Practice Periodical on Structural Design and Construction

The writers recently created a fuzzy discrete multicriteria optimization model for automated design of large steel structures subjected to the actual constraints of commonly used design codes. In this work, the model is used to perform a comparative study of optimum designs of steel high rise building structures using AISC allowable stress design and load and resistance factor design (LRFD) codes. Results are presented for two large structures, a 36-story space moment-resisting frame with cross bracings and a 144-story super high-rise building structure with over 20,000 members. LRFD code results in the cost savings in the range of 3.0–6.9% for the 36-story steel structure and 1.7–4.3% for the 144-story steel structure. When serviceability (stiffness) is more of a controlling factor, the LRFD code in general yields a much smaller advantage for weight savings.

A series of horizontally curved bridges were analyzed using simple finite-element models. The analyses included using a typical truckload and also the dead load as the primary forces on bridges. In each analysis, the behavior of bridges was investigated, and the major internal forces developed in members were determined. Specifically, an increase in bending moment and the existence of a torsional moment in cases where the horizontal angle of curvature is large (about 20–30°) was observed. The significance of these moments, compared with the maximum bending moment of a comparable straight bridge, was noted. Bridges used in the analysis were assumed to be composed of single spans with about $30.5\text{-}\mathrm{m}$ (100-ft) span lengths (the chord length was set at 30.5-m for all bridges), steel girders, and an 203-mm (8-in.) reinforced concrete slab. The finite-element analyses consisted of a three-dimensional idealization using simple beam elements to model top and bottom flanges of the girders and plate bending elements modeling the girder webs and the slabs. The analyses revealed that this simple modeling could effectively be used in analyzing curved bridges. The analyses showed that the bending moment in girders of a curved bridge can be about 23.5% higher compared with moments in girders of a straight bridge of similar span and design configuration. As a result of the curved geometry of the bridge, a torsional moment is developed in the girders. The magnitude of this moment was found to be about 10.3% of the maximum bending moment of a comparable straight bridge.

In this paper, the effect of soil–structure interaction on the seismic performance of seismic-isolated bridges is studied. For this purpose, two typical seismically isolated bridges are selected. The selected bridges have distinct features to represent those bridges with: (1) Heavy superstructure and light substructure and (2) light superstructure and heavy substructure. Detailed structural models of both bridges excluding and including the soil–structure interaction effects are first constructed. Iterative multimode response spectrum analyses of the bridges are then conducted considering the nonlinear behavior of the isolation bearings. The analyses results have revealed that soil–structure interaction effects may be neglected in the seismic analysis of seismic-isolated bridges with heavy superstructure and light substructure constructed on stiff soil. However, the soil–structure interaction effects need to be considered for bridges with light superstructure and heavy substructures regardless of the stiffness of the foundation soil. In soft soil conditions, soil–structure interaction effects need to be considered regardless of the bridge type.

Multilevel parking structures are often constructed using prestressed concrete double-Tee beams that form their floor and roof diaphragms. Mechanical flange connectors are typically used to connect the flanges of these beams. Cracking of the concrete around the connectors is a common problem requiring significant person-hours to repair and maintain. This paper presents suggested design load levels that may significantly reduce the cracking in these structures based on the results of 49 monotonic displacement control tests performed on 6 different types of commercially available mechanical flange connectors embedded in concrete slabs. The slabs were designed to be representative of the overhang on a typical precast concrete double-Tee beam. Three different types of monotonic tests were performed: horizontal shear, vertical shear, and tension. Basic statistics were then used to analyze the data from each of these three test types and the load ranges were divided into four regions, termed cracking unlikely, cracking possible, cracking likely, and cracking probable.

This paper reports on the results obtained on the applicability of the diagnostic cyclic load test method in comparison with the existing $24\mathrm{h}$ test procedure adopted in ACI-318. A parking garage, owned by St. Louis County, St. Louis, Missouri, scheduled for demolition during the summer of 2002 was used as a research test bed before demolition. This structure, a two-story steel and reinforced concrete (RC) frame with one-way RC slabs built in 1970’s, was ideal, in terms of size and construction system, for performing comparative field experimentation on load testing. Investigation and validity of acceptance criteria of existing and proposed testing methods were performed. Two identical RC slabs were tested, according to both the standard procedure (ACI-318-02) and the proposed diagnostic load testing. In both instances, the applied total test load was such that the slab did not pass the load test. This allowed characterizing the critical test parameters that govern acceptability and draw conclusions on their values. After load testing, both slabs were loaded until partial collapse was reached. This allowed making observations on the margin of safety with respect to collapse, a determination that is not generally possible in a proof test. The analysis of the experimental data provides professionals with evidence on the validity of in situ assessment for the adequacy of structural members.

A general methodology for the earthquake resistant design and rehabilitation of damaged masonry historical structures is presented. The whole process is illustrated through a case study: The rehabilitation of Zoodohos Pigi Holy Temple in Athens; a structure that suffered extensive damage during the September 1999 Athens earthquake. The procedures followed in the design, together with a description of the actions taken for the rehabilitation of the Temple and its strengthening against future earthquake actions, are reported.

Lack of housing and the high costs of constructing housing units are problems faced by all nations. A viable solution to the lack of housing in many parts of the world may be found in traditional earthen construction methods. In Perú, ancestral building methods such as adobe, tapial, and quincha take advantage of the local resources for housing construction. These construction methods have been used for centuries. They do not require commercially processed materials or a skilled labor force. Unskilled local labor can satisfactorily construct a house using these construction methods. This paper presents a description of the quincha construction methods as applied in Perú.

The kinetic and potential energy of water discharged from a hydraulic retention structure can cause erosion in the zone immediately downstream and adjacent to the structure. Therefore, special erosion protection is necessary in the downstream discharge zone of these structures. A protection type that has given satisfactory results in Perú is the use of rock block pavements. The blocks effectively form a plate to resist the impact and abrasive action of the discharge flow. This paper details the construction process of one particular hydraulic structure that used rock blocks for erosion protection. The blocks were installed after the structure had experienced significant erosion of the stilling basin below its inflatable dam. This work was performed at the Hydroelectric Power Station Maria Auxiliadora del Quiroz located on the river Quiroz in northern Perú.