in codes of practice. As with all empirical models, they should only be applied within the bounds of the tests from which they were derived which restricts the wide application of innovative materials as expensive testing must be performed to adjust existing empirical formulae or develop empirical formulae specific to the new materials. There is, therefore, a strong need to develop a generic, mechanics-based model to describe shear failure, which is the subject of this paper. The model is based on the mechanics of partial interaction, that is, slip between reinforcement and adjacent concrete which allows for crack formation and widening and is commonly referred to as tension-stiffening and slip across sliding planes in concrete associated with shear failure, which is referred to as shear friction.

In the companion paper, based on the theories of partial interaction and shear friction, a mechanics-based segmental approach, which can cope with any cross section and material property, was developed to simulate the shear behavior and failure of prestressed concrete beams with and without stirrups. The included equations and mechanisms are purely mechanics-based and independent of empirical material properties. In this paper, this numerical approach has been applied to describe the shear behavior of prestressed RC members. The effect of prestress on the shear behavior is explained, and the results of parametric studies on stirrup effectiveness are also shown. Published test beams with and without stirrups, 102 of them, have been analyzed by the proposed model and analytical results show good agreement with the experimental data. The average predicted results for the beams without stirrups being 96% of the test results and that for the beams with stirrups being 91% with coefficients of variation of 0.10 and 0.08, respectively. The equations provided by the ACI standard have been used to calculate the shear strength of the same test specimens, and the ACI shear provisions are shown to be quite conservative with an average of 67 and 74% and coefficients of variation of 0.29 and 0.18 for beams with and without stirrups. The influence of the random nature of cracks on the shear strength is also investigated.

Circular arches subjected to in-plane loading are restrained with discrete lateral bracings to improve their out-of-plane stabilities in many cases. The arch segment between two adjacent bracings may buckle out of plane if the effective length of the arch segment is sufficiently large. During out-of-plane buckling, adjacent arch segments may provide elastic restraints which increase the out-of-plane stability of the arch segment significantly. This paper is concerned with out-of-plane elastic buckling of circular arch segments with elastic end restraints. The analytical method for deriving the out-of-plane buckling loads of circular arches with equal rotational restraints or equal warping restraints at both ends is formulated. For the convenience of structural designers, simple approximate formulas for predicting the out-of-plane buckling loads of these arches are developed by the curve-fitting method. As for circular arches with unequal rotational restraints, the approximate formula for the buckling load of the arch with equal rotational restraints is modified with a reduction factor. Comparisons with the finite-element results and the analytical solutions show that the predictions by approximate formulas are sufficiently accurate.

This article presents an investigation of redistribution of moments in normal-strength concrete (NSC) and high-strength concrete (HSC) continuous beams. A nonlinear computer model is introduced and validated by experimental results of HSC continuous specimens. A numerical test is performed on two-span continuous beams where the concrete strength varies between 30 and 90 MPa so as to cover both NSC and HSC beams. Various tensile steel ratios over the center support ${\rho }_{s2}$ and midspan ${\rho }_{s1}$ are used. Some rules related to moment redistribution are examined. The study confirms that the moment redistribution is dependent on the stiffness of the critical sections. The analysis also indicates that full redistribution of moments is more likely to be developed in HSC beams than in NSC beams. The results of a parametric study, where the ratio ${\rho }_{s2}/{\rho }_{s1}$ is fixed at 0.8, show that at a given steel ratio, a higher concrete strength registers higher redistribution of moments except when ${\rho }_{s2}<1.55\mathrm{precent}$. The effect of concrete strength on the moment redistribution is generally reflected in various codes.

For structures sensitive to wind directionality, methods for the estimation of wind effects require the use of time series of directional wind speeds that cover time periods exceeding the length of the mean recurrence interval (MRI) of interest to the design. This study proposes a procedure for generating such time series from relatively short wind data sets. First, an algorithm is developed for estimating the parameters of the distributions of the directional wind speeds, given that the size of the data sample within one or more directional sectors can in some instances be too small for statistical inference purposes. Once the distribution parameters are estimated, a simple Monte Carlo procedure is used for data generation. The wind speed data being generated can be used within the framework of the database-assisted design approach to determine wind effects on buildings by accounting for wind directionality.

