Practice Periodical on Structural Design and Construction

Exterior decks must be designed to resist all applicable load cases. Vertical (gravity) loads are well defined, but less is known about designing decks for lateral loading. The focus of this study was to better understand the ultimate strength and load paths of two common deck constructions subjected to monotonic lateral loading. A portion of a conventional light-frame wood-floor diaphragm was built, to which the decks were attached. One deck was constructed with a lateral hold-down tension connector and the other deck had no hold-down tension connector. The lateral resistance and load path of each deck were investigated by applying a monotonic force through the centroid of the deck surface. The ledger board was connected to the house rim board with lag screws. Forces in each lag screw and hold-down connecting the deck to the diaphragm were recorded. Preliminary tests revealed a weakness in the deck joist–to–deck ledger connection; this was resolved by using joist hangers that featured a perpendicular fastener attachment and manufacturer-approved screws. With this weak link reinforced, the connection between the deck ledger and the house rim board was investigated and it was found that it remained structurally intact with no observed damage up to a maximum load of approximately 31 kN for both deck constructions (with and without the tension hold-down connector). The main failure mechanism was splitting of the top edges of the joists (tension perpendicular to grain) caused by a resisting force couple created by pairs of deck board screws fastening the deck boards to the joists. In both cases and as expected, the lags screws near the end of the ledger experienced the greatest tensile forces.

I-joists may be used as floor joist and roof-rafter members in residential construction but require different installation practices compared with solid-sawn lumber because of I-joist geometry and design. The building codes in this paper contain clear specifications for the installation of sawn-lumber products. Because I-joists are proprietary and installation requirements vary by brand, manufacturer literature is incorporated by reference into the building codes discussed herein. The engineered and proprietary nature of I-joists may be unfamiliar to carpenters and other trade professionals, resulting in installation errors. I-joist installations that do not comply with manufacturer specifications are considered code violations. Through use of the Delphi method, an expert-validated inspection methodology was developed by interviewing code officials, home inspectors, and engineered-wood-product manufacturers. This paper summarizes the results, including best practices for inspection methods and I-joist installation errors most likely to occur. Effective inspection methods include the top-down method, a circular inspection pattern on each level of the structure (the nautilus method), and a comparison of repeating members in a support structure (the pattern method). Common I-joist installation errors include improper (1) holes, cuts, and notches; (2) bearing; (3) bracing; (4) blocking; (5) hanger hardware installation; and (6) rim-joist installation. Application of the recommended inspection practices can improve the detection of I-joist construction errors.

This paper presents a methodology to compare various Tainter gate strut-arm retrofit techniques based on the longevity corrosion maintenance (LCM) factor. The rating system is designed to encourage agencies to select retrofits that will better upgrade existing conditions to meet current design standards for hydraulic steel structures and achieve a long design life. An overview of past Tainter gate failures, governing strut-arm load cases, past strut-arm retrofit strategies, current design standards for hydraulic steel structures, and the consequences of welding or bolting to existing structures has been considered in this study as evidence to support the proposed Tainter gate retrofit comparison methodology. An example problem illustrates how to determine the LCM factor and assign a LCM grade for three retrofit scenarios.

Rational and sophisticated structural solutions are essential requirements for structural designers, as a consequence of architectural design evolution and new building management concepts. Thus, waffle slabs turn out to be an interesting alternative, despite their laborious numerical modeling. It is necessary to increase knowledge about the structural behavior of and improve the theoretical models used for the simulation of these slabs. To better understand the behavior of RC waffle slabs, and more realistically quantify stresses and displacements of this kind of element under actual work conditions, a real-scale ribbed slab was tested and the results are presented in this paper. The chosen structure, designed to serve as a parking floor, was instrumented with strain and deflection gauges to assess the deformations and deflections developed under some induced loading conditions. A grillage model and a three-dimensional finite-element model were used for the numerical study. The data collected indicates that both strategies can be used to obtain adequate estimates of deflections and bending moments.

The behavior of a solid shear wall is well understood, and the rigidity of the wall can be accurately determined using a simple hand-calculated approach. However, the computation of the rigidity of a shear wall with openings is significantly more complex than that of a solid wall and, therefore, can only be accurately determined by using the computer-aided FEM. Although several conventional simplified hand-calculated procedures are available for practicing structural engineers, results from those procedures are highly approximate and may not be reliable. Therefore, a more accurate hand-calculated procedure, which considers the rotation at the tops of the piers and the effective length of the piers, is proposed to calculate the rigidity of shear walls with openings. A total of three different configurations of shear walls with openings are used as examples to assess the accuracy of the newly proposed hand-calculated method. The accuracy of the results derived from the newly proposed hand-calculated procedure has significantly been improved over the conventional hand-calculated procedures.