Journal of Structural Engineering

The aim of this work is to establish a systematic methodology for generating automatically different tessellations and double-layer grids (DLGs) following a newly defined, specific nomenclature. This particular nomenclature defines the notation of mosaics and DLGs in a synthesized and unique manner, and can generate and design them after the parameters expressed in their own names. By means of an algorithm and some computational codes, it is possible to recreate in 3D any DLGs directly from their own names. The current nomenclature for tessellations is also analyzed and found to have severe disadvantages, such as the excessive length of their notations and their nonunique character. A new nomenclature is proposed to define and generate $n$-uniform mosaics consistently and unequivocally in a manner consistent with the current nomenclature used for Archimedean (regular and semiregular) tessellations.

This paper presents a new methodology for cost optimization of the preliminary layout design of three-dimensional (3D) reinforced concrete (RC) frames. This approach is capable of being easily employed for the optimal layout design of a realistic large RC structure that accounts for constraints imposed by design standards. The new approach considers modeling, structural analysis, concrete member design, and discrete optimization together with data on the cost of systems and materials. The methodology is comprised of two parts. First, using the cross-sectional action effects as design variables, a heuristic cost function is presented as an alternative to traditional cost functions for layout optimization of RC structures. Using the presented cost function, a structural optimization problem is formulated for column layout design of 3D RC frames. Then, an ant system algorithm, a discrete method, is proposed to solve the cost optimization problem. Two comparative design examples are included to demonstrate the performance of the new methodology and the excellent convergence of the ant colony optimization algorithm.

This research investigated the shear behavior of five full-scale partially grouted masonry shear walls (PG-MWs). The walls were built using concrete masonry units, with horizontal reinforcement ratios ranging from 0.085 to 0.169%. The specimens had horizontal spacing between vertical grouted cells ranging from 610 (24 in.) to 1,219 mm (48 in.). All the specimens were tested under constant gravity load and incrementally increasing in-plane loading cycles. This research showed that there appears to be a maximum horizontal reinforcement ratio after which no additional shear capacity is achieved. As indicated by the experimental results, the maximum value appears to be approximately 0.1% for specimens with horizontal spacing between vertical grouted cells of 1,219 mm (48 in.). Increasing the horizontal reinforcement beyond this level did not increase the shear strength of the test specimens. In addition, the current provisions of the Masonry Standards Joint Committee (MSJC), the New Zealand code for masonry structures, Fattal’s model, and the strut and tie model were used to predict the shear strengths of the test specimens. The current MSJC shear equations overestimated the strength of PG-MWs with horizontal spacing between the vertical grouted cells of 1,219 mm (48 in.). A significant source of this error is from overestimating the contribution of the horizontal reinforcement. In addition, the current MSJC equations overestimated the masonry contribution to the shear strength of PG-MWs. For partially grouted walls with horizontal spacing between vertical grouted cells of 813 mm (32 in.) or less, and a horizontal reinforcement ratio of 0.085%, the MSJC shear equations are adequate. Shear equations by other codes and researchers were unconservative, as well. The strut and tie models were able to predict the shear strength of the test specimens within $\pm 16\%$.

This paper addresses the long-standing problem of the equilibrium of the circular, pointed, and elliptical arches commonly found in historical masonry buildings and bridges that are subjected to their own weight and the weight of superimposed masonry walls. The equilibrium problem is studied by applying two different complementary methods: the first is a simple extension and analytical re-reading of the Durand-Claye stability area method; the second is based on the application of a nonlinear elastic one-dimensional model, already used by the authors in previous studies. It is assumed that the arch’s constituent material has limited compressive strength and null tensile strength. In addition, the load transferred to the arch by the wall is determined under the common assumption that each vertical strip of wall bears directly down on the underlying arch element. The study focuses on the maximum height that the superimposed wall can reach under equilibrium conditions while maintaining acceptable values of arch residual stiffness. One noteworthy finding is confirmation of the decidedly better behavior of pointed and elliptical flat arches compared with that of circular arches.

The macro-finite-element (MFE) modeling proposed in this paper is dedicated to the calculation of the deflection of already cracked reinforced concrete beams under service loading at the stabilized cracking stage. MFEs are beam finite elements, characterized by their average moment of inertia, calculated using nonlinear assumed distributions of steel strain, concrete strain, and neutral axis between two consecutive bending cracks. The results of the MFE model are successfully compared with experiments performed on five RC beams, including square- and T-section beams and two concretes (grades 30 and 40 MPa). A successful application of the MFE method to a statically indeterminate beam is also presented. The MFE modeling is appealing for use in practice because of its computational simplicity.

Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experimental measurements and numerical results based on FE models in which the values of the constitutive parameters are set equal to their experimentally identified mean values and in which the values of the constitutive parameters are optimized through FE model updating, respectively. The results presented in this study show that uncertainties in the constitutive parameters of timber, concrete, and shear connectors have a significant influence on the correlation between the experimental and numerical results. In addition, the optimal values of material parameters obtained using the FE model updating procedure may show substantial variations with respect to the parameters’ mean values as identified in the experimental testing. Prospective developments directed toward design applications and based on the obtained results are also discussed.

