Journal of Structural Engineering

This paper presents results of an experimental investigation of specially detailed ductile perforated steel plate shear walls (SPSWs) designed to accommodate utility passage, and having anchor beams with reduced beam sections connections. Single-story, single-bay SPSW frames are subjected to quasi-static cyclic loading up to their maximum strength and displacement capacity. The tested specimens also had low yield strength steel infill panels. Two specimens make allowances for penetration of the panel by utilities. The first, having multiple holes specially laid out in the steel panel, also has the characteristic of reduced panel strength and stiffness compared to the corresponding SPSW having a solid panel. The second such specimen utilizes quarter-circle cutouts in the panel corners, which are reinforced to transfer the panel forces to the adjacent framing. A SPSW with solid panel is also tested for reference purposes. All specimens resisted an imposed input history of increasing displacements to a minimum drift of 3%. The perforated panel reduced the elastic stiffness and overall strength of the specimen by 15% as compared with the solid panel specimen.

This paper presents a comparison of analytical and experimental results from an investigation of specially detailed ductile perforated steel plate shear walls (SPSWs). These SPSWs had low yield strength steel infill panels, anchor beams with reduced beam sections connections, and were specially detailed to accommodate utility passage through the wall while remaining ductile. Finite-element models of full SPSWs and subelement strips are developed using the finite element software package ABAQUS/Standard to facilitate a comparison with experimental results and to investigate the influence of localized distribution of panel stress and strain between perforations. Based on the analytical and experimental results, recommendations for the design of these special detailed perforated SPSWs are presented.

The Limit States Australian/New Zealand Standard AS/NZS 4600:2005 and the North American Specification (NAS) for the Design of Cold-Formed Steel Structural Members 2001 (2004 Supplement) include the newly developed direct strength method of design (DSM). In both standards, the method presented (Chapter 7 of AS/NZS 4600:2005, Appendix 1 of NAS) is limited to pure compression and pure bending. The situation of combined bending and shear as occurs in a continuous purlin system is not considered. In order to extend the DSM to purlin systems, it is necessary to prescribe and calibrate a method for combined bending and shear. Eight different test series on purlin sheeting systems with single, double, and triple spans and both uplift and downwards load cases as well as screw and concealed sheeting have been performed at the University of Sydney over a $10\text{-}\text{year}$ period. As many of these tests consisted of continuous lapped purlins where combined bending and shear occurred at the purlin section just outside the end of the lap, it is possible to use these test data to propose an extension to the DSM. Furthermore, calibration of the proposals using the limit states design methodology is included in the paper. This paper makes two proposals for combined bending and shear, and calibrates them both for the full sets of vacuum rig test data.

This paper investigates the effects of unsymmetrical loadings on the strength and behavior of simply supported deep beams. An experimental program consisting of 14 specimens has been carried out. Test results including crack patterns, load-deflection responses, steel and concrete strains, and failure loads are presented and discussed with the effects of load inequality (LI) and load asymmetry (LA). Conclusions are drawn on the effects of LI and LA on deep beam behavior. The ACI 318-05 strut-and-tie method is found to slightly overestimate the beam shear capacity. The writers proposed a direct strut-and-tie method (STM) for predicting the failure loads of unsymmetrically loaded deep beams. By adopting an interactive failure criterion, no preset empirical stress limit is required in the model. A load parameter Π is introduced such that the proposed STM can simulate both the effects of LI and LA. It is shown that the proposed STM is a generalized form that embodies the special cases of single-point and two-equal-point symmetric loading conditions. Besides, the model gives promising results in predicting the possible failure modes. The STM predictions are in good agreement with test results as well as finite-element predictions of 14 specimens.

