Practice Periodical on Structural Design and Construction

In short, the quality of construction allows several problems to be identified regarding buildings’ operating behavior, with the important problems ascribed to errors in project design. Often, during architectural design, the architect is deprived of a set of references which enable analysis of all concerns with regard to the proper operating behavior of proposed solutions. To overcome this problem, this paper seeks to contribute a clarification of the main problems concerning the maintenance of buildings and their implications in drafting the project. Architectural design affects a building’s operating behavior, as aspects can be identified to favorably bring about such behavior, as concerns the element of the constructive system’s external wall openings.

Design of bridges for seismic effects has changed significantly since it was originally included in the AASHTO Standard Specifications for Highway Bridges (the standard specifications) as Division IA in 1991. In addition to design changes, the seismic hazard in many areas of the United States has changed significantly in the AASHTO LRFD Bridge Design Specifications (the LRFD specifications) based on a change in the return period of the design earthquake and seismological research. A new option for seismic design, the AASHTO Guide Specifications for LRFD Seismic Bridge Design (the guide specifications), has been published providing an alternative, displacement-based design procedure. This paper provides a case study of three existing bridges in Alabama designed according to the standard specifications. The seismic resisting system of the existing bridges was redesigned based on the guide specifications and the LRFD specifications. The paper explores the effect of changes in design procedures and seismic hazard on detailing of bridges in a moderate seismic zone. The two specifications are compared for the worst-case hazard in Alabama; i.e., Seismic Design Category B. The results demonstrate that using the guide specifications results in larger spacing of lateral reinforcing in the plastic hinge regions of substructure components and drilled shafts resulting in more economical designs.

Commercial software for structural analysis and design has significantly evolved in recent years. Nowadays, they are more user-friendly, in addition to providing engineers with more modeling options to solve complex problems and geometries. Tapered elements in general and haunched beams in particular were traditionally difficult to model in the past; therefore, most commercial software did not include them in their element libraries. Recently, leading commercial software worldwide for structural analysis such as ETABS or STAAD-Pro allow engineers to model haunched beams in the elastic range of response. However, the technical information provided within the software’s manual does not always describe the details of the numerical modeling; i.e., whether it is based on rigorous traditional methods or is just an approximation based upon the calculus of variations. In this paper the approximations obtained with commercial software for a set of RC frames with symmetric haunched beams under lateral loading in the elastic range of response are reported when compared with those obtained with a traditional beam theory in which shear deformations are included. It is shown that the modeling used in commercial software is in general reasonable; however, it leads to an underestimation of the lateral displacements. Depending on the software and the modeling option used, lateral displacements vary from 62 to almost 100% of those calculated using traditional beam theory.

It is a key economic criterion for multistory residential and office buildings to have a shallow floor that minimizes floor height and saves in the cost of architectural, mechanical, and electrical systems. This paper presents the development of a new precast concrete floor system that eliminates the need for column corbels and beam ledges while being shallow. The proposed system can achieve a span-to-depth ratio of 30 and flat soffit while being consistent with prevailing erection techniques. The proposed system consists of continuous precast columns, prestressed rectangular beams, hollow-core (HC) planks, and cast-in-place composite topping. The paper presents the construction sequence of the new system and focuses on testing HC-beam connections without ledges in a full-scale specimen. Testing results indicate that a 30-cm-deep flat soffit precast floor system has adequate capacity to carry gravity loads (including 488 kg/m² live load) in a $9.14\text{-}\times 9.14\text{-m}$ bay size. Also, testing shows that shear capacity of the proposed HC-beam connections without ledges can be accurately predicted using the shear friction theory.

A new method is presented for the design of prismatic steel compression members that has significant advantages over current methods in certain cases. It enables designs to be obtained for members having elastic end restraints, significant initial out-of-straightness, or lateral loading, cases not amenable to an accurate solution using current methods. It is also much simpler and quicker to use for the design of members subject to applied end-moments, as is typically the result of the computerized analysis of rigid frames. It is not claimed to be a revolutionary breakthrough in the analysis of the behavior of steel columns; rather, it is intended to be a practical, user-friendly design office tool. The theoretical basis of the method and the derivation of practical design aids are described. Examples demonstrate the application of the method and, when possible, compare the results with current methods.

Durability concerns are of prime interest in designing RC structures, especially for offshore platforms and nuclear containment structures exposed to an aggressive environment. Most of these structures have been built using high-strength concrete (HSC) with a thick concrete cover. However, most of the available design approaches concerning the cracking control of RC members were empirically developed for members of normal strength concrete with normal concrete covers. This investigation focused on the development of simple design equations for predicting the cracking behavior and cracking control of thick HSC members. The proposed model takes into account the influence of most factors affecting the cracking response, such as the concrete tensile strength, bond strength, reinforcement ratio, reinforcement arrangement in concrete sections in perpendicular directions, and steel strain. Based on this investigation, cracking control design curves are developed to limit the crack width to certain values according to the exposure condition. These curves are ready for engineers to use in order to ensure cracking control in thick HSC members.

The remarkable construction skills of the Inca are manifested in the superb site preparation, foundation design, and drainage of Machu Picchu. Decade-long field studies at the pre-Columbian archaeological site of Machu Picchu revealed that the Inca possessed the ability to prepare for structures that endure. This is evident in the vast amount of Inca construction that still exists for engineers to study and admire. Inca construction was sustainable because of their high standard of care, even in the absence of a written language, use of the wheel, or availability of iron or steel. This paper contains examples of good ancient site preparation, foundations, and drainage at Machu Picchu and details of a foundation failure and an ancient landslide. These examples serve to illustrate the site’s challenging conditions for construction and the remarkable skills of the Inca engineers in addressing these difficulties.