Spandrel beams in precast concrete buildings are widely used to support double-tee deck beams, particularly in parking garages. Spandrel beams of deep cross-sections, resisting eccentric loads from double-tee beams, can be susceptible to excessive lateral deformations and serviceability failures before reaching their strength limits. However, closed-form solutions for estimating lateral deflections in such members are not available in the technical literature. In this paper, approximate analytical solutions for the deflection of beams with thin rectangular sections are derived from second-order elastic analysis, and they are proposed for use in estimating maximum lateral deflections in spandrel beams under eccentric and uniformly distributed loads. Continuous lateral support is provided at the elevation of the floor deck to the spandrel beams. Thus, two cases are considered: one for laterally restrained beams under typical service conditions, and a second for laterally unrestrained beams prior to the establishing the floor deck connections, or if those connections fail prematurely during service or under extreme loading. An equivalent loading method is proposed to obtain the approximate analytical solutions, in which the differential equations of equilibrium governing the problem are simplified by replacing the actual loading in the spandrel beams with a substitute loading. Numerical solutions are also obtained from three-dimensional finite element analyses and their results are found to be in close agreement with the analytical solutions for two of the three common types of load-bearing precast, prestressed concrete spandrel beams.

The condition of eccentric discharge is known to be one of the most critical for the design of thin-walled cylindrical metal silos. Significant progress has been made in recent years in devising a relatively realistic set of representative pressures for this load case. However, the consequences these may have on the predicted structural behavior of a silo are not yet fully understood. This paper presents a detailed parametric study into the behavior of a custom-designed slender silo under a set of unsymmetrical pressures describing the action of an eccentric parallel-sided pipe flow channel of varying cross-sectional areas. The results are compared with the reference axisymmetric case of concentric discharge. It is found that the predicted behavior is very complex indeed, and that geometric nonlinearity is of much greater significance for cylindrical shells under unsymmetrical load patterns than under symmetrical patterns. Further, it is found that eigenmode-affine imperfections, which are very deleterious under axisymmetric loading patterns, are instead beneficial to the buckling strength of a silo under eccentric discharge, thus making them unsuitable for use in design for this load condition.

Cold-formed steel (CFS) framed gypsum shear walls are common elements on light-frame structures, and they may be designed as the primary lateral force-resisting (LFR) system or function as secondary LFR elements. This paper presents the results of monotonic and reversed cyclic gypsum shear wall tests and discusses wall performance in detail. Increased strengths and wall toughness may be achieved with closer intermediate panel fastener spacing, and the difference between monotonic and reversed cyclic shear wall responses, although different, may not be significant. Additionally, aspect ratio and abutting supported vertical panel joints have little effect on shear wall performance. The scope of testing also introduces three new panel attachment configurations for design. Overall, this paper’s discussion provides a helpful supplemental commentary on the performance of CFS framed gypsum shear walls.

The 2010 AISC specification establishes the direct analysis method (DM) as the standard stability analysis and design procedure. Although the DM has important benefits over conventional stability design methods, the interface between the DM, the AISC seismic provisions, and the seismic design requirements in ASCE-7 is not fully established. Because the DM, which was developed for design scenarios that do not contain seismic loading, includes the effects of initial geometric imperfections and inelastic behavior owing to residual stresses, it is critical to explore the impact of these parameters on the seismic behavior of typical steel buildings. To examine these issues, a series of steel special moment-resisting frame models were subjected to monotonic pushover, cyclic pushover, and response history analyses. The observed behavior was used to draw comparisons between systems with and without residual stresses and initial imperfections. Cyclic strength degradation at beam-to-column connections was also considered to examine the potential interaction it may have with the other parameters. Whereas the well-known impact of strength degradation on cyclic stability was noted, residual stresses and initial imperfections did not have any appreciable effect on stability behavior for the systems considered. The analyses conducted in this study indicate no clear benefit to using the DM when designing regular ductile steel systems in high seismic regions and simpler design methods may be equally effective.

A series of subassembly tests were conducted to investigate the behavior of the self-centering steel plate shear wall (SC-SPSW) system under cyclic loading. The SC-SPSW system utilizes thin steel web plates to provide energy dissipation and the primary strength and stiffness of the system, whereas posttensioned (PT) beam-to-column connections provide recentering capabilities. In this new system, the web plate is intended to yield under cyclic loading, whereas the boundary elements and PT connection elements remain undamaged. The web plate can then be replaced relatively easily following significant inelastic cycles. This experimental program studies the effects of various design parameters on the system and connection response and compares the response with approximate analytical formulas. The experimental results show that the SC-SPSW system has high ductility, high initial stiffness, recentering capabilities, an overall system response as anticipated, and more energy dissipation than expected.

This paper compares the elastic stiffness of reduced beam section (RBS) beams with either flange or web reductions. The former has received considerable attention. However, recently the latter has been shown to have superior plastic rotation capacity and energy dissipation characteristics and is generally more amenable to retrofitting strategies. Initially, a closed-form elastic stiffness matrix for a RBS beam with web reduction is derived from first principles. Its performance is then compared with its reduced flange counterpart using data that are available in the literature. The differences between the two approaches are highlighted in a small parametric study.