Review Category : Construction Issues

CFS Load-Bearing Prefabricated Panels

Off-site construction is the future of the building industry. It aims to speed up on-site construction schedules, address skilled worker shortages, and achieve better pre-coordination. Given their lightweight nature, cold-formed steel (CFS) framing projects are uniquely situated to use prefabricated panels. The panels can be complete with all the framing, sheathing, and possibly finishes installed in the fabrication facility.

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Is the Process Compromising the Service Life of Encapsulated PT?

Unbonded post-tensioned (PT) concrete slab construction is commonly used for many types of structures, from high-rise towers to low-rise concrete podiums and parking structures. Since the adoption of ACI 318-14, Building Code Requirements for Structural Concrete and Commentary, many jurisdictions now require fully encapsulated PT tendons for building applications in all environments to prevent moisture intrusion and improve durability. The effectiveness of full encapsulation, however, can be highly dependent on the PT system installation, specifically the cutting of the tendon tails. This operation may not be done with enough precision and care to protect the grease caps, which encapsulate the tendon tails and complete the PT system’s continuous moisture barriers.

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Temporary and permanent shoring is often a necessary factor when designing/constructing new building structures in urban areas. The National Council of Structural Engineers Associations’ (NCSEA) Excavation Shoring Design Guide was created and published to aid structural engineers by providing a single source document. The Guide incorporates all the available codes from the federal government and state agencies so engineers can adequately guide the design team and owners to have the most economical project. 

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The use of masonry began with unreinforced dry-stack (mortarless) construction. For millennia, stone has been laid dry without mortar. The Great Pyramid of Giza (c. 2600 BC) is an example of limestone and granite ground smooth and fits tight without mortar (Figure 1). There are numerous examples of residences, walls, fortresses, and towers constructed using dry-stack masonry throughout the world. Unreinforced, these structures rely on gravity and friction to maintain their stability.

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Building density in urban settings is growing across the United States. Owners, developers, contractors, and engineers are becoming more sensitive to the detrimental effects of construction activities on neighboring structures. Construction activities disturb the soil in the construction zone and its immediate surroundings. The new construction team should identify all potential risks associated with the planned construction activities before the commencement of the site work.

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Rapid transportation by metro has become an indispensable development for many modern cities. Due to the depth and length of the tunnels, these urban subway lines are often built using circular tunnel boring machines (TBM). Two common types of TBMs are slurry TBMs and earth pressure balance (EPB) TBMs. While the tunnel shield and completed segmental tunnel linings (usually discrete precast concrete panels assembled together or precast rings) are relatively safe, the TBM excavation process can be potentially dangerous. This article looks at some measures and good practices to avoid sinkholes (Figure 1) during closed-face tunneling. The intricacies of tunneling and TBMs are much broader than the overviews included here.

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Preventing Damage Caused by Ground Loss and Water Loss

Deep excavation projects in highly urbanized and built-up environments must be designed and constructed with additional care. The design of these projects needs to deal with lateral wall movement, ground settlement, ground loss, and subsurface water pressure changes, all of which can lead to damage to adjacent structures (Figure 1). Damage can be in the form of cracks on non-structural walls (appearance), jammed windows and doors or dysfunctional services (functionality), and, in severe cases, cause structural members to be distressed (safety). Work suspension limits, usually for building settlement and inclinometers, may be breached. The project team could potentially face delays, claims, and additional costs due to expensive rectification work.

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Modular, rapidly erectable, and deployable structures are critical for disaster relief, military operations, and the accelerated construction of bridges and buildings. Through various innovative means and methods, permanent or temporary structures can be rapidly constructed in challenging environments, such as rural and austere regions where access to construction equipment is difficult or in heavily congested urban locations where construction time is severely limited.
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5 Factors for Joist and Deck Specification

The growth of e-commerce has bolstered warehouse and distribution center construction, with new project starts forecast to increase in 2021. Here are 5 areas where collaboration between the specifying engineer and the joist/deck supplier improves construction efficiency, shortens project timelines, and reduces total project costs.

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STRUCTURE magazine