This research aims to identify and characterize the behavior of dissimilarly sheathed, load bearing, cold-formed steel studs under axial and lateral load. A series of tests on single studs, set in track, and sheathed with either oriented strand board, gypsum board, or combinations thereof are completed. The tests approximate the behavior of a sheathed stud within a larger wall. In each test, a predetermined level of axial load (or displacement) is introduced into the stud and lateral displacement (load) is then applied and increased until failure. This configuration results in axial load, bending, and (potentially) torsion on the stud. Observed failure modes for studs sheathed on only one face include torsion and/or fastener pull-through. For studs sheathed on both faces, failure modes include torsion, local buckling, fastener pull-through, and bearing (particularly for gypsum-sheathed studs). Analysis of the torsional response indicates the important role of the sheathing in limiting torsion and in determining the demands on the member and fastener. The observed member limit states compared favorably with the direct strength method of design even when direct torsion is not explicitly considered. New models for strength prediction in the connection limit states are explored. A model based on the torsional capacity of the fastener-sheathing system, limited by first failure in either pull-through or bearing, provides the best agreement with the observed connection limit states. Recommendations for design are provided.

This paper focuses on the flexural-torsional buckling and ultimate resistance of parabolic steel arches with box sections subjected to full-span uniformly distributed vertical load by using finite-element numerical analyses. First, analyses on prebuckling internal forces and flexural-torsional buckling loads are performed and compared with the existing theories. They show that parabolic arches under uniformly distributed vertical load are actually subjected to combined axial compressive and in-plane bending actions, rather than pure compression in the classic theory. Because the bending moment is substantial for shallow arches, the classic theory with the assumption of pure compression does not predict exactly the flexural-torsional buckling load. Second, the flexural-torsional ultimate resistance of parabolic arches is explored based on extensive finite-element numerical results, resulting in a design method based on a modified slenderness. The rise-to-span ratio is found to have a great effect on the flexural-torsional performance and resistance of parabolic arches, and for shallow arches the existing design method based on axial compressive force at the arch end cannot give good predictions for the resistance of arches. By introducing and adopting the modified slenderness of arches with distributed vertical load, which accounts for the effect of the in-plane bending moment, the column curve $b$ in GB50017, AISC 360-10, or Eurocode No. 3 can be used to predict the flexural-torsional resistance of both deep and shallow arches.

As a new type of nonprismatic built-up columns, the shuttle-shaped steel tubular latticed (SSTL) column is widely used in engineering structures. However, there are no methods available to test its ultimate resistance design and little research about its behavior. This article investigates the elastic buckling behavior of three-tube SSTL columns only with horizontal web members and subject to an axial load, and it is found that the SSTL column may buckle in a symmetric flexure-dominated mode or an antisymmetric shear-dominated mode, depending on distributions of sectional flexural stiffness and shear stiffness along the column length. The formulas for predicting elastic buckling loads are derived by accounting for the effects of sectional shear deformations. With the elastic buckling loads obtained, formulas for the effective slenderness and the normalized effective slenderness are proposed. The resistance design procedure for SSTL columns only with horizontal web members is developed in association with Chinese code GB50017 and Eurocode 3. Comparisons with finite element results demonstrate the proposed procedure can provide reasonably accurate predictions for the resistances of SSTL columns.

The bond properties between concrete and steel reinforcement influence structural stiffness and deformation behavior as a result of tension stiffening. In specific cases, the load-bearing capacity of engineering structures depends on the deformation behavior and may be affected by load history because of unloading and reloading (UR) cycles. The bond stress-slip relationship of the original tension chord model was modified to make it applicable for general UR cycles in the elastic and plastic states of the reinforcing steel by reducing the admissible bond shear stress, thus taking into account the progressive and irreversible damage to the concrete around the ribbed bar attributable to yielding and the load history. The residual tension stiffening in the elastic state is influenced by the degree of slip reversal, for which an analytical function was found that is dependent on the crack spacing, bond strength, and stress levels before and after unloading. The proposed analytical model was successfully validated with experimental results.

Buildings with masonry infill walls (MIWs) in reinforced concrete (RC) frames are commonly used all around the world. It is well known that infill walls may affect the strength, stiffness, and displacement ductility of the structural system. Different approaches have been adopted in different codes and guidelines to consider the stiffness and strength contribution of MIWs on RC frame behavior. This study compares the ability of the existing guidelines to estimate stiffness, strength, and deformability of RC frames with MIWs by using a compiled experimental database composed of 51 experiments from 24 different studies. Alternative expressions are proposed in this study to provide improved estimates of stiffness and deformability of infilled RC frames.