When the corner radius ratio $\rho$ is defined as $2r∕b$ (corner radius divided by half breadth of column), circular and sharp cornered square columns are just two special cases when $\rho =1$ and 0, respectively. It is quite logical that a confined concrete strength model for columns with a corner radius should degenerate into a model for circular and sharp cornered square columns when $\rho =1$ and 0, respectively. However, this is not the case in any of the existing models, except for the early one by Mirmiran et al. in 1998. Extensive experimental testing on fiber-reinforced polymer (FRP)-confined concrete columns that have a continuous variation of $\rho$ from 0 to 1 has been undertaken by the writers. Based on the experimental findings, a rational procedure is proposed for developing a unified strength model for FRP-confined concrete columns with an arbitrary corner radius. A comprehensive database has been established by collecting all of the available experimental results from the open literature for evaluation of the unified model. The proposed procedure is applicable to concrete columns confined not only by FRP materials but also other materials such as steel plates.

Site-built wood-frame (light-frame) construction is the most common form of construction for residential structures in the United States. Such structures have suffered significant damage in recent earthquakes, and wood-frame construction practices in the western United States (WUS) have improved considerably in the last $2\text{decades}$ . On the other hand, little is understood about the expected performance of wood-frame structures located in the central and eastern United States (CEUS), where the seismicity is moderate compared to the WUS and construction practices seldom provide earthquake resistance. This paper examines the seismic performance of typical one- and two-story wood-frame structures in the CEUS. Six structures with two foundation types were considered, for which conditional limit state probabilities (fragilities) were evaluated considering three possible failure mechanisms: excessive interstory drift, wall uplift, and sill plate splitting. This examination shows that seismic damage to wood-frame structures in the CEUS under earthquakes of moderate intensity is unlikely to lead to loss of life, but may result in significant financial losses. An evaluation of two possible retrofit strategies illustrates how the expected seismic performance of the CEUS structures can be improved by adding more anchor bolts and perimeter sheathing nails to the shear walls.

Fifteen shear walls, each constructed with either conventional or engineered sheathing nails, were tested under fully reversed cyclic loads. Four types of conventional nails (named 0.113, 0.113R, 0.131, and 0.148 nails) and three types of engineered nails (named EN1, EN2L, and EN2H nails) were used. Walls with EN1 nails exhibited the highest ultimate load capacity; walls with 0.148 and 0.131 nails had 18 and 26% reduction in load capacity when compared to walls with EN1 nails. The ultimate load of walls with EN2H nails, though 15% less than that of walls with EN1 nails was greater than that of any other wall. The load capacity of walls with EN2H nails was 8% greater than that of walls with EN2L nails and greater than that of walls with 0.113 and 0.131 nails by 24 and 14%, respectively. Walls with 0.113 and 0.113R had basically the same load capacity. The stiffest walls were those with 0.148 nails with stiffness 10% greater than those with EN1 nails. The stiffness of walls with EN1 nails was effectively equal to that of walls with 0.131 nails. The stiffnesses of walls with EN2L and EN2H nails were basically the same. The stiffness of walls with EN2 nails was 20 and 26% smaller than that of walls with 0.113 and 0.131 nails, respectively. Walls with 0.113R were the least stiff walls; their stiffness was 44% lower than that of walls with 0.148 nails. The displacement capacity of walls with EN1 nails was 89 and 97% of that of walls with 0.131 and 0.148 nails, respectively. Walls with 0.113 and 0.131 nails had essentially the same displacement capacity. Compared to walls with 0.113 and 0.131 nails, walls with EN2L nails had an 8% increase while walls with EN2H nails had a 4% decrease in displacement capacity. Walls with 0.113R nails exhibited the lowest displacement capacity, only 75% of that of walls with EN1 nails. Walls with EN1 nails dissipated slightly more energy than those with 0.148 nails; they dissipated approximately 16% more energy than those walls with 0.131 nails. Walls with EN2H and 0.131 nails dissipated basically the same amount of energy. Walls with EN2L nails dissipated 5% less energy than walls with EN2H and 0.131 nails. Walls with EN2L and EN2H nails dissipated, respectively, 5 and 10% more energy than walls with 0.113 nails. Walls with 0.113R nails dissipated the lowest amount of energy, 75% of that dissipated by walls with EN1 nails.

