Practice Periodical on Structural Design and Construction

It has been documented that labor performance or labor productivity is adversely affected by congested work areas and stacking of trades. Limited data are available that help to quantify losses in labor productivity due to congestion, or to document the severity of problems resulting from workspace congestion. Stacking of trades is often discussed in the context of construction claims, yet congested work areas can occur on projects where there are no claims and for reasons other than the stacking of trades. This suggests that a level of acceptance exists about the inevitability of workspace congestion, and the resulting losses in field productivity and profit. This paper presents a detailed and illustrative case study focused on the documentation of workspace congestion and the resulting effects on labor productivity. A description of the project conditions are provided, along with quantitative and qualitative data collection methods used in the field. The measured productivity rates in the field are then compared to baseline productivity rates based on historical data. Sources of lower productivity are then attributed to causal disruptions observed in the field, and the adverse effects due to congestion, poor weather, or workforce management are calculated.

Past hurricanes such as Andrew and the recent spate of hurricanes in Florida and elsewhere have shown the potential and extent of structural damage due to windborne debris during such storms. The loss of building exterior envelope and the subsequent structural damage to buildings due to such debris impact can be significant. Recent building codes have incorporated wind missile impact criteria for the roof and wall assemblies of coastal buildings. In this study, typical wall and roof assemblies for Florida residential and light commercial coastal construction were identified. In conjunction with a review of prior large wind missile testing results, assemblies that are yet to be tested were tabulated. These assemblies were tested for the Florida Building Code (FBC) large wind missile impact criteria. Based on the test results, a comprehensive list of wall and roof assemblies that passed the FBC test was developed. Also recommended were assemblies that should be avoided for the construction of residential and/or light commercial buildings.

A compressive strength model for confined concrete wrapped with fiber-reinforced polymer (FRP) has been developed which is an extension of Mohr’s strength theory. This model explicitly relates the confined compressive stress, $f_{\mathrm{cc}}^{\prime }$ , to the confining pressure, $f_l^{\prime }$ . It is shown that in the general form this model requires information about the uniaxial compressive strength, $f_c^{\prime }$ , the uniaxial tensile strength, $f_t^{\prime }$ , and a quantity, $n$ , relating to the shape of Mohr’s envelope of ultimate strength states. A second-order parabolic model, developed analytically, is proposed for use with FRP-confined concrete. The proposed model has been verified using existing tests of normal strength concrete $(f_c⩽8000\mathrm{psi})$ specimens confined by FRP wrap and tube previously reported in the engineering literature. For comparison, an empirical model using the same data was also developed. An application example for strengthening a reinforced concrete bridge column is also provided.

This paper presents a case study on a high-performance concrete (HPC) bridge in Tennessee. The bridge is a twin bridge with high-strength concrete (HSC) beams in one bridge lane and normal-strength concrete (NSC) beams in the other bridge lane. The compressive strength of HSC and NSC were $92$ and $49\mathrm{MPa}$ , respectively. The bridge was instrumented for strains and temperatures in precast beams, cast-in-place decks, and diaphragms during various construction stages. Test results presented in this paper include temperature changes in the concrete, time-dependent strains and cambers of precast HSC and NSC beams, and strain changes of deck and diaphragm. It was observed that the HSC members exhibited rapidly developed early-age creep and shrinkage strains, rapidly developed time-dependent cambers, and apparent differential shrinkage relative to the deck concrete. Recommendations for design and construction of HSC bridges are also presented in the paper.

This paper discusses the results of post-construction environmental monitoring studies performed on a 3.4-km-long industry access truck route with unstabilized F-fly ash subbase. The road utilized approximately $\mathrm{60,000}{\mathrm{m}}^3$ of ponded F-fly ash as road subbase, generated by a nearby power plant. Long-term environmental monitoring has been an integral part of the project since the construction of the road in October 2002. Six, 9-m-deep boreholes were developed as monitoring wells around the project site to evaluate the direction of groundwater flow and changes in water quality over time. Preconstruction water quality studies were performed on water samples collected from the monitoring wells in June 2000, to establish baseline water quality data for groundwater. Samples of fly ash taken from the stockpile were subjected to leaching studies prior to construction of the road. In total, five water quality samples were collected from the monitoring wells at regular intervals, as part of the postconstruction monitoring effort. Almost all the trace element levels in groundwater comply with Illinois Classes I and II standards, and have exhibited a general decreasing trend. Overall, the fly ash subbase has performed without any significant adverse environmental effects on the groundwater and neighboring soils.