Practice Periodical on Structural Design and Construction

Masonry is the most executable and adaptable building material worldwide, but the seismic performance of masonry structures has always been a big concern. A new mortarless, interlinked block masonry system (slotted blocks with viscoelastic interlinked elements) is investigated. The slotted blocks are cast by using plain conventional concrete, and the viscoelastic link elements are prepared by using the ply of old/used radial rubber tires. The slotted concrete blocks with interlinked viscoelastic elements are integrated in such a way to restrict translational and rotational movements of the blocks under extreme earthquake loading conditions. This study addresses the concept of energy dissipation through friction and damping. Frictional damping in the system is achieved through block surfaces in contact with each other, and damping is achieved with the yielding of viscoelastic link elements without damaging the concrete blocks. The capacity-based principle is implemented in the conceptual design of the interlinked block masonry system in which the yield strength of the interlinked viscoelastic link element is kept low compared with the blocks. A single-room full-scale model of an interlinked block masonry system is tested on a shake table under design basis earthquake (DBE) and maximum considered earthquake (MCE) conditions per the most severe seismic Zone V of India considering soft soil conditions. The peak ground accelerations (PGAs) corresponding to both conditions are 0.18 and 0.36g, respectively. The acceleration along the height of the structure is measured with the help of triaxial force balanced accelerometers, and the relative displacement between the blocks is estimated by analyzing selected frames with the help of a high-speed camera. The test results authenticate the significant performance of the developed interlinked block masonry system with viscoelastic links by completely dissipating energy at the bottom portion of the structural model without damaging the blocks.

In cold-formed light-frame steel construction, wood structural panels can be connected to framing members with adhesives, staples, pins, and screws. Although screws are the most commonly specified fastener, steel pins have been used in construction for many years. Unlike that of screws, the design of connections with pins is still largely based on manufacturer-provided data. This paper examines the behavior of shear connections in which wood structural panels are attached to cold-formed steel framing using knurled steel pins. The results of a series of tests are presented for a range of thicknesses of cold-formed steel and wood structural panels. On the basis of observed behavior, expressions are proposed to compute connection peak-shear strength. The expressions are given in a form that can be easily adapted for other pin-connection configurations.

Previous studies by the authors discussed the behavior of unstiffened and stiffened extended shear-tab connections, highlighted the differences between both types, and discussed the applicability of stabilizer plate requirements to skewed extended shear-tab connections. This study presents a parametric study and proposes a design procedure for skewed extended shear-tab connections based on results obtained from a finite-element analysis for 300 models with different configurations. The variable parameters used for this study are plate thickness, the distance between the weld line and the bolt line, the skewed angle, and the number of bolts. These parameters were investigated in terms of the connection’s vertical displacement, the plate twist along the bolt line, the plate twist along the weld line, and the connection shear capacity. Modifications to the current connection lateral stability checks in the literature will also be addressed. The proposed design procedure on this study is the specific procedure for the skewed extended shear-tab connections. This procedure is compared with the current design procedure in the AISC manual.

Flat plate–voided concrete slab systems, which have been used for many years in Europe and other parts of the world, are becoming increasingly popular in the United States because of their many inherent benefits. Such benefits include reduced weight, which results in smaller seismic forces and larger superimposed loads for given span lengths; economical longer spans; reduced floor-to-floor heights; accelerated construction schedules; and inherent fire resistance that meets the fire-rating requirements of the International Building Code (IBC). This paper presents (1) the history and recent research on flat plate–voided concrete slab systems, (2) flexural and shear strength design requirements, (3) deflection requirements, (4) vibration criteria for human comfort and sensitive equipment, (5) fire-rating requirements in accordance with the IBC, (6) typical installation sequences, and (7) a summary of the main benefits of flat plate–voided concrete slab systems. The paper shows that such systems can be designed using the provisions of the American Concrete Institute (ACI) for strength and serviceability and can satisfy the minimum requirements for vibration control and fire resistance.