Mathematical models for capturing the effects of intrinsic damping are based upon a multitude of simplifying assumptions. In this work, common equivalent linear models are reviewed, and their implementations for modeling energy dissipation on the system and material scales are compared in simple, representative examples. It is shown that several independent methodologies result in approximately the same predicted responses for systems with uniform dissipative characteristics if certain assumptions are made regarding the frequency dependence of intrinsic damping. However, these assumptions result in divergences of predicted responses when extended to composite systems with nonuniform dissipative characteristics. As no analytical or validated numerical solutions for the dynamic response of composite systems with nonuniform dissipative characteristics exist, it is unclear as to which methodologies most closely predict composite system behavior. Further work in developing models to capture nonuniform intrinsic damping characteristics must be performed to generate a fully robust means for capturing energy dissipation across all levels of complexity in engineering systems.

The impact response of reinforced and posttensioned concrete members with ultrahigh-performance fiber-reinforced concrete (UHPFRC) overlay was studied. This paper presents the results of nine drop weight slab strip tests. Major parameters for the tests were the reinforcement configuration of the concrete substrate, the addition of reinforcing bars in the UHPFRC layer, and the static system. Two reinforced and posttensioned concrete slabs were tested for reference. Five slab strips were tested under static loading conditions for comparison. A three-point bending and a cantilever system were used in the drop weight tests to induce flexural compression or tension in the upper UHPFRC layer. The addition of a UHPFRC overlay improved the structural response: no crushing or spalling occurred in the UHPFRC at the impact location. The UHPFRC had a load distributing function, which led to reduced crack widths in the substrate and lower member deflections.

This paper presents a summary of updates made to the hurricane simulation model that has formed the basis of the hurricane wind speeds given in ASCE 7 for the period 1998 through 2010. Since the development of the model used for the ASCE 7-98 wind speeds, significantly more hurricane data have become available to improve the modeling process. These new data have resulted in an improved representation of the hurricane wind field, including the modeling of the sea-land transition and the hurricane boundary layer height, a new model for hurricane weakening after landfall, and an improved statistical model for the Holland $B$ parameter. The new hurricane hazard model yields hurricane wind speeds that are lower than those given in ASCE 7-05 even though the overall rate of intense storms (as defined by central pressure) produced by the new model is increased compared to those produced by the hurricane simulation model used to develop the ASCE 7-98 through ASCE 7-05 wind speeds. Estimates of uncertainties in predicted wind speeds are obtained by propagating the uncertainties in key model input variables (such as central pressure) through to the wind speed prediction stage. The two parameters controlling the overall wind speed prediction uncertainty are the modeling Holland $B$ parameter and central pressure. These variables are responsible for $\sim 70\%$ of the overall wind speed modeling uncertainty.

One approach to the optimal design of passive controllers in linear structures for earthquake engineering applications makes use of active control tools. Usually, when this approach is adopted, the actual objective function is a time integral of a functional of given mathematical structure of response quantities and control forces. This approach has been used for the design of added dampers and is appealing due to its simplicity and the minor computational effort it requires. In adapting the active control approach to passive control, it has often been assumed that an objective function of this kind is suitable. It has been a widespread opinion in the passive control community, however, that minimization of such a smeared quantity that has a predetermined mathematical structure cannot lead to truly optimal added damper schemes. This paper formally addresses this issue and shows that what has been suspected for some time is indeed the case. The optimal location and size of each of the added dampers and, thus, the total added damping for given structures are attained here by directly solving the practical optimization problem as a reference. For the same total added damping, an active control approach is then used to find its own optimal location and size of each of the added dampers. A time history analysis is finally carried out for an a priori chosen ensemble of earthquakes to yield the envelope of maximal interstory drifts. It is shown that the active control approach is not satisfactory, in the practical sense, since it leads to much larger maximal interstory drifts.

Walls of low-rise wood light-frame buildings are commonly employed as the primary means for resisting damaging effects of horizontal forces caused by events like hurricanes and earthquakes. Here test data show how openings for doors and windows influence the in-plane shear stiffness and load capacity of light-frame wall panels sheathed with oriented strand board. Findings contribute to improved design data.