May 28, 2020 at 2:12:23 PM
Students Design Explorations of Precast for an Extreme Climate
Guest blog by Doug Noble and Karen Kensek
2017 PCI Foundation Studio in the School of Architecture at the University of Southern California continued the tradition of examining precast concrete in the context of Joshua Tree National Park.
Fourth-year undergraduate architecture students were asked to design an entrance gate to the national park along with a restroom facility and small exhibition spaces. Joshua Tree National Park is about a two-hour drive from downtown Los Angeles, and the location presents the students with special opportunities to take advantage of precast concrete.
Students were challenged to design for the extreme climate, the distant construction location, the fragile condition of the natural landscape, a high-risk seismic zone, and the lack of easy access to normal utilities such as water and power. Students were forbidden to respond to the difficult climate with standard mechanical equipment.
Joshua Tree National Park is a hot-dry extreme climate. Wild temperature swings occur on the same day. Daytime temperatures routinely exceed 100 degrees, while nighttime temperatures regularly fall below freezing. Joshua Tree is very large, and has different climate zones, all hot and dry. Rainfall is typically less than five inches a year, but sudden rainfall and flash flooding also occur. The high-mass properties of precast can be carefully designed to take advantage the temperature swings to store thermal energy. High-mass concrete walls and roof elements left exposed to cold temperatures at night can be designed to give that cooling back to the interior spaces during the heat of the day. Similarly, precast exposed to high daytime temperatures can help keep a building warm at night.
The natural landscape is very slow to recover from damage. Areas in the park that were impacted by construction more than 50 years ago still show the signs of this impact. Students were charged with absolutely minimizing construction yard work areas, and we emphasized the possibilities for plant-produced precast as a solution.
Joshua Tree National Park is a very high seismic zone (think San Andreas fault and many similar geologic conditions). Students needed to understand how precast assemblies can be tuned for movement, and how high-mass and high-seismic are not always natural enemies.
The PCI Foundation studio at USC is supported locally by Clark Pacific and PCI West. Students toured two Clark Pacific precast plants. One plant visit was to learn about structural concrete: columns, beams, double-T's, and hollow-core. The other plant was for building envelopes. For students who had not previously heard of precast, the tours were eye-openers. Doug Mooradian and Ruth Lehmann from PCI West also supported the studio with lectures, desk-critiques, and studio reviews.
This year we went beyond the standard walking tour and powerpoint presentations of precast plants and precast building case studies. For the first time, our students actually got directly involved in physically making precast, including GFRC. Led by Brad Williams and Sal Cruz from Clark Pacific, the USC Architecture students received safety training followed by a full direct exposure to all of the steps in making precast and GFRC. Clark Pacific went well beyond any reasonable expectations and dedicated considerable staff resources. Sal Cruz taught the students to wire-tie rebar, and Robert Villa added expert advice and demonstrated additional advanced wire-tie techniques. Villa's hands were too fast, and he patiently slowed down his demonstration until the students could repeat it successfully using a training rebar frame. Leni Garcia and his GFRC team demonstrated the techniques, and then had each student do the work themselves. Rich Hundall and Alfred Toves were instrumental throughout the day as Williams kept up constant communication with his team by radio, always advising the Clark Pacific team as to what the USC group was doing and what was coming next. The students moved from station to station always just in time for the next step, and the students learned that timing was very important when spraying up the next GFRC layer or working quickly with the concrete in the mold.
The students were very pleased and excited to be hands-on, and we plan to do this again for each semester in the future.
This work was valuable as an educational exercise, but there is also a research component to our work with the PCI Foundation Studio. We are working towards building a full-sized and fully functional "thermal battery" as a demonstration display for the visitors center at Joshua Tree National Park. The precast elements we created this semester were cast in a very dark black and we will be conducting tests regarding thermal capacity, absorption pace, thermal expansion and other tests as we prepare to make the real thing. We plan for the thermal battery to complement the visitors center experience as a demonstration to park visitors how this kind of system can function. Joshua Tree National Park has millions of visitors each year, and we plan for the PCI Foundation / Clark Pacific thermal battery to be functioning in place and on display for decades.
The semester ended with a competition-style jury review, and several projects were selected by juror teams to receive PCI Foundation scholarships as prizes. Competitions can often encourage students to work harder, and they also function as methods for making others aware of the work we are doing. A side benefit is that several students will include words like "precast" and "PCI Foundation" and "Clark Pacific" on their resumes for years to come.
The USC School of Architecture is grateful for the opportunity to participate in the PCI Foundation studio, and we thank Clark Pacific for their very generous gifts of time, materials and expertise.
On a personal note, Karen Kensek and Doug Noble would like to take a moment to thank Doug Mooradian for his years of dedication to the PCI Foundation Studio at USC. There is no good way to express the high level of support that happens out of sight of the PCI Foundation. Mooradian meets with us many times each semester. He is here at USC giving lectures and providing input on projects all semester long. He custom-tailors his standard lunch-and-learn powerpoint presentations to adjust them for the needs of students. Of course we understand that he is especially dedicated to our studio because he is an alumnus of the USC School of Architecture, but we also recognize that he has been contributing this level of support at other programs. Doug Mooradian has served the industry very well as a fierce champion of precast and a dedicated supporter of the PCI Foundation studio. We know we are getting a strong new champion in Ruth Lehman (and she has already been to USC to help the students and to serve on the jury). We know that we will have the continued powerful support of Bob Clark and Brad Williams and their team at Clark Pacific. But we will miss Doug Mooradian and we thank him for his years of help in the USC PCI Foundation studio.