The predicted green residential market growth in the coming years and the increasing environmental awareness in society have led to an imperative need for home builders to sharpen their understanding of the additional costs and benefits of green residential practices. To aid home builders in this need, this paper presents some key observations based on a thorough examination of the costs and benefits of green single-family homes certified by the National Green Building Standard (NGBS). These observations were verified via interviews with green home builders and included the following: (1) Climate zones and local codes are the base to determine the additional costs and benefits of green buildings. (2) Additional construction costs to achieve green certification are higher in hot and humid climate zones. (3) After satisfying local code requirements following the International Energy Conservation Code (IECC), NGBS bronze or silver certification entails a very low additional construction cost. (4) Payback periods to cover additional construction costs at the NGBS bronze, silver, and gold levels might be as low as 3 years or less. (5) A client base of homebuyers who are willing to buy affordable, smaller, and greener homes exists in today’s market. (6) Prioritizing inclusion of specific green features (e.g., advanced framing techniques) facilitates achieving NGBS bronze, silver, and even gold certification at a potentially very low additional cost. This paper describes the key factors that determine the costs and benefits of green residential projects and presents a framework to facilitate cost–benefit analysis when considering green certification for homes.

The light rail transit (LRT) project located in Palembang, Indonesia, is being built to address traffic congestion and support the success of the 2018 Asian Games, a multinational sports event. The project consists of constructing a railroad network along with several stations located at an elevation aboveground, supported by reinforced concrete (RC) piers. A problem arises when it is not possible to cast concrete for the cantilevers on some piers located on the roads with a high frequency of traffic congestion. One solution to this problem is to replace the RC piers with hybrid piers. The hybrid piers are modifications of the RC piers in which steel frames replace the concrete for the cantilevers. The use of these hybrid piers opens up the possibility of offsite fabrication of the steel cantilevers so that the erection can still take place during off-peak hours and take less time. The use of these hybrid piers is relatively new for construction projects in Indonesia; the Palembang LRT project is the first project to have used this method. For this reason, it is important to understand this method’s design principles and effects on the construction process, especially about the connections between the steel and concrete structures. The hybrid piers are better than the RC piers, because the hybrid piers eliminate the need for concrete casting, a process that often causes obstructions to traffic flow. This method has the potential to be an alternative to pier construction for regions with high traffic volumes and high risk of traffic congestion.

This paper reports on the construction of a 31.4- to 33.1-m-deep subway station in Shanghai, China. This underground transit project was complicated further by the in situ hydrogeological condition, congested construction environment, and additional side-by-side deep excavations for other underground facilities. To protect the urban environment, challenges of this project, including potential risks, were evaluated in advance, and corresponding countermeasures to cope with potential risks were considered in the design and construction. To achieve the best project performance and verify design and construction considerations, a long-term field instrumentation program that lasted from May 2012 to April 2016 was implemented to monitor performance of the subway station pit and the adjacent ground and superstructures. Field data revealed that displacements of earth-retaining structures and the ground were within the local deformation control criteria. With the exception of a local leaking accident, no through-wall-seepage flow, piping, sand boiling, soil flow, rupture of pit base, or hydraulic uplifting of basal soils took place during the construction. The monitored cumulative settlements of adjacent buildings exceeded the specified criterion, but most buildings underwent only rigid tilt settlements and were rarely damaged. Experiences and lessons learned from this project will be useful for future design and construction of deeply buried infrastructures in densely populated cities.

Structural steel simple shear connections must satisfy strength requirements while providing adequate ductility. Although strength design has established limit states, providing adequate rotational ductility within a shear connection is less rigorous. Neglecting to provide adequate ductility can potentially cause premature sudden failure and, consequently, an unsafe connection. In this paper, an improved rotational ductility design formula based on the current approach outlined in 2011 by the American Institute of Steel Construction (AISC) is developed. In this modified approach, additional design parameters for bolt pitch and tensile strength are included. The ductility design is formulated for determining maximum framing-angle thickness and minimum bolt-diameter requirements. The proposed design approach is discussed and compared with the current design approach of the